Abstract

SILVA-ARIAS, Alejandro; PAEZ-ACUNA, Liliana Andrea; GOMEZ-GUTIERREZ, Pedro David  and  RINCON-MARTINEZ, Daniel Andrés. Petrographic study and possible sources of the San Cayetano formation basal clasts to the south of the San Jacinto fold belt, north of Colombia. bol.geol. [online]. 2019, vol.41, n.1, pp.15-28. ISSN 0120-0283.  https://doi.org/10.18273/revbol.v41n1-2019001.

It is considered that the basal clasts of the San Cayetano Formation in the San Jacinto Fold Belt (CPSJ) reveal part of the tectonic events related to the South American margin interaction with an intraoceanic magmatic arc of the Caribbean Plate. These clasts come from an intra-oceanic arch dismantling (88-73 Ma), and from arch accretion to the South American continental margin; therefore they contribute to the South Caribbean post-collisional tectonics understanding. This study is focused on clasts lithological diversity analysis in the San Cayetano Formation basal conglomerate levels, in order to establish its source and support its origin respecting to old magmatic systems configuration existing in the Colombian Caribbean. The basal clasts at the south of Magangué High contain mafic affinity igneous clasts (basalts with and without vacuoles, and gabros) and metamorphic clasts (serpentinites, ortogneis and amphibolites) of an ultramafic-mafic protolith. The San Cayetano Formation clasts (Lower Paleogene) are tectonically related to an Arc environment, revealing rapid erosion and a minimal transport effect (Not Dissected to Dissected); therefore, these clasts come from sources close to the CPSJ, with a similar tectonic configuration to the current NW Colombian Caribbean margin.

Keywords : Clasts; San Cayetano Formation; San Jacinto Fold Belt; Magangué High.

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