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Paleontology of the Paleozoic Rocks of the Llanos Orientales Basin, Colombia
By Hernando DUEÑAS–JIMÉNEZ, Victoria Elena CORREDOR–BOHÓRQUEZ and Jorge MONTALVO–JÓNSSON
Paleontological data on Paleozoic fossils of the Llanos Orientales Basin of Colombia is presented here. Some of these data have not been published previously and comes from technical reports prepared for oil operators that now form part of the S.G.C. library. These data contribute to a better understanding of the Paleozoic Era in Colombia. During the Devonian Period, some organisms managed to occupy terrestrial environments. Before that, life occurred exclusively in marine environments. This transgression of life included terrestrial plants that produced fern spores. In the principal depocenters of the Llanos Orientales Basin , up to 6000 m of Paleozoic sediments are present. They include (i) Cambrian strata, determined by associations of acritarchs; (ii) Ordovician strata, identified in many wells by the presence of acritarchs, chitinozoans, very well preserved trilobites (Jujuyaspis spp., Helieranella negritoensis and Triarthus sp.), and graptolites (Janagraptus sp., Didymograptus extensus and Dyctionema spp.); and finally, (iii) the Devonian and Carboniferous strata which are erosional remnants that contain characteristic associations of trilete spores and acritarchs. Sediments from the Late Ordovician, Silurian, and the Permian periods have not been reported in the basin, most likely because they were periods of erosion or non–deposition. The good preservation of the palynomorphs is evidence that the Paleozoic rocks of the Llanos Orientales Basin are not metamorphosed, and should not be considered as the economic basement of the basin.
Keywords: Paleozoic, palynomorphs, acritarchs, trilobites, Llanos Basin.