Little Elk Creek, South Dakota
Archean Basement and Red-White Gates Monocline

Steven Dutch, Professor Emeritus, Natural and Applied Sciences, University of Wisconsin - Green Bay

Geologic map of the Little Elk Creek area. Ti = Tertiary intrusive rocks, Sp = Spearfish Formation and Q = Quaternary and late Tertiary alluvium.

Geologic and topographic map of Little Elk Creek. It's not a hard walk from the Archean rocks through the Red and White Gates but it entails either a return hike or arranging a pickup at the other end.

Diagrammatic cross section along Little Elk Creek. Other Tertiary uplifts in the West are bounded by thrust faults, and faults are often the cause of monoclines in general. Although no thrust fault has yet been identified along the eastern front of the Black hills, either in outcrop or geophysically, one is very likely to exist. The Red Gates and White Gates are spectacular monoclines.

Archean Outcrops

Left and below: Archean outcrops on Little Elk Creek
Left and below: closeups of Archean rocks

View down Little Elk Creek

Little Elk Creek Canyon

Left: Paha Sapa Limestone on the summit with Deadwood Sandstone just visible in the trees.

Below: the trail along Little Elk Creek. With a few rough exceptions where it has been washed away, the trail is easy, even potentially drivable. Unlikely as it sounds, there was probably once a railroad up the canyon. In the days before motor vehicles, railroads were the only practical way to get large loads in an out of the Black hills.

The trail at one point climbs above the stream because the original trail is washed out.
The trail drops steeply back to the stream.
Paha Sapa Limestone (gray) underlain by Deadwood Sandstone (red).


Red Gate

Deadwood Sandstone beginning to show a dip toward the monocline.

Looking downstream at the Red Gates
Approaching the Red Gate

Sample drill hole, possibly for paleomagnetic studies.

White Gate

Approaching the White Gates. The Red Gates are behind us.
Cliff of Paha Sapa Limestone
Looking up-valley toward the White Gates.

Left and below: slickensides in the Deadwood Sandstone.
Left and below: gently dipping Paha Sapa at stream level.

Red Gates in the shaded foreground with a cliff of Paha Sapa sunlit in the distance.

  Left: vertically dippin Paha Sapa. 

Minnelusa Sandstone

Looking back up-canyon.
Below: A volcanic ash bed has been scooped out, possibly for clay.  

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Created 22 June 2007, Last Update 06 June 2020