The Aiuruoca region involves part of Mantiqueira Range (from 1.800 to 2.350 m high) and Alto Rio Grande Plateau (from 900 to 2.000 m high) presenting a complex morphotectonic framework which resulted from two tectonic events (Paleogene and Neogene-Quaternary). The events were recognized by faults mapping and control on drainage rearrangement and distribution and deformation of superficial deposits. The first one, extensional, is related to the Atlantic opening processes, and the second one, transcurrent, to intraplate neotectonics.
The Cenozoic tectonic activity modified the landscape by rearrangements of drainage and relief forms, preferencially along the dextral ENE-WSW and E-W transcurrent zones originated or reactivated during the rifting in Late Cretaceous-Early Tertiary.
The progressive advance of fragmentation towards the hinterland in the Paleogene implicated truncation, tilting and subsidence of ENE blocks, and progressive migration of regional divide to this direction causing parcial capture of the upper interior hydrographic basins by headward retreat that inverted their flow.
Since Late Tertiary, the area has been submitted to transcurrent tectonics with transpressional component and reactivation of earlier structures, with differential uplift of ENE blocks and increasing tilting towards NNW, inverting the tendency of divide migration. This process has provided the rearrangement of the upper basins of the Grande, Preto and Ingaí rivers by capture, diversion and beheading processes indicated by asymmetry and morphological and geological features, with growth of the Aiuruoca basin. Two captures was dated by C14 of organic horizons and paleosoils with 30.070 ± 370 and 7.300 ± 80 y. B.P., and the palaeoenvironment was reconstituted by palynologic analysis.
This activity persists nowadays as indicated by imminent drainage rearrangement processes.
*Supported by FAPESP (95/04417-3) and CNPq (142263/1995-8)