Reconstituição paleoambiental da Vereda Carrasco da Raposa, Parque Estadual da Serra do Cabral, MG, Brasil, por meio de estudos palinológico e isotópico

Pollen and stable isotopes (C and N) analyses from sediments of Carrasco da Raposa palm swamp (VCR) allowed the paleoenvironmental reconstruction of the last 21,000 years in the region of the Parque Estadual da Serra do Cabral- PESC, MG, Brazil. The results demonstrated that during the influence of Last Glacial Maximum, between 21,150 and 18,850 cal. years BP, the climate conditions in the Serra do Cabral were colder and less humid than in the present; between 1,850 and 3,550 cal. years BP a warmer and wetter climate was recorded; from 1,650 cal. years BP the establishment of the palm swamp occurred in the studied area. Concerning the phytophysionomic changes, a succession of vegetation with a predominance of grassland formations was observed: “Campo Limpo” associated with forest formations at the base, “Campo Sujo” and “Campo Rupestre” associated with Cerrado forest formations in the middle, and the installation of the palm swamp with the presence of Mauritia flexuosa trees towards the top. The isotopic data (C and N) indicated that between 21,150 and 6,500 cal. years BP, there was a probable mixture of C3 and C4 plants as sedimentary organic matter source, but with the predominance of C3 plants, with δ13C values of ~-24 ‰ to -21.5 ‰. Values of C/N (1.5 to 11.5) suggested the predominance of phytoplankton and the δ15N values (3.5 ‰ to ~1.0 ‰) evidenced the mixture of algae and land plants. Around 3,550 cal. years BP to the present, there has been a decrease in the values of C/N (1.5 to ~6), confirming a flooded environment with greater influence of algae in the sedimentary organic matter.A análise palinológica e de isótopos estáveis (C e N) dos sedimentos da Vereda Carrasco da Raposa (VCR) permitiu a reconstituição paleoambiental dos últimos 21.000 anos AP na região do Parque Estadual da Serra do Cabral (PESC), MG, Brasil. Os resultados mostraram que durante a influência do Último Máximo Glacial, entre 21.150 e 18.850 anos cal. AP, as condições climáticas na Serra do Cabral eram mais frias e com menor umidade do que as atuais; entre 18.850 e 3.550 anos cal. AP o clima passou a ser mais quente e com maior umidade; a partir de 1.650 anos cal. AP houve o estabelecimento da vereda, em condições semelhantes e/ou comparáveis às atuais. Quanto às mudanças fitofisionômicas, foi observada uma sucessão da vegetação com predomínio de Formações Campestres do Cerrado associadas a traços de Formações Florestais na base, Campo Sujo Úmido e Campo Rupestre associados a elementos de mata típicos do Cerrado na porção mediana do perfil; em direção ao topo a partir de 1.650 anos cal. AP houve a instalação da vereda, com a ocorrência dos buritis (Mauritia flexuosa). Os dados isotópicos de C e N indicaram que entre 21.150 e 6.500 anos cal. AP havia uma provável mistura de plantas C3 e C4 como fonte da matéria orgânica sedimentar, mas com o predomínio de plantas C3, com valores de δ13C entre ~-24‰ e -21,5‰. Os valores de C/N (1,5 a 11,5) indicaram o predomínio de fitoplâncton e os valores de δ15N (3,5‰ a ~1,0‰) evidenciaram a mistura de algas e plantas terrestres. Em torno de 3.550 anos cal. AP até o presente a diminuição nos valores de C/N (1,5 a ~6) confirmou um ambiente alagado e com maior influência algal na composição da matéria orgânica sedimentar

Holocene Vegetation and Climate inferences from Phytoliths and Pollen from Lagoa do Macuco, North Coast of Espírito Santo State (Brazil)

An interproxy approach focused on phytoliths and pollen, including radiocarbon dating and sediment particle-size analyses, has been carried out at Lagoa do Macuco, Linhares municipality, Espírito Santo State, Brazil. Three pollen zones were identified: the first one (MAC-C I) indicates the presence of mangrove vegetation between 7700 cal yr BP and 4396 cal yr BP; the second one a displacement of the vegetation from the lower areas to the more elevated margins of the valley (MAC-C II, from between 4396 to 1287 cal. yr BP) and third one (MAC-C III), representing the period of the current lake evolution, between 1287 cal. yr BP and the present day. The displacement of the mangrove seems to be connected to the landward migration of the palaeo-estuary and the flooding of the lower parts of the valley, reflecting the relative sea-level highstand, which occurred after 7000 cal yr BP. The phytolith analysis indicated four main zone. The phytolith zone I (7700-7100 cal yr BP) did not show the presence of phytoliths. The phytoliths zone II (7100-3400 cal yr BP) indicates the presence of an open vegetation predominantly of grasses while phytolith zone III (3400-400 cal yr BP) shows a phase with more forested vegetation. Finally, the phytolith zone IV (400 cal yr BP to modern) has a decrease in tree cover and the setting of vegetation with a strong grasses component. Phytoliths indices indicate trends of humidity and temperature at a more local scale, allowing understanding the environmental conditions during the formation of the current lake

Climate changes in Northeastern Brazil from deglacial to Meghalayan periods and related environmental impacts

Changes in insolation driven by precession and obliquity are considered the major driver of tropical precipitation on orbital time scales, and responsible for vegetation and physical landscape changes during the Late Holocene over tropical South America. Here we investigate the environmental changes in the karst region of Chapada do Apodi - Northeastern Brazil (NEB), using a multi-proxy approach including carbon (delta C-13), oxygen (delta O-18) and strontium (Sr-87/Sr-86) isotopic analyses on speleothems from different caves, carbonate bedrock, and clastic cave deposits. This approach reveals that the balance between soil formation and erosion and their alternating impact on vegetation and precipitation changes occurred in response to variations in the position and intensity of the Intertropical Convergence Zone (ITCZ) over the region. The high delta C-13 and delta O-18 and low Sr-87/Sr-86 values at 4,200 yrs BP indicate a massive episode of soil erosion, resulting in the exposure of carbonate bedrocks over a large area of the karst terrain. This event marks the beginning of the Meghalayan chronozone, characterized as the aridification of this region, decline in soil production, drying out of underground drainages, and increased dominance of dry-adapted flora species, characteristic of a more open vegetation (caatinga). We investigated if the Holocene climatic changes affected human occupation in the NEB and found that the overall demographic course is virtually identical to the well-established curve characterized by population deflation during Middle Holocene. (C) 2020 Elsevier Ltd. All rights reserved