Geochemistry of Cretaceous Oceanic Red Beds — A synthesis

Abstract

This paper summarizes the geochemistry of Cretaceous Oceanic Red Beds (CORBs), their depositional conditions and their significance in reconstructing marine environments. We report major and minor element compositions of carbonate, clayey, and siliceous CORBs and compare these with average element compositions of carbonates, deep sea carbonates, deep sea clays, and average shale compositions. Element distributions in carbonate CORBs are mostly similar to average carbonate compositions. In particular, Sr concentrations are more comparable to average carbonates than deep sea carbonate Sr concentrations. Clayey CORBs are high in Al, Ti, K, and Fe. Their minor element compositions are more similar to average shale than deep sea clay, which generally has higher values in minor elements. In comparison, siliceous CORBs have at least two times lower Al but higher Si concentrations than clayey CORBs. We further speculate on possible reactions involved in iron mobilization and CORB formation.