Lower Aptian ammonite and planktonic foraminifera integratedbiostratigraphy and the age of the OAE1a in the Morella sub-basin, Maestrat Basin (eastern Spain)

Abstract

A correlation between planktonic foraminifera and ammonite biostratigraphic biozonations has for the first time been established for the lower Aptian of the Morella sub-basin (northern Maestrat Basin). The planktonic foraminifera zones recognized are Globigerinelloides blowi, Globigerinelloides aptiensis, Leupoldina cabri and Hedbergella luterbacheri. The identified ammonite zones include the Deshayesites forbesi, Deshayesites deshayesi and Dufrenoyia furcata zones, and the Roloboceras hambrovi and Deshayesites grandis subzones. The boundary between the G. aptiensis and L. cabri zones was recorded in the uppermost part of the Deshayesites forbesi Zone, coinciding with the middle part of the R. hambrovi Subzone. The H. luterbacheri Zone spans almost the entire Deshayesites deshayesi Zone and the whole Dufrenoyia furcata Zone. The Oceanic Anoxic Event (OAE1a) has also been calibrated against the two biostratigraphic schemes. This event spans almost all the G. aptiensis and the basal part of the L. cabri planktonic foraminifera zones and largely coincides with the R. hambrovi ammonite subzone. This study provides an extended and accurate biostratigraphic framework for the Morella sub-basin, helping to better constrain the age of stratigraphic intervals where ammonites are scarce or absent, that may also serve as a correlation tool for the analysis of other coeval marine sedimentary successions in the western Tethys..