The geomorphological evolution of the Serra do Espinhaço is discussed based on: a) a critical analysisof previous papers about the geomorphology of the range, b) new interpretation based on own field data,c) regional interpretation, considering informations about the evolution of adjacent areas west and east ofthe range (São Francisco River, Doce River and Jeqitinhonha-Araçuaí Rivers Basins). The global contextis presented as a synthetical characterization of the main geological conditions, regional physiographyand drainage system organization and anomalies.The regional geomorphological organization is rigid controlled by the geology: a) the shape of therange reproduce the original collisional arc developed during the proterozoic orogeny, b) the existence oftwo strongly diferenciated plateaux (Planalto Meridional and Planalto Setentrional) reflect the litho-structuralcontrast between the southern and northern parts of the range, c) the morphology expresses the associationbetween lithological resistance to erosion and the tectonic organization in all scales.The morphology of the higher portions of the plateaux is characterized by relicts of two tertiaryplanation surfaces. They are probably peneplains resulting from erosion under tropical humid climaticconditions. During the Pleistocene, the valleys recorded the formation of several stepped terraces. thespacial variation on its dislevelments reflects the intensity of crustal uplifts and the position of the streamsin the drainage system hierarchy. The hillsides were, during the Upper Pleistocene, covered by two finecolluvial layers. In both cases, the cenozoic sediments register evidences of humid and hot paleoclimaticconditions.The Serra do Espinhaço acquired its present main physiography after the Miocene, which wascharacterized by tectonic stability. During the Pliocene, a strong compressional tectonic event reactivatedthe main precambrian thrust faults and detachment planes. As a consequence, the high scarp related to thewest thrust front was enhanced together with a eastward tilting of the plateaux. At the same time, in thePlanalto Setentrional, several valley heads of the São Francisco drainage basin were deviated and capturedby the Jequitinhonha Basin drainage system. In the Planalto Meridional, the geological conditions (porouslithology and anticline structure) favoured the capture of streams by the São Francisco Basin drainagesystem.As a consequence of the compressional forces that uplifted the range, an extensional stress fielddeveloped in the eastern border, generating grabens structures where the main rivers installed its valleys.The neotectonic activity is also recorded in several parts of the range and adjacent areas by normal, reverseand strike-slip faults in pleistocenic alluvial and colluvial deposits. Fault planes data analysis indicates ageneral NW-SE compressional stress field that remains up to the present time, as confirmed by results ofseismological data.(*)

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A number of significant informations about the evidences and characteristics of a neotectonic activity in the Brazilian Platform have been gathered in the last year in different parts of the country. These permit the definition of main structural features due to reactivation of Precambrian geossutures: Crustal Descontinuity of the Two Brazils (CDTB), Crustal Descontinuity of the Right Amazonian Margin (DCMDA), Minas- Alagoas Crustal Descontinuity (DCMA), Tocantins-Araguari Crustal Descontinuity (DCTA), Crustal Descontinuity of the Upper São Francisco (DCASF), Crustal Descontinuity of the Upper Rio Grande(DCARG), Crustal Descontinuity of the Pernambuco Lineament (DCLP), Crustal Descontinuity of the Midle-Upper Paraná (DCMAP), Crustal Descontinuity of the Paraíba do Sul (DCPS).In many of them, continental rifts and individual sedimentary basins have been generated. Some were submitted to a younger compression, resulting in its tectonic inversion. These main discontinuities control the macrorelief and the regional drainage pattern, as well as the orientation and subdivision of the main hidrographic basins.Blocks limited by these discontinuities are fragmented by faults of different types and sizes resulting in a regional structure alternating subsidence and uplift.The western extremity of the Amazon Basin is partially disrupted by blind inverse faults related to the Andean Orogeny. The central and Eastern areas are cut by Riedel Shears due to E-W dextral shearing.The oriental coastal province displays different patterns from south to north. The southern and southeastern regions, are dominated by Cenozoic uplift with tilting of blocks to W and NW and domnwarping of the off-shore blocks. In the Northeastern region morphological doming is related to transpressive conditions due to E-W dextral shears.The geological and seismological data indicate horizontal, roughly NW-SE oriented compressive stresse at least in the N, NE and Center- SE areas. Gravimetric data confirm the morphotectonic interpretation.

Forms scarps and affects local base level in small rivers. In the states of Sergipe and Alagoas, this fault (lineament) establishes the contact between the regions comprised of internal plateaus and the coastal tablelands. In the state of Bahia, the fault establishes the margin of the Mezosoic Tucano-Jatobá basins and the Recôncavo basin, where it has a very impressive scarp. RECURRENCE INTERVAL: Unknown SLIP RATE: Unknown, probably <1 mm/yr. TIME OF MOST RECENT OF MOVEMENT: Quaternary (< 1.6 Ma) Comments The timing is based on geomorphological evidence and on faults that affect Pliocene sediment of the Barreiras Group. It is probable that, at least in the state of Bahia, fault activity extends to the Holocene, as is suggested by evidence of subsidence in the Todos os Santos Bay.

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