What soils cause foundation problems in south-central Oklahoma?

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

In short: South-central Oklahoma mixes very different ground. Around Durant, clays formed from Cretaceous shale have smectite-rich subsoils that crack deeply in dry periods ¹. The Arbuckle Mountains contain limestone and dolomite karst ⁵, while sandy soils on Cretaceous sandstone are well drained and Red River floodplain sands are frequently flooded where unprotected ²⁴. Drought settlement and wetting heave on the clays are the main foundation issues.

Cities covered: Ardmore, Ada, Durant, Sulphur and Duncan.

What is the climate like?

Rainfall rises from west to east across the region. USDA descriptions give mean annual precipitation of about 33 to 39 inches for Zaneis soils, and about 37 to 45 inches for Durant soils ¹³. Mean annual temperatures run about 59 to 66 °F ¹²³. See drought and wet cycles.

What is the ground made of?

Cretaceous clays (Durant area)

Durant soils are very deep, moderately well drained clays weathered from Cretaceous clayey shale and claystone on broad, gently sloping ridges ¹. Key facts from the USDA description ¹:

• Classified as smectitic with vertic-like (Udertic) properties.
• Very slow permeability.
• Cracks wider than 1 cm and deeper than 30 inches form during dry periods.
• Type location in Bryan County; part of the Grand Prairie land resource area.

Smectite clays swell when wet and shrink and crack when dry, and the cracks do not fully close on rewetting ⁷. See Cretaceous shales, clays and sandstones.

Sandy uplands and red-bed soils

• Bernow: deep, well drained sandy and loamy soils from Cretaceous sandstone, on hillslopes of 0 to 12 percent, with type location in Bryan County ².
• Zaneis: well drained soils from interbedded Permian sandstone and shale, with soft rock at 40 to 60 inches; the series was established in Carter County ³.

Red River floodplain

Kiomatia soils are well drained, rapidly permeable sandy alluvium on natural levees of the Red River floodplain, and are frequently flooded for brief periods in most years where unprotected ⁴. See Quaternary alluvium and terraces and creeks and flood history.

Arbuckle karst

The Oklahoma Geological Survey reports limestone and dolomite karst mainly in the Ozark region, the Arbuckle Mountains and the Limestone Hills north of the Wichita Mountains ⁵. USGS explains that soluble rock dissolved by groundwater can leave caverns, and that sinkholes may open suddenly beneath clay-rich cover ⁶.

What are the main soils?

What are the common foundation problems?

• Perimeter drying settlement on Durant and similar clays during drought.
• Center heave when water collects under slabs on the same clays.
• Flood and erosion exposure on Red River and creek floodplains.
• Possible karst voids near the Arbuckles.

The Oklahoma Geological Survey also lists Love and Carter Counties among the state's principal seismic areas, and gives typical Oklahoma earthquake magnitudes of about 1.8 to 2.5 ⁵.

Related

• Cretaceous Shales, Clays and Sandstones
• Arbuckle Carbonates
• Shrink-Swell and Active Zone
• Southeast (Ouachitas & Red River)
• OKC Metro