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U.S. DEPARTMENT OF THE INTERIOR OPEN-FILE REPORT 2009–1189 U.S. GEOLOGICAL SURVEY Version 1.0 Tm 105°15’ Qc Qac 105°7’30” Qac QTso 105° 37°30’ Qls 37° CORRELATION OF MAP UNITS 30 m deep, respectively, and are deflation basins (Pillmore, 1976). Some of the Contact—Solid where location is certain; dashed where approximately located Tsfc Qc Tsfr Qls Ku Qa Tsfc Qac other natural closed depressions in the eastern part of the map area may also have Qa Qls ^s Scratch boundary—Arbitrary line that separates sedimentary rocks mapped as Ku Qbao Kv SURFICIAL DEPOSITS formed chiefly by eolian deflation. Estimated thickness 2 m Jm Tpc TKr Poison canyon Formation (Tpc) and Raton Formation (TKr) east of line, from Tm Qls Tm Qa QTsy BEDROCK TKpr Qac Alluvial and Eolian those mapped as Poison Canyon and Raton Formations, undivided ( ) Qc mass-movement Mass-movement deposits Qa Tsfc Qf Tps Alluvial deposits deposits Tsfr Ku Qbey deposits Rocks that postdate the Laramide orogeny, Subdivided into: Shoreline Tsfr Tsfc Qc Jm Qls Tiom Tm Tpc Sedimentary rocks Tsfc Tat Tm Qa Holocene Tsfr Qbeo Tvf Conglomerates, mainly prevolcanic (lower Oligocene and Eocene)—Boulder Lineament Qls Qsw Qac Qf Qt Qbs Tvf Ta ^s Qc Qls conglomerates with clasts of various local Proterozoic lithologies, especially 68 Ta Ta Qsw Qty ? Normal fault—Solid where location is certain; dashed where approximately located, Qsw Qgp Qbay Ku Qa quartzite; but including much lesser clasts of andesites (Ta) in uppermost part; dotted where concealed. Bar and ball on downthrown block. Dip symbol and Tsfr Kdp Qa Qsw Qe Tsfc Tsfc Tat Qbai Qti Qgb Qbai boulders range to at least 2 m and are generally well rounded; matrix consists of number indicate measured dip of fault plane Qc ? ? ? QTsy deep maroon colored red clay where locally (rarely) exposed; generally equiva- Tat Qto Qbao Qac Qc TKr QUATERNARY lent to “Prevolcanic sedimentary rocks” of Lipman and Reed (1989) Thrust fault—Solid where location is certain; dashed where approximately located, Tvf P*sc Je QTsy Pleistocene Qc dotted where concealed. Sawteeth on upper (tectonically higher) plate Ta Qls Jm Qbey Santa Fe Group (Miocene to Oligocene)—Syntectonic sedimentary and volcanic rocks deposited as fill in basins of the Rio Grande rift; everywhere divided into: Strike-slip fault, left-lateral offset—Solid where location is certain; dotted where Tvf Ku Kt Ku Qbeo concealed. Arrows show relative motion Qac Qbao Tiom Tsfc Alluvial facies—Pebble to cobble sand-matrix conglomerate, pebbly sandstone Tm Qls TKr Qsw ? Qa Qa QTsy and siltstone; poorly to moderately consolidated; ochre-colored to light red; large Strike-slip fault, right lateral offset—Solid where location is certain. Arrows show Ta Qa clasts derived mainly from local Proterozoic bedrock and much lesser local relative motion Qc ^s Jm Qsw QTso Tvf ? volcanic rocks (andesite, rhyolite, and tuff; Ta, Tfl, and Tat); only very locally Je Qc Ku Quaternary normal fault Qls Pliocene present below Amalia Tuff (Tat), and there lacking in local volcanic clasts; Tps stratigraphically high exposures are commonly capped by mafic lava flows Kv Tps BEDROCK (Tm); thus probably ≥ 12 Ma (Kirkham and others, 2005) throughout most if not Landslide scarp Xgg Kdp Qbai Qsw all