QUATERNARY LANDSCAPES IN NORTHWESTERN PENNSYLVANIA FROM LIDAR

Hillshade models derived from State Lidar data make excellent base maps, at a scale of ~1:125,000 and larger, for examining the Quaternary landscape history in northwestern Pennsylvania. This region was repeatedly glaciated during the Wisconsinan Stage, and hosts a wide range of subglacial and glacial margin landforms, that include both active and stagnant ice features. Common landforms include tunnel valleys, drumlins, kames, kettles, and laterally extensive end moraines. Local valley-blocking end moraines, associated with long outlet glaciers, can be traced back to the broader margins of the Laurentide Ice Sheet. Large proglacial lake landforms (beach ridges, sand spits, and wave cut escarpments) are also apparent, and glacial outwash and younger Holocene terraces line major valley axes. Many of these landforms have not been formally mapped in any detail.

The majority of previous surficial mapping efforts in NW PA were accomplished in the late 1950’s and early 1960’s, prior to the availability of high resolution topographic data. Prior mapping focused on documenting the position of laterally extensive ground/end moraine systems, and did not distinguish many individual landforms, sometimes superposed, that can now easily be seen on Lidar. When geo-referenced, these images also aid in identifying potential sites for field investigations to test stratigraphic relationships, and to target areas for sampling related to age determination, as the timing of ice sheet advance and retreat is poorly constrained for this region.