El Mixtón: Late Hemphillian, Mexico

List of taxa
Where & when
Geology
Taphonomy & methods
Metadata & references
Taxonomic list
Mammalia - Tayassuidae
"Locality ZJ 30 -8"
Mammalia - Antilocapridae
cf. Cosoryx sp.
cf. Plioceros sp.
Mammalia - Perissodactyla - Equidae
Mammalia - Perissodactyla - Rhinocerotidae
Mammalia - Carnivora - Felidae
Mammalia - Carnivora - Canidae
Mammalia - Megalonychidae
Genus aff. Pliometanastes
see common names

Geography
Country:Mexico State/province:Zacatecas
Coordinates: 21.7° North, 103.0° West (view map)
Paleocoordinates:23.6° North, 100.5° West (Wright 2013)
Basis of coordinate:estimated from map
Time
Period: Neogene
10 m.y. bin: Cenozoic 6
Key time interval: Late Hemphillian
Age range of interval: 9.4 - 4.7 m.y. ago
Stratigraphy
Formation:Juchipila
Stratigraphic resolution:formation
Lithology and environment
Primary lithology:fine,coarse,volcaniclastic sandstone
Secondary lithology: conglomerate
Lithology description: West of the Achoque ́n dam (Fig. 3), in an area that we refer to as El Mixto ́n, is exposed a .80-m-thick fossil-bearing stratigraphic succession that begins close to the bottom of an arroyo, where massive (1–5 m thick) beds of green tuffaceous claystone are interlayered with thinner, more indurat- ed strata of calcareous claystone with abundant ostracods and gastropods (Fig. 4). Resting atop this shallow lacustrine succes- sion is a thin bed of unconsolidated white ash-fall material composed of felsic glass shards and small, rounded grains of black obsidian. In this part of the succession, camelid and proboscidean footprints were found. Moving up the section, the green tuffaceous claystone beds alternate with pale red, sometimes with irregular green spots, tuffaceous mudstone, and rare layers of epiclastic-volcanic, fine- to medium-grained, distinctly laminated sandstone that in places displays convoluted and/or graded bedding. The clastic succession above the first sandstone layer in the section lacks beds with ostracods and gastropods, and the proportion of reddish claystone and mudstone steadily increases upward. Higher up in the section exists an approximately 12-m-thick succession composed of several ero- sion-resistant beds of medium- to coarse-grained, slightly con- glomeratic (clasts up to 1 cm) epiclastic-volcanic sandstone that in places displays structures such as convoluted bedding, bioturba- tion, normal graded bedding, cross bedding, and shallow channels (several meters wide and tens of centimeters deep). Associated with these sandstone beds are thin, clay-rich, unconsolidated horizons that are interpreted as paleosols. Both the cemented conglomeratic sandstone beds and loose paleosols contain mammal fossils. Without any apparent break, this coarse-grained interval is followed by ,10 m of finer sediments (mudstones and sandy clays) in thick, massive beds with alternating green and red colors. Near the top of the exposed section, the proportion of conglomeratic sandstone and fine-grained conglomerate notably increases, as does the maximum clast size (up to 5 cm), while the finer-grained, reddish mudstone layers decrease. Close to a dirt road that leads from the paved road (Mexico 54) to this locality and up to a cliff-forming outcrop of felsic ignimbrite, the Pliocene sedimentary succession is covered by talus deposits derived from the Oligocene ignimbrite.
Environment:terrestrial indet.
Taphonomy
Modes of preservation:body
Size of fossils:macrofossils
Collection methods and comments
Reason for describing collection:taxonomic analysis
Metadata
Also known as:ZJ 30-10; ZJ 30-3; ZJ 30-8
Database number:157349
Authorizer:J. Marcot Enterer:J. Marcot
Modifier:J. Marcot Research group:vertebrate
Created:2014-06-14 14:16:49 Last modified:2025-02-22 15:12:02
Access level:the public Released:2014-06-14 14:16:49
Creative Commons license:CC0
Reference information

Primary reference:
51759. O. Carranza-Castaneda, J. J. Aranda-Gómez, X. Wang and A. Iriondo. 2013. The Early-Late Hemphillian (Hh2) Faunal Assemblage From Juchipila Basin, State of Zacatecas, Mexico, and Its Biochronologic Correlation with Other Hemphillian Faunas in Central Mexico. Contributions to Science, Natural History Museum of Los Angeles County 521:13-49 [J. Marcot/J. Marcot/P. Mannion]