of map area Sedimentary Volcanic Intrusive Bedding lines Qc Tsfr Volcaniclastic facies—Boulder to pebble sand-matrix conglomerate of mainly Qa Qbao Tm Tmi Horizontal bedding Tiom Miocene volcaniclastic composition; clasts of local andesite, rhyolite, and tuff (Ta, Tfl, |Zg P*sc Tvf Qbey Qsw Qa Tat 30 Qbeo and ), along with much lesser intermixed clasts of local Proterozoic bedrock; Inclined bedding—Showing strike and dip Je Qc Tsfc Tsfr includes minor tuffaceous layers which appear to be reworked rather than ^ Qa 3 Qac s Ku Inclined bedding—Showing strike and dip. Top direction of beds known from local Qac Qto Tfl Tiof juvenile Qa Tps Tiom features. Top of bed indicated by ball Kdp Qty Tat Volcanic rocks Jm Qsw TERTIARY Xgg Ta Vertical bedding Qc Qa Tiom Qa Qa Tm Mafic lava flows (Miocene)—Basalt and basaltic andesite lava flows with sparse Tvf Qti Oligocene Qbao Kt plagioclase and olivine phenocrysts; dated at ~12 to ~15 Ma to the north of map 39 Ta Qc Ta Tioa Overturned bedding—Showing strike and dip *Mme Qsw (40Ar/39Ar, whole-rock; Kirkham and others, 2005); interbeds of alluvial facies Tat Qc TKr 15 Qac Qls Qbay of Santa Fe Group (Tsfc) locally included where too thin to map separately Inclined flow foliation or layering in igneous rock—Showing strike and dip Qa TKpr Tvf 53 Tfl Ku Qf Tfl Rhyolite lava (Oligocene)—Rhyolite lava with <0.5 percent phenocrysts of feldspar Inclined foliation in metamorphic rock—Showing strike and dip Tat Ta TKr Eocene Xgg Ku Tiom and quartz in a light grayish-blue groundmass; locally sperulitic or reddened by 40 Qbeo Qc Inclined foliation in igneous rock—Showing strike and dip Qa oxidation; probably equivalent to “rhyolitic lava flows (Tr)” mapped by Lipman Qc Qc Qsw Tfl and Reed (1989) southwest of map 31 Lineation—Showing bearing and plunge Xgg Qa Tpc Paleocene Ku Qa Tat Amalia Tuff (Oligocene)—Peralkaline rhyolite ash-flow tuff; mainly densely welded, Overturned anticline Qc Qbay TKpr TKprc Qac Qty Kv with 10 to 20 percent phenocrysts of quartz and alkali feldspar (transitional Tsfr Qac Qls TKr sanidine-anorthoclase), and sparse to rare pyroxene, fayalite and sodic Coal bed Qsw Tiom Qty Qsw amphibole; dated at 25.5 Ma (40Ar/39Ar, feldspar; Lipman and Reed, 1989) Dry hole Kv Unconformity Tiom Qbao Ta ^s Qbay Ku Qf Andesites (Oligocene)—Thick sequence of lava flows, tuffs, lahars, and lesser Qgb Je Kdp Ku Kv Qc Kt Upper Cretaceous interbedded volcaniclastic conglomerates and sandstones; mainly of andesitic Qa Tmi Qls Qbey Kv Kt CRETACEOUS composition but includes some dacites and rhyolites; equivalent to Conejos Qbai Ku Qa Qbao Qsw Interior Formation of the San Juan Mountains; equivalent rocks to southwest of map have Tsfc Qa seaway Ku been called “precaldera volcanic rocks,” which Lipman and Reed (1989) divide Qc Qc TKpr into 15 map units ranging in age from ~30 to ~26 Ma Qgb Tiom Qc Qty Ku Qa Kdp Lower Cretaceous TKr Qgp Qac Unconformity Intrusive rocks INTRODUCTION Tiom Tiom Jm Qc Jm Upper Jurassic Tmi Mafic dike (Miocene)—Basaltic andesite dike with sparse plagioclase phenocrysts This geologic map covers four 7.5-minute quadrangles: The Wall, NM−CO (New Mexico− JURASSIC Tioa Kt and quartz xenocrysts; presumed to be related to Xenocrystic basaltic andesite Colorado), Vermejo Park, NM−CO, Ash Mountain, NM, and Van