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°12'

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'

3946

3115.2

3375

901.1

3113.2

1061.1

1142.1

903

3968

3967

3966

3964

3963

3947 3945 3943 3942 3941

3940

3939

3935

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

3371

3378

1537

1536

1535

1534

1524

1520

1519

1518

1515

1514 1513

1512

1511

1508 1510

1501 1502

2227

900.1

3114.3

3113.1

3076.1

3075.1

2228.2

2228.1

1128.1

926

906

905

901

900

899

3971

3970

3969

3965

3944

3938

3937

3936

3934

3933

3154

3118

3115

3109

3105

3104

3103

3101

3100

3098

3097

3084

3082

3081

3080

3079

3412 3411

3410

3374

3373

1532

1517

1516

1509

1507

1506 1505

1504 1503

2228

1134

1133 1132 1131 1130 1129

3154.2

3154.1

3115.5

3114.5

3114.2

3113.5

3100.1

2236.9

2236.8

2236.7

2236.6

3371.2

3371.1

2236.4

2236.3 2236.2

2236.1

2227.2

2227.1

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

549

547

543 545

527

526

525

523

521

519

517 513 515

511 509

499

498

497

496 495

483

481 479

477

475

474

471 473 469

467

465

834

833 832

831

830

828 829

827

3119

3113

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

1820 1819

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

1787 1786

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

1304

1303

1302

1301

1300

1299

1298

1297

1296

1295

1294

2236

1200

1192

1191 1190

1167

1166 1165

1164

1163 1162 1161 1160 1159 1158

1157

1156

1155

1154 1153 1152 1151

1149 1150 1147 1148 1145 1146 1144 1142 1143 1140 1141

1139

1138 1137

1135

1128

1090

1084

1079 1078 1077

1076 1075 1074

1073

1072

1071 1070 1068 1069 1067

1066

1065 1064

1061

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

3113.4

3113.3

2236.5

1842.1

1675.1

1509.1

1192.1

1167.1 1162.1

1155.1

1144.1

1139.1 1136.1

1136

1134.1

1076.1 1075.1

1067.1

1054.1

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

G1 i_mfgS

A2 i_cgS

A1 r_cgS

D2 i_mcgS / pcbG

G2 i_mfgS

F i_cgS / pcbG

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

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

16 17 18

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

JEFFREYS LEDGE

TILLIES BANK

U.S. Department of the Interior

U.S. Geological Survey

Prepared in cooperation with the

National Oceanic and Atmospheric Administration

Scientific Investigations Map 3341

Map D, sheet 3

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.

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 station data types, 

sheet 3 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

Sheet 3.—Seabed geology and station data types

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

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

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

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

[Symbols are combined at stations where more than one kind of data were collected. 

See table 4 for a list of station numbers]

Station with seabed photograph(s)

Station with seabed video imagery

Station with sediment grain-size analysis

Station where sediment sample could not be collected