The Sihailongwan Maar Lake, northeastern China as a candidate Global boundary Stratotype Section and Point for the Anthropocene series

Abstract

Sihailongwan Maar Lake, located in Northeast China, is a candidate Global boundary Stratotype Section and Point (GSSP) for demarcation of the Anthropocene. The lake’s varved sediments are formed by alternating allogenic atmospheric inputs and authigenic lake processes and store a record of environmental and human impacts at a continental-global scale. Varve counting and radiometric dating provided a precise annual-resolution sediment chronology for the site. Time series records of radioactive (239,240Pu, 129I and soot 14C), chemical (spheroidal carbonaceous particles, polycyclic aromatic hydrocarbons, soot, heavy metals, δ13C, etc), physical (magnetic susceptibility and grayscale) and biological (environmental DNA) indicators all show rapid changes in the mid-20th century, coincident with clear lithological changes of the sediments. Statistical analyses of these proxies show a tipping point in 1954 CE. 239,240Pu activities follow a typical unimodal globally-distributed profile, and are proposed as the primary marker for the Anthropocene. A rapid increase in 239,240Pu activities at 88 mm depth in core SHLW21-Fr-13 (1953 CE) is synchronous with rapid changes of other anthropogenic proxies and the Great Acceleration, marking the onset of the Anthropocene. The results indicate that Sihailongwan Maar Lake is an ideal site for the Anthropocene GSSP.

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

“…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). In the Sihailongwan Lake core, statistical analysis of all measured proxies identified a 1954 change point, but the rapid increase in 239+240 Pu activities at 88 mm (1953 CE) was selected as the preferred GSSP level (Han et al, 2023), supported by rapid increase in radioactive 129 I concentrations from ~1950; alternatively, the base of the lowermost dark-yellow lamina at 85 mm (1955–1956) forms a prominent lithological boundary. For the Crawford Lake core, the GSSP is proposed at 15.6 cm depth, at the base of the calcite lamina deposited in the summer of 1950 CE, selected because of the rapid rise in key markers between 1950 and 1954 and in particular the primary guide of 239+240 Pu having a significant initial upturn at ~1950 CE (McCarthy et al, 2023).…”

“…The Sihailongwan Maar Lake, China succession described by Han et al (2023) comprises varves of clastic silt and clay (winter) interlaminated with layers of algae and organic matter (summer-fall). Varve counting produces a robust chronology corresponding with radiometric ( 210 Pb, 137 Cs) dating.…”

Sedimentary DNA reveals phytoplankton diversity loss in a deep maar lake during the Anthropocene

“…S1). Detailed methods have been published previously by Han et al (2023). By comparing the established core age model (SHLW21-Fr-13), age-depth models for other parallel sediment cores were built according to varve counting and distinct marker layers (Supporting Information Fig.…”

“…The proxies and analytical methods with the corresponding core numbers are listed in Supporting Information Table S1. The data used in this study were generated by Han et al (2023), and the specific measurement method for these proxies is provided in the Supporting Information.…”

“…Most physicochemical indicators have exhibited rapid changes since the mid-20 th century (see Han et al 2023 for more details). The levels of 129 I, 239,240 Pu, Soot 14 C, SCPs, and PAHs were very low prior to the 1950s and showed a rapid increase after the 1950s (Fig.…”