Bioproductivity rise in the East Baltic epicontinental sea in the Aeronian (Early Silurian)

The occurrence of black shale in deep shelf environments, chertification in shoreward carbonate facies, barite occurrences, positive δ 13C excursions in carbonate sections and enhanced micritic limestone accumulation give evidence of a primary bioproductivity rise suggesting upwelling in the Aeronian of the East Baltic. The end-Rhuddanian onset of the rise in primary bioproductivity corresponds to the beginning of black shale formation on the deep shelf and micritic limestone formation on the shallower shelf. The bioproductivity maximum was in the mid-Aeronian, judging from the highest values of δ 13C. Upwelling ceased and primary productivity decreased at the end of Aeronian.