The Berriasian-Valanginian boundary interval based on calpionellids from the Taraises Formation, Cuencame de Ceniceros, Durango, NW Mexico: Biostratigraphic, paleoecologic and paleobiogeographic significance

摘要

A section from the lower part of the Taraises Formation located in the central-east part of Durango State, northern Mexico was studied. The succession consists of a grey and reddish limestone interstratified with marl levels. The calcareous strata provide a microfossil assemblage that consists of calpionellids, planktonic and benthonic foraminifera, and radiolarians. Based on the first appearance of Calpionellites darderi the Berriasian Valanginian boundary was defined for the first time from the Taraises Formation.