IDAHO GEOLOGICAL SURVEY TECHNICAL REPORT 99-2 MOSCOW-BOISE-POCATELLO LINK AND STANFORD

Qc Ql Qm Qs Ql Qc QTfg pIPc Qtg QTr Tsup Qc Qal Ql Og PIPw TRtu Ql QTfg Qtg Qls Og Qc TRd QTr Ql Mmc 17 Tslr Tsud Qal Qal Qal Ql 40 45 Tsud 23 Tsu Qc Mmc 35 20 pIPm QTfg Qbh Qbh Tsud 68 C– sw C– sw Qal Qal 60 Qfg OC– su Ql Qc Og Tsud Tsud 14 Zcl 38 C– Zc Qc 45 Os Qc Tsud TRd Ql C– n Og 25 pIPc Qm Qal Zi Qc – C– sw OC– su QTr Zcu C– g OCsu 55 Os pIPm Qtg Ql 73 C– sw Os Og Mlf Tb 15 13 45 C– n Qal Tsud 68 C– sw 40 C– sw Qfg 35 C– e 35 Tsud 31 Ql Tb – C– n QTr Zcl C– Zc C– e Cbo C– n QTfg Qbh Dh 48 32 C– sw Tsub 51 40 Tsud 51 C– n C– sw Os Qam 80 Qc C– n Sl 32 C– e Tsu Mlf Dh Ql 52 C– e C– Zc C– g Qfg Tsub Qls OC– su Qfg – 75 Qc Csw Ts Ts Qal Qc 29 Ml Qam Ql 34 Qc 35 Ql Qm Ml Ql Of C– Zc Qtg Qc Zm 56 18 Mlf Tsub 60 Zm 25 20 Qal Qtg Qm 19 Ts Tsud Qal 25 Mlf 26 Qal Zcu C– Zc C– g 24 Qfg Qm C– Zc Qbh Tsu Ts Qtg Zcl Zi Qc Zm C– bo Ql Ts 11 Qtg Tsub Zi Zm Tsud Qal C– n Qc 35 Zm 32 40 Qam Qam 40 C– Zc C– g Zi C– bo C– sw 35 33 Qfg C– n 25 Qm Ts Ql C– g 13 28 – Zm Zm 29 Zm Qm C– e CZc C– Zc Tsud Qbh Tsub Qc C– g 10 40 – C– Zc Qm Qtg CZc Zm 25 Qal Ql Ql 40 30 16 Tsud 31 32 Qtg 52 27 Tsma Qtg Tsud – C– e Ce Zcu Ql Tsu Zi Qc 20 C– Zc 26 Qfg Qc Zm 25 Zm Zm 29 Qfg Qm Tsud Qc C– g Qal Zm 28 34 Qc Qfg Ql Zm Zcu C– Zc 30 35 Zm Qtg Tsu Tsud 21 Qfg C– e 30 Qm Qtg C– e Ql Ql Qbh C– ls Tsud C– g Zi Zm Tsud Tsud Tsub C– g Zcl C– g 27 Qal Ql Zm Zcl C– Zc Qal Ql 24 Qls Qc Zcu C– Zc Qc 20 Zm Qal 30 C– g Tsuc Zcl Zpu Qfg Qtg Ql Ql Zi Zcu Zm Zc Qfg 42 Zi Qc Qc 35 Qc Ql – C– e C– Zc Qam Ql Zcl Qc CZc 25 Qtg Qal Qfg Qal Zpb 30 45 C– g 30 Ql Qc Ql C– g 15 Ql Zps Ql Zi 30 18 QTfg Qfg Zc Zcl Qfg Zm 25 15 25 Tsup 68 15 C– Zc Zm Qtg 25 Qfg Zc Zpu 63 53 Zcl 65 71 Zm 50 17 Zm Qc – 8 Qs Qm Ql Ql CZc 17 Zi Qam Ql 42 – Tsud Qc 68 CZc Zi Os Ql Ql Zcu 60 QTfg Qc Qbh Tsup C– Zc Zm Zcu Zm Qfg Ql Zc Zc Zcl 18 QTfg 18 Ql 33 55 C– g Zm Tsur C– g Zcl C– e Zi 49 Qm Qm 18 Tsuc Zpu 37 35 C– bo C– n 27 Q Og Q Ql Ql 33 Zcu Zb Ql 40 56 C– g C– e Zps Ql Ql Zi Ql Qm 40 C– Zc Zm

24 17 T Qc 30 36 C– n

Qbh 31 Zcl S U 29 – 45 68 20 Zi 26 OCs Ts Ts C– Zc 21

Zpb R 47 Zcl 35 13 C– Zc 17 Zcl Zm Zcl Zcl 34 H Zm C– Zc

T C– bo Zb 33 20 C– Zc Ts Q 40 Ql Zcu 38 C– g Qfg 36 Zi C– g 37 C– g 35 62 35 Zpa 54 C– Zc 34 37 33 C– n 6 C– g Zpu 22 Zi C– g OC– s 21 Qal Ql 32 Zcu 22 C– Zc Zpu Zcl Zm C– e Zm C– Zc – 32 Ts Ts Ql Qtg Ql 25 Ql 31 C– g Ce Ql Ql Qfg 37 32 Zcl 19 32 34 50 Ql Zm 20 C– e 60 Zpb – Zcl 38 15 12 Qs Zcu CZc 87 THRUST 26 – Qfg 19 79 Zcu Zm – C– bo CZc Qal 36 24 35 Cbo OC– su – 18 Q Q 20 24 Qfg 26 37 CZc 64 Zpa CANYON Zm 62 45 39 30 C– g Ql 54 Ql 30 25 Zcu C– e