Gênese e evolução de turfeiras nas superfícies geomórficas da serra do espinhaço meridional – MG

Abstract

The Serra do Espinhaço - SdEM has predominantly quartzite lithologies and is characterized by differ altitudes and dissected areas intermingled the planning surfaces, where, in the depressions occur peatlands. These planation surfaces are the result of a succession of denudation and depositional events compartmentalized relief along the geodynamic evolution of the ridge. The aim of this study was to map the peatlands of the northern part of the ridge and discuss the genesis and evolution of pedoenvironments the geomorphic surfaces of the SdEM. The determination of the area and mapping of peatland was conducted through field work, images and aerial photographs analysis. Sampling was carried out in eight peatlands in the northern portion of SdEM. Samples for dating and characterization of the photosynthetic cycle were collected with the help of vibracoring at different depths, depending on local attributes, for determining the carbon isotope (?13C and 14C). The northern portion of SdEM occupies an area of 1,180,109.00 ha, which were mapped 14,287.55 ha of peatlands, which represents 1.2% of the total area. In peatlands dominated the stages of advanced decomposition (sapric), followed by intermediate (hemic). Four levels of geomorphical surfaces were identified throughout the length of SdEM: Surface I (S1), Surface II (S2), Surface III (S3) and Surface IV (S4). Considering the altimetry as the main factor, the S1 was cronocorrelated with Post-Gondwana Surface and S2 cronocorrelated with the South American Surface. The Surface III (S3) had correspondence with the South American Surface I and Surface IV (S4), in turn, with the South American Surface II. Most peatlands developed in Quaternary between the Pleistocene and Holocene, formed on Post-Gondwana Surface (S1) and in the South American Surface (S2) in altimetric levels ranging between 1,100-1,400 meters. The predominance of plants with photosynthetic cycles CAM and C3 showed colonization of SdEM by species such as bromeliads, cacti and some euphorbiaceae typical of rupestrian fields and trees and shrubs along the Pleistocene-Holocene transition, reflections of local and regional environmental changes occurred in the Quaternary, possibly associated with paleoclimates.