Consulta: subjectFacets:"Organic geochemistry"
Registros recuperados: 4
Data/hora: 17/06/2024 07:30:50

Geochemical methods to infer landscape response to Quaternary climate change and land use in depositional archives: A review
Provedor de dados: 5
Autores: Francke, Alexander; Holtvoeth, Jens; Codilean, Alexandru; Lacey, Jack H.; Bayon, Germain; Dosseto, Anthony.
Understanding and quantifying the processes and geochemical cycles associated with catchment erosion, the development of soils and weathering horizons, and terrestrial habitat change beyond the scales of modern observations remain challenging. Such research, however, has become increasingly important to help predict future landscape change in light of increasing land use and rapid global warming. We herein review organic and inorganic geochemical tools applied to depositional archives to better understand various aspects of landscape evolution on geological time scales. We highlight the potentials and limitations of inorganic geochemical analytical methods, such as major element geochemistry, metal and radiogenic isotopes, and in-situ cosmogenic nuclides,...
Tipo: Text
Palavras-chave: Quaternary landscape evolution; Catchment erosion; Terrestrial habitat change; Land use; Fluvial; Lacustrine; Inorganic geochemistry; Organic geochemistry; Radiogenic isotopes; Metal isotopes; Uranium isotopes; Cosmogenic nuclides.
Ano: 2020
URL: https://archimer.ifremer.fr/doc/00632/74383/74084.pdf

Carbon and silica megasink in deep-sea sediments of the Congo terminal lobes
Provedor de dados: 5
Autores: Rabouille, C.; Dennielou, Bernard; Baudin, F.; Raimonet, M.; Droz, Laurence; Khripounoff, Alexis; Martinez, P.; Mejanelle, L.; Michalopoulos, P.; Pastor, Lucie; Pruski, A.; Ragueneau, Olivier; Reyss, J.-l.; Ruffine, Livio; Schnyder, J.; Stetten, E.; Taillefert, M.; Tourolle, Julie; Olu, Karine.
Carbon and silicon cycles at the Earth surface are linked to long-term variations of atmospheric CO2 and oceanic primary production. In these cycles, the river-sea interface is considered a biogeochemical hotspot, and deltas presently receive and preserve a major fraction of riverine particles in shallow water sediments. In contrast, periods of glacial maximum lowstand were characterized by massive exports of sediments to the deep-sea via submarine canyons and accumulation in deep-sea fans. Here, we calculate present-day mass balances for organic carbon (OC) and amorphous silica (aSi) in the terminal lobe complex of the Congo River deep-sea fan as an analogue for glacial periods. We show that this lobe complex constitutes a megasink with the current...
Tipo: Text
Palavras-chave: Present; Paleoceanography; South Atlantic; Inorganic geochemistry; Organic geochemistry; Sedimentology-marine cores.
Ano: 2019
URL: https://archimer.ifremer.fr/doc/00511/62289/66720.pdf

Short scale (6 h) temporal variation of sinking fluxes of planktonic and terrigeneous lipids at 200 m in the NW Mediterranean Sea
Provedor de dados: 5
Autores: Mejanelle, L.; Dachs, J.
Drifting sediment trap measurements were carried out at high temporal frequency in the northwestern Mediterranean Sea in the course of the DYNAPROC 2 campaign, during the transition between late summer to autumn conditions. Molecular biomarkers were analyzed in selected subsets of consecutive samples collected for 6 h at 200 m depth. Fluxes of n-alkanes, long-chain alkenones, sterols and steroid ketones show high variability between consecutive 6-h samples, comparable in range to seasonal variability. n-Alkane export ranges from 1.4 to 29.7 mu g m(-2) d(-1), fluxes of C(37) alkenones varies from 0 to 14.2 mu g m(-2) d(-1). Fluxes of sterols, steroid ketones and C(30) alkane diol respectively range from 31 to 377, 2.2 to 46 and 0.3 to 9.3 mu g m(-2) d(-1)....
Tipo: Text
Palavras-chave: Long chain alkenones; North pacific ocean; Short term changes; Sediment traps; Fatty acids; Particulate matter; Alkyl diols; Alboran sea; Marine dinoflagellate; Organic geochemistry.
Ano: 2009
URL: https://archimer.ifremer.fr/doc/00210/32098/30555.pdf

Relationship of the tetra-unsaturated C-37 alkenone to salinity and temperature: Implications for paleoproxy applications
Provedor de dados: 5
Autores: Sikes, El; Sicre, Ma.
This study assesses the relationship to salinity and temperature of the levels of the tetra-unsaturated 37-carbon methyl alkenone (C-37:4) in the surface ocean. U-37(K'), a measure of the relative abundances of the C-37:2 and the C-37:3 alkenones, has a well constrained linear relationship to temperature in the open ocean [Prahl and Wakeham, 1987] and is a well-established technique for estimating past sea surface temperatures in the sediments (e. g. [Muller et al., 1998]). Unlike the di- and tri-unsaturated C-37 alkenones, the temperature response of the tetra-unsaturated C-37 alkenone is less certain [Sikes et al., 1997], and recent work has suggested a relationship to salinity instead [Rosell-Mele, 1998; Schulz et al., 2000]. Our study examined 106...
Tipo: Text
Palavras-chave: Alkenones; Paleosalinity; Marine organic geochemistry; Organic geochemistry; Paleoceanography; Organic marine chemistry.
Ano: 2002
URL: https://archimer.ifremer.fr/doc/00223/33414/31886.pdf