sign in sign up
<<
Home , Madera Group

BUREAU OF GEOLOGY AND MINERAL RESOURCES A DIVISION OF NEW MEXICO INSTITUTE OF MINING AND TECHNOLOGY Unit Descriptions for the Arroyo del Agua 7.5' quadrangle NMBGMR Open-file Map Series OFGM-124 Cretaceous stratigraphy on the Arroyo del Agua quadrangle follows that of Landis and Last Modified 05 March 2014 Dane (1967), Saucier (1974) and Owen et al. (2005). The intertongued Dakota-Mancos Jt Todilto Formation (Middle ). The Todilto Formation consists of a Qrf Rock Fall (Holocene). Building-sized blocks of Poleo Formation that have succession is referred to here as the for mapping purposes, because lower, -dominated interval (Luciano Mesa Member, Jt (ls)) overlain locally by broken away from the edge of the sandstone cliff in the recent past (0358913 N 4003825 a gypsum interval (Tonque Arroyo Member; (Jtg) (Lucas et al., 1985, 1995; Kirkland et Py Yeso (Early ). Orange-red medium-grained, moderately to well- 106°42'30"W 106°40'0"W most of the Dakota members and all of the Mancos members are generally too thin to sorted sandstone with large-scale (eolian) crossbeds, or more rarely, laminated sand sheet 343000 344000 345000 346000 347000 348000 349000 350000 351000 352000 353000 E, NAD 27); the Ponderosa pine trees affected by the fall are dead, but the wood decay al., 1995). The Luciano Mesa Member is 2 to 8 m thick and consists mostly of thinly map separately. Furthermore, the Mancos member that is present (Clay Mesa member) is bedding. These strata are equivalent to the De Chelly Sandstone of the Qal Kd Kbc process is not very advanced. laminated, dark gray or yellowish gray, kerogenic limestone. Beds near the base of the Kbc Kbc 4 7 Qal 5 6 very sandy, so it is treated as a member of the Dakota Formation. Qal Ql 1 Qc 10 Qal Qc (Baars, 1962; Krainer et al. 2005) (Meseta Blanca Member of the Yeso Formation of 2 Qal 8 Qc 7 Qsly Young landslide deposit (Holocene). Unconsolidated, hummocky deposit of member are usually sandy, and microfolding of the thin limestone laminae is common. Kbc Kbc Kbc Kd Kd Dakota Sandstone (). (includes Clay Mesa Member of Mancos Northrop and Wood, 1946 ). The eolian sandstone gradationally overlies or is 4 Kbc Kbc Kbc Trassic Salitral Formation shale that slumped downslope in the recent past (350084 N The overlying Tonque Arroyo Member is up to 30 m of white to light gray gypsum Qc Kbc 2 14 Qal Qal Shale, of the intertongued Dakota-Mancos succession). Tan to yellow-brown quartzose interbedded with the arkosic fluvial deposits of the Arroyo del Agua Formation and is 5 Qc Kbc Qc 17 Kd interbedded with carbonate. A thin limestone bed (0.5 to 2.0 m) is deposited on the Qc 4002658 E, NAD 27); vegetation on the deposit is not fully reestablished and Poleo sandstone, dark gray and brown carbonaceous shale, and minor greenish gray mudstone overlain with prominent unconformity by basal strata of the Chinle Group. The unit thins Kd Qc 14 7 Creek is downcutting through the deposit. gypsum of the Tonque Arroyo Member in many places along the Mesa Alta escarpment.. Qc 6 Jm 5 Kbc to the northeast; the line of termination for the unit trends northwest. Along the 3 Kbc Qc Qc and bentonite. Members include, from lowest to highest (oldest to youngest): Encinal Total Todilto Formation thickness is up to 38 m. 6 Kd 2 Qc Qal Alluvium (Holocene). Unconsolidated clay, silt, sand, and gravel deposited in termination, the Yeso Group sand deposits are discontinuous and range in thickness from 3 Kd Kd Kbc 4012000 Canyon, Oak Canyon, Cubero, and Paguate members. The Encinal Canyon Member is Three lithologic relationships are associated with the Tonque Arroyo Member in the Kbc major modern drainages and tributaries; up to 5 m thick. 4 2 Kbc 6 zero to 3 to 5 m, suggesting a facies change to a more fluvial environment toward the Kbc Qc highly variable in thickness, ranging from 0 to 18 m and averaging 2 to 4 m. This tan Arroyo del Agua area: (1) gypsum interbedded with carbonate is preserved (classic 2 Qc Qal Kbc Qes Eolian and alluvial deposits (Holocene). Unconsolidated windblown tan-to- northeast. Up to 20 m thick. 