Geology of the Espinaso Formation (), north-central New Mexico: Summary

PAUL F KAUTZ* I RAYMOND V INGERSOLL ( DePartmem °f Geology, University of New Mexico, Albuquerque, New Mexico 87131 W. SCOTT BALDRIDGE Geosciences Division, MS 978, Los Alamos National Laboratory, Los Alamos, New Mexico 87545 PAUL E. DAMON Ì Laboratory of Isotope Geochemistry, Department of Geosciences, University of Arizona, MUHAMMAD SHAFIQULLAH ( Tucson, Arizona 85721

INTRODUCTION flows (Fig. 2). Facies studies indicate that upper third show normative compositions the lower Espinaso sandstones were depos- of calcic latite, calcic quartz latite, and In the Hagan basin of north-central New ited by distal braided streams of the "Bijou nepheline latite, respectively. These compo- Mexico, Espinaso Ridge contains the larg- Creek type" (Miall, 1978). Middle Espinaso sitions are consistent with derivation from est and least deformed exposures of the conglomerates and sandstones suggest both the Cerillos Hills and the Ortiz Moun- Oligocene Espinaso Formation (Stearns, deposition by proximal braided streams of tains, and they are similar to those of other 1943) (Fig. 1). The Espinaso primarily con- the "Scott type" (Miall, 1978). Upper Espi- Oligocene igneous rocks in the area (for sists of 430 m of volcanic detritus eroded naso lahars and conglomerates were depos- example, La Cienega area; Sun and Bald- from eruptive centers in the Ortiz Moun- ited by proximal braided streams subject to win, 1958). Sandstones in the Espinaso are tains and Cerrillos Hills (Stearns, 1953). debris flows similar to the "Trollheim type" composed mostly of plagioclase and inter- The Espinaso is conformable and grada- (Miall, 1978). The fine grain size and mediate to felsic volcanic lithic fragments. tional with the underlying Galisteo upward-fining megasequences of the up- The most distinctive characteristics of the Formation (Gorham and Ingersoll, 1979; permost Espinaso suggest the waning of sandstones are high-plagioclase to total- Stearns, 1943), and is overlain unconfor- volcanic activity, decrease of paleoslope, feldspar ratios, low quartz, lack of nonvol- mably by the Neogene or and lowering of relief in source areas (Fig. canic lithic fragments, and high percentages related strata (Kelley and Northrop, 1975). 2). of microlitic volcanic lithic fragments. Sub- Paleocurrent measurements show radial tle changes in sandstone composition from SEDIMENTOLOGY patterns, suggesting that the deposits along north to south along Espinaso Ridge may Espinaso Ridge were formed on two coa- reflect derivation from two sources (Cerril- The Espinaso Formation primarily con- lescing alluvial fans (Fig. 3). The Ortiz los vs. Ortiz); but overall, petrology is sists of water-laid immature volcaniclastic magmatic center clearly was the source for remarkably uniform throughout the Espi- sandstones, conglomerates, and boulder sediments along the southern half of Espi- naso Formation. conglomerates interbedded with matrix- naso Ridge. Sediments along the northern supported, pebble to boulder, debris-flow half of Espinaso Ridge probably had their AGE deposits. Some air-fall and ash-flow depos- source in the Cerrillos magmatic center, its and lava flows are interbedded locally. although derivation from a northern part of Four new K-Ar ages are reported here for Sedimentary structures, facies relations, the Ortiz center cannot be ruled out (Fig. 3). the following samples: 34.6 ± 0.7 m.y. and upward coarsening megasequences in- (calcic-quartz-latite clast near middle of dicate that the lower 300 to 350 m of the PETROLOGY Espinaso); 34.3 ± 0.8 m.y. (calcic-latite Espinaso were deposited on prograding clast near base of Espinaso); 26.9 ± 0.6 alluvial fans by braided streams and laharic Clasts in the conglomerates range from m.y. (nepheline-latite flow near top of Espi- andesitic to latitic. Chemical analyses of naso); and 25.1 ± 0.6 m.y. (olivine-tholeiite •Present address: Oil Conservation Commis- two clasts near the base and the middle of flow near base of overlying Santa Fe sion, P.O. Box 1980, Hobbs, New Mexico 88240. the formation and from a lava flow in the Group. Weber (1971) reported a clast age of

This article is based on a paper presented at a symposium entitled "Cenozoic Continental Deposits and Fossils of New Mexico," held in April 1981.

