. Data collected in 1978-79 in cooperation with 

U.S. Bureau of Land Management under Memoranda 

of Understanding AA551-MU8-24 and AA551-MU9-4 
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Shallow Stratigraphy of the 

New England Continental 

Margin 

By DENNIS W. O'LEARY 

Data collected in 1978-79 in cooperation with 

U.S. Bureau of Land Management under Memoranda 

of Understanding AA551-MU8-24 and AA551-MU9-4 

Description and analyses of Upper Cretaceous through Pleistocene 

strata based on high-resolution seismic-reflection profile data, 

with discussions on provenance and unconformities 

U.S. GEOLOGICAL SURVEY BULLETIN 1767 
DEPARTMENT OF THE INTERIOR 

DONALD PAUL HODEL, Secretary 

U.S. GEOLOGICAL SURVEY 

Dallas L. Peck, Director 

UNITED STATES GOVERNMENT PRINTING OFFICE: 1988 

For sale by the Books and Open-File Reports Section, U.S. Geological Survey, 

Federal Center, Box 25425, Denver, CO 80225 

Ubrary of Congress Cataloging In Publication Data 

O'Leary, Dennis W. 

Shallow stratigraphy of the New England continental margin. 

(U.S. Geological Survey bulletin ; 1767) 

Bibliography: p. 

Supt. of Docs. no. : I 19.3:1767 

1. Geology, Stratigraphic-Cretaceous. 2. Geology, Stratigraphic-Cenozoic. 3. 

Geology-New England. 4. Continental margins-New England. I. Title. II. 

Series. 

QE75.B9 no. 1767 557.3 s 86-600396 

[QE685] [551.7'7'0974) 
CONTENTS 

Abstract 1 

Introduction 1 

Seismic-profile data illustrated in this report 3 

Regional seismic stratigraphy 3 

Surficial layer 3 

Foreset unit 3 

Upper slope unit 4 

Lower slope unit 5 

Layered rise unit 7 

Lithostratigraphy and ages of the seismic units 9 

Surficial layer 9 

Foreset unit 13 

Upper slope unit 17 

Lower slope unit 19 

Layered rise unit 21 

Provenance and depositional history 24 

Unconformities and erosional history 29 

Synthesis 31 

Conclusions 34 

References cited 36 

FIGURES 

1. Map showing tracklines of seismic-profile data across Georges Bank and 

along New England Continental Slope and Upper Rise 2 

2. Sketch showing schematic stratigraphy and outcrop pattern along continental 

margin of New England 4 

3. Map showing location of major geographic features, COST wells, ASP 

holes, and AMCOR holes along New England Continental Shelf and 

Continental Slope 5 

4-19. Seismic reflection profiles showing: 

4. Iselin line 128 across Georges Bank 6 

5. Gilliss line G28 south of Martha's Vineyard 6 

6. Fay line L across Georges Bank 7 

7. Iselin line 114 at western end of Georges Bank 8 

8. Iselin line 117 at head of Oceanographer Canyon 8 

9. Iselin line Ill off Great South Channel 9 

10. Gilliss line G29 south of Martha's Vineyard 10 

11. Iselin line 139 between Powell and Lydonia Canyons 11 

12. Iselin line 13 across slope south of Martha's Vineyard U 

13. Iselin line 139 along upper slope east of Powell Canyon 13 

14. Gil/iss line G5-5A across lower slope wedge east of Corsair 

Canyon 14 

15. Iselin line 127 across lower slope-upper rise off Georges Bank 15 

16. Iselin line 120 across slope crossed by Lydonia Canyon 16 

17. Iselin line Il-lA across rise south of Martha's Vineyard 17 

Contents Ill 
IV Contents 

18. Fay line R across northwestern part of Georges Bank 18 

19. Gil/iss line G34 along upper slope south of Nantucket Island 20 

20. Isopach map showing lower slope wedge off continental slope of New 

England 21 

21, 22. Seismic reflection profiles showing: 

21. Gil/iss line G45 along lower slope south of Nantucket Island 23 

22. Gil/iss line G25 along upper rise south of Martha's Vineyard 24 

23. Isopach map of Neogene sediment beneath continental rise 28 

24. Sketch showing Tertiary-Quaternary stratigraphic configuration across 

continental shelf and upper slope 29 

25. Sketch showing inferred relations between shallow New England Margin 

stratigraphy and stratigraphy of North American basin 30 

26. Diagram showing timing of relative rises and falls in sea level along New 

England Continental Margin 31 

27. Diagram showing major operative relations of climatic-tectonic states and 

erosion-deposition across continental borderland 33 

28. Diagram showing major episodes of deposition and mass wasting on North 

Atlantic Continental Slope 34 

29. Schematic relations of provenance, New England Margin stratigraphy, and 

deep-sea stratigraphy through time 35 

TABLES 

1. Ages, lithologies, and paleoenvironmental aspects of seismic units described in 

text and shown in figure 2 22 

2. Composition of some important muscovite-bearing granitic rocks of south-central 

New England 25 
Shallow Stratigraphy of the New England Continental 

Margin 

By Dennis W. O'Leary 

Abstract 

A seismic stratigraphy of the New England Outer 

Continental Margin, from 65°30' W. to 71000' W., is determined on the basis of high-resolution seismic-reflection 

profile data collected by the U.S. Geological Survey. The 

seismic units are named, from youngest to oldest, the 

surficial layer, the foreset unit, the upper slope unit, the 

lower slope unit, and the layered rise unit. Seafloor and 

subbottom sampling indicate the lithologic makeup of the 

units. 

The surficial layer, a sandy unit approximately 35 m 

thick, terminates generally as a gently prograded ramp, 

roughly along the 160-m isobath. The surficial layer is 

probably composed mostly of fluvial outwash of Wisconsinan age. The foreset unit, named for the distinctive succession of foreset reflections within approximately the upper 

300m, is made up predominantly of silty deltaic sediment 

of Pliocene(?) and Pleistocene age. The foreset unit is 

probably mainly of pre-Wisconsinan glacial origin. About 

150 m of the unit is homoclinal and probably includes 

detrital Miocene-Pliocene marine sediment and a thin, 

basal upper Oligocene interval. The upper slope unit consists mostly of middle Eocene calcareous strata, except at 

the northeastern end of Georges Bank where the unit consists of graywacke. The upper slope unit is generally about 

350 m thick. The lower slope unit is predominantly Upper 

Cretaceous calcareous siltstone and may include strata as 

young as Paleocene and as old as Neocomian. The lower 

slope unit also includes a wedgelike subunit along the 

lower slope, which is partly disconformable on older strata 

of the unit. The lower slope wedge appears to consist of 

displaced Upper Cretaceous strata and perhaps primary 

prograded deposits. In places, strata of the upper slope 

unit are incorporated into the wedge also. The layered rise 

unit is a partly onlapping and partly homoclinal unit, which 

is unconformable on the lower slope wedge. The layered 

rise unit includes a lower subunit correlative(?) with the 

Eocene upper slope unit and an upper subunit correlative 

with the Pleistocene foreset unit. A middle subunit that 

pinches out against the slope is a prominent part of the 

layered rise unit west of 69°15' W. and is probably Oligocene to Miocene in age. 

The units represent four major suites of detrital 

deposits, and each suite reflects a source area stressed by 

tectonism and (or) climate. These suites are (1) degraded 

Upper Cretaceous arkose and low-rank graywacke formed 

under dry-winter, tropical conditions and shed from an 

igneous terrane uplifted consequent to intrusion of the 

White Mountain magma series (lower slope unit), (2) upper 

Oligocene secondary deposits derived from an emergent 

coastal plain during a period of relatively intensified climatic 

stress (foreset unit), (3) middle to upper Miocene primary 

detritus shed from rejuvenated northern Appalachian 

Mountains during a time of gradually increasing climatic 

severity (foreset unit), and (4) Pleistocene graywacke of 

mixed coastal-plain-hinterland provenance produced by 

glacial weathering and erosion (foreset unit). The Eocene 

graywacke at the eastern end of Georges Bank is a marginal part of an Upper Cretaceous through Neogene 

detrital suite deposited mainly on the Scotian Shelf. 

Strata laid down across the slope were deformed 

during three major episodes of mass wasting in Late Cretaceous, Oligocene, and late Pleistocene time. During these 

episodes, the slope served as a source of sediment for the 

layered rise unit. 

INTRODUCTION 

In 1978-79, the U.S. Geological Survey (USGS) in 

cooperation with the Bureau of Land Management produced a systematic high-resolution seismic-reflection survey of the New England Continental Slope and Upper 

Rise under Memoranda of Understanding AA551-

MU8-24 and AA551-MU9-4. More than 5,900 km 

of seismic-profile data were collected. Profiles were spaced 

10-20 km apart across the slope and were approximately 7 km apart along the slope from 65°30' W. to 

71 °00' w. (fig. 1 ). 

This report summarizes the regional seismic stratigraphy. The main topics are the physical characteristics of 

the Upper Cretaceous through Pleistocene seismic units, 

the ages and inferred history of the units, and the regional 

lithostratigraphic correlations of the units. The report also 

speculates on provenance and environmental conditions, 

particularly the relation between climate and hinterland uplift and the lithologies of the units. Finally, the 

report discusses the relevance of unconformities that 

bound the seismic units to concepts of changing sea level, 

especially the hypothesis of Vail and others (1977a). 

Introduction 
/oo0, 

-~~ • . NANCUCKUO>""\ i MARTHA's ~ ISLAND ! 

VINEYARD . 

25 50 MILES 

25 50 KILOMETERS 

-o 

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EXPLANATION 

-- R/V Fay 1975 

_ _ _ R/V Iselin 1978 

_______ R/V Gil/iss 1979 

-2oom- Bathymetry in meters 

Figure 1. Tracklines of seismic-profile data across Georges Bank and along the New England Continental Slope and 

Upper Rise. Circled numbers correspond to text figures in this report. 

Although the summary centers on the seismic data, 

it also draws on the conclusions of earlier high-resolution 

seismic-reflection studies (Ewing and others, 1963; 

Roberson, 1964; Krause and others, 1966; Garrison and 

McMaster, 1966; Hoskins, 1967; Knott and Hoskins, 

1968; Emery and others, 1970; Garrison, 1970; Lewis and 

others, 1980) and draws on bottom and subbottom 

records from two Continental Offshore Stratigraphic Test 

(COST) wells, seven Atlantic Margin Coring Project 

(AM COR) holes, two Atlantic Slope Project (ASP) holes, 

and many short cores, dredge hauls, and submersible grab 

samples. Most of the data were acquired after 1975, and 

many of them are unpublished. In some instances, I have 

2 Shallow Stratigraphy of the New England Continental Margin 

relied on sparse or unique observations and samples to 

explore the link between terrestrial and marine geology of 

New England. 

The seismic data were obtained during USGS Iselin 

cruise 7-78-2 and USGS Gil/iss cruise 7903-3 (fig. 1 ). 

Details of the cruises and the data are described by Bailey 

and Aaron (1982a,b). Some use also is made of seismic 

data collected in 1975 from USGS Fay cruise 003 (fig. 1 ). 

The methods of analysis and data preparation are 

described in detail by O'Leary (1986). The data are 

available from the National Geophysical Data Center, 

Boulder, Colo.; original profiles may be examined at the 

USGS, Woods Hole, Mass. 
SEISMIC-PROFILE DATA ILLUSTRATED IN 

THIS REPORT 

The seismic units are illustrated in the text by 

segments of seismic-profile data. These data represent 

echoes of the seafloor and of underlying stratal surfaces 

generated in response to repeated acoustic (that is, seismic) pulses from the survey instrument. Each profile is a 

record of the time (2 seconds ( s) or less) during which the 

pulse leaves the airgun or the sparker and returns to the 

recorder as a succession of echoes that reflect and 

disclose the stratigraphic section. The term seismic stratigraphy describes this process; reflectors are the stratal 

surfaces that produce the echoes. 

The time it takes for the seismic pulse to leave its 

source and for the echo to return is called the two-way 

traveltime. The velocity of sound varies from 1,500 m/s (in 

water) to possibly as much as 2,500 m/s in the deeper 

strata (Roberson, 1964). Because the acoustic interval 

velocities are unknown in the area of this study, a correct 

and uniform depth scale cannot be provided with each 

figure. The two-way traveltime is the only constant reference. Water depths are easily estimated, however, because 

1 s (two-way traveltime) is approximately equivalent to 

750-m water depth. 

In some records, the echo trace of the seafloor is 

recorded twice because the initial echo was strong enough 

to bounce back from the ocean-atmosphere interface and 

generate a second seafloor echo, which was recorded 

while the primary sub seafloor echoes were being received. 

This second echo is called a multiple. Because it is 

superimposed on the echo traces of the stratigraphic 

section, the multiple is identified in some figures so that 

the reader will not mistake it for a stratigraphic feature. 

REGIONAL SEISMIC STRATIGRAPHY 

Fwe major seismic units make up the shallow 

seismic stratigraphic section (within 0.8-s acoustic penetration) of the New England Continental Margin (fig. 2 

and table 1). The units are named, from top to bottom, 

the surficial layer, the foreset unit, the upper slope unit, 

and the lower slope unit. The fifth unit, the layered rise 

unit, is a partly correlative succession that underlies the 

continental rise. All units crop out at various places along 

the continental slope, mainly along the sides of slope 

canyons. 

Surficial Layer 

The surficial layer (fig. 2 and table 1) is a relatively 

thin (20-45 m) blanket that covers much of the Outer 

Continental Shelf (Garrison, 1970; Lewis and others, 

1980). Northeast of Corsair Canyon (fig. 3), the surficial 

layer extends across the slope to an undetermined depth, 

but elsewhere the seaward contact skirts the outer shelf, 

mostly landward of the 160-m isobath. The surficial layer 

terminates as a ramp (fig. 4) that has 30-40 m relief and 

a slope of 0.5° to 1.8° (Hoskins, 1967). The ramp crest, or 

brow, lies between 105 and 140m below sea level. The 

ramp crest marks the abrupt declivity known as the shelf 

break. 

In places, particularly south of Martha's Vineyard, 

Mass., the surficial layer is thinned, probably by wave or 

current erosion, or is missing. In these places, the shelf 

break (fig. 5) is represented in profile by a bevel at about 

140-m depth. The bevel marks the seaward edge of a 

wave-planed surface that is partly cut on the underlying 

foreset unit and is partly extended by redeposition of 

planed sediment. 

In many places along the outer shelf, the base of the 

surficial layer is complicated by irregular filled depressions (fig. 6) or channels(?). These filled depressions and 

the surficial layer constitute a total thickness of as much 

as 80 m (Lewis and others, 1980). Filled channels, which 

are approximately 150m deep (based on acoustic interval 

velocity= 1,500 m/s), are present around the heads of the 

major shelf-indenting canyons. A large filled channel (fig. 