4012000 cross-bedded quartz sandstone, with thin to medium bedding, commonly has woody plant 3 Kbc 7 Qc Kbc Tonque Arroyo Member); (2) a limestone microbreccia left by dissolution the gypsum of Kbc Qal 4 14 brown silt and clay deposited in low-elevation spots and on pediment surfaces. Fluvially 4 impressions at the upper contact. Bioturbation is not common in the Encinal Canyon Qc reworked; contains lenses of gravel. Usually 1 to 3 m thick, but can be 10 m thick. the Tonque Arroyo Member is present; or (3) the Tonque Arroyo member is interbedded Kbc IP-PC Cutler Group (-Permian) Qal Kd Sandstone. The fine- to medium-sized sand grains are subangular to subround and well- with a green to red medium-grained quartz sandstone in two places along the escarpment 6 Kbc Kbc Qc Colluvium (Holocene). Hillslope colluvial deposits composed of pebble to We assign the oldest siliciclastic red beds in the Chama Basin to the Cutler Group. Lucas Jm Kbc boulder size, unconsolidated debris derived from local volcanic and sedimentary rocks. sorted. The Oak Canyon Member is a black, muddy siltstone interbedded with thin (<1 (344730 4009647, 347100 4009590). Thus, the Todilto Formation in the vicinity of and Krainer (2005) divided Cutler strata into two, mappable lithostratigraphic units, the Qt 5 Qc Kbc 2 Qal Kbc Kbc 2 Jm m) beds of ledgy and often lenticular, white to orange, cross-bedded, bioturbated Kd Kbc Kbc Kbc Qcbt designates colluvium composed mainly of Bandelier Tuff. Qc refers to colluvium Arroyo del Agua contains a record of places where gypsum was deposited and is still El Cobre Canyon and Arroyo del Agua formations. Several lithologic criteria allow the Jm 5 1 Qc 4 Js made up of a variety of lithologies. Up to 35 m thick. sandstone. The Cubero Member is a white, massive, thick-bedded, bioturbated preserved, areas where the gypsum was deposited, but has since dissolved away, and two formations to be distinguished: Jm Ql Kbc Kbc Kbc Kbc Qls Jtg sandstone that is 7-8 m thick. The Clay Mesa Member (of the ) is black places where the gypsum is interbedded with clastic shoreline deposits. A chaotic breccia Contrasting features of the El Cobre Canyon and Arroyo del Agua formations. Qc Kd 2 3 Qtn Terrace deposits (middle to Holocene). Alluvial silt, sand, cobble, Kbc 4 Jm 000 Kbc 2 70 4011 and boulder deposits of rounded to subrounded local Mesozoic sandstone and well- sandy shale to shale with thin (2-3 cm) beds of ripple-laminated sandstone that is 1-3 m that contains angular blocks up to 1 m across is often preserved along the contact Qc Kbc 6 Pca Arroyo del Agua Formation (Early Permian) -- Orange siltstone, 7 Jm Qc thick. The Paguate Member is orange to tan, with fine-to medium- grained, subangular, between the limestone microbreccia and overlying basal Summerville sandstone. The 4011000 Jm 5 Qal rounded quartzite recycled out of older (Permian Cutler Group or arkosic sandstone and minor intraformational and extraformational conglomerate. The Kbc Qal Qal Qc Kbc 5 ^cu Abiquiu Formation) deposits. The two highest terraces contain 10 to 20% Pedernal Chert well-sorted sand grains. The Paguate Sandstone is often intensely bioturbated, but in breccia can contain blocks of: (1) basal Summerville sandstone only; (2) blocks of Kd 6 siltstones are thick, slope-forming units with abundant calcrete nodules between thin Qal Qc Kbc Js Summerville sandstone and limestone mircrobreccia; or (3) blocks of Summerville Kd Qc derived from the Miocene Abiquiu Formation. At least three terrace levels (1= oldest, 3 = places remnant cross-bedding, ripple marks, and thin to thick bedding is preserved. It sandstone sheets that are arkosic and trough crossbedded. Up to 130 m thick. 11 Jm youngest) are present along the Rio Puerco and Salitral Creek, one at 49 m, one at 36 m, forms a bold cliff along exposed escarpments of Mesa Alta and is 25-30 m thick. The sandstone and the gypsum-capping limestone. The timing of brecciation post-dates the IPPce El Cobre Canyon Formation (Late Pennsylvanian-Early Permian). Qls 6 Qc Kbc and one at 12 m above modern grade. 1 to 3 m thick. Dakota Sandstone is 40 to 56 m thick. lithification of both the limestone and the sandstone, as well as the microbreccia-forming Brown siltstone, sandstone and extraformational conglomerate that overlies Proterozoic Kd Jm Kd ^cu Jm Jm 5 dissolution event. basement in the subsurface and is conformably overlain by the Arroyo del Agua 6 Qc Qpn Pediment gravels (middle Pleistocene to Holocene). Unconsolidated deposits 4 4 Jm Qe Kd Jm 2 Jm Formation. Siltstone beds of the El Cobre Canyon Formation contain numerous rhizoliths Kbc 64 Kbc of angular to subangular pebbles to boulders of Mesozoic sandstone, limestone and Kbc (). White, light yellow, orange, and 6 Jm Kbc Kbc Qls gypsum resting on surfaces graded to the level of the highest terraces (1= oldest, 3 = and comprise relatively thin, slope-forming units between multistoried sandstone beds Qc Jm Jm Js 4010000 buff, conglomeratic sandstone with thin lenses of pale green and pink mudstone (Saucier, Kd Kbc Jm 2 Jm 3 youngest. The largest surface, covering several km , is on Poleo Mesa, which is cut on Je (). Trough crossbedded and ripple- that are arkosic, micaceous, coarse grained and trough crossbedded. On the Arroyo del Jm Jm Qls 1974). Small-scale trough cross-bedding and cut-and-fill structures are associated with Qls Jm Qa