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The late quaternary period in Pardo river basin (MG e SP): morphometric analysis and paleoenvironmental evidences preserved in soils and sediments of floodplains

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Author(s):
Andre Luiz de Souza Celarino
Total Authors: 1
Document type: Doctoral Thesis
Press: Campinas, SP.
Institution: Universidade Estadual de Campinas (UNICAMP). Instituto de Geociências
Defense date:
Examining board members:
Francisco Sérgio Bernardes Ladeira; Alessandro Batezelli; Luiz Carlos Ruiz Pessenda; Alfredo Borges De Campos; Márcia Regina Calegari
Advisor: Francisco Sérgio Bernardes Ladeira
Abstract

Floodplains are depositional features of a channel valley conected to a specific climatic or hidrologic condition of the drainage basin, in this sense, sediments are temporarily stored and agradation or degradation processes will be responsible for the dynamics of these units. As a function of this dynamics, mostly in humid tropics, floodplain deposits are fastly chemically weathered and soil horizons could evolve, yielding nutrients and chemicall elements responsible for the ocupation of a typical vegetation, as an answer of climatic, sedimentary, hidrologic and pedologic conditions. These geomorphologic units have a high diversity of terrestrial, transitional and aquatic habitats in different stages of evolution, the river-floodplain system brings high degree heterogeneity of physical, chemical and biotic processes, therefore, such areas have an important ecological potential and are able to preserve data from past environments. The aim of this work was to understand such informations about the evolution of Pardo River basin, from its headwaters in Minas Gerais state to the mouth, at Grande River, at the borders of São Paulo state and "triângulo mineiro". Preliminarily, some morphometric features were carried out in order to identify evidences of recent adjustments in the basins that changed channel dynamics, particularly the drainage anomalies distribution, longitudinal profiles, structural lineaments and faults. Regarding these basic informations, 14 soil profiles were selected in the floodplains of Pardo river and their affluents, where 7 were studied regarding chemical, grain size and micromorphology features, associating them to the architecture of sedimentation and to weathering processes, including 14C and OSL (Optically stimulated luminescence) datings. The results showed that weathering processes are very significant even tough in situations where pedogenesis could be ocasionaly interrupted by floodplain deposits. Most of these processes are still running, micromorphology analysis has revealed transformation of Biotite/Muscovite into clay minerals in several profiles. Macromorphology has revealed that in some situations the soil forming processes were able to generate Bt horizons, unusual in poorly drained areas such as floodplains, for that reason the sedimentary facies method used was essential, only by using it we could identify the deposit architecture and its relative position on floodplain, which could support or not chemical weathering processes. Records of climates colder and drier than today were identified between 35000 and 17000 years BP, situation kept until the last glacial maximum (? 17000 BP). In the Middle Holocene (6000 a 3845 years BP) climate changed to a warmer and wetter than today condition, where grass phytoliths prevailed despite an increase of palms as well as an impoverishment of 13C signal. In Upper Holocene the climate changed to a typical warm and humid tropical condition, with higher participation of trees, schrubs and palms phytoliths, which indicated a vegetation closer to the savannas that are spread today mostly on upper parts of the basin (AU)

FAPESP's process: 11/00261-3 - The Quaternary at Pardo river Basin (MG and SP): palaeoenvironmental evidences preserved on soils of floodplains and terraces.
Grantee:Andre Luiz de Souza Celarino
Support Opportunities: Scholarships in Brazil - Doctorate