Gravity and structural architecture of the western North Patagonian region, Argentina

We study the western North Patagonian region of Argentina using gravity and geological methods. The first derivative of the Bouguer anomaly shows a gravity high west of the Limay River and Arroyo Comallo, forming a semicircular pattern, all linked to the Devonian Colohuincul Complex and older rocks. In contrast, the gravity lows are due to Permian granites, Jurassic volcanic rocks, and Jurassic and Cretaceous sedimentary rocks of the Neuquén Basin, with the latter reaching a thickness of 2 km but restricted to the northern part of the area. We identified five groups of geological and Euler lineaments, some possibly formed in the Devonian, with episodic movements during the Permian and Jurassic, and connected to the Limay Fault Zone. Between 257 and 250 Ma, a second group linked to strike-slip regional faults helped form the volcanically derived Los Menucos and Laguna Blanca complexes. From 191 to 187 Ma, the third system of lineaments, marked by rift structures and volcanic calderas and associated with the second rifting episode in the Neuquén basin, was active in the region. The development of pull-apart basins associated with strike-slip faults occurred between 192 and 185 Ma, representing the fourth group. The last group comprises several fault- and curved-acidic-dike swarms, dated at 188 Ma and 187 Ma, and extensional fractures related to dextral movement of the Limay Fault Zone. The Río Limay and Arroyo Comallo between the Piedra del Águila and Comallo localities form the dextral strike-slip Limay fault zone, potentially marking the boundary between the North Patagonian region and the Neuquén Basin.