Chronology of Cenozoic tectonic events in western Venezuela and the Dutch Antilles Islands based on integration of offshore seismic reflection data and onland geology




Gorney, David Luke

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Newly acquired BOLIVAR seismic reflection data from offshore western Venezuela and the Dutch Antilles are combined with existing geologic and geophysical data sets to examine the complex chronology of tectonic events affecting the onshore Falcon basin and the adjacent offshore basins. This study also describes the seismic acquisition, processing, and interpretation methods applied to the BOLIVAR seismic reflection data and used in this study. Three tectonic phases are constrained using these data: 1) Paleogene back-arc opening of the 3 to 6 km thick Falcon-Bonaire basin is the initial tectonic phase that occurred along east-west striking normal fault systems that have locally been inverted by later tectonic phases. These normal faults control the oldest depositional sequences and parallel the trend of the Bonaire basin. 2) northwest-striking normal faults crosscut these older normal faults and form deep submarine rifts that contain up to 4 km of sedimentary fill, forming deep water channels between the Dutch Antilles islands. Offshore well data and the age of onshore sediments in the Falcon basin indicate that this second phase rifting occurred in the late Oligocene through the early Miocene. 3) inversion of the Falcon basin commenced during the middle Miocene; this inversion phase is reflected in the present-day pattern of east-northeast-trending fold belt that can be traced over 200 km in the Falcon basin; a second fold-thrust belt (La Vela) can be traced over a distance of 175 km parallel to the Falcon coast; restoration of imbricate thrusts seen on seismic lines perpendicular to the Falcon coast indicates a minimum of 7 km of northeast-southwest directed thin-skinned shortening


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