OC– s 11 40 Zm Zps 12 26 C– e C– e Zpa Zcl Zps Zb Zb 23 BEAR 55 Ql 8 Qtg Zpa Zcu Zpb 22 Zpu 54 Zcl Zcu Qc Q Tslb Ql 54 Zcu 11 C– e 25 Zpa 22 C– sw N Q Ql 39 11 Zi 40 Zcl – Tslr Ql 65 52 22 C– g Cn C– e C– g 8 – YO 22 Ql Cbo 20 28 C– bo 21 20 42 Qfg 48 Qp Zm AN 36 Qbh Ql 6 29 Zi 69 Zm C– Zc Qbh Ql 30 C Zm Q Tsma Zm 36 53 37 Ql 53 Zcl 17 C– g 42 Zpu 46 C– e Zcu Qls Zpu 35 12 40 Ql Zpu Ql 22 C– n C– e Qal Ql 30 30 Ql C– g C– e Zc 52 Ts Ql Zcl Zps Zi 32 48 26 Ql 62 Ql C– Zc Zpa 43 42 75 42 Qfg Zcu Zm C– Zc 74 34 25 30 15 Zpa Ql C– bo Zm C– e 10 Ts C– g Qtg 26 Zcl C– Zc 39 Zi 37 15 OC– s Qtg Qs Ql Ts Qfg Zc 38 Zpa 40 47 71 10 Zcl 38 BEAR OC– s Tb 36 25 25 C– n Qsu Qal Zps 43 C– Zc C– g 47 40 Zcu Qm 39 47 Zcu C– g C– bo 8 30 52 Ql 32 32 36 C– e Qal Qal Zc C– g Qal 37 20 52 C– n Zm C– e 35 Q Tb Zpu Zb Ql 60 67 5 18 Tslb Ql 31 C– Zc Zpb Zcl Qfg 21 75 C– e Ql 31 Qls Qp 30 OC– s Qtg 31 Ql 23 11 38 – Qp 11 Ce Zcu 22 Qs Qfg 51 Zm 29 17 Qsu Qfg Qfg 17 Qm Qp Of Ql 31 Qfg Zcl 12 C– n OC– s 42 Qfg Qfg 68 Zi Qc Sl Tslb Ql Zm Os Os Tsma Zi Qls Qfg Of 19 Qtg 23 Zcl Of 4 40 47 33 39 Ts Tsur 46 Tsuc Ql Qfg – Qp 27 Tslb Qal Zc 28 19 Ce Zi 17 Q Qs 15 Tslr 22 Qal C– e Zcu 8 40 Zi Zm 65 Ts Zm C– Zc 35 Ql Ql 41 Sl 12 10 Qtg 50 33 56 41 Qm Qal Tb Zi 23 Zcu Qc Ql 27 Zi Qsu 41 59 C– e C– bo Zm Zm Q Of Tslb Zc 48 56 31 Ql C– e 6 Tslr 28 35 Qal 6 1 Qtg Tw C– Zc Qls Zpu 25 45 36 45 Zi C– g Ql Ql 60 C– bo 15 Ts 33 Tsma Ql 33 10 45 Qc Of Qam 38 42 Tsul Zpa Tsur Ts Twn Tn Ql Qfg Zm 26 41 35 34 OC– s Qal Qfg C– Zc 48 35 C– sw C– Zc Zps Zcl 12 Of 11 C– g Qal 6 14 Qsu 41 – C– bo 49 60 Os Cg C– e Ql 29 24 Ql Tw Tslb Tsur C– gc 28 45 Zm C– bo Zm Qc Q Zi Zm Qls 45 Og Qs Qr 54 – – 36 Qls Zi Tsur Qal 18 Ts Ml Ml 47 Cg 53 Ce 31 Q Qtg Ql 45 29 35 22 17 25 C– g Tsuc Zi Zpa 36 34 Q Tslb C– Zc Zi 42 Zi Ql Of Tsur C– g 20 Tn Dh C– Zc 49 Zcl 32 30 Qbh 56 17 Zm 24 C– Zc Os 31 Of Og Qam Qtg Qfg 36 35 Zb 39 45 55 Os Ql Tsup 49 Qls Zcl 33 Zcu Of C– Zc C– e Q 40 C– gc C– e 33 36 C– e Zpa Zc 5 Tn Tn Sl 35 30 Zpu Zc OC– s Qal Qal 41 Tsuc 55 35 15 8 Qr C– n Qal 38 Zi Ql Tsmt C– Zc Tsuc Ts Zm 32 24 Os Tslb Qal Tsma Ql 35 40 Qc C– g 23 Tsmt Ql C– Zc 32 Zm Tb Tw C– bo Zm Qal Zpa C– Zc Qp 36 23 C– bo Tmv Tw Mdu Tslb 30 C– g Zi Tmv 50 38 22 Ql – Qsu Qfg C– e Qc 40 CZc – 18 Qls Tslb C– bo QTr Qc 50 25 Zpa 26 Cn Tsur Qc 45 5 – C– e Zi 30 45 42 32 Qal Ql Tslb Cn 40 72 C– e C– e 31 Qfg – C– Zc C– g Zm 36 C– g Os Qtn Cn Qal Zm Qc C– e 18 Tb 35 25 Zm C– g Tsur 30 – 40 Q 8 60 Tsma 18 Ql C– sw Ce QTfg 25 Q Qal Ql – Tsur 25 – Zc Qc Csw Cbo Ts 30 C– n Og 60 Ts C– n C– sw Ql 30 Zi 22 Qal 20 Q C– bo Ts Of Tslb C– n 40 C– sw C– n 24 32 Zc Ql Ts Q Tslb Ql C– sw 25 Zc 