A deep water‐resource and stratigraphic test well near the center of Nantucket Island, about 40 miles (64 km) off the New England Coast, has encountered freshwater at greater depth than predicted by the Ghyben‐Herzberg principle. An uppermost lens of fresh‐water, which occupies relatively permeable glacial‐outwash sand and gravel to a depth of 520 ft. (158 m), is probably in hydrodynamic equilibrium with the present level of the sea and the height of the water table. However, two zones of freshwater between 730‐820 ft. (222‐250 m) and 900‐930 ft. (274‐283 m) are anomalously deep. A third zone extending from 1150‐1500 ft. (350‐457 m) contains slightly salty ground water (2 to 3 parts per thousand dissolved solids). Several explanations are possible, but the most likely is that large areas of the Continental Shelf were exposed to recharge by precipitation during long periods of low sea level in Pleistocene time. After the last retreat of glacial ice, seawater rapidly drowned the shelf around Nantucket Island. Since then, about 8000 years ago, the deep freshwater zones which underlie dense clay layers have not had time to adjust to a new equilibrium. Under similar circumstances freshwater may remain trapped under extensive areas of the Continental Shelf wherever clay confining beds have not permitted saltwater to intrude rapidly to new positions of hydrodynamic equilibrium. The implications are far reaching because all continental shelfs were exposed to similar hydrologic influences during Pleistocene time.

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About 36 wells are in use, pumping 30 to 500 gallons a minute each. The total annual pumpage is close to 1,361 million gallons, or 3.7 million gallons a day. Most of the water is used for brewing and distilling, the rest for air conditioning and miscellaneous industrial purposes. Considerably more water than is now pumped probably can be developed in this area, but test drilling and pumping tests should precede the planning of large installations. Pier 8. Bedrock at 430 (?) ft. 0. S. Corps of iSnglneers test boring 0-1. Log available. 0. S. Corps of Engine srs test boring D-69. Log available. U. S. Corps of Engineers test boring D-5-30. Log available. U. S. Corps of Engineers test boring D-5-29. Log available. U. S. Corps of Engineers test boring D-5-53. Log available. Kentucky Department of Highways test boring U-2. Log available. Kentucky Department of Highways test boring M-7. Log available. Drilled to rook. Temperature 56*. Do. 12 ft. drawdown at 375 gallons per minute. Log available. Drilled to rock. Unused. Observation well. Unused. Unused. Log and partial analysis available. Log available. Analysis available. Do. Unused. Well is covered. Log available.

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Cl Introduction____________________________________________________ 1 Geographic features______________________________________________ 3 Geologic features..-.______________________________ 6 Consolidated formations of pre-Pleistocene age ____________ _ _____ 6 Alluvium of Pleistocene age___________________________________ 7 Ground water_____________________________________________________ 8 Source and movement________________________________________ 8 Occurrence.________________________________________________ 11 Yield of wells._______________________________ 12 Hydrologic characteristics of the aquifer________________________ 13 Chemical character of ground water_____ _____________________ 20 Conclusions_____________________________________________________