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144° 50’ 144° 40’

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ALASKA

Tanacross Quadrangle

State of AlaskaDepartment of Natural Resources

Division of Geological & Geophysical Surveys

ALASKA

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APPROXIMATE MEANDECLINATION, 2008

CONTOUR INTERVAL 100 FEETDATUM IS MEAN SEA LEVEL

SCALE 1:63,360

The State of Alaska makes no express or implied warranties (including warranties for merchantability andfitness) with respect to the character, functions, or capabilities of the electronic data or products or theirappropriateness for any user's purposes. In no event will the State of Alaska be liable for any incidental,indirect, special, consequential, or other damages suffered by the user or any other person or entity whetherfrom the use of the electronic services or products, or any failure thereof or otherwise. In no event will the StateofAlaska's liability to the Requestor or anyone else exceed the fee paid for the electronic service or product.

DGGS publications can be purchased or ordered from the Fairbanks office at:Alaska Division of Geological & Geophysical Surveys3354 College RoadFairbanks,AK 99709-3707451-5000 (phone) dggspubs@alaska.gov451-5050 (fax) http://www.dggs.dnr.state.ak.us

ALASKA DIVISION OF GEOLOGICAL &GEOPHYSICAL SURVEYS

RECONNAISSANCE INTERPRETATION OF 1978-1983 PERMAFROST, ALASKA HIGHWAY CORRIDOR, PART OF THE TANACROSS C-6 QUADRANGLE, ALASKA

byR.D. Reger¹ and T.D. Hubbard²

2010Affiliations¹ Reger’s Geologic Consulting, Soldotna, Alaska² Alaska Division of Geological & Geophysical Surveys

Interpreted permafrost field verification by:R.D. Reger, D.N. Solie, T. D. Hubbard (2008)

Air photo interpretation by:R.D. Reger (2007)

GIS layers digitized by:G. Davidson, T. D. Hubbard, S. Panda (2008, 2009)

Digital cartography by:P. Gallagher and G. Speeter (2009)

Topographic base map from:Tanacross C-6 Quadrangle,U.S. Geological Survey digital raster graphic images, 1997.Map projection: UTM zone 7Datum: NAD 27

Maps Showing Location of Study Area

PRELIMINARY INTERPRETIVE REPORT 2009-6c Reger and Hubbard(2010) SHEET 1 of 4

Explanatory text accompanies map

Explanatory Material for Permafrost Map

Introduction

Permafrost, or perennially frozen ground, is rock or soil that remains continuously colder than 0°C for 2 yrs or longer (Muller, 1947; Ferrians and others, 1969; Péwé, 1966, 1982). Based on the interpretation of ~1:65,000-scale false-color, infrared aerial photographs, this map illustrates the inferred extent and estimated ice content of permafrost between the ground surface and a depth of ~20 ft (6 m) in the proposed corridor straddling the Alaska Highway between the Robertson River and Tetlin Junction in the Tanacross Quadrangle on the dates of the aerial photographs taken in July 1978, August 1980, and July 1983. The presence or former presence of permafrost and the ground-ice content are inferred from several indicators, including vegetation, slope and aspect, landform, soil type, local drainage, and terrain features, such as open-system pingos, polygonal ground, and thermokarst pits, gullies, and ponds (Kreig and Reger, 1982). Because of a lack of subsurface data, our interpretation should be considered tentative until validated by multi-year ground-temperature measurements that confirm the persistence of frozen ground. Permafrost classifications in areas that were burned just prior to August 1980 are less reliable than in unburned areas because the vegetation was destroyed or significantly altered and, in these areas, interpretation of permafrost is based primarily on landform and setting, which are less diagnostic than vegetation. The user is cautioned that this map has not been verified by field observations, except very locally, although we have considerable field experience in the Tanana River valley and during our interpretation referred to available published and unpublished reports. Physical properties of map units are extrapolated from similar deposits in the region and from previously published reports and data. Detailed subsurface investigations should be completed prior to development.

