Determination of organic degradation rates in 100My old sediments: Application to Cretaceous black shale intervals from Demerara Rise, ODP Leg 207

摘要

Highlights?SOM degradation rate and reactivity in Cretaceous black shales investigated.?Solid state13C NMR, FTIR and bulk elemental composition used for quantification.?Effects of early diagenesis readily distinguished from those of long term diagenesis.?The 100My SOM at Demerara Rise had extremely low to non-quantifiable reactivity.AbstractThick organic-rich, Albian to Santonian, black shale sequences were recovered from Ocean Drilling Program Sites 1261 and 1257 on the Demerara Rise, offshore Surinam, at depths of 564 and 174m below seafloor (bsf) respectively. Total organic carbon (TOC) concentration varies between 3.9 and 17.3wt%. Rock-Eval pyrolysis parameters and elemental analysis indicate that the kerogen samples are of Type II, thermally immature and with well preserved organic matter. The hydrogen index (HI) values fluctuate between 608 and 765mghydrocarbon(HC)/gTOC and correla