AN OCCURRENCE OF PERIGLACIAL STRUCTURES AT LANGÅ, JYLLAND By LEIF CHRISTENSEN Abstract An occurrence of periglacial features, located 2 km east of Langå between Line C and Line D, the two outermost ice margins of the Wiirm glaciation in Jylland, is described. The features, which include soil polygons, involutions and other deformational structures were probably formed in Oldest Dryas Time. The deformational structures and involutions probably developed as the result of liquefaction and differential pressure distribution in water saturated, unconso- lidated sediments beneath solifluction layers of variable thickness. INTRODUCTION While mapping Quarternary Deposits for the Geological Survey of Den- mark during the summer of 1966 under the direction of Professor GUNNAR LARSEN, an occurrence of intensely disturbed structures in glacial and glacio- fluvial material was found 2 km east of Langå (Fig. 1). This occurrence is situated between the Main Stationary Line (Line C) in central Jylland and the Eastern Jylland Stationary Line (Line D). LOZINSKI (1909) was one of the first workers to use the term "peri- glacial". It has become a widely used term, which covers, 1) the ice free areas adjacent to Pleistocene ice sheets, 2) the climate which existed in these ice free areas, with strong winds, low temperatures and many fluctuations around the freezing point at certain seasons, and 3) the phenomena caused by such a climate (see also BRYAN, 1946). Fossil periglacial phenomena have previously been found west of the Main Stationary Line in Central Jylland. The described phenomena consist of aeolian features (CAILLEUX, 1942) and congeliturbates, which include solifluction layers, soil polygons, stone stripes, ice wedges (ANDERSEN, 1963, NØRVANG, 1942, 1943, 1946 and RASMUSSEN, 1960) and polygonal patterns on aerial photographs (SVENSSON, 1963). The processes which were responsible for the formation of these phenomena took place during the Wiirm glaciation, when the ice was situated at the Main Stationary Line in central Jylland. Some processes, however, continued into late glacial time (NØRVANG, 1946) with the retreat of the ice to Line D in eastern Jylland Fig. 1. Location of the Langå exposure. (Segment of M 2113 on the scale of 1:20.000. Copyright Geodetic Institute), x indicates locality. Key map shows position of Langå, lines C and D. (Modified from S. HANSEN and K. MILTHERS, in SORGENFREI and BERTHELSEN, 1954, p. 27).