sign in sign up
<<
Home , Carmel Formation, Entrada Sandstone, Jurassic, Owl Rock, Wingate Sandstone

New Mexico Geological Society Downloaded from: http://nmgs.nmt.edu/publications/guidebooks/12

Triassic and rocks of the Albuquerque area Clay T. Smith, 1961, pp. 121-128 in: Albuquerque Country, Northrop, S. A.; [ed.], Geological Society 12th Annual Fall Field Conference Guidebook, 199 p.

This is one of many related papers that were included in the 1961 NMGS Fall Field Conference Guidebook.

Annual NMGS Fall Field Conference Guidebooks Every fall since 1950, the New Mexico Geological Society (NMGS) has held an annual Fall Field Conference that explores some region of New Mexico (or surrounding states). Always well attended, these conferences provide a guidebook to participants. Besides detailed road logs, the guidebooks contain many well written, edited, and peer-reviewed geoscience papers. These books have set the national standard for geologic guidebooks and are an essential geologic reference for anyone working in or around New Mexico.

Free Downloads

NMGS has decided to make peer-reviewed papers from our Fall Field Conference guidebooks available for free download. Non-members will have access to guidebook papers two after publication. Members have access to all papers. This is in keeping with our mission of promoting interest, research, and cooperation regarding in New Mexico. However, guidebook sales represent a significant proportion of our operating budget. Therefore, only research papers are available for download. Road logs, mini-papers, maps, stratigraphic charts, and other selected content are available only in the printed guidebooks.

Copyright Information

Publications of the New Mexico Geological Society, printed and electronic, are protected by the copyright laws of the United States. No material from the NMGS website, or printed and electronic publications, may be reprinted or redistributed without NMGS permission. Contact us for permission to reprint portions of any of our publications. One printed copy of any materials from the NMGS website or our print and electronic publications may be made for individual use without our permission. Teachers and students may make unlimited copies for educational use. Any other use of these materials requires explicit permission. This page is intentionally left blank to maintain order of facing pages. NEW MEXICO GEOLOGICAL SOCIETY TWELFTH FIELD CONFERENCE 121

TRIASSIC AND JURASSIC ROCKS OF THE ALBUQUERQUE AREA CLAY T. SMITH New Mexico Institute of Mining and Technology

