Delimitation of tectonostratigraphic terranes of the southern-central region of Argentina: aeromagnetic evidences.

Abstract

The geological interpretation of the high-resolution aeromagnetic data of the La Pampa province, in addition to the low-density magnetic information from the region of the Neuquina and Colorado basins, leads to define the precise boundaries of the Chilenia, Cuyania, Pampia and Patagonia terranes, and the Río de la Plata Craton within the study region. The data from the high-resolution. aeromagnetic survey, in particular, are compared and studied in conjunction with all the available geological information. This results in a map of the solid geology of this region largely covered by Quaternary sediments, in which eleven pre-Cenozoic and two-Cenozoic lithomagnetic units are represented. A number of structures of different magnitudes, as well as their relative chronology, are also recognized, i.e., regional faulting, sub-regional faulting/fracturing/shearing and the most conspicuous magnetic fabric of the basement which reflects its main planar structures. Three different basements are distinguished on the basis of their contrasting magnetic character, and are interpreted to integrate the Cuyania and Pampia terranes and the Río de la Plata craton, separated from each other by large-scale discontinuities. In the western part of the study region an additional master discontinuity separates the Chilenia and Cuyania terranes. In the southernmost area, WNW-trending structures are predominant, particularly a master NNE-vergent thrust that indicates the truncation of the cuyana-Pampia suture and is regarded to be related to the collision of the patagonia terrane. An east-west - trending, convex to the north, arch-shaped regional magnetic high and an equally shaped positive residual Bouguer anomaly located immediately to the south of 39°S, whose activation, during the Mesozoic gave rise to the Huincul Dorsal, indicate the interruption of the distinct submeridional structures of the Chilenia, Cuyania and Pampia terranes to the north and would represent the suture zone of the Patagonia terrane with Gondwana.