| Chapter 1 and 2 show that Denmark Strait slope-sedimentation is controlled by climatic cycles, waxing and waning of nearby ice sheets, and strength and direction of bottom currents. Based on sedimentary and stable isotope data the chapters conclude that iceberg rafting and bottom currents supplied sediment to Snorri Drift during the last 200,000 years. During Marine Isotope Stages 2 and 6 iceberg-rafting was dominant providing coarse, poorly sorted, bimodal grain size sediment, while contourite-only deposition was active for prolonged periods during warmer intervals such as the Holocene and substage 5e. During this time the North West Atlantic Deep Water deposited fine, well-sorted sediment with a strong silt mode, which migrates due to the strength of the current. For a considerable part of this core's history both processes were simultaneously depositing sediment.; Chapter 3 determines that Sr and Nd isotopic compositions can distinguish sediment carried by two major East Greenland ice streams draining the Scoresby Sund and Kangerlussuaq regions. The East Greenland margin samples separate into two groups: (1) The Scoresby Sund Trough Mouth Fan samples have low epsilonNd values that range from -16 to -12 and 87Sr/ 86Sr ratios between .719 and .725 reflecting Precambrian basement contribution. (2) The Kangerlussuaq Trough and shelf samples have much higher epsilonNd values ranging between -8 and +3 and 87Sr/ 86Sr ratios between .705 and .712, reflecting a Tertiary basalt contribution.; Chapter 4 reconstructs Greenland's glacial history during Stages 2 & 3 and describes the ice sheet's interaction with the oceanography and depositional processes of Denmark Strait. There are four main lithofacies present on the SE Greenland slope indicative of the extent of the ice sheet. During Stage 2 the Greenland Ice Sheet was extended onto the shelf where two types of sedimentation occurred. (1) Iceberg rafting became dominant transporting abundant coarse, unsorted sediment, or (2) Debris flows and/or turbidites were generated on the slope. (3) During the warmer periods of Stage 3 the Greenland Ice Sheet retreated and sedimentation was achieved mainly through contourite deposition. (4) The fourth type of ice-sheet-influenced sedimentation is the IRD deposition that produced layers similar to the Heinrich Events that formed by the periodically-surging ice sheet. |
