Most people who drive State Road 446 along the eastern shore of Monroe Lake are looking at the water. On the afternoon of October 15, 2026, a group of no more than twenty will be looking at the ground instead — specifically at a bed of crinoid fossils at Allens Creek State Recreation Area.
The event is called ROCKS, ROCK! Crinoid Fossil Bed Hike. It starts at 2 p.m. and runs about two hours, covering roughly two miles of trail, including what the DNR frankly describes as "a couple significant hills." It is free, but registration is required by October 13, and the group is capped at twenty people. The DNR recommends it for teens and adults. And there is one firm rule, stated in capital letters on the event listing: NO COLLECTING PERMITTED.
That last point is the tell that this is not a rock-hounding trip. The point is to read the landscape, not to carry pieces of it home. As the DNR puts it, participants will "take a walk back in time to reconstruct what the landscape was like here during the Mississippian Period" — examining what fossils can tell us about the past, how they form, and why there are so many of them at this particular spot.
To understand why there are so many, you have to go back to a time when Indiana was not Indiana. During the Mississippian subperiod, much of what is now the American Midwest lay beneath a warm, shallow sea. Southern Indiana's Mississippian limestones formed in that water, which teemed with crinoids — commonly called sea lilies — along with corals and brachiopods. Crinoids are not plants. They are echinoderms, animals in the same phylum as starfish, sea urchins, and sand dollars. A living crinoid looked like a small, feathery chandelier anchored to the seafloor by a long, jointed stalk, with arms lined with tiny tube feet that captured plankton drifting past. At their Paleozoic peak, crinoids were so abundant that entire limestone formations across North America and Europe are composed largely of their skeletal remains.
That is the rock the hike is walking on. The Salem Limestone, the formation that underlies much of southern Indiana, preserves fossils dating to the Mississippian and is quarried as the building material known as Indiana limestone, or Bedford limestone. The formation is named for Salem, Indiana, in Washington County. So the fossil bed at Allens Creek is not a curiosity isolated from the rest of the state's history; it is the raw material of it.
Allens Creek itself has a reputation among people who pay attention to such things. According to the Sycamore Land Trust, more than 80 species of crinoids have been discovered at Allens Creek, just four miles southwest of the trust's Peninsula Preserve. That concentration is exactly the kind of thing the hike is designed to explain: why this location, out of all the shoreline and hillside around Monroe Lake, holds so many.
The lake above the fossil bed is much younger than the fossils below it. Monroe Lake is a reservoir about ten miles southeast of Bloomington, the largest lake entirely within Indiana. It was created by damming Salt Creek. The lake's shoreline and recreation areas — Fairfax on the west side, Allens Creek on the east — are the product of that mid-century engineering, which means the hike's two-mile route crosses a landscape with two very different ages layered onto it: a reservoir bottom measured in decades, and a fossil bed measured in hundreds of millions of years.
The trailhead for the area is the Turkey Trot Trail, a 1.75-mile out-and-back route that begins at Allens Creek State Recreation Area and follows what was once an old gravel road through woodlands down to the shore of the lake's Salt Creek arm. In winter, with the leaves down, the trail offers views of the water on both sides. The fossil hike covers a comparable distance, with the hills that come with this part of Monroe County.
For anyone who has ever picked up a crinoid stem fossil — the small, ridged stone discs that look like tiny stacks of coins or segments of a broken screw — and wondered what they were, the hike is a chance to get the answer in the place where the animal actually lived. Crinoid fossils have given paleontologists insight into the ecology of ecosystems long since altered by extinction and evolution, and the segmented architecture of the stems, cups, and arms is preserved in the limestone in extraordinary detail. Indiana is, in fact, one of the best places on Earth to see this: the most famous crinoid fossil locality in the world, prized for both abundance and preservation, is at Crawfordsville, Indiana, where entire crowns have been recovered.
But the Allens Creek hike is not about collecting a specimen. It is about standing on a hillside above a man-made lake, looking at a slab of stone that was once seafloor, and being able to say what lived there and why. The DNR's framing — reconstructing a landscape — is the whole point. The fossils are the evidence; the hike is the argument.
Space is limited to twenty, and registration closes October 13. Sign-up is through the DNR's registration link. Participants should expect two hours of walking, a couple of real climbs, and a view of Monroe Lake from a shore that has been accumulating stories for a very long time.