Planation surfaces of centralwestern Argentina

Abstract

The region of central western Argentina is situated in a complex geological and tectonic setting with transitional features between major environmental, tectonic, and geomorphological domains. Preserved remnants of planation surfaces, which form the summit of major geological units, occur as discontinuous and isolated exposures with a remarkable geographical distribution along 600 km (33°-39° S). The main goal of this chapter is to summarize the available information and describe the main features and geological context of the planation surfaces preserved in the areas of the San Rafael block, Payenia, the Chical-có plain, and the Chadileuvú block situated in the southern part of Mendoza and western La Pampa provinces, central western Argentina. The common feature of the areas under analysis is the occurrence of remnants of planation surfaces at different altitudes which cut across bedrock of different composition (igneous, metamorphic, and sedimentary units) and varied age ranging from the Middle Proterozoic (Grenvillian age) to Middle Triassic continental sedimentary rocks. The development may have begun in the Triassic, before the Gondwana breakup and more than one planation surface might be present. During the Late Miocene synorogenic deposits covered the planation surface at the San Rafael block, very likely Payenia, and the Chical-có plain; no conclusive evidence is available in the area of the Chadileuvú block. As a result of tectonic activity (circa 7-6 Ma?), the region was fractured, differentially uplifted, and started a general exhumation process that partially removed the Late Miocene sedimentary cover from the San Rafael block and the eastern margin of Chical-có plain.