Cenozoic Vertebrates from Socorro County, Central New Mexico Gary S
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New Mexico Geological Society Downloaded from: http://nmgs.nmt.edu/publications/guidebooks/60 Cenozoic vertebrates from Socorro County, central New Mexico Gary S. Morgan, Spencer G. Lucas, and David W. Love, 2009, pp. 321-336 in: Geology of the Chupadera Mesa, Lueth, Virgil; Lucas, Spencer G.; Chamberlin, Richard M.; [eds.], New Mexico Geological Society 60th Annual Fall Field Conference Guidebook, 438 p. This is one of many related papers that were included in the 2009 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. 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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. NewCENOZOIC Mexico Geological VERTEBRATES Society Guidebook, 60 FROMth Field Conference, SOCORRO Geology COUNTYof the Chupadera Mesa Region, 2009, p. 321-336. 321 CENOZOIC VERTEBRATES FROM SOCORRO COUNTY, CENTRAL NEW MEXICO GARY S. MORGAN1, SPENCER G. LUCAS1, AND DAVID W. LOVE2 1New Mexico Museum of Natural History, 1801 Mountain Road, NW, Albuquerque, NM 87104 2New Mexico Bureau of Geology and Mineral Resources, 801 Leroy Place, Socorro, NM 87801 ABSTRACT—The Cenozoic vertebrate record from Socorro County in central New Mexico consists of 20 faunas ranging in age from Eocene through Pleistocene. The Carthage Local Fauna (LF) of middle Eocene age (Bridgerian North American land- mammal “age”—NALMA) is the oldest of these faunas. The presence of the brontothere Telmatherium restricts the age of the Carthage LF to late Bridgerian (Twinbuttean, 46-46.5 Ma). The two other Paleogene vertebrate sites in Socorro County are both ichnofaunas, including three trackways of Eocene artiodactyls from the Baca Formation in the Gallinas Mountains and two artiodactyl tracks from Oligocene volcaniclastic sediments in the San Mateo Mountains. Despite the widespread occurrence of Miocene rocks of the Popotosa Formation in Socorro County, the only fossil so far reported from this unit is a complete skull, lower jaws, and partial skeleton of the oreodont Merychyus major from a late Miocene (late Clarendonian NALMA) site on the Bosque del Apache National Wildlife Refuge near San Antonio. Pliocene (Blancan NALMA) sites from the Ceja and Palomas formations in the Rio Grande valley include Abeytas, Arroyo de la Parida, Sevilleta, Silver Canyon, and Veguita. The best known of these is the Arroyo de la Parida LF with 14 species of vertebrates, including the gomphothere Rhynchotherium tlascalae, indicating an late early Blancan age (~3 Ma). Pleistocene sites are distributed throughout the county, including: Lake San Agustín, VLA, and White Lake from the Plains of San Agustín in northwestern Socorro County; Lemitar, San Antonio, and Socorro from the Rio Grande valley; and Chupadera Arroyo and Mockingbird Gap from the eastern portion of the county. INTRODUCTION Andres Mountains in the southeastern corner. Several structural Although not as well known for Cenozoic vertebrate fossils basins associated with the Rio Grande rift are found in Socorro as other regions of New Mexico, Socorro County in the south- County, all of which have produced vertebrate fossils of Neo- central part of the state has produced several important faunas gene age (Connell, et al., 2005). The southern Albuquerque basin (Fig. 1). The best known of these are the middle Eocene (Bridg- in the northernmost portion of the county includes the Veguita, erian) Carthage Local Fauna (LF) (Lucas et al., 1982; Lucas and Williamson, 1993; Lucas, 1997) and the early Pliocene (Blancan) Arroyo de la Parida LF (Tedford, 1981; Lucas and Morgan, 1996; Morgan et al., 2008a). In all, there are 20 named Cenozoic verte- brate faunas from Socorro County (Fig. 1), with at least one fauna representing every epoch from the Eocene through the Pleisto- cene, including: Eocene (2 faunas), Oligocene (1 fauna), Mio- cene (1 fauna); Pliocene (7 faunas), and Pleistocene (9 faunas). The total number of Cenozoic vertebrate localities in Socorro County is actually well over 50, as several of the faunas consist of multiple sites (e.g., the Carthage LF includes 5 sites: Lucas, 1997; the Arroyo de la Parida LF is derived from more than 30 sites: Morgan el al., 2008a). Cenozoic geologic formations in the county that have produced vertebrate fossils include the Eocene Baca and Hart Mine formations, the Miocene Popotosa Forma- tion, and the Pliocene Ceja and Palomas formations, together with widespread unnamed deposits of late Pleistocene age. In addition, a mammal trackway is known from Oligocene volca- nic rocks in the San Mateo Mountains. Fig. 2 is a stratigraphic column showing the geologic formations and chronologic distri- bution of Cenozoic vertebrate sites in Socorro County. Socorro County is located near the geographic center of New FIGURE 1. Map of Socorro County, New Mexico showing location of Mexico and is bissected from north to south by the Rio Grande. Cenozoic vertebrate localities. Numbers correspond to the following Most of Socorro County is included within the Basin and Range sites, Eocene: 1. Carthage; 2. Gallinas Mountains track site. Oligocene: 3. San Mateo Mountains track site. Miocene: 4. Bosque Del Apache. physiographic province, including the Rio Grande rift (Hawley, Pliocene: 5. Veguita; 6. Abeytas; 7. Sevilleta; 8. Arroyo de la Parida; 2005). The region is geologically complex with several promi- 9. Fite Ranch; 10. Tiffany Canyon; 11. Silver Canyon. Pleistocene: 12. nent mountain ranges, including the Magdalena Mountains and VLA; 13. White Lake; 14. Lake San Augustin; 15. Lemitar; 16. Socorro; San Mateo Mountains in the western part of the county, Chu- 17. San Antonio; 18. Indian Well Wilderness; 19. Chupadera Arroyo; 20. padera Mesa in eastern Socorro County, and the Oscura and San Mockingbird Gap. 322 MORGAN, LUCAS & LOVE VERTEBRATE FOSSIL LOCALITIES FROM SOCORRO COUNTY Eocene Carthage Near Carthage in Socorro County (Fig. 1, site 1), siliciclastic red beds overlie the coal-bearing Cretaceous strata mined there, so their Late Cretaceous or Cenozoic age was long certain, but fossils were needed to provide a more precise age determination. Gardner (1910, p. 454) reported the first direct evidence of their age—a fossil mammal tooth, “possibly Palaeosyops,” a kind of middle Eocene brontothere (rhinoceros-like perissodactyl). Lucas et al. (1982) followed up on Gardner’s discovery, documenting teeth of a middle Eocene (Bridgerian NALMA) brontothere they identified as cf. Manteoceras. Subsequent collecting near Car- thage yielded unidentified turtle shell fragments, armor plates of a glyptosaurine lizard (cf. Glyptosaurus) and teeth and jaw frag- ments of various mammals: two kinds of rodent (Reithroparamys huerfanensis and Leptotomus parvus), many teeth of the bron- tothere Telmatherium (= Manteoceras; Mader, 1989, 2008), the horse Orohippus pumilus and a primate, Notharctus tenebrosus (Lucas, 1983, 1985, 1997; Lucas and Williamson, 1993; Lucas et al., 1982, 1983). These fossils come from a relatively thin FIGURE 2. Stratigraphic column showing the geologic formations and chronologic distribution of Cenozoic vertebrate sites in Socorro County. stratigraphic interval about 15 m thick in strata long termed the Baca Formation. However, Lucas and Williamson (1993) named these strata the Hart Mine Formation, arguing that their relatively Abeytas and Sevilleta sites, derived from Pliocene sediments coarse-grained facies and deposition in a separate basin distin- of the Ceja Formation, upper Santa Fe Group. Vertebrate sites guishes them from the Baca Formation to the west. At Carthage, from the Socorro basin include fossils from the Miocene Popo- the Bridgerian vertebrate-fossil-bearing interval is about 130 tosa Formation, lower Santa Fe Group, on the Bosque del Apache meters above the base of the Hart Mine Formation (Lucas and