Beppu Bay, Japan, as a candidate Global boundary Stratotype Section and Point for the Anthropocene series

Abstract

For assessment of the potential of the Beppu Bay sediments as a Global Boundaries Stratotype Section and Point (GSSP) candidate for the Anthropocene, we have integrated datasets of 99 proxies. The datasets for the sequences date back 100 years for most proxy records and 1300 years for several records. The cumulative number of occurrences of the anthropogenic fingerprint reveal unprecedented increases above the base of the 1953 flood layer at 64.6 cm (1953 CE), which coincides with an initial increase in global fallout of 239Pu+240Pu. The onset of the proliferation of anthropogenic fingerprints was followed by diverse human-associated events, including a rapid increase in percent modern 14C in anchovy scales, changes in nitrogen and carbon cycling as recorded by anchovy δ15N and δ13C, elevated pollution of heavy metals, increased depositions of novel materials (spheroidal carbonaceous particles, microplastics, polychlorinated biphenyls), the occurrence of hypoxia (Re/Mo ratio) and eutrophication (biogenic opal, TOC, TN, diatoms, chlorophyll a), unprecedented microplankton community changes (compositions of carotenoids, diatoms, dinoflagellates), abnormally high spring air temperatures as inferred from diatom fossils, and lithological changes. These lines of evidence indicate that the base of the 1953 layer is the best GSSP level candidate in the stratigraphy at this site.

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

“…The second marine site is within an isolated basin located in relatively shallow coastal waters of Beppu Bay, Japan (Kuwae et al, 2023). It differs from the East Gotland Basin site in displaying annual varves and numerous turbidite layers.…”

Part 1: Anthropocene Series/Epoch: stratigraphic context and justification of rank The Anthropocene Epoch and Crawfordian Age: proposals by the Anthropocene Working Group

“…Some sites emphasised the first appearance of a measurement above background levels, e.g., just before 1950 CE in Crawford Lake (McCarthy et al, 2023, using the updated age model in McCarthy et al, 2024), 1953± 4 CE in East Gotland Basin (Kaiser et al, 2023), 1946-1947 Searsville Lake (Stegner et al, 2023), 1945 CE in the Palmer ice core (Thomas et al, 2023) and 1945 CE in the Karlsplatz anthropogenic deposits . Other sites noted the first prominent upturn in the signal, e.g., 1952 CE in Crawford Lake (see Part 2), 1953 CE in Sihailongwan Maar Lake ), 1954CE in Beppu Bay (Kuwae et al, 2023 and wider NW Pacific (Yokoyama et al, 2023), 1956CE in West Flower Garden Reef (DeLong et al, 2023 and 1952 CE in the Śnieżka peat .…”

Executive Summary: The Anthropocene Epoch and Crawfordian Age: proposals by the Anthropocene Working Group

“…1) Beppu Bay, Japan:The proposal is detailed inKuwae et al (2023). Beppu Bay is a small, deep depression located close to the coast of northeastern Kyushu.…”