Environmental control of the genesis of Tahitian reef-microbialites during the last deglacial sea-level rise

Abstract

The genesis of microbialites (microbial carbonates) in coral reefs is under discussion. The occurrence of unusually high volumes of thick microbialites (up to 80 vol. % of drilled cores, IODP 310) in post-Last Glacial Maximum reefs of Tahiti has been interpreted to reflect environmental change during the rapid last deglacial sea-level rise. A better understanding of the microbialite formation would allow for using them to reconstruct the last deglacial sea level curve and changing environmental conditions. Geobiological, geochemical, and sedimentological analyses were performed on laminated and dendritic deglacial Tahitian microbialites in order to investigate the processes and environmental conditions leading to their formation. The results of this thesis indicate a deglacial environment, which was possibly influenced by an intensified primary productivity. It is demonstrated, that sulphate-reducing bacteria most likely dominated the microbial community and played the major role in inducing the precipitation of the microbial carbonates in the coral reefs of Tahiti.