Testing the Possible Linkages Between the Miocene Reticulofenestra Event, the Biogenic Bloom, Tropical Gateways, and Sea Level Changes

Emily Browning¹, R. Mark Leckie¹, Paul McClain¹, Steve Nathan¹, and Cedric John^2
1Geoscience, University of Massachusetts, Amherst, MA
²Intgrated Ocean Drilling Program, College Station, TX

The most significant reorganization of Neogene tropical nannofossil communities, the “Miocene Reticulofenestra Event” (MRE) (~8.85-8.79 Ma) is characterized by a collapse in the relative abundance of the prominent calcareous nannofossil genus Reticulofenestra across the tropics, and subsequent recovery dominated by small Reticulofenestra. The MRE coincides with the waning stages of the late middle to late Miocene ‘carbonate crash’ (~12-9 Ma) and the initiation of the ‘biogenic bloom’ (~9.0-4.0 Ma). Both the ‘carbonate crash’ and ‘biogenic bloom’ represent major perturbations of the carbon cycle, the former affecting pelagic carbonate production and preservation, while the later is characterized by a major phase of organic carbon production and burial. The rapid onset of the MRE and the gradual recovery of Reticulofenestra abundance suggests a rapid triggering mechanism, such as a threshold event in the ocean-climate system. We hypothesize, based on our preliminary analysis of calcareous nannofossil and planktic foraminiferal assemblages and stable isotope data from the western equatorial Pacific (ODP Site 806), that both the biogenic bloom and the MRE were linked to changes in sea-level and closure of the Indonesian gateway. We are now extending the MRE study to the eastern Australian margin (Marion Plateau; ODP Sites 1192-1195), where a highly integrated middle to late Miocene stratigraphic framework will allow us to test for possible relationships between the MRE and carbonate platform collapse, sea level change, Indonesian Seaway closure, and ocean circulation.

AAPG Search and Discovery Article #90078©2008 AAPG Annual Convention, San Antonio, Texas