Environmental and geochemical characterization of the oceanic anoxic event 2 (Cenomanian-Turonian) in central Mexico
Fernando Nuñez-Useche
National Autonomous University of Mexico (UNAM)
Institute of Geology/Department of Paleontology
Mexico City, Mexico
[email protected]
Oceanic Anoxic Events (OAEs) represent short periods of widespread and synchronous deposition of organic carbon-rich sediments as result of global perturbations of carbon cycle. The OAE 2 event, which occurred around the Cenomanian/Turonian boundary, is one of the most prominent oceanic anoxic events in the mid-Cretaceous. This event has been documented in northern Mexico in the Indidura and Agua Nueva Formations and in southern Mexico in the Morelos Formation.
The Cenomanian/Turonian (C/T) boundary in central Mexico is recorded in deep-water successions of the Soyatal and Agua Nueva Formations. These transgressive units are mainly constituted by dark-gray laminated limestones with planktonic foraminifera and thin layers of shale. Near de C/T boundary, these units contain carbonaceous layers probably related with the OAE 2 which are the target of this investigation.
The integral study herein proposed combined the use of sedimentlogical (field descriptions and analysis of the microfacies succession) geochemical (total organic carbon, carbon and oxygen isotopes, mayor elements and trace metals concentrations) and biostratigraphic (determination of planktonic foraminifera through the examination of thin-sections) tools for the study of the stratigraphic sections of the Soyatal and Agua Nueva Formations that contain the organic-rich deposits in central Mexico. The objectives of this study are to identify and understand the paleoenvironmental conditions and the mechanisms responsible for the deposition and preservation of organic matter-rich sediments in central Mexico.
AAPG Search and Discovery Article #90157©2012 AAPG Foundation 2012 Grants-in-Aid Projects