Fossil Hunting in Pennsylvania

Pennsylvania’s name literally means “Penn’s Woods,” but long before any forests stood here, the Keystone State was covered by tropical seas and steaming coal swamps. The fossils of both environments are abundant and accessible today, making Pennsylvania an excellent state for beginners and experienced collectors alike.

Why Pennsylvania?

Pennsylvania straddles two of the most fossil-rich intervals in the Paleozoic Era. During the Middle Devonian (about 380-390 million years ago), a shallow marine sea covered much of the state, depositing thick sequences of shale and limestone loaded with brachiopods, crinoids, corals, and trilobites. These rocks are beautifully exposed in road cuts across the central part of the state.

Later, during the Pennsylvanian Period (about 300-320 million years ago) — which takes its name from this state — vast coastal swamps blanketed eastern Pennsylvania. The vegetation of these swamps eventually became the anthracite coal that powered the Industrial Revolution, and the shales surrounding the coal seams preserve exquisite plant fossils: giant fern fronds, scale-bark trees 100 feet tall, and ancient horsetails.

The Montour Preserve fossil pit is a standout destination — a dedicated collecting site specifically maintained for the public where Devonian marine fossils are plentiful and free for the taking.

What You’ll Find

Middle Devonian marine fossils (~380-390 million years old):

• Brachiopods — Extremely abundant; Mucrospirifer with its distinctive wing-shaped shell is iconic
• Crinoid stems — Disc-shaped segments and occasional calyx fragments
• Horn corals (Rugosa) — Solitary corals, sometimes well preserved
• Bryozoans — Lace-like and branching colonial forms
• Trilobites — Phacops rana (Pennsylvania’s state fossil) with its distinctive compound eyes
• Bivalves and gastropods — Various clam and snail species

Pennsylvanian coal-age plant fossils (~300-320 million years old):

• Fern fronds — Neuropteris, Alethopteris, and other seed ferns
• Lycopsid bark — Lepidodendron (scale tree) bark impressions with diamond patterns
• Calamites — Ribbed stems of ancient horsetail relatives
• Sigillaria — Another scale tree with distinctive ribbed bark
• Stigmaria — Root systems of lycopsid trees
• Rare: insect wings and impressions

Best Time to Visit

• Spring (April-May): Freeze-thaw over winter fractures shale and exposes fresh fossils; Montour Preserve fossil pit is refreshed by erosion
• Fall (September-October): Pleasant temperatures, low vegetation at road cuts
• After rain: Erosion washes sediment off fossils and exposes new material
• Winter can work at road cuts: Cold weather means low vegetation obscuring exposures, but dress warmly

Tips for Pennsylvania Collecting

1. Start at Montour Preserve — the fossil pit is beginner-friendly, free, and you are almost guaranteed to find brachiopods and crinoid stems
2. Bring a rock hammer and chisel — Devonian shale splits along bedding planes, revealing fossils on the freshly exposed surfaces
3. Check road cut rubble — the loose rock at the base of road cuts is where fossils accumulate; never climb on unstable road cut faces
4. Look for black shale at strip mines — plant fossils are preserved in dark carbonaceous shale immediately above and below coal seams
5. Split thin shale layers — coal-age plant fossils are often found as compressions between thin shale sheets
6. Visit the Carnegie Museum of Natural History — Pittsburgh’s museum has an exceptional paleontology collection including fossils from Pennsylvania localities
7. Wear safety gear at old mines — strip mine sites can have unstable slopes, open pits, and loose footing; sturdy boots and a hard hat are wise
8. Connect with the Delaware Valley Paleontological Society — they organize field trips to productive sites across the state

Collecting Sites

Legal Rules for Pennsylvania

Key Geological Formations

• Hamilton Group (Middle Devonian)
• Mahantango Formation (Middle Devonian)
• Allegheny Formation (Pennsylvanian)
• Catskill Formation (Upper Devonian)

Local Fossil Clubs & Museums

• Delaware Valley Paleontological Society
• Pennsylvania Earth Sciences Association
• Carnegie Museum of Natural History
• Academy of Natural Sciences of Drexel University
• State Museum of Pennsylvania