SMITHSONIAN CONTRIBUTIONS TO THE

EARTH SCIENCES

NUMBER 8

DanielJ. Stanley,

Donald]. P. Swift,

Norman Silverberg,

Noel P.James,

and Robert G. Sutton

Late Quaternary

Progradation and

Sand Spillover on

the Outer Continental

Margin Off Nova Scotia,

Southeast Canada

.APR 1 } iQ/>-

SMITHSONIAN INSTITUTION PRESS

CITY OF WASHINGTON

1972
ABSTRACT

Stanley, Daniel J., Donald J. P. Swift, Norman Silverberg, Noel P. James, and

Robert G. Sutton. Late Quaternary Progradation and Sand Spillover on the

Outer Continental Margin Off Nova Scotia, Southeast Canada. Smithsonian

Contributions to the Earth Sciences, number 8, 88 pages, 1972.—Three distinct

sediment types have prograded seaward from the outer shelf to the slope and rise

in the vicinity of Sable Island Bank southeast of Nova Scotia during late Quaternary

time. On the slope, the oldest facies recovered in cores is* a brown to brick red,

irregularly stratified, pebbly-sandy-clayey silt. Locally it is covered by an olive gray,

clayey silt with a low sand and pebble content. This more homogenous gray facies

displays abundant biogenic structures. A third facies, a thin layer of very fine, gray

sand and muddy sand, locally covers brown and olive gray sediments on the slope

and upper rise. All three facies contain similar light, heavy, and clay mineral suites.

The regional distribution of these facies has been determined by core traverses

normal to the shelf edge, including one passing down the axis of The Gully (largest

submarine canyon in the area), and another extending down the dissected slope

off Sable Island Bank. The brown, late Pleistocene unit is exposed on the floor of

The Gully and on its dissected deep-sea fan; postglacial bottom processes have kept

younger sediments from accumulating in these areas. The brown beds also are

exposed on the lower slope and rise off Sable Island in areas of slumping or nondeposition. The olive gray facies, late Pleistocene-Holocene in age, occurs primarily

on the slope; it is thicker on flanks of slope valleys and thinner or absent on the

divides. It is absent on part of the lower slope and upper rise. On the lower rise,

tan mud with a coarse fraction rich in Foraminifera and shell debris may be the

equivalent of the olive gray slope facies.

These sediments reflect changes in the sedimentary regimen during the postWisconsinan transgression. The observed sequence starts with the Wisconsin low

stand of the sea when glacial drift, including reddish-brown, fluvioglacial sediments,

were deposited over the Nova Scotian Shelf as far as Sable Island Bank. Periglacial

outwash spread across the bank and flowed seaward around it. Deposition of the

slope and rise brown facies is associated with this period; textural inhomogeneity

suggests downslope transport by mass movement. Pebbly lenses resulted, in part,

from ice-rafting prevalent during this phase. The contact between brown and the

overlying olive gray, clayey silt facies is often abrupt, commonly occurring within

several centimeters; this change is correlated with the rise of the late Quaternary

sea above the margin of Sable Island Bank.

As the sea transgressed across Sable Island Bank in late glacial time, fines winnowed from fluvioglacial sediment were moved north of the Bank (into the Gully

Trough) and seaward onto the slope. Coarse materials no longer reached the slope

with former frequency, and the fines were supplied at a markedly lower rate. This

decrease in sedimentation rate on the slope coincides with an increase in the organic

fraction and bioturbation. Suspended fines were reduced to a gray hue as they

passed through the sediment-water interface whose rate of upward growth was

now an order of magnitude smaller. The Pleistocene-Holocene boundary of approximately 10,000 years B.P. occurs within the olive gray facies. As sea level attained

its near-present position, and the present configuration of bottom currents was

established, the lag (modified relict or palimpsest) sands on the Nova Scotian Shelf

began a pattern of radial dispersal that may now be observed on Sable Island and

associated banks. This bottom current activity has resulted in the development of

spillover sands on the upper slope and deposition of thin discontinuous layers

(including someturbidites) on the slope and rise and in The Gully Canyon.

Official publication date is handstamped in a limited number of initial copies and is recorded

in the Institution's annual report, Smithsonian Year.

UNITED STATES GOVERNMENT PRINTING OFFICE

WASHINGTON : 1972

For sale by the Superintendent of Documents, U.S. Government Printing Office

Washington, D.C. 20402 - Price $1.25 (paper cover)
Contents

Page

INTRODUCTION 1

GEOGRAPHY AND TOPOGRAPHY OF THE STUDY AREA 2

General Setting 2

Morphology of the Outer Margin near Sable Island Bank 3

The Gully Submarine Canyon 3

Slope and Upper Rise off Sable Island Bank 6

SUBMERGED TERRACES AND SEA-LEVEL CHANGES 9

SEDIMENT DISTRIBUTION PATTERNS ON THE OUTER NOVA SCOTIAN SHELF .. . 9

General Textural Composition of the Shelf 9

General Mineralogical Composition of Surficial Shelf Sediments 13

GENERAL DESCRIPTION OF SLOPE AND RISE SEDIMENTS 16

Cores Examined 16

Four Outer Continental Margin Facies 17

Physical and Biogenic Stuctures in Slope Cores 19

Sediment Sequences on the Lower Rise and Abyssal Plain 22

TEXTURAL ANALYSES OF OUTER MARGIN SEDIMENTS 24

Outer Shelf near Sable Island Bank 24

Gully Trough and The Gully Canyon 26

Continental Slope South of Sable Island Bank: Upper Slope Samples ... . 31

Upper Slope to Lower Rise Traverse 32

MINERALOGICAL COMPOSITION OF OUTER MARGIN DEPOSITS 33

Sable Island Bank Sediments 33

Gully Trough Sediments 36

The Gully Canyon Sediments 40

Continental Slope Sediments 43

Upper Slope to Rise Traverse 50

CLAY MINERALOGY ON THE OUTER MARGIN OFF NOVA SCOTIA 56

Slope off Sale Island Bank 56

Slope and Rise Traverse South of Sable Island Bank 59

Clay Mineral Suite in the South Area 62

FORAMINIFERA AND STRATIGRAPHY OF SURFICIAL CONTINENTAL MARGIN

SEDIMENTS 62

INTERPRETING SEDIMENTARY SEQUENCES AND STRATIGRAPHY 65

Slope and Upper Rise Facies 65

Lower Continental Rise Facies 67

SEDIMENT DISPERSAL AND SPILLOVER ON SHELF-EDGE BANKS 67

Introduction 67

Sedimentation During Subaerial Exposure 67

Sedimentation During and Subsequent to Inundation 68

Radial Dispersal and Sediment Spillover 69

'•it
SMITHSONIAN CONTRIBUTIONS TO THE EARTH SCIENCES

Page

QUATERNARY PROGRADATION ON THE NOVA SCOTIAN OUTER MARGIN :

A SUMMARY 70

Introduction 70

Brown Sediment Time 70

Gray Sediment Time 75

Surficial Sand Time 76

ACKNOWLEDGMENTS 76

LITERATURE CITED 77

APPENDIX—Description of Gores Collected South of the Nova Scotian Shelf

by the Lamont-Doherty Geological Observatory of Columbia University .. . 82

INDEX 87

NOVA SCOTIAN

SHELF

Bathymetric Chart

(40-fathom Isobaths)

Fm

40

80

120

160

50n.mi 200

(km.

FIGURE 1 .—Bathymetric chart of the Nova Scotian Shelf showing localities discussed in text.

1, Cape Breton Island; 2, Northeast Channel; 3, Laurentian Channel; 4, Georges Bank;

5, Browns Bank; 6, La Have Bank; 7} Emerald Bank; 8, Sable Island Bank; 9, Banquereau

Bank; 10, La Have Basin; 11, Emerald Basin; 12, Sambro Bank; 13, The Gully submarine

canyon. Shaded area on shelf ( < 146 m deep) was subaerially exposed (partially covered by

ice) during the maximum Pleistocene low stand of sea level (Stanley et al. 1968).
DanielJ. Stanley,

DonaldJ. P. Swift,

Norman Silverberg,

Noel P.James,

and Robert G. Sutton

Late Quaternary

Progradation and

Sand Spillover on

the Outer Continental

Margin Off Nova Scotia,

Southeast Canada

Introduction

The surface of the wide, presently submerged, continental margin bordering the peninsula of Nova Scotia

and Cape Breton Island, southeast Canada, has been

modified in recent geological time by marked glacial

erosion and deposition and by the effect of sealevel fluctuations. These two phenomena were to

a large degree responsible for modifications of topography and sediment distribution on the Nova

Scotian Shelf as reviewed in a number of earlier

studies, including those of Upham (1894), Goldthwait

(1924), Johnson (1925), Shepard (1931), and Shepard et al. (1934). More recent marine geological

investigations bearing in one way or another on the

effects of ice and eustatic changes on the Nova

Scotian margin have been reported by Shepard

(1963), Heezen and Drake (1964), Hubert (1964),

Nota and Loring (1964), Cok et al. (1965), Marlowe

(1965, 1969), Rvachev (1965), Silverberg (1965),

Clarke et al. (1967), Conolly et al. (1967), Hubert

Daniel J. Stanley, Division of Sedimentology, Department of

Paleobiology, National Museum of Natural History, Smithsonian Institution, Washington, D.C. 20560. Donald J. P.

Swift, Institute of Oceanography, Old Dominion University,

Norfolk, Virginia 23508. Norman Silverberg, Department

of Oceanography, University of Washington, Seattle, Washington 98105. Noel P. James, Department of Geological

Sciences, McGill University, Montreal, Quebec, Canada.

Robert G. Sutton, Department of Geological Sciences, University of Rochester, Rochester, N. Y. 14627.

and Neal (1967), James and Stanley (1967, 1968),

King (1967a and b, 1969), Medioli et al. (1967),

Stanley (1968), Stanley and Cok (1968), Stanley et al.

(1968), Prest and Grant (1969), Stanley and Silverberg (1969).

To date, however, little attempt has been made to

synthesize Quaternary sedimentation on the outer

Nova Scotian margin. The present study is an attempt

to detail petrologic characteristics and stratigraphy of

the uppermost sedimentary sections on the outermost

shelf, slope, and rise off Nova Scotia, particularly

in the area southeast of Sable Island Bank. This

report summarizes and synthesizes the following petrologic and topographic data collected by the authors:

core samples from the Nova Scotian Slope and Rise

and Sohm Abyssal Plain (collected by the LamontDoherty Geological Observatory) south of the Nova

Scotian Shelf (Sutton 1964) ; core samples along a

traverse south of Sable Island Bank collected by

Stanley and Swift on the CSS Hudson in December

1964; cores samples and topographic data collected

off Sable Island Bank (Silverberg 1965) ; cores, bottom sediment grab samples, photographs, and topographic data gathered from the northern and eastern

margins of Sable Island Bank (James 1966). Synthesis of this material makes it possible to demonstrate

how late Pleistocene to Holocene glacioeustatic events

affecting the Nova Scotian Shelf and mainland left

a marked imprint on the sedimentary cover beyond

the shelf-break. In addition to an interpretation of
SMITHSONIAN CONTRIBUTIONS TO THE EARTH SCIENCES

late Quaternary progradation, particular attention is

paid to postglacial and modern sediment-dispersal

processes that have resulted in the spillover of reworked relict (palimpsest after Swift et al. 1971)

sands from the shelf to the slope and rise environments

beyond.

Geography and Topography of the Study Area

General Setting

The continental shelf off the Atlantic coast of Nova

Scotia,1 an area of about 120,000 km,2 is over 700

km in length and extends from the Northeast Channel northeastward to the Laurentian Channel (Figure 1). It is a broad northeast-southwest-trending

platform, about 100 km wide off the southwest coast

of Nova Scotia and about 250 km wide off Cape

Breton Island. The shelf is narrowest off the northeast coast of Cape Breton in the area of St. Paul's

Island. The shelf displays the typical dissected to1

 The three main continental margin provinces are called

Nova Scotian Shelf, Nova Scotian Slope, and Nova Scotian

Rise. Use of the abbreviated name Scotian Shelf and Scotian

Slope is discouraged to minimize possible confusion with

another glaciated region, the Scotian Sea in higher latitudes

of the South Atlantic.

pography of glaciated margins with deep basins and

linear troughs (Shepard et al. 1934, Holtedahl 1955,

Stanley, et al. 1968). The shelf depth is extremely

variable and locally deeper than 375 m. One point

on Sable Island Bank is actually emergent: Sable

Island, nearly 200 km from the mainland. The continental shelf differs from the nonglaciated shelf

south of the Gulf of Maine in several respects: it is

considerably wider, displays a much higher degree

of relief and dissection, and becomes shallower, not

deeper, along much of its seaward margin. The

Northeast Channel, a linear, U-shaped depression,

separates the Nova Scotian Shelf from the Gulf of

Maine. The northeastern margin of the Nova Scotian

Shelf is delineated by another broad, northwest-southeast-trending trough, the Laurentian Channel. The

shelf is widest in the region adjacent to the Laurentian

Channel, and extends for a distance of about 250 km

from the southeast coast of Cape Breton to the seaward edge of Banquereau Bank.

The Nova Scotian Shelf is distinguished by its

pronounced relief and extremely complex topography,

particularly on the eastern half of the shelf (Figure 1).

Morphologic cross-shelf gradients do not approach

the exponential curvature associated with mature

construction, "equilibrium" neritic platforms. PhysNOVA SCOTIAN

SHELF

Bathymetric Chart

(40-fathom Isobaths)

)km

1000^^^1829

FIGURE 2.—Inner, central, and outer physiographic provinces of the Nova Scotian Shelf as

defined in Stanley and Cok (1968). S.I.B. = Sable Island Bank. B.B. = Banquereau Bank.
NUMBER 8

iographic provinces of the shelf are well displayed

on Canadian Hydrographic Service Fisheries Charts

4040, 4041, and 4350. The shelf may be divided into

three major physiographic zones that are oriented

roughly parallel to the Nova Scotian mainland (Stanley and Cok 1968) ; these are referred to as the inner,

central, and outer shelf provinces and delineated ^n

Figure 2.

Morphology of the Outer Margin Near

Sable Island Bank

The outer Nova Scotian Shelf region emphasized in

this study is generally broad and flat, and is shallower

to the east where two large banks—Banquereau Bank

and Sable Island Bank—are less than 90 m deep.

