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An exploratory method to detect tephras from quantitative XRD scans: Examples from Iceland and east Greenland marine sediments

Holocene

By:
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DOI: 10.1177/0959683606069384

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Abstract

Tephras, mainly from Iceland, are becoming increasingly important in interpreting leads and lags in the Holocene climate system across NW Europe. Here we demonstrate that Quantitative Phase Analysis of x-ray diffractograms of the < 2 mm of marine sediment fraction (ie, sand, silt and clay) from Iceland and East Greenland can detect peaks in volcanic glass concentrations (weight%) even though discrete tephra layers are not visible; thus it provides a rapid overview of the probable location of volcanic glass within sediment sequences. Experiments in spiking samples from Baffin Bay and an artificial mixture of minerals with known weight% fractions of an Icelandic tephra (Hekla 4) demonstrate a significant correlation (r2 = 0.92 and 0.97) between known and estimated weight percentages, although the slope of the measured to observed weight% is around 0.65 and not 1.0 as expected. In core B997-321PC off North Iceland we identify tephras from point counting in the > 150 um fraction and identify these same peaks in XRD scans - two of these correlate geochemically and chronologically with Hekla 1104 and 3. At a distal site to the WNW of Iceland, on the East Greenland margin (core MD99-2317), the weight% of volcanic glass reaches values of 11% at about the time of the Saksunarvatn tephra. The XRD method identifies the presence of volcanic glass but not its elemental composition; hence it will assist in focusing attention on specific sections of sediment cores for subsequent geochemical fingerprinting of tephras. ?? 2006 SAGE Publications.

Additional Publication Details

Publication type:
Article
Publication Subtype:
Journal Article
Title:
An exploratory method to detect tephras from quantitative XRD scans: Examples from Iceland and east Greenland marine sediments
Series title:
Holocene
DOI:
10.1177/0959683606069384
Volume
16
Issue:
8
Year Published:
2006
Language:
English
Larger Work Type:
Article
Larger Work Subtype:
Journal Article
First page:
1035
Last page:
1042
Number of Pages:
8