Abstract

LUGO, Patricia; TRUSKOWSKI, Irene; LOPEZ, Liliana  and  LO MONACO, Salvador. Geochemical and biostratigraphical evaluation of the type locality of the querecual formation outcropping at northeastern Anzoátegui state, Venezuela. Rev. Fac. Ing. UCV [online]. 2009, vol.24, n.2, pp.27-37. ISSN 0798-4065.

Redox conditions of sedimentation and foraminifer biostratigraphy analysis were performed on rocks from the Querecual Formation, the main source rock of the eastern Venezuelan crude oil. The objective was to determine the oceanic anoxic events (OAEs) in this section and correlate them with worldwide OAEs. These events favour preservation of the organic matter, with the consequence of high total organic carbon concentration (TOC) and high V/Cr, V/V+Ni, Cu+Mo/Zn, U/Th ratios. The chronostratigraphy was determined by foraminifer biostratigraphy. The TOC, trace and rare earth elements concentration data were integrated with the foraminifer biostratigraphy. The results show that high TOC values are located in the stratigraphic intervals of Late Cenomanian, Late Turonian, Coniacian and Santonian; and V/Cr, V/V+Ni, Cu+Mo/Zn, U/Th ratios indicate anoxic conditions that diminish roughly from bottom to top; with the Turonian stratigraphic intervals presenting the higher levels of anoxia. Rare earth elements (REE) concentrations, especially U enrichment, also confirm anoxic conditions in this stratigraphic section

Keywords : Querecual Formation; Oceanic Anoxic Events (OAEs); Foraminifer biostratigraphy; Redox indicator elements; Cretaceous.