Title

Seismic analysis of paleocurrent features in the Florida Straits: Insights into the paleo-Florida Current, upstream tectonics, and the Atlantic-Caribbean connection

Date of Award

2005

Availability

Article

Degree Name

Doctor of Philosophy (Ph.D.)

Department

Marine Geology and Geophysics

First Committee Member

Gregor Eberli, Committee Chair

Abstract

Although numerous studies have constrained the timing of oceanographic change over the past 25 My in the Caribbean and Atlantic through geochemical proxies, there is no complete and direct record of the shallow-water limb of North Atlantic circulation. The purpose of this study is to provide a direct record of the history of the paleo-Florida Current by utilizing the paleo-geomorphic record. Current derived geomorphic features identified in multi-channel seismic data record the temporal evolution of the Florida Current. The age control for these Neogene deep-water sediments comes from the correlation of Ocean Drilling Program Leg 166 dates into the seismic data. Additional Cretaceous-Paleogene ages come from the Great Isaac Well-1, located on the northwest corner of Great Bahama Bank.Currents in the Florida Straits are capable of forming both erosive and constructional sedimentary features including erosive channels, deep-water discontinuities, sediment waves and drift deposits. The geomorphic record indicates that the upper limb of the North Atlantic MOC varied in concert with the deep-water limb of the MOC, and with shoaling of the CAS. Current activity through the seaway decreased around 15 Ma, about the same time as Atlantic deep-water cooling and the slow down of thermohaline overturn. Initial shoaling of the CAS strengthened the paleo-Florida Current around 12.2 Ma, at the same time as the North Atlantic MOC began to increase. A strengthening of flow at 6.4 Ma, ∼2 My before observed salinity increases in the Caribbean, suggests that enhanced thermohaline overturn in the North Atlantic was not solely related to salinity changes in the western boundary current. Shoaling of the seaway as early as the late Miocene may have been responsible for an invigorated MOC. A decrease in the flow of currents around 3.6 Ma suggests a decrease in the North Atlantic MOC took place that was unrelated to closure of the CAS.In contrast to the Florida Straits, the Santaren Channel has been a deep-water reentrant since before the Middle Cretaceous. Opening of the channel to the Florida Straits was the result of thrust-fault loading that led to progressive drowning of carbonate platforms away from the Cuba-Bahama collision zone. During foreland basin evolution, several platforms drowned and became buried by deep-water sediments. Drowning occurred earliest in the southernmost region in the Late Cretaceous and latest in the northernmost region in the early Miocene. The progressive drowning away from the collision zone indicates that long-lived thrusting and loading in the Cuba-Bahama collision zone, rather than sea-level changes, caused the platforms to drown.

Keywords

Geology

Link to Full Text

http://access.library.miami.edu/login?url=http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&res_dat=xri:pqdiss&rft_dat=xri:pqdiss:3177065