The Albuquerque area may be defined as the Albu- the upper part, although this is not the case in exposures querque-Belen basin of the Rio Grande depression ( Kelley, in parts of the Lucero Mesa area (Kelley and Wood, 1946). 1952) and the adjacent associated platforms, uplifts, chan- Maroon, reddish purple, and brown colors are prominently nels, and constrictions (see Fig. 1). The present con- developed and often serve as identifying features for this figuration is chiefly the result of and rock sequence. Locally the sandstones and conglomerates diastrophism and little relation to the distribution of may be buff to nearly white in color and stand out sharply Triassic and Jurassic rocks except as it controls the out- against the bright-red mudstone slopes. Bentonitic clays crops of these beds. are abundant in the mudstone units and the alternate Many of the units so well known in the classical sec- shrinking and swelling of the soil in the semi-arid south- tions of the Plateau region are either missing or western climate results in characteristic "crazed" exposures. have merged with other members until all become un- In the upper part of the lower sendy facies, petrified wood recognizable. The areas in which outcrops occur are widely and chert pebbles are locally abundant. scattered, commonly confined to the mountain blocks, or to The was named by Gregory (1917) isolated structural basins and complexly faulted zones from exposures in Chinle Valley, ; Gregorys ori- along the margins of the Rio Grande depression. ginal description of the formation did not include the TRIASSIC ROCKS , which he considered a separate Traditionally, the Triassic has been subdivided formation. McKee and others (1959) included the Shina- into tripartite units usually labeled lower, middle, and up- rump as a lower member of the Chinle formation and in- per. As additional information has been collected it is dicated that it extends little if any distance east of the obvious that such a separation is not everywhere appli- New Mexico-Arizona stateline. Other local members of cable. McKee and others (1959) utilized three intervals, the Chinle formation have been described in Arizona, such A, B, C, in ascending order, in their treatment of the Trias- as the , Rock member, and sic rocks of the United States, although recognizing that in- Sonsela sandstone member, but these cannot be extended terval B has a very restricted distribution. The intervals A, very far to the east or north (Stewart, 1957). Wood and B, and C of their paper are correlative with the German Northrop (1946) subdivided the Chinle formation in the tripartite division of the Triassic, as well as with accepted Nacimiento uplift into four units, in ascending order: Agua groupings of the Alpine European stages. Zarca sandstone, Salitral , Poleo sandstone, and the The classic section consisting of the upper Chinle beds. These units are not readily recognizable Moenkopi, Shinarump, and Chinle formations is assigned to away from the type localities northwest of the Jemez intervals A and C by McKee and others (1959) and has Mountains and were not individually delineated on the been enlarged through inclusion of the Wingate forma- Nacimiento uplift map. Along the north flank of the Zuni tion of the Glen Canyon in the C interval by Harsh- Mountains, Smith (1954) mapped a lower member, a mid- barger, Repenning, and Irwin (1957). The dle sandstone member, and an upper member of the Chinle of eastern New Mexico, West , Oklahoma, and south- formation; these beds had originally been erroneously western Colorado is apparently confined to the C interval described by Darton (1928) as Moenkopi, Shinarump, and and has not been as extensively subdivided as has the Chinle formations. The lower and middle members in the Colorado Plateau section. Zuni Mountains suggest correlation with t4 lower Petri- In the Albuquerque area only rocks of the C interval fied Forest and the Sonsela sandstone members of the Ari- are present, corresponding to the German or the zona section while the upper member contains combined Karnian, , and stages of the layers and lenses similar to the member. In the European marine sequence. The Albuquerque area lay on Lucero Mesa area Kelley and Wood (1946) divided the a shelf between a western basin containing more than Chinle formation into two units: a lower red shale member 2,000 feet of Chinle sediments in the Zuni Mountains-St. and the overlying Correo sandstone member; they also Johns area, and an eastern basin containing more than recognized a thick unit between the Chinle formation and 2,000 feet of Dockum sediments in and near Lea County, the underlying Paleozoic which they referred to New Mexico, and Yoakum County, Texas. Correlation be- the Shinarump conglomerate; however, it seems likely that tween Chinle-type sediments west and north of Albuquer- these beds are merely the lower sandy facies of the Chinle que, and Dockum-type sediments east and south of Albu- formation and may correlate much more closely with the querque has been difficult because of the intervening Santa Rosa sandstone member of the Dockum group to the present-day Rio Grande structural trough. The southerly east, or with the Agua Zarca, Salitral, and Poleo members depositional margin of the Triassic rocks induced facies farther north. The Correo sandstone member has a very changes that are rapid and unpredictable owing to local local distribution and is not recognized away from Mesa variations in tectonic activity. Local names have been in- Gigante in the northern part of the Lucero Mesa area. troduced in several areas, including some originating in West of the Albuquerque area, the Chinle formation is the Albuquerque area, and the relationships between such a thick mass of red mudstone, siltstone, and sandstone with local units are not always clear (see Table 1). marly beds and intercalated conglomerate lenses. A sandy The Triassic sediments of the Albuquerque area are facies occupies the lower one-third to one-half of the forma- predominantly fine-grained sandstone, siltstone, and mud- tion while mudstone and shale are predominant in the up- stone with intercalated lenticular conglomerate and coarse- per portion. The lower sandy facies averages 300 to 500 grained sandstone beds. In most places the lower part of the feet thick from the Lucero Mesa area to the New Mexico- section contains more sandstone and is coarser grained than Arizona stateline, whereas the upper shaly portion ranges 7° .7Fri / ILW:AIDLIICEUNRTS BASIN / . ABIOUIU / -1-4-4.4. (EMBAY EN T /ENASCOP / .s.4. SAN PEDRO <4./ EMBAYMENT t

2 UPLIFT ,./ 36 ,..-- - . • `.. I-- . ... ESPANOLA co u_ _ <1 _I : JEMEZ • -• -4.-- : a) a_ IX 0 •. CALDERA i... .. O ..... 8 SI N ,i- N (._, Lai Z O z Cy q 1— 0 San te F ♦ 0 4., , 0- /... zu22-.4 y>rviy....i 6N1 bi: R. Cr 2 A .:014 :2ASANTA Is / 7 . EMBAYMENT 444

:IV 4 N ../01 ..•• 1 1 ..... Q ALBUQUERQU- j / sr

/3 Q 4 Albuquerque 4 z (/) 14• 1 35° QD t V A 0 BELEN : EXPLANATIOEXPLANATION • tA .i_ R. - 1.1.. yr 1 c, r - // ,

Rio Grande CL)104 17 Q depression 111 :elan : 2 CO cr N 14., .--....,• — - • :AS I 2 Unfaulted boundary cr LADRO -1 fv/1 c..(11)UP IF • / n 1

.44 T :A 17 High angle fault 44 halves 4.....6..b.on downthrovin side ?1°111111°1

4 / u- i LAJENSE •6 z- r / / / -cg <\ Thrust fault BtA/SIN li ....j3t..,i, A CHUPAD ER ...1.-0..e• A i: 0 9 i- Cr -I PLATFOR M 0 :, cc ..0 CV /Z .11 ,,,e.,. !-- G ° . SOC •rr j — 6 0 6 /2

