An Early Cretaceous lacustrine record: Organic matter and organic carbon isotopes at Bernissart (Mons Basin, Belgium)

The early Cretaceous Bernissart lake deposits (Mons Basin, Belgium) constitute an important historical site in the field of palaeontology. In this study, we focus on the organic matter (OM) content of the 50 m-long borehole core, "Ber 3", drilled at Bernissart. Organic data (Rock-Eval, palynofacies, ) and carbon-isotope measurements on bulk OM and selected, isolated wood fragments were collected. The OM distribution exhibits two total organic carbon (TOC) cycles (12 m and 38 m-thick, respectively) that are stacked in a lower frequency cyclic pattern. A general increase of in situ aquatic production and preservation of OM through time is evidenced within the freshwater masses. A spectral analysis of a high-resolution gamma-ray record demonstrates that the sedimentation was controlled by orbitally-induced climatic changes. Precession, obliquity and short- and long-term eccentricity cycles are recognized.