35 – OC– su C– Zc Qtg Tw Tslb Os C– n Ce C– Zc OC– s Qr Qtn 40 C– bo 15 C– e Zc – Mgl Ql Og Os 20 C– g 25 45 Ce Qs Tl Tw Of Ql C– n OC– su Qc 50 C– n C– bo 52 Os Tsma Ts 35 40 40 C– g – 32 C– e Tmv Qfg Og Os Qc Ce Qc Qc QTfg 9 Of Zm 26 C– e 40 Tmv Tn Ql C– sw 55 36 C– n C– e 32 35 Tsma C– bo Zi 85 Os Og 20 15 C– g C– e 26 Qc C– g Qs Tl Qsu Tsma 35 Og OC– su Ql 60 Qls Of Os Os C– e 45 Zm 50 28 Ts C– n Qr Tmv Mgl 10 34 24 Os Os Os 22 Qfg Qfg C– bo C– sw OC– s Q Og Qcb Qr Tsma Tslb C– sw Tsuc C– bo – Ts Qcb Tslb Og C– sw Og Qfg 40 Ql Tsuf 35 Ql 25 C– n C– bo 35 C– Zc 40 29 Cn 50 C– n 25 58 60 Qm Og Og Qc 10 25 Ql Tw Ql Og 40 OC– su C– Zc 45 Og Tmv Tmv Tmv PIPo Of Os Os Qc 26 29 Tl Ql IPoc – Os Of Qc Os 20 – Qr 27 Cn Tsuc Zb 45 Cn Qls 52 38 Of Qal – Os Qs Ts Qal Os OC– su 30 Csw 15 Zpa 20 Qal Tslr Og Os C– sw 15 Qc QTfg Qm 8 Zps 23 Os 9 60 Ql 15 Tl Tsur C– n 42 Qc Tsuc Qc Zpu Qc Og IPob Tslb Tsma Ql 25 C– n Tmv Qc Og Zc 34 Sl Q Os Ts Mdl 15 Ql C– bo 28 C– e 18 Tw Tslb Mdu Ql 45 40 Qc 33 OC– su Qal 40 Ql C– e 16 18 6 Mdl Db 30 Tl Tslb Mgl 56 C– n C– n Tmv IPoc Tslb Ql Tsma 26 15 Tmv 18 IPob 10 Zps 55 IPoc Mdu Ml Db Qc Ts 14 Qal Db Ml Qfg Qc 35 64 Ql Qfg 9 16 Ql Mdu Ts 52 15 Tmv IPob Ql Qc 32 Tsma Tsuc Zi C– bo 28 14 Dh Ts 9 Mdl Qc Tmv IPob Of Ml 35 OC– s 27 14 24 Mgl Tsur Qc Zm Tl 40 Ml 65 20 Q Tmv Tsur 18 Sl Ql 25 8 Og Qcb 17 PIPo 17 Mgl Ml Tsuf 41 37 25 Mdu 30 Zps 30 55 10 Zi Tmv Sl Mdu Zpu 5 50 Qal Tmv Tmv 22 Of 45 Of Sl Tmv Sl 40 Ts Tw IPoc 15 Os Q Qal Dh Of Zps Zi 70 Ts 35 IPob IPoc 15 Qfg 20 38 38 27 18 25 40 Qfg 2Ml0 Qal Of 21 Tsma 45 31 Mgl 35 Qc 50 32 25 IPob Qc Tmv Qal 30 45 Sl Os Og Zc 13 Of Db Mdl Qfg 34 Qfg Sl Ql Tsuc Zb PIPo 37 Db Ml Ql Qal Tw Tmv Qfg Qal Ml Qfg Zpa 30 Ts Tmv 22 Ts Qc QTfg Ts Dh 40 – Qp Ql PIPod Dh Mdl Ce IPoa 31 Mdl Mgl Mdu 30 Of Zm Qfg 35 Db Ts 45 45 Ts Of Ql Tsur Qfg 25 31 Mgu IPob Mdu Ml 10 Of IPMm 8 Mdl Of 24 PIPo Sl 7 Db Ql Zpa Sl IPob 7 Dh Mdu 25 Sl Tsuc 29 IPoc Dh Mdl Qc Os Zc Qp Qfg Of Mdu Mdl Tsuc 20 Qp IPoa 45 Mdl Db Sl Db Ql QTfg Os Tmv 26 IPMm Ml Tslr IPob Db Dh Os Os Ml 35 Qm Qal Tsur Mdu Sl Db Of 12 Of Ql Of Sl Zp Zi Tmv Dh Tsma Og 24 50 Of Qal Qc Tsur 40 5 Mdu Dh Ml Qp Mgl IPoc 22 Db 16 35 Ql Qp 5 Of Tmv 21 PIPo Of Sl 8 4 50 C– sw 32 Ts IPob 30 Dh Mgl Mdu Dh Zc Zc Os 35 Mgm Mgu Ml Qfg Of 30 Os 40 17 Ml Ts Qc 16 22 Db Db Mdl Sl OC– su Os Sl Ql Of Mgu IPoa PIPod Of Sl Ml Of Qc Of Qfg Tmv 43 30 Mdl Ql Og Os Qfg 55 Db Zp Ql Os Dh Ml Sl Qc Sl Mdu 30 Zp 40 Mdl Os IPMm 26 Db Of Os Og 30 Of PIPod Mdu Dh Os Tsur C– e 25 Qal Tmv Mdl 14 IPoc Sl Of Tsug Tsur Ql IPMm 17 25 IPoa 14 20 Tsul 30 15 Tsuc Qtn IPob 8 50 45 Tsur Db 32 C– sw Sl Tmv 18 18 Of Os Tsur 15 Ql