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Quaternary geology of northwestern Pennsylvania

By
Gary M. Fleeger
Gary M. Fleeger
Pennsylvania Geological Survey, 3240 Schoolhouse Road, Middletown, Pennsylvania 17057-3534, USA
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Todd Grote
Todd Grote
Department of Geography and Geology, 205 Strong Hall, Eastern Michigan University, Ypsilanti, Michigan 48197, USA
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Eric Straffin
Eric Straffin
Department of Geosciences, Edinboro University of Pennsylvania, Edinboro, Pennsylvania 16444, USA
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John P. Szabo
John P. Szabo
Department of Geology & Environmental Science, University of Akron, Akron, Ohio 44325, USA
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Published:
January 01, 2011

Abstract

Northwestern Pennsylvania was glaciated by the Grand River sublobe of the Erie Lobe. Glacial advances occurred at least three times during the pre-Illinoian (Slippery Rock, Mapledale, and Keefus), once during the Illinoian (Titusville), and four Late Wisconsinan (Kent, Lavery, Hiram, and Ashtabula) tills have been identified. While the area was studied for over 50 years by George White and associates, there are numerous details that remain unknown. The Titusville Till, which comprises the bulk of the glacial sediment, contains up to five separate sheets separated by sand and gravel. The origin of the numerous sheets is still not clear. The Kent glaciation resulted in extensive deposition in proglacial lakes and caused numerous local drainage diversions. Interpretations of the surficial geology around Conneaut Lake have changed a couple of times. Originally interpreted to be formed by a lobe of Hiram ice, it was later determined to be part of a widespread area of Lavery ice. Recent work supports the original Hiram interpretation. Since glaciation, streams in northwestern Pennsylvania have incised into the glacial sediments and have developed fine-grained floodplains within glacially scoured valleys. Lake sediments and alluvial stratigraphy suggests that general climate amelioration during the Holocene epoch was interrupted by episodes of landscape instability. Deforestation by European settlers is the most recent event appearing in the stratigraphic record and resulted in deposition of as much as 2 m of post-settlement alluvium.

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GSA Field Guide

From the Shield to the Sea

Richard M. Ruffolo
Richard M. Ruffolo
GAI Consultants, Inc. Pittsburgh Office 385 East Waterfront Drive Homestead, Pennsylvania 15120-5005 USA
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Charles N. Ciampaglio
Charles N. Ciampaglio
Wright State Universityâ?"Lake Campus 7600 Lake Campus Drive Celina, Ohio 45822 USA
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Geological Society of America
Volume
20
ISBN electronic:
9780813756202
Publication date:
January 01, 2011

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