Late Cenozoic to Recent Geologic and Biotic History of the Snake River

Workshop March 24 to 26, 2014 Red Lion Hotel - Pocatello, Idaho

Supporting partners

Suggested citation: Abstracts of the workshop on Late Cenozoic to Recent Geologic and Biotic

History of the Snake River, March 24–26, 2014, Pocatello, Idaho;

http://geology.isu.edu/Papers/SRPProceedings.pdf

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Map of Snake River region

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Contents Program……………………………...9 Abstracts…………………………….. 13

Map of Pocatello showing relevant locations.

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Workshop on Late Cenozoic to Recent Geologic and Biotic History of the Snake River

March 24-26, 2014, Pocatello, Idaho

Sunday, March 23 - 5 pm-8 pm. Registration and Ice Breaker at Red Lion. Cash Bar. Participants encouraged to mix. Posters will be in place.

Monday, March 24th – 8:00 am to 5:00 pm On-site Registration begins at 7:30 am

8:00 am Welcome and Opening Remarks – Robert Hershler and Paul K. Link

Theme Session 1 – Miocene to Recent Geologic and Biogeographic History of the Snake River and its Watershed; Convener: Paul K. Link

8:30-9:00 GEOLOGIC CONSTRAINTS ON PALEODRAINAGE OF THE SNAKE RIVER SYSTEM SINCE EOCENE TIME – Paul K. Link

9:00-9:30 BIOGEOGRAPHIC STUDIES RELATING TO SNAKE RIVER HISTORY: RECENT PROGRESS AND FUTURE CHALLENGES – Robert Hershler

Theme Session 2 – The Complex History of the Course of the Mainstem Snake River and the Associated Volcanic Constructs of the Snake River Plain; Con-vener: Scott S. Hughes

9:30-9:50 INTEGRATION, FRAGMENTATION. RE-ROUTING OF THE SNAKE RIVER OVER TIME – James W. Sears

9:50-10:30 DISCUSSION

10:30-10:50 BREAK

10:50-11:10

FLUVIAL SANDS AT 6000 FT IN THE KIMAMA DRILL CORE (PROJECT HOTSPOT, CENTRAL SNAKE RIVER PLAIN, ID): HEISE FIELD VOLCANOGENIC ZIRCONS AND THE LATE MIOCENE PALEO-WOOD RIVER – Katherine E. Potter

11:10-11:30 LATEST PLIOCENE TO RECENT BIG LOST RIVER DRAINAGE ISOLATION AND INTEGRATION, IDAHO – Mary K.V. Hodges

11:30-11:50 DIVERSION(S) OF THE LOWER BEAR RIVER IN GEM VALLEY, SOUTHEAST IDAHO, BY A TECTONO-VOLCANIC VALVE – Susanne U. Janecke and Robert Q. Oaks, Jr.

11:50-12:10 REGIONAL VOLCANICS AND THEIR INFLUENCE ON SNAKE RIVER HABITAT AND HISTORY – Scott S. Hughes

12:10-12:30 DISCUSSION 9

12:30-1:10 LUNCH

1:10-1:30 HYDROLOGIC OVERVIEW OF THE SNAKE RIVER PLAIN AQUIFERS – Roy Bartholomay

1:30-1:50 EXAMPLES OF FLUVIAL AND VOLCANIC INTERACTIONS FROM THE OWYHEE RIVER: IMPLICATIONS FOR LANDSCAPE EVOLUTION – Cooper C. Brossy et al.

1:50-2:10 PLIO-PLEISTOCENE INTERACTIONS INVOLVING BASALT FLOWS AND THE SOUTH FORK OF THE SNAKE RIVER BETWEEN SWAN VALLEY AND RIRIE, IDAHO – Dan K. Moore et al.

2:10-2:30 MIOCENE AND PLIOCENE PALEODIVERSITY AND STRATIGRAPHY OF THE WESTERN SNAKE RIVER PLAIN, THE OREGON-IDAHO GRABEN, AND NEARBY BASINS – Nathan E. Carpenter and Gerald R. Smith

2:30-2:50

UP TO FOUR DEEPWATER PLUVIAL LAKES IN CACHE VALLEY, UTAH-IDAHO, INCLUDING THE CUTLER DAM LAKE CYCLE AT ~1445 M AND POSSIBLE LITTLE VALLEY LAKE CYCLE AT ~1585 M: EVIDENCE FOR POSSIBLE EXCAVATION OF CUTLER NARROWS PRIOR TO 420 KA – Robert Q. Oaks et al.

2:50-3:20 DISCUSSION

3:20-3:40 BREAK

Theme Session 3, Part I – Biogeographic Histories of Regional Aquatic-Riparian Organisms and Their Relationship to the Evolution of the Snake River Drainage; Convener: Robert Hershler

3:40-4:10 FISH DNA AND FOSSILS SUGGEST PACIFIC NORTHWEST AND SNAKE RIVER PLAIN ORIGINS OF MOST WESTERN AMERICAN FRESHWATER FISH DIVERSITY – Gerald R. Smith and Thomas E. Dowling

4:10-4:30 EVOLUTIONARY AND BIOGEOGRAPHIC HISTORY OF ANADROMOUS SALMONIDS IN THE SNAKE RIVER BASIN – Robin S. Waples

4:30-4:50 BIOGEOGRAPHIC HISTORY OF PEBBLESNAILS (GENUS FLUMINICOLA) IN THE SNAKE RIVER REGION – Hsiu-Ping Liu and Robert Hershler

4:50-5:10 ON THE BIOGEOGRAPHIC AND PHYLOGEOGRAPHIC STRUCTURE OF THE SNAKE RIVER SHRUB STEPPE ECOREGION: EMERGING INSIGHTS FROM MAMMALS – Brett R. Riddle

5:10-5:40 DISCUSSION

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5:40-6:00 POSTERS

CONTROLS ON THE PLEISTOCENE EVOLUTION OF THE UPPER SNAKE RIVER BETWEEN ST ANTHONY AND BLACKFOOT, IDAHO – William M. Phillips

SNAKE RIVER ERPOBDELLID LEECHES (HIRUDINIDA): MULTIPLE DISTRIBUTION PATTERNS IN WESTERN UNITED STATES AND THEIR PALEOGEOGRAPHY – Peter Hovingh

There may be additional ISU student posters.

--------------------------------------------- Vans to Idaho Museum of Natural History will leave Red Lion at 6:15 pm and

6:30 pm. 7:00 pm – Conference Dinner at Idaho Museum of Natural History. Tour Heli-

coprion Exhibit with Jesse Pruit. Welcome by Museum Director Herb Maschner and Smithsonian representative Bob Hershler

Tuesday, March 25th – ALL DAY (meet at 8:00 am)

8:00 am ori-entation FT 8:30 am to 7:30 pm

FIELD TRIP, led by Paul Link, Susanne Janecke, Robert Q. Oaks, & Scott Hughes; to Portneuf Gap, Marsh Valley Gem Valley, -PacifiCorp Grace Fish Hatchery (Mark Stenberg), Oneida Narrows and Cache Valley (Bob Oaks and Susanne Janecke), -Massacre Rocks and Snake River. Participants ride in rental vans driven by ISU Student Drivers.

Vans will go directly to Portneuf Valley Brewing. They will also be available for those who want to return to hotel to get their own cars.

7:30 pm – Dinner at Portneuf Valley Brewing Company sponsored by Snake Riv-er Section, Society of Mining Engineers, Speaker Jim Sears, University of Montana, Cenozoic Drainage History of the Northern Rockies.

Wednesday, March 26th – 8:00 am to 2:00 pm Theme Session 3, Part II – Biogeographic Histories of Regional Aquatic-Riparian Organisms and Their Relationship to the Evolution of the Snake River Drainage; Convener: Brett R. Riddle

8:00-8:20 SALMONS, TROUT AND CHAR OF THE MIOCENE CHALK HILLS AND PLIOCENE GLENNS FERRY LAKES ON THE SNAKE RIVER PLAIN, IDAHO AND OREGON – Ralph F. Stearley and Gerald R. Smith

8:20-8:40 BUILDING THE FRESHWATER BIODIVERSITY ATLAS: DNA BARCODING AT RIVERSCAPE SCALES TO IDENTIFY EVOLUTIONARY LINEAGES OF FISHES IN THE COLUMBIA RIVER BASIN – Michael K.

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Young et al.

8:40-9:00 MOLECULAR STUDIES OF FISHES AS THEY RELATE TO INTERRELATIONSHIPS AMONG THE BONNEVILLE, LAHONTAN AND SNAKE RIVER BASINS – Dennis K. Shiozawa et al.

9:00-9:20 MICROBIOLOGY AND GEOCHEMISTRY OF IDAHO HOT SPRINGS – Timothy S. Magnuson et al.

9:20-9:40 SNAKE RIVER CONNECTIONS TO THE GREEN AND COLORADO, UPPER KLAMATH, AND SACRAMENTO DRAINAGES INDICATED BY MIO-PLIOCENE FISH DISTRIBUTIONS – Gerald Smith and Jon Spencer

9:40-10:30 DISCUSSION

10:30-10:40 BREAK

Theme Session 4 – Human Use of the River Basin and its Impact on Regional Biogeography; Convener: Robert W. Van Kirk

10:30-10:50 PRE-EUROAMERICAN USE OF THE NATURAL RESOURCES IN THE UPPER SNAKE RIVER BASIN – Nicholas A. Holmer and Richard N. Holmer

10:50-11:20 THE IMPORTANCE OF THE WATER TO THE SHOSHONE-BANNOCK PEOPLE – Elese Teton

11:20-11:50 ANTHROPOGENIC CHANGES TO THE BIOGEOGRAPHY OF THE MIDDLE SNAKE RIVER – James A. Chandler

11:50-12:10 EFFECTS OF IRRIGATION SEEPAGE AND GROUNDWATER FLOW ON FLUVIAL AND PALUSTRINE HABITATS IN THE UPPER SNAKE RIVER BASIN – Robert W. Van Kirk

12:10-12:30 ELEVATION-DEPENDENT RESPONSES OF STREAMFLOW TO CLIMATE WARMING IN MOUNTAIN WATERSHEDS – Christopher J. Tennant et al.

12:30-1:00 WORKSHOP SUMMARY – OPEN DISCUSSION OF PUBLICATION VENUE

1:10-2:00 GROUP LUNCH – Summary, Continued Discussion of Publication Venue

2:00 Adjourn

NOTE: Participants staying overnight may wish to meet informally (e.g., for dinner) fol-lowing the meeting.

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HYDROLOGIC OVERVIEW OF THE SNAKE RIVER PLAIN AQUIFERS. Roy C. Bar-tholomay, U.S. Geological Survey Idaho National Laboratory Project Office, 1955 N. Fremont, Idaho Falls, Id. 83415, email: rcbarth@usgs.gov.

Introduction: The Snake River and its intercon-

nected Snake River Plain aquifers are a lifeblood of Idaho’s economy. The principal aquifer systems are the eastern Snake River Plain (ESRP) aquifer and the western Snake River Plain (WSRP) aquifer (Fig.1).

The ESRP aquifer is formed by the headwaters of the Snake River near Island Park, Idaho along with mountain snowmelt. Water moves through the predom-inantly younger (quaternary) basaltic rocks and travels in a predominantly southwest direction. About 86 per-cent of the water discharges back to the Snake River through a series of springs and seepages along the en-tire river system, but mostly between Twin Falls and Hagerman, Idaho [1-2].

The WSRP aquifer system is composed of uncon-solidated and weakly consolidated Tertiary and Qua-ternary sedimentary rocks along with some basaltic rocks that outcrop most extensively near Mountain Home, Idaho [1]. Water moves from the northern and southern edges of the western plain to the Snake River [2].

Water flow: In the ESRP aquifer, most of the wa-ter moves horizontally through quaternary Snake River Group basalt interflow zones and vertically through joints and interfingering edges of interflow zones. In-filtration of surface water, heavy pumpage, geologic conditions, and seasonal fluxes of recharge and dis-charge locally affect the movement of groundwater [3]. The ESRP aquifer is recharged principally from infil-tration of applied irrigation water, infiltration of streamflow, groundwater inflow from adjoining moun-tain drainage basins, and infiltration of precipitation. Aquifer discharge is primarily from spring flow to the Snake River and from water pumped for irrigation [3].

A significant proportion of the groundwater moves through the upper 200–800 feet of basaltic rocks [4]. Hydraulic conductivity of basalt in the upper part of the aquifer ranges from 0.01 to 32,000 feet per day (ft/d) from wells at and near the Idaho National Labor-atory (INL) [5]. Hydraulic conductivity of older basalts in the ESRP are lower, ranging from about 0.002 to 0.03 ft/d [4].

Water flow in the WSRP aquifers is most produc-tive in the alluvial sand and gravel in the Boise River valley; transmissivity in the Boise River valley ranges from 5,000 to 230,000 ft2/d [2]. Natural recharge takes place along the margins of the plain from mountain snowmelt and from precipitation and irrigation on the plain. Primary discharge takes place near some of the

reaches of the Snake River and the Boise River where head increases with depth [2].

Along much of its length, the Snake River gains large quantities of groundwater. On the ESRP in 1980, the river gained about 1.9 million acre-feet of water between Blackfoot and Neeley, Idaho, and about 4.7 million acre-feet between Milner and King Hill, Idaho, mostly from spring flow along the north side of the river [2]. On the WSRP, river gains from groundwater are much smaller (about 0.7 million acre-feet) relative to the ESRP; gains are mostly from seepage of groundwater [2].

Estimated velocity and age of water: Horizontal flow velocities of about 2–25 ft/d have been calculated based on the movement of various constituents in dif-ferent areas of the ESRP aquifer at and near the INL [6,7]. These flow velocities equate to a travel time of about 120–1,500 years for water to travel from the Island Park area to springs that discharge at the termi-nus of the ESRP aquifer. Several wells at and near the INL yield mostly water older than 50 years (modern) [7]. Estimates of the age of geothermal waters that are recharging the ESRP aquifer range from about 17,700 to 20,300 years [8].

Vertically averaged horizontal hydraulic conductiv-ity of the upper 500 ft of alluvial aquifers in the WSRP ranges from about 4 to 40 ft/d, with higher values ex-pected in individual sand and gravel zones [2]. Esti-mated ages for older water for several samples collect-ed in deeper wells from the WSRP ranged from 2,700 to about 10,000 years [9].

References: [1] Whitehead, R.L. (1992) USGS Prof. Pap.,

1408-B, 1-32. [2] Lindholm, G.F. (1996) USGS Prof. Pap., 1408-A, 1-59. [3] Garabedian, S.P. (1992) USGS Prof. Pap.,1408-F 1-102. [4] Mann, L.J. (1986) USGS WRIR 86-4020, 21. [5] Anderson, S.R. et al. (1999) USGS WRIR 99-4033, 1-38. [6] Plummer, L.N. et al. (1998) Ground Water, 38, no. 2, 264-283. [7] Busen-berg, E et al. (2001) USGS WRIR01-4265, 1-144. [8] Wood, W.W. and Lowe, W.H. (1988) USGS Prof. Pap.,1408-D 43. [9] Hopkins, C.B. (2013) USGS SIR 2013-5115, 1-36.

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Biographical Sketch of presenter:

Roy Bartholomay has been involved with geohy-drologic studies at the Idaho National Laboratory (INL) since 1987. His research interests focus primari-ly on the water quality and geochemistry of the eastern Snake River Plain aquifer system at and near the INL. Roy serves as the Project Chief of the U.S. Geological Survey’s INL Project Office in Idaho Falls, Idaho.

Figure 1. Location of eastern and western Snake River Plain aquifer systems.

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EXAMPLES OF FLUVIAL AND VOLCANIC INTERACTIONS FROM THE OWYHEE RIVER: IMPLICATIONS FOR LANDSCAPE EVOLUTION. Cooper C. Brossy1, Lisa L. Ely2, P. Kyle House3, Elizabeth B. Safran4, Jim E. O’Connor5, Duane E. Champion6, Cassandra R. Fenton7, Ninad R. Bondre8, Caitlin A. Orem9, Gordon E. Grant10, Christopher D. Henry11, and Brent D. Turrin12, 1Fugro Consultants, Inc., 1777 Botelho Drive, Suite 262, Walnut Creek,California 94546 (c.brossy@fugro.com); 2Dept. of Geol. Scienc-es, Central Washington University, Ellensburg, Washington; 3USGS, Flagstaff, Arizona; 4Lewis and Clark College, Portland, Oregon; 5USGS, Portland, Oregon; 6USGS, Menlo Park, California; 7Scottish Universities Environmental Research Centre, East Kilbride, United Kingdom; 8The Royal Swedish Academy of Sciences, Stockholm, Sweden; 9Dept. of Geosciences, University of Arizona, Tucson, Arizona; 10U.S. Forest Service, Corvallis, Oregon; 11Nevada Bureau of Mines and Geology, Reno, Nevada; 12Dept. of Earth and Planetary Sciences, Rutgers University, Pisca-taway, New Jersey.

Introduction: Actively downcutting rivers are

commonly disrupted by discrete events from the sur-rounding landscape, such as lava flows or large mass movements. These disruptions are independent of slope, basin area, or channel discharge, and can domi-nate aspects of valley morphology and channel behav-ior for many kilometers. We document and assess the effects of one type of disruptive event, lava dams, on river valley morphology and incision rates at a variety of time scales, using examples from the Owyhee River in southeastern Oregon.

The impacts of lava dams on long-term landscape evolution depend largely on how long the dams persist and, less obviously, on the secondary effects of hillslope processes involving incised lava flows. The persistence of lava dams in part relates to the eruption setting and lava-water interactions [1,2.3]. Little atten-tion has been paid to important secondary effects of lava dam emplacement on hillslope morphology and process. These secondary effects potentially extend geomorphic influences of the lava incursions on river valley morphology in both time and space.

Geologic Setting: The Owyhee River drains ~30,000 km2 of Nevada, Idaho, and southeastern Ore-gon, flowing northward into the Snake River just up-stream of Hells Canyon. Within the study reach, the river flows through a series of steep-walled bedrock gorges up to 400 m deep, formed in massive Miocene rhyolite flows. The narrow gorges alternate with broad valleys 1–2 km wide in Neogene volcaniclastic and lacustrine sediment capped by basalt flows [4,5,6]. The capture of the paleo-Owyhee River watershed by the western Snake River Plain occurred ca. 7 Ma [7].

