Seeking a Holocene drift ice proxy: non‐clay mineral variations from the SW to N‐central Iceland shelf: trends, regime shifts, and periodicities

Abstract

Quantitative X-ray diffraction analysis of the <2 mm 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 the NW 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 À2 a À1 ) 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 d 18 O data on planktonic foraminifera) and intervals of moraine building.

Unraveling Sediment Transport Along Glaciated Margins (the Northwestern Nordic Seas) Using Quantitative X-Ray Diffraction of Bulk (< 2mm) Sediment

“…I use data from JR51-GC35 because the qXRD results on MD99-2269 only reported quartz, plagioclase, and calcite wt%s (Moros et al, 2006). However, the quartz wt% data from JR51-GC35 closely parallels the MD99-2269 data (Andrews, 2009) (Fig. 7B).…”

“…6), it has higher wt% of quartz, saponite, ferruginous smectite, and Fe-chlorite than samples from East Greenland or Iceland. Quartz and k-feldspars do not occur in any significant amounts within the bedrock of Iceland (Eiriksson et al, 2000) and they have, therefore, been used as an index of ice-rafting debris (IRD) (Eiriksson et al, 2000;Moros et al, 2006;Andrews, 2009;Andrews et al, 2009b) (e.g. Fig.…”

Multidecadal to millennial marine climate oscillations across the Denmark Strait (~ 66° N) over the last 2000 cal yr BP

“…(Axford et al, 2011) versus the smoothed (5-point average) weight% calcite (blue) from the combined HU93030-019B and MD99-2322; (B) 15 yr calcite wt% (blue) and regime shift mean values versus the radiocarbon calibrated probability distribution for Baffin Island vegetation (Miller et al, 2012) (red); (C) quartz wt% (grey line with filled circles), regime shifts (black line) and the trend (heavy grey line). been presented at 250 and 100 yr resolution (Andrews, 2009;Andrews et al, 2009b). We focus on three high-resolution records that span the last 2000 cal yr, namely MD99-2263 (Andrews et al, 2009a;Olafsdottir et al, 2010), MD99-2269 Moros et al, 2006;Stoner et al, 2007), and B997-316PC3 .…”

An inter-laboratory investigation of the Arctic sea ice biomarker proxy IP&lt;sub&gt;25&lt;/sub&gt; in marine sediments: key outcomes and recommendations

“…In recent years, a number of proxy-based approaches to sea ice reconstruction have been developed and employed to provide new insights into sea ice conditions (and changes to these) for both the Arctic and the Antarctic (e.g. Gersonde and Zielinski, 2000;Knies et al, 2001;Sarnthein et al, 2003;de Vernal et al, 2005;Belt et al, 2007;Andrews, 2009;Armand and Leventer, 2010;Polyak et al, 2010;Stein et al, 2012). Many sea ice proxy methods are based on the characteristic signatures provided by various biological species that are either closely associated with, or influenced by, sea ice cover (e.g.…”