Date of Award
Master of Science (MS)
W. David Liddell
During the Early Ordovician organic buildups formed in shallow seas across the world. This project contains a literature review on these organic buildups with a focus on those occurring in the warm, shallow seas of North America, but also includes a study on organic buildups formed in the cold water region of Russia. The goal of the study was to characterize these Early Ordovician organic buildups in order to identify similarities and differences in their occurrence. The second part of this project is a preliminary study on organic buildups occurring in the Early Ordovician Garden City Formation in Boss Canyon, Utah.
This project found that warm, shallow-water organic buildups of the Early Ordovician were small scale structures that were typically 1-3 meters in height and several meters in width, with the length variable depending on location. The organic buildups were biotically relatively simple structures formed by algae, lithistid sponges and Calathium with accessory organisms of brachiopods, cephalopods, trilobites, echinoderms, gastropods, ostracods, algal remains and conodonts. The organic buildups are composed of massive to faintly-laminated mudstone to wackestone to packstone to boundstone. Large in situ organisms are found on the organic buildups, while internally they are found as skeletal components. Rock surrounding the organic buildups includes limestone and shale. Channels dissect the organic buildups and some organic buildups show evidence of subaerial exposure. Formation of the organic buildups was dependent on local conditions.
Cold water organic buildups are several meters long and generally less than a meter high. These organic buildups have a calcareous-clay composition. The mound core is composed of clay topped by a carbonate cap and overlain by a hardground surface. Formation of the organic buildups was by dense concentrations of sessile siliceous sponges. Accessory organisms include brachiopods, echinoderms, ostracods, pelmatozoans, bryozoans and conodonts.
Pearce, Heidi, "A Study of the Bioherms of the Early Ordovician Garden City Formation and a Literature Review of Early Ordovician Organic Buildups" (2012). All Graduate Plan B and other Reports. 193.
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