PIPod IPoc 63 45 13 30 Os Qc Tsur IPoa Sl 25 – 40 Of Ql Ql PIPod 3 37 30 Ts Cbo IPoa 45 45 28 23 14 IPob IPoc 23 Tmv 10 Qtn IPoc 11 Ql Og Zps IPob Ql 28 35 PIPo Tsur 15 OC– su 15 12 45 15 Tsug Qfg Tsur Qc Qc Tsur Tsuc Sl Tmv Ts Qal 10 Ts 30 Tsuc Tsur PIPod Qal 20 Tsma Ql C– g 8 3 30 40 Ts 24 8 40 C– e 30 Qc 10 Os Ts Ql – Of PIPod PIPod Ql Og Sl Tsuc 35 Csw 15 Ql Ts 35 5 Ts Ql Os Qal Os Os Tsuf C– bo C– e 25 Os Tsug Ql 25 Tsma OC– su 50 5 Ts 14 Ql 20 PIPo 28 C– bo 16 30 57 QTfg Of Qal 31 21 Ql C– n 28 22 C– n 35Qc Tsur Ts IPob 33 Qc 45 Og Ql Of Sl Og Ql Qfg IPob 30 Tsur PIPod 34 IPob Of 40 C– bo20 Tmv 30 10 28 C– sw Os Os 35 Qfg Qfg Os Sl Tsuc 30 Qtn Dwc IPoc Ql Tsur Qc 40 23 24 IPoa 45 45 Of IPoc 10 Qc Tsug C– sw Ql Tsma Qc Mgb Dh 25 Qal Os C– n 28 24 23 IPMm Of Ts Ts 38 PIPod 30 Os 5 Tsul 35 Qtn 30 Os Ql 33 PIPod Db Og Qc 10 Os PIPo PIPo 18 15 25 20 C– bo 8 Ql Og Qal Og Tsub 20 Ql 20 Qc Ts Tsub C– e 21 20 Qfg IPob 25 23 15 25 Zpu Tsur 79 Tslr Ts IPoa Ql 20 22 Db Mh 15 Ql Os 35 Ql IPoa 8 15 Og Ts 14 12 8 Ql Qfg 50 Tsur Ql 20 IPob PIPo Dwc Zb Tsur C– g 42 32 Ql IPMm 25 60 38 Ts 27 Ml IPoa 35 Sl Qc Os Tsur Ts Tslr Qfg IPoa 23 10 10 Of Ql Tslr IPoc Ts Sl Zp Ts 32 PIPod 12 15 15 Tsur Tsma 20 15 35 Sl 64 Ql Of Qc PIPod Qal Ql Ts Ts Og Ql Qfg Qc 10 Qm Tsma IPoc Ql Qfg 35 Qfg Ts Mh Qc 21 Qfg Qc Qal PIPo IPob 20 6 Tsuc 20 Tslb Tsma 22 30 Qc Of Qc Qal 45 30 Qc PIPo 15 Qfg 25 Ql 15 Qc Tsur Tslr Tslr Ql IPob Tsur Tsub Qal IPob IPoa 20 IPoa Ql PIPo IPoc Mgb IPMm Ts Qc Tsug 16 PIPod 14 30 PIPo Mgl 40 Ql Tsub Os Of Sl Tsub Of Ts Tslr IPMm PIPo 25 Dh 20 Ts

Base map from USGS, 1:100,000 digital raster graphic. Digital cartography and GIS data capture by Jane S. Freed, Loudon R. MN Stanford, and Vance T. MacKubbin. Projection and 10,000-meter grid, zone 12, Universal Transverse Mercator. SCALE 1:100,000 GN Data capture, map compilation, and map preparation funded in part 25,000 foot grid ticks based on Idaho coordinate system, east zone. o o 1 0 12345 1 0 12 3 by the U. S. Geological Survey’s STATEMAP program. 1 01 16 KILOMETERS MILES 1927 North American Datum. Contour Interval 50 Meters Original geologic map data used in this compilation are available in a fully IDAHO attributed Geographic Information System (GIS) format. Map version 5-15-2001. UTM grid and 1984 magnetic north QUADRANGLE LOCATION declination at center of map Idaho CORRELATION OF MAP UNITS Geological Survey Digital Mapping and GIS Qs Qal Qc Ql Qtg G EOLOGIC MAP C OMPILATION OF THE POCATELLO 30 X 60 MINUTE QUADRANGLE, IDAHO ? u n c o n f o r m i t y Qtn ? Qm Paul Karl Link and Loudon R. Stanford u n c o n f o r m i t y Q ? 1999 Quaternary ?

