This paper presents results of an experiment in which data from a combination of geophysical<br>methods (resistivity, induced polarization, electromagnetic profiling, and magnetic profiling)<br>were used to identify shallow geologic and hydrogeologic structure, and to provide a model for<br>groundwater flow in a dynamic beach environment. Based on this study, the beach appears to be<br>underlain by a thin beach sand, overlying bedrock. Within the overlying sediments, a patch of<br>glacial till was mapped toward the ocean side of the beach. Bedrock has lithologic variability, as<br>evidenced by a non-uniform magnetic response. In particular, a northeast-southwest trending<br>magnetic body, believed to be a basalt dyke, was detected by its magnetic response.<br>During the transgressive phase of the tidal cycle, saline groundwater flow appeared to be quite<br>rapid, extending ahead of the surfical water by at least 4 m, as evidenced by the electromagnetic<br>response. During the regressive phase, a slug of saline water remained up beach from the high<br>tide mark for several hours prior to draining. Also during this regression, we observed<br>electromagnetic evidence for two fracture zones, or other preferential groundwater flow<br>pathways. These fracture zones appear to contain a relatively constant concentration of saltwater,<br>while surficial sediments above and to the side are flushed with fresh groundwater during tidal<br>regression.


Article metrics loading...

Loading full text...

Full text loading...

This is a required field
Please enter a valid email address
Approval was a Success
Invalid data
An Error Occurred
Approval was partially successful, following selected items could not be processed due to error