7), truncated by the east wall of Welker Canyon (fig. 3) at 

about 170-m depth, seems to be cut through the surficial 

layer; both the fill and the surficial layer are probably 

wave-planed along profile I14 (fig. 7). Near where it 

crosses the 140-m depth contour, Oceanographer Canyon 

(fig. 3) is partly filled by what appears to be channel-fill 

sediment, although sediment from the surficial layer may 

be included also (fig. 8). A 425-m-deep filled channel 

extends through the foreset unit and into the upper slope 

unit between Welker and Oceanographer Canyons (fig. 3 ). 

Foreset Unit 

The surficial layer rests on a planed surface, which 

is underlain by seaward-dipping layers of the foreset unit 

(Garrison, 1970). The unit is named foreset because the 

distinctive downdip-flattening and converging reflectors 

of the unit (figs. 2, 6, and 9) probably represent foreset 

bedding. The foreset unit comprises a succession of 

distinct prograded depositional packages or groups, each 

of which is separated by a convex erosional surface (fig. 6; 

Lewis and others, 1980). The updip ends of all the foreset 

layers are truncated (figs. 6, 9), but topset flattening, 

which is visible in some Fay 003 profiles (Lewis and 

others, 1980), indicates that only a few tens of meters 

could have been eroded. Typical rates of reflector-dip 

flattening indicate individual depositional group thicknesses of approximately 200-250 m. The apparent dips of 

the foreset reflectors vary greatly from group to group 

and generally become steeper toward the slope. Steep 

downdip-converging reflectors are interlayered with less 

steeply inclined continuous homoclinal intervals; these 

intervals probably represent marine deposits. 

Regional Seismic Stratigraphy 3 
WEST 

foreset 

unit 

upper slo~ 

unit 

lower slope 

unit 

EAST 

8 

A 

Figure 2. Schematic stratigraphy and outcrop pattern along the continental margin of New England. Generalized 

locations of profiles A and 8 are shown in figure 3. Reflector A, point B, and subunits a, b, and c are part of the lower slope 

unit described in text (p. 19). 

Homoclinal layers, in part probably bottomset 

strata, form the basal part of the foreset unit along most 

of the outer shelf (fig. 9). Beneath the outer shelf along 

Georges Bank, the inferred cumulative thickness of 

bottomset layers and of conformable underlying strata 

amounts to as much as 200 m, bringing the total maximum thickness of the unit to nearly 500 m (Stetson, 

1936). 

From the Great South Channel (fig. 3) westward, 

the entire foreset unit is typically almost homoclinal and 

comprises two subunits. The younger subunit offlaps the 

older subunit, and the older subunit offlaps the subjacent 

unit across the outer shelf-upper slope. Seaward of the 

shelf break, layers of both groups are very nearly conformable (fig. 10) and make up a total thickness of 

340-460 m. All or most of the upper subunit is terminated along a zone of scarps at about 750-m depth on the 

upper slope brow (figs. 2, 10). Much of the lower subunit 

thins (60-90 m thick) and continues down across the 

lower slope in marked unconformity on underlying units. 

4 Shallow Stratigraphy of the New England Continental Margin 

The foreset succession forms a complex and prograded wedge on a broadly uneven but consistently 

seaward-sloping surface. The average dip of the surface 

(west of Martha's Vineyard, fig. 3) is estimated at about 

4.8 m!km (Garrison, 1970). 

Upper Slope Unit 

The upper slope unit (fig. 2) is paraconformable 

with the foreset unit, but the upper slope unit is distinguished by its strong and continuous reflections. On 

strike, the reflections are irregularly warped and flexed 

and define lenticular intervals over distances of kilometers (fig. 11); downdip, beneath the outer shelf, the 

reflections are fairly smooth and parallel (figs. 9, 10). The 

upper slop~ unit ranges in thickness from 200 to 400 m 

along the upper slope, but in places the upper slope unit 

is markedly thicker because of relief along the basal 

contact (figs. 2, 11). 

Along most of the slope west of Corsair Canyon, the 

upper slope unit includes two acoustically distinct subun-
N.H42° ----~------, .. 

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. I R I . ·. :_.=:~· \~: : : : 

.( 

. -:·.·. 

8 

0 25 50 miles 

0 25 50 

A I===±===J kilometers 

-100-Bathymetry in meters 

Figure 3. Location of major geographic features along the New England Continental Shelf and Continental Slope and 

location of COST wells G-1 and G-2, ASP holes 17 and 18, and AMCOR holes 6013, 6014, 6016, and 6019. For 

stratigraphic sections along profiles A and 8, see figure 2. 

its. The upper subunit (fig. 11, subunit a-b) is relatively 

thin and is characterized by continuous strong parallel 

reflections that are broken locally by acoustic gaps. A 

weakly reflective basal layer fills shallow depressions in 

the top of the lower subunit, which is very slightly 

offlapped; the basal contact of the upper subunit cuts 

across reflectors of the lower subunit downdip. The lower 

subunit (fig. 11, subunit b-e) is thicker and more regularly layered than the upper subunit; the lower subunit 

also fills depressions in the underlying unit and crosscuts 

strata downdip (fig. 12). 

Along the slope off Georges Bank, the upper slope 

unit is ordinarily exposed by truncation across a steep 

(8°-9°), concave to nearly rectilinear face at depths 

between 500 and 1,000 m (fig. 2). Where extensive lateral 

erosion has occurred, the top of the outcrop face is 

marked by a concave recess. The floor of the recess 

apparently consists of dissected basal strata of the foreset 

unit and eroded upper strata of the upper slope unit (fig. 

4). Smaller benches mark the outcrop interval of the 

upper slope unit to depths as great as 970 m, but most 

benches are present above 750 m. 

West of Hydrographer Canyon (fig. 3 ), the upper 

slope unit and the upper slope surface are nearly conformable down to 750- to 1,000-m depths where the unit 

seems to be largely exposed and partly, or even entirely, 

cut away. Dip of the unit across the upper slope in the 

Hydrographer Canyon region ranges from 1.2° to 1.4°. In 

places, the unit extends across the lower slope and attains 

a regional dip of about 7° down to the rise (fig. 10). 

Lower Slope Unit 

The lower slope unit is separated from the upper 

slope unit by an erosional contact. Along dip beneath the 

outer shelf and upper slope, the unconformity is marked 

by truncation of the seaward-dipping older beds (fig. 12); 

on strike, the contact appears to be an irregular surface of 

Regional Seismic Stratigraphy 5 
foreset unit, 

(/) 

c 

2 

0 

u 

LU 

(/) 

2 

concave 

recess 

0 

I 

5 km 

I 

0 

N 

0 

2 

considerable relief and is broadly similar in profile to the 

present slope surface (fig. 13), particularly along the 

lower slope-upper rise. 

Beneath the upper slope and the outer shelf off 

Georges Bank, the lower slope unit comprises two unconformable subunits: an acoustically transparent to chaotic 

subunit (fig. 13, subunit c-d) and a flat -surfaced subunit 

of parallel reflectors (fig. 13, subunit d). Subunit c-d fills 

deep incisions in subunit d. West of Powell Canyon, 

parallel reflectors are increasingly evident in the upper 

subunit, and the contact with the lower subunit becomes 

indistinct in places because of poor acoustic contrast. The 

layered lower subunit is truncated along the slope but is 

largely covered by onlapping strata from the rise (fig. 2); 

the subunit is probably exposed in the larger canyons. 

Much of the outcrop zone of the lower slope unit is 

mantled by a seaward-thickening wedge (fig. 2), which is 

~ Figure 4. Iselin airgun line 128 across Georges Bank 

outer shelf-upper slope. USU, upper slope unit; LSU, 

lower slope unit. Arrow indicates intersection of profile 

138. Vertical exaggeration -16:1. 

Skm 

Figure 5. Gil/iss sparker line G28 across shelf break south of Martha's Vineyard, Mass. 

6 Shallow Stratigraphy of the New England Continental Margin 
0 2 km 

Figure 6. Fay sparker line L across Georges Bank showing surficial layer and upper part of foreset unit. Homoclinal lower 

part is faintly recorded below 0.3 s. 

made up of at least two subunits having weak, subparallel 

to distorted layering and reverse-dipping reflector segments (fig. 10). The subunits are bounded by upslope 

converging horizons of locally great relief (figs. 14, 15). 

The upper subunit of the wedge appears to drape-fill 

broad troughs or depressions in the lower subunit (figs. 

14, 15). In places, the upper subunit approaches conformity with the overlying strata of the layered rise unit (fig. 

15), although the entire subunit is distinguished by weaker, 

finer reflections. 

The wedge is included in the lower slope unit 

because, as the wedge flattens out beneath the lower 

slope-upper rise, the wedge becomes acoustically indistinguishable from the underlying intervals. Also, in places, 

the updip end of the wedge appears to be stratigraphically 

continuous with upper levels of the lower slope unit 

beneath the outer shelf-upper slope. The wedge is particularly continuous with the upper, chaotic subunit 

(subunit c--d). 

Layered Rise Unit 

The layered rise unit is a thick, complex interval of 

mostly well-layered strata that form the upper rise (fig. 2 

and table 1). The contact of the layered rise unit with the 

lower slope unit is commonly a surface of considerable 

relief (fig. 14), but as the distance increases seaward from 

the slope, the layered rise unit becomes progressively 

more conformable. On the rise off Georges Bank, at 

depths greater than the 4,000-m isobath, the unit is 

difficult to discriminate from the underlying strata that 

presumably represent the lower slope unit. 

Along Georges Bank, the uppermost beds of the 

layered rise unit form a homoclinal succession as much as 

500 m thick that extends as high on the slope as the 950-m 

contour in places (fig. 15). The updip end of the homocline is so deeply eroded that, in many profiles, the lower 

slope appears to be a cuesta having stratal surfaces that can 

be projected into those of the truncated upper slope 

(fig. 16). 

Regional Seismic Stratigraphy 7 
Cl) 

c 

z 

0 

(..) 

UJ 

Cl) 

~ 

UJ .. 

~ 

i= m.2s 

> <t 

a: 

1--

>- <C 

3: I 

0 

3: 

1--

.so 

N 

0 Skm 

Figura 7. Iselin sparker line 114 across outer shelf at western end of Georges Bank showing homoclinal strata of the 

foreset unit and planed surficial layer incised by filled channel. 

en 

0 

z 

0 

u 

w 

en 

~ 

w" 

~ 

~.50 

> <( 

a: 

I-

>- <( 

s: 

0 

s: 

INW 

0 

SCALE CHANGE 

0-1 sec,I50-300Hz+ 0-2sec, 70-120Hz 

SE 

-0 

1 

2km 

-2 

Figura 8. Iselin airgun line 117 showing stratigraphic features associated with head of Oceanographer Canyon. Note: A 

scale change was made in seismic recording at point A. To northwest, the profile was recorded at 1-s sweep, 15D-300 

Hz; to southeast, the profile was recorded at 2-s sweep, 7D-120 Hz. 

8 Shallow Stratigraphy of the New England Continental Margin 
N 

0-

,+~:':'~-:-'~------

I 

2-1· 

-- - ~+--,-

0 

-

,_.j 

c 

NJ 

s 

foreset layerin~ 

10km 

Figure 9. Iselin airgun line 111 showing inferred stratigraphic relations across outer shelf-upper slope off the Great 

South Channel. USU, upper slope unit. Heavy vertical lines indicate inferred fractures. Vertical exaggeration -12:1. 

West of 69°15' W., the layered rise unit forms a 

relatively abrupt contact with the steep lower slope (figs. 

2, 10), and pronounced erosional forms are not present 

along dip. The unit progressively thickens along strike 

west of 69°15' W. mainly because of the addition, from the 

west, of a tonguelike, acoustically transparent or weakly 

layered interval that forms an important middle subunit 

(fig. 2 and table 1). The middle subunit is capped by as 

much as 200 m of layered strata that form an upper 

subunit, and it is underlain by a distinctive parallel-layered 

subunit (fig. 17). In places, the upper subunit is stratigraphically continuous with the foreset unit; the lower 

part of the lower subunit is stratigraphically correlative 

with the upper slope unit (figs. 10, 17). The transparent 

to weakly layered middle subunit pinches out against the 

slope (figs. 10, 17). 

East of 69°15' W., seismic subunits are not well 

discriminated, and stratigraphic continuity with the upper 

slope is implied, in rare instances, by dip projection across 

the eroded slope (fig. 16). 

LITHOSTRATIGRAPHY AND AGES OF THE 

SEISMIC UNITS 

The surficial layer, foreset unit, and upper slope 

unit compose a Cenozoic section that attains a maximum 

thickness of nearly 900 m along the outer shelf. The 

layered rise unit represents an equivalent section on the 

continental rise, at least in part. The lower slope unit is 

probably all Upper Cretaceous, but it may include strata 

as high as Paleocene and, in places, as low as upper Lower 

Cretaceous. 

All of the seismic units consist of distinctly terrigenous sediment, except for the upper part (and much of the 

lower part) of the upper slope unit, which is chiefly 

hemipelagic chalk, marl, and limestone. 

Surficial Layer 

The surficial layer has been widely sampled 

(Hathaway and others, 1979; Bothner and others, 1980), 

Uthostratigraphy and Ages of the Seismic Units 9 
Cl) 

Cl 

2 

0 

u 

LU 

Cl) 

~ 

LU~ 

N 

0- top lower subunit of the foreset unit 

~ 

~1 LU 

> <( 

a: 

1-

1 scarp at upper slope brow 

>- / <( 

3\= 

0 

3: 

1-

2-

0 10km s 

.-4 

-5 

Figure 10A. Gil/iss airgun line G29 showing continental slope south of Martha's Vineyard, Ma~s. USU, upper slope unit. 

Vertical exaggeration ...., 14: 1. 

and in every instance it consists of sand. In places, the 

sand is fine and silty; elsewhere, particularly toward the 

east end of Georges Bank, the sand is coarse, gravelly, and 

shelly. Samples obtained from the upper 16.5 m of 

AMCOR hole 6014 (fig. 3; Hathaway and others, 1976) 

suggest that, locally, coarse channel deposits are an 

important part of the unit. 

The surficial layer is probably essentially a composite outwash train of Wisconsinan age. West of the Great 

South Channel (fig. 3), the surficial layer underlies Nantucket Shoals (Groot and Groot, 1964) and appears to be 

stratigraphically continuous with outwash exposed on 

Nantucket Island and outer Cape Cod (R.N. Oldale, oral 

commun., 1984). In the Great South Channel, heads of ice 

may have been located as far south as 40~0' N., as 

indicated by the Fay 003 seismic data (Lewis and others, 

1980). Bothner and Spiker (1980) describe till from core 

samples nearly 6 m long from the margins of the Great 

South Channel (approximately 40°55' N.), which gave 

radiocarbon dates of at least 20,000 years B.P. Geotechnical analysis of one core sample indicated compaction 

compatible with the weight of a 15-m -thick column of ice 

(Bothner and Spiker, 1980). 

