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Tracking the provenance of Greenland-sourced, Holocene aged, individual sand-sized ice-rafted debris using the Pb-isotope compositions of feldspars and 40Ar/39Ar ages of hornblendes
The provenance of sand-sized ice-rafted debris (IRD) sourced from Greenland is currently difficult to determine. Such knowledge, if it could be ascertained with a high degree of certainty, could be applied to the Greenland-proximal marine records to improve both our understanding of modern-day spatial patterns of iceberg rafting and the past history of the Greenland Ice Sheet (GIS). Recent studies have highlighted the utility of the Pb-isotope composition of individual sand-sized feldspars and the Ar-40/Ar-39 ages of individual sand-sized hornblendes in this regard. However, before any such provenance toolkit can be applied to the palaeo-record, it is necessary first to determine whether this approach can be used to track the sources of known recent Greenland-proximal IRD deposition. To this end we present new records of the Pb-isotope composition and the Ar-40/Ar-39 ages of individual sand-sized grains of feldspars and homblendes, respectively, from modern Greenland glacifluvial and ford sands and Holocene to modern Greenland-proximal marine sediments. These new data demonstrate that sand-sized feldspars and hornblendes glacially eroded by the GIS exhibit distinct intra- and inter-tectonic terrane differences in their Pb-isotope compositions and ages and that these differences are clearly expressed in the geochemistry and geochronology of sand-sized IRD deposited in marine sediments around Greenland. Although overlap exists between some Greenland-proximal IRD 'source fields' defined by these data, our approach has the potential to both better understand spatial patterns of Greenland-derived IRD in the modern day as well as during past episodes of iceberg calving.
Keyword(s)
Greenland, ice rafted debris, Ar-Ar, Pb isotopes, icebergs, provenance
Full Text
File | Pages | Size | Access | |
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Publisher's official version | 12 | 2 Mo | ||
MMC 1. This document contains text that details the specifics of our laser ablation MC-ICP-MS method and construction of the Gaussian curves used to present our Ar–Ar geochronological data | 4 | 317 Ko | ||
MMC 2 All raw data is presented in Tables S1, S2 and S3, which detail the Pb–Pb isotope ratios of Greenland sources (S1) and marine sinks (S2), in... | - | 75 Ko |