Agua quadrangle, upper part contains numerous vertebrate fossils, primarily of Early 4010000 Js Qls the approximate contact between the Poleo and Petrified Forest formations of the Chinle laminated, cliff-forming sandstone. The Entrada Sandstone (only the Slick Rock Member Jm 4 Qls the conglomeratic channels. Petrified wood is locally present in gravels. Conglomerate Jm Js Jm Kd Kd 2 Group. Most of the Poleo Mesa pediment surface is covered with eolian silt (Qe). is present in the Chama Basin: Lucas et al., 2005a) is 60 to 76 m of very fine- to medium- Permian amphibians and reptiles (e.g., Langston, 1953; Berman, 1993; Lucas et al., Jm Qls Js Js 11 Qls Qts Jm Js Jm clasts are mostly varicolored quartzite and chert pebbles up to 2.5 cm in diameter, with 2005c). Up to 90 m thick. Js Qls 8 16 Approximately 1 to 10 m thick. grained, moderately well sorted sandstone that forms bold cliffs along escarpments and Jtg Jtg Qc minor sandstone and limestone clasts. Chert gravel is present fairly uniformly throughout Jtg Je Jtg Jm mesa tops. Trough crossbeds and ripple laminations are the dominant bedforms. Colors IPgb- Guadalupe Box Formation. (Late Pennsylvanian). Recently defined by Krainer Jtg ^cpd 10 Q1s Landslide deposits (middle Pleistocene to Holocene). Unconsolidated, unsorted Qls Jm Jmb 10 the unit vertically, in contrast to the Ghost Ranch area, where gravel is rare in the upper et al. (2005) ( =Upper arkosic limestone member of the Madera Group of Northrop and Je Jtg Js Je Je Qls Jm Js deposits composed of locally derived, relatively cohesive blocks of bedrock. are shades of yellow, light brown and grayish orange. Up to 76 m thick. ^cu Jm 8 5 6 part of the unit. Pebbly conglomerate makes up less than 50% of the unit. Laminar low- Wood (1946)). Interbedded red to green micaceous, arkosic sandstone, gray sandy, Qls Qc ^cu ^cu 14 Landslides along the escarpment of the Rio Puerco in the south-central part of the Je ^cu Qp2 Qp2 8 Js Qls arkosic limestone, gray, fossiliferous, sandy arkosic, cross-bedded limestone, and red, Js ^cm 8 angle wedge and high-angle planar wedge cross-bedding is common in the sandier Qc ^cu 13 Qal quadrangle are composed of blocks of Poleo Formation, which typically are rotated so 9 ^cp ^cp green, and black shale and siltstone. Most common fossils are columnals. Some Qc ^cu Qls Jtg Qls Jtg ^cpd portions of the formation. The sandstone is fine to medium grained, quartzose, and 14 000 that tops of the blocks dip toward the canyon rim, and the slides sole into the underlying All Triassic strata on the Arroyo del Agua quadrangle are assigned to the Upper Triassic Qal Qoa Qp2 Js Je Qc 4009 arkosic clasts are up to 2 cm in diameter and are angular. Upper contact gradational with ^cu ^cu Je Jtg ^cu ^cp kaolinitic. locally containing a minor percentage of quartz and chert granules and Je Je shales of the Salitral Formation. Numerous remnants of once extensive landslide deposits Chinle Group (Lucas, 1993). Triassic stratigraphy follows Lucas and Hunt (1992) and Qls Qp3 ^cu ^cpd Qls 10^cl clastic red beds of the overlying Cutler Group; lower contact not exposed. 4009000 Qc ^cpd Qc Qc are preserved on and along the base of Mesa Alta escarpment in the northern part of the pebbles. 40 to 50 m thick. Lucas et al. (2003, 2005b). Ql Qc Qc 44 Qls *Pca Qls Qal ^cu ^cu Qls ^cu Qoa Qp3 ^cu TRc Chinle Group (). Three informal units are mapped at the 1:24,000 Qal Qc Ql Qls Qal Qoa Qal quadrangle. The base of the landslides often rests on shales of the Jurassic Summerville Qp3 ^cu Qc Ql Qls Qoa ^cpd ^cp Formation or Triassic Chinle Group, and top is typically hummocky. The distinctive Jurassic scale, from younger to older: Qal 20 Qls Qls ^cu Qoa ^cu ^cu ^cu *Pca ^cpd 1 11 Jurassic stratigraphy on the Arroyo del Agua quadrangle follows Lucas et al. (2005a), TRcu an informal upper unit that contains the Rock Point Formation and the Qoa ^cu Qls Qoa Qal ^cpd 15 Qal composition of these landslides, made up of gypsum, limestone, and sandstone debris, 10 Qls Correlation of Map Units for the Arroyo del Agua 7.5-Minute Quadrangle ^cp indicates they were derived locally from Jurassic and Cretaceous strata to the north. which is based on the regional stratigraphy of Anderson and Lucas (1992, 1994, 1995, Petrified Forest Formation. (where exposure permits the Petrified Forest Formation is Qls Qls ^cu ^cm Qes Qes Qoa ^cl 1996, 1997) and Lucas and Anderson (1997, 1998). Qoa ^cu These landslides were deposited either on older alluvium (Qoa) sediments or directly divided into the Painted Desert Member (TRcpd) and the Mesa Montosa (TRcm) Qls 1 12 Qoa Qoa 36°12'30"N Qoa Qc 36°12'30"N upon mudstone of the upper Chinle Group. Remnants commonly possess a sinuous, Jm - Brushy Basin Member. (). member). The