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

摘要冰岛西北半岛的晚第四纪冰的范围和厚度以及去冰年代学都没有得到很好的约束。主要研究人员将开展一项合作研究项目，研究冰岛西北部hunafloall西部海岸线和高地以及邻近的hunafloall海槽的冰川和去冰川历史。该提案建立在1996年、1997年和1999年的海上巡航和2000年夏季进行的试点项目的基础上。该项目的目的是解决冰岛西北部部分地区的晚第四纪冰期历史，并将陆地记录与海洋记录联系起来。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”的一个非常古老的争论提供新的见解。“对于冰岛，至少有两种模式可以重建下冰川极大期（LGM）和随后的退缩期间的冰川范围，但这些模式仅基于有限的放射性碳测年。在西北半岛，冰川重建模式从无无冰区的大范围冰盖模式到无冰区存在于高高原上且维管植物在冰川作用下存活的避难所模式。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。来自Hunafloaall海槽的高分辨率3.5 kHz声学地层学和海洋岩心表明，LGM的范围可能相对有限。在hunafloall，一个含有有孔虫的基层被一层薄（2米）的富含ird的冰川-海洋和海洋沉积物覆盖。富含ird的泥的基本日期表明，冰川消融发生在13000年前。这些岩石的年代是有限的，大约20年前。如此薄的消冰层序与冰岛西南部的消冰沉积物厚度达到10-40+ m形成了鲜明对比。hunafloall实际上没有消冰沉积物令人困惑，并对邻近的NW半岛的冰范围和年代学提出了严重的问题。宇宙成因同位素暴露定年技术将用于限制冰川范围的“最大”和“最小”模式。具体来说，3He和36CI同位素将用于确定玄武岩高地表面、端碛和侧碛以及冰川不稳定的年代。沉积物样品的年代学和物理性质将用于联系陆地和海洋记录。首席研究员将继续他们的实地和实验室调查：1)沿这条海岸线的垂直和横向冰川范围，包括收集样品进行宇宙成因同位素暴露测年；2)消冰和冰川扩张的模式和时间；(3)对海洋岩心进行研究，以区分冰碛物和冰碛物，并更准确地确定冰川消融的开始时间；4)相对海平面的变化作为冰负荷和历史的度量。实地工作将继续进行，并扩大2000年夏季开始的试点项目，该项目由科罗拉多大学、冰岛大学、哥德堡大学和爱丁堡大学参与。

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.