Mesozoic radiolarites – accumulation as a function of sea surface fertility on Tethyan margins and in ocean basins

• DOI: 10.1111/sed.12022
• Publication Date: 2013-01-23T09:50:58Z
• Authors: Peter O. Baumgartner
• Keywords: Paleogene

Abstract Radiolarites, commonly comprising chert‐shale couplets, feature prominently in the Mesozoic stratigraphy of Neotethyan realm. The origin and significance these deposits, especially with regard to understanding palaeoproductivity that region, remains controversial. This study examines transport processes accumulation rates radiolarians/radiolarites, as well chronology radiolarite sedimentation based on revised data from Southern Alps new Balagne Nappes, Alpine Corsica. Results suggest spatio‐temporal distribution carbonate silica Tethyan margins was governed by extensive lateral radiolarian tests topographic highs basins. Palaeoclimatic, rather than palaeotectonic, changes seem have triggered surface fertility which, turn, brought about major facies observed marginal basins: Regional platform demise – possibly due eutrophication onset deposition Early Bajocian can be correlated a positive shift carbon isotope curve, whereas recovery end correlates gradual decline δ 13 C‐values. existence vigorous trans‐Pangaean, equatorial current system could produced regional upwelling is questioned because evidence for Middle Jurassic Cretaceous oligotrophic conditions Proto‐Caribbean Central Atlantic. ‘Caribbean River Plume Model’ proposed possible alternative Western Tethys. Dissolved nutrients may been dispersed low salinity lids originated river plumes rivers tropical Africa warm‐temperate Eurasia. Vast areas pre‐Late world ocean must accumulated radiolarites at (<4 g cm −2 10 −3 years) represented condensed, long‐lived (>50 Myr) sections many Circumpacific terranes. Radiolarian chert claystone normal pelagic sediment during Ordovician time far‐offshore, open oceanic settings, where dilution terrigenous material periplatform shallow‐water carbonates absent.