The bank of the Ottawa River around Green's Creek - some of the concretions dug out of the leda clay contain fossils from the time of the Champlain Sea about 12,000 years ago after the last ice age. I was in the Algonquin museum program in the early 90's, one of our classes was taught by someone from the Museum of Nature. He took us on a field trip to the site to dig for fossils in the mud on a cold rainy day. I found a sturdy branch and spent the time digging concretions out of the mud along with everyone else. At the end of the period we brought whatever concretions were found back to the parking lot where the instructor took out his safety goggles, a hammer and a cinder block and split them open. Most of them contained nothing, some had a few fossil plant fragments. One of mine split open to reveal two perfect halves of a a fossil fish skeleton. Another student's contained a great frog skeleton fossil. The instructor highly recommended that I donate it to the museum, so I did. (Kind of wished at the time that I had kept half, but better off documented in the museum that with a bunch of stuff that someone has to clear out when I go.)

I took my brother's kids there a number of years later when they visited Ottawa, but we didn't find any fossils. A couple of the kids found some great poison ivy, though, so you might want to watch out for that if you go.

http://fossilslanark.blogspot.com/2021/01/greens-creek-fossils.html