Publication Date

2014-06-20

Availability

Open access

Embargo Period

2014-06-20

Degree Name

Master of Science (MS)

Department

Marine Geology and Geophysics (Marine)

Date of Defense

2014-05-13

First Committee Member

Gregor P. Eberli

Second Committee Member

Donald F. McNeill

Third Committee Member

Larry C. Peterson

Fourth Committee Member

James S. Klaus

Abstract

The record of sea-level oscillations during the last interglacial highstand comes from different geological archives around the world and from the marine oxygen-isotope record from deep-sea cores. In this study, tidally influenced ooid shoals of the Miami Limestone and coeval deposits in the Bahamas were chosen for to document the record of sub-orbital sea-level oscillations within the last interglacial highstand, Marine Isotope Stage 5e (MIS 5e). This study combines detailed sedimentological and stratigraphic investigations of cores and outcrops of the Pleistocene Miami Limestone with a LIDAR-based digital elevation model (DEM) to relate the facies of the ooid sand body to the geomorphologic structure and depositional geometries. The oolitic facies of the Miami Limestone is approximately 300 km2. Using the precise LIDAR-based DEM, two morphologically distinct areas are observed in this ooid sand body: (1) Tidal bar and channel system and (2) a prograding barrier bar. Two main facies, mottled and cross-bedded, are identified within the oolitic facies and related to the depositional environment. In several cores, characteristic features of subaerial exposure are found, such as dissolution, red staining, caliche crusts, and burrow-filling quartz. Two U/Th age dates, <155.2 ± 1.1 kyrs and 126.9 ± 0.9 kyrs, respectively, indicate that this exposure horizon formed during the last sea-level highstand (MIS 5e), thus documenting a sea-level oscillation within MIS 5e. It is likely that the seaward accretion of the prograding barrier bar to the tidal bar and channel system is related to the MIS 5e sea-level oscillation. Thus, the oscillating sea level during MIS 5e is largely responsible for sedimentological complexity and stratigraphic heterogeneity within the Miami Limestone. The surface morphology of the Pleistocene Miami Limestone is very similar to portions of the modern ooid shoal systems in the Bahamas. In addition, comparison of the elevations of the shoal crests from the Miami Limestone with time-equivalent oolitic grainstone shoals in the Bahamas (Ocean Cay and New Providence Island) yielded several meters of difference. These shoal crest elevations provide an estimation of the amplitude of sea-level oscillation during MIS 5e, which is up to 17 meters. The implications of these high-frequency sea-level oscillations of several meters amplitude during MIS 5e are twofold. First, it indicates that rapid climate changes and concomitant waxing and waning of ice sheets can occur within warm periods. Secondly, the depositional heterogeneity and stratigraphic complexity observed in the Miami Limestone are likely a combined result of syndepositional topography and the sea-level oscillations during MIS 5e.

Keywords

sea-level changes; Miami Limestone; ooid shoals; reservoir heterogeneity; climate changes

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