Qam Qcb Qfg Qls Qsu Zpa Papoose Creek Formation (Late Proterozoic)—Distinctive thinly interbedded Qbh INTRODUCTION Tsub Starlight and Salt Lake Formations, upper member (upper Miocene)—Basalt Mdu Deep Creek Formation, upper member (Upper )—Thin-bedded INDEX TO SOURCES Qp 0.6 brown argillite and gray siltite; contains irregular siltstone dikes on cm-scale; Qr lava; includes vent-facies deposits of basalt cinder cones in Hawkins and limestone with abundant dark chert; 1,500 feet (457 m). OF GEOLOGIC MAPPING 925-1,320 feet (280-400 m). This map was digitally compiled from geologic maps covering the area (see Lava Hot Springs quadrangles; includes andesite dikes (Ta of Platt, 1985); o Mdl Deep Creek Formation, lower member (Upper Mississippian)—Shale and 43

? Index to Sources of Geologic Mapping). Some units were combined or thickness varies, <100 feet (30 m). Zb QTfg Blackrock Canyon Limestone (Late Proterozoic)—Gray, locally sandy limestone 5 simplified for readability. Geologic edge-match discrepancies between map siltstone; 760 feet (232 m). 10 CENOZOIC and dolomite; lenticular; 0-1,150 feet (0-350 m). 20 sources were reconciled where possible in the compilation; however, the Tsuf Salt Lake Formation, upper member (Pliocene and Miocene)—Frothy facies; 20 7 8 Mlf 2 basaltic tuff-breccia on northern margin of Hawkins Basin eruptive center; Little Flat Formation (Upper to Lower Mississippian)—Thin-bedded, brown- Zp QTr ? ? ? field work necessary to resolve remaining problems was beyond the funded Pocatello Formation (Late Proterozoic). 1 5.0 thickness <100 feet (30 m). weathering, sandy and silty limestone; <1,600 feet (488 m). 17 9 Tl scope of this project. 16 Tmv Zpu Pocatello Formation, upper member (Late Proterozoic)—Laminated siltite Tb Ml Lodgepole Limestone (Lower Mississippian)—Gray, thin-bedded bioclastic cherty 3 Tsud Tsup Starlight Formation, upper member (upper Miocene)—Rhyolite porphyry and phyllite; calcareous at base; <1,420 feet (430 m). and lava; includes rhyolite of west Pocatello (<1,100 feet or 335 m; Ar-Ar limestone; includes rocks mapped as Madison Limestone(?) on Paps Mountain 13 15 18 Tw 6.0 DESCRIPTION OF MAP UNITS 6 Twn age of 7.9 ± 0.4 Ma, Kellogg and others, 1994) and rhyolite of Two and a southeast of American Falls; <500 feet (152 m). Zps Pocatello Formation, Scout Mountain Member (Late Proterozoic)—Two Tsug 19 Tn Half Mile Creek (<200 feet or 61 m; K-Ar age of 9.1 ± 0.3 Ma, Kellogg and horizons of diamictite containing glacially striated stones; upper diamictite Db Beirdneau Formation (Upper )—Dolomitic sandstone and quartzite; 11 Tsud 7.0 Qal Alluvium (Holocene and Pleistocene)—Includes older alluvium. Marvin, 1988). is overlain by pink dolomite marker bed, cross-bedded quartzite, and siltstone; 14 12 4 Tsuf crops out in Deep Creek Range; 360 feet (110 m). o medial portion of unit contains sandstone and cobble conglomerate; thickness 42 30 Tsul o o o Tsub Tertiary Q Unconsolidated materials, undifferentiated (Holocene and Pleistocene). Tsuc Starlight and Salt Lake Formations, upper member (upper Miocene)— 113 112 30 112 Tsup 8.0 (Ma) Dh Hyrum Dolomite (Upper and Middle Devonian)—Light to dark gray dolomite; varies <3,500 feet (1,070 m). Tsu Conglomerate; locally tuffaceous; lowest stratigraphic unit exposed in Lava Tsur about 500 feet (152 m); includes rocks mapped as Jefferson Formation in Qls Landslide deposits (Holocene, Pleistocene, and Pliocene)—Includes older Hot Springs quadrangle. Zpb Pocatello Formation, Bannock Volcanic Member (Late Proterozoic)—Mafic American Falls and Bradley Mountain quadrangles. Ts 9.0 landslide deposits. metavolcanic greenstone; local pillow breccia and diabase; forms tongue Tsur Starlight and Salt Lake Formations, upper member (upper Miocene)— 1. Burgel, W.D., 1986, Structural geology of the Rapid Creek area, Pocatello Tsuc Dwc Water Canyon Formation (Lower Devonian)—Light gray, thin-bedded sandy within Scout Mountain Member; <1,380 feet (420 m). Ql Loess (Holocene and Pleistocene)—Extensive aeolian silt mantle; <100 feet Rhyolite fallout tuff, tuffaceous gravel, and lacustrine limestone; generally Range, north of Inkom, southeast Idaho: Idaho State University M.S. thesis, 10.0 dolostone with argillite and sandstone in upper part; <607 feet (185 m). (30 m). between 7 and 9 Ma. 72 p. Tsmt 10.2 Tsma Qs Dune sand (Holocene)—Mainly along Snake River. Sl Laketown Dolomite (Upper and Middle )—White-weathering dolomite; 2. Carr, W.J., and D.E. Trimble, 1963, Geology of the American Falls quadrangle, Tsul Starlight Formation, upper member (upper Miocene)—Gravity slide block. SYMBOLS Idaho: U.S. Geological Survey Bulletin 1121-G, 44 p. 11.0 locally bioclastic; about 1,000 feet (305 m). 