Aportes a la bioestratigrafía del Aptiense–Albiense en la cuenca oriental de Venezuela con base en foraminíferos y nanopláncton calcáreo

Abstract

Outcrop sequences reported in the literature as Aptian–Albian were studied using foraminifera and calcareous nannofossils. The use of two fossils groups minimize the uncertainly for correlation with the world stratigraphic cycles. For this sequences located at Pico García, La Paloma Hill and Grande–Los Hoyos Hill (Monagas, Serranía del Interior) and Borracha and Chimana Islands (Anzoátegui) 152 samples were collected in the more shale sediments. The result shows that bed rocks from Barremian(?)–early Aptian (KS6 foraminiferal zone) outcrop in Pico García and Borracha island. The presence of the Schackoina cabri zone is confirmed, foraminiferal zone KS7, with 3 meter thick and age between 125.5 to 124 Ma, with possible presence in Chimana Island. The lack of planktonic markers between late Aptian and middle Albian force to use large foraminifera (dominated by Orbitolina texana) which have a long life span. The look for other sections with deeper sediments for refining this age interval is suggested by our results. Late Albian is characterized by the presence of Eiffelithus turriseiffelli and Ticinella primula, at the base of Querecual Formation highlight an 103.13 Ma age for Borracha Island meanwhile at Grande–Los Hoyos Hill (Serranía del Interior), the presence of Rotalipora appenninica and Ticinella primula at the base of the same formation gives an 101.92 Ma age.