stratigraphically highest unit in the Chile Group is the Rock Point Qrf Qlsy Qc ^cpd Qal Qls Qal 13 Qe 4008000 All Morrison strata on the Arroyo del Agua quadrangle are assigned to the Brushy Basin Formation, a reddish brown to gray-red siltstone and fine-grained sandstone. The Qoa ^cpd linear distribution extending away from the escarpment. The landslide debris appears to Qls Qoa 10 41 12 ^cp Qal Qes ^cm ^cu Qes Member, which is a variegated pale greenish gray, grayish yellow green, pale olive, sandstone can locally be a coarse-grained sandstone or a granule conglomerate. The 000 Qal ^cu ^cu have, in places, flowed in narrow channels incised into Qoa and TRcu that parallel, but 4008 ^cu ^cu Qc Qcbt Qls ^cm 7 Qes yellowish brown, and pale reddish brown bentonitic mudstone with a few beds of trough- thinly interbedded sandstone and siltstone beds form a ribbed cliff where the Rock Point Qes Qal are topographically above, the present system of arroyo drainages. These deposits may Qt Qp ^cm 7 Qoa 7 nn Qc Qes/Qoa Qes/Qoa be up to 35 m thick. crossbedded pebbly sandstone. Locally, the base of the Morrison Formation is a thin (up outcrop is not deeply weathered. Where weathered, the Rock Point Formation is an H 4 ^cp ^cp Qes/Qoa ^cm to 8 m thick) interval of trough-crossbedded sandstone and interbedded mudstone. This orange slope. The Rock Point base is the first persistent bed of sandstone above slope- Qes Qal ^cm 15 ^cm Qoa Older Alluvium (middle to late Pleistocene). Ridgely (1979) used the term Qoa Qc ^cm Qal ^cp ^cm ^cm ^cm basal interval is likely correlative to the Salt Wash Member of the Morrison Formation to forming mudstone of the Painted Desert Member of the Petrified Forest Formation. The 8 24 “older alluvium” for unconsolidated Quaternary sediments on the Arroyo del Agua Q Qbt 10 ^cp Qal quadrangle between the Mesa Alta escarpment, northern Mesa Montosa, and Salitral the west and south. However, this interval is neither thick enough, persistent enough, nor top of the Rock Point is a sharp contact with the overlying eolian sandstone of the Slick 5 5 A' ^cu ^cm 8 29 lithologically distinctive enough to separate from the Brushy Basin Member. The upper Rock Member of the Jurassic Entrada Sandstone. The Rock Point Formation in the

Qal Qal Creek. This unit is composed of two distinct, but complexly interbedded facies that are P Qes/Qoa 4 Qbo ^cu ^cm 18 part of the Brushy Basin is, in places (e.g., 353408 4011319 to 352908 4010853, NAD Chama Basin is up to 30 m thick (Lucas et al., 2003). The Petrified Forest Formation, Qes Qes 000 not mapped separately. One facies, which can make up more than 50% of the deposit, is ^cp Qes/Qoa Qal Qes/^cu Qp 4007 ^cu 36 27), dominated by an interval that is ~ 30 m thick composed of white to pale green which is reddish-brown bentonitic mudstone that forms extensive slopes and dissected *Pca a brown to reddish-brown siltstone with scattered lenses of gypsum and sandstone gravel QTg ^cu ^cm badland areas where exposed, consists of two members, the Painted Desert 4007000 and carbonate nodules. The red-brown silt is likely reworked from upper Chinle Group sandstone interbedded with green siltstone that may be correlative to the Jackpile 3 5 ^cu 4 Member (TRcpf) and the Mesa Montosa (TRcm) member. The overlying Painted Desert 16 15 Member of the Morrison Formation in the southern San Juan Basin. The sandstone in the 4 13 2 mudstone. Paleosols are frequently preserved. Black to dark brown siltstones P Qes/Qc 11 3 Te y 2 4 ^cp Member is up to 176 m of reddish brown, bentonitic mudstone and thin ledges and lenses Qal 9 interbedded with white fine-grained carbonate deposits that superficially resemble upper part of the interval is a pale green, thin to medium tabular bedded, medium to very ^cp ^cp 2 Qal 3 fine-grained litharenite with well-sorted, subrounded quartz grains. The lower part of the of ripple-laminated or crossbedded sandstone. Its base is a thick mudstone bed above the Qc Qls 8 3 ^cl volcanic ash are present in at least four localities across the area. The fine-grained facies Kd ^cp 10 3 ^cl 6 Qal Qls highest sandstone ledge of the Mesa Montosa Member. Its top is a sharp contact with Qc ^cl Qls ^cu 4 most commonly overlies the second facies, but in places, it underlies it. The second facies interval consists of 3 m thick beds of cross-bedded white to red, medium-grained, well- ^cp 2 ^cl ^cm siltstone/sandstone of the Rock Point Formation (locally), or sandstone of the Jurassic 11 Qc rounded, well-sorted, litharenite that is conglomeratic at the base; the clasts are Kbc 2 4 Qes 5 2 15 is a sandy to silty, pebble to cobble unconsolidated gravel in channels that cut either into Entrada Sandstone can rest directly on the Painted Desert