RECONSTITUIÇÃO PALEOBIOGEOCLIMÁTICA DE ÁREAS CÁRSTICAS, ARQUEOLÓGICAS E TURFEIRAS NA SERRA DO ESPINHAÇO MERIDIONAL, MG, ATRAVÉS DE BIOMINERALIZAÇÕES DE SÍLICA

Abstract

This thesis aims to contribute to understanding the conditions responsible for the evolution of the Espinhaço Mountain Range (SdEM) landscape throughout the Quaternary through multiproxy analyses, such as silica biomineralizations (phytoliths), granulometric analyses and 14C-AMS dating. Three areas were selected for the survey, from which 52 soil and sediment samples were taken. In Area 1, there are carbonatic caves (Pau-Ferro Cave) and siliciclastic caves (Monte Cristo Cave). The Cabeças Archaeological Complex is located in Area 2, while Area 3 includes a peat bog at the head of the Araçuaí River. Two profiles were collected at the Monte Cristo Cave, one with sediment inside the cave and one with Organosol outside. In the Pau-Ferro Cave, a Neolithic Litolic profile was collected. In Area 2, sediments were collected inside the Cabeças 4 archeological site, in addition to an Organosol profile close to the site. In area 3, samples were selected every 20 cm in the core from the Rio Preto peat bog, close to the head of the Araçuaí River. The results were relevant for inferring the main environmental changes that occurred in the region. In karst environments (Monte Cristo Cave and Pau-Ferro Cave), phytoliths were well preserved and provided answers in the geomorphological scope and evolution of the caves. In the Monte Cristo Cave, it was possible to identify the allochthonous origin of the sediments and the dynamics of alterite redistribution through the primokarst from 4440/4230 cal years BP to 660 to 550 cal years BP. Through phytolith analysis, it was also possible to observe that there was no change in vegetation, which was always in rupestrian fields. The indices show an increase in temperature over time and favorable conditions for evolution of the cave. In the Pau-Ferro Cave, phytolith analyses indicate predominantly open vegetation, although in many places a dry forest is currently found, which may interfere with vegetation formation and phytophysionomies in different ways, essentially characterized by soil scarcity and edaphic conditioning. In this area, a colder, drier episode between 440 and 250 cal years BP is observed. In the archaeological context, the comparison of phytoliths from the Cabeças 4 Archaeological Site with the nearby Organosol showed similarities in the results. This indicates that both samples helped understand the paleoclimatic conditions conducive to human occupations from 14200/13850 cal years BP to 800 / 680 cal years BP. Through phytolith analysis of the Rio Preto peat bog, it was possible to define 4 climatic phases, it being the most chronologically comprehensive study area, since 25,000 cal years AP. Through these results, it was possible to observe that, even in different areas, the trend from 25,000 years cal BP until the present day, was the presence of periods oscillating between decrease and increase in temperature, as well as in humidity, ending with the highest temperature and stable humidity. Therefore, it was possible to relate local and regional climate trends within a geochronological perspective, contributing to the paleoclimatic reconstitution of the Espinhaço Mountain Range. In addition, local results can be associated with regional studies and with global events from 25,000 cal years BP, encompassing from the Upper Pleistocene (Upper) up to 440 cal years BP, the Upper Holocene (Meghalayan). Keywords: Paleoclimatic Reconstitution, Phytoliths, Quaternary