NEW MEXICO BUREAU OF GEOLOGY AND MINERAL RESOURCES A DIVISION OF NEW MEXICO INSTITUTE OF MINING AND TECHNOLOGY NMBGMR Open-file Geologic Map 166 Last Modified 21 May 2008

106°15'0"W 106°12'30"W 106°10'0"W 106°7'30"W 388000 389000 390000 391000 392000 393000 394000 395000 396000 397000 398000 399000 Ta Qayh 36°22'30"N 000 Qtru Tlpc Ttdml Qayh Xoq Ttdml Ttdml 4026 Qayh Ter Tlpc 20 Ta 14 Ttdml QUATERNARY COLLUVIAL, EOLIAN, AND LANDSLIDE DEPOSITS Ttpl Lower unit of Plaza lithosome (lower to middle ) – Light-colored, weakly altered, and weakly to strongly cemented channel-fill Ta Tlpc Talpc Ttdml Qttu Ter Tr Ta Qthu Ttdml Qayh complexes interbedded with subordinate fine intervals similar to unit Ttcfl. Channel-complexes include pebbly sandstone and sandy Qayh Qayh Xoq Xoq Ttdml Ta Qayh 117 Xoq Xoq Ttduh Qtru Quaternary terrace deposit, undifferentiated (middle to upper Pleistocene) – Sandy gravel deposits deposited by El Rito Creek that were pebble conglomerate. Beds are planar to lenticular to cross-stratified (up to 50 cm-thick foresets), and laminated to very thinly to medium- Qayh Tg3 11 6 Ttdml 58 Qayh 7 10 Qayh 8 71 86 Qct Colluvium and talus (Holocene to Pleistocene) – Hillslope mantles of quartzite and basaltic gravel in a sandy matrix that form downslope of not correlated to one of the six terraces liste d above. Lithologic properties are similar to that of Qtr. 1-5 m-thick. , bedded (minor thick-bedded). Cross-stratification seems to be less common than higher in the Plaza lithosome. Gravel consist of very fine to Qayh Ta Ttdml 54 Tg3 Qayh 7 47 Qtru Quaternary terrace deposit, undifferentiated (middle to upper Pleistocene) – Sandy gravel deposits deposited by El Rito Creek that were very coarse pebbles with 3-5% cobbles . Clasts are dominated by altered dacite-andesite, with 1-5% quartzite, 1-10% rhyolite and welded Ttdml 6 Qthu Qthu Tlpc Ta Ttdml high-level grave deposits and on the northern slopes of Sierra Negra. Loose to weakly consolidated and probably 1-2 m-thick. Ta Qayh Qayh not correlated to one of the six terraces listed above. Lithologic properties are similar to that of Qtr terraces. 1-5 m-thick. , ( is absent to very sparse), trace granite, trace gneiss, and trace to 1% basalt; locally, non-welded tuff is as much as 15%. Dacite Tr Tlpc Qayh 11 10 Qayh 5 Ttdml Ta 61 Qao clasts are lighter than those higher in lithosome P and possibly have slightly less coarse plagioclase phenocrysts, but otherwise mineral assem- Ta Tg3 Tr Ta Ta 5 5 10 Qc Colluvium over unidentified (Holocene to Pleistocene) – Qtt Quaternary terrace deposits associated with tributaries of El Rito Creek (middle to upper Pleistocene) – Sandy gravel terrace deposits blages are similar and the apparent difference may be partly due to alteration from hydrothermal(?) waters responsible for the varying degrees Ttdml Qayh Qayl Ta Qayh Ttdml Tt Clayey-sandy gravel typically located on slopes beneath terrace surfaces that obscures underlying strata. Not described in detail, but position that underlie distinct treads 6-25 m above mod ern channel elevations along major tributary drainages to El Rito Creek. We generally did not of silica-cementation (minor ) of this unit. Channel-fill sand is typically light gray to very pale brown, and fine- to very coarse-grained. Tr Qao Ta Qao Qayl on the footslope strongly suggests that the material is colluvial. Probably 1-2 m-thick. notice multiple treads within individual drainages (other than the lower Qao), suggesting that Qtt may possibly represent a single aggrada- Sand is locally tuffaceous. More than 120 m-thick. Qayh Qayh Ttdml Qao 23 tional/degradational cycle that is correlative between drainages. No effort was made to trench into these deposits to describe texture or soil 6 27 Tr Tlpc Qayh Qao Ttcfl – Chama-El Rito Member, Tesuque Formation, lower fine-grained deposits (lower to middle Miocene) – Very pale brown to pinkish gray to Qao 4 Tlpc 4025000 development; description based on surface characteristics. Correlation between drainages and from place to place within drainage basins was Tg3 Qayl Tlpc 5 7 Tr Ttduh pink, fine-grained sand and silty fine sand deposits below unit Tpt east of El Rito Creek. These deposits are lighter colored, better consolidated Qtru Qayh Ta Qc Colluvium over unidentified (Holocene to Pleistocene) – generally not attempted, except where such terraces obviously grade into one of the El Rito Creek terrace deposits (Qtr). In these cases the 000 Tlpc Qayh and cemented, and commonly exhibit more distinctive bedding than fine-grained sand intervals up-section. The lighter color and cementation 4025 Tr Ttdml Ta 5 Tlpc Ta Clayey-sandy gravel typically located on slopes beneath terrace surfaces that obscures underlying strata. Not described in detail, but position tributary terrace deposits were numbered to match their equivalent El Rito Creek terrace. 1-3 m-thick. Ta Ttdml Ta 8 may be partly due to circulation of warm groundwater following emplacement of dikes and phreatomagmatic volcanism in the middle Miocene. Ta Qayh Ttc Qayh on the footslope strongly suggests that the material is colluvial. Probably 1-2 m-thick. : Qayh Ta Ta Qayh Strata generally consist of thin to thick, tabular to broadly lenticular beds of very fine- to fine-grained sandstone and silty sandstone. Beds are 13 Qayh Tg2 5 Tlpc Ta 10 Qtt5 – Upper lower Pleistocene gravel terrace. Correlates with terrace deposit Qtr5. Qayh Ttdml Qayh internally massive to planar-laminated to trough crosss-laminated (also very thin-bedded). Sand is very fine- to fine-grained. Locally scattered Qafy Qayh Qayh 9 in the sand are medium to coarse, dacitic(?) sand grains. Sand is locally very slightly tuffaceous and weakly to well cemented. Minor (3-15%) Ttdml 1 Ta Qls Landslide deposits (Pleistocene) – Subsided, deformed and internally faulted blocks of basalt and underlying Tesuque Formation on the steep Ter Ttdml Ttc 3 4 Qtt4 – Lower middle Pleistocene gravel terrace. Correlates with terrace deposit Qtr4. Qayh Ta Tlpc Ttdml slopes of Sierra Negra. Surface is hummocky. Landslide is typically elongated in the transport direction (latter shown by arrows on the map). very thin beds or planar-laminations of light brown to light reddish brown clay and clayey very fine- to fine-grained sandstone. Unit includes Qayh Ter Qayh Ttdml subordinate volcaniclastic, coarse channel-fills similar to those described in unit Ttpl. Ta Ta Many landslides have steep head-scarps as tall as 100m. Locally, the landslide deposits are subdivided by relative age based on inset and cross- Qayh Qtru Qtr5 Ta Qayh Ttdml Qayh Qtt3 – Middle Pleistocene gravel terrace. Correlates with terrace deposit Qtr1. Ttdml cutting relations as follows: Tlpc Cordito Member of the (upper to lower Miocene) – Gravelly sand, sandy gravel, and sand beds. Gravelly 7 Ta Ttdml Qayl 6 Ttduh sediment is in very thin to medium, broadly lenticular to lenticular beds that may be internally planar-laminated. Gravel is composed of rhyo- 20 Qayh 5 Ttc 18 8 8 Tg3 Coarse gravel underlying uppermost, extensive high-level geomporphic surfaces (upper ) – This unit ranges in thickness from 2 lite (including minor possible rhyodacite) with subordinate welded and non-welded tuff, trace to 5% quartzite, and minor dacite (generally 5 Qayh Qlso – Older landslide deposits porphyritic). Rhyolite clasts are commonly banded and grayish, or crystalline with quartz phenocrysts. Gravel