Geologic Map of the Southern Portion of the Clayton Quadrangle, Custer

IDAHO GEOLOGICAL SURVEY TECHNICAL REPORT 20-02 BOISE-MOSCOW IDAHOGEOLOGY.ORG KROHE AND OTHERS

CORRELATION OF MAP UNITS Cash Creek Quartzite (middle Cambrian)—Quartzite, gray to 4TA09: Cambrian quartzite of Cash Creek (Єc) 5TA09: Ordovician Kinnikinic Quartzite (Ok) EOLOGIC AP OF THE OUTHERN ORTION OF THE LAYTON UADRANGLE, USTER OUNTY, DAHO Cc light-gray on weathered surface, light-gray to off-white on fresh G M S P C Q C C I Unconsolidated Sedimentary and Mass Movement Deposits surface. Unit is fine to coarse grained with pebbly layers and lenses 30 1785 n= 86 n= 87 (Hobbs and Hays, 1990); grains are subrounded and moderately to 1860 20 poorly sorted. All sand is quartz, there is no feldspar. Unit is medium Qls Qal Qc Qcq QUATERNARY to thick-bedded, has blocky weathering and is a cliff former. Unit 25 Volcanic Rocks has sharp contacts with the overlying Єs and underlying Єcb. The ------Unconformity------CENOZOIC unit is ~396 m thick. Nicholas J. Krohe, Daniel T. Brennan, Paul K. Link, David M. Pearson, and L. Trent Armstrong 15 Lower carbonate of Squaw Creek (middle to early Cambrian)— 20 Tcv TERTIARY Ccb 1958 Idaho State University, Department of Geosciences Eocene Carbonaceous siltite, dark-gray to light-gray on weathered surface, dark purplish-gray to light-gray to turquoise on fresh surface. Unit is 2020 (modified from Plate 1 in Krohe, 2016, ISU M.S. Thesis) Sedimentary Rocks fine to very fine grained and well sorted. Unit contains mainly quartz 15 sand with some micaceous and calcareous layers. Unit is strikingly 10