(:, Ctx V I I 1 I . • ..c■,), -1.s,. >- ., : W Scale !riles 340 -.. • ! N. 107° 106 Figure 1. ALBUQUERQUE AREA (after Kelley, 1954) NEW MEXICO GEOLOGICAL SOCIETY • TWELFTH FIELD CONFERENCE 123

from a few hundred feet to more than 1,500 feet in thick- New Mexico and Arizona. evidence coupled with ness. At least part of the variation in thickness of the up- intertonguing between the underlying Chinle formation and per member may be due to pre-Jurassic erosion. The ap- the Rock Point member places all of the restricted Wingate pearance of coarser grained units in the upper parts of the sandstone in the Triassic. Although the Lukachukai mem- formation to the south suggests also some depositional ber extends considerably farther east than the Rock Point variation. A thickening of nearly 20 feet per mile occurs member, neither of these units is present in the Albuquerque between the east end of Mesa Gigante and Ramah on the area; the Lukachukai member is reported to pinch out a few south side of the Zuni Mountains. miles south and east of Laguna, New Mexico. The Dockum beds were described by Cummins in 1890 Faunal evidence suggests that deposition of Dockum as conglomerate, sandstone, and red clay, 150 feet thick, beds began prior to the deposition of the Chinle formation. near Dockum, Texas (Wilmarth, 1938, p. 616). McKee In Arizona and southern no hiatus is present between and others (1959) showed thicknesses in excess of 2,000 the latest stages of Triassic deposition and the overlying feet along the southern part of the Texas-New Mexico Jurassic deposits. During Triassic time the locus of deposi- stateline and thicknesses of 1,000 to 1,500 feet in east- tion appears to have shifted westward and sedimentation central New Mexico. Southeast of the Albuquerque area continued after deposition in eastern New Mexico and considerable thicknesses of Triassic rocks have been re- west Texas had ceased. Correlation is difficult because of moved by erosion. Locally, near Cerrito del Lobo, the the variable lithologies and the fact that are scarce Dockum rests upon metamorphic rocks as a and poorly preserved. A continuous evolution from primi- result of pre-Triassic erosion. Lithologically, the Dockum tive in the Tecovas beds of west Texas through beds are similar to the Chinle units, although the bentonitic more advanced forms in the Petrified Forest member of the layers so common in the Arizona section are subordinate or Arizona section to highly advanced types in the Redonda lacking in the Texas and eastern New Mexico exposures. member of the Dockum group and the Rock Point member Several members, principally of local significance, were of the provides the framework on which described east of the Albuquerque area. A lower sandy Table 1 is based. The lower sandy facies in the Albuquer- facies similar to the lower unit in the Nacimiento and Zuni que area is represented by the Agua Zarca, Salitral, and Mountains sections is called the Santa Rosa sandstone Poleo members to the west, or the Santa Rosa sandstone member and an upper mudstone facies, the Redonda mem- to the east. It contains no diagnostic fossils and correla- ber. In Texas, the Camp Springs conglomerate, the Tecovas tions within this part of the section are extremely tenuous. and Trujillo formations, and the Sloan Canyon formation The large collections of fossils described from have been assigned to the Dockum beds. McKee and others the Ghost Ranch area north of the Albuquerque area are (1959) placed the Pierce Canyon red beds, which underlie confined to the upper shaly member of the Chinle forma- the Santa Rosa sandstone in southeast New Mexico, in the tion and merely provide an upper limit to the age of the Triassic ( ?) as the lowest unit in the Dockum group, al- lower sandy facies; the Ghost Ranch fauna is correlated though there is some evidences suggesting a age with forms from the upper part of the Petrified Forest mem- for these rocks. ber and from shale units below the Redonda and Sloan McKee and others (1959) estimated that the Triassic Canyon members. rocks in the Albuquerque area had an original thickness JURASSIC ROCKS between 500 and 1,000 feet. These thicknesses do not The Jurassic rocks of the Albuquerque area represent include any rocks correlated with the Wingate or Kayenta a complex of marine ( ?) and non-marine units which, formations since these beds do not extend this far east. as they are traced toward the southern edge of the Al- Outcrops to the north and south of the Albuquerque area buquerque area, coalesce into a single inseparable mass show some thinning; north of the Jemez uplift Triassic of sandstone and finally wedge out by intraformational rocks wedge out against the Precambrian core of the and interformational unconformities. The classic Jurassic Brazos uplift. In the latitude of Socorro more than 400 section of the Colorado Plateau region contained the Glen feet of Triassic rocks are present with less than 100 feet Canyon group, the , and the Morrison of this thickness assignable to a lower sandy (Santa Rosa?) formation. Local member and formational names have facies. Kelley and Silver (1952, p. 108) stated that Trias- been applied and extended without benefit of faunal con- sic rocks are absent in the 75 miles south trol and considerable nomenclatural confusion has resulted. of Socorro; it is not clear whether pre- erosion or McKee and others (1956) subdivided the Jurassic system Triassic non-deposition is indicated by such absence. The into four units, in ascending order, A, B, C, and D. The thinning of the lower sandy facies as compared with areas unit boundaries do not necessarily coincide with time or to the north, west, and east is suggestive of non-deposition. formational but in a general way the four intervals Originally the Wingate sandstone was considered the can be correlated with the European stages. Rocks from lower member of the and placed in the uppermost portion of interval B, most of interval C, and the Jurassic. However, Harshbarger, Repenning, and Irwin a part of interval D are exposed in the Albuquerque area. (1957) restricted the Wingate sandstone of Dutton (1885) Table 2 illustrates the relationships between the units of to the lower half of the type section at Fort Wingate, New the Albuquerque area and adjoining regions. Three units Mexico; they recognized two members, a lower Rock Point of the San Rafael group plus the have member and an upper Lukachukai member within the re- been recognized to the west and north of the Albuquerque stricted Wingate over much of the Navajo Reservation of area. Similar units also extend eastward at least to the Texas-New Mexico stateline, but all strata pinch out south- This maximum appears to be low. In an unpublished ward in response to a combination of pre-Cretaceous - thesis, Harrison (1949) reported about 2,100 feet in the sion and non-deposition. Hagan basin—a figure generally believed to be excessive. The oldest Jurassic beds in the Albuquerque area are —Ed. massive alternating evenly bedded and cross-bedded sand- Table / — Proposed Correlation of Triassic Rocks between the Albuquerque and adjacent Areas u.s.ceol.Surveyl Eastern Arizona North Flonk, Zuni Albuquerque Area Eastern N.E. New Mexico European Stages Poleotectonic Gregory Mtns.,N. exicoic Western Texas Alpine German Mop Inter vols UnitsM I West East New Mexico o Moenave 0 ---,

