Organische Geochemie der höheren Unterkreide Nordwestdeutschlands : Ablagerungsmilieu und Zyklik

This thesis represents the organic geochemical contribution to a multidisciplinary research project, which was established to study the boreal Cretaceous. The "Boreal Cretaceous Cycles Project" (BCCP) looks for sedimentary, biotic and geochemical cycles within rock profiles to elucidate the linkage between sediment accumulation, palaeoceanography and climate-forcing elements. The BCCP started with the assumption of an Albian temperature maximum that is often compared to the recent warming of the atmosphere and therefore called the "Cretaceous Greenhouse". The sampies were collected from cores drilled in the Lower Saxony Basin in Northwest Germany. They cover a stratigraphie sequence from Late Barremian to Late Albian times. By high resolution analysis of the Late Albian (research borehole Kirchrode 1/91) rhythmic sedimentation with three different frequencies was identified reflecting the precession, obliquity and eccentricity cycles. They provide a time resolution down to the 10$^{4}$-year level. Climatic variations influencedthe supply of terrigenous clastics during this time interval. For the older parts of the sediment pile there is some evidence for cyclic sedimentation as weil, but this needs further confirmation. The upper Lower Cretaceous in NorthwestGermany can be subdivided into two stratigraphie intervals, which are characterized by different environmental settings. The older sediments (Barremian - Late Aptian/" Fish-Shale") were deposited within a marginal basin with restricted water circulation. Below surface water of only average productivity, TOC-rich shales accumulated in oxygen-depleted bottom water. The oxygen deficiency is indicated by an undisturbed lamination, by high amounts of bituminite and by geochemical data. In contrast to this, extremely low TOC values and a dominance of recycled, terrigenous macerals are typical for the younger interval. This residual kerogen type indicates fully oxygenated bottom water conditions. The observed oceanographic change documented in the evolution of the sediments is related to globalwarming, following transgression and opening of new seaways