70°09' 70°07' 70°05' 70°03'

70°10' 70°08' 70°06' 70°04'

Prepared in cooperation with the

National Oceanic and Atmospheric Administration

Scientific Investigations Map 

M

STELLWAGEN BANK NATIONAL MARINE SANCTUARY

N I N E T Y M E T E R B A N K S

NORTH 

NINETY

BANK

SOUTH

NINETY

BANK

EAST

NINETY

BANK

MIDDLE

NINETY

BANK

U.S. Department of the Interior

U.S. Geological Survey

Scientific Investigations Map 3341

Prepared in cooperation with the National Oceanic and Atmospheric Administration

Seabed Maps Showing Topography, Ruggedness, 

Backscatter Intensity, Sediment Mobility, 

and the Distribution of Geologic Substrates 

in Quadrangle 6 of the Stellwagen Bank National 

Marine Sanctuary Region Offshore of Boston, 

Massachusetts
Cover. Sun-illuminated topographic imagery and boulder ridges shown on Map A of this report.
Seabed Maps Showing Topography, Ruggedness, 

Backscatter Intensity, Sediment Mobility, 

and the Distribution of Geologic Substrates 

in Quadrangle 6 of the Stellwagen Bank National 

Marine Sanctuary Region Offshore of Boston, 

Massachusetts

By Page C. Valentine and Leslie B. Gallea

Prepared in cooperation with the National Oceanic and Atmospheric Administration

Scientific Investigations Map 3341

U.S. Department of the Interior

U.S. Geological Survey
U.S. Department of the Interior

SALLY JEWELL, Secretary

U.S. Geological Survey

Suzette M. Kimball, Acting Director

U.S. Geological Survey, Reston, Virginia: 2015

For more information on the USGS—the Federal source for science about the Earth, its natural and living 

resources, natural hazards, and the environment—visit http://www.usgs.gov or call 1–888–ASK–USGS.

For an overview of USGS information products, including maps, imagery, and publications, 

visit http://www.usgs.gov/pubprod/.

Any use of trade, firm, or product names is for descriptive purposes only and does not imply endorsement by the 

U.S. Government.

Although this information product, for the most part, is in the public domain, it also may contain copyrighted materials 

as noted in the text. Permission to reproduce copyrighted items must be secured from the copyright owner.

Suggested citation:

Valentine, P.C., and Gallea, L.B., 2015, Seabed maps showing topography, ruggedness, backscatter intensity, sediment 

mobility, and the distribution of geologic substrates in quadrangle 6 of the Stellwagen Bank National Marine Sanctuary

region offshore of Boston, Massachusetts: U.S. Geological Survey Scientific Investigations Map 3341, 10 sheets, 

scale 1:25,000, and 21-p. pamphlet, http://dx.doi.org/10.3133/sim3341.

ISSN 2329-132X (online)
iii

Contents

Abstract...........................................................................................................................................................1

Introduction.....................................................................................................................................................1

Map A. Sun-Illuminated Topography and Boulder Ridges ....................................................................3

Map B. Seabed Ruggedness .....................................................................................................................5

Map C. Backscatter Intensity and Sun-Illuminated Topography..........................................................7

Map D. Distribution of Geologic Substrates ............................................................................................8

Description of Map Units (Also Printed on Map D Sheets) ...........................................................9

Map E. Sediment Mobility .........................................................................................................................11

Map F. Distribution of Fine- and Coarse-Grained Sand........................................................................12

Map G. Distribution of Substrate Mud Content .....................................................................................13

Mapping Methods........................................................................................................................................14

Seabed Sediment Collection, Processing, and Analysis ......................................................................17

Seabed Photographs...................................................................................................................................18

Photograph collection methods .......................................................................................................18

Photograph processing methods.....................................................................................................18

Image information and accessibility ...............................................................................................18

Data Catalog .................................................................................................................................................18

Data Layers and Data for Quadrangle 6..........................................................................................19

References Cited..........................................................................................................................................20

Appendix 1. Supplementary, Previously Published Data Layers From the Stellwagen Bank 

National Marine Sanctuary Region Relevant to Quadrangle 6 ..............................................21
iv

Oversize Items

[Available for download at http://dx.doi.org/10.3133/sim3341]

 Map A.—Sun-Illuminated Topography and Boulder Ridges

 Map B.—Seabed Ruggedness

 Map C.—Backscatter Intensity and Sun-Illuminated Topography

 Map D.—Distribution of Geologic Substrates

 Sheet 1.—Seabed geology

 Sheet 2.—Seabed geology and stations

 Sheet 3.—Seabed geology and station data types

 Sheet 4.—Seabed geology and sun-illuminated topography

 Map E.—Sediment Mobility

 Map F. —Distribution of Fine- and Coarse-Grained Sand

 Map G.—Distribution of Substrate Mud Content

 Table 4. Grain-size analyses of sediment samples and assignment

 of stations to geologic substrates
v

Figures

1. Map showing location of quadrangle 6 ....................................................................................2

2. Sun-illuminated topographic imagery and boulder ridges shown on Map A ....................3

3. Seabed ruggedness imagery shown on Map B ......................................................................5

4. Backscatter intensity and sun-illuminated topographic imagery shown

on Map C........................................................................................................................................7

5. Geologic substrates and sun-illuminated topographic imagery shown 

on Map D, sheet 4.........................................................................................................................8

6. Distribution of mobile and immobile substrates shown on Map E.....................................11

7. Distribution of fine- and coarse-grained sand substrates and immobile

boulder ridges shown on Map F...............................................................................................12

8. Distribution of substrate mud content and immobile boulder ridges

shown on Map G.........................................................................................................................13

Tables

1. Areas of the seabed represented by boulder ridges..............................................................4

2. Geographic names for quadrangle 6.........................................................................................4

3. Areas of the seabed represented by ruggedness intervals..................................................6

4. Grain-size analyses of sediment samples and assignment of stations

to geologic substrates ...............................................................................................................14

5. Sediment textural characteristics of mapped geologic substrates...................................15

6. Geologic substrate symbols, names, and brief descriptions ..............................................16

7. Characters used in substrate names to describe the physical attributes

of substrates................................................................................................................................17
vi

Conversion Factors

Multiply By To obtain

Length

millimeter (mm) 0.03937 inch (in.)

centimeter (cm) 0.3937 inch (in.)

meter (m) 3.281 foot (ft) 

meter (m) 1.094 yard (yd)

kilometer (km) 0.5400 mile, nautical (nmi)

Area

square meter (m2 ) 10.76 square foot (ft2)

square kilometer (km2 ) 0.2916 square nautical mile (nmi2)

square kilometer (km2 ) 0.3861 square mile (mi2 )

Map Projection Information

Mercator; Geodetic Reference System 1980; horizontal datum: North American Datum of 1983

Longitude of central meridian 70°19' W.; latitude of true scale 41°39' N.

False easting 0 m; false northing 0 m ; vertical datum: Mean Lower Low Water

Digital Image Resolution

The resolution of pixels in spatial datasets follows the conventions used in the spatial data and 

modeling communities. The format is “n-meter resolution,” where n is a numerical value for the 

length. The usage translates into a pixel with a length of n on all sides that covers an area of 

n meters ×n meters.
vii

Grain-Size Classification

Grade1

Grain size

Range1

(millimeter)

Scale2

(phi)

Gravel, boulder

Gravel, cobble

Gravel, very coarse pebble

Gravel, coarse pebble

Gravel, medium pebble

Gravel, fine pebble

Gravel, granule

Sand, very coarse

Sand, coarse

Sand, medium

Sand, fine

Sand, very fine

Silt

Clay

Mud (silt + clay)

256 to <4,096

64 to <256

32 to <64

16 to <32

8 to <16

4 to <8

2 to <4

1 to <2

0.5 to <1

0.25 to  <0.5

0.125 to <.25

0.062 to  <0.125

0.004 to < 0.062

< 0.004

< 0.062

– 8 to –11

– 6 to –7

–5

– 4

–3

–2

–1

0

1

2

3

4

5 to 8

9, 10, 11, ...

5 and higher

1

Udden, 1914; Wentworth, 1922; Folk, 1954; Blair and McPherson, 1999.

2

Krumbein, 1936.

To convert particle diameter (D) in millimeter (mm) to phi units (φ): φ = – 

φ To convert particle diameter (D) in phi units (φ) to mm: D = 2–

log D 2 = –3.3219 log D10

Composite Grain-Size Classification Used in This Study

Composite grade

Grain size

Range Scale 

(millimeter) (phi)

Gravel (G ) 2 2 8 to <64 –3, – 4, and –5

Gravel (G ) 1 1 2 to <8 –1 and –2

Coarse-grained sand (cgS) 0.25 to <2 2, 1 and 0

Fine-grained sand (fgS) 0.062 to <0.25 4 and 3

Seabed Maps Showing Topography, Ruggedness, 

Backscatter Intensity, Sediment Mobility, 

and the Distribution of Geologic Substrates 

in Quadrangle 6 of the Stellwagen Bank National 

Marine Sanctuary Region Offshore of Boston, 

Massachusetts

By Page C. Valentine and Leslie B. Gallea

Abstract

The U.S. Geological Survey (USGS), in cooperation 

with the National Oceanic and Atmospheric Administration’s 

National Marine Sanctuary Program, has conducted seabed 

mapping and related research in the Stellwagen Bank 

National Marine Sanctuary (SBNMS) region since 1993. The 

area is approximately 3,700 square kilometers (km2) and is 

subdivided into 18 quadrangles. Seven maps, at a scale of 

1:25,000, of quadrangle 6 (211 km2) depict seabed topography, 

backscatter, ruggedness, geology, substrate mobility, mud 

content, and areas dominated by fine-grained or coarse-grained 

sand. Interpretations of bathymetric and seabed backscatter 

imagery, photographs, video, and grain-size analyses were 

used to create the geology-based maps. In all, data from 

420 stations were analyzed, including sediment samples from 

325 locations. The seabed geology map shows the distribution 

of 10 substrate types ranging from boulder ridges to immobile, 

muddy sand to mobile, rippled sand. Mapped substrate types 

are defined on the basis of sediment grain-size composition, 

surface morphology, sediment layering, the mobility or 

immobility of substrate surfaces, and water depth range. 

This map series is intended to portray the major geological 

elements (substrates, topographic features, processes) of 

environments within quadrangle 6. Additionally, these maps 

will be the basis for the study of the ecological requirements 

of invertebrate and vertebrate species that use these substrates 

and guide seabed management in the region. 

Introduction

The Stellwagen Bank National Marine Sanctuary 

region lies offshore of Boston, Massachusetts, extending 

from Stellwagen Bank in the south to the southern part of 

Jeffreys Ledge in the north (fig. 1). The region includes 

the SBNMS and is subdivided into 18 quadrangles with 

a combined area of approximately 3,700 square kilometers (km2

). This publication presents maps at a scale 

of 1:25,000 that portray the physical characteristics of the 

seabed in quadrangle 6 (211 km2). Interpretations of seabed 

substrates, topographic features, and processes are based on 

multibeam bathymetric and backscatter imagery that show 

seabed topography and the relative reflectivity (representing 

hardness and softness) of seabed substrates; and on sediment 

grain-size analyses and video and photographic imagery 

that provided data used to interpret the features and patterns 

observed in the sonar imagery.

Three maps in this series focus on regional physical 

characteristics of the seabed such as topography (Map A), 

ruggedness (Map B), and backscatter (Map C ). Interpretive 

maps show the distribution of 10 substrates, which range 

from boulder ridges to immobile, muddy fine-grained 

sand to mobile, rippled, coarse-grained sand (Map D, 

sheets 1–4), and also provide overviews of substrate 

mobility (Map E ), the distribution of substrates dominated 

by fine- or coarse-grained sand (Map F ), and the distribution 

of substrate mud content (Map G).
2 Seabed Maps of Quadrangle 6 in the Stellwagen Bank National Marine Sanctuary Region Offshore of Boston, Mass.

A substrate is characterized not just by sediment type (mud, sand, gravel), but also by surficial features (for example, 

ripples), sediment layering (for example, finer sediment partly covering coarser sediment), and sediment movement. The 

methodology employed to delineate seabed substrates is discussed in the Mapping Methods section of this report.

