About Us

The Hill Annex Paleontology Project is a volunteer-initiated research project examining the roughly 90-million-year-old Cretaceous soils scattered across Minnesota. These deposits lay hidden under our feet by a thick layer of sand and gravel from the geologically recent glacial period. Only erosion and human excavation, like open pit iron mining, now expose these materials for our examination. The Hill Annex Mine and former State Park are a scientifically historic locality for reports on these Cretaceous deposits, labeled as the Coleraine Formation.

Minnesota, during this prehistoric period, was on the eastern edge of a great seaway that extended from the Gulf of Mexico to the Arctic Ocean, bisecting North America in two. As sea levels rose and fell, many different environments existed along this ocean shoreline. The Mesabi Iron Range of northern Minnesota was believed to be a giant estuary river system flowing from east to west.

Fossils from the deposits indicate near shore marine and tidal zone habitats. They are represented by fossils in the form of snails, shellfish (oysters, clams, mussels), ammonites, bony fish, sharks, a scattering of reptiles and plant materials. We aim to examine the historic science, preserve any old and new materials, and report a greater understanding of not just the Coleraine Formation but the wider Cretaceous Minnesota regional picture..