On the western section of the shelf, Browns Bank,

La Have Bank, and Emerald Bank are somewhat

deeper and their upper surfaces average about 100 m.

This series of generally flat banks along the outer

continental shelf between Georges Bank, south of the

Gulf of Maine, and the Great Bank off Newfoundland falls physiographically and geologically within

the Submerged Atlantic Coastal Plain Province. The

bottom relief is slight over most broad shelf bank tops

(slope of 1 to 1000): smooth undulations are due

to the presence of migrating subaqueous sand dunes

(James and Stanley 1968). The shelf actually emerges

on Sable Island Bank as Sable Island, the only such

island on the outer shelf off northeast North America.

Sable Island Bank, a sand-covered platform approximately 250 km in length, has a maximum width

of about 115 km when using the 90 m (50 fm) isobath

as the bank margin (Figure 3). This Bank, the longest

such feature on the outer Nova Scotian Shelf, lies

between Banquereau Bank (to the east-northeast) and

Emerald Bank (to the west-south west) and covers an

area of approximately 17,000 km.2 Sable Island, at approximately 60 °W longitude, 43°50'N latitude, is

located on the eastern margin of the Bank, about 185

km southeast of Cape Canso and 334 km southeast of

Halifax on the Nova Scotian mainland. The Island,

a low (1-20 m), east-west trending, arcuate bar of

sand flats and dunes about 39 km long and 1.5 km

wide, has been recently described (James and Stanley

1967). Extremely gentle gradients east and south of

Sable Island are 1:880 and 1:330 respectively, and

1:280 north of the island (Figure 4). More than

one-half of the Bank lies at depths of less than 55

meters. The western part of Sable Island Bank, known

as Western Bank, is separated from Emerald Bank

by a shallow depression, the Western Gully; Western

Bank lies at depths of about 55 to 90 m.

The morphology and sediments of Sable Island

Bank have been discussed in earlier studies by Upham

(1894), Johnson (1925), Shepard et al. (1934) and

more recently by Marlowe (1965, 1967), Rvachev

(1965), James and Stanley (1967, 1968), Stanley and

Cok (1968), Stanley and Silverberg (1969).

A region of irregular submarine topography, The

Gully Trough, separates Sable Island Bank, Middle

Bank, and Banquereau Bank (Figure 3). The dominant feature of this dissected area is a broad valley

oriented east-west with a tributary-like branch entering from the north between Middle Bank and Banquereau Bank. The Gully Trough includes isolated

topographic highs rising up to a depth of 110 m and

basins deepening to 200 m. The central portion

deepens slowly from west to east and, on swinging

south off the east bar of Sable Island, deepens abruptly to form The Gully submarine canyon. This feature

is part of a broad relict dendritic pattern leading

southward toward the main canyon. The fluvioglacial

origin of this depression (see Figure 11) is discussed

in a later section.

The Gully Submarine Canyon

The seaward margin of the Nova Scotian Shelf is

dissected at several localities, but nowhere as much

as in the headward region of The Gully, the large

impressive submarine canyon between Sable Island

Bank and Banquereau Bank. The morphology of The

Gully Canyon, extending well onto the Nova Scotian

Shelf and bordering the eastern margin of the Sable

Island Bank (Figure 3), has been detailed elsewhere

(Marlowe 1967, 1969, Stanley 1967). This depression

is a sinuous, steep-walled, V-shaped submarine valley,

that displays most of the criteria of "type" submarine

canyons (Shepard and Dill 1966).

Marlowe (1964, page 17) in his preliminary study

of this area describes the physiography as follows:

The width of the canyon, as defined by the 400 meter contour, increases from one mile near its head to more than

eight miles at the seaward edge of the continental shelf. The

walls of the canyon are steep, attaining a gradient as high

as 1:2 below the 400 meter contour. In profile, the canyon

is V-shaped. Its course is slightly sinuous and it trends generally southward, with a deflection to the southeast at about
SMITHSONIAN CONTRIBUTIONS TO THE EARTH SCIENCES

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SMITHSONIAN CONTRIBUTIONS TO THE EARTH SCIENCES

the 2200 meter contour. Its longitudinal gradient varies

between 1:18 and 1:9. Side canyons occur along the west

wall.

The Gully divides Sable Island Bank from Banquereau Bank, and its shelfward continuation, the

Gully Trough, bifurcates and forms north- and northwest-trending troughs in the area of Middle Bank

(Figure 3).

Slope and Upper Rise Off Sable Island Bank

The southeastern margin of Sable Island Bank forms

the east northeast-west southwest trending shelf-break

and slope. The transition from shelf to continental

slope (gradient > 1:40) occurs within a distance of

2 to 4 km (Figures 4, 5). The slope bordering the

seaward edge of the Bank is approximately 240 km

in length and extends from the southwest margin

of the Bank (at about 62°00'W longitude, 43°00/N

latitude) to the Gully Canyon at about 59°07'W

longitude, 43°45'N latitude). A detailed chart of the

slope and uppermost rise south and southeast of

Sable Island Bank (Silverberg 1965, his figure 2) was

contoured at a 50-fm (91 m) interval using soundings

of Canadian Hydrographic Service boat sheets as

a base (a simplified version of this chart contoured

at 100-fm interval is shown on Figure 6). This data

was collected to depths of about 2000 m on the CSS

Kapuskasing in 1960 and 1961. DECCA navigation

( ± 1 nautical mile accuracy) was used to control

the position of traverses spaced 2.4 to 3.2 km apart

across the maximum slope inclination. The chart,

prepared by Silverberg at a scale of one inch to approximately five nautical miles, covers the area 59° 00'

to 62°00'W longitude and 42°30' to 44°00'N latitude

(see inset, Figure 6). The same soundings have been

NAUTICAL MILES

O-i

25

50

150

200

3 0 0

Fm.

SABLE ISLAND BANK

BOTTOM PROFILES

INDEX MAP

FIGURE 5.—Bottom profiles (from PDR traces) across the southern and eastern margins of

Sable Island Bank (see inset).
NUMBER 8

XX

N. Mlltt After Silvtrbtrg (1965)

FIGURE 6.—Dissected Nova Scotian Continental Slope southwest of Sable Island (modified

after chart by Silverberg, 1965). Note smooth, nonscalloped slope west of the Kapuskasing

Canyon, in contrast with areas between Sackville Canyon and Sable Island Canyon. Cores

(Sc-1 to Sc-20) are detailed in Silverberg (1965). Depth in fathoms.

contoured in a somewhat more generalized fashion

by the Canadian Hydrographic Service on their Fisheries Charts 4040 and 4041 (at a scale of 1:300,000).

The slope and rise immediately adjacent to The Gully

Canyon (Figure 16) have been charted (Marlowe

1967). Also available are several profiles of the slope

(Heezen et al. 1959) and of the rise beyond (Pratt

1967).

The break between shelf and slope (gradient 1:40)

occurs at depths ranging from 110 to 146 m, but

most frequently between 119 to 137 m. The shelfbreak occurs at similar depths along most of the

outer margin between Newfoundland and area south

of New England (Uchupi 1968). Gradients from

1:10 to 1:25 characterize the upper slope (Figures

4, 5). Only three large depressions were found actually to head on the outer shelf margin at depths of

less than 200 m in the region west of The Gully:

(a) Sable Island Canyon, about 5 km wide at approximately 60°03"W longitude, 43°35'N latitude

(almost due south of Sable Island) ; (b) Sackville

Canyon, about 4 km wide at 61°09'W longitude,

43°10'N latitude; and (c) Kapuskasing Canyon,

about 3 km wide at 61°17'W longitude, 43°16'N

latitude. A small narrow ridge, approximately 1.5X3

km, extends from the shelf edge toward the slope at

59°15'W longitude and 43°41'N latitude.

The slope becomes considerably dissected below

600 m where more than twenty large north northwestsouth southeast-trending depressions 1 to 8 or more

km across are noted on the charts between 59° and

61 °W longitude. Cross-sectional profiles parallel to

the slope indicate that most valleys tend to be U-shaped

rather than V-shaped (Figure 7). Gradients along the

top of intervalley ridges are approximately 1:20; that

of valley axes are commonly about 1:12. Submarine

valleys and gullies are straight to slightly sinuous,

and most extend to the base of the slope. Some valleys

appear to lack tributaries but this may be an artifact

resulting from an insufficiently tight sounding net.

Relief of several larger depressions exceeds 500 to 700

m on the upper continental rise, but none of the

valleys appear to extend as far as the Sohm Abyssal

Plain to the south (Pratt 1967). Certain valleys such

as Kapuskasing Canyon, heading near the shelf-break,

appear to die out near the base of the slope. It is noteworthy that most valleys head at depths greater than

400 to 700 m, and in some cases below 900 m. Large

broad mounds, some of them covering an area exceed-
SMITHSONIAN CONTRIBUTIONS TO THE EARTH SCIENCES

fms

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sgp

fms

D

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L

5

nautical miles

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FIGURE 7.—Profiles across the upper slope showing position of cores on valley floor and margins

and intervalley highs. Geographic location of cores are shown in Figure 6. Depth in fathoms.
NUMBER 8

ing 25 km,2 occur beyond the distal termination of

gullies at base-of-slope depths.

In striking contrast with this scalloped and dissected topography is the smoother more regular slope

(gradient about 1:20) south of Western Bank and

west of 61°30'W latitude. The shelf north of the

undissected slope region (Western Bank) is generally

deeper (60 to 100 m) than the bank area east of

61°30'W latitude. There are two possible explanations

for the high relief on the slope south of Sable Island:

(a) Sable Island Bank may have acted as a sediment

barrier preventing the filling of valleys cut in Pleistocene time or earlier on the slope, or (b) conversely,

Sable Island Bank provided an unusually large volume of sediment to the slope during the Pleistocene,

and the high rate of sedimentation, in turn, induced

overloading and, eventually, slumping. The latter hypothesis of submarine valley formation seems most

probable. Analyses of seismic profiles [Uchupi 1969

(his figure 4), Emery et al. 1970] and cores (Stanley

and Silverberg 1969) collected on the continental

slope and rise off Sable Island Bank do, in fact, support a slumping hypothesis. Much of this slumping

took place during Quaternary time, and there is further evidence to suggest that this process is still active

in this general area at present. The 1929 Grand Banks

slump which occurred northeast of the study area is

the best documented example (Heezen and Drake

1964).

The boundary between slope and rise is difficult to

establish precisely; the decrease in gradient from 2° to

less than 1 ° is gradual. Downslope profiles show local

breaks in slope near The Gully at about 950, 1300,

and 1700 m (Marlowe 1967); some of these terracelike features are probable structural benches. The rise

is somewhat steeper, wider, and deeper (1000 to 1500

fm) than in some areas off the northeast United States

continental margin (Heezen et al. 1959, Pratt 1967).

The combined width of the slope and rise southeast of

the Bank is approximately 180 nautical miles (334

km). The density of sounding notations and available

profiles in water deeper than 1800 m does not, at this

time, permit compilation of a detailed topographic

chart of the lower rise southeast of Sable Island Bank.

Submerged Terraces and Sea-Level Changes

A recent survey (Stanley et al. 1968) of submerged

terraces has identified the position and depth of

notches, benches, and other morphological features

identified as terraces on the Nova Scotian Shelf. Two

groups of terraces are particularly pronounced. The

frequently encountered terrace at approximately 66

fm (121 m) is attributed to the maximum low stand

of sea level during the last glacial stage as indicated by

Curray (1965), Shepard and Curray (1967), and

Milliman and Emery (1968). A lower, well-defined

terrace at approximately 80 fm (146 m), cut just below the seaward edge of the outer shelf and on the

steep northern margins of the outer banks, probably

records one of the maximum lowerings of Pleistocene

sea level. Faunal evidence at this horizon in other regions does not rule out an early Wisconsinan age (J.

Ewing et al. 1960, M. Ewing et al. 1960), but there

is strong indirect evidence to attribute the 80-fm terrace to an earlier glacial stage probably the Illinoian,

or third major glacial episode (Donn et al. 1962).

The Nova Scotian Shelf is morphologically so irregular and highly dissected that even a small change in

sea level would alter markedly the configuration of the

exposed continental platform seaward of the Nova

Scotian mainland (Berger et al. 1966). Even during a

maximum low stand, as recorded by the terrace at

approximately 146 m, several large, deeply incised

areas of the shelf probably remained covered with

lakes or with ice or both. These deep depressions,

shown as the nonhachured sectors on the shelf on Figure 1, include basins south of Halifax, linear troughs

southeast of Cape Breton, and The Gully Trough, an

extension of The Gully submarine canyon. These lows,

almost certainly related to fluvioglacial drainage and

ice transport (Stanley and Cok 1968) have received

fine-grained sediments from adjacent topographic

highs since the postglacial rise in sea level.

Sediment Distribution Patterns on the Outer

Nova Scotian Shelf

General Textural Composition of the Shelf

It is necessary to review the dominant petrologic

trends on the Nova Scotian Shelf proper in order to

properly interpret mineralogical patterns and facies

changes on the continental slope and rise. The regional grain size-distribution pattern is summarized on

a simplified textural facies map (Figure 8). This facies map is based on over 1000 samples collected on
10 SMITHSONIAN CONTRIBUTIONS TO THE EARTH SCIENCES

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SABLE ISLAND

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FIGURE 8.—Generalized regional size distribution of surficial sediment on the Nova Scotia Shelf

(Stanley and Cok 1968).

the shelf (Stanley and Cok 1968, their figure 4). A

textural classification, modified after Folk (1954), is

used in which three end-members are recognized:

gravel (fraction coarser than 2.0 mm); sand (fraction

from 0.0625 to 2.0 mm) ; and mud (fraction finer

than 0.062 mm, including both silt and clay). Intermediate textural admixtures consisting of mud and

sand, of gravel and sand, and of gravel, sand, and

mud are also depicted on Figure 8. The resulting distribution of textural types brings out the pattern of

"outward increasing gradation," e.g., the offshore

coarsening of sediment described by Shepard et al.