Several of the maps in this series (A, B, and C) have been published previously at a scale of 1:60,000 (Valentine, 2005); 

they are presented here at higher resolution (1:25,000). Map A was published previously at 1:25,000 (Valentine and others, 

1999, 2010), but did not show the distribution of boulder ridges. Maps D (sheets 1–4), E, F, and G are new interpretations 

of geological substrate composition, surficial features, and mobility.

The purpose of the map series is to provide a range of information about the distribution of physical attributes of the 

seabed in quadrangle 6 at a scale (1:25,000) that is justified by the density of data. High resolution information will serve 

as a foundation for further study of seabed processes such as sediment transport, for ecological studies of vertebrate and 

invertebrate species that use these substrates as habitat, and for planning and managing usage of the seabed.

Figure 1. Shows location of quadrangle 6 (highlighted in yellow). Stellwagen Bank National Marine 

Sanctuary boundary is shown as a dashed line. Bathymetric contours are labeled in meters.

Merrimack River

0 10 20 KILOMETERS

0 5 10 MILES

CAPE COD

CAPE

ANN

Plymouth

Provincetown

Gloucester

BOSTON

BASIN

MAS SACHUSETTS

BAY

GULF

OF

MAINE

71°00' W 70°45' W 70°30' W 70°15' W 70°00' W

40

200

100

100

100

100

80

80

80

80

40

80

80

40

100

80

40

40

CAPE COD BAY

8

5

9

121110

4

1 2 3

1514

181716

13

7

42°45' N

42°30' N

42°15' N

42°00' N

41°45' N

6

RACE POINT CHANNEL

STELLWAGEN

STELLWAGEN

BANK

TILLIES BANK

JEFFREYS LEDGE
Map A. Sun-Illuminated Topography and Boulder Ridges 3

Map A. Sun-Illuminated Topography and Boulder Ridges

Map A (see figure 2) shows seabed topographic imagery derived from multibeam sonar bathymetric data contoured at a 

5-meter (m) interval. Water depths range from 35 m on Stellwagen Bank in the west to 180 m in the valleys in the east that 

separate the Ninety Meter Banks. Boulder ridges <1 m and ≥1 m in height are shown as semi-transparent polygons overlying 

topography. They represent an area of 3.0 km2 in quadrangle 6 (table 1). 

The seabed represents a glaciated terrain modified by postglacial sediment transport processes. For a description of seabed 

features in this quadrangle, see a map showing sun-illuminated topography (Valentine and others, 1999, 2010). To view maps 

and descriptions of seabed topography and the distribution of boulder ridges and bedrock outcrops in the entire Stellwagen 

Bank National Marine Sanctuary region, see Maps A, B, and F of Valentine (2005).

Figure 2. Sun-illuminated topographic imagery and boulder ridges shown on Map A.

70°13' 70°10' 70°08' 70°06' 70°04' 70°02'

42°18'

42°19'

70°13' 70°11' 70°09' 70°07' 70°05' 70°03'

42°14'

42°16'

42°18'

42°19'

42°14'

42°16'

70°11' 70°09' 70°07' 70°05' 70°03'

70°12' 70°10' 70°08' 70°06' 70°04'

42°17'

42°15'

42°13' 42°13'

42°15'

42°17'

70°12'

70°02'

Prepared in cooperation with the

National Oceanic and Atmospheric Administration

U.S. Department of the Interior

U.S. Geological Survey

Mercator projection

Geodetic Reference System 1980; North American Datum of 1983

Longitude of central meridian 70°19' W; latitude of true scale 41°39' N

False easting 0 m; false northing 0 m

This map is not intended for navigational purposes.

Map A.—Sun-Illuminated Topography and Boulder Ridges

Seabed Maps Showing Topography, Ruggedness, Backscatter Intensity, Sediment Mobility, and the

Distribution of Geologic Substrates in Quadrangle 6 of the Stellwagen Bank National Marine Sanctuary Region 

Offshore of Boston, Massachusetts

By

Scientific Investigations Map 3341

Map A

EXPLANATION OF MAP SYMBOL

DESCRIPTION OF MAP UNITS

Possible shipwreck site

Boulder ridges <1 m in height—Equivalent 

to geologic substrate C of Map D

Boulder ridges ≥1 m in height—Equivalent 

to geologic substrate C of Map D

Merrimack River

0 20 km

CAPE COD

CAPE

ANN

Plymouth

Provincetown

Gloucester

BOSTON

BASIN MAS SACHUSETTS BAY

GULF

OF

MAINE

71°00' W 70°45'W 70°30'W 70°15'W 70°00'W

40

200

100

100

100

100

80

80

80

80

40

80

80

40

100

80 40

40

CAPE COD BAY

8

5

9

10 11 12

4

1 2 3

14 15

181716

13

7

42°45'N

42°30'N

42°15'N

42°00'N

41°45'N

6

RACE POINT CHANNEL

STELLWAGEN

STELLWAGEN BANK

TILLIES BANK JEFFREYS LEDGE

Any use of trade, firm, or product names is for descriptive purposes only and does not imply 

endorsement by the U.S. Government

Digital files available at http://pubs.usgs.gov/sim/3341/

Suggested citation: Valentine, P.C., and Gallea, L.B., 2015, Sun-illuminated topography and boulder 

ridges, map A of Seabed maps showing topography, ruggedness, backscatter intensity, sediment 

mobility, and the distribution of geologic substrates in quadrangle 6 of the Stellwagen Bank 

National Marine Sanctuary region offshore of Boston, Massachusetts: U.S. Geological Survey 

Scientific Investigations Map 3341, scale 1:25,000, http://dx.doi.org/10.3133/sim3341.

STELLWAGEN BANK NATIONAL MARINE SANCTUARY

S T E L L W A G E N B A N K

N I N E T Y M E T E R B A N K S

NORTH 

NINETY

BANK

SOUTH

NINETY

BANK

EAST

NINETY

BANK

MIDDLE

NINETY

BANK

SCALE 1:25 000 

ONE CENTIMETER ON THE MAP REPRESENTS 250 METERS ON THE SEA FLOOR 

CONTOUR INTERVAL 5 METERS

DATUM MEAN LOWER LOW WATER

1 .5 0 1 2 3 4 KILOMETERS

1 .5 0 1 2 NAUTICAL MILES 
4 Seabed Maps of Quadrangle 6 in the Stellwagen Bank National Marine Sanctuary Region Offshore of Boston, Mass.

Table 1. Areas of the seabed represented by boulder ridges.

[Boulder ridges are segregated into two height categories, <1 meter (m) and ≥1 m. Areas of the seabed represented by boulder ridges and 

bedrock outcrops in all 18 quadrangles in the Stellwagen Bank National Marine Sanctuary (SBNMS) region are listed in table 1 of Map F of 

Valentine (2005). Abbreviation used: km2, square kilometer]

Region

Area of

 imaged seabed 

(km2

)

Area of boulder ridges in quadrangle 6 and its SBNMS portion

(km2

)

Area of boulder ridges in quadrangle 6 and its SBNMS portion 

(percent)

<1 m ≥1 m <1 m ≥1 m

Quadrangle 6 211 0.5 2.5 0.2 1.2

SBNMS portion of quadrangle 6 157 0.4 1.9 0.2 1.2

Table 2. Geographic names for quadrangle 6.

[Named geographic features that lie within quadrangle 6 of the Stellwagen Bank National Marine Sanctuary region are listed below. Most 

features were named during the mapping project, and a link to the official description is provided. Some feature names are historical; no official 

description is available for them. To view the location and description of all of the named geographic features in the Stellwagen Bank National 

Marine Sanctuary region, see Valentine (2005)]

Geographic name Description

East Ninety Bank http://woodshole.er.usgs.gov/project-pages/stellwagen/html/geonames.html#eastninetybank

Middle Ninety Bank http://woodshole.er.usgs.gov/project-pages/stellwagen/html/geonames.html#middleninetybank

Ninety Meter Banks http://woodshole.er.usgs.gov/project-pages/stellwagen/html/geonames.html#ninetymeterbanks

North Ninety Bank http://woodshole.er.usgs.gov/project-pages/stellwagen/html/geonames.html#northninetybank

South Ninety Bank http://woodshole.er.usgs.gov/project-pages/stellwagen/html/geonames.html#sninetybank

Stellwagen Bank First mapped by Henry S. Stellwagen in 1854–1855; and named for him in 1854 by Alexander Bache,

Superintendent of the U.S. Coast Survey. http://stellwagen.noaa.gov/about/discovery.html

In quadrangle 6, 5-m and 1-m topographic contours were generated from bathymetric data collected by the Simrad EM1000 

multibeam sonar echo sounder used in the mapping survey. On Map A, only 5-m contours are shown. They accurately represent 

the morphology of seabed features such as large and small banks and valleys and some of the boulder ridges. However, as 5-m 

contours do not adequately show the characteristic hummocky relief of the seabed in areas dominated by gravel deposits and 

small boulder ridges, they are supplemented by 1-m contours on maps B and D–G in areas of relatively rough seabed. See the 

Mapping Methods section of this report for further explanation of the use of 1-m contours.

Several geographic features were named during the mapping project (table 2). A possible shipwreck site is noted on the map. 
Map B. Seabed Ruggedness 5

Map B. Seabed Ruggedness 

Map B (see figure 3) shows the results of an analysis of multibeam sonar bathymetric data to calculate seabed ruggedness, 

a measure of changes in elevation (water depth) over small areas. It is based on a terrain ruggedness index (TRI) developed by 

Riley and others (1999) to quantify topographic heterogeneity on land. The TRI of Riley and others measures the sum change

in elevation between a central grid cell (pixel) and its eight neighboring grid cells, found by squaring the eight differences 

in elevation, summing the squared differences, and taking the square root of the sum. Here, a seabed TRI is used to measure 

ruggedness more directly by calculating the average change in elevation between a central pixel and its eight neighbors, found 

by averaging the absolute values of the eight differences in elevation (see Map D of Valentine, 2005). Comparing the two 

methods, a central pixel (representing a positive feature) with an elevation (water depth) value of 10 m and eight neighboring 

pixels with values of 15 m would have a TRI value of 14.1 m using the method of Riley and others (1999) and a seabed 

TRI value of 5.0 m using the method employed here.

70°13' 70°10' 70°08' 70°06' 70°04' 70°02'

42°18'

42°19'

70°13' 70°11' 70°09' 70°07' 70°05' 70°03'

42°14'

42°16'

42°18'

42°19'

42°14'

42°16'

70°11' 70°09' 70°07' 70°05' 70°03'

70°12' 70°10' 70°08' 70°06' 70°04'

42°17'

42°15'

42°13' 42°13'

42°15'

42°17'

70°12'

70°02'

Prepared in cooperation with the

National Oceanic and Atmospheric Administration

U.S. Department of the Interior

U.S. Geological Survey

Colors represent the average change in elevation, in centimeters (cm), between a central area (13-meter [m] pixel) and the surrounding eight pixels (total area analyzed is 

three pixels by three pixels, or 39 × 39 m in size). For example, on the map, blue represents central pixels having an average elevation change of >70 to 80 cm with 

respect to their surrounding eight-pixel areas. Note the elevation-change increments in the color scale vary from 10 cm to 50 cm to 100 cm. A lter was applied to the 

ruggedness index image to smooth the boundaries between the mapped increments. The lter calculated the mean of the seabed terrain ruggedness index (TRI) value of 

each pixel and its eight neighboring pixels in a three-pixel by three-pixel grid that measures 39 × 39 m.

This index represents the range of seabed ruggedness observed in the Stellwagen Bank National Marine Sanctuary region. In quadrangle 6, seabed ruggedness ranges 

from 0–30 to >300–400 cm.

See Mapping Methods for explanation of topographic contour intervals. 