Methods: Individual lava flows and fluvial depos-its were mapped, dated, and correlated on the basis of stratigraphic and geographic position, soil develop-ment, mineralogy, geochronology, geochemistry, rem-anent paleomagnetism and analysis of LiDAR data. The specific approaches are described in several refer-ences [8, 9,10].

Results and Discussion: At least six sets of basal-tic lava flows entered and dammed the Owyhee River during two periods in the late Cenozoic ca. 2 Ma–780 ka and 250–70 ka, creating various temporal and spa-tial impacts on the river channel profile, rates of verti-cal incision, and valley geomorphology. The geometry of most Owyhee River lava dams is strongly asymmet-ric; the lava flows extend no more than 3 km upstream from their point of entry but as many as 30 km down-stream when lava flowed downvalley on a dry channel bed. The upstream faces of the best preserved dams form steep, blunt escarpments where active lava fronts were quenched by their impounded lakes. Deltas >10-m- thick of hyaloclastite and lava pillows with up-stream-dipping foresets reflect upvalley delta progra-dation into lakes impounded behind growing lava dams [8].

Lacustrine deposits containing identified tephra units of known ages indicate that the lava dams were stable for periods of >104 years, and several (Bogus Rim, Saddle Butte and West Crater) were sufficiently impermeable for lakes to form and subsequently fill with sediment to elevations approaching the dam crests. Each of the lacustrine sequences consist of sand, silt, and clay, and are capped by fluvial gravel [9]. Using present topography and a conservative lake-surface elevation of 1200 m, the Bogus Rim lava-dam lake would have inundated approximately 1170 km2 and extended more than 60 km upstream. The smaller lakes that formed behind the Saddle Butte dam (maxi-mum lake elevation 1044 m) and the West Crater lava dam (maximum lake elevation 1030 m) were close to 80 m deep at the dam crests and would have extended 30–40 km upstream.

Removal of the lava dams was episodic, but none show evidence of catastrophic failure. After a period of initial stability, the dams were ultimately incised by fluvial erosion. The most recent lava dam, formed by the West Crater lava flow ca. 70 ka, persisted for at least 25 ky before incision began, and the dam was largely removed within another 35 ky. Dated boulder

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bars and strath surfaces suggest the initiation of this episode of relatively rapid incision was synchronous with the increased transport of fluvial sand and gravel across the dam surface once the lake filled with sedi-ment. Thick accumulations of river gravels upstream of the Saddle Butte and Bogus Rim dams support the conclusion that the transport of coarse bed-load sedi-ment over the lava dams was an essential factor in dam removal. In reaches where the dams abutted Tertiary sediment, the river carved a new path around, rather than through, the dams. Repeated filling of the valley bottom and blockage of the river over 104 year time-scales may have significant biologic implications by alternately impounding and releasing sediment and by creating both calm and swiftwater habitats.

Most of the intracanyon lava flows do not appear to have exerted a lasting impact on the river valley profile at time scales >106 years, despite repeatedly filling the valley bottom. Net average long-term incision of the Owyhee River canyon, since the emplacement of the Bogus Rim lava flow (≤1.7 Ma), is 0.18 mm/yr; and episodic incision rates through individual lava flows were up to an order of magnitude greater. This long-term rate is comparable to incision rates of other lava-dammed rivers (e.g., the Boise River (0.05–0.10 mm/yr) [11] and Colorado River (0.05–0.175 mm/yr) [12,13] and is also consistent with the average 0.12 mm/yr lowering of Lake Idaho due to the incision of the Snake River through Hells Canyon over the last 4 my [14], which ultimately controls the Owyhee River base level.

However, the lava dams did produce direct and var-ied consequences on the river channel and regional geomorphology, some of which have persisted to today or generated secondary effects. The early, most volu-minous lower Bogus and Bogus Rim lava flows creat-ed a perturbation in the vertical profile of the river that lasted ~106 years, whereas the later, smaller lava flows caused profile perturbations on timeframes of 104 years. Lava volume and dam size almost certainly in-fluenced the duration of the lava dams in the river sys-tem. The time required to fill the reservoir with sedi-ment, changes in relative base level, climate, sediment supply to the reservoir and valley geometry probably contributed to the river’s response to individual lava dams as well.

One of the broadest regional geomorphic effects of the lava flows has been to redirect the river and subse-quent lava flows to different parts of the canyon. The most extensive lava flow, Bogus Rim, produced a prominent, upvalley-facing escarpment across the val-ley that reorganized tributary drainages and funneled subsequent lava flows to entrance points around its periphery. The association of gradually sloping, down-

valley lava flows and blunt, upvalley-facing escarp-ments is a common landscape element that has influ-enced the geomorphology of the Owyhee region during much of the late Cenozoic.

The influx of large volumes of lava into the valley shifted the river position laterally multiple times. This process created a distinct valley morphology character-ized by relatively flat, broad basalt shelves bounded by steep cliffs, which are now the loci of landslides and locally persistent sources of large diameter sediment to the river. Specifically, the steep canyon walls of Ter-tiary sediment capped by basalt lava are particularly prone to rotational slumps, earthflows and rock falls, some of which also dammed the river. The intracanyon lava flows thus indirectly continue to impact biologi-cally significant aspects of the landscape like channel morphology and local bedload 104–106 years beyond the lifetime of the lava dams.

References: [1] Hamblin, W. K. (1994) GSA Memoir 183. [2]

Howard, K.A. and Fenton, C.R. (2004) GSA Abs. with Programs, vol. 36, no. 4, p. 85. [3] Crow, R. et al. (2008) Geosphere, v. 4, 183-206. [4] Plumley, P. S. (1986) University of Idaho M.S. thesis. [5]Evans, J. G. (1991) USGS Map MF-2167. [6] Ferns, M. L., et al. (1993) DOGAMI Map GMS-78. [7] Beranek, L.P. et al. (2006) GSA Bulletin, v. 118, no. 9-10, 1027-1050. [8] Brossy, C.C. (2007) Central Washington University M.S. Thesis. [9] Orem, C.A. (2010) Central Washing-ton University M.S. Thesis. [10] Ely et al. (2012) v. 124; no. 11/12; 1667–1687. [11] Howard, K. A., et al. (1982) in Bonnichsen, B., and Breckenridge, R. M., eds., Cenozoic Geology of Idaho: Moscow, Idaho Bu-reau of Mines and Geology, 629-644. [12] Pederson, J., et al. (2002) Geology, v. 30, 739-742. [13] Karlstrom, K.E., et al. (2007) GSA Bulletin, v. 119, 1283-11312. [14] Wood, S.H. and Clemens, D.M., (2002) in Bonnichsen, B., et al. eds., Tectonic and Magmatic Evolution of the Snake river Plain Volcanic Province: Idaho Geol. Survey Bulletin, v. 30, 69-103.

Biographical Sketch of presenter:

Cooper Brossy is a Geologist with Fugro Consult-ants, Inc., in Walnut Creek, Ca. He previoulsy worked for the Bureau of Land Management at Craters of the Moon National Monument and Preserve supporting scientific research on Public Lands.His research inter-ests include Quaternary geology, geomorphology, and volcanology.

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MIOCENE AND PLIOCENE PALEODIVERSITY AND STRATIGRAPHY OF THE WESTERN SNAKE RIVER PLAIN, THE OREGON-IDAHO GRABEN, AND NEARBY BASINS. Nathan E. Carpenter1 and Gerald R. Smith2, 1Orma J. Smith Museum of Natural History, The College of Idaho, Caldwell, Idaho 83605, nate@paleopubs.com; 2Museum of Paleontology, University of Michigan, Ann Ar-bor, Michigan 48109.

Mio-Pliocene fossil fishes and mammals in water-

laid sediments interbedded with basalts and tephras in southeast Oregon and southwest Idaho facilitate de-tailed radiogenic, biostratigraphic, and paleoecological interpretations. Fossils chronicle substantial changes in diversity from mesic lowland swamp forests in the middle Miocene to more open, xeric habitats and larger lakes in the late Miocene and early Pliocene. The first evidence of diverse fishes in western United States began with colonization of the Sucker Creek swamps and associated Payette habitats from the northwest at a time of widespread plant and mammal localities near the Oregon-Idaho border during the Barstovian North American Land Mammal Age, about 15.9-12.5 Ma. Periodic caldera eruptions caused fluctuations in as-semblages of diverse forests, moderately diverse an-cient mammals, and sparse fishes and mollusks in the Sucker Creek-Payette area. These occurred in a frost-free climate, indicated by presence of giant tortoises and plants whose modern analogs live in the tropics today. Additional species of fishes and mammals col-onized small drainages in the Juntura, then Drewsey and associated formations in eastern Oregon, and the Poison Creek, then Chalk Hills formations in south-western Idaho, from 12.5 to 4.8 Ma. These trends oc-curred as plant and mammal assemblages were chang-ing in response to global cooling to seasonal climates, regional rain-shadow effects, and xeric habitats. Mammal, fish, mollusk, ostracod, and diatom diversity increased with rifting of the Western Snake River Plain and mixing of faunas with encroachment of the Chalk Hills Formation westward across the Oregon-Idaho Graben. The appearance of new forms from outside the region and the evolution of local species provide addi-tional insight into the timing of these events. Diversity peaked with influx of cool aquatic fauna from the north to the Western Snake River Plain about 4.5 Ma, while the Glenns Ferry Lake was deepening and cooling, and as the Snake River delta at Hagerman built out at the head of the lake. These events created remarkably rich mammal faunas and the richest known mollusk, fish, ostracod, and diatom assemblages in the late Cenozoic of the western United States. Aquatic and mammal diversity was largely extirpated with the cold climate and drainage of the Glenns Ferry Lake through Hells Canyon near the end of the Pliocene.

Biographical Sketch of presenter:

Nathan Carpenter is a consulting engineer, owner of PaleoPublications, and Curator of Paleontology at the Orma J. Smith Museum of Natural History, The College of Idaho, Caldwell. His research interests cen-ter around the later Neogene biota of the Pacific Northwest and the evolution of associations with a special emphasis on fossil beavers.

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ANTHROPOGENIC CHANGES TO THE BIOGEOGRAPHY OF THE MIDDLE SNAKE RIVER. James A. Chandler, Idaho Power Company, P.O. Box 70, Boise, ID 83707, jchan-dler@idahopower.com.

Human use associated with Europoean settlement

into the Northwest and the Snake River basin has sig-nificantly altered the biogeographic riverscape that was present upon their arrival. Over a period of approxi-mately 70 years, anadromous fish (Pacific salmon On-corhynchus spp. and Pacific lamprey Entosphenus tridentatus ) above the present-day Hells Canyon Dam on the Snake River were gradually extirpated from their historical distributions. This extirpation included nine large river basins and the mainstem Snake River. This extirpation was caused by the construction of fed-eral and private dams and by the degradation of fish habitats from various land uses.

The Eastern Snake Plain Aquifer (the Aquifer) dis-charge into the Snake River was a shaping influence on the evolution and distribution of fish in the Middle Snake River. The large discharge of 14.5 – 15.5 °C ground water moderates both summer and winter tem-peratures of the river, and this moderating influence diminishes downstream until larger tributary inflows begin to dominate the thermal regime of the river.

The core population of Snake River fall Chinook salmon was located in the Middle Snake River in the direct influence of the Aquifer discharge. It is estimat-ed that upwards of 500,000 adult fall Chinook salmon returned to the Snake River. Production potential of fall Chinook salmon declined as thermal conditions became colder overwinter and warmer over summer as distance from the Aquifer increased. The moderating water temperatures of the Aquifer allowed for early emergence and migration of juveniles. Construction of Swan Falls Dam displaced the core population to the downstream extent of the Aquifer influence and com-bined with commercial fishing, reduced the population to only a few thousand by the middle of the 20th centu-ry. Construction of the Hells Canyon Complex, espe-cially Brownlee Reservoir, although eliminated access to the remaining accessible portion of the Aquifer in-fluence, altered the thermal regime of the Snake River to favor production of fall Chinook salmon in the Snake River.

Also associated with Europoean settlement were introductions of many alien species of fish that have expanded their range into favorable habitats. It is es-timated that the native fish assemblage in the Middle Snake River was comprised of 6 families representing 16 species. Today, the native species assemblage up-stream of Hells Canyon Dam has been reduced to 5 families and 14 species. However, established alien

species in the Middle Snake River include an addition-al 7 families and 17 species. The percent of native spe-cies in the fish species assemblage is declining in the Middle Snake River as species richness is increasing. Some sections of the Middle Snake River are now al-most entirely comprised of alien species whereas; the sections within the immediate influence of the Aquifer discharge are still dominated by native species.

Biographical Sketch of presenter:

James Chandler is the Fisheries Program Supervi-sor for Idaho Power Company. Research focus of the Fisheries Program is on fish assemblages and their habitats in the Snake River, with special focus on white sturgeon, Snake River fall Chinook salmon, bull trout and resident fish communities.

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BIOGEOGRAPHIC STUDIES RELATING TO SNAKE RIVER HISTORY: RECENT PROGRESS AND FUTURE CHALLENGES. Robert Hershler, National Museum of Natural History, Smithsonian Institution, Washington D.C. 20013-7012, hershlerr@si.edu.

The late Cenozoic to Recent biogeographic history of the Snake River region long has been a compelling focus of inquiry yet remains understudied. The classic works of Dwight Taylor, Charles Repenning and oth-ers outlined compelling regional biogeographic scenar-ios that have become firmly entrenched in the literature (e.g., Fig. 1), yet there have been few explicit tests of these hypotheses. Although some of the regional ele-ments have been investigated in sufficient detail to enable comprehensive biogeographic treatments (par-ticularly fishes) other groups are still little studied and poorly known (e.g., most invertebrate taxa). Addition-ally, whereas the complexly layered history of Snake River basin is amenable to molecular phylogenetic studies utilizing calibrated clocks there have been rela-tively few such investigations compared to, for exam-ple, the large body of work relating to Pacific North-west glacial refugia and mesic forest disjunctions. Here I discuss a series of topics relating to Snake River history that may provide fruitful opportunities for bio-geographic study, and provide examples of such inves-tigations when available. These include (1) the east-ward migration of a topographic high along the Snake River plain resulting from passage of the North Ameri-can plate over the Yellowstone hot spot (or some other mechanism); (2) the history of Lake Idaho and the course of its outlet prior to the cutting of Hells Can-yon; (3) the history of the lower Snake River tributar-ies prior to their integration with the rest of the (mod-ern) watershed; (4) the regionally extensive late Ceno-zoic volcanism; (5) the history of the Snake River Plain aquifer and its contribution to the base flow of the Snake River; and (6) the Bonneville and other mega-floods.

There is a obvious need for additional research on the biogeographic history of the Snake River region, especially with respect to the invertebrate fauna. Workshops (such as this) may help generate additional interest and may also identify new, testable hypotheses that will further attract students and other investigators.

Figure 1. Hypothesized route of the ancestral

Snake River during the Pliocene (blue shaded) based on distributions of mollusks [1]; modern Snake River basin grey shaded.

References: [1] Taylor D.W. and Bright R.C. (1987) pages 239-

256 in Kopp R.S. et al. (eds.) Cenozoic Geology of Western Utah. Sites for Precious Metal and Hydro-carbon Accumulations, Utah. Geol. Assoc. Publ. 16. Biographical Sketch of presenter:

Robert Hershler is a Curator in the Department of Invertebrate Zoology at the Smithsonian Institution’s National Museum of Natural History. He studies the systematics, evolution, biogeography and conservation of North American freshwater gastropods.

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LATEST PLIOCENE TO RECENT BIG LOST RIVER DRAINAGE ISOLATION AND INTEGRATION, IDAHO. Mary K. V. Hodges, U.S. Geological Survey, Idaho Water Science Center, Idaho National Laboratory Project Office, 1955 N. Fremont, Idaho Falls, Id. 83415, email: mkhodges@usgs.gov.

Introduction: The Big Lost River, Little Lost Riv-

er, and Birch Creek were tributaries to the main Snake River in Idaho until the late Pliocene, about 2.5 Ma, when they were diverted to the north and east by the construction of the Axial Volcanic Zone and the Arco-Big Southern Butte volcanic rift zone [1, 2]. Since the late Pliocene, sediment from these streams has been trapped in a small, closed, subsiding basin, the Big Lost Trough, where deposition is controlled by cli-mate, subsidence, and basalt eruptions [2, 3]. Aggrada-tion of the river sediments and basalt flows in the sub-siding Big Lost Trough cause the Big Lost River to flow northeast, while the direction of regional ground-water flow is to the southwest. Sediment is trapped in the Big Lost Trough; the water enters the Snake River Plain aquifer through playas, locally termed “sinks,” and is eventually discharged into the main Snake River at Thousand Springs, about 200 km to the southwest [4]. Subsidence, sediment deposition and episodic bas-alt eruptions in and around the basin have resulted in a 0.2 to 1 km thick package of basalt and sediment, which forms the solid part of the eastern Snake River Plain aquifer in the Big Lost Trough [4].

During wet climate cycles, lakes formed in the ba-sin, resulting in fine-grained, clay-rich layers; during dry cycles, wind reworked surface sediments [2, 3]. Prior to 1.2 Ma, sediment from the northern streams (Crooked Creek, Medicine Lodge Creek, and Beaver Creek, Fig.1) also contributed sediment to the Big Lost Trough, but at 1.2 Ma, the eruption of Circular Butte diverted the northern streams away from the Big Lost Trough [2, 3, 5].

Basalt eruptions about 300,000 years ago may have isolated the Big Lost River drainage from the Little Lost River and Birch Creek drainages, preventing Up-per Snake River mountain whitefish from migrating into those streams.

