Evaluación petrográfica de la secuencia sedimentaria "Areniscas de El Tambor": consideraciones diagenéticas

Abstract

The sedimentary sequence known as “Areniscas de El Tambor; is located between The Carbonera and Jaji areas in the northwest of the Merida city, Venezuela. This sequence outcrops along the northern flank in the Venezuelan Andes. Neither a definition of sedimentary facies nor a petrography and diagenetic characterization had been conducted on this sequence. Based on field work the sedimentary sequence has an average thickness of about 1850 m. This study was focused in a sandstone litofacies identified in the entire sequence whose average thickness is 1100 m.. The sedimentary sequence was subdivided into three Petrofacies, the lower one consist of cuarzoarenites and sublitarenites, the intermediate one is characterized by grawackes and lithic wackes and the upper one consist of sublitarenites with presence of pyrite, glauconite and coal. The petrophysic and geochemistry analysis show diagenesis that ranges from shallow to intermediate, with epidiagenesis that contributed to the formation of porosity either by fracturing or dissolution.