Research ArticleGEOCHEMISTRY

Volcanic origin for Younger Dryas geochemical anomalies ca. 12,900 cal B.P.

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Science Advances  31 Jul 2020:
Vol. 6, no. 31, eaax8587
DOI: 10.1126/sciadv.aax8587
  • Fig. 1 Depth below datum (BDT) profiles against total Os abundances (ppt) and 187Os/188Os ratios of Hall’s Cave sample section.

    (A) Depth versus total Os abundances (ppt). (B) Depth versus 187Os/188Os ratios. Local datum used in this study was placed by Toomey, 1986 (23). UR, unradiogen. UR1 to UR5 represent five unradiogenic Os peaks. Depth values are the basal depth of the 1-cm-thick excavation interval relative to the datum. Six ages were calibrated using direct AMS 14C measurements with 95.4% confidence intervals and then used to calculate the rest of the dates with linear interpolation between the dated levels.

  • Fig. 2 CI chondrite–normalized incremental mixing model of CI chondrite material into an upper continental crust–like target.

    From 0.5 to 5.0% mixing lines use 0.5% increment, beneath are the 0.05 and 0.25% lines. HSE patterns of Hall’s Cave unradiogenic Os sediments (blue dotted pattern) and radiogenic Os sediments (pink shadow) compared with average upper continental crust (UCC) (18, 26), Clearwater East Impact melt rock, Canada (51), and Petriccio K/T boundary, Italy (52). Cl chondrite values used for normalization are from Wasson and Kallemeyn (27).

  • Fig. 3 Osmium isotope results and mixing models between Hall’s Cave crusts and mantle-like Os end members.

    (A) 187Os/188Os versus 1/Os concentration (ppt) for Hall’s Cave sediments with four mixing models for this study. Parameters used for the models are listed in table S4 (B) Mixing models close-up view on the lower left end of (A). Upper continental crust (18, 26), data for bulk sediments, bulk spherules and spherule surface films, and residues were for the Melrose (PA) YD site from Wu et al. (22).

  • Fig. 4 CI chondrite–normalized HSE patterns of all gas condensates and the average of the Kudryavy volcano gas condensates, Kurile Islands.

    Upper continental crust is from Park et al. (26) and Esser and Turekian (18). The HSE patterns for the Os isotope radiogenic and unradiogenic groups from Hall’s Cave are in pink shadow and blue dotted pattern, respectively. All Kudryavy volcano gas condensates (abbreviated to vlc. gas cond.) (38) are plotted as yellow shadow whose average is presented as the yellow line. Cl chondrite values used for normalization are from Wasson and Kallemeyn (27).

  • Fig. 5 Binary plots of HSE elements and ratios of Hall’s Cave samples.

    (A) Ir versus Ir/Pt, (B) Pt/Os versus Os, (C) Pt versus Pd. compared to upper continental crust (18, 26), Clearwater East Impact melt rock, Canada (51); Petriccio K/T boundary, Italy (52); Kudryavy volcano gas condensates, Kurile Islands (38); Tolbachik volcano gas condensate, Kamchatka (45); Erta Ale volcano gas (abbreviated to vlc. gas), Ethiopia (39) and confirmed impact craters, Popigai, Russia (53); Morokweng, South Africa (16); Serenitatis basin, Moon (54); MORB, mid-ocean ridge basalts (55, 56); OIB, ocean island basalts (57, 58); Volcanic arcs (36); and komatiites (29, 59). (A) Ir versus Ir/Pt. (B) Pt/Os versus Os. (C) Pt versus Pd. See text for more information.

Supplementary Materials

  • Supplementary Materials

    Volcanic origin for Younger Dryas geochemical anomalies ca. 12,900 cal B.P.

    N. Sun, A. D. Brandon, S. L. Forman, M. R. Waters, K. S. Befus

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    • Tables S1 to S5
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