formation 0.PLo (n 0— I ,,, 0 Sheep Pen 0m,, Lukachukai °i LukachukaiLukachuka CD sandstone Rhaetian member member I = 1. — n ;0 Rock Point Redondo Sloan Canyo — member m member formation

Owl Rock . member -.., B 0 Trujillo o -, Shale 0 formation Interval — Upper 0 = ° 9 memberme o — m D Upper n m ember Correo o x C member 0 member c — C Upper Part x- 3 0 3 (-) c = Petrified Red = _. iS" 3 = Forest member Shale ,0 ,0 –t , Norian Keuper CD 3 member un 0 0 0 C CD -3 C C 0 o -0 _., Sonsela M idd le C 0 member member -... -a Tecovas 3 ° Poleo ss. Santa Santa 0 3 Salitral sh. Rosa Rosa formation _ Lower Part 0 o .... sandstone sandstone m Petrifie ?-- Forest member Lower 0 Aguo Zarca member Lower sandstone Sandstone member — —? -- —

Shinarump Camp Springs conglomerate membere m b e r _?____

Dockum Karnian beds

Pierce Canyon red beds

Ladinian Interval Muschel- B _ ___0__ _?__ kalk Interval Scythian A

. . 7 NEW MEXICO GEOLOGICAL SOCIETY 0 TWELFTH FIELD CONFERENCE 125

stone layers assigned to the Entrada formation. The En- facies intertongue and grade upward into recognizable trada formation disconformably overlies the Chinle or Morrison beds. Farther west and to the south Harshbarger, Dockum beds, although no angularity can be measured in Repenning, and Irwin (1957) have recognized the Cow individual outcrops. The Entrada formation was named by Springs sandstone as a thick eolian sandstone unit which Gilluly and Reeside in joint conference with Moore and is equivalent to parts of the Entrada, Todilto, upper San Gregory (Wilmarth, 1938) from exposures on Entrada Rafael group, and Morrison beds. Pre-Upper Cretaceous Point in the , Utah. At the type locality erosion has destroyed most of the evidence for such a unit the formation is alternating thin- and thick-bedded, red in the Albuquerque area, but a southerly increase in sand- sandstone and siltstone grading upward into massive red- stone in the Morrison formation as well as in the Todilto brown earthy sandstone. Traced eastward from the type limestone and overlying upper San Rafael units along the locality, the develops an upper clean western side of the Albuquerque area is very suggestive buff-white sandy facies often referred to as the slick-rim (Silver, 1948). Entrada, and the red silty facies of the type locality be- In the San Rafael Swell two formations comprise the comes very thin. Harshbarger, Repenning, and Irwin upper part of the San Rafael group: the marine lime- (1957) describe a third facies that underlies the other two stones and of the Curtis and the overlying Summer- facies and is a clean sandy facies; its distribution is re- ville siltstones, sandstones, and mudstones. The Curtis stricted to the northwestern part of the Navajo Reservation formation extends only a few miles south and east of the in Arizona. Harshbarger, Repenning, and Irwins (1957) San Rafael Swell, but Harshbarger, Repenning, and Irwin terminology is adopted for this paper: the lowest unit is (1957) recognize the as far south the lower sandy facies; the typical unit of Entrada Point and east as Ft. Wingate, New Mexico, and correlate it is the medial silty facies; and the slick-rim unit is the with the "buff shale and brown-buff sandstone members upper sandy facies. Only the medial silty facies and the of the Morrison formation" (Kelley and Wood, 1946) in upper sandy facies are present in the Albuquerque area. the Lucero Mesa area. The Summerville formation was The medial silty facies is recognized only in the western named by Gilluly and Reeside (1928) from exposures on portion, where it is 10 to 50 feet of even-bedded fine- Summerville Point in the San Rafael Swell. At the type grained buff to white sandstone in 1- to 2-foot layers locality the boundary between the underlying Curtis forma- interbedded with platy red mudstone and siltstone ranging tion and the Summerville is arbitrary, but to the south and from a few inches to 2 feet in thickness. The sandstone is east Harshbarger, Repenning and Irwin (1957) recognize stained red from the interbedded mudstone and the whole a lower silty facies and an upper sandy facies in the weathers to a steep slope or cliff. The medial silty member Summerville which they believe correspond to the Curtis is overlain by the upper sandy facies which consists of buff and Summerville formations of the type localities. In the to brown sandstone, predominantly evenly bedded at the western part of the Albuquerque area the upper sandy base and grading upward into a mixture of small-scale, facies of the Summerville is thought to be present, asso- simple, and planar cross-stratification; the uppermost parts ciated with tongues of the Cow Springs sandstone. The of the upper sandy facies are yellowish to white in color Summerville beds are distinguished from adjacent rocks by and contain even-bedded layers. Locally, the upper sandy good sorting, fineness of grain, and