Stratigraphic test well, Nantucket Island, Massachusetts
Circular
773
By: David W. Folger, J.C. Hathaway, R. A. Christopher, P. C. Valentine, and C. W. Poag
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Abstract
The U.S. Geological Survey, in cooperation with the Massachusetts Water Resources Commission and the Nantucket Conservation Foundation, continuously cored 514 m of sediment and volcanic rock in a stratigraphic and water-quality test near the geographic center of Nantucket Island. Stratified sediments were divided texturally into three zones: the upper zone (0-128 m) contains mostly coarse sand and gravel; the middle zone (128-349 m) contains mostly silty clay and a few beds of sand and silt; and the lower zone (349-457 m) contains soft, unconsolidated, clayey sand. Below the lower zone, a saprolite, composed mostly of clay, grades abruptly downward at 470 m into partially altered basalt that extends to the bottom of the hole at 514 m. Calculations based on the Ghyben-Herzberg principle predicted a zone of freshwater 120-150 m thick. This principle is the theory of hydrostatic equilibrium between freshwater and more dense seawater in a coastal aquifer; it states that for each meter of ground-water elevation above sea level, the freshwater lens will depress the saltwater interface about 40 m below sea level. Freshwater or low-salinity brackish water was found in sediments far below the depth predicted by the Ghyben-Herzberg principle. These interstitial waters are probably relict ground water emplaced during times of low sea level during the Pleistocene. (Woodard-USGS)
Suggested Citation
Folger, D.W., Hathaway, J., Christopher, R.A., Valentine, P.C., Poag, C.W., 1978, Stratigraphic test well, Nantucket Island, Massachusetts: U.S. Geological Survey Circular 773, iii, 28 p. :ill., maps ;26 cm., https://doi.org/10.3133/cir773.
ISSN: 2330-5703 (online)
| Publication type | Report |
|---|---|
| Publication Subtype | USGS Numbered Series |
| Title | Stratigraphic test well, Nantucket Island, Massachusetts |
| Series title | Circular |
| Series number | 773 |
| DOI | 10.3133/cir773 |
| Year Published | 1978 |
| Language | ENGLISH |
| Publisher | U.S. Geological Survey, |
| Description | iii, 28 p. :ill., maps ;26 cm. |