| Summary: | A major change in oceanic sedimentation from mid-Cretaceous organic carbon-enriched deep-sea deposits to predominantlyUpper Cretaceous oceanic red beds (CORBs), represented mainly by deep-sea red shales and marls, occurred during the LateCretaceous and early Tertiary in the Tethys. A variety of earth processes such as organic carbon draw-down, tectonic,palaeoceanographic, eustatic and palaeoclimatic changes, or a combination of these could cause such a change, the main significanceof which is that it demonstrates that the deep ocean basins ceased to be the preferential burial site for organic carbon. A compilationof available data on CORB occurrences, composition, and age indicate that: (1) CORBs are found in a broad geographic beltextending from the Caribbean across the central North Atlantic, southern and eastern Europe to Asia; with limited occurrences inthe Indian ocean; (2) both the first and the last occurrences of CORBs are diachronous; (3) CORBs are of pelagic and hemipelagicorigin and were deposited in a variety of environments from continental slope to deep oceanic basin, above and below the carbonatecompensation depth (CCD); (4) total organic carbon (TOC) is mostly !0.1%; haematite is relatively abundant, up to 10% in redshales; (5) the termination of CORB deposition in the Alps, Carpathians, and Himalayas was mostly a result of major tectonicevents associated with intensification of continental plate migration and initial stages of collision of the Indian and Asian plates andthe African and European continental plates. We suggest that changes in dissolved oxygen in the deep ocean were mainly the resultof changes in the location and formation of deep water and changes in ocean circulation. It is more than probable that a score ofdifferent earth processes, including changes in climate, all acting in concert, were involved in such a major change in the deep-seaenvironment and location of the carbon reservoir.
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