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Hell Creek Natural Area
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Digital Geologic Quadrangle MapSylamore Quadrangle
DGM-AR-00844
Map and cross section digitized by Nathan Taylor
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Scale:Horizontal: 1 inch = 2000 feet
Vertical: 1 inch = 400 feet (Exaggeration: 5X)
Sea Level
200
400
600
800
1000
1200
1400
East Twin Creek
Brandenburg Mountain
Cove Hollow
Bishop Hollow
Sheep Hollow
White River
Dry CreekTwin Creek
Fault
Roasting Ear Fault
Sea Level
200
400
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AnticlineHell Creek
West Twin Creek
A A'NorthSouth
Description of Map Units
The topographic base is a Digital Raster Graphic (DRG). The DRG is a scanned image of a U.S. Geological Survey standard series topographic map published in 1964. Some of the colors of the DRG have been modified. 10,000-foot grid based on Arkansas coordinate system, north zone. (Lambert Conformal Conic). 1000-meter Universal Transverse Mercator grid ticks, zone 15 shown in blue. 1927 North American Datum.
Scale 1:24000
CONTOUR INTERVAL 20 FEETNATIONAL GEODETIC VERTICAL DATUM OF 1929
1 0 10.5Miles
1,000 0 1,000 2,000 3,000 4,000 5,000 6,000 7,000Feet1 0 10.5 Kilometers
QUADRANGLE LOCATION
Alluvial and terrace deposits (Quaternary) – Unconsolidated clay, silt, sand and gravel deposited by major streams and covering bedrock.
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Karst with scallop marks developed in Plattin Limestone, Hell Creek.
Joint Frequency
Rose diagram of strike frequency of joints recorded within the Sylamore Quadrangle.
n = 536
030
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150180
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ROAD CLASSIFICATION
( State Route
Medium-duty Light-duty
Unimproved road
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Kimmswick Limestone (Middle Ordovician) - Typically fine- grained, bioclastic limestone with micritic zones. Limestone is gray to white fresh with characteristic “sugary” appearance. Gray weathered. Micrite is gray both fresh and weathered. Outcrop locally splits into “nuggets” approximately 2 – 3 inches in diameter when struck with a hammer presumably due to the stylolites. Rare phosphate pebbles, chert lenses, and sinkholes. 0 – 40 ft (12 m) thick. Unconformable with the underlying Plattin Formation.
References
Acknowledgments: This map was produced for The National Cooperative Geologic Mapping Program (STATEMAP), a matching-funds grant program administered by the U.S. Geological Survey, under Cooperative Agreement Award G11AC20219. Special thanks to the private landowners who graciously allowed access to their properties. Very special thanks to Angela Chandler for her tireless dedication to this mapping project. Disclaimer: This map was digitized using ArcGIS ArcView 10 software on computers at the Arkansas Geological Survey (AGS). The AGS does not guarantee the accuracy of this map, especially when reproduced on any other system, with any other software or at a larger scale. As mapping continues and is refined, the data presented on this map may be updated. For the latest edition of this and other AGS maps and publications, please call Publication Sales at 501-296-1877, or visit the Vardelle Parham Geology Center, 3815 West Roosevelt Road, Little Rock, Arkansas 72204. This map is also available on our website in Portable Document Format at http://www.geology.ar.gov/geologicmaps/dgm_24k.htm. Suggested citation for this map: Rains, Daniel S. and Hutto, Richard S., 2012, Geologic map of the Sylamore quadrangle, Izard and Stone Counties, Arkansas: Arkansas Geological Survey, Digital Geologic Map, DGM-00844, 1 sheet.
2012 MAGNETIC NORTH DECLINATION AT CENTER OF SHEET
34' 19"
^ MN
IntroductionThis map depicts the bedrock geology of the Sylamore 7.5
minute topographic quadrangle of Stone and Izard counties, Arkansas. In this area over 1700 ft (518 m) of carbonate and clastic sedimentary rocks of Middle Ordovician to Late Mississippian age (approximately 470 – 320 Mya) are exposed.
Illustration of the geology of the Sylamore quadrangle was complicated by a lack of lateral persistence of some rock units. In areas where the Kimmswick Limestone (Ok) is too thin to be depicted at the scale of the map, it is combined into a single map unit with the Fernvale Limestone (Of). This convention was also followed for the Plattin and Joachim formations. Where the Joachim Dolomite is too thin to be depicted it is combined with the Plattin Limestone and they are depicted as a single unit (Op).
The geology of the Sylamore quadrangle was mapped in 1973 by E.E. Glick of the USGS for the 1:500,000 scale geologic map of Arkansas. This map builds on previous work but uses more detailed stratigraphy and depicts structure in greater detail. The geologic information on this map is based on field observations made between July 2011 and April 2012. Data collection sites were recorded using a Garmin GPSmap 76S global positioning satellite receiver. Bedrock dipping at less than 2º is depicted as horizontal.
