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'

A

B

MIDDLE

NINETY

BANK

EAST

NINETY

BANK

SOUTH

NINETY

BANK

NORTH 

NINETY

BANK

STELLWAGEN BANK NATIONAL MARINE SANCTUARY

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

STELLWAGEN BANK

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

A2 i_cgS

D2 i_mcgS / pcbG

G1 i_mfgS

A1 r_cgS

G2 i_mfgS

F i_cgS / pcbG

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

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, Seabed geology and stations, sheet 2 of

Distribution of geologic substrates, map D 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

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

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

16 17 18

13

7

42°45'N

42°30'N

42°15'N

42°00'N

41°45'N

6

Gloucester

RACE POINT CHANNEL

STELLWAGEN

BANK

STELLWAGEN BASIN

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.

Scientific Investigations Map 3341

Map D, sheet 2

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

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

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 

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)

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

EXPLANATION OF MAP SYMBOLS

[See table 4 for kinds of data collected, source information, grain-size analyses, and 

assignment of stations to geologic substrates]

Video/photo transect and station location—Line shows the ship’s drift path during 

videography of the seabed. Still photographs were collected during some video 

drifts. Dot represents the end of the video transect and location of sediment 

sample, if collected.

A1 r_cgS

D1 i_cgS / pcbG

C i_cbG

E i_cgS

F i_cgS / pcbG

G1 i_mfgS

G2 i_mfgS

B r_cgS / i_cbG

D2 i_mcgS / pcbG

A2 i_cgS

1507

U.S. Department of the Interior

U.S. Geological Survey

Prepared in cooperation with the

National Oceanic and Atmospheric Administration

Sheet 2.—Seabed geology and stations

Map D.—Distribution of Geologic Substrates

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

903

3968

3967 3966

3945 3947

3943

3942 3941

3940 3939

3114

3110

3108

3107

3106

3102

3099

3096

3095

3094

3093

3092

3091

3090

3089

3088

3087

3086

3085

3083

3077

3076

3075

3074

3073

3072

3071

3070

2356

3378

1537

1536

1535

1534

1524

1520

1519

1518

1515

1514 1513

1512

1511

1510 1508

1501 1502

3114.3

3076.1

3075.1

2228.2

2228.1

1128.1

3946

3115.2

1142.1

926

906

905

899

3944

3938

3937

3936

3118

3115

3109

3105

3104

3103

3101

3100

3098

3097

3084

3082

3081

3080

3079

1532

1517

1516

1509

1507

1506

1505

1504 1503

2228

1134

1133 1132 1131 1130

1129

3115.5

3114.5

3114.2

13

957

956

931

930

929

928

927

925 924

904

902

696

694

692 691 690

688

686 684

682

680 678

561

560

559

557 555

553

551

543

527

526

525 523

521

519

517 513 515

509 511

499 498

497

496

495

483

481 479

477 469

467

465

834

833 830 831 832

827

3119

3078

1847 1846

1845

1844

1843

1842

1841

1840

1839 1838 1837 1836

1835

1834

1833

1832

1831

1830

1829

1828

1827

1826

1825 1824

1823

1822

1821

1819 1820

1818

1817 1816

1815

1814

1813 1812

1811

1810

1809

1808

1807

1806 1805

1804

1803

1802

1801 1800

1799

1798

1797

1796

1795

1794

1793

1792

1791

1790

1789

1788

1786 1787

1785

1784

1699

1533

1531 1530

1529

1528

1527

1526

1525

1523

1522

1521

1345

1331

1330

1326

1325

1324

1323

1322

1307

1306

1305

1303

1302

1301

1300

1299

1298

1297

1296

1295

1294

1200

1191 1190

1166 1165

1164

1163 1161 1160

1159 1158

1157

1156

1154 1153 1152 1151

1150 1149 1148 1147 1146 1143 1145 1141 1140

1138 1137

1135

1128

1090

1084

1079 1078

1077 1076 1075 1074

1073

1072

1071 1070 1068 1069

1067

1066

1065 1064

1060 1059

1058

1056

1055

1054 1053

1052 1051

1050

1049

1047

930.1

927.1

924.1

906.1

903.1

902.1

3119.1

3115.4

3115.3

3115.1

3114.4

3114.1

1842.1

1675.1

1509.1

1192.1

1167.1 1162.1

1144.1

1139.1

1136.1 1134.1

3100.1

473

1304

829

3412

3410

3411

3971

3969

3154.1

2236.2

2236.4

2236.1

3970

3963

3964

3113.1

3371

900.1 547

900 3965

3371.2

545

3374

901

3113.4

3373

2227.2

3113.2

3371.1

3372.2

3372.1

3372

INSET MAPS 

473

3154.1

474

2236.2

1304

3971

3970

3969

2236.4

2236.1

2236

3154.2

2236.8

829

3411

3412

3410

2236.9

3154 2236.6

2236.5

828

2236.3

475

2236.7

A

900

900.1

2227.2

545

3374

3371.1

3371

3373 3371.2

3113.1

2227.1

901

3113.5

3375

3935

3933

3113.3

3113.2

2227

901.1 3963

547

3965

3964

3934

3113.4

3113

B