Abstract

GONZALEZ DIAZ, Emilio F  and  DI TOMMASO, Inés. La depresión del "bajo" del diablo" (NE del Chubut): Una propuesta geomórfica acerca de su origen y su evolución. Rev. Asoc. Geol. Argent. [online]. 2013, vol.70, n.2, pp.279-290. ISSN 0004-4822.

The Bajo del Diablo depression is located in the NE of Chubut Province. Its outer and inner morphology are analyzed. Their origin by deflation is proposed, an schematic layout shows the geomorphic evolution developed during the Quaternary climatic change. Unfortunately, absolute time reference is not available. A protoriver Chubut developed a local psephitic alluvial fan or upper level (Pa, Pm and Pb) during Sangamon Interglacial times (±120.000 ybp). A pre-river Chubut built the medium level ( T1 and T2). Denudation exhumed Tertiary friable sediments, as a core surrounded by the coarse psephite´s levels. Cold, dry and windy condition were established during the Last Glacial time. Deflation and weathering processes began the core overdeepening. This process developed a shallow gently sloped depression (Pfannen). Latterly in a wet pluvial interval an ephemeral lake developed. Its progressive reduction -shown by many littoral ridges, any of them set at lower height- meant that again the previous cold, dry and windy conditions appeared. Deflation again overdeepening the depression. During this process the bedrock primary relief of the Jurassic volcanic rocks were exhumed. With the end of glacial times, new wet conditions dominated, fluvial and mass-wasting processes enlarged the depression as it is today, with abrupt slopes and more depth (Wannen). Two schematic profiles show the geomorphic feature connection.

Keywords : Deflation; Ephemeral lake; Littoral ridge; Pluvial interval; Last Glaciación.

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