Ice-rafted debris in sites of ODP Leg 114

All holes drilled during Leg 114 contained ice-rafted debris. Analysis of samples from Hole 699A, Site 701, and Hole 704A yielded a nearly complete history of ice-rafting episodes. The first influx of ice-rafted debris at Site 699, on the northeastern slope of the Northeast Georgia Rise, occurred at a depth of 69.94 m below seafloor (mbsf) in sediments of early Miocene age (23.54 Ma). This material is of the same type as later ice-rafted debris, but represents only a small percentage of the coarse fraction. Significant ice-rafting episodes occurred during Chron 5. Minor amounts of ice-rafted debris first reached Site 701, on the western flank of the Mid-Atlantic Ridge (8.78 Ma at 200.92 mbsf), and more arrived in the late Miocene (5.88 Ma). The first significant quantity of sand and gravel appeared at a depth of 107.76 mbsf (4.42 Ma). Site 704, on the southern part of the Meteor Rise, received very little or no ice-rafted debris prior to 2.46 Ma. At this time, however, the greatest influx of ice-rafted debris occurred at this site. This time of maximum ice rafting correlates reasonably well with influxes of ice-rafted debris at Sites 701 (2.24 Ma) and 699 (2.38 Ma), in consideration of sample spacing at these two sites. These peaks of ice rafting may be Sirius till equivalents, if the proposed Pliocene age of Sirius tills can be confirmed. After about 1.67 Ma, the apparent mass-accumulation rate of the sediments at Site 704 declined, but with major fluctuations. This decline may be the result of a decrease in the rate of delivery of detritus from Antarctica due to reduced erosive power of the glaciers or a northward shift in the Polar Front Zone, a change in the path taken by the icebergs, or any combination of these factors.