ABSTRACT Perched on a cliff above Lake Erie in western New York, USA, Graycliff blends use of local stone with design elements of Organic Architecture that architect Frank Lloyd Wright had experimented with at Taliesin, his stone residence and studio in Wisconsin. Graycliff stone walls were built with Tichenor Limestone and glacial erratics including gneisses and granites. Middle Devonian fossils including corals, crinoid columns, and brachiopods are displayed prominently on Graycliff walls. The diamond shapes of some Tichenor Limestone boulders, formed by intersecting natural fractures found in nearby bedrock, provided an organic theme for architectural details. The relationship between fractures and small faults and folds interpreted as post-glacial pop-ups in the Graycliff area suggest that fractures key to the diamond shape formed during deep burial, possibly with enhancement during uplift and post-glacial isostatic rebound. Medina sandstone coping and paving stones were recycled from Buffalo, New York, sidewalks and likely were quarried along the Erie Canal. A natural gas well on the property produces from Medina sandstone deep underground. Many elements of organic design at Graycliff occur in later Wright-designed houses with significant stone components, including plan-view orientation of the house that fits both Wright’s organic design ideal and the natural terrain; windows that provide exceptional views of natural features of the site; and irregular edges of wall stone and pavers. Exposures of the Tichenor Limestone and adjacent shales in nearby Penn Dixie Fossil Park provide the opportunity to observe and collect fossils from rock strata displayed on Graycliff walls and exposed in the lakeshore cliff. Small faults and folds partially exposed in the quarry at Penn Dixie may be pop-up structures analogous to interpreted post-glacial pop-up structures well exposed in cliffs at Ripley Beach and elsewhere along the western New York lakeshore.

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.

ABSTRACT The Erie lakeshore in Pennsylvania, west of the city of Erie, has many geological features that are ripe for study, teaching, and use as a vehicle for public science outreach. Features and processes on display include rapid slope failure and erosion of lakeshore bluffs, Pleistocene till in the bluffs, well-developed ancient sandy beach ridges atop till, and thin Upper Devonian sandstones that were deposited by storms. A wide variety of sedimentary, igneous, and metamorphic rocks can be found among cobbles eroded from till and rounded on lakeshore beaches, providing opportunities for teaching the identification of rocks, minerals, and Paleozoic marine fossils. Small fans at the bases of lakeshore bluffs have morphologies derived from distinct modes of sediment transport and deposition, with the potential to serve as analogs in better understanding large submarine fans. In winter, ice volcanoes can occur on the shoreline. Opportunities for teaching about geologic time are provided by localities where recent sedimentary processes, Pleistocene deposits, Paleozoic sedimentary rocks, and Precambrian igneous and metamorphic rocks can all be seen.

ABSTRACT Fallingwater is a UNESCO World Heritage Site that showcases a unique organic architectural design by Frank Lloyd Wright. Rising from bedrock in Mill Run, Pennsylvania, USA, Fallingwater incorporates large boulders into interior living spaces and is oriented with the geometry of a landscape created by the interplay of mountain and climate. Built to showcase local sandstone, Fallingwater is of the terrain. Building stone was quarried near the house from a 2-m-thick zone of quartzose medium to thin-bedded, fine- to very fine-grained sandstones in the Pennsylvanian upper Pottsville Formation. The building stone has abundant trace fossils and ripple marks, and is interpreted to have been deposited in shoreface environments with some tidal influence, or possibly in tidal flat environments. The house rests on sandstone bedrock of the Homewood sandstone, a Middle Pennsylvanian unit within the upper Pottsville Formation. At Fallingwater, the Homewood sandstone is interpreted to fill an incised valley with coarse, fluvial sandstones common in the lower part of the valley fill and finer-grained fluvial sandstones with possible evidence of marine or brackish influence in the upper fill. The Fallingwater building stone unit overlies the Homewood sandstone, above an interpreted marine flooding surface. Thickening of the Homewood sandstone in synclines suggests that deposition was influenced by Alleghanian deformation. Natural fractures in competent bedrock controlled the orientation of Bear Run at Fallingwater, and the fit of the house within the three-dimensional landscape of the valley, stream, and waterfall. Variation in natural fractures in bedded versus massive sandstone layers appears to have controlled the azimuths of the edges of the waterfalls at Fallingwater. Creation of the Fallingwater sandstone member of the Pottsville Formation is proposed.