(1934). Regional trends are neither strictly parallel,

nor normal to the coast of Nova Scotia, and the overall patchiness of sediment distribution indicates that

the shelf is by no means "at grade" or in equilibrium

with present hydrographic conditions. The shallow

outer banks are covered largely by sand or sand-gravel

admixtures; deep basins and troughs on the center

shelf are commonly floored with mud, and mud-sand

admixtures; and much of the remainder of the inner

and mid-shelf regions, particularly at intermediate

depths, are covered with gravel-sand-mud admixtures

that are till-like in textural composition.

The textural distribution pattern suggests that grain

size bears some relation to (a) geographic position

and distance from shore, and (b) depth. The correlation of grain size with depth is largely a function of

recent erosional and depositional processes on the

shelf. No major rivers, for instance, drain the mainland of Nova Scotia, and little sediment is provided

to the shelf, with the exception of some fine-grained

material that bypasses river mouths (Stanley 1968).

Thus, much of the present sedimentary pattern reflects relict distribution ("remnant from a different

earlier environment" according to Emery 1952, page
NUMBER 8 11

1105), subsequently modified by Holocene processes

of reworking. The distribution of gravel-sand-mud admixtures of the upper sediment surface indicates, for

instance, the widespread cover of poorly sorted diamictites transported onto the shelf by glacial ice.

The dominance of sand on much of Emerald Bank,

Sable Island Bank, and Banquereau Bank is probably

related to (a) the buildup of glacial out wash deposits

at the frontal ice contact areas on the northern margins of these banks, and to (b) the subsequent removal

by winnowing of finer grade fractions from originally

more poorly sorted deposits. That much of these

"fines" have probably been redeposited landward in

deep areas of the center shelf region north and northwest of the banks following the last rise in sea level

was suggested in an earlier study (Stanley and Gok

1968). We shall show in subsequent sections that some

of the silt and clay winnowed from bank tops was also

redeposited seaward on the continental slope and in

canyon-subsea fan complexes during the late Pleistocene and early Holocene. This seaward dispersal of

fines began prior to the time when sea level began to

cover the bank areas and migrate landward across the

shelf. Thus, as a result of this transgression, recently

transported fine-grained sediments are concentrated

over relict (Pleistocene) sediment in inner and center

shelf regions and beyond the shelf-break, while coarser

lag deposits remain on the outer banks, including

those on the eastern half of the Nova Scotian Shelf.

Details of the textural distribution on Sable Island

Bank are available elsewhere (James and Stanley

1968).

The lateral variation of sorting observed on the

Nova Scotian Shelf (Figure 9) substantiates these

conclusions. A scale showing the relative degree of

sorting is based upon the total number of phi classes

that make up the size distribution of a sample at each

station. Thus, the fewer the number of size classes, the

SABLE ISLAND

Q) V. WELL WELL MODERATE POOR V POOR

BOULDER CONCENTRATION

O 1,0 30 60

NAUTICAL MILES

FIGURE 9.—Regional variability of sediment sorting and distribution of boulder concentrations

on the Nova Scotian Shelf (Stanley and Cok 1968).
12 SMITHSONIAN CONTRIBUTIONS TO THE EARTH SCIENCES

better the sorting, and vice versa. The best sorted

sediments are those located on the shallow outer banks

(particularly on the eastern half of the shelf), areas

covered predominantly with sand. Areas displaying

the poorest degree of sorting occur in elongate belts

on the inner and center shelf regions; these elongate

areas generally are composed of gravel-sand-mud

admixtures.

Areas of boulder concentration on Figure 9 are

generally closely related with the distribution of linear

belts of poorly to very poorly sorted sediment. This

"boulder-diamictite" association clearly defines major

dispersal trends. These trends, reflecting moraines

and boulder trains, extend from the present coastline

toward the center shelf and outer shelf edge on the

western half of the Nova Scotian Shelf. Other petrologic criteria have also resulted in the delineation of

certain of these glacial moraines on the shelf (King

>* Glacial stria

^ " Drumlm etc.

•*/.•••. Esker • tunnel valley

**+y End moraine

I

FIGURE 10.—Glacial features indicative of ice flow on Nova Scotia and adjacent areas patterns

(Prest and Grant 1969, their figure 3 with the authors' permission).
NUMBER 8 13

1969). Moderate to very poorly sorted sediments indicative of glacial ice transport predominates on the

eastern half of the shelf north of Emerald Bank, Sable

Island Bank, and Banquereau Bank.

General Mineralogical Composition of Surficial Shelf

Sediments

The relation between mainland tills and sediment offshore has been demonstrated by plotting the distribution of lithic (rock) fragments and heavy minerals in

the sand-size fractions and by examining the composition of the pebbles and boulders in the coarse fraction

(James and Stanley 1968, Stanley and Gok 1968).

The sum of mineralogical data, evaluated in light of

the textural and morphological data, also serves to

delineate the coverage of glacial deposits on the shelf.

The mineralogical composition of inner shelf sediments is similar to that of glacial drift on the mainland.

Much of the coarse fraction is composed of Paleozoic

material of the type cropping out on Nova Scotia. The

regional distribution indicates a linear belt approximately 60 km wide that is roughly parallel to the

mainland and is rich in rock (lithic) fragments (10 to

over 75 percent rock fragments in the 0.6 to 1.0 mm

fraction; 5 to 25 percent in the 0.4 and 0.6 mm fraction ). Heavy mineral assemblages distinguished on the

mainland beaches (Nolan 1963) can be correlated

reasonably well with those on the inner and center

shelf regions. Glacial tongues that traversed the mainland in south and southeast directions (and toward

the northeast in sections of Cape Breton) according to

Goldthwait (1924), Grant (1963) and Prest and Grant

(1969, their figure 3) undoubtedly continued beyond

the present coast. Generalized ice flow trends on the

Nova Scotian mainland are depicted on Figure 10.

Diagnostic heavy minerals (such as augite) or rock

fragments (granite pebbles from the Cobequid Mountains) are useful for pinpointing specific source locations. Linear troughs and channels carved into the shelf

(Stanley et al. 1968) indicate the general transport

path of the glacial tongues (Figure 11).

Reddish brown tills, containing iron stained grains,

are found on the Atlantic coast of Nova Scotia, and

it is likely that they extended further onto the shelf.

These mainland tills were derived from source areas

(Carboniferous and Triassic) located in Bay of Fundy,

Prince Edward Island, and New Brunswick regions.

FIGUGE 11.—Probable major glacial and fluvioglacial drainage patterns on northeastern sector of

the Nova Scotian Shelf (Stanley and Cok 1968).
14 SMITHSONIAN CONTRIBUTIONS TO THE EARTH SCIENCES

Heavily stained quartz (Stanley and Cok 1968, their

figures 9, 10) and lithic grains of sand size, so

abundant on the outer banks, are also valuable provenance indicators. It is almost certain that much of

the glacial and fluvioglacial materials preserved on

the outer banks originated in Carboniferous and

Triassic terrains lying several hundreds of kilometers

to the northwest. Many of the pebbles and cobbles collected on Sable Island Bank have been identified as

Paleozoic in origin of the type cropping out on Nova

Scotia (James and Stanley 1968).

A relatively anomalous mineralogical province

occurs on the central shelf northwest of Sable Island

Bank. The presence of nodules, quartzitic and glauconitic sandstone fragments, varieties of corroded

garnet, and other heavy minerals of the type not found

elsewhere on the shelf suggests a supply from local

bedrock source areas exposed on this sector of the

shelf. It is conceivable that such isolated ledges include

Tertiary and Cretaceous strata (occasionally dredged

by scallop fisherman) that were eroded by moving ice.

Evidence of Cretaceous strata on the shelf has, in fact,

been cited by Dall (1925), Stephenson (1936), King

et al. (1970), and others. The seaward dipping prePleistocene Coastal Plain deposits forming the submerged cuestas on the Nova Scotian shelf are evident

in high-resolution subbottom seismic profiles (Uchupi

1969).

Mineralogical data provide additional support for

the conclusion tljat Pleistocene glacial tongues at one

time (although not necessarily during the Wisconsinan) extended seaward as far out as the shelf edge

on the southwestern part of the shelf and as far as the

Sable Island Bank-Banquereau Bank regions on the

northeastern shelf. A paleogeographic reconstruction

displaying the zone of ice coverage is shown in Figure

12. This schema shows that a considerable amount of

ice-borne glacial marine sediment was rafted onto

the slope and rise beyond by bergs breaking off the

glacial front during glacial stages. Bottom photographs

and dredge hauls (Cok 1970) on the slope and rise

show that this did take place. In particular, photographs collected during the search for the submarine

Thresher, whose hull bottomed at the base of the slope

southeast of the Northeast Channel (Brundage et al.

1967) reveals concentrations of large boulders, some

over 3 m in diameter, which were undoubtedly initially

ICE COVERAGE

DURING MAXIMUM

ADVANCES

FIGURE 12.—Ice coverage on the Nova Scotian Shelf during the Pleistocene, as interpreted

from sediment distribution and topography (Stanley and Cok 1968). 1, Probable extent of

glacial ice during maximum advances; 2, outwash area; 3, area of berg-borne sediment.
NUMBER 8 15

nt oxw

<//////'////,'//////,'/''///''///'''"//<'''///' '/''//A

ICE COVER

OPEN WATER

CURRENTS

MAIN WIND DIRECTION

DURING BREAK-UP

^'//y'/y////////'

NAUI MILES

S1*W 4 / N 57*W 45*N

FIGURE 13.—A, Maximum ice-coverage and dominant surface current patterns on the eastern

portion of Nova Scotian Shelf during ice breakup in the spring, B, Major sedimentological

provinces on the northeastern Nova Scotian Shelf (explanation in text). Note that the sector

of ice-rafted material (B) coincides with zone of seasonal ice-coverage shown in A. The outer

banks, zones of intense erosion and textural unmixing, are blanketed by a surficial sand and

gravelly sand lag.
16 SMITHSONIAN CONTRIBUTIONS TO THE EARTH SCIENCES

transported into deep water by ice-rafting during

glacial stages.

Attention has also been called to the importance of

recent (Holocene) ice transport of sediment as a result

of seasonal breakup and movement of ice from the

Gulf of St. Lawrence (Stanley and Cok 1968) onto

the Nova Scotian Shelf (compare the ice distribution

pattern in Figure 13A with area B in Figure 13B) . This

addition of modern ice-rafted material on the shelf

edge near Sable Island Bank and Banquereau Bank

should not be overlooked. Postglacial to modern icerafting would probably also account for thin discontinuous patches of fine to coarse material on the slope

and rise.

General Description of Slope and Rise Sediments

Cores Examined

Recognition of sedimentary facies on the continental

slope and upper rise off Nova Scotia is based on a

study of four sets of cores discussed in this and following sections:

(a) 20 piston cores (Figure 14) collected on the

100

2 0 0

3 0 0

4 0 0

5 0 0

t_

o

u 6 0 0

Q.

Q

700

Topographic

Htghs

Valley

Sides

Valley

Axes

Flat

Terrain

15-2 13 20 15 9 11 12 3 7 19 14

Core Numbers (Sc-)

8 5 1 10 17 4 16 18

FIGURE 14.—Cores collected on upper and middle slope southeast of Sable Island Bank (Silverberg 1965). Dark cross-hatchure pattern depicts reddish-brown facies; oblique hatchure depicts

olive gray facies; stipples denote uppermost sandy facies.
NUMBER 8 17

slope adjoining the southern margin of Sable Island

Bank and described by Silverberg (1965).

(b) 5 piston cores (Figure 15) collected by Stanley

and Swift on the CSS Hudson in 1964, along a northsouth transect, from the slope due south of Sable

Island to the rise.

(c) Cores (Figure 16) collected by Marlowe (1964)

in the vicinity of The Gully Canyon and adjacent

slope and detailed in James (1966), Stanley (1967)

and Stanley and Silverberg (1969).

(d) 30 cores (Figure 17) collected by the LamontDoherty Geological Observatory on the slope and rise

off Nova Scotia, and examined by Sutton (1964).

Selected Lamont-Doherty cores collected in this area

have also been described by Ericson et al. (1961),

Hubert (1964), Hubert and Neal (1967, and Conolly

etal. (1967).

Only those lithologic aspects of cores pertinent to

this study are presented in this paper. Detailed graphic

and photographic logs of most cores (a) and (c) are

available in the references cited above. Logs of cores

(d), also available from the Lamont-Doherty Geological Observatory core collection library and from the

National Oceanographic Data Center, are included in

the Appendix.

Four Outer Continental Margin Fades

Earlier studies have shown that the predominant

surficial textural type on the slope and rise is mud

(silt and clay, largely of terrigenous origin) with varying, but minor, amounts of gravel, sand, and coarse

silt. Thin layers of clean sand, and occasionally gravel,

are also noted. Muddy sediments generally display

either an olive gray or a reddish-brown coloration.

Cores Sol to Sc-20 (Figure 14) and Hud 30-9 to

Hud 30-14 (Figure 15) display both sediment types

on the slope proper and in The Gully Canyon.

The olive gray mud generally overlies the brown

facies (Heezen and Drake 1964; Conolly et al. 1967).

The contact between these two sediment types can be

sharp or gradational. Interbedded olive gray and

brown sediments are noted in some cores. Olive gray

mud, generally less than 2 to 3 m thick, covers the reddish-brown unit on much of the upper- and mid-slope

region. Occasional thin partings of sand occur within

the gray, but more commonly within the brown facies.

A third sediment type noted in several cores on the

slope is a relatively clean sand unit that occurs in thin

laminae (2 to 15 cm) at the uppermost surface. A

fourth facies, observed on the upper rise (cores Hud

30-9A, B), is a pale yellowish-brown mud that covers

the reddish-brown facies.

A simpified sediment distribution chart of the slope

based on the coring program is shown in Figure 18.

Both olive gray mud and brown mud and sand-siltmud facies appear to be irregularly distributed across

the slope. The patchy distribution is a function of

topography in the sample locality. On the upper slope,

for instance, brown sediment was recovered only near

the tops of ridges and along relatively flat sections of

the slope. Coring suggests that (a) deposition of the

olive gray facies has been greater in valleys than on

intervalley highs, or (b) that non-deposition or erosion

and removal of the gray facies has been more important on topographic highs, or (c) both factors are

in force. One core, Sc-16, collected on a relatively

undissected sector of the upper slope provides a representative section. Core Sc-16, penetrating both

olive gray and brown facies, serves as a base upon

which to compare the thickness of the gray sediment.

