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YOUNG, GORDON A., Petroleos de Venezuela S.A., Caracas, Venezuela

ABSTRACT: Tectonics of the Venezuelan Borderland: An Interpretation of Magnetometer Surveys

Over 46,000 km of shipborne magnetic surveys and over 64,000 km of aeromagnetic surveys cover the offshore Venezuelan Borderland. The information from these surveys has been assembled into a total intensity map, together with its vertical gradient reduction, and interpreted with respect to the regional tectonics.

The distribution and shape of the igneous intrusions and metamorphic rock masses can be clearly recognized as well as the major sedimentary troughs. Areas with similar frequencies and trend directions have been grouped into magnetic provinces in order to better delineate the different structural styles and picture the forces that acted on the basement rocks.

The most prominent structures of the Borderland are the nappes and the major transcurrent faults, along which the provinces moved toward the southeast. In the Margarita Province the Margarita-Testigos and La Blanqilla nappes are the most conspicuous. The Delta Province, to the East, is characterized by the complex compression zones that have moved southeastward along the border of the craton. The La Vela region to the West comprises a complex of overriding magnetic provinces.

In the exploration for traps with possible accumulations of hydrocarbons, the interpretation of the vertical gradient is the most important as it provides considerable detail on structural patterns. The structures determined by vertical gradient maps coincide very well with those determined by seismic methods in those areas covered by seismic, and thusly, the magnetic maps serve as a reliable guide to structures in areas not yet covered by seismic surveys.

AAPG Search and Discovery Article #90988©1993 AAPG/SVG International Congress and Exhibition, Caracas, Venezuela, March 14-17, 1993.