Date of Award

4-2019

Degree Name

Master of Science

Department

Geological and Environmental Sciences

First Advisor

Dr. Stephen E. Kaczmarek

Second Advisor

Dr. William B. Harrison III

Third Advisor

Dr. Peter Voice

Keywords

Niagaran reefs, depositional model, sequence stratigraphy, paleo wind direction, oil and gas reservoir

Access Setting

Masters Thesis-Open Access

Abstract

Depositional models for the Silurian reefs in the Michigan Basin suggest that internal facies are either (i) randomly distributed within a symmetrical reef structure, or (ii) highly asymmetrical and strongly controlled by paleo-wind direction. To further test the applicability of these models, internal facies distributions were mapped using high-resolution core and log data in two sets of Silurian reefs. The results suggest that the relationship between reef geometry, facies distribution and proposed paleo-wind direction is more inconsistent than recently proposed. More specifically, facies descriptions from the Silurian reefs suggest the following. First, overall reef geometry and facies distributions are not controlled by single paleo-wind direction, but rather the overall reef geometry supports the interpretation that multiple paleo-wind directions occurred throughout the time of the reef growth. Facies distributions also don’t support a single paleo-wind direction during the time of reef growth. Second, in addition to the local ecological and hydrodynamic controls, internal facies distributions appear to be controlled by relative sea-level fluctuation in the reef shallow carbonate platforms. This interpretation is based on cyclical facies changes that reflect oscillations in depositional energy conditions and exposure, which reflect changes in circulation and sea level change during Silurian reef growth. The results of this study challenge existing models and suggests that a single paleo-wind direction should not be used to predict reef internal facies distribution in the Silurian reefs.

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