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Summary Information for Field Activity 2003-038-FA

Area of Operations: Chincoteague Bay, Maryland, United States, North America, North Atlantic

Dates: August 14, 2003 to August 22, 2003

Chief scientist: John Bratton

   David Krantz, Univ. of Toledo

Objectives: Study of submarine ground water including borehole geophysics, porewater squeezing, sediment sampling and groundwater sampling.

Type of Activity: Sampling; Drilling; Downhole electromagnetic induction/gamma logging;Drilling
Downhole electromagnetic induction/gamma logging

Information to be derived: Downhole geophysical logs

Summary: On August 14-22 a USGS-led team undertook a complex subsurface field effort to study the occurrence and chemistry of submarine ground water beneath Chincoteague Bay, Maryland as a follow-up to earlier surface geophysical studies. The area was made famous by Marguerite Henry’s 1947 children’s book (and later Disney movie), Misty of Chincoteague, about the wild ponies that live on the adjacent barrier islands, Chincoteague and Assateague. Chincoteague Bay is experiencing nutrient over-enrichment that is of concern to its primary managers, the National Park Service and the Maryland Department of Natural Resources. Submarine discharge of ground water recharged in agricultural areas on land is suspected to be a major contributor of nitrogen to the bay. Offshore work consisting of drilling, geophysical logging, and sampling was performed from a barge platform, and was augmented with onshore logging of existing wells. The maximum drilling depth reached by the barge rig was 72 feet beneath the sediment surface. The field team included John Bratton, Sarah Kelsey, and Dirk Koopmans (USGS-GD-Woods Hole and contractors); David Krantz and Abby Norton (University of Toledo); John Earle (USGS-WRD-Denver); and J.K. Bohlke and Craig Tobias (USGS-WRD-Reston). Drilling contractors from Hillis-Carnes Engineering and a barge/tug pilot provided by Hi-Tide Marine Construction consistently overcame difficult mechanical, geological, and meteorological conditions to get the science done. Special thanks go out to National Park Service colleagues from Assateague Island National Seashore, Brian Sturgis and Carl Zimmerman, who provided logistical support, shuttle boats, and lodging. The fieldwork was conducted safely and efficiently and produced excellent scientific results. Noteworthy discoveries included the presence of a plume of fully fresh ground water greater than 25 feet thick extending more than 1/2 mile offshore along the western side of the bay (Public Landing), a similar plume at the northern end of the bay (South Point), hypersaline brines underlying part of Assateague Island, and a widespread buried peat present at the base of the bay’s Holocene sediments. Downhole gamma and electromagnetic induction logs were obtained from eight locations. Ground water samples were collected from nine temporary subestuarine wells, surface water was obtained from eight locations, and pore water was squeezed from 35 sediment samples. Additional analyses for age dating, nutrients, and stable isotopes will be performed over the coming months.

Contact: John Bratton (

InfoBank: uses the identifier B-1-03-MD. Visit this site for more information.

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Platform Info:

Publications resulting from these data

Bratton, John F., Bohlke, John Karl, Krantz, David E., and Tobias, Craig R.,2009, Flow and geochemistry of groundwater beneath a back-barrier lagoon; the subterranean estuary at Chincoteague Bay, Maryland, USA: Marine Chemistry, v. 113, no. 1-2: p. 78-92. (Also available at

Bratton, J.F.,2007, The importance of shallow confining units to submarine groundwater flow, in Sanford, W., Langevin, C., Polemio, M., and Povinec, P., eds., A New Focus on Groundwater-Seawater Interactions: International Association of Hydrological Sciences, v. 312: p. 28-36

Bratton, John F.,2010, The three scales of submarine groundwater flow and discharge across passive continental margins: The Journal of Geology, v. 118, no. 5: p. 565-575. (Also available at

Data Types and Locations:



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