Copper Basin Thrust Sheet Number laminated to thinly bedded, weathers fissile to flaggy, and has an Number Clayton-Bayhorse Section MISSISSIPPIAN 2102 2691 oily sheen. Unit has undergone phyllite-grade metamorphism and 10 2561 ---Unconformity--- forms slopes. Both upper and lower contacts are sharp. The unit is ~175 m thick. 5 Upper and Middle 1433 Osm Quartzite of Boundary Creek (early Cambrian to 5 Ordovician CZbc Neoproterozoic)—Quartzite, tan to light-gray on weathered CMsr Squaw Creek Section Ok ORDOVICIAN surface, light-gray to off-white on fresh surface. Unit contains fine to Middle medium sand, with pebble layers near base. Sand is subrounded, Ordovician 0 0 Occ Oe moderately to well sorted and is all quartz. Thick to thin bedding, 500 1000 1500 2000 2500 3000 3500 500 1000 1500 2000 2500 3000 3500 with anastomosing bedding present in some thinly bedded layers. Age (Ma) Age (Ma) ---Unconformity------Unconformity--- Unit weathers blocky and forms cliffs. A sharp contact is present Middle Cambrian with the overlying Occ and the basal contact is a fault or covered by 5NK15: Cambrian quartzite of Cash Creek (Єc) DTB17-17: Cambrian-Neoproterozoic Clayton Mine Quartzite (ЄZc) Cs Eocene Challis Volcanic Group. The unit is ~91 m thick. 14 CAMBRIAN n= 300 n= 91 Unmapped Thrust Fault Cc 1769 Quartzite west of Squaw Creek (Neoproterozoic?)—Quartzite, dark 1774 Igneous Rocks Lower Cambrian CZq 80 Ccb weathered surface, gray to off-white on fresh surface. Unit is fine to 12 ------Unconformity------coarse grained, moderately sorted, with subangular to subrounded CZc 70 Intrusive Rocks CZbc grains, predominately quartz. Unit is medium to thick Thrust Fault bedded,weathers blocky and forms cliffs. The contacts of the unit are 10 60 Zg Normal Fault fault-bounded or covered by Eocene Challis Volcanic Group, thus ca. 601 Ma CZq the thickness is undetermined 50 8 Ediacaran Zsq CLAYTON-BAYHORSE SECTION 40 Normal Fault Number 1844 6 Zr CZc NEOPROTEROZOIC Clayton Mine Quartzite (middle Cambrian? to Neoproterozoic)—Quartzite; weathered surface is pink to 30 Zb dark-gray to brownish-tan, fresh surface is dark grayish-tan to 4 off-white. Unit is coarse to medium grained, with local vein quartz 20 Zgc pebbles and silty layers. Unit is poorly sorted; grains are rounded Qc to subrounded. Unit mainly contains quartz, with some altered 2582 2 Zd 10 (only shown in cross-section) Cryogenian feldspar. Contains planar and trough cross-beds, weathers blocky and is a cliff former. The lower contact of the Oc is gradational with Zt the Osq and the upper contact with the Oe is a sharp 0 0 667 Ma Qal disconformity. The unit is ~975 m thick. 500 1000 1500 2000 2500 3000 3500 500 1000 1500 2000 2500 3000 3500 Age (Ma) Age (Ma) Zsq Interbedded siltstone and quartzite (Neoproterozoic)— Quartzite; pinkish-gray on weathered surface, pinkish-white on fresh surface. 3TA09: Cambrian-Neoproterozoic quartzite of Boundary Creek (ЄZbc) DTB17-18: Cambrian-Neoproterozoic Clayton Mine Quartzite (ЄZc) Unit is predominately fine grained but can range from fine to coarse 20 Challis Volcanic Group, undifferentiated (Eocene)—Volcanic flows 14 Tcv grained with local vein quartz pebble layers. Unit is moderately Tcv 5NK15 Unmapped and tuffs, rusty orange to dark brown or dark gray on weathered n= 79 14 n= 109 33 SYMBOLS sorted, grains are sub-rounded; bedding is m-thick with sharp surface, tan to gray on fresh surface. Fine- to medium-grained Cs 54 contacts between beds. Some ripple marks are present. Unit 1180 Cc Tcv groundmass; 1-10% phenocrysts (often eroded out), phenocrysts 12 2707 weathers to a blocky cliff former. Thickness ranges from 215-610 m. 12 Contact: dashed where approximately located. <1mm in length. Unit contains plagioclase and pyroxene, and forms 1714 ridges; large granitic boulder was found in a lava flow just east of 34 Siltstone: Weathered surface is reddish-brown, fresh surface 10 C lower Squaw Creek. light-brown; silt to very-fine sand particles, sharp contacts, weathers 10 Qc Normal fault: ball and bar on downthrown side; 1440 platy, thin bedded to laminated. 1790

8NK15 dashed where approximately located; dotted r 69 8 NEOPROTEROZOIC INTRUSIVE ROCKS 2474 e

where concealed. b 8 Dolomite: Dark-brown weathered, gray-brown on fresh surface, fine to Qal m