Along the northeastern flank of Georges Bank, 

head of outwash is indicated by lag deposits having 

multimodal gravel fractions (Schlee and Pratt, 1970, figs. 

10 Shallow Stratigraphy of the New England Continental Margin 
foreset 

unit 

lower slope un1t 

0 

8 

10km 

Figure 108. Interpretative line drawing of Gil/iss airgun line G29 showing relations of seismic stratigraphic units described 

in text. 

0 5km 

Figure 11. Iselin airgun line 139 along upper slope between Powell and Lydonia Canyons showing upper slope unit. 

Upper subunit a-b; lower subunit, b-e. Vertical exaggeration -10:1. 

Uthostratlgraphy and Ages of the Seismic Units 11 
en 

Cl 

2 

a 

u 

LU 

en 

2 

: :.~; ~.':, I),~::~:- • 

~y ':. ~.~ i. ; ~: ._, . :: : i<t<( """' ~; . · top LS 

structural : ~ , 

culmination 

projected 

outcrop depth-~~ 

S of USU 2-~- .. ' ' .. 

~,~~~~;~r .sl.ope t\:f;w&Ejg~·: 

:1 ' • :' :' t~ : ' ' 

4-

0 

1 

-2 

Skm 

Figure 12. Iselin airgun line 13 across slope south of Martha's Vineyard. USU, upper slope unit; LSU, lower slope unit. 

Heavy lines indicate inferred faults. Vertical exaggeration -9:1. Reflector A and point Bare features discussed in text (p. 19); 

for schematic representation, see figure 2. 

8, 15). Gravel modal distributions indicate that two late 

Wisconsinan(?) ice lobes advanced over the north side of 

Georges Bank between 66° W. and 68° N., possibly as far 

south as 42° N. 

Both the prograded ramp crest of the surficial layer 

and the beveled surface where the ramp rests have been 

identified as relict Pleistocene shores (Ewing and others, 

1963; Garrison and McMaster, 1966; Knott and Hoskins, 

1968); the ramp crest is called the Franklin shore (100- to 

120-m depths), and the beveled surface is called the 

Nichols shore (130- to 165-m depths). The difference in 

elevations between the two shores is essentially the thickness of the surficial layer (typically 30--40 m, and always 

less than 65 m). 

Radiocarbon dates from the distal margin of the 

surficial layer on Georges Bank approximate an age of 

10,000 B.P. (Bothner and others, 1980). These dates must 

reflect marine redeposition because most recent ice in the 

12 Shallow Stratigraphy of the New England Continental Margin 
E 

.50-

2.5-

0 

w 

skm 

Figure 13. Iselin airgun line 139 along upper slope east of Powell Canyon showing lower subunit of up~r slope unit (b:"C) 

and upper subunit of lower slope unit (c-d), which fills depressions within the lower subunit (d). Vert1cal exaggerat1on 

-10:1. 

Gulf of Maine was present not much later than 15,000 

B.P. (J.P. Schafer, oral commun., 1982). 

The age and composition of the channel fill are 

unknown. A few preliminary conclusions about the filled 

channels can be drawn from the seismic data: 

1. Three generations of filled channels exist. The oldest 

channels are blanketed by the surficial layer and by 

the latest group of foreset beds on which the surficial layer rests; the oldest channels are the largest. 

The next younger generation of channels represents 

the basal part of the surficial layer, and these channels partly fill canyon heads. The youngest generation 

of channels cuts the surficial layer. 

2. The older channels presumably were cut during episodes of subaerial exposure that occurred toward the 

close of the major foreset deposition on Georges 

Bank and before Wisconsinan ice retreat from Georges Bank. 

3. Locations of the older channels presumably are 

related to the positions of the shelf-indenting canyons. 

Some of the larger filled channels are intersected by 

the canyon walls. The channels may be graded to the 

canyon heads, but the RN Iselin and RN Gilliss 

seismic data do not indicate that the channels are 

part of a shelfwide network. For more information, 

compare Lewis and others (1980) and Knott and 

Hoskins (1968). 

4. Most of the channel fill displays a structure resembling 

that of sidewall drape and fill, but horizontal parallel 

layering is evident in some of the channel fill. Laminated acoustic reflections suggest that, during the 

phase of channel filling, some of the channels formed 

rias and were filled with estuarine rather than fluvial 

sediment. 

Foreset Unit 

At least the upper 300 m of the foreset unit 

probably consists of dominantly dark-gray clay and silt 

and has interlayers of fine sand (Hathaway and others, 

1976). This interval also features a range of what may be 

deltaic sediments, from relatively deep-water silts and fine 

calcareous sands to higher energy, shallow-water micaceous sands and shelly sands. 

A diatom and silicoflagellate assemblage, probably 

of early Pleistocene age (1.8-0.9 m.y.), was obtained from 

AM COR holes 6013 (figs. 3, 9) and 6013B in sediment of 

the foreset unit sampled between 46.5 and 184m below 

the seafloor (Abbott, 1980). The assemblage included 

abundant benthic brackish to nonmarine forms indicative 

of a very shallow inner neritic depositional environment 

(Abbott, 1980). A middle Pleistocene (Brunhes: 

-630,000 yr) to late Pleistocene dinoflagellate assemblage (Abbott, 1980) was found in foreset strata penetrated by AMCOR hole 6019 (fig. 3) on the northwest 

corner of Georges Bank. 

A core from Nantucket Shoals (fig. 3; 4()058.4' N., 

6g>23' W.), which penetrated at least 20 m of gray silt 

below about 30 m of white-to-buff, fine-to-medium sand 

Uthostratlgraphy and Ages of the Seismic Units 13 
en 

C) 

z 

0 

u 

L.U 

en 

~ 

>-

<( 

$ 

6 

$ 

I3-

()' "CC~~ .., 

0 

~ 

bend in profile 

slw E 

==·~ : 1 

0 5km 

Figure 14. Gil/iss airgun line G5-5A showing lower slope wedge east of Corsair Canyon (fig. 3). LRU, layered rise unit. 

Vertical exaggeration -16: 1. 

(surficial layer) (Groot and Groot, 1964), implies a 

stratigraphic tie between the pre-Wisconsinan glacial drift 

of Martha's Vineyard and of Nantucket and the foreset 

unit along the outer shelf. The gray silt (foreset unit) 

contains a large component of reworked Eocene pollen 

and primary Quaternary Tsuga pollen (Groot and Groot, 

1964). No dinoflagellates were found in the silt. 

Thin-bedded, silty sediment of the foreset unit is 

exposed in the upper reaches of many slope canyons 

(Valentine and others, 1980; J.S. Schlee, written commun., 

14 Shallow Stratigraphy of the New England Continental Margin 
NW 

1- !'I. 

:-) 

0 

I 

skm 

I 

0.' 

~: 

SE 

I .--3 

4 

Figure 15. Iselin airgun line 127 showing lower slope-upper rise off Georges Bank between Munson and Nygren Canyons 

(fig. 3). LRU, layered rise unit. Vertical exaggeration -11:1. 

1982; Slater, 1982). Ryan and others (1978) reported 

pre-Wisconsinan Pleistocene sub horizontally bedded, 

sandy mudstone cropping out in Heezen Canyon (fig. 3) at 

water depths as great as 1,070 m. Nearly 92 m of 

Pleistocene silty sand on lower Maestrichtian sediment 

was penetrated by ASP hole 18 (fig. 3) below 1,000-m 

water depth on the west side of Veatch Canyon (Valentine, 

1981; Poag, 1982a). Approximately the same thickness of 

inferred Pleistocene, dark-gray, sandy-silty compact clay 

and soft-to-hard, dark-greenish-gray glauconitic silt and 

clay was discovered in ASP hole 17 (Manheim and Hall, 

1976) on the east side of Veatch Canyon below 1,200-m 

water depth (fig. 3). 

The lower, homoclinal 150-200 m of the foreset 

unit is probably mainly Miocene and may include strata 

as old as Oligocene. Reflectors beneath the outer shelf 

Uthostratigraphy and Ages of the Seismic Units 15 
en 

c 

z 

0 

c..J 

w 

en 

~ 

w .. 

:iE 

SE 

1.5-i-· 

!:3 2.5 w 

> 

< a: 

1-

> 

< 3F 

0 

~ 

Lydonia Canyon 

' 

0 5km 

NW 

_.-0 

1 

Figure 16. Iselin airgun line 120 showing slope crossed by Lydonia Canyon. LRU, layered rise unit. Vertical exaggeration 

-12:1. 

are traceable updip in some of the Fay 003 profiles (Lewis 

and others, 1980) to deformed strata of possible Miocene 

age along the north side of Georges Bank (fig. 18). 

Downdip projection of inferred Miocene horizons in R/V 

Fay lines T and P (Lewis and others, 1980) suggests that 

the Miocene section penetrated by AMCOR hole 6016 

(fig. 3; Hathaway and others, 1979) should pinch out 

beneath approximately the 160-m isobath between Welker 

and Hydrographer Canyons (figs. 3, 9). However, the top 

of the Miocene section at AMCOR site 6016 may not 

represent the top of the Miocene section downdip because 

of erosional planing along the Great South Channel. 

More or less indurated strata of latest Miocene or 

earliest Pliocene age probably crop out at depths above 

approximately 400 m along most of the upper slope off 

Georges Bank. Stetson (1949) obtained indurated, finegrained, greenish sandstone of Yorktown(?) age from 

outcrops at 233-m depth in Lydonia Canyon. He dredged 

similar loose fragments from Hydrographer and Corsair 

Canyons. He also obtained, from Lydonia Canyon, friable 

quartzose greensand, which he considered to be of 

Pliocene age. The gray silty clay of Pleistocene age 

discovered in ASP holes 17 and 18 (Manheim and Hall, 

1976) at depths below 1,200 m on the slope grades down 

to hard green-gray, glauconitic silty-sandy clay through an 

interval about 150 m thick. The glauconitic lower part of 

this interval may be Miocene. Miocene and probable 

Miocene sediment encountered near the bottoms of some 

AMCOR holes (Hathaway and others, 1979) included 

glauconitic, plastic, silty clay beneath Georges Bank and 

16 Shallow Stratigraphy of the New England Continental Margin 
E 

2-

\ 

4-

N 

Skm 

Figure 17. Iselin airgun line 11-1A showing rise south of Martha's Vineyard. USU, upper slope unit; LRU, layered rise unit. 

dark olive-gray, plastic, slightly silty clay beneath the 

upper slope. 

The presence of Globigerina opima opima at 369 m 

below sea level (Poag, 1982a) indicates upper Oligocene 

sediment at the COST G-2 site (fig. 3). Well cuttings that 

were taken from the 340- to 348-m (below sea level) 

interval of COST well G-2 consist of 90 percent buff to 

light-yellow, slightly micaceous, calcareous mud that has 

about 1 percent limonitic siltstone and has traces of 

hematite and calcite (Miller and others, 1982). If the well 

cuttings are Oligocene, then as much as a 30-m thickness 

of Oligocene strata may be present at the COST G-2 site. 

Fragments of lignite, chert, and brown glauconitic siltstone that were recovered in cuttings from COST well G-1 

(Miller and others, 1982) also may represent Oligocene 

sediment. 

Upper Oligocene, buff-colored, calcareous, silty clay 

and brown, glauconitic, sandy clay and siltstone were 

obtained from outcrops in Oceanographer Canyon at 

886-m depth {Gibson and others, 1968; Trumbull and 

Hathaway, 1968). Gibson {1970) reports a dredge sample 

from Oceanographer Canyon at 1,046-m depth. The 

sample was Oligocene, brown, clayey, glauconitic limestone that contained quartz grains. 

Upper Slope Unit 

Eocene strata crop out across the expanse of slope 

occupied by the truncated upper slope unit. At the northeastern end of Georges Bank, detrital sediment makes up 

all or a major part of the unit. Exposures in Corsair 

Canyon comprise noncalcareous, muscovitic, brown silty 

mudstone (Ryan and others, 1978) and flaggy, semiindurated buff-brown sandstone and siltstone that dip 

apparently 100-15° seaward (Dillon and Zimmerman, 

1970). 

Submarine observations in Heezen Canyon (Ryan 

and others, 1978) indicate that the Eocene section here 

includes two lithologically distinct subunits. Ryan and 

others {1978) document approximately 250m of steeply 

dipping {10°-20° downcanyon) lower middle to upper 

middle Eocene, chiefly brown, noncalcareous, silty mudstone interbedded with glauconitic calcareous grainstone. 

The lower middle Eocene detrital facies becomes progressively more calcareous upsection and eventually becomes 

a distinctly marly sediment interbedded with glauconitic 

calcarenite and calcareous grainstone. Approximately 450 

m above the lower middle to upper middle Eocene 

section, Ryan and others {1978) discovered a 70-m-high 

cliff of subhorizontally bedded to massive uppermost 

middle Eocene chalk resting on Lower Cretaceous strata. 

The Eocene sediment in Heezen Canyon may have been 

emplaced by mass movement, but the seismic structure of 

the upper slope unit supports Ryan's inference of a 

depression-fill facies at the base of the unit. 

Westward from Heezen Canyon, the upper member 

of the upper slope unit seems to consist exclusively of 

Uthostratigraphy and Ages of the Seismic Units 17 
0 5km 

figure 18. Fay sparker line R across northwestern part of Georges Bank showing details of foreset unit. USU, upper 

slope unit. 

calcareous sediment of late middle Eocene age. The rock 

varies laterally from a true chalk to a calcareous clay or 

glauconitic marl, and argillaceous limestone crops out at 

a depth of 950 m on the east wall of Veatch Canyon 

(Valentine, 1981). Toward the west end of the survey area, 

the entire upper slope unit becomes more monotonous 

and marly. 

West of Veatch Canyon, the lower part of the upper 

slope unit is apparently exposed in many places across the 

lower slope to depths as great as 1,775 m. Samples 

obtained from the region west of Veatch Canyon include 

lower Eocene, pale-yellow to green, compact, silty clay 

(Gibson, 1965); upper lower Eocene chalk and lower 

Eocene yellow limestone (Gibson, 1970); chalk (Northrop 

and Heezen, 1951); and pure foraminiferal chalk (Stetson, 

1949). 

The upper slope unit evidently extends beneath 

Georges Bank into the Gulf of Maine as a persistent, 

distinctive, calcareous unit. Data on the Eocene section at 

COST well G-2 are uncertain because of poor sampling. 

