Publication Date:
2016-06-29
Description:
Quantitative X-ray diffraction analysis of the 〈2mm sediment fraction was carried out
on 1257 samples (from the seafloor and 16 cores) from the Iceland shelf west of 188 W. All but one core
(B997-347PC) were from transects along troughs on theNW to N-central shelf, an area that in modern
and historic times has been affected by drift ice. The paper focuses on the non-clay mineralogy of the
sediments (excluding calcite and volcanic glass). Quartz and potassium feldspars occupy similar
positions in an R-mode principal component analysis, and oligoclase feldspar tracks quartz; these
minerals are used as a proxy for ice-rafted detritus (IRD). Accordingly, the sum of these largely foreign
minerals (Q&K) (to Icelandic bedrock) is used as a proxy for drift ice. A stacked, equi-spaced 100 a
record is developed which shows both low-frequency trends and higher-frequency events. The
detrended stacked record compares well with the flux of quartz (mg cm-2 a-1) at MD99-2269 off
N Iceland. The multi-taper method indicated that there are three significant frequencies at the 95%
confidence level with periods of ca. 2500, 445 and 304 a. Regime shift analysis pinpoints intervals
when there was a statistically significant shift in the average Q&K weight %, and identifies four IRDrich
events separated by intervals with lower inputs. There is some association between peaks of IRD
input, less dense surface waters (from d18O data on planktonic foraminifera) and intervals of moraine
building.
Type:
Article
,
PeerReviewed
Format:
text
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