How does the Wellington Formation affect Oklahoma foundations?

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

In short: The Wellington Formation is an early Permian mix of sandstone, shale and mudstone in central Oklahoma, lying below and east of the Garber Sandstone. Because its layers change quickly from sand to clay, soils on it range from shallow and loamy to deep and highly expansive. Foundation behavior has to be judged lot by lot from the mapped soil.

What is the Wellington Formation rock?

The Wellington Formation is made of sands, shales and mudstones ². A USGS review describes the Wellington and Garber as interbedded, lens-shaped sandstone, shale and siltstone deposited in similar delta environments during the early Permian ¹. A lens is a bed that thins and pinches out sideways, which is why the rock under one house can differ from the rock under the next.

The Garber Sandstone and Wellington Formation together form the primary flow system of the Central Oklahoma aquifer, often called the Garber-Wellington aquifer ¹. The aquifer covers roughly 2,000 square miles ².

Where it is

Rock layers in central Oklahoma tilt west at about 35 to 40 feet per mile in most locations ². The USGS lists the aquifer units as the Admire, Council Grove and Chase groups, the Wellington Formation and the Garber Sandstone ¹. See the Garber Sandstone and Hennessey Shale pages.

What soils form on the Wellington Formation?

Series	Parent material	Depth to rock	Shrink-swell clues
Renfrow	Weathered Permian clayey shale ³	More than 60 in ³	Vertic cracks at least 5 mm wide; slickensides ³
Kirkland	Clayey sediments over Permian shale ⁶	About 82 in (208 cm) in the typical pedon ⁶	Slickensides in the subsoil ⁶
Zaneis	Interbedded Permian sandstone and shale ⁴	About 40–60 in ⁴	Fine-loamy subsoil ⁴
Lucien	Permian sandstone with clay, siltstone or sandy shale ⁵	10–20 in; 14 in typical ⁵	Loamy, shallow ⁵

Vertic features, such as wide cracks and slickensides (polished shear faces in clay), are the soil survey's signs of strong shrink-swell. Renfrow's description requires cracks at least 5 millimeters wide within about 4 feet of the surface for part of most years ³.

Soil scientists rate shrink-swell by linear extensibility, the percent a soil's length changes between moist and dry, with under 3 percent low and 9 percent or more very high ⁷. Map-unit values for a specific lot are listed in the USDA Web Soil Survey.

What does the Wellington Formation mean for foundations?

Clay sites

On Renfrow and Kirkland, slow-draining clay with slickensides ³⁶ shrinks in drought and swells when wet. Renfrow has low saturated hydraulic conductivity and high runoff ³, so water tends to run off rather than soak in evenly. See perimeter drying settlement and perimeter wetting heave.

Sandy and shallow sites

On Lucien, rippable sandstone at 10 to 20 inches and very high runoff ⁵ point toward erosion and uneven bearing. Zaneis, with rock at 40 to 60 inches and moderate permeability ⁴, sits between the two extremes. See erosion, undermining and washout voids.

Mixed sites

Because sand and clay lenses alternate ¹, a single house can span both. Differences in support across a footprint can show up as cracking at the transition. See differential movement at additions and soil testing and lab values.

Common questions

What is the Wellington Formation?

It is an early Permian rock unit of sands, shales and mudstones in central Oklahoma. Together with the Garber Sandstone it forms the main water-bearing part of the Central Oklahoma aquifer.

Are Wellington soils sandy or clayey?

Both. Because the rock mixes sandstone and shale in lens-shaped beds, soils on it range from shallow, loamy soils like Lucien to deep, expansive clays like Renfrow.

How can I tell what is under my lot?

Check the USDA Web Soil Survey for the mapped soil series. A clay series such as Renfrow and a shallow loamy series such as Lucien behave very differently even a short distance apart.

Sources

Review of the general geology and solid-phase geochemical studies in the vicinity of the Central Oklahoma aquifer (Circular 1019) U.S. Geological Survey
OK County Groundwater Model (Project 174601) Association of Central Oklahoma Governments
Official Soil Series Description: RENFROW Series USDA Natural Resources Conservation Service
Official Soil Series Description: ZANEIS Series USDA Natural Resources Conservation Service
Official Soil Series Description: LUCIEN Series USDA Natural Resources Conservation Service
Official Soil Series Description: KIRKLAND Series USDA Natural Resources Conservation Service
Linear Extensibility (definition and shrink-swell classes, after NRCS National Soil Survey Handbook) UC Davis California Soil Resource Lab

Was this page helpful?