Pennsylvanian - About 323–299 million years ago · Countywide
Ancient wetlands lay the groundwork for Preston’s coal
Vegetation accumulated in waterlogged wetlands across the region during Pennsylvanian time. Some plant material survived decay as peat. Later, heat and pressure from burial transformed peat into coal. Repeated changes in the landscape left coal seams among layers of other sedimentary rocks. Those deposits, including the Upper Freeport coal in Preston County, would eventually become part of the county’s mining history.
Research status: Verified to source
- Additional source
University of Iowa Museum: Pennsylvanian Coal Swamp — peat-to-coal explanation; numerical age labels are not used here
Visit source ↗ (mnh.uiowa.edu)