THE MEDIAL BLANCAN (LATE PLIOCENE) ARROYO DE LA PARIDA LOCAL FAUNA, SOCORRO COUNTY, NEW MEXICO
CONNELL, Sean D., New Mexico Bureau of Mines and Mineral Resources, 2808 Central Ave SE, Albuquerque, NM 87106
LOVE, David W., New Mexico Bureau of Mines and Mineral Resources, 801 Leroy Place, Socorro, NM 87801
JACKSON-PAUL, Patricia B., New Mexico Bureau of Mines and Mineral Resources, 2808 Central Ave SE, Albuquerque, NM 87106
Vertebrate fossils were first reported in 1936 from Arroyo de la Parida
in the Socorro Basin, about 6 km NE of Socorro, Socorro County, New Mexico.
The Arroyo de la Parida local fauna is derived from a >70 m-thick succession
of sand and gravel that constitute the axial-river (ancestral Rio Grande)
facies of the Palomas Formation. This facies interfingers with and is
overlain by piedmont deposits derived from the eastern-basin margin. No
fossils have been recovered from the overlying piedmont interval. Ten
species are represented: the land tortoise Hesperotestudo; the
ground sloth Megalonyx cf. M. lepostomus; the horses Equus
cf E. cumminsii, E. scotti and E. simplicidens; two
camels, a large species of Camelops and a small species of Hemiauchenia;
the small pronghorn antilocaprid Capromeryx; and two proboscideans, Rhynchotherium
falconeri and Stefomastodon sp. Five of these species are restricted
to Blancan faunas, and the most biostratigraphically diagnostic is Rhynchotherium,
which became extinct in the late Pliocene (~2.2 Ma). The lower jaws of
R. falconeri from Arroyo de la Parida were collected near the top
of the local section, suggesting that the entire fauna, most of which
occurs some 40 m lower in the section, is older than ~2.2 Ma. An early
Blancan age for the Arroyo de la Parida local Fauna is excluded by the
presence of E. scotti, Camelops sp. And the small Hemiauchenia,
which first appear in New Mexico faunas during the medial Blancan (2.5-3.7
Ma). The absence of South American immigrants that arrived following the
Great American Interchange suggests that the Arroyo de la Parida local
fauna is older than 2.7 Ma. The Arroyo de la Parida local fauna is thus
interpreted to be medial Blancan (2.7-3.7 Ma) in age and is younger than
the 4.9-Ma trachyandesite flow at San Acacia, which is exposed about 13
km to the north.
Sealey, P.L., Morgan, G.S., Lucas, S.G., Connell, S.D., Love, D.W., Jackson-Paul, P.B., 2001, The medial Blancan (upper Pliocene) Arroyo de la Parida local fauna, Socorro County, New Mexico [abstract]: Geological Society of America, Abstracts with Programs, v. 33, n. 5, p. A-56.
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New Mexico Bureau of Geology & Mineral Resources
New Mexico Institute of Mining & Technology
801 Leroy Place
Socorro, NM 87801-4796
information: (575) 835-5420
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