--> ABSTRACT: Sea Level and Surface Current Controls on Late Quaternary Off-Bank Transport from Pedro Bank, a Deeply Submerged Carbonate Platform on the Northern Nicaragua Rise (Caribbean Sea), by James P. Schwartz, Andre W. Droxler, John J. G. Reijmer, Karen S. Glaser; #91020 (1995).

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Sea Level and Surface Current Controls on Late Quaternary Off-Bank Transport from Pedro Bank, a Deeply Submerged Carbonate Platform on the Northern Nicaragua Rise (Caribbean Sea)

James P. Schwartz, Andre W. Droxler, John J. G. Reijmer, Karen S. Glaser

Pedro Bank, an isolated carbonate platform submerged under 25 to 35 m of water on the Northern Nicaragua Rise (Caribbean), exports neritic carbonates into the deep adjacent environments either by settling through the water column or by gravity flows along the sea floor. Both off-bank transport processes are controlled by sea level fluctuations, since the flooding of the bank top within the photic zone during periods of high sea level essentially turns on the neritic production. Here, as in the Bahamas, late Quaternary turbidite layers mostly occur during interglacial highstands. Based on their composition, two types of turbidites have been identified. The neritic type mainly consists of pellet packstones and grainstones with coralline algae, clasts, and Halimeda, whereas the second type consists of pelagic foraminifer grainstones with pteropods, in addition to bank-derived grains such as coralline algae, benthic foraminifers, and Halimeda plates. Accumulation rates of fine bank-derived aragonite (g/cm/ky2) are several times to an order of magnitude higher during interglacial highstands as compared to glacial lowstands within a 40 km wide periplatform halo around the bank.

Contrary to the Bahamas, where the preferential wind pattern (windward versus leeward) has a major impact on off-bank transport direction, Pedro Bank, is instead preferentially affected by the northwesterly surface flow of the Caribbean Current. Despite the relatively deep submersion of Pedro Bank, fine sediments produced on the bank top are dominantly carried into downcurrent periplatform environments. However, very little difference has been observed in the frequency of turbidite layers between cores located upcurrent (southeast) and downcurrent (northwest) of Pedro Bank.

AAPG Search and Discovery Article #91020©1995 AAPG Annual Convention, Houston, Texas, May 5-8, 1995