Upper middle Eocene sediment at the well site may 

consist of less than 35 m of glauconitic calcareous mudstone and thin glauconitic quartzose limestone having 

abundant bryozoan and molluscan fragments (Poag, 

1982a; Valentine, 1982). The top of the dated interval is at 

least 370 m below sea level. Fragments of middle Eocene 

limestone were obtained also from the uppermost sample 

of COST well G-1, which is located about 66 km westnorthwest of COST well G-2 (fig. 3); approximately 37m 

of Paleogene (middle Eocene?) sediment, unconformable 

on Upper Cretaceous strata, is at the COST G-1 site 

(Poag, 1982a). 

AMCOR hole 6019 on the north side of Georges 

Bank penetrated middle Eocene, light-green-gray, calcareous clay underlain by dark- to bright-green, glauconitic, 

calcareous clay interlayered with hard, gray to white, 

bioclastic limestone layers, 61.3 m beneath the seafloor 

(Hathaway and others, 1976). C.A. Kaye (written commun., 1984) found pebbles of "glauconitic, sandy, hard 

limestone with oyster shells, etc." along the outer beach of 

Cape Cod. Presumably, this is the same limestone 

recorded from AMCOR hole 6019. 

Nearly 140 km northwest ofAMCOR hole 6019, at 

Fippennies Ledge in the Gulf of Maine (fig. 3), calcare18 Shallow Stratigraphy of the New England Continental Margin 
ous opaline chert fragments of late middle to late Eocene 

age were found; the rock seems to have been originally a 

sandy glauconitic limestone (Schlee and Cheetham, 1967). 

The regional dip of the Eocene section, from Pippennies Ledge to a water depth of 450 m on the continental slope off Georges Bank is 1.25 m/km. A projection of 

inferred Miocene and Eocene horizons from apparent 

dips in Fay lines T and P (Lewis and others, 1980) 

suggests that the top of the Eocene lies no shallower than 

480 m beneath the 200-m isobath (assuming acoustic 

interval velocity= 2,000 m/s). 

Lower Slope Unit 

Seafloor sampling and observations along the New 

England Continental Slope show that the lower slope unit 

represents an Upper Cretaceous section that consists 

typically of fine-grained, predominantly calcareous, terrigenous strata (that is, thin-bedded to massive, gray 

clayey siltstone, marl, and fine-grained sandstone) ranging in age from Maestrichtian to Coniacian (Trumbull 

and Hathaway, 1968; Valentine, written commun., 1977; 

Valentine and others, 1980; Valentine, 1981; Poag, 1982a). 

The entire section consists of an open marine, mostly 

bathyal facies (C.W. Poag, written commun., 1984). 

Beneath Georges Bank, however, the Upper Cretaceous section includes beds of markedly different facies 

than those of beds of the same age exposed on the slope, 

and, in the COST G-1 and G-2 wells, strata younger than 

Campanian are missing. The highest Cretaceous strata 

penetrated by the COST wells are Campanian and lower 

Santonian (Poag and Schlee, 1985). The strata include 

white to tan, pebbly, poorly to well-sorted, weakly consolidated micaceous quartz arenite that has a clay or calciticsideritic matrix. The strata are interbedded with gray, silty, 

glauconitic to calcareous mudstone and siltstone, pyritic 

and carbo!laceous shales, and lignite beds (Arthur, 1982). 

Cenomanian strata at the COST G-2 well site form an 

interval that is only 18-23 m thick and that consists of 

glauconitic gray shale and claystone having pyritized 

microgastropods (Poag, 1982a). This interval represents 

a distinctly marine environment similar to the environment indicated by strata exposed on the slope. 

The lower slope unit may include strata as young as 

Paleocene. Silty claystone of Paleocene age has been 

collected from Oceanographer and Veatch Canyons 

(Gibson and others, 1968; Valentine, 1980), and a thin 

Paleocene interval may be present at the COST G well 

sites (Poag, 1982a). Paleocene sediment was probably 

penetrated by wells on Nantucket Island (Folger and 

others, 1978). 

The lower subunit of the lower slope unit off 

Georges Bank may include or even consist of mostly 

Lower Cretaceous strata. A 112-m-thick interval of massive to medium-bedded limestone and calcareous feldspathic sandstone crops out between 1,188 and 1,350 m in 

Heezen Canyon (Ryan and others, 1978). Ryan and 

others (1978) designated this section Lower Cretaceous 

mainly on the basis of Calpionellopsis simplex and C. 

oblonga identified (but not illustrated) in one sample. 

Similar rock was obtained from Oceanographer Canyon 

below a depth of 1,517 m (Ryan and others, 1978). 

Seismic-profile data indicate that the lower slope 

unit is stratigraphically complex along the slope. West of 

Veatch Canyon, three distinct subunits appear in the lower 

slope unit (fig. 2, subunits a, b, and c). The uppermost 

subunit (a) is a weakly parallel-layered interval about 215 

m thick that crops out on the slope at depths between 

1,125 and 1,215 m. Subunit a is probably equivalent to 

subunit c--d along Georges Bank (see fig. 13).The uppermost subunit unconformably overlies a less well-layered 

middle subunit (b) at least 150 m thick along an uneven 

and presumably erosional surface (reflector A, figs. 2, 

12). Reflector A truncates seaward-dipping reflectors of 

the middle subunit (fig. 12) that fade out downdip against 

an irregular culmination rising beneath the mid slope 

(figs. 2, 12). The lowest subunit (c) is a thick, seawardthickening, strong reflector interval, which seems to have 

collapsed and splayed downdip, seaward of point B (figs. 

2, 12), and then formed a horizon that does not crop out 

but seems to follow the dip of the slope. Subunits b and c 

are probably equivalent to subunit d along Georges Bank 

(see fig. 13). 

A thick, downwarped, weak but parallel-layered 

succession appears low in (at the base of?) subunit c (figs. 

12, 19). Because the succession is near the limit of the 

survey acoustic penetration, its stratigraphic affinities are 

not known; the succession may represent the top of a 

strongly reflective Lower Cretaceous carbonate deposit, 

perhaps partly exposed in the carbonate strata reported 

off Georges Bank (Ryan and others, 1978; fig. 2). 

The acoustically transparent culmination that rises 

beneath the midslope may represent an eroded longitudinal ridge that is locally breached or downdropped-most 

notably at Alvin Canyon-to form seaward-dipping reentrants filled with sediment that extend down into the lower 

slope wedge. The inferred reentrant fill could have its 

source in subunit b (fig. 2) of the lower slope unit. Farther 

east, along Georges Bank, the filled depressions in the 

lower subunit also may represent filled reentrants opening into the lower slope wedge (fig. 13, subunit d). 

The wedge that fronts the lower slope along most of 

the New England margin may be formed largely of 

displaced Upper Cretaceous strata, Lower Cretaceous 

strata, and lesser amounts of prograded primary sediment. The primary sediment could be fed, in part, through 

the reentrants or incisions. During latest Cretaceous time, 

coarse detrital sediment (Stetson, 1949; Ryan and others, 

1978) was supplied, at least locally, to the slope off 

Georges Bank. 

Uthoatratlgraphy and Ages of the Seismic Units 19 
Cl.) 

c 

z 

c 

(.) 

w 

Cl.) 

~ 

w' 

::2 

w 1.5-

~ 2.5 > <( 

a: 

I-

> 

0 

~ 

~ 

E 

0 10km 

Figure 19. Gil/iss airgun line G34 along upper slope south of Nantucket Island. LSU, lower slope unit; LRU, layered rise 

unit. Vertical exaggeration -15:1. 

The Campanian-Paleocene(?) unconformity (or 

unconformities) at the COST G well sites suggests that 

the Upper Cretaceous strata on Georges Bank might have 

been at least a partial source of Upper Cretaceous detrital 

sediment found on the slope. The detrital sediment may 

be represented by a block of Maestrichtian calcareous, 

glauconitic sandy mudstone found by Ryan and others 

(1978) in Corsair Canyon. The Maestrichtian sample 

contained 10-20 percent quartz, 2-5 percent feldspar, 

10-20 percent glauconite, 5-10 percent foraminifera, and 

sparse muscovite in a silty clay matrix. The coarse fraction 

included 50-60 percent quartz as very coarse (1-2 mm), 

well-rounded, pitted and frosted grains to fine (0.2 mm), 

angular to subangular grains. Glauconite was botryoidal 

to well rounded. Commenting on the bimodal character of 

the Maestrichtian sample, Ryan and others (1978) stated, 

"texturally it shows a strong resemblance to the Pleistocene and recent canyon deposits." This Maestrichtian 

rock, like the nearby upper lower Eocene indurated 

detrital sediment, is a low-rank graywacke, but the rock 

includes both a preexisting sedimentary component and a 

hinterland component. 

The detrital rocks at the northeastern end of Georges Bank (Dillon and Zimmerman, 1970; Ryan and 

others, 1978) resemble the silicic mudstone-siltstone of 

the Banquereau Formation (Mciver, 1972), a terrigenous 

unit that prograded over the Maestrichtian Wyandot 

Chalk on the Scotian Shelf (Given, 1977). Calcareous 

detrital Maestrichtian sediment forms the lower part of 

the Banquereau Formation (Mciver, 1972). Maestrichtian 

strata must crop out in Corsair Canyon between a depth of 

1,452 m, where the sample described by Ryan and others 

(1978) was found, and a depth of 1,342 m, where the 

lowest exposure of Eocene detrital sediment was observed 

(Ryan and others, 1978). These observations indicate that 

as much as 110 m of largely Maestrichtian sediment, 

equivalent to basal Banquereau, could be at the northern 

end of Georges Bank. 

The deltaic or progradational aspects of the lower 

slope strata and the presence of high-relief unconformities were recognized by Ryan and Miller (1981), Schlee 

and Fritsch (1982), Poag (1982b ), and Schlee and others 

(1985). The lower slope wedge is probably equivalent to 

seismic unit D of Schlee and others (1985), which is 

inferred to represent channel fills and slump deposits 

associated with sedimentary aprons that were formed at 

the base of an ancestral slope, probably in late 

Campanian-Maestrichtian time (Schlee and Fritsch, 

1982). Similar features, such as slope-front fill and basin 

fill facies (Sangree and Widmier, 1977), were identified 

and interpreted by Poag (1982b) as predominantly siliciclastic debris flows equivalent to the Cenomanian Hatteras Formation of the deep Atlantic basin and to the 

upper part of the Upper Cretaceous Dawson Canyon 

Formation on the Scotian Shelf. 

Ryan and Miller (1981) associated "laterally discontinuous, low-amplitude reflectors" with an arkosic 

sandstone and conglomerate containing metamorphic rock 

fragments, microcline, and 10-20 percent bioclastic particles, which they sampled below a water depth of 1,517 m 

in Oceanographer Canyon. The rocks were inferred to be 

possibly Neocomian (Ryan and Miller, 1981). They may 

be part of the lower slope wedge. 

The lower slope wedge west of about 69° W. was 

mapped and interpreted by Mountain (1981) as a fan 

deposit that includes sediment ranging in age from Late 

Cretaceous to possibly as young as Eocene; the Paleogene 

20 Shallow Stratigraphy of the New England Continental Margin 
80° 

-500-- Isopach in meters 

•105 DSDP Drillsite 

--zoo-- Bathymetry 

Seaward limit of 

Au unconformity 

~., ', -'/------ ...... ,,"' ,.....,.--- 1 , ' n 

_.../ --

/ 

I' 

I 

/ 

/ 

Figure 20. Isopach map showing lower slope wedge off continental slope of New England. Au, eroded seismic horizon. 

From Mountain, 1981, fig. 4.29. 

section alone is inferred to be as thick as 1,700 m 

(Mountain, 1981; fig. 20). 

East of 69° W., the wedge is not a pronounced 

constructional feature, although the subsurface structure 

of the wedge is locally very complex, and its structural 

relief is high (fig. 14 ). Emery and others (1970) and 

Uchupi and others (1977) interpreted the wedge, or parts 

of it, as a pre-Late Cretaceous ridge complex that extends 

as far northeast as the Grand Banks. However, Given 

(1977) interprets a large area of the slope and outer shelf 

above the ridge complex in the region of Sable Island, 

Nova Scotia, as a latest Cretaceous slump or submarine 

fan complex. Farther west, off the Scotian Shel~ Swift 

(1985) identified upper Paleocene-lower Eocene fan 

deposits as thick as 500 m along the upper rise. 

Layered Rise Unit 

The tripartite layered rise unit, which includes an 

upper layered subunit, a middle transparent subunit, and 

a lower parallel-layered subunit (fig. 2 and table 1 ), is 

recognizable over wide areas of the western Atlantic basin 

(for example, Emery and others, 1970, fig. 160). The 

layered rise unit is well documented from Deep Sea 

Drilling Project (DSDP) holes 105 and 106 (Hollister and 

others, 1972) and DSDP hole 388 (Benson and others, 

1978) and is also well illustrated by the high-resolution 

seismic-reflection profiles acquired at those sites in preparation for drilling. 

The upper layered subunit cored by the DSDP 

holes ranges in thickness from 35 m to 350 m. It consists 

of soft, greenish-gray, Pleistocene silty clay composed 

chiefly of quartz, illite, and chlorite. The silty layers also 

contain glauconite, pyrite, and heavy minerals. Siderite, 

dolomite, and organic material are common in the more 

pelitic layers that dominate the lower part of the interval. 

Nonglauconitic Pliocene clay layers were penetrated 

toward the base of the upper layered subunit. 

The middle transparent subunit includes pelitic 

sediment of Pliocene through early Oligocene(?) age. At 

DSDP site 106, about 150 m of Pliocene clay and 500 m 

of lower to middle Miocene clay represent the transparent 

subunit. The subunit consists of dark-greenish-gray silty 

clay containing abundant siderite, zeolites, sphalerite, 

pyrite, and less common rhodocrosite. At site 388, the 

clay content is high (71-84 percent) and is nearly uniform 

throughout the section. The arenaceous fraction contains 

40-50 percent quartz and 12-19 percent feldspar. Carbonaceous matter (0.3-0.6 percent) is rare to common. Most 

core samples showed a high gas (C02 , H2S, CH4 ) content 

(Hollister and others, 1972). 

The parallel-layered subunit at DSDP site 106 is 

Eocene (C.W. Poag, written commun., 1985). Strata typically consist of hard, silicified, grayish-green mudstone 

that has dusky-yellowish-green zones and variegated, firm 

but plastic, silty clay that has abundant iron-manganese 

oxides. The dominant clay mineral is montmorillonite. 

Fine-grained palagonite and sphalerite are common 

throughout. Zeolites (mainly clinoptilolite) are common. 