Member. In the vicinity of Qes C 3 3 3 the underlying Petrified Forest Formation of the Chinle Group or into the fine-grained intrabasinal siltstone. Total Morrison thickness up to 85 m thick. ^cp ^cm 349493 4008607 (NAD27), downward tapering wedges of sandstone that are 0.5 to 1 m Qls 000 Js (Middle to Late Jurassic). (includes the Bluff ^cm *Pca 4006 facies. Cut-and-fill channel structures are common. The rounded to angular clasts in the long are present in the mudstone of the Painted Desert Member at the Painted Desert Jm Symbols 18 ^cp ^cm Sandstone (Late Jurassic), because the Bluff Sandstone is difficult to trace laterally). The 2 ^cm 3 10 gravel are local Mesozoic sandstone, limestone, or gypsum. The clasts are generally < 20 4006000 Member/Entrada contact. We interpret these as sandstone dikes that filled fissures in the 5 ^cm ^cp Qal cm, but boulders up to <80 cm can occur locally. Minor amounts of well-rounded pebbles Bluff Sandstone is light gray, very fine grained, well sorted sandstone with crossbeds in Js Contact 10 ^cm underlying lithified Chinle Group strata when the Entrada Sandstone was deposited on 22 ^cu 4 of quartzite are locally present in the gravel. These pebbles are likely to thick sets. Consists of two members not mapped separately.The lower, Junction Creek Jtg 5 4 the J-2 unconformity surface that separates the Chinle and Entrada. The lower, Mesa Jt 2 ^cp J Jt(ls) 2 2 Qls 12 Member comprises most of the formation (30-40 m thick) and is mostly pale yellowish Dashed contct 4 have been derived from conglomeratic beds in the Cretaceous Burro Canyon Formation. Montosa Member is made of up to 24 m of mostly sandstone and lesser amounts of Qes 12 green and light olive gray, very fine grained, well sorted sandstone with crossbeds in Qls The older alluvium is present south of the east-west oriented Mesa Alta escarpment that Je 7 ^cm mudstone and siltstone that range in color from reddish brown to green; the sandstone Normal fault Qls dominates the northern part of the quadrangle, and the alluvial units appear to be thick sets. These are primarily eolian deposits similar to the type section of the Junction beds are typically ripple-laminated to thinly-laminated. The Mesa Montosa Member TRcpf Ball on downthrown side; 5 Qc TRcu 65 15 juxtaposed against the upper Chinle Group and are clearly overlain by landslide deposits Creek Member near Durango, Colorado (Goldman and Spencer, 1941). The overlying TRcm arrow shows direction 13 2 forms a ribbed slope, 4 to 24 m thick, between coarser-grained Poleo Formation ^cp ^cm 2 Qls Recapture Member is 6 to 14 m thick and is mostly maroon, pale brown, grayish red, and of dip derived from the escarpment. The clasts become more rounded south of the escarpment. TRcp 4005000 sandstone below, and slope-forming mudstone of the Painted Desert Member of the ^cm light greenish gray gypsiferous siltstone, fine-grained sandstone and mudstone. Recapture Strike and dip 2 In places, the upper fine-grained facies appears to form a fan that dips 5 to 10° south or Petrified Forest Formation above. The Petrified Forest Formation is up to 200 m thick. 0-30 13 6 TRcl ^cp strata lithologically resemble underlying Summerville strata. Their fine-grained Tr c First number is direction of dip 4005000 ^cu 13 southeast of the escarpment. Pebble imbrication measurements suggest a meandering TRcp Poleo Formation. Yellow-brown, yellow- gray, white and red, medium 5 2 and second number is amount of dip 10 ^cm 3 Qal braided stream channel system trending southeast. Where exposed along incised arroyos, gypsiferous lithotypes indicate that these strata do not belong to the Morrison Formation *Pca to fine-grained, micaceous, cross-bedded, quartzose sandstone, conglomeratic sandstone 11 22 3 (contra Ridgely, 1977, 1979), but instead are assigned to the Recapture Member of the Py 9 6 Qt3 a minimum thickness of 10 m is indicated. and conglomerate. The conglomerate in the Poleo Formation is is often black and 4 Bluff Sandstone (Lucas and Anderson, 1997, 1998; Lucas et al., 2005). 44 to 47 m thick. Flow Foliation 4 5 contains both intrabasinal siltstone and nodular calcrete clasts and extrabasinal siliceous Qls Qb Bandelier Tuff (early Pleistocene). Pumaceous air-fall tephra, nonwelded to Pca 3 3 2 *Pca The Summerville Formation below the Bluff interval is thinly and cyclically- (chert and quartzite) clasts. This unit forms prominent white cliffs. The base of the unit is 2 Qt3 weakly welded rhyolitic ash-flow tuff, and local volcaniclastic sediments; divided into P 2 ^cl bedded, maroon, grayish red and yellowish gray siltstone, sandy siltstone, fine ^cp 1 two members, from younger to older: sharp (corresponds to the Tr-4 unconformity of Lucas, 1993) and the upper contact is IPPce gypsiferous sandstone and mudstone. In the Chama Basin, the Summerville Formation Qbt Tshirege Member. White to orange to pink non-welded to weakly gradational into the overlying Mesa Montosa Member of the Petrified Forest Formation. 