A late Aptian planktic foraminiferal assemblage and pyrite framboids from the “Otates Horizon”, Cerro Boludo, Hidalgo, Mexico: paleoecological and paleoenvironmental implications

Abstract

Cretaceous carbonate deposits are widely distributed along the Sierra Madre Oriental thrust belt from northern Veracruz to southern Nuevo León. At Cerro Boludo (Hidalgo), dark marly limestone samples were collected from the “Otates Horizon”. The samples include a well-preserved planktic foraminiferal assemblage composed of Globigerinelloides algerianus Cushman and ten Dam, 1948, Globigerinelloides ferreolensis (Moullade, 1961), Globigerinelloides barri (Bolli, Loeblich and Tappan, 1957), Globigerinelloides aptiensis Longoria, 1974, Globigerinelloides blowi (Bolli, 1959), Hedbergella roblesae (Obregón de la Parra, 1959), H. occulta Longoria, 1974, H. luterbacheri Longoria, 1974, H. similis Longoria, H. trochoidea Longoria, 1974, H. semielongata Longoria, 1974, Pseudoplanomalina cheniourensis (Sigal, 1952) and Schackoina cenomana Schacko, 1897. Radiolarians are also present. Based on the planktic foraminiferal assemblage we recognized the Globigerinelloides algerianus Total Range Zone of early late to middle late Aptian age.

The paleonvironmental reconstruction inferred from the lithology and the foraminiferal association suggests an open pelagic deposit, besides the occurrence of pyrite framboids and the organic matter indicate oxygen-depleted conditions in a meso to eutrophic setting probably linked to the “late Aptian anoxic event”.