T57 Utilizing 2-D and 3-D Near-Surface Geophysics to Generate Improved Surface and Subsurface Geologic Maps

Sunday, 1 November 2015
1:30 PM - 5:30 PM
Room 322/323

INTERIOR SEDIMENTARY STRUCTURE OF THE JACKSVILLE ESKER, PENNSYLVANIA

Paper number: T57-4
Program: Technical Sessions
Time: 2:15 PM – 2:30 PM

Authors

Abstract

The scope of this study was to image the interior sedimentary structure of the Jacksville Esker using ground penetrating radar. Imaging internal sedimentary structure will help aid in the understanding of the glacial system and help strengthen the call of preserving the esker. The Jacksville Esker is the best preserved esker in Pennsylvania and is currently at risk of being mined for gravel and sand resources. Prior to the survey some information on the glacial system was available from the DCNR and a few select authors. Initial mapping and observation was done in the field and in conjunction with work done by Gary Fleeger and Jocelyn Lewis – Miller from the 74th Annual Field Conference of Pennsylvania Geologist.

GPR data was acquired using a Mala GPR with a 100MHz antenna set with a trace interval of one centimeter. The data of the interior of the esker was excellent due to the low clay and silt content. Processed data revealed sedimentary layers of varying thicknesses continuously pinching in and out. The data also shows several large entrained boulders along the bottom of the profile with intermixed cobbles throughout.

The data indicates a high energy environment with very little overall organization beyond a group of foreset beds in the North – Western area of the esker. Flow within the esker would have been fluctuating both seasonally and daily. Depending on environmentally controlled conditions the esker beds would have time to set and become more resilient while others would be immediately scoured away with the next high flow. The study shows that the esker has no discernible interior structure and that the sedimentary structure is based on local constraints of available volume for flow, the volume of the flow itself as well as velocity and what is being transported.This study provides insight to the outflow characteristics of a continental size ice sheet immediately at the terminus in regards to outflow and sedimentary load.