Reconstrução paleoambiental de um depósito sedimentar por análises multiproxy, Turvo, Estado do Paraná, Brasil

Abstract

-PALEOENVIRONMENTAL RECONSTRUCTION OF A SEDIMENTARY DEPOSIT BY MULTIPROXYANALYSIS, TURVO, STATE OF PARANÁ, BRAZIL. This research presents results of paleoenvironmental analysis that was achieved in a sedimentary record of 44 cm depth, recovered from a remnant of Mixed Rain Forest, located near the urban area in Turvo, Paraná. The record was dated ( 14 C) at two depths: 14,553 cal. years BP (44 cm) and 6.090 cal. years BP (22 cm). Besides the dates, five analyzes of δ 13 C were performed and increasing values from base (-19.0 ‰) to top (-22.9 ‰) were obtained. Samples containing 20 g were extracted from the record on 2 cm intervals (22 samples); then the sediment dissolution (2 g) via chemical treatment was processed according to the protocol used in palynology with subsequent preparation of permanent slides (50 ul material). The slides were observed under an optical microscope, where the count of 400 identifiable phytoliths by gap were determined and the concentration of phytoliths was estimated by random observation in 12 optical fields by gap (x 640). The adaptation indexes to drought (Iph%), climate (Ic%) and water stress (% Fs) were calculated. Two paleoenvironmental areas were established: (i) Zone I, between 44 and 32 cm with a prevalence of drier conditions than current ones, that were evidenced by the increase in the rates of drought adaptation and water stress rates and mixture of C 4 and C 3 plants (pro C 4 ); (ii) Zone II, from 30 cm to the top, characterized by a gradual increase in humidity, low rate of drought adaptation and impoverishment of the isotopic signal with C 3 plants predominance, which was interpreted as an improvement in the moisture conditions and/or available high humidity in the soil. The interpretations corroborate studies for the south and west-central region in Brazil.

Considerações Paleoambientais do Holoceno Médio por Meio de Fitólitos na Serra do Cadeado, Paraná

“…O pesquisador alemão Prof. Reinhard Maack (1989Maack ( -1969) elaborou a hipótese da presença de climas mais secos que o atual em território paranaense durante o Quaternário, principalmente em decorrência da presença de vegetação de Cerrado em vários municípios do interior. Pesquisas como a de Behling (1997), e outras mais recentes, como as de Ladchuk et al (2016) -estudo palinológico na região de Campo Mourão/PR e Rasbold et al (2016) -estudo de fitólitos em Turvo/PR 2016, têm apontado a existência de clima mais seco que o atual durante o Holoceno Médio, Diante do exposto, a pesquisa mostra resultados interessantes para o entendimento das condições paleoambientais paranaenses, bem como as primeiras considerações sobre o ambiente no Holoceno Médio na Mesoregião Centro Oriental Paranaense. Vale ressaltar que o depósito sedimentar estudado, formado por uma lagoa sem nome, localizada a 1.206 m s.n.m, alimentada apenas pelo lençol freático e pela chuva, possui condição ideal para pesquisas dessa natureza.…”

Preservação de fitólitos em solo no Parque Nacional do Iguaçu, Paraná

“…Com relação aos fitólitos, as morfologias "Short cells" -"Bilobate", "Cross", "Rondel", "Saddle" e "Trapeziform" -estão associadas a distintas subfamílias de Poaceae, por tal fato, podem apresentar mudanças na vegetação (Rasbold et al, 2016).…”

“…O morfotipo "Brachiform" também é produzido por diversas famílias de gramíneas (Rasbold et al, 2016), assim, não possuindo valor taxonômico.…”

“…Nesse sentido, diversos trabalhos foram elaborados utilizando fitólitos como "proxy" principal para avaliação da paleovegetação, como exemplo os estudos de Parolin et al (2017), Rasbold et al (2016), Rito et al (2018), Souza et al (2019) e Watling et al (2020).…”

Paleoenvironmental Characterization of a High-Mountain Environment in the Atlantic Forest in Southeastern Brazil

“…Studies aiming at reconstituting past environmental factors can use tools known as proxy indicators (pollen, spores, sponge spicules, phytoliths, among others), which can be interpreted as local records of climate change (Borba-Roschel et al, 2006;Calegari et al, 2013;Coe et al, 2013Coe et al, , 2014Calegari et al, 2015Calegari et al, , 2017aRasbold et al, 2016;Silva Neto et al, 2018). Sites must be favorable to these types of studies, such as soils with high contents of OM under conditions that can preserve material deposited (Salgado-Labouriau, 1994;Suguio, 1999).…”