The middle valley of the Doce river is situated at the central to eastern portion of the Minas Gerais State (SE Brazil) and corresponds to a depressed area associated with a tectonically-controlled evolution during Cenozoic times. In this area, it was carried out a regional geomorphologic investigation based on the analysis of the altimetric variations and on the fluvial dissection degree. Detailed structural analysis of the joints and faults affecting Cenozoic sediments support the interpretation of the neotectonic controls on relief compartmentalization. Three major geomorphologic compartments could be distinguished, as following: a) Doce River Middle Valley (MVRD) Depression, that is characterized as an hilly domain with altimetric ranges between 200 and 500 meters and low fluvial dissection (from 50 to 200 meters of altimetric difference associated with fluvial dissection); b) High Topographic Domain at the Eastern Side of the MVRD Depression, characterized by altimetric ranges between 500 and more than 1,100 meters and medium to high fluvial dissection (from 200 to 400 meters); and c) High Topographic Domain at the Western Side of the MVRD Depression, characterized by altimetric ranges between 500 and 1,100 meters and high fluvial dissection (from 200 to more than 400 meters). This main relief compartmentalization can be related to a first Cenozoic tectonic phase (Neogene E-W sinistral transcurrence). The NW-SE distensive stress associated with this tectonic event results on the main NNE-SSW orientation of the major high and low topographic blocks which represent a block-faulted morphology. Remarkable NW-SE to E-W segmentation of the major compartments is controlled by tectonic structures associated with a second Cenozoic tectonic phase (Pleistocene to early Holocene E-W dextral transcurrence). This tectonic event has greatly influenced on the development of a regional lacustrine system and on the retention of a relatively thick Holocene depositional package. The final damming of the lacustrine bodies has been documented as controlled by a third Cenozoic tectonic event, that is characterized as an Holocene NW-SE extensional phase.
*Supported by FAPESP, CAPES and CEPG-UFRJ.