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OLLI Course
Geology and Environmental Geology of the State College Area
David H. Eggler, Instructor
Emeritus Professor of Petrology, The Pennsylvania State University
814-571-1960, eggler@geosc.psu.edu
Course website: www.geosc.psu.edu/public/CALL/index.htm

INTRODUCTION  The Nittany Valley is the westernmost valley of the folded Ridge-and-Valley province of Pennsylvania.  To its west, over Bald Eagle Mtn, is the Appalachian Plateau, characterized by essentially flat-lying and younger rocks, that extends all the way to Cleveland, Ohio.  The Nittany Valley is an anticlinorium, a large-scale fold with older rocks at its core, and with smaller-wavelength folds within it, notably the syncline of Mount Nittany.
     The Appalachians were built during four periods of mountain-building, called orogenies, each corresponding to plate collisions and therefore compression of the lithosphere.  These are: (1) the Grenville (1200->900 my), (2) the Taconian (478->438 my), when an island arc and several microcontinents collided with Laurentia (ancient North America), (3) the Acadian (387->350 my), and (4) the Alleghenian (260->230), when N. America collided with Africa.  The earliest Nittany Valley sediments, the Gatesburg Formation -- mixed sandstones and carbonates -- formed between (1) and (2), when Laurentia (ancient North America) was tectonically quiet but began to subside, so the continent was flooded with an inland sea.  The Ordovician carbonates (Os, On, Oa, Ob in the cross-section) represent a variety of animals living in that shallow, warm sea.  The Reedsville shale (Or) -> Bald Eagle sandstone (Oo) -> Juniata sandstone (Oj) sequence (Ordovician age) marks the onset of the Taconian orogeny, when emerging mountains to the east shed sediments into the inland seaway.  Sediments to the west, on the Appalachian Plateau, record the Acadian orogeny and the transition to the Alleghenian orogeny.  Those sediments were present in the Nittany Valley region but have been eroded off.  Finally, the Alleghenian collision deformed the sediments by folding and thrusting, producing most of the structures (anticlines, synclines, faults) we see today.

 KARST TOPOGRAPHY The #1 factor in geoenvironmental problems in the Nittany Valley is karst, characterized by sinkholes, movement of water largely underground rather than in surface streams, and fairly rapid movement of groundwater, especially in fracture zones.  Karst is created by solution of limestone by acidic surface waters. Fracture zone intersections are primary well sites.  If pollutants work their way down to the water table, they can potentially travel from one end of the valley to the other and, because of the deep water table, are difficult to treat.  Nittany Valley streams, unless polluted, are high-quality because of the dominant limestone bedrock.