Bremmer Park, NM. The study Qsw Qa Je Middle Jurassic Qc Qbai Post-tectonic area straddles the boundary between the eastern flank of the Sangre de Cristo Mountains and the Qty Qsw Qls Ku Unconformity (Tbx) of Lipman and Reed (1989), to south of map. If this proposed correlation Qac Qac is correct, Tmi is similar in age to the oldest of the Mafic lava flows (Tm) of western margin of the Raton Basin. This foreland basin formed immediately eastward of these QTsy Kt ^s Qls Qc Qti Qbao TRIASSIC northern part of map area, based on stratigraphic position mountains during their initial uplift, in the Late Cretaceous through early Eocene Laramide orogeny QTso Qa Lower Permian PERMIAN (Lindsey, 1998). Subsequently, the Sangre de Cristo Mountains were extensively modified during P*sc Tiom Basalt and lamprophyre intrusions (Miocene to late Oligocene)— Dikes and sills formation of the Rio Grande rift, from ≥26 Ma to present (Chapin and Cather, 1994). One effect of P*sc Ku Colorado of basalt and lamprophyre composition, with a visibly granular groundmass; Ku Qf PENNSYLVANIAN that modification is that the Sangre de Cristo Mountains now consist of several contiguous, but Xfa Qc Qc Trough presumed to be related to the intrusive complex at Spanish Peaks (~20 to ~26 Je Qbay topographically distinct, component ranges. In that context, the map area covers part of the Kv Qls Kt Kv Qsw *Mme Ma); not related to any known local volcanic rocks southern Culebra Range, as well as the northeastern part of the Devil’s Park graben (Kirkham and Qac MISSISSIPPIAN Kt Tiof Felsic intrusion of Ash Mountain (Oligocene)—Very large hypabyssal intrusion of others, 2005)—a small intermontaine basin that is satellitic to the San Luis Basin, that is an Ku Unconformity Qac rhyolitic composition, probably a sill emplaced within very steeply dipping beds; outlying, early-formed part of the Rio Grande rift, and that separates the Culebra Range from the Tiom TKr appears identical to rhyolite lava (Tfl) in phenocryst and groundmass character Taos Range, to the southwest. The major local part of the Rio Grande rift is the San Luis Basin, TKpr which lies to the west of map area. Dikes |Zg EARLY PALEOZOIC Tioa Intermediate-composition intrusions (Oligocene)—Hypabyssal sills and dikes of Je Ku QTsy Field work for this map was carried out by Fridrich, Shroba, and Hudson during the summer of NEOPROTEROZOIC andesitic (diorite porphyry) composition; probably related to andesites (Ta) Mixed 2006. This new mapping was built upon earlier mapping by Pillmore that was conducted primarily Qf Qa Laramide-age syntectonic sedimentary rocks of Raton Basin Tioa Qsw Metaintrusive metavolcanic during the 1970s. Pillmore’s mapping of the eastern half of the study area (the Vermejo Park, NM− and CO, and Van Bremmer Park, NM quadrangles) has been published in two U. S. Geological Survey Qsw Qa metasedimentary TKpr Poison Canyon and Raton Formations, undivided (Paleocene and Upper 36°52’30” Xag Kdp open-file reports (Pillmore, 2003a, 2003b). His unfinished mapping of the two quadrangles that Qsw 36°52’30” Cretaceous)—Combined unit mapped in central to southern part of map area Xgg Xag Xp constitute the west half of the study area was used in this study as a starting point.

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