The Delaware Geological Survey (DGS) has published a new geologic map of the Bethany Beach and Fenwick Island area in eastern Sussex County titled Geologic Map of the Bethany Beach and Assawoman Bay Quadrangles, Delaware.
Geologic Map 18 presents the results of research by Kelvin W. Ramsey and Jaime Tomlinson of the DGS and is the first web-only map published by the DGS.
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.
Rapid, significant groundwater recharge occurred in response to tropical storms Irene and Lee.a
Tropical storms Irene and Lee caused a 9-1/2 foot rise of the water table in western Sussex County near Laurel. Groundwater levels and temperatures in Qb35-08 were collected with an automated pressure-temperature datalogger system. At the same time, rainfall and soil moisture data were recorded by the DEOS Laurel Airport station located approximately 5 miles from the well.
This project will assess tsunami hazard from the above mentioned and other relevant tsunami sources recently studied in the literature and model the corresponding tsunami inundation in affected US East coast communities. We will combine ocean scale simulations of transoceanic tsunami sources, such as Lisbon 1755 like or Puerto Rico Trench co-seismic events, and CVV collapse, with regional scale simulations of these events, along with the regional scale SMF events, in order to establish the relative degree of hazards for East Coast communities. Detailed inundation studies will be conducted for highest-risk East Coast communities, and results of these studies will be used to construct a first-generation of tsunami inundation maps for the chosen communities.
The complex geologic history of the surficial units of the Harbeson Quadrangle is one of deposition of the Beaverdam Formation and its subsequent modification by erosion and deposition related to sea-level fluctuations during the Pleistocene. The geology is further complicated by periglacial activity that produced dune deposits and Carolina Bays scattered throughout the map area.
The Delaware Geological Survey (DGS) currently monitors groundwater levels in a network of wells in Delaware. Long, time-series of water levels in major aquifers serve as critical baseline data for resource management and analyses of aquifer response to pumping, climatic variability, drought hazards, seawater intrusion, and interaction with streams and their ecosystems.
In 2000, A. Scott Andres, a senior scientist and hydrologist with the Delaware Geological Survey, released findings that disclosed a unique formation at the swamp.
In geologic time, the swamp isn't that old.
It formed about 22,000 years ago in a fresh-water, cold-climate marsh and boreal forested swamp.
Organic matter started building up and a cold wind blew in silt, clay and sand from nearby dunes and surrounding high ground. More sediment washed in with runoff from streams.
Thin sheets of sand likely spread during times when the land thawed.
Conditions began to change about 10,000 years ago as the climate warmed, forming a temperate-forested swamp, bog and flood plain.
There was more erosion and movement of organic-rich sediment to the fresh-water swamp. Today, it's considered the northernmost Southern forest on the East Coast.