Fernvale Formation (Upper Ordovician) - Typically massive, coarse-grained, fossiliferous limestone. Gray to white with pink mottles on fresh surfaces. Weathered outcrops are characteristically rounded, moss- covered, and friable. Fossils are mostly indistinct fragments although barrel-shaped crinoid segments are a notable exception. Ranges from 0-80 ft (0-30 m) thick. Unconformable with the underlying Kimmswick or Plattin formation.
Joachim Dolomite (Middle Ordovician) - Typically very fine granular dolostone with local interbedded fine- to medium- grained sandy limestone. The dolostone is tan to buff to gray on fresh surfaces and weathers light gray. The sandy limestone is gray on fresh and weathered surfaces. Ranges from very thin- to thick-bedded. Common small clear calcite vugs. The upper dolostone locally contains relatively larger calcite veins that stand in relief on weathered surfaces. The lower Joachim Dolomite locally contains breccia units composed of calcareous sandstone with angular dolostone rip- up clasts. Rare karst features include springs and sinkholes. Ranges from 5 – 140 ft (1 – 43 m) thick. Conformable with the underlying St. Peter Formation.
Plattin Limestone (Middle Ordovician) - Typically thin- and flat-bedded micrite. Light- to medium- gray on fresh surfaces and light-gray weathered. Common clear to white calcite blebs. Rare buff to light-yellow, very fine-granular limestone interbeds. Rare calcareous greenish-gray shale interbeds near base. Common well-developed karst features including disappearing streams, caves, sinkholes and springs. Springs are very common along the lower contact with the Joachim Formation. Local rare fossil fragments include corals, gastropods, and bryozoans. 40 – 180 ft (12 – 55 m) thick. Unconformable with the underlying Joachim Formation.
St. Peter Sandstone (Middle Ordovician) – Typically massive, fine- to medium-grained sandstone. White to buff on fresh surfaces. Brown to dark-greenish-gray to gray on weathered surfaces. Well-sorted and well-rounded. Locally contains minor clay. Faint thin- beds and cross-beds can be identified rarely. Usually calcareous and friable. Contains relatively resistant, cylindrical “sandstone pipes” ranging in diameter from approximately 4 in. to 3 ft (10 cm – 1 m). Springs and sinkholes are very common. Unconformable with the underlying Everton Formation. Ranges from 20 – 140 ft (6 – 43 m) thick.
Arkansas Natural Heritage Commission Official Site, Arostotle Web Design, 2010, Arkansas Natural Heritage Commission, 28 May 2012 < www.naturalheritage.com/>
Braden, A. K., Ausbrooks, S. M., and Smith, D. K., 2002, Geologic Map Of The Fiftysix Quadrangle, Stone County, Arkansas: Arkansas Geological Commission, Digital Geologic Map, DGM-AR-00290, 1 sheet.
Craig, W. W., 1975, Stratigraphy and Conodont Faunas of the Cason Shale and the Kimmswick and Fernvale Limestones of Northern Arkansas in Contributions to the Geology of the Arkansas Ozarks: Arkansas Geological Commission, Miscellaneous Publications 12, p. 61 – 95.
Frezon, S.E., Glick, E. E., 1959, Pre – Atoka Rocks of Northern Arkansas: Shorter Contributions to General Geology, Geological Survey Professional Paper 314 – H, p. 171 – 187.
Glick E. E., 1973, Preliminary Geologic map of the Sylamore quadrangle, Izard and Stone Counties, Arkansas: Arkansas Geological Commission, Geologic Worksheet, 1 sheet.
Ingram, R. L., 1954, Terminology for the Thickness of Stratification and Parting Units in Sedimentary Rocks: Geological Society of America Bulletin, v. 65, p. 937 – 938.
McFarland, J.D. 2004, Stratigraphic Summary of Arkansas: Arkansas Geological Commission, Little Rock, Arkansas, 38p.
Suhm, Raymond W., 1975, The Calico Rock Sandstone Member of the Everton Formation (Ordovician), Northern Arkansas: Arkansas Academy of Science Proceedings, Vol. XXIX
Mbv Batesville Sandstone (Chesterian) - Typically consists of very fine- to fine-grained, thin- to thick-bedded silty sandstone. Brownish-gray on fresh surfaces. Buff to brown on weathered surfaces. Commonly cross-bedded. Solution vugs common near base. Rarely calcareous near top. 0 - 120 ft (0 - 37 m) thick. Conformable with the underlying Moorefield Formation
Mm Moorefield Formation (Meramecian) - Typically consists of silty shale and limy siltstone. The shale is brown on fresh surfaces, tan on weathered surfaces and locally calcareous. The limy siltstone is medium to dark gray fresh, tan to brown weathered and thin-bedded. Ranges from 60 – 80 ft (18 – 24 m) thick. Appears to be unconformable with the underlying Boone Formation.
Topographic map of the Sylamore quadrangle. Dots indicate locations of data collection points.
Arkansas Geological SurveyBekki White, State Geologist and Director Geologic Map of the Sylamore Quadrangle,
Izard and Stone Counties, ArkansasDaniel S. Rains and Richard S. Hutto
2012SYLAMORE QUADRANGLEARKANSAS - VAN BUREN CO.
