ThePalomas Formation ofsouth-central New Mexico- a lormaldefinition by RichardP. Lozinskyand John W. Hawley, New Mexico Bureau of Minesand Mineral Resources, Socono, NM 87801 Abstract HancockFormations in the Mesilla and Hueco and fahns (1955a,b) described the "Palomas Upper SantaFe Group deposits occurring Bolson of New Mexico and Tgxasby Strain gravels" as a unit that intertongued with up- in the Palomas,Engle, and San Marcial Ba- (1966,7969),the Camp Rice Formation in the per SantaFe strata. However, Kelley and Sil- sins of the southern Rio Grande rift are here Rincon Valley-Jornada Basin area by Seager ver (L952)followed Bryan's (1938)terminology named the Palomas Formation. The term et al. (1971), and the Sierra Ladrones For- in designating the basin fill (exclusiveof "val- "Palomas gravel" was first applied to Plio" mation in the Socorro and Albuquerque Ba- ley fill and pediment-cappinggravel") asSanta Pleistocenebasin fill in the region in 7907; sins by Machette (I978a, b). Recently,the gap Fe Formation. however, the unit has never been defined in detailed mapping of the upper Santa Fe In ground-water studiesof the Palomasand formally. It consistsof alluvial-fan and coal- Basins,Murray (1'959,pp. 7- deposits (piedmont facies) and deposits in the Palomasand Engle Basins Animas Creek escent-fan (1,967, ancestralRio Grande fluvial deposits (axial- was partially filled by Lozinsky (1982,1986). 8) and Davie and Spiegel p.9) rec- river facies). Maximum thicknesses range He proposedthat upper SantaFe Group de- ognized that exposedbasin-fill depositsare from 100 to more than 130 m locally. For- posits in the Elephant Butte area be desig- the "Palomas gravels." Davie and Spiegel mation deposition probably began before 5 nated the PalomasFormation. (1967)included thesedeposits in the "upper Ma and continued until 400,000to 500,000 Use of the term "Palomas" to designate part of the SantaFe group" and showed that years ago The formation can be distin- upper Cenozoicdeposits in this region is not they comprised alluvial-fan (piedmont), ax- guished from other upper Santa Fe Group new (Keroheret al., 1966,p.2905). Qordon ial-river, and transitional facies. The U.S. deposits bv its extensive oiedmont facies and Graton (1907)and Gordon (191.0,p.237, GeologicalSurvey (Heyl et al., 1983)recently and relativ-elynarrow belt axial-river of de- Gravel" to designate posits.Older SantaFe units (Miocene-latest pl. XII) initially referredto the basinfill crop- used the term "Palomas Oligocene),which do not contain axial-river ping out along PalomasCreek as the -"Palo- "purplish-graygravel and sand about 300m facies,occupy remnantsof early rift basins mas gravel." Harley (I%a, pp.29-30, pl. II) that predate development of the present referredto the coarse-grained,upper part of system of basins and uplifts. the basin fill as the "Palomasgravel," but he consideredthe older basin-filldeposits to be Alsoin this issue Introduction at leastpartly equivalentto the late Tertiary Roleof clayminerals in SantaFe Formation. Kottlowski (1953,1955) Upper Cenozoic basin fill in the Rio Grande disposaland storage of rift is generally referred to as the Santa Fe Formation or Group, a term first proposed hazardousmaterials P.79 by Hayden (1873) for deposits in the Santa Porphyry-typemineralization Fe area. The first definitive statement about andalteration, Organ the southern extension of the Santa Fe For- mation was by Bryan (1938, p. 205): miningdistrict P.83 Galleryof Geology The main body of sedimentarydeposits of P.87 the Rio Grande depression, from the north Paleontologyand correlation end of San Luis Valley to and beyond El of a LowerCretaceous Paso,is considered to be the same general ageand to belongto the SantaFe formation. outlierin RooseveltCountY P.88 Service/News p. 95 Baldwin (lz Spiegel and Baldwin, 1963, pp. 38-39) formally proposed that the formation NewMexico Geological Society be raised to group status and considered: t{ abstracts p. 96 \'o@ . [the group] to be a broad term includ- t Taxeson naturalresource ing sedimentary and volcanic rocks related UJ t o t oroduction p. 98 to the Rio Grande trough, with a range in n"' ? +t ' p.99 age from middle(?) Miocene to Pleisto- t t lndexto volumeI cene(?). <\ Staffnotes p.100 t ?