even, thin bedding. facies intertongues with the overlying Todilto limestone, Intraformational crumpling and slump structures are com- whereas a short distance away angularity of 10 to 15 de- mon, often bounded by undisturbed layers of essentially grees may be measured. identical material. The layers are red to reddish brown The Todilto limestone was originally described by Gre- and seldom vary in color throughout the entire range in gory (1917) from exposures at Todilto Park, New Mexico. grain size from sandstone to claystone. Some repres- Todilto Park is near the western margin of deposition of entatives of the Summerville formation may be present on the Todilto limestone and the type section contains much the east side of the Albuquerque area, but they cannot be clastic material which is not present in the Albuquerque easily distinguished from the lower part of the Morrison area. The lower part of the formation is sandy, particularly formation. in those areas where the formation intertongues with the un- The Morrison formation includes the youngest Jurassic derlying Entrada. Elsewhere the base of the unit is thin- rocks in the Albuquerque area. The name Morrison forma- bedded, platy, fetid gray limestone with intercalated layers tion was first published by Cross (1894) for the exposures of black or greenish mudstone and shale; limestone beds near the town of Morrison, Colorado. The formation has are from 2 to 12 inches in thickness and the shaly layers subsequently been extended over most of the Western 4 inches or less. The basal limestone is usually from 12 to Interior of the United States. Local facies names have been 15 feet thick, although extremes of less than 5 feet and used extensively but McKee and others (1956) restricted more than 25 feet are known. The limestone grades up- these to seven fairly widespread units (see Table 2). In ward into lenticular massive gypsum, locally very pure, the Albuquerque area the principal unit is the Brushy Basin that may reach thicknesses of more than 100 feet. The member, although a lower sandy facies in the Brushy northern part of the Albuquerque area appears to have Basin member to the east and north may represent equiva- been the center of an evaporite basin during Todilto time lents of the Recapture, , or Salt Wash because the gypsum deposits decrease in thickness and members. The white sandstone member in the Lucero Mesa uniformity away from it. area (Kelley and Wood, 1946) is interpreted as a tongue The upper contact of the Todilto limestone exhibits of the Cow Springs sandstone by Harshbarger, Repenning, considerable change from west to east across the Albu- and Irwin (1957). The Brushy Basin member of the Mor- querque area. On the eastern side the gypsum layers are rison formation is the most extensive unit as well as the overlain disconformably by sandstone and mudstone as- most uniform. It consists of variegated, green, gray, buff, signed to the lower part of the Morrison formation. On the and pink mudstone and siltstone interbedded with buff to western side several sandstone, siltstone, and mudstone white, lenticular sandstone beds. The sandstone layers are Table 2—Proposed Correlation of Jurassic Rocks between the Albuquerque and adjacent Areas U.S.Geol.Survey Utah Poleotectonic Eastern Northeastern North Flank, Zuni Albuquerque Area Eastern European Mop Intervals Arizona Mtns,New Mexico West East New Mexico Stages

C 1 Brushy 0 co - Brushy K Brushy Brushy Brushy o o - - -, c-) 3c g Basin -, 0 a> 0,- o c-, O K Portlandian -0. Brushy Basin = o Basin Basin Basin 0- E 3 -.< 7, ci Brushy , o 0 (--) o 0 cr o member o - Basin `-:, member -9, memberb °_, WO (706 . u) s member III- member Interva . 0 = -0 Basin 3 °0 !At) , 0 o o member o Westwater o ,0 7 1•4 -, ,,, -,, D 3 Westwater - member 0 0 0 0 -. 7 3 cP Westwater , 0 member ° 0 to 3 " o _. -(3. member tr) -.. - 3 -o 3 cn _ (A — member 3 ; 0 3 3 0 3 Recapture 0 = 0 0 Recapture °, " "" (f) -.. - member o - - o ch - 0- 0 0 = o -. Kimmerid - a. member 7 0 Salt Wash (A 3 Recapture Lower Lower igian member a... Salt Wash White Lower mo, member Sandstone member sandy member member Bluff cr) (I) Bluff member sandstone 0 § sandstone -? ? Brown (E (l) 3 (f) ----i 0 CD 0 (J) 3 ° Summerville c -, Upper Upper o- ° buff 7 < 7 c o 3 Curti s -, - sandy member -, x sandstone CD, 73 formation 0 — m 3 0 0 — member o 3 CD 0 - CD 0 —,, member Interval 0 — —., (1) 0 , c o - formation o ,0 -. ct 0 ,o - -, o Loer _ < _„ _ Buff .0 Curtis - Lower C o silty vo - o shale Z," c 3 -, member -, dz, 0 formation -0 3 -, member 5 c member o 0 D C -0 C Press sandstone r; Upper sandy mern, m Upper sandy member -10 n Upper _ Upper sandy member -?.. Entrada Entrada sandstone - sandy member 2 Medial . Sandstone (Ocate ss., Exeter ss,) Cal lov n silty member Medial silty member 2-, Medial silty m. Interval Twin Carmel Carmel Creek formation formation B formation