Layers of black, highly carbonaceous, pyritic clay alternate with greenish-gray clay layers toward the bottom of 

the interval. 

Uthostratigraphy and Ages of the Seismic Units 21 
Table 1. Ages, lithologies, and paleoenvironmental aspects of seismic units described in text and shown in figure 2 

Depositional 

Unit Age Lithology Inferred source environment 

Surficial layer ............ Pleistocene Medium-coarse sand, Glaciated crystalline Braided to lobate 

(Wisconsinan). silty sand, shelly upland and earlier fluvial outwash train. 

sand. drift. 

Foreset unit .............. Middle Pleistocene to Qayey silt, silt, fine to Neogene regolith and Outwash delta to 

late Oligocene (?). coarse sand(?). bedrock, marginal to sublittoral lagoonal 

inner coastal plain. to subtidal regressive and transgressive, mid- to inner 

shelf, marine outer 

shelf. 

Upper slope unit: 

Upper subunit ......... Middle to late Oay, silty clay, marl, Paleogene latosol, Lagoonal, neritic to 

Eocene. bioclastic limestone, biogenic pelagic. bathyal (shelf and 

siliceous chalk, slope). 

foraminiferal chalk. 

Lower subunit .......... Early to middle Marly limestone, clay, Hemipelagic to Marl- Neritic to bathyal 

Eocene. marl, to siliceous time uplands. (shelf and slope). 

siltstone. 

Lower slope unit ......... Late Paleocene (?) Qayey, calcareous silt, Hemipelagic drift, Alluvial fan to fluvial 

to late Early marl, fine silty sand, Late Cretaceous deltaic, paludal, 

Cretaceous (?). calcareous sandstone latosol; Jurassic bathyal marine. 

and limestone. strata, grussified Debris wedge: lower 

Debris wedge: brec- granitic upland. slope to upper rise. 

cia, olistostrome, Debris wedge: Creslide debris. taceous strata and 

primacy sediment. 

Layered rise unit: 

Upper layered Holocene to Fine sand, silt to clay Hemipelagic drift, dis- Bathyal, upper rise. 

subunit .............. Pliocene (?). (graded beds). tal outwash, glacial 

ice-drop (distal 

equivalent of foreset 

unit). 

Middle transparent Early Pliocene(?)to Qay and silty clay. Hemipelagic drift, Bathyal, upper rise. 

subunit .............. early Oligocene(?). long slope drift, distal deltaic from midAtlantic shelf. 

Lentil ................. Early to middle Probably relatively Mid- to upper slope Bathyal, upper rise. 

Oligocene(?). coarse fragmental Eocene strata. 

slide debris. 

Lower parallel-......... Eocene .............. Calcareous to sili- Biogenic and hemi- Bathyal, upper rise. 

layered subunit. ceous clay. pelagic drift. 

DSDP sites 105, 106, and 388 are located in water 

depths between 4,500 and 5,000 m (fig. 20). The sites are 

in the vicinity of 35°30' N., 69°15' W., which is more than 

400 km due south of Veatch Canyon. A single-channel, 

seismic-reflection profile that extends from DSDP hole 

105 to Georges Bank (Schlee and others, 1976) demonstrates the stratigraphic continuity of at least the upper 

two subunits of the layered rise unit from the DSDP sites 

to the New England Slope. The lower parallel-layered 

subunit could not be traced along the profile because of a 

poor acoustic record and a greatly thickened suprajacent 

section between the DSDP sites and the lower slope 

(Mountain, 1981). However, Emery and others (1970) 

identified the top of the parallel-layered subunit as an 

important chronostratigraphic marker (horizon A), which 

they traced from the Sohm and Hatteras abyssal plains to 

the base of the New England Continental Slope. Schlee 

and others (1976) traced horizon A from the vicinity of 

DSDP site 105 to the lower slope off Maryland. Whether 

or not horizon A represents an early Tertiary diagenetic 

phenomenon (Schlee and others, 1976), an early Tertiary 

age accords with an Eocene age for the subunit inferred 

on the basis of correlation with the upper slope unit. 

Stratigraphic (seismic) continuity between the layered rise unit and structurally higher units beneath the 

New England Outer Shelf tends to support the implications 

of the DSDP data. The upper layered subunit of the 

layered rise unit is correlative with the foreset unit (fig. 

22 Shallow Stratigraphy of the New England Continental Margin 
en 

c 

z 

0 

u 

LLI 

en 

z 

E 

2-. ·:. 

4-

w 

0 10km 

Figure 21. Gil/iss airgun line G45 along lower slope south of Nantucket Island showing lentil in layered rise unit. Vertical 

exaggeration -16: 1. 

lOB). The upper layered subunit is therefore mainly 

Pleistocene and near the slope may include strata as old as 

late Miocene. The lower part of the deep parallel-layered 

subunit of the layered rise unit is correlative with the 

upper slope unit (fig. lOB). This lower part of the subunit 

is therefore partly middle Eocene. The transparent 

subunit separates the upper layered subunit (equivalent 

to the foreset unit) and the deep parallel-layered subunit 

(equivalent to the upper slope unit) at 690ZO' W. Because 

it onlaps the lower slope and the strata along the rise to 

the east, the transparent subunit essentially resembles a 

gigantic ponded interval, and its link to an updip source is 

uncertain. 

The layered rise unit displays a great deal of variation on strike, in contrast to its regularity downdip. Much 

of the variation is a result of internal deformation within 

the transparent subunit, but a considerable amount of 

lateral intertonguing occurs, particularly west of 6~ W. 

This intertonguing suggests that at least some of the unit, 

particularly a highly reflective fanlike lentil (Mountain, 

1981) within the transparent subunit (figs. 2, 10, 12, and 

18), is derived from local sources along the slope. Along 

strike, the lentil culminates opposite embayments (including Atlantis Canyon) in the lower slope (fig. 21); the 

culminations suggest that the lentil is made up of coalescent fans debouched from these embayments. The lentil 

thins to seaward and climbs the section (fig. 10); the lentil 

thickens to the west and occupies more section upward 

and downward. Ultimately, the part of the transparent 

subunit below the lentil is pinched out, and the lentil lies 

directly on the deep parallel-layered subunit and on the 

lower slope wedge (figs. 2, 22). The lentil may be an 

Oligocene deposit. 

Attempts have been made to work out a lithostratigraphic and chronostratigraphic succession for the North 

Atlantic upper rise section on the basis of multichannel 

seismic-reflection data and DSDP well logs (Poag, 1982b; 

Schlee and others, 1985). The location of the layered rise 

unit in this lithostratigraphic and chronostratigraphic succession is very uncertain. The upper layered subunit of 

the layered rise unit is probably equivalent to subunit D3 

of Schlee and others (1985). Subunit D3 is considered to 

be equivalent to the Miocene-Pleistocene part of the 

Blake Ridge Formation. Subunit D3 has a blanketlike 

aspect but presumably includes broadly overlapping channels and fans and onlapping layers (Schlee and others, 

1985). 

Most of the lower two subunits of the layered rise 

unit are incorporated in subunit D2 of Schlee and others 

(1985). The transparent subunit of the layered rise unit is 

Lithostratigraphy and Ages of the Seismic Units 23 
en 

c 

z 

0 

(..) 

w 

en 

~ 

w~ 

~ 

i= rrj3.5 

> <C 

a: 

1-

>-

<C 

3F 

0 

~ 

E w 

0 10km 

Figure 22. Gil/iss airgun line G25 along upper rise south of Martha's Vineyard showing contact between lower slope 

wedge and layered rise unit (LRU). 

probably equivalent to the late Oligocene-early Miocene 

part of the Blake Ridge Formation (Schlee and others, 

1985; Poag, 1982b). Subunit D2 lies on a high-relief 

unconformity (Au of Schlee and others, 1985), which 

probably represents the top of the wedge deposit along 

the lower slope (Mountain, 1981). In places, the unconformity is draped by inferred Eocene beds of the layered 

rise unit, but in places these Eocene beds seem to be 

broken and included in the wedge deposit. Where Eocene 

strata are part of the wedge, the base of the layered rise 

unit rests on the Au unconformity; where Eocene beds 

drape the wedge, the layered rise unit rests on the K-T 

unconformity. Therefore, the unconformity, if there is 

only one, is probably diachronous. The channel debris 

cited by Schlee and others (1985) at the base of subunit 

D2 is probably the uppermost (deltaic?) part of the 

wedge. 

PROVENANCE AND DEPOSITIONAL 

HISTORY 

The position of the regional drainage divide in New 

England indicates that all of New England, except the part 

of Vermont west of the Green Mountain axis, formed the 

source terrane for the Upper Cretaceous strata that are 

now offshore. Among the important source rocks in the 

New England watershed are the lower Paleozoic calcareous and quartz-muscovite schists of eastern Vermont and 

New Hampshire and the Silurian-Devonian calcareous to 

pelitic metasiltstones of central Maine. Smectite-bearing 

sediment derived from ultramafic rocks, magnesium carbonates, and black shales of western Vermont would have 

been shed largely to the west and thus would have been 

sequestered from the New England Coastal Plain. 

On the basis of composition, rocks most likely to 

have been sources of the Upper Cretaceous, muscovitic, 

kaolinitic, quartz arenite are muscovite-bearing peraluminous granites of the New Hampshire magma series 

(table 2) and Ordovician muscovitic granites and younger 

alkalic granites of southeasternmost New England 

(table 2). 

Muscovite granites, although widespread, form relatively small and isolated plutons in a terrane dominated 

by high-grade rocks that are rich in biotite, garnet, and 

sillimanite and mafic metaigneous rocks. The high-grade, 

magnesium-rich country rocks could not have been widely 

exposed in Late Cretaceous time; they may have been 

covered by an extensive terrane consisting mostly of 

muscovite-bearing granitic rocks. Perhaps these country 

rocks were covered by a batholith, analogous to the Sierra 

Nevada batholith, as proposed by Hamilton and Myers 

(1967). 

There is evidence, for example, that the Bethlehem 

Gneiss and the Kinsman Quartz Monzonite originally 

may have been nearly coextensive over much of the 5,000 

km2 of central and southwest New Hampshire (Nielson 

and others, 1976). The gravity study of the New Hamp24 Shallow Stratigraphy of the New England Continental Margin 
Table 2. Composition of some important muscovitebearing granitic rocks of south-central New England 

Chemical Bolton 

composition gneiss1 

{J2ercent) 

Si02 .......... 75.35 

Al203 ........ 13.03 

Fe0 +Fe01 .... 1.56 

CaO .......... 1.33 

MgO ......... .21 

~0 .......... 5.14 

N~O ......... 2.44 

1 Emerson, 1917, p. 82. 2 Finlay, 1902. 3 Emerson, 1917, p. 231. 4 Emerson, 1917, p. 231. 

Sterling 

Barre Weste~ granitegranlte2 granite gneiss4 

{J2ercent) {J2ercent} {J2ercent} 

69.89 71.64 73.05 

15.08 15.66 14.53 

2.50 2.34 2.96 

2.07 2.70 2.06 

.66 5tr 5tr 

4.29 5.60 5.39 

4.83 1.59 1.82 

6tr=trace. 

shire plutonic series shows that the plutons form intrusive 

sheets no more than 2.5 km thick. If New Hampshire ever 

had such a batholith, it was probably several kilometers 

above the present structural level and probably formed by 

sheet intrusions 2-3 km thick. The intrusions were most 

likely broken by cross-cutting, late, alkalic-rich phases, 

such as the Concord and Barre Granites (Nielson and 

others, 1976). 

Besides alkalic or peraluminous source rocks low in 

magnesium, kaolinization requires heavy precipitation, 

relatively acid runoff, and either good drainage or high 

evaporation to produce repeated leaching (Keller, 1957). 

Thus, the Late Cretaceous climate of New England must 

have been characterized by an annual cycle of a hot, rainy, 

monsoonlike season alternating with a relatively cool, dry 

season; this cycle subjected the plutonic upland terrane to 

intense hydrolytic weathering and grussification. Feldspar 

became kaolinized, and quartz and muscovite became 

disaggregated and were stored in an upland regolith, 

which was periodically flushed down to the coastal piedmont and continental shelf. 

From the beginning of Cenomanian time, fluvial 

aggradation of the quartz arenite across the New England 

Shelf seems to have been halted periodically by increasingly wider marine transgressions. The best preserved 

record of these transgressions perhaps is represented by a 

6- to 10-m-thick stratum of glauconitic-micaceous silt, 

presumably a lagoonal or shallow brackish water deposit 

(Kaye, 1983), exposed at Gay Head on Martha's Vineyard, Mass. Offshore, this stratum may be represented in 

the COST G well sections by an upper Cenomanian-lower 

Turonian interval of gray shale and argillaceous .nestone (Arthur, 1982), which may be correlative w1lh the 

Turonian Petrel Limestone Member of the "Wyandot 

Formation of the Scotian Shelf (Given, 1977). 

The latest phase of fluvial aggradation that occurred 

on the shelf perhaps is represented in the ConiacianSantonian section penetrated by the COST G-1 well, 

where strata that are similar to Raritan beds exposed at 

Gay Head, Martha's Vineyard (Kaye, 1983), and Block 

Island (Sirkin, 1974) are recorded (Arthur, 1982). A 

subsequent Campanian transgression is indicated by a 

thin (0.8 m) layer of Santonian-lower Campanian gray silt 

exposed at Gay Head (Kaye, 1983), by similar sediment as 

young as Maestrichtian recovered from the USGS 6001 

well on Nantucket (Folger and others, 1978; Valentine, 

1981), and by Campanian sediment recovered at the 

COST G-2 site (Poag and Schlee, 1985). 

Changes in nearshore depocenters also may have 

influenced the supply of sediment to the outer shelf 

toward the latter part of Late Cretaceous time. An 

important erosional unconformity separates the 

Cenomanian Raritan Formation of Long Island from 

overlying Santonian beds (Perlmutter and Todd, 1965; 

Sirkin, 1974). The relatively thick ( -1,200 m) Santonian 

through Maestrichtian section beneath Long Island is 

thought to be a dominantly subaqueous deltaic deposit 

(Sirkin, 1974) or lagoonal-estuarine deposit (Perlmutter 

and Todd, 1965). In contrast, the Santonian-lower Campanian(?) section exposed at Gay Head, Martha's Vineyard, perhaps is represented by only 0.8 m of dark-gray 

silt, rich in coniferous plant debris (Kaye, 1983). The 

equivalent subsurface section on Martha's Vineyard and 

Nantucket is probably less than 120m thick (Folger and 

others, 1978; Hall and others, 1980). The impressive 

thickness and the relatively coarse, heterogeneous makeup 

of the post-Raritan section beneath Long Island (Suter 

and others, 1949) are in contrast to the equivalent section 

in Massachusetts and in New Jersey. The contrast implies 

that the Long Island area lay within an important depocenter called the Raritan embayment (Olsson, 1978), 

which perhaps had shifted westward from its position in 

Cenomanian time. A northeasterly source is indicated for 

upper Maestrichtian (Monmouth) detrital sediment in the 

northern New Jersey Coastal Plain (Martino, 1978). 

