Research ArticleGEOLOGY

Lake sediments with Azorean tephra reveal ice-free conditions on coastal northwest Spitsbergen during the Last Glacial Maximum

See allHide authors and affiliations

Science Advances  23 Oct 2019:
Vol. 5, no. 10, eaaw5980
DOI: 10.1126/sciadv.aaw5980
  • Fig. 1 Overview map of the Svalbard archipelago.

    Our study site, Lake Hajeren, is highlighted with a green dot; the green inset marks the extent of the detailed map in fig. S1. Modern glacier extent is shown, along with (most credible) reconstructed ice margin positions after (45) for key intervals: 32 to 30 ka B.P. (referred to as ~30 ka B.P.) (the onset of late Weichselian sedimentation in Hajeren), c. 20 ka B.P. (when the lake was overrun by nonerosive ice), and c. 11 ka B.P. (when lacustrine sedimentation resumed). We also indicate the localities of the sea ice reconstructions from the Yermak plateau and the western Svalbard margin that are shown in Fig. 5 (47).

  • Fig. 2 Stratigraphic context of analyzed unit 4 sediments from Lake Hajeren.

    (A) Down-core density, magnetic susceptibility (MS), and water content (compared to dry sediment weight) measurements. (B) Clam-calibrated chronology. The core image on the left-hand side marks the sampling locations of the analyzed material shown in the other panels using corresponding numbers or letters. (C) Computed tomography (CT) slice that highlights the laminated nature of the investigated sediments. (D) Plate(s) of dated plant macrofossil remains from dated horizons. Plates 1 and 3 show representative material from the horizon previously dated by (13) (table S2), while material from horizon 2 was dated for this study. (E) X-ray diffraction (XRD) diffractograms of the clay (<6 μm) and silt (6 to 63 μm) fraction of unit 4 sediments, plotted together with reference stick patterns of the most abundant minerals—muscovite, quartz, and illite. Photo credit: Willem van der Bilt, University of Bergen.

  • Fig. 3 Overview maps with the locations of discussed tephra sites and samples.

    (A) North Atlantic region, delineating insets (B) and (C) with rectangles and marking active volcanoes with black triangles. Discussed eruptive centers are shown in different colors. (B) Azores archipelago, showing the Terceira rift after (58) and marking mentioned volcanoes on the islands of São Miguel and Terceira. (C) The Lake Hajeren study site and northwest Spitsbergen. (D) Terceira Island, delimiting Lajes-Angra Ignimbrite (LAI) deposits from the Pico Alto volcano (25).

  • Fig. 4 Tephra concentrations and geochemistry.

    (A) Shard counts in the analyzed horizon (9539) and adjacent 1- and 10-cm core intervals (table S3). (B) Total alkali-silica (TAS) diagram, comparing the normalized geochemical composition of analyzed shards from Lake Hajeren with reference glass material from Trachytic (T) volcanic sources and eruptions from North Atlantic and Mediterranean sources. (C) FeO(t) versus CaO biplot to distinguish Azorean tephras from other sources and one another (inset) after (28, 32). Inset red crosses visualize analytical uncertainty based on secondary standard measurements. Ellipses encapsulate 95% of plotted reference material from the Azores (Fig. 3B) and Pico Alto from Terceira (Fig. 3C). Table S4 lists data sources. (D) Calibrated radiocarbon ages of the analyzed tephra horizon from the Lake Hajeren study site and the Summed Probability Distribution of published dates (n = 3) at the base of the LAI Ignimbrite (table S5) (25, 39).

  • Fig. 5 PBIP25-derived changes in seasonal sea ice conditions during the discussed time interval of 30 to 11 ka B.P. from the western Svalbard margin (core PS93/006-1) and eastern Yermak plateau (core PS92/039-2) after (12).

    The time spans covered by analyzed unit 4 in core HAP0212 and the overlying hiatus are highlighted, while we show the calibrated range of the 14C age (LuS 10868, green bell curve; also see table S2) that separates both intervals.

Supplementary Materials

  • Supplementary material for this article is available at http://advances.sciencemag.org/cgi/content/full/5/10/eaaw5980/DC1

    Fig. S1. Overview maps of our study area and site.

    Fig. S2. The full stratigraphy and chronology of investigated core HAP0212.

    Table S1. Major and minor oxide data of glass standards, along with calculated means and (weighted) SDs (2σ) of replicate measurements.

    Table S2. Overview of presented radiocarbon (14C) samples.

    Table S3. Glass (tephra) shard counts in 10-cm slices of core HAP0212, as well as 1-cm resolution counts for the selected 276.5- to 285.5-cm interval shown in Fig. 4A.

    Table S4. Published ages and reference glass data sources for specific eruptions from particular volcanic sources that are discussed and shown in the main text (Figs. 3 and 4).

    Table S5. Published radiocarbon ages that were taken from the base of LAI deposit and used to calculate the onset of the eruption (Fig. 4D).

    Table S6. Major and minor oxide data (normalized), along with basic statistics (including the coefficient of variation), of the analyzed (n = 4) tephra shards presented in this study.

  • Supplementary Materials

    This PDF file includes:

    • Fig. S1. Overview maps of our study area and site.
    • Fig. S2. The full stratigraphy and chronology of investigated core HAP0212.
    • Table S1. Major and minor oxide data of glass standards, along with calculated means and (weighted) SDs (2σ) of replicate measurements.
    • Table S2. Overview of presented radiocarbon (14C) samples.
    • Table S3. Glass (tephra) shard counts in 10-cm slices of core HAP0212, as well as 1-cm resolution counts for the selected 276.5- to 285.5-cm interval shown in Fig. 4A.
    • Table S4. Published ages and reference glass data sources for specific eruptions from particular volcanic sources that are discussed and shown in the main text (Figs. 3 and 4).
    • Table S5. Published radiocarbon ages that were taken from the base of LAI deposit and used to calculate the onset of the eruption (Fig. 4D).
    • Table S6. Major and minor oxide data (normalized), along with basic statistics (including the coefficient of variation), of the analyzed (n = 4) tephra shards presented in this study.

    Download PDF

    Files in this Data Supplement:

Stay Connected to Science Advances

Navigate This Article