Bajoc ion

c-) o Too rcian i1: CD 0 Navajo o Navajo Nugget 0 sandstone 0 sandstone Interval o 0 PI iensbachian = 7 sandstone •< .< o o A = o ,o Sinemurian ga Kayenta -, Kayenta -, o o c c -o formation -cs formation NEW MEXICO GEOLOGICAL SOCIETY • TWELFTH FIELD CONFERENCE 127

often coarse grained and conglomeratic and some of the flat, featureless plain which was bounded to the south by finer grained layers are marly. North of the Albuquerque a gentle rise to a broad belt of low hills which extended area the Brushy Basin member contains bentonitic layers across the southern part of New Mexico and Arizona (Mo- and glass shards indicative of volcanic activity during latest gallon Highlands of Harshbarger, Repenning, and Irwin, Jurassic time. To the south and west the sand content 1957); to the north, parts of the old Uncompahgre positive of the Brushy Basin member increases and the member area were uplifted and intermittently shed sediment south- cannot be distinguished from the upper part of the Cow ward. Westward, the plain sloped very gently toward a Springs formation. Similar difficulties may arise to the marine shelf whose maximum eastward extent was in cen- west where the Westwater Canyon member can be tral Arizona and which in turn extended westward into a separated from the upper part of the Cow Springs. Facies miogeosyncline whose trough occupied most of changes are very rapid in the Albuquerque area because of and western Utah. Deposition began in time proximity to the southern depositional margin of the Juras- in the Nevada miogeosyncline and in the Arizona shelf area sic rocks. Likewise, thicknesses vary greatly in relatively with limestone and fine-grained clastics. The older Defiance short distances because of pre-Upper Cretaceous erosion. and Zuni positive areas, although greatly reduced, ap- Correlation and relative ages of the Jurassic rocks parently marked the eastern limit of deposition of the are less certain than for the Triassic beds. Fossils have not early Triassic beds. The red mudstones and siltstones of been found in the Entrada sandstone, Summerville forma- the Moenkopi formation do not extend east of this area. tion, or Cow Springs formation in this area. The Morrison In the Albuquerque area erosion was leveling the region, formation has yielded fragmentary remains. Ac- exhuming ancient positive elements ( Pedernal high) to the cording to S. A. Northrop (personal communication, July southeast. 23, 1961), a few pieces of bone, some of which were Erosion continued throughout early and middle Trias- radioactive, were collected by W. L. Chenoweth from the sic time, but by the beginning of the , gentle, variegated member of the Morrison formation at several irregular warping began to deform the region into local localities in Valencia County during the summer of 1952, basins and uplifts. Deposition of Dockum beds began in notably in the Mesa Gigante-Suwanee Peak area. In his central West Texas with a relatively fine-grained siltstone unpublished masters thesis, Chenoweth (1953) noted that and mudstone but as warping continued conglomerate and although the variegated member of Kelley and Wood had sandstone were deposited particularly near the margins of been correlated by several workers with the Brushy Basin the basins. The Albuquerque area developed as a low member, he believed it to be older and probably equivalent shelf separating basins to the southeast and west where to the Chaves or Recapture member. Dinosaur bones col- more than 2,000 feet of terrestrial mudstone, siltstone, and lected by Chenoweth and a bone collected by J. E. Self sandstone accumulated. The late Triassic was tra- during the summer of 1953 from the Morrison formation versed by sluggish streams meandering generally westward near Grants were submitted by Northrop to E. H. Colbert, and eventually reaching the marine waters in Arizona. of the American Museum of Natural History, who reported The late Triassic deposits are all continental and contain that three well-known dinosaur genera are represented, as some marl and limestone. Exterior drainage was main- follows: tained across the basins and evaporite sequences are lack- : near Grants ing. By late Triassic time the Defiance and Zuni positive : near Acoma and also near Suwanee Peak areas had disappeared, but the Uncompahgre uplift was : west side of Mesa Gigante still weakly active. Uplift of the Mogollon Highlands to The Todilto limestone has yielded fresh- or brackish- the south of the Albuquerque area apparently kept pace water and a few with marine affinities, but with the sinking of the depositional area, because little none of the forms is particularly diagnostic. The Curtis change in the type sedimentation is visible throughout the formation in the San Rafael Swell has a characteristic ma- Chinle and Dockum beds. Locally, conglomerate and sand- rine fauna as does the immediately be- stone layers suggest minor variations in uplift and erosion low the Entrada sandstone in the same locality. Practically of the source areas. all the dinosaur fauna reported from the Morrison forma- By the end of the Triassic the source areas of sedi- tion comes from areas far to the north so that age assign- ment for the Albuquerque area had been leveled and ments and correlations must rest largely upon lithologic deposition ceased. Orogenic movements were not a fac- grounds. Except for parts of the Todilto-Summerville se- tor because farther west no hiatus occurs between Triassic quence all the Jurassic rocks in the Albuquerque area are and Jurassic sediments. However, the climate did become eolian or fluviatile floodplain deposits; the Todilto-Sum- more arid and some erosion undoubtedly occurred during merville sequence is thought to represent rather abnormal time in the Albuquerque area. Farther west marine or tidal-flat [possibly lacustrine? Ed.] conditions. the Lukachukai member of the Wingate sandstone was The uppermost parts of the Brushy Basin member may also accumulating as extensive sand dunes, and broad upwarp- contain units that may be Lower Cretaceous ( Burro Canyon, ing to the north and east brought about. changes in the Stokes and Phoenix, 1948) in age, although in the Al- drainage patterns. The Rock Point member of the Wingate buquerque area evidence for this has been removed by sandstone accumulated in a basin whose axis trended pre-Upper Cretaceous erosion. northeast-southwest. SEDIMENTATIONAL HISTORY During early Jurassic time a gradual realignment of the The early was an interval during which depositional areas took place and marine waters invaded epeirogenic forces were active, but no major orogenies took the Western Interior region from the north. The earliest place in the southwestern region. The extensive contin- Jurassic beds were the fluviatile and eolian deposits of the ental seas which had flooded the area during the Pennsyl- Kayenta, Navajo, and Nugget formations of Arizona and vanian and Permian periods did not reappear until the Utah, but in early time abundant marine Cretaceous period. The Albuquerque area was a nearly faunas in the Twin Creek formation of Utah, Idaho, and 128 NEW MEXICO GEOLOGICAL SOCIETY 0 TWELFTH FIELD CONFERENCE