A surficial third facies of clean to muddy sand layers

is more frequently cored on topographic highs.

The lithological logs of the CSS Hudson short piston cores (Hud 30-9A, -9B, -11, -13, and -14) collected south of Sable Island Bank are shown on

Figure 15. The most obvious features are summarized

as follows:

(a) The slope core (Hud 30-14) penetrated olive

gray, silty to clayey mud,

(b) The base-of-slope core (Hud 30-13) displays

the coarsest texture (sand, silt, and pebble fraction

present with predominant mud) of the five cores and

is brown in color,

(c) The rise core (Hud 30-11), also brown, consists

of somewhat fewer coarsely textured horizons,

(d) The two lower rise cores (Hud 30-9A and -9B)

are considerably finer grained than (b) or (c), and

the uppermost (tan to light yellow-brown) sections

are lighter in color than the brown and reddish brown

material in (b) and (c).

The cores collected in The Gully Canyon area by

Marlowe (1964) are also variable in texture (mud,

sand, and pebble fraction) and color (gray, brown,

and mixtures thereof). They present color and textural characteristics comparable to those in upper

Nova Scotian Slope cores collected by Silverberg

(1965). The position and logs of cores collected by
18 SMITHSONIAN CONTRIBUTIONS TO THE EARTH SCIENCES

LU

CO

cc

tr

LU

o

LU

CO

tr

o

LU

CO

en

LU

Q_

a.

LU

CO

ro

B

3 8. 3 «j

a * S |

•§11 1

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Sa313WllN33 Nl31V0S

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NUMBER 8 19

000

A-173-8

• CORE

o SNAPPER SAMPLE

A LAMONT CORE

® LONG CORE

(DEPTH IN FATHOMS)

DJS 35

59°00'

FIGURE 16.—Cores in the vicinity of The Gully Canyon

(collected by Marlowe 1964, and others).

Lamont-Doherty Geological Observatory and examined by Sutton (1964, this study) are shown on Figure

17.

Physical and Biogenic Structures in Slope Cores

The occurrence of abundant thin laminations, sandy

strata, isolated pebbles, and interbedded gray-andbrown sediment types and the lack of petrographic

homogenity clearly indicates that sedimentation rates

have fluctuated considerably on the outer margin in

the study area. Processes responsible for the downslope transfer of terrigenous sediments have also varied.

The presence of laminated (current-produced) sand,

silt, and mud units, isolated (ice-rafted) pebbles

(Stanley and Cok, 1968, their figure 12) and boulders (Brundage et al. 1967) in mud, contorted

(slumped) strata, and graded (turbidite) beds (Stanley 1970) are obvious and frequently observed structures on the Nova Scotian Slope. Bioturbate structures (produced by burrowing organisms) account

for still another group of structures commonly visible

in cores.

In comparison, cores that consist largely of clay and

fine silt, when split, appear homogenous and generally

do not reveal internal structures of either sedimentary

or organic clearly. X-radiography, a technique that

reveals features not apparent to the naked eye, was

used in the inspection of both split (method in Bouma

1964) and unsplit cores (Stanley and Blanchard

1967). Internal structures observed in cores Sc-1 to

Sc-20 can be grouped broadly into the following

categories:

(a) Regular layering: alternating light and dark

(dense and less dense) bands continuous across the

core section.

(b) Irregular layering: discontinuous, often lens- or

pod-shaped, bands.

(c) Indistinct layering: bands which are only faintly

distinguishable, or which show gradational contacts.

(d) Mottling: pods or irregular bodies of contrasting density which exhibit no preferred orientation in

the core. These may be indistinct, displaying no clear

boundary with the other material in the sediment, or

they may be distinct, with sharp boundaries.

(e) Flow-in: undulating or contorted, vertically

oriented pattern found near the lower sections of some

cores. Flow-in structures are an artifact of coring, i.e.,

sediment is drawn into the core liner as the coring

device is raised from the bottom. Flow-in commonly

occurs in instances where the core barrel did not completely enter the sediment.

Internal structures observed in cores Sc-1 to Sc-20

are depicted on Figure 19. It is apparent from this

figure that no one internal structure is restricted to a

specific sediment facies, although assemblages of

primary structures are of some use in distinguishing

particular sediment types.

The surface sand facies is easily distinguished.

Radiographs show that these sands contain bands of

closely spaced fine mottles (burrows in some cases)

with scattered, distinct, large patches (aggregates of

granules and small pebbles).

The olive gray, muddy sediment type is characterized by a general scarcity of internal structures. Some

cores show sections of regular and irregular layering
20 SMITHSONIAN CONTRIBUTIONS TO THE EARTH SCIENCES

SOHM ABYSSAL PLAIN

FIGURE 17.—Gores on the Nova Scotian slope and rise and in the Sohm Abyssal Plain collected

by Lamont-Doherty Geological Observatory and examined by R. Sutton (lithologic description

and appropriate Lamont core number are provided in the Appendix).
NUMBER 8 21

BANQUEREAU

eraiized Distribution

of Late Quaternary Sediments on

Outer Nova Scotian Continental Marain.

[Solocene relict sediments on outer banks;

'spill-over fades,on slope and rise.

Largely Holocene gray-green facies,

on slope.

Largely Holocene light gray-brown,

hemipelagic facies, on rise.

Pleistocene brown glacio-marine facies

exposed, on slope and rise.

Pleistocene relict glacial and fluviolacial facies,on shelf. ""

FIGURE 18.—Map showing generalized distribution of late Quaternary surficial sediments on

the outer continental margin off Nova Scotia (Stanley and Silverberg 1969).

(e.g., Sc-5, Sc-8, and Sc-15) but for the most part,

the olive gray facies consists of long sections of homogenous sediment. The widely scattered, indistinct, large

and small mottles and irregular layers (e.g., Sc-1, -2,

-3, -7, and -10) are probably the result of bioturbation.

The major characteristics of the brown sediment

type are a widespread occurrence of distinct mottles

(in some cases, pebbles), and a sediment column comprising numerous, thin alternating zones of varying

texture and stratification. Regular layering is most

extensive in core Sc-4, and distinct mottling is noted

at the base of core Sc-16. The longest section of brown

sediment penetrated (core Sc-9) shows the diversity

of lithologies characteristic of this facies.

In muddy sediments the burrowing and feeding habits of benthic fauna can completely modify physically

produced stratification features by shifting and reworking the sediment. Moore and Scruton (1957) noted
22neters

t

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5Dep Core

CORE Sc100

150

200

250

1

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0

SL-

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3

%

SMITHSONIAN CONTRIBUTIONS TO THE EARTH SCIENCES

8 9 10 11 12 13 14 15 15-2 16 17 18 19 20

• ' 1

"' >:

OKI

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1 a

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sa

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MOTTLES LAYERS

coarse fine regular irregular

distinct Eg E3 5 5 9

indistinct Q ED £3 SB

FLOW H0M0 -

IN GENEOUS

lisa •

FIGURE 19.—Nova Scotian Slope core (Sc) logs showing sedimentary and biogenic structures

as observed in core photographs and X-radiographs.

that a complete gradation (from regular and irregular

layering, to distinct and indistinct mottling, to homogeneous sediment) can develop depending upon the

rate of sedimentation, sediment type, and intensity of

faunal activity. Reversal of this process, i.e., the layering of an originally near-structureless sediment section

by faunal activity, can also be induced. Preservation of

original primary sedimentary structures generally

occurs in areas where sedimentation rates are particularly high or where bioturbation by mud-feeding

organisms is uncommon or both.

Interpretation of slope sediments in the light of

these observations indicates that the olive grey sediment type was deposited rather slowly. The occurrence

of indistinct large mottles indicates that the process of

homogenization did not go to completion. The fine

nature of the regular layering preserved in some core

sections suggests that there were periods of less intense

bioturbation or somewhat higher rates of sedimentation.

The disruption of layering is also apparent in the

older brown sediment. However, preservation of

thicker sections of stratified layers indicates that rates

of sedimentation were higher during deposition of

this facies. The variable character of the preserved

strata, which include sandy layers, irregular and regular layering, and indistinct mottling, is evidence

that the rate of deposition of the brown sediment was

not constant, but apparently fluctuated considerably.

The occurrence of sand and pebbles in the brown

sediment, as noted on the radiographs is another

significant difference between the two types of sediment. The higher sedimentation rate and variable

nature of the brown sediment is also confirmed by a

textural study, as demonstrated in following section.

Sediment Sequences on the Lower Rise

and Abyssal Plain

The following is a summary of descriptions of 30

cores collected on the slope, rise, and Sohm Abyssal

Plain south of the Nova Scotian Shelf.

A typical sedimentation rhythm, or sequence, in

Sohm Abyssal Plain cores and in certain cores of the

Nova Scotian Lower Rise consists of the following:

TOP 1. Gray foram lutite

2. Pale red foram lutite, grades

down to darker red at base

3. Mottled red lutite

4. Red lutite; bedding absent;

forams and mottling rare

(Te2)
NUMBER 8 23

BOTTOM

5. Laminated silt (Td)

6. Silt with current ripples, clay

blebs, and forams (Tc)

7. Silty sand usually laminated (Tb)

8. Sand (Ta)

The symbols closely follow those proposed by Bouma

(1962). The lower sand (Ta) is interpreted as the

lower portion of a turbidite, indentified by relatively

poor sorting, absence of bedding, and rarity of forams

and burrows (Figure 20). Rapid emplacement would

best explain this combination of features. The silty

sands (Tb) and rippled and laminated silts (Tc-Td)

represent the fining upward and progressive changes

in the flow regime expected during the later phases

of turbidity current flow (Figure 21). The red

lutite unit (Tei-Te3) is interpreted as the fallout of

finer particles suspended in the water following the

emplacement of the coarser sediment. This fallout,

rapid at first (Tei), declines progressively (Te2) after

several hours (or days) so that the sedimentation rate

is low enough to permit reworking by burrowers

(Figures 22, 24). Red lutite contribution gradually

FIGURE 20.—Brown sandy silt (Ta). Locality 28 (Lamont

core V7-7O) at 322 to 330 cm depth in core.

FIGURE 21.—Cross-laminated, fine-grained, foram-rich sand

(Tb-Tc). Locality 24 (Lamont core V7-38) at 438 to 440

cm depth in core.

decreases (Tea) so that the nonturbidite contribution

(Te4) takes over as an increasing percentage of the

total contribution (Figures 25). The gray foram lutite

is interpreted as a nonturbidite accumulation. The

increased foram content (Te2-Te4) is cited as evidence

of this decreasing sedimentation rate.

Sediment sequences in the lower rise tend to be

thicker (100 cm or more) and contain more sand and

silt than those of the abyssal plain (Figure 17). The

southward thinning of the sequences is cited as

evidence of (a) the northward source of the Ta-Te3

units and (b) dominant dispersal patterns toward the

south. Just north of the New England Sea Mounts,

thick gray foram lutites may have originated by processes other than turbidity currents. In some places,

numerous silt laminae and beds are associated with

Te2-Te3 units suggesting that bottom currents, winnowing sediment, have removed some of the finer

fractions. It is conceivable that this reworking would,

over a period of time, produce a carpet or veneer of

grains too coarse to be moved by bottom currents.

This lag deposit would, in essence, form a protective

cover over finer grade sediments beneath it. Resuspended fines are probably transported by bottom

currents some distance from the initial site of Ta-Td

bottom current resuspension would account for the

turbidite deposition. This combined turbidity current-
24 SMITHSONIAN CONTRIBUTIONS TO THE EARTH SCIENCES

FIGURE 22.—A, Interbedded red lutites and laminated silts (Td-Tei). Locality 29 (Lamont core

V16-213) at 268 to 272 cm depth in core, B, Locality 1 (Lamont core A164-46) at 206 to

215 cm depth in core.

presence of red lutite laminae in many parts of the

Sohm Abyssal Plain.

The frequent absence of burrowing in sands and

silts could be interperted as a preference of the organisms for lutite over sands and silts rather than an

indicator of sedimentation rate. This hypothesis, however, is dismissed because burrowed silt units occur on

the upper rise (Figure 26).

Many of the sedimentation cycles, or rhythms, are

incomplete. Those in the more distal parts of the

abyssal plain lack the lower Ta or Ta-Tb sections.

These deposits are thus considered to be the finer

grained deposits from a weaker, diluted current. Elsewhere, on the other hand, upper units may be missing.

In some cores virtually every rhythm is truncated at

the top, suggesting greater current activity than at

nearby localities where the rhythms are virtually complete. Local variations of bottom topography might

explain these differences. Where coarser sediments

comprise the upper part of the rhythm, and subdivisions are not clear-cut, only the symbol "Te" is used

(Figure 23).

Textural Analyses of Outer Margin Sediments

Outer Shelf Near Sable Island Bank

Following sections summarize petrographic studies of

core and bottom grab samples collected on the outer

continental margin southeast of Nova Scotia. A total

of 114 samples (Figure 3) collected on and in the

direct vicinity of Sable Island Bank were examined

(James 1966, James and Stanley 1968). Size measurement was obtained with a rapid sediment analyzer

(Schlee 1966a); a size interval of }4</> was selected

and textural parameters including mean, sorting,

skewness, and kurtosis were calculated using the

formulae of Folk and Ward (1957).

Sand is the dominant textural grade covering most

of the banks (Figures 8, 29). Mean grain size is independent of depth. In general, medium- to coarse-
NUMBER 8 25

FIGURE 23.—Poorly sorted silt with faint burrows (Te).

Locality 28 (Lamont core V7-7O) at 15 to 22 cm depth

FIGURE 25.—Gray foram-rich lutite with faint mottling due

to burrowing (Te3-Te4). Locality 1 (Lamont core A164-46)

at 15 to 20 cm depth in core.

FIGURE 24.—Micro-mottling in red lutite (Te2). Locality 24

(Lamont core V7-38) at 108 to 112 cm depth in core.

grained sand occupies the area north of a line running

east northeast-west southwest across the bank through

Sable Island; south of the line, sand is fine to very fine

grained. The best sorted sand (very well to well sorted

according to Folk and Ward 1957, and Folk 1966)

forms a broad band trending east-west across the

center of the bank, whereas poorly sorted sediment is

present north and south of Sable Island (Figure 30).

Finely skewed sediment covers the western part of the

bank and an area east of the east terminal bar, and

coarsely skewed sediment is present directly south and

northwest of Sable Island.