consists of pebbles and cobbles Ter 18 Qayh 7 Qayh Qayh to 8 m thick, suggesting burial of a dissected landscape by alluvial fill. The fill consists predominantly of cobble to boulder gravel, with clasts Ter 4 Qayl 4024000 Qlsm – Middle landslide deposits with very minor boulders. Sand is commonly in medium to thick, tabular to broadly lenticular beds. Common sand colors include pinkish Tr Qayh Ttdml as large as 1 m across but typically the largest clasts are about 50 cm across. Clast composition is estimated to be 75-85% gray quartzite, 1-2% Ttdml Tlpc gray, pink, to light brownish gray. Sand is very fine- to very coarse-grained (mostly fine- to very coarse-grained). Estimate 0-5% tuff. Unit Tg3 Qayh 20 Ta Ttduh Qlsy – Younger landslide deposits white vein quartz, generally less than 1% granitic and metarhyolitic clasts, and the remainder being volcanic clasts of widely variable composi- 4024000 Ttdml gradationally overlies the more tuffaceous, white-colored Abiquiu Formation and gradationally underlies the grayer Plaza lithosome (Tesuque Tr Tg3 Qtru Qayh tion, texture, and color. Quartzite cobbles and boulders are typically rounded to well rounded; some quartzite clasts in nearly every exposure 20 9 Ttduh 8 Formation). Upper contact placed where felsite clasts (i.e., rhyolite and felsic tuff clasts) are less than 10% of the gravel assemblage. In the Tr Qafy exhibit partial red cortexes, which may indicate derivation from El Rito Formation outcrops. The surface of this gravel deposit projects above Qse 58 Qtru Qayh Qayh These interpreted ages are relative to surrounding landslides and do not imply that the unit is everywhere the same absolute age. For example, quadrangle to the north, this unit is mapped lower in the section and interfingers southwestward with the Abiquiu Formation. Unit is well con- Qayh Ttdml the Guaje-bearing terrace deposit southwest of Medanales and thus is older. The surface of this deposit may correlate to the higher, extensive Qtru Ta Tlpc 67 8 solidated and non-cemented. Approximately 30-60 m-thick. 7 whereas Qlsy is younger than an adjoining Qlsm landslide, it may not be the same absolute age as a Qlsy on the other side of Sierra Negra. Pliocene surfaces preserved in the Española Basin (e.g., top of Puye Formation, top of Servilleta Basalt capping Black Mesa, and the Rio del 3 Tlpc Tlpc Qayh Qayh Qayl Oso surface of Manley, 1976); if so, this surface is likely late Pliocene in age (ca. 2-3 Ma). Ta Abiquiu Formation (upper Oligocene to lower Miocene) – Tuffaceous, pebbly sandstone, sandstone, and clayey-silty sandstone with minor 3 Qayh Ttdml Tr Ta Ta conglomerate; colors range from white and beige to red-brown to orange near faults north of Sierra Negra. Volcanic clasts include a variety of Qayh Ttduh Qlsb Landslide deposits consisting of factured basalt flows (Pleistocene) – Basalt flows similar to unit Tb that have been displaced downward Qayh Ttduh and deformed by mass-wasting processes. Locally extensively fractured as to leave a dense collection of large boulders on the surface. Tg2 Coarse gravel preserved north of El Rito (lower Pliocene) – Sandy gravel located at top of exposure west of the painted “E” north of El Rito. intermediate to felsic rocks types, with rhyolitic clasts prominent in all outcrops and clasts of Amalia Tuff seen at numerous localities. Quartz- Qse 6 Qayh Ttduh This deposit consists of very poorly sorted, sandy gravel of mixed quartzite and felsic volcanic clasts (about 2/3 quartzite and foliate quartzite ite pebbles and cobbles are commonly present as well; quartzite typically composes less than 10% of the gravel size class but some beds con- Tg3 Qtru Qls Qayh Ta 65 Qayh Qse Sheetwash and eolian deposits with minor stream-channel alluvium (Holocene to upper Pleistocene) – Accumulations of fine- to medium- to 1/3 felsic volcanic clast). Gravel is clast-supported, subrounded to rounded, and contains pebbles with 30-40% cobbles and 10% boulders. tain >90% quartzite. This formation comprises the bulk of the hills north of El Rito. Gravel here includes pebbles and local cobbles plus minor Qafy 26 Ta Ttdml Ta Ttduh Ttdml grained sand with variable amounts of gravel, especially where associated with terrace units. Mostly mapped as a thin deposit capping the Tg3 Beds are vague, thin to thick, and lenticular to broadly lenticular. Weakly consolidated. 6-12 m-thick. boulders. Clasts here are composed of welded tuff and tuff, rhyolite, and 1-20% quartzite. Sand is fine- to very coarse-grained (mostly me- Qao Qayh Qayl Ttduh surface. In the higher-elevation parts of this surface, the Qse unit preferentially thickens into shallow channels, although it still consists primar- dium- to coarse-grained). Moderately to well consolidated and weakly to moderately cemented by tuff. In the quadrangle to the north, and Qtru Qtr5 Ttduh Qayh 4023000 ily of fine- to medium-grained sand. This suggests reworking of primarily eolian materials. Qse also forms a broad hillslope mantle along the Qayh Tg1 Coarse gravel above eastern basalt-capped mesa on Sierra Negra (uppermost Miocene) – Subrounded pebbles and cobbles of felsic vol- partly on th is quadrangle, this unit interfingers northeastward into the Corditto Member of the Los Pinos Formation. Greater than 250 m-thick, Ta Qayh Qayh TtdmQayh margin of an unnamed drainage south of Sage Tank. The apparent abundan ce of fine sand, albeit admixed with large quantities of quartzite 000 Tg3 Qayl Qayh Ttdml canic clasts and quartzite that appear to lie above the basalt that caps the mesa east of Sierra Negra. It has been reported that similar gravel except on the immediate footwall of the Potrero fault. 4023 Ta 3 Qttu 11 8 Ttduh gravel, led us to map this latter area as Qse rather than Qct, but either could be defended at this location. Unit also locally caps the drainage Qayh Ttcf underlies the basalt, but we have not confirmed this. 1-2 m-thick. Talpc Undivided Abiquiu-Los Pinos Formations (upper Oligocene to lower Miocene) – Interfingering Abiquiu and Los Pinos Formations Tr Tg3 Qayh 11 63 Ttduh divide east of El Rito Creek. Here, it consists of light yellowish brown, clayey-silty (estimate 1-10% fines) very fine- to very coarse-grained Tlpc Qayl 5 Qayh (Corditto Member), where exposure was too poor to differentiate. See descriptions of the two units above. Approximately 30 m-thick where Tlpc Ttduh Ttdm sand (mostly very fine to fine sand) that is massive. Note that this deposit also covers Pleistocene-age terrace deposits, but we chose not to Tg3 Qayh Ttdml mapped on this quadrangle (near the northern boundary). Tg3 65 Qayh depict it in order to better present the terrace deposits, which we felt were more impo rtant. Sediment is moderately consolidated, non- Qayh Qayh 13 Qayh cemented, and 1-2 m-thick. Tr Ritito Conglomerate (Oligocene) – Quartzite-rich pebble to cobble gravel with lenses and layers of white, quartzofeldspathic sand as much as Qc/Ta Qayh Ta Qayl Ttdml 71 65 Ttcf , BASIN-FILL DEPOSITS 3 Tlpc Qao Ttduh 8 m thick. North of El Rito, a prominent arroyo immediately west of the painted “E” offers exposures of medium to thick, tabular to irregular Qayh Tlpc Ttdml 4 Ta Tlpc Qayh beds of sandy gravel and pebbly sand. Here, pebbles, cobbles, and boulders are matrix-supported and consist of quartzite (boulders and cobbles 71 Qayh QUATERNARY AND PLIOCENE ALLUVIAL DEPOSITS Tto Ojo Caliente Sandstone Member