Wyoming attest to the invasion of the boreal seas. During provided a local source for the eolian sands but most of middle Jurassic time the seaway extended southward be- the material was derived from far to the east and west of yond the Arizona-Utah stateline, and tidal-flat and flood- the area. Pre-Upper Cretaceous erosion has removed any plain deposition extended considerably farther south and very beds as well as Lower Cretaceous rocks east. Rejuvenation of the low-lying Mogollon Highlands that might have accumulated in the Albuquerque area, but in southern Arizona and New Mexico blocked deposition the proximity of the Jurassic depositional margin to the to the south and provided a source of abundant sand from south would seem to have precluded extensive deposition. the earlier Navajo and Wingate accumulations. Harsh- In summary, the Albuquerque area was a stable plat- barger, Repenning, and Irwin (1957, p. 44) pointed out form during most of Triassic and Jurassic time. A total of that an uplift to the southwest at the close of Kayenta time less than 2,000 feet of sediment was deposited and much eliminated the gap between the old Cordilleran geanti- of the material is fine-grained siltstone, sandstone, or mud- cline to the west and the Mogollon Highlands to the south stone. Minor downwarping and uplift are reflected in and also provided much of the source area for the upper local sandstone and conglomerate layers, but no orogenic Jurassic sediments in the southern Cordilleran region. In movements of any magnitude disturbed the stability of the the Albuquerque area deposition did not begin until late platform. Subsequent structural complexity and extensive in middle Jurassic time. The medial silty member of the erosion hamper detailed correlation between various facies, Entrada sandstone marked the easterly edge of tidal-flat but the stable nature of the area throughout the entire and floodplain deposition. Above these layers was spread Mesozoic is unquestioned. the fluviatile and eolian blanket of the upper sandy facies of the Entrada sandstone. The upper sandy facies of the BIBLIOGRAPHY Entrada sandstone was the first Mesozoic unit to spread Anderson, R. Y., and Kirkland, D. W., 1960, Origin, varves, and cycles eastward over the old Uncompahgre positive area and it of Jurassic , New Mexico: Am. Assoc. Petroleum Geologists Bull., v. 44, p. 37-52. had multiple sources. In the Albuquerque area most of the Chenov4eth, W. L., 1953, The variegated member of the Morrison Entrada sandstone was derived from sources to the south formation in the southeastern part of the , Valencia and east. County, New Mexico: Univ. New Mexico unpub. masters thesis, Continued uplift of the Mogollon Highlands resulted p. 30, 33-34, 62. Cross, Whitman, 1894, Pikes Peak, Colorado: U. S. Geol. Survey Geol. in a restriction of the Entrada depositional basin and the Atlas, Folio 7. limestone and evaporite deposits of the Todilto limestone Darton, N. H., 1928, "Red Beds" and associated formations in New began to form. The environment of deposition of the Mexico: U. S. Geol. Survey Bull. 794 [1929]. Todilto limestone is uncertain (Anderson and Kirkland, Dutton, C. E., 1885, Mount Taylor and the Zuni Plateau: U. S. Geol. 1960). The scarcity of fossils and the fetid nature of the Survey 6th Ann. Rept., p. 105-198. beds suggest an abnormal condition and yet desiccation Gilluly, James, and Reeside, J. B., Jr., 1928, Sedimentary rocks of the was never complete enough to result in saline deposits. San Rafael Swell and some adjacent areas in eastern Utah: U. S. Harshbarger, Repenning, and Irwin (1957) postulated a Geol. Survey Prof. Paper 150-D. Gregory, H. E., 1917, Geology of the Navajo country, a reconnaissance gulf with a restricted channel which allowed alternating of parts of Arizona, New Mexico, and