Are there gypsum sinkholes in western Oklahoma?

Reviewed by Preston, Oklahoma foundation repair consultant · Updated 2026-10-14

In short: Gypsum, salt, limestone and dolomite can dissolve in groundwater, leaving voids that may cause the ground above to sag or collapse. In western Oklahoma, gypsum of the Permian Blaine Formation lies close to the surface in places. Settlement that keeps going, or that doesn't follow the usual wet-dry seasonal pattern, is one reason soluble rock is considered during an investigation.

What is karst?

Karst is a landscape formed where rock dissolves in water. The U.S. Geological Survey groups two families of soluble rock ¹:

• Carbonates: limestone and dolomite.
• Evaporites: gypsum and salt, minerals left behind when ancient seas evaporated.

Roughly 18% of the nation's total area sits on soluble rocks with karst features or the potential for them ¹. The USGS lists sinkholes among the principal causes of land subsidence, meaning sinking of the ground surface, and notes subsidence in areas underlain by soluble rocks such as limestone, gypsum or salt ².

A sinkhole is a depression or collapse at the surface over a dissolved void.

Where is gypsum found in western Oklahoma?

The Cottonwood soil series formed in material weathered from massive gypsum, mostly alabaster, of the Permian-age Blaine Formation ³. It occurs in southwestern Oklahoma and northwest Texas ³. In these soils:

• hard gypsum bedrock lies 3 to 20 inches below the surface ³;
• the gypsum layer itself is about 5 to 15 feet thick ³; and
• water moves through the gypsum bedrock very slowly to moderately ³.

The Blaine and related gypsum units are described on Permian gypsum units, and the region on Northwest (Gypsum Hills).

What about limestone and dolomite?

The Oklahoma Geological Survey notes that marine carbonate rocks of Late Cambrian and Ordovician age underlie most of the state, and that carbonates reach more than 8,000 feet thick near the Southern Oklahoma Aulacogen, described as part of a failed triple junction, an ancient rift that stopped developing ⁵. Carbonate rock is one of the two soluble-rock families with karst potential ¹; see Arbuckle carbonates and Mississippian cherty limestone.

What are the field signs of karst?

These are the kinds of observations that prompt a closer look for voids:

• a sudden depression or sinkhole in a yard or field, or ponding in a new spot;
• settlement that continues after repair or doesn't match seasonal moisture patterns;
• a pier that suddenly drops or loses resistance during installation; and
• similar sudden problems on neighboring lots.

What are the limits of the maps?

The USGS karst map shows where soluble rock occurs, but it does not rate hazards such as sinkhole collapse ¹. It is a first approximation intended to guide more detailed study of specific areas ¹. Site-level answers come from borings and, in some cases, geophysical surveys that image the ground below.

The Oklahoma Geological Survey collects reports of sinkholes through an online form linked from its FAQ page ⁴.

What should repairs consider on soluble rock?

Because water drives dissolution, controlling surface drainage near a suspected void is a common first concern; see surface drainage and grading. Repair approaches are described on void and compaction grouting and working with engineers.

Related

• Karst Subsidence and Sinkholes
• Oklahoma Geologic Provinces
• Erosion Creeks and Slopes
• Northwest (Gypsum Hills)
• Southwest (Lawton and Red Plains)