SURFICIAL GEOLOGIC MAPPING OF PIKE COUNTY, PENNSYLVANIA

Pike County is located in northeastern Pennsylvania north of the late Wisconsinan glacial border. Northeastern Pennsylvania has been glaciated at least four times, but deposits and landforms related to only the youngest of these, the late Wisconsinan glaciation, have been observed. Thin (< 6 feet) till covers much of the higher elevations with thicker deposits on slopes, in lowlands, and as drumlins. Moraines formed as till knobs and ice-contact stratified drift formed as kame knobs, terraces, and eskers, are found in valleys and low-lying areas. Other surficial deposits include glacial outwash that has thicknesses up to 315 feet in the Delaware River valley, along with alluvium, colluvium, wetlands, and peat bogs. Surficial materials on steep to moderate slopes are subject to landslides and debris avalanches. Coarse-grained glaciofluvial and post-glacial fluvial deposits are potential high-quality drinking water sources and sources of economically important sand and gravel.

Recently acquired quality level 2 LIDAR data was used to update existing mapped surficial units and any other previously unmapped deposits. Many previously obscured glacial features and evidence of mass movements are now visible and mappable. Select sites were field checked to verify and confirm the validity of the existing mapped surficial units and previously unmapped deposits. Carbon-14 dating of glaciolacustrine sediments and optically stimulated luminescence dating of glaciofluvial, and post-glacial fluvial deposits has been performed to define the timing of ice retreat and to definitively date the glacial deposits. Sediment cores were collected at three natural glacial basins that extended into varved, mineragenic glacial sediments and eighteen carbon-14 dates (9 macrofossil and bulk sediment pairs) were taken from post-glacial sediments above the deglacial transition, to constrain the age of ice melt and retreat across the landscape. Nineteen optically stimulated luminescence dates were collected to target glaciofluvial and post-glacial fluvial deposits. All data is compiled into a county wide 1:50,000 scale, surficial geologic map.