Ramshorn gabbro (Neoproterozoic)—Pyroxene gabbro, dark gray u Tcv Thrust fault: teeth on upper plate; dashed where Zg medium grained, some sandy layers, sharp contacts, weathers blocky. 1750 2650 N on weathered surface, dark green on fresh surface; fine to Number 6 678 Occ approximately located; dotted where concealed. 6 medium-grained groundmass, phenocrysts ~1 mm in length. OrZr Ramshorn Slate (Neoproterozoic)—Slate, brownish-green on Tcv Phenocrysts predominately consist of plagioclase and weathered surface, light brownish-green on fresh surface. Unit Tcv 4 47 Anticline axial trace, dashed where approximately clinopyroxene. Intrusion occurs predominately in sills with minor contains predominately silt and clay sized particles; some fine- to 4 dikes. Unit only intrudes the Zr within the map area. U-Pb age of 34 located; dotted where concealed. medium-sand interbeds. Unit is laminated to thin-bedded, weathers 17 baddeleyite from a similar intrusion within the Bayhorse Lake platy; typically strongly cleaved near intrusions and is a slope CZq 2 2 Ccb quadrangle indicates a 601 ± 27 Ma crystallization age (Brennan former. Gabbro (Zg) only intrudes Ramshorn Slate within the field Cc 49 and others, 2020). 35 Tcv Strike and dip of bedding. area. Unit is of Neoproterozoic (Ediacaran) age (Brennan and others, 2020). The basal contact is a sharp erosional disconformity 0 0 SEDIMENTARY ROCKS with the underlying Bayhorse Dolomite; upper contact with the Osq 15NK15 500 1000 1500 2000 2500 3000 3500 500 1000 1500 2000 2500 3000 3500 Detrital zircon sample. Sedimentary and low-grade metasedimentary rocks are dominant in is gradational. The unit is ~610 m thick. 15NK15 Age (Ma) Age (Ma) 46 the Clayton quadrangle. The Paleozoic section within the Bayhorse region consists of Middle Ordovician and younger rocks that appear 15NK15: Cambrian quartzite of Boundary Creek (Єbc) 8 30 10NK15: Neoproterozoic Ramshorn Slate (Zr) Fault breccia observed. to unconformably overlie Middle Cambrian and older rocks, Lower strata of the Bayhorse Anticline section are exposed to the northeast suggesting that much of the Upper Cambrian and Lower Ordovician near Bayhorse. Shown here in cross-section. n= 286 31 CZbc 2528 n= 101 section present in southeastern Idaho is missing here. The Squaw 25 12 Creek section is interpreted to be a slightly more complete Bayhorse Dolomite (Neoproterozoic)—Gray to tan/orange, primarily 24 Zb 66 stratigraphic package, transported from the west on the hanging wall dolo-micritic mudstone. Locally contains chert nodules, dark-gray 2462 2668 of the inferred Squaw Creek thrust fault (see cross section C-C’). silicified chert lithic (pisolite?) grainstone beds, and rare fine-grained 10 3TA09 Qc INTRODUCTION sandy laminations that infrequently show cross-stratification. 20 1174 Tcv 47 Overlies Garden Creek Phyllite in apparent ~10 m gradational 4TA09 2 Paleozoic and older strata were folded during the Sevier orogeny Osm The Bayhorse-Clayton region of Custer County, Idaho displays the (Late Jurassic to Late Cretaceous). The Sevier thrust belt is contact. Approximately 375 m thick. 8 45 thickest relatively intact succession of Neoproterozoic strata north of dominated by west-dipping, laterally continuous thrusts that largely 15 64 the Snake River Plain and west of the Lemhi Arch. The Clayton Garden Creek Phyllite (Neoproterozoic)—Dark-gray to nearly black, 40 do not involve basement. The field area is located southwest of the Zgc quadrangle contains thick exposures of these sedimentary and main Sevier fold thrust belt as defined by Skipp (1988). Within this slightly calcareous phyllite. Overlies in apparent conformity the 6 Number 1711 80 23 Qls Number 4 metasedimentary rocks. Bedrock geologic units within the Clayton mapping area, the Salmon River assemblage was thrust over the basal dolomite of Bayhorse Creek. Approximately 500 m thick. Qcq 10 12 quadrangle crop out at the surface or are covered by a thin layer of Saturday Mountain Formation along the Copper Basin thrust. The 1125 1398 soil, colluvium, or Challis Volcanic Group. Areas with thicker inferred Squaw Creek thrust is interpreted to be cut by a younger 4 Basal Dolomite of Bayhorse Creek (Neoproterozoic)—Light- to 1430 19 54 Qal Quaternary deposits are mapped as Quaternary. normal fault. Zd 1632 74 medium-gray, weathers grayish-orange to brown, thin to medium 5 665 33 Initial detrital zircon work in the area was conducted by Armstrong tabular bedded, sandy dolomicritic mudstone. Lower contact is in 2 2640 (unpublished). The map is primarily the result of field mapping REGIONALLY EXTENSIVE PALEOZOIC STRATA apparent depositional conformity above the tuff of Daugherty Gulch. Approximately 50 m thick within the Daugherty drill hole (Jacob, Qc 36 conducted in the summer of 2015 (Krohe, 2016), previous mapping Qcq 1990). 65 by others in the region (Hobbs and others, 1991), and detrital zircon MCsr Salmon River assemblage (Mississippian-Cambrian?)—Argillite, 0 0 CZc work in 2015 and 2016. The stratigraphic ages shown here are purplish-black to dark-gray to tan-gray on weathered surface. 500 1000 1500 2000 2500 3000 3500 Tuff of Daugherty Gulch (Neoproterozoic)—Volcanic lithic tuff showing 500 1000 1500 2000 2500 3000 3500 based on recent mapping of the Bayhorse anticline to the northeast, Grainsize is clay, silt, with fine-grained sand that is well rounded and B’ Zt lower-greenschist-facies metamorphism. Contains ~50% clasts of Age (Ma) Age (Ma) additional detrital zircon samples (Brennan, 2018), and dating of the well sorted. Bedding is laminated to thin, and anastomosed in some rhyolite, lesser quartz and metasandstone (< 25 cm) in fine grained crosscutting ca. 601 Ramshorn gabbro sills in the Bayhorse Lake regions; some small-scale cross-bedding is present locally. Unit 8NK15: Neoproterozoic-Cambrian quartzite (ЄZq) Zr matrix. Age is 664 ± 7 Ma (SHRIMP: Lund and others, 2010), 668 ± 52 quadrangle (Brennan and others, 2020). weathers platy and forms slopes. The MЄsr is in fault contact above 10 0.8 (CA-TIMS: Isakson, 2017). Shown only in cross-section. DETRITAL ZIRCON INTERPRETATION the underlying Osm via the Copper Basin thrust. The upper contact 2457 n= 104 66 9 Several thrust faults of the greater Bayhorse region were remapped Analyses were performed at the Arizona LaserChron Center. The 26 85 Zsq 53 is not exposed. The unit thickness is unknown, but is at least 1000 20 as normal faults (Krohe, 2016; Brennan, 2018), which has m. numbers above the peaks are ages in Ma, which are picks from