12.0 Qc Colluvium and talus deposits (Holocene and Pleistocene). Starlight Formation, middle member (upper Miocene)—Glassy welded tuff; 3. Corbett, M., 1978, Preliminary geologic map of the northern Portneuf Range, Tslb Tsmt Of Fish Haven Dolomite (Upper )—Dark-gray fetid dolomite; locally Contact: dashed where approximately located; no contact between units 13.0 overlies Arbon Valley Tuff Member in Michaud and Arbon quadrangles; 8 Bannock and Caribou counties, Idaho: U.S. Geological Survey Open-File Travertine (upper Pleistocene)—Hot spring deposits, locally along fault zones; cherty and abundantly bioclastic; about 1,000 feet (305 m). indicates an unresolved edge-match discrepancy between geologic 14.0 Qtn feet (2 m). Report 78-1018. <500 feet (152 m). source maps. Tslr 15.62 4. Crane, T.J., and P.K. Link, Idaho State University unpublished mapping and Os Swan Peak Quartzite (Middle Ordovician)—White vitreous quartzite, locally Tsma Starlight Formation, middle member, Arbon Valley Tuff Member (middle High-angle fault: dashed where approximately located; dotted where Oriel, S.S., unpublished mapping. Qfg Alluvial fan gravel (Pleistocene). bioturbated, with local basal sandy dolomite; <1,190 feet (363 m). concealed; ball and bar on downthrown side. Miocene)—Tan, quartz and sanidine crystal-rich, biotite-bearing rhyolitic 5. Hladky, F.R., K.S. Kellogg, S.S. Oriel, P.K. Link, J.W. Nielson, and R.E. Amerman, TRtu ash-flow and fallout tuff; locally pumiceous; Ar-Ar age of 10.2 Ma (Kellogg Lower MESOZOIC Qm Michaud Gravel (upper Pleistocene)—Deposits of Bonneville Flood; about Og Garden City Formation (Lower Ordovician)—Light gray bioclastic limestone Low-angle normal fault: dashed where approximately located; dotted 1992, Geologic map of the eastern part of the Fort Hall Indian Reservation, TRd 14,500 years ago; 50-80 feet (15-24 m). and others, 1994); <300 feet (91 m). and intraformational conglomerate; 850 feet (259 m). where concealed; hachure on upper plate. Bannock, Bingham, and Caribou counties, Idaho: U.S. Geological Survey Miscellaneous Investigations Series 2006, scale 1:50,000. Tslb Starlight Formation, lower member (upper Miocene)—Porphyritic and Qam American Falls Lake Beds (upper Pleistocene)—Clay with some lacustrine silt, O s St. Charles Formation (Lower Ordovician and Upper ). Thrust fault: dashed where approximately located; dotted where Ppc nonporphyritic basalt flows, basaltic tuff, and breccia; local eruptive center concealed; sawteeth on upper plate. 6. Hladky, F.R., and K.S. Kellogg, unpublished geologic map of the western part sand, and fluvial deposits; locally rich in vertebrate ; above Raft of the Fort Hall Indian Reservation, Bannock, Bingham, and Power counties, Ppm in northern end of Arbon Valley. O su St. Charles Formation, upper member (Lower Ordovician and Upper Formation; <80 feet (24 m). Strike-slip fault showing relative motion: dashed where approximately Idaho, scale 1:50,000. u n c o n f o r m i t y Cambrian)—Brownish thin-bedded dolomite; sandy at base; 330 feet located; dotted where concealed. Lower Tslr Starlight Formation, lower member (upper and middle Miocene)—Rhyolite 7. Kellogg, K.S., S.S. Oriel, R.E. Amerman, P.K. Link, and F.R. Hladky, 1989, PIPod Qcb Cedar Butte Basalt (upper Pleistocene)—Lava flow erupted north of Snake River; (100 m). formed dam for ancestral American Falls lake about 70,000 years ago (Scott and air-fall tuff; local limestone and gravel; Ar-Ar age from rhyolitic ash near 71 21 Strike and dip of bedding: ball indicates top direction was determined. Geologic map of the Jeff Cabin Creek quadrangle, Bannock and Caribou IPoc Upper and others, 1982); 25-100 feet (8-30 m). base is 15.62 Ma (D.W. Rodgers, written commun., 1999); >1,970 feet, sw St. Charles Formation, Worm Creek Member (Upper Cambrian)—Tan- counties, Idaho: U.S. Geological Survey Geologic Quadrangle Map 1669, PIPo PIPw (600 m). IPob weathering, fine-grained subarkosic sandstone; locally bioturbated basal Vertical bedding. scale 1:24,000. Pennsylvanian Qsu Sunbeam Formation (upper Pleistocene)—Alluvial and colluvial deposits below brown dolomite in Portneuf Range; >500 feet (152 m). 8. Kellogg, K.S., 1990, Geologic map of the South Putnam Mountain quadrangle, IPoa Middle tu Thaynes Formation, Fort Hall and Ross Fork Limestone Member (Lower Triassic)— American Falls Lake Beds; <100 feet (30 m). Horizontal bedding. Bannock and Caribou counties, Idaho: U.S. Geological Survey Geologic Thin-bedded silty limestone and shale; locally bioclastic; thickens eastward n u n c o n f o r m i t y Lower Nounan Formation (Upper and Middle Cambrian)—Gray limestone and dolomite; Quadrangle Map 1665, scale 1:24,000. Qbh Big Hole Basalt (upper Pleistocene)—Basalt flows north of the Snake River to 5,500 feet (1,650 m). locally bioclastic and silty; 900 feet (274 m). 20 Strike and dip of overturned bedding. 9. McQuarrie, N., D.W. Rodgers, W.D. Burgel, and C.F. Hersley, in progress, IPMm above the Raft Formation; <150 feet (46 m). Preliminary geologic map of the Inkom quadrangle, Bannock County, Idaho: d Dinwoody Formation (Lower Triassic)—Tan to olive mudstone and limestone; bo Bloomington Formation (Middle Cambrian)—Thin-bedded, light gray, locally 17 Idaho Geological Survey Technical Report, scale 1:24,000. Qtg Terrace gravel (Pleistocene)—Includes pediment gravel and Sterling and Aberdeen locally bioclastic; about 1,000 feet (305 m). nodular bioclastic and micritic limestone interbedded with green shale; Strike and dip of foliation. Mgu Upper 10. Othberg, K.L., in progress, Surficial geologic map of the Pocatello North terrace deposits above Michaud Gravel; also includes benches in east and <1,700 feet (518 m) in Bannock Range; thins drastically in Portneuf Range 20 Mgb Mgm Mh Mmc west bench Pocatello Valley; <200 feet (61 m). Ppc Phosphoria Formation, cherty shale member (Lower Permian)—Thin-bedded, to 900 feet (274 m). Strike and dip of fracture cleavage. quadrangle, Bannock County, Idaho: Idaho Geological Survey Technical locally cherty mudstone and argillaceous chert; 345-360 feet (105-110 m). Report, scale 1:24,000. Mgl Mississippian ? ? Qp Basalt of Portneuf Valley (upper Pleistocene)—Two valley-confined basalt flows e Elkhead Limestone (Middle Cambrian)—Dark and light gray, thick-bedded, Vertical fracture cleavage. 