of the Tesuque Formation (middle Miocene) – Very pale brown, cross-stratified sandstone. Sand is typi- Tlpc Tlpc 9 Qayh Ttdml Ttcf Qayh are exclusively quartzite) and felsic volcanic rocks (i.e., rhyolite and tuff) and trace basalt. Boulders decrease up-section. Matrix consists of Qtr5 Ttdml Qayh Qayh 75 cally upper-fine to lower-medium grained . Redder (oranger) hues are present near known or inferred faults, where cementation is also con- Tlpc Qayh Qayh Qayl Younger alluvium occupying the lower topographic positions on valley floors (i.e., modern stream channels and adjoining floodplains) white, fine- to very coarse-grained sand that is tuffaceous. Near the western boundary of the quadrangle, this unit contains 10-15% orange Qttu Tlpc 7 Qayh 14 spicuous. The largest outcrop area is north of Alamosa Canyon and west of Alamosa No. 2 Tank, where roughly 30 m of nearly flat-lying Ttcf (upper Holocene to modern) – Generally sandy gravel and gravelly sand. Contains abundant quartzite cobbles and boulders where drainage granite and metarhyolite, 1-2% white vein quartz, sparse intermediate-volcanic pebbles up to about 1 cm-across, and the remainder of the Ta Ta Qayh 77 Ttduh (probably gently NE dipping) sandstone is moderately cemented and forms a dissected mesa. Cross-bedding is clearly apparent in this outcrop Qayh Ttdml Ttduh 61 3 basins include Ritito Conglomerate, the upper unit of the Plaza lithosome, or Pliocene-Pleistocen e terrace deposits; otherwise, pebbles are the o o gravel is quartzi te. Rounded to well rounded clasts are overall finer than in Tg3 and better rounded than in El Rito Formation (Ter). Unit is Qttu Qayh 4022000 belt and cross-bed sets are typically 3- 5 m thick; wind directions range from southwest to slightly northwest (cross bed dips toward 35 -105 ). Ttdml Qayl Qayh main gravel-type. Pebbles are subrounded to subangular and composed mostly of felsic to intermediate volcanic clasts with minor quartzite correlative to Ritito Conglomerate (Barker, 1958) and lower member of Abiquiu Formation (Moore, 2000; Smith, 1995). 80-90 m-thick. Qafy Qayh Qayh 7 Ttduh Orange, lithified outcrops of Tto also locally form conspicuous buttes on the proximal hanging walls of mapped faults. Tto was also mapped 000 51 clasts, whereas cobbles and boulders typically consist of subrounded to rounded quartzite with minor felsic to intermediate volcanic clasts. for discontinuous exposures of unlithified, well-sorted, fine-medium sand mantled in quartzite-gravel colluvium both north and south of the Ter El Rito Formation (Eocene?) – Red, lithified conglomeratic sandstone, sandstone, and mudstone. Well exposed in a horst block in Angel 4022 Qttu Qayh Ttdml Qayh 6 72 Ttduh Ttduh Sand is very pale brown to light gray to gray and very fine- to very coarse-grained (mostly medium- to very coarse-grained), and has a compo- Canyon and poorly exposed along the base of Stone Canyon. Clasts are >90% quartzite and the remainder are vein quartz, granite, and 6 Qayh Ttdm mouth of canyon through which State Road 137 passes. A thin interval of this unit is preserved on the hanging-wall of an east-down fault in the Qayh Qayh sition consistent with lithologies present upstream in a given drainage. Bar and swale topography, in addition to recent stream-related channeli- metarhyolite. Clasts are subangular to rounded and range in size up to 1 m across. The lithified character, red color, and more angular clasts A Qayh Ttduh Qayh A' southeast corner of the quadrangle. Unit gradationally overlies the Chama-El Rito Member, and interfingers with the upper Chama-El Rito Qttu zation, produce as much as 1-1.5 m of relief. Probably only 1-2 m-thick in smaller drainages, and 3-5 m-thick under larger drainages. Unit Member in Alamosa Canyon (as illustrated in Figure 4). Weakly to moderately consolidated where not cemented. Preserved thicknesses are distinguish El Rito from Ritito. 30 m-thick where on quadrangle. Ta 6 Qayh Qthu Qayh Ttduh unconformably overlies thicker sand and gravel interval that is late Pleistocene to Holocene in age. A cuttings log for a well located approxi- greatest (50 m) in upper Alamosa Canyon. VOLCANIC ROCKS Ttduh Qayh 7 mately 1 km southeast of El Rito suggests that this older interval is approximately 10 m-thick. Ttdml Ttdml Qayh 7 Ttdml 5 Qayh Tb Basalt flows (Miocene-Pliocene) – Basalt flows occur at two localities. Flows that cap the summit and eastern mesa of Sierra Negra are Qayh Qayh 8 Ttdml Ttdml 8 Ttcf Chama-El Rito Member, Tesuque Formation, fine-grained deposits (middle Miocene) –Very fine- to fine-grained sand (locally lower- sparsely pophyritic basalt with laterally variable textures. Phenocrysts consist of plagioclase and 1-4% olivine. Basalt on the summit is only 3- 36°20'0"N Qse Qayh Ttdml Qayl 36°20'0"N Qayi Younger alluvium occupying intermediate topographic positions on valley floors (upper Holocene) – Sand, silty sand, and gravel occupy- Ttdml 4 medium sand) and silty sand exhibiting colors of orange, pink, very pale brown, or reddish yellow. Pink to orange colors seem to be most 6 m-thick. The eastern mesa is underlain by as many as 3 basalt flows having a cumlative thickness of 20-25 m immediately west of the fault 6 Qayh ing intermediate terrace positions on valley floors. Unit is probably a cut-and-fill deposit into unit Qayh or a strath cut into Qayh. 1-3 m-thick. 13 Qayh Qayh 77 common. Strata are typically in medium to thick, tabular beds that are internally massive or planar-laminated. Sand locally has minor medium- that crosses the central part of the mesa, and a cumulative thickness of 30-35 m immediately east of this fault (including rubble zones between Qayh Qayl to very coarse-grained volcanic grains and very fine pebbles, either scattered or in very thin lenses. Minor interbeds of planar-bedded or the flows). The second locality is the low hill southeast of Sage Tank composed of fine-grained basalt containing ~10% olivine phenocrysts Qayh Qttu Ttdml Qayh Tg3 Qayh Ttduh Qayh trough-cross bedded, medium to coarse sandstone with dispersed granules of volcanic rock types. 1-5% interbeds of brown, light brown, or less than 1 mm across. The hill is surrounded by younger Tg3 gravel and almost certainly is within a crater defined by the distribution of Qayh 3 4021000 Qayh Younger alluvium occupying higher topographic positions on valley floors (middle to upper Holocene) – Very pale brown to pink sand, Qao Qayh Qayl reddish brown clay and clayey-silty very fine- to fine-grained sand. 1-5% interbeds of pink to very pale brown siltstone. Unit overlies Ttc in phreatomagmatic tuff outcrops to the southwest and east (Tpt). Vesicular zones suggest the presence of flows such that this hill may rep- Qayl 7 silty sand, and gravel occupying the higher terrace positions on the floor of valleys (below the Qtr and Qtt Pleistocene units). In the headwa- 000 Ttc Qtr5 the western part of the quadrangle, and is mapped as tongues within unit Ttpm in the eastern part of the quadrangle. Beds of this unit are com- resent a small shield volcano within the hydromagmatic tuff ring crater; alternatively this hill could be an eroded plug within the crater. The 4021 Qafy Qayh 8 Ttdml Qayl ters of Arroyo del Perro this unit is a sheetlike, graded, hillslope mantle of gravelly sand that is a mixture of sheetwash and eolian deposits 40 39 Ttdml mon (15-50% of sediment volume) in unit Ttpu, but were