Tectonostratigraphic and Hydrocarbon Framework of the Colombian Offshore Margin from the Magdalena Delta to Panama

Jiang, Xiangyun ¹; Mann, Paul ¹; Escalona, Alejandro ^2
1 Institute for Geophysics, University of Texas at Ausin, Austin, TX.
² Department of Petroleum Engineering, University of Stavanger, Stavanger, Norway.

The offshore margin of Colombia is underlain by the South Caribbean or Sinu belt, a northwest-facing and active accretionary wedge composed of folded and thrusted sedimentary rocks of at least Oligocene-Recent age. Using 10,000 km of industry seismic data and 12 offshore wells, we identify four tectonostratigraphic sequences within the deformed wedge or in the less deformed basins overlying it that range in age from Oligocene to Pleistocene and extend as semi-continuous features for 380 km from the Magdalena delta to Panama. We have mapped 10 major thrusts and associated anticlines which deform the underlying prism and can be followed for 90 km along strike of the prism. Sequence 1 of Oligocene age has low frequency and variable amplitude on seismic data, is deformed as part of the main accretionary prism, and is correlated to coarse conglomerate of the Pavo Formation in 2 offshore wells and onshore outcrops of the Sinu belt in coastal Colombia. Sequence 2 of early Miocene age has low frequency and high amplitude, is 300-1000 m in thickness, is deformed as part of the main prism, and is correlated to mud, silt, sand and limestone of the Floresanto Formation in 8 offshore wells and onshore outcrops. The top of sequence 2 is defined by a widespread angular unconformity of middle Miocene age that separates the highly deformed prism sequences 1 and 2 from the less deformed sequences 3 and 4 deposited in two overlying piggyback basins (San Bernardo and Fuerte). Sequence 3 of late-middle Miocene to Pliocene age has high frequency, variable amplitude, is 250-1500 m in thickness, and is correlated to turbiditic siltstone of the Pajuil Formation in 11 offshore wells and onland outcrops. Sequence 4 of late Pliocene-Pleistocene age has low frequency, low amplitude, is 200-1800 m in thickness, and is correlated to conglomerate of the Corpa Formation in 10 offshore wells and onland outcrops. The piggyback basins are formed during late Miocene to Pliocene age. The San Bernardo basin, located in the modern shelf margin, has a subsidence pattern that may relate with Oblique-slip. The Fuerte basin in the southern part of the area may relate with the Panama subduction. Source rocks in the area correspond to early Oligocene and early Miocene age organic-rich source rocks with generation potential since the middle Miocene. Reservoir rocks are middle Miocene-Pliocene deepwater turbidites sourced by Magdalena River and more localized sources in the adjacent mountain belts.

AAPG Search and Discovery Article #90090©2009 AAPG Annual Convention and Exhibition, Denver, Colorado, June 7-10, 2009