6 research outputs found
Holocene Vegetation and Climate inferences from Phytoliths and Pollen from Lagoa do Macuco, North Coast of EspĂrito 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, EspĂrito 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
Recommended from our members
An 11,000-year record of depositional environmental change based upon particulate organic matter and stable isotopes (C and N) in a lake sediment in southeastern Brazil
The aim of this paper is to reconstruct an 11,000-year history of depositional environmental change in southeastern Brazil, based upon the integration of particulate organic matter and stable isotope (C and N) data from a 136-cm sediment core from Lake Canto Grande. These proxies are used to explore the evolution of terrestrial and marine influence on the lake. Isotopic (δ13C: -7.8‰ to -31.9‰; δ15N: -0.07‰ to 4.9‰) and elemental (total organic carbon - TOC: 0.58% to 37.19%; total nitrogen - TN: 0.08% to 1.73%; C/N: 0.3 to 54.7) values recorded in Lake Canto Grande suggest that the sedimentary organic matter was derived from mostly C3 land plants and freshwater phytoplankton. Particulate organic matter and cluster analyses distinguished four associations characterized by the predominance of amorphous organic matter, followed by phytoclasts and palynomorphs. These results indicate two different phases of lake evolution. The first phase (136 - 65 cm; ~10,943 cal yr. B.P. to ~8,529 cal yr. B.P.) is recorded by sand layers interbedded with mud, which contain amorphous organic matter (AOM, 45-59%) and phytoclasts (opaques - OP: 6-18%; non-opaques – NOP: 17-23%) which indicate a floodplain area. The second phase (65 – 0 cm; ~8,529 cal yr. B.P. to ~662 cal yr. B.P.) comprises mud, AOM (68-86%) and palynomorphs (PAL, 8-16%) related to lake establishment comparable to modern conditions. Thus, characterizing particulate organic matter, in combination with stable isotopes, proved to be invaluable proxies for lacustrine paleoenvironmental change through the Holocene
FitĂłlitos como indicadores de mudanças ambientais durante o Holoceno na costa norte do estado do EspĂrito Santo (Brasil)
Um testemunho de 12 metros de profundidade e idade de ~47260 anos cal AP na sua base foi coletado na planĂcie deltaica do litoral norte do estado do EspĂrito Santo. Esse trabalho teve como principal objetivo a caracterização do conjunto de fitĂłlitos, auxiliado pelas fácies sedimentares, dados isotĂłpicos (C e N) e datações 14C para reconstituir o paleoambiente. Os valores de carbono orgânico total - COT (0,16% a 3,28%), nitrogĂŞnio total - N total (0,01% a 0,09%), δ13C (-4,25‰ a -28,06‰), δ15N (-6,19‰ a 15,75‰) e da razĂŁo C/N (7,8 a 99) mostraram em linhas gerais que a matĂ©ria orgânica sedimentar foi originada a partir de fitoplâncton, e da mistura de plantas C3 e C4. A análise de fitĂłlitos foi efetuada ao longo de 1,50 metros do perfil, e a partir dos agrupamentos por similaridade foi possĂvel o estabelecimento de trĂŞs intervalos que refletem mudanças na vegetação e provavelmente no clima a partir de ~7589 anos cal AP. No intervalo 1 (~7589 anos cal AP a ~5441 anos AP – idade interpolada), a assemblĂ©ia fitolĂtica e os Ăndices estatĂsticos de fitĂłlitos calculados refletem uma vegetação composta pela mistura de árvores e gramĂneas C3 e C4, semelhante e/ou comparável Ă vegetação de restinga, provavelmente sob clima quente e Ăşmido. A análise de fitĂłlitos do intervalo 2 (~5441 anos AP – idade interpolada a ~143 anos cal AP) sugeriu a presença de uma vegetação em mosaico provavelmente constituĂda por diferentes formações da restinga, sob influĂŞncia de clima quente e sazonal, com perĂodos de estresse hĂdrico. A diminuição da densidade arbĂłrea, assinalada pelo Ăndice D/P, e a formação da vegetação semelhante Ă atual, herbácea e com sinais de antropização, ocorreu nos Ăşltimos ~200 anos (Intervalo 3), sob clima quente e Ăşmido. Os dados de fitĂłlitos sĂŁo inĂ©ditos para a costa do EspĂrito Santo e mostram o potencial destes bioindicadores em estudos de reconstituição paleoambiental
Recommended from our members
Cold and humid Atlantic forest during the late glacial, northern EspĂrito Santo state, southeastern Brazil
The Atlantic Rainforest, covering the area from the northern Espirito Santo to Southern Bahia states, has been considered as a stable forest during Pleistocene Glacial times. Despite the modelling and phylogenetic studies, this hypothesis has never been tested with empirical paleo-data and vegetation reconstruction. By using palynology, radiocarbon dating, carbon and nitrogen elemental and isotope of organic matter, we reconstructed the vegetation dynamics and inferred climatic changes since Late Pleistocene in the centre of this global biodiversity hotspot. Our results show that the forest biome was resilient to Last Glacial Maximum - LGM conditions, but floristics has changed when compared to nowadays. Since late glacial, the dense forest changed from cold to warm specimens. Major vegetation changes also occurred during early and mid-Holocene less humid conditions, with an opening of the forest, suggesting that future drought may have negative impacts and highlighting the importance of forest conservation to keep the Atlantic Rainforest biodiversity