Detrital zircons: Zircons are hard, resistant, natu-rally-occurring mineral grains, the ages of which can be determined by U/Pb dating.. In Idaho and most western states, the complex bedrock geology of each first-order stream will have a distinct age-population of detrital zircons (DZ). Sand, including detrital zircons, is carried by first order streams to larger second- and third- order streams where it may be deposited. DZs can be extracted from both surface and subsurface sand deposits, and analyzed for ages. The age-population signature of the zircons allows identification of the stream from which the zircons came [1, 8, 9, 17 The Big Lost River DZ signature includes abundant Chal-lis-age zircons (42 to 52 Ma), Neoproterozoic (650 to

740 Ma,) zircons from an orthogneiss exposed in the Pioneer Mountains metamorphic core complex, and mixed Paleozoic and Proterozoic age (1,400 to 2,000 Ma) zircons [1, 2, 9]. In addition to its unique DZ age signature, Big Lost River sediment is generally more coarse-grained than that of the Little Lost River and Birch Creek. The Little Lost River DZ signature in-cludes abundant 1,650- to 1,750-Ma zircons recycled through the Mesoproterozoic Lemhi Group, and 42- to 52-Ma Challis magmatic grains. The Birch Creek and northern stream DZ age-population signature includes: (1) a large group of 1,000 to 2,000 Ma zircons and a small group of 2,500 to 3,000 Ma zircons likely recy-cled from Mesoproterozoic to Ordovician strata ex-posed in the Beaverhead Mountains and Lemhi Range; (2) ca. 500 Ma zircons derived from the Ordovician Beaverhead pluton exposed in the Beaverhead Moun-tains; (3) 70 to 100 Ma zircons derived from the Creta-ceous Idaho batholith; and (4) several groups of <20 Ma zircons derived from Snake River Plain volcanic rocks [7].

Radiometric and other dating: Radiometric age dates can be obtained from geologically young olivine tholeiite basalts [5, 6, 10, 11, 14]. Methods used in-clude K-Ar, 40Ar/39Ar, and 14C radiometric dating. Age dates have been obtained on basalt flow groups ex-posed at the surface and from drill cores at the Idaho National Laboratory (INL) [5, 14]. Ages of surface INL basalt flow groups range from about 13 ka to 1.2 Ma [5, 10, 14,]; the oldest age obtained from subsur-face basalts is 1.44 Ma [16]. Older basalt flow groups exist in the subsurface, but obtaining reliable ages on older rocks below the water table has not yet been ac-complished.

Paleomagnetic studies: Paleomagnetic inclina-tions and polarities derived from surface and subsur-face basalt flow groups are a reliable means of distin-guishing one basalt flow group from another. These data can be used to trace basalt flow groups from sur-face vents to the subsurface, and to correlate basalt flow groups in the subsurface [1, 6, 12, 13].

The Big Lost River system drainage changes: In addition to defining the stratigraphic layering of basalt flow groups, radiometric age and paleomagnetic data can also be used to trace former location of the main course of the Big Lost River system. The 542 ± 5 ka, reversed polarity Big Lost basalt flow group is thickest in the subsurface at the Radioactive Waste Manage-ment Complex (RWMC) in the southern part of the INL. This flow is found in drill core from wells 16.6 km NNE (NPR Test-WO2) and 18.3 km to the ENE

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(ARA COR 005) of the RWMC. At 542 ± 5 ka, when the Big Lost basalt flow group erupted, the course of the Big Lost River was 8 to 15 km east of its current location. Flows from the Axial Volcanic Zone such as Mid Butte (234 ± 11 ka) [14], and Vent 5252 (350 ± 40 ka, [18] have pushed the Big Lost River westward since the eruption of the Big Lost basalt flow group.

The environmental effect of drainage disruption is neatly illustrated by examining mountain whitefish populations. A genetically distinct population of moun-tain whitefish (Prosopium williamsoni) exists in the Big Lost River drainage, but not in the Little Lost or Birch Creek basins [20]. The Big Lost variety is most closely related to the upper Snake River (above Sho-shone Falls) mountain whitefish, but differs genetically in ways that indicate that it has been isolated from the main upper Snake River population for about 165,000 to 330,000 years [20]. Upper Snake mountain white-fish migrated to the Big Lost valley through ancient Lake Terreton, but did not find their way into the Little Lost or Birch Creek drainages, most likely because the 292 ± 58 ka Crater Butte basalt flow [21], which co-vers the surface of the Big Lost Trough west of the modern Big Lost River [5], cut off the Little Lost River and Birch Creek from the Big Lost River and from Lake Terreton. As the climate became warmer and drier, Pleistocene Lake Terreton dried up, isolating the Big Lost mountain whitefish.

References:

[1] Hodges, M.K.V. et al (2009) J. Volc. and Geo-therm. Res 188, 237-249. [2] Geslin, J.K. et al. (2002) GSA Spec. Pap. 353, 11-26. [3] Bestland, E.A. et al. (2002) GSA Spec. Pap. 353, 27-44. [4] Ackerman et al.

(2006) SIR 2006-5122, 68p. [5] Kuntz, M.A. et al. (1994) USGS Miscellaneous Investigations Series Map I-2330. [6] Champion, D.E. and Lanphere, M.A. (1997) USGS Open-File Report 97-700. [7] Durk, K.A. et al. (2007) GSA Abstracts 36/6, 613. [8] Beranek, L.P. et al. (2006) GSA Bull. 118, 1027-1050. [9] Ges-lin, J.K. et al. (1999) Geol. 27, 295-298. [10] Kuntz, M.A. et al. (2007) USGS Scientific Investigations Map 2969. [11] Kuntz, M. A. et al. (1980) USGS Open-File Report 80-388. [12] Champion, D. E et al. (2011) USGS SIR 2011-5049I. [13] Champion, D.E. et al. (2013) USGS Scientific Investigations Report 2013-5012. [14] Hodges, M.K.V. et al. (2012) AGU Fall Meeting. Abstract number V13B-2831. [15] Carroll, A. and Bohacs, K. (1999) Geology, v. 27, p. 99-102. [16] Lanphere, M.A. et al. U.S. Geological Survey Open-File Report 94-686, 48 p. [17] Link P.K. et al. (2002) Id. Geol. Surv. Bull. 30, 105-119. [18] Champion, D.E. et al. (1988) J. Geophys. Res., v.93 p. 11667-11680. [19] Link, P.K. et al. (2005) Sed. Geol. 182, 101-142. [20] Campbell, M.R. and C.C. Kozfkay (2006) Native Species Investigations, Project F-73-R-25. Report Number 06-18. Idaho Department of Fish and Game, Boise, ID. [21] Kuntz, M.A. et al. (2003) ID Geol Surv Map GM-35, Moscow, ID.

Biographical sketch of presenter: Mary Hodges has worked for the U.S. Geological

Survey Idaho National Laboratory Project Office of the Idaho Water Science Center, since 2004. She is inves-tigating the subsurface geologic framework of the Snake River Plain aquifer beneath the Idaho National Laboratory.

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PRE-EUROAMERICAN USE OF THE NATURAL RESOURCES IN THE UPPER SNAKE RIVER BASIN. Nicholas A. Holmer1 and Richard N. Holmer2, 1Idaho Virtualization Laboratory, Stop 8096, 921 So. 8th Ave Museum Building, Pocatello, Id. 83209-8096, holmnic4@isu.edu, 2Richard N. Holmer, Department of Anthropology, Stop 8005, Idaho State University, Pocatello, Idaho 83204, holmrich@isu.edu

Introduction: Archaeological evidence docu-ments that the Snake River Plain and surrounding mountains have been occupied by Native Americans for the last 13,000 years. For their entire pre-reservation history they were highly-mobile and flexi-ble hunter-gatherers allowing them to adapt to signifi-cant environmental changes, including the end of the Pleistocene. This shift from the Pleistocene to the Hol-ocene is marked by a consistent warming period that lasted roughly five thousand years during which the annual average temperature changed by about five degrees (Fahrenheit) (Figure 1). During these envi-ronmental shifts we see equivalent shifts in the flora and fauna located on and around the Snake River Ba-sin; not only in the location of particular species, but in the presence and absence of them as well. These shifts in the availability of natural resources throughout a season and from season to season helped determine a particular lifeway for these native inhabitants.

The fundamentals of this lifeway during the 19th Century were recorded by the renowned ethnographer Julian Steward in 1936 after interviewing six elderly men and women most of whom were in their teens when the Fort Hall Reservation was created in 1867. 1,2 His primary interest was the human ecology of their traditional lifeway – i.e., what natural resources where critical for their survival, where were these resources obtained, and what technology was employed to ac-quire and process them. What becomes obvious while studying Steward’s publications is that there was a significant difference in lifeway between those who lived up-river from Shoshone Falls (the Northern Sho-

shone and Bannock) and those who lived down-river (the Western Shoshone). The fundamental difference was the availability of anadromous fish below the falls which significantly affected both residence and mobili-ty patterns – a fact that is obvious in the archaeological record since the end of the Pleistocene. In addition, the plains and mountains above the falls supported higher densities of certain highly-desirable animals, particu-larly the bison. This resulted in a diet more geared to-wards hunting large and small game while supplement-ing their diet with roots and bulbs - i.e. bitterroot and camas. To adequately summarize the Native American use of natural resources along the Snake River would require two papers - therefore, we have decided to fo-cus on the native lifeway above the falls. Summary of the traditional lifeway in the Upper Snake River Basin. Food and other natural resources were pursued and obtained through seasonal mobility. The most consistent element of this mobility was the general location of the winter base camp. In the Upper Snake River Basin most base camps were located around the Fort Hall Bottoms in places that provided some protection from the winter winds. The surround-ing area provided a constant source of fresh spring water which typically remained unfrozen year round. The Bottoms yielded fish and waterfowl throughout the winter augmented by an occasional ungulate. Ex-cavations at the winter camp at Wahmuza yielded de-tailed subsistence information.3 In spring when stored food supplies were exhausted families would range out in search of resource patches. Success depended on accumulated knowledge from ancestral generations and word-of-mouth from those camping nearby. By summer families were usually in high country camping near meadows and fishing streams. Although a wide range of plants and animals were harvested, the main objective was to dig roots, tubers and bulbs both for immediate consumption and for storage for the long winter months. Camas, yampah, bitterroot, and other plants were the major source of protein and calories; plus they can be dried for extended storage. Although just outside of the Snake River Drainage, the excava-tions at Dagger Falls document (via the chemical sourcing of obsidian) the movements of families from the Snake River Plain into the upper reaches of the Salmon River drainage.4

When the leaves on trees began to change color at the end of summer families would begin their long trek back toward the Fort Hall Bottoms carrying as much preserved food as possible (dried roots and fish). They

Figure 1. Average annual temperature change for the Upper Snake River Basin for the last 15k years.

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gathered in large groups on the banks of the Snake River in the Fort Hall Bottoms to socialize, celebrate, and share information. The most important activity was to plan for the fall hunt – either bison on the plains, pronghorn in the tributary valleys, or bighorn sheep in the adjacent mountains. Fall hunting camps are documented archaeologically at the Birch Creek Shelters,5 and at Weston Canyon Rockshelter 6 among other sites.

The above cycle of movement in search of re-sources is often call the “annual round” and each phase within the round has been documented by several ar-

chaeological excavations. In addition, the broad pat-terns in the round have been confirmed and clarified through x-ray florescence analyses of the obsidian tools carried, used and either lost or discarded during the round. The Upper Snake River Basin is unique in this aspect because it is surrounded by a dozen chemi-cally distinct sources and almost all stone tools were made from this valuable material (Figure 2).6

The most important aspect to keep in mind is that the round for each family one year may be very differ-ent the next year and the next. Flexibility was the key – taking advantage of any new information and avoiding the areas overharvested the year(s) before.

References: [1] Steward J (1938) Smithsonian Inst.

BAE Bul. 120. [2] Steward J (1943) Culture Element Distributions: XXIII Northern and Gosiute Shoshoni. Berkeley: Univ. of Cal. Anthro. Records 8(3):263-392. [3] Holmer R (1986) Shoshone-Bannock Culture His-tory, SCAR Lab Rep. of Invest. 86-16, ISU [4] Holmer R (1989) Dagger Falls, Idaho Archaeologist 12(1)3-13. [5] Swanson E (1972) Birch Creek, Idaho State Uni-versity Press. [6] Plager S (2001) Patterns in the Dis-tribution of Volcanic Glass across Southern Idaho. Master’s Thesis, ISU.

Biographical Sketch of presenter:

Nicholas A. Holmer, M.Sc., is currently employed as a photographer, 3D scanning technician and com-parative vertebrate osteologist at the Idaho Virtualiza-tion Laboratory, at the Idaho Museum of Natural His-tory. He also is an Instructor in the Department of An-thropology where he teaches Forensic Anthropology. His research interests include: human and comparative vertebrate osteology, activity related skeletal change, paleopathology, human ecology, paleo-diet reconstruc-tion and food web analysis.

Figure 2. Locations of all known artifact-quality obsidian sources in the Snake River Basin.

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*SNAKE RIVER ERPOBDELLID LEECHES (HIRUDINIDA): MULTIPLE DISTRIBUTION PATTERNS IN WESTERN UNITED STATES AND THEIR PALEOGEOGRAPHY. Peter Hovingh, 721 Second Avenue, Salt Lake City, Utah 84103; phovingh@xmission.com.

Introduction: Leeches were collected from under stones and debris from Columbia River (325 sites) and Snake River (495 sites) Basins. Including literature and museum collections, 29 species were noted for this region. Herein the distributions of Erpobdellid leeches are presented with paleogeographic analysis. Erpob-dellid distributions are described in 3 scales: western North America, Columbia and Snake River Basins, and western United States. Two clades are noted: the Euro-pean clade (Nephelopsis in North America) and the North American clade (Nearcticobdella, Mooreobdel-la, and Motobdella) [1], suggesting origins by the Eo-cene.

Results: Erpobdellid distributions suggest Miocene origins with no morphological evolution. Nearcticob-della [Erpobdella] punctata is the most widespread, suggesting active mobility or great survivor skills, and is found in the Snake River tributaries and not in the river. Nephelopsis obscura is mostly limited to habi-tats of the Rocky Mountain orogeny and terrane plat-eaus east of Fraser River. It is found in the headwaters of the Snake River and Big Wood River.

Three other species display divergent patterns in western United States. Nephelopsis parva is most common in eastern Bonneville Basin and upper Snake River and the most common leech in the Snake and Boise Rivers. It is absent in the tributaries of the Mid-dle and Lower Snake River. Population isolates occur in the Pit, upper Sacramento, and Klamath Lost Rivers, suggesting paleogeographic connection between north-eastern California and the upper Snake River >6 My through northern Nevada [2,3].

Closely related to Nephelopsis parva [4], Neph-elopsis lahontana, occurs as 3 population isolates: eastern Nevada (Steptoe Basin), northeastern Califor-nia and northwestern Nevada, and Oregon. If these 3 populations (subspecies) had a common ancestor, this ancestor distribution should predate the rotation of the Klamath Range from the Blue Mountains and predate the Basin and Range extensions.

The final Erpobdellid Mooreobdella microstoma is found in the Mississippi Basin [5] from Yellowstone River (Montana) to Texas in the Great Plains. It was the 2nd most abundant species in Snake River dredg-ings below Shoshone Falls, and in Clearwater River where N. parva is absent. Its presence in Klamath-Lost

River and upper Sacramento River suggests the Mio-cene Fish Hook pattern of Taylor [6,7] for mollusks and fish. M. microstoma occurs south to Kern and Sa-linas River and to Los Angeles Basin. East of the Sier-ra Nevada, it occurs from Smoke Creek to Owens Riv-er and eastward to Little Colorado, Virgin, and Gila River. It is absent from the Pit River, Eagle Lake, and Madeline Plains.

References: [1] Oceguera-Figueroa, A. et al. (2010) Zool. Scripta, 40, 194-203. [2] Repenning, C.A. (1995) U.S.G.S. Bulletin 2105. [3] Wagner, H.M. et al. (1997) San Bernardino County Mus. Ass. Quart. 44, 13-21. [4] Hovingh, P. (2004) Hydrobiologia 517, 89-105. [5] Hovingh, P. et al. (2008) West. N. Amer. Nat-uralist 68, 210-224. [6] Taylor, D.W. (1966) Malacol. 4, 1-172. Taylor, D.W. (1985) Late Cenozoic History of the Pacific Northwest: interdiscipinary studies on the Clarkia Fossil Beds of northern Idaho, Pacific Di-vision, AAAS, San Francisco. Biographical Sketch of presenter: Peter Hovingh is retired from a career in biochemistry (complex carbohydrates) at the University of Utah. Natural history interest includes western North Ameri-ca waters in polar, temperate, and arid regions and in aquatic fauna as amphibians, mollusks, and leeches. The MX missile defense proposal stimulated him to survey the distribution of aquatic fauna in the Great Basin. Surveys have occurred between 1979 and 2013 in western North America north of Mexico.

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REGIONAL VOLCANICS AND THEIR INFLUENCE ON SNAKE RIVER HABITAT AND HISTORY. Scott S. Hughes, Department of Geosciences, Idaho State University, hughscot@isu.edu.

Introduction: The Snake River flows through ter-

rains dominated by Miocene – Recent volcanism relat-ed to the greater Snake River Plain – Yellowstone and Columbia River basalt systems. From headwaters at 9400 feet (2900 m) elevation near the continental di-vide to its confluence with the mighty Columbia River at 400 feet (120 m), the Snake is influenced by volcan-ic landforms reflecting myriad eruptive styles and as-sorted compositional varieties. Most types are found in the Snake River Plain (SRP), which contains basaltic lava fields, volcanic cones, shields, domes, and silicic ash-flow tuffs. Primary features such as lava tubes, layered lavas, tumuli, collapse pits, and related features such as hoodoos, cliffs, ledges, waterfalls, lakes and marshes produce a variety of habitats.

Magmatism Post Yellowstone Hotspot: Volcan-ics and interbedded sediments cover the eastern SRP, a 250 x 65 mile (400 x 100 km) topographic and struc-tural depression lying southwest of Yellowstone within the surrounding Basin and Range province [1-3]. Monogenetic basaltic shields and lava fields dominate the upper volcanic sequence, which overlies diachro-nous Miocene-Pliocene rhyolite tuffs and lavas associ-ated with the time-transgressive Yellowstone hotspot [4,5]. Many shields geochemically reveal evidence that separate magma batches intruded into mid-crustal realms where they underwent extensive fractionation and magma-mixing [6-8]. Ubiquitous shields and lava fields coalesced regionally to produce basaltic lava plains [9], representing a style of volcanism analogous to similar features on other planetary bodies. Less ubiquitous chemically evolved compositions in the sequence include eruptions at Craters of the Moon, Cedar Butte and several rhyolite domes [2,6,10,11].