6 (as used by Lucas and Anderson, 1998; Lucas et al., 2005) consists of two, *Pca 4004000 welded rhyolitic, ash-flow tuff (ignimbrite). The tuff contains abundant phenocrysts of The Poleo Formation is about 48 m thick ^cl lithologically-distinct units that Lucas et al. (2005) referred to informally as the lower and *Pce ^cp sanidine and quartz, rare microphenocrysts of black clinopyroxene, trace TRcl an informal lower unit that contains the Salitral Formation and the 4004000 3 ^cl upper members. These two units merit formal recognition because of their distinctiveness *Pca *Pca microphenocrysts of hypersthene and fayalite, and pumice fragments in a fine-grained Shinarump Formation. The Salitral Formation is dominantly green, purple and red ^cl Qes and ready recognition in quadrangle-scale mapping. ^cp Qls Qt3 matrix of vitric ash. The sanidine typically displays blue iridescence. The tuff is smectitic mudstone with calcrete nodules. The unit tends to be olive gray to reddish- Qrf2 Qc 7 As Lucas et al. (2005) noted, the lower member of the Summerville Formation in brown silty mudstone near the base (Piedra Lumbre Member) and a maroon to reddish- *Pca *Pca *Pce composed of multiple flow units in a compound-cooling unit (Smith and Bailey, 1966; 36°10'0"N ^cl 36°10'0"N Broxton and Reneau, 1995); includes basal white pumiceous tephra deposits (1-2 m the Chama Basin is the same unit that Goldman and Spencer (1946) named the “Bilk brown mudstone (Youngsville Member) near the top. An orange chert bed that is 2 to 20 *Pce Qc *Pce Qt Qt2 Creek Sandstone Member of the Morrison Formation” in the Telluride-Durango area of cm thick is common in the Piedra Lumbre Member. A sandstone bed at the top of the *Pca Qt3 thick) of the Tsankawi Pumice. Qbt forms conspicuous orange to tan cliffs on Loma 20 southwestern Colorado. Therefore, we apply Goldman and Spencer’s (1941) name to the Redonda and along the southern edge of the quadrangle, east of Mesa Ojitos, where the Piedra Lumbre Member, the El Cerrito Bed, is a local yellow to reddish brown Lawrence 40 39 *Pca tuff infills a rugged northeast-trending paleocanyon. Ar/ Ar age is 1.22 ± 0.01 Ma lower member of the Summerville Formation in the Chama Basin. Here, the Bilk Creek conglomeratic sandstone that is as much as 10 m thick on Mesa Montosa. The base of *Pca 4003000 Osburn ^cl Qt2 Qes (Izett and Obradovich, 1994; Spell et al., 1996). Up to 75 m thick. Member of the Summerville Formation is ~ 12-15 m thick and is repetitively-bedded the El Cerrito bed marks a profound change in the degree of alteration of the rocks by *Pce Qt3 Qt2 3 20 Qt3 Qbo Otowi Member. White to pale pink, generally poorly welded rhyolitic gyspiferous sandstone, siltstone, and limestone that forms a ribbed cliff or slope. This paleoweathering during Triassic time. Below the El Cerrito bed, both the Shinarump 4003000 ^cp 20 *Pce yellowish green to light brown unit overlies the Tonque Arroyo Member of the Todilto Formation and the Piedra Lumbre Member of the Salitral Formation can be mottled; 3 ash-flow tuff containing abundant phenocrysts of sanidine and quartz, and sparse mafic Qls Qes Qt3 *Pce Formation and locally appears to interfinger with it. The overlying Mesa Alta Member of mottling is rare above the base of the El Cerrito Bed. The Salitral Formation varies Zeigler 2 Py phenocrysts; sanidine may display a blue iridescence. Contains abundant accidental lithic *Pce L the Summerville Formation (named here) overlies the Bilk Creek Member in the Chama greatly in thickness, ranging from 3 to 30 m. The Shinarump Formation (= Agua Zarca a Qtl fragments; consists of multiple flow units in a compound cooling unit. The stratified w Qlsy *Pce r ^cl Qc Basin. Formation of previous usage: e.g., Wood and Northrop, 1946; Dubiel, 1989; Lucas and e 6 pumice fall and surge deposit at base of unit (Guaje Pumice) is not found in this area. n ^cp ^cl ce Qbo discontinuously fills in rugged topography on a pre-Toledo caldera age volcanic We name the upper member of the Summerville Formation in the Chama Basin the Mesa Hunt, 1992) consists of white, red, orange, and brown quartz sandstone, conglomeritic 3 Py surface and the upper surface can be quite undulatory due to erosion. Qbo disontinuously Alta Member. The name is for Mesa Alta on the Arroyo del Agua quadrangle where the sandstone, and extrabasinal conglomerate that includes clasts of quartz, chert, and 4 caps Ojitos Mesa and fills an inset valley along the southeast edge of the quadrangle. type