C reorganized the Neoproterozoic-Ordovician stratigraphy into a Excel. Samples labeled “TA” were analyzed by Trent Armstrong for o 46 38 REFERENCES CITED B 44 p 55 straight stratigraphic section. This straight section has allowed Saturday Mountain Formation (Upper and Middle p 71 52 14 Osm undergraduate research in 2010, “NK” samples were analyzed by e Osm Zg Ordovician)—Dolomite, dark-gray to purplish-gray to tannish-gray

r several lithologically similar units to be correlated. Nick Krohe in 2016, and “DTB” samples were analyzed by Daniel B 37 Bennett, E.H., 1986, Relationship of the trans-Challis fault system in 2540 a on weathered surface, light purplish-gray on fresh surface. Unit is 15

s Brennan in 2018. See Brennan (2018) for discussion of the entire i

n Tcv 58 24 Zg fine crystalline, well sorted, with thin to massive bedding; central Idaho to Eocene and Basin and Range extensions: Geology,

t Clayton-Bayhorse detrital zircon sample suite. h 36 44 9 v. 14, no. 6, p. 481–484.

32 r 23 non-effervescent to slightly effervescent when scratched. u

s

t Interbedded chert layers and shales are present in some sections; 56 Ok Zg DESCRIPTION OF MAP UNITS Breckenridge, R.M., Lewis, R.S., Adema, G.W., and Weisz, D.W., 2003, In the Clayton-Bayhorse section, a sandstone layer in the Ramshorn 46 unit is highly fractured with quartz and calcite vein fill. Unit weathers 1832 Osm Zg 10 Slate (Zr; 10NK15) contains significant Grenville-aged grains, 75 blocky and can spark upon hammer strike. The unit lies conformably Miocene and younger faults in Idaho: Idaho Geological Survey Map Number 42 28 consistent with Ediacaran units (in particular the Papoose Creek 21 72 46 Qal Alluvium (Quaternary)—Unconsolidated clay- to gravel-sized above the Ok. The MЄsr is structurally above the Osm. The Osm unit 8, scale 1:1,000,000. particles within modern drainages. Angularity of the grains Formation) in southeastern Idaho (Brennan, 2018). The sample from is ~915 m thick. Black shale at the base of the unit in sec. 22, T. 11 the lower Clayton Mine Quartzite (DTB17-18) also contains 63 varies and composition is dependent upon the bedrock of the N., R. 17 E., yielded probable late Middle Ordovician fauna (Hobbs Brennan, D.T., 2018, Geologic mapping and detrital zircon provenance of Tcv significant Grenville-aged grains. The upper Clayton Mine Quartzite drainage. Unit thickness varies. the Bayhorse anticline, Custer Country Idaho: Revised 5 and Hays, 1990). 685 sample (DTB17-17) shows a distinct change in provenance with the 36 24 Neoproterozoic to lower Paleozoic stratigraphy: Idaho State Ok Qc Colluvium (Quaternary)—Locally sourced, poorly sorted, silt- to Ok Kinnikinic Quartzite (Middle Ordovician)—Quartz arenite University M.S. thesis, 155 p. loss of Grenville-aged grains and presence of a significant ca. 1780 boulder-sized deposits of various compositions. Unit thickness Ma age peak. This provenance change is correlated with the rise of 44 Zsq (quartzite); weathered surface is dark grayish to tan, fresh surface 48 Zg varies. is light-gray. Unit is thin- to medium-bedded. Grains are fine sand, the Transcontinental Arch (cutting off the supply of Grenville-aged 78 Brennan, D.T., Pearson, D. M., Link, P. K., and Chamberlain, K. R., 2020, vitreous; grains are well sorted and well rounded. Unit weathers 0 grains) in Early Cambrian time. Middle Ordovician Ella Dolomite 29 Colluvium composed of quartzite (Quaternary)—Quartzite-bearing Geologic map of the Bayhorse anticline, Custer County, Idaho: Idaho Zg Qcq blocky. The Ok lies in gradational stratigraphic contact with the 500 1000 1500 2000 2500 3000 3500 overlies the Clayton Mine Quartzite, suggesting that much of the Qcq colluvium. Grain size ranges from clay to boulder and clast Geologic Survey Technical Report, scale 1:24,000. 