DeVries, Stephanie; Giles, David
University of Tennessee at Chattanooga
Place of Publication
Silica deposits are common in Proterozoic carbonate platforms and are interpreted to form early in the diagenetic history of the carbonate strata. Black early diagenetic chert deposits are often associated with evidence of ancient microbial mats, or stromatolites. Proterozoic chert nodules can contain well-preserved microfossils, because silicification occurs rapidly; however, silica deposition has changed over time and it is unclear if similar deposits exist in the Cambrian period after silica-utilizing organisms evolved. The Copper Ridge Dolomite in the Knox Group, northwest Georgia, which was deposited in the late Cambrian to early Ordovician, contains black chert nodules that follow the structure of stromatolitic fabrics. Unlike Proterozoic stromatolites, the Copper Ridge stromatolites do not preserve many individual microfossils, but the patterns observed in the silicified stromatolites provide insight into the silicification process and later diagenetic processes. Petrographic analysis of the Knox Group stromatolites performed in this study identifies the preservation of stromatolitic layers through the precipitation of silica, and multiple episodes of alteration by diagenetic fluids. In an effort to better understand the silicification patterns observed, silicification experiments aimed at recreating silicification in the lab were begun with the aim of comparing the Knox Group stromatolitic fabrics to the fabrics of lab-created silica rock. Correlating these two fabrics can help identify the geochemical environment of silicification of the Knox Group stromatolites during the late Cambrian and early Ordovician.
B. S.; An honors thesis submitted to the faculty of the University of Tennessee at Chattanooga in partial fulfillment of the requirements of the degree of Bachelor of Science.
Knox Group; Geology, Stratigraphic--Cambrian; Geology, Stratigraphic--Ordovician; Geology--Georgia
Ritchey, Evan, "Petrographic observations of stromatolites in the late Cambrian to early Ordovician Knox Group, Northwest Georgia and their relationship to stromatolitic fabrics over geologic time" (2023). Honors Theses.