Textural patterns present on the island continue

offshore (James and Stanley 1967). Sand north of the

island is coarser than that to the south. Best sorted

sand is present off the southeastern beach and east bar.

Finely skewed sediment dominant on the southwestern

part of the island is also present seaward off the beach.

Sorting has been found to be more sensitive to environment than either mean grain size or skewness; sand in
26 SMITHSONIAN CONTRIBUTIONS TO THE EARTH SCIENCES

FIGURE 26.—Brownish gray clayey foram-rich silt with mottling (Te3-Te4). Locality 27 (Lamont core V-67) at 10 to

16 cm depth in core.

FIGURE 27.—Recumbent fold structures in slumped silty

lutite. Locality 19 (Lamont core SP12-1) at 120 to 126 cm

depth in core.

the predominantly eolian environment (dunes cover

much of the island) is consistently better sorted than

beach and offshore sand.

Textural parameters of the sediment on Sable Island

Bank are, in general, interrelated: coarse sand generally is poorly sorted and coarsely skewed; fine sand

commonly is well sorted and finely skewed. The local

variations superimposed on this pattern can be used to

determine directions of sediment movement.

Gully Trough and The Gully Canyon

The size distribution of samples collected in The Gully

Canyon (Figure 31) and its shallow extension, the

Gully Trough (Figure 32) on the shelf, are plotted.

Most samples are admixtures of sand, gravel, and mud

as shown on a Folk (1954) textural triangle.

In the Gully Trough the textural distribution appears to be depth dependent. At depths of less than 80

m sediment is dominantly sand; samples below 180 m

in the trough contain a predominant mud (silt and

FIGURE 28.—Slumped silty lutite with darker zones of lutite

cut by burrows. Locality 19 (Lamont core SP12-1) at 102

to 106 cm depth in core.
NUMBER 8 27

61OQ

44

00

43

30

6100 5900

SABLE ISLAND BANK

MEAN GRAIN SIZE (M7 )

(After Folk ond Word , 1957)

 z

I I < C 1 0 COARSE

\fii'±\ 1,0 - 2. 0 MEDIUM SAND

|..'1*| 2. 0 " 3. 0 F'NE SAND IN I UMTS

t-~-] ^>3. 0 VERY FINE SAND

FIGURE 29.—Regional variation of mean grain size of surficial sediments on Sable Island Bank

and adjacent area (James and Stanley 1968).

6100 30 6000 30 5^00

6100 5900

SABLE ISLAND BANK

SORTING

(After Folk ond Word,1957)

I I <O3 5 V.WELL

0.35-0. 5 WELL SORTED

0.5 - 0.71 MODERATELY WELL

>0.71 MODERATELY

FIGURE 30.—Relative sorting (calculated after Folk and Ward 1957) of sediment on Sable

Island Bank (James and Stanley 1968).
28 SMITHSONIAN CONTRIBUTIONS TO THE EARTH SCIENCES

THE GULLY CANYON

(TEXTURE)

GRAVEL

MUD SAND

FIGURE 31.—Textural distribution of surficial sediment in The Gully Canyon (classification

after Folk 1954). See Figures 3 and 16 for sample location.

clay) fraction. The textural type is generally more

varied between 80 and 180 m: sand and gravel occur

between 80 and 140 m; sand, gravel and mud between

120 and 160 m, and sand and mud between 160 and

180 m. There is some overlap of these textural zones.

Small bank tops and isolated hummocks within the

Gully Trough are covered with sand. Intermediate

depths contain sand and gravel with or without a mud

admixture, and below 160 m, as well as in isolated

basins, mud is prevalent. Sediment on the western section of this region, between Banquereau Bank and

Sable Island Bank, comprises gravel to a depth of 175

m and clean sand in water deeper than 260 m.

A preliminary examination of cores collected in

The Gully Canyon indicates that sediment consists

mainly of sand and mud with minor amounts of

gravel and cobble-size particles (Marlowe 1964).

There appears to be a general increase in mud (silt

and clay) content with increasing depth. Muddy sand

predominates at a depth of 900 m on the east wall of

the canyon and again at a depth of 2,860 m in the

axis. Glean sand is found at 1,400 m in the axis of the

canyon.

Samples analyzed in detail (James 1966) and

plotted on a Folk (1954) textural triangle show a

local variation superimposed on the general trend of
NUMBER 8 29

GULLY TROUGH

(TEXTURE)

59*00'

)*? ^

FIGURE 32.—Textural distribution of surficial sediment in the Gully Trough north of Sable

Island Bank (classification after Folk 1954). See Figure 3 for location.

2 5 -

clOSc-I n Sc-2 Sc-3 Sc-4

H 1—1 1 1 ++

-I 1

"5-2-1012 3 -2-10 1 2 3 -2- 1 012 3 -2-1012 3

phi units

2 5 -

Sc-5 n Sc-7

10-

Sc-I I

,, - H r

Sc-I3

FIGURE 33.—Grain-size histograms of surficial sediment collected with a bottom grab at core

locations on the upper and middle continental slope off Sable Island Bank.
30 SMITHSONIAN CONTRIBUTIONS TO THE EARTH SCIENCES

80

50

10

0.1

phi units

FIGURE 34.—Cumulative coarse fraction size curves of surficial sediment collected with a

bottom grab at core locations on the upper and middle continental slope off Sable Island Bank.

SLOPE-RISE

TRAVERSE CORES (HUD)

Cloy UPPER SLOPE CORES (S O

(after SHmbwg.1968)

* BROWN

* GRAY

* SURFACE SAND

Clay

Sand

FIGURE 35.—Size distribution of upper and middle slope (Sc) cores are shown on left textural

triangle (classification of Shepard 1954). Triangle on right shows textural distribution of cores

collected on slope-rise traverse (see Figure 71).
NUMBER 8 31

decreasing grain size with increasing depth (Figure

31). Sable Island Bank above 200 m and the upper

reaches of The Gully Canyon are composed primarily

of sand or sandy gravel. Most of the northern portion

and the west wall of the canyon are covered with

muddy sand. A zone of sandy mud drapes from the top

of Banquereau Bank, down the east wall, and across

the mouth of the canyon. Mud is predominant west of

the axis near the mouth of the canyon.

Continental Slope South of Sable Island Bank: Upper

Slope Samples

The grain size distribution of surficial samples recovered with a Dietz-Lafond snapper grab samples used

as a trigger for cores Sc-1 to Sc-20 was measured. Sizefrequency histograms of these surface sediments,

plotted in Figure 33, show that two groups of sediment

can be distinguished on the basis of textural examination. Samples Sc-5 and Sc-13 from the relatively clean

surface sand layer are relatively coarse-grained and

show a small secondary mode in the coarse sand and

fine pebble range; sorting is poor. The second group of

sediments comprises predominantly very fine sand with

only traces of coarse sand. Cumulative frequency

curves, plotted on a probability scale (Figure 34), show

the spread of the size classes and indicate the poor sorting of the surficial sediment. Samples Sc-2 and Sc-3 are

somewhat better sorted but contain less sand (the

modes lie in the silt range). In general, coarsergrained sediments are more poorly sorted than those

which are finer.

Samples from cores Sc-1 to Sc-20 were selected

at 10 cm vertical intervals, and these were dispersed,

centrifuged, and sieved (method in Silverberg 1965).

Textural analyses serve to distinguish a brown and

olive gray facies: the gray sediment contains mainly

very fine-grained sand, between 105 and 63 microns,

and the grain-size distribution is relatively uniform

(most olive gray samples would be classified as silt,

clayey silt, and sandy silt). On the other hand, the

brown sediment sand fraction, also largely finegrained, does contain a somewhat higher amount of

coarse sand. The brown- facies also displays a greater

sample-to-sample grain-size variation. Analysis of the

uppermost surface sand facies shows that its size distribution is similar to that of most sands of the brown

facies.

A size-fraction coarser than 2 mm, mostly in the

Core Sc-9

'.v.v.v.v.v.w.v

•50

-100

•200

•25 U

• • < Pebbles .•$#* Sand

I Silt Clay

FIGURE 36.—Textural variation within an upper slope (Sc-9)

core penetrating a surficial sand layer above the reddish brown

section (see also Figure 14).

granule range, was recovered in some samples; the

grain-size distribution shows a continuum between

granules and the coarse sand grades. There is no

strong indication of bimodality.

The size distribution of 117 upper slope core samples

is plotted on a triangular textural diagram (see left

triangle in Figure 35). The pebble fraction has been

included with the sand component. Each sediment
32 SMITHSONIAN CONTRIBUTIONS TO THE EARTH SCIENCES

Core Sc-IO

•50 &

-100 €•:

-150 •*:

-200 £

-250

Pebbles Si&x Sand Silt Clay

FIGURE 37.—Textural variation within an upper slope (Sc10) core penetrating an olive gray section (see also Figure

14).

type (surface sand fades, and brown and gray sediment types) is depicted on a textural triangle (classification after Shepard 1954). The surface sandy facies

comprises sand and silty sand; the brown facies samples

occupy mainly sand-silt-clay, sandy silt, and sand

positions on the triangle; and the olive gray sediment

type generally comprises silt and clayey or sandy silt.

It is readily apparent that the brown sediment type

shows a more variable textural distribution than does

the gray. There are some "anomalous" brown sediment

samples such as Sc-18-175 and Sc-4-100; these are

markedly less sandy than most such samples. The

former sample is from a brown layer within a core of

olive gray sediment and the latter from a core showing laminations. Samples of olive gray sediment tend

to be concentrated about the silt end-member, but

show a continuous scattering toward the sand apex.

The textural variation in several slope cores is

illustrated in logs in Figures 36, 37, and 38. The upper

surficial sediment of core sections in occasionally more

sandy than lower portions, as shown in cores Sc-9 and

Sc-10. There are, however, cores of olive gray sediment in which this tendency is reversed. In general,

core sections of the brown facies (Sc-9) are more

sandy than those of the olive gray facies (Sc-10), but

again some exceptions to this are noted. The vertical

variability in texture is considerably greater within

brown than in the olive gray sediment sections. The

logs also show that the pebble fraction is common in

the brown facies (Figures 36, 38) and rare in the olive

gray (Figure 37.) Noteworthy is the abrupt change in

texture between the gray and brown layers (note

change at about 210 cm in Gore Sc-16, Figure 38).

Upper Slope to Lower Rise Traverse

Samples from the five short piston cores (Hud 30-9A

to -14), selected at 2 to 10 cm intervals (Figure 15)

were sieved and centrifuged to determine grain-size

data. Methods are the same as those to examine the

upper slope (Sc) cores. It is interesting that resulting

textural data is closely comparable to that obtained in

the study of cores Sc-1 to Sc-20.

The sand-silt-clay ratios of these traverse core

samples (data shown on right triangle in Figure 35)

;

ndicate that the bulk of material consists of clayey

silt. The olive gray slope core (Hud 30-14) contains

some sandy silt and pure silt; most of the sand fraction

is of very fine sand grade. The brown upper rise cores

(HUD 30-13 and HUD 30-11) contain more poorly

sorted sand fractions. In addition, core Hud 30-13

contains pebbly horizons and a large proportion of

sediment in the sand-silt-clay class. The two upper

rise cores are texturally dissimilar; the shoaler, more

nearshore one (HUD-30-13) contains up to 80 percent sand and also pebbly horizons. In both cores,
NUMBER 8 33

Core Sc-16

• 5 0

-100

-150

• • < Pebbles

:

:?:wX Sand Silt Hi Clay

FIGURE 38.—Textural variation within an upper slope (Sc16) core penetrating 210 cm of olive gray section above the

reddish-brown facies. This core displays a representative and

reasonably complete section of late glacial to modern sequence

on the slope south of Sable Island Bank.

however, the sand fraction is distributed more or less

equally over all five Wentworth-Udden grades.

The two tan and yellowish-brown lower rise cores

consist of well-sorted very fine, silty clay, clayey silt,

and silt, and are fairly uniform except the base of core

HUD 30—9A which is possibly a stratum of turbidite

origin.

An analysis of the textural parameters of samples

from 30 Lamont-Doherty cores collected on the slope,

rise, and abyssal plain south of Nova Scotia shows

no obvious differences that are strictly related to water

depth (Table 1). These outer margin core samples

are generally finer grained and less well sorted than

adjacent shelf deposits. Sedimentation units on the

slope and upper rise are coarser grained than those

on the lower rise and Sohm Abyssal Plain. The variability of sorting values provides a means of distinguishing sediments from the different environments

(this variability probably reflects differing modes of

sediment transport processes). Kurtosis values of

slumped (contorted) and of turbidite (graded) sediments are significantly lower than those moved and

modified by marine currents (laminated). Variation

in grain roundness does not appear to bear any relation to the environmental province or mode of origin

but is believed to reflect the character of the original

sediment sources.

Mineralogical Composition of

Outer Margin Deposits

Sable Island Bank Sediments

The composition of light and heavy minerals of the

sand-size fraction (0.062—2.00 mm) of surficial samples collected on Sable Island Bank was examined.

Iron-stained quartz is by far the most abundant sandsize component on Sable Island Bank. Its distribution

and that of the less abundant feldspar (generally < 15

percent), also coated with ocherous hematite, is

variable on the bank (James and Stanley 1968, their

figure 6). Shell fragments of sand to pebble size (ranging from < 1 to > 10 percent of the total sample),

particularly those in shallow water, show evidence of

considerable wear due to abrasion as a result of sediment transport. The percent of mica ranges from

trace to 5 percent.

The transparent heavy mineral suite is dominated

by garnet (> 50 percent of the transparent species);

the relative percentage of hornblende, kyanite, and

tourmaline together accounts for 16 to over 32 percent of the suite. Extremely high percentages of

opaque mineral species (mostly magnetite and ilmenite) locally account for over 50 percent of the heavy
34 SMITHSONIAN CONTRIBUTIONS TO THE EARTH SCIENCES

TABLE 1.—Textural data measured for 39 samples from Lamont-Doherty cores (S, slope; U.R., upper rise; L.R.f

lower rise; A. P., Sohm Abyssal Plain). Numbers at left refer to core localities shown in Figure 17. Sample

numbers are listed under "laboratory code"

Loc.

No.

1

2

3

4

5

6

7

9

10

11

12

13

14

15

16

17

18

19

20

21

22

23

24

25

26

27

28

29

30

Lanont - No.

