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Named stone

Plattsmouth and Winterset cherts

Also called Plattsmouth chert, Winterset chert, Eastern Kansas Pennsylvanian cherts

A kind of chert (and flint)

Plattsmouth and Winterset chertsChert (and flint)Plains

Description

Plattsmouth and Winterset cherts are two of the Pennsylvanian-age cherts that early peoples gathered and used in eastern Kansas, along with Westerville chert. Winterset chert sits in the upper part of the Winterset Limestone Member of the Dennis Limestone; in Wyandotte County it is mostly black or bluish with occasional white streaks, a colour the county survey says no other local limestone shows, and in Johnson County it forms scattered grey to black nodules. Plattsmouth chert comes from the Plattsmouth Limestone Member of the Oread Limestone; in northeastern Kansas it forms black, brown and grey nodules 1 to 8 inches across, spotted with white or grey silica fossil replacements and cut by thin black shale partings. Like other Kansas cherts, both are tough stones that heating improves.

How to identify it

Colour
Winterset: mostly black or bluish with occasional white streaks in Wyandotte County (KGS, Wyandotte County); grey to black in Johnson County (KGS, Johnson County). Plattsmouth: black, brown and grey (Galle and Waugh 1966).
Texture
Plattsmouth: nodules 1 to 8 inches across with discontinuous thin black shale partings that run on into the limestone (Galle and Waugh 1966).
Inclusions
Plattsmouth: white or grey siliceous replacements of fossils (Galle and Waugh 1966).
Heat treatment
Kansas cherts in general are tough, modest-quality stones that controlled heating improves dramatically; heat treatment was known in Kansas from Paleoindian times (Reynolds and Lees 2004).

Geology

Winterset chert: a persistent zone of flint nodules in the upper part of the Winterset Limestone Member of the Dennis Limestone, Missouri Series, Pennsylvanian; the member is about 30 feet thick in Wyandotte County (KGS, Wyandotte County). Plattsmouth chert: nodules throughout the Plattsmouth Limestone Member of the Oread Limestone, Shawnee Group, Late Pennsylvanian; the member is 11 to about 20 feet thick from Leavenworth to Doniphan County (Galle and Waugh 1966).

Where it comes from

Plains

States

Quarries and outcrops

  • Winterset Limestone Member outcrops, Wyandotte and Johnson counties, Kansas
  • Plattsmouth Limestone Member outcrops, Doniphan, Atchison and Leavenworth counties, northeastern Kansas

Used by

  • Collected and used by early peoples in eastern Kansas (Reynolds and Lees 2004); no period is given

Look-alikes

Stones that are easy to confuse with Plattsmouth and Winterset cherts.

  • Westerville chert, the third eastern Kansas Pennsylvanian chert named by Reynolds and Lees (2004)
  • Other dark Pennsylvanian limestone cherts of the region

Sources

  1. Reynolds, John D., and William B. Lees. 2004. The Archeological Heritage of Kansas. Kansas Historical Society.kansashistory.gov (opens in a new tab)
  2. Galle, O. Karmie, and Wanda N. Waugh. 1966. Compositional Variance in the Plattsmouth Limestone Member (Pennsylvanian) in Kansas. Kansas Geological Survey Bulletin 180, part 1.kgs.ku.edu (opens in a new tab)
  3. Kansas Geological Survey. Geology of Wyandotte County, Kansas: Stratigraphy (online edition of the 1935 county report).kgs.ku.edu (opens in a new tab)
  4. Kansas Geological Survey. Geohydrology of Johnson County, Kansas: Kansas City Group (online edition).kgs.ku.edu (opens in a new tab)

All materials