Geology

The rock layers under Oklahoma and how deep firm ground usually is.

• How do cherty limestone soils affect NE Oklahoma foundations?Weathered cherty limestone leaves very gravelly soils, dense fragipans and some karst, so foundation concerns center on water, voids and rocky digging.
• How do Oklahoma river floodplain and terrace soils affect homes?Floodplain and terrace deposits range from soft wet clay to sandy dunes and expansive claypans, so the soil series, not the river, predicts behavior.
• How do Ouachita Mountain rocks affect southeast Oklahoma homes?Tightly folded sandstone, shale and chert form steep slopes with thin, rocky soils, so slope movement, erosion and fill matter more than clay swell.
• How do Panhandle Ogallala and loess soils affect foundations?Panhandle soils formed in Ogallala deposits capped by loess and sand. They are dry most of the year, so movement follows sudden moisture changes.
• How do Pennsylvanian shale clays affect Oklahoma foundations?Pennsylvanian shale under Tulsa and eastern Oklahoma weathers into poorly drained clays that hold perched water and often swell and shrink strongly.
• How do Tulsa-area sandstone ridges affect Oklahoma foundations?The sandstone forms shallow, loamy, well-drained soils, so slopes, fill, erosion and uneven rock matter more than clay swell on these lots.
• How do western Oklahoma red beds affect foundation soils?Soft red sandstone and siltstone form shallow silty soils, while claystone and old river clays form expansive clay soils.
• How do Wichita granite and outwash affect Lawton-area foundations?Around the Wichita Mountains, soils formed in granite outwash over red clay, such as Foard, are sodium-rich, very slowly permeable and prone to shrink-swell.
• How does Arbuckle limestone affect Oklahoma foundations?Hard Arbuckle limestone and dolomite surface in south-central Oklahoma. Shallow rock and karst, not clay swell, are the main foundation questions there.
• How does Garber Sandstone affect Oklahoma foundations near OKC?It weathers into loamy, well-drained soils often shallow to soft rock that swell less than red clays, so drainage, erosion and shallow rock matter most.
• How does limestone north of Tulsa affect Oklahoma foundations?Pennsylvanian limestone beds can weather into Apperson soil, a very expansive clay over hard limestone about 3.5 to 5 feet down.
• How does the Wellington Formation affect Oklahoma foundations?Wellington layers shift quickly from sand to clay, so soils range from shallow and loamy to deep and highly expansive and must be judged lot by lot.
• What Cretaceous rocks and soils lie under southern Oklahoma?Layers of clay, shale, marl, limestone and sand; the clay and shale weather into very expansive soils, while sand layers give loose, well-drained soils.
• What is Hennessey shale and how does it affect Oklahoma foundations?Red Permian shale west of OKC that weathers into swelling red clay soils, which shrink in drought and swell when wet, driving seasonal foundation movement.
• Why does western Oklahoma gypsum cause sinkholes?Gypsum beds like the Blaine Formation, and deeper salt, dissolve in groundwater and form caves, sinkholes and voids, a different risk from clay movement.