Holocene Spatiotemporal Redox Variations in the Southern Baltic Sea

Low oxygen conditions in the modern Baltic Sea are exacerbated by human activities; however, anoxic also prevailed naturally over Holocene. Few studies have characterized specific paleoredox (manganous, ferruginous, euxinic) and their frequency southern sub-basins during these ancient events. Here, we apply a suite of isotope systems (Fe, Mo, S) associated elemental proxies (e.g., Fe speciation, Mn) to specifically define water column redox regimes through Holocene sill-proximal sill-distal transect (Lille Belt, Bornholm Basin, Landsort Deep) using samples collected Integrated Ocean Drilling Program Expedition 347. At Lille there is evidence for manganous/ferruginous most cored interval following transition from Ancylus Lake Littorina but with no clear excursion more reducing or euxinic Thermal Maximum (HTM) Medieval Climate Anomaly (MCA) sub-basin, combination pore Fe, solid phase Mo concentration data point Lake-to-Littorina HTM only brief excursions intermittently weakly this interval. western Proper Deep, new S bolster previous records speciation two distinct periods suggest that sulfide accumulation beyond transient levels was largely restricted sediment-water interface. Ultimately, combined all three locations indicate enrichments typically indicative euxinia may be best explained deposition as oxides events likely analogous periodic incursions oxygenated North waters observed today, subsequent pyrite formation sulfidic waters. Additionally, multiple basins argue against widespread conditions, has been demonstrated Bothnian MCA. Instead, similar each past event become progressively increasing distance sill.