The complete article, of which this is a summary, appears in Part ¡1 of the Bulletin, v. 92, no. 12, p. 2318-2400.

Geological Society of America Bulletin, Part I, v. 92, p. 980-983, 3 figs., December 1981.

980

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Figure 1. Location map of Espinaso Ridge, Hagan basin, Cerrillos Hills, Ortiz Moun- tains, and other features in study area. (This figure appears as Fig. 1 in Part II.)

Downloaded from http://pubs.geoscienceworld.org/gsa/gsabulletin/article-pdf/92/12/980/3430150/i0016-7606-92-12-980.pdf by guest on 01 October 2021 Figure 2. Schematic cross sections of Ortiz Mountains magmatic center and its western flank, where Espinaso For- mation exposed along Espinaso Ridge was deposited (after Fig. S of Disbrow and Stoll, 1957). (1) During Galisteo deposition (Eocene). (2) During depo- sition of transition between Galisteo and Espinaso. (3) Early Espinaso time. (4) Middle.Espinaso time. (5) Late Espi- naso time. (6) Latest Espinaso time. Symbols: Jte = Todilto and Entrada Formations; Jm = Jurassic Morrison Formation; Kd = Dakota Formation; Km = Cretaceous Mancos Formation; Kmv = Cretaceous Mesaverde Group; Tg = Eocene ; V = Volcanics and volcani- clastics; G = Gravel (including conglom- erates, debris-flow deposits, and some interbedded sandstones and pyroclastic deposits); S = Sandstone (including in- terbedded conglomerates and pyroclastic deposits). (This figure appears, as Fig. 21 in Part II.)

Figure.3. Schematic dispersal directions for Espinaso deposits along Espinaso Ridge. Paleocurrent data show predominantly northwest transport along southern half of ridge and predomi- nantly southwest transport along northern half of ridge. This prob- . CERRILLOS (i CENTER ably reflects two coalescing alluvial fans with sources in the Ortiz and Cerrillos magmatic centers (A). Alternatively, deposition may have occurred on two separate fans, both of which were derived from thè Ortiz center (B). Available data do not differentiate these ORTIZ I'CENTER alternatives. (This figure appears as Fig. 22 in Part II.) /

