Date of Graduation
Surficial deposits and soils along the northwestern footslopes of the Northern Blue Ridge in south-central Pennsylvania illustrate the geomorphic evolution of unglaciated landscapes that experienced late Cenozoic climate fluctuations. Geologic, geomorphic, and pedogenic investigations were used to document soil-landform-parent material relationships and create surficial geology maps. Deep exposures within three sand and gravel pits suggest fluvial processes, primarily tractive fluvial transport and valley aggradation, were the dominant mechanisms for alluvial fan development. Fan architecture suggests multiple depositional events, intermixed with episodes of landscape stability and weathering, were responsible for complex facies assemblages. Field and laboratory data revealed three lithostratigraphic units (Qaf1, Qaf2, and Qaf3) that were used to reconstruct the geomorphic history and assign relative geologic ages. Four soil pedons related to the different alluvial fan deposits are polygenetic, having undergone changes in soil forming factors in varied environmental settings throughout the Quaternary. Geomorphic reconstructions suggest the four pedons represent welded soils or relict paleosols that have unique developmental histories on distinct alluvial fan surfaces. Welded soils have experienced shallow burial by younger alluvial fan materials, with subsequent pedogenic modification and integration of the two sola. Relict paleosols escaped burial by younger alluvial fan deposits along the footslope and have been exposed on the landscape for extended periods, experiencing multiple fluctuations between cold periglacial and warm temperate climate end-members. Relict paleosols show variations in pedogenic properties within the solum, indicating changes in the soil forming processes from initial pedogenesis through Holocene interglacial conditions. Though no absolute age control is available, comparison to other alluvial landforms within the region suggests the oldest deposits, Qaf1, are early Pleistocene, Pliocene, or possibly Miocene, intermediate aged Qaf2 deposits are middle Pleistocene in age, while the youngest, Qaf3, are late Pleistocene.
Grote, Todd, "Late Cenozoic stratigraphy and landscape dynamics in the unglaciated central Appalachians: A case study from the Northern Blue Ridge, south-central Pennsylvania, United States." (2006). Graduate Theses, Dissertations, and Problem Reports. 8962.