Several prominant lava fields, including Hells Half Acre, Wapi, Cerro Grande, Shoshone, North and South Robbers, and basaltic members of Craters of the Moon fields exhibit fresh surfaces no older than ~15ka. The youngest eruptions at ~2ka thus imply active magma-tism in the eastern SRP-Yellowstone system. Although research over the past few decades confirms the asso-ciation of Yellowstone volcanism with a mantle plume [12,13], the plume contribution to SRP magma genera-tion may be subordinate to the regional effects of Basin and Range lithospheric extension [14].

Volcanics in the Greater Snake River Basin: The SRP is a significant depository for volcanics, yet late Cenozoic volcanics are also exposed in various tribu-tary regions. At the northeast end of the SRP, Henry’s Fork and Teton rivers wend through latest Pliocene to

Pleistocene (<2.1 Ma) tuffs erupted from Yellowstone calderas. Immediately to the southeast, basaltic volcan-ics of the Pleistocene Blackfoot, Gem Valley and Wil-low Creek lava fields, with the attendant scoria (cin-der) cones, silicic domes and lava flow sequences par-tially fill basins that contain the Blackfoot, Bear and Portneuf rivers. Along the northern and southern mar-gins of the SRP the Big Lost, Big Wood, Boise, and Portneuf rivers debouch through remnant rhyolitic tuffs of the Miocene – Pliocene Twin Falls, Picabo and Heise volcanic centers. Southwest of the SRP, thick sequences of Miocene welded tuffs of the Twin Falls and Bruneau-Jarbidge volcanic fields are dissected into numerous steep-walled canyons by Rock Creek, Salm-on Falls Creek, and the Bruneau and Jarbidge rivers. Capped by Pleistocene basaltic lavas, they have eroded into high cliffs of tuff and basalt along the Snake River Canyon from Shoshone Falls near Twin Falls to the Bruneau River. Further downstream, through Pliocene – Pleistocene basalts and sediments, and Miocene tuffs of the western Snake River Plain, impressive sequenc-es of Columbia River basalt and older Tertiary volcan-ics are evident in the Imnaha, Salmon and Grande Ronde rivers flowing into the Snake River.

Volcanic Landforms and Habitat: Complex pro-cesses produced numerous ecological habitats along the Snake River. The following list summarizes key landforms, studied by volcanologists and biologists separately, that would be worthy of future interdisci-plinary studies:

Mafic Low Shields & Lava Fields. Monogenetic shields likely erupt over a span of months to a few decades, producing overlapping tube-fed lava flows and topographically controlled lava fields (Fig. 1).

Aeolian, lacustrine and fluvial sediment mark temporal hiatuses between eruptions, which control the regional pattern of the Snake River by creating elevated topog-raphy and confining sediment basins.

Collapse Pits and Lava Tubes. Extensive lava tube networks and pit-craters at vents collapse leaving cliffs, ledges, and alcoves. Protected from wind, often canopied by overhanging rock, they are perfect for owls and other birds of prey. Open fractures and con-

Fig. 1. Wapi lava field and Pillar Butte comprise a low shield dated at ~2ka [2].

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nected pockets may lead far underground into snake dens many meters back from the cliff face.

Tumuli and Lava Flow Surfaces. Pahoehoe lavas have up to 15m surface relief, with tension gashes, due to tumuli and irregular inflation of lava toes and lobes (Fig. 2). Open crevasses collect soil enabling ferns and shrubs to proliferate.

Eruptive Fissures and Extension Cracks. Open

eruptive fissures and related tension cracks, are either large enough to provide cliffs and shelter in a manner similar to collapse pits or, if smaller, provide shelter for ferns and shrubs.

Lava and Tuff Cliffs. Cliffs formed in lava flow se-quences are similar to collapse pits and tubes although many occur at great distances from their vent, produc-ing massive, vertically jointed walls. Erosional cliffs in unwelded tuff or crudely layered pyroclastic fallout are friable and less competent.

Cinder and Spatter Cones. Basaltic scoria (ash, la-pilli, bombs and blocks) cinder cones reflect more ex-plosive processes than do spatter eruptions normally associated with SRP eruptions. Cinder cones are found only in regions of more evolved, slightly more viscous basaltic compositions such as those at Craters of the Moon. In some cases, basalt scoria is produced during rapid interation of erupting magma with near-surface water near the Snake River.

Tuff Rings Tuff Cones. Hydrovolcanic tuff rings

(maars) and tuff cones depend on magma-water explo-sive interaction for ash production. Examples from the eastern SRP include Split Butte, Menan Buttes (Fig. 4), and Massacre Rocks, which is an eroded tuff cone SW of American Falls. Palagonitized basaltic glass, ejected blocks, and crudely layered sequences represent explo-sive pulses of sticky tephra that welded into units with variable resistance to erosion. Tuff rings and cones farther downstream demonstrate the influence of the Snake River on eruptions. Roughly half of 83 volca-noes along the Snake River in the western SRP, repre-sent hydrovolcanism – tuff cones or rings [15]. By

contrast, only six of 128 volcanoes in the Bruneau-Jarbidge and Twin Falls regions are clearly hydro-volcanic, four in close proximity to a river.

Columbia River Basalts. Downstream of the SRP, high cliffs and colluvial slopes create a spectacular landscape as the Snake River flows steeply through the 17 – 5.5Ma Columbia River Basalt Group. Strikingly different from the SRP, the topography is closely asso-ciated to Pleistocene glaciation, particularly in the ad-jacent Wallowa Mountains.

Although decades of scientific study has led to an overall understanding of volcanism, the complete pic-ture will rely on a better understanding of the relations between volcanic landforms and various habitats that also must be considered in future studies.

References: [1] Leeman W.P. (1982a) Id. Bur. Mines & Geol. Bull. 26, 155-177. [2] Kuntz M.A. et al. (1992) Geol. Soc. Am. Mem. 179, 227-267. [3] Hughes S.S. et al. (1999) pages 143-168 in Hughes S.S. and Thackray G.D., eds., Guidebook to the Geolo-gy of Eastern Idaho, Id. Mus. Nat. Hist. [4] Armstrong R.L. et al. (1975) Am. J. Sci. 275, 225-251. [5] Pierce K.L. and Morgan L.A. (1992) Geol. Soc. Am. Mem. 179, 1-53. [6] Hughes S.S. et al. (2002) pages 151-173 in Link, P.K. and Mink L.L., eds., Geol. Soc. Am. Spec. Pap. 353. [7] Shervais J.W. et al., (2006) Geolo-gy, 34, 365-368. [8] Miller M.L. and Hughes S.S. (2009) J. Volc. Geoth. Res. 188, 153-161. [9] Greeley R. (1982) J. Geophys. Res. 87, 2705-2712. [10] Kuntz M.A. et al. (1986) Geol. Soc. Am. Bull. 97, 579-594. [11] McCurry M. et al. (2008) Bull. Vol. 70, 361-383. [12] Pierce K.L. and Morgan L.A. (2009) J. Volc. Ge-oth. Res. 188, 1-25. [13] Smith R.B. et al. (2009) J. Volc. Geoth. Res. 188, 26-56. [14] Leeman W.P. et al. (2009) J. Volc. Geoth. Res. 188, 57-67. [15] Bonnich-sen Bill and Godchaux M.M. (2002) Id. Geol. Surv. Bull. 30, 233-312.

Biographical Sketch of presenter: Scott Hughes has studied the geochemical evolution of basaltic magma and associated tectonic-volcanic systems over the last 35 years. His research since 2000 has included the physical volcanology and petrologic evolution of ba-saltic systems on Earth as analogs to other planets.

Fig. 2. Inflated lava flow margin in the Cerro Grande lava field.

Fig. 3. Spatter ramparts along Kings Bowl eruptive fissure.

Fig. 4. North Menan Butte tuff cone at confluence of the Snake and Henry’s Fork rivers.

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DIVERSION(S) OF THE LOWER BEAR RIVER IN GEM VALLEY, SOUTHEAST IDAHO, BY A TECTONO-VOLCANIC VALVE. Susanne U. Janecke and Robert Q. Oaks, Jr., De-partment of Geology 4505 Old Main Hill, Utah State University, Logan, Utah 84322-4505.

The lower Bear River of Utah and Idaho was once

a tributary of the Snake River that flowed along the NE edge of the Great Basin. Similar biological communi-ties in the upper Bear and Snake Rivers attest to this phase of its history. Basalt flows in Gem Valley, Ida-ho, diverted the lower Bear River southward into the Bonneville Basin during the late Pleistocene [1] [2] [3]. However, there is no consensus about the timing, location, and mechanism of this major diversion [4][5]. Landscape and image analysis reveals previously un-mapped active normal faults and characterizes Late Pleistocene to Holocene(?) volcanic fields. Our dis-covery of a meandering basalt flow SE of Bancroft, Idaho, suggests that fault-guided basaltic volcanism created a “switching valve” for the Bear River where it enters Gem Valley from the east. This tectono-volcanic valve causes northward flow of the Bear River to switch abruptly to southward flow or back again, as basalt flows in the east-central part of Gem Valley flows into the river bed. We envision a mechanism in which flow of the Bear River and lava competed to occupy the same lowest terrain within graben of the East Gem Valley fault zone. Whenever a new basalt flow blocked the river’s northern route, the Bear River was diverted south to fill Lake Thatcher in southern Gem Valley. Eventually lava dams grew high enough for Lake Thatcher to overflow south into the Great Basin. Incision of Oneida Narrows was the final step in the transfer of the Bear River.

Introduction: Gem Valley is an unusual Basin and Range graben in SE Idaho. The slip rate on the basin- bounding normal faults is low, consistent with its posi-tion in the inner, inactive zone of the tectonic parabola centered on the Yellowstone hot spot. Quaternary vol-canism built basaltic shield volcanoes and cinder cones in and near the eastern margin of the basin, near the midpoint of its active basin-bounding fault. Features unusual for an active graben include: a drainage divide near the middle of the basin, a grossly radial, westward slope of the basin floor, away from the main normal fault, and the position of the lowest points of the valley floor in the distal north and south ends of Gem Valley. These features are the product of volcanic processes that outpaced tectonic subsidence.

The Bear River in Utah, Idaho, and Wyoming makes a hairpin turn in SE Idaho. The upper Bear Riv-er flows NNW ~300 km from the northwest Uinta Mountains through Bear Lake Valley to Soda Springs, Idaho. Entering central Gem Valley, the river turns

sharply south, and flows through Oneida Narrows into Cache Valley, through the Cutler Narrows into Lower Bear River Valley, and into the Great Salt Lake. This lower reach of the Bear River, downstream of Soda Springs was diverted from a paleo Bear River that once flowed into the Snake River and was part of the greater Columbia drainage basin [1-4]. Commonalities of fish species in the upper Bear River and the Snake River drainages are a result of this early history.

Diversion of the lower Bear River was initiated by basalt flows in Gem Valley that diverted the river southward and at times formed a freshwater lake [1-8]. However, older and incomplete geologic mapping in Gem Valley does not identify specific lava dams, vents, or other details. The location, age, geometry, and frequency of diversion are poorly constrained.

Our discovery of a meandering Late Pleistocene basalt flow southeast of Bancroft, Idaho, identifies the specific site of one diversion and provides the means to date diversion events. We examine how the volcanic landforms and active faulting in Gem Valley interacted [conspired] to divert the Bear River into Lake Thatcher and the Great Basin.

Methods: We mapped the Quaternary faults, vol-canic centers, and their outflow products in the Gem Valley area. High resolution imagery in Google Earth and digital-elevation models produced many new in-sights into the geology of Gem Valley. Drillers’ logs of water wells provided subsurface control.

Volcanism in the Gem-Blackfoot Volcanic field: The major basaltic and minor rhyolitic volcanism of

Figure 1. Tectono-volcanic valve model of the diversion of the Bear River in the central part of Gem Valley. Digital elevation model show highlands in white and deeper surfaces in blue. One basalt flow in the northwest corner solidified in the meandering shape of the paleo-Bear River that it occupied.

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the Gem-Blackfoot volcanic field erupted from ~100 cinder cones and fissure eruptions within a 70 km long NNE-trending belt. A NNE-trending magnetic high coincides with the volcanic belt. Lava flows that erupt-ed from these vents cover a large area adjacent to the alignment of vents. Groups of volcanic vents at Niter, Alexander, and on the east flank of the Soda Springs Hills, give way northward to more evenly distributed cinder cones, fissure vents, and domes.

Three groups of volcanics vents in and near Gem Valley interacted with a wide zone of active faults and fissures along the east margin of Gem Valley. Volcanic flows erupted from fault-controlled fissures and built three shield volcanoes in Gem Valley near active nor-mal faults. Together they produced a SW-sloping ba-jada of loess-covered basalt flows in central Gem Val-ley. As these grew, they diverted the paleo and modern Bear River around the distal edges of the three shield volcanoes. When the shield volcanoes blocked the cen-ter of Gem Valley they pushed Late Pleistocene Lake Thatcher to the north and south, and eventually trig-gered the spillover of the lake into the Bonneville Ba-sin, in the south [2, 3, 6].

Two of the vent clusters in Gem Valley were active long enough to produce sizable shield volcanoes. The northern Tenmile shield volcano is highly asymmetric because its flows all erupted from ~200 m higher ele-vations to the east within the Blackfoot volcanic field. The lava flows emanating from the Blackfoot field, flowed southwest through Tenmile Pass between the Chesterfield Range and Soda Springs Hills and then spread, fanlike, across the floor of northernmost Gem Valley. We propose that the paleo-Bear River flowed in the low area between this northern shield volcano and the Alexander shield volcano to the south based on the presence of a ~4 km long meandering former reach of the Bear River choked by lava SE of Bancroft. Lava dams appear to have formed small ponds at times be-hind low lava dams.

The ~15 x ~15 km Alexander shield volcano erupt-ed from the NNW-striking Alexander fissure to form the largest volcano in Gem Valley. It filled Gem Val-ley progressively from east to west, and most of the shield volcano is downslope and west of its vent clus-ters near the eastern margin of Gem Valley. The mod-ern Bear River flows south along the NE edge of this shield volcano in a narrow graben of the East Gem fault zone, then turns southwest and flows along the SE edge of the Alexander shield volcano.

The third group of volcanic centers lie ~4 km N30°W of Niter, Idaho. Twelve closely spaced maars and tephra cones lie on a plateau very close to the highest altitude of Lake Thatcher and an the inset ter-race to the west. Most of the volcanoes form a pro-

nounced E-W trending alignment at 42.535° N. The effusive volcanic activity around this group of vents was too limited to build a shield volcano. The distinc-tive explosive morphology of the tuff cones and maars is unique in the area, and strongly suggests eruption during a high-water phase of Lake Thatcher. Drillers’ logs of water wells show thicknesses between 25 to 40 m of the basalt flows nearby.

Implications: The zone of active faulting and vol-canism along the course of the Bear River near Alex-ander, Idaho, is probably the most important area in Gem Valley for the biogeography of the Bear River. The Alexander shield blocked the Bear River’s access to Gem Valley. The present river flows along the edges of the extending Alexander shield. Graben in the East Gem Valley fault zone captured the Bear River as it entered from the east near Soda Springs. Depending on the most recent normal faulting and volcanic activity, the Bear River could flow either north or south along the range-front fault zone in one of its graben toward lower terrain at the north and south edges of the Alex-ander volcano. When the river flowed south, it ponded to form Lake Thatcher. When the Bear River was di-verted back to a northern course, along the NE and then NW edge of the Alexander shield volcano, it flowed more directly to the Snake River. Our observa-tions suggest that the interplay of volcanism and nor-mal faulting had produced such a balanced topography that only subtle changes in the landscape were required to divert the Bear River. This mechanism accounts for the numerous diversions of the Bear River reported in prior studies [4, 5] and could produce a northward di-version of the Bear River in the future. The drainage divide of the northern Great Basin shifted northward about 40 km in the Late Pleistocene as the Bear River flowed through one actively, extending volcanic field, and skirted the edges of two others. More field work and dating are planned to test these hypotheses.

References: [1] Gilbert G.K., (1890) USGS mono-graph 1; [2] Bright, R.C. (1960) MS thesis; [3] Bright, R.C. (1963) Ph.D.; [4] Bouchard D.P., et al., (1998) Paleo3. [5] Hart et al., (2004) GSA Bull. [6] This study. [7] Malde, H.E. (1968) USGS Prof. Pap. 596. [8] Pederson et al., (2011) GSA Ann. Meeting, Ab-stract. [9] Hochberg, A., (1996) M.S. Thesis, Utah State Univ.

Biographical Sketch of presenter:

Susanne U. Janecke is a Professor specializing in

regional tectonics at Utah State University. Her re-search interested focus on extensional and strike-slip related processes and basins.

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GEOLOGIC CONSTRAINTS ON PALEODRAINAGE OF THE SNAKE RIVER SYSTEM SINCE EOCENE TIME. Paul K. Link, Department of Geosciences, ID State University, link-paul@isu.edu.

The Snake River contains several segments that

cross multiple geologic provinces. In the last 15 mil-lion years the Snake, Columbia and Colorado River systems have developed in response to Basin and Range extension and associated magmatism, as well as volcanic activity of the Yellowstone-Snake River Plain (YSRP) hotspot [1-3] and the Columbia River basalts [4]. Geochronologic methods using detrital zircons (DZ) have precision of at best 105 yr, and reveal drain-age changes on a half-million (0.5x106) yr scale. Tephrachonology can attain the 104 yr scale. Genetic methods suggest change on the 104 yr scale. Anthropo-genic environmental effects are on the 102 yr scale.

Modern Snake River. Today, several tributaries to the Snake have hook-shaped paths demonstrating cap-ture of previous stream courses by the southwest flow-ing Pliocene to Holocene river [5]. Surface uplift as-sociated with the YSRP hotspot plume migrated north-eastward across eastern ID; it has tracked the locus of volcanism since 10 million years ago (Ma) [6]. In the wake of the hotspot, a) thermal subsidence, b) changes in the base level of the Snake River, as ultimately con-trolled by the outlet to the Pacific, and, c) on the 10 thousand year (k.y.) scale, construction of basaltic edi-fices, has controlled the regional and local courses of the Snake River system in ways that are traceable us-ing DZ extracted from fluvial sands [7-11].

