Microbialite Distribution in a Lacustrine Rift Basin; Great Salt Lake, Utah

Robert Baskin
University of Utah

Great Salt Lake (GSL) provides an ideal location for examining environmental and chemical influences on the heterogeneity of microbialite distributions in a lacustrine rift basin. A variety of microbialite morphologies have been observed in GSL, including giant, ramified columnar forms (tens of meters in diameter and height) to smaller benthic forms (meters in diameter and height) to widespread biofilms. While the larger columnar forms seem to be limited to a specific area of the lake, the benthic forms are pervasive in the shallower waters and appear to be controlled by depth-related factors such as light penetration and/or wave-base energy. The influence of tectonic controls on microbialite distribution throughout GSL is evidenced by the abrupt occurrence of microbialites in areas of structural microtopographic highs. The relation between these highs and corresponding onlapping sediments trapped in hanging wall lows is repeated in many of the surveyed transects and likely occurs throughout the lake. Some microbialite growth appears very recent, occurring after Pleistocene Lake Bonneville; whereas in other areas, large ramified columnar forms appear long-lived, keeping pace with sediment accumulation. Examination of tectonic and chemical influences on the occurrence and distribution of microbialites in GSL provide insight into understanding fossil distributions and if distributions are related to evolution of the biological components of microbialite formation or variant environmental conditions.

AAPG Search and Discovery Article #90169©2013 AAPG Rocky Mountain Section 62^nd Annual Meeting, Salt Lake City, Utah, September 22-24, 2013