Shale compaction in a section of Cretaceous Dakota Sandstone, northwestern North Dakota

Abstract In a section of Dakota Sandstone containing interlaminated sandstone and shale, the original thickness of shale laminae is determined by use of contorted sandstone dikes. Each dike projects downward, generally, from a sandstone lamina into the underlying shale unit. The original thickness of the shale laminae was, on the average, 2.6 times the present thickness.