Ambridge, PA: Twin road cuts
Coal Forest and marine environment
~ 299 - 300 Million Years Old
Upper Pennsylvanian, Westphalian D to Stephanian A
Conemaugh Group: Mahoning Formation and Brush Creek Marine Zone
Stratiographic Column and corresponding geologic time units of the Upper Pennsylvanian
This table is from page 8 of:
Oleksyshyn, J. (1982). Fossil plants from the anthracite coal fields of eastern Pennsylvania.
Harrisburg, PA: Pennsylvania Geological Survey.
In this table, if you look at the Appalachian region, you can find the Conemaugh
Group, which is upper Pennsylvanian. The Conemaughian time-stratiographic unit stretches
from approximately 293 to 301 million years ago.
In this Conemaugh group, I placed the Brush Creek Marine
Zone and the Mahoning Formation (In red). You can see the Mahoning Formation is roughly
300 million years old. About a million years later, the sea came in, creating the Brush Creek Marine
Zone, about 299 million years ago.
It can also be seen the Brush Creek Marine Zone and Mahoning correspond to Late Westphalian D to
Early Stephanian A.
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