Stable organic carbon isotope stratigraphy across Oceanic Anoxic Event 2 of Demerara Rise, western tropical Atlantic

Ocean Drilling Program (ODP) Leg 207 recovered expanded sections of organic-carbon-rich laminated shales on Demerara Rise (western tropical Atlantic). High-resolution organic carbon isotope and total organic carbon (TOC) records are presented, which span the Cenomanian-Turonian boundary interval (CTBI), including the Oceanic Anoxic Event (OAE) 2, from four sites oriented along a NW striking depth transect. These records represent the first high-resolution carbon isotope records across OAE 2 from the South American margin of the tropical Atlantic. Due to the scarcity of age significant fossils, the main purpose of this study was to develop a detailed carbon isotope stratigraphy in order to correlate the CTBI across the depth transect and to tie this to biostratigraphically well-defined sections in the Western Interior Basin (Pueblo, USA), boreal shelf seas (Eastbourne, England), and western Tethys (Oued Mellegue, Tunisia). All four sections studied document a 6‰ increase of δ¹³C_org values at the base of the CTBI, which is followed by an interval of elevated δ¹³C_org values and a subsequent decrease. Our results supply an important stratigraphic base for subsequent paleoceanographic studies on Late Cenomanian to Early Turonian sediments from Demerara Rise and elsewhere.