Western SRP. The WSRP is a northwest-trending, fault-bounded rift basin that began to develop about 11 Ma [13-15]. Rifting was related to Basin and Range extension, loading by basaltic lava and sills, and exten-sional strike-slip faulting of the 15 Ma Oregon-ID gra-ben [16]. The WSRP contains Upper Miocene to Pleistocene arkosic and tuffaceous river and lake sedi-ments of the Idaho Gp., overlain by interbedded basalt and sediment of the Snake River Gp.

Provenance of Zircon Grains. DZ studies in the Snake River system (Fig. 1) use the concept of drain-age-basin order [17] to characterize sedimentary prov-enance [18-20]. Complex multimodal provenance sig-natures (regional or continental scale, 2nd and 3rd order drainage systems, with zircon grains recycled through Proterozoic or Paleozoic sandstones, Fig. 1, D and H) are distinct from unimodal, likely local magmatic spec-tra, often from 1st order local drainage systems (Fig. 1, A and B). The northern U.S. Rockies contain specific magmatic source areas for a) 700 to 650 Ma rift-related Pocatello Fm. and paragneiss intruding the Wildhorse Gneiss Complex in the Pioneer Mtns., b) 640 to 490 Ma Big Creek-Beaverhead alkalic plutons of the Lem-hi Arch, c) 150 Ma in northern NV, d) 95 to 60 Ma

Atlanta and Bitterroot lobes of the Idaho batholith, d) 50 to 45 Ma Challis magmatic rocks, e) Oligocene and early Miocene (35 to 20 Ma) southward younging “ignimbrite flareup” volcanic rocks mainly in NV, e) Basin- and Range lavas and f) the bimodal (YSRP) hotspot system (Fig. 1H).

Figure 1. Representative DZ patterns from ID rivers, [from 17, Fig. 5 and 6] preserving figure numbering. WSRP samples A and B represent a local, magmatic source in 1st order drainage basins. Samples D and H represent complex age distributions and suggest re-gional to continental scale 2nd and 3rd order drainage. The Idaho batholith was rapidly uplifted after about 60 Ma. Much of the material eroded in Eocene time went southwest into the Franciscan trench complex and west into the Eocene Tyee Fm. [21]. On the east, the Challis magmatic belt provided Eocene sediment to the Green River Basin in WY [22].

Idaho Group, Lake Idaho. On the WSRP, on the margins of 7 to 2 Ma Lake Idaho, middle and Upper Miocene Idaho Gp. lacustrine and fluvial sediment contains locally derived, mainly Cretaceous, magmatic zircons (Fig. 1A and B). Marginal to and within Lake Idaho basalt eruptions disrupted fluvial systems [23]. Late Miocene fish fossils in the Idaho Gp. have affinity

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with those in the Sacramento R. system, suggesting an outlet to the southwest [24-25].

Unified Snake River Drainage. There is no evi-dence of a through-going Snake River with headwaters east of the Idaho batholith until after 7 Ma. On the WSRP, zircon provenance from the central Idaho thrust belt only appears in Upper Miocene to Holocene fluvial sands [19].

Glenns Ferry Fm. In the Hagerman area [26-27] Upper Miocene and Pliocene Glenns Ferry Fm. sands represent a paleo-Wood River with provenance to the north in the Idaho batholith and the adjacent thrust belt to the east in the Pioneer Mtns.

Hells Canyon Outlet. At about 2.5 Ma an outlet for the Snake to the north was cut through Hells Cyn. and to the Columbia R. [12]. The giant beaver and the pygmy muskrat [26], species restricted to riparian zones, are found both in the Pliocene strata at Hager-man and in the Ringold Fm. near Hanford WA.

Tuana Gravel. At about 2 Ma the northward-prograding Tuana Gravel brought Jurassic magmatic grains from the Contact Pluton north of Wells, NV, to the SRP system [28].

Eastern SRP. In the ESRP, Pliocene sediment from drillholes within the volcanically silled Big Lost Trough were sourced from the Big Lost River to the southwest, reflecting isolation from the main Snake River [7-8; 29]. In the Kimama drillhole, two interbeds contain abundant 5.8 to 6.2 Ma (Heise volcanic field) euhedral zircons, and sparse Proterozoic recycled DZ [30]. This signature is interpreted as representing the south-draining paleo-Wood River. Subsequently, over a thousand meters of basalt from the Axial Volcanic Zone of the SRP accumulated from 5 Ma to the Holo-cene, effectively excluding fluvial sands from the Kimama area [30-31]. Drillholes at Wendell and Mountain Home in Pliocene Glenns Ferry Fm. contain a 650-700 Ma magmatic zircon population interpreted to be from the paleo-Big Lost River [20]. The Big Lost River was captured into ponded drainage in the Big Lost Trough by 2.5 Ma [7-8]. Loess on the SRP contains the same DZ populations as nearby fluvial sands. The wind acts to integrate the DZ system [18].

Bear River. The Bear River in extreme SE ID was captured by drainage into the Bonneville Basin about 120 ka [32]. Molluscs in the Bear River system have affinity with those of the Yellowstone reach of the Snake River system rather than with those of the west-ern Snake River west of Shoshone Falls, further sug-gesting isolation from the WSRP [33].

Southwest MT. The middle and Late Miocene Renova Fm. lacks 50 to 45 Ma Challis grains, so a direct drainage connection with central ID is unlikely [34-35]. However, Idaho batholith aged-grains are present. In the uppermost Miocene Sixmile Creek Fm., 6 Ma YSRP magmatic zircons are abundant, sug-

gesting drainage from eastern ID. The Continental Divide in the Tendoy Mtns. formed less than 6 Ma [36-37].

[1] Pierce, K.L. and Morgan, L.A. (1992) GSA Mem. 179,1-54. [2] Pierce K.L. and Morgan L.A. (2009) J. Volc. Geoth. Res 188, 1-25. [3] Sears J.W. (2013) GSA Today, 4-11. [4] Hooper P. et al. (2002) Id. Geol. Surv. Bull. 30, 59-67. [5] Ore H.T. (1999) in Guidebook to the geology of eastern ID. IMNH Poca-tello, 254–255. [6] Rodgers D.W. et al. (2002) ID Geol. Surv. Bull. 30, 121-155. [7] Geslin J.K. et al. (1999) Geol. 27, 295-298. [8] Geslin J.K. et al. (2002) GSA Spec. Pap. 353, 11-26. [9] Bestland E.A. et al. (2002) GSA Spec. Pap. 353, 27-44. [10] Link P.K. et al. (2002) Id. Geol. Surv. Bull. 30, 105-119. [11] Kuntz M. A. et al. (2007) USGS Sci. Invest. Map 2969. [12] Wood S.H. and Clemens D.M. (2002) Id. Geol. Surv. Bull. 30, 69-103. [13] Bonnichsen B. and Godchaux M. M. (2002) Id. Geol. Surv. Bull. 30, 233-312. [14] Malde H.E. and Powers H.A. (1962) GSA Bull. 73, 1197-1210. [15] Malde H.E. (1991) GSA DNAG, K-2, 251-280. [16] Cummings M.L. et al. (2000) GSA Bull. 112, 668-682. [17] Ingersoll et al. (1993) Sedimentolo-gy 40, 937-953. [18] Link P.K. et al. (2005) Sed. Geol. 182, 101-142. [19] Beranek L.P. et al. (2006) GSA Bull. 118, 1027-1050. [20] Hodges M.K.V. et al. (2009) J.. Volc. Geotherm. Res. 188, 237-249. [21] Chetel et al. (2011) GSA Bull. 123, 71-88. [22] Du-mutru et al. (2013) Geol. 41, 187-190. [23] Bonnich-sen B. et al., (2008) Bull. Volc 70, 315-342. [24] Wheeler H.E. and Cook E.F. (1954) Jour. Geol. 62, 525-536. [25] Smith G.R. (1982) Id. Bur. Mines Geol. Bull. 26, 519-541. [26] Repenning et al. (1995) USGS Bull 2105. [27] Link P.K. et al. (2002) Id. Geol. Surv. Bull. 30, 105-119. [28] Sadler J. and Link P. K. (1996) Northwest Geol. 26, 46-64. [29] Durk K. A. et al. (2007) GSA Abstracts 36/6, 613. [30] Potter K.E. et al. (2013) GSA Abstracts 45/5, 7-8. [31] Helm-Clark, C.M. and Link, P.K. (2007) Great Rift Science Sympo-sium. IMNH, Pocatello, 57-66. [32] Link et al (1999) in Guidebook to Geol. of E. ID, IMNH, Pocatello, 251-266. [33] Taylor D.W. and Bright R.C (1987) Utah Geol. Ass. Pub 16, 239-256. [34] Stroup C.N. et al. (2008a) Arizona Geol. Surv. Digest 22, 529-546. [35] Link et al. (2008) MT Bur. Mines and Geol Open-file 569. [36] Fritz, W.J., and Sears, J.W. (1993) Geol. 21, 427-430. [37] Stroup C.N. et al. (2008b) Northwest Geol. 37, 69-84.

Biographical Sketch of presenter:

Paul Link has studied the regional geology of the northern Rockies with students and colleagues at Idaho State University since 1980. He is co-author on the new 2012 Idaho Geologic Map. In the last 15 years he has applied detrital zircon geochronology to a variety of geologic problems.

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BIOGEOGRAPHIC HISTORY OF PEBBLESNAILS (GENUS FLUMINICOLA) IN THE SNAKE RIVER REGION. Hsiu-Ping Liu1 and Robert Hershler2, 1Department of Biology, Metropolitan State University of Denver, Denver, CO 80217, hliu1@msudenver.edu; 2National Museum of Natural History, Smithsonian Institution, Washington D.C. 20013-7012.

The lithoglyphid gastropod genus Fluminicola, commonly referred to as pebblesnails, is composed of 25 currently recognized (and many taxonomically un-described) species that are distributed in the Pacific Northwest. Fluminicola is an attractive subject for biogeographic studies relating to drainage history be-cause of its close linkage with lotic habitats and ab-sence of any evidence that these animals have been dispersed by waterfowl. Here we report the results of molecular phylogenetic studies of two pairs of pebble-snail sister species that are pertinent to Snake River history. The split between one of the species pairs (F. coloradensis, F. fuscus) suggests an estimated 2.4-1.8 ma dispersal barrier in the western Snake River plain [1] that is roughly consistent with divergence of aquat-ic oligocheate lineages (genus Rhynchelmis) [2]. Our molecular data also suggest that F. coloradensis dis-persed across the divides separating the upper Snake River, Salmon River, Bonneville, and upper Colorado River basins during the late Quaternary. Some of these dispersal events probably occurred via aquatic connec-tions while others (e.g., involving the Salmon and up-per Colorado River basins) may have been mediated by headwater transfers. The divergence of the second species pair (F. gustafsoni, F. virens) delineates an old vicariance event (3.4-3.2 ma) between areas composed of the Clearwater and lower Salmon River basins, and the Columbia River basin [3].

References: [1] Liu, H.P. et al. (2013) Monographs Western

North American Naturalist 6, 87-110. [2] Zhou H. et al. (2010) Zoologica Scripta 39, 378-393. [3] Hersh-ler, R. and Liu, H.P. (2012) J. Moll. Stud. 78, 321-329.

Biographical Sketch of presenter:

Hsiu-Ping Liu is an associate professor in the De-partment of Biology at the Metropolitan State Univer-sity of Denver. She is interested in molecular genetics, conservation and evolution of North American fresh-water gastropods.

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MICROBIOLOGY AND GEOCHEMISTRY OF IDAHO HOT SPRINGS. Timothy S. Mag-nuson1, Jon C. Rask2, and Leslie Baker3. 1Department of Biological Sciences, Idaho State University, Pocatello ID. Email: magntimo@isu.edu, 2NASA Ames Research Center, Moffett Field CA, 3Department of Geological Sciences, University of Idaho, Moscow ID.

The Snake River Plain and surrounding areas har-

bor numerous and unique hot spring thermal areas, due in part to heat sources beneath the Snake River Plain. Although there are some data on the general features of these areas, such as temperature surveys, no systematic effort has been made to study in detatil the microbiolo-gy and associated geochemistry of these springs. We have focused our efforts on an unusual thermal area in S Idaho, Worswick Hot Springs. This system is located approximate 20 N of Fairfield ID, along Little Smoky Creek, Sawtooth National Forest. Worswick is com-posed of over 20 distinct thermal features, with tem-peratures ranging from 37°C to 90°C. The pH of the springs is alkaline, with average pH values around 9. Radiation levels were measured in 2011 and 2013 and showed radiation associated with hot thermal sources and channels. Despite these conditions, there is abun-dant microbial activity associated with the thermal waters. Worswick thus represents a ‘multi-extreme’ environment where microbes must cope with tempera-ture, radiation, and pH extreme. Preliminary radiation and temperature/pH surveys were conducted during NASA Spaceward Bound expeditions 2011 and 2012. Using a Micro-R-Meter that is sensitive to gamma and x-rays, radiation measurements were gathered around the field site. Our preliminary data suggested that the radiation levels along the stream channel vary by at least a factor of two, ranging from 14.5 µrem/hr up to 35.5 µrem/hr. Water samples were analyzed for total elemental composition using inductively-coupled plasma-mass spectrometry (ICP-MS), and this analysis revealed some very interesting properties of the hot spring waters. Potential sources of radiation were de-tected and include Th, Sr, and U present in several of the 6 sites tested. Also of great interest is a generally high amount of metals such as Fe, Zn, and As (Fe and As being potential electron donors/acceptors). X-ray fluorescence (XRF) measurements made in 2013 show similar patterns for rock/mineral composition sur-rounding the springs. Gas analysis of thermal waters revealed high CO, and presence of H2, 2 gasses central to extremophile metabolism. Microbiological assess-ment of the site has resulted in cultivation of several types of thermohilic orgamisms. Geobacillus spp. are abundant, and are well-known biomass- and metal-transforming microbes. Sulfur-oxidizing and sufate-reducing microbes are also present. Worswick is a mi-crobiologically and geochemically diverse and unusual

environment that supports abundant microbial growth, and could be a resource for useful microbes for bio-technological applications in bioremediation and clean energy.

Biographical Sketch of presenter:

Dr. Magnuson is a Microbiologist and Professor in the Department of Biological Sciences at Idaho State University in Pocatello, Idaho. His work spans micro-bial physiology, biochemistry, and ecology, and his research group explores a variety of topics, including the microbiology of extreme environments, toxic metal transformation, and biofuel production.

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PLIO-PLEISTOCENE INTERACTIONS INVOLVING BASALT FLOWS AND THE SOUTH FORK OF THE SNAKE RIVER BETWEEN SWAN VALLEY AND RIRIE, IDAHO. Dan K. Moore1 and Glenn F. Embree1, Toby Dossett1, Tyler Reed1, Sherri McIlrath1, 1Brigham Young University - Idaho (Dept. of Geology, BYU-Idaho, Rexburg, ID, 83460-0510; moored@byui.edu).

Abstract: The South Fork of the Snake River

flows northwest within the Swan Valley graben from Alpine, WY to Ririe, ID. Our detailed geologic map-ping along the river, its tributaries, and adjacent loess-covered benches illuminates the history of interactions between basalt flows and the river. Two periods of basaltic volcanism are recorded in Swan Valley. Both influenced drainage patterns in the valley. The ~4 Ma basalt of Swan Valley erupted onto the gravels and volcanic deposits that formed the valley floor after the eruption of Kilgore tuff and before the eruption of Huckleberry Ridge tuff. The basalt of Swan Valley formed a broad constructive edifice in the Conant Val-ley area which separated the Pine Creek from the Snake River. At about 2 Ma, following emplacement of the Huckleberry Ridge tuff, basalt erupted on Ante-lope Flat. This eruption dammed the ancient Snake River and Pine Creek drainages in at least two places, filled their channels with basalt, and created a reservoir that extended ~51 km to the south into Swan and Star Valleys. Dam structures are dominantly composed of variably-palagonitized hyaloclastite with intercalated basaltic lava flows that locally have pillow basalt ba-ses. Overtopping of the Conant Valley dam caused the capture of the paleo-Pine Creek drainage by the Snake River and the formation of the current river channel.

Biographical Sketch of presenter:

Dan Moore is a professor of geology and an associ-ate dean at Brigham Young University – Idaho. His recent research includes field and petrogenetic studies in the Yellowstone – Snake River Plain volcanic prov-ince and the Absaroka volcanic field. He is also inves-tigating the relationship between point defects in geo-logic materials and conditions of formation. His schol-arly interests include concepts of time and the strengths and limitations of abductive reasoning in the geosciences; the relationship between science and reli-gion; and mastery-focused teaching approaches.

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UP TO FOUR DEEPWATER PLUVIAL LAKES IN CACHE VALLEY, UTAH-IDAHO, INCLUDING THE CUTLER DAM LAKE CYCLE AT ~1445 M AND POSSIBLE LITTLE VALLEY LAKE CYCLE AT ~1585 M: EVIDENCE FOR POSSIBLE EXCAVATION OF CUTLER NARROWS PRIOR TO 420 KA. Robert Q. Oaks, Jr., Susanne U. Janecke, Tammy M. Rittenour, Michelle Nelson, and Thad L. Erickson: Department of Geology, Utah State Univer-sity, Logan, Utah 84322-4505.

Abstract: A gravel pit southeast of Newton Hill,

Utah, in western Cache Valley, northern Utah, exposes the first evidence of pre-Bonneville lake cycles within Cache Valley. A well-developed paleosol beneath deepwater deposits of Lake Bonneville is developed within ~1 m of colluvial loess unconformably overly-ing lacustrine shore-facies gravel. The soil and upper contact of the underlying high-angle gravel clinoforms are near the level of the lower Provo shoreline (~1445 m asl), and yielded OSL ages of 40 and 60 ka respec-tively. This first evidence for the Cutler Dam lake in Cache Valley is unexpected because it is ~84 m higher than lacustrine deposits and a soil 10 km southwest near Fielding, Utah, that were interpreted to be close to the highest altitude of the Cutler Dam lake cycle (Ovi-att, 1986). Gravels near 1485 m at the top of the pit lie between the Provo and Bonneville shorelines, and have a preliminary OSL age of around 165 ka, contempora-neous with the Little Valley lake cycle. The Bonne-ville highstand exceeded the altitude of these prior lake cycles by up to 100 m.

