Geochemical Signatures of Paleoclimate Changes in the Sediment Cores from the Gloria and Snorri Drifts (Northwest Atlantic) over the Holocene-Mid Pleistocene

Abstract

A multiproxy study of the sediment cores taken from the Snorri Drift, formed under the influence of the Iceland–Scotland bottom contour current, and from the Gloria Drift, located southward Greenland at the boundary of Irminger and Labrador Seas, was performed. This area undergoes a variable mixing of polar waters with the warm North Atlantic current, whose intensity and direction seemed to change dramatically with the alteration of warming and cooling periods during the six marine isotope stages MIS 1-6. The relative age of this core does not exceed 190,000 cal yr BP; the average sedimentation rate was 1.94 and 2.45 cm/kyr in the Gloria and Snorri Drifts core respectively. In both the cores, the sediment records showed the downcore co-variation of ice-rafted debris (IRD); and terrigenous elements, such as Si, Al, Ti, Cr, and Zr, were revealed; their values were clearly higher in the glacial periods (MIS 2, 4, and 6) compared to interglacials (MIS 1, 3, and 5). The downcore rhythmic distributions of these elements, as well as Al/Si, Ti/Al, Fe/Al ratios exhibit an opposite trend with that of δ18O values, biogenic components (CaCO3, BioSiO2), and Si/Fe and Mn/Fe ratios.

Geochemistry and Weathering Indices of Yedoma and Alas Deposits beneath Thermokarst Lakes in Central Yakutia

“…Overall, the Sr/Ca ratio of the alas lake core was showing much smaller values compared to the Yedoma lake core (Table 2; p < 0.1). This is suggesting a higher biogenic influence on the carbonate amount in the sediments below the alas lake and a predominantly lithogenic (clastic) carbonate input in the Yedoma deposits (Wien et al, 2005;Demina et al, 2019). Beside the predominantly lithogenic carbonate input in the Yedoma deposits, as supposed above, this ratio drops in Y-SU-III (1,672 cm bls) suggesting a short-term biogenic Ca input in this sediment unit.…”

Global Ocean Sediment Composition and Burial Flux in the Deep Sea

“…An important data gap in the Arctic Ocean was recently addressed by a surface sediment survey from the 68th expedition of RV Akademik Mstislav Keldysh (AMK68) to the Barents Sea (northwest Russian Arctic) in July–August 2017 (Kravchishina et al., 2019). Dried sediments from 27 stations from the upper 0.5 cm of multi‐cores were analyzed at the Shirshov Institute of Oceanology, Russian Academy of Sciences, by X‐ray fluorescence spectrometry for elemental composition using published methods (Budko et al., 2019; Demina et al., 2019). CaCO 3 and biogenic opal were analyzed at the University of Southern Mississippi by UIC coulometer for CaCO 3 and molybdate‐blue spectrophotometry after heated alkaline extraction for biogenic opal (Mortlock & Froelich, 1989).…”

Elemental and Mineral Composition of the Barents Sea Recent and Late Pleistocene−Holocene Sediments: A Correlation with Environmental Conditions

“…Heavy minerals are presented by the epidote-hornblende association with rather high zircon content (to 12% of total heavy fraction), while in the Early Holocene sediments, reduced amounts of clay minerals were found. In cores from the contourite drifts Snorri and Gloria (North Atlantic, 60 • N), the Al/Si, Ti/Al, and Fe/Al ratios varied synchronously to ice-rafted debris (IRD) counts; these downcore distributions showed an opposite trend with variation of Si/Fe, Mn/Fe, δ 18 O values and content of CaCO 3 , BioSiO 2 during MIS 1-6, thus distinguishing the glacial-interglacial periods [73]. Coincident with these tendencies, the cooling periods in the Early Holocene and Subboreal stage were characterized by the growth of Si/Al and Ti/Al ratios recorded in core PSh-6050 [29].…”

“…The elevated content of Mn, as a redox-sensitive element, was used in the sediments of the Lomonosov Ridge in the Arctic Ocean to identify anoxia conditions caused by long-term ice cover [74]. Redox conditions and post-sedimentation change in bottom sediments can be traced by Mn/Fe proxy; down the core, change in Mn/Fe ratio is caused by difference in redox kinetics of these elements: increase in Mn/Fe occurs under the oxic conditions, while suboxic condition and anoxia lead to a decrease in the Mn/Fe ratio [25,73,[75][76][77]. In AMK-5194, the Mn/Fe ratio (0.009 on average) is almost two times less than that in UCC (0.016), which may indicate the slightly reduced condition throughout the core, and it is confirmed by findings of the rare hydrotroilite concrections in the Holocene sediments.…”