SEABED TERRAIN RUGGEDNESS INDEX

0–30 >30–40 >40–50 >50–60 >60–70 >70–80 >80–90 >90–100 >100–150 >150–200 >200–300 >300–400 >400–500 >500–600

Interval >30 to 100 cm

(10-cm increments)

Interval >1 to 2 m

(50-cm increments)

Interval >2 to 6 m

(100-cm increments)

Scientific Investigations Map 3341

Map B

STELLWAGEN BANK NATIONAL MARINE SANCTUARY

S T E L L W A G E N B A N K

N I N E T Y M E T E R B A N K S

NORTH 

NINETY

BANK

SOUTH

NINETY

BANK

EAST

NINETY

BANK

MIDDLE

NINETY

BANK

Any use of trade, firm, or product names is for descriptive purposes only and does not imply 

endorsement by the U.S. Government

Digital files available at http://pubs.usgs.gov/sim/3341/

Sd iiVliPCd GllLB2015Sbd dB f Sbd 

Map B.—Seabed Ruggedness

Seabed Maps Showing Topography, Ruggedness, Backscatter Intensity, Sediment Mobility, and the

Distribution of Geologic Substrates in Quadrangle 6 of the Stellwagen Bank National Marine Sanctuary Region 

Offshore of Boston, Massachusetts

Merrimack River

CAPE

ANN

Plymouth

Provincetown

Gloucester

BOSTON

MAS SACHUSETTS BAY

GULF

OF

MAINE

71°00'W 70°45'W 70°30'W 70°15'W 70°00'W

40

200

100

100

100

100

80

80

80

80

40

80

80

40

100

80 40

40

CAPE COD BAY

8

5

9

10 11 12

4

1 2 3

14 15

181716

13

7

42°45'N

42°30'N

42°15'N

42°00'N

STELLWAGEN

6

BASIN

TILLIES BANK

STELLWAGEN BANK

RACE POINT CHANNEL

JEFFREYS LEDGE

Mercator projection

Geodetic Reference System 1980; North American Datum of 1983

Longitude of central meridian 70°19' W; latitude of true scale 41°39' N

False easting 0 m; false northing 0 m

This map is not intended for navigational purposes.

SCALE 1:25 000 

ONE CENTIMETER ON THE MAP REPRESENTS 250 METERS ON THE SEA FLOOR 

1 .5 0 1 2 3 4 KILOMETERS

1 .5 0 1 2 NAUTICAL MILES 

CONTOUR INTERVAL 5 METERS

ADDITIONAL 1-METER CONTOURS INCLUDED TO SHOW BOTTOM ROUGHNESS

DATUM MEAN LOWER LOW WATER

Figure 3. Seabed ruggedness imagery shown on Map B.
6 Seabed Maps of Quadrangle 6 in the Stellwagen Bank National Marine Sanctuary Region Offshore of Boston, Mass.

For Map B, seabed TRI values were calculated to determine the average change in water depth between a central 13-m 

pixel and the eight pixels that surround it, an area measuring 39×39 m. Subsequently, a smoothing filter was applied to the 

ruggedness index image. The filter calculated the mean of the seabed TRI value of each pixel and its eight neighboring 

pixels. Map colors represent the average change in elevation, in centimeters (cm), which is shown in 10-cm increments in the 

30 to 100 cm range, in 50-cm increments in the >100 to 200 cm range, and in 100-cm increments in the >200 to 600 cm range. 

Average changes in elevation less than 30 cm are not shown in color. For example, on the map, blue represents central pixels 

having an average elevation change of >70 to 80 cm with respect to their surrounding eight-pixel areas.

Seabed ruggedness ranges from a low of 0 to 30 cm in much of quadrangle 6 to a high of 200 to 400 cm on the steep 

flanks of the Ninety Meter Banks (substrate F of Map D) in the eastern part of the quadrangle. Ruggedness values in the 

0 to 30 cm range represent an area of approximately 188 km2, whereas values in the >200 to 400 cm range represent only 

0.4 km2 (table 3). To view maps and a description of seabed ruggedness and slope of the entire Stellwagen Bank National 

Marine Sanctuary region see Maps D and E, respectively, of Valentine (2005).

Table 3. Areas of the seabed represented by ruggedness intervals.

[Areas of seabed are represented by four ruggedness intervals of 0 to 30 centimeters (cm), >30 to 100 cm, >100 to 200 cm, and >200 to 400 cm. Data in 

columns 3 and 4 are rounded to one decimal place. Areas of seabed represented by ruggedness intervals in all 18 quadrangles of the Stellwagen Bank National 

Marine Sanctuary (SBNMS) region are listed in table 1 of Map D of Valentine (2005). Abbreviation used: km2, square kilometer]

Region Area

(km2

)

Area of seabed within four ruggedness intervals

(km2

)

Area of seabed within four ruggedness intervals

(percent)

0–30 cm >30–100 cm >100–200 cm >200–400 cm 0–30 cm >30–100 cm >100–200 cm >200–400 cm

Quadrangle 6 211 187.7 20.2 2.4 0.4 89.1 9.6 1.2 0.2

SBNMS portion of

quadrangle 6

157 150.4 6.4 0.4 0 95.7 4.1 0.2 0
Map C. Backscatter Intensity and Sun-Illuminated Topography 7

Map C. Backscatter Intensity and Sun-Illuminated Topography

Map C (see figure 4) shows imagery of seabed backscatter intensity derived from multibeam sonar data. Backscatter 

intensity values (1–8) are a measure of the strength of sound waves reflected from the seabed. When color-coded and 

mapped, they reveal patterns that are a useful guide for delineating the geographic extent of substrate types. Backscatter 

values of yellow to red (6–8) represent relatively hard substrates and those of blue to blue-green (1–3) relatively soft 

substrates. Highest values (7, 8) are found on a portion of Stellwagen Bank (substrates C and D1 of Map D) and on the tops 

of the Ninety Meter Banks (substrates C and D2) and represent boulder ridges and pebble, cobble, boulder gravel partially 

veneered by coarse-grained sand. Lowest values (1, 2) are found in the deepest parts of the valleys that separate the Ninety 

Meter Banks (substrates G1, G2) and represent muddy, fine-grained sand. Intermediate values (3–6) represent both fine- and 

coarse-grained sand that constitute much of the seabed in the quadrangle. Interpretations of backscatter intensity patterns in 

quadrangle 6 are based on sediment grain-size analyses and video and photographic imagery of the seabed. It is not possible 

to recognize the substrate types mapped in this report using backscatter intensity alone. 

Figure 4. Backscatter intensity and sun-illuminated topographic imagery shown on Map C.

70°13' 70°10' 70°08' 70°06' 70°04' 70°02'

42°18'

42°19'

70°13' 70°11' 70°09' 70°07' 70°05' 70°03'

42°14'

42°16'

42°18'

42°19'

42°14'

42°16'

70°11' 70°09' 70°07' 70°05' 70°03'

70°12' 70°10' 70°08' 70°06' 70°04'

42°17'

42°15'

42°13' 42°13'

42°15'

42°17'

70°12'

70°02'

Prepared in cooperation with the

National Oceanic and Atmospheric Administration

U.S. Department of the Interior

U.S. Geological Survey

SEABED BACKSCATTER INTENSITY INDEX

Scientific Investigations Map 3341

Map C

STELLWAGEN BANK NATIONAL MARINE SANCTUARY

S T E L L W A G E N B A N K

N I N E T Y M E T E R B A N K S

NORTH 

NINETY

BANK

SOUTH

NINETY

BANK

EAST

NINETY

BANK

MIDDLE

NINETY

BANK

Merrimack River

0 20 km

CAPE

ANN

Plymouth

Provincetown

Gloucester

BOSTON

MAS SACHUSETTS BAY

GULF

OF

MAINE

71°00'W 70°45'W 70°30'W 70°15'W 70°00'W

40

200

100

100

100

100

80

80

80

80

40

80

80

40

100

80 40

40

CAPE COD BAY

8

5

9

10 11 12

4

1 2 3

14 15

181716

13

7

42°45'N

42°30'N

42°15'N

42°00'N

41°45'N

6

RACE POINT CHANNEL

STELLWAGEN BASIN

STELLWAGEN BANK

TILLIES BANK JEFFREYS LEDGE

Mercator projection

Geodetic Reference System 1980; North American Datum of 1983

Longitude of central meridian 70°19' W; latitude of true scale 41°39' N

False easting 0 m; false northing 0 m

This map is not intended for navigational purposes.

Map C.—Backscatter Intensity and Sun-Illuminated Topography

Seabed Maps Showing Topography, Ruggedness, Backscatter Intensity, Sediment Mobility, and the

Distribution of Geologic Substrates in Quadrangle 6 of the Stellwagen Bank National Marine Sanctuary Region

Offshore of Boston, Massachusetts

SCALE 1:25 000 

ONE CENTIMETER ON THE MAP REPRESENTS 250 METERS ON THE SEA FLOOR 

CONTOUR INTERVAL 5 METERS

DATUM MEAN LOWER LOW WATER

1 .5 0 1 2 3 4 KILOMETERS

1 .5 0 1 2 NAUTICAL MILES 

Soft Seabed Type Hard

Low 1 2 3 4 5 6 7 8 High

Any use of trade, firm, or product names is for descriptive purposes only and does not imply 

endorsement by the U.S. Government

Digital files available at http://pubs.usgs.gov/sim/3341/

Suggested citation: Valentine, P.C., and Gallea, L.B., 2015, Backscatter intensity and sun-illuminated 

topography, map C of Seabed maps showing topography, ruggedness, backscatter intensity, 

f f S
8 Seabed Maps of Quadrangle 6 in the Stellwagen Bank National Marine Sanctuary Region Offshore of Boston, Mass.

Map D. Distribution of Geologic Substrates

Figure 5. Geologic substrates and sun-illuminated topographic imagery shown on Map D, sheet 4.

70°13' 70°10' 70°08' 70°06' 70°04' 70°02'

42°18'

42°19'

70°13' 70°11' 70°09' 70°07' 70°05' 70°03'

42°14'

42°16'

42°18'

42°19'

42°14'

42°16'

70°11' 70°09' 70°07' 70°05' 70°03'

70°12' 70°10' 70°08' 70°06' 70°04'

42°17'

42°15'

42°13' 42°13'

42°15'

42°17'

70°12'

70°02'

A1 r_cgS

B r_cgS / i_cbG D1 i_cgS / pcbG

C i_cbG

E i_cgS

D2 i_mcgS / pcbG

F i_cgS / pcbG

G2 i_mfgS

G1 i_mfgS

A2 i_cgS

A1 r_cgS

D2 i_mcgS / pcbG

F i_cgS / pcbG

STELLWAGEN BANK NATIONAL MARINE SANCTUARY

S T E L L W A G E N B A N K

N I N E T Y M E T E R B A N K S

NORTH 

NINETY

BANK

SOUTH

NINETY

BANK

EAST

NINETY

BANK

MIDDLE

NINETY

BANK

DESCRIPTION OF MAP UNITS

[Grain-size composition of each map unit is given as mean weight percent for each grain-size category 

(table 5). Weight percent values may not add to 100 due to rounding. Texture characteristics for 

substrates B, D1, D2, and F represent the partial sediment veneer overlying gravel. Substrate unit names 

(tables 6, 7) describe sediment grain-size composition, surficial morphology, sediment layering, and the 

mobility or immobility of their surfaces. See Conversion Factors for grain-size classification of 

sediment grades (Wentworth, 1922) and composite sediment grades of this study. Sand is divided into 

two composite grades: fine-grained sand (fgS; 0.062 to <0.25 mm) and coarse-grained sand (cgS; 0.25 

to <2mm). Gravel is also divided into two composite grades: Gravel1

 (G1; 2 to <8 mm) and Gravel2 (G2; 

8 to <64 mm). Abbreviations: r, rippled; i, immobile; m, muddy (≥10 weight percent mud); fgS, 

fine-grained sand; cgS, coarse-grained sand; G1, Gravel1; G2, Gravel2; p, pebble; c, cobble; b, boulder. 

The notation “i_cGS / pcbG” means “immobile, coarse-grained sand; partial veneer on pebble, cobble, 

boulder gravel.” See Mapping Methods for further explanation]

Rippled, coarse-grained sand—Substrate A1 is a mobile sand deposit on the upper 

flank of Stellwagen Bank. Depth range is 30 to 56 m. Mean weight percents per 

grain-size category: mud, <1; sand, 90 (fgS, 3; cgS, 88); gravel 9 (G1, 8; G2, 1). 

