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The AAPG/Datapages Combined Publications Database

AAPG Bulletin


Volume: 65 (1981)

Issue: 5. (May)

First Page: 908

Last Page: 908

Title: Sedimentation on North Shelf of Puerto Rico: ABSTRACT

Author(s): David M. Bush, Zev N. Grossman, Orrin H. Pilkey

Article Type: Meeting abstract


Regional sediment analyses along 100 km of the north shelf of Puerto Rico show the area to be a site of modern sedimentation. Sediments delivered to the steep, narrow, high-wave-energy north shelf by the Rio de la Plata, the Rio Grande de Manati, and the Rio Grande de Arecibo are in or approaching textural and compositional equilibrium with shelf processes. Modern sediments are being deposited over relict shelf sediments which are not in textural or compositional equilibrium. Relict and recent sands are easily distinguished by their contrasting color, composition, and texture.

The river sands are predominantly dark colored and can contain a large percentage of mud. Upon entering the nearshore, they are entrained in the dominant westward littoral and shelf currents produced by persistent northeast trade winds. Minor eastward transport occurs partly as a result of an easterly component of tidal currents. Where terrigenous deposits are continuous between rivers, sediments sources have been delineated using X-ray diffraction of the heavy mineral suites.

The relict calcareous shelf sands are predominantly light colored and of biogenic origin. They are occasionally isolated in nearshore shadow zones behind promontories or exposed in mid-shelf windows. Some mixing of relict and recent sands occurs immediately off the river mouths. The high wave-energy winnows the nearshore sands clean. Mid-shelf to basin transport of mud occurs in a series of storm-generated resuspensions.

A low level of terrigenous contamination of carbonates indicates limited overlap between shelf sediment facies. Indeed, boundaries between sediment types are very sharp, often less than 200 m wide. This suggests localized controls on depositional processes.

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Copyright 1997 American Association of Petroleum Geologists