| Popis: |
Comparison of biomarker distributions in an oil and in sedimentary rock samples from an offshore well in Korea Bay Basin indicates that an Upper Jurassic, ∼500 m thick, mudstone zone could form the source rock for the oil. The organic material in this zone appears to be H-rich and of sufficient abundance, from pyrolysis measurements, to generate oil. It seems to derive primarily from bacterial lipids, as reflected in high levels of bacterial hopanoids and predominance of amorphous kerogen macerals. A higher plant wax contribution to the organic matter is indicated by an OEP in n -akanes>C 20 , and there may also be an autochtonous algal contribution. Sedimentological and biomarker evidence is consistent with input from a river delta prograding into a deep freshwater lake. Biomarker distributions suggest that pronounced bacterial reworking of allochthonous higher plant material had occurred in probably anoxic conditions. High heat flows in a rapidly subsiding extensional basin probably account for the observed extensive aromatisation of monoaromatic steroidal hydrocarbons at a relatively early stage of sterane isomerisation. |
