--> Abstract: A Quantitative Approach to Define the Potential of Microbial Mat Induced Sedimentary Structures as from Indicator of Depositional Setting, by Sushanta Bose and Henry S. Chafetz; #90078 (2008)

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A Quantitative Approach to Define the Potential of Microbial Mat Induced Sedimentary Structures as from Indicator of Depositional Setting

Sushanta Bose and Henry S. Chafetz
University of Houston, Houston, TX

Microbial mat induced sedimentary structures (MMISS) are abundant within the pool-like, supratidal lows (up to 25cm deep, 15m wide) of Follet’s Island, Texas. A systematic measurement of the relative depth, thickness of microbial mats, and related MMISS at 30cm intervals along seven profiles across the pools revealed that the size and distribution of MMISS and mat thickness are strongly related to centimeter scale variations in depth.

Thickness of microbial mats increases from 2 to 25mm from periphery to ~18cm depth followed by an abrupt decrease in the mat thickness below ~20cm due to enhanced grazing. Polygons of desiccation-cracked mats are abundant within 7 -20cm depth interval. Polygon peripheries are typically curled-up, and the curl height and size of the polygons varies with mat thickness. Maximum height of the curl (up to 7cm) and maximum diameter of the crack-polygon (up to 46cm) correspond to the maximum thickness of the mat. Similarly, the size of gas domes, which occur at the shallower depths, increase with mat thickness. The characteristically wrinkled sediment surface is more common in the shallower sites whereas the sieve-like-surfaces are common in deeper locations. Overall, the pool surfaces can be quantitatively subdivided into several ring-like MMISS-zones that correspond to variation in depth.

The pools represent the general relationship between depth and distribution of MMISS on a tidal flat, where movements of tidal water across a relatively flat surface are controlled mainly by small topographic variations. Therefore, type, morphology, and distribution of MMISS potentially reflect subtle variations in tidal flat topography

 

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