Holocene-Pleistocene Geology of a Transect of from Isolated Carbonate Platform, NW Caicos Platform, British West Indies

J A Toni Simo¹, Gene Rankey³, Sean Guidry⁴, Christopher E. Harris¹, Humberto Guarin³, Amy Ruf², Tina Hughes¹, Christine Iannello¹, Aram N. Derewetzky², and R Scott Parker^1
1ExxonMobil Upstream Research Company, Houston, TX
²ExxonMobil Indonesia, Jakarta, Indonesia
³University of Miami, Miami, FL
⁴ExxonMobil Develpment, Houston, TX

A marine field and outcrop study of the NW part of the Caicos platform illustrates the Holocene flooding of an irregular Pleistocene substrate of different ages. The Pleistocene substrate extent significantly influences the thickness of Holocene sediments and in combination with circulation the facies types. Field study using 2D seismic (CHIRP) sub-bottom profiler and collocated surface sampling on the shelf north of Providenciales and North Caicos, and platform interior south of Providenciales provide an image of the top-Pleistocene surface, the Holocene sediment thickness, and the present distribution of facies, components and grain size.

Outcrop mapping and Uranium Thorium age dating of shell material from Providenciales infers the growth and sequence development during the Pleistocene. Providenciales has two discontinuous core ridges of eolian and subtidal deposits with ages ranging between 160 and 302 Ka. Cutting the island core and prograding away from it are shingles (up to 4 parasequences) of marine and eolian sediments deposited during 140-90 Ka representing the transgression and high stand of isotopic stages 5e and c. Comparison of the elevation of Pleistocene marine deposits (> 12 m) and published sea level curves for the area indicate the need for uplift or higher sea levels for the island. The Pleistocene surface exerts control in the position of Holocene reefal accumulations, and the position of tidal inlets. A pronounced difference in composition and grains size of Holocene sediments exists between the open shelf north and platform interior south of Providenciales, but maximum thicknesses are similar, close to 2m. On the open shelf, tidal sands grade seaward to coarse skeletal sands, rocky bottoms and reefs. On the platform interior, the sediments are oolitic beaches, patch reefs and peloidal grainstones.

AAPG Search and Discover Article #90078©2008 AAPG Annual Convention, San Antonio, Texas