New Mexico Geological Society Downloaded from: http://nmgs.nmt.edu/publications/guidebooks/22 Lexicon of stratigraphic names used in south-central Colorado amd northern New Mexico, San Luis Basin Christina Lochman-Balk and James E. Bruning, 1971, pp. 101-111 in: San Luis Basin (Colorado), James, H. L.; [ed.], New Mexico Geological Society 22nd Annual Fall Field Conference Guidebook, 340 p. This is one of many related papers that were included in the 1971 NMGS Fall Field Conference Guidebook. Annual NMGS Fall Field Conference Guidebooks Every fall since 1950, the New Mexico Geological Society (NMGS) has held an annual Fall Field Conference that explores some region of New Mexico (or surrounding states). Always well attended, these conferences provide a guidebook to participants. Besides detailed road logs, the guidebooks contain many well written, edited, and peer-reviewed geoscience papers. 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No material from the NMGS website, or printed and electronic publications, may be reprinted or redistributed without NMGS permission. Contact us for permission to reprint portions of any of our publications. One printed copy of any materials from the NMGS website or our print and electronic publications may be made for individual use without our permission. Teachers and students may make unlimited copies for educational use. Any other use of these materials requires explicit permission. This page is intentionally left blank to maintain order of facing pages. 101 LEXICON OF STRATIGRAPHIC NAMES USED IN SOUTH- CENTRAL COLORADO AND NORTHERN NEW MEXICO, SAN LUIS BASIN by CHRISTINA LOCHMAN-BALK AND JAMES E. BRUNING New Mexico Institute of Mining and Technology Socorro, New Mexico This lexicon is an alphabetical listing of the stratigraphic L. lower names used in the Guidebook of The New Mexico Geolog- lent. lenticular ical Society-22nd Field Conference. Unit names (forma- lithog. lithographic tion or group) system or period. Names printed in bold- mass. massive face are currently accepted by the U.S. Geological Survey. min. minimum Many of the names printed in caps and lower case are occas. occasional those that the Survey has had no occasion to consider for perst. persistent use. por. porous prcd. predominantly 1) Areal distribution given in original description. sdy. sandy 2) Reference in which unit was first defined or men- slit. slightly tioned. transit. transitional 3) Type locality. U. upper 4) Short lithologic description (and thickness) at the unclif. undifferentiated type locality or in the type area. 5) Age to stage; contacts; emending or refining de- ALBOROTO RHYOLITE—U. Oligocene scriptions of note; additional areal distribution; 1) SW Colorado. additional information on thickness, Ethology, 2) E. S. Larsen, 1917, Colo. G. Survey Bull. 13, p. 20, and character of the beds in the area of the 22nd 36; Larsen and Cross, 1956, U.S.G.S. Prof. Pap. 258, Field Conference (1971). p. 132-143. The following glossary of abbreviations contains those 3) Alboroto Peak, San Cristobal Ouadr., Hinsdale Co., used in the list of names that are not widely used and Colo. known. Most abbreviations used herein for lithologic de- 4) Low. part (1/5) of tridymite rhy.-thin flows and scription are well known to all geologist, and are not in- assoc. tuffs (0-500') Up. part (4/5) of biotite horn- cluded in the glossary. blende latite and rhyolite (0-3,000'). 5) Disconf. on Sheep Mtn. Otz. Latite; overlain conf. alt. alternating by Huerto Otz. Latite; covers over 100 mi. in San ascend. ascending, in ascending order Juan Mtns., max. thick. in Creede Quad.; Low. pt. btw. between incl. (Campbell Mtn. rhy., Willow Creek rhy.) .,= calc. calcareous Bachelor Mtn. Rhyolite, Outlet Tunnel qtz. latite; calcar. calcarenites Up. pt. incl. Equity and Phoenix Park qtz. latites;= char. characterized Fish Canyon Tuff-La Garita Otz. Latite and An- conf. conformable or conformably. Used also &site of Saguache Cr. (27.8 m.y.). with prefixial "un" and "dis." L. membs. = Blue Mesa Tuff, Dillon Mesa Tuff. cont. continental Sapinero Mesa. Tuff. U. memb. Fish Canyon correl. correlative or correlated Tuff (Olson, Hedlund and Hansen, 1968). depos. deposited descend. descending, in descending order Antero Formation—Oligocene desig . designated 1) Cent. Colorado. equiv. equivalent 2) J. T. Stark et al., 1949, Geol. Soc. Am. Mem. 33, p. fang. fanglomerate 63. flue. fluviatile 3) In Ts. 12-15 S., Rs. 75-76 W., south and west of gradat. gradational Hartsel, Park Co., Colo. gr.g grain (ed ) 4) Lake seds.