Total organic carbon content and redox-sensitiv trace metal concentrations of selected late Cenoman claystones from DSDP Hole 93-603B

• Main Authors: Kuypers, Marcel MM, Lourens, Lucas Joost, Rijpstra, W Irene C, Pancost, Richard D, Nijenhuis, Ivar A, Sinninghe Damsté, Jaap S
• Format: Dataset
• Language: English
• Published: PANGAEA 2004
• Subjects: 93-603B; Carbon; organic; total; Deep Sea Drilling Project; DEPTH; sediment/rock; DRILL; Drilling/drill rig; DSDP; DSDP/ODP/IODP sample designation; Glomar Challenger; Leg93; Manganese/Aluminium ratio; Molybdenum/Aluminium ratio; Nickel/Aluminium ratio; Rock type; Sample code/label; Vanadium/Aluminium ratio; X-ray diffraction (XRD); Zinc/Aluminium ratio; North Atlantic
• Online Access: https://doi.pangaea.de/10.1594/PANGAEA.712950; https://doi.org/10.1594/PANGAEA.712950

The Cenomanian/Turonian (C/T) intervals at DSDP Sites 105 and 603B from the northern part of the proto-North Atlantic show high amplitude, short-term cyclic variations in total organic carbon (TOC) content. The more pronounced changes in TOC are also reflected by changes in lithology from green claystones (TOC<1%) to black claystones (TOC>1%). Although their depositional history was different, the individual TOC cycles at Sites 105 and 603B can be correlated using stable carbon isotope stratigraphy. Sedimentation rates obtained from the isotope stratigraphy and spectral analyses indicate that these cycles were predominately precession controlled. The coinciding variations in HI, OI, delta13Corg and the abundance of marine relative to terrestrial biomarkers, as well as the low abundance of lignin pyrolysis products generated from the kerogen of the black claystones, indicate that these cyclic variations reflect changes in the contribution of marine organic matter (OM). The cooccurrence of lamination, enrichment of redox-sensitive trace metals and presence of molecular fossils of pigments from green sulfur bacteria indicate that the northern proto-North Atlantic Ocean water column was periodically euxinic from the bottom to at least the base of the photic zone (<150 m) during the deposition of the black claystones. In contrast, the green claystones are bioturbated, are enriched in Mn, do not show enrichments in redox-sensitive trace metals and show biomarker distributions indicative of long oxygen exposure times, indicating more oxic water conditions. At the same time, there is evidence (e.g., abundance of biogenic silica and significant 13C-enrichment for OC of phytoplanktic origin) for enhanced primary productivity during the deposition of the black claystones. We propose that increased primary productivity periodically overwhelmed the oxic OM remineralisation potential of the bottom waters resulting in the deposition of OM-rich black claystones. Because the amount of oxygen used for OM remineralisation ...