11. Oriel, S.S., adapted by P.K. Link, unpublished mapping, scale 1:100,000. Mlf Ppm Phosphoria Formation, Meade Peak Phosphatic Shale Member (Lower Permian)— Mdu of the Portneuf River, each flow about 50 feet (15 m) thick; erupted from locally oolitic and bioclastic limestone with red silt laminae; <2,050 feet 12. Platt, L.B., 1985, Geologic map of the Hawkins quadrangle, Bannock County, Blackfoot lava field about 580,000 years ago (Scott and others, 1982). Dark-colored phosphatic shale, mudstone, and pelletal phosphorite; locally (625 m); includes Blacksmith and Bancroft Limestones, undifferentiated, Ml Lower Anticline: Trace of axial plane; large arrow indicates direction of plunge. Idaho: U.S. Geological Survey Miscellaneous Field Studies Map 1812, scale bioclastic; 120-180 feet (37-55 m). <1,310 feet (400m) on Clifton Creek, Hawkins, and Scout Mountain Mdl 1:24,000. Qr Raft Formation (upper or middle Pleistocene)—Massive lacustrine silt and clay quadrangles. P w Wells Formation, lower part (Lower Permian and Upper Pennsylvanian)— Overturned anticline: Trace of axial plane; large arrow indicates direction 13. Platt, L.B., 1995, Geologic map of the Clifton Creek quadrangle, Bannock beds with local basal gravel; crops out above the Massacre Volcanics and of plunge. to west; <230 feet (70 m). Limestone; locally bioclastic and cherty; limey sandstone and quartz arenite; g Gibson Jack Formation (Middle and Lower Cambrian)—Green and gray argillite, and Power counties, southeastern Idaho: U.S. Geological Survey Miscellaneous Pzr <2,400 feet (732 m). Field Studies Map 2278, scale 1:24,000. Db Upper fine-grained sandstone, and lenticular limestone; locally bioclastic; 2,480 Syncline: Trace of axial plane; large arrow indicates direction of plunge. QTfg Older fan gravels, undifferentiated (Pleistocene-Pliocene?)—Marsh Valley 14. Platt, L.B., unpublished mapping of the Bradley Mountain quadrangle, scale Devonian P o feet (756 m). Dh Middle bench. Oquirrh Formation (Lower Permian and Upper and Middle Pennsylvanian)— 1:24,000. Lower PALEOZOIC Limestone; locally cherty and fossiliferous; siltstone; chert-pebble gc Gibson Jack Formation, member C (Middle and Lower Cambrian)—Pale- Overturned syncline: Trace of axial plane; large arrow indicates direction Dwc of plunge. 15. Platt, L.B., Geologic map of the Scout Mountain quadrangle, Bannock County, QTr Rhyolite and andesite porphyry (Pleistocene and Pliocene)—Small outcrops of conglomerate. colored shaly argillite with interbeds of sandstone up to 100 feet (30 m) u n c o n f o r m i t y Idaho: Idaho Geological Survey Geologic Map 22, scale 1:24,000. brown rhyolite flow with quartz phenocrysts on Clifton Creek quadrangle thick and discontinuous argillaceous limestone; locally bioclastic; <1,000 Upper and P od Oquirrh Formation, unit D, cherty unit (Lower Permian and Upper 16. Riesterer, J.W., P.K. Link, and D.W. Rodgers, in progress, Geologic map of Silurian and dark andesite porphyry on Pocatello North quadrangle. feet (305 m). Sl Middle Pennsylvanian)—Tan-weathering sandy limestone and brownish tan bedded the Bonneville Peak quadrangle, Bannock and Caribou counties, Idaho: u n c o n f o r m i t y REFERENCES Idaho Geological Survey Technical Report, scale 1:24,000. Tmv Massacre Volcanics (Pliocene and upper Miocene)—Basalt eruptive center; chert; 1,100 feet (335 m). gb Gibson Jack Formation, member B (Middle and Lower Cambrian)—First Upper diktytaxitic, locally olivine-bearing basalt lava; pyroclastic tuffs and tuff- thick quartzite above Camelback Mountain Quartzite; 115 feet (35 m). Kellogg, K.S., and R.F. Marvin, 1988, New potassium-argon ages, geochemistry, 17. Rodgers, D.W., and K.L. Othberg, in progress, Geologic map of the Pocatello Of oc Oquirrh Formation, unit C, upper limestone (Upper Pennsylvanian)—Gray breccias that lie unconformably on the Little Creek Formation; includes and tectonic setting of upper Cenozoic volcanic rocks near Blackfoot, Idaho: South quadrangle, Bannock and Power counties, Idaho: Idaho Geological Os and blue-gray limestone and silty limestone with minor chert-pebble ga Middle Ordovician diabase dikes and gabbro; thickness up to 300 feet ( (91 m). Gibson Jack Formation, member A (Middle and Lower Cambrian)—Tan U.S. Geological Survey Bulletin 1806, 19 p. Survey Geologic Map, scale 1:24,000. conglomerate; contains locally abundant corals; <2,000 feet (610 m). Og quartzite and siltstone with olive micaceous argillite beds; 365 feet (111 m). Kellogg, K.S., S.S. Harlan, H.H. Mehnert, L.W. Snee, K.L. Pierce, W.R. Hackett, 18. Scott, W.E., 1982, Surficial geologic map of the eastern Snake River Plain and Lower Tl Little Creek Formation (lower Pleistocene or upper Pliocene)—Mainly basaltic o o ob and D.W. Rodgers, 1994, Major 10.2-Ma rhyolitic volcanism in the eastern adjacent areas, 111 E. to 115 W., Idaho and Wyoming: U.S. Geological OC– su tuff and breccia erupted from vent near Massacre Rocks; <75 feet (23 m). Oquirrh Formation, unit B (Upper and Middle Pennsylvanian)—Sandy Pzr Paleozoic rocks, undifferentiated (Paleozoic)—Includes Cambrian limestone OC– s Snake River Plain, Idaho—Isotopic age and stratigraphic setting of the Arbon Survey Miscellaneous Investigations Map 1372, scale 1:250,000. C– sw limestone, calcareous sandstone, and limestone; generally not cherty; north of Pocatello Creek. Upper 19. Trimble D.E., and W.J. Carr, 1976, Geology of the Rockland and Arbon Formation bioclastic; 800 feet (244 m). Valley Tuff Member of the Starlight Formation: U.S. Geological Survey St. Charles Tb Basalt (Pliocene?)