not differentiated there. Moderately to well consolidated and generally non- basalt flows on Sierra Negra have returned a K/Ar age of ~5 Ma (Baldridge et al., 1980) and a Ar/ Ar age of 5.56±0.12 Ma (Maldonaldo and Ttdml Qttu Ttdml Qayh Qayh similar to Qse. This unit differs from Qse in its tendency to form a distinct geomorphic surface and to be continuously traceable from the hill- Qayh Qc/Tt Qtr3 Qayl Qayh Qayh cemented (localized strong cementation). Maximum preserved thickness of 55 m, but individual tongues mapped within unit Ttpm may be as Miggins, 2007). The basalt at the second locality is probably middle Miocene in age (40Ar/39Ar age is pending). Qayh slope position down into fill terraces in the fingered headwater tributaries of Arroyo del Perro and the main branch of Alamosa Canyon. The Qttu TtdmlTtdml 8 little as 6 m-thick. Ttdml Qayh Qayh alluvial-fill part of the unit is about 3-m thick and consists of a basal sandy gravel layer about 1 m thick overlain by orange and brown sands Tbi Basalt dikes and plugs (Miocene to Pliocene) – Largest dike consists of en echelon segments that form ridges along the western quad boundary Qse Qayh 7 Qayh Qayh Qayh and local clay-silt beds. Soil development seems to be minimal in the few places where examined in cut-banks. Along lower El Rito Creek, just east of Madera Cañon. This basalt is a fine-grained, olivine-phyric rock that is indistinguishable from the Tb hill southeast of Sage Tank. Qse Qc/Tt Ttdml Ttdml Qayh Qao Qayh Ttdml this unit forms a thick fill at least 6 m-thick. Here, it consists of medium to thick, tabular to broadly lenticular beds of very fine- to medium- This map unit also includes a plug on the northern flank of Sierra Negra; this rock contains 2-5% olivine and ~1-2% plagioclase phenocrysts Qayh 13 Qayh Ttc Chama-El Rito Member, Tesuque Formation (middle Miocene) – Pink to orange, fine-grained sandstone, silty sandstone, and siltstone Qc/Tt 3 Ta Qayl Ttdml 13 10 8 Qayh grained sand with subordinate coarse to very coarse sand and minor pebbles. Minor thin, tabular beds of silty very fine- to fine-grained sand. interbedded with gray pebble gravel. Unit assigned for thick intervals (greater than 30 m) where fine-grained sand is subequal to or exceeds 0.5-2 mm across. There is also a 0.5-3.0 m-wide dike mapped 0.5 km east-southeast of CCC spring, which has 2-3% black olivine and 25% Qafm Qafm Qayh Tlpc Qayh Qayh Qayh Also minor very thin- to medium, lenticular beds of sandy pebbles with minor cobbles. Surface of unit typically rises 1-4 m above adjacent black-green pyroxene(?) crystals in a black, aphanetic groundmass (both 0.1-1.0 mm).. Qayh Qayh 9 volcan iclastic, coarse channel-fills. Unit contains more volcaniclastic channel-fills than Ttcf. Fine sand is similar to that described in unit Ttcf Qc/Tt Ta Tlpc Qayh 8 active channels. Base of unit lies unconformably over scoured Tesuque or Abiquiu Formations, except in larger drainages where it likely over- Qtr5 Qayl Qayh above. Coarse channel-fills tend to be 1-2 m thick and consist of tightly packed gravel with subangular to subrounded clasts generally 1-4 cm Tpt Phreatomagmatic tuff and lapilli tuff – Pale green to tan, and locally orange, planar-bedded and cross-bedded hydromagmatic tuff. Thickest Qayl Tg3 Qc/Tt Qtr5 Qayh lies an older late Pleistocene-Holocene gravelly sand-sandy gravel. A cuttings log for a well located approximately 1 km southeast of El Rito Tg3 Qayu Qayh Qayh and rarely larger than 10 cm across. Visual estimates of composition indicate about 5-10% quartzite and the remainder volcanic pebbles. The deposit is about 30 m-thick below the escarpment SW of Tuck Tank and exhibits easterly to southerly transport, based on cross bedding, which Tto Ttdml 9 Qayh suggests that this older interval is approximately 10 m-thick. Ttc 11 5 volcanic pebbles are overw helmingly light-gray to pink, and in some cases white, hornblende-biotite-plagioclases rocks, suggesting andesitic/ is consistent with derivation from a vent centered beneath the basalt hill southeast of Sage Tank. These deposits also likely correlate to a small Qc/Tt Qtr2 Qayl Qayl 4020000 Tto Qayh dacitic composition; more felsic clasts are very scarce or absent, but exceed 15% in the eastern part of the quadrangle above the upper Ttp unit. outcrop area in an unnamed canyon southwest of the basalt hill, where a steep contact with Ttc implies the margin of a crater filled with in- Qtru Tto Qayh Although the orange-and-gray striped character of Chama-El Rito outcrops is pretty typical, both the fine and coarse layers are distinctly whiter ward-dipping tuff. Outcrops in the headwaters of Arroyo del Perro may correspond to the same event, and similar tuffs are found near the top 4020000 Qayh 10 12 10 Qayh Qayu Undivided valley-floor alluvium (Holocene) – Sand, silty sand, and gravel of deposits Qayh, Qayi, and Qayl that were not individually dif- Qayh Ttc Qtr1a in the vicinity of faults north of Sierra Negra. This unit gradationally overlies Ttpu in the eastern quadrangle. Thickness on the east margin of of Sierra Negra. East of El Rito Creek a 3-30 m-thick belt of phreatomagmatic deposits lies between units Ttpm and Ttpl. These deposits are Qayl Qayh ferentiated. Tg3 Qayh Qayh Qayi the quad decreases northwards from approximately 120 m to 50 m. Unit is at least 250 m-thick in the southwestern part of the quadrangle, and slightly greenish and consist of sandstone and gravelly sandstone that are cross-stratified in various angles. Sand is very fine- to very coarse- Qc/Tt Qayh 10 Qayh Qayh Qayh Qayh Ttc possibly up to 500(?) m-thick. grained and includes a mix of minor, altered, basaltic sand with more abundant sand similar to that seen in units Ttpl and Ttcfl. Gravel con- Tg3 Qtr3 Qayh 7 Qayh Qao Sandy alluvium occupying the highest topographic positions on valley floors (upper Pleistocene to middle Holocene) – Isolated remnants sists of basalt, dacite-andesite pebbles of the Tesuque Formation, and minor Proterozoic clasts. Well consolidated and locally cemented. Qc/Tt Tto Qtr6 Qayh Tg3 Qc/Tt Qayh of sandy gravel that are 1-3 m higher than adjoining Qayh deposits. Up to approximately 3-5 m-thick. PROTEROZOIC ROCKS Ttdml Qayh Ttpu Upper unit of Plaza lithosome, Tesuque Formation (middle Miocene) – Coarse channel-fill complexes (up to several meters thick) of peb- Qayh Xoq Ortega Quartzite (Paleoproterozoic) – Light gray, coarse-grained, vitreous, laminated quartzite. Laminations are planar, wavy, to low-angle Qayh Qaf Younger deposits (Upper Pleistocene to Holocene) – Sandy gravel to gravelly sand to clayey sand alluvium forming fans at the bly sand to sandy gravel, possessing greater than 10% felsite clasts, intercalated with fine-grained, pink to orange sand. Gravelly sediment is cross-stratified. ~5% lenticular pods of vein quartz. Biotite, as well as aligned silliminite, are concentrated in primary foliation planes, which Tg3 Qayh Qayl mouths of low-order drainages and along terrace risers on the west side of El Rito valley. Unit appears to grade with the Qtr4 terrace tread. clast- to sand-supported and in laminated to very thin to medium beds. These beds are broadly lenticular to planar (most common), but locally Qao Qayl Qayh themselves appear to follow original bedding. Locally present are flattened, very fine to very coarse quartz pebbles that are shortened perpen- Thickness unknown. lenticular and planar-cross-stratified (up to 2 m-thick foresets). Gravel includes pebbles with 5-7% cobbles and 1% boulders. Clasts consist Qayh dicular to the primary foliation planes. 