Abstract

ESTEVES, Iván et al. An integrated organic/inorganic  chemostratigraphy study in Paleocene Barco Formation at the Lobaterita River, Táchira State, Venezuela. Rev. Téc. Ing. Univ. Zulia [online]. 2007, vol.30, n.Especial, pp.370-379. ISSN 0254-0770.

In order to achieve an integrated organic-inorganic chemostratigraphic study in Paleocene Barco Formation in the Lobaterita River, San Pedro del Río, Edo. Táchira, Venezuela, several analyses were carried out, those including lithostratigraphic description, bulk rock sampling, columbymetric COT determination, major and minor elements concentration by ICP-OES and neutron activation, bitumen extraction, SARA isolation, as well as saturated and aromatic fractions analysis by gas chromatography coupled to mass spectrometry. Results indicate that the unit under study is poor in organic matter and thermally overmature, and was deposited in internal shallow shelf environment. Section shows eustatic changes evidences, which occurred with episodic and possibly cyclical characteristics. Two major changes were inferred in hydrodynamics of the sedimentary environment: a regressive event and a transgressive one. The organic matter is terrestrial in the basal part of the section changing towards mixed/marine in the intermediate zones, finally terrestrial in the upper part of the section. The unit is composed by a complete stratigraphic sequence and partial one, where at least two changes occurred in the level of the sea.

Keywords : Chemostratigraphy; chemofacies; geochemistry; Barco Formation.