Quick Search:    advanced search

GSW Home   GeoRef Home   My GSW Alerts   Contact GSW   About GSW   Journals List   Help

This Article Figures Only Full Text Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in Web of Science Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Johnson, J. Articles by Grotzinger, J. P. Search for Related Content GeoRef GeoRef Citation

Affect of Sedimentation on Stromatolite Reef Growth and Morphology, Ediacaran Omkyk Member (Nama Group), Namibia

Department of Earth, Atmospheric and Planetary Sciences, 54-822 Massachusetts Institute of Technology, Cambridge, MA 02139 e-mail: joelj{at}mit.edu

J. P. Grotzinger

Department of Earth, Atmospheric and Planetary Sciences, 54-822 Massachusetts Institute of Technology, Cambridge, MA 02139 *Current Address: Division of Geological and Planetary Sciences California Institute of Technology, Pasadena, CA 91125 e-mail: grotz{at}gps.caltech.edu

Superbly preserved reefs of Ediacaran age in Namibia give clues to environmental controls on stromatolite-thrombolite growth morphology and nucleation. Digital mapping and Measured stratigraphic sections reveal parasequences featuring meter-scale alternation of shallow marine shale and stromatolitic-thrombolitic microbialites associated with other clastic carbonates (grainstones, mudstones). Stromatolite-thrombolite column width, spacing and height vary systematically with the type of sediment being deposited, with growth inhibited during shale deposition. Columns are generally wider and more closely spaced during carbonate sediment deposition and narrower and more widely spaced during shale deposition. While stromatolite growth should be sensitive to sediment type explicitly, we also interpret sediment type as a general proxy for changing environmental conditions (e.g. water depth, turbidity) that may directly affect reef growth. A simple rule-based numerical simulation of microbialite growth is formulated based on the field interpretations of sedimentological and topographic growth controls. The model cannot explain detailed morphologic attributes, but can recreate correlations between stromatolite column widths, column spacing and layer bed thickness as a function of sediment type.