Substrate A1 is equivalent to the mobile portion of adjacent substrate B; and it is 

similar to adjacent immobile substrate A2 which lies at deeper depths (53–77 m) 

on the lower flank of Stellwagen Bank and contains more fine-grained sand (11 

weight percent)

Immobile, coarse-grained sand—Substrate A2 is an immobile sand deposit on the 

lower flank of Stellwagen Bank. Depth range is 53 to 77 m. Mean weight 

percents per grain-size category: mud, 1; sand, 83 (fgS, 11; cgS, 72); gravel, 16 

(G1

, 11; G2, 5). Substrate A2 is similar to adjacent mobile substrate A1 which lies 

at shallower depths (30–56 m) and contains less fine-grained sand (3 weight 

percent). It contains less mud and fine-grained sand than substrate E

Mean weight percents per grain-size category: mud, <1; sand, 92 (fgS, 5; cgS, 

86); gravel, 8 (G1

, 7; G2, 1). Cobbles and boulders are identified on the basis of 

video and photographic imagery. Boulder ridges (substrate C) are present. The 

mobile sand layer of substrate B is equivalent to adjacent mobile substrate A1

Immobile, cobble, boulder gravel—Substrate C is immobile gravel that forms 

topographic ridges where cobbles and boulders are piled upon one another and are 

separated by voids. It is identified on the basis of video and photographic images 

of mapped topographic ridges. It is present on the flank of Stellwagen Bank 

where it is associated with substrate B (36–58 m) and substrate D1 (50–83 m), 

and on the tops of North, East, and Middle Ninety Banks where it is associated 

with substrate D2 (87–105 m). Equivalent to boulder ridges <1 m and ≥1 m on 

Maps A, E, F, and G

Immobile, coarse-grained sand; partial veneer on pebble, cobble, boulder 

gravel—Substrate D1 is a layered substrate of immobile sand overlying immobile 

gravel on the flank of Stellwagen Bank. Depth range is 50 to 83 m. Mean weight 

percents per grain-size category: mud, 4; sand, 50 (fgS, 16; cgS, 34); gravel, 45 

(G1

, 11; G2, 34). Pebbles, cobbles, and boulders are identified on the basis of 

video and photographic imagery. Boulder ridges (substrate C) are present. 

Substrate D1 is similar to substrate D2 which lies at deeper depths (87–105 m) on 

the tops of North, East, and Middle Ninety Banks and has higher mud content (12 

weight percent)

Immobile, muddy, coarse-grained sand; partial veneer on pebble, cobble, boulder 

gravel—Substrate D2 is a layered substrate of immobile sand overlying immobile 

gravel on the tops of North, East, and Middle Ninety Banks. Depth range is 87 to 

105 m. Mean weight percents per grain-size category: mud, 12; sand, 76 (fgS, 22; 

cgS, 55); gravel, 12 (G1

, 8; G2, 4). Pebbles, cobbles, and boulders are identified 

on the basis of video and photographic imagery. Boulder ridges (substrate C) are 

presentSubstrate D2 is similar to substrate D1 which lies at shallower depths 

Immobile, coarse-grained sand—Substrate E is an immobile sand deposit on the 

lower flank of Stellwagen Bank. Depth range is 66 to 122 m. Mean weight 

percents per grain-size category: mud, 4; sand, 82 (fgS, 18; cgS, 64); gravel, 14 

(G1

, 9; G2, 5). Boulder ridges are absent. Substrate E is similar in mud content to 

substrate D1 and contains more mud and fine-grained sand than substrate A2

Immobile, coarse-grained sand; partial veneer on pebble, cobble, boulder 

gravel—Substrate F is a layered substrate of immobile sand overlying immobile 

gravel on the flanks of the Ninety Meter Banks. Depth range is 90 to 148 m. 

Mean weight percents per grain-size category: mud, 9; sand, 69 (fgS, 25; cgS, 

44); gravel, 22 (G1

, 13; G2, 9). Pebbles, cobbles, and boulders are identified on 

the basis of video and photographic imagery. Boulder ridges are absent. 

Substrate F is similar to substrates D1 and D2, except that F lies at deeper depths, 

and the partial veneer of coarse grained sand on the gravel is more extensive

Immobile, muddy, fine-grained sand—Substrate G1 is an immobile muddy sand 

deposit in valleys between Stellwagen Bank and the Ninety Meter Banks. Depth 

range is 85 to 171 m. Mean weight percents per grain-size category: mud, 10; 

sand, 88 (fgS, 78; cgS, 10); gravel, 1 (G1

, 1; G2, 1). Substrate G1 is similar to 

substrate G2 which lies at deeper depths (125–185 m) and has higher 4 phi sand 

(58 weight percent) and higher mud content (23 weight percent)

Immobile, muddy, fine-grained sand—Substrate G2 is an immobile muddy sand 

deposit in deep parts of valleys lying between the Ninety Meter Banks. Depth 

range is 125 to 185 m. Mean weight percents per grain-size category: mud, 23; 

sand, 77 (fgS, 77; cgS, 1); gravel, 0. Substrate G2 has the highest mud content of 

all substrates in quadrangle 6

A1 r_cgS

A2 i_cgS

C i_cbG

D1 i_cgS / pcbG

D2 i_mcgS / pcbG

E i_cgS

F i_cgS / pcbG

G1 i_mfgS

G2 i_mfgS

Prepared in cooperation with the

National Oceanic and Atmospheric Administration

Scientific Investigations Map 3341

Map D, sheet 4

Mercator projection

Geodetic Reference System 1980; North American Datum of 1983

Longitude of central meridian 70°19' W; latitude of true scale 41°39' N

False easting 0 m; false northing 0 m

This map is not intended for navigational purposes.

SCALE 1:25 000 

ONE CENTIMETER ON THE MAP REPRESENTS 250 METERS ON THE SEA FLOOR 

1 .5 0 1 2 3 4 KILOMETERS

1 .5 0 1 2 NAUTICAL MILES 

CONTOUR INTERVAL 5 METERS

ADDITIONAL 1-METER CONTOURS INCLUDED TO SHOW BOTTOM ROUGHNESS

DATUM MEAN LOWER LOW WATER

Merrimack River

0 20 km

CAPE COD

CAPE

ANN

Plymouth

Provincetown

BOSTON

MAS SACHUSETTS BAY

GULF

OF

MAINE

71°00'W 70°45'W 70°30'W 70°15'W 70°00'W

40

200

100

100

100

100

80

80

80

80

40

80

80

40

100

80 40

40

CAPE COD BAY

8

5

9

10 11 12

4

1 2 3

14 15

181716

13

7

42°45'N

42°30'N

42°15'N

42°00'N

41°45'N

6

Gloucester

RACE POINT CHANNEL

STELLWAGEN BASIN

STELLWAGEN BANK

JEFFREYS LEDGE

TILLIES BANK

U.S. Department of the Interior

U.S. Geological Survey

The geologic substrates of quadrangle 6 were formed by glacial processes of erosion and deposition, were subsequently 

modified by the effects of rising postglacial sea-level, and presently are affected by storm and tidal currents. A discussion of the 

morphology of seabed features in this quadrangle and their origin can be found in Valentine and others (1999, 2010). Map D 

(see figure 5) shows the distribution of 10 substrates characterized by grain-size composition, surface morphology, sediment 

layering, the mobility or immobility of their surfaces, and water depth range. For layered substrates, grain-size analysis was 

performed on samples collected from the upper layer of sand that partially covers pebble, cobble, or boulder gravel. Substrates 

range widely in character from ridges of piled boulders to smooth, muddy, fine-grained sand. The shallow surfaces of banks 

are characterized by relatively coarse sediments, including coarse-grained sand, complex substrates of sand partially covering 

gravel, and boulder ridges in some parts. The deep valleys are floored by relatively fine sediments which increase in mud 

content with water depth. The flanks of banks are transition zones where substrates grade from shallower coarse sediment to 

deeper fine sediment. For further explanation of substrate analysis, see the Mapping Methods section of this report (table 4).
Map D. Distribution of Geologic Substrates 9

Sheet 1. Seabed geology.—Map D, sheet 1 shows the distribution of 10 geologic substrates.

Sheet 2. Seabed geology and stations.—Map D, sheet 2 shows the distribution of 10 geologic 

substrates and locations of sampling stations and video drift tracks.

Sheet 3. Seabed geology and station data types.—Map D, sheet 3 shows the distribution of 

10 geologic substrates and locations of stations and data types (grain-size analyses, photo and 

video imagery) used to recognize substrates.

Sheet 4. Seabed geology and sun-illuminated topography.—Map D, sheet 4 (see figure 5) shows 

the distribution of 10 geologic substrates overlaid on sun-illuminated topography to show the 

relationship between substrate types and seabed features.

Description of Map Units (Also Printed on Map D Sheets)

[Grain-size composition of each map unit is given as mean weight percent for each grainsize category (table 5). Weight percent values may not add to 100 due to rounding. Textural 

characteristics for substrates B, D1, D2, and F represent the partial sediment veneer overlying gravel. Substrate unit names (tables 6, 7) describe sediment grain-size composition, 

surficial morphology, sediment layering, and the mobility or immobility of their surfaces. 

See Conversion Factors for a grain-size classification of sediment grades (Wentworth, 1922) 

and composite sediment grades of this study. Sand is divided into two composite grades: 

fine-grained sand (fgS; 0.062 to <0.25 mm) and coarse-grained sand (cgS; 0.25 to <2 mm). 

Gravel is also divided into two composite grades: Gravel1

 (G1; 2 to <8 mm) and Gravel2

(G2; 8 to <64 mm). Abbreviations: r, rippled; i, immobile; m, muddy (≥10 weight percent mud); 

fgS, fine-grained sand; cgS, coarse-grained sand; G1, Gravel1; G2, Gravel2; p, pebble; c, cobble; 

b, boulder. The notation “i_cgS / pcbG” means “immobile, coarse-grained sand; partial veneer 

on pebble, cobble, boulder gravel.” See Mapping Methods for further explanation]

A1 r_cgS—Rippled, coarse-grained sand.—Substrate A1 is a mobile sand deposit on the 

upper flank of Stellwagen Bank. Depth range is 30 to 56 m. Mean weight percents per grainsize category: mud, <1; sand, 90 (fgS, 3; cgS, 88); gravel, 9 (G1

, 8; G2, 1). Substrate A1 is 

equivalent to the mobile portion of adjacent substrate B; and it is similar to adjacent immobile 

substrate A2 which lies at deeper depths (53–77 m) on the lower flank of Stellwagen Bank and 

contains more fine-grained sand (11 weight percent).

A2 i_cgS—Immobile, coarse-grained sand.—Substrate A2 is an immobile sand deposit on the 

lower flank of Stellwagen Bank. Depth range is 53 to 77 m. Mean weight percents per grainsize category: mud, 1; sand, 83 (fgS, 11; cgS, 72); gravel, 16 (G1

, 11; G2, 5). Substrate A2 is 

similar to adjacent mobile substrate A1 which lies at shallower depths (30–56 m) and contains 

less fine-grained sand (3 weight percent). It contains less mud and fine-grained sand than 

substrate E.

B r_cgS / i_cbG.—Rippled, coarse-grained sand; partial veneer on immobile, cobble, boulder 

gravel—Substrate B is a layered substrate of mobile sand overlying immobile gravel on the 

shallow flank of Stellwagen Bank. Depth range is 36 to 58 m. Mean weight percents per 

grain-size category: mud, <1; sand, 92 (fgS, 5; cgS, 86); gravel, 8 (G1, 7; G2, 1). Cobbles 

and boulders are identified on the basis of video and photographic imagery. Boulder ridges 

(substrate C) are present. The mobile sand layer of substrate B is equivalent to adjacent mobile 

substrate A1. 

C i_cbG—Immobile, cobble, boulder gravel.—Substrate C is immobile gravel that forms 

topographic ridges where cobbles and boulders are piled upon one another and are separated 

by voids. It is identified on the basis of video and photographic images of mapped topographic 

ridges. It is present on the flank of Stellwagen Bank where it is associated with substrate B 

(36–58 m) and Substrate D1 (50–83 m), and on the tops of North, East, and Middle Ninety 

Banks where it is associated with substrate D2 (87–105 m). It is equivalent to boulder ridges 

<1 m and ≥1 m on Maps A, E, F, and G.
10 Seabed Maps of Quadrangle 6 in the Stellwagen Bank National Marine Sanctuary Region Offshore of Boston, Mass.

