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

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 inter-preted 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 (similar to 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.

Automated summary

This study presents the first record of two late Albian ammonites, Elobiceras (Elobiceras) sp. and Pervinquieria (Pervinquieria) pricei (Spath), from northwest Algeria. These ammonites were collected from the Mcharref Formation, which is interpreted as a lagoonal carbonate ramp located south of Tiaret city based on facies analysis. The recognition of the well-known Pervinquieria (Pervinquieria) pricei biozone from the study area significantly improves the age assignment for the studied sections. The identified biozone shows a strong correlation with Tethyan, European, American, and Asian biozones, indicating a cosmopolitan distribution during the late Albian time.