The proximal aspects of the Upper Cretaceous 

succession in New England are uncertain, but the aggraded Cenomanian beds exposed on Martha's Vineyard, 

Mass. (Kaye, 1983), exposed on Block Island, R.I. (Sirkin, 

1974), and penetrated by wells on Long Island, N.Y. 

(Brown and others, 1972; Sirkin, 1974), cannot be far 

from the source area. A lateritic regolith as much as 60 m 

thick has been identified below the Lloyd Sand Member(?) of the Raritan Formation at the west end of Long 

Island (Blank, 1978), and kaolinized bedrock, recognizable to depths as great as 90 m below the present bedrock 

surface, has been reported from the Boston basin (Kaye, 

1967a). 

Evidence of terrigenous or proximal Eocene sediment in the New England region is scarce and controversial (Zeigler and others, 1960). Kaye (1967b) found 

fragments of bauxite in Pleistocene drift of Martha's 

Provenance and Depositional History 25 
Vineyard, Mass. The fragments consist mainly of gibbsitic 

pisolites in a matrix dominated by gibbsitic oolites containing about 15 percent solution-etched quartz grains and 

lesser amounts of siderite and carbonized plant matter. 

Kaye {1967b) inferred formation of bauxite during late 

Paleocene to early Eocene time when bauxite was being 

formed elsewhere along the emergent Atlantic Coastal 

Plain (Overstreet, 1964). 

Gibbsite forms under consistently wet, tropical 

conditions, which also lead to the solution of silica. The 

presence of acid water, humic materials, or extended dry 

periods is required to preserve silica (Keller, 1957). The 

character of sedimentation beginning in early Eocene 

time can probably be attributed to the influence of 

tropical climatic conditions when thick vegetational cover 

prevailed and only clay and dissolved silica, byproducts of 

bauxite formation, were carried out to the deep sea. 

Under tropical conditions, particularly during transgression, wlcanigenic and siliceous phases would be especially noticeable and perhaps would dominate the detrital 

fraction of primarily calcareous hemipelagic units. 

Towe and Gibson {1969) inferred a volcanigenic 

origin for cristobalite, clinoptilolite, and montmorillonite 

found in samples of latest early Eocene chalk from the 

Atlantic Continental Slope. According to Riech and von 

Rad {1979), however, the flooded shelves of Eocene time 

tied up much carbonate, thus raising the carbonate compensation depth (CCD) and producing a silica-rich ocean. 

They concluded that the silica component of the Eocene 

chalk obtained in DSDP cores is largely biogenic rather 

than terrigenous and that the chalk perhaps was derived 

from plankton blooms. Poag (1985a) likewise attributes a 

biogenic origin to the silica component in lower Eocene 

sediment along the continental slope and the continental 

rise off New Jersey. 

Upper Oligocene sediment obtained along the slope 

from New Jersey to Nova Scotia is distinctly terrigenous 

compared to the underlying middle Eocene strata 

(Gibson, 1970; Poag, 1985a). The upper Oligocene sediment indicates a reactivation of the terrestrial source 

area, including the inner shelf, under similar climatic 

conditions that seem to have prevailed in Late Cretaceous 

time. To the north, on the Scotian Slope, upper Oligocene 

(Chattian) strata dredged from the Gully (Marlowe and 

Bartlett, 1968) included compact, laminated to massive, 

dark-brown (apparently slightly bituminous) siltstone that 

had varying amounts of vegetal fragments, very fine 

angular quartz grains, and diatoms. In the coastal plain of 

Maryland, Delaware, and New Jersey, nearshore upper 

Oligocene strata comprise an olive-gray to brownishyellow, glauconitic clayey silt and medium- to coarsegrained, quartzose and glauconitic, locally shelly sand 

(Olsson and others, 1980). The unit includes weathered 

Eocene clasts, and much of the glauconite is weathered 

and polished (Olsson and others, 1980). 

Some indication of the late Oligocene climatic and 

physiographic conditions in the New England region is 

preserved in the Brandon Lignite of western Vermont. 

The lignite is a swamp deposit laid down on white sandy 

gravel, which presumably formed during the preceding 

era of kaolinization and bauxite formation. Flora of the 

Brandon Lignite indicate a warm temperate or subtropical environment very similar to the environment of northem Florida and similar to the present extensive Atlantic 

and Gulf Coastal Plain nonalluvial freshwater swamps. 

These freshwater swamps are poorly drained, topographically extensive basins free of inundation by floodplain 

deposits (Barghoom and Spackman, 1950). The Brandon 

flora also indicate that an average annual temperature 

was perhaps 11 °C higher than the present temperature in 

Vermont and that there was probably a greater amount 

and more uniform distnbution of precipitation (Tiffney 

and Barghoorn, 1976). Of the dicotyledonous genera of 

the Brandon flora, 32.6 percent are presently native to 

Vermont; this percentage places the assemblage in late 

Oligocene to early Miocene time (Traverse and 

Barghoom, 1953). If the Brandon Lignite represents late 

Oligocene environmental conditions in the New England 

hinterlands, it is evident that very little primary sediment 

was available to the shelf during late Oligocene and early 

Miocene time. 

Lower Miocene strata may be present beneath the 

New England Inner Shelf or Slope. Lower Miocene brown 

silty clay was obtained from the slope in 847 m of water at 

3go44.6' N., 710J9.9' W. (Gibson, 1970). The very thin 

( < 3.5 m) greensand that unconformably overlies 

Cenomanian arenite at Gay Head, Mass., provided two 

glauconite K/Ar dates that average 5.2 m.y. but provided 

paleontological ages that ranged from latest early Miocene 

to late Miocene (Kaye, 1983). Much of the pollen in the 

Gay Head unit is reworked from lower Eocene deposits 

(Frederiksen, 1979). Similar greensand found near Marshfield, Mass., includes Late Cretaceous, early Eocene, and 

Paleocene sporomorphs (Kaye, 1983), and the greensand 

is considered to be middle Mi9cene in age (Frederiksen, 

1984). 

The Gay Head Greensand (Kaye, 1983) is rich in 

nodular phosphate, principally dense, hard, dark-gray to 

black, microcrystalline apatite or vivianite, which forms 

the matrix of the thin, basal quartz conglomerate. Nodules 

also embed glauconite grains and fossil fragments, but all 

carbonate shell material has been leached from the greensand (Kaye, 1983). 

The greensand is essentially a bone bed (Reif, 

1982), a lag deposit accumulated during a slow transgression across a stable, nearly flat terrain during a time of 

subtropical climate. The abundant organic remains in 

bone beds are thought to be an important source for 

associated phosphate mineralization (Termier and Termier, 1963). Downward percolating ground water may 

26 Shallow Stratigraphy of the New England Continental Margin 
have been the agent that effected diagenetic phosphate 

replacement and nodule formation (Adams and Burkart, 

1968). At Gay Head, phosphate replacement and precipitation may have been followed or accompanied by a 

period of subaerial weathering during which the upper 

third of the greensand was oxidized (Kaye, 1983). 

The Gay Head Greensand is overlain by a sapropelic, ferruginous clay-silt, the Devils Bridge Oay of Kaye 

(1983), which is probably Pliocene in age (Frederiksen, 

1984). The Devils Bridge Oay is overlain by the Yorktownequivalent Lobsterville Sand (Kaye, 1983). 

The dark-gray, clayey, micaceous silt of Miocene 

age obtained from AMCOR hole 6016, and perhaps the 

ferruginous clay-silt (Devils Bridge Clay of Kaye, 1983) 

exposed on Martha's Vineyard, may represent a preYorktown Neogene section that extends over large parts of 

the shelf. The thin arenaceous layer of Yorktown age (the 

Lobsterville Sand of Kaye, 1983) that caps the section 

seems to be of regional extent also (Stetson, 1949; Gibson, 

1970). 

No unequivocal Miocene strata crop out onshore, 

between Gay Head and New Jersey, and greensand is 

conspicuously absent in the subsurface on Long Island 

(Crosby, 1900). The oldest post-Cretaceous sediment on 

Long Island is the Mannetto Gravel. The Mannetto 

Gravel consists almost entirely of silty quartz sand that 

has sparse clasts of deeply weathered gneiss or schist. The 

gravel is exposed in isolated patches on the tops of divides 

or hills. The unit generally is considered to be Pleistocene 

because of its crystalline clast content and its presumed 

similarity to later outwash (Suter and others, 1949). Suter 

and others (1949) noted that the Mannetto Gravel closely 

resembles the Bridgeton-Pensauken Formations of New 

Jersey in terms of composition, in degree of weathering, 

and in physiographic setting. They noted that the Mannetto Gravel could be an upper Tertiary deposit, a possibility considerably strengthened since the BridgetonPensauken Formations are now known to be Miocene 

(Owens and Minard, 1975). 

The Jameco Gravel, which also overlies Cretaceous 

beds, is distinctly different from the Mannetto Gravel. 

The Jameco Gravel is much more widespread; it tends to 

fill buried valleys, and it contains a fresh, polycrystalline 

clast component, which includes diabase (Suter and others, 1949). Crosby (1908) insisted that the Jameco Gravel 

is Tertiary, although not necessarily of nonglacial origin. 

Rampino and Sanders (1981) do not exclude the possibility that the Jameco Gravel may be as old as Tertiary. 

Crosby (1908) correlated the overlying clay (Gardiners 

Clay?) with Chesapeake-age units of the Miocene, and he 

noted that the clay contains abundant lignite and segregations of iron sulfide. The Gardiners Clay(?) beneath 

Long Island also contains glauconite (Suter and others, 

1949). The presence or absence of Miocene strata on 

Long Island is unresolved, but the post -Cretaceous-preWisconsinan section on Long Island resembles the section 

in New Jersey. Whatever its age, this Long Island section 

probably represents updip remnants of the foreset unit. 

Maps of the Delmarva Peninsula made by Owens 

and Minard (1975) showed two major successions of 

braided stream deposits trending seaward across southern 

New Jersey and Delaware. The older succession, the 

Bridgeton Formation, consists chiefly of quartzose, 

reddish-brown to orange sand and gravel. The Bridgeton 

Formation is capped in many places by a gtbbsite-bearing 

latosol as much as 5 m thick (Owens and Minard, 1979). 

The Bridgeton Formation is cut by the Pensauken Formation, a succession of fine to coarse sand and gravelly sand, 

similar to the Bridgeton, but the Pensauken Formation 

has a large primary component of Piedmont rock fragments (Owens and Minard, 1975). The base of the 

Pensauken Formation is as much as 200 m below sea level 

(Owens and Minard, 1979). The Pensauken Formation is 

probably upper Miocene; it interfingers downdip with 

marine beds, which contain late Tertiary warmtemperature flora (Owens and Denny, 1979) and 

which are apparently older than glauconitic sediment 

(upper St. Mary's) dated at 6.4±5 m.y. old (Owens and 

Minard, 1979). 

Middle to late(?) Miocene deltaic deposition across 

the New Jersey Shelf (Schlee and Grow, 1980; Valentine, 

1980; Poag, 1985b) is probably correlative with the 

Bridgeton-Pensauken fluvial complex. A BridgetonPensauken delta system may also account for the 

high rate of Neogene sedimentation along the rise off 

New Jersey (Mountain, 1981), and the delta system may 

explain part of the huge volume of post-Au sediment on 

the rise (that is, the transparent subunit of the layered rise 

unit). In roughly 20 m.y., one-third of all the sediment 

ever deposited in the western North Atlantic basin has 

accumulated above the Au unconformity (Mountain, 1981; 

fig. 23). 

The fragmental Miocene-Pliocene record of New 

England gives slight evidence of a middle Miocene transgression, of a late to post-middle Miocene regression, 

and of an early Pliocene regression (fig. 24) during a time 

of changing climate. During most of Miocene time, 

southeastern Massachusetts was apparently heavily forested; a humid, subtropical climate prevailed, similar to 

the climate indicated by the Brandon Lignite but slightly 

cooler (Frederiksen, 1984). The younger Neogene beds, 

the Devils Bridge Oay and the Lobsterville Sand, contain 

pollen that indicate a cool, temperate climate (Kaye, 

1983). 

Terrigenous lower Miocene sediment (Gibson, 

1970), the abundance of rock fragments in middleMiocene sediment relative to older strata (Kaye, 1983), 

and particularly the large influx of deltaic sediment on the 

New Jersey Shelf may reflect regional uplift in the Appalachians (Gibson, 1970; Owens and Minard, 1979), as 

Provenance and Depositional History 'ZT 
-500- Isopach in meters 

• 105 DSDP Drillsite 

--2oo-- Bathymetry 

f 

I 

I 

I 

I 

I 

I 

I 

I 

I 

/ 

I 

I '' 

? 

< / 

,...../,,.... ______ ',/-"' r---"" 

'"'' ..... r " I ,- / ,J 

I ~~<fl' I 'j; 

-~~~:~/ ... .Jt...r-S" J ,..~ 

.... ------..--- .,...~'-: ----' 

~_.--~~~~-m~~~~~~~--~--~~--~--~~--~--~~--~~--~--~--25° 

Figure 23. Isopach map of Neogene sediment (that is, upper part of layered rise unit) beneath continental rise. From 

Mountain, 1981, fig. 4.35. 

well as increasing climatic stress toward the close of the 

epoch. The Adirondack dome, which has undergone 

nearly 2,000 m of uplift since the beginning of Miocene 

time (Gable and Hatton, 1983), must have been a particularly active source terrain for middle Miocene detritus 

west of the New England divide. 

Following deposition of the Devils Bridge ClayMarshfield Center Formations of Massachusetts (Kaye, 

1983), virtually no primary sediment was transported to 

the New England Shelf until extremely high rates of glacial 

outwash deposition ensued in Nebraskan(?) time (Kaye, 

1983) or at least in Illinoian time (Oidale and Eskanasy, 

1983). Most of this outwash deposition occurred on 

Georges Bank and is represented by the upper part of the 

foreset unit. 

