Organic Petrography of Lower Cretaceous Shales at DSDP Leg 47B Site 398, Vigo Seamount, Eastern North Atlantic

Abstract

The type and maturity of the organic matter of the Lower Cretaceous shales of DSDP Site 398 are investigated by microscopy. The sediments are shown to contain a predominance of particles of higher plant origin. Both bimodal vitrinite reflectance histograms and anomalous fluorescence indicate the presence of recycled organic matter. The relative content of recycled particles is quantified, and the origin discussed. Recycled organic particles reach a peak in the Albian and Aptian of the Lower Creteceous. A low maturity gradient is indicated with vitrinite reflectance values in the 0.5 to 0.6 per cent range at 1700 meters. The sediments are considered as fair liquid hydrocarbon source rocks, but are immature.