The Delaware Geological Survey (DGS) at the University of Delaware released a report that provides new insights into the underground geology and hydrology of southeastern Sussex County, Delaware.

The report, “Stratigraphy and Correlation of the Oligocene to Pleistocene Section at Bethany Beach, Delaware,” summarizes the results of geological investigations conducted on a 1,470-foot-deep research borehole drilled at Bethany Beach, Del.

The objective of the project was to obtain a continuous record of the sediments that underlie coastal Sussex County in order to better understand the geological history of the area and the geological characteristics of shallow and deep aquifers.

A specialized drilling method called wireline coring was used to obtain a nearly continuous series of cylindrical samples of subsurface sediments, usually in five or 10 feet intervals. The sediments recovered range from thousands of years old near the surface (Pleistocene) to approximately 30 million years old (Oligocene) at nearly 1,500 feet of depth.

Wireline geophysical logs were run in the borehole to obtain a continuous instrumental record of the physical characteristics of the formations penetrated by the drilling.

The report was prepared by Peter P. McLaughlin Jr., senior scientist at DGS, along with coauthors Kenneth G. Miller and James V. Browning from Rutgers University, Kelvin W. Ramsey, Richard N. Benson, and Jaime L. Tomlinson from DGS, and Peter J. Sugarman from the New Jersey Geological Survey.

The report, also known as DGS Report of Investigations No. 75, includes detailed documentation of sediment types, geologic ages and ancient environments of the formations that underlie Bethany Beach, making the research location a valuable reference section for the subsurface geology of eastern Sussex County.

The findings document the history of sea-level changes over the last 30 million years and the effects of these changes on the geologic record.

Most importantly for local residents, the improved understanding of subsurface geology and correlations provide an improved understanding of the shallow and deep confined aquifers of coastal Sussex County, some of which are used for public, domestic and agricultural water supplies.

The report is part of the Delaware Geological Survey's ongoing mission to understand the geology and hydrology of Delaware and to advise, inform and educate Delawareans about the results of such investigations for use in such areas as water resources, agriculture, public health, economic development, land-use planning, geologic hazards, environmental protection, energy and mineral resources, emergency management and recreation.

Report of Investigations No. 75 is available in PDF format at the Delaware Geological Survey reports web site.

Printed copies of the publication may be requested by contacting the Survey at (302) 831-2833 or via email at [delgeosurvey@udel.edu].