WYOMING STATE GEOLOGICAL SU RVEY OPEN FILE REPORT 2016-4 Th omas A. Drean, Director and State Geolog ist Ervay Basin SW 1:24,000-scale Laramie, Wyoming Bedrock Geolog ic Map (M Interpreting the past, providing for the future E R A IL R A E ) N S C P C M A H ( G ) (ERVAY BASIN) Qal 46 Qls ^cr EXPLANATION ^cr Kf Kmr CORRELATION OF MAP U NITS Qp 21 45 DESCRIPTION OF MAP U NITS Cenozoic Qal Holocene Qls Qve Qp ? QU AT ERNARY Kt Pleistocene Qal ^Pg Qal ? ? ? j Alluvium (Holocene)— U nconsolida ted to poorly consolida ted sa nd, silt, cla y, coa rse gra vels, a nd 34 Pliocene 31 20 ? cobbles, m a inly a long loca l interm ittent strea m courses; loca lly interm ixed with colluvium . T hickness Qp Jm Kcv U nconform ity T NEOGENE less tha n 8 m (26 ft) ^cp Js 24 ^ca E Qls Tsr Miocene Landslide deb ris (Holocene and Pleistocene[?])— Blocks a nd slum ps of loca lly derived bedrock from 29 10 R steep a nd unsta ble slopes; m ost com m on in Cloverly Form a tion a s well a s Wa gon Bed Form a tion Qp U nconform ity *t 19 a long Bea ver Rim . T hickness less tha n 122 m (400 ft) 11 T CENOZ OIC 20 ^cr Twr Oligocene Qve I Volcanic eluvium (Holocene and Pleistocene[?])— U nconsolida ted rem na nts derived from in situ *Ma *t R U nconform ity wea thering of Ra ttlesna ke Hills volca nic rocks; gra des into Ra ttlesna ke Hills volca nics a nd volca nic *t A A conglom era tes within Wa gon Bed Form a tion. T hickness less tha n 3 m (10 ft) T Tv PAL EOGENE Qp 80 T R Qp L 33 26 Twb Eocene Pediment deposits (Holocene and Pleistocene[?])— U nconsolida ted suba ngula r pebble a nd cobble E Y 34 Mm gra vels in a coa rse sa ndy m a trix of loca lly derived sedim enta ry rocks. T hickness less tha n 3 m (10 ft) S Twdr Twdr N 19 Qp j Qal _gv A U nconform ity Jasper, jasperoid (Pleistocene[?] and Pliocene[?])— Ja speroid of unknown genesis, ora nge to red, 62 K 19 wea kly bedded. T hickness not determ ined E 26 *t ^Pg Kf Tsr _gv *Ma U pper Creta ceous Split Rock Formation (Miocene)— Interbedded sa ndstone a nd conglom era te; not exposed in outcrop but Kmr 60 4 inferred a s the lower porous sa ndstone sequence from Cola a nd Sutherla nd (2014). T hickness less 19 CRET ACEOU S 6 Kt tha n 30 m (100 ft) ^Pg Mm 24 64 Mm L ower Creta ceous 18 Kcv Twr *t 40 _f 29 Wh ite River Formation (Olig ocene)— White well-indura ted silty sa nd a nd whitish-ta n reworked a sh 17 8 with fine- to m edium -gra ined lithic fra gm ents; conta ins a bunda nt biotite a nd gla ss sha rds, a long with Mm U nconform ity 1 52 _gv *t persistent thin pum icite beds (L ove, 1970). Disconform a ble ba sa l conta ct scours into the underlying 10 Jm U pper Jura ssic MESOZ OIC Wa gon Bed Form a tion. Occurs only on the northwestern edge of Bea ver Rim . T hickness 47 34 Wfr 32 40 JU RASSIC a pproxim a tely 0–49 m (160 ft) Js H 5 48 19 Middle Jura ssic I Tv 25 L _gv Rattlesnake Hills volcanic rocks, undifferentiated (Eocene)— Volca nic flows, breccia s, a nd _f U nconform ity 56 _gv L Wfr S a gglom era tes a ssocia ted with the Ra ttlesna ke Hills volca nics ra nge in com position from phonolite Mm 16 Mm 80 ^cp 45 24 (Hoch, 1991) to tra chyte to da cite; interfingers with Wa gon Bed Form a tion. U -Pb zircon 10 U pper T ria ssic geochronology from topogra phica lly highest outcrop yields 45.2 ± 0.2 Ma . T hickness less tha n 6 m ^ca 54 16 T RIASSIC 16 51 (20 ft) ^cr L ower T ria ssic Twb 30 _f Wag on Bed Formation (Eocene)— T hree distinct fa cies exist in m a p a rea . Conglom era te conta ins ^Pg ^Pg Perm ia n PERMIAN cobbles a nd pebbles of predom ina tely Ra ttlesna ke Hills volca nics, U T Creek Form a tion, a nd Sa ca wee Wfr 84 59 U nconform ity orthogneiss, with