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

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 ε_Nd(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 (ε_Nd(0) =-3.5 to -11.5).  South of Denmark Strait, fine grained detritus within H1 and H4 from core SU9024 also have ε_Nd(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 ε_Nd(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 ε_Nd(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 ε_Nd(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.