Stiff A B

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36.9 ± 1.2 m.y. from the middle of the ACKNOWLEDGMENTS and Mineralogists, Pacific Section, Pacific Espinaso. All of these data are in agreement Coast Paleogeography Symposium 3, p. 1-13. with the paleontologically bracketed age of Financial assistance was provided to Dickinson, W. R., and Snyder, W. S., 1978, Plate Oligocene for the Espinaso and with radio- Kautz by the New Mexico Bureau of Mines tectonics of the Laramide orogeny: Geolog- metric dates of intrusive rocks in possible and Mineral Resources and the New Mex- ical Society of America Memoir 151, source areas (for example, Bachman and ico Geological Society. Acknowledgment is p. 355-366. Mehnert, 1978; Baldridge and others, 1980; made by Ingersoll to the donors of the Pet- Disbrow, A. E., and Stoll, W. C., 1957, Geology of the Cerrillos area, Santa Fe County, New roleum Research Fund, administered by the Jaffe and others, 1959). All of the available Mexico: New Mexico Bureau of Mines and evidence suggests that intermediate to silicic American Chemical Society, for partial Mineral Resources Bulletin 48, 73 p. magmatic activity began soon after the end support of this research. Support for Bal- Gorham, T. W., and Ingersoll, R. V., 1979, of the Eocene (38 m.y. B.P.) and continued dridge was provided by the Office of Basic Evolution of the Eocene Galisteo basin, until approximately 26 m.y. B.P. Mafic and Energy Sciences of the U.S. Department of north-central New Mexico: New Mexico Geological Society Guidebook 30, Energy. The geochronologic work of ultramafic magmatism began abruptly at 25 p. 219-224. m.y. B.P., coincident with deposition of Damon and Shafiqullah was supported by Jaffe, H. W„ Gottfried, D., Waring, C. L„ and basal Santa Fe sediments. Thus, the base of National Science Foundation Grant EAR- Worthing, H. W„ 1959, Lead-alpha age the Santa Fe Group in the Espinaso Ridge 7811535. determinations of accessory minerals of igneous rocks (1953-1957); U.S. Geological area is uppermost Oligocene (Oligo-Mio- The following provided assistance in a Survey Bulletin 1097-B, p. 65-148. cene boundary at 24 m.y. B.P. (Van Couver- variety of ways: R. R. Butcher, C. E. Kelley, V. C., and Northrop, S. A., 1975, ing, 1978). Chapin, W. E. Elston, A. Fleming, M. Geology of the Sandia Mountains and vicin- Frietze, J. Kautz, W. E. Kautz, A. M. ity, New Mexico: New Mexico Bureau of TECTONICS Kudo, D. J. Lynch, C. E. Stearns, and S. G. Mines and Mineral Resources Memoir 29, 136 p. Wells. Miall, A. D., 1978, Lithofacies types and verti- The Galisteo-Espinaso-Santa Fe sedi- cal profile models in braided river deposits: mentary record is the result of regional tec- REFERENCES CITED A summary: Canadian Society of Petroleum tonic processes related to plate interactions Geologists Memoir 5, p. 597-604. on the Pacific coast. Galisteo sediments are Stearns, C. E., 1943, The Galisteo Formation of Atwater, T., 1970, Implications of plate tectonics north-central New Mexico: Journal of nonvolcanic synorogenic deposits resulting for the Cenozoic tectonic evolution of west- Geology, v. 51, p. 301-319. from the Laramide orogeny (Paleocene- ern North America: Geological Society of 1953, Early Tertiary vulcanism in the Eocene). Espinaso sediments were formed America Bulletin, v. 81, p. 3513-3536. Galisteo-Tonque area, north-central New in direct response to intermediate-silicic Bachman, G. O., and Mehnert, H. H., 1978, New Mexico: American Journal of Science, K-Ar dates and the late Pliocene to Holocene volcanism active during the widespread v. 251, p. 415-452. geomorphic history of the central Rio Stewart, J. H., Moore, W. J., and Zietz, I., 1977, mid-Tertiary magmatic episode (Oligocene). Grande region, New Mexico: Geological East-west patterns of Cenozoic igneous Santa Fe sediments accumulated in broad Society of America Bulletin, v. 89, rocks, aeromagnetic anomalies, and mineral basins formed during the earliest phase of p 283-292. deposits, Nevada and Utah: Geological the Rio Grande rift, which is characterized Baldridge, W. S., Damon, P. E„ Shafiqullah, M„ Society of America Bulletin, v. 88, p. 67-77. and Bridwell, R. J., 1980, Evolution of the Sun, M.-S., and Baldwin, B., 1958, Volcanic by regional extension and bimodal volca- central Rio Grande rift, New Mexico: New rocks of the Cienega area, Santa Fe County, nism (Neogene). Timing of these events is potassium-argon ages: Earth and Planetary New Mexico: New Mexico Bureau of Mines coincident with flattening of the subducted Science Letters, v. 51, p. 309-321. and Mineral Resources Bulletin 54, 80 p. slab and a magmatic null during the Coney, P. J., and Reynolds, S. J., 1977, Cordi- Van Couvering, 1978, Status of late Cenozoic lleran Benioff zones: Nature, v. 270, p. Paleocene-Eocene (Damon and others, boundaries: Geology, v. 6, p. 169. 403-406. Weber, R. H., 1971, K-Ar ages of Tertiary ig- 1964; Dickinson and Snyder, 1978), steep- Damon, P. E., Mauger, R. L., and Bikerman, neous rocks in central and western New ening of the subducted slab and resultant M:, 1964, K-Ar dating of Laramide plutonic Mexico: Isochron/West 1, p. 33-45. extensive intermediate-silicic volcanism and volcanic rocks within the Basin and (Oligocene) (Coney and Reynolds, 1977; Range province of Arizona and Sonora: International Geological Congress, 22nd, Stewart and others, 1977), and regional Proceedings, pt. 3, p. 45-55. extension of the western U.S. following first Dickinson, W. R., 1979, Cenozoic plate tectonic encounter with the Pacific plate and forma- setting of the Cordilleran region in the tion of the San Andreas transform (latest United States, in Armentrout, J. M., Cole, Oligocene and Neogene) (Atwater, 1970; M. R., and TerBest, H., Jr., eds., Cenozoic MANUSCRIPT RECEIVED BY THE SOCIETY paleogeography of the western United Dickinson, 1979). OCTOBER 8, 1981 States: Society of Economic Paleontologists MANUSCRIPT ACCEPTED OCTOBER 8, 1981

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