| In multiple manuscripts this dissertation addresses the general topic of Late Cenozoic ice-rafting along the SE Greenland margin and in the North Pacific Ocean. The development of ice-rafted debris (IRD) mass accumulation rate (MAR) records is the primary method used to decipher the history of ice-rafting in these two regions.; The oldest record of ice-rafting in this compilation is from Site 918 off the SE Greenland margin. Here, the IRD MAR record indicates that glaciers extended to sea level in SE Greenland beginning in the Late Miocene, suggesting that SE Greenland was the cradle of the Greenland Ice Sheet (GIS). A series of large and periodic IRD MAR peaks are present from the Early Pliocene to the Mid Pleistocene; these "mega-peaks" are commonly associated with times of North Atlantic Deep Water suppression. This pattern of ice-rafting suggests that the growth of the GIS in SE Greenland was very dynamic and may have affected global climate by means of meltwater input into the northern North Atlantic. The IRD MAR records from Site 918 and 919 off SE Greenland indicate that the behavior of the GIS during the Pleistocene was also characteristically complex and contains dramatic temporal variations in ice-rafting, including evidence of a massive calving event during the Mid-Pleistocene Transition and patterns of ice-rafting that are inconsistent with global ice-volume signals.; A synthesis of the best North Pacific Pleistocene IRD data available to date is also contained in this dissertation. Important regional differences in the ice-rafting histories of the NW and NE Pacific are evident from this synthesis, and reflect the differences in IRD input and transport in the two sides of this vast ocean basin. These differences are most pronounced during an interval of time bounded by two globally-recognized climatic transitions, the Mid-Pleistocene Transition and the Mid-Brunhes Transition.; Lastly, an argument for ice-rafted gypsum grains is presented. Isotopic and sedimentological evidence are used to explain the occurrence and origin of coarse-grained gypsum from multiple high-latitude marine settings. Results indicate that the gypsum is terrestrial in origin, forming in high-latitude glacially-dominated landscapes, and was transported to the present marine locations by icebergs and/or sea ice. |