22 15 C’ Osm above, and the Oe below. The unit is ~230 m thick. Age (Ma) Upper Cambrian and Lower Ordovician section is missing. Ok composition is entirely quartzite. This unit underlies a large portion Gehrels, G., and Pecha, M., 2014, Detrital zircon U-Pb geochronology of the central map area. Unit thickness varies. Oe Ella Dolomite (Middle Ordovician)—Sandy dolomite to dolomite, The Squaw Creek section shows this same provenance change. At 52 Zg and Hf isotope geochemistry of Paleozoic and Triassic passive dark-brown to brownish-tan on weathered surface, gray on fresh Link, P. K., Stewart, E. D., Steel, T., Sherwin, J., Hess, L. T., and the base, samples 15NK15 and 3TA09 of the Cambrian Quartzite of 33 Qls Landslide (Quaternary)—Landslide or slumped material ranging from margin strata of western North America: Geosphere, v. 10, p. 49–65. 15 Qls surface. Grain-size is silt to fine sand; thick to medium bedding, McDonald, C., 2016, Detrital zircons in the Mesoproterozoic upper Boundary Creek contain significant Grenville-aged grains plus MCsr silt- to boulder-sized material. Contains predominantly boulders of 22 52 weathers blocky. The Oe lies disconformably over the Oc and Belt Supergroup in the Pioneer, Beaverhead and Lemhi Ranges, distinct small populations of 680 to 660 Ma grains, likely locally quartzite. Unit thickness varies. Hobbs, S.W., and Hays, W.H., 1990, Ordovician and older rocks of the conformably with a gradational contact below the Ok. Montana and Idaho: The Big White arc: in Maclean J.S., and Sears, derived. The stratigraphically higher samples (5NK15 and 4TA09) 25 67 Bayhorse area, Custer County, Idaho: U.S. Geological Survey Brachiopods and conodonts from the base of the section yield an J.W. eds., Belt Basin: Window to Mesoproterozoic Earth: Geological contain mainly grains about 1780 Ma, and no Grenville-aged grains. 25 Ok Bulletin, v. 1891, 40 p. CHALLIS VOLCANISM AND CENOZOIC EXTENSION early Middle Ordovician age (Hobbs and Hays, 1990). The unit is Society of America Special Paper 522, p. 163-183. The Middle Cambrian Cash Creek Quartzite is unconformably 39 ~215 m thick. 53 CZc Zr Hobbs, S.W., Hays, W.H., and McIntyre, D.H., 1991, Geologic map of the overlain by an Ordovician dolostone, which we correlate to the Ella 26 Middleton, L.T., 1980, Sedimentology of Middle Cambrian Flathead 29 In Eocene time (55-40 Ma) volcanic rocks produced by the Challis Bayhorse area, central Custer County, Idaho: U.S. Geological Dolomite. This suggests that Upper Cambrian and Lower Ordovician SQUAW CREEK SECTION Sandstone, Wyoming: Ph.D. Thesis, University of Wyoming, 364 p. strata are missing. We interpret the Squaw Creek section to correlate 40 magmatic event covered a large portion of central Idaho (Moye and Survey Miscellaneous Investigations Series Map I-1882, Scale 42 Zg 76 MCsr others, 1988). Volcanic deposits from this time are found throughout 1:62,500, 14 p. with the Clayton Mine Quartzite, to be slightly more stratigraphically Zg central Idaho and western Montana (Janecke, 2007). Most of the Upper carbonate of Cash Creek (Lower Ordovician?)—Dolomite, Moye, F.J., Hackett, W.R., Blakley, J.D., and Snider, L.G., 1988, Regional complete above the Clayton Mine Quartzite than the 33 66 40 41 15 Occ geologic setting and volcanic stratigraphy of the Challis volcanic volcanism and plutonism occurred from 51-45 Ma, but some dark reddish-gray to gray on weathered surface, dark-gray on fresh Isakson, V. H., 2017, Geochronology of the tectonic, stratigraphic and Clayton-Bayhorse section, and to have been transported from the field, central Idaho, in Link, P.K. and Hackett, W.R. eds., Guidebook Tcv Zg plutonism persisted until as late as 40 Ma (Moye and others, 1988). surface. Unit is fine-grained, with some sandy layers; well-sorted, magmatic evolution of Neoproterozoic to early Paleozoic, North west on the inferred Squaw Creek thrust fault (consistent with Hobbs Tcv medium to thickly-bedded. Sandy layers of the unit are 100% to the Geology of Central and Southern Idaho: Idaho Geological 26 45 Zg Lava flows and tuffs from the Challis magmatic event covered ~1/3 American Cordillera and Cryogenian glaciation: Boise State and others, 1991, see cross section C-C’). 