What is the Paleo Site?
About 300 million years ago, in the Pennsylvanian period, the ground under Rim Country was the floor of a warm, shallow sea, and the lime mud that settled there became the grey Naco Formation that SR 260 cuts through between Payson and Kohls Ranch. One of those cuts turned out to be extraordinarily rich. Paleontologists have worked the Kohls Ranch locality for decades and call it one of the most productive Pennsylvanian fossil beds in Arizona; when the state realigned SR 260 the original main cut went under the new pavement, and the Forest Service kept the exposure beside it open as the Paleo Site: a large paved pull-off, a pedestrian gate, two interpretive signs (one an Eagle Scout project) and a slope of weathered limestone and shale about 15 miles east of Payson.
What is in the slope are brachiopods, the ribbed, clam-shaped shells that dominated these seas, in several species and by the hundreds; crinoid stem segments like stacks of tiny washers; lacy bryozoans; horn corals; and small bivalves. Most of it is loose in the gravel or barely attached to soft shale. The Tonto National Forest allows limited personal collecting of invertebrate fossils, so the handful your kids carry back to the car is legal. It is for families, for anyone who has driven past the sign a dozen times on the way to the lakes, and for the kind of adult who keeps a rock on the dashboard.
What you get is a guaranteed find in the first few minutes, a free lot and a lesson in deep time with no hike attached. What you do not get is a toilet, water, shade, a trail, or a monument; Google’s label is wrong. A place where a six-year-old finds a 300-million-year-old shell before the car has cooled, it is.
How to do the Paleo Site right
Know the rules before you pick anything up. Surface collecting and non-powered hand tools only, negligible disturbance, personal or educational use, nothing for sale or trade. Leave the big slabs with several fossils in them for the next family. No vertebrate fossils anywhere on national forest land, ever, including shark teeth; you will not find any here, but it is the law. Stay inside the fence, away from the highway.
Get there. Loop 101 north to SR 87, the Beeline, 75 miles to Payson, then east on SR 260 about 15 miles. Just past milepost 267, in the divided section before Kohls Ranch, a green sign reads Paleo Site and a short ramp drops right into a paved lot. It is eastbound only; from the Rim side, continue to a safe turnaround and come back. The exit is short, so brake early, especially with a trailer. Figure about 115 minutes from Old Town. The lot is large and rarely full; the slope beyond the gate is a two-minute walk.
Pick the season. Any dry day works at 5,500 feet. October through May is the comfortable window. Midday in June and July is a glare oven on grey rock; go early. July and August afternoons bring monsoon storms off the Rim, and the morning after rain is the best collecting of the year, because the shale weathers out fresh pieces every time it is wet.
Bring the right kit, which is almost nothing. A paint scraper or an old screwdriver to tease a brachiopod out of soft shale, a cheap hand lens, a hat, water and a sandwich bag per child. No hammer, no pry bar; the surface-only rule makes them pointless. Teach the two shapes before you start: the ribbed clamshell of a brachiopod and the stacked-coin stem of a crinoid. Once a child sees one, they see fifty.
Work the slope, not the gate. The first twenty feet past the fence are picked over. Walk farther in and higher up, where the talus holds more than the main face does and the loose pieces are better preserved. Keep children off the steep part above the highway fence and watch the loose rock underfoot.
Facilities. None: no toilet, no water, no shade, no trash can. The nearest restrooms are at Kohls Ranch and the Horton day-use site four miles east, or in Payson. Pack out everything.
Dogs. Allowed on leash in the lot and on the slope. Carry water for them; the rock is hot by late morning in summer.
Skip it if you want a day, not a stop. The Paleo Site is 45 minutes. Treat it as the warm-up for Horton Creek, four miles east, or the geode field off the Control Road at Geode Hill for a full rockhounding day, and camp at Christopher Creek if you are staying over.
A seafloor the highway department cut open
The oldest story here is the rock. In the Middle Pennsylvanian, roughly 300 million years ago, central Arizona lay near the equator under a shallow tropical sea that advanced and retreated across the continent many times. Each advance left lime mud and shell beds; each retreat left shale and silt. Stacked and hardened, those cycles became the Naco Formation, a few hundred feet of grey limestone and shale that sits on top of the older Redwall limestone across the Mogollon Rim country and is, in turn, buried under the Supai red beds and the Coconino sandstone that form the Rim itself. The Naco is everywhere under Payson; it is only visible where a canyon or a road cuts into it.
The people who knew this country first were not interested in the brachiopods. The slopes below the Rim were Tonto Apache and Yavapai land, hunted and farmed along Tonto Creek and the East Verde, until the Army campaigns of the 1870s and the removals to San Carlos; the Tonto Apache Tribe’s small reservation sits beside Payson today. Anglo ranchers and the Payson townsite followed in the 1880s, and in 1905 the federal government proclaimed the Tonto National Forest, which has managed these roadside outcrops ever since. The road itself, from Payson east toward Kohls Ranch and Heber, grew from a wagon track into a state highway over the twentieth century, and every widening sliced a little deeper into the Naco.
Those cuts made the site. Geologists had known the Naco for decades (it is named for Naco, the border town where it was first described), but the exposures along SR 260 near Kohls Ranch turned out to be unusually fossil-rich, with brachiopods, crinoids, bryozoans, corals, snails, clams and even the occasional shark tooth weathering out of the soft shale between limestone ledges. In 1976 D. C. Brew and Stanley Beus of Northern Arizona University published a description of the Middle Pennsylvanian fauna near Kohl Ranch in the Journal of Paleontology, and the roadcut became a standard locality: a place university field trips stopped, amateur collectors drove to from Phoenix and Tucson, and fossil-club newsletters mapped by milepost.
Then the highway department came back. In the 2000s ADOT rebuilt SR 260 between Payson and the top of the Rim as a four-lane divided highway, and the realignment buried the classic cut under the new roadbed. What survived was the exposure beside it. The Forest Service developed that slope as a signed pull-off from the eastbound lanes, fenced it from the traffic and put up interpretive panels; one of the signs was an Eagle Scout project by a Payson-area Scout, Ben Mohler, and the site has carried the name Indian Gardens Paleo Site in Forest Service references since. We could not pin the exact year the signs went up, so we have said the 2000s and left it there.
What has not changed is the policy, which is the quietly remarkable part. Most public land in Arizona forbids taking anything; the Tonto’s rules for invertebrate and plant fossils allow limited, non-commercial hobby collecting with hand tools and negligible disturbance, and the Paleo Site is the one place where the forest has effectively said yes, here, go ahead. That is why the gate area is picked clean and why the rule about leaving the big slabs matters: the site renews itself only as fast as the rain can weather new shale.
Why it matters
The Paleo Site explains the ground the whole Rim country stands on. Every cliff above Payson, every lake on the Rim, sits on hundreds of feet of seafloor, and this is the one place a child can hold a piece of it that she found herself and keep it legally. It also shows how Arizona’s public land actually works: a highway cut, a university paper, a Forest Service rule and a Scout’s sign add up to a destination nobody planned. The limestone is not going anywhere, and the rain keeps bringing more of it to the surface. For a Scottsdale family it is the easiest half hour you will add to a Rim trip, and the stop the kids will remember after they have forgotten the lake.