Water wells were analyzed throughout Cache Val-ley. They reveal two, or probably four, deepwater clays in southern Cache Valley above thick aquifer gravels. The simplest interpretation of these continuous clays is deposition during the Bonneville, Cutler Dam, Little Valley, and Pokes Point Lake cycles, although some older deep lakes could have formed in Cache Valley without interconnection westward. The total thickness of Quaternary deposits is low, and generally less than 60-100 m, thickening up to 300 m near the East Cache fault and SW of Logan, Utah. These data indicate that Cutler Narrows probably formed prior to 420 ka (Pokes Point lake cycle).

Summary: The present outlet of Cache Valley, just below Cutler Dam in the Cutler Narrows, is 1317 m, in Paleozoic bedrock. The Bear River flows SW from Cache Valley into Salt Lake Valley through Cut-ler Narrows. This course probably was superimposed onto bedrock here from a deep consequent canyon cut into the overlying Salt Lake Formation (Tsl) (Oaks, 2000; cf. Hunt, 1982, Gilbert, 1890). WSW displace-ment on the Beaver Dam low-angle normal fault through more than 1.5 km laterally (Goessel, 1999; Oaks, 2000) probably lowered the divide significantly, perhaps with a low near the present canyon of the Bear

River. Overflow, possibly from a lake in Cache Val-ley, incised deeply through the Tsl and then into Paleozoic bedrock. Because the canyon is cut through the highest bedrock along the Cache Butte Divide, and faults mapped therein are entirely cross-axial to the river (Oviatt, 1986), Cutler Narrows is superimposed, not subsequent, in origin. Unless the overflow came from the west, its level would have been lower than that north of Red Rock Pass and across the Oneida Narrows then.

In southern Cache Valley well-log data indicate there are two, and possibly four, clay-rich units, about 9 m and 18 m thick, that are laterally continuous. The top of the underlying aquifer lies between 1314 m and 1341 m near US Highways 89/91, near and slightly above the level at the foot of Cutler Dam. Both of the deepwater lake clays have interbedded gravels near their midpoints that resemble the laterally discontinu-ous gravels along stream courses at the present surface. This suggests subareal exposure and possibly four Quaternary deepwater lakes recorded in the Cache Valley subsurface. At least five lake cycles have been identified from cores and outcrops in the Bonneville Basin west of Cache Valley. These are the Lava Creek (~620 ka), Pokes Point (~420 ka), Little Valley (~150 ka), Cutler Dam (~70 ka), and Lake Bonneville (~25 ka) lake cycles (Oviatt et al., 1987, 1999). We propose that the latter four cycles may be recorded in Cache Valley.

In a gravel pit SE of Newton Hill, a paleosol and underlying shore-facies gravels near the lower, young-er Provo lake level of Janecke and Oaks (2011a,b) are overlain by deepwater Bonneville deposits and then Provo sandy gravels. The paleosol and underlying imbricated shoreline deposits have yielded OSL ages of 40 to 60 ka, contemporaneous with the Cutler Dam lake cycle. This suggests that the level of the Cutler Dam lake cycle may be~ 84 m higher than originally proposed, raised from ~ 1360 m to ~ 1445 m asl. At the top of this pit are gently west-dipping iron-stained gravels truncated by an extensive, gently south-sloping plain capped by the modern soil near ~1585 m. These gravels lie between the Provo and Bonneville shore-lines in altitude, and correspond to the level of the Lit-tle Valley lake cycle. This is supported by a prelimi-nary OSL age estimate of ~165 ka.

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Only the deposits of the most recent glacial-lake cycle were identified previously in Cache Valley. Our evidence suggests that as many as three pre-Bonneville lake deposits are present in Cache Valley, and that cutting of Cutler Narrows likely predates the oldest such deposits.

References: [1] Gilbert G.K., (1890) USGS mono-graph 1; [2] Goessel, K.M. et al. (1999) Utah Geolog-ical Association Publication 27; [3] Hunt, C.B. (1982) Utah Geological Association Publication 10; [4] Janecke, S.U. and R.Q. Oaks, Jr. (2011a) Geological Society of America Field Guide; [5] Janecke, S.U. and R.Q.Oaks, Jr. (2011b) Geosphere, v. 7, n. 6.; [6] Oaks, R.Q., Jr. (2000) Final Report for Bear River Water Conservancy District, Box Elder County, and Utah Division of Water Resources, 116 p.; [7] Oviatt, C.G. (1986) Utah Geological Survey, Map 91; [8] Oviatt, C.G. et al. (1987) Quaternary Research, v. 27; [9] Oviatt, C.G. et al. (1999) Quaternary Research, v. 52.

Biographical Sketch of presenter:

Robert Q. Oaks, Jr. is Emeritus Professor of Geolo-gy at Utah State University. He currently studies both deep and shallow subsurface geology via field map-ping, gravity, and drillers’ logs of water wells in Gem Valley in SE Idaho, Cache Valley in Idaho and Utah, and adjacent Box Elder County.

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*CONTROLS ON THE PLEISTOCENE EVOLUTION OF THE UPPER SNAKE RIVER BETWEEN ST ANTHONY AND BLACKFOOT, IDAHO. William M. Phillips1, 1Idaho Geological Survey, University of Idaho, 875 Perimeter Drive MS 3014, Moscow, ID 83844-3014, phillips@uidaho.edu.

Geologic mapping by the Idaho Geological Survey

has clarified tectonic, volcanic, and climatic controls on the Pleistocene evolution of the upper Snake River. Since 2005, fifteen 7.5-minute quadrangles have been mapped and released on the IGS website at www.idahogeology.org. The mapping has used opti-cally stimulated luminescence to date terrace deposits and loess, geochemical and paleomagnetic analyses to correlate volcanic rocks, and thousands of domestic water well logs to trace units in the shallow subsurface. The study area consists of quadrangles along the allu-vial Snake River and major tributaries from St Antho-ny to just north of Blackfoot. Tectonic control is most evident at the junction of the South Fork and Henrys Fork. Here, accommodation space for a major Pleisto-cene depocenter has been created by normal faulting and subsidence. The Grand Valley fault zone enters the Snake River Plain in this area and splays into multiple northeast-steeping normal faults. The depocenter con-tains over 400 ft of unconsolidated, saturated sedi-ments. Basaltic magma intruded into the depocenter, forming tuff cone and tuff ring complexes of Menan Buttes. Basaltic shield volcanoes form a topographic high west of the Snake River, pinning the course of the river between the basalts and uplands underlain by late Miocene-early Pleistocene rhyolites and basalts. Large basalt flows temporarily dammed the river, forming reaches underlain by shallow basalt and knickzones at Idaho Falls and St Anthony. Fine-grained deposits as-sociated with lava dams influence the region of high water tables at the confluence of the South Fork amd Henrys Fork. Climatic controls in the form of glacia-tion of the Snake River headwaters in the Yellowstone-Grand Teton produced several of the most obvious and economically important features of the study area. Gravel-dominated outwash was deposited in the late Pleistocene. At these times, the Snake River in the study area formed at wide braid plain. A large gravel fan was deposited at the confluence of the South Fork and Henrys Fork. Loess derived from glacial meltwa-ters was deposited throughout the region. With cessa-tion of glaciation, the Snake River metamorphosed into a dominantly single-thread meandering stream.

Biographical Sketch of presenter:

Bill Phillips joined the Idaho Geological Survey in 2004. His Idaho-based research focuses primarily on the late Miocene - Pleistocene geology of the upper Snake River including surficial sediments and both basaltic and rhyolitic volcanic rocks.

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FLUVIAL SANDS AT 6000 FT IN THE KIMAMA DRILL CORE (PROJECT HOTSPOT, CENTRAL SNAKE RIVER PLAIN, ID): HEISE FIELD VOLCANOGENIC ZIRCONS AND THE LATE MIOCENE PALEO-WOOD RIVER Katherine E. Potter, Department of Geology, Utah State University, kepotter126@aggiemail.usu.edu

The Kimama drill site is located on the axial volcanic high of the central Snake River Plain (SRP), NE of Twin Falls, Idaho. The 1912 m (6,275 ft) Kimama core, drilled as part of PROJECT HOTSPOT, provides a record of basaltic lava flows, aeolian loess, and fluvi-al sand on the central SRP from the Late Miocene (6.4 Ma) through Pleistocene (0.72 Ma) (Fig. 1). Ar/Ar and paleomagnetic dating establish a relatively linear basalt accumulation rate of ~335 m/m.y. (~1,100 ft/my), and a projected bottom hole age of 6.4 Ma [4]. Detrital zircons in the Kimama drill core provide a snapshot of two fluvial incursions from 6.2 Ma to 5.8 Ma. Provenance of Zircon Grains. Detrital zircons were recovered from five samples within two upward fining sandstone interbeds near the bottom of the core, at 1842-1844 m (6044-6050 ft) and 1707-1748 m (5602-5737 ft) depth. These were analyzed for U-Pb and εHf at the Arizona LaserChron laboratory. Ratios of U-Pb and Lu-Hf provide a ‘multi-dimensional’ comparison among Neogene magmatic zircons and pre-Neogene detrital zircons. The lower parts of both interbeds contain mainly Mio-cene detrital zircons of the Yellowstone-Snake River Plain (YSRP) magmatic system (10 to 5 Ma) plus what we interpret as inherited 2.6 and 2.1 Ga zircon grains. Higher sands contain zircon groupings representing the Challis magmatic event (50 to 45 Ma), Idaho batholith (100 to 90 Ma), recycled Paleozoic magmatic grains, plus recycled Grenvillean and Meso- and Paleoprote-rozoic grains. We interpret the interbeds to represent two incursions of the Wood River system [2]. Each fluvial succession systematically changes upward from dominantly hotspot zircons to mainly detrital grains. Variable Ar-chean and Proterozoic populations in the upper inter-bed suggest a paleo-Wood River tributary that tapped the structurally uplifted Pioneer core complex. U-Th/He apatite ages from the Pioneer Core Complex show evidence for rapid exhumation since 33 Ma, with a rate of ~0.3 km/my. Thermochronology also docu-ments an extensional exhumation event at ~10 Ma [5]. The 5.8 Ma estimated age of the upper interbed sug-gests unroofing of the Pioneer core and breaching of the Wildhorse detachment occurred by that time.

Volcanogenic Zircon Grains. A large fraction of the grains represent Neogene primary magmatic zircons formed during eruptions of rhyolite ash from the YSRP magmatic system. Four U-Pb age populations of vol-canic zircons are observed: 7.1 Ma, 6.7 Ma, 6.2 Ma, and 5.8 Ma. The fresh, rod- and blade-shapes, with minimal rounding, suggest a primary fallout origin. The ages of volcanic zircon grains in the Kimama core are coincident with eruptive events from the Heise volcanic center. Kimama grain populations of 5.84 ± 0.13 Ma are coeval with the 5.84 ± 0.03 Ma tuff of Wolverine Creek. Grain populations of 6.22 ± 0.078 Ma are coeval with the 6.23 ± 0.01 Ma Walcott Tuff. Grain populations of 6.858 ± 0.091 are possibly related to the tuff of Edie School, dated at 6.61 ± 0.01 Ma. Volcanic zircons dated at 7.25 ± 0.014 Ma are roughly coeval with the 7.27 ± 0.03 Ma VPT-1 tephra of Grand Valley, an eruptive unit associated with Heise volcan-ism [1]. Volcanogenic detrital zircons were ejected during cal-dera-forming eruptions in the Heise volcanic field, transported westward by aeolian or fluvial processes, and deposited at the base of fluvial sands. The young-est zircon grains match the projected age of the core derived from accumulation rate alone, so that deposi-tional lag time could not have been more than 100 k.y.. Therefore, the age of the interbeds approximates the age of youngest zircons in each unit, 5.8 ± 0.1 Ma at 1749 m depth and 6.2 ± 0.1 Ma at 1844 m depth. Hf isotopic compositions of hotspot zircons vary from εHf of -7.3 to -3.9, and the variation is highly correlat-ed with age: volcanogenic zircons with ages of 7.1, 6.7, 6.2, and 5.8 Ma have corresponding Hf of -7.3, -6.4, -4.9. -3.9. This progressive increase in εHf in the younger zircons indicates an increase in mantle-derived Hf through time. Previous whole-rock Hf iso-tope analyses of volcanic rocks on the SRP have yield-ed similar results. The top of the upper succession contains the only sig-nificant population of Paleozoic grains within the Kimama core. We suggest that after 5.8 Ma, the source of the paleo-Wood River system shifted westward to west of the Pioneer thrust fault. After 5.6 Ma, basaltic volcanism along the Axial Vol-canic Zone (AVZ) diverted the paleo-Wood River sys-tem southward to the reach the Hagerman area be-tween 3.8 and 3 Ma.

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Yellowstone-SRP volcanism from 10 Ma to 5 Ma in the central SRP is broadly coeval with exhumation and breaching of the Pioneer core complex and devel-opment of the Wood River System. U-Pb age data of detrital zircons in the Kimama core record volcanic events as young as 5.8 Ma superimposed upon an ac-tive extensional system. Epsilon Hf data from Neogene volcanic zircons provide evidence that younger Heise field grains are compositionally dominated by mantle-derived melts, while older Heise field grains retain a greater crustal-derived signature. Previous whole-rock Hf isotope analyses of volcanic rocks on the SRP have yielded similar results [3], suggesting that YSRP lavas record changes in the age and composition of continen-tal lithosphere from west to east. Furthermore, Hf analyses provide a chemical record of an increasing mantle plume component in the composition of later lavas. Summary. Our new data on fluvial-derived volcanic and detrital zircons suggest: 1) Neogene volcanic ac-tivity in the Heise volcanic center began as early as 7.3 Ma, 2) YSRP volcanism coincided with the unroofing of the Pioneer core complex as early as 10 Ma, and 3) the Wood River System originally flowed south and east into the central SRP before being smothered and diverted southwestward by recurrent volcanism from the AVZ. The lower fluvial sands in the Kimama core record incursions of the paleo Wood River into depos-

its of Heise ash. The ash was rapidly eroded, and over-lain by distal sands derived from the mountains to the north. References [1] Anders M.H. et al. (2009) GSA Bull. 121, 837-856. [2] Link P.K. et al. (2005) Sed. Geo. 182, 101-142. [3] Hanan B. B. (2013) pers. commun. [4] Potter K.E. et al. (in prep). [5] Vogl J.J. et al. (2010) GSA Abstracts 42/5, 595.[6] Watts, K.E. et al. (2011) J. Pet. 52, 857-890. Biographical Sketch of Presenter: Katherine Potter is a PhD candidate at Utah State Uni-versity where she studies volcanic stratigraphy on the Snake River Plain

Figure 1: Paleomagnetic and lithologic stratigraphy of the Kimama core with probability-density curves and histograms of sampled detrital zircons. Plots are shown for 0 to 150 Ma and 0 to 3500 Ma grains. Two upward-fining interbeds are recognized. Each interbed changes upward from mainly Heise field Miocene zircons to Paleozoic and Proterozoic zircons derived the paleo-Big Wood River drainage.

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ON THE BIOGEOGRAPHIC AND PHYLOGEOGRAPHIC STRUCTURE OF THE SNAKE RIVER SHRUB STEPPE ECOREGION: EMERGING INSIGHTS FROM MAMMALS. Brett R. Riddle, School of Life Sciences, University of Nevada Las Vegas, Las Vegas, NV 89154-4004. brett.riddle@unlv.edu.

While the Snake River shrub steppe ecoregion –

including the Snake River Plain - is not included in the hydrographic or physiographic Great Basin, it is a part of the floristic Great Basin [1]. A simple Dice similari-ty analysis confirms the similarity of mammal biotas from the Snake River and Great Basin shrub steppe ecoregions [2], but there are intriguing signatures of a more complex history of biogeographic and phylogeo-graphic processes across these regions. To date, few extant mammal lineages appear to be endemic within the Snake River ecoregion – although those thus far identified provide clues to broader clade and geograph-ic histories that might become tractable in studies of adaptive evolution and speciation within a Quaternary timeframe [3] [4]. Molecular biogeographic analyses of other taxa are beginning to provide seemingly sur-prising patterns and times of clade divergence and dis-tribution between the Columbia Plateau, Snake River, and Great Basin [2]. Finally, the Snake River region appears to have acted as a corridor for Quaternary en-try of arid taxa from the east that have subsequently diverged into a unique set of western intermontane clades [5] [6]. My goal is to offer a template from these snapshots that demonstrate an emerging view of the complex role of the Snake River ecoregion as both a center of differentiation and a corridor facilitating dispersal among adjacent ecoregions.

[1] Grayson D. K. (2011) The Great Basin: A Nat-

ural Prehistory. Univ. Calif. Press. [2] Riddle B.R., et al. (2014) Journal of Mammalogy, 95, xxx-xxx. [3] Patton J. L. and Smith M. F. (1994) Systematic Biolo-gy, 43, 11-26. [4] Hafner J. C. and Upham N. S. (2011) Journal of Biogeography, 38, 1077-1097. [5] Riddle B. R., and Honeycutt, R. L. (1990) Evolution, 44, 1-15. [6] Wilkinson, J. pers. comm. Biographical Sketch of presenter:

I am a Professor at the University of Nevada Las

Vegas. I consider myself a biogeographer with interest in the historical relationships between landscapes and biotic diversification in western North America. I nor-mally focus on mammals, but also a range of other vertebrates and invertebrates.

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INTEGRATION, FRAGMENTATION. RE-ROUTING OF THE SNAKE RIVER OVER TIME. James W. Sears1, 1University of Montana, Missoula MT 59812 james.sears@umontana.edu.

Introduction: A recent hypothesis proposes that,

in late Miocene and Pliocene time, the eastern Snake River Plain bisected a late Oligocene-early Miocene paleovalley that formerly drained north from the Grand Canyon of Arizona through SE Idaho to Canada [1].