60 m of exposed thickness on this quadrangle, but total thickness is much greater. Qttu Tto Tto Qtr2 Qayh Ttc predominately of dacite-andesite clasts with 10-50% rhyolite and felsic tuff clasts (welded and non-welded, includes Amalia Tuff), 1-5% inter- Qayu 9 Ttc Qc/Tt Qafo Qtr4a Ttdml Qayh mediate intrusive clasts (e.g., graniodiorite, quartz diorite, and tonalite -- weathered intermediate clasts have a slightly greenish color), 1-3% 000 Qgo1 Older alluvial fan deposits (middle Pleistocene) – Sandy gravel to gravelly sand alluvium forming a broad, east-sloping alluvial fan at the Qtr6 Qayl 4019 orange granite, 1-5% quartzite, and 1-3% basalt. Channel-fill sand may have orangish gray to gray colors. Channel-fill sand is poorly sorted DEEP STRATIGRAPHIC UNITS DEPICTED ON CROSS-SECTION BUT NOT LISTED ON MAP Qayh Qayl 7 headwaters of Alamosa Canyon. Unit appears to grade with the Qtr1 terrace tread, but its eastward slope suggests deposition by small tributary Qtr6 Qayl and very fine- to very coarse-grained. Generally non-cemented (about 10% strong to moderate cementation) and weakly to moderately consoli- 4019000 Ta streams or slopewash processes rather than deposition by El Rito Creek. Unit generally less than 5 m-thick. Qayh Qtr6 Ttdml Ttc dated. The lesser degree of consolidation and cementation of this unit compared to the underlying Ttpm unit commonly results in a topog- lPPcu Undivided Cutler Group – Red to orange to brown siltstone, sandstone, and conglomerate. Sand consists of commonly medium- to coarse- grained, moderately to poorly sorted, angular arkoses and lithic arenite. Includes the Arroyo del Agua and El C obre Canyon Formations Qc/Tt Ttdml Ttduh raphic slope decrease near its basal contact. In the northeastern quadrangle, the base of this unit was drawn above Ttpm where the percentage Tg3 of felsite clasts exceeded 10%. However, in the southeastern quadrangle, the upper 20-30 m of the middle unit of the Plaza lithosome (Ttpm) (summarized from Lucas and Krainer, 2005). Qao Qtr Quaternary terrace deposits associated with El Rito Creek (Pleistocene) – Sandy gravel terrace deposits along El Rito Creek. The sand is Qct Qayh Ttdml contains appreciable felsite clasts (at or above 10%). Because this gradation was difficult to identify precisely, we mapped the base of the lPm Madera Group – Limestone with minor sandstone and conglomerate. Qao Qtr1 Qayl pale brown to light gray and mostly medium- to very coarse-grained. Gravel consists of pebbles and cobbles, with 2-5% boulders, that are Qtr3 Qayu Qc/Tt Qao upper unit above this gradation; specifically, at the base of a thick, orangish, fine sand interval above which fine sands occupied greater than XYu Undivided Paleo and MesoProterozoic rocks – Quartzite, gneiss, and crystalline intrusions. Includes Ortega quartzite and metavolcanic Ttc Ttc Qayh 10 Qayh clast-supported and imbricated. Boulders and cobbles are subrounded to rounded and contain >80% quartzite, with the remainder being rhyo- 15% of the strata (over about a 30 m stratigraphic interval). Unit interfingers with the Chama-El Rito Member a short distance south of the rocks. Qse 10 Qayh lite, dacite, and andesite clasts. Volcanic clasts dominate the pebble fraction in the lower terraces, but higher ter races have an approximately Qao Qayl Qtr6 Ttdml Ttc quadrangle’s south boundary, and gradationally underlies this member on this quadrangle. Unit gradationally(?) overlies Ttpm in the eastern REFERENCES Ttc Ttdml subequal volcanic : quartzite ratio and the volcanic fraction is dominated by felsic clasts. In the pebble fraction, there are also minor myloni- Tpt 10 Qayh part of the quadrangle. Near the northeastern corner of the quadrangle, this unit may interfinger northeastward with a unit similar to Ttpml, but Qc/Tt Qayu Qc/Tt Qc/Tt Ttdml tized quartzite and 1-2% granitoid clasts. 1-5 m-thick, except where noted, with the lower terraces appearing to be thicker than the higher ter- poor exposure there makes this inference uncertain. 120-150 m-thick. Baldridge, W.S., Ferguson, J.F., Briale, L.W, Wang, B., Eckhardt, K., Evans, D., Schultz, C., Gilpin, B., Jiracek, G.R, and Biehler, S., 1994, The western margin of the in Ttduh northern New Mexico: an aborted boundary: Geological Society of America Bulletin, v. 106, p. 1538-1551. Qtr3 Qc/Tt races. Terrace surfaces (treads) are well-preserved , typically extensive, and overlain by 1-2 m of Qse. Note that Qse was not mapped over Qtru 9 Ttdml Qayh Barker, F., 1958, and Tertiary geology of the Las Tablas quadrangle, New Mexico: New Mexico Bureau of Mines and Mineral Resources Bulletin 45, 104 p. Tb Qse Qayu Qayh Qayl Qtr terraces because doing so obscures the underlying terrace – we think the latter is more important to depict on the map. Six main Bingler, E.C., 1968, Geologic map of the El Rito Quadrangle, Rio Arriba County, New Mexico: State Bureau of Mines and Mineral Resources , Geologic Map 20, scale 1:24000. Birkeland, P.W., 1999, Soils and geomorphology: New York, Oxford University Press, 430 p. Qtr3 Ttdml 4018000 levels were recognized that are listed below; note that locally some of these levels are subdivided based on slight differences of tread (terrace Ttpw Western tongue of Plaza lithosome, Tesuque Formation (lower to middle Mioccene) – Tongue of volcaniclastic conglomerate mapped Qayu Ta Qayh Tg3 Qayh Ttc Qayh Compton, R.R., 1985, Geology in the field: New York, John Wiley & Sons, Inc., 398 p. Qayl Qtr3 Qayh surface) height (e.g., Qtr4a, Qtr4b, and Qtr4c). The difficulty in correlating these sub-levels contribute to the irregularity of the profile (Figure between lower Arroyo del Perro and Arroyo del Perro del Oeste. Similar to unit Ttpm in color, bedding, and texture, but with an estimated Dethier, D.P., and McCoy, W.D., 1993, Aminostratigraphic relations and age of Quaternary deposits, northern Española Basin, New Mexico: Quaternary Research, v. 39, p. 222-230. Qse Dethier, D.P., and Reneau, S.L., 1995, Quaternary History of the western Española Basin, New Mexico: New Mexico Geological Society, 46th Field Conference Guidebook, Geology of the 4018000 Qtm Qc/Tt Qc/Tt Qayh Tpt Qayh Qc/Tt Qc/Tt Qayl 3). Note that the lower terraces (Qtr6 through Qtr3) diverge slightly in a downstream direction (i.e., about 6 m divergence over 7 km. 10-20% welded tuff, tuff, and minor rhyolite clasts. Other minor clasts include: trace to 1% intermediate intrusives (e.g., granodiorite, tonalite, Santa Fe Region, p. 289-298. Ttc Dethier, D.P., Halverson, N., Marrack, L., Meagher, M., Oelkers, E., Harrington, C.D., Sarna-Wojcicki, A., and Meyer, C.E., 1990, Occurrence of the Lava Creek B tephra layer in the Qse Qayh quartz diorite), trace to 1% orange granite, trace basalt, and trace quartzi te. Remainder of clasts consists of light to dark gray to purplish gray, northwestern Española Basin: New Mexico Geology, v. 12, no. 4, p. 77-82. Qao Tpt Qayl Qafo Qafo Qtr2 Qc/Tt Qayh Qayh Qayh Qtr6 – Lower Pleistocene gravel terrace. Unit is more discontinuous than the aforementioned older units, being found only locally in the commonly porphyritic dacite to andesite. Unit probably correlates with Ttpm to the east. The slight difference in clast composition between Galusha, T., and