Chronostratigraphic Database for Upper Cretaceous Oceanic Red Beds (CORBs)

Abstract An integrated, testable chronostratigraphic database of Late Cretaceous bioevents in numerous reference sections was constructed in order to test the global synchrony of Upper Cretaceous oceanic redbeds—CORBs—and to measure precisely their rates of sediment accumulation. Graphic correlation was the method of choice because it is based on species checklists and because the range projections are transparent and testable. Stage boundaries are defined by GSSP or key reference sections with ammonites, planktic foraminifera, and nannofossils, as well as with magnetochrons. Sequence boundaries and other sedimentary markers as defined in reference sections are projected into the database by graphic correlation of the co-occurring fossils. The database scale is calibrated to radiometric ages of Upper Cretaceous stages that are generally similar to those of the 2004 time scale. This database is used in three areas to interpret deposition of CORBs, the North Atlantic, the Swiss Pre-Alps, and the Eastern Austrian Alps. North Atlantic CORB intervals in six cores range in age from Turonian to Maastrichtian. This succession was deposited within two distinct deep water masses. A Turonian–Santonian oxygenated water mass with a relatively shallow calcite compensation depth (CCD) hosted red-bed deposition and diversification of benthic foraminifera. Deep-water, low pH conditions existed in the North Atlantic during Late Cretaceous submarine volcanism. The well oxygenated Campanian–Maastrichtian water mass was above the CCD, and calcareous fossils were preserved during a second benthic foraminifer diversification event. Red marine clay and turbidites alternated with gray and green beds. Rates of sediment accumulation generally were higher during the Campanian–Maastrichtian period than during the earlier period. CORB strata in the Swiss Pre-Alps were deposited at different times in different places for varying durations and at different rates beginning in the Aptian and continued sporadically into the Santonian. In the Eastern Alps Upper Cretaceous marine red beds are interbedded with siliciclastic and calcareous facies deposited in the Penninic Ocean between colliding plates. Oldest CORB deposition is recorded in the Albian and became persistent during the Campanian. Interbedded red and gray strata record climatic forcing during tectonically controlled transgressive events. The duration of CORB deposition generally was shorter in epicontinental basins than in oceanic basins, but the average rate of sediment accumulation tended to be similar in epicontinental and oceanic basins. Even-bedded CORBs were deposited at the sameaverage duration as homogeneously bedded deposits, but even-bedded CORBs accumulated faster than homogeneous deposits. Many repetitively interbedded oceanic red beds were deposited at rates close to orbital frequencies and may have been related to climatic forcing.