Figure 1. Hypothetical connection of Bell River ba-

sin to SE Idaho in Miocene time. The hypothesis is based on interpretations of the

provenance of ancient stream deposits that have been faulted into the Rocky Mountains of southwestern Montana and adjacent Idaho, and into the Great Basin of Idaho, Utah, and Nevada. The faulted stream de-posits are interlayered with volcanics that erupted from mega-calderas along the path of the Yellowstone hot spot. The volcanics provide a detailed chronology for the fragmentation and re-routing of the Snake River drainage and for establishment of the modern Conti-nental Divide and Great Basin. The headwaters of the modern Snake River may have been tributary to the Oligo-Mio paleovalley. The Snake River was evidently diverted from its former course in late Miocene time, to flow into Lake Idaho near Boise [2]. From Lake Idaho, it eventually flowed through Hell's Canyon to join the Columbia River basin [3].

Nevadaplano Rift System: The hypothesis states that, in late Oligocene time, about 26 million years ago, the Rio Grande Rift and associated volcanic high-lands diverted runoff from the southern Colorado Plat-eau toward the west. It proposes that drainage flowed through the proto-Grand Canyon, and entered a broad continental rift system on the east flank of the Ne-vadaplano, a high plateau centered in Nevada, that was

analogous to the Altiplano of the South American An-des [4]. The rift system propagated south from south-western Montana to southern Nevada and Utah from 48 to 28 million years ago, and followed the structural trend of the older Sevier mountain belt. As it swept southward, the rift probably incorporated streams that had formerly followed strike-valleys in the mountain belt. Super-eruptions from large calderas accompanied the southward advance of the rift [5], and volcanic ash swept down the rift into lake basins in Idaho and southwestern Montana.

Basin-Range: Upon initiation of basin-range fault-ing, about 17 million years ago, rugged new source rocks arose within the rift system, and the thick, ash-rich, Oligo-Mio deposits were tectonically tilted, scoured by deep erosion, and buried by thick gravel beds. The period of deep erosion coincided with the Miocene Climatic Optimum, when unusually heavy precipitation and runoff characterized the West [6). The river gravel beds are dominated by resistant rock types that typify bedrock of the central-eastern Great Basin, but that are absent farther north. There appear to have been two main stream channels that brought dis-tinctive gravel northward. A western channel tapped sources in the Paleozoic Antler mountain belt of cen-tral Nevada, bringing meta-chert, meta-quartzite, and cherty litharenite pebbles. An eastern channel tapped sources in southeastern Idaho and western Utah, bring-ing a variety of white, pink, and purple quartz-arenite pebbles. The two channels confluenced south of the modern position of the Continental Divide near Moni-da Pass, Idaho/Montana. The eastern branch may have been a Miocene version of the upper Snake River, with a tributary coming in from the east that tapped western Wyoming and the northern Colorado Plateau [7].

Yellowstone Hotspot: The paleovalley was cut off by the passage of volcanic mega-calderas of the Yel-lowstone hotspot [8]. The eastern Snake River Plain follows the track of these calderas. The calderas are progressively younger from southwest to northeast [8]. The track of calderas first intersected the paleovalley system about 10 million years ago, in the vicinity of Twin Falls. Topographic disruptions associated with the calderas - doming, faulting, and volcanism - began to re-arrange the drainage around the eastern Snake River Plain. By 6 million years ago, the gigantic Heise caldera complex raised a volcanic plateau north of Ida-ho Falls [9].

The western channel of the Miocene river system was diverted into Lake Idaho from the west side of the

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plateau. The eastern channel skirted the east flank of the plateau and flowed down a NW-trending graben valley between the nascent Beaverhead and Tendoy ranges. Rhyolite ash-flow tuff and basalt flowed NW down the graben and, in Montana, turned NE into the original trend of the paleovalley (Fig. 2).

Figure 2. Snake River diverted around Heise Vol-

canic complex at ~ 6.62 million years ago. By 5 million years ago, continued uplift diverted

the paleo-stream around the SE end of the Tendoy Range (Fig. 3). It then flowed along the NE side of the Tendoy Range, cross-cutting its former course near Dell, Montana. Then, by 4.45 million years ago, uplift of the Tendoy Range and the Centennial Range pinched off the paleoriver channel at Monida Pass. The headwaters of the Snake River were then diverted to the west in the collapsed wake of the Yellowstone hotspot, where basalt flows blanketed the old mega-calderas.

Figure 3. Drainage diverted around SE end of Ten-

doy Range at about 5 million years ago. References: [1] Sears, J.W. (2013) GSA Today, 4-11. [2]

Beranek L.P. et al. (2006) GSA Bull. 118.1027-1050.

[3] Orr, E. et al. (1999) Geology of Oregon, Kendell-Hunt. [4] DeCelles, AJS 304, 105-168. [5] Mix, H.T. et al. (2011) Geology 39, 87-90. [6] Zachos, A.B. et al. (2001) Science 292, 686-693. [7] Ferguson, C.A. (2013) GSA Abst. w. Prog. 45, 634. [8] Pierce, K.L. and Morgon, L.A. (1992) GSA Mem. 179,1-54. [9] Morgan, L.A., and McIntosh, W.C. (2005) GSA Bull. 117, 288-306.

Biographical Sketch of presenter:

James Sears is a Professor of Geology at the Uni-versity of Montana, Missoula. He studies structural geology and tectonics, with a strong field emphasis. He has a long-time interest in the tectonic disruption of Miocene drainage basins in the western interior.

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MOLECULAR STUDIES OF FISHES AS THEY RELATE TO INTERRELATIONSHIPS AMONG THE BONNEVILLE, LAHONTAN AND SNAKE RIVER BASINS. Dennis K. Shi-ozawa1, Derek Houston2, Peter Unmack3, Sun Oh4, David Neely5, and R. Paul Evans6, 1Department of Biology Brigham Young University, Provo, UT 84602, shiozawa@byu.edu, 2Department of Ecology, Evolution, and Organ-ismal Biology, Iowa State University, Ames, IA 50011, derek.houston@gmail.com, 3Department of Biology Brigham Young University, Provo, UT 84602, peter.mail2@unmack.net, 4Department of Biology Brigham Young University, Provo, UT 84602, sunisbeautiful@yahoo.com, 5Tennessee Aquarium Conservation Institute, 201 Chest-nut St., Chattanooga, TN 37402, dave.neely@gmail.com 6Department of Microbiology and Molecular Biology Brigham Young University, Provo, UT 84602, evansp@byu.edu.

The Snake River system appears to be an important

center of diversification for many native fishes in the interior of western North American. We have exam-ined mitochondrial DNA data for three groups of west-ern fishes, two cottids and the cutthroat trout. All have genetic signatures reflecting a key association with the Snake River Basin. The cutthroat trout may have ini-tially dispersed via a Snake River-Pit River connection and, then, through subsequent headwater transfers and major drainage captures, were able to access the Bonneville Basin, Colorado River Basin and Columbia River drainages. In this scenario the capture of the Snake River into the Columbia River Basin may have had a major role in the diversification of the cutthroat trout. Cottids show what may be a dual set of invasion routes. Cottus beldingii and its associated species may have followed the same route as the cutthroat trout, while Cottus bairdii may have gained access to the Upper Snake River Plain through stream capture events from the Upper Missouri River system as the Yellowstone Hot Spot moved progressively to the east. Evidence suggests that a second wave of invasions of a Cottus bairdii -like fish is currently underway in some of the eastern Lost River streams.

Biographical Sketch of presenter:

I am professor and chair of the Department of Biol-ogy and am the curator of fishes in the Monte L. Bean Life Science Museum, Brigham Young University, Provo, Utah. My research interests include the bioge-ography of aquatic organisms (fish and invertebrates) in Western North America and the roles of ecological factors in the structuring of aquatic communities.

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FISH DNA AND FOSSILS SUGGEST PACIFIC NORTHWEST AND SNAKE RIVER PLAIN ORIGINS OF MOST WESTERN AMERICAN FRESHWATER FISH DIVERSITY. Gerald R Smith1and Thomas E Dowling2 1Museum of Zoology, University of Michigan, Ann Arbor MI 48109, grsmith@umich.edu. 2Department of Biological Sciences, Wayne State University, Detroit MI 48202.

Molecular phylogeography and fossils of four groups of diverse fishes of the Snake River and its former connectives provide evidence for Pacific Northwest centers of origin. Distribution patterns demonstrate Snake River connections to the Sacramen-to, Klamath, Columbia, Lahontan, Bonneville, and Green River drainages in the past 13 million years. Western suckers (Catostomidae) and minnows (Cy-prinidae) show a general pattern beginning with 15-11 Ma fossils in Washington and Oregon and later disper-sal through changing hydrographic connections. Mountain Suckers (Subgenus Pantosteus, Catostomi-dae) existed in the Miocene of Washington and Ore-gon, and the Pliocene of Idaho and Nevada. Stream connections facilitated their evolution into a northern species group inhabiting the Columbia, Snake, Lahon-tan, Bonneville, upper Green, and Missouri River Ba-sins, and a southern species group that diversified into the Snake, Green, Upper and Lower Colorado rivers, Los Angeles, Rio Grande, and Mexico. Northern and southern groups were both present on the Snake River Plain in the Pliocene; both groupings are supported by their mitochondrial genomes. River Suckers (Catosto-mus; Catostomidae) are first known from the Snake River Plain about 10.5-8.5 Ma; diversity later peaked there with three species at about 3 Ma. This group di-versified into ten northern species in the Sacramento, Lahontan, Owens, Columbia, Snake, Bonneville, Colo-rado, and Missouri river basins, and a less diverse southern group in the lower Colorado River Basin and Mexico. Fossil Speckled Dace (Rhinichthys osculus group; Cyprinidae) are found in the Late Miocene and Pliocene of Washington, Oregon, Idaho, and Nevada; the oldest is from Ellensburg, Washington, 11.3 Ma. Speckled Dace are now the most widespread fish spe-cies in western United States, diagnosed in two molec-ular clades. A northwest group lives in the Columbia, Sacramento, Snake, northern Bonneville, Lahontan, Owens, Amargosa, and coastal drainages in northern California, Oregon, and Washington. A southern group lives in the upper and lower Colorado, Sevier, and Los Angeles watersheds. Molecular patterns support a middle Miocene origin in Oregon. Pike minnows (Ptychocheius) are an ancient monophyletic group first known from Columbia River fossils, about 15 Ma. Specimens are in the Miocene and Pliocene of south-east Oregon and the Snake River Plain, then later in

northeast Arizona and southern Nevada. They now live in the Sacramento, Columbia-Snake, and Colorado drainages, and peripheral connectives. Pairwise molec-ular distances, 9-11% among the three major species, imply separation in the late Miocene, about 6 Ma, when calibrated with fossils. All four of the above catostomid and cyprinid groups, plus sculpins (Cottus), and others, originated in the Northwest at a time of low aquatic diversity elsewhere in the western United States. Vicariance and dispersal hypotheses both help explain distributional history.

Biographical Sketch of presenter:

Gerald Smith is Professor Emeritus in the Depart-ment of Ecology and Evolutionar Biology and the De-partment of Earth and Environmental Sciences at the University of Michigan. He studies distribution, pale-ontology, and evolution of North American freshwater fishes.

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SNAKE RIVER CONNECTIONS TO THE GREEN AND COLORADO, UPPER KLAMATH, AND SACRAMENTO DRAINAGES INDICATED BY MIO-PLIOCENE FISH DISTRIBUTIONS. Gerald Smith1 and Jon Spencer2, 1Museum of Paleontology, University of Michi-gan. Ann Arbor, Michigan 48109, grsmith@umich.edu; 2Jon Spencer, Arizona Geological Survey, Tucson, Arizona 85701.

Seven fish genera of the Sacramento River are shared with the Late Miocene Bidahochi Formation of northeastern Arizona. The preferred hypothesis to ex-plain suggested that hydrographic connections oc-curred between the Snake River Plain and the Green River on the east and the Sacramento River on the west [1]. The faunas of the Late Miocene Chalk Hills For-mation (8.1-6.4 Ma), Glenns Ferry Formation (4.8-1.8 Ma) of the Snake River Plain, and Cache Valley For-mation in Northern Utah (8-6 Ma) include most of these genera. Mollusks [2] and two other fish, Deltistes (Lost River Sucker) and Mylocheilus (Peamouth), are shared with the Klamath basin. Orthodon (blackfish), Ptychocheilus (pike minnows), Pogonichthys (split-tails), Gila (chubs), Mylopharodon (hardheads), Lavin-ia (hitches), and Archoplites (sunfishes) occur in the Bidahochi Formation and the Sacramento River; all but Pogonichthys are known from the Chalk Hills and Glenns Ferry formations [3, 1]. These distinct genera are almost entirely missing in contemporaneous fossil and recent assemblages in the Lahontan basin, suggest-ing that major fluvial connections were independent of that basin. Standing against the Sacramento-Snake-Green River hypothesis is absence of published evi-dence of large fluvial channels across southern Ore-gon. Also, fish dispersal between western Idaho and the Colorado Plateau was not accompanied by delivery of Colorado Plateau sands to the Chalk Hills For-mation [4]. Furthermore, molecular phylogeography of the gastropod, Pyrgulopsis (Natricola), supports a connection between the Snake River Plain and the Humboldt drainage, Nevada, not southern Oregon [5]. Three primary geological interpretations support the northern fluvial hypothesis: The proposed course of the upper Snake River to the Sacramento River prior to its capture by the Columbia River through Hells Canyon [6]; the hypothesized stream capture from the upper Green River to the upper Snake River (Beranek et al. 2006); and the identification of possible muscovite and K-feldspar from the Idaho Batholith in the Wildcat Formation on the Klamath peneplain [7]. Temporal overlap of these events in the earliest Pliocene presents a constrained connection time to be tested.

References. [1] Spencer, J.E., G.R. Smith, T.E. Dowling, 2008,

Middle to late Cenozoic geology, hydrography, and fish evolution in the American Southwest, in Reheis, M.C., Hershler, R., and Miller, D.M., eds., Late Ceno-

zoic Drainage History of the Southwestern Great Basin and Lower Colorado River Region: Geologic and Bio-tic Perspectives: Geological Society of America Spe-cial Paper 439, p. 279–299. [2] Taylor, D. W. 1985. Evolution of freshwater drainages and molluscs in western North America, p. 265-321, IN: C. J. Smiley (ed.) Late Cenozoic history of the Pacific Northwest. AAAS, San Francisco, 417 p. [3] Smith, G.R., K. Swirydczuk, P.G. Kimmel, B.H. Wilkinson, 1982, Fish biostratigraphy of late Miocene to Pleistocene sedi-ments of the western Snake River Plain, Idaho, in Bonnichsen, B., and Breckenridge, R.M., eds., Ceno-zoic Geology of Idaho: Idaho Bureau of Mines and Geology Bulletin 26, p. 519–541. [4] Beranek, L.P., P.K. Link, C.M. Fanning, 2006, Miocene to Holocene landscape evolution of the western Snake River Plain region, Idaho: Using the SHRIMP detrital zircon prov-enance record to track eastward migration of the Yel-lowstone hotspot: Geological Society of America Bul-letin, v. 118, p. 1027–1050. [5] Hershler, R., and H.-P. Liu, 2004. A molecular phylogeny of aquatic gastro-pods provides a new perspective on the biogeographic history of the Snake River region. Molecular Phyloge-netics and Evolution, 32: 927-937. [6] Wheeler, H.E., and E.F. Cook, 1954, Structural and stratigraphic sig-nificance of the Snake River capture, Idaho-Oregon. Journal of Geology, 62(6): 525-536. [7] Aalto, K.R., W.D. Sharp, P.R. Renne, 1998, 40Ar/39Ar dating of detrital micas from Oligocene–Pleistocene sandstones of the Olympic Peninsula, Klamath Mountains, and northern California Coast Ranges: provenance and paleodrainage patterns. Canadian Journal of Earth Sci-ence, 35: 735–745.

Biographical Sketch of presenter:

Gerald Smith is Professor Emeritus in the Depart-ment of Ecology and Evolutionar Biology and the De-partment of Earth and Environmental Sciences at the University of Michigan. He studies distribution, pale-ontology, and evolution of North American freshwater fishes.

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SALMONS, TROUT AND CHAR OF THE MIOCENE CHALK HILLS AND PLIOCENE GLENNS FERRY LAKES ON THE SNAKE RIVER PLAIN, IDAHO AND OREGON. Ralph F. Stearley1 and Gerald R. Smith2, 1Department of Geology and Geography, Calvin College, North Hall, 1740 Knollcrest Circle SE, Grand Rapids, MI, 49546 2Museum of Paleontology, University of Michigan, Ann Arbor 48109.

We report on nine lineages of salmons, trouts, and

chars in the late Miocene in the North Pacific Basin, at a time of vigorous coastal upwelling and rich primary productivity. The lacustrine fossil fish assemblage from the Late Miocene Chalk Hills Formation (8.1 to 6.4 Ma), southwest Idaho and southeast Oregon, exhib-its the greatest salmonine diversity of any Cenozoic paleontological site known--five of these nine lineages. This fauna includes Oncorhynchus ketopsis, a small, landlocked ancestor of the modern chum salmon; On-corhynchus salax, a landlocked salmon about twice as large as a kokanee; and a 35 cm landlocked sister spe-cies to the 3 m Pacific planktivorous salmon, On-corhynchus rastrosus. Large and abundant top salmon-id predators in the system included a 1 m redband trout, Oncorhynchus lacustris, and a 1.4 m char, Salvelinus larsoni. Salmonids comprise twenty percent of the fish species in the Chalk Hills Lake. At about 6 Ma the char and two of the salmon were extirpated, but at about 5 Ma a trout, two salmon, and two whitefish species replenished the deep Glenns Ferry rift lake. Salmonids then comprised five of 32 species. A mod-ern ecological analog is Kootenay Lake, in the upper Columbia River drainage, British Columbia, which hosts a westslope cutthroat trout, a large redband trout, a kokanee, a char, and two whitefish among 17 spe-cies. The salmonids of the lakes on the Snake River Plain pose an important hydrographic puzzle because the Columbia River drainage has only scant evidence of Miocene and Pliocene salmonids at the time of their diverse presence in the Snake River drainage. Thou-sands of identified fish specimens in the White Bluffs and Taunton fish faunas of Washington’s Ringold Formation, on the banks of the Columbia River above the junction with the Snake River, lack salmonids ex-cept for one pair of large Oncorhynchus rastrosus den-taries from the base of the section. Salmonid and other faunal similarities to the Sacramento suggest a past connection. Idaho Batholith age muscovites and K-feldspar in Klamath area deposits of late Miocene-early Pliocene age and mollusk fossils suggest that the ancestral Snake River flowed west to the upper Kla-math River. Alkaline strata and zeolitic alteration of tuffs suggest that the lakes periodically lacked an out-let. Geological evidence for the capture of the upper Snake River by a tributary to the Salmon and Colum-bia rivers at the oxbow, near the head of Hells Canyon,

was thoroughly developed by Harry Wheeler and Earl Cook six decades ago. Many lines of geologic and bio-geographic evidence suggest capture and drainage of the Glenns Ferry Lake through Hells Canyon in the latest Pliocene.

