Suborbital Hydrological Variability Inferred From Coupled Benthic and Planktic Foraminiferal‐Based Proxies in the Southeastern Mediterranean During the Last 19 ka

Abstract

We present a high‐resolution study covering the past 19 ka from the southeastern Mediterranean Sea, based on benthic foraminiferal faunas and their stable oxygen and carbon isotopes. These data are integrated with previously published and newly acquired planktic foraminiferal data from the same sediment core in order to investigate the benthic‐planktic coupling and its response to past suborbital climate variability. On a millennial timescale, foraminiferal communities and their isotopic signatures vary following three main time periods (late glacial, sapropel S1 [~10.1–6.5 ka], and mid‐Holocene to Late Holocene). Within these intervals, we identified short‐timescale changes related to the carbon export and hydrological conditions. During the deglaciation, and except for the Younger Dryas, the coupled benthic‐planktic data indicate an overall poorly mixed water column with a low productivity. During S1 event, our data confirm the presence of a highly stratified water column, with enhanced primary productivity export to the deep sea, being associated to high Nile River activity. While the foraminiferal ecosystem is strongly driven by the combined influence of overturning circulation and the Nile River activity until the end of the African humid period, we suggest a more regional eastern Mediterranean climatic‐driven response of the foraminiferal community over the mid‐Holocene to Late Holocene. A strong multicentennial variability, probably associated to solar forcing, was found for both benthic and planktic records, and a supplementary 1,600‐year mode was found for the benthic data, suggesting a potential overturning circulation‐driven forcing for the latter.

High resolution paleo-environmental changes during the Sapropel 1 in the North Ionian Sea, central Mediterranean

“…However, there is a lack of consensus on the precise mechanisms and the exact sequence of climatic and oceanographic events that lead to the formation of Sapropels. It is generally accepted that Sapropels are the result of complex interactions between regional climatic, oceanographic and biogeochemical processes as a response to shifting global climate patterns (De Lange et al, 2008; Grimm et al, 2015; Le Houedec et al, 2020; Mercone et al, 2000, 2001; Rohling et al, 2015; Tachikawa et al, 2015; Vadsaria et al, 2019). Sapropel 1 (S1) is the only sapropel event that appears during Early-Mid-Holocene (interglacial period), between 10.8 ± 0.4 and 6.1 ± 0.5 kyrs BP (De Lange et al, 2008; Incarbona et al, 2019).…”

“…Third, enhanced surface ocean stratification also resulted in reduced ventilation rates of the deep waters through deep water convection (i.e. reduction in dissolved oxygen export) that in turn favoured the preservation of the organic matter due to the establishment of dysoxic conditions (Abu-Zied et al, 2008; De Lange et al, 1999, 2008; Drinia et al, 2016; Grimm et al, 2015; Le Houedec et al, 2020; Louvari et al, 2019; Rohling et al, 2015; Schmiedl et al, 2010). All these factors together could contribute to the formation of the Eastern Mediterranean (EMED) S1 layer.…”

Deoxygenation dynamics above the western Nile deep-sea fan during sapropel S1 at seasonal to millennial time-scales

“…We have added two deeper cores, MD04-2726 and MS27PT (retrieved at 1060 and 1390 m w-d, respectively), for which S/Cl ratios were published previously (Ménot et al, 2020;Revel et al, 2015). The S/Cl ratio traces the diagenetic formation of sulfur minerals such as pyrite (FeS 2 ), greigite (Fe 3 S 4 ) or pyrrhotite (Fe 7 S 8 ) from the pore-water sulfides (Liu et al, 2012;Matthews et al, 2017;Revel et al, 2015). This process is favoured by oxygen depletion, which leads to the accumulation of dissolved sulfides in the pore waters and precipitation of solid iron sulfides.…”

Ecological Constraints of Plankton Bio-Indicators for Water Column Stratification and Productivity: A Case Study of the Holocene North Aegean Sedimentary Record

“…The recent Holocene subdivision (Greenlandian, Northgrippian, and Meghalayan) confirms the traditional understanding of an evolution from wetter (Greenlandian) to gradually drier (Northgrippian and Meghalayan) climatic conditions. Moreover, Holocene sediments of the Aegean Sea include the most recent sapropel S1 that was deposited during the Holocene Climatic Optimum (10.8-6.1 ka cal BP; [8,9]) under reduced oxygen and productive conditions [10][11][12][13][14][15][16][17][18]. Therefore, the sedimentary archive corresponding to this time interval can be considered as a…”