7.5 MINUTE SERIES (TOPOGRAPHIC)589 590 92 00'°
36 00'°
3983
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55'
T. 16 N.
T. 15 N.
600,000FEET
3972000mN
T. 15 N.
T. 14 N.
35 52' 30"°92 00'°
(MARCELLA)
7655 IV SW
INTERIOR - GEOLOGICAL SURVEY, RESTON, VIRGINIA - 1978
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(MELBOURNE 1:62,5
00)
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UNITED STATESDEPARTMENT OF THE INTERIOR
GEOLOGICAL SURVEY
7556 II SW
(CALICO ROCK) 5'7556 II SE
(BOSWELL) 2' 30" 1 990 000 FEET 588587586584583582
92 07' 30"°35 52' 30"°
3984
A
A'
Calcareous Sandstone
Interbedded Sandstone and Siltstone
Sandstone Unconformity
Dolomite
Stratigraphic Column
Calico Rock
Sandstone
Period
System
MemberForm
ation
Ordo
vician
Carb
onife
rous
1100
0 m.0 ft.
100
200
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100200
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12001300
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Miss
issipp
ian
400
Boone Formation
Everton Formation
St. Peter Sandstone
Plattin LimestoneJoachim Dolomite
Kimmswick LimestoneFernvale limestone
Moorefield FormationBatesville Sandstone
Stage
ChesterianMeramecian
Osagean/Kinderhookian
Upper
Middle
Correlation of Map UnitsHolocene andPleistocene Quaternary
Mississippian
Unconformity
UnconformityMb
MbvMm
Qat
MeramecianChesterian
Osagean/Kinderhookian
Ordovician
Unconformity
Unconformity
Unconformity
Ok
Op
Unconformity
Unconformity
Upper
Middle
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Everton Formation (Middle Ordovician) – Consists of interbedded dolostone, limestone and sandstone. The dolostone and limestone are typically dark-gray on weathered surfaces and range from light-gray to light-greenish-gray on fresh surfaces. Texture is mostly very fine- to fine-granular and locally sandy. Calcite veins are common and quartz veins are rare. Typically very thin- to thin-bedded. Stromatolites are prevalent. Typically hummocky- to ripple-bedded and locally bioturbated. The sandstone is white to buff on fresh surfaces and gray weathered. Grains range from fine to medium and subangular to rounded. Typically calcareous. Ranges from thin- bedded to massive. Sandstone intervals vary in thickness from 1 inch to several feet and are interspersed throughout the formation although they are not abundant relative to the carbonate units. Up to 500 ft (152 m) thick. Conformable with the underlying Calico Rock Sandstone Member (Suhm, 1975).
Calico Rock Sandstone Member - Calcareous, poorly-sorted, subangular sandstone. White to buff on fresh surfaces and gray weathered. Thin-bedded to massive. Stratigraphically positioned approximately 400 ft (122 m) below the top of the Everton Formation. Up to 100 ft (30 m) thick.
Boone Formation (Osagean) - Typically consists of thick- bedded, fine-granular to coarse-bioclastic limestone interbedded with chert in nodules and anastomosing beds. Limestone is usually gray fresh and weathered. Common fossils include crinoids and brachiopods though others have been noted (see McFarland, 2004). Phosphate pebbles and pyrite crystals are rare. Chert is commonly white to gray on fresh and weathered surfaces, but weathers tan locally. Geomorphology is characterized by erratic rolling hills with abundant sinkholes and springs, covered by unconsolidated regolith, composed primarily of red clay, and chert gravel. St. Joe Limestone Member (Kinderhookian to Osagean) Poorly exposed or absent. Where recognized, it consists of less than 2 feet of bioclastic, coarse- grained limestone. Gray fresh with faint pink and green- mottles. Gray on weathered surfaces. Phosphate pebbles and pyrite nodules are common. Manganese dendrites, calcite vugs and the absence of chert distinguish it from the upper Boone formation. Locally there is a pinkish- to light brownish-gray, fine- to medium-grained chert- and sandstone-pebble-conglomerate, up to 2 ft (.6 m) thick at the base. Undifferentiated Silurian and upper Ordovician rocks are also included in the Boone Formation because they are too thin and localized to be depicted separately. These consist primarily of red-mottled, gray micritite with fossil fragments and pyrite inclusions (Lafferty Limestone), and dark red to pale green conglomeratic sandstone and siltstone with shale interbeds and dark red and gray algal buttons (Cason shale). Where present these are noted with a yellow dot (see Symbols). Total thickness of the Boone Formation up to 400 ft (122 m). Unconformable with the underlying Ordovician units.
Symbols
o45 Strike and Dip
Contact
FAnticline axis
SMonocline axis
Silurian Outcropw Gravel pit
Mine or quarryuNatural Area
Line of cross-sectionA A'
Normal fault - dashed where concealed^ - Indicates downdropped block
^
- Indicates dip of fault planeRR45
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