The North Dakota Geological Survey brings its public dig back to the Pembina Gorge each summer to hunt sea monsters in the Pierre Formation, 80 million years old and some of the oldest surface rock in the state, laid down when the Western Interior Seaway covered North Dakota. Diggers have found mosasaurs, giant squid, sea turtles, Xiphactinus and Enchodus fish and Hesperornis birds, mostly as single bones: a mosasaur jaw here, a Xiphactinus vertebra there. In 2026 it ran for ten days in August, $50 for a full day (age 15 and up) or $30 for a half day (family days from age 10), with registration opening on 31 January, first come, first served. Vans run diggers out to the site from Walhalla and the survey supplies every tool; bring lunch, a hat and a camera. Everything you find goes to the State Fossil Collection in Bismarck.
Mosasaurs, giant squid, sea turtles, Xiphactinus, Hesperornis · Late Cretaceous, ~80 mya
This ground is protected. Photograph it, record it, leave it where it lies. On US federal land the Paleontological Resources Preservation Act 2009 makes collecting vertebrate fossils an offence, and penalties are real.
Other places on the map within a couple of hours.
