(Table 1) Diatom biostratigraphy in ODP Site 164-997 sediments

Ocean Drilling Program Site 997 is located on the Blake Ridge, which underlies a periphery of the subtropical central gyre and is under the profound influence of the warm saline Gulf Stream as well as the Western Boundary Undercurrent (WBUC), which carried the clastic materials to the Blake Ridge as sediment drift. The shipboard study of nannofossils and sedimentary particles revealed a downward increase in sedimentation rate and a higher concentration of diatoms in three stratigraphic intervals (Shipboard Scientific Party, 1996). Thus, the stratigraphic change in diatom accumulation rate is important to understand the paleoceanographic and depositional history of this region. We have been studying the time-progressive change of diatom flora at Site 997 by quantitatively observing the flora in 141 samples selected from the entire sequence recovered from Holes 997A and 997B. These samples were chosen to represent a time interval of 50 k.y. Some of the results currently obtained through this study are presented in this data report.