Blick, J.C., 1971, of the Santa Fe Group, New Mexico: Bulletin of the American Museum of Natural History, v. 144, 127 p. Qayh Qse Qtr3 Qayh Geohydrology Associates, Inc., 1979, Preliminary assessment of water resources near Las Placitas and El Rito, New Mexico: unpulished report for Charles F. Horne and Associates, Inc. and Qtm 30 Qayl Qtr1 Ttc Qayl southern part of the quadrangle and near Placitas. Strath is 10-14 m above the modern stream. Probably correlates to the 15-6 m-high terrace this unit and Ttpm is attributed to a more western stream eroding slightly different older sediment in what is now the Tusas Mountains. About Qttu Tto Qayh Qc/Tt 8 the Placitas Mutual Domesti c Water Consumers Association, 37 p(?) Qse Ttc 12 Qse Qse Qayu Qayh of Dethier and Reneau (1995, fig. 2), which has an inferred age of 26-44 ka based on radiocarbon dating. Probably correlates to the Qtc7 ter- 30 m-thick. Ingram, R.L., 1954, Terminology for the thickness of stratification and parting units in sedimentary rocks: Geological Society of America Bulletin, v. 65, p. 937-938, table 2. Tpt Qayh Qayh Qc/Tt Ingersoll, R.V., Cavazza, W., Baldridge, W.S., and Shafiqullah, M., 1990, Cenozoic sedimentation and paleotectonics of north-central New Mexico: Implications for initiation and evolution Qtr1 race on the Medanales quadrangle to the south (Koning et al., 2004). Inferred age of 26-40 ka. of the Rio Gran de rift: Geological Society of America Bulletin, v. 102, p. 1280-1296. 60 Ttdml Qayh Ttdm Qayh Ttc Ttc Tbi Qayh Qayh Qayh Tto Kelley, V.C., 1978, Geology of Espanola Basin, New Mexico Bureau of Geology and Mineral Resources, Geologic Map 48, scale 1:125,000. 4 Tg3 Tg3 Qao Qtr1 Qayu Qayu Qayh Koning, D.J., and Manley, K., 2003, Geologic map of the San Juan Pueblo 7.5-minute quadrangle, Rio Arriba and Santa Fe counties, New Mexico: New Mexico Bureau of Geology-- and Tpt 50 Ttpm Middle unit of Plaza lithosome, Tesuque Formation (lower to middle Miocene) – Gray to brownish gray to pale brown, slightly tuffaceous Mineral Resources, Open-file Geol ogic Map OF-GM-70, scale 1:24,000. Qayl Qayh Qtr5 – Upper lower Pleistocene gravel terrace. Strath is 12-21 m above the modern stream (mostly 18 m). Correlates with terrace deposits Tto Qayh Tpt 8 Qayl (estimate 1-5% tuff), sandy pebbles and pebbly sand in very thin to medium, le nticular to broadly lenticular to planar beds. Locally cross- Koning, D., May, J., Aby, S., and Horning, R., 2004, Geologic map of the Medanales 7.5-minute quadrangle, Rio Arriba county, New Mexico: New Mexico Bureau of Geology-- and Mineral Qayh Qayh Qc/Tt Qayh Qtr4and Qtc6 in the Medanales quadrangle to the south, which in turn have an inferred age of 40-70 ka (Koning et al., 2004; Dethier and Re- Resources, Open-file Geologic Map OF-GM-89, scale 1:24,000 Qtr1 Ttc Ttc Qc/Tt 55 Qc/Tt neau, 1995; Dethier and McCoy, 1993); we favor an age closer to 70 ka. This terrace locally is as much as 6 m-thick. stratified and includes about 10% U-shaped, discrete channel-fills 10-50 cm-thick. Gravel are matrix- to clast-supported and consist of very Koning, D. J.; Karlstrom, K. E.; May, J.; Skotnicki, S. J.; Horning, R.; Newell, D.; and Muehlberger, W. R., 2005,Preliminary geologic map of the Ojo Caliente 7.5 minute quadrangle, Rio Qao Ttc Qc/Tt Qayh Arriba and Taos counties, New Mexico: New Mexico Bureau of Geology, Open-file Geologic Map-101, Scale 1:24,000. Ta 11 Qse Ttc Qayh Ttdm fine to very coarse pebbles and minor cobbles (~5%); the majority of pebbles are very fine to medium. Clasts consist of purplish gray, porphy- Qttu Qayl Qtr5 Ttdl Ttc Koning, D.J., Kelley, S.A., and Kempter, K.A., 2007a, Geologic structures near the boundary of the Abiquiu embayment and – a long history of faulting [non-reviewed Ttc Qtr4a Ttdl Ttdm 4017000 ritic dacite to andesite, in which many of the coarser pebbles have greater than 10% plagioclase phenocrysts up to 8 mm-long in addition to 3- mini-paper]: New Mexico Geological Society Guidebook, 58th Field Conference, Geology of the Jemez Region II, .p. 43-46. Ta Ttc Qtr3 Tpt Ttcf Qtr4 – Lower middle Pleistocene gravel terrace. Strath is 21-38 m above the modern stream. Correlates with terrace deposits Qtr3 and Koning, D. J., Karlstrom, K. E., Salem, A., Lombardi, C., 2007b, Preliminary geologic map of the La Madera quadrangle, Rio Arriba County, New Mexico: New Mexico Bureau of Geology, Qayu Qayh Ttcf Tto Ttdm Ttduh 10 % hornblende and biotite up to 3 mm. Other clasts include light gray, white, and pinkish white dacites that often are weathered and have 5- Ttc Tto Qao Qayh Qayl Qtc5in the Medanales quadrangle to the south, which have an inferred age of ca. 130 ka (Koning et al., 2004; Dethier and Reneau, 1995; Open-fill Geologic Map-141, 1:24,000. Ttc 7 Qayh Qayh Ttdl th 4017000 Qayh 50 Qao Qayl Ttdl Ttdm Ttduh Dethier and McCoy, 1993). 15% mafic phenocrysts (typically hornblende and minor biotite) and less than 15% plagioclase phenocrysts, 1-12% quartzite, and 1-15% rhyo- Lucas, S.G., and Krainer, K., 2005, Stratigraphy and correlation of the Permo- Cutler Group, Chama Basin, New Mexico: New Mexico Geological Society, 56 Field Confer- Qayh Qayh Qayl Qc/Tt Ttdml Qc/Tt Ttc ence Guidebook, Geology of the Chama Basin, p. 145-159. Ttc Qayh Tpt Ttcf Qayh lite and welded tuffs (increasing up-section in the middle to upper part of the unit). Channel-fill sand is gray to light gray to pinkish gray and Manley, K., 1976, The Late Cenzoic History of the Española basin, New Mexico [Ph.D. thesis]: University of Colorado, 1-171 pp. Qayh Qayl Qao Qayh Qayh May, J., 1980, Neogene geology of the Ojo Caliente-Rio Chama area, Española Basin, New Mexico [Ph.D. thesis]: Albuquerque, New Mexico, University of New Mexico, 204 p. Qayh Qse Qao Qc/Tt Qc/Tt Ttdm Qayh 36°17'30"N very fine to very coarse-grained (mostly medium- to very coa rse-grained). Ttpm grades upward into Ttpu and laterally (southward) into unit 36°17'30"N Qse Qayl Qayl Ttdl Ttdl 10 Ttcf Qtr3 – Middle Pleistocene gravel terrace. Strath is 43-61 m above the modern stream. Correlates wih terrace deposit Qtr1 in the Medanales May, J., 1984, Miocene stratigraphic relations and problems between the Abiquiu, Los Pinos, and Tesuque formations near Ojo Caliente, northern Española Basin: New Mexico Geological Qttu Qtr4a Ttcf Ttc; this southward transition appears to occur just south of the southern border of the quadrangle. Most of unit has less than 15% fine sand Society, 35th Field Conference, Guidebook, p. 129-135. Ttcf Qao Tto Qc/Tt Ttcf 8 quadrangle to the south, which in turn has an interpreted age of 250-400 ka (Koning et al., 2004; Dethier and Reneau, 1995; Dethier and Moore, J.D., 2000, Tectonics and volcanism during deposition of the Oligocene--lower Miocene Abiquiu Formation in northern New Mexico: Albuquerque, N. Mex., University of New Qayh Qafo Qayh 10 Qc/Tt Ttdm 13 Qayh beds similar to unit Ttcf (over a given >30 m stratigraphic interval, excluding mapped tongues of unit Ttcf), although the lower 20-30 m has as Ttc Qtr1 Ttc Ttc Qc/Tt Ttdm Qayl Qayh McCoy, 1993). Mexico, M.S. Thesis 147 p., 3 pl. Ta Qttu Qtr2 Qtr2 Qayh much as 40-50% of these fine sandstone interbeds . Unit corresponds to Los Pinos tongue of May (1980 and 1984). Base of unit placed above Munsell Color, 1994 edition, Munsell soil color charts: New Wind sor, N.Y., Kollmorgen Corp., Macbeth Division. Qse Qao Qayh Sarna-Wojcicki, A.M., Morrison, S.D., Meyer, C.D., and