Delimitation of the Paranapanema Proterozoic block: A geophysical contribution

Abstract

This study focuses on the basement structure of the Paran Basin in South America, based on geological and geophysical data. It is a large intracratonic basin formed from the Late Ordovician until the Cretaceous, when a sequence of continental flood basalts eruptions covered the entire basin, preceding the break-up of Western Gondwana. Isostatic modeling was applied to large gravity surveys comprising more than 12,000 gravity stations. The residual Bouguer anomaly pattern, representing the crustal contribution of the crystalline basement, as well as the sedimentary and volcanic layers of the basin, reveals similarities between the basement gravity signature and the exposed rock. The stress patterns of the Late Ordovician and Cretaceous tectonic events present a geographically coincident maximum, and the correlation between gravity highs and the main attenuation (beta factor) suggests the presence of some preexistent suture zones. The resultant mosaic of gravity blocks and the location of major faults give support to the presence of an important Proterozoic cratonic feature, here referred to as Paranapanema block.