Description of Map Units (Also Printed on Map D Sheets)—Continued

D1 i_cgS / pcbG.—Immobile, coarse-grained sand; partial veneer on pebble, cobble, boulder 

gravel—Substrate D1 is a layered substrate of immobile sand overlying immobile gravel on 

the flank of Stellwagen Bank. Depth range is 50 to 83 m. Mean weight percents per grain-size 

category: mud, 4; sand, 50 (fgS, 16; cgS, 34); gravel, 45 (G1, 11; G2, 34). Pebbles, cobbles, 

and boulders are identified on the basis of video and photographic imagery. Boulder ridges 

(substrate C) are present. Substrate D1 is similar to substrate D2 which lies at deeper depths 

(87–105 m) on the tops of North, East, and Middle Ninety Banks and has higher mud content 

(12 weight percent). 

D2 i_mcgS / pcbG.—Immobile, muddy, coarse-grained sand; partial veneer on pebble, cobble, 

boulder gravel—Substrate D2 is a layered substrate of immobile sand overlying immobile 

gravel on the tops of North, East, and Middle Ninety Banks. Depth range is 87 to 105 m. 

Mean weight percents per grain-size category: mud, 12; sand, 76 (fgS, 22; cgS, 55); gravel, 12 

(G1, 8; G2, 4). Pebbles, cobbles, and boulders are identified on the basis of video and photographic imagery. Boulder ridges (substrate C) are present. Substrate D2 is similar to substrate 

D1 which lies at shallower depths (50– 83 m) on the flank of Stellwagen Bank and has lower 

mud content (4 weight percent). 

E i_cgS.—Immobile, coarse-grained sand—Substrate E is an immobile sand deposit on the 

lower flank of Stellwagen Bank. Depth range is 66 to 122 m. Mean weight percents per grainsize category: mud, 4; sand, 82 (fgS, 18; cgS, 64); gravel, 14 (G1

, 9; G2, 5). Boulder ridges are 

absent. Substrate E is similar in mud content to substrate D1 and contains more mud and finegrained sand than substrate A2.

F i_cgS / pcbG.—Immobile, coarse-grained sand; partial veneer on pebble, cobble, boulder 

gravel—Substrate F is a layered substrate of immobile sand overlying immobile gravel on the 

flanks of the Ninety Meter Banks. Depth range is 90 to 148 m. Mean weight percents per grainsize category: mud, 9; sand, 69 (fgS, 25; cgS, 44); gravel, 22 (G1

, 13; G2, 9). Pebbles, cobbles, 

and boulders are identified on the basis of video and photographic imagery. Boulder ridges are 

absent. Substrate F is similar to substrates D1 and D2, except that F lies at deeper depths, and 

the partial veneer of coarse grained sand on the gravel is more extensive.

G1 i_mfgS.—Immobile, muddy, fine-grained sand—Substrate G1 is an immobile muddy 

sand deposit in valleys between Stellwagen Bank and the Ninety Meter Banks. Depth range 

is 85 to 171 m. Mean weight percents per grain-size category: mud, 10; sand, 88 (fgS, 78; 

cgS, 10); gravel, 1 (G1, 1; G2, 1). Substrate G1 is similar to substrate G2 which lies at deeper 

depths (125–185 m) and has higher 4 phi sand (58 weight percent) and higher mud content 

(23 weight percent).

G2 i_mfgS.—Immobile, muddy, fine-grained sand—Substrate G2 is an immobile muddy sand 

deposit in the deep parts of valleys lying between the Ninety Meter Banks. Depth range is 

125 to 185 m. Mean weight percents per grain-size category: mud, 23; sand, 77 (fgS, 77; 

cgS, 1); gravel, 0. Substrate G2 has the highest mud content of all substrates in quadrangle 6.
Map E. Sediment Mobility 11

Map E. Sediment Mobility

Map E (see figure 6) shows the 10 geologic substrates of Map D classified as four substrate types on the basis of the 

mobility of their surfaces as determined by the presence or absence of sand ripples and gravel features observed in video and 

photographic imagery. Mobile, rippled sand represents substrate A1. A combination of mobile, rippled sand and immobile 

gravel features that the sand partially covers represents substrate B. Boulder ridges (two mapped units based on height above 

the seabed), which are large, immobile features of gravel substrate, represent substrate C. Immobile sediment is represented 

by all other substrates based on the absence of sediment ripples.

Figure 6. Distribution of mobile and immobile substrates shown on Map E.

70°13' 70°10' 70°08' 70°06' 70°04' 70°02'

42°18'

42°19'

70°13' 70°11' 70°09' 70°07' 70°05' 70°03'

42°14'

42°16'

42°18'

42°19'

42°14'

42°16'

70°11' 70°09' 70°07' 70°05' 70°03'

70°12' 70°10' 70°08' 70°06' 70°04'

42°17'

42°15'

42°13' 42°13'

42°15'

42°17'

70°12'

70°02'

U.S. Department of the Interior

U.S. Geological Survey

Scientific Investigations Map 3341

Map E

STELLWAGEN BANK NATIONAL MARINE SANCTUARY

S T E L L W A G E N B A N K

N I N E T Y M E T E R B A N K S

NORTH 

NINETY

BANK

SOUTH

NINETY

BANK

EAST

NINETY

BANK

MIDDLE

NINETY

BANK

Mercator projection

Geodetic Reference System 1980; North American Datum of 1983

Longitude of central meridian 70°19' W; latitude of true scale 41°39' N

False easting 0 m; false northing 0 m

This map is not intended for navigational purposes.

DESCRIPTION OF MAP UNITS [Sediment mobility is based on the presence of sand ripples observed in video and 

photographic imagery. See Mapping Methods for explanation of topographic contour 

intervals]

Mobile sediment—Rippled sand; equivalent to substrate A1 of Map D

Mobile and immobile sediment—Rippled sand overlying immobile cobble 

and boulder gravel; equivalent to substrate B of Map D

Immobile sediment—Sand, sand partial veneer on gravel, and muddy sand; 

equivalent to substrates A2, D1, D2, E, F, G1, and G2 of Map D

Boulder ridges <1 m in height—Equivalent to substrate C of Map D

Boulder ridges ≥1 m in height—Equivalent to substrate C of Map D 200

100

80 40

Merrimack River

0 20 km

CAPE COD

CAPE

ANN

Plymouth

Provincetown

Gloucester

BOSTON

MAS SACHUSETTS BAY

GULF

OF

MAINE

71°00'W 70°45'W 70°30'W 70°15'W 70°00'W

Location Map.—Shows quadrangle 6 (highlighted in yellow). Stellwagen Bank 

National Marine Sanctuary boundary is shown as a dashed line. Bathymetric 

contours are labeled in meters.

40

100

100

100

100

80

80

80

80

40

80

80

40

40

CAPE COD BAY

8

5

9

10 11 12

4

1 2 3

14 15

181716

13

7

42°45'N

42°30'N

42°15'N

42°00'N

41°45'N

6

RACE POINT CHANNEL

STELLWAGEN BANK

BASIN STELLWAGEN

JEFFREYS LEDGE

TILLIES BANK

Map E.—Sediment Mobility

Seabed Maps Showing Topography, Ruggedness, Backscatter Intensity, Sediment Mobility, and the

Distribution of Geologic Substrates in Quadrangle 6 of the Stellwagen Bank National Marine Sanctuary Region

Offshore of Boston, Massachusetts

By

Page C. Valentine and Leslie B. Gallea

2015

Any use of trade, firm, or product names is for descriptive purposes only and does not imply 

endorsement by the U.S. Government

Digital files available at http://pubs.usgs.gov/sim/3341/

Suggested citation: Valentine, P.C., and Gallea, L.B., 2015, Sediment mobility, map E of Seabed 

maps showing topography, ruggedness, backscatter intensity, sediment mobility, and the 

distribution of geologic substrates in quadrangle 6 of the Stellwagen Bank National Marine 

Sanctuary region offshore of Boston, Massachusetts: U.S. Geological Survey Scientific 

Investigations Map 3341, scale 1:25,000, http://dx.doi.org/10.3133/sim3341.

ISSN 2329-132X (online)

http://dx.doi.org/10.3133/sim3341

Prepared in cooperation with the

National Oceanic and Atmospheric Administration

SCALE 1:25 000 

ONE CENTIMETER ON THE MAP REPRESENTS 250 METERS ON THE SEA FLOOR 

1 .5 0 1 2 3 4 KILOMETERS

1 .5 0 1 2 NAUTICAL MILES 

CONTOUR INTERVAL 5 METERS

ADDITIONAL 1-METER CONTOURS INCLUDED TO SHOW BOTTOM ROUGHNESS

DATUM MEAN LOWER LOW WATER
12 Seabed Maps of Quadrangle 6 in the Stellwagen Bank National Marine Sanctuary Region Offshore of Boston, Mass.

Map F. Distribution of Fine- and Coarse-Grained Sand

Map F (see figure 7) shows nine geologic substrates of Map D (excluding substrate C, boulder ridges) classified as two 

substrate types on the basis of grain-size analysis (table 5). Both the unlayered substrates (A1, A2, E, G1, G2) and the upper 

parts of layered substrates (B, D1, D2, F) have higher weight percentages of sand than of gravel or mud. Substrates included 

in the coarse-grained sand composite (A1, A2, B, D1, D2, E, F) contain ≥50 mean weight percent sand, of which the largest 

portion is coarse-grained sand (2+1+0 phi). Substrates in the fine-grained sand composite (G1, G2) also contain ≥50 mean 

weight percent sand, but the largest portion is fine-grained sand (3+4 phi), and it has a higher mud content than the coarsegrained sand substrate.

Figure 7. Distribution of fine- and coarse-grained sand substrates and immobile boulder ridges shown on Map F.

70°13' 70°10' 70°08' 70°06' 70°04' 70°02'

42°18'

42°19'

70°13' 70°11' 70°09' 70°07' 70°05' 70°03'

42°14'

42°16'

42°18'

42°19'

42°14'

42°16'

70°11' 70°09' 70°07' 70°05' 70°03'

70°12' 70°10' 70°08' 70°06' 70°04'

42°17'

42°15'

42°13'

42°15'

42°17'

70°12'

70°02'

Prepared in cooperation with the

National Oceanic and Atmospheric Administration

U.S. Department of the Interior

U.S. Geological Survey

42°13'

Scientific Investigations Map 3341

Map F

STELLWAGEN BANK NATIONAL MARINE SANCTUARY

S T E L L W A G E N B A N K

N I N E T Y M E T E R B A N K S

NORTH 

NINETY

BANK

SOUTH

NINETY

BANK

EAST

NINETY

BANK

MIDDLE

NINETY

BANK

DESCRIPTION OF MAP UNITS [Fine-grained and coarse-grained sand content is given as mean weight percent. Grain 

sizes are listed in phi units. See table 5 for textural characteristics of individual 

substrates. See Mapping Methods for explanation of topographic contour intervals]

Substrate dominated by fine-grained sand—Muddy sand in which 

fine-grained sand (3 and 4 phi combined) constitutes the largest portion 

of the sand fraction; equivalent to substrates G1 and G2 of Map D

Substrate dominated by coarse-grained sand—Sand and sand partial 

veneer on gravel in which coarse-grained sand (2, 1, and 0 phi 

combined) constitutes the largest portion of the sand fraction; equivalent to substrates A1, A2, B, D1, D2, E, and F of Map D

Boulder ridges <1 m in height—Equivalent to substrate C of Map D

Boulder ridges ≥1 m in height—Equivalent to substrate C of Map D

Any use of trade, firm, or product names is for descriptive purposes only and does not imply 

endorsement by the U.S. Government

Digital files available at http://pubs.usgs.gov/sim/3341/

Suggested citation: Valentine, P.C., and Gallea, L.B., 2015, Distribution of fine- and coarse-grained 

sand, map F of Seabed maps showing topography, ruggedness, backscatter intensity, sediment 

mobility, and the distribution of geologic substrates in quadrangle 6 of the Stellwagen Bank 

National Marine Sanctuary region offshore of Boston, Massachusetts: U.S. Geological Survey 

Scientific Investigations Map 3341, scale 1:25,000, http://dx.doi.org/10.3133/sim3341.