The Pleistocene foreset groups of the New England 

Shelf probably were derived mainly from upland regolith 

(Kaye, 1967a,b; Feininger, 1971) and from coastal plain 

sediment that originally occupied the Gulf of Maine and 

coastal lowlands farther west (Kaye, 1983). On Martha's 

Vineyard, the earliest drift consists largely of reworked 

Neogene sediment; the glacial origin of the drift is revealed 

only by its faceted and striated crystalline clasts (Kaye, 

1983). The later foreset groups are derived, in part, from 

28 Shallow Stratigraphy of the New England Continental Margin 
Figure 24. General inferred Tertiary-Quaternary stratigraphic configuration across the continental shelf and upper continental slope between 70° W. and 71° W. Relative thicknesses greatly distorted for diagrammatic purposes. 

earlier drift sequences and from Tertiary strata torn from 

the top of Georges Bank and the Great South Channel 

during ice advance. 

Along the rise, however, deposition evidently continued undiminished from late Miocene into glacial times. 

The composition of the terrigenous fraction is almost 

constant throughout the Pliocene-Pleistocene section at 

DSDP site 106B (Hollister and others, 1972). Here too, 

the uniformity of composition, of structure, and of accumulation rates throughout the Miocene-Pliocene section 

strongly suggests a common source and process of sedimentation during this time span (Lancelot and others, 

1972). Along the New Jersey Slope, however, numerous 

unconformities and allochthonous sedimentary components attest to the influence of mass wasting and local 

contributions from the slope during the Miocene-Pliocene 

epochs (Poag, 1985a). 

The Hudson Channel drainage way was probably 

the main site of debouchement of Pliocene-Pleistocene 

sediment to the western North Atlantic Continental Rise 

(Mountain, 1981 ). Pleistocene sediments that cut and 

overlie the Pensauken Formation of the Delmarva Peninsula apparently issued from the present Delaware drainage system (Owens and Minard, 1979). If the Hudson 

were the source of the Pensauken Formation (Owens and 

Minard, 1979), then the Hudson fan would be entirely a 

Pliocene-Pleistocene construction. The Hudson River 

must have been a conduit for fine outwash from the 

Mohawk and Champlain Valleys for a period of time 

before and after outwash deposition took place on the 

New England Shelf. 

UNCONFORMITIES AND EROSIONAL 

HISTORY 

During Late Cretaceous time, extensive and locally 

severe erosion probably occurred at relatively frequent 

intervals across the New England Outer Shelf and Slope. 

This episodic erosion perhaps was correlative to a phase 

of multiple transgressive and regressive oscillations that 

occurred across the New Jersey Margin from Campanian 

into Paleocene time (Olsson, 1978; Poag, 1985b). The 

unconformable subunits of the lower slope unit, and 

especially the lower slope wedge, imply that erosion on 

the New England Shelf during the times represented by 

Late Cretaceous regional unconformities (Poag and 

Schlee, 1985) was accompanied by extensive mass movement and erosion along the slope. For example, if Maestrichtian beds are present at Corsair Canyon, as implied 

by the sample recovered by Ryan and others (1978), then 

the Eocene-Neocomian(?) contact observed by Ryan and 

others (1978) in Heezen Canyon 35 km to the west could 

represent at least 1,725 m of missing section (Mciver, 

1972), which was presumably removed in postMaestrichtian time. Unfortunately, sampling along 

the lower slope is insufficient to assign lithostratigraphic 

identities to the Upper Cretaceous seismostratigraphic 

subunits or to ascertain the lateral continuity of the 

subunits. Therefore, the stratigraphic meaning and extent 

of these implied hiatuses are unknown. The inferred Late 

Cretaceous-early Paleogene episode of erosion probably 

ended by latest Paleocene to earliest Eocene time. The 

erosion was succeeded by the deposition of lower and 

middle Eocene strata of the upper slope unit. 

The unconformity that separates the upper slope 

unit from the lower slope unit (fig. 25) is the earliest 

regional unconformity clearly shown in the seismic 

records of the New England Outer Shelf-Upper Slope. 

Along the lower slope, the unconformity is represented by 

the erosional contact between the layered rise unit and the 

lower slope wedge (fig. 25). The unconformity is widely 

recognized along the Atlantic Shelf (Poag and Schlee, 

1985). Perhaps the unconformity extends as far north as 

the Scotian Shelf, where at least locally, a Maestrichtian to 

upper Paleocene section appears to be missing from the 

Unconformities and Erosional History 29 
Q) 

c. 

0 

u;.~ 

.!.C 

Q):::l 

c. 

c. 

:::l 

Plantagenet Formation 

Figure 25. Inferred relations between shallow New England Margin stratigraphy and North American basin stratigraphy (Jansa and others, 1979). Relative thicknesses greatly distorted for diagrammatic purposes. Horizons Au, A\ and Ac 

are prominent seismic reference horizons (Jansa and others, 1979). 

Banquereau Formation (Jansa and Wade, 1975). To the 

south, along some parts of the New Jersey Slope, the 

unconformity perhaps is represented by a postPaleocene(?) erosional gap of 17-18 m.y. that separates 

lower Maestrichtian from lower Eocene strata (Poag, 

1980). Onshore, the erosional gap is represented by a 

small disconformity separating the upper Paleocene 

Vincentown Formation from the lower and middle Eocene 

Manasquan Formation (Olsson, 1978; Poag, 1985b). 

The unconformity may be present on the rise south 

of Grand Banks where a 10-m.y. stratigraphic gap between 

upper Paleocene and upper lower Eocene nannofossil 

ooze and chalk is indicated at DSDP hole 384 (Riech and 

von Rad, 1979). However, along the rise off New England, 

an apparently conformable contact exists between the 

lower Eocene Bermuda Rise Formation and a thin, 

apparently discontinuous terrigenous section (a distal 

extension of the lower slope wedge?) at the top of the 

Upper Cretaceous-upper Paleocene Plantagenet Formation (Jansa and others, 1979; fig. 25). 

The disconformity that divides the upper slope unit 

into two subunits (fig. 25) is perhaps a lithologic contact 

as well as an erosional contact along the northeast end of 

Georges Bank and elsewhere beneath the outer shelf. 

This contact may be represented on the lower rise by the 

Ac horizon of Jansa and others (1979), which generally 

separates a succession of silicified claystone and radiolarian and calcareous mudstone and chert beds of the lower 

to middle Eocene Bermuda Rise Formation from the 

basal (middle Eocene) biogenic-siliceous clay and cherty 

mudstone of the Blake Ridge Formation (fig. 25). 

A major regional disconformity separates upper 

middle Eocene strata (upper slope unit) from Miocene 

strata and from presumably thin, upper Oligocene strata 

(basal foreset unit) along the outer shelf-upper slope; the 

contact can be traced down the slope and across the upper 

rise as an angular unconformity overlain by onlapping 

Neogene(?) strata (fig. 25). As the rise flattens, the 

unconformity gradually becomes a conformable surface 

representing the Eocene-Miocene contact within the Blake 

Ridge Formation (horizon A\ of Jansa and others, 1979) 

or a widespread eroded horizon (AU, of Mountain, 1981) 

at the base of the formation (fig. 25). 

The gap between the upper slope unit and the 

foreset unit may actually incorporate two periods of 

erosion; one period separates Eocene from Oligocene 

strata, and one period separates Oligocene from Miocene 

strata (fig. 25). In the New Jersey area, the two gaps are 

clearly distinguished. The earlier gap encompasses an 

upper Eocene and lower Oligocene section (Olsson, 

1978). The later gap perhaps is expressed by a 9-m.y. 

hiatus between upper Oligocene and middle Miocene 

strata in the COST B-2 well section (Poag, 1980). 

In the New England region, the inner shelf may have 

been exposed from latest Eocene through middle Miocene 

time. The post-middle Miocene unconformities implied in 

the Neogene strata exposed at Gay Head, Mass., suggest 

that during middle and most of late Miocene time, the 

New England Inner Shelf was flooded only for relatively 

short periods of time. 

The Pleistocene part of the foreset unit is broken by 

a major disconformity that extends from the shelf down to 

30 Shallow Stratigraphy of the New England Continental Margin 
the upper rise. Presumably the disconformity represents 

an important pre-Illinoian interglacial stage when mass 

movement occurred on the slope, channel incision 

occurred on the outer shelf, and subaerial erosion 

occurred on the inner shelf (Hathaway and Kaye, 1972). 

Several intraformational disconformities within the foreset 

unit may be interstadial surfaces that bound outwash 

sequences. 

The processes by which depositional sequences and 

their bounding unconformities are formed have been 

investigated in detail and have been tied genetically to 

eustatic changes in sea level, most notably by Vail and 

others (1977a). Examination of figure 26 shows that the 

inferred major intervals of erosion of the New England 

Tertiary System, based on the present study, correspond 

fairly well with eustatic lowerings of sea level of Vail and 

Hardenbol (1979). If the unconformities along the New 

England Margin do have interregional significance, the 

question is whether the unconformities were formed 

according to the mechanism postulated by Vail and others 

(1977a, 1984). 

The Late Cretaceous-early Paleogene depositional 

pattern across the New England Continental Margin and 

the equivalent section on the lower continental rise (Jansa 

and others, 1979; Vail and others, 1984) certainly signal a 

relative rise in sea level. But the deeply incised and 

truncated Upper Cretaceous subunits of the slope and the 

seismic facies of the lower slope wedge (Poag, 1982b; Vail 

and others, 1984; Schlee and others, 1985) imply that sea 

level fell below the Late Cretaceous shelf edge of New 

England at least once during Late Cretaceous-early Paleogene time, an occurrence perhaps indicated by a global 

sea-level fall at 65 Ma (Vail and others, 1980). In places, 

strata of the layered rise unit, which lie conformably 

beneath the interval correlative with the upper slope unit, 

onlap the lower slope (fig. 25). The position of the strata 

implies a pre-late early Eocene lowstand. The very top of 

this interval might be represented by the detrital section 

exposed in Heezen Canyon (Ryan and others, 1978). If 

this onlapping interval is Paleocene or lower Eocene, the 

interval could well be attributed to lowstand deposition, as 

defined by Vail and others (1984). 

A Chattian (late 0 ligocene) global lowstand (Vail 

and Hardenbol, 1979) also should have fallen below the 

shelf edge. If the fanlike lentil, which onlaps the lower 

slope above strata correlative with the upper slope unit, is 

lower Oligocene, then lowstand deposition (Vail and 

others, 1984) would again be indicated. However, much of 

the onlapping sediment above the lentil probably is mainly 

middle to upper Miocene. This sediment probably was 

derived from the New Jersey area during a highstand and 

was not brought directly across the New England Shelf in 

late Oligocene (Chattian) or early Miocene time. Also, 

upper Oligocene sediment sampled along the New 

England-New Jersey Margin was deposited in deep water 

300 

200 

~ 100 

~ 

~ 0 

-100 

inferred episodes 

1 of erosion 

-200~~~~~~~~riiTTIIIIIIrrTTTIIIrrr 

Figure 26. Relations between inferred major episodes of 

erosion along the New England Continental Margin (this 

study) (dashed line) and timing of eustatic changes of sea 

level during the Tertiary (from Vail and Hardenbol, 1979, 

fig. 1) (solid line). 

(Olsson, 1978; Poag, 1982a). The onlapping lentil may 

not indicate coastal onlap as defined by Vail and others 

(1984); the lentil may be a laterally restricted unit, which 

may have been derived entirely from the slope by mass 

wasting, regardless of sea level. 

The only exposed marine strata that clearly seem to 

have been deposited during rising sea level on the New 

England Shelf is the upper Miocene Gay Head Greensand. This unit does not display evidence of the coastal 

aggradation that, according to the Vail hypothesis (Vail 

and others, 1977a), accompanies rising sea level. The 

upper part of the foreset unit was deposited from melting 

ice during times of low but rising sea level, although the 

mode of deposition (coastal offlap) indicates falling sea 

level (Vail and others, 1977a), and the Pleistocene foreset 

succession does contain direct evidence (that is, filled 

channels along the outer shelf) that sea level stood below 

the shelf edge following deposition. However, the present 

slope canyons cut the presumed low stand deposits; there 

is no evidence that the canyons ever funneled sediment 

from the shelf to the rise during deposition of the foreset 

unit, as postulated by Vail and others (1984). None of the 

present canyon heads are axial to catchment basins on the 

shelf to provide sediment for submarine fans, and none of 

the present canyon heads are extended across the shelf by 

buried valleys, as postulated by Vail and others (1984). 

SYNTHESIS 

Sedimentary rocks of the New England Continental 

Shelf contain virtually the only record of the combined 

tectonic and climatic stresses that affected the New 

England Uplands during a prolonged period of erosion 

spanning Late Cretaceous through Cenozoic time. To 

interpret this record, some pattern or sequence of environmental transitions must be found that links the shelf to 

the upland and that explains the nature of the stratigraphic 

changes through time. 

Synthesis 31 
The spatial relation between source and shelf 

strata can be considered to be similar to the relation 

of a persistently positive craton bordered by a persistently 

subsiding platform where marine conditions generally 

prevailed. If we accept the premise that the shelfhinterland terrain of the New England region constitutes 

a cratonic regime (Fairbridge and Finkl, 1980) through 

time, then we can suppose that two opposing environmental states characterized by an association of climate and 

sea level alternately determined the regional conditions 

under which erosion and deposition occurred (fig. 27). 

These two opposing environmental states are the 

thalassocratic-biostatic state and the epeirocratic-rhexistatic state (Fairbridge and Finkl, 1980). 

The thalassocratic state is characterized by high sea 

level, a humid, maritime climate, and thick vegetation; it is 

a stable state when deep chemical weathering occurs, iron 

is retained in the regolith, and soluble products (mainly 

calcium and silica) are carried off by streams that have 

small suspended loads (fig. 27). Wave, storm, and tidedominated processes of deposition occur on the flooded 

shelves; intertidal and paludal environments are widespread, and in tropical climates, carbonate platform sediments dominate the section (Klein, 1982). 

The epeirocratic state is characterized by low sea 

level and an unstable, continental climate, which may be 

arid, humid, or glacial. Under the influence of the unstable climate, the regolith is stripped and denudation occurs. 

Marine deposits tend to be terrigenous (fig. 27). During 

the epeirocratic state, regression may be followed by 

fluvial or aeolian deposition, perhaps accompanied by 

erosional truncation of underlying marine beds (Klein, 

1982). 

Interpreting the New England region as a cratonic 

regime is an oversimplification, however. The concept of 

alternating climatic states and sea levels is complicated in 

the New England region by source area tectonism, which 

increases primary source yield and forces regression. For 

example, under temperate conditions, hinterland uplift 

could generate large, interregional cratonic deltas (Klein, 

1982), and a carbonate sequence of the thalassocratic 

state may be succeeded, without break, by thick deltaic 

and fluvial strata. 

