DGS Geologic Map Series
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Browsing DGS Geologic Map Series by Subject "Bethany Beach"
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Item Geologic Map of Offshore Delaware(Newark, DE: Delaware Geological Survey, University of Delaware, 2020-02) Mattheus, C.R.; Ramsey, K.W.; Tomlinson, J.L.Delineation of map units is based on sediment-core descriptions (e.g., texture, color, and composition) from 469 locations and seafloor morphology, which was assessed from a seamless NOAA/USGS topo-bathymetric model (Pendleton et al., 2014). The latter was integrated with high-resolution ‘chirper’ seismic reflection data, collected in 2013 by the Delaware Division of Natural Resources and Environmental Conservation (DNREC) and in 2015 as part of the 2015-2017 Bureau of Ocean Energy Management (BOEM) Atlantic Sand Assessment Project (ASAP), using sweep frequency pulses of 2-12 kHz and 0.7-12 kHz, respectively. Stratigraphic mapping based on these data allowed seafloor composition to be inferred across areas of limited core coverage (e.g., Federal waters, beyond 3 miles from shore) and facilitated the delineation of unit boundaries based on subsurface trends and seafloor geomorphology. A minimum surface-unit thickness of 1 ft served as the cut-off for geologic mapping of the seafloor, given the vertical resolution constraints of geophysical data. If surficial sediments were <1 ft thick, the underlying unit was mapped. Unit names and descriptions conform to those established in prior subsurface work along the Delaware barrier shoreline by Ramsey (1999), a synthesis of the Delaware coastal plain geology (Ramsey, 2010), and a previous map which included portions of the offshore surface geology (Ramsey and Tomlinson, 2012).Item Geologic Map of the Bethany Beach and Assawoman Bay Quadrangles, Delaware(Newark, DE: Delaware Geological Survey, University of Delaware, 2012-12) Ramsey, K.W.; Tomlinson, J.L.The geologic history of the surficial units of the Bethany Beach and Assawoman Bay Quadrangles is that of deposition of the Beaverdam Formation and its subsequent modification by erosion and deposition related to sea-level fluctuations during the Pleistocene. The geology reflects this complex history onshore, in Indian River Bay and Assawoman Bay, and offshore in the Atlantic Ocean. Erosion during the late Pleistocene sea-level lowstand and ongoing deposition offshore and in Indian River Bay during the Holocene rise in sea level represents the latest of several cycles of erosion and deposition.