Slates and unconformity
46.664880°N 92.404079°W The slates show different dip angles where the unconformity exists.
Thompson Formation slates were cut by dikes 1.2 billion years ago. Just downriver from the site here is an exposure of a small anticline formed in the slates. The amount of lava flows associated with the exposed plumbing system that relates to a hot spot once under present-day Lake Superior (estimated at 480,000 cubic miles) was greater than the amount created by the Deccan Trap. Some of the dikes show columnar jointing.