Rapid tunnel‐valley formation beneath the receding Late Weichselian ice sheet in Vendsyssel, Denmark
Rapid tunnel‐valley formation beneath the receding Late Weichselian ice sheet in Vendsyssel, Denmark
复制标题
丹麦文德西塞尔晚威克塞尔冰盖下快速形成的隧道谷
DOI：
10.1111/j.1502-3885.2009.00105.x
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发表时间：
2009
期刊：
影响因子：
2.2
通讯作者：
E. Auken
中科院分区：
文献类型：
--
作者：
P. Sandersen;F. Jørgensen;N. K. Larsen;J. Westergaard;E. Auken
瞬变电磁（TEM）数据和导线测井的解释导致了一个复杂的模式的掩埋隧道山谷的描绘，沿着与新的证据冰川构造错位层在退缩冰碛在丹麦的中部。TEM数据进行了比较，最近的地层调查结果的基础上的岩性和生物地层分析的钻孔样品和约会与光释光（OSL）和放射性碳。这提供了晚第四纪岩石地层的空间分布概况，并估计了隧道谷的时代。隧道山谷通常长5-10公里，宽1公里，局部侵蚀深度超过180米b.s.l.。 这些山谷被解释为是在斯堪的纳维亚冰盖的整体魏克塞尔晚期衰退期间，在冰盖的最外层部分的暂时停滞和轻微的再前进期间，由冰下融水侵蚀形成的。隧道谷的形成发生在主冰推进的退却之后。20 kyr BP和晚冰期海洋淹没之前c。 18 kyr BP. 根据隧道山谷和地形的出现，划定了与东北主推进后退有关的四个冰缘位置和与穿越旺德西塞尔的东部再推进后退有关的七个冰缘位置。所有隧道谷都是在几千年的时间间隔内形成的，每个冰缘位置的隧道谷的形成时间只有几百年或更短。
Interpretation of Transient ElectroMagnetic (TEM) data and wire‐line logs has led to the delineation of an intricate pattern of buried tunnel valleys, along with new evidence of glaciotectonically dislocated layers in recessional moraines in the central part of Vendsyssel, Denmark. The TEM data have been compared with recent results of stratigraphical investigations based on lithological and biostratigraphical analyses of borehole samples and dating with Optically Stimulated Luminescence (OSL) and radiocarbon. This has provided an overview of the spatial distribution of the late Quaternary lithostratigraphical formations, and the age of the tunnel valleys has been estimated. The tunnel valleys are typically 5–10 km long, 1 km wide and are locally eroded to depths of more than 180 m b.s.l. The valleys are interpreted to have been formed by subglacial meltwater erosion beneath the outermost part of the ice sheet during temporary standstills and minor re‐advances during the overall Late Weichselian recession of the Scandinavian Ice Sheet. The formation of the tunnel valleys occurred after the retreat of the Main ice advance c. 20 kyr BP and before the Lateglacial marine inundation c. 18 kyr BP. Based on the occurrence of the tunnel valleys and the topography, four ice‐marginal positions related to the recession of the northeastern Main advance and seven ice‐marginal positions related to the recession from the following eastern re‐advance across Vendsyssel are delineated. All the tunnel valleys were formed within a time interval of a few thousand years, giving only a few hundred years or less for the formation of the tunnel valleys at each ice‐marginal position.