section of the unit is located (sec. 19-20, T23N, R3E). The type section is units 15- quartzite (Lucas et al., 2003) interbedded with or sitting on olive gray to reddish-brown 7 4002000 Z 2 ^cm 25 of the Mesa Alta measured section of Lucas et al. (2005, p. 190, fig. 3). At the type silty mudstone. Local mineralization (copper, uranium) produces colors that range from eig Qc Very difficult to distinguish from upper Bandelier Tuff in hand samples; best ler Qc black to yellow to green. Trough crossbeds are the dominant bedform. Petrified wood is 4002000 Qls distinguished by poorer degree of welding, greater tendency to form slopes instead of section, the Mesa Alta Member is ~ 96 thick, which appears to be a maximum thickness *Pca Qbo in the Chama Basin, where the unit is 61-96 m thick. The type section is interbedded rare. The basal contact is sharp; the basal contact corresponds to the Tr-3 unconformity *Pce ^cm ^cl cliffs, more abundant lithic fragments, less abundant iridescent sanidine, and stratigraphic 7 40 39 siltstone, gypsiferous sandstone and mudstone that forms a grayish red- and white-banded of Pipiringos and O’Sullivan (1978) and Lucas (1993). Sandstone beds in the 20 Py position beneath the Tsankawi Pumice. Ar/ Ar ages 1.61± 0.01 to 1.62±0.04 Ma (Izett *Pca 4 Shinarump Formation are absent to thin (1 to 2 m) in the Rio Puerco valley, but locally Py *Pca and Obradovich, 1994; Spell et al., 1996). Up to 65 m thick . slope between the Bilk Creek Member (below) and the Bluff Sandstone (above). Kelley 10 are as much as 20 m thick. In many places in the Rio Puerco valley, color-mottled shale Qc ^cl In the Four Corners, and across much of southeastern Utah, the Summerville Qbo Py 38 of the Shinarump Formation sits directly on altered, weathered Yeso Group or uppermost Qc 4 Formation has been divided into two members—the Beclabito (lower) and Tidwell ^cl Quaternary to Tertiary Cutler Group; the Shinarump sandstone may be absent or channel sandstone of (upper) members (Lucas and Anderson, 1997). These members, however, are not the Qls Qal QTg Fluvial gravel (early Pleistocene to ). Unconsolidated subround fluvial Shinarump lithology may be 2 to 4 m above the contact with the Permian rocks. 000 ^cp 4001 gravel is present under the Otowi Member of the Bandelier Tuff on Triassic Chinle same two Summerville members that are present in the Chama Basin. Thus, the Tidwell 38 8 Osburn Py Group strata on Ojitos Mesa. The gravel is composed primarily of clasts of Pedernal Member is mostly laterally equivalent to the Bluff Sandstone (Lucas and Anderson, Pennsylvanian-Permian 4001000 Qc ^cl Chert, Pennsylvanian limestone, and Proterozoic granite and quartzite clasts recycled out 1997), so that the Summerville Formation in the Chama Basin is equivalent to the The oldest strata exposed on the Arroyo del Agua quadrangle are Pennsylvanian- Osburn ^cl Qc Py 6 Qls of the lower Abiquiu Formation. This gravel, which is up to 2 m thick, may correlate Beclabito Member to the northwest. Strata we term Summerville Formation were Permian siliciclastic red beds of the Cutler Group ( of Smith et al., Qc Py ^cl with the Puyé Formation in the northeastern . assigned to the Morrison Formation by Smith et al. (1961) and Ridgley (1977, 1979), 1961) and overlying Yeso Group. Stratigraphy employed here follows Lucas and Krainer ^cl Kilometers 58 23 Py Qbo although Ridgley (1989) did assign what we term the lower member of Summerville (2005) and Lucas et al., 2005). 01234 5 13 ^cp Qls Qbo 44 ^cl ^cu 22 4 Formation to the Wanakah Formation. 74 to 111 m thick. Py 20 7 Qbo *Pca Qls Qc 11 ^cl ^cp 6 Qbo Qbo 56 Qc 7 9 11 27 40 4000000 53 Qal ^cp 8 45 4000000 38 *Pca ^cu *Pce ^cp 5 8 41 23 Qc ^cl 14 5 *Pca Py ^cl *Pca 32 37 7 Py Qc 30 Qc 4 Qbo *Pca *gb 9 *Pca 13 QTg Py 18 24 *Pca 7 Qc ^cl *Pca 8 24 42 5 Py Qc ^cp Qc ^cl 4 5 Py 28 15 Py 3999000 ^cu Qbt Qal Qcbt Qcbt Qc Qbt ^cu ^cp Qcbt Qbt Qbt Py Qbt ^cl 36°7'30"N Qbo 36°7'30"N A 343000 344000 345000 346000 347000 348000 349000 350000 351000 352000 353000 106°45'0"W 106°42'30"W 106°40'0"W

Base map from U.S. Geological Survey 1984, from photographs taken 1976, field checked in 1976, edited in 1984. 1927 North American datum, UTM projection -- zone 13N 1000-meter Universal Transverse Mercator grid, zone 13, shown in red Geologic map of the Arroyo del Agua 1:24,000

FRENCH LAGUNA quadrangle, Rio Arriba County, New Mexico ECHO 1010.5 MILE MESA PEAK AMPHITHEATER

NEW MEXICO 1000 0 1000 2000 3000 4000 5000 6000 7000 FEET Arroyo

