Periglacial wedge‐casts and patterned ground in the midlands of Ireland


  • Colin A. Lewis University College, Dublin



Two groups of ice‐wedge and ground‐wedge casts have been identified in the study area. Both are located in outwash sands and gravels of Midlandian age formed during ice retreat from the vicinity of the Caher and Roscrea moraines respectively. They probably formed between 18000 and 10000 B.P. (the Nahanagan Stadial). At least some of them are associated with patterned ground, and ice‐wedge and ground‐wedge polygons were probably widespread on sand and gravel deposits during the latter part of the Midlandian. The ice‐ and ground‐wedge casts evidence a period (or periods) in which annual ground temperatures of at least —5°C occurred, following the retreat of Midlandian ice from the Caher and Roscrea positions. Ice‐wedge casts are almost entirely lacking in eskers, and it is suggested that ice‐wedges and ice‐veins formed only where sufficient surface and/or ground water was available. The parameters controlling ice‐wedge and ice‐vein development therefore include suitable low temperature and suitable water conditions.

Author Biography

Colin A. Lewis, University College, Dublin

Department of Geography



How to Cite

Lewis, C. A. (2016). Periglacial wedge‐casts and patterned ground in the midlands of Ireland. Irish Geography, 12(1), 10–24.



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