Abstract
A widespread platinum (Pt) anomaly was recently documented in Greenland ice and 11 North American sedimentary sequences at the onset of the Younger Dryas (YD) event (~12,800 cal yr BP), consistent with the YD Impact Hypothesis. We report high-resolution analyses of a 1-meter section of a lake core from White Pond, South Carolina, USA. After developing a Bayesian age-depth model that brackets the late Pleistocene through early Holocene, we analyzed and quantified the following: (1) Pt and palladium (Pd) abundance, (2) geochemistry of 58 elements, (3) coprophilous spores, (4) sedimentary organic matter (OC and sedaDNA), (5) stable isotopes of C (δ13C) and N (δ15N), (6) soot, (7) aciniform carbon, (8) cryptotephra, (9) mercury (Hg), and (10) magnetic susceptibility. We identified large Pt and Pt/Pd anomalies within a 2-cm section dated to the YD onset (12,785 ± 58 cal yr BP). These anomalies precede a decline in coprophilous spores and correlate with an abrupt peak in soot and C/OC ratios, indicative of large-scale regional biomass burning. We also observed a relatively large excursion in δ15N values, indicating rapid climatic and environmental/hydrological changes at the YD onset. Our results are consistent with the YD Impact Hypothesis and impact-related environmental and ecological changes.
Highlights
Interest in lacustrine paleoenvironmental records such as White Pond, has recently increased due to evidence of an extraterrestrial (ET) impact that is proposed to have caused the Younger Dryas (YD) climatic anomaly[3]
Bayesian analysis of 22 AMS dates from an ~1-meter section of core obtained from deeply buried lacustrine sediments at White Pond confirm the presence of the YD onset within stratigraphic Unit II dating to ca.[12,835] to 12,735 cal yr BP
Subsequent declines in coprophilous spores are observed during the YD onset, including a pre-Holocene Sporormiella minimum at 12,752 ± 54 cal yr BP; a significant core hiatus that spans the later YD to early Holocene precludes a robust assessment of the timing of megaherbivore extinction at White Pond
Summary
Interest in lacustrine paleoenvironmental records such as White Pond, has recently increased due to evidence of an extraterrestrial (ET) impact that is proposed to have caused the YD climatic anomaly[3]. Recent studies by Wolbach et al.[17,18] have provided additional evidence in the form of multiple proxies for large-scale biomass-burning and a brief impact winter triggered at ~12,800 years ago Those studies were based on analyses of large numbers of terrestrial, lacustrine, marine, and ice core records with peaks in biomass-burning proxies such as charcoal, pyrogenic carbon (soot and aciniform carbon, as described in Wolbach et al.18), and combustion aerosols, such as ammonium. These cores are well-suited for this objective because they contain sediments that bracket the Pleistocene-Holocene transition and include a well-dated (~10 cm-thick) YD onset sequence (modeled age: 12,835–12,735 cal yr BP at 95% confidence interval)[21]
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