ISSN 2329-132X (online)

http://dx.doi.org/10.3133/sim3341

SCALE 1:25 000 

ONE CENTIMETER ON THE MAP REPRESENTS 250 METERS ON THE SEA FLOOR 

1 .5 0 1 2 3 4 KILOMETERS

1 .5 0 1 2 NAUTICAL MILES 

CONTOUR INTERVAL 5 METERS

ADDITIONAL 1-METER CONTOURS INCLUDED TO SHOW BOTTOM ROUGHNESS

DATUM MEAN LOWER LOW WATER

200

100

80 40

Merrimack River

0 20 km

CAPE COD

CAPE

ANN

Plymouth

Provincetown

Gloucester

BOSTON

MAS SACHUSETTS BAY

GULF

OF

MAINE

71°00'W 70°45'W 70°30'W 70°15'W 70°00'W

Location Map.—Shows quadrangle 6 (highlighted in yellow). Stellwagen Bank 

National Marine Sanctuary boundary is shown as a dashed line. Bathymetric 

contours are labeled in meters.

40

100

100

100

100

80

80

80

80

40

80

80

40

40

CAPE COD BAY

8

5

9

10 11 12

4

1 2 3

14 15

181716

13

7

42°45'N

42°30'N

42°15'N

42°00'N

41°45'N

6

RACE POINT CHANNEL

BASIN STELLWAGEN

STELLWAGEN BANK

JEFFREYS LEDGE

TILLIES BANK

Mercator projection

Geodetic Reference System 1980; North American Datum of 1983

Longitude of central meridian 70°19' W; latitude of true scale 41°39' N

False easting 0 m; false northing 0 m

This map is not intended for navigational purposes.

Map F.—Distribution of Fine- and Coarse-grained Sand

Seabed Maps Showing Topography, Ruggedness, Backscatter Intensity, Sediment Mobility, and the

Distribution of Geologic Substrates in Quadrangle 6 of the Stellwagen Bank National Marine Sanctuary Region

Offshore of Boston, Massachusetts

By

Page C. Valentine and Leslie B. Gallea

2015
Map G. Distribution of Substrate Mud Content 13

Map G. Distribution of Substrate Mud Content

Map G (see figure 8) shows nine geologic substrates of Map D (excluding substrate C, boulder ridges) classified as 

five substrate types on the basis of mean mud weight percent (table 5). Mud content generally increases with water depth. 

Substrates containing ≤1 weight percent mud occupy the shallow flank (A1, B) and part of the steep southern flank (A2) 

of Stellwagen Bank. Substrates containing >1 to 5 weight percent mud occupy the northern flank of the bank (D1 and E). 

Substrates containing >5 to 10 weight percent mud occupy the flanks of the Ninety Meter Banks (F) and the shallow parts of 

the valleys between those banks and Stellwagen Bank (G1). A substrate containing >10 to 20 weight percent mud lies on the 

tops of North, East, and Middle Ninety Meter Bank (D2). A substrate containing >20 to <50 weight percent mud, the highest 

of all substrates in this quadrangle, occupies the deep parts of the valleys that separate the Ninety Meter Banks (G2).

Figure 8. Distribution of substrate mud content and immobile boulder ridges shown on Map G.

70°13' 70°10' 70°08' 70°06' 70°04' 70°02'

42°18'

42°19'

70°13' 70°11' 70°09' 70°07' 70°05' 70°03'

42°14'

42°16'

42°18'

42°19'

42°14'

42°16'

70°11' 70°09' 70°07' 70°05' 70°03'

70°12' 70°10' 70°08' 70°06' 70°04'

42°17'

42°15'

42°13' 42°13'

42°15'

42°17'

70°12'

70°02'

Prepared in cooperation with the

National Oceanic and Atmospheric Administration

U.S. Department of the Interior

U.S. Geological Survey Scientific Investigations Map 3341

Map G

STELLWAGEN BANK NATIONAL MARINE SANCTUARY

S T E L L W A G E N B A N K

N I N E T Y M E T E R B A N K S

NORTH 

NINETY

BANK

SOUTH

NINETY

BANK

EAST

NINETY

BANK

MIDDLE

NINETY

BANK

DESCRIPTION OF MAP UNITS

[Mud content is given as mean weight percent. See table 5 for textural characteristics of 

individual substrates. See Mapping Methods for explanation of topographic contour 

intervals]

Mud content ≤1—Equivalent to substrates A1, A2, and B of Map D

Mud content >1 to 5—Equivalent to substrates D1 and E of Map D

Mud content >5 to 10—Equivalent to substrates F and G1 of Map D

Mud content >10 to 20—Equivalent to substrate D2 of Map D

Mud content >20 to 50—Equivalent to substrate G2 of Map D

Boulder ridges <1 m in height—Equivalent to substrate C of Map D

Boulder ridges ≥1 m in height—Equivalent to substrate C of Map D

Merrimack River

0 20 km

CAPE COD

CAPE

ANN

Plymouth

Provincetown

Gloucester

BOSTON

MAS SACHUSETTS BAY

GULF

OF

MAINE

71°00'W 70°45'W 70°30'W 70°15'W 70°00'W

Location Map.—Shows quadrangle 6 (highlighted in yellow). Stellwagen Bank 

National Marine Sanctuary boundary is shown as a dashed line. Bathymetric 

contours are labeled in meters.

40

200

100

100

100

100

80

80

80

80

40

80

80

40

100

80 40

40

CAPE COD BAY

8

5

9

10 11 12

4

1 2 3

14 15

181716

13

7

42°45'N

42°30'N

42°15'N

42°00'N

41°45'N

6

RACE POINT CHANNEL

STELLWAGEN BANK

BASIN STELLWAGEN

JEFFREYS LEDGE

TILLIES BANK

Any use of trade, firm, or product names is for descriptive purposes only and does not imply 

endorsement by the U.S. Government

Digital files available at http://pubs.usgs.gov/sim/3341/

Suggested citation: Valentine, P.C., and Gallea, L.B., 2015, Distribution of substrate mud content, 

map G of Seabed maps showing topography, ruggedness, backscatter intensity, sediment mobility, 

and the distribution of geologic substrates in quadrangle 6 of the Stellwagen Bank National Marine 

Sanctuary region offshore of Boston, Massachusetts: U.S. Geological Survey Scientific 

Investigations Map 3341, scale 1:25,000, http://dx.doi.org/10.3133/sim3341.

ISSN 2329-132X (online)

http://dx.doi.org/10.3133/sim3341

SCALE 1:25 000 

ONE CENTIMETER ON THE MAP REPRESENTS 250 METERS ON THE SEA FLOOR 

1 .5 0 1 2 3 4 KILOMETERS

1 .5 0 1 2 NAUTICAL MILES 

CONTOUR INTERVAL 5 METERS

ADDITIONAL 1-METER CONTOURS INCLUDED TO SHOW BOTTOM ROUGHNESS

DATUM MEAN LOWER LOW WATER

Mercator projection

Geodetic Reference System 1980; North American Datum of 1983

Longitude of central meridian 70°19' W; latitude of true scale 41°39' N

False easting 0 m; false northing 0 m

This map is not intended for navigational purposes.

Map G.—Distribution of Substrate Mud Content

Seabed Maps Showing Topography, Ruggedness, Backscatter Intensity, Sediment Mobility, and the

Distribution of Geologic Substrates in Quadrangle 6 of the Stellwagen Bank National Marine Sanctuary Region

Offshore of Boston, Massachusetts

By

Page C. Valentine and Leslie B. Gallea

2015
14 Seabed Maps of Quadrangle 6 in the Stellwagen Bank National Marine Sanctuary Region Offshore of Boston, Mass.

Mapping Methods

Topographic features are accurately represented by 5-m 

bathymetric contours where the seabed is relatively smooth. 

However, 5-m contours, especially where they are widely 

spaced, do not adequately show the characteristic hummocky 

relief of the seabed in areas dominated by gravel deposits 

and small boulder ridges. In such areas on Maps B and 

D– G, the 5-m contours are supplemented by 1-m contours 

to display complex, low-relief topographic features. In areas 

of relatively smooth seabed where gravel features are absent, 

the 1-m contours are not shown. In these areas, changes in 

water depths recorded by the sonar are not resolvable to 

the extent that they can be contoured at a 1-m interval and 

produce usable information. Such contours produce incoherent 

patterns of lines that misrepresent topographic complexity. 

Bathymetric data are used for seabed ruggedness analysis, 

which delineates topographic features by measuring changes 

in elevation over small areas. For a description of the use 

of bathymetric data to compute seabed ruggedness, see the 

Map B section of this report.

Geologic substrates of the seabed are characterized 

by their physical properties. Multibeam topographic and 

backscatter imagery, video and photographic imagery, 

and sediment grain-size analyses were used to recognize 

10 substrates (Map D, sheets 1–4). Backscatter imagery 

revealed patterns on the seabed characterized by soft to hard 

(muddy to sandy to gravelly) substrates and their relationship 

to seabed topography. Video and photographic imagery 

showed gravel and piled boulder ridge substrates (which are 

difficult to sample), seabed structures related to sediment 

mobility (sand ripples), and partial layering of finer over 

coarser sediments.

Grain-size analyses of seabed samples provided information on mud, sand, and gravel content (table 4). For layered 

substrates (for example, sand partially covering gravel), 

only the top layer was collected and analyzed for sediment 

texture. Individual samples were compared on the basis of 

their textural composition, with special emphasis placed on 

the following:

1. weight percent of phi (φ) grain sizes; 

2. significant phi grain sizes (≥10 weight percent of 

the sample); 

3. mud, sand, and gravel weight percents; 

Combining the traditional five sand grades into two 

composite grades (fine- and coarse-grained sand) was a key 

factor in delineating substrate types. See the Conversion 

Factors section of this report for a grain-size classification 

of sediment grades and composite sediment grades of this 

study (fgS, cgS, G1

, G2 ) in millimeters (mm) and equivalent 

phi units. Gravel particles larger than 6.4 cm (–5 phi) were not 

collected in this study, although cobbles and boulders were 

observed in seabed imagery.

The geologic substrates shown on Map D are described 

on the basis of grain-size composition, significant phi grain 

sizes present, sediment layering, sediment mobility, surface 

morphology, and water depth range (tables 5–7). Each geologic 

substrate is identified by a unique symbol that uses letters 

and numbers such as A1, A2, B, and so forth. A substrate 

is identified and briefly described by a two-part name that 

combines the unique symbol with a non-unique combination of 

characters (table 7) that describe the major physical attributes 

of the substrate. For example, the two-part substrate name 

“B r_cgS / i_cbG” means “substrate B — rippled, coarse-grained 

sand; partial veneer on immobile cobble, boulder gravel.” In 

the present approach to substrate classification, the need to 

construct two-part names that are both informative and brief can 

produce names for two (or more) substrates in which substrate 

symbols are unique but the descriptive parts of the names are 

identical. This is the case for substrates A2 and E (i_cgS), 

D1 and F (i_cgS / pcbG), and G1 and G2 (i_mfgS). Differences 

between substrates that have identical physical attributes 

listed in their names are documented in the Description of 

Map Units section and tables 5 and 6 of this report.

Table 4. Grain-size analyses of sediment samples and 

assignment of stations to geologic substrates.

[Table 4 in Excel format is available at http://dx.doi.org/10.3133/sim3341. 

Grain-size analyses of sediment samples for this quadrangle and the other 

17 quadrangles of the Stellwagen Bank National Marine Sanctuary region 

have been published in USGS Data Series 469 (Valentine and others, 2010)]

4. sand fraction subdivided into fine-grained sand, fgS 

(3 and 4 phi), and coarse-grained sand, cgS (0, 1, 

and 2 phi), in weight percents; 

5. gravel fraction (granules and pebbles only) subdivided 

into G1 (–1 and –2 phi), and G2 (–3, –4, and –5 phi), 

in weight percents; 
Mapping Methods 15

Table 5. Sediment textural characteristics of mapped geologic substrates.

