Organic geochemistry of Cretaceous black shales

• Main Authors: Dunham, Keith W, Meyers, Philip A, Ho, Eileen S
• Format: Other/Unknown Material
• Language: English
• Published: PANGAEA 1988
• Subjects: 103-637A; 103-638B; 103-638C; 103-639A; 103-639C; 103-640A; 103-641A; 103-641C; DRILL; Drilling/drill rig; Joides Resolution; Leg103; North Atlantic Ocean; Ocean Drilling Program; ODP; North Atlantic
• Online Access: https://doi.pangaea.de/10.1594/PANGAEA.743874; https://doi.org/10.1594/PANGAEA.743874

Organic-carbon-rich 'black shales' and adjacent organic-carbon-poor rocks from three different Cretaceous settings encountered during ODP Leg 103 have been studied by organic geochemical methods. Rock-Eval analysis, carbon isotope data, and lipid biomarkers show organic matter to contain varying proportions of marine and continental materials. In Hauterivian-Barremian organic-carbon-rich marlstone turbidites, large amounts of land-derived organic matter are found. Aptian-Albian black-colored shales are interspersed within green claystones, from which they differ by containing more marine organic matter. An abbreviated layer of black shale from the Cenomanian/Turonian boundary is dominated by well-preserved marine organic matter. Downslope transport and rapid reburial within a predominantly oxygenated deep-water setting created most of these examples of black shales, except for the Cenomanian-Turonian deposits in which deep-water anoxia may have been involved.