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A quantitative x-ray diffraction inventory of volcaniclastic inputs into the marine sediment archives off Iceland: a contribution to the Volcanoes in the Arctic System programme ArchiMer
Andrews, John T.; Kristjansdottir, Greta B.; Eberl, Dennis D.; Jennings, Anne E..
This paper re-evaluates how well quantitative x-ray diffraction (qXRD) can be used as an exploratory method of the weight percentage (wt%) of volcaniclastic sediment, and to identify tephra events in marine cores. In the widely used RockJock v6 software programme, qXRD tephra and glass standards include the rhyodacite White River tephra (Alaska), a rhyolitic tephra (Hekla-4) and the basaltic Saksunarvatn tephra. Experiments of adding known wt% of tephra to felsic bedrock samples indicated that additions >= 10 wt% are accurately detected, but reliable estimates of lesser amounts are masked by amorphous material produced by milling. Volcaniclastic inputs range between 20 and 50 wt%. Primary tephra events are identified as peaks in residual qXRD glass wt%...
Tipo: Text Palavras-chave: X-ray diffraction; Tephras; Iceland Holocene.
Ano: 2013 URL: https://archimer.ifremer.fr/doc/00265/37578/36528.pdf
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A robust, multisite Holocene history of drift ice off northern Iceland: implications for North Atlantic climate ArchiMer
Andrews, John T.; Darby, Dennis; Eberle, Dennis; Jennings, Anne E.; Moros, Matthias; Ogilvie, Astrid.
An important indicator of Holocene climate change is provided by evidence for variations in the extent of drift ice. A proxy for drift ice in Iceland waters is provided by the presence of quartz. Quantitative x-ray diffraction analysis of the < 2 mm sediment fraction was undertaken on 16 cores from around Iceland. The quartz weight (wt.)% estimates from each core were integrated into 250-yr intervals between -0.05 and 11.7 cal. ka BP. Median quartz wt.% varied between 0.2 and 3.4 and maximum values ranged between 2.8 and 11.8 wt.%. High values were attained in the early Holocene and minimum values were reached 6 7 cal. ka BP. Quartz wt.% then rose steadily during the late Holocene. Our data exhibit no correlation with counts on haematite-stained quartz...
Tipo: Text Palavras-chave: Ice rafted debris; Iceland; Quartz; Drift ice; Holocene; Arctic basin.
Ano: 2009 URL: https://archimer.ifremer.fr/doc/00218/32943/31420.pdf
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