Evidencias bioestratigráficas de los procesos erosivos ocurridos durante el Mioceno Medio. Estados Anzoategui y Monagas. Cuenca oriental de Venezuela.

• Autores: C. de Guerra, M. Bolívar, N. Di Gianni, H. Sánchez
• Localización: Geotemas (Madrid), ISSN 1576-5172, Nº. 3, 1, 2001 (Ejemplar dedicado a: XIV Congreso Nacional de Sedimentología, IV Congreso del Cretácico de España), págs. 185-186
• Idioma: español
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• Resumen

  • Recent biostratigraphic studies, based on palynomorphs, foraminifera and calcareous nannofossils analises, in addition with sedimentological and well log characterization, have confirmed the tectonic evolution and magnitude of the erosive processes occurred during Miocene time in the eastern basin ofVenezuela. In the study area, the stratigraphic section is represented by a Cretaceous marine sequence deposited in a passive margin tectonic regime, a Paleogene sequence which reflects minor erosive effects or hiatuses, and a Neogene sedimentary package deposited in a very active margin. During the lower part of the early Miocene, as a consequence of the Caribbean plate drift, the platform subsided progressively to the south and southeast, the shoreline is oriented southward and the main detritic source is located in a northwest direction. At the end of the early Miocene-lowermost middle Miocene, compressive effects continued and the Pirital block is uplifted.

    Over 5,500 meters of Cretaceous and Tertiary sediments previously deposited on a passive margin regime were eroded. Well P11 shows a Cretaceous-Tertiary boundary represented by Barremian sediments overlain by a middle Miocene unit. During middle-late Miocene the Pirital block deepens and rapidly dips to the south. On top of this paleosurface, the Morichito Fm. is deposited reworking Cretaceous and Tertiary strata formerly eroded. In the wells P11, P6 and P7 this lithostratigraphic unit exhibits conditions of restricted marine environments. A major compressive tectonic event took place during the late Miocene and the Pirital high is formed. A great part of the middleMiocene Morichito Fm. dissappeared by erosion, as can be observed in well P5 where it is totally absent. Over 1,500 meters of sediments were eroded during this time.