1,722,047 research outputs found
Pollen and Spores in Marine Sediments from the East Atlantic -A View from the Ocean into the African Continent
No full textLate Quaternary vegetation and climate dynamics in the Serra da Bocaina, southeastern Brazil
No full textLate Quaternary vegetation, fire and climate dynamics were studied by pollen and charcoal analysis in the Serra da Bocaina, in the coastal ranges of southeastern Brazil, Rio de Janeiro and S (a) over tildeo Paulo States. Samples were taken from two cores, Serra da Bocaina I and 2. Seven radiocarbon dates indicate deposits of Late Pleistocene to Holocene age. During the period between 18,570 and 14,570 cal BP wide-spread grassland ("campos") with frequent fires existed in the higher Serra da Bocaina; taken together with other evidence, this indicates relatively dry and cold climatic conditions for this period. Upper montane forest occurred in protected valleys or on slopes at lower elevations. The conifer Araucaria angustifolia has been present in the Serra da Bocaina since the Late Pleistocene, but populations have fluctuated. An erosion hiatus in the Late-glacial period, evidenced by reworked deposits lacking pollen, was probably caused by increased rainfall during the Younger Dryas period. Upper montane forest taxa expanded during the Holocene, especially after 7260 cal BP. Indications are that the early and mid Holocene were dry and relatively warm, with an annual dry season longer than present day. Modern patches of campos in the Serra da Bocaina are remnants of more expansive grasslands during glacial times. (c) 2006 Elsevier Ltd and INQUA. All rights reserved
Multibeam bathymetry raw data (Atlas Hydrosweep DS echo sounder entire dataset) of RV METEOR during cruise M12/1
No full textMultibeam bathymetry raw data using the ship's own Atlas Hydrographic Hydrosweep DS multibeam echo sounder was not continuously recorded during RV METEOR cruise M12/1. Data was recorded on 24 days between 1990-03-14 and 1990-04-13. This dataset contains a survey in the North and South Atlantic Ocean, covering mostly deep-water areas. The approximate average depth of the entire dataset is around 4200m.
The data are archived at the Federal Maritime and Hydrographic Agency of Germany (Bundesamt für Seeschifffahrt und Hydrographie, BSH) and provided to PANGAEA database for data curation and publication. No ancillary sound velocity profiles (SVP) files from the cruise are archived at the BSH, thus no SVP files are added to this dataset. Data analysis of the multibeam raw data could not reveal whether the SVP has been changed during the survey.
This publication is conducted within the efforts of the German Marine Research Alliance in the core area 'Data management and Digitalization' (Deutsche Allianz Meeresforschung, DAM).
Data are unprocessed and therefore contains incorrect depth measurements (artifacts) without further processing. Note that refraction errors can be expected due to the lack of proper SVP. Overall, it appears that the data quality is rather good to moderate since the gridded hillshade data showed relatively few obstacles. All files have been renamed from the suffix *.0 (stored at BSH) to *.dux.
Data can be processed e.g. with the open source software package MB-System (Caress, D. W., and D. N. Chayes, MB-System: Mapping the Seafloor, http://www.mbari.org/products/research-software/mb-system/, 2022)
Carbohydrate composition of various size fractions of sediment core GIK13093 in Harrington Sound, Bermuda
No full textCarbohydrate composition of various size fractions of sediment core GIK13093 in Harrington Sound, Bermud
Age and carbon isotope composition of sediment core GIK13093 from Harrington Sound, Bermuda
No full textAge and carbon isotope composition of sediment core GIK13093 from Harrington Sound, Bermud
Chemical analyses of sediment core GIK13093 from Harrington Sound, Bermuda
No full textChemical analyses of sediment core GIK13093 from Harrington Sound, Bermud
Amino acid composition of sediment core GIK13093 from Harrington Sound, Bermuda
No full textfraction 6-20 µm of the sediment was analysed, data given in mole
Stable isotope composition of different foraminifera from core GIK13093, Harrington Sound, Bermuda
No full textforaminifera picked from the >63 µm fractio
Neotropical vegetation response to rapid climate changes during the last glacial period: Palynological evidence from the Cariaco Basin
No full textWe present new palynological information from the anoxic Cariaco Basin, off Venezuela, that provides insight into the response of northernmost South American vegetation to rapid climate changes between 68 and 28 ka, specifically during North Atlantic Heinrich events (HEs) and Dansgaard/Oeschger cycles. We defined three different vegetation modes: (1) an interstadial mode characterized by the highest pollen concentration and the maximum extension of semi-deciduous and evergreen forests; (2) a stadial mode characterized by increases of salt marshes, herbs, and montane forests; and (3) a Heinrich event mode characterized by the lowest pollen concentrations, abrupt increases of salt marshes, and decreased forest abundance. Similarly, indices of C4/C3 plants show increases during stadials with clear peaks during the onset of HEs, though grasslands did not become dominant during these periods. We alternatively propose that these expansions of C4 plants are associated with the expansion of coastal salt marshes. Our vegetation record suggests the prevalence of humid conditions during interstadials, dry and cold conditions during stadials, and dry and cold conditions together with changes in sea level during HEs. This new palynological evidence supports previous interpretations that main environmental changes in northernmost South America were driven by latitudinal displacements of the Intertropical Convergence Zone and sea-level changes. (C) 2007 University of Washington. All rights reserved
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