Pattern, style and timing of British-Irish Ice Sheet retreat: Shetland and northern North Sea sector
Pattern, style and timing of British-Irish Ice Sheet retreat: Shetland and northern North Sea sector
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DOI：
10.1002/jqs.3163
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发表时间：
2019-11-21
影响因子：
2.3
通讯作者：
Cofaigh, Colm O.
中科院分区：
文献类型：
--
作者：
Bradwell, Tom;Small, David;Cofaigh, Colm O.
设得兰群岛周围的近海地区仍然是前英国-爱尔兰冰盖研究最少的地区之一，有几个长期存在的科学问题尚未解决。这些关键问题包括：（i）本地来源的“设得兰群岛冰帽”相对于入侵的芬诺斯堪的亚冰盖的优势;（ii）末次盛冰期冰川作用的流动结构和样式（iii）英国-爱尔兰和芬诺斯堪的亚冰盖汇合的性质;（iv）冰盖分离的原因、类型和速率;以及（v）冰盖解偶联对随后冰川消退克里思的更广泛影响。作为英国Chrono项目的一部分，我们提出了新的地质（海底岩芯），地貌，海洋地球物理和地质年代学数据，从最后的英国-爱尔兰冰盖（北纬59.5度以北）的最北端，以解决这些问题。该研究涵盖了CA。面积约为爱尔兰大小，包括设得兰群岛及其周围大陆架、部分大陆坡和挪威海峡西缘。我们收集和分析数据，从陆上在设得兰群岛和沿着关键断面离岸，建立最连贯的图片，到目前为止，前冰盖消融在这一重要部门。除了新的海底测绘和第四纪沉积物分析，我们使用一个多代理套件的新的同位素年龄评估，包括32个宇宙成因核素暴露年龄从冰川运输的巨石和35个放射性碳年代从冰消期海洋沉积物，开发一个天气全部门的重建相结合的强大的陆上和海上地质证据与贝叶斯年代序列建模。结果表明，广泛的和显着的空间波动的大小，形状和流动配置的冰盖/冰帽集中在，或以东的奥克尼-设得兰群岛平台，之间类似于30和类似于15 ka BP。在其最大程度上。26-25 ka BP，该冰盖与东部的芬诺斯堪的纳维亚冰盖合并。在25和23 ka BP之间，这一地区的冰盖经历了一个显着的大小减少，从约。85 000至
The offshore sector around Shetland remains one of the least well-studied parts of the former British-Irish Ice Sheet with several long-standing scientific issues unresolved. These key issues include (i) the dominance of a locally sourced 'Shetland ice cap' vs an invasive Fennoscandian Ice Sheet; (ii) the flow configuration and style of glaciation at the Last Glacial Maximum (i.e. terrestrial vs marine glaciation); (iii) the nature of confluence between the British-Irish and Fennoscandian Ice Sheets; (iv) the cause, style and rate of ice sheet separation; and (v) the wider implications of ice sheet uncoupling on the tempo of subsequent deglaciation. As part of the Britice-Chrono project, we present new geological (seabed cores), geomorphological, marine geophysical and geochronological data from the northernmost sector of the last British-Irish Ice Sheet (north of 59.5 degrees N) to address these questions. The study area covers ca. 95 000 km(2), an area approximately the size of Ireland, and includes the islands of Shetland and the surrounding continental shelf, some of the continental slope, and the western margin of the Norwegian Channel. We collect and analyse data from onshore in Shetland and along key transects offshore, to establish the most coherent picture, so far, of former ice-sheet deglaciation in this important sector. Alongside new seabed mapping and Quaternary sediment analysis, we use a multi-proxy suite of new isotopic age assessments, including 32 cosmogenic-nuclide exposure ages from glacially transported boulders and 35 radiocarbon dates from deglacial marine sediments, to develop a synoptic sector-wide reconstruction combining strong onshore and offshore geological evidence with Bayesian chronosequence modelling. The results show widespread and significant spatial fluctuations in size, shape and flow configuration of an ice sheet/ice cap centred on, or to the east of, the Orkney-Shetland Platform, between similar to 30 and similar to 15 ka BP. At its maximum extent ca. 26-25 ka BP, this ice sheet was coalescent with the Fennoscandian Ice Sheet to the east. Between similar to 25 and 23 ka BP the ice sheet in this sector underwent a significant size reduction from ca. 85 000 to