Abstract

MEDINA, Rubén A; SCASSO, Roberto A  and  MEDINA, Francisco A. Geología y estratigrafía de los bancos fosfáticos del cretácico inferior en el área del Cerro Salado, Cuenca Neuquina, Argentina. Rev. Asoc. Geol. Argent. [online]. 2016, vol.73, n.4, pp.520-537. ISSN 0004-4822.

The geological map and sedimentological study of the cerro Salado and surrounding areas in the Neuquén Province was carried out, with emphasis in the study of the Vaca Muerta and Quintuco Formations. The Vaca Muerta Formation is constituted by 20 m of black shales and bears early-mid Berriasian ammonites. The Quintuco Formation is 218 m thick and it was informally divided into three members constituted by varying proportion of gray shales and sandstones, fossiliferous limestones and coquinas, and thin tuff beds. It bears middle Berriasian to early Valanginian ammonites. The phosphatic beds in the Quintuco Formation are wackestones, bioclastic rudstones and hybrid sandstones forming condensed beds with variable mechanical reworking. They were grouped into four phosphatic intervals. Phosphatic particles are mainly nodules and subordinated, partially or totally phosphatized shells. The Vaca Muerta Formation was accumulated on external ramp to basin environment. The Quintuco Formation deposits are assigned to middle to outer ramp environments. Water depth variation was caused by sea-level oscillations. On average water depth was less than expected according to the previous paleogeographic sketch maps. This might be caused by the synsedimentary uplift of the Dorso de los Chihuidos a large structure located few tens of km to the east of the cerro Salado area. The phosphogenesis took place during sea highstands and low clastic sedimentation rates, whereas reworking by waves and currents and concentration of phosphatic particles occurred during periods of sea-level rise and fall.

Keywords : Phosphates; Quintuco Formation; Cerro Salado; Neuquén Basin; Lower Cretaceous.

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