Publication Date

2014-08-08

Availability

Embargoed

Embargo Period

2016-08-07

Degree Type

Dissertation

Degree Name

Doctor of Philosophy (PHD)

Department

Marine Geology and Geophysics (Marine)

Date of Defense

2013-10-29

First Committee Member

Gregor P. Eberli

Second Committee Member

Peter K. Swart

Third Committee Member

James S. Klaus

Fourth Committee Member

Eberhard Gischler

Fifth Committee Member

Flavio S. Anselmetti

Abstract

Glover’s Reef is a coral atoll located outside of the Belize Barrier Reef, 30 km from the coast of southern Belize. A single-channel seismic survey of approximately 111 km of grid lines reveals that almost 90% of the surveyed lagoon patch reefs sit on Pleistocene topographic highs. In contrast to previous theories that emphasize the role of karst processes during sea-level low stands in creating topography, records from ten rotary cores into modern reef deposits indicated that the Pleistocene topographic highs are comprised of in situ reef facies: “Reefs sit on reefs”. Although Pleistocene reef deposits formed the template for Holocene reef development, the filling of this template was highly influenced by the predominant easterly trade winds of the region. Satellite facies mapping, Holocene reef profiles, coral assemblages, and sediment distribution all reveal asymmetrical windward-leeward patterns on both a platform and a patch reef scale. Rotary cores with 2-9 meters of Pleistocene reef successions contain up to three units separated by exposure horizons. Improvements in Pleistocene dating methodologies have made determining both the relative and independent age of these successions possible, despite poor preservation of original coral mineralogy. Amino acid geochronology indicates that the youngest two Pleistocene units are relatively close in age, while the third unit is significantly older. U-Th dating of corals from the two youngest Pleistocene units places them both in Marine Isotope Stage (MIS) 5e, approximately 117-125k years before present. An exposure within MIS 5e deposits indicates suborbital sea-level change within a sea-level high stand, an event that has only recently been identified in other regions and has not been previously documented for Belize. Documentation of coral reef ecological response to this high frequency sea-level change will help in the identification of this event in other Late Pleistocene reef deposits and may aid the forecast of coral reef response to present and predicted sea-level rise.

Keywords

Atoll; Suborbital Sea-level Cycles, Carbonate Sedimentology; Coral Reef

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