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

• Published in: Earth and Planetary Science Letters
• Main Authors: White, Lee F., Bailey, Ian, Foster, Gavin L., Allen, Georgina, Kelley, Simon P., Andrews, John T., Hogan, Kelly, Dowdeswell, Julian A., Storey, Craig D.
• Format: Text
• Language: English
• Published: Elsevier Science Bv
• Subjects: geo; envir; Greenland; Ice Sheet
• Online Access: https://doi.org/10.1016/j.epsl.2015.10.054; https://archimer.ifremer.fr/doc/00421/53292/54130.pdf; https://archimer.ifremer.fr/doc/00421/53292/54131.pdf; https://archimer.ifremer.fr/doc/00421/53292/54132.xlsx

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.