11 12 32 of the Clayton quadrangle, obscuring the bedrock beneath. The quartz. The unit is poorly exposed in the area west of Squaw Creek. Survey Bulletin 27, p. 87–98. 73 University Ph.D. thesis, 477 p. A 32 10NK15 northeastern portion of the quadrangle was not mapped for this The lower contact with the Єs is an unconformity and the upper The lowest known unit in Squaw Creek area (8NK15: ЄZq) lies an Skipp, B., 1988, Cordilleran thrust belt and faulted foreland in the 35 Tcv 21 A’ reason. contact is fault-bounded or not exposed. A small collection of Jacob, T., 1990, Late Proterozoic(?) tuff near Challis, Idaho: Northwest undetermined stratigraphic distance below the quartzite of Boundary Zg conodont fossils from the Cash Creek section yielded an Ordovician Beavehead Mountains, Idaho and Montana: in Schmidt, C.J. and Creek (Єbc), given its structural position in the footwall of a normal 30 23 Geology, v. 15, p. 97–106. 65 Oe The Challis volcanic field was controlled by a NE-striking extensional age (Cordylodus sp. and Drepanodus suberectus) (Hobbs and Perry, W.J., Jr., eds., Interaction of the Rocky Mountain Foreland and fault. The ages of detrital zircons in this sample are distinct; there are 33 Hays, 1990). The unit is ~215 m thick. Cordilleran thrust belt: Geological Society of America Memoir 171, p. 14 49 16 48 system named the Trans-Challis fault system (Bennett, 1986). Janecke, S.U., 2007, Cenozoic extensional processes and tectonics in no Grenville-aged grains. There are 2540 to 2450 Ma age-peaks, a 45 NE-striking faults and Eocene volcanic rocks suggest a NW-SE 237-266. few grains near 1830 Ma, and a few near 685 Ma. The ~2450 Ma MCsr 35 Shale (middle Cambrian)—Shale to slate, dark-tan to red on weathered the northern Rocky Mountains: southwest Montana and eastern 34 CZc extension direction that began and ended during Challis volcanism. zircons may have been derived from the Farmington zone of eastern Cs surface, gray to purplish-gray on fresh surface. Unit is thin-bedded Idaho: Northwest Geology, v. 36, p. 111–132. 47 Ok 32 Some NNE-SSW-striking normal faults (north-western portion of the Strickland A., Miller. E.L., Wooden J.L., 2011, The timing of Tertiary Idaho and northern Utah (Yonkee and others, 2014). The 2540 Ma 60 Osm to laminated, weathers platy, and forms slopes. A sharp contact is field area) within the Clayton quadrangle may be related to metamorphism and deformation in the Albion-Raft River Grouse grains may be reworked from western facies of the Uinta Mountain Oe present with the underlying Єc. The unit lies under an erosional Kingsbury-Stewart, E.M., Osterhout, S.L., Link, P.K., Dehler, C.M., 2013, 54 Trans-Challis extension. Creek metamorphic core complex, Utah and Idaho; The Journal of Group, or may be derived from the Grouse Creek block (Strickland MCsr disconformity with the overlying Occ and is poorly exposed in the Sequence stratigraphy and formalization of the Middle Uinta 53 CZc Zsq Geology, v. 119, p. 185-206. and others, 2011; Kingsbury-Stewart and others, 2013). 