TECTONIC AND CLIMATE INDUCED UPHEAVAL OF THE NORTHERN ANDES DURING THE LAST 12 MY

We document the collision of the, -Cocos plate-, Cabo Corrientes aseismic Ridge against northern South America (at ~7ºN) during the middle Miocene and explore how climate conditions might have foster a major orogenic pulse in the Andes of Colombia. We anticipate that similar to the central and southern Andes, mountain upheaval is related to the infilling of the trench, climate, the morphology of the subducted plate and the degree of lubrication of the coupling zone. Seismic, gravimetric, magnetometric, well logs, field data and bathymetric elevation models suggest that tectonic segmentation of the northern Andes and the location of climate-induced sediment yield to the Panama trench might have resulted in regional differences in upheaval intensity. The Garrapatas Fault, located at the inflection point of the arc, is interpreted as a paleo-transform fault responsible of segmentation in western Colombia. While the northern and southern segments are characterized by a rough basaltic seafloor, chaotic sedimentation over the trench, a relatively dry coupling zone, large magnitude earthquakes, high-angle landward dipping normal faults, mountain uplifting that reaches 4 km and Quaternary volcanic activity, the central segment is characterized by a smooth seafloor and a trench infilled by laminated sediments, a coupling zone that is relatively wet, low magnitude earthquakes, major strike slip faults, and Quaternary volcanic centers that progressively disappear northward. Similar to today, climate conditions depend on the mean position of the ITCZ and the intensity of the Choco, low atmospheric, jet, paleoceanographic evidences suggest that the paleo-Choco jet might be absent between ~12 and ~8 Ma. With the upheaval of the Western Cordillera and Serrania del Baudo the paleo-Choco jet would have found an effective barrier thus creating the Choco rainshadow, except for the ~12 to ~9 Ma interval.