Lithostratigraphic, Geophysical, and Hydrogeologic Observations From a Boring Drilled to Bedrock in Glacial Sediments Near Nantucket Sound in East Falmouth, Massachusetts

Scientific Investigations Report 2019-5042
Prepared in cooperation with the Cape Cod Commission
By: , and 

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Abstract

In spring 2016, a 310-foot-deep boring (named MA–FSW 750) was drilled by the U.S. Geological Survey near Nantucket Sound in East Falmouth, Massachusetts, to investigate the hydrogeology of the southern coast of western Cape Cod. Few borings that are drilled to bedrock exist in the area, and the study area was selected to fill a gap between comprehensive geologic datasets inland to the north and marine geophysical data from beneath Nantucket Sound to the south. A permanent monitoring well (MA–FSW 750–0100) was installed in the boring upon the completion of the drilling and core collection. Observations from sediment cores and surface and borehole geophysical measurements were used to delineate three zones relevant to understanding groundwater flow at the study location. Shallow sands and gravels (0–107 feet [ft] below land surface [bls]) underlain by silt-rich fine and very fine sand (107–175 ft bls) form a zone of high permeability underlain by a zone of relatively lower permeability, referred to as the “shallow high-permeability” and “low-permeability” zones, respectively. A sharp lithological contact separating the shallow high-permeability and low-permeability zones may affect vertical flow of groundwater. Fine to coarse sand with intervals of clay and silt from 175 to 300 ft bls represent a deep zone of relatively high permeability, referred to as the “deep high-permeability” zone. A compacted, nonsorted unit (identified as basal till) and the bedrock surface were encountered at 300 and 305 ft bls, respectively. Hydraulic conductivity estimates from nuclear magnetic resonance logs and sediment grain-size distribution analyses indicated that the shallow high-permeability zone contributes substantially to the capacity of the aquifer to transmit groundwater at the study location. Results from geophysical surveys indicate a gradual transition from fresh to saline groundwater in the interval from 105 to 160 ft bls. Freshwater at the study site is present in the saturated unconsolidated sediments only in the 75 ft between 30 ft (the water table) and 105 ft bls in the shallow high-permeability zone. Sediments shallower than 175 ft bls closely resemble the downward fining post-Wisconsinan age deltaic and lacustrine deposits present in many parts of western Cape Cod; sediments deeper than 175 ft appear to be the product of earlier depositional processes more local to the southern coast of western Cape Cod. This study highlights how high-resolution observations of cored material coupled with a multitool geophysical approach can characterize a single boring to help better understand regional glacial history and hydrogeology.

Suggested Citation

Hull, R.B, Johnson, C.D., Stone, B.D., LeBlanc, D.R., McCobb, T.D., Phillips, S.N., Pappas, K.L., and Lane, J.W., 2019, Lithostratigraphic, geophysical, and hydrogeologic observations from a boring drilled to bedrock in glacial sediments near Nantucket sound in East Falmouth, Massachusetts: U.S. Geological Survey Scientific Investigations Report 2019–5042, 27 p., https://doi.org/10.3133/sir20195042.

ISSN: 2328-0328 (online)

Study Area

Table of Contents

  • Abstract
  • Introduction
  • Methods of Well Construction, Data Collection, and Analysis
  • Lithostratigraphic Characterization of the Study Area
  • Hydrogeological Characterization of the Study Area
  • Summary
  • References Cited

Additional publication details

Publication type Report
Publication Subtype USGS Numbered Series
Title Lithostratigraphic, geophysical, and hydrogeologic observations from a boring drilled to bedrock in glacial sediments near Nantucket Sound in East Falmouth, Massachusetts
Series title Scientific Investigations Report
Series number 2019-5042
DOI 10.3133/sir20195042
Year Published 2019
Language English
Publisher U.S. Geological Survey
Publisher location Reston, VA
Contributing office(s) Eastern Geology and Paleoclimate Science Center, WMA - Earth System Processes Division, New England Water Science Center
Description Report: 27 p.; Data Releases
Country United States
State Massachusetts
Other Geospatial Nantucket Sound
Online Only (Y/N) Y
Additional Online Files (Y/N) N