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Kuerten S.,State University of Mato Grosso do Sul | Parolin M.,Laboratorio Of Estudos Paleoambientais Da Fecilcam Lepafe | Assine M.L.,Claro | McGlue M.M.,University of Arizona | McGlue M.M.,U.S. Geological Survey
Journal of Paleolimnology | Year: 2013

Sponge spicules are siliceous microfossils that are especially useful for analysis of sandy fluvio-lacustrine sediments. Sponge spicules in a long sediment core (~550 cm below surface), consisting of fine sand, sandy silt, and organic-rich mud, recovered from the floodplain of the Nabileque River, southern Pantanal, Brazil (S20°16′38. 3″/W57°33′00. 0″), form the basis of a novel paleoenvironmental interpretation for this region. Optically stimulated luminescence dates constrain the timing of deposition to the middle-late Holocene and all spicules identified are typical of the Brazilian cerrado biome. The base of the section is dominated by Oncosclera navicella Carter 1881, Metaniaspinata Carter 1881, and Corvospongilla seckti Bonetto and Ezcurra de Drago 1966, which indicate a lotic to semi-lotic environment strongly influenced by an actively meandering river channel at ~6. 7-5. 7 ka BP. The appearance of Heterorotula fistula Volkmer-Ribeiro and Motta 1995, Dosilia pydanieli Volkmer-Ribeiro 1992 and Radiospongilla amazonensis Volkmer-Ribeiro and Maciel 1983 at ~340 cm downcore suggests a reduction in flowing water and a more stable lentic environment, consistent with deposition in an oxbow lake. This oxbow lake environment existed during an interval of regional aridity between ~4. 5 and 3. 9 ka BP. Spicules, as well as phytoliths and diatoms, are highly variable moving up-section, with species from both lotic and lentic ecosystems present. Above ~193 cm, the total abundance of spicules declines, consistent with wetter climate conditions and development of an underfit river similar to the modern floodplain. Results support hypotheses related to migration of the Paraguay River inferred from geomorphological studies and add a key southern-region dataset to the emerging Holocene database of paleoenvironmental records from the Pantanal wetlands. © 2012 Springer Science+Business Media Dordrecht. Source


Rasbold G.G.,Laboratorio Of Estudos Paleoambientais Da Fecilcam Lepafe | Rasbold G.G.,Federal Technological University of Parana | Monteiro M.R.,Laboratorio Of Estudos Paleoambientais Da Fecilcam Lepafe | Monteiro M.R.,Federal Technological University of Parana | And 4 more authors.
Iheringia - Serie Botanica | Year: 2011

Phytoliths can be considered the most durable terrestrial fossil records, constituting an important proxy indicator for paleoenvironmental and archeological studies. This study shows the Butia paraguayensis (Barb. Rodr.) L. H. Bailey (Arecaceae) phytoliths forms, typical specie from cerrado vegetation (Brazilian savanna), considered endangered, as well as its isotopic signal (δ 13C). "Globular echinate" forms were predominants. The δ 13C results was of -29.1 %, characterizing the plant as a C 3 type. Source


McGlue M.M.,University of Arizona | Silva A.,Federal University of Mato Grosso do Sul | Zani H.,National Institute for Space Research | Corradini F.A.,Federal University of Para | And 9 more authors.
Quaternary Research (United States) | Year: 2012

The Pantanal is the world's largest tropical wetland and a biodiversity hotspot, yet its response to Quaternary environmental change is unclear. To address this problem, sediment cores from shallow lakes connected to the Upper Paraguay River (PR) were analyzed and radiocarbon dated to track changes in sedimentary environments. Stratal relations, detrital particle size, multiple biogeochemical indicators, and sponge spicules suggest fluctuating lake-level lowstand conditions between ~11,000 and 5300. cal. yr BP, punctuated by sporadic and in some cases erosive flood flows. A hiatus has been recorded from ~5300 to 2600. cal. yr BP, spurred by confinement of the PR within its channel during an episode of profound regional drought. Sustained PR flooding caused a transgression after ~2600. cal. yr BP, with lake-level highstand conditions appearing during the Little Ice Age. Holocene PR flood pulse dynamics are best explained by variability in effective precipitation, likely driven by insolation and tropical sea-surface temperature gradients. Our results provide novel support for hypotheses on: (1) stratigraphic discontinuity of floodplain sedimentary archives; (2) late Holocene methane flux from Southern Hemisphere wetlands; and (3) pre-colonial indigenous ceramics traditions in western Brazil. © 2012. Source


Rasbold G.G.,Laboratorio Of Estudos Paleoambientais Da Fecilcam Lepafe | Rasbold G.G.,Federal Technological University of Parana | Parolin M.,Laboratorio Of Estudos Paleoambientais Da Fecilcam Lepafe | Caxambu M.G.,Federal Technological University of Parana | Pessenda L.C.R.,University of Sao Paulo
Iheringia - Serie Botanica | Year: 2012

The research characterizes and quantifies the phytoliths in Chloris elata Desv., Chloris gayana Kunth, and Tripogon spicatus (Ness) Ekman (Chloridoideae). Phytolith extraction from root, stalk, leaf and panicle/spike was carried out by acid dissolution (HNO3 and H2SO4); after counting and identification, saddle (87.1% without similarity to other morphologies) and bilobate (6.8%) morphotypes were predominant in the three species. The measurements for these morphotypes and others considered representative indicate no significant changes between the species. In the histological sectioning (leaf and stalk), it was found that the saddle type shows more organized and uniform patterns in the leaf than the stalk; the distances between the saddle was higher in the stalk (average 22.8 um) and lower in the leaf (average 11.3 um). The species showed δ13C values between -14.6‰ and 14.9‰ (C4photosynthetic pathway plants). The silica biomineralization percentage was lower for C. elata (1.87%) and higher for C. gayana (5.12%). Source

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