, δ 13C) OF EARLY EOCENE FISH-APATITE FROM HOLE 913B: AN INDICATOR OF THE EARLY

Fish-apatite (teeth and bone fragments) of early Eocene age from Ocean Drilling Program Hole 913B (Greenland Basin) was analyzed, in the absence of biogenic calcite, for stable isotopic (δ 1 8 θco, 2 ~, δ13C) composition to determine paleosalinity. Comparisons are made with isotopic results for early Eocene fish-apatite from Deep Sea Drilling Project (DSDP) Hole 550 (northeastern Atlantic) and the R0snaεs Clay Formation (Denmark). These two sites represent fully marine and semimarine conditions, respectively. The δ^Ocα, 2- values of the fish-apatite from Hole 913B are 4.3%o to 8.1%c more negative than the fish-apatite values from DSDP Hole 550, and 1.9%o to 6.1%o more negative than the values from the R0snses Clay Formation. The results indicate reduced salinity in the early Eocene Greenland Basin relative to the open ocean. Using the present salinity/ δ' 8O relationship in the North Atlantic, the salinity in the Greenland Basin was 22 ppt to 28 ppt. The reduced salinity is in agreement with an isolated early Eocene Greenland Basin, as suggested in earlier geophysical and paleontological studies. It is also likely that other parts of the Norwegian-Greenland Sea, such as the Lofoten Basin, exhibited brackish water conditions. Because of similar oxygen-isotopic composition of fish-apatite and excellently preserved foraminifer tests in the samples from the R0snaεs Clay Formation as well as DSDP Hole 550, we consider the fish-apatite δ 1 8 θ c o, 2- t o be a reliable instrument for paleosalinity determination. It is possible that the fish-apatite was exposed to diagenesis and isotopic reequilibration shortl