| Popis: |
A 1.2 m long core section of Kimmeridge Clay, showing cyclic-like TOC variations between ∼ 2 and ∼ 10%, was sampled at approximately centimetre intervals and investigated by Rock-Eval pyrolysis and biomarker analysis. The main quantitative and qualitative organic matter (OM) variations can be attributed to the addition of variable amounts of autochthonous OM to a background of about 1% TOC of terrestrial inputs. The degree of preservation of the autochthonous OM increases regularly with increasing TOC up to about 6%. Molecular evidence indicates that most of the alteration of the autochthonous OM occurred in the water column, rather than in the sediment. Above 6%, TOC variations reveal that OM accumulation control is directly led by autochthonous paleoproduction (without any notable change in the degree of preservation of the primary planktonic input). Consistent with other work, the present results show that anoxia must be regarded as a simple consequence of high organic matter preservation resulting from high primary production. |