\ Hawley et al. (1969) reviewed the status of o ZI I EL research on the Santa Fe Group in south- J o\ Gomingsoon o 1\ central New Mexico and first described ref- Pointof RocksCanyon-a photo erence sections for upper and lower parts of t oz'oo' the group. essay FIGURE 1-Generalized tectonic map of south- Recent detailed mapping of basin fill in centralNew Mexico.Shaded area was coveredby Fluidinclusion study of the Waldo- southern New Mexico has led to formal def- Lozinsky (1982, 7986). Lines with hachures are Graohicmine inition of a number of formations within the normal faults (hachures on downthrown side; Santa Fe Group. The upper Santa Fe has been dashedwhere inferred). Solid and hatched lines CutlerFormation red beds subdivided into: tfrre Camp Rice and Fort delineate major uplifts. thick" exposed along and betlveen Alamosa MAGDALENA and Cuchillo Negro Creeks in the north- MTNS western part of the Palomas Basin. However, their map unit may also include lower Santa Fe deposits. Maxwell and Oakman (1985)used the term "Palomas Gravel" in the same gen- \ eral sense as Palomas Formation is used in \ this paper, but they did not include the rock unit in the Santa Fe Group. Despite long usage, the name Palomas has Marcial never become adopted fully. No type section SAN MARCIAL has ever been described, and the rock-strati- graphic unit has not been defined formally. The objectives of this article and a compan- ion paper by Lozinsky and Hawley (1986)are o.76 to define formally the Palomas Formation as SAN a lithostratigraphic unit that comprises all upper Santa Fe deposits in the Palomas, En- and San Marcial Basins (Fig. 1) between MATEO gle, Derry and San Marcial (Fig. 2), and to de- scribe a composite type section of the for- MTNS mation in the northern Palomas Basin (Table EXPLANATION 1). Due to its varied lithologic character, the Palomas is here designated as a formation ffit tt:rii:l rather than a gravel. axial-river facies Description of the Palomas Formation The Palomas, Engle, and San Marcial Ba- o in the southern part the J p ied mont sins are located of J proximaI Rio Crande rift and cover an area of 3,800 km' (Fig. 1). The Palomas Formation is ex- o ENGLE subfacies f, FI posed throughout these basins (Fig. 2), and o BASIN ll p iedmo nt it can be divided into two major facies: pied- distal-medial mont and axial river. The composite type sec- subfaciesw 4. dated 6., c basalt flows UJ a New AAexnc@ --' basin GEOLOGY bound aries . Scienceand Service volume 8, No. 4, November 1986 facies and Editor: Deborah A. Shaw Draftqs: Chetre Pelletier, Cindie Salisbury, lrean Rae, subf a cies and Monte Brown contacts Published quarterly by New Mexico Bureau of Mines and Mineral Resoulces PALOMAS a division of New Mexio lnstitute of Mining & Ibchnology BAS IN BOARD OF REGENTS X Ex Officio o Toney Anaya, Couernor of Nm Mexico J Las Palomas 4, 4.5 my Alan Morgan, Superintendent of Public lnstruction o J ash z 2 Appointed qt measured Steve To(es, Pres., 1967-1991, Socono tr Judy Floyd, Sec.lTreas.,19771987, Ins Cruces o section Gilbert L. Cano, 7985 1991, Albuquerque -1985-1989, Lenton Malry, Albuquerque O 5 ml Donald W Morris, 1983-1989, Los Alamos r---+--aJ New Mexico lnstitute of Mining & Technology v 5 Km Presidffit.. .. LaurenceH.Lattman Y o New Mexico Bureau of Mines & Mineral Resources I Direcfor.. ....... FrankE.Kottlowski ) DeputVDirector ...... Georges.Austin o Subscriptions: lssued quarterly, Februart May, August, Derry November; subscription price $6.0O/calendar year. Editoriql mafter Articles submitted for publication should be in the editor's hands a minimum of five (5) months before date of publication (February, May, August, or November) and should be no longer than 20 typewrit- ten, double-spaced pages. All scientific papers will be reviewed by at least two people in the appropriate field of study. Address inquiries to Deborah A. Shaw, Editor of Nru Mexko GeoIoW, New Mexico Bureau of Mines & Ha Mineral Resources, Socorro, NM 87801 Published as public domain, therefore reproducible without per' mission. Source credit leqilested. Circulation:1,600 FICURE 2-Geologic map of the Palomas Formation showing aerial extent of facies and P/iflteri Universiry of New Mexico Printing Plant subfacies and locations for dated basalt flows, volcanic ash, ani measured sections. November 1986 NezuMexico Geolosa tion (Table L) comprises three measured consist of gravelly deposits of coalescent al- (Table 1, sections 1 and 2). The thickest axial- sections. The mostly constructional Cuchillo luvial fans, occur in the deep arroyo valleys river deposit described herein (7.1 m) occurs geomorphic surface caps the piedmont facies west of I-25 between Caballo Dam and San in measured section 1, units 1 and 5; how- and marks the end of Palomas Formation Marcial (e.g., valleys of Percha, Animas, Seco, ever, fluvial sequencesexposed along the Rio deposition (Lozinsky and Hawley, 1986). Cuchillo Negro, Alamosa, Nogal, and Mul- Grande valley are commonly much thicker. ligan Gulch arroyos). Piedmont gravels of The moderately to well sorted, fine- to me- Piedmont facies this subfacies are illustrated in Hawley (1978, dium-grained sand is typically light gray and pp. 91,-92)and Seager et al. (1984, fig. 6). arkosic. Gravel lenses commonly occur along The piedmont facies composes the major The term distal refers to a distant source the bottom of trough crossbeds. CIay lenses portion of the Palomas Formation. It rests area and long transport.