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

Andrews, J. T. and Eberl, D. D. and Kristjansdottir, G. B. (2006) An exploratory method to detect tephras from quantitative XRD scans: examples from Iceland and east Greenland marine sediments. Holocene, 16 (8). pp. 1035-1042. ISSN 0959-6836 DOI https://doi.org/10.1177/0959683606069384

Text The Holocene-2006-Andrews-1035-42.pdf - Published Version Restricted to Registered users only Download (470kB)

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 μm 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.

Item Type:	Article
Uncontrolled Keywords:	2007 AREP IA53 2006 P
Subjects:	01 - Climate Change and Earth-Ocean Atmosphere Systems
Divisions:	01 - Climate Change and Earth-Ocean Atmosphere Systems
Journal or Publication Title:	Holocene
Volume:	16
Page Range:	pp. 1035-1042
Identification Number:	https://doi.org/10.1177/0959683606069384
Depositing User:	Sarah Humbert
Date Deposited:	16 Feb 2009 13:01
Last Modified:	11 Apr 2014 09:29
URI:	http://eprints.esc.cam.ac.uk/id/eprint/110

Actions (login required)

View Item