Tectonostratigraphic evolution of the northeastern Maturin foreland basin, Venezuela

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Title: Tectonostratigraphic evolution of the northeastern Maturin foreland basin, Venezuela
Author: Taboada, Gustavo Adolfo
Abstract: The study uses subsidence analysis of three deep wells to basement combined with sequence stratigraphic mapping to show that a 85 ,000 km² area of the Eastern Venezuelan foreland basin in the region of the Orinoco Delta underwent three main stages of foreland -related subsidence that followed a protracted Cretaceous - late Oligocene period of precollisional , passive margin formation . Phase 1 consists of increased foreland basin subsidence in the late Oligocene to middle Miocene (23 - 13 Ma ) at average sedimentation rates of 0 .14 mm /yr . Clastic rocks of Phase 1 include the Freites Formation , a 1 .2 km -thick section of greenish -gray fissile shale and shaly sandstone deposited in shallow marine - neritic environments . Seismic facies show progradation of Phase 1 clastic rocks as a wedge from the NE and NNE . Clastic rocks deposited during the accelerated Phase 2 in the middle to late Miocene (13 -11 Ma at sedimentation rates of 1 .45 mm /yr ) include the La Pica Formation , a 2 .7 km -thick section of gray silt and fine -grained sandstone deposited in shallow marine /coastal proximal environments . Seismic facies show progradation of Phase 2 clastic rocks as a wedge to the northeast . Phase 3 consists of decelerating foreland basin subsidence in the period of late Miocene -mid Pliocene (11 -6 Ma at average sedimentation rates of 0 .86 mm /yr ) . Sedimentary rocks deposited during this period include the Las Piedras Formation , a 1 .45 km -thick section of sandstone , carbonaceous siltstone and shale deposited in deltaic environments . Seismic facies show a progradation of Phase 3 clastic rocks as a wedge to the northeast and east -northeast . Deeper marine environments and more rapid subsidence rates of Phases 1 and 2 are interpreted as an underfilled foreland basin controlled by active thrusting along the Serrania del Interior at the northern flank of the basin . Deltaic environments and slower rates of Phase 3 are interpreted as an overfilled foreland related to rapid seaward progradation of the Orinoco Delta and its filling of the former , dynamically - maintained interior seaway . Paleogeographic maps constrained by wells and seismic lines show a large regression of the Orinoco River towards the west across the Columbus basin and Eastern Venezuelan basin during the late Miocene and the Paleocene . In this foreland basin setting , the effects of thrust -related tectonic subsidence and early deposition of the Orinoco Delta play a larger role in the early Miocene -Pleistocene sequences than eustatic effects .
URI: http : / /hdl .handle .net /2152 /ETD -UT -2009 -08 -224
Date: 2010-06-04

Citation

Tectonostratigraphic evolution of the northeastern Maturin foreland basin, Venezuela. Master's thesis, The University of Texas at Austin. Available electronically from http : / /hdl .handle .net /2152 /ETD -UT -2009 -08 -224 .

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