Planktic Foraminiferal Paleoecological Events - Tool for High Resolution Biochronostratigraphic Correlations – Cenomanian-Turonian Time, San Felipe Formation, NE Mexico

Nebrigic, Dragana D.¹ (1) The University of Texas at Dallas, Richardson, TX

The Cenomanian-Turonian time interval is marked by major dynamic changes registered in ocean/atmosphere system. Profound turnover in marine communities related to the peak of sea level rise, widespread anoxia and intense episode of organic carbon burial led to incomplete taxonomic documentation of biostratigraphic important primary markers.

Bioevents of fourty-five species of planktic foraminifera have been utilized during the course of this study to establish high resolution biostratigraphic framework for the Cenomanian-Turonian interval. They became extremely reliable tool for high resolution biostratigraphic analysis for the region since ammonite biozonation lack significant amount of data which leads to general lacking of ammonite control of the Cenomanian-Turonian successions and weakening the multitaxial biozonation scheme. In order to increase the resolution of available data base, there was a need to consider other type of events beside the first and last occurrence of fossil taxa, traditionally applied in establishing of a biostratigraphic framework. Thirty-five biohorizons were delineated utilizing major paleoecological changes within foraminiferal community in an attempt to increase the resolution obtained utilizing “conventional” “two-phase” planktic foraminiferal evolutionary bioevent (the extinction of Rotalipora and Thalmanninela succeeded by Dicarinella and Marginotruncana). This approach might be considered as a valuable correlation tool in high resolution stratigraphic analysis.