Tunnel valleys are major features of glaciated margins and they enable meltwater expulsion from underneath a thick ice cover. Their formation is related to the erosion of subglacial sediments by overpressured meltwater and direct glacial erosion. Yet, the impact of pre‐existing structures on their formation and morphology remains poorly known. High‐quality 3D seismic data allowed the mapping of a large tunnel valley that eroded underlying preglacial delta deposits in the southern North Sea. The valley follows the N–S strike of crestal faults related to a Zechstein salt wall. A change in downstream tunnel valley orientation towards the SE accompanies a change in the strike direction of salt‐induced faults. Fault offsets indicate important activity of crestal faults during the deposition of preglacial deltaic sediments. We propose that crestal faults facilitated tunnel valley erosion by acting as high‐permeability pathways and allowing subglacial meltwater to reach low‐permeability sediments in the underlying Neogene deltaic sequences, ultimately resulting in meltwater overpressure build‐up and tunnel valley excavation. Active faults probably also weakened the near‐surface sediment to allow a more efficient erosion of the glacial substrate. This control of substrate structures on tunnel valley morphology is considered as a primary factor in subglacial drainage pattern development in the study area.

中文翻译：

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盐致顶断层控制北海南部第四纪隧道河谷的形成

隧道谷是冰川边缘的主要特征，它们使融水从厚厚的冰盖下面排出。它们的形成与超压融水和直接冰川侵蚀对冰下沉积物的侵蚀有关。然而，预先存在的结构对其形成和形态的影响仍然知之甚少。高质量的 3D 地震数据允许绘制侵蚀北海南部冰前三角洲沉积物的大型隧道山谷。该山谷沿着与 Zechstein 盐壁相关的顶部断层的 N-S 走向。下游隧道谷向东南方向的变化伴随着盐致断层走向方向的变化。断层偏移表明在冰前三角洲沉积物沉积过程中顶部断层的重要活动。我们提出，顶部断层通过充当高渗透性通道并允许冰下融水到达下伏的新第三纪三角洲序列中的低渗透性沉积物，促进了隧道河谷的侵蚀，最终导致融水超压积聚和隧道河谷开挖。活动断层可能也削弱了近地表沉积物，从而更有效地侵蚀冰川基质。这种对隧道谷形态的基底结构的控制被认为是研究区冰下排水模式发展的主要因素。最终导致融水超压积聚和隧道谷开挖。活动断层可能也削弱了近地表沉积物，从而更有效地侵蚀冰川基质。这种对隧道谷形态的基底结构的控制被认为是研究区冰下排水模式发展的主要因素。最终导致融水超压积聚和隧道谷开挖。活动断层可能也削弱了近地表沉积物，从而更有效地侵蚀冰川基质。这种对隧道谷形态的基底结构的控制被认为是研究区冰下排水模式发展的主要因素。