Abstract

VARGAS-GONZALEZ, Valentina et al. Provenance of the El Cerrito Formation in the San Jacinto Folded Belt: Paleogeographic implications for the colombian Caribbean. Bol. geol. [online]. 2022, vol.44, n.3, pp.39-63.  Epub Nov 21, 2022. ISSN 0120-0283.  https://doi.org/10.18273/revbol.v44n3-2022002.

A provenance study of an Upper-Miocene sedimentary sequence drilled by the ANH-Los Pájaros-1X well was carried out to unravel the sediment sources and sedimentary environments of the San Jacinto Folded Belt. Our findings indicate that the sequence studied was deposited in deltaic systems that oscillated between prodelta-front and delta plain environments. The average ratio of sandstones samples is Q36F24L40; where the lithics identified correspond to andesites, quartzites, shales, granites, mudstones and sandstones, which indicates multiple sources of detrital materials delivered into the basin by a complex fluvial network. Analyses of heavy minerals show a high proportion of hornblende and pyroxene, perhaps implying an igneous source. The minor content of apatite, biotite, muscovite, tourmaline, and zircon suggests a provenance related to felsic igneous rocks, although intermediate plutonic and volcanics or metamorphic rocks cannot be discarded. The maximum deposition age given by the U/ Pb dates indicates that the sedimentary sequence is not older than the late Miocene (9.7-9.1 Ma), which allows a stratigraphic correlation with the El Cerrito Formation. According to available paleogeographic reconstructions for this period, large rivers, and deltaic systems prograded towards NW of Colombia. The main sources of sediments were thus located to the south in the Central and Western cordillera, as well as in paleo-highs of the Lower Magdalena Valley associated with tectonic environments of magmatic arcs and recycled orogens. Contribution of sediments with geochronologic signatures typical of rocks with Panama-Choco Block affinity seem to be evidenced by detrital U/Pb ages between 43.4-40.7 Ma. On the other hand, the frequent presence of late Miocene zircons, together with the high proportion of volcanic lithics suggest the influence of magmatic activity from the Western Cordillera and the Cauca river trough.

Keywords : Northern Andes; Age U/PB Zircon; Conventional petrography; Heavy minerals; Upper Miocene.

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