Research ArticleENVIRONMENTAL STUDIES

Annual radiocarbon record indicates 16th century BCE date for the Thera eruption

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Science Advances  15 Aug 2018:
Vol. 4, no. 8, eaar8241
DOI: 10.1126/sciadv.aar8241
  • Fig. 1 Annual data and IntCal13.

    (A) Annual bristlecone pine data (1700–1500 BCE; blue) and Irish oak data (1661–1576 BCE; green) are shown relative to the IntCal13 raw data (red) and all show 2σ error. The majority of our annual data fall within the 2σ error of the IntCal raw data. (B) Calibration curves for pine (blue) and oak (green) constructed in the same way as IntCal13 (red) are shown with 1σ error. From 1700 BCE to c.1660 BCE, and after 1540 BCE, good agreement is shown between our data and the IntCal13 raw data. Between c.1660 BCE and c.1540 BCE, both species, from growth environments c.7900 km apart, indicate a clear and sustained offset from IntCal13.

  • Fig. 2 IntCal raw data with IntCal13 and IntCal98 curves.

    Raw determinations of multiyear blocks of north European oak making up IntCal13, 1700–1500 BCE with the derived IntCal13 curve. Comparison with the IntCal98 curve provides an example of how the addition of extra data and changes in the statistical methodology used to produce the curve has changed the shape over the years. The dashed line shows the midpoint of the ICCP17 curve, which is less offset from IntCal98.

  • Fig. 3 Examples of the change in date range for materials from key Thera contexts.

    (A) Combined oak and pine ICCP17 calibration curve (blue) compared with IntCal13 (red), with 1σ error quoted as standard. The shift in the OxCal probability distribution for the olive branch (B) (based on model 5, Table 1) and the seeds (C) (based on model 1, Table 1) are color-coded relative to each curve. The black dashed line (upper right) shows the earliest possible start date for the Egyptian New Kingdom within the archaeological framework, with the solid line indicating the more conventional range. Single vertical lines mark bristlecone pine “marker years” at 1597, 1560, 1546, and 1544 BCE referred to in the text. Note the presence of pronounced solar cycles in the plateau region, especially between 1560 and 1520 BCE. These features will be the focus of future work to improve calibration and chronological synchronization for this time period.

  • Table 1 Volcanic destruction layer radiocarbon determinations calibrated to IntCal13 and ICCP17.

    Using OxCal 4.3, we compare results for a number of previously published modeling scenarios. Models 1 to 3 show different modeled approaches to the assemblage of annual materials from pre-eruption contexts on Akrotiri (8, 9, 15, 41). Models 4 and 5 show different modeled approaches for the Santorini olive branch, with assumptions of annual growth (10); annual growth with counting uncertainties of 25 and 50% (10); or an ordered sequence of unknown years, which moves from older to younger (13). All values for the olive branch represent posterior estimates of the outermost ring except model 7 (a simple ordered sequence), where the value relates to the estimated age of the outermost measurement.

    SamplePublished model justificationPosterior mean cal BCE
    (2σ/95% credible interval)
    IntCal13ICCP17
    Akrotiri seed assemblage1: Archaeological assemblage represents a phase (number of different years)
    before the eruption (Tau boundary function) (9, 15)
    1625
    (1646–1606)
    1581
    (1619–1536)
    Akrotiri seed assemblage2: Selected archaeological assemblage represents the same year before the
    eruption (adjusted for volcanic context, 3326 ± 11 14C B.P.) (41)
    1608
    (1658–1535)
    1576
    (1614–1539)
    Akrotiri seed assemblage3: Selected archaeological assemblage represents the same year before the
    eruption (unadjusted, 3345 ± 9 14C B.P.) (41)
    1637
    (1664–1614)
    1587
    (1664–1541)
    Olive branch segments4: Accepts olive increments as measured by Friedrich et al. (10) are annual1615
    (1626–1605)
    1589
    (1610–1567)
    Olive branch segments5: Ring count is increased by 25%, and gap uncertainty set to
    25% of section count (10)
    1611
    (1627–1596)
    1574
    (1608–1511)
    Olive branch segments6: Gap uncertainty set to 50% of the ring count (10)1622
    (1721–1597)
    1577
    (1612–1528)
    Olive branch segments7: Treats sequence of olive segments as ordered but with no information
    on ring counts/gaps (13)
    1614
    (1642–1559)
    1570
    (1614–1538)

Supplementary Materials

  • Supplementary Materials

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    • Table S1. Annual determinations of Irish oak and North American bristlecone pine used in this study.

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