Plunketts Creek (Loyalsock Creek) - Geology

Geology

Plunketts Creek is in the southern edge of the dissected Allegheny Plateau, near the Allegheny Front. The underlying bedrock is sandstone and shale, mostly from the Mississippian sub-period, with rock from the Devonian period in the north of the watershed. The northern edge of the Plunketts Creek drainage basin is formed by Burnetts Ridge and Popple Ridge. Plunketts Creek flows along the north side of Camp Mountain and, on turning south at Proctor, forms a water gap between it and Cove Mountain (to the west).

The watershed has no oil or conventional natural gas fields. However, a potentially large source of natural gas is the Marcellus shale, which lies 1.5 to 2.0 miles (2.4 to 3.2 km) below the surface here and stretches from New York through Pennsylvania to Ohio and West Virginia. Estimates of the total natural gas in the black shale from the Devonian era range from 168 to 516 trillion cubic feet (4.76 to 14.6 trillion m³), with at least 10 percent considered recoverable.

The Pennsylvania Bureau of Topographic and Geologic Survey's "Distribution of Pennsylvania Coals" map shows no major deposits of coal in the Plunketts Creek watershed, and only one deposit nearby in the Loyalsock Creek watershed (in southern Plunketts Creek Township). However, Meginness (1892) refers to coal mines in Plunketts Creek Township, and there is an unnamed tributary of Plunketts Creek in "Coal Mine Hollow" on the right bank between Dry Run and King Run, so it seems a small coal mine operated there in the past.

Much of the Plunketts Creek valley (and those of its tributaries) is composed of various glacial deposits. Closer to the mouth, there are large deposits of alluvium, as well as alluvial fan and alluvial terraces. Many of the glacial deposits are associated with the Wisconsin glaciation, with stratified drift and till, as well as outwash present. The alluvium is "10 feet (3 m) or more thick in the lower reaches of the Plunketts Creek valley", but only "6 feet (2 m) thick in headward tributary valleys". The outwash is described as "stratified sand and gravel that form terrace remnants along the flanks of Loyalsock Creek and Plunketts Creek valleys".