Hillhouse, J.W., 1987, Correlation of upper Cenozoic tephra layers between sediments of the western United States and comparisoooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooo Qayh Qayh Qtr4a Qtr5 Qayh Qayh Qayh Qayh Ttc the highest beds of Tpt, Ttcfl and Ttpl in the southeastern quadrangle. In the northeastern part of the quadrangle, where unit Tpt is absent, the Qse Ttc Qayh Qayh Qtr2 Tto 9 Qayh Qtr2 – Upper middle Pleistocene gravel terrace. Strath is 73-88 m above the modern stream. Probably correlates to terrace deposit Qtc4 in Qse Ttdl Qayh Ttdl Qayh lower and middle parts of lithosome P are similar and lumped in a combined unit (Ttpml) that is lithologically similar to what is described Qtr2 Tpt Qayh Qayh the Medanales quadrangle to the south, which has an inferred age of 250-400 ka based on amino-acid ratios of gastropods (Dethier and Qafo Qafo Qse Qayl Ttdl 10 here. Well consolidated and weakly to moderately cemented by calcium carbonate and tuff, locally producing cliffs and ledges in the land- Qayu Qayh Ttcfl Qayh Qayl McCoy, 1993). Tbi Ttcf Qayh Ttdl Ttdm Ttc scape. Approximately 200-260 m-thick. Ta Ttcf 75 Qayh Tto Qtr4a Qayh Qtr4b Qtr5 Qayh . Tto Qayh 11 72 11 8 Ttcf 8 9 Qse Qttu 8 Qtr3b Ttdl Ttc Qtr1 – Upper Pleistocene gravel terrace. Strath is 98-104 m above the modern stream. The extensive surface of Qog1 grades into this sur- Tg3 Qayu Qtr3a Ttdl Qayh 000 Tpt Ttc Qao Qayh Qayl Qayh Qayh Qayh 4016 face. Based on its strath height, this terrace is inferred to correlate with terrace deposits containg the Lava Creek B Ash (620 ka; Sarna- 14 Qse Ttdl Qayh Qayl Ttpml Undivided lower to middle Plaza lithosome, Tesuque Formation (lower to middle Miocene) – Generally similar to the middle lithosome P 76 Qafo Qafo Qafo Ttc Qc/Tt Ttdm 8 Qayh Wojcicki et al., 1987) along the Rio Chama south of Medanales (Koning et al., 2004; Dethie r et al., 1990; Dethier and Reneau, 1995). Its strath 4016000 7 Qse Tto Qayl Qayh Ttdl Qayh unit, but extends down-section past the projected phreatomagmatic interval (Tpt) and so includes strata probably time-equivalent to Ttpl. 300- Ttc Qayh 70 Qayh Ttdm height is similar to terrace deposits mapped as Qtv5 and Qtoc5 on the La Madera and Ojo Caliente quadrangles to the northeast and east Qafo Qayh Qc/Tt Ttcfl 8 Qayh 400 m-thick. 36 Qafo Qse Ttdl Qayh Ttc (Koning et al., 2007b and 2005). These deposits were also correlated to the Lava Creek B ash-bearing terrace deposits along the Rio Chama. 60 12 Ttcf Qayh Ttdl Ttcf Ttduh Ta Qafo Ttc Ttc Qayi 15 Qayh Qtr3b Qayh Qtr4b Qayl 10 Ttdm Qafo Tpt Ttc Qtt3 Qayh 7 Qayl FIGURE 5 Qayh Ta Qayl Qayh Ttdm Ttdm Ttc Qafo Qse 4 Ttcf Ttcf Qtr3b Qc/Tt Qtr4b Qtr5 Ttdl Ttdl Ttcfl PALEOCURRENT DATA ON THE EL RITO 7.5-MINUTE 23 Ttc Qtr1b Qtr5 Qayl QayhQayh Qafo 26 Qse Ttcf Ttcf 10 Qayh Qtr2 Qse Qayh Qtr3b Qayh Qayh QUADRANGLE Tbi 23 15 Qtt3 Qayu Qc/Tt Qayh Qayh Qayh Qayl Ta Qayh Qayh Qttu Qayh Qtr3b Qayh Qayh Data plotted in rose diagrams Symbols plotted on map Ta Qafo Qayl Qtr4a Ttdm Qtr3a Qayh Qtr4b Ttdl 10 Ttcf 10 Qse Qct 9 Qao Qc/Tt 5 Qayl Upper Plaza lithosome (Ttpml) Qse Qse Qtr3ab 10 Qse Ttcf Ttdm Qayh Bi-directional paleocurrent measurement - Solid Qct Qtt4 Qayl Qtr3b Qc/Tt 10 Qayl Qayh N ball on vector is located at measurement Qse 4 Qayh Qayl Ttdl Ttduh location. Primarily measured using channel Qse Qayh trends (abbreviated as "c") or the trend of a 2 Qayh Ttcfl Ttdm Ttc 000 6 Qc/Tt Qayh Qtr5 Qtr5 77 9 Ttcf 4015 single channel margin (abbreviated as "cm"). Qse Qls Qc/Tt Qc/Tt gr Although bi-directional, only one arrow head may Qayh Qayh 8 2 cm Qttu Ttdm Ttcfl FIGURE 4 be depicted that shows the authors' preferred Qtt4 Tpt Ttdl Qayh Ttdm 9 EXPLANATION OF MAP SYMBOLS 2 cm, tx 000 Qls Qtt3 Qse FIGURE 2 270 direction; this preference is based on surrounding 4015 Qls Qls Qayh Qayh 3c, cm Ttc Qayl Qayh Ttduh Qayh Qayl mono-directional paleocurrent data and source Qayl Qtr6 Ttdl 2 cm Qtr1a Qtt4 Qtt5 Qtr4b Qayl 57 Qse Ttc 0 Qayi area considerations. A double-sided arrow is Qc/Tt Qayl Qayl Ttdm Ttcf 8 Qayl A A' shown where there is no preference. Different Qls Ttc Qayu Qao Ttdm Qayh Qayh Qayu Ttc Qse Qayh Qayh Qayh Qc Qc Southwest Northeast lengths of vector is proportional to number of 7 Qayh Qayh Qse Qct Tt Ta measurements at a site -- top, upper middle,

Qtr4a Qtr5 CENE Qtr3ab HOLO- Cross-section line endpoints lower middle, and lower vectors to the left (with Qayl Ttcf Qc/Tt Ttdl 11 8 Qayh Qao Qct Qayl 65 Qtt5 Qtr4b Qse Qtr6 Ojo Caliente Sandstone Member, Tesuque Fm one arrow head) reflect one, two, three, and four 9 Qayh Qaf Qtr5 Qtt5 measurements, respectively. Paleocurrent Qlsm Qtr4b Qayh Ttdl Ttdm Ttdm Qayh Ttduh Ttc 0.01 ~70-80 ka azimuth value and type of data (e.g., "c" for 4 Qtr3ab Ttdl Ttcfl Ttcf late ? Qtr4 Qtt4 Geologic contact - Solid where exposed; dashed where approximately located; dotted Qlsm Ttcf Ttc Qayh Qtr1b Qtr5 Ttdm Ttdm Ttduh channels) is also listed next to the vector Qttu Qse Qayh Ttdml Ttdl Ttcf 8 ? Qtt Qtu ? where concealed beneath younger alluvium,; queried where uncertain or inferred. Filled Qlsm Qayh Ttdl Qayh 5 Mono-directional paleocurrent measurement - Qc/Tt Qtr4a Ttduh Qtt3 tx Ttc Qtr3c 8 Ttcf 7 Qls Qlsb Qtr3 circles denote areas where there is uncertainty of interpretation. Solid ball on vector is located at measurement Qayh Qayh Qayl Qc/Tt 12 Ttdm Ttcf 2i Qtr3ab Qayh 3i location. Primarily measured using clast Ttduh Ttduh Ttc middle imbrication (abbreviated as "i"). Different lengths Qtru Qtr6 Ttdl Ttdl Qayh Key 270 4i Qayh Tpt Qtr4b Ttcfl Approximate location of lateral gradation or interfingering contact of units; dotted where upper Plaza lithosome (15-13.5 Ma) of the vector is proportional to the number of clast Tpt Tbi Qttu 8 Qtr5 8 Ttcfl Ttcf Rose Diagram Uni-Directional Ttdl ~620 ka Qtr2 buried beneath younger alluvium. Total Number of Points = 172 measurements at a site. (5 clast measurements in Qtt5 Qc/Tt Qayh Qayh Ttdl Qayh each bin). The number of clasts measured is Tpt Qlsm Ttcf Qayh Qayh Ttduh Qtr5 80 Ttduh Bucket Size = 30 degrees Error Size = 0 degrees Qayh 4014000 shown by the number preceeding the i. Qttu Qayh Qttu Qc/Tt Qtt4 Qayh 8 Ttduh Ttc Paleocurrent azimuth value is also listed next to Tto Qtr1b Qayh Qtr6 Ttdl Ttdm Normal fault - Solid where exposed; dashed where approximately located; dotted where 0 56 Qse Qttu Ttdl 6 55 Qayh Qayh the vector 000 Qayl Qtr3ab Qtr4c Ttdm Qtr4c Qayh 45 concealed; queried where uncertain. Ball and bar are on downthrown block. Number by tic 4014 Qse 13 11 Ttcfl Qayh 1 70-340

Qse Qls early Qc/Tt Qayl Qayh 6 Qayh Qayl Qayh ? denotes the location and value of fault dip attitude (dip value - dip azimumth). Arrow and Plaza litho- Qlsb 69 Qc/Tt 10 7 Ttcf Qayh MIddle Plaza lithosome (Ttpm) Combined mid-lower Plaza lithosome (Ttpml) Qls Qayh associated number denotes plunge direction and magnitude of slickenside lineations, if any. Ttcf Qtr5 Qayh Ttdm Qayh Qayh N Qtt3 Qtr2 Ttdl scale change Filled circles denote areas where there is uncertainty of interpretation. some N Ttc Qttu Qayh Ttc Ttdl Qtr5 Qayh Ttdl 63 Ttc Qttu Qc/Tt Ttdl Qayh 14 Ttcf Qgo1 ~1.6 Ma Qtr1 middle Tpt 11 Ttc Ttcfl Qayh Ttduh Tg3 Chama-El Rito Mbr of Tg1 11 Q tr1b Qtr4ab Qtr5 Ttdl 13 Ttcf Qayh Ttduh Syncline - showing trace and plunge of inferred crest line; dashed where approximate. (23-15 Ma) Tb Qlsm Qayh Qttu 11 Qayh Qtr4c Ttdl Ttc Tg2 Ttdl Qtru Ttdm Qayh Ttc Tb Qc/Tt 19 Ttcf Qayh PLIOC. ? Tesuque Fm (20?-13.5 Ma) Qls Qtr2 11 8 5 5.3 Qayh Qayh 61 Qayh 5 Qayh Tb Tbi Qtt3 Qayh Qc/Tt Qayh Qayh Anticline - showing trace and plunge of inferred crest line; dashed where approximate. Ttc Qls Qlsm Qayh 58 Ttcf Tg1 ? Tto Qtr3c Qtr4c Ttdm 11 Qayh Ttc ? Qct Ttc Ttdw Qtr5 Qayi late lower Qayh Qttu 10 7 Ttdl Ttdl Ttcf Ttduh Qayl Ttc Ttdw Qayh Qtr2 Qayi Ttcfl 5 57 Ttduh 10 Qse Qayh Qtr4ab 3 5 5 Qse Qayh 11 Qtr1b Tpt 13 Ttdm 7 Ttdm Qayh Qayh 2 11.2 Attitude of bedding; number in front of dash is dip magnitude, number behind dash is lower Qayh 56 Ttdm 8 Qayh 000 Ttdw Qc/Tt 76 5 4013 07-320 dip azimuth. Qse Ttdw Qayl Qayh Qtr6 4 Ttdm 3 Qayh Qayh Qayh Tto Ttc Qayh Qtr4c Qayi 67 Ttc Ttpu 000 Qlsy Ttcf Ttc