Biographical Sketch of presenter:

Ralph Stearley received his Ph.D. in vertebrate paleontology at the University of Michigan in 1990. Since 1992 he has taught geology and paleontology at Calvin College. His research interests include the Ce-nozoic history of the western North American fish fau-na, and the history of the historical disciplines of geol-ogy, archaeology, and paleontology.

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ELEVATION-DEPENDENT RESPONSES OF STREAMFLOW TO CLIMATE WARMING IN MOUNTAIN WATERSHEDS. Christopher J. Tennant1, Benjamin T. Crosby2, and Sarah E. Godsey3, 1Department of Geosciences, Idaho State University (921 S 8th Ave, STOP 8072, Pocatello, ID 83209-8072), 2&3 Department of Geosciences, Idaho State University.

Warming will affect snowline elevation, potentially

altering the timing and magnitude of streamflow from mountain landscapes. Presently, the assessment of po-tential elevation-dependent responses is difficult be-cause many gauged watersheds integrate drainage are-as that are both snow- and rain-dominated. To predict the impact of snowline rise on streamflow, we mapped the current snowline (1980 m) for the Salmon River watershed (Idaho, USA) and projected its elevation after 3 °C warming (2440 m). This increase results in a 40% reduction in snow-covered area during winter months. We bolster this analysis by collecting stream-flow records from a new, elevation-stratified gauging network of watersheds contained within high (2250 – 3800 m), mid (1500 – 2250 m) and low (300 – 1500 m) elevations that isolate snow, mixed, and rain-dominated precipitation regimes, respectively. Results indicate that lags between percentiles of precipitation and streamflow are much shorter in low elevations and that their annual percentiles (Q25 & Q75) of streamflow occur 30 – 50 days earlier than in mid- and high-elevation watersheds. Extreme events in low elevations are dominated by low- and no-flow events whereas mid- and high-elevations experience large magnitude floods. Only mid- and high-elevation watersheds are strongly cross-correlated with catchment-wide flow of the Salmon River, suggesting that changes in contribu-tions from low-elevation catchments may be poorly represented using mainstem gauges. As snowline rises, mid-elevation watersheds will likely exhibit behaviors currently observed only at lower elevations. Stream-flow monitoring networks designed for operational decision making or change detection may require mod-ification to capture elevation-dependent responses of streamflow to warming. Biographical Sketch of presenter:

I am currently a PhD student in the Department of Geosciences at Idaho State University. My work fo-cuses on identifying linkages between climate and hy-drology and geomorphology. I try to contribute to sci-entific theory, as well as practical applications with my work.

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EFFECTS OF IRRIGATION SEEPAGE AND GROUNDWATER FLOW ON FLUVIAL AND PALUSTRINE HABITATS IN THE UPPER SNAKE RIVER BASIN. Robert W. Van Kirk1, 1Senior Scientist, Henry’s Fork Foundation, P.O. Box 550, Ashton, ID, 83420, rob@henrysfork.org.

Introduction: Surface and groundwater hydro-

logic regimes are major determinants of habitat types and organisms found in fluvial and palustrine systems. Anthropogenic alterations of hydrologic regimes can therefore affect species composition, abundance, and geographic distribution of stream, riparian, and wet-land biota. The effects of large dams on hydrologic regimes and fluvial systems in the Snake River and other large river basins have been well described [1]. However, in irrigated landscapes in the western U.S., water withdrawal, irrigation seepage, and return flow via groundwater pathways can have substantial affects on hydrologic regimes, even in river reaches that are unaffected by upstream dams. Although the im-portance of irrigation seepage to the Eastern Snake Plain Aquifer is well known [2], the effects of historic and current irrigation practices on stream hydrologic regimes have not been well described. This paper pro-vides evidence that at multiple spatial scales, irrigation has increased the influence of groundwater on stream hydrologic regimes in the upper Snake River basin.

Methods: A water-budget approach was applied to

nested watersheds representing three orders of magni-tude in spatial and hydrologic scale (Table 1). The largest of the three is the entire upper Snake River ba-sin, defined as the surface and groundwater catchment of the Snake River upstream of King Hill. Water budg-ets were developed from hydrologic data, published information (e.g., [1]), and hydrologic models [3,4,5]. Primary water budget components were surface water supply, irrigation diversion, canal seepage, evaporative losses, crop evapotranspiration (ET), direct irrigation application seepage, groundwater recharge, and return flows to the surface water system via ground and sur-face pathways. Using 1979-2008 water supply condi-tions, hydrographs at USGS gage stations were simu-lated for unregulated conditions (no irrigation), and for current and historic (pre-sprinkler) irrigation practices.

Table 1. Nested watersheds used in this study.

Basin

Area (km2)

Water supply (m3a-1)

Irrigation withdrawal (m3a-1)

Upper Teton 4.0×102 3.7×108 1.1×108 Henrys Fork 8.0×103 3.4×109 1.5×109 Upper Snake 9.3×104 1.4×1010 1.2×1010

Results: At all three spatial scales, crop ET ac-counted for no more than about 40% of total irrigation

withdrawals. Between one-half and two-thirds of total irrigation withdrawal was recharged to groundwater and returned to the surface system as aquifer discharge (Fig. 1). Evaporative loss and surface-pathway return flows were very minor water-budget components. Ca-nal and irrigation-application seepage comprised over 40% of total groundwater recharge in all three study basins and over 50% of total recharge in the two larg-est basins (Fig. 2). Unregulated stream hydrographs showed dominance by runoff of snowmelt during spring and summer, followed by rapid recession to relatively low base flow (Fig. 3). Relative to unregu-lated hydrographs, irrigation-influenced hydrographs showed decrease in magnitude of the snowmelt peak, more gradual recession to base flow, and increased stream flow during late summer through winter as a result of increased groundwater inputs (Fig. 3). The effect of flow through groundwater pathways was greatest under historic irrigation practices, when flood, sub-irrigation and other surface application methods were used and irrigation seepage was high. Conversion to pipe-and-sprinkler systems since the 1970s has de-creased irrigation seepage and hence the influence of groundwater on hydrologic regimes.

Fig. 1. Fate of surface water withdrawn for irrigation.

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Fig. 2. Distribution of groundwater recharge sources.

Fig. 3. Modeled 30-year mean hydrographs for the Teton River at the S. Leigh Creek gage (USGS 13052200) under unregulated conditions and current and pre-sprinkler irrigation practices.

Discussion: Except in river reaches immediately

downstream of large dams and diversions, the primary effects of surface-water irrigation on stream hydrologic regimes in the upper Snake River basin have been to decrease spring-time peak flows as water is withdrawn for irrigation and increase late-summer through early-spring base flows as irrigation seepage returns to the stream via groundwater flow. Stream channels in groundwater-dominated fluvial systems tend to have smaller active floodplains and riparian areas and less complex in-stream habitat than those dominated by surface runoff [6], providing a mechanism for shifts in

species assemblages. In the presence of invasive com-petitors, lowered peak flows can disadvantage native fish species that evolved in snowmelt-dominated sys-tems [7], providing another mechanism for biotic shifts. Increased water tables and springs associated with groundwater return flows have created wetland habitats that were not present prior to irrigation [8], allowing establishment and/or expansion of palustrine species. Given the spatial extent of canal systems in the upper Snake River basin (e.g., 750 linear km in the Henrys Fork watershed alone), strips of riparian and wetland vegetation along canals themselves comprise a nontrivial amount of habitat created by irrigation [5,8]. Although habitats and ecosystems created and main-tained by irrigation seepage have been studied in other irrigated regions of the western U.S. [9], such ecoys-tems remain poorly described and understood in the upper Snake River basin.

References: [1] Collier M. et al. (1996) USGS

Circ., 1126. [2] Johnson G. S. et al. (1999) J. American Water Resources Assoc., 35, 123-131. [3] Apple B. D. (2013) M. S. Thesis, Humboldt State Univ. [4] Peterson K. D. (2011) M. S. Thesis, Humboldt State Univ. [5] Van Kirk R. et al. (2012) http://www.humboldt.edu/henrysfork/. [6] Bayrd G. B. (2006) M. S. Thesis, Idaho State Univ. [7] Van Kirk R. W. et al. (2010) J. Biological Dynamics, 4, 158-175. [8] Fiege M. (1999) Irrigated Eden, Univ. Washington Press. [9] Peck D. E. and Lovvorn J. R. (2001) Wet-lands, 21, 370-378.

Biographical Sketch of presenter:

Rob Van Kirk is Senior Scientist at the Henry’s Fork Foundation in Ashton, Idaho and Professor Emer-itus of Mathematics and Statistics at Humboldt State University in Arcata, California. His research interests include hydrology, hydrogeology, fluvial geomorphol-ogy, fisheries biology, and aquatic ecology. He has applied interdisciplinary research integrating these subject areas to management of water and fisheries in the upper Snake River basin since 1994. He has served as a consultant to Idaho Department of Fish and Game, Idaho Department of Water Resources, and U.S. Bu-reau of Reclamation, among other agencies and organ-izations.

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Upper Teton Henrys Fork Upper Snake

Dist

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ion

of R

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Direct PrecipitationStream Seepage/Tributary UnderflowIrrigation Seepage

0

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48

EVOLUTIONARY AND BIOGEOGRAPHIC HISTORY OF ANADROMOUS SALMONIDS IN THE SNAKE RIVER BASIN. Robin S. Waples (NOAA Fisheries, Northwest Fish-eries Science Center, 2725 Montlake Blvd. East, Seattle, WA 98112; robin.waples @noaa.gov).

Introduction: It has been proposed [1] that the

main reason there are many species of Pacific salmon but only one of Atlantic salmon is that geological fea-tures of western North America have been much more dynamic over the past 10-20 million years. These same dynamic processes produce a range of habitats that support local adaptations within species, and these diverse arrays of locally-adapted populations promote long-term viability of the species, in much the same way that a diversified portfolio of investments reduces risk [2]. However, because salmon habitats are dy-namic, reflecting disturbance regimes shaped by vol-canic eruptions, landslides, wildfires, and floods, the patterns of local adaptation also must vary over time. Thus, we expect that if we could take snapshots of Pacific salmon populations at different times in the past, we would consistently find a mosaic pattern of local adaptation, but that fine-scale details of the pat-tern would differ over time [3].

We estimate that about 30% of historic (pre-European settlement) populations of Pacific salmon in the contiguous U.S. have been extirpated, with many of the losses caused by large dams in the Upper Co-lumbia River and Snake River that blocked access to thousands of miles of spawning habitat [4]. Three na-tive species of anadromous salmonids still occur as ESA-listed species in the Snake River basin: sockeye salmon (Oncorhynchus nerka), chinook salmon (O. tshawytscha), and steelhead (the anadomous form of rainbow trout, O. mykiss); a fourth (coho salmon, O. kisutch) survived in some Snake River drainages into the second half of the 20th Century before being extir-pated. Contemporary populations for all three extant species that occur in the Sawtooth Valley of Idaho are the highest-elevation (> 2000 m) spawning salmon in the world, and these populations undergo the longest (sockeye and steelhead) or among the longest (chi-nook) freshwater migrations (>1500 km) of any salm-on [5]. The three extant species show contrasting bio-geographic patterns.

Over 70% of historic sockeye populations in the contiguous U.S. have been lost; those that remain show the mosaic pattern of population genetic structure typi-cal of the species, with most lake-dependent popula-tions being strongly isolated. The remaining popula-tion in Redfish Lake, Idaho is strongly divergent from all other sockeye, although closely related populations of the resident form of O. nerka (koakanee) occur in other Stanley Basin lakes [6]. All steelhead from the

Interior Columbia River (east of the Cascades) belong to the inland subspecies O. mykiss gairdneri. Whereas most coastal populations are dominated by anadro-mous fish, the costs of migration are higher for interior populations, and resident forms (rainbow trout) play important roles in most populations. Anthropogenic changes such as dams and water diversions further increase the costs of migration and might favor an evo-lutionary shift toward freshwater residency [7]. Interi-or Columbia chinook salmon are from two divergent lineages (fall-run and spring-run) having strongly cor-related suites of genetic and life history traits. The fall-run lineage is genetically more similar to coastal forms than it is to spring chinook salmon from the In-terior Columbia. The spring-run lineage has no close genetic relatives, although populations in the upper Fraser River have similar life history traits [8]. Two perhaps-not-inconsistent hypotheses about events near the end of the Pleistocene have been proposed to ex-plain these patterns: 1) the repeated and catastrophic Bretz floods extirpated the mainstem-spawning and rearing fall chinook populations, while the spring-run populations persisted in upper tributaries; subsequent recolonization of mainstem areas by coastal popula-tions would explain genetic similarities with contem-porary Interior Columbia and Snake fall-run popula-tions. 2) Stream-captures allowed movement of spring-run populations between upper-level tributaries of the Snake and Fraser Rivers.

Salmon in the Pacific Northwest are at a potential tipping point in their evolutionary history. Anthropo-genic changes over the last two centuries have eroded historic diversity and caused the loss of populations, evolutionarily significant units, and other major com-ponents of biodiversity [4]. Furthermore, about half the remaining populations in the contiguous U.S. are listed as Threatened or Endangered under the federal Endangered Species Act [9], and many populations in British Columbia are depressed as well [10]. If con-servation efforts are effective, these remaining compo-nents of biodiversity should allow Pacific salmon to continue diversify and to play dominant roles in their ecosystems. However, if most of the populations that are currently at risk are lost, the fabric of biodiversity might be so tattered that it would compromise the abil-ity of these species to respond to future evolutionary challenges.

References: [1] Montgomery D. R. (2000) Geolo-gy 28, 1107–1110. [2] Schindler D. E. et al. (2010)

49

Nature 465, 609-612. [3] Waples R. S. et al. (2008) Evolutionary Applications 1, 189-206 [4] Gustafson R. et al. (2007) Conservation Biology 21, 1009-1020. [5] Waples R. S. et al. (2001) J. Fish Biology 59 (Sup-plement A), 1-41. [6] Waples R. S. et al. (2011) Trans. Am. Fish. Soc. 140, 716-733. [7] Waples R. S. et al. (2008) Molecular Ecology 17, 84-96. [8] Waples R. S. et al. (2004) Evolution 58, 386-403. [9] Good T. P. et al. (2005) NOAA Tech. Memo., NMFS-NWFSC-66. [10] Holt C. A. et al. (2009) DFO Can. Sci. Advis. Sec. Res. Doc. 2009/058.

Biographical Sketch:

Robin Waples is a Senior Scientist and former Di-

rector of the Conservation Biology Division at NOAA Fisheries in Seattle. He has a background in popula-tion genetics and evolutionary biology, and a major theme of his research is to use scientific principles to address real-world problems in conservation and man-agement of biodiversity. For over a decade, he headed a group charged with developing the scientific basis for listing determinations and recovery planning for Pacific salmon and steelhead under the U.S. Endan-gered Species Act. Recent work has involved evaluat-ing evolutionary responses by salmon to major anthro-pogenic changes to their environments, including habi-tat modification, harvest, hatchery management, and climate change.

50

BUILDING THE FRESHWATER BIODIVERSITY ATLAS: DNA BARCODING AT RIVERSCAPE SCALES TO IDENTIFY EVOLUTIONARY LINEAGES OF FISHES IN THE COLUMBIA RIVER BASIN. Michael K. Young1, Kevin S. McKelvey2, Richard Cronn3, and Mi-chael K. Schwartz2, 1U.S. Forest Service, Rocky Mountain Research Station, 800 E. Beckwith Avenue, Missoula, MT 59801; mkyoung@fs.fed.us, 2U.S. Forest Service, Rocky Mountain Research Station, 800 E. Beckwith Avenue, Missoula, MT 59801, 3U.S. Forest Service, Pacific Northwest Research Station, 3200 SW Jefferson Way, Corvallis, OR 97330.

Introduction: There is growing interest in broad-scale biodiversity assessments of species and their lin-eages, particularly of aquatic taxa in basins undergoing rapid climate change. Genetic tools have been used for such assessments for decades, but spatial sampling considerations have largely been overlooked. Limited geographical coverage of many species represented in public databases, as well as sample misidentification and a poorly developed taxonomy, also represent a challenge to delineating and identifying the conserva-tion units that constitute species. Here, we demonstrate how intensive sampling efforts across the ranges of species and across river basins influenced identifica-tion of taxa and conservation units in portions of the Columbia River basin. Preliminary analyses of whole-mitome sequences of westslope cutthroat trout from throughout their North American range revealed broad divergence between some populations in adjacent river basins and shed light on their post-glacial recoloniza-tion of North America. Similarly, comparable analyses of the taxonomically challenging sculpins of the upper Columbia and Snake River basins indicated wide-spread polyphyly and paraphyly in the current cottid phylogeny, as well as abundant cryptic diversity that includes a host of undescribed groups that warrant sta-tus as named taxa[1] (one of which was recently de-scribed[2]). Genetic assessments based on spatially robust sampling designs hold promise to reveal previ-ously unrecognized biodiversity among freshwater fishes and inform paleohydrological reconstructions of western North America.

References: [1] Young MK et al. (2013) Molecular Ecology Re-

sources, 13, 583–595. [2] LeMoine et al. (2014) Zootaxa, 3755, 241–258.

Biographical Sketch of presenter:

Michael Young is a Research Fisheries Biologist with the USDA Forest Service, Rocky Mountain Re-search Station. He has published extensively on the ecology, status, and monitoring of freshwater fishes in the Rocky Mountains. He is currently working on the use of genetic tools for the discovery, delineation, and detection of conservation units of riverine freshwater species across the northwestern U.S.

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