riegeln.

1909 Q. Jrnl. Geol. Soc. 65 345 Transverse rock-barriers or ‘riegel’ were known to stretch frequently across glaciated valleys.

1912 W. H. Hobbs Earth Features xxvi. 377 When the backward grades upon the valley floor are especially steep, the rock step becomes a rock bar, or riegel, of which nearly every Alpine valley has its example.

1957 G. E. Hutchinson Treat. Limnol. I. i. 71 The basins are divided by transverse ridges, presumably Riegeln or rock bars.

1968 R. W. Fairbridge Encycl. Geomorphol. 745/1 Partly worn-down cross-valley bars of resistant rock (‘riegels’) remain, impounding lakes, though these have commonly been drained by rivers that have cut gorges through the riegels since the melting of the glaciers.

2002 J. Menzies & W. W. Shilts in J. Menzies Mod. & Past Glacial Environments 246/2 The presence of riegel bedrock steps and associated basins in many glacial troughs remains a difficult problem.