Multidimensonal Study of Fenestrate Microbialites

This study focuses on rock samples that contain fenestrate microbialite communities collected from the 2521+-3 million year old Gamohaan Formation in South Africa. These rocks contain fossil biofilms left behind by the bacteria as organic inclusions preserved in calcite. We identified growth structures which can help us better understand the interactions of the bacteria with the ecosystem. Using the method of serial sectioning, an equally spaced amount (~130 µm) was removed from the rock using a grinding wheel and polishing powder to obtain a well polished surface.  144 of these surfaces were scanned from sample D501-K49. The scans were rendered into a volume in the Keck CAVES which allowed the exploration and manipulation of 3D data sets. The 2D scans showed 3-10 mm thick largest organic veins with three types of branches expanding away from them. The first branch had elongated fingers that did not reach the next main organic vein. The second had elongated fingers that connected with the next main vein, the third structure had short-stubby fingers with circular end features that did not connect to the next main vein. Using the Keck CAVES, the 2D features were found to be tube-like structures branching off main thick organic inclusions. Analyzing the growth structures of these ancient microbialites through serial sectioning and the Keck CAVES, we are able to identify features that can provide us with more information on the grown of early microbialites.