Quaternary morphology and paleoenvironmental records of carbonate islands
Toomey, Michael R.
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LocationTahaa, French Polynesia
Great Bahama Bank
Here I use a simple numerical model of reef profile evolution to show that the presentday morphology of carbonate islands has developed largely in response to late Pleistocene sea level oscillations in addition to variable vertical motion and reef accretion rates. In particular, large amplitude ‘ice-house’ sea-level variability resulted in long lagoonal depositional hiatuses, producing the morphology characteristic of modern-day barrier reefs. Reactivation of carbonate factories, transport of coarse reef material and rapid infilling of shallow water accommodation space since deglaciation makes these unique sites for reconstructing Holocene climate. Integration of new tropical cyclone reconstructions from both backbarrier reef (central Pacific) and carbonate bank (the Bahamas) settings with existing storm archives suggests a coordinated pattern of cyclone activity across storm basins since the late Holocene. Seesawing of intense tropical cyclone activity between the western Pacific (~0-1000 yrs BP) and North Atlantic/Central Pacific (~1000-2500 yrs BP) appears closely tied with hydrographic patterns in the tropical Pacific and El Niño-like variability. Decoupling of North Atlantic (inactive) and South Pacific (active) tropical cyclone patterns during the mid-Holocene suggests precession driven changes in storm season insolation may constrain ocean-atmosphere thermal gradients and therefore cyclone potential intensity on orbital timescales.
Submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy at the Massachusetts Institute of Technology and the Woods Hole Oceanographic Institution February 2014
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