Lilydale quarry: Located across the river from downtown St. Paul, Lilydale is probably the most famous fossil collecting site in the Twin Cities. Rock from the fossil-rich site was quarried by the now-defunct Twin Cities Brick Company and used for making bricks.Courtesy Mark RyanEarlier this week a story appeared in the Minneapolis Star Tribune about fossil hunting in Lilydale Regional Park just across the river from the Science Museum. This has been a long-time favorite site to collect fossils from Minnesota’s ancient past. I’ve collected there often and at other sites around the region.
Fossil cephalopods: Specimen on the left was found at the Lilydale Quarry site. The slab on the right contains two small cephalopod fossils and was found near Shadow Falls in St. Paul, MN. Late Ordovician.Courtesy Mark Ryan
Ordovician fossils: Typical fossil-filled shale slab found around the Twin Cities’ fossil collecting areas. Late Ordovician.Courtesy Mark RyanAbout 450 million years ago, the North American continent was situated along the equator, and a warm shallow sea covered much of Minnesota. Sea life was abundant as confirmed by the tremendous amounts of marine fossils that be found around here. Rock formations of sandstone, limestone, and shale line the Mississippi River. The layers are flat and fairly undisturbed from when they were laid down during the Ordovician Period. Most of the fossils come out of the Decorah shale and Platteville limestone.
Shadow Falls: Marcus Kenney and sons Elijah and Benny hunting for fossils at Shadow Falls. The easily accessed site is located near the Mississippi at the west end of Summit Avenue in St. Paul, MN.Courtesy Mark RyanI’ve been collecting fossils in this area for over three decades, and autumn has always been my favorite time to get outdoors, soak up some sun, and hunt for the elusive trilobite, or monstrous cephalopod (one of the largest found can be seen in the Science Museum’s Dinosaurs & Fossils gallery). You don’t really need much equipment, just a good eye, and maybe something to carry what you collect. Sometimes I like to have a mat or something to kneel on, but that’s me. I’ve been out quite a few times in the last six months and have found some very nice specimens.
Elusive trilobite: Molted trilobite tail. Trilobites are highly coveted by collectors. Late OrdovicianCourtesy Mark RyanThe Minnesota Geological Survey has plenty of information about Minnesota’s geology and prehistoric past. Click on the link to download their publication titled Fossil Collecting in the Twin Cities Area. It includes various collecting sites around southeastern Minnesota and illustrations of the fossils you’re likely to find there, such as bryozoans, brachiopods, gastropods, trilobites, horn coral, pelecypods, and cephalopods.
Fossil collecting Lilydale Regional Park (pdf file)
More trilobite info
List of fossil sites and equipment
More about horn coral
Roadside attraction: Pat Ryan hunts for fossils in the Decorah shale outcropping in a highway ditch near Cannon Falls, MN. The highly fossiliferous site is located about 2 miles southeast of the town center.Courtesy Mark Ryan
More than enough fossils: Close-up of fossils littering the ditch near Cannon Falls, MN. Fossils at this site are found mostly weathered out of the matrix allowing for the collection of some great individual specimens.Courtesy Mark Ryan
Trapped in time: Fossil of a cephalopod (possibly baculites?) in situ, near Cannon Falls, MN. Late Ordovician.Courtesy Mark Ryan
Fossil of Ordovician predator: Fossil cephalopod (possibly baculites?) collected near Cannon Falls, MN. Late Ordovician. Baculites were ammonites with a straight tusk-like shell. The cephalopods occupied the top of the food chain during the Ordovician.Courtesy Mark Ryan
Fossil coral: Fossil coral (Favosites?) found near Cannon Falls, MN. Late Ordovician. Other than cephalopods, this is the largest single fossil I’ve ever found in the Decorah shale. I believe it’s some sort of striated coral.Courtesy Mark Ryan
Lots of fossils: Bryozoa litter the ground at an exposure near Cannon Falls, MN. Bryozoa were microscopic animals that often formed coral-like colonies or fan structures and are the most common fossils found in the Decorah shale around southeast Minnesota.Courtesy Mark Ryan
Down and dirty: Pat Ryan digs out a cephalopod fossils found on the flats of a Decorah shale exposure near Cannon Falls, MN.Courtesy Mark Ryan
Close-up of cephalopod: Large cephalopod segment found by my brother Pat at Decorah shale exposure near Cannon Falls, MN. Another piece of the same specimen was found about 2 feet away.Courtesy Mark Ryan
Rare find: Trilobite head in matrix, found near Cannon Falls, MN. Late Ordovician. Heads of the ancient arthropods are extremely rare. This is only the second trilobite head I’ve found in three decades collecting fossils around the Twin CitiesCourtesy Mark Ryan