USGS 13736 - Tamaulipas, Mexico (Yegua Formation) (Eocene of Mexico)

Also known as USGS 13736

Where: Tamaulipas, Mexico (26.4° N, 99.2° W: paleocoordinates 28.4° N, 89.6° W)

• coordinate based on nearby landmark

• outcrop-level geographic resolution

When: Yegua Formation (Claiborne Group), Middle Eocene (48.6 - 37.2 Ma)

• The succession of Claiborne Group in northeastern Mexico is exceptionally thick and well correlated to those units of the same name in Texas on the basis of faunal similarity. The Yegua Formation is the highest formation of the Claiborne Group and has a thickness of around 1500 m. For the most part the Yegua Formation in non-marine. The lower Yegua Formation is 60 m thick and comprises about 60 ft of basal shale, clay, sand, and oyster beds and about 100 m of scarp-making sandstone, this sequence is again repeated above. Collection from horizon near top of the Yegua Formation

• bed-level stratigraphic resolution

Environment/lithology: coastal; shelly/skeletal, sandy mixed carbonate-siliciclastic sediments

• Siliciclastic, and apparently fully marine.
• Sandy coquina out of which the shells have been leached.

Size class: macrofossils

Preservation: cast, mold/impression

Reposited in the USNM

Collection methods: quarrying,

• Collections reposited in USGS and USNM collections.

Primary reference: J. Gardner. 1945. Mollusca of the Tertiary formations of Northeastern Mexico. Geological Society of American Memoir 11 [M. Kosnik/M. Kosnik/M. Kosnik]more details

Purpose of describing collection: taxonomic analysis

PaleoDB collection 43041: authorized by Austin Hendy, entered by Austin Hendy on 09.08.2004

Creative Commons license: CC BY (attribution)

Taxonomic list

• Exhaustive for mollusca.
Bivalvia
 Protobranchia - Nuculanidae
Orthoyoldia psammotaea Dall 1898 pointed nut clam