Description of permafrost map units

Symbols indicate the inferred continuity of permafrost in upper-case letters and the estimated ice content in lower-case letters. For example, ‘Dm’ indicates that discontinuous permafrost with low to moderate ice content is inferred between the ground surface and a depth of ~20 ft (6 m). Classes of permafrost continuity are consistent with classes used in previous mapping in Alaska (Ferrians, 1965; Kreig and Reger, 1982; Brown and others, 1998):

Symbol Description

F CONTINUOUSLY FROZEN—More than 90 percent of the area is inferred to be underlain by permafrost

D DISCONTINUOUSLY FROZEN—Between 50 and 90 percent of the area is inferred to be underlain by permafrost

S SPORADICALLY FROZEN—Between 10 and 50 percent of the area is inferred to be underlain by permafrost

G GENERALLY UNFROZEN (ISOLATED MASSES)—Between 0 and 10 percent of the area is inferred to be underlain by permafrost

U NO PERMAFROST—Seasonally frozen but the ground is inferred to be warmed to a temperature above 0°C at least once during any 2 yr period

r MODERATE TO HIGH ICE CONTENT—Estimated to typically contain 50 to >1,000 percent soil moisture relative to dry weight m LOW TO MODERATE ICE CONTENT—Estimated to typically

contain 25 to 50 percent soil moisture relative to dry weight

l LOW ICE CONTENT—Estimated to typically contain 6 to 25 percent soil moisture relative to dry weight

MAP SYMBOLS

------- PHOTOINTERPRETIVE BOUNDARY—All boundaries are inferred or approximately located

? QUESTIONABLE IDENTIFICATION

☼ INTACT OR BREACHED OPEN-SYSTEM PINGO

● A LOCALITY DISCUSSED IN REPORT

References cited

Brown, J., Ferrians, O.J., Jr., Heginbottom, J.A., and Melnikov, E.S., 1998, Revised 2001, Circum-arctic map of permafrost and ground-ice conditions: Boulder CO: National Snow and Ice Data Center/World Data Center for Glaciology. Digital media.

Ferrians, O.J., Jr., 1965, Permafrost map of Alaska: U.S. Geological Survey Miscellaneous Geologic Investigations Map I-445, 1 map sheet, scale 1:2,500,000.

Ferrians, O.J., Jr., Kachadoorian, Reuben, and Greene, G.W., 1969, Permafrost and related engineering problems in Alaska: U.S. Geological Survey Professional Paper 678, 37 p.

Kreig, R.A., and Reger, R.D., 1982, Air-photo analysis and summary of landform soil properties along the route of the Trans-Alaska Pipeline System: Alaska Division of Geological & Geophysical Surveys Geologic Report 66, 149 p.

Muller, S.W., 1947, Permafrost or permanently frozen ground and related engineering problems: Ann Arbor, Michigan, J.W. Edwards, Inc., 231 p.

Péwé, T.L., 1966, Permafrost and its effect on life in the North: Corvallis, Oregon State University Press, 40 p.

———1982, Geologic hazards of the Fairbanks area, Alaska: Alaska Division of Geological & Geophysical Surveys Special Report 15, 109 p.

Index map

°

Dm?

G

Sl

Dm

Sl?

Fr

G?

Sm?Sm

Fr?

Dr

Fm

Dl Dl?

CONTINUOUSLY FROZEN, MODERATE TO HIGH ICE CONTENT

CONTINUOUSLY FROZEN, LOW TO MODERATE ICE CONTENT

DISCONTINUOUSLY FROZEN, MODERATE TO HIGH ICE CONTENT

DISCONTINUOUSLY FROZEN, LOW TO MODERATE ICE CONTENT

DISCONTINUOUSLY FROZEN, LOW ICE CONTENT

SPORADICALLY FROZEN, LOW TO MODERATE ICE CONTENT

SPORADICALLY FROZEN, LOW ICE CONTENT

GENERALLY UNFROZEN (ISOLATED PERMAFROST MASSES)

NO PERMAFROST

EXPLANATION OF MAP UNITS(All map units may not appear on this sheet)

U

Fm?