The mixed-bed glacial landform imprint of the North Sea Lobe in the western North Sea
The mixed-bed glacial landform imprint of the North Sea Lobe in the western North Sea
复制标题
北海西部北海叶混层冰川地貌印记
DOI：
10.1002/esp.4569
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发表时间：
2019
影响因子：
3.3
通讯作者：
Roberts D
中科院分区：
文献类型：
--
作者：
Roberts D
在最后一次冰期循环中，英国-爱尔兰冰盖的一个有趣特征是北海冰瓣（NSL）;从福斯湾注入，向南流动，平行于英国东海岸。NSL的形成和行为的控制长期以来一直存在争议，但在北海南部，最近的工作表明，NSL形成了一个动态的，振荡的陆地边缘在变形床上运行。然而，再往北，人们对NSL的行为或它在什么条件下运行知之甚少。本文分析了新的声学、沉积和地貌数据，以评估英格兰东北部近海NSL的冰川陆地系统印记和冰消历史。冰下冰碛物（AF 2/3）形成了一个不连续的镶嵌体，散布在海底的基岩露头中，在前进和后退过程中，冰下沉积物的部分挖掘和平流产生了大规模的冰川线理和接地带楔。由此产生的“混合床”冰川陆地系统是从具有净沉积物盈余的陆地皮埃蒙特-叶缘到部分侵蚀的、准稳定的、海洋终止的动态切换的产物，冰流波瓣随着NSL向北撤退。冰海沉积物（AF 4）覆盖下面的冰下混床印记，并指出随着北海成为19.9至16.5 ka cal BP之间的潮汐条件，被淹没了在此期间，NSL衰退的主要控制因素是通过福斯湾冰流起始区和接地线处水深的冰通量变化;混合床陆地系统的发展是对接地线不稳定性的响应。© 2018约翰威利父子有限公司
During the last glacial cycle an intriguing feature of the British‐Irish Ice Sheet was the North Sea Lobe (NSL); fed from the Firth of Forth and which flowed south and parallel to the English east coast. The controls on the formation and behaviour of the NSL have long been debated, but in the southern North Sea recent work suggests the NSL formed a dynamic, oscillating terrestrial margin operating over a deforming bed. Further north, however, little is known of the behaviour of the NSL or under what conditions it operated. This paper analyses new acoustic, sedimentary and geomorphic data in order to evaluate the glacial landsystem imprint and deglacial history of the NSL offshore from NE England.Subglacial tills (AF2/3) form a discontinuous mosaic interspersed with bedrock outcrops across the seafloor, with the partial excavation and advection of subglacial sediment during both advance and retreat producing mega‐scale glacial lineations and grounding zone wedges. The resultant ‘mixed‐bed’ glacial landsystem is the product of a dynamic switch from a terrestrial piedmont‐lobe margin with a net surplus of sediment to a partially erosive, quasi‐stable, marine‐terminating, ice stream lobe as the NSL withdrew northwards.Glaciomarine sediments (AF4) drape the underlying subglacial mixed‐bed imprint and point to a switch to tidewater conditions between 19.9 and 16.5 ka cal BP as the North Sea became inundated. The dominant controls on NSL recession during this period were changing ice flux through the Firth of Forth ice stream onset zone and water depths at the grounding line; the development of the mixed‐bed landsystem being a response to grounding line instability. © 2018 John Wiley & Sons, Ltd.