Scientific Investigations Map 3233, Materials Selector

Purpose of Selector

The Scientific Investigations Map "Bedrock Topography of Western Cape Cod, Massachusetts, Based on Bedrock Altitudes from Geologic Borings and Analysis of Ambient Seismic Noise by the Horizontal-to-Vertical Spectral-Ratio Method" by Gillian M. Fairchild, John W. Lane, Jr., Emily B. Voytek, and Denis R. LeBlanc, is presented here as several downloadable components: map sheets, pamphlet, geographic information system (GIS) files, instructions, tables, and individual page-sized figures.

Map Sheet — ARCH E size 36-by-48-inch sheet paper or 36-inch plotter roll, for high-resolution printing on a commercial press or plotter. (145,059 KB) This file may take several minutes to download and draw.

Map Sheet — Lowered resolution ARCH E size document for Internet-optimized viewing. (77,424 KB)

Pamphlet — Auxiliary document optimized for Section-508-handicap compliance. (2,943 KB)

GIS materials — An assortment of .sbn, .sbx, .shp, .xml, .dbf, .prj, .shx, and .rrd files in one WinZip package (4.5 MB). Package includes all files necessary to load shapefiles of the bedrock contours and the raster of the bedrock surface into a GIS for viewing or for data use. Data contained in the .zip file was current as of October 4, 2012. Revisit the SIM 3233 Web site in the future for potential data updates.

GIS instructions — An information document about how to use ArcGIS Explorer. (513 KB)

The data in SIM 3233 have been approved for release and publication by the Director of the USGS. Although the materials have been subjected to rigorous review and are substantially complete, the USGS reserves the right to revise the data pursuant to additional data collection, analysis, and review. Furthermore, the data are released on condition that neither the USGS nor the U.S. Government may be held liable for any damages resulting from its authorized or unauthorized use. Any use of trade, firm, or product names is for descriptive purposes only and does not imply endorsement by the U.S. Government.

GIS software — If you don't have ArcGIS or ArcMap, you may download ArcExplorer from ESRI. Check operating requirements at, then download software choice from

Tables (jump to list)

Page-sized figures (jump to list)

Introduction (from pamphlet)

The bedrock surface of western Cape Cod defines the lower boundary of groundwater models that are used to predict the transport of groundwater contaminants originating on the Massachusetts Military Reservation (MMR). The bedrock surface is represented by a no-flow boundary in the models, and the topography of the surface plays an important role in determining the patterns of groundwater flow. The bedrock surface has been characterized in the past by using the results of seismic refraction surveys and geologic borings drilled to bedrock (Oldale, 1969; Air Force Center for Environmental Excellence (AFCEE), 2006). The horizontal-to-vertical spectral-ratio (HVSR) method, which is a passive seismic technique that uses an analysis of the horizontal and vertical components of ambient seismic noise (microtremors), has been introduced as a method to collect data on the depth to bedrock in a manner that is noninvasive and less expensive than drilling (Lane and others, 2008). These advantages are beneficial in an area such as western Cape Cod, where the land is occupied by residential and commercial properties, and depths to bedrock commonly exceed 200 feet (ft). The Toxic Substances Hydrology Program of the U.S. Geological Survey (USGS), working cooperatively with the Army National Guard (ARNG) and the Air Force Center for Engineering and the Environment (AFCEE), used the HVSR method during 2008–10 to estimate bedrock depth in areas for which there was little information from drilling and to prepare a map of the altitude of the bedrock surface for western Cape Cod.

The purpose of this report is to present an updated topographic map of the bedrock surface beneath western Cape Cod, Massachusetts, for use in groundwater-flow models of the Sagamore lens of the Cape Cod aquifer. The bedrock surface was first mapped by Oldale in 1969, and the map was updated in 2006 by using bedrock altitudes estimated during the drilling by AFCEE and ARNG to identify the boundaries and sources of the contaminant plumes originating on the MMR (AFCEE, 2006). The borings are concentrated on the MMR and in the immediately surrounding area. This report updates the bedrock-surface map with new data points collected by using the HVSR method as well as data from additional borings drilled to bedrock since the 2006 map was prepared.

