Paleoenvironment and sea-level change in the early Cretaceous Barents Sea implications from near-shore marine sapropels
The late Volgian (early "Boreal" Berriasian) sapropels of the Hekkingen Formation of the central Barents Sea show total organic carbon (TOC) contents from 3 to 36 wt%. The relationship between TOC content and sedimentation rate (SR), and high Mo/Al ratios indicate deposition under oxygen-free bottom water conditions, and suggests that preservation under anoxic conditions has largely contributed to the high accumulation of organic carbon. Hydrogen index values obtained from Rock-Eval pyrolysis are exceptionally high, and the organic matter is characterized by well-preserved type II kerogen. However, the occurrence of spores, freshwater algae, coal fragments, and charred land-plant remains strongly suggest proximity to land. Short-term oscillation probably reflecting Milankovitch-type cyclicity are superimposed on the long-term trend of constantly changing depositional conditions during most of the late Volgian. Progressively smaller amounts of terrestrial organic matter and larger amounts of marine organic matter upwards in the section may have been caused by a continuous sea-level rise.