Estratigrafía de la región al poniente de Puerto Madryn, provincia del Chubut, República Argentina

HALLER MJ

Neuquén

Congreso; VII Congreso Geológico Argentino; 1979

The Tertiary stratigraphy of the Patagonia coast in the Northeast of the province of Chubut is studied. It also comprises some minor ranges located in the West. The basement consists of low metamorphosed sedimentary rocks (La Tranquera Formation) intruded by the La Irene Granite (Permian). Some porphyric rocks of Cerro del Ingeniero Formation are tentatively associated to the same magmatic cycle. This basement is covered by a volcanic sequence (Marifil Formation, Upper Triassic-Middle Jurassic). A Tertiary sedimentary complex is unconformable overlaying the volcanic rocks. The oldest sedimentary rocks, tuffs and terrigenous clastics (Camiña Formation) are supposed to be of a lower Eocene age. Claystones, sandstones and limestones (Sierra Chata Formation) and sandstones and tuffitic mudstones (Catalina Formation) represent the Eocene-Upper Oligocene times. A Miocene sea regression is registered by sandstones and mudstones (Puerto Madryn Formation). During the Upper Pliocene and Lower Pleistocene took place the stripping of the Tertiary deposits and the deve1opment of the aggradation surface of Rodados Patagónicos (Patagonian Gravels). A limited regression, registered by gravels and sands with abundant mollusk shell fragments (San .Miguel Formation) took place during the Holocene.