Qtr2 middle 4013 Qayh Ttdm 5 Qse Ttpw 300 m (1000 ft) upward transition to dacitic gravel Qayh Ttdw Qayh 56 67 Ttcfl Ttdm 3 Ttduh Qse 64 15 Ttpm Tb Tbi Tpt 07 Attitude of overturned bedding; number is dip magnitude. Tb 9 Ttcf MIOCENE Tb Qayl Qc/Tt Ttdm Qayl 61 Qayh Tpt Qayl 16.4 Key Key 5 Qse Ttc Qayh Qayh Qtr4c Qayi Ttdm Qayh Ttpml Ttpl 10 10 Qayi 4 Qayh Rose Diagram Uni-Directional Qayh Qayh Qc/Tt Ttdm Ttdm 6 65 Ttduh Beds that dip less than 2 degrees. Abiquiu Fm Rose Diagram Uni-Directional Qayh Ttdw Qc/Tt Total Number of Points = 89 Total Number of Points = 72 Qayh Qayl Qayi Ttcfl Qayh 55 Bucket Size = 30 degrees Error Size = 0 degrees Bucket Size = 30 degrees Error Size = 0 degrees Ttdw Ttdm Qayh (Ma) Time 54 Qtr3 Qayl Qlsy Qayh 13 Qayi Ttcfl Ttdm 66 Qayh Qayh Ttduh 20 5 Qayh Ttduh early ? ? Cordito Mbr, Los Pinos Fm Qayh Qayl Bi-directional paleocurrent measurement - Solid ball on vector is located at (27-20? Ma) 0 33 Qse Qayh Ttc Qayh 45 Tpt Qtr2 Ttdw Qtr4c Qayh Qayl 4 Qayh ? gr 0 24 Qse Tto Qse Qayl Qc/Tt Qayi Qayh Ttcfl Ttduh Qayh measurement location. Primarily measured using channel trends (abbreviated as "c") Ttc Qayh 10 Qtr3 Ttcf Ttduh Qayh 6 Ta Tlpc Talpc 2 cm Qls 11 Qc/Tt Qayi Qayh 62 76 5 9 Qayh Ttc Tto or the trend of a single channel margin (abbreviated as "cm"). Although bi-directional, 10 Qao Qayh Qtr4a Ttcf 5 Qayh Qayh Qayh 23.8 2 cm, tx Hindsdale basalt Qls Qlsy Tpt Ttdm Ttcf Qayh ? only one arrow head may be depicted that shows the authors' preferred direction; this Abiquiu Formation (Ta) Lower Plaza lithosome (Ttpl) Qttu Qayh Qtr3 Ttdm Qayh Qayh 25 270 Ta Ttc Qayh Qayh Qe Ttdw Qtr4b Ttdl Qtr5 Ttcfl Tpt 64 Ttduh Ttduh Qse 3c, cm preference is based on surrounding mono-directional paleocurrent data and source Ttc Qayl Qayh Ttdm Qtr3 Qayh Qayh 8 late Qse Qls Ttdw Ttcf Qtr4c Qayh Qse 2 cm area considerations. A double-sided arrow is shown where there is no preference. Ttdw Qayl Ttcf Qayh Ttduh Qayh Different lengths of vector is proportional to number of measurements at a site -- top, 36°15'0"N 36°15'0"N 28.5 Ritito Fm (Oligocene) Tr upper middle, lower middle, and lower vectors to the left (with one arrow head) reflect 388000 389000 390000 391000 392000 393000 394000 395000 396000 397000 398000 30 106°7'30"W OLIGOCENE one, two, three, and four measurements, respectively. Paleocurrent azimuth value and El Rito Fm (Eocene)

106°15'0"W 106°12'30"W 106°10'0"W early type of data (e.g., "c" for channels) is also listed next to the vector 33.9 35 ? Mono-directional paleocurrent measurement - Solid ball on vector is located at tx measurement location. Primarily measured using clast imbrication (abbreviated as 2i late "i"). Different lengths of the vector is proportional to the number of clast ? 3i measurements at a site. (5 clast measurements in each bin). The number of clasts 40 40.0 Oretga Quartzite 270 4i measured is shown by the number preceeding the i. Paleocurrent azimuth value is Base map from U.S. Geological Survey 1995, from photographs taken 1947. Ter also listed next to the vector EOCENE

middle Proterozoic quartzite Revised from aerial photographs taken 1990. field checked (partial) in 1995. Mesozoic- strata 1927 North American datum, UTM projection -- zone 13N 43.6 45 1000-meter Universal Transverse Mercator grid, zone 13, shown in red Eolian cross-stratification dip direction - Solid ball on vector is located at the measurement ees Error Size = 0 degrees early As old as 55 Ma? Geologic map of the ? location. 0 6 1:24,000 Paleoproterozoic Xoq Water-supply well used in making cross-section VALLE MOGOTE El Rito quadrangle, GRANDE LA MADERA 1 0.5 0 1 MILE PEAK PEAK Rio Arriba County, New Mexico. NEW MEXICO 1000 0 1000 2000 3000 4000 5000 6000 7000 FEET

CANJILON SE ELEl RITO OJO CALIENTE May 2008 Rito 1 0.5 0 1 KILOMETER

Magnetic Declination by CONTOUR INTERVAL 20 FEET March, 2006 1 2 3 ABIQUIU MEDANALES LYDEN 9º 46' East NATIONAL GEODETIC VERTICAL DATUM OF 1929 Daniel J. Koning , Gary A. Smith , and Scott Aby FIGURE 1 Map areas of respective authors At Map Center 106°15’ 1New Mexico Bureau of Geology and Mineral Resources, 801 Leory Pl., Socorro, NM, 87801 106° 7’30” 2 36°22'30" New Mexico Bureau of Geology and Mineral Resources Department of Earth and Planetary Sciences, University of New Mexico, Albuquerque, NM 87131 QUADRANGLE LOCATION 3 Muddy Spring Geology, Box 488, Dixon, NM 87527 Open-file Map Series OF-GM 166 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 Daniel 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 Koning (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, of rock and deposits and the occurrence of structural features. Geologic and fault contacts are Director and State Geologist, Dr. J. Michael Timmons, Geologic Mapping Program Manager). 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 After this map has undergone scientific peer review, editing, and final cartographic geologic mapping, compilation of published and unpublished work, and photogeologic interpretation. Gary 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 Gary Smith (GM) series. This final version will receive a new GM number and will supercede contact onto a topographic base map; therefore, the accuracy of contact locations depends on the Smith this preliminary open-file geologic map. New Mexico Bureau of Geology and Mineral Resources scale of mapping and the interpretation of the geologist(s). Any enlargement of this map could cause New Mexico Tech misunderstanding in the detail of mapping and may result in erroneous interpretations. Site-specific 801 Leroy Place conditions should be verified by detailed surface mapping or subsurface exploration. Topographic Scott Socorro, New Mexico and cultural changes associated with recent development may not be shown. Aby 87801-4796 DRAFT Cross sections are constructed based upon the interpretations of the author made from geologic Daniel Koning mapping, and available geophysical, and subsurface (drillhole) data. Cross-sections should be used as Dan [505] 835-5490 Scott an aid to understanding the general geologic framework of the map area, and not be the sole source Koning http://geoinfo.nmt.edu of information for use in locating or designing wells, buildings, roads, or other man-made structures. Aby 36°15' 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 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 EL RITO 7.5-MINUTE QUADRANGLE, NM reviewed and published by the New Mexico Bureau of Geology and Mineral Resources. The views and conclusions contained in this document are those of the authors and should not be interpreted as 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.