unconsolida ted boulders a s la rge a s 2 m (7 ft) in dia m eter. T uffa ceous siltstone a nd 64 cla ystone a re whitish gra y, poorly consolida ted to well indura ted, a nd ra rely exposed except for one 8 Wfr 20150925RL-07 *t brillia nt white outcrop on the west side of Bla ck Mounta in. L a pilli tuff is a white to light-gra y fine- 61 A Pennsylva nia n PENNSY L VANIAN 30 N gra ined a nd poorly consolida ted well-indura ted a sh with la rger cla sts of gla ss a nd feldspa r a nd a sh- T 64 *Ma I C rich cla sts up to 15 cm (6 in). U -Pb zircon geochronology of Wa gon Bed tuffs yields a ges of 47.9 ± 32 L I Wfr Qal N E U pper Mississippia n 0.3 a nd 45.4 ± 0.2 Ma . Ba sa l conta ct is disconform a ble; interfingers with Ra ttlesna ke Hills volca nics. 19 29 U nconform ity PAL EOZ OIC Mm MISSISSIPPIAN T hickness is highly va ria ble with a m a xim um of 122 m (400 ft) Mm 19 Wfr L ower Mississippia n Twdr 62 Wind River Formation (Eocene)— Va riega ted yellowish-brown to ora nge cla ystone, siltstone, 63 _gv _f U nconform ity *t sa ndstone, a nd conglom era te interbedded with white tuffs (L ove, 1970); sa ndstones a re a rkosic, 82 _gv U pper Ca m bria n m edium to coa rse gra ined with a n a bunda nce of a ngula r qua rtz gra ins; conglom era tes a re CAMBRIAN predom ina tely com prised of Preca m bria n igneous a nd m eta m orphic cobbles. Ba sa l conta ct is ^Pg _gv _f Middle Ca m bria n Mm disconform a ble. T hickness is highly va ria ble but genera lly less tha n 300 m (1,000 ft) Qal U nconform ity Mesozoic Wpg 16 _f Kf Frontier Formation, main b ody (U pper Cretaceous)— Interbedded siltstone, bla ck sha le, a nd gra y to Wmsh brown, fine- to coa rse-gra ined sa ndstone. Middle a nd lower sa nd beds a re fine to m edium gra ined, 27 *Ma well sorted with rounded gra ins; suba ngula r da rk lithics give sa ndstones a ‘sa lt a nd pepper’ Twdr Wfr Wesh ^Pg a ppea ra nce. Sa ndstones crea te sm a ll ridges between less resista nt sha les, siltstones, bentonites, a nd Qal 34 Neoa rchea n Wfr ARCHEAN PRECAMBRIAN coa ls. Overla in by Wa ll Creek Sa ndstone Mem ber, not exposed on m a p. Ba sa l conta ct is conform a ble 27 ^Pg a nd sha rp. T hickness a pproxim a tely 204 m (670 ft) (Bogrett, 1951) ^Pg 31 Wutg 34 UT Creek 12 Formation 19 Kmr *t Wuta Mowry Sh ale (U pper Cretaceous)— Orga nic, bla ck to da rk-gra y, siliceous sha le tha t conta ins a bunda nt 58 *t fish sca les a nd num erous bentonite beds. Bedding a nd la m ina tions a re usua lly less tha n two Vbs Mesoa rchea n 25 centim eters thick. Wea thers silver gra y a nd form s prom inent slopes a nd resista nt ridges. Ba sa l conta ct 87 12 is conform a ble (Roth, 1955). T hickness is 116 m (380 ft) (Bogrett, 1951) 17 31 ) K Kt *Ma A Th ermopolis Sh ale (Lower Cretaceous)— Nonresista nt, da rk-gra y to bla ck, fissile, bioturba ted sha le a nd E ) P S L siltstone tha t is nonca lca reous a nd ca rbona ceous; occa siona l thin resista nt siltstones a nd sa ndstones D L Qal I L H E 17 Twb I throughout; iron concretions a re present nea r the top (Peka rek, 1978). Ba se is conform a ble. S Mm F A R Approxim a tely 58 m (190 ft) thick (Bogrett, 1951) A G ( 17 G ( K cv Cloverly Formation (Lower Cretaceous)— Resista nt buff to gra y, brown-wea thering, qua rtz a nd chert 22 16 pebble conglom era te with rounded pebbles a nd gra nules a t ba se, va riega ted sha le a nd cla ystone in Qve _gv 23 MAP SYMBOLS m iddle, a nd ca pped by a fine-gra ined cross-bedded, sla bby sa ndstone a nd loca lly by a white 18 recrysta llized lim estone. T he conglom era tic unit form s a ridgetop in the m a pped a rea; com m only Certain— Estim ated location <25 m broken by la ndslides.