Periglacial geomorphology of summit tors on Bodmin Moor, Cornwall, SW England

Three maps are presented that portray the periglacial geomorphology of the three summit areas of Bodmin Moor, Cornwall, SW England, including Brown Willy (scale 1:2630), Kilmar/Bearah/Sharp tors (scale 1:3335) and Rough/Little Rough/Showery tors (scale 1:2175). Landform elements include castellated tors with well-developed cantilevered or precariously balanced corestones, summit blockfields, rock-fronted lobes thought to record former permafrost creep, patterned ground (stripes) and lower slope accumulations of crudely stratified growan or weathered granite residue. The altitudinal arrangement of these periglacial landforms appears to be a signature of a well-established periglacial landsystem and hence the Bodmin Moor granite massif is a suitable exemplar for a mature upland periglacial landsystem unaffected by glacierization.

本次展示的三张地图，系统呈现了英格兰西南部康沃尔郡博德明荒原三处峰顶区域的冰缘地貌（periglacial geomorphology），具体覆盖范围包括：布朗威利峰（比例尺1:2630）、基尔马尔/比拉/夏普花岗岩突丘（tor）群（比例尺1:3335），以及拉夫/小拉夫/肖里花岗岩突丘群（比例尺1:2175）。本次研究涉及的地貌要素包括：发育完备的城垛状花岗岩突丘，其带有悬臂状或摇摇欲坠的平衡岩芯块；山顶岩屑堆；被认为记录了古多年冻土蠕变过程的岩前舌状体；条纹状花纹地面（patterned ground）；以及缓坡地带产出的粗层理growan（康沃尔地区所称的花岗岩风化残积物）或风化花岗岩残积堆积物。上述冰缘地貌的高程分布格局，清晰体现出一套成熟稳定的冰缘地貌系统的标志性特征，因此博德明荒原花岗岩岩基可作为未受冰川作用影响的成熟高地冰缘地貌系统的理想典型范例。