Print this pageAAPG ANNUAL CONFERENCE AND EXHIBITION
Making the Next Giant Leap in Geosciences
April 10-13, 2011, Houston, Texas, USA
Role of Panama Arc-Indentor for Late Cenozoic Deformation in Colombia and Implications for Regional Distribution of Hydrocarbons
(1) Jackson School of Geosciences, Univ of Texas at Austin, Austin, TX.
(2) Dept of Geosciences, National University, Bogota, Colombia.
Eastward-directed collision of the Panama arc-indentor with continental crust of northwestern South America beginning about 12 Ma (late Middle Miocene) provides a fundamental tectonic control on the distribution of sedimentary basins, active surface faults, geometry of subducted slabs, and distribution of hydrocarbons in Colombia. To establish tectonic controls on slab geometry beneath Colombia and its sedimentary basins, we present two regional tomographic profiles based on over 1674 earthquakes located by the Colombian regional network showing subducted slabs to depths of 275 km and supported by coincident gravity and magnetic profiles. These results constrain the location of the Caldas slab tear, a ~240-km-long east-west tear delineating two separate subducted slabs beneath Colombia. The tear separates a shallowly-dipping (20-30°) subduction zone beneath northern Colombia composed of thick Caribbean crust and the Panama arc-indentor from a more steeply-dipping (30-40°) slab beneath southern Colombia composed of normal oceanic crust of the Nazca plate. The Caldas slab tear is collinear with the extinct east-west Sandra oceanic spreading ridge on the subducting Nazca plate and likely formed as that preexisting, thick-skinned lithospheric weakness was subducted at the Pacific margin of Colombia. We compare our improved slab geometry beneath Colombia to the distribution and basement depth of basins and hydrocarbon distribution in Colombia. This comparison shows that: 1) basins north of the northern shallower dipping slab show more extensive areas of shallow basement and fewer areas of known hydrocarbons than deeper and more hydrocarbon-rich basins south of the tear; 2) the Barinas-Llanos foreland basin of southwestern Venezuela and Colombia adjacent to the Panama arc-indentor shows a deeper and more hydrocarbon-rich foreland that may reflect a directed push with accompanying “hot flash” of fluids from the Andes into the foreland; and 3) the southern Llanos foreland basin opposite the area of steeper subduction exhibits shallower basement and fewer hydrocarbons.