The Geologists at the DGS have found evidence of faulting in core samples collected from core holes drilled in Smyrna (Hc34-51) and Woodland Beach Wildlife Area (Hd25-07). There are two zones found in Hc34-51; one that is between 157 and 162 feet below land surface that consists of multiple fault surfaces and fractured sediments, or breccia, and another one at 251 feet below land surface with one single fault surface. At the other site, Hd25-07, multiple core holes contained brecciated material and fault surfaces between 137 and 162 feet below land surface. The fault surfaces are characterized by waxy mud surfaces with planar to wavy surfaces. These faults also show evidence of parallel striae, and step like features. This type of feature is also known as a slickenslide. The slickenslides indicate that the material below the fault moved downward relative to the material above the fault. In other words, there is reason to believe this is a normal fault. The brecciated zones contain angular fragments of parent sediments, which are a result of brittle failure or fracturing of the sediment. Some of the fragments are marked with slickenslides, which is common in many fault zones. There is no evidence or indicators to determine how far these sediments could have possibly moved.
It would be interesting to continue this study to see if there is more evidence of faulting further North of this area around the same depths. This is an ongoing 30 month long project and the DGS will be drilling more core holes and collecting core samples from Kent County, which is south of New Castle County. Perhaps there will be evidence of faulting in those core samples. Additional information about the project can be found at: http://www.dgs.udel.edu/projects/delaware-groundwater-monitoring-network
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