If you’re into geology and might be planning a trip to Wind Cave National Park in southwestern South Dakota, well, the info that follows is something of a hidden treasure.

Really! A small, hand-lettered sign in an obscure spot at the visitor center’s help desk mentioned an above-ground, geology driving tour. Spotting it last summer, I quickly asked for the informational sheets and my friend and I soon went a-touring.

The kicker is this – the info is not readily available by any series of links on the park’s website. However, determined googling and searching on my part allowed me find this treasure! I’ll share some of the info here, as well as a link to the virtually hidden web page, so you can peruse all the information yourself. I edited this a little for length and renumbered the last stops separately. (They had been 7a and 7b. Formatting of numbers does not do well with that change, or maybe it’s just me, haha).

For further background, a geologic timeline, educational questions on the stops and a map, go to


Driving tour: Use your odometer to measure mileage between stops.

1. Pahasapa Limestone – Geologic age: Mississippian. Directions: Go down the central stairs of the visitor center and exit the building through the double doors directly ahead. Once outside, follow the trail 225 yards to the cave's natural entrance Limestone is a sedimentary rock deposited in oceans. It is mainly composed of calcium carbonate. Pahasapa Limestone is gray to light tan and forms steep slopes or cliffs. 

2. Minnekahta Limestone – Geologic age: Permian. Directions: From the visitor center, drive 3.6 miles to this stop. Exit the south end of the visitor center parking lots, turn right onto route 385 South. Near the park's south boundary, you will see outcrops from road cuts. This is the Minnekahta Limestone. It is a thinly bedded gray to purplish-gray slabby limestone. Caves rarely form in this limestone because it is so thinly bedded that the ceilings would collapse.

3. Minnelusa Formation – Geologic age: Pennsylvanian and Permian. Directions: Drive 3.9 miles north on route 385. Park at the Wind Cave Canyon trailhead, which is next to a sewage lagoon. A short hike on the trail (1-mile round trip) is required. Outcrops of this formation are on the left side of the canyon. The Minnelusa Formation consists of interbedded limestones, sandstones and shales. It is yellow to red, with the shales being a grayish cream. Interbedded means that the limestones, sandstones and shales alternate with distinct horizontal layers.

4. Deadwood Sandstone – Geologic age: Cambrian. Directions: The distance is 2.2 miles to the Deadwood Sandstone. Continue north for 1.7 miles on route 385 to the junction of route 87. Turn right and drive 0.5 miles. Look for a large basin on the left side of the road. Much of the Deadwood Sandstone is on the north end and at the bottom of the basin. Sandstone is sedimentary rock composed mostly of grains of quartz that vary in size. The Deadwood Sandstone is brown to light gray in color.

5. Pegmatites – Geologic age: Precambrian. Directions: Continue north on route 87 for 1.8 miles. The pegmatites are found at a parking area on the right side of the road called “Ancient Foundations.” Pegmatites are part of the Precambrian core of the Black Hills. They are extremely coarse grained igneous rocks that formed deep within the earth. The large crystals indicate that they cooled very slowly.

6. Schists – Geologic age: Precambrian. Directions: Walk or drive 0.2 miles north of Stop No. 5 (pegmatites). There is an outcrop of schists along the left side of the road. Park at the small parking area on the right side. Be careful of traffic on this curved road. Like pegmatite, schist is part of the Precambrian core of the Black Hills. Schist is a metamorphic rock composed of shiny mica minerals. It is identified by distinct foliation, which is a geologic term meaning very fine layering. Distinct foliation indicates that great pressures occurred within the earth. Rock layers form at right angles to the source of pressure.

7a. Spearfish Formation – Geologic age: Permian and Triassic Directions: The distance is 8.4 miles from Stop No. 6 (schists) to the Spearfish Formation. Continue north on route 87 for 4.4 miles. Just before you enter Custer State Park, turn onto a gravel road called NPS 5. Drive 4 miles to a lone pine tree on the right side of the road. Park at the parking area to the left. Look to the valley below. The Spearfish Formation is composed of red shales and siltstones, both are extremely fine-grained sedimentary rocks. The red color comes from iron oxides. The Spearfish Formation is often called Red Valley. The shales and siltstones have formed a valley because they are easily eroded in the semi-arid Black Hills climate.

7b. Inyan Kara Group – Geologic age: Cretaceous and Jurassic. Directions: Same as Stop No. 7. The Inyan Kara Group consists of iron rich sandstones and claystones that form the hogback ridge that defines the outer rim of the Black Hills.

Lisa Brainard still enjoys lifelong pursuits of the outdoors, history and travel following a serious accident and stroke in September 2012. She’s written this column weekly for about 15 years.