The area of the map presented in this report is on western Cape Cod (fig. 1) and includes the towns of Bourne (as far west as the Cape Cod Canal), Mashpee, Falmouth, and Sandwich, and the western portion of the town of Barnstable. The MMR covers the northwestern part of this area (fig. 1). The study area overlies unconsolidated glacial drift deposits that consist of medium-to-coarse-grained glaciofluvial sand and gravel outwash overlying fine-to-medium-grained glaciolacustrine sand and silt, with sandy moraines near the northern and western coasts. These deposits form the Sagamore lens of the Cape Cod aquifer, which underlies the entire area (Walter and Whealan, 2005). The underlying bedrock is primarily granodiorite (Oldale and Barlow, 1986; Oldale, 1992). The surficial topography of the study area is characterized by gently sloping areas on the outwash plains and hummocky terrain on the moraines.

The aquifer, which consists of the unconsolidated glacial sediments, is an unconfined system that is surrounded by saltwater. The water table in the unconfined glacial sediments reaches a maximum altitude of approximately 70 ft at the eastern boundary of the MMR (Walter and Whealan, 2005). Several contaminant plumes originate on the MMR from historical defense-related activities (Massachusetts National Guard, 2012). The direction of movement of each contaminant plume depends on the position of the source of the contamination on the groundwater mound. Groundwater modeling has been used extensively to assist in predicting the fate and transport of the various contaminants originating on the MMR (AFCEE, 2006; Masterson and others, 1996; Walter and Masterson, 2003; Walter and LeBlanc, 2008).

Tables as Excel (.xlsx) files

Table 1-1. Locations, altitudes of land and bedrock surfaces, and depths below land surface to bedrock for geologic borings where bedrock was hit during drilling, western Cape Cod, Massachusetts. (56 KB)

Table 1-2.  Locations, altitudes of land surface, estimated altitudes and depths below land surface of the bedrock surface, and fundamental resonance frequencies at locations of horizontal-to-vertical spectral-ratio (HVSR) measurements, western Cape Cod, Massachusetts. (28 KB)

Table 1-3. Locations, altitudes of land surface, maximum altitudes of the bedrock surface, and depths below land surface for geologic borings where bedrock was not hit and drilling was extended to at least 200 feet below land surface, western Cape Cod, Massachusetts. (51 KB)

Figures as individual (.pdf) page-sized illustrations

Figure 1. Location of study area near the Massachusetts Military Reservation, western Cape Cod, Massachusetts. (1,002 KB)

Figure 2. Closeup photographs showing A, a single broadband, three-component seismometer, and B, the seismometer and data-collection system as typically deployed in the field. (55,505 KB)

Figure 3. Example from site 00MW0584 of the graphical representation of the raw seismic data. (1,413 KB)

Figure 4. Example of the Geopsy output graph of the fundamental resonance frequency determined by the spectral plot of the ratio of the averaged-horizontal to vertical components of the ambient seismic noise at site 00MW0584. (856 KB)

Figure 5. Topographic map of the bedrock surface beneath western Cape Cod as interpreted from horizontal-to-vertical spectral-ratio measurements, seismic refraction surveys, and geologic borings, western Cape Cod, Massachusetts. (5,077 KB)

Figure 6. Topographic map of the bedrock surface beneath the area near Snake Pond as interpreted mostly from geologic borings, western Cape Cod, Massachusetts. (1,078 KB)

Figure 7. Topographic map of the bedrock surface beneath the area near Ashumet Pond as interpreted mostly from geologic borings, western Cape Cod, Massachusetts. (3,536 KB)

Figure 8. Topographic map of the bedrock surface beneath Cape Cod, Martha’s Vineyard, and Nantucket, Massachusetts. (19,927 KB)

Figure 1-1 (Appendix). Locations of geologic borings and horizontal-to-vertical spectral-ratio measurements used to prepare the topographic map of the bedrock surface, western Cape Cod, Massachusetts (1,127 KB). The map is presented as a layered PDF. (Layers feature may not work through web browser; download and save the document, and then use Adobe Acrobat Pro or Adobe Reader to open the file. Choose layers icon in the left-side menu, and then click eye symbols on and off to see the different layers.)

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Tables manufactured: December 2012
GIS materials packaged: October 2012
(Please check the Web site for any subsequent revisions or updates.)