A 164 - 46

A 164 - 47

A 164 - 48

A 164 - 49

A 164 - 54

A 164 - 55

A 173 - 8

- 8

- 8

A 173 — 10

A 173 - 11

A 173 - 12

A 173 - 13

A 173 - 14

C 25 - 10

KM 1 - 2

KM 1 - 5

KM 1 - 6

KM 1 - 7

SP -12 - 1

12- 2

12- 3

12- 4

V - 2 - 4

V - 7 - 36

- 38

- 38

- 38

V - 7 - 63

- 63

V - 7 - 68

- 6B

V - 7 - 69

V - 7 - 70

V - 16 - 213

- 213

V - 17 - 209

- 209

-209

Lab.

Code

192

193

194

82

195

196

78

77

76

198

199

200

201

202

207

208

210

211

212

73

215

216

217

220

225

226

63

64

243

244

22

21

245

246

247

248

3

2

1

Depth

Core (cm)

2B-30

28-30

18-20

163-5

360-2

250-2

80-2

190-2

B00-2

260-2

30-2

300-2

120-2

10-12

30-2

150-2

12-14

136-8

B0-2

305-7

102-4

77-9

352-4

20-2

80-2

401-3

410-2

442-4

10-12

30-2

60-2

B0-2

98-1BO

150-2

10-12

60-2

170-2

190-2

205-7

Water

Depth (F

2610

2580

2530

510

1230

1820

1490

1490

1490

900

1426

1150

1600

1410

910

750

136

310

450

700

680

1300

1310

2000 ?

2508

2508

2508

2508

220

220

2143

2143

1600

700

2065

2065

2453

2453

2453

Location

A.P.

A.P.

A.P.

S.

U.R.

L.R.

U.R.

U.R.

U.R.

5.

A.P.

U.R.

L.R.

U.R.

S.

S.

5.

5.

S.

s.

s.

U.R.

U.R.

L.R.

A.P.

A.P.

A.P.

A.P.

S.

5.

L.R.

L.R.

U.R.

U.R.

L.R.

L.R.

L.R.

L.R.

L.R.

Round.

.43

.49

.50

.40

.39

.45

.46

.51

.46

.49

.49

.42

.47

.46

.50

.45

.40

.35

.44

.42

.47

.52

.46

.37

.45

.48

.36

.40

.48

.42

.48

.39

% Heavy

2.77

2.08

1.71

0.54

1.38

0.36

1.67

0.29

4.97

0.89

1.23

D.78

2.94

1.24

0.46

0.97

0.57

a.76

1.27

1.05

1.06

0.67

2.49

0.27

0.47

2.01

2.56

1.19

1.70

0.19

1.87

2.31

4.44

% less

than

.063mm

.0

21.0

25.6

24.82

63.5

43.1

11.85

6.40

4.57

77.2

65.9

60.2

44.8

68.1

85.3

73.0

27.7

31.5

62.3

2.73

58.3

46.1

32.9

100

72.0

1.6

6.4

14.05

32.0

53.7

.12

.07

75.0

63.3

74.1

7.37

0.97

0.37

Anal.

H.M.

yes

yes

yee

yes

yes

yes

yes

yes

yes

yes

yes

yes

Mean 0

3.25

3.21

3.58

2.22

2.01

3.06

3.21

3.06

3.06

2.44

1.10

1.35

2.47

1.95

2.68

3.13

3.21

3.24

2.89

0.98

2.30

2.46

2.40

3.04

1.09

1.03

2.80

3.60

3.60

1.66

1.24

0.95

2.59

2.46

2.76

1.74

1.12

Sort.

0.46

0.59

0.42

1.20

1.56

0.97

0.44

0.54

0.46

1.19

0.94

1.57

1.02

1.B3

1.26

0.79

1.23

0.60

1.14

1.39

1.15

1.09

1.15

0.49

1.11

1.25

0.84

0.43

0.33

0.61

0.80

1.94

1.20

0.91

0.62

0.61

1.18

Skewness

-4.46

-12.57

-14.25

-4.08

-3.23

-8,33

-7.25

-6.98

-3.91

-3.33

-1.75

-2.54

-2.99

-3.23

-3.75

-6.46

-12.00

-11.3B

-8.50

0.44

-4.27

-4.78

-4.61

-13.86

0.29

0.69

-5.33

-23.08

-IB.23

-0.10

D.31

0.22

-4.73

-0.63

-5.58

-0.05

-1.30

Kurtosis

9B

331

288

61

37

123

231

167

130

45

29

33

51

30

38

89

173

247

119

31

64

71

66

274

45

37

B5

728

601

69

50

19

58

30

133

90

32
NUMBER 8 35

59 00 43

30

GULLY TROUGH

DISTRIBUTION OF

BROWN-STAINED QUARTZ

>64

32-64

DID 16-32

FIGURE 39.—Relative percentage of brown iron-stained quartz (calculated from the total quartz

content only) in the 250-1000 and 62-250 micron-size fractions of Gully Trough samples.

43_ 30 6000 30

GULLY TROUGH

DISTRIBUTION OF

GREEN-STAINED QUARTZ

> 8

4-8 RELATIVE

CD <4 oi

FIGURE 40.—Relative percentage of green-stained quartz (calculated from the total quartz

content only) in the 250-1000 and 62-250 micron-size fractions of Gully Trough samples.
36

43

30

2000-500 u -7

44

00

43,

44

00

30

SMITHSONIAN CONTRIBUTIONS TO THE EARTH SCIENCES

6000 30 59 00 43

500 - 125 u

6000

GULLY TROUGH

DISTRIBUTION OF

ROCK FRAGMENTS

>8

4-8

I 1 <4

RELATIVE

30

44

00

FIGURE 41.—Relative percent of rock fragments (calculated from the quartz -f- rock fragments

portion of the sample only) in the 500-2000 and 125-500 micron-size fractions of Gully Trough

samples.

mineral assemblage. Iron nodules and dark green to

black glauconite grains (1 to over 4 percent of the

light mineral fraction) are noted in samples on the

southern portion of the bank.

i i I I I I I I I I I I I I I I I I I I I I I I | I I I

I III '

0 50 100 150 200 250

DEPTH (METERS)

FIGURE 42.—Relation between percent of rock fragments and

depth in the 250-500 micron-size fraction of sediments in

the Gully Trough area. Note increase in the amount of rock

fragments between the 140 and 200 meter depth range.

Angular as well as well-rounded pebbles recovered

locally on the bank include rock types that appear

similar to those cropping out on the Nova Scotian

mainland (i.e., including Devonian igneous rocks, Carboniferous elastics, Triassic basalt, and states, schists,

and metamorphics of the lower Paleozoic Meguma

Group. Some glauconitic sandstone, of the type not

found on the mainland, is probably derived from some

now-submerged coastal plain Tertiary or Cretaceous

bedrock cropping out nearby on the shelf. A detailed

mineralogical study of Nova Scotian surficial sediments has recently been compiled by A. E. Cok (1970).

Gully Trough Sediments

The mineralogical composition of the sand-size fraction of surficial Gully Trough samples, examined by

James (1966), can be summarized as follows.

QUARTZ.—Three types of quartz are present in

significant quantities:

(a) Orange to red iron-stained quartz, possibly

indicative of subaerial exposure.
NUMBER 8 37

250-125

30

44

00

GULLY TROUGH

DISTRIBUTION OF

GLAUCONITE

>4

2-4

I 1 <2

FIGURE 43.—Percentage of glauconite in the 250-500 and 125-250 micron-size fractions of

Gully Trough samples.

(b) Clear quartz, suggesting possible removal of

iron-stain by abrasion.

(c) Green-stained quartz, the origin of which is

unknown (flame spectrophotometry indicates that the

stain is due to the presence of iron). Weller (1960)

has indicated that iron coloration can be used as an

index of the oxidation state: red indicates a high

degree of oxidation, and green a low degree of oxidation. Keller (1953) suggests that a green color in

some sediments may also be due to the presence of

iron in such marine clays as illite and montmorillonite.

The data suggest that the distribution of particular

quartz-types is depth controlled. The amount of redstained quartz is relatively high at depths above 120

m; this type of quartz decreases to a low at about 20

m (Figure 39). The relative percentage of greenstained quartz, generally low at most depths, increases

with depth to a high at the 110 to 145 m depth range,

and then decreases at greater depths (Figure 40).

ROCK FRAGMENTS.—Rock fragments are relatively

sparse on Banquereau Bank, the eastern portion of

Sable Island Bank, and in The Gully Canyon off the

eastern end of Sable Island Bank. Rock fragments,

on the other hand, are relatively abundant in the

central deeper portion of the Gully Trough (Figure

41). Figure 42 shows the relative percentage of rock

fragments in the 250-500 micron fraction (rock fragments of this size are present in almost all samples in

this area) plotted against depth. This diagram indicates that the rock fragments are most abundant

between 140 and 200 m (Figure 42).

GLAUCONITE.—Glauconite content in the coarse

fraction (250-500 micron) is relatively high between

Middle Bank and Banquereau Bank and the central

portion of the Gully Trough and its extension toward

The Gully Canyon (Figure 43). No correlation is

noted between the amount of glauconite and depth,

nor does there appear to be a relation between the

regional distribution and grain size.

This glauconite may have originated from erosion

of (a) older bedrock cropping out in the area, or

(b) from pebbles of glauconitic sandstone, or (c) it
38

43

30

44

00

44

00

30

SMITHSONIAN CONTRIBUTIONS TO THE EARTH SCIENCES

6000 30 59 00 43

SAMPLE

Distribution of

HEAVY MINERALS

>4

2-4

I I < 2 by wt.

44

oc

FIGURE 44.—Relative percentage, by weight, of heavy minerals present in the 125-250 micronsize fraction of Gully Trough samples. The sample station locations are shown in the lower map.

may be authigenic and forming at present. Its corroded appearance, however, tends to suggest a relict

origin.

HEAVY MINERALS.—Heavy minerals are most abundant on the banks and topographic highs in the Gully

Trough (Figure 44). Bank surfaces have been subjected to current activity resulting in removal of

fines and concentration of heavy minerals as lag

deposits. The heavy mineral content is generally low,

below 200 m, with the exception of the region of The

Gully Canyon between Banquereau Bank and Sable

Island Bank. The latter region may be receiving sediment of well-sorted material that originates on bank

tops.

Opaque heavies and zircon show similar distribution trends: high values on the isolated topographic

highs and bank tops, and in the deepest areas (Figure 45). At intermediate depths off the western end

of Sable Island Bank, however, these minerals are

sparse. A plot of opaques versus depth (Figure 47)

shows that above 120 m the relative percentage of

opaques is consistently above 50 percent, whereas

below 160 m it ranges about 35 percent. This variation

probably reflects depositional differences with depth:

a shallower zone of reworking with "mature" sediments, and a deeper, quieter deposition zone of unmixing ("immature" sediments) occurring between

120 and 160 m.

Weathered heavy mineral species are abundant in

basins and areas deeper than 200 m, suggesting that

they may be the result of in situ chemical destruction

of several mineral species (Figure 45).

Garnet, hypersthene, and staurolite have a similar

distribution pattern in this region (Figure 46), i.e.,

abundant on the western portion of Sable Island Bank

and Middle Bank with lower percentages in the deeper

axis of the depression. The relatively high percentage

of garnet on the bank tops seems to confirm the

"mature" (reworked lag) nature of sediment exposed

at shallower depths than those in deeper regions.

The distribution patterns of hornblende, kyanite,

and tourmaline are similar. Their concentrations are

low on the banks and highs in the deep central region,

except in a deep area between Sable Island Bank and

Banquereau Bank (Figure 46). The percentage of

garnet, on the other hand, shows a generally consistent
6000 30

GULLY TROUGH

DISTRIBUTION OF

HEAVY MINERALS

ALTERITE OZ

X7Z\ >4 (Z3 HIGH RE L

DID 2-4 CZH MEDIUM <y '

• <2 HH] LOW °

FIGURE 45.—Relative percentage of alterite in the nonopaque portion of the heavy minerals

in the 125-250 micron-size fraction. In lower map, relative abundance of zircon and opaque

heavy minerals in the 125-250 micron-size fraction in Gully Trough samples.

59 00 43

6000 30 59 00

GULLY TROUGH

DISTRIBUTION OF

HEAVY MINERALS

H-K-T G-H-S

f^)>40

QIXI 30-40 E53 50-60

I I <30 ["0 40-501 )<40

FIGURE 46.—Relative percentage of hornblende + kyanite + tourmaline (in upper diagram),

and garnet + hypersthene + staurolite (in lower diagram) in the nonopaque 125-250 micronsize fraction of Gully Trough samples.
40 SMITHSONIAN CONTRIBUTIONS TO THE EARTH SCIENCES

80-r

6ULLY TROUGH

HEAVY MINERALS

VS.

DEPTH

GARNET

6Or

100 200 300

DEPTH (METERS)

x SAMPLES FROM "THE GULLY"

OPAQUES

0 100 200 300

DEPTH (METERS)

FIGURE 47.—Variation with depth of the relative percentage

of garnet (upper graph) and opaque minerals (lower graph)

in the Gully Trough. Garnet decreases progressively with

depth. Opaque heavies also decrease with depth, and particularly so below 120 m.

decrease with increasing depth (Figure 47). Thus,

it appears that hydraulic selectivity is the dominant

factor governing the heavy mineral distribution in The

Gully Trough. Hornblende, kyanite, and tourmaline,

all of relatively low specific gravity, have probably

been winnowed out of surficial relict (Pleistocene)

deposits on the banks and transported to deeper areas.

The Gully Canyon Sediments

The Gully Canyon and its deep upper slope-shelf

extension due east of Sable Island morphologically

separates Sable Island Bank from Banquereau Bank.

The mineralogical composition of the sand fraction

of samples from the upper parts of cores was determined (James 1966).

IRON-STAINED QUARTZ.—The relative amount of

brown-colored, iron-stained quartz (Figure 48) does

not appear closely related to grain size, as is the case

on Sable Island Bank. Most samples rich in stained

quartz are fine grained although a smaller amount of

stained quartz occurs as coarse (1.0—2.0 mm) sand.

