An investigation of the provenance and post-depositional thermal history of the Cenozoic Amagá Formation from the transition between the Cordillera Central and Oriental, Colombia

Abstract

The Oligo-Mioceno Amaga Formation comprises at least 1500 m of non-marine quartzose and lithic sandstones, carbonaceous shale and coals preserved in a roughly linear basin along the Cauca Valley, west of the Romeral fault system in the transition between the Western and Central Cordillera of Colombia. We have used AFTA® apatite fission track analysis and ZFTA zircon fission track analysis to provide unique constraints of the provenance and post-depositional the thermal and burial histories of a suite of Amaga Formation sandstones from the vicinity of Santa Fe de Antioquia (near Medellin). Independent constraints on the maximum temperatures experienced by associated coal seams have been determined from vitrinite reflectance data. These results have important implications for the source of the Amaga Formation sediments and the tectonic evolution of the adjacent Altiplano Antioqueno of the Central Cordillera, where AFTA data show clear evidence of kilometre-scale denudation during the Late Eocene to Early Miocene (40 to 20 Ma) and since the late Early Miocene (18 to 0 Ma), overlapping with the deposition of the Amaga Formation. The ability of AFTA to provide direct constraints on the time at which both sedimentary and “basement” sequences were uplifted and eroded in tectonically complex regions provides a powerful tool for understanding the tectonic evolution of Colombia during the Cenozoic.