Abstract

RAMIREZ S, DIEGO A; LOPEZ C., ADRIANA; SIERRA L., GLORIA M.  and  TORO V., GLORIA E.. AGE AND PROVENENCE OF THE VOLCANICLASTIC SEDIMENTS OF THE COMBIA FORMATION IN SOUTHWEST ANTIOQUIA - .. Bol. cienc. tierra [online]. 2006, n.19, pp.9-26. ISSN 0120-3630.

Petrographic and paleocurrent studies carried out within the Combia Formation, Antioquia and Caldas states- , suggest that this formation formed from volcanic and volcaniclastic flows originated east and west of the present Cauca river valley. Fission track studies in zircons obtained in different stratigraphic sections, also within the Combia Formation, yield Cretaceous, Late Paleocene - Early Eocene and Late Miocene ages, which have been interpreted as being the result of syntectonic events generated along the Romeral Fault System, where reworking of both, the cretaceous basement and the Amagá Formation (Oligocene-Miocene), took place at the same time as the volcanic events, sometime between 10 and 6 M.a. Among all fission track ages obtained in this study there is one in ash falls with no reworking, that stands out: 53,4 ± 1,4 Ma .This result suggest that the volcanic activity associated with the Combia Formation could have begun earlier, in Paleocene, and no in Miocene as has been commonly accepted.

Keywords : Combia Formation; Neogene Vulcanism; Paleocurrents; Fission Tracks; Petrography.

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