--> Abstract: Penecontemporaneous Diagenesis in Bahamian Microbialites, by Noah Planavsky and Robert N. Ginsburg; #90078 (2008)

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Penecontemporaneous Diagenesis in Bahamian Microbialites

Noah Planavsky and Robert N. Ginsburg
Marine Geology and Geophysics, University of Miami, Miami, FL

The discovery of extensive fields of stromatolites, first in Shark Bay, Western Australia and later in the Exuma Islands of the Bahamas, initiated an enormous amount of study on modern microbial deposits. These modern analogues have added valuable new concepts about the genesis of these most ancient traces of life on earth. Although all of the Bahamian mounds were initially described as stromatolites, implying the presence of laminations, it was soon noted that there is a large amount of fabric variation in the columns. The internal fabric varies from a completely laminated to an irregular, mottled fabric. The columns composed predominately of mottled fabrics have been classified as thrombolites. There has been considerable progress in understanding the origin and lithification of laminations, but models for thrombolite morphogenesis remain speculative. We propose a new model for morphogenesis of subtidal Bahamian thrombolites. The growth model is focused on detailed descriptions and interpretations of the microbialite fabrics in the context of our observations and published descriptions of the benthic communities and physical processes. Our findings suggest that variations in the amount and style of penecontemporaneous diagenesis rather than differences in surfical benthic communities cause the disparate internal morphologies of the Bahamian microbialites.

 

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