The East Gotland Basin (Baltic Sea) as a candidate Global boundary Stratotype Section and Point for the Anthropocene series

Abstract

The short sediment core EMB201/7-4 retrieved from the East Gotland Basin, central Baltic Sea, is explored here as a candidate to host the stratigraphical basis for the Anthropocene series and its equivalent Anthropocene epoch, still to be formalized in the Geological Time Scale. The core has been accurately dated back to 1840 CE using a well-established event stratigraphy approach. A pronounced and significant change occurs at 26.5 cm (dated 1956 ± 4 CE) for a range of geochemical markers including 239+240Pu, 241Am, fly-ash particles, DDT (organochlorine insecticide), total organic carbon, and bulk organic carbon stable isotopes. This stratigraphic level, which corresponds to a change in both lithology and sediment colour related to early anthropogenic-triggered eutrophication of the central Baltic Sea, is proposed as a Global Boundary Stratotype Section and Point for the Anthropocene series.

Downward migrating microplastics in lake sediments is a tricky indicator for the onset of the Anthropocene

“…contamination during samples preparative procedure). Same can be concluded from other studies 9,[30][31][32][33][34] .…”

“…MPs have been identi ed in signi cant amounts below 1950 also in other studies with well-dated sediment records 9,10,[30][31][32][33][34] . For example, the Santa Barbara basin record, where a varved sediment structure denotes the absence of physical mixing, shows a clearly increasing trend in fragments and lms starting from sediments older than 1950 (see Brandon, et al 10 supplementary data).…”

“…However, despite exponential growth in the number of studies on MPs in sediments in general, there are very few studies reporting MP pollution ndings from well-dated sediment pro les 9,10,[30][31][32][33][34] . Hence, the usability of MP pro les as supplementary marker for the Anthropocene remains speculative.…”

Candidate sites and other reference sections for the Global boundary Stratotype Section and Point of the Anthropocene series

“…For the Śnieżka peat, 1952 CE is chosen based on a prominent increase in 239+240 Pu activity (Fiałkiewicz-Kozieł et al, 2023), while at Beppu Bay, the initial upturn in Pu values in 1953 CE is chosen. For the East Gotland Basin, changepoint analysis of 239+240 Pu and 241 Am indicates a prominent upturn at 26.5 cm depth (1956 ± 4 CE), coinciding with a prominent colour change (Kaiser et al, 2023). Further change point analyses of anthropogenic pollutants (SCPs, MPs, metals, DDT, PAHs, coprostanol) and organic proxies (TOC, TN, δ 15 N, δ 13 C, brassicasterol, tetrahymanol) indicate that for these proxies the most significant change occurs at 25.5 cm (1960 ± 4 CE).…”

“…The East Gotland Basin is a deep anoxic basin within the largely enclosed Baltic Sea (Kaiser et al, 2023). The single sediment core EMB201/7-4 shows a clear colour change at ~27 cm depth (1956 ± 4 CE), with homogeneous grey silty clay with low organic carbon content below and brown to black, organic-rich sediments above.…”