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The AAPG/Datapages Combined Publications Database

AAPG Bulletin

Abstract


Volume: 52 (1968)

Issue: 3. (March)

First Page: 539

Last Page: 539

Title: Continental-Shelf Sediments Off Eastern Venezuela: ABSTRACT

Author(s): Neil J. Maloney

Article Type: Meeting abstract

Abstract:

The continental shelf between Carupano and Barcelona, Venezuela (63° to 64° 45^prime W. long.), exhibits large variations in size and topography. East of Margarita Island the shelf is 80-100 km wide. The southern, landward part is an east-sloping depression which extends from a depth of 20 fm east of Margarita to more than 63 fm west of Trinidad. The northern border of the depression is formed by the bank passing from Margarita to Los Testigos Islands. It is 12 to 20 fm deep except at Daring Shoal which shallows to 4 fm.

The depression is covered with olive-green silt containing 20-40 percent sand. Calcareous sand, rich in shell material, occurs on the bank. Algae and corals are abundant in the samples from Daring Shoal. Silty sand is present north of the bank to a depth of 100 fm. Silts with less than 5 percent sand occur below this depth.

An open shelf, 40 km wide, is north of Margarita. The sediments range from clayey silt to silty sand. Narrow, shallow straits characterized by strong currents are south of Margarita. Sand and gravel are the dominant sediment types in the straits.

West of Cumana the shelf is less than 5 km wide. The shelf and upper slope to 110 fm are covered with calcareous sand; olive-green, clayey silt with less than 5 percent sand occurs below this depth. The highest concentrations of sand are on the central and outer parts of the shelf, suggesting that it is a relic sand.

Islands, bays, and gulfs are the main topographic features on the shelf between Mochima Bay and Barcelona. The outer parts of the bays contain calcareous sand, and the inner, more protected, parts are covered with sandy to clayey silts. The alluvial sand is being deposited on intrabay deltas. North of the islands the shelf is 4 to 8 km wide. Sands are present in the east but grade into silt and clayey silt on the west opposite Barcelona.

The sediment distribution is related to the bottom topography, ocean currents, and depth. Fine-grained sediments have accumulated in the depressions and protected areas. The topographic highs and open-shelf areas contain calcareous sand. No sand occurs in the surface sediment at depths greater than 110 fm.

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