A ground penetrating radar (GPR) survey has been conducted across and longitudinally along Jordan Ridge in the Natchaug River Valley near North Windham, Connecticut. 50 MHz radar-signal frequency provided the most detailed data for the longitudinal profile, but 100 MHz provided better data for the cross profile. Depth of penetration was 20 m.

Jordan Ridge is a segmented ice-channel fill of 3-4 km length that terminates at a bedrock col leading to a short gorge. The southern most segment has recently been exposed by on-going deep excavation. The lower portion exposed 8 +/- m of unstratified cobble gravel, overlain by 12 +/- m of stratified gravel. The surface of the unstratified gravel is approximately planar and inclined slightly in the uphill direction. The stratified section contains layers of imbricated cobbles and boulders and tabular cross-beds and scour-fill cross-beds, all interpreted to indicate southeasterly flow during deposition. The stratified layers are cut by a near vertical, and in places undercut, erosion surface that is filled with unstratified cobble gravel.

One GPR survey was conducted across the ridge approximately 35 m (at the time) from the working face of the gravel operation. The cross-section shows prominent fluvial cut-and-fill channels and collapse features, that have since been confirmed by excavation. Bedding of the cut and fill section appears inclined and nearly parallel to the present-day surface. This dip has yet to be confirmed by excavation and may be an artifact. A longitudinal profile shows the underlying bedrock becoming increasingly shallow southeasterly toward the bedrock col at the end of the ridge. In addition, deeper stratification in the longitudinal profile is inclined toward the northwest in shingle fashion.

We interpret these data to suggest that the ridge initially formed as an esker and later became an open channel in the ice.