Ice Extent and Late Glacial and Deglacial History of W. Hunafloi, NW Iceland: Combining Terrestrial and Marine Evidence

冰岛西北部 W. Hunafloi 的冰范围以及晚冰期和冰消期历史：结合陆地和海洋证据

• 批准号: 0004233
• 负责人: John Andrews
• 金额: $ 20.5万
• 依托单位: University of Colorado at Boulder
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2001
• 资助国家: 美国
• 起止时间: 2001-04-01 至 2005-09-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0004233&HistoricalAwards=false
• 关键词: Ice; Extent; Late; Glacial; Deglacial

ABSTRACTOPP-0004233AndrewsThe late Quaternary extent and thickness of ice and the deglacial chronology of the Northwest Peninsula of Iceland are poorly constrained. The Principal Investigators will conduct a collaborative research project on the glacial and deglacial history of the western coastline and uplands of western Hunafloi, NW Iceland, and the adjacent marine trough, Hunafloaall. The proposal builds on marine cruises in 1996, 1997 and 1999, and on a pilot field program conducted in the summer of 2000. The purpose of the project is to resolve the late Quaternary glacial history of part of NW Iceland and to correlate the terrestrial record with the marine record. This research will add new insight into the glacial history of marine arctic margins and a very old debate on biological "refugia."At least two models for the reconstruction of glacial extent during the Lower Glacial Maximum (LGM) and subsequent retreat have been suggested for Iceland, but these are based on only limited radiocarbon dates. In the NW Peninsula, the glacial reconstructions vary from an extensive ice cover model with no ice free areas to a refugia model in which ice free areas existed on the high plateaus with vascular plants surviving glaciation. These studies are based entirely on terrestrial glacial evidence and interpretations, but this must be intimately linked to the offshore sedimentary record of glacial and marine sediments. High-resolution 3.5 kHz acoustic stratigraphy and marine cores from the Hunafloaall trough suggest that the LGM extent may have been relatively restricted. In Hunafloaall, a basal dimicton containing foraminifera, is overlain by a thin (2 m) sequence of IRD-rich glacial-marine and marine sediments. Basal dates on the IRD-rich muds indicate deglaciation occurred by 13 thousand years ago (ka). Dates from the dimictons are finite and 20 ka. Such a thin deglacial sequence provides a major contrast with SW Iceland where the deglacial sediments reach thickness of 10-40+ m. The virtual absence of deglacial sediments in Hunafloaall is perplexing and raises serious questions of ice extent and chronology on the adjacent NW Peninsula.Cosmogenic isotope exposure dating techniques will be used to constrain "maximum" and "minimum" models of glacial extent. Specifically, 3He and 36CI isotopes will be used to date the basaltic upland surfaces, end and lateral moraines, and glacial erratics. Tephrachronology and physical properties of the sediment samples will be used to link the terrestrial and marine records. The Principal Investigators will continue their field and laboratory investigations on: 1) the vertical and lateral extent of glaciation along this coastline, including collection of samples for cosmogenic isotope exposure dating; 2) the pattern and timing of deglaciation and any subsequent glacier expansion; 3) investigation of the marine cores with the view toward discriminating between tills and glacial marine dimictons, and with a focus on more accurately dating the onset of deglaciation; and 4) changes in relative sea level as a measure of ice load and history. The field work will continue and expand a pilot program that began in summer of 2000, involving the Universities of Colorado, Iceland, Goteborg, and Edinburgh.

冰岛西北部半岛晚第四纪冰的范围和厚度以及冰消年代学的局限性很小。 主要研究人员将对冰岛西北部Hunafloi西部海岸线和高地以及邻近的海槽Hunafloaall的冰川和冰消历史进行合作研究项目。 这项建议是以1996年、1997年和1999年的海上航行和2000年夏季进行的一项试验性实地方案为基础的。 该项目的目的是解决冰岛西北部部分地区的晚第四纪冰川历史，并将陆地记录与海洋记录相关联。 这项研究将为海洋北极边缘的冰川历史和关于生物“避难所”的古老争论增添新的见解。至少有两种模型可以重建冰岛在下冰川最大期（LGM）和随后的退缩期间的冰川范围，但这些模型只基于有限的放射性碳年代。 在西北半岛，冰川重建从广泛的冰盖模式，没有无冰区，避难所模式，无冰区存在于高原与维管植物生存冰川。 这些研究完全基于陆地冰川的证据和解释，但这必须与冰川和海洋沉积物的近海沉积记录密切相关。 高分辨率的3.5千赫声学地层学和海洋核心从Hunafloaall槽表明，LGM的范围可能已经相对有限。 在Hunafloaall，一个基础的dimicton包含有孔虫，是由一个薄的（2米）序列的IRD丰富的冰川海洋和海洋沉积物覆盖。 IRD丰富的泥基年龄表明，冰川消退发生在13000年前（ka）。 从dimictons日期是有限的和20 ka。 如此薄的冰消期层序与冰岛西南部形成了鲜明对比，冰岛西南部的冰消期沉积物厚度达到10-40+ m。Hunafloaall实际上没有冰退沉积物是令人困惑的，并提出了严重的问题，冰的范围和年代学在邻近的西北半岛。宇宙成因同位素暴露测年技术将被用来限制“最大”和“最小”模型的冰川范围。 具体而言，3 He和36 Cl同位素将用于测定玄武岩高地表面，端部和侧冰碛，以及冰川erratics。 沉积物样品的年代学和物理性质将被用来连接陆地和海洋记录。主要调查人员将继续进行以下方面的实地和实验室调查：1）沿沿着这条海岸线的冰川作用的垂直和横向范围，包括收集用于宇宙成因同位素暴露年代测定的样本; 2）冰川消退和任何随后冰川扩张的模式和时间;（3）海相岩芯调查，以区分冰碛物和冰期海相双粒细胞，重点是更准确地确定冰川消退的开始时间; 4）相对海平面的变化作为衡量冰负荷和历史的一种手段。 实地工作将继续并扩大2000年夏天开始的试点项目，涉及科罗拉多大学、冰岛大学、哥德堡大学和爱丁堡大学。