Late Quaternary high‐resolution biomarker and other sedimentary climate proxies in a Northeast Atlantic Core

Abstract

Abstract. We studied variations in terrigenous input and sea surface temperature over the last 208 ka using a multiproxy approach, involving direct comparison of terrigenous and marine molecular biomarker, foraminiferal abundance, and other sedimentological data for the same horizons in a single northeast Atlantic core (core T88-9P; 48o23 ' N, 25o05 ' W, 3193 m water depth, 790 cm core length) with a well-resolved •5180 stratigraphy. The abundances of three landderived, long-chain compound classes, the n-alkanes (C27, C29, and C 3 l), the n-alkanoic acids (C24, C26, and C28), and the n-alkanols (C24, C26, and C28) show glacial/interglacial related changes in the past 208 ka which generally parallel the weight percent noncarbonate. The abundances of these three compound classes are higher in glacial than in interglacial sediments. Such changes are consistent with the expected higher dust inputs during glaciations as well as enhanced advection of particulate matter in current systems. Ice-rafted debris (Heinrich events) may also contribute to the terrigenous biomarker record. The sea surface temperature (SST) signals derived from the alkenone unsaturation index (uK'37) give an average SST during interglacial periods of 13øC, which is about 3-4øC higher than the average glacial SST estimate. The uK'37 -derived SST values dropped markedly in some Heinrich layers, while sometimes leading the onset of the layer; the percent Neogloboquadrina pachyderma(s), which is another frequently used qualitative temperature proxy, generally shows maxima coinciding with the layers. Our results show that most Heinrich layers were produced during times of intensely cold waters in the eastern North Atlantic. They demonstrate that sufficient alkenones are present in the sediments for alkenone stratigraphy to be used as a tool for the assessment of short-term variations in sea surface temperatures even in these oligotrophic North Atlantic waters.

Strengthening of North American dust sources during the late Pliocene (2.7 Ma)

“…The presence of extensive loess deposits between 45 and 35°N in the interior of North America (Bettis et al, 2003) indicates that the margins of the North American ice sheets were a major dust source during the last glacial, in-line with modeling results (Ganopolski et al, 2010). Studies using the accumulation of organic biomarkers derived from terrestrial higher plant leaf waxes in marine sediments from the northern North Atlantic, downwind from the North American continent, demonstrate similar results with increased aeolian input of terrestrial material during the last glacial (López-Martínez et al, 2006;Madureira et al, 1997).…”

“…They are a major component of modern dust even in remote ocean areas (Conte and Weber, 2002;Conte et al, 2003;Gagosian et al, 1981;Simoneit et al, 1977) as they can easily be removed from the leaf surface by wind or rain, especially by sandblasting during dust storms, or entrained as part of soil and transported over large distances. Numerous studies therefore used the accumulation of these lipids in distal marine sediments far from major fluvial inputs to infer changes in aeolian input to the open ocean (e.g., López-Martínez et al, 2006;Madureira et al, 1997;Martínez-Garcia et al, 2009. Indeed, several studies have shown that the concentrations and fluxes of these organic biomarkers agree well with those of independent inorganic tracers for windborne lithogenic material (e.g.…”

Assessment of lipid compounds and phosphorus in mangrove sediments of Santa Catarina Island, SC, Brazil

“…21,22 These compounds are abundant in plant epicuticular waxes, 23 but long-chain n-alkanes and n-alkanoic acids can also be found in marine algae. [24][25][26] …”

Compostos orgânicos em sedimentos marinhos: uma viagem ao fundo do Oceano Atlântico Norte

“…Os trabalhos enfocam, por exemplo, a importância que o registro quantitativo dos compostos orgânicos (normalmente denominados de biomarcadores) tem para estudos sobre produtividade primária (biomassa de fitoplâncton), fluxo de material terrestre, mudanças climáticas e presença de poluentes [5][6][7][8][9] . Entretanto, devido ao alto custo dos cruzeiros científicos que são necessários para os trabalhos em oceanos e pela própria dificuldade de se coletar amostras em regiões onde a coluna d'água pode atingir mais de 4000 m de profundidade, poucos trabalhos têm examinado a composição lipídica da matéria orgânica presente em sedimentos abissais, particularmente no Oceano Atlântico [10][11][12] . O presente trabalho foi desenvolvido como parte do projeto britânico BOFS (do inglês "Biogeochemical Ocean Flux Study ", 1990 -1994), que tinha como objetivo avaliar o ciclo do carbono orgânico no Atlântico Norte, sendo, portanto, uma ótima oportunidade para se identificar alguns dos grupos de compostos orgânicos encontrados em sedimentos oceânicos.…”