[Textural characteristics for unlayered substrates (A1, A2, E, G1, G2) are based on grain-size analysis. For layered substrates (B, D1, D2, F), textural 

characteristics are based on grain-size analysis of the upper layer of sand that partially veneers pebble, cobble, or boulder gravel. The underlying gravel is 

identified based on video imagery. Substrate C is not listed as it consists of boulder ridges identified by seabed topography and visual inspection using video 

and photographic imagery. Weight percent values may not add to 100 due to rounding; <1 means ≤0.5 weight percent. A sand (4, 3, 2, 1, 0 phi), mud (>4 phi), 

or gravel (G1, G2) grain size is termed “significant” in a substrate if its mean weight percent for all samples of a substrate type is ≥10. Abbreviations used: 

fgS, fine-grained sand (3 and 4 phi combined); cgS, coarse-grained sand (0, 1, and 2 phi combined); G1, Gravel1 (–1 and –2 phi combined); G2, Gravel2 (–3, 

–4, and –5 phi combined); m, meter]

Geologic 

substrate 

symbol

Number

of

samples

Sample 

water depth 

range;

mean

(m)

Mean weight percent of

significant grain sizes, 

phi (φ) units

Weight percent

Samples Mud fgS cgS Sand G1 G2 Gravel

A1 128 30–56 2φ (14), 1φ (45),

0φ (28)

Range 0–1 <1–15 50–98 52–99 <1–26 0–21 <1–47

41 Mean <1 3 88 90 8 1 9

A2 26 53–77 3φ (10), 2φ (19),

1φ (35), 0φ (19)

Range <1–1 2–37 32–93 44–98 1–36 0–35 1–55

62 Mean 1 11 72 83 11 5 16

B 22 36–58 2φ (19), 1φ (40),

0φ (27)

Range 0–1 2–21 65–97 78–99 <1–20 0–8 <1–22

48 Mean <1 5 86 92 7 1 8

D1 28 50–83 3φ (14), 2φ (15),

1φ (11), G1

 (11), G2 (34)

Range 1–9 3–46 7–64 15–92 2–31 3–75 5–81

61 Mean 4 16 34 50 11 34 45

D2 15 87–105 >4φ (12), 3φ (15),

2φ (21), 1φ (23), 0φ (10)

Range 8–22 11–42 34–65 55–89 1–14 0–25 3–34

94 Mean 12 22 55 76 8 4 12

E 31 66–122 3φ (16), 2φ (26),

1φ (28), 0φ (10)

Range 2–10 3–48 24–87 38–98 0–28 0–26 0–53

80 Mean 4 18 64 82 9 5 14

F 21 90–148 3φ (17), 2φ (16),

1φ (17), 0φ (11)

Range 5–14 8–54 20–65 39–91 0–27 0–32 0–54

111 Mean 9 25 44 69 13 9 22

G1 39 85–171 >4φ (10), 4φ (29),

3φ (49)

Range 2–18 44–94 0–39 80–97 <1–5 1–7 0–8

113 Mean 10 78 10 88 1 1 1

G2 9 125–185 >4φ (23), 4φ (58),

3φ (19)

Range 19–29 70–80 0–2 71–81 0–0 0–0 0–0

145 Mean 23 77 1 77 0 0 0
16 Seabed Maps of Quadrangle 6 in the Stellwagen Bank National Marine Sanctuary Region Offshore of Boston, Mass.

Table 6. Geologic substrate symbols, names, and brief descriptions.

[Textural characteristics for substrates B, D1, D2, and F represent the partial sediment veneer overlying pebble, cobble, or boulder gravel. See table 5 for 

textural characteristics of individual substrates; see table 7 for explanation of characters used in the substrate name to describe the physical attributes of 

substrates. Abbreviations used: m, meter; wt pct, weight percent]

Geologic 

substrate 

symbol

Substrate name Substrate name translation Brief description and comparison to other substrates

A1 A1 r_cgS A1—Rippled, coarse-grained sand Substrate A1 is equivalent to the mobile portion of adjacent substrate B; and it is similar to adjacent immobile 

substrate A2 which lies at deeper depths (53–77 m) on 

the lower flank of Stellwagen Bank and contains more 

fine-grained sand (11 wt pct).

A2 A2 i_cgS A2—Immobile, coarse-grained sand Substrate A2 is similar to adjacent mobile substrate A1 

which lies at shallower depths (30–56 m) and contains 

less fine-grained sand (3 wt pct). It contains less mud 

and fine-grained sand than substrate E.

B B r_cgS/i_cbG B—Rippled, coarse-grained sand; 

partial veneer on immobile cobble, 

boulder gravel

Boulder ridges (substrate C) are present. The mobile sand 

layer of substrate B is equivalent to adjacent mobile 

substrate A1.

C C i_cbG C—Immobile, cobble, boulder gravel It is present as boulder ridges on the flank of Stellwagen 

Bank where it is associated with substrate B (36–58 m) 

and substrate D1 (50–83 m), and on the tops of North, 

East, and Middle Ninety Banks where it is associated 

with substrate D2 (87–105 m).

D1 D1 i_cgS/pcbG D1—Immobile, coarse-grained sand; 

partial veneer on pebble, cobble, 

boulder gravel

Substrate D1 is similar to substrate D2 which lies at 

deeper depths (87–105 m) on the tops of North, East, 

and Middle Ninety Banks and has higher mud content 

(12 wt pct). It is also similar to substrate F which lies 

at deeper depths on the flanks of the Ninety Meter 

Banks. Boulder ridges (substrate C) are present.

D2 D2 i_mcgS/pcbG D2—Immobile, muddy, coarsegrained sand; partial veneer on 

pebble, cobble, boulder gravel

Substrate D2 is similar to substrate D1 which lies at 

shallower depths (50–83 m) on the flank of Stellwagen 

Bank and has lower mud content (4 wt pct). Boulder 

ridges (substrate C) are present.

E E i_cgS E—Immobile, coarse-grained sand Substrate E is similar in mud content to substrate D1 

and contains more mud and fine-grained sand than 

substrate A2.

F F i_cgS/pcbG F—Immobile, coarse-grained 

sand; partial veneer on pebble, 

cobble, boulder gravel

Substrate F is similar to substrates D1 and D2, except 

that F lies at deeper depths on the flanks of the Ninety 

Meter Banks, and the partial veneer of coarse grained 

sand on the gravel is more extensive.

G1 G1 i_mfgS G1—Immobile, muddy, finegrained sandSubstrate G1 is similar to substrate G2 which lies at 

deeper depths (125–185 m) and has higher 4 phi sand 

(58 wt pct) and higher mud content (23 wt pct).

G2 G2 i_mfgS G2—Immobile, muddy, finegrained sandSubstrate G2 has the highest mud content (23 wt pct) 

of all substrates in quadrangle 6. See description for 

substrate G1.
Seabed Sediment Collection, Processing, and Analysis 17

Table 7. Characters used in substrate names to describe the physical attributes of 

substrates.

[Sand substrates (≥50 weight percent sand) are classified as fine-grained sand (fgS) or coarse-grained sand 

(cgS) depending on which represents the largest weight percent in the sand fraction. Abbreviation used: mm, 

millimeter]

Attribute

characters

of substrate 

name

Substrate attribute character description, grain size

(phi [φ] units)

b Boulder; diameter ≥256 mm (–8 φ and larger particles)

c Cobble; diameter 64 to <256 mm (–6 and –7 φ)

cgS Coarse-grained sand; diameter 0.25 to <2 mm (2, 1, and 0 φ)

fgS Fine-grained sand; diameter 0.062 to <0.25 mm (4 and 3 φ)

G Gravel, ≥50 weight percent; diameter ≥2 mm (–1 φ and larger particles)

i Immobile

m Muddy; ≥10 to <50 weight percent mud (clay+silt); diameter <0.062 mm (>4 φ)

p Pebble; diameter 4 to <64 mm (–2, –3, –4, and –5 φ)

r Rippled

S Sand, ≥50 weight percent; diameter 0.062 to <2 mm (4, 3, 2, 1, and 0 φ)

/ “Partial veneer on.” For example, “i_cgS/pcbG” means “immobile, coarse-grained 

sand; partial veneer on pebble, cobble, boulder gravel”

Seabed Sediment Collection, 

Processing, and Analysis

As a part of the process of mapping the sea floor, the 

USGS developed the SEABed Observation and Sampling 

System (SEABOSS) to collect samples and video and 

photographic images of the seabed to aid in the interpretation 

of seabed sonar imagery. A modified Van Veen sediment grab 

sampler is mounted in the center of the SEABOSS frame, 

which ensures the sampler is properly oriented on the seabed 

when a sample is collected. Before deployment, the sampler 

bucket’s jaws are opened by collapsing the extended arms to 

a near-horizontal position and locking them in place with two 

catches. The sampler operates passively to sample the seabed; 

it is not spring loaded. 

To collect a sediment sample, the SEABOSS frame was 

lowered gently onto the seabed, reducing tension on the cable, 

which caused the two locking catches to be automatically 

released by gravity. As the cable was retrieved, the grab 

sampler’s arms were pulled upward, closing the bucket around 

the sediment, and the SEABOSS was lifted off the seabed. 

The SEABOSS was retrieved and set upon a wooden 

platform that kept the sampler bucket and camera systems 

above the deck. The sampler’s arms were held in the upright 

position manually or by tension on the cable, the two doors 

on the upper side of the bucket were opened, and the sediment 

was removed. For this project, the upper 2 cm of sediment, 

representing the surface of the seabed, were removed with a 

rectangular shovel 2-cm deep and stored in a plastic bag for 

grain-size analysis. The remaining sediment was dumped 

into a tray on the deck below the sampler and discarded, after 

which the sampler was washed in preparation for sampling 

at the next site. Further information on the SEABOSS can be 

found in Valentine and others (2000).

Grain-size analyses of the sediment samples were 

performed at the USGS Woods Hole Coastal and Marine 

Science Center in Woods Hole, Massachusetts, by using a 

standard suite of analytical methods (Poppe and others, 2005). 

This laboratory has been in operation since 1963 and has 

analyzed many thousands of sediment samples collected by 

the USGS in New England.
18 Seabed Maps of Quadrangle 6 in the Stellwagen Bank National Marine Sanctuary Region Offshore of Boston, Mass.

Seabed Photographs

Photograph collection methods

In addition to collecting sediment samples, the 

SEABOSS is equipped to record video and photographic 

imagery of the seabed. 

The SEABOSS is not a towed system. It incorporates 

a modified Van Veen sediment grab sampler, a still camera, 

two color video cameras, and an array of lasers into a frame 

that is lowered to the seabed from a stationary vessel which 

is then allowed to drift. A navigation receiver is placed on the 

ship at the location from where the SEABOSS is launched. 

The navigation system uses global positioning system (GPS) 

techniques, so locations of photographs are accurate to within 

10 m. During deployment, the camera system hangs directly 

below the side of the ship, and the recorded navigation data 

closely approximate the position of the camera system near 

the seabed. 

The ship was oriented so that wind and waves would 

not cause it to drift over the conducting cable attached to the 

SEABOSS. The winch operator used a video feed from the 

system to maintain the cameras at the proper height above 

the seabed; the scientist used the video feed to decide when 

to trigger the still camera and record the time the photo was 

taken. The height of the camera above the seabed (76 cm; 

30 inches [in.]) and the size of objects in the images were 

determined by viewing a pattern of laser beams on the seabed.

All photographic images were acquired with a Photosea 

underwater-camera system.

Photograph processing methods

Exposed film was developed in bulk 250-exposure rolls 

by a commercial film-processing company. The bulk rolls 

of negatives were then sent for scanning to a commercial 

digitizing company where the negatives were scanned by 

using Kodak Photo CD software (into PCD format images). A 

PCD image file of each negative was generated and archived 

on CD–ROM. PCD images can be used to generate images at 

resolutions ranging from 96×64 pixels to 3072×2048 pixels. 

The PCD images were converted to Joint Photographic 

Experts Group (JPEG) format (Valentine and others, 2010; 

available for downloading in two resolutions: medium 

[1536×1024 pixels], and high [3072×2048 pixels]).

Image information and accessibility

Each photographic image was taken at a height of 

approximately 76 cm (30 in.) above the seabed and represents 

an area of 0.39 m2 (4.17 ft2) that measures 76 cm (30 in.) wide 

and 51 cm (20 in.) long. The data tag on the right-hand margin 

of the image displays information in the following format: 

NNNYYHHMM, where NNN is the image number on the film 

roll, YY is the last 2 digits of the year, and HH and MM are 

time in hours and minutes, respectively.