—Includes basalt of Buckskin Basin first mapped by Hladky – Cn and others, 1992. Diktytaxitic vesicular basalt; <500 feet (152 m). Zc Camelback Mountain Quartzite (Lower Cambrian and Late Proterozoic)—Light Bulletin 2091, 18 p. quadrangles, Power County, Idaho: U.S. Geological Survey Bulletin 1399, oa C– bo Oquirrh Formation, unit A, lower limestone (Middle Pennsylvanian)—Tan purple to white, locally pebbly quartzite with local channelized basal cobble Scott, W.E., K.L. Pierce, J.P. Bradbury, and M.M. Forester, 1982, Revised Quaternary 115 p. Twn Walcott Tuff and Neeley Formation (upper Miocene). or light gray cherty limestone; locally bioclastic; >2,000 feet (610 m). 20. Trimble D.E., 1976, Geology of the Michaud and Pocatello quadrangles, C– e conglomerate; <1,420 feet (430 m). stratigraphy and chronology in the American Falls area, southeastern Idaho, in Bill Bonnichsen and R.M. Breckenridge, eds., Cenozoic Geology of Idaho: Bannock and Power counties, Idaho: U.S. Geological Survey Bulletin 1400, Cambrian Mm Manning Canyon Shale (Lower Pennsylvanian and Upper Mississippian)—Dark- Tw Walcott Tuff (upper Miocene)—Purplish gray, densely welded rhyolite ash-flow Mutual Formation (Late Proterozoic)—Purple and maroon medium- to coarse- Idaho Bureau of Mines and Geology Bulletin 26, p. 581-596. 88 p. Middle colored shale and argillite with interbedded limestone, siltstone, and Zm C– gc tuff above Neeley Formation; corrected K-Ar date of 6.5 Ma (Kellogg and grained, locally pebbly, feldspathic quartzite and conglomerate; sparse and Marvin, 1988); <16 feet (5 m). sandstone; 1,200 feet (366 m). discontinuous siltite interbeds; <3,000 feet (914 m) in Bannock Range; thins – – Cgb Cg drastically in Portneuf Range to <1,400 feet (427 m). Tn Neeley Formation (middle Pliocene to upper Miocene)—Tan to orange, tuffaceous Mmc Monroe Canyon Limestone (Upper Mississippian)—Dark gray limestone with C– ga Lower clayey sandstone and rhyolitic tuff; <100 feet (30 m). abundant horn corals in lower part and abundant chert in upper part; >1,000 Zi Inkom Formation (Late Proterozoic)—Olive green and dark purple siltite and feet (305 m). C– Zc fine sandstone; about 825 feet (250 m). Ts Starlight and Salt Lake Formations, undifferentiated (Pliocene? and middle and Mh upper Miocene). Humbug Formation (Upper Mississippian)—Tan, calcareous quartz sandstone; Zc Caddy Canyon Quartzite (Late Proterozoic). Zm 656 feet (200 m). Tsug Brigham Group Zi Starlight and Salt Lake Formations, upper member (Pliocene? and upper Zcu Caddy Canyon Quartzite, upper member (Late Proterozoic)—Trough cross- Miocene)—Locally tuffaceous gravel and conglomerate; uppermost Mgb Great Blue Limestone (Upper Mississippian). Zcu bedded purple and maroon quartzite with discontinuous siltite intervals and Zc Zcd stratigraphic unit in Lava Hot Springs quadrangle; >200 feet (61 m). cobble conglomerate marker bed near top; thicknesses are 1,300-2,000 feet Mgu Great Blue Limestone, upper limestone member (Upper Mississippian)— Zcl (460-600 m) in the Bannock Range and 600-800 feet (183-244 m) in the Tsud Salt Lake Formation, upper member (Pliocene? and upper Miocene)— Thin-bedded cherty nodular dolomite and limestone; 850 feet (259 m). Zpa Portneuf Range. Neoproterozoic PRECAMBRIAN Diamictite; poorly exposed boulder-rich deposits; in Portneuf Range unit Mgm Great Blue Limestone, middle shale member (Upper Mississippian)—Dark contains mainly Ordovician Swan Peak Quartzite boulders; thickness varies Zcd Caddy Canyon dolomite marker bed (Late Proterozoic)—Marker of cream- shale, local quartzite, and limestone concretions; 400 feet (122 m). Zb to 300 feet (91 m); mapped by Hladky and others (1992). colored dolomite between upper and lower members; <10 feet (3 m). Zpu Mgl Great Blue Limestone, lower limestone member (Upper Mississippian)— Tsu Starlight and Salt Lake Formations, upper member (Pliocene? and upper Zcl Caddy Canyon Quartzite, lower member (Late Proterozoic)—Well-bedded Light gray thick-bedded limestone; locally cherty and abundantly bioclastic; Miocene)—Deposits of rhyolitic tuff, gravel, and conglomerate with local quartzite with local tan and green siltite beds; thicknesses are 1,650-2,300 Zp Zps 1,195 feet (364 m). basaltic and rhyolitic lavas, ash-flow tuffs, and basaltic vents; thickness in feet (500-700 m) in the Bannock Range and as great as 4,970 feet (1,515 Pocatello Formation Zpb Lava Hot Springs quadrangle is >5,900 feet (1,800 m). m) in the northern Portneuf Range.

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