Abstract

Brazil’s only mountain range rises in a north-south direction for 1200km and, although segmented in the north-central part of the state of Minas Gerais, remained unbroken as a sedimentary basin until the Stenian period, when a tectonic inversion occurred due to the collision of a continental block from the east. The continental collision led to the formation of an orogen, and the associated directional faulting caused the orogen to rupture, irreversibly displacing the southern segment to the NW. The protruding orogen compelled the arching of the crust on its western front following the advance of tectonic stacking, where the foreland basin represented by the Conselheiro Mata Group was established. The five formations of this group alternate between pelitic sedimentation from shallow marine environments and sandy sedimentation from beach and coastal environments, an alternation that marks tectonic pulses with subsidence events versus silt-up due to progradation. The orogenic edifice, being so tall, surpassed the altitudes of the snow line, becoming a disperser of glaciers, which recorded rocks then exposed in the upper parts of the mountain range in their glacial deposits. Terminal moraines promoted the amalgamation of the two segmented parts with tillites that do not present clasts of rocks from the Pedro Lessa Suite (~920-906Ma), thus referring the Jequitaí Glaciation to the end of the Mesoproterozoic (therefore, the first post-Huronian glaciation). The glaciogenic fringes surrounding the termination of both segments of the Serra do Espinhaço testify that the mountain range was already segmented, and since the Jequitaí glaciation is of the alpine type, that the two segments of the mountain range were already orogenic entities.

Keywords:Espinhaço mountain range; Mesoproterozoic orogeny; 1Ga jequitaí glaciation