Crop-marks revealing large-scale patterned ground structures in cultivated areas, southwestern Jutland, Denmark

Subsurface large-scale patterned ground structures, observed as crop-marks in cereal fields with spring-barley and oats have been detected in southwestern Jutland. It is assumed that the structures revealed are fossil ice-wedge polygons. Mode of origin, time of formation and palneoclimatic significance of ice-wedge casts are discussed. Texture of poorly layered wedge-fill materials can be distinguished from that of the stratified materials transected by the wedges, causing stress conditions in crop, in dry summers, seen as differential growth and cereal ripening. The water-holding capacity is highest in wedge-fill materials. Plants growing above the ice-wedge casts arc able to withstand a certain deficiency in precipitation during spring and early summer. Cereals growing outside ice-wedge casts suffer owing to lack of available moisture, and growth may be restricted, even to the extent that the plants can wither. Consequently, crop-marks of variable growth appear in the fields. A growth season with high precipitation makes it difficult to trace crop marks.