The amount of coarse iron-stained quartz decreases

downslope along the canyon trend. A zone poor in

iron-stained quartz parallels the 500 fm isobath just

west of the canyon axis. Sediment of very fine sand

grade within the canyon axis contains a relatively

high amount of iron-stained quartz. A zone relatively

rich in iron-stained quartz of all sizes occurs at about

400 fathoms on the east (Banquereau) margin of

the canyon.

ROCK FRAGMENTS.—Sediment of sand grade in the

central portion of the canyon contains proportionately

lesser lithic fragments than on the banks, particularly

Banquereau Bank. A zone of lithic-rich sediment extends from Banquereau Bank seaward toward deeper

areas near the mouth of the canyon (Figure 49). This

trend suggests a provenance from Banquereau Bank.

SHELL-FRAGMENTS.—Sediment in and near the

canyon axis contains relatively lower amounts of shell

fragment than on the canyon walls and mouth (Figure 50). The shell-rich area extends from the eastern

and southeastern margins of Sable Island Bank downslope into the canyon.

GLAUGONITE.—Glauconite-poor sand covers the

eastern margin of Sable Island Bank as well as sections of the upper reaches of The Gully Canyon (Figure 51). Areas of high (8 percent) glauconite content

occur at intermediate depths (100 to 800 m) on the

west wall (Sable Island Bank side) of the canyon,

as well as along most of the Banquereau margin. The

in situ origin of glauconite in this area cannot be

ruled out. It is more probable, however, that glauconite-rich strata cropping out along the canyon margins serve as a source for this mineral.

MICA.—Mica is rare to absent in surficial sediment

on Sable Island Bank and in the upper reaches of

The Gully Canyon (areas of intense bottom current

activity), but is present in low amounts on Banquereau

Bank and in the mid sectors and lower sectors of The
NUMBER 8 41

Rolatlvo %

m^> 20

E^S^l 5-20

1 1<5

A

B

C

P

m

 > 600 M

• 500-250 yu

* 250-125 /*

• 125-62 M

THE GULLY CANYON

Distribution of

Brown stalnoi Quarts

FIGURE 48.—Relative percent of brown iron-stained quartz (calculated from the total quartz

content only) present in different size fractions in The Gully core samples. Note relatively high

amounts in fine-grained stained quartz in the axis of the canyon.

Gully (Figure 49). The platy shape of mica results

in its deposition with quartz and other minerals of

different (generally smaller) size and density in deeper,

less current agitated environments beyond the shelfbreak, an observation made elsewhere by Doyle et al.

(1968) and Lyall et al. (1971).

HEAVY MINERALS.—The heavy mineral content of

both the 62 to 125/A and the 125 to 25(fyt fractions

in Gully samples were examined. The 62 to 125/u,

distribution is perhaps most reliable in that the very

fine sand fraction is present in most samples examined,

including muddy ones. The proportion of opaque minerals in the coarser (125 to 250ft) fraction increases

southward and apparently bears no relation with the

physiography of the canyon. The relative percent of

opaques present in the finer fraction, however, is

related to some degree with canyon morphology, i.e.,

samples in the axis of the canyon containing less

opaques than those in the upper canyon reaches (Figure 52).

The distribution of zircon is more irregular, particularly in the smaller grain-size fraction (Figure 53).

In the coarser fraction, zircon is relatively abundant

in the upper reaches and at the mouth of the canyon

but sparse in the central portion. Hornblende and

tourmaline display nearly identical distribution patterns and thus are plotted together (Figure 54). Garnet (Figure 55) has a distribution pattern that closely

resembles those of hornblende and tourmaline but

shows opposite trends, i.e., where garnet content is

high, hornblende and tourmaline content is low, and

vice versa. The three mineral species are believed to

have a similar source origin and thus can be discussed

together. In the coarser size fraction, garnet is low

in a region extending from Banquereau, down the

east wall and across the mouth of the canyon; in the

axis of the canyon, at about 700 fm, the opposite

trend is noted, i.e., high garnet values are present.

In the finer fraction, garnet percentages are relatively

high and hornblende and tourmaline relatively low

in two linear belts parallel to the axis, and between

300 and 400 fm on either side of the canyon. It is

possible that these linear trends along both margins

of the canyon are related to local sources cropping
THE GULLY CANYON

DISTRIBUTION OF

ROCK FRAGMENTS

%

MICA

THE GULLY CANYON

DISTRIBUTION OF

GLAUCONITE

^ "° RELATIVE

• <8 %

FIGURE 49.—A, relative percentages of rock fragments.

B, presence of mica in surficial sediment of The Gully Canyon.

5300

THE GULLY CANYON

DISTRIBUTION OF

SHELL FRAGMENTS

100

1 -100

LZH 1

FIGURE 50.—A, percent of shell fragments in the 500-1000

micron-size fraction in The Gully Canyon, B, sample station locations (samples designated with symbol m were

donated by J. Marlowe, Bedford Institute of Oceanography).

FIGURE 51.—Percent of glauconite in the (A) 125-250 and

(B) 62-125 micron-size fractions in The Gully Canyon

samples.

THE GULLY CANYON ^ >6 0

DISTRIBUTION OF £X3 30 eo

OPAQUE HEAVY MINERALS \ZJ <3O

FIGURE 52.—Relative percent of opaque heavy minerals of

the (A) 125-250 and (B) 62-125 micron-size fractions in

The Gully Canyon samples.
NUMBER 8 43

125-250/1

B

THE GULLY CANYON

DISTRIBUTION OF

ZIRCON

>8

<8

RELATIVE

FIGURE 53.—Relative percentage of zircon in the (A) 125-

250 and (B) 62-125 micron-size fractions in The Gully Canyon samples.

out along the canyon walls. Sediments displaying relatively high hornblende and tourmaline values occur

on Banquereau Bank and extend down the canyon

wall across the mouth of the canyon.

The distribution of hypersthene in the coarser fraction is similar to patterns of opaque heavies and zircon,

i.e., high values in the upper reaches and mouth of

the canyon and lower values in the central part of

The Gully (Figure 56). In the finer grain sizes, two

linear highs of hypersthene on either side of the canyon, between 100 and 300 fm (like hornblende-tourmaline), also suggest that there may be a local source

of sediment cropping out along the margin of the

upper reaches of the canyon.

Relative percentages of kyanite are relatively low

on both banks and in the center of the canyon but

increase along the canyon walls between 400 and 500

fm (Figure 57). Staurolite is asymmetrically distributed about the axis of the canyon, i.e., low on the

Banquereau Bank margin and high on the Sable

Island Bank margin. In the very fine sand fraction,

staurolite is abundant along both margins of the canyon but uncommon near the canyon axis (Figure 58).

Both light and heavy minerals are similar to those

reported in Oligocene and Miocene rocks cropping

out along the walls of The Gully Canyon (Marlowe

1969). It is probable that erosion and in situ weathering of exposed sedimentary rock ledges has contributed

at least a minor amount of sediment to the canyon

fill. The primary source, however, of the mineral suite

observed here, as elsewhere on the outer margin, is

plutonic, metamorphic, and sedimentary rock terrains

some two hundred or more kilometers to the northwest.

Continental Slope Sediments

Mineralogical analyses of the coarser-than-silt fraction

(> 62ju) of slope cores Sc-1 to Sc-20 (Silverberg

1965) are reported below. Quartz, the dominant component of the sand-size fraction, occurs in many forms.

Many of the grains are iron-stained and the surfaces

may be smooth, pitted, or frosted. An almost complete

gradation, from well rounded to very angular grains,

B

THE GULLY CANYON

DISTRIBUTION OF

HORNBLENDE a TOURMALINE

RELATIVE

FIGURE 54.—Relative percentage of hornblende -}- tourmaline in the (A) 125-250 and (B) 62-125 micron-size fractions

in The Gully Canyon samples.
125-250/1

THE GULLY CANYON

DISTRIBUTION OF

GARNET

S 3 >64

C^J 32 64 RELATIVE

• <32 %

FIGURE 55.—Relative percent of garnet in the (A) 125-250

and (B) 62-125 micron-size fractions in The Gully Canyon

samples.

THE GULLY CANYON

DISTRIBUTION OF

HYPERSTHENE

ES3 >s

< 8

RELATIVE

FIGURE 56.—Relative percentage of hypersthene in the (A)

125-250 and (B) 62-125 micron-size fractions in The Gully

Canyon samples.

THE GULLY CANYON

DISTRIBUTION OF

KYANITE

C53 >s

I 1 < S RELATIVE

FIGURE 57.—Relative percentage of kyanite in the (A) 125-

250 and (B) 62-125 micron-size fractions in The Gully Canyon samples.

I25-2SQAI

B.

THE GULLY CANYON

DISTRIBUTION OF

STAUROLITE

FIGURE 58.—Relative percentage of staurolite in the (A)

125-250 and (B) 62-125 micron-size fractions in The Gully

Canyon samples.
NUMBER 8 45

OLIVE GRAYFACIES

100 0 100 microns O

Percentage of

Total Sand

50 100

6-56

7-67

SURFACE SAND

13-5

>150

105

62

150

105

62

150

105

62

150

105

62

150

105

62

300

150

105

62

Quartz

Rock fragments

Mica

Dark terr

Glauconite

Carbonate hash

Shell fragments ••• •

Forammifera ^^^ H

FIGURE 59.—Mineralogical variation of the coarse fraction with grain size in selected slope

(Sc) core samples (olive gray and surface sand facies).
46 SMITHSONIAN CONTRIBUTIONS TO THE EARTH SCIENCES

BROWNFACIES

microns 0

Percentage of

Total Sand

5 0 100

Quartz

Rock fragments

Mica 1

Dark terr.

Glauconite

Carbonate hash

Shell fragments ••• •

horammifera HBHol

FIGURE 60.—Mineralogical variation of the coarse fraction with grain size in selected slope

(Sc) core samples (brown facies).
NUMBER 8 47

is found in most samples. Ubiquitous accessory components are feldspar, mica, rock fragments, shell material, and Foraminifera. Glauconite, dark terrigenous

grains, and carbonate "hash" are additional components which may also be present. Mica occurs mostly

as flakes of muscovite; small amounts of biotite and

phlogopite are noted. Fragments of red, green,, and

grey siltstone; red and gray sandstone; quartzite;

mica schist; quartz-biotite gneiss; basalt; and granite

are the principle lithologies comprising the lithic fraction.

Shell material consists of fragments in various stages

of destruction. The bulk of shell fragments is relatively

fresh although some of the larger smooth and rounded

grains show evidence of abrasion. Foraminifera tests

make up most of the shell component: many broken

individuals are noted in grain counts. In this study,

only those fragments which could definitely be identified as Foraminifera were counted. The remainder

are included in a general component category. Black

grains, concentrated with foraminifers during the

CCI4 flotation procedure, displayed conchoidal fracturing, granular and ribbed fine structure. Combustion, using relatively low temperature flames, indicates

that this substance is a hydrocarbon, probably coal

(indication of a terrigenous origin, perhaps Cape

Breton). Other components of this fraction appear

to be biotite aggregates, and altered amphiboles and

pyroxenes.

Carbonate hash is the term adopted to describe

aggregates of pale, greenish, flaky material, fine shell

fragments, and occasionally scattered quartz grains,

all loosely cemented by carbonate material. A flaky

material often present is probably an altered clay

product. Glauconite grains are generally dark green,

somewhat knobbly grains with a smooth or finely pitted

surface.

Mineralogical data plotted as relative percentages

on graphic logs show compositional variation with

grain size in selected samples (Figures 59—61) :

QUARTZ.—The amount of quartz clearly increases

with decreasing grain size. Most grains are angular

in all size fractions but there is a general trend of

increasing angularity with decreasing grain size.

FORAMINIFERA.—Tests, generally smaller than 300/JL,

tend to be concentrated in the 150 to 300/A fraction;

relative percentages decrease regularly in finer size

fractions. This, however, does not imply a decrease in

total numbers, for the total number of grains, including quartz, increases with decreasing grain size and

the proportion of Foraminifera tends to be masked

by other components. Actual counts of the foraminifers in concentrates shows that there is indeed a higher

proportion of tests in the fine fractions.

ROCK FRAGMENTS.—In those samples where the

lithic fraction is abundant, there appears to be a

direct relation between frequency and grain size. A

larger number of sand-size basalt fragments occurs

in smaller size fractions.

SHELL.—Although the frequency is relatively constant in different grain sizes, there is a tendency, in

some samples, of a higher shell fraction in the finer

sizes. Complete valves of pelecypods and partially

broken gastropods occasionally are found in the

coarser than 300fx fraction.

MICA.—Many samples show an increase in mica

flakes with decreasing grain size; in some samples,

however, this trend is not obvious.

DARK TERRIGENOUS GRAINS.—This material consists of ferromagnesian and opaque heavy minerals.

It is more commonly encountered in the finer sizes

and is most abundant in the very fine sand grade.

GLAUCONITE AND CARBONATE HASH.—There is no

marked relation between grain size and frequency of

these components although glauconite and carbonate

fragments are slightly more abundant in the finer

sand sizes.

It must be noted that data were obtained using a

percentage determination so that all components are

actually dependent variables. Furthermore, the figures

have been adjusted so that minor components are

exaggerated and the major components subdued. The

most variable components (excluding quartz) are

lithic fragments and Foraminifera, and strong trends

shown by these components invariably result in modifying the remaining mineralogical components. There

is a general tendency for the total carbonate material

to decrease directly in ratio with grain size. This

change is gradual: the increasing percentage of shells

and carbonate hash complements the sharp decline of

Foraminifera with decreasing grain size.

Examination of core Sc-16 indicates that quartz

and dark terrigenous components generally vary directly, as do mica and glauconite. Shells and foraminifers and occasionally carbonate hash also display

similar trends.

The minor components generally show more variable

changes in percentage than the major components.
48 SMITHSONIAN CONTRIBUTIONS TO THE EARTH SCIENCES

CORE Sc-1 6

0 100 0 100 microns 0

Percentage of

Total Sand

50 100

150

200

220

••••«!

240

Quartz

Rock fragments

Glauconite

Carbonate hash

Shell fragments

Forammifera

FIGURE 61.—Mineralogical variation of the coarse fraction with grain size in the representative

upper slope core (Sc-16). Top three samples are olive gray fades; the lower two are brown

facies.
NUMBER 8 49

FACIES

• brown

• olive gray

• surface sand

Rock Fragments

Terrigenous Carbonate

FIGURE 62.—Coarse fraction mineralogical components in

three facies cored (Sc cores) on the continental slope.

