Date of Award:

5-2015

Document Type:

Thesis

Degree Name:

Master of Science (MS)

Department:

Geosciences

Department name when degree awarded

Geology

Committee Chair(s)

W. David Liddell

Committee

W. David Liddell

Abstract

The Bloomington Formation (~425 m thick) is a latest Middle Cambrian (~506.5-505 Ma.), mixed warm water, carbonate and shale unit on the Cordilleran passive margin in northern Utah and southern Idaho. The Hodges Shale and Calls Fort Shale Members are shale dominated and the Middle Limestone Member is a thick carbonate. Fossil diversity and abundance is surprisingly low for a Middle Cambrian carbonate/shale formation. Present, however, are 10-50 cm thrombolite mud mounds, associated with Girvanella oncoliths. These mud mounds represent shallow water carbonates that experienced a small flooding event that gives the mud mounds time and proper conditions to build up. Oxygen isotope values range from -12.9 to -20.8 per mil and analysis indicates that the carbon isotopes are reliable. Carbon isotope results show negative shifts with a range of values of 1.0 to -4.7 per mil. A negative excursion at the base of the Hodges Shale Member may correlate to a similar excursion in the base of the Wheeler Formation that represents the DICE event. The Bloomington Formation represents deposition during a second order sea level rise. Flooding is indicated by shale-dominated packages that overlie carbonates with a shallowing-upward trend in both the Hodges Shale Member and Calls Fort Shale suggesting flooding events at each boundary.

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