Print this pageCretaceous Paleogeography and Sedimentation in the Upper Magdalena and Putumayo Basins, Southwestern Colombia
Integrated analysis of seismic, well logs, surface geology and biostratigraphic data from the Cretaceous section of the Upper Magdalena Valley (UMV) and Putumayo basins of southwestern Colombia reveals a diachronous sedimentation pattern, as well as tectonic controls in the mid and late Cretaceous. Cretaceous deposits contain both the source and the main reservoirs in these important hydrocarbon basins.
The distribution of basal Cretaceous deposits in SW Colombia indicates a strong control of the pre-Cretaceous paleo-topography. Cretaceous sedimentation advanced from the northern UMV basin to the Putumayo basin in the south. A paleo-high along the western extension of the Florencia-Vaupés arch may have formed a barrier between the two basins, as suggested by the youngest age of the basal Cretaceous deposits and the reduced thickness of the entire Cretaceous sequence.
Cretaceous deposition initiated in the northern UMV basin with the fluvial sediments of the Yaví Formation in Barremian times, while in the south the oldest Cretaceous sediments are Late Albian in age. In the Oriente (Ecuador) and Putumayo basins, fluvial to tidally-influenced sedimentation began in Aptian times corresponding to the Hollín and Caballos formations respectively, while in the northern Putumayo basin the oldest Cretaceous rocks are of Cenomanian to Turonian age. In the Late Albian-Cenomamian a compressive pulse correlating with the Mochica event in Peru produced structures in the basin, with reduced thickness of the Cenomanian Bambuca shale developed.
Progressive marine sedimentation is also observed in a diachronous pattern, with first marine deposits varying from Aptian in the northern UMV to Turonian in northeastern Putumayo basin. Marine sedimentation continued until the Campanian-Early Maastrichtian when widespread erosion led to the non-preservation of the upper portion of the Cretaceous marine sequence. Coarse grained deposits of this age unconformably overlie marine shales along the western border of the UMV basin, suggesting a rapid uplift of the Central Cordillera.
The Late Maastrichtian to Paleocene sequence was deposited in brackish to fresh-water environments and exhibits in some areas a basal sandstone or conglomerate. The lower erosive contact of this sequence is a paraconformity marked by an abrupt change in depositional environments, associated with a deformation episode well documented in northwestern South America.
AAPG Search and Discover Article #90100©2009 AAPG International Conference and Exhibition 15-18 November 2009, Rio de Janeiro, Brazil