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Variations in esker morphology and internal architecture record time-transgressive deposition during ice margin retreat in Northern Ireland
Proceedings of the Geologists' Association Pub Date : 2021-04-19 , DOI: 10.1016/j.pgeola.2021.03.002
Ben J. Stoker , Stephen J. Livingstone , Iestyn D. Barr , Alastair Ruffell , Robert D. Storrar , Sam Roberson

The architecture and evolution of the subglacial hydrological system plays a key role in modulating ice flow. Eskers provide an opportunity to understand subglacial hydrology at a broader perspective than contemporary studies. Recent research has established a morphogenetic classification for eskers, but these studies have been limited to topographically simple regions of a single ice sheet. We present an updated map of esker distribution in Northern Ireland based on 5-m resolution elevation data. We also present a high-resolution map of the glacial geomorphology of SW Northern Ireland, based on ~ 0.4-m resolution elevation data. Ground Penetrating Radar data from four sites along the > 20-km long Evishanoran Esker system in central Northern Ireland are combined with geomorphological observations to provide insight into depositional processes and controls on esker formation. Esker architecture indicates two styles of deposition, including an initial high energy flow event in a subglacial conduit and delta foreset deposition close to the ice sheet margin during ice margin retreat. These delta foreset deposits can be used to reconstruct former ice margins. We identify that local topographic complexity and geological structures (e.g., faults) are important controls on esker formation. The broad-scale esker architecture remains the same despite variable esker planform morphology, suggesting hydrological conditions alone cannot explain esker morphology. This study provides further evidence that morphogenetic relationships cannot be based solely on remote sensing data and must be supported by robust field observations, especially where post-glacial processes may distort esker morphology (e.g., peat infilling).



中文翻译:

北爱尔兰冰缘退缩期间 esker 形态和内部结构的变化记录了时间海侵沉积

冰下水文系统的结构和演化在调节冰流方面起着关键作用。Eskers 提供了一个机会,可以从比当代研究更广泛的角度来理解冰下水文学。最近的研究已经为 eskers 建立了形态发生分类,但这些研究仅限于单个冰盖的地形简单区域。我们根据 5 米分辨率高程数据展示了北爱尔兰 esker 分布的更新地图。我们还根据 ~  0.4 米分辨率的高程数据展示了北爱尔兰西南冰川地貌的高分辨率地图。沿线四个站点的探地雷达数据 > 北爱尔兰中部 20 公里长的 Evishanoran Esker 系统与地貌观测相结合,可以深入了解沉积过程和对 esker 形成的控制。Esker 结构显示了两种类型的沉积,包括冰下管道中的初始高能量流事件和冰缘退缩期间靠近冰盖边缘的三角洲前缘沉积。这些三角洲前缘沉积物可用于重建以前的冰缘。我们确定当地地形复杂性和地质结构(例如,断层)是 esker 形成的重要控制因素。尽管 esker 平面形态可变,但大尺度 esker 架构保持不变,这表明仅水文条件无法解释 esker 形态。这项研究提供了进一步的证据,表明形态发生关系不能仅仅基于遥感数据,必须得到可靠的实地观察的支持,特别是在冰后过程可能会扭曲 esker 形态的情况下(例如,泥炭填充)。

更新日期:2021-04-19
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