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Pennsylvania, US



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State Fossil:
State fossil from Pennsylvania

Phacops rana
This trilobite was common in the shallow sea that covered most of North America during the Devonian (~ 405–365 million years ago). Phacops had large eyes and could grow to around 15 cm in length.

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Paleontology and geology

The Precambrian: During the Precambrian, Pennsylvania was mainly a low, featureless plain sloping gently southeastward toward the sea. Most of Pennsylvania's exposed Precambrian rocks are metamorphic and igneous, and thus lack fossils.

The Paleozoic: Paleozoic rocks are well represented in Pennsylvania. Warm, shallow seas covered much of the state through the early Paleozoic, when Pennsylvania lay at the eastern edge of Laurentia. The seas teemed with marine organisms whose fossils can be found today in many rocks throughout the state. The Carboniferous witnessed the collision of the former continent of Gondwana with Laurentia to form the supercontinent of Pangea. A huge mountain range—part of which would become the Appalachians—arose from this tectonic activity. Vast deltas formed as the newly-uplifted mountains eroded and streams carried the sediments westward across the state. The shallow seas retreated, leaving much of the state as a low-lying, swampy plain, covered with scale trees (lycopods), ferns, and horsetail rushes. By the end of the Paleozoic, the swamps had dried out and Pennsylvania had become an upland region where erosion predominated over deposition.

The Mesozoic: Mesozoic rocks are present mainly in the rift basins of the eastern part of the state. These fault valleys developed as tectonic activity pulled apart the supercontinent of Pangea and began opening the Atlantic Ocean. Red beds are the dominant rocks of the Mesozoic in Pennsylvania and are formed from sediments deposited in rivers, streams, lakebeds, and in the rift basins. Lava flows are interbedded with the red beds. Fern spores and pine pollen are common in these rocks, as are footprints left behind by dinosaurs that roamed the landscape.

The Cenozoic: The Early Cenozoic is poorly represented in Pennsylvania. There are a few outcrops in the far southeastern corner of the state that have been identified as Tertiary by some geologists, but as Cretaceous by others. The Late Cenozoic is well represented by glacial materials deposited by the Quaternary (Pleistocene) ice sheets that covered much of the state during this time. Fossil plants, including willow and sedge, indicate a tundra-type environment for parts of the state not covered by ice at the end of the Pleistocene.

Links to more on Pennsylvania paleontology

Organizations | Education and Exhibits | Research and Collections | Resources


Museums (showing 1 of 1 listings)

The Academy of Natural Sciences: The Academy of Natural Sciences includes four floors of exhibitions and activities centering on the environment and its diverse species that will educate and entertain visitors of all ages.

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Colleges and Universities (showing 1 of 1 listings)

University of Pennsylvania: The Department of Earth & Environmental Sciences at the University of Pennsylvania, Philadelphia, has undergraduate and graduate programs in geology and paleobiology.

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Education and Exhibits

Physical Exhibits (showing 2 of 2 listings)

State Museum of Pennsylvania: Paleontology and Geology Exhibits: Explore the history and diversity of life on Earth in the Hall of Paleontology and Geology. Take a walk through geologic time and discover some of the life forms that once lived in Pennsylvania millions of years ago.

Bonehunters Quarry: Bonehunters Quarry, Carnegie Museum of Natural History, Pittsburgh: Experience the thrill of hands-on excavation.

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Virtual Exhibits (showing 2 of 2 listings)

Who's Who at Red Hill: This website describes the geology and outstanding fossil record of this Late Devonian fossil site located in central Pennsylvania.

Devonian Times: An education website on early tetrapod evolution featuring Red Hill, a Late Devonian locality in Pennsylvania. Information on associated fishes, invertebrates and plants is also included,

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Research and Collections

Ongoing Research Projects (showing 1 of 1 listings)

Carnegie Museum: Invertebrate Paleontology Section: The Carnegie Museum of Natural History Section of Invertebrate Paleontology has more than 100 years of research, field work, educational outreach (PALS), and exhibits on Phanerozoic life. Our collections number more than three-quarters of a million specimens with some 11,000 type and figured specimens published in more than 300 professional publications. Our type and collection strengths are concentrated in the Lower and Upper Paleozoic rocks of the Appalachians, mid-continent, and western Interior Seaway. 

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Curriculum and Classroom Resources (showing 1 of 1 listings)

Teacher-Friendly Guides to Geology: Provides teachers with an intuitive and jargon-free review of the geology of different regions of the United States. 

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Field Guides (showing 1 of 1 listings)

Dinosaur Footprints and Trackways From the Northeastern U.S.: This webpage details footprints from the Triassic and Jurassic periods of the northeastern United States. Information includes photographs of footprints, along with information on stratigraphic horizon and correlation, age, and taxonomy.

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