Late Quaternary Variations in Sediment Provenance and Ice Sheet Dynamics: NE Sector of the Laurentide, Innuitian and the W/NW Margin of the Greenland Ice Sheets

OPP-99-06812Farmer首席调查者将利用西北大西洋冰川海洋沉积物中的新动力、锶和铅同位素数据以及粘土-粉砂矿物学，在上一次完整冰川周期的时间尺度上研究Laurentide和格陵兰冰盖的动力学。他们的基本前提是，冰川海洋中不到65微米的矿物学和同位素组成将使他们能够重建各种冰盖的范围及其内部动力学。该项目由两个主要部分组成。首先，他们将确定细粒冰川沉积物的同位素和矿物学特征，这些沉积物被输送到巴芬湾和拉布拉多海不同冰山来源的海洋环境中。点源特征的样本存在于其目前的岩心和表层沉积物样本收集中，或可从加拿大地质调查局的岩心储存库设施获得。这些数据对于向下研究冰川沉积物来源至关重要，因为它们将表明：1)来自冰盖特定部分的沉积物是否在矿物学和同位素上是不同的，以及2)每个冰山来源是否提供了同位素和矿物学上均一的沉积物。在尝试从沉积物来源研究重建冰盖动力学之前，必须确定这些特征。在第二部分，首席调查员将对现有的三个岩心进行具体的向下研究，以确定沉积物来源、沉积类型、冰盖反应的阶段以及冰盖/海洋相互作用的变化。这些岩心是沿着冰山运输轨迹选定的，应该显示出来自不同来源地区的日益复杂的沉积物混合物。所选择的岩心来自巴芬湾北部(HU77029-006)，哈德逊海峡口以东的一个地点(HU97048-007)，以及南部的拉布拉多中央陆架上的卡特赖特马鞍处(HU87033-017)。他们的分析将集中在H139704S-007上，因为它是一个新的核心。他们将通过获得更多的放射性碳测年来扩大年代学控制，并进行一整套沉积学、有孔虫、稳定同位素和物源研究。这将使他们能够将该岩心中的数据与目前研究中的数据进行比较，并将岩心下部的矿物学和同位素变化与冰川“点”源的变化进行比较。这一对比应该会为过去5万年来西北大西洋周围冰盖的范围、形态和动态的变化提供新的见解。

AbstractOPP-99-06812FarmerThe Principal Investigators will use neodymiun, strontium, and lead isotopic data, and clay-silt mineralogy from glacial marine sediments in the NW Atlantic Ocean to study Laurentide and Greenland ice sheet dynamics on time-scales of the last full glacial cycle. Their basic premise is that the mineralogic and isotopic compositions of the less than 65 micron fraction from glacial marine will allow them to reconstruct the extent of the various ice sheets and their internal dynamics. The project consists of two main parts. First, they will determine the isotopic and mineralogic character of fine-grained glacial sediments delivered to the marine environment at various "point" sources of icebergs in Baffin Bay and the Labrador Sea. Samples for the point source characterizations exist within their present core and surface sediment sample collections, or are available from the Core Repository Facility at Geological Survey of Canada. These data are critical for downcore studies of glacial sediment provenance because they will indicate if 1) sediments derived from a given portion of the ice sheets are mineralogically and isotopically distinct, and 2) if each iceberg source has provided isotopically and mineralogically homogeneous sediment. These characteristics must be established before any attempt to reconstruct ice sheet dynamics from sediment provenance studies can be attempted.In the second part, the Principal Investigators will undertake specific downcore studies on three existing cores to determine changes in sediment provenance, style of deposition, phasing of ice sheet reactions, and ice sheet/ocean interactions. These cores have been selected along the iceberg transport trajectory and should show increasingly complex mixtures of sediment from different source regions. The cores selected are from northern Baffin Bay (HU77029-006), from a site east of the mouth of Hudson Strait (HU97048-007), and, south, from Cartwright Saddle on the central Labrador shelf (HU87033-017). Their analyses will concentrate on H139704S-007 because it is a new core. They will expand the chronological control by obtaining additional radiocarbon dates and undertake a full suite of sedimentological, foraminiferal, stable isotopic, and provenance studies. This will enable them to compare data in this core with data from present studies and to compare downcore mineralogic and isotopic variations to those of the glacial "point" sources. This comparison should provide new insights into changes in the extent, configurations, and dynamics of ice sheets around the NW Atlantic over the past 50 thousand years.