Utah: U. S. Geol. Survey desiccation and renewal of marine waters. They proposed Prof. Paper 93, p. 42. a connection just southwest of the Four Corners area. How- Harrison, E. P., 1949, Geology of the Hagan coal basin: Univ. New ever, a northeasterly connection to the eastern Colorado Mexico unpub. masters thesis, 177 p. Harshbarger, J. W., Repenning, C. A., and Irwin, J. H., 1957, Strati- evaporite basin, which in turn was connected to the Sun- graphy of the uppermost Triassic and the Jurassic rocks of the dance sea to the north, is also a possibility. The thick Navajo country: U. S. Geol. Survey Prof. Paper 291. gypsum deposits indicate that the central part of an es- Kelley, V. C., 1952, Tectonics of the Rio Grande depression of central sentially land-locked basin lay in the Albuquerque area. New Mexico, in New Mexico Geol. Soc. Guidebook of the Rio Following the withdrawal of the Todilto sea, erosion re- Grande country, 3d Field Conf.: p. 93-105. , 1954, Tectonic map of a part of the upper Rio Grande moved portions of the evaporite deposits, although deposi- area, New Mexico: U. S. Geol. Survey Oil and Gas Inv. Map tion was still continuing farther west in the old marine basin. OM-157. Jurassic deposition in the Albuquerque area closed Kelley, V. C., and Silver, Caswell, 1952, Geology of the Caballo Mountains: Univ. New Mexico Pub. in Geol., No. 4, p. 108. with the Morrison formation. The exact nature of the Kelley, V. C., and Wood, G. H., Jr., 1946, Lucero uplift, Valencia, hiatus between the Todilto and Morrison is not known, be- Socorro, and Bernalillo Counties, New Mexico: U. S. Geol. Survey cause correlatives of the intervening units in the more Oil and Gas Inv. Prelim. Map 47. complete plateau section cannot be recognized in the McKee, E. D., and others, 1956, Paleotectonic maps, Jurassic system: U. S. Geol. Survey Misc. Geol. Inv. Map 1-175. sandy facies below the typical Brushy Basin member. Re- McKee, E. D., and others, 1959, Paleotectonic maps, Triassic system: lief on the contact between the units rarely exceeds a few U. S. Geol. Survey Misc. Geol. Inv. Map 1-300. tens of feet and is often less than one foot; layers above Silver, Caswell, 1948, Jurassic overlap in western New Mexico: Am. and below the boundary are essentially parallel. It seems Assoc. Petroleum Geologists Bull., v. 32, p. 69-81. Smith, C. T., 1954, Geology of the Thoreau quadrangle, McKinley and likely that the Albuquerque area remained close to base Valencia Counties, New Mexico: New Mexico Bur. Mines and level during the time represented by the Curtis, Summerville, Mineral Res. Bull. 31. Salt Wash, Recapture, and Westwater deposition farther Stewart, J. H., 1957, Proposed nomenclature of part of upper Triassic west; certainly deposition and erosion were at a minimum. strata in southeastern Utah: Am. Assoc. Petroleum Geologists Bull., v. 41, p. 441-465. The Brushy Basin member of the Morrison formation Stokes, W. L., and Phoenix, D. A., 1948, Geology of the Egnar-Gypsum was a floodplain deposit of mudstone and siltstone with Valley area, San Miguel and Montrose Counties, Colorado: U. S. occasional channel-sandstone and conglomerate lenses. Geol. Survey Oil and Gas Inv. Prelim. Map 93. Petrified wood and bone fragments are common in the Wilmarth, M. G., 1938, Lexicon of geologic names of the United States: U. S. Geol. Survey Bull. 896, p. 691. coarser grained portions of the member. It spread over the Wood, G. H., Jr., and Northrop, S. A., 1946, Geology of the Nacimiento entire Rocky Mountain region grading abruptly into eolian Mountains, San Pedro Mountain, and adjacent plateaus in parts sandstone along the southern margin of the depositional of Sandoval and Rio Arriba Counties, New Mexico: U. S. Geol. area. In the Albuquerque area the Mogollon Highland Survey Oiland Gas Inv. Prelim. Map 57. 0