33 area west of Squaw Creek. An early Middle Cambrian age has been Mountain Group (Neoproterozoic), central Uinta Mountains, Utah: a 48 DTB17-18 Following Eocene extension and volcanism, Basin and Range assigned to the shale on the basis of distinctive fossil evidence closer look at the western Laurentian Seaway at ca. 750 Ma: extension (NE-SW) began at ~16 Ma. The active Basin and Range Yonkee, W.A., Dehler, C.D., Link, P.K., Balgord, E.A., Keeley, J.A., Hayes, The highest quartzite in the stratigraphic section is the Kinnikinic 5TA09 DTB17-17 (Nisusia sp., Pagetia sp., Spencia sp., Gogia sp., undetermined Precambrian Research, no. 236, p. 65-84. D.S., Wells, M.L., Fanning, C.M., and Johnston, S.M., 2014, Quartzite (5TA09). Consistent with the Kinnikinic elsewhere, the 14 faults generally strike NW-SE (dipping SW) in east-central Idaho, but 63 corynexochoid trilobites (cranidia only) and ptychoparioid trilobites Tectono-stratigraphic framework of Neoproterozoic to Cambrian the closest active fault to the mapping area is the Lone Pine Peak Krohe, N.J., 2016, Structural framework and detrital zircon provenance of sample displays zircon age peaks at 1860, 1960, 2100 and 2690 Ma. of early Middle Cambrian aspect) (Hobbs and Hays, 1990). The unit strata, west-central U.S.: Protracted rifting, glaciation, and evolution Tcv fault, ~10 km to the east (Breckenridge and others, 2003). the southern portion of the Clayton quadrangle, Custer County, The unique presence of 2000-2100 Ma grains is attributed to a is ~ 61 m thick. of the North American Cordilleran margin: Earth-Science Reviews, v. Qal Idaho: M.S. thesis, Idaho State University, 125 p. northern provenance in the Peace River Arch (Gehrels and Pecha, 136, p. 59–95. 2014). Oe Ok B B’ MCsr 3,500 m W E 9,500 ft Tcv CZc Qal Zsq Squaw Creek section in subsurface Clayton-Bayhorse section, in footwall of (stratigraphically below Oe), in hanging wall Zsq 9,000 ft Tcv inferred Squaw Creek thrust C-C’ of inferred Squaw Creek thrust Qcq Tcv Zr Osm 3,000 m MCsr Zr 8,000 ft Zr Qal Zsq 7,000 ft Ok Base map from USGS Digital Raster Graphic This map and explanatory information is submitted for publication 2,500 m Zb (ft) Elevation SCALE 1:24,000 with the understanding that the United States Government is Oe CREEK ELEVENMILE LAKE Control by USGS and USC & GS 1 0.5 0 1 BAYHORSE BAYHORSE MILE authorized to reproduce and distribute reprints for governmental use. Zr Osm 6,000 ft Topography by photogrametric methods from aerial FEET Zgc Zb 1000 0 1000 2000 3000 4000 5000 6000 7000 BALD Research supported by the U. S. Geological Survey, National THOMPSONCREEK Zb photographs taken 1957. Field checked 1963. CLAYTON MOUNTAIN 1 47’ 12.1 Cooperative Geologic EDMAP Mapping Program, under USGS IDAHO KILOMETER award number G15AC00178; and Idaho State University. The views Zgc Polyconic Projection: Idaho coordinate system, central zone 1 0.5 0 1 2,000 m Zd 5,000 ft ZIEGLER and conclusions contained in this document are those of the authors QUADRANGLE BASIN (Transverse Mercator), Zone 11. LIVINGSTONCREEK POTAMANPEAK LOCATION CZc 1927 North American Datum. Contour interval 40 feet and should not be interpreted as necessarily representing the official Zgc Zt MAP LOCATION 62 Supplemental contour interval 20 feet policies, either expressed or implied, of the U. S. Government. UTM GRID AND 2019 MAGNETIC NORTH 4,000 ft DECLINATION AT CENTER OF MAP Elevation (m) Ok Zd This Technical Report is a reproduction of a map originally submitted as part of a master's thesis. Its content and U.S. National Grid ? 1,500 m Cs Zsq Zt format and interpretations may not conform to IGS 100,000-m Square ID Oe 3,000 ft standards. 700 PK QK Cc ? Krohe, N.J., 2016, Structural framework and detrital zircon Zr provenance of the southern portion of the Clayton quadrangle, Grid Zone Designation 2,000 ft Custer County, Idaho: Idaho State University M.S. thesis, 125 p. 11T

