OXYGEN-ISOTOPE COMPOSITION OF MARINE SHEL LS AND RELATIONSHIP TO DEGLACIATION OF THE COASTAL MARGINS OF THE UNGAVA PENINSULA

Oxygen Isotope composition of marine shells and relationship to deglac iation of the coastal margins of the Ungava Peninsula. delta(PDB) O-18 values for shells living in the marine environment around the margins of the Ungava Peninsula during the postglacial interval from 6 ka unt il the present day are relatively homogeneous, and comparable to moder n values. During the deglacial period from 9 to 6 ka delta(PDB) O-18 v alues were much more variable. C-14 ages on shells in basal marine sed iments contribute to an understanding of this variability. With the in ception of a final deglacial phase, a large marine embayment opened up progressively in Hudson Strait between 9 and 8 ka. The positive tende ncy of delta(PDB) O-18 values in the open marine basin of eastern Huds on Strait sites, contrasts markedly with the negative tendency for val ues in fjords and estuaries filled with ice tongues descending from th e Ungava plateau. Ocean water brought into eastern Hudson Strait by th e Baffin current appears to have been subjected to variable degrees of dilution by ice sheet meltwater. No signal is apparent, either in the delta(PDB) O-18 values or C-14 ages, to support the concept of the ex clusion of this current from Hudson Strait by a readvance of Quebec-La brador based ice onto southernmost Baffin Island between 8.9 and 8.4 k a (the postulated Noble Inlet re-advance). It appears doubtful whether any major ice sheet surge has occurred in eastern Hudson Strait since the earlier Gold Cove re-advance of 9.9 to 9.6 ka.