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Carbonates and Evaporites

, Volume 1, Issue 1, pp 13–24 | Cite as

Bioclastic carbonates of Margarita Island, Venezuela, as a key to exploration

  • Nicolas G. 
  • Munoz J. 
Articles

Abstract

Reef-derived bioclastic carbonates interlayered with autochthonous deep marine shales are known from the Eocene section of Margarita Island in northeastern Venezuela. They consist mainly of turbidity-current deposited graded biocalcirudites, biocalcarenites, and biocalcisiltites that usually show the Bouma sequence. They alternate with pelagic shales containingglobigerina and radiolaria. There are also very common intercalations of reworked and sorted, thinly bedded biocalcilutite and biocalcisiltite oozes, most probably redeposited by marine bottom currents. This unit belongs to the Punta Carnero formation which crops out near the Margarita Island International Airport.

A laterally equivalent terrigenous unit known as the Pampatar Formation crops out in the Pampatar area. It is a monotonous alternation of greywackes and shales, which are essentially barren of fossils, establishing clear facies changes between the eastern and western parts of the Eocene flysch. Beautiful sedimentary erosional, constructive and deformational structures are abundant. Especially outstanding is the Bouma sequence, and the intraformational slumps.

The entire Eocene section, estimated at 1250 meters, has several slump and slide structures within the stratigraphical succession. Paleocurrent data indicate both northern and southern source areas that were complex metamorphic ranges bordered by sedimentary units. Phyllite, quartzite and high-rank schists can be found. There are also sources from acid and ultrabasic igneous rocks, volcanics (mainly andesites), Cretaceous limestones and bedded cherts, reefal pre-Eocene limestones, conglomerates, greywackes, and shales. Eocene reefs bordered the western part of the basin. Coarsening-upward bedding allows the differentiation of prograding fan lobes with a turbidite facies model.

The necessity for identification of these bioclastic carbonates in offshore oil exploration, their characteristics, and their geological location within the Caribbean plate have created great interest, and there are excellent costal outcrops on the beautiful Margarita Island.

Keywords

Shale Eocene Turbidite Venezuela Radiolaria 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

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Copyright information

© Springer 1986

Authors and Affiliations

  • Nicolas G. 
    • 1
  • Munoz J. 
    • 1
  1. 1.Universidad Central de Venezuela and Consultores CSCCararasVenezuela

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