Late Albian ammonites from northwest Algeria: Biostratigraphic, paleobiogeographic and paleoenvironmental inferences

Abstract

Albian rocks of northwest Algeria are commonly clastic deposits with poor dating markers. This study records two late Albian ammonites from northwest Algeria for the first time. They are Elobiceras (Elobiceras) sp. and Pervinquieria (Pervinquieria) pricei (Spath). These ammonites are collected from the Mcharref Formation interpreted here to be deposited south of Tiaret city under a lagoonal carbonate ramp setting based on facies analysis. The recognition of the well-known early late Albian ammonite Pervinquieria (Pervinquieria) pricei biozone from the study area highly improves the assigned age for the studied sections. The unconformity surface separates the lower and upper members of the Mcharref Formation coincides with the upper boundary of this biozone. The correlation of this boundary with the global sequence boundaries in the frame of ammonite biozones reveals that it equivalent to the SB KAl 6 (∼103.8 my ago) that marks the end of the identified biozone everywhere. Therefore, the recorded biozone shows an excellent correlation between the study area and that of Tethyan, European, American, and Asian biozones. Paleobiogeography of the recognized biozone indicates a cosmopolitan distribution that is interpreted here as a response to the widespread distribution of the Tethyan shallow water that reached to form a connection with the northern and southern Atlantic oceans during the late Albian time.