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THE MUD-DIAPIR TREND IN THE EASTERN VENEZUELAN BASIN

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Abstract

The Eastern Venezuelan basin is located south ofthe Serrania del Interior Oriental range, which represents the easternmost branch of the Andean uplift (Figure I). The northernmost boundary of the Serrania del Interior Oriental range, is controlled by right lateral strike-slip motion. It includes the El Pilar Fault system, a major dextral fault, considered to be the main contact between Caribbean and South American plates ; it's dextral movement, seems to have started in the Upper Miocene; current slip rate is about I cm / year and total offset is around 70 km . An igneous - metamorphic and sedimentary Caribbean belt, lying to the north of the El Pilar fault, was progressively thrusted over, against the South American passive margin (from west to east), during the Eocene / Miocene times.Towards the east, the Serrania del Interior Oriental range, ends up against a series of plio / pleistocene grabens (i.e. San Juan) , related to a NE - SW tectonic extension. The mud diapir tract and its related structures occupies an WSW - ENE trending belt that stretches from Tonoro, to the west, to Pedernales in the Orinoco delta. These features, two hundred kilometers long and ten wide, have also been reported offshore and onshore in Trinidad with various degrees of activity that range from mud emanations to mud volcanoes, which occasionally rise above sea level. Also associated to this diapir trend a number of oil and gas seeps as well as asphalt lakes have been discovered. The age of diapirism seems to be restricted to a period from Pliocene to Recent. Seismic transects perpendicular to diapir development evidence both their geometry and growth .
THE MUD-DIAPIR TREND IN THE EASTERN VENEZUELAN BASIN GIRALDO,ALVAREZ, ODEHNAL
Internal
Geodynamique andine Andean Geodynarnics Geodinarnica Andina, 2002
THE MUD-DIAPIR TREND IN THE EASTERN VENEZUELAN BASIN GIRALDO,ALVAREZ, ODEHNAL
Internal
Geodynamique andine Andean Geodynarnics Geodinarnica Andina, 2002
THE MUD-DIAPIR TREND IN THE EASTERN VENEZUELAN BASIN GIRALDO,ALVAREZ, ODEHNAL
Internal
Geodynamique andine Andean Geodynarnics Geodinarnica Andina, 2002
THE MUD-DIAPIR TREND IN THE EASTERN VENEZUELAN BASIN GIRALDO,ALVAREZ, ODEHNAL
Internal
Geodynamique andine Andean Geodynarnics Geodinarnica Andina, 2002
THE MUD-DIAPIR TREND IN THE EASTERN VENEZUELAN BASIN GIRALDO,ALVAREZ, ODEHNAL
Internal
Geodynamique andine Andean Geodynarnics Geodinarnica Andina, 2002
Article
This paper presents a structural and stratigraphic analysis of the foreland-fold-belt of the Eastern Venezuelan Basin and the main conclusions about shale tectonic mechanisms in the area. The deformation of the foreland-fold-belt has been investigated analyzing the growth strata architecture preserved on the structure fold limbs. Three contractional episodes are proposed for the Eastern Venezuelan Basin: 1) Oligocene to middle Miocene, 2) late Miocene to Pliocene and 3) Pleistocene. The first episode produced contractional listric faults inside the shale and long displacement blind thrusts in the underlying Cretaceous units. The second episode produced the deformation of the Cenozoic strata into overlapping east-west-trending, convex northward anticlines that covers more than 200 kilometers in length and 40 kilometers wide, break-through normal faults product of a high sedimentary load that overcomes contraction and the formation of short-displacement blind thrusts in the underlying Cretaceous units. The last episode is related to an oblique compression and the formation of high angle extensional faults with dextral movement and NW-SE strike. The role of the shale tectonics in the evolution implies that shale deforms in two stages: 1) folding and 2) normal faulting of the crest of the anticline (Break through normal faulting). Folding controlled the sediment distribution during most of the Neogene strata, while the normal faulting of the anticlines represent basin potential for hydrocarbon. The best potential hydrocarbon plays in the basin are related to oblique-collision restricted basins and controlled by break-through normal faults and the presence of NW-SE strike faults that connect the HC source with the reservoirs. Results from this research imply that the role of sedimentation is fundamental for the overburden sand distribution and tectonic constrain of the folds.
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