THE AMAGA FORMATION (EOCENE?-MIOCENE) IN THE CAUCA-PATIA DEPRESSION: A RECORDER OF MAJOR MORPHOTECTONIC AND PALEOGEOGRAPHIC EVENTS BETWEEN THE WESTERN AND CENTRAL CORDILLERAS

The Amaga Formation (AF) is a coal-bearing, continental siliciclastic succession presently situated in the Cauca river depression between the Central and Western cordilleras. The sequence is intruded by intermediate porphyritic bodies and covered by volcaniclastic units. It was deposited in discrete events from the Eocene(?)-Oligocene to the Late Miocene, experiencing intervals of inversion (uplift-exhumation). These characteristics make it suitable for documenting morphotectonic, magmatic and paleogeogprahic process in the Northern Andes, particularly in relation with the docking of the Panama-Choco block (PCB), Nazca-South America subduction, Miocene magmatismc, and pulses of uplift exhumation of the cordilleran massifs in its flanks and the basin itself.

Through more than 5 years of international and interinstitutional collaboration we have produced abundant data from the AF and neighboring cordilleran massifs allowing us to generate a robust reconstruction of morphotectonic and sedimentary process in this geographic/geologic milieu. Our work includes outcrop and borehole datasets in sediment-stratigraphy, U/Pb geochronology + Hf (detrital and ingenuous/metamorphic zircons), integrated provenance analyses (heavy minerals, zircon morphology, geochronology, etc.), apatite and zircon thermochronology, paleomagnetic and structural studies, palynology, vitrinite reflectance, coal chemistry, etc. Integrated analyses and interpretation of such datasets allows us to produce a coherent morphotectonic and paleogeographic history for this important segment of the Northern Andes, right on the area of direct influence of the PCB docking and continued collision of the PCB with South America, illuminating subjects such as uplift and exhumation of cordilleran massifs, sediment production-routing-deposition, coal-bearing basin development (burial/exhumation, net changes in paleoelvation, etc.), paleoclimate-paleoecology, etc.