Clastic dikes formed beneath an active glacier

Abstract

Abstract Clastic dikes (dykes) consisting of diamicton and sand were observed in a diamicton bed and in an underlying bed of gravel at a site in the province of Skåne, southern Sweden. In the diamicton bed, a clastic sill made up of laminated sand and gravel also occurs. Features resembling the observed dikes, but made up of only diamicton have been named till wedges. The dikes dip 45–90° and are parallel to each other in the horizontal plane. The largest dikes are 0.8–2.5 m wide and at least 4.0–5.5 m deep. The dikes and the sill were formed beneath an active glacier which fractured the bed. The dikes became infilled with drift from above. Although the dikes and the sill may have been produced when the glacier bed was unfrozen, it seems more likely that they were formed when frozen-bed conditions prevailed.