GALLINA ARROYO May 2006 DELdel AGUA YOUNGSVILLE Agua 1010.5 KILOMETER by Magnetic Declination 1 2 3 4 5 CONTOUR INTERVAL 20 FEET February, 2005 Kelley, S.A. , Lawrence, J.R. , Zeigler, K.E. , Osburn, G.R. , and Lucas, S.G. NACIMIENTO CERRO PEAK JAROSA DEL 10º 7' East NATIONAL GEODETIC VERTICAL DATUM OF 1929 1 GRANT NMBGMR, Socorro, NM, 87801 At Map Center 2 Lawrence GeoServices Ltd. Co., 2321 Elizabeth Street NE, Albuquerque, NM 87112 Photograph showing paleochannel filled by the Tshirege Member of the Bandelier Tuff New Mexico Bureau of Geology and Mineral Resources 3 Department of Earth and Planetary Science, University of New Mexico, Albuquerque, NM 87131 (Qbt) inset against Permian Yeso Group (Py),(Py), Shinarump (TRcsh), SalitralSalitral (TRcs), and Open-file Map Series 4 Earth and Planetary Science Dept., Washington University, St. Louis, MO 63130 Poleo (TRcp) formations of the Triassic Chinle Group, and the Otowi Member of the QUADRANGLE LOCATION 5 New Mexico Museum of Natural History and Science, Albuquerque, NM 87104 Bandelier Tuff (Qbo). Southeast side of OjitosOjitos Mesa (channel located at approximately OFGM 124 352600 399100, NAD27), view toward west. This draft geologic map is preliminary and will undergo revision. It was produced from either scans of hand-drafted originals or from digitally drafted original maps and figures using a wide variety of software, and is currently in cartographic production. COMMENTS TO MAP USERS It is being distributed in this draft form as part of the bureau's Open-file map series Mapping of this quadrangle was funded by a matching-funds grant from the STATEMAP program SW NE (OFGM), due to high demand for current geologic map data in these areas where of the National Cooperative Geologic Mapping Act, administered by the U. S. Geological Survey, A geologic map displays information on the distribution, nature, orientation, and age relationships STATEMAP quadrangles are located, and it is the bureau's policy to disseminate and by the New Mexico Bureau of Geology and Mineral Resources, (Dr. Peter A. Scholle, Director and State Geologist, Dr. J. Michael Timmons, Geologic Mapping Program Manager). of rock and deposits and the occurrence of structural features. Geologic and fault contacts are geologic data to the public as soon as possible. irregular surfaces that form boundaries between different types or ages of units. Data depicted on this geologic quadrangle map may be based on any of the following: reconnaissance field A A' After this map has undergone scientific peer review, editing, and final cartographic geologic mapping, compilation of published and unpublished work, and photogeologic interpretation. production adhering to bureau map standards, it will be released in our Geologic Map Locations of contacts are not surveyed, but are plotted by interpretation of the position of a given (GM) series. This final version will receive a new GM number and will supercede New Mexico Bureau of Geology and Mineral Resources contact onto a topographic base map; therefore, the accuracy of contact locations depends on the 9400 this preliminary open-file geologic map. Pi n ab e t al New Mexico Tech scale of mapping and the interpretation of the geologist(s). Any enlargement of this map could cause 9000 misunderstanding in the detail of mapping and may result in erroneous interpretations. Site-specific fault MesaPoleo Sa l i t r a l Cr e ek 801 Leroy Place 8600 conditions should be verified by detailed surface mapping or subsurface exploration. Topographic pC Co yo t e Socorro, New Mexico and cultural changes associated with recent development may not be shown. 8200 Pce MesaMontosa monocline IPgb TRcp MesaMontosa monocline DRAFT 87801-4796 7800 Cross sections are constructed based upon the interpretations of the author made from geologic TRcp mapping, and available geophysical, and subsurface (drillhole) data. Cross-sections should be used as 7400 [505] 835-5490 Pca TRcl TRcp an aid to understanding the general geologic framework of the map area, and not be the sole source El ev at7000 f e ) TRcl Pca http://geoinfo.nmt.edu of information for use in locating or designing wells, buildings, roads, or other man-made structures. Pce TRcp IPgb 6600 Pca IPPce TRcl TRcl IPPce IPgb Pca This and other STATEMAP quadrangles are (or soon will be) available The map has not been reviewed according to New Mexico Bureau of Geology and Mineral Resources pC IPgb for free download in both PDF and ArcGIS formats at: standards. The contents of the report and map should not be considered final and complete until IPPce reviewed and published by the New Mexico Bureau of Geology and Mineral Resources. The views and pC IPgb conclusions contained in this document are those of the authors and should not be interpreted as pC pC http://geoinfo.nmt.edu/publications/maps/geologic/ofgm/home.html necessarily representing the official policies, either expressed or implied, of the State of New Mexico, or the U.S. Government.