Características sedimentológicas y ambiente depositacional de las rocas aflorantes en la sección estratigráfica a escala 1: 100 de la Formación La Luna, en el sector del Cementerio en el municipio de Gramalote, Norte de Santander.

Abstract

In the municipality of Gramalote, Norte de Santander, more specifically in the Cementerio sector, the sedimentological characteristics and depositional environment of the outcropping rocks in the 1:100 scale stratigraphic section of the La Luna Formation were determined. For this purpose, a 1:10,000 scale mapping was carried out in order to delimit the base and top of the surveyed section, using both the open polygonal method and the swabbing method. The in situ samples were analyzed under stereoscopic magnification, obtaining detailed information on mineralogy, fossil content and internal structures. This study analyzes the depositional environment, which varies from a restricted platform type VIII to an open platform type VII, and from a SS slope platform type IV to deeper areas of the basin, the analysis of the facies characteristics reveals the predominance of carbonatic components, mainly limestone rocks, together with detrital and phosphate materials, these detrital materials, indicative of calm and low energy waters, suggest a deposition in an environment of low input of terrigenous material in the La Aguada member, slow sedimentation allowed the preservation of fine sediments, while the presence of sparite in the bottom sediments suggests a predominance of calcareous material. During sedimentation of the Chejendé and Tímbetes members, chert intraclasts transported from deeper areas by upwelling currents were found; In the Tímbetes member, the presence of rhombic and euhedral grains in phosphatic limestone rocks suggests an incipient dolomitization process, thus reflecting a moderate diagenetic process, this member shows the highest phosphate concentration due to high biological productivity, anoxic or suboxic conditions and high phosphate solubility in the deep marine environment; finally, in the Ftanita del Táchira member, the facial characteristics suggest sedimentation in a transitional, hemipelagic to pelagic environment. This anoxic sedimentation in the basal part of the Ftanita del Táchira member may have been modified by paleoceanographic conditions that allowed the circulation and sedimentation of chert characteristic of this member.