High frequency bedding rhythms from eight DSDP/ODP sites of upper Albian age are investigated with sedimentological, organic geochemical and inorganic geochemical techniques in order to understand processes responsible for the accumulation of organic matter-rich sedimentary sequences in marine environments. The studied sites are located on a cross-section from the coasts of Northern Africa to North America. Sites with sediments that were deposited at a wide range of paleowater-depths were selected to allow the reconstruction of paleo-oceanographic conditions. High frequency analysis was performed to generate a data base that is used to detect the controlling factors of short term sedimentary fluctuations.
Results obtained thus far indicate the location of an upwelling center off the coast of North Africa during Albian time. The deposited bedding rhythms are interpreted to be generated by terrigenous dilution cycles coupled with productivity/redox cycles. The sediments are organic matter-rich (TOC: 1.5-23%) and contain elevated amounts of selected trace elements. The sedimentary sequences from sites located at the central part of the Atlantic at the paleo-ridge slopes are characterized by CCD fluctuation cycles. The sediments are organic matter-poor and were deposited under oxic bottom water conditions. Sites located on the abyssal plain off the coast of North America contain moderate amounts of mainly refractory terrigenous derived organic matter deposited under an oxic water column.
The study will ultimately allow to refine models for the prediction of source rock occurrences in the open marine environment during "global green-house" conditions.