A c. 1 m thick carbonaceous claystone from the type locality of the Lower Cretaceous Skyttegård Member (Rabekke Formation), Bornholm, has been investigated by organic pétrographie and organic geochemical methods in order to assess the depositional environment of the claystone and the thermal maturity of
the organic matter. The claystone was deposited in a low-energy, anoxic lake
which occasionally was marine influenced. The organic matter is terrestrial and
can be classified as kerogen type III and lib. Detrital organic matter and cutinite
are characteristic components. The organic matter is allochthonous but the transport distance was short, and the plant material was probably mainly derived from
plants growing at the edge of, or nearto, the lake. Source-specific biomarkers
such as norisopimarane suggest that the plant litter was derived from a gymnospermous, low-diversity vegetation. Evidence for early angiospermous plants
cannot be demonstrated with any certainty. A huminite reflectance value of
0.24%Rm and several geochemical parameters indicate that the organic matter is
highly immature. It has only experienced coalification corresponding to the peat
stage. Estimates show that, prior to uplift, the claystone was buried to a maximum of approximately 260 m. Reflectance data further suggest that a maximum
c. 550 m thick sediment package was removed by erosion prior to deposition of
the ?uppermost Jurassic-Lower Cretaceous sediments on Lower Jurassic strata.
Lamina characteristics of gas-bearing shale fine-grained sediment of the Silurian Longmaxi Formation of Well Wuxi 2 in Sichuan Basin, SW China
