Organic geochemistry: Highlights in the deep-sea drilling project

Abstract

Organic geochemistry has evolved within the Deep Sea Drilling Program (DSDP) from having little more than an ad hoc advisory function to its present state of a fully fledged international research program. On-board organic geochemistry has prima facie involvement with drilling safety decisions through continual monitoring of htdrocarbon accumulation, migration and generative potential. Areas of petroleum and hydrocarbon gas fields, if even suspected, must for the present be avoided, for reasons of safety and pollution until adequate technology enables probing such regions (e.g. continental margins and marginal basins). Investigations of organic diagenesis in marine sediments throughout the growing organic geochemistry regime within DSDP have resulted in a wealth of knowledge, oft times at the peripheries of petroleum genesis, which is not only useful at the present, but provides a solid base from which to launch future studies. Throughout the genesis of organic geochemistry, within DSDP, shore-based studies have resulted in the improvement and expansion of on-board analytical techniques and assessment of organic diagenesis and thermal profiling. Several on-shore laboratories have actively participated in the study of the organic constituents of DSDP core-samples since initiation of the project. These investigations are reviewed from an “area of interest” aspect and general results given as to source and maturation of the organic matter present in deep sea sediments. Applications to palaeoenvironment, thermal history, petrogenesis, and general sedimentology are considered. Taken as a whole, the results of organic geochemical investigations within the DSDP program yield much information on the transformation of organic matter in marine sedimentary environments and the overall flux of carbon through geologic time. Studies begun in the Eastern Pacific active margin and geothermal sites (Legs 63–69) and the impending return to the Atlantic (Legs 70–81), most notably the Cape and Angola Basins, with associated Cretaceous shales, afford an excellent continuation to these studies.