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.

Supplement to: Dunham, Keith W; Meyers, Philip A; Ho, Eileen S (1988): Organic geochemistry of Cretaceous black shales and adjacent strata from the Galicia margin, North Atlantic Ocean. In: Boillot, G; Winterer, EL; et al. (eds.), Proceedings of the Ocean Drilling Program, Scientific Results, College Station, TX (Ocean Drilling Program), 103, 557-565