Geologic map of the Lower Valley quadrangle, Caribou County, Idaho
<p><span>The Lower Valley 7.5-minute quadrangle, located in the core of the Southeast Idaho Phosphate Resource Area, includes Mississippian to Triassic…
Public-domain full text preserved in the Mountain Man Mining Library. Original source: pubs.usgs.gov.
Any use of trade, firm, or product names is for descriptive purposes only and does not imply endorsement by the U.S. Government. If printed on an electronic plotter directly from digital files, note that dimensional calibration may vary between electronic plotters and between X and Y directions on the same plotter, and paper may change size due to atmospheric conditions; therefore, scale and proportions may not be true on plots of this map. Digital files available at ://doi.org/10.3133/sim3215 Suggested citation: Oberlindacher, H.P., Hovland, R.D., Miller, S.T. , Evans, J.G., and Miller, R.J., 2018, Geologic map of the Lower Valley quadrangle, Caribou County, Idaho: U.S. Geological Survey Scientific Investigations Map 3215, 6 p., 1 sheet, scale 1:24,000, ://doi.org/10.3133/sim3215. Geologic Map of the Lower Valley Quadrangle, Caribou County, Idaho By H. Peter Oberlindacher, R. David Hovland, Susan T. Miller, James G. Evans, and Robert J. Miller ISSN 2329-132X (online) ://doi.org/10.3133/sim3215 tc al dsm Qa Qs QTb QTls QTs ta tb Ppc Ppg Ppm
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B-2 Table 1. Potassium-argon age determination. number
K-Ar age Description, unit B-1 2.1 ± 0.9 Ma basalt, QTb By Teledyne Isotopes Inc., Westwood, New Jersey, 1981 B-3
1.6 ± 0.7 Ma basalt, QTb B-2
2.2 ± 1.0 Ma basalt, QTb Sample Disturbed surface, as of field mapping in 1979 and 1980; may include open pits, waste disposal areas, and mining facilities; where dsm overlaps with disturbed surface as of 1984 photorevision, dsm is generally less extensive, and faults, contacts, and structures are commonly concealed, except in open pits that have not been backfilled Alluivum (Holocene)—Unconsolidated, poorly sorted gravel, sand, silt, and clay Surficial deposits (Holocene and Pleistocene)—Undifferentiated older alluvium and hillwash Basalt (Pleistocene or Pliocene)—Dark gray crystalline vesicular olivine basalt; sample B-1 was dated at 2.1 ± 0.9 Ma; sample B-2 was dated at 2.2 ± 1.0 Ma, sample B-3 was dated at 1.6 ± 0.7 Ma (Teledyne Isotopes, written commun., 1981, see table 1) Sedimentary deposits (Quaternary and (or) Tertiary) Landslide deposits (Quaternary and (or) Tertiary) Thaynes Formation (Lower Triassic) Portneuf Limestone Member Upper part—Yellowish-beige to reddish-brown sandstone and blue-gray limestone; local crossbedding and dolomitization of sandstone; limestone locally contains gray chert nodules; about 107 m thick, top not exposed Lower part—Gray limestone, generally cliff-forming; minor very fine-grained sandstone and siltstone; about 153 m thick Member C—Olive to brown siltstone containing dark-gray limestone nodules in upper part; interbedded with yellowish-brown sandstone and limestone near top; gray to black fissile siltstone and minor dark-gray limestone in lower part; about 213 m thick Member B—Yellowish-brown calcareous platy siltstone and minor nodular gray limestone; about 183 m thick Member A—Dark-gray to black silty limestone; Meekoceras ammonite zone at base; about 168 m thick Ankareh Formation (Lower Triassic) Lanes Tongue—Reddish-brown to red sandstone and siltstone; 60 m thick; top not exposed; where present, separates upper and lower parts of the Portneuf Limestone Member of the Thaynes Formation Dinwoody Formation (Lower Triassic)—Consists mainly of interbedded siltstone, limestone, and subordinate sandstone. The true thickness of the Dinwoody Formation in the quadrangle cannot be determined because of poor exposure and structural complications. Cross-sectional data yield a thickness of about 519-610 meters. The Dinwoody Formation is mapped as undifferentiated except in the southern part of the quadrangle, where it is divided into five informal units: Upper part—Brownish-gray limestone and siltstone Middle and upper parts—Undifferentiated Middle part—Blocky-weathering olive-gray to brownish-gray siltstone and minor very fine-grained sandstone and limestone Lower and middle parts—Undifferentiated Lower part—Olive-gray