Seabed photographs have been modified to an 

Exchangeable Image File Format (EXIF) so that important 

image metadata and data can be displayed in the comment 

EXIF tag of the JPEG images. For access to seabed images, 

see Valentine and others (2010).

Data Catalog

This report contains geographic information system 

(GIS) data in both vector and raster format. The vector data 

are provided in shapefile format compatible with Esri ArcView 

and ArcGIS software. These data are in the Geographic North 

American Datum of 1983 (NAD 83) coordinate system. The 

raster data are provided in Esri binary grid format in a custom 

Mercator projection with the following parameters: longitude 

of central meridian 70°19' W., latitude of true scale 41°39' N., 

false easting 0 m, false northing 0 m, datum NAD 83. Data 

layers archived here should not require additional processing 

to be used in Esri software. 

[Abbreviations used: m, meter; ft, foot; s, second]

Camera Photosea model no. 1000A; rated to 305 m 

(1,000 ft)

Strobe Photosea model no. 1500S; rated to 457 m 

(1,500 ft); flash 1/750 s

Lens Nikkor underwater 28-mm lens with a 

+1-diopter lens attachment; aperture set 

between f11 and f16; focus set at 0.8 m 

(2.5 ft)

Film Kodak Portra 400 NC color film; bulk roll 

10-m (33-ft) long with 250 exposures; 

exposure time 1/150 s
Data Catalog 19

Each GIS data layer from this publication is cataloged 

below for easy access. The descriptions of the individual data 

layers are included below the filename. A separate column 

contains a browse graphic showing the data layer extent and 

coverage. Clicking on this graphic will open a larger version 

of the image in a new browser window.

The files necessary to load each dataset into a compatible 

GIS have been compressed into a single zipped file along 

with Federal Geographic Data Committee (FGDC)-compliant 

metadata (HTML, text, and XML formats). A second XML 

metadata format file, generated and viewable by ArcCatalog, is 

also included in the zipped file. For convenience, the FGDCcompliant HTML, text, and XML versions of the metadata 

for each dataset have links provided below. The geologic 

Data Layers and Data for Quadrangle 6

[Abbreviations used: NAD 83, North American Datum of 1983; MB, megabyte; m, meter]

Data-layer name and description View Metadata Download

SIM3341_geologic_interp—Polygon shapefile of HTML SIM3341_geologic_interp.zip

the geologic substrate interpretation of the seabed Text File size: 0.6 MB

in quadrangle 6. Attribute fields can be used XML

to symbolically illustrate the seven individual 

interpretive maps presented in this publication. 

The layer files representing this symbology are 

included in the zipped file. (Geographic, NAD 83)

SIM3341_1m_contours—Polyline shapefile of the HTML SIM3341_1m_contours.zip

1-m contours in quadrangle 6. These particular Text File size: 0.6 MB

contours are used in some areas to reveal small XML

features not shown by 5-m contours. (Geographic, 

NAD 83)

SIM3341_13mbathy—Esri binary grid of the HTML SIM3341_13mbathy.zip

13-m×13-m cell-size bathymetry of quad- Text File size: 2.5 MB

rangle 6 used as the basis for the generation of XML

the 1-m contours and the terrain ruggedness 

analyses. (Custom Mercator projection, NAD 83)

SIM3341_stations_geology—Point shapefile HTML SIM3341_stations_geology.zip

of station locations and Excel file of sediment Text File size: 0.3 MB

grain-size analyses and assignment of stations to XML

substrate types. (Geographic, NAD 83)

interpretation zipped file also contains the symbology layer 

files necessary to replicate the seven individual interpretive 

maps (A– G) presented in this publication.

Data layers generated for this report are supplemented 

by a linked list of previously published data layers from the 

Stellwagen Bank National Marine Sanctuary region that are 

relevant to quadrangle 6. Included in these data layers are the 

photograph locations and sediment sample analyses used in 

the geologic substrate interpretations.

To download the data from the table below, right mouse 

click on the link in the ‘Download’ column. Select ‘Save 

Target As...’ to save a compressed zipped file to the local hard 

drive. The download file size is indicated under the file name. 

Uncompress the zipped files using an extraction utility.
20 Seabed Maps of Quadrangle 6 in the Stellwagen Bank National Marine Sanctuary Region Offshore of Boston, Mass.

References Cited

Blair, T.C., and McPherson, J.G., 1999, Grain-size and textural 

classification of coarse sedimentary particles: Journal of 

Sedimentary Research, v. 69, no. 1, p. 6–19. [Also available 

at http://dx.doi.org/10.2110/jsr.69.6.]

Folk, R.L., 1954, The distinction between grain size and 

mineral composition in sedimentary-rock nomenclature: 

Journal of Geology, v. 62, no. 4, p. 344 –359. [Also 

available at http://www.jstor.org/stable/30065016.] 

Krumbein, W.C., 1936, Application of logarithmic moments

to size frequency distributions of sediments: Journal of

Sedimentary Research, v. 6, no. 1, p. 35–47. [Also available

at http://dx.doi.org/10.1306/D4268F59-2B26-11D7-

8648000102C1865D.]

Poppe, L.J., Williams, S.J., and Paskevich, V.F., eds., 2005, 

U.S. Geological Survey east-coast sediment analysis; 

Procedures, database, and GIS data: U.S. Geological Survey 

Open-File Report 2005–1001, 1 DVD–ROM. [Also available at http://pubs.usgs.gov/of/2005/1001/.]

Riley, S.J., DeGloria, S.D., and Elliot, R., 1999, A terrain 

ruggedness index that quantifies topographic heterogeneity: 

Intermountain Journal of Sciences, v. 5, no. 1–4, p. 23–27. 

[Also available at http://download.osgeo.org/qgis/doc/

reference-docs/Terrain_Ruggedness_Index.pdf. Note the 

correction to the initial published code in which the final 

sum was incorrectly squared instead of taking the square 

root of it.]

Udden, J.A., 1914, Mechanical composition of clastic 

sediments: Geological Society of America Bulletin, v. 25, 

p. 655–744. [Also available at http://dx.doi.org/10.1130/

GSAB-25-655.]

Valentine, P.C., ed., 2005, Sea floor image maps showing 

topography, sun-illuminated topography, backscatter intensity, ruggedness, slope, and the distribution of boulder ridges 

and bedrock outcrops in the Stellwagen Bank National 

Marine Sanctuary region off Boston, Massachusetts: 

U.S. Geological Survey Scientific Investigations Map 2840, 

scale 1:60,000, 1 DVD–ROM. [Also available at 

http://pubs.usgs.gov/sim/2005/2840/.]

Valentine, Page, Blackwood, Dann, and Parolski, Ken, 

2000, Seabed observation and sampling system: 

U.S. Geological Survey Fact Sheet FS–142–00. 

[Also available at http://pubs.usgs.gov/fs/fs142-00/. 

Also see WHSC Ground-truth systems, Seaboss, 

accessed July 28, 2015, at http://woodshole.er.usgs.gov/

operations/sfmapping/seaboss.htm.]

Valentine, P.C., Gallea, L.B., Blackwood, D.S., and Twomey, E.R.,

2010, Seabed photographs, sediment texture analyses, and 

sun-illuminated sea floor topography in the Stellwagen 

Bank National Marine Sanctuary region off Boston, 

Massachusetts: U.S. Geological Survey Data Series 

DS–469, accessed July 28, 2015 at http://pubs.usgs.gov/

ds/469/.

Valentine, P.C., Unger, T.S., and Baker, J.L., 1999, 

Sun-illuminated sea floor topography of quadrangle 6 

in the Stellwagen Bank National Marine Sanctuary off 

Boston, Massachusetts: U.S. Geological Survey Geologic 

Investigations Map I–2706, scale 1:25,000. [Also available at http://pubs.er.usgs.gov/publication/i2706 and at 

http://pubs.usgs.gov/ds/469/.]

Wentworth, C.K., 1922, A scale of grade and class terms 

for clastic sediments: Journal of Geology, v. 30, no. 5, 

p. 377–392. [Also available at http://www.jstor.org/

stable/30063207.]
Appendix 1 21

Data layer Location of data and associated metadata Source

Seabed raster data

Sun-illuminated sea-floor topography; and 

TIFF world file

http://pubs.usgs.gov/sim/2005/2840/DATA/sunillum/sunillum.zip Valentine, 2005

Backscatter intensity and sun-illuminated 

sea-floor topography; and TIFF world file

http://pubs.usgs.gov/sim/2005/2840/DATA/backscatter/bcksctter.zip Valentine, 2005

Sea-floor ruggedness; and TIFF world file http://pubs.usgs.gov/sim/2005/2840/DATA/rugged/ruggedimage/

ruggedimage.zip

Valentine, 2005

Esri binary grid used as the basis for the 

terrain rugged analyses (custom Mercator 

projection, NAD 83)

http://pubs.usgs.gov/sim/2005/2840/DATA/rugged/rugged.zip Valentine, 2005

Sea-floor slope; and TIFF world file http://pubs.usgs.gov/sim/2005/2840/DATA/slope/slopeimage/

slopeimage.zip

Valentine, 2005

Esri-formatted GIS files of features and surfaces; and seabed photographs

Stellwagen Bank National Marine Sanctuary 

boundary

http://pubs.usgs.gov/sim/2005/2840/DATA/SBNMS_boundary/

sbnmsbnd.zip

Valentine, 2005

Quadrangle boundaries http://pubs.usgs.gov/sim/2005/2840/DATA/quadbnd/quadbnd.zip Valentine, 2005

Bathymetric contours http://pubs.usgs.gov/sim/2005/2840/DATA/bathy/bathy.zip Valentine, 2005

Boulder ridges <1 meter in height http://pubs.usgs.gov/sim/2005/2840/DATA/ridges/ridges0.zip Valentine, 2005

Boulder ridges ≥1 meter in height http://pubs.usgs.gov/sim/2005/2840/DATA/ridges/ridges1.zip Valentine, 2005

Bedrock outcrops http://pubs.usgs.gov/sim/2005/2840/DATA/bedrock/bedrock.zip Valentine, 2005

Sea-floor ruggedness http://pubs.usgs.gov/sim/2005/2840/DATA/rugged/rugged.zip Valentine, 2005

Sea-floor slope http://pubs.usgs.gov/sim/2005/2840/DATA/slope/slope.zip Valentine, 2005

Seabed observation stations—Video drift 

track locations

http://pubs.usgs.gov/sim/2005/2840/DATA/videotrack/sbnmsallvid.zip Valentine, 2005

Seabed observation stations—Sediment 

sample locations and Excel file of 

grain-size analyses

http://pubs.usgs.gov/ds/469/DataCatalog/sb_sedsamples.zip Valentine and 

others, 2010

Photographic images of the seabed—

Locations of individual photographs

http://pubs.usgs.gov/ds/469/DataCatalog/sb_photolocs.zip Valentine and 

others, 2010

JPEG images of the seabed from 

quadrangles 1–18 in medium and 

high resolution

http://pubs.usgs.gov/ds/469/html/DataCatalog.html Valentine and 

others, 2010

Appendix 1. Supplementary, Previously Published Data Layers 

From the Stellwagen Bank National Marine Sanctuary Region 

Relevant to Quadrangle 6

Appendix 1

Prepared by the USGS Science Publishing Network

Edited by Natalie Juda, Reston PSC

Layout by Caryl J. Wipperfurth, Raleigh PSC

Web support by Angela E. Hall, Reston PSC

For more information concerning this report, 

please contact:

Coastal and Marine Geology Program Coordinator

U.S. Geological Survey

913 National Center

Reston, VA 20192

Home page: http://marine.usgs.gov
42°18'

42°19'

70°13' 70°11' 

42°14'

42°16'

70°12' 

42°13' 

42°15'

42°17'

U.S. Department of the Interior

U.S. Geological Survey

S T E L L W A G E N B A N K

Valentine and Gallea—Seabed Maps of Quadrangle 6 in the Stellwagen Bank National Marine Sanctuary Region Offshore of Boston, Mass.—Scientific Investigations Map 3341

ISSN 2329-132X (online)

http://dx.doi.org/10.3133/sim3341