At the beginning of Late Cretaceous time, central 

and southern New England was an uplifted terrain. Fission 

track dates from igneous and metamorphic apatites from 

high-grade rocks of the central Connecticut upland suggest that 3-5 km of rock was removed within the past 110 

m.y. (Denny, 1982), after the culminating White Mountain intrusive episode at about 115 Ma (Doherty and 

Lyons, 1980). The New England Upland was certainly 

shedding granitic debris well into the Cenomanian age. 

The lateral uniformity and composition of the Cretaceous 

alluvial-littoral facies and its broad extent indicate the 

influence of stable, near-tropical conditions of the thalassocratic state while this erosion occurred. 

The Late Cretaceous New England landscape was 

probably a seasonally arid, high-relief, pine-clad, granitic 

upland broken by forested valleys underlain by Jurassic 

redbeds; the uplands graded down to a broad piedmont 

floored with alluvial fans that extended out across a 

braided coastal plain, which was rich in paralic vegetation. 

In middle Cenomanian time and perhaps in Coniacian 

and Santonian time, the Late Cretaceous fluvial-dominated floodplain-delta system (Reading, 1978; Potter and 

others, 1980) extended, at least intermittently, on what is 

now Georges Bank as far seaward as the site of COST 

well G-1. A similar environment is envisioned for the 

Scotian Shelf during deposition of the upper ( Cenomanian) part of the Logan Canyon Formation (Given, 1977). 

Initially, deposition of the Upper Cretaceous marine 

facies seems to have taken place across the New England 

Margin with little complication. Schlee and others (1985) 

envision a smooth, subdued transition from shallow shelf 

to gently sloping continental rise during this time (fig. 28: 

1). Mountain (1981) also notes that, at least on the New 

Jersey Margin, reflectors in Upper Cretaceous sequences 

indicate uniform, uninterrupted seaward dip from the 

shoreline to a gently sloping, very broad continental rise. 

By latest Cretaceous time, however, conditions changed 

markedly, and a steep, eroded slope was formed (Mountain, 1981 ). Gibson (1970) states that major subsidence in 

the Hudson Canyon area had occurred by early Maestrichtian time. The high-relief unconformities and the filled 

depressions within the lower slope unit probably were 

originally sites of structural collapse, internal deformation, and bulk downslope transport (fig. 28: 2). 

As hinterland relief became depressed and as weathering became a more dominant process toward the close 

of the Cretaceous period, the influx of primary detrital 

sediment to the outer shelf abated (Gibson, 1970). Along 

the New England and New Jersey Shelves, transgressive 

conditions dominated the shelf from late Campanian time 

onward (Olsson, 1978). 

At the beginning of Eocene time, the New England 

coastal region was a low-relie~ tropical landscape fringed 

by estuaries, broad swamplands, and shallow, sandy 

shores. Eocene flora of the Gulf Coastal Plain extended, 

with little variation, from the Gulf Coast to what is now 

the region of coastal New England (Frederiksen, 1984). 

Presumably, the bauxite-forming conditions of the coastal 

plain of Georgia (Overstreet, 1964) also existed on the 

New England Coastal Plain. Although the shelf seems to 

have been exposed at the beginning of the epoch, by 

middle Eocene time the entire New England Shelf appears 

to have become a flooded platform similar in environment 

to the present Florida-Bahama platform. True thalassocratic conditions prevailed in the New England regipn. 

32 Shallow Stratigraphy of the New England Continental Margin 
Thalassocratic-biostatic state: 

Uplift: deposition forces regression 

proximal deltaic 

and interdeltaic 

organic-rich lutite 

Low-relief craton: eustatic transgression 

distal calcareous 

shale, laminated 

hemipelagic deposits 

distal calcareoussiliceous pelagic 

deposits 

Epeirocratic-rhexistatic state: 

Uplift: deposition follows regression 

Low-rei ief craton: eustatic regression 

mechanical weathering, 

foreland-shelf erosion 

proximal clay-bound 

fluvial arenites, 

aeolian and beach 

sand 

prograded 

fluvial/deltaic 

deposits and 

distal graded 

lutites 

barrier 

bar, tide 

flat, and 

distal 

paludal 

silts 

Figure 27. Major operative relations of climatic-tectonic states and of erosion-deposition episodes across the continental 

borderland (after Fairbridge and Finkl, 1980). 

Throughout the Eocene epoch, virtually no primary sediment was passed to the shelf except for an influx 

of graywacke at the northern end of Georges Bank 

(Banquereau Formation, Jansa and Wade, 1975); the 

influx of graywacke may reflect uplift of the Cobequid 

Mountains beginning in Maestrichtian time. By late middle Eocene time, graywacke deposition at the northern 

end of Georges Bank had abated, and chalk (or at least 

calcareous hemipelagic sediment) was laid down uniformly along and across the New England Slope (fig. 28: 

3). In general, Paleogene deposition along the New 

England Margin was dominated by pelagic conditions and 

occurred at bathyal depths (C.W. Poag, written commun., 

1985); the remarkably uniform but relatively thin Eocene 

chalk-marl of the New England region simply blanketed 

the margin that existed at the close of the Mesozoic era. 

Evidence exists in the seismic profiles, however, that 

the Eocene section was structurally deformed, at least 

locally, before formation of the Oligocene disconformity 

and that local slope steepening occurred. In places, the 

upper slope unit appears to have been incorporated into 

the lower slope wedge and to have been warped and 

downfaulted across the slope (fig. 28: 4) in an episode of 

deformation (perhaps local subsidence; Poag and Schlee, 

1985) that occurred along the North Atlantic lower slope 

at the close of Paleogene time. 

A period of relatively rapid seawater cooling t .gan 

some time in early late Eocene time and proceeded until 

late Oligocene time when bottom water temperature 

reached a minimum (Savin and others, 1975). By early 

Oligocene time, a worldwide regression was underway, 

which ultimately resulted in a sea-level drop of at least 

250 m (Vail and others, 1977b) by the middle of the epoch 

and resulted in imposition of generally epeirocratic conditions in the New England region. Perhaps the opaline, 

cherty limestone from Fippennies Ledge in the Gulf of 

Maine (Schlee and Cheetham, 1967) represents a 

duricrust that was formed on exposed Eocene limestone 

during latest Eocene or early Oligocene time. The character of the upper Oligocene sediment suggests no hinterland uplift and no consequent influx of primary detritus. 

Nevertheless, the increased detrital component relative to 

the detrital component of the Eocene section indicates 

influence of increased climatic energy in Oligocene time, 

which intensified stream planation of nearshore units and 

unlocked the Oligocene regolith. 

A shallow, gradually transgressive sublittoral environment is indicated by the upper Oligocene strata 

beneath the inner shelf of New Jersey (Olsson and others, 

1980). The middle to late Oligocene transgression was 

not extensive across the New England Shelf; the New 

England Inner Shelf must have been exposed from late 

Eocene until middle Miocene time, as indicated by sporomorph content of the Gay Head Greensand (Frederiksen, 1984). Amelioration of climate began in early 

Miocene time (Savin and others, 1975). By late middle 

Miocene time, southern New England was bound by a 

lagoonal-estuarine coastline fringed with warm, temperate to subtropical forest of the thalassocratic state. 

During Miocene time, deposition patterns on the 

Scotian and New Jersey Shelves began to be strongly 

influenced by uplift in the Maritime Provinces and especially in the central Atlantic Piedmont (Hack, 1982), 

respectively. Uplift of the White Mountains also is inferred 

Synthesis 33 
1 

2 

3 

DRAPED CALCAREOUS SILTSTONE AND CLAYSTONE 

EARLY LATE CRETACEOUS 

FIRST EPISODE OF REGIONAL MASS WASTING DURING 

CONTINUING DEPOSITION 

LATEST CRETACEOUS- PALEOCENE 

DRAPED CHALK, MARL, SILICEOUS LIMESTONE 

EXPLANATION 

4 

5 

6 THIRD EPISODE OF REGIONAL WISCONSINIAN OUTWASH MASS WASTING, MAINLY SLIDING AND INTERNAL 

DEFORMATION; FORMATION OF THE CONTINENTAL SLOPE 

LATE PLEISTOCENE 

~ Mass wasting deposits ~~ Foreset beds ~ Normally be"dded (marine) strata 

Figure 28. Major episodes of deposition and mass wasting on the North Atlantic Continental Slope. 

to have begun in Miocene time (Mathews, 1975; Denny, 

1982), and Connecticut is inferred to have been elevated 

by about 500 m during approximately the same time 

interval (Denny, 1982). Also, climatic conditions seem to 

have grown increasingly cooler and drier (Alt, 1974) as 

the Miocene epoch drew to a close; by early Pliocene 

time, a trend toward the epeirocratic state was underway, 

possibly due to extensive polar ice buildup (Savin and 

others, 1975). Under these environmental conditions, 

increasing supplies of primary sediment were available to 

the Atlantic Margin in Neogene time. By middle Miocene 

time, distal deltaic deposition was underway on the New 

Jersey Shelf and Upper Slope (Schlee and others, 1976; 

Poag, 1980) at rates as high as 24 cm/1,000 yr (Poag, 

1982a; Poag, 1985b). Although sediment transport across 

the shelf seems to have been minimal in the New England 

area, sediment derived from the Central Appalachians by 

way of the Delmarva Peninsula during Miocene time 

apparently contributed greatly to the New England Continental Rise west of Georges Bank. 

Neogene sediment transport to the New England 

Outer Continental Shelf culminated during successive 

Pliocene-Pleistocene deglaciations (fig. 28: 5). Relatively 

short but intense periods of outwash-generated progradation increased the regional relief of the continental slope 

by nearly 200 m. Elevation of Georges Bank was increased 

by morainal deposition. Virtually the entire Cenozoic 

sedimentary volume of the Gulf of Maine was excavated 

and redeposited on and across Georges Bank, the slope, 

and the upper rise during the Pliocene-Pleistocene 

epochs. Any proximal preglacial deposits that existed on 

the New England Inner Shelf consequent to Miocene 

uplift were obliterated by glaciai erosion and were incorporated into the prograded successions of foreset beds of 

Pleistocene age on the outer shelf. 

The continental slope then underwent a third episode of mass wasting, which resulted in the present deeply 

incised and truncated slope terrain (fig. 28: 6). Wisconsinan and Holocene deposition have scarcely muted the 

rough surfaces of the destructional landforms cut in the 

Neogene and pre-Wisconsinan Pleistocene section and in 

older units exposed along the slope. 

CONCLUSIONS 

Gimate and tectonism are the sources of energy 

that drives subaerial erosion. These energy sources pro34 Shallow Stratigraphy of the New England Continental Margin 
hinterland 

tectonics climate 

Pleist epeirocratic 

(glacial) 

+ thalassocratic 

" I (temperate c I humid) § I 

:i 

uplift epeirocratic 

(warm, arld) 

thalassocratic 

(subtropical) 

moderate epeirocratic 

uplift (humid) 

(tropical) 

" c 

§ 

i w 

~ ~ ~ I I I 

0 I I I 

c: White Mtn 

~ uplift dry tropical 

slope rise 

deep sea stratigraphy 

Blake Ridge 

Formation 

_,....,...~""""-Au"""'-

Ac 

Explanation 

"' 

Bermuda Rise 

Formation 

Plantagenet 

Formation 

"\., 

" 

b- j Clay-silt ~Coarse terrigenous 

sediment 

L<>:·~: I Silt-sand 8 Marl chalk 

Hatteras Formation 

\ 

\ 

\ 

I 

Figure 29. Schematic relations of provenance (climate and tectonism), New England margin stratigraphy, and deep-sea 

stratigraphy through time. Blank areas in section indicate times of apparent nondeposition; actual stratigraphic thickness is 

not implied. Au and A0 are prominent seismic reference horizons within the deep-sea stratigraphic section (Jansa and 

others, 1979). 

vide for delivery of sediment to the sea and, to an extent, 

are responsible for the mineralogical makeup of sediment 

that reaches the sea. Four main suites of terrigenous 

sediment, generated in response to source area tectonism 

and climatic stress, form the Upper Cretaceous through 

Pleistocene stratigraphic framework of the New England 

Continental Margin (fig. 29). In order of decreasing 

volumetric importance, these suites are (1) Pleistocene 

graywacke of mixed coastal plain-hinterland provenance 

produced by glacial weathering and erosion, (2) degraded 

Upper Cretaceous arkose formed under dry-winter, tropical conditions and shed from an igneous terrane that was 

uplifted consequent to intrusion of the White Mountain 

batholith, (3) middle to upper Miocene primary detritus 

shed from rejuvenated northern Appalachians during a 

time of gradually increasing climatic severity, and ( 4) 

upper Oligocene secondary sediment stripped from an 

emergent coastal plain during a period of relatively intensified climatic stress. 

The shallow stratigraphy of the New England Continental Margin does not manifest a cyclic pattern of 

erosion and deposition directly tied to changes in sea level, 

as postulated by Vail and others (1977a). The relative 

rises in sea level during Cenozoic time were not accompanied by measurable coastal aggradation because no 

primary sediment sources were sufficiently active in New 

England, except during Pleistocene deglaciations. This 

absence of aggradation is in distinct contrast to conditions 

on the Scotian Shelf throughout the Cenozoic and to 

conditions on the New Jersey Shel~ particularly in middle 

Miocene time. 

The onlapping strata of the New England Rise do 

seem to substantiate the mechanism of lowstand deposition presented by Vail and others (1984). Accurate age 

dates for these strata are needed to support the theory 

however, because evidence of bypass across the shelf (Vail 

and others, 1984) is not apparent. At least some of the 

unconformities on the slope, as well as onlapping rise 

Conclusions 35 
strata, may be attributed to episodic mass wasting, which 

may be unrelated to changes in sea level. Most of the 

Miocene sediment along the New England Rise probably 

was transported from the U.S. mid-Atlantic Coast region. 

The shallow stratigraphy of the New England Continental Margin supports the Vail hypothesis in some, but 

not all, ways. Perhaps the association of sea level with 

interregional unconformities and coastal onlap is not a 

cause-and-effect relation, but merely an instance of congeneric phenomena for which a deeper associative cause 

must be sought (Poag and Schlee, 1985). 

Oimate, source area tectonism, and sea level are 

mutually independent enough that their interactions have 

resulted in unique shelf-slope-rise configurations following each major episode of deposition. The continental 

slope itself perhaps is a fourth independent factor in the 

history of the New England Margin. The slope has 

undergone erosional and depositional activities that disrupt the stratigraphic continuum from inner shelf to rise; 

the slope seems to have acted as an independent source of 

sediment for the rise during Late Cretaceous, early 

Oligocene, and at least twice in Pleistocene time, during 

or immediately preceding periods of relative sea-level fall. 

Although this timing implies a causal relation with sea 

level, it does not clearly point to the lowstand deposition 

mechanism postulated by Vail and others (1984). 

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40 Shallow Stratigraphy of the New England Continental Margin