shaly siltstone and minor silty limestone Phosphoria Formation (lower Permian) Cherty shale member—Dark-gray to grayish brown cherty siltstone and mudstone and minor phosphatic siltstone and phosphatic mudstone; 48 m thick Rex Chert and cherty shale members—Undifferentiated Rex Chert Member—Gray to bluish-gray chert, locally light gray to white; minor argillaceous chert; ledge forming; 10-12 m thick Meade Peak Phosphatic Shale Member—Dark-brown phosphorite, siltstone, mudstone and minor limestone and sandstone; phosphorite concentrated in upper and lower parts of member; swale-forming; rarely exposed; about 40-50 m thick Park City Formation (lower Permian) Grandeur Tongue—Light-gray to brownish-gray dolomite and minor siltstone, chert, and phosphatic chert; ledge-forming Wells Formation (Permian and Pennsylvanian) Upper member (lower Permian)—Brownish-gray to reddish-brown quartzose sandstone and quartzite and dark- to light-gray dolomite beds, lenses, and nodules; quartzose sandstone and quartzite are locally crossbedded; about 520 m thick Lower member (lower Permian and Middle Pennsylvanian)—Gray limestone and quartzite and siltstone; limestone locally cherty and sandy; 293 to 316 m thick Phosphatic marker bed—In upper part of lower member of Wells Formation; a 0.5- to 1.2-m-thick phosphorite and phosphatic silty mudstone bed occurs 33 m below top of formation Chesterfield Range Group (Upper Mississippian) Monroe Canyon Limestone—Dark gray limestone and minor siltstone and sandstone; locally dolomitic; contains large horn corals and brachiopods near top of formation; at least 281 m thick; base not exposed EXPLANATION OF MAP SYMBOLS Disturbed surface, as 1984 photorevision; present topography differs from that shown on map; faults, contacts, and structures originally mapped in disturbed surface areas may be concealed, or removed, or their locations may be altered as a result of subsequent mining activity; open pits, where present, are large elongate trenches that follow the locus of the Meade Peak Phosphatic Shale Member of the Phosphoria Formation; may include dsm Contact—Dotted where concealed; dashed where approximate Fault—Dotted where concealed Normal fault—Ball and bar on downthrown side Strike-slip fault—Arrows indicate relative horizontal movement Thrust fault—Sawteeth on upper plate Generic fault—Unknown or unspecified orientation Fold—Showing trace of axial surface; dotted where concealed Anticline—Showing crestline and direction of plunge Syncline—Showing troughline and direction of plunge Overturned anticline—Showing crestline and direction of plunge Overturned syncline—Showing troughline and direction of plunge Strike and dip of bedding Strike and dip of overturned bedding Horizontal bedding Sample location for K-Ar determination (see table 1) DESCRIPTION OF MAP UNITS Unconformity Unconformity Unconformity Unconformity Unconformity Unconformity Unconformity Holocene Holocene and Pleistocene Pleistocene or Pliocene Lower Triassic Lower Permian Lower Permian and Middle Pennsylvanian Upper Mississippian QUATERNARY QUATERNARY AND (OR) TERTIARY TRIASSIC PERMIAN PERMIAN AND PENNSYLVANIAN MISSISSIPPIAN CORRELATION OF MAP UNITS Qa dsm Qs QTs QTb QTls tpu tc tb ta al du d dm dmu dlm dl Ppc Ppr
Ppm Ppg Pwu P wl Mmc IDAHO MAP LOCATION SCALE 1:24,000 1 MILE 1 KILOMETER APPROXIMATE MEAN DECLINATION, 2018 111/2° MAGNETIC NORTH TRUE NORTH Base from U.S. Geological Survey 1:24,000 Lower Valley, 1984 Transverse Mercator UTM 1927 Zone 12 Geology mapped in 1979 and 1980 by H. Peter Oberlindacher, R. David Hovland, and Susan T. Miller and compiled in 1998 by James G. Evans. GIS database and digital cartography by Robert J. Miller and Barry C. Moring. Edited by Claire Landowski; digital cartographic production by Donna L. Knifong Manuscript approved for publication May 5, 2012 U.S. Department of the Interior U.S. Geological Survey Scientific Investigations Map 3215 Pamphlet accompanies map Qs Qa Qa QTb Ppg dsm
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A N T ICLIN E ENOCH VALLEY FA ULT R AS MUSSE N FAULT RA SMU SSEN FA ULT BLACKFOOT FAULT WOO LEY VALLEY ANTICLINE W O OL EY R AN G E SYNCLIN E SYNCL IN E TRAIL R E E K Ppg Ppc S CH MID SYNCLI NE Qs P*wl Ppg Ppr P*wl Ppr Ppc 111°22'30 111°22'30" 111°30' 111°30' 42°52'30" 42°52'30" 42°45' 42°45'