-3 mems., ascend.—thin algal lss. at base, gran. granular tuff, sss., cgls., minor shs., basal cgls. lentic., poor. gray. gravel sort. tuff interb. with shs., up to 100' thick; mid interb. interbedded memb. fine gr. pumice, tuffs (50') at base, overlain 102 NEW MEXICO GEOLOGICAL SOCIETY-TWENTY-SECOND FIELD CONFERENCE by lent. dense shs. and fossil. algal lss.; up memb. 3) N. side of Rock Cr. along U.S. Hwy. 24 (1938) 0.2 cgls. with ss. intcrb. (600'-2,000' ). m. N. of Gilman, Eagle Co., Colo. 5) White River age; vert. fossils, fresh water gastro., 4) Interb. drk. gry. argill. lss. and lam. carbonac. shs., ostracods, algae, wood: Disconf. on Blafour Fm., thin sss., and a few imp. coals (25'-200') increase to unconf. overlain by Wagontongue Fm., deposits of S. to 1,100' in Chaffee and Gunnison Cos., (Dings Lake Antero. and Robison 1957). 5) Desmoinesian; raised to Fm. by Brill (1944), re- Abiquiu Tuff—Miocene places Weber Sh. for basal Penn. in Colo.; unconf. 1) N. Cent. New Mexico. on Leadville Ls., overlain conf. and gradat. by Min- 2) H. T. U. Smith, 1938, Jour. Geol. v. 46, p. 944. turn Fm.; Dings and Robinson rccogn. 3 mcmbs., 3) Along the Chama Valley west of Abiquiu, Rio ascend.-drk. sh.; intcrb. lss. and shs.; shs. with qtzite. Arriba Co., New Mexico. 4) Wh., It. gry. to orange, fin. lamin. to mass. bed. tuff Big Baldy Andesite (see Informal Names List) and vole. cgl., stream laid, few intcrb. lava flows; forms steep cliffs (1,000'-1,250' ). Biscara Member (of Los Pinos Formation)—Miocene? 5) Disconf. on El Rito Fm., unconf. on Precamb. gran- or Pliocene? ite; overlain conf. and gradat. by Santa Fe Fm.; E. of Biscara—Esquibel member; Biscara intrusive andesite El Rito Cr. cgls. and sss. pred. intcrb. with tuff. 1) N. Cent. N. Mex. layers in up. pt. up. pt. of Los Pinos Fm. and low. 2) Fred Barker, 1958, N. Mex. Bur. Min. and Miner. pt. of Santa Fe Fm.; Consid. memb. of Santa Fe Fm. Res. Bull. 45, p. 44. by Budding, Pitrat and Smith (1960 ). 3) In Biscara Canyon 1.5 mi. from mouth, Las Tablas Ouad., Rio Arriba Co., N. Mex. ALAMOSA FORMATION—Pliocene-Pleistocene 4) Interb. tuffac. sss., tuff, cgls. and vole. flow brecc.; 1) S. Cent. Colorado. low. unit of gry. rhy. tuff, water-laid tuffac. cgls.; 2) C. E. Sicbenthal, 1910, U.S.G.S. Wat. Sup. Pap. 240, up. unit of poor. sort. cgls. of qtzite, pegmat. in ark. p. 40. matrix (650'-700'). 3) Hansen Bluff, E. bank Rio Grande Riv., SE. of 5) Unconf. on Precamb. rocks; overlain disconf. by Alamosa, and logs of test wells, T. 39 N., T. 40 N., Jarita Memb. and Cordito Memb. overlap from S. R. 11 E., (W. J. Powell, 1958), Alamosa Co., Colo. to N.; grades N. into Biscara-Esquibel Memb. 4) Buff-red uncon. gray., sss., silt, clay; qtz. pebb.; br. to blu-gry. clay in up. pt; all lithol. rapid lat. and vert. Biscara-Esquibel Memb.—(of Los Pinos Formation)— changes (0-2,000' ). Miocene? or Pliocene? 5) Siebenthal put top below first perst. fine ss. or clay; Undif. sss., tuff, cgls., and vole. flow brecc. of low. Powell includes all Recent ss. and gray.; deepest: Los Pinos Fm. below Jarita Bas.; mapp. as single unit gray. at 72'; below blu. clay alter. with fine ss.; great. by Fred Barker, 1958. thick near depo. center of San Luis Valley; fresh water snails and vert. frags. age Late Plio. and/or BLANCO BASIN FORMATION—Oligocene? Early Pleisto. 1) SW Colorado. 2) E. S. Larsen, 1935, U.S.G.S. Bull. 843, p. 48. BACHELOR MOUNTAIN RHYOLITE—U. 3) E. side of Chama Riv., near S. edge of Summitville Oligocene _Ouad. Archuleta Co., Colo. 1) SW Colorado. 4) Ark. sss., cgls., shs., no vole. mater.; 3 memb., ascend., 2) T. A. Steven and J. C. Ratte, 1965, U.S.G.S. Prof. brit. red, soft, mdy., sss. and shs.; brok. cliff of interb. Pap. 475-D, p. D57. wh. sss. and red shs.; cliff of wh. sss. (500'-600'). 3) Bachelor Mtn. NW of Creede, Mineral Co., Colo. 5) Unconf. on Cret. fms. and Animas Fm., overlain 4) Lt. gry. dens. weld. rhy. tuff at base grad. up to com- conform. by Conejos Fm.; F. B. Houton (1957 )— pact weld. tuff in mid., to por.