Climatic and tectonic settings as a driver of late Quaternary landscape in the Southern Espinhaço range lowlands, Minas Gerais (Brazil)

Abstract

Climatic changes and tectonic events play an important role into the denudational and sedimentation processes. The Southern Espinhaço Range (SER) is an important N-S continental elevate terranes in the state of Minas Gerais, Southeastern Brazil. The SER is primarily composed for Paleo-Mesoproterozoic quartzites, with Neoproterozoic pelites and carbonates. At the moment, only one study considered the unconsolidated sediments in the SER highlands (fluvial terraces and alluvial plains) were carried out. Here, four unconsolidated sediment profiles associated to alluvial fan system dominated by gravity flows (D1), fluvial terraces (D2 and D4) and lacustrine environment (D3) in the SER lowlands were studied, using sedimentary facies, chemical weathering indexes, and Single-Aliquot Regenerative Optically Stimulated Luminescence technique (SAR OSL). The main chemical weathering reactions in the fresh rocks were silicate incongruent dissolution (muscovite and biotite) and partial hydrolyses of microcline and albite forming kaolinite and illite, with quartz being unweathered. The unconsolidated sediments have high maturity, being originated under intense weathering conditions, with warm and humid climate. OSL ages in the SER lowlands varying from 47.45 ± 3.68 ka to 1.92 ± 0.15 ka, revealing old ages in relation to samples dated in the SER highlands (from 26.35 ± 4.47 ka to 0.18 ± 0.04 ka). These sedimentary profiles were deposit under a mix of paleoclimatic context, prevailing dry climate between ∼50 and ∼29.5 ka and ∼7 and ∼3 ka, and wet conditions from ∼29.5 to 7 ka and <3.1 ka. Fluvial incision at D2 and D4 and the presence of lacustrine environment elevated 30 m above the current base level, as well as the presence of faults that displace blocks in sedimentary profiles, indicated the importance role of |tectonic in the study area. Thus, climate changes and tectonic events control the landscape evolution in SER.