2007 GSA Denver Annual Meeting (28–31 October 2007)

Paper No. 10
Presentation Time: 1:30 PM-5:30 PM

AN EAST GREENLAND PROVENANCE FOR LATE QUATERNARY ICE-RAFTED SEDIMENTS IN THE NORTHERNMOST NORTH ATLANTIC


VERPLANCK, Emily P., Dept. of Geological Sciences and CIRES, University of Colorado, Campus Box 399, Boulder, CO 80309, FARMER, G. Lang, Dept. of Geological Sciences and CIRES, University of Colorado, Campus Box 399, Boulder, CO 80309-0399, ANDREWS, John T., INSTAAR and Dept. of Geological Sciences, Univ. of Colorado, Box 450, Boulder, CO 80309-0450 and MILLO, Christian, Lab. Geochimie des Isotopes Stables, Institut de Physique du Globe de Paris, 2, place Jussieu, Paris, 75251, France, Emily.Verplanck@Colorado.EDU

Neodymium and strontium isotopic data were obtained from fine-grained (<63µ) sediment deposited in the northern North Atlantic over the past 40 Ka to determine the provenance of ice-rafted detritus deposited adjacent to East Greenland.  In the Blosseville Basin, north of Denmark Strait (core PS62-017-4), fine-grained detritus deposited during Heinrich events 1-3 all have similar εNd(0) values ranging from -7.4 to -12.3.  Detritus deposition at this location between the Heinrich events have essentially the same Nd isotopic compositions (εNd(0) =-3.5 to -11.5).  South of Denmark Strait, fine grained detritus within H1 and H4 from core SU9024 also have εNd(0)=-3.8 to -11.3.  These isotopic compositions overlap those of glaciomarine sediments and tills deposited within both Kangerlussuaq and Scorsby Sund along East Greenland.  As a result, we suggest that the lower εNd(0) fine-grained sediments deposited both within and between the sampled Heinrich events were dominantly derived from Paleoproterozoic rocks comprising adjacent portions of the continent.  The higher εNd(0) sediments at both core locations most likely contain detritus derived from either East Greenland Tertiary basalts or Icelandic volcanic rocks.  Further to the south, both ambient and H1,3 and 4 sediments from core HU91-045 range towards significantly lower εNd(0) values (-12 to -28) and clearly were derived from sources distinct from those of contemporaneous sediments deposited further north.  The Sr isotopic compositions of these sediments (87Sr/86Sr = .7097- .7194) are significantly lower than that of glacial detritus delivered through Hudson Strait by the Laurentide ice-sheet during H1, 3 and 4, and so reveal that these sediments were not derived from North America.  Instead, low 87Sr/86Sr Archean to Paleoproterozoic rocks found at the southernmost end of Greenland are more likely sediment sources.  We conclude that much of the isotopic variability observed in Late Quaternary sediments deposited in the northernmost North Atlantic reflect variations in the isotopic compositions of adjacent portions of the East Greenland continent, indicating that East Greenland ice has been responsible for delivering a significant amount of sediment to the northern North Atlantic over the past 40 Ka.