Paper No. 5
Presentation Time: 9:35 AM
CRETACEOUS OCEANIC RED BEDS (CORBS): PAST, PRESENT AND FUTURE
HU, Xiumian, School of Earth Sciences and Engineering, Nanjing University, Hankou Road 22, Nanjing, 210093, China, WANG, Chengshan, Department of Earth Sciences, China University of Geosciences, Beijing, Beijing, 10083, China, SCOTT, Robert W., University of Tulsa, 149 West Ridge Road, Cleveland, OK 74020 and WAGREICH, Michael, Department of Geodynamics and Sedimentology, University of Vienna, Althanstrasse 14, Vienna, A-1090, Austria, huxm@nju.edu.cn
Cretaceous Oceanic Red Beds (CORBs) are reddish to pinkish to brownish sedimentary rocks deposited in Aptian through Maastrichtian pelagic marine environments, and are grouped into three end members: carbonate CORBs, clayey CORBs and siliceous CORBs. The occurrence of oceanic red beds has been known for at least 140 years. However, detailed investigations on paleoceanographic and paleoclimatic implications related to CORBs were initiated by during late 1990s. Since 2001, CORBs have been the scientific topic of three International Geosciences Programmes, IGCP 463, IGCP 494, and subsequently IGCP555. Attention has been paid to the global distribution, correlation, and significance of the oxidation of these deposits for palaeoceanographic reconstructions, and their relationships to the distinctly different mid-Cretaceous black shales. A series of meetings and workshops, with sponsored symposia were held. Up to now, a number of publications including scientific peer-reviewed papers and meeting abstracts were published both in international and regional journals.
A major achievement has been to provide evidence that CORBs are globally distributed, which indicates major paleoceanographic conditions changed globally in the Cretaceous ocean. The driving force of such changes could be changes in ocean circulation, bioproductivity, changes in nutrient and/or sediment input, or in palaeoclimate, or any combination of the above. Work on the projects led to the recognition that oceanic red beds were also deposited or repeatedly during the “mid-Cretaceous greenhouse” period. Sedimentologic, geochemical, paleoceanographic studies show that CORBs were deposited under highly oxic, oligotrophic, and probably low-productivity conditions, with much less organic carbon burial. Wang et al. proposed a hypothesis that the CORBs may be a possible consequence of OAEs, which needs to be further tested . A few topics for future research will be discussed, including coloring of the CORBs, paleoceanographic and paleoclimatic controls and their feedback on the formation of the CORBs, linkage with OAEs, and other Phanerozoic deep-water red limestones.
