- GeoRef, Copyright 2004, American Geological Institute. Reference includes data from Bibliography and Index of North American Geology, U. S. Geological Survey, Reston, VA, United States
Two sandstone sills in Precambrian rocks near Jasper are up to 22 feet long and one foot thick. Each extends laterally from the base of a bank of a scour channel eroded in slate and filled in by sandstone. Intrusion took place while the sediments were unconsolidated as the result of variation in confining pressure caused by differential compaction.