See more from this Division: Topical Sessions
See more from this Session: Biofilms and Biomineralization: Evidence from Ancient and Modern Systems
Abstract:
Thin sections of each fabric were scanned for fossil microbes in the Scanning Electron Microscope (SEM) at the UNM, at a uniform magnification of 4000X to allow quantification of microbes per square micron for specific petrographic fabrics.
In smooth crust, the micrite layers have 0.5 x 10-4 filaments/micron2, the spar layers have 2.0 x10-4 filaments/micron2, and the outer-most micrite layers have 4.0 x 10-4 filaments/micron2. In knobby crust, the spar layer has 3.8 x 10-4 filaments/micron2, the laminated micrite area has 3.3 x 10-4 filaments/micron2, and the clotted micrite has 6.0 x 10-4 filaments/micron2. In the pool finger itself, a clotted micrite area contains 19.4 x 10-4 filaments/micron2, while an outer-most micrite area has 4.0 x 10-4 filaments/micron2, and a second dense clotted micrite area has 5.3 x 10-4 filaments/micron2.
These data indicate that the dense, clotted micrite is more microbial than the layered micrite and/or layered spar. In particular, the ends of pool fingers, which are commonly connected by U-loops, contain the most fossil evidence. This is significant, because it confirms that the combination of clotted micritic fabric with u-loops is a biosignature.
See more from this Division: Topical Sessions
See more from this Session: Biofilms and Biomineralization: Evidence from Ancient and Modern Systems