Research ArticleENVIRONMENTAL STUDIES

Deglaciation of the Pacific coastal corridor directly preceded the human colonization of the Americas

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Science Advances  30 May 2018:
Vol. 4, no. 5, eaar5040
DOI: 10.1126/sciadv.aar5040
  • Fig. 1 North American Ice Sheet extents and potential colonization pathways.

    Extent of the Cordilleran and Laurentide ice sheets at 19 ka ago (white) and 15.5 ka ago. Areas of exposed continental shelf at 19 ka ago are shown in brown (6). Yellow stars indicate locations of offshore marine data discussed in the main text.

  • Fig. 2 New 10Be ages from southeastern Alaska.

    Study region showing previously hypothesized CIS extent (white) and regions of potentially exposed continental shelf (solid gray; determined by subtracting 125 m from modern sea level) during the LGM (30). Sampling sites for 10Be dating were selected within areas hypothesized by Carrara et al. (30) to have been ice-free during the LGM. Boulder (normal text) and bedrock (italicized text) 10Be ages (thousand years; 1 SD external uncertainty) constrain CIS (black) and local deglaciation (blue) and demonstrate that sampling sites were not ice-free refugia. The location of Shuká Káa cave on Prince of Wales Island is marked with an orange star.

  • Fig. 3 Climate records and key chronologies along the Pacific coast.

    (A) Alkenone-derived sea surface temperature reconstruction from the Gulf of Alaska (36). (B) Ice-rafted debris from core MD0299, collected near Vancouver Island (23). (C) Composite diagram of individual 10Be ages from southeastern Alaska (gray and light blue lines; this study), summed 10Be ages for CIS deglaciation (black lines; this study), and local deglaciation (blue lines; this study). (D) Timing of the first pulse of human migration to the Americas [black square; (13)], the ecological opening of the inland corridor [purple triangle; (8)], and 14C ages from Shuká Káa (dark green lines; this study) and other caves in southeastern Alaska (light green lines; this study). (E) Timeline of selected cave fauna from southeastern Alaska [(29); this study]. Dots represent the means of the total range of each calibrated 14C age (this study). Vertical gray bar denotes the timing of maximum CIS extent in southeastern Alaska determined from the cave fauna 14C ages and 10Be ages reported in this study.

Supplementary Materials

  • Supplementary material for this article is available at http://advances.sciencemag.org/cgi/content/full/4/5/eaar5040/DC1

    fig. S1. Map of southeastern Alaska with labeled islands.

    fig. S2. Representative boulder and bedrock samples collected for 10Be dating.

    fig. S3. Normal kernel density estimates of 10Be ages.

    fig. S4. Fossilized mammal bone 14C ages from caves in southeastern Alaska.

    fig. S5. Box-and-whisker plot of fossilized cave bone δ13C values from Prince of Wales Island.

    fig. S6. Sensitivity testing of the fossilized cave bone 14C age calibration.

    fig. S7. Fossilized cave bone δ13C values and marine carbon percentages through time.

    table S1. 10Be sample information.

    table S2. 10Be ages calculated with alternative production rates and scaling schemes.

    table S3. Fossilized cave bone sample information used for 14C calibration.

    Reference (66)

  • Supplementary Materials

    This PDF file includes:

    • fig. S1. Map of southeastern Alaska with labeled islands.
    • fig. S2. Representative boulder and bedrock samples collected for 10Be dating.
    • fig. S3. Normal kernel density estimates of 10Be ages.
    • fig. S4. Fossilized mammal bone 14C ages from caves in southeastern Alaska.
    • fig. S5. Box-and-whisker plot of fossilized cave bone δ13C values from Prince of Wales Island.
    • fig. S6. Sensitivity testing of the fossilized cave bone 14C age calibration.
    • fig. S7. Fossilized cave bone δ13C values and marine carbon percentages through time.
    • table S1. 10Be sample information.
    • table S2. 10Be ages calculated with alternative production rates and scaling schemes.
    • table S3. Fossilized cave bone sample information used for 14C calibration.
    • Reference (66)

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