Applying sandstone petrofacies to unravel the Upper Carboniferous evolution of the Paganzo Basin, northwest Argentina

摘要

A compositional study of sandstones belonging to the lower section of the Paganzo Group (Middle Carboniferous-Early Permian) in the Paganzo Basin (northwestern Argentina) helps unravel the stratigraphic and paleogeographic evolution of the basin. Three morpho-tectonic units constitute the complex basement of the basin: (1) to the east, the igneous-metamorphic basement of the Sierras Pampeanas and Famatina systems; (2) to the west, the Precordillera, made up of Early and Middle Paleozoic sedimentary rocks; and (3) the Upper Paleozoic volcanic arc along the western boundary with the Rio Blanco Basin. On the basis of sandstone detrital modes of the Lagares, Malanzan, Loma Larga, Guandacol, Tupe, Punta del Agua, and Rio del Penon formations, seven petrofacies are distinguished: quar-tzofeldespathic (QF), quartzofeldespathic-metamorphic enriched (QF-Lm), quartzofeldespathic-sedimentary enriched (QF-Ls), mixed quartzolithic (QL), quartzolithic-volcanic (QLv), volcanolithic-quartzose (LvQ), and volcanolithic (Lv). The spatial and temporal distribution of these petrofacies suggest an evolutive model for the Upper Paleozoic sedimentary filling of the basin that includes three "petro-somes": (1) the basement petrosome, a clastic wedge of arkosic composition that diachronically prograded and thinned from east to west; (2) the recycled orogen petrosome, revealing the Protoprecordillera as a positive element in the western Paganzo Basin during the Namu-rian; and (3) the volcanic arc petrosome, recording volcanic activity along the western margin of Gondwana during the Westphalian.