Field Excursions to the Appalachian Plateaus and the Valley and Ridge for GSA Connects 2023
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This volume offers guides for GSA Connects 2023 in Pittsburgh, Pennsylvania, USA, that cover a diverse range of geologic time and processes from the Paleozoic to Recent. Chapters address Paleozoic and Pleistocene glaciation; the interplay of geology and climate in shaping the landscape; and aspects of cultural geology, including Frank Lloyd Wright’s Fallingwater and the setting of Youngstown, Ohio, USA.
Special geologic features of Ohiopyle State Park, Pennsylvania, USA
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Published:September 25, 2023
ABSTRACT
With waterfalls and the deepest gorge in Pennsylvania, Ohiopyle State Park provides opportunities to observe a variety of habitats and three-dimensional (3-D) exposures of the Pennsylvanian sandstone most responsible for shaping Laurel Highlands landscapes. Evidence for the relationship between bedrock, ancient climates, and the landscape can be observed at some of the most scenic natural features of the park: Baughman Rock Overlook, Cucumber Falls, Ohiopyle Falls, Meadow Run Waterslide and Cascades, and Youghiogheny River Entrance Rapid. Channel azimuths and lateral variations in thickness of upper Pottsville fluvial/deltaic sandstone suggest that deposition was influenced by deformation of this part of the Allegheny Plateau during the Alleghanian orogeny. Geologic features of Pottsville sandstone outcrops include a 10-m- (~33-ft-) long Lepidodendron fossil and a 3-D exposure of a meter-high Pennsylvanian subaqueous sand dune and scour pit. Cosmogenic age dating has indicated very slow erosion of hard sandstone in an upland location at Turtlehead Rock and informed estimation of Pleistocene/Holocene waterfall retreat rates of Ohiopyle and Cucumber Falls. Bedrock exposures supporting scour habitats along the Youghiogheny River occur only in a limited area of Youghiogheny Gorge where knickpoint migration and bedrock erosion were relatively recent. Geologic factors, including locations of major tributaries, development of bars that constrict river flow, and proximity of Homewood sandstone outcrops as sources of boulder obstacles in the river, contributed to the class, location, and nature of whitewater rapids in the lower Youghiogheny River.
- Alleghany Orogeny
- Ames Limestone
- Carboniferous
- Catskill Formation
- Cenozoic
- Conemaugh Group
- Cuyahoga Formation
- deltaic environment
- depositional environment
- Devonian
- Dunkard Group
- field trips
- fluvial environment
- fluvial features
- fossils
- Glenshaw Formation
- gorges
- guidebook
- incised valleys
- Lepidodendron
- Lower Mississippian
- Lycopsida
- Mauch Chunk Formation
- Mississippian
- Monongahela Group
- Paleozoic
- Pennsylvania
- Pennsylvanian
- Pittsburgh Coal
- Plantae
- Pleistocene
- Pottsville Group
- Pteridophyta
- Quaternary
- road log
- United States
- Upper Mississippian
- Upper Pennsylvanian
- valleys
- waterfalls
- Laurel Highlands
- Morgantown Sandstone
- Benwood Limestone
- Casselman Formation
- Monongahela Formation
- Oswayo Formation
- Allegheny Formation
- Carmichaels Formation
- Shenango Formation
- Freeport Coal
- Homewood Formation
- Burgoon Formation
- Ohiopyle State Park
- Maple Summit Formation
- Murrysville Formation
- Youghiogheny River Gorge