Pennsylvanian - About 323–299 million years ago
Sand and mud become the county’s rock layers
During Pennsylvanian time, rivers and shifting lowland environments deposited sand and mud across the region. Burial and cementation turned these materials into sandstone and shale. These layers became part of the bedrock of the future county. Much later, erosion exposed resistant sandstone at places such as Coopers Rock, leaving cliffs and rock masses that visitors can see today.
Research status
This entry has been checked against its named source.
The timeline wording accurately reflects the source listed below. This status does not necessarily mean the event has been independently corroborated against additional records.
Sources and further reading
Where this entry comes from
WVGES: Historical Geology of West Virginia — sedimentation and coal-forming environments; see date caveat in Research Notes
Geological descriptions reviewed by Dr. Joe Lebold, West Virginia University.
Research notes
What the evidence establishes
The broad period dates the depositional setting, not every individual sandstone bed. Renton identifies local Pottsville sandstone at Coopers Rock; modern cliff exposure occurred much later.
Sandstone and coal formation describe overlapping environments, not a strict before-and-after sequence. Coopers Rock is a county-border-area example.
Numerical boundaries follow the ICS June 2026 chart. WVGES’s older overview contains outdated numerical dates; it is used for depositional processes, not those dates.
Modern place names locate the evidence; they do not imply that present-day communities or county boundaries existed at the time.
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