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The AAPG/Datapages Combined Publications Database

AAPG Special Volumes


Memoir 108: Petroleum Geology and Potential of the Colombian Caribbean Margin, 2015
Pages 247-269

Chapter 10: Earthquake, Tomographic, Seismic Reflection, and Gravity Evidence for a Shallowly Dipping Subduction Zone beneath the Caribbean Margin of Northwestern Colombia

Rocio Bernal-Olaya, Paul Mann, Carlos A. Vargas


Earthquake hypocenter relocations, earthquake focal mechanisms, P-wave Previous HitvelocityNext Hit anomaly tomography, interpretation of deep-penetration seismic reflection lines, and gravity modeling are integrated to define an ESE, 110°-dipping zone of shallow subduction beneath northwestern Colombia. These data define a 15- to 16-km-thick (9.3–9.9 mi), late Cretaceous oceanic plateau (Caribbean plate) that is actively subducting with anomalous low Benioff zone seismicity at a Previous HitdipNext Hit of 3–8° over a down-Previous HitdipNext Hit distance of 200 km (124 mi) beneath a deformed sedimentary wedge (South Caribbean deformed belt). At a down-Previous HitdipNext Hit distance of 450 km (280 mi) from the frontal thrust of the accretionary wedge and at a Previous HitdepthNext Hit of 130 km (81 mi), tomographic data show that the largely aseismic, subducting Caribbean plate bends and steepens to a Previous HitdipNext Hit of 28°–50°. In the Previous HitdepthNext Hit range of 80–130 km (50–81 mi), tomographic data show that the subducted Caribbean slab exhibits a low-Previous HitvelocityTop anomaly that we interpret as evidence for slab delamination and enhanced dehydration by rising asthenosphere. Tomographic data beneath the middle Magdalena Basin of northern Colombia show a thick, cold continental lithosphere (ca 60–100 km [37–62 mi]) while gravity data beneath the lower Magdalena Basin show a thin continental crust (24–27 km [15–17 mi] thick) beneath which the Caribbean slab dips in the range of 40–50°. Minor subduction-related volcanism is present in the eastern Cordillera likely as a result of shallow subduction limiting the size of the mantle wedge that is needed for slab melting and arc-related volcanism. Understanding the subduction setting of northern Colombia is fundamental for understanding its heat flow, tectonic history, controls on subsidence, and other parameters needed for petroleum exploration both onshore and offshore.

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