Mid-early late Albian foraminiferal assemblage from the El Abra Formation in the El Madroño locality, eastern Valles-San Luis Potosí Platform, Mexico: Paleoenvironmental and paleobiogeographical significance

Abstract

Albian-Cenomanian carbonate deposits of the El Abra Formation are widely distributed in the folded Sierra Madre Oriental. At the El Madroño locality, this stratigraphic unit contains an abundant, diverse and well-preserved fossil association composed of foraminifers and algae as well as rudists and other kinds of bivalves, gastropods, as well as corals, echinoids, and sponges. The El Madroño site is located in the NE extreme of the state of Querétaro in central-eastern Mexico. The foraminiferal assemblage is well-preserved and consists mostly of orbitolinids: Dictyoconus walnutensis (Carsey, 1926), Paracoskinolina sunnilandensis (Maync, 1955b), Coskinolinoides texanus (Keijzer, 1942), as well as Buccicrenata subgoodlandensis (Vanderpool, 1933), Novalesia angulosa (Magniez, 1972), Mayncina sp., Istriloculina sp., Arenobulimina sp., Buccicrenata sp. and r strategist planktic foraminifers such as Favusella washitensis (Carsey, 1926), Muricohedbergella simplex (Morrow, 1934), and M. albiana (BouDagher-Fadel, et al., 1996). Among the calcareous algae are Cayeuxia kurdistanensis Elliott, 1957, Terquemella americana (Konishi and Epis, 1962), Acroporella sp., Triploporella sp., and the encruster Lithocodium aggregatum Elliott, 1956. The age assignment of the deposit is based on the benthic foraminifer Dictyoconus walnutensis, which is considered a regional marker of middle Albian age, however this succession spans to the early Albian. The paleoenvironmental reconstruction, inferred from the lithology and benthic assemblage, suggests a warm shallow- water platform.