C C’ 3,500 m 10,000 ft t NW rus SE k th ree A A’ w C qua d S 9,000 ft rre Clayton-Bayhorse section 9,000 ft nfe Clayton-Bayhorse section I W Salmon River Assemblage E 3,000 m Qcq 3,000 m Zg 8,000 ft B-B’ Zg Zsq 8,000 ft Tcv Tcv Zsq Tcv Qc Qc Qcq Tcv 7,000 ft Tcv 7,000 ft Zr 2,500 m Squaw Creek section Elevation (ft) MCsr Osm 2,500 m

Osm Qal (ft) Elevation Qal Zr Oe 6,000 ft 6,000 ft CZc Zsq Zr MCsr Cc Ok Zb st t CZq CZc ru rus Ccb 2,000 m th th CZc 5,000 ft 2,000 m 5,000 ft sin sin ? Ba Ba Zb er er Oe Zr CZbc t pp pp rus Co Co k th ree Zb Zgc Elevation (m) C 4,000 ft ? 4,000 ft Elevation (m) Zgc

Osm Zsq uaw Sq Zsq 1,500 m Zb ed Zd Zd 1,500 m err Ok Cs 3,000 ft Inf Zgc 3,000 ft Zt Zr Zt Zr Oe Zgc ? ? Cc Zd 2,000 ft 2,000 ft

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