Abstract

BARBOSA-ESPITIA, Ángel Antonio; PARDO-TRUJILLO, Andrés  and  FOSTER, David. Provenance of Lower Eocene strata of the San Jacinto Fold Belt (Colombian Caribbean): paleogeographic, and magmatic implications. Bol. geol. [online]. 2025, vol.47, n.3, pp.13-38.  Epub Nov 10, 2025. ISSN 0120-0283.  https://doi.org/10.18273/revbol.v47n3-2025001.

The Eocene infill of the San Jacinto Fold Belt (SJFB) contains information of the paleogeographic and magmatic evolution of the northwesternmost corner of the Andes. This information is clue to find prospective rocks for hydrocarbons and CO2 storage reservoirs. In this study, we report new sandstone petrography and detrital zircon U-Pb geochronology analyses from three Lower Eocene boreholes drilled at two locations in the SJFB in order to investigate the provenance, paleogeography and magmatic contribution to the basin. The combined provenance analysis reveals multiple sources of detritus, including arc-like igneous, metamorphic and sedimentary rocks with two main U-Pb age populations (Cretaceous-Paleogene and Permian-Triassic). These ages and composition of the detritus are consistent with rock sources in the basement of the Lower Magdalena Valley (LMV) and the Central Cordillera (CC), transported to the SJFB by a short-distance drainage network. Eocene zircons found in the studied rocks suggest that arc magmatism was locally active with sources located at the Sierra Nevada de Santa Marta (SNSM) or nearby. Furthermore, vertical and geographic variability of sandstones compositional maturity in the studied wells seem to be controlled by the depositional paleoenvironment, being the sandstones from the deeper northern part of the basin more mature (less proportion of lithics in the QFL diagram) than their shallower southern counterpart.

Keywords : Caribbean basins; Lower Magdalena Basin; Paleogeography; Northern Andes; Provenance; Magmatism.

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