These fluctuations of both groups are random, however, and no distinct tendencies were noted within the

three major Nova Scotian Slope sediment types (surface sand, olive gray and brown facies).

The olive gray and reddish brown sediment types

are most easily distinguished by their accessory components: a predominantly calcareous fraction in the

gray sediment facies, and predominantly terrigenous

assemblage in the brown facies. The same lithic fragments are found in both sediment facies, but brown

sediments generally show a greater variety of petrologic types in any one sample as well as a higher

proportion of red-colored sedimentary fragments. This

contrast was noted clearly in analyses of coarse sand

in brown and olive gray sediment types in representative core Sc-16.

The quartz-feldspar fraction also tends to be more

inportant in brown sediment, while glauconite and

carbonate fragments are more abundant in the gray

facies. There does not appear to be a major difference

in content of dark terrigenous grains in the two sediment types. The absolute amount of mica, Foraminifera, and shells is lower in the brown sediment type,

but the relative proportions generally remain the

same in both olive gray and brown sediments.

The abrupt change of lithology at a depth of 210

cm in core Sc-16 reflects the contact between the

reddish-brown and the gray sediments. A plot of rock

fragments, total carbonate, and total terrigenous fraction on a triangular diagram emphasizes mineralogical

differences between the two facies (Figure 62). Figure 62 highlights the greater variability of carbonate

fraction in the gray sediment type and the higher

amount of rock fragments in brown sediment.

The relatively clean sand facies found at the top

of some cores (samples Sc-9-1, Sc-13-5, and Sc-15-0)

consists of predominantly terrigneous components; the

accessory fraction of the sand is mostly rock fragments.

The similarity of the upper sand layer and the sand

fraction in the brown facies is noteworthy.

The concentration of heavy minerals in the 62 to

500/u, size range is low; the total weight of the heavies

recovered is generally less than 1 percent and only

rarely exceeds 2 percent (Figure 63). The variation

in amount of heavy minerals is similar to that of light

and dark terrigenous components. The abundance of

heavy minerals does not vary significantly between the

brown and gray sediments. Sediments that are fine

grained generally contain a higher proportion of heavy

minerals which, because of their small inherent size,

tend to be concentrated in the finer sand grades.

Opaque grains account for 20 to 60 percent (most

commonly between 25 and 35 percent) of the heavymineral fraction. The abundance of nonopaque mineral species forming the predominant suite and found

in all samples is shown in Figure 64. Hornblende is

the most abundant transparent heavy mineral encountered (relative percentages range from 10 to 42

percent, but most frequently from 25 to 35 percent).

Garnet accounts for 10 to 30 percent of the heavies,

but individual counts vary widely between these limits.

Hypersthene ranges from 5 to 20 percent (generally

about 12 percent). Augite may account for as much

as 20 percent of the heavy mineral counts but, like

garnet, is a mineral showing much variability from

sample to sample.

Other heavy mineral species show considerably

more variation from sample to sample. Altered minerals, for example, are the most commonly encountered grains (to 24 percent) making up this accessory

suite. Andalusite, zircon, and tourmaline are found in

almost all of the 21 Sc-core samples analyzed, and

each may attain 8 percent of the sample. Epidote

and staurolite, not as common, form up to 10 percent
50 SMITHSONIAN CONTRIBUTIONS TO THE EARTH SCIENCES

200

O 50

O

O

50

OLIVE GRAY FACIES

* .

BROWN FACIES

• •

• +

• •

• •

2 3 0 1

Weight in grams of 62 - 500 AC fraction

FIGURE 63.—Concentration of heavy minerals in the olive gray and brown sediment types.

and 5 percent of the nonopaques, respectively. Saussurite, occurring in six samples, ranges from 3 to 11

percent. Titanite, mica, brookite, kyanite, chloritoid,

and sillimanite are encountered infrequently. The

regional uniformity of both predominant heavy and

accessory mineral suites is noteworthy. Furthermore,

there does not appear to be a notable difference between heavy mineral assemblages of the brown and

the olive gray sediment facies (Figure 64).

Upper Slope to Rise Traverse

The coarser than 62 micron fraction of samples from

the slope-rise traverse (cores HUD 30-9 to 14) was

sieved into five Wentworth-Udden size classes, and

each fraction was weighed and percentages computed.

The sand-size and coarser components observed were

clean (nonstained) quartz and feldspar grains, ironstained quartz and feldspar grains, reddish rock fragments, gray rock fragments, shell debris, Foraminifera,

and glauconite. Counts were made of each of these

components in each size fraction according to the

technique described by Shepard (1963). Two hundred

grains were counted when sufficient sand-size material

was available. Those samples where there were less

than 200 grains available for counts can be identified

in Figure 65: if all fractions of a sample weighed less

than 0.05 grams, then each fraction was arbitrarily

assigned an equal share of the size distributed, and

columns of the histograms are therefore equal in

height (example: HUD 30-11, sample 15-17). If

some fractions weighed over 0.05 grams and some

weighed less, then the former were assigned their

correct weight on the histogram, while each of the

latter received an equal share of the remainder. In

the mineralogical analyses shown in Figure 65, where

two or more histogram columns are of equal height,

their counts are less than 200 grains, and their weight

percent values are arbitrary. The single exception is

core sample HUD 30-9A-35-37, whose two columns

are, coincidentally, of equal weight.

After foraminifers and heavy minerals were extracted, the residue was stained for feldspar following

the methods of Keller and Ting (1950).
Brown Facies

per cent 1 0 0

I I

Non-Opaques

Hornblende >>::[:|:[x-:-_:-_:: Augit e

Opaques

Garnet Hypers thene

FIGURE 64.—Principal heavy minerals suite in surface sand,

olive gray and brown sediment types from cores (Sc) collected on Nova Scotian Continental Slope.

Quartz is the most abundant of the major terrigenous constituents, ranging between 70 and 96 percent

(Figures 66, 67 and Table 2). The grains are predominately subangular to subrounded (Powers 1953)

and of the common quartz variety (Folk 1964). Wellrounded grains of medium to coarse sand are present

in trace amounts. Silica overgrowths were noted on

several of these, and the grains are believed to be

derived from Paleozoic sandstones of the Maritime

Appalachians.

A variety of quartz which appears to be of significance to this study is stained with iron oxide (Figure

51

68). The coating ranges in color from moderate red

(5R 4/6, Rock Color Chart Committee, 1963) through

dusky red (5R 3/4), and dark yellowish orange

(10YR 6/6) to moderate brown (5YR 3/4). Under

the binocular microscope, iron-stained grains appear

filmed with opaque, earthy matter that is thin to

absent on convex surfaces, but thick and clotted on

concavities and fissures. This distribution suggests that

the coatings predate transportation, during which

process the coatings were partially removed by abrasion. There are at least two earlier stages in the present

sedimentary cycle where the coatings might have been

formed. Emery (1965:5) described the Atlantic shelf

of North America as floored primarily by sands that

are "coarse . . . iron-stained, and somewhat solution

pitted." Emery concludes that these sands are relict

stream and littoral deposits from Pleistocene low

stands of the sea. The iron coatings of the grains may

have formed also during subaerial weathering of the

original Piedmont source area (Judd et al. 1969).

It may have formed in part during the present stage

of the sedimentary cycle, during subaerial exposure

of the shelf, due to mobilization of iron hydroxide

present in the fine fraction of the sediment (Van

Houten 1968) or from intrastratal solution of iron

hydroxides and oxides (Van Houten 1968, Norris

1965). The coatings may conceivably still be forming

on the coarser sands of shallow banks where bottom

circulation is sufficient to provide a flow of aeriated

water, but not sufficiently intense to abrade grain surfaces. As noted in earlier sections, similar iron-stained

sands are abundant on the Nova Scotian shelf (Stanley and Cok 1968), including Sable Island Bank.

In addition, the iron-stained quartz of our cores

probably received parts of its pigment during an earlier sedimentary cycle. Conolly et al. (1967:131), for

instance, describe reddish-brown glaciomarine sediments from the Laurentian Channel between Nova

Scotia and Newfoundland which contain "Calcite,

quartz, and feldspar grains with relic iron oxide rims

and red calcite-cemented lithic sandstone fragments

and arkosic rock fragments derived principally from

Triassic (and/or Carboniferous-Permian) sediments

of Appalachian Canada or from their reworked derivations." Calcite-cemented reddish sandstone fragments are present in some of our cores as Conolly

and others have described them. Some of these fragments were sufficiently friable to break down to ironstained sand grains as we manipulated them. Iron-
52

o

(E

UJ

Q.

HUD 30-14

0-2 cm

10-12

23-25

35-37

0-2 em

le-io

19-21

22-23

25-27

40

20

0

40

20

0

40

20

^ 35-37

F

45-47

65-67

1 2 3 4

PHI UNITS

SMITHSONIAN CONTRIBUTIONS TO THE EARTH SCIENCES

HUD 30-11 HUD 30 - 9B HUD 30 - 9A

2-4 em

5-7

15-17

35-37

145-47

55-57

65-67

72-73

I

20

75-77

85-87

0 1 2 3 4

PHI UNITS

0-2 cm

110-12

13-15

20-22

35-37

40-41

KEY

CLEAR 'QUARTZ AND FELDSPAR

IRON STAINED QUARTZ AND FELDSPAR

REDDISH ROCK FRAGMENTS

GRAY ROCK FRAGMENTS (RARE)

HEAVY MINERALS (RARE)

SHELL FRAGMENTS

FORAMINIFERA

MISCELLANEOUS (COMPONENTS EACH

LESS THAN 3% COMBWED)

6LAUC0NITE

20

0

2 0

0

20 |

i

40

20

0

80-

60-

40-

20

0

10-12 cm

16-18

22-24

26-28

35-37

48-49

35-57

65-67

Q.

UJ

Q

75-77

1

5

82-84

90-92

0 1 2 3 4

PHI UNiTS

FIGURE 65.—Mineralogical analysis showing frequency distributions of the coarse fraction of

samples from slope and rise (HUD-30) cores southeast of Sable Island Bank (see Figures 15

and 18 for core locations).
NUMBER 8 53

Quartz.chart

. ORTHOQUARTZITE

CORE 14

CORE 13

CORE 11

CORE 9A

CORE 9B

FMdspar.mka Labile rock fragments

FIGURE 66.—Composition of coarse fractions of slope and

rise (HUD-30) core samples in terms of major terrigenous

components (classification after Folk 1954).

stained quartz correlates more closely with clear

quartz than with reddish rock fragments (Figure 68).

We believe, however, that this is a sorting phenomenon

rather than an indication of genesis, and that ironstained quartz in our cores is of both Pleistocene and

Paleozoic origin, in a ratio that we have no means of

determining.

Feldspar grains comprise 4 to 27 percent, and average 17 percent of the major terrigenous constituents.

The potassium feldspar is predominantly orthoclase,

and is more abundant (62—82 percent) than plagioclase. Less than 5 percent of the feldspar grains are

sufficiently altered to be distinguished from quartz

without staining.

Rock fragments comprise less than 10 percent of

the terrigenous constituents of the coarse fraction

(Figure 65). Pale yellowish-brown (10YR 6/2) to

olive gray (5Y 4/1) siltstones comprises 53 percent

of all rock fragments, and dusky red (5R 3/4), moderate red (5R 4/6), and dark reddish brown (10R

3/4) comprise 30 percent (Figures 67, 69). Finegrained rock fragments with marked foliation (slates

or shales) comprise 8 percent of the rock fragments.

Gneiss, granite, amphibolite, and red and gray sandstone fragments are present in trace amounts. The

sourceland for the study area, the Canadian Maritimes

consists of ihree terrains: (1) a terrain of low to

medium grade metasediments and metavolcanics of

lower Paleozoic age intruded by granite; (2) PermoCarboniferous basins containing reddish, drab, and

greenish-gray, coarse to fine continental elastics; and

(3) more restricted Triassic basins containing a similar sequence. The suite of lithologies present in our

samples reflect original lithologic frequency distributions strongly modified by selective destruction of the

mechanically unstable very fine and very coarsegrained rock types.

The sole rock type that is sufficiently abundant and

distinctive to be considered a tracer is a fine- to coarsegrained, reddish sandstone. Its composition ranges

from subgraywacke to subarkose. The pigment ranges

from dusky red (5R 3/4) through moderate red

(5R 4/6) to moderate reddish brown (10R 4/6).

Some fragments have a carbonate cement; others

have no obvious cement. These fragments closely resemble the ones described by Conolly and others

(1967) from the Laurentian Channel. These workers

suggest that the fragments were derived from the

Triassic and Permo-Carboniferous rocks of Prince Edward Island and Nova Scotia. The fragments in our

cores, however, might also have traveled directly

across the Nova Scotian Shelf (Stanley and Cok

1968) ; reddish tills, derived from the Triassic and

upper Paleozoic of Northern Nova Scotia (Grant

1963) are, in fact, exposed along the sea cliffs on the

Atlantic Coast of Nova Scotia.

Glauconite comprises up to 10 percent of the coarse

fraction (Table 1). Grains range from a moderate

greenish-yellow color (10Y 7/4) and a frequently

irregular shape to a dusky green (5G 3/2) or greenishblack (5G 2/1) variety which is commonly ellipsoidal

and sub rounded to rounded or rounded/broken. The

mineral is confined to the very fine sand fraction,

where its relative abundance correlates closely with

the relative abundance of quartz and also with the

relative abundance of this size fraction. Both light

and dark glauconite were noted in HUD-30 cores;

grains with lightness values of 5 or greater (equivalent

to medium dark gray or darker) comprise 69 percent.

There is apparently no statistically significant difference between the light to dark glauconite ratios of

the two most glauconitic-rich cores (i.e., HUD 30-14

on the slope and HUD 30-13 on the upper rise).

Dill (1968), in a detailed analysis of glauconite on

the North Carolina continental slope, detected a

systematic variation in color and properties of this
54 SMITHSONIAN CONTRIBUTIONS TO THE EARTH SCIENCES

FIGURE 67.—Photo-micrographs illustrating coarse fraction assemblages in slope and rise (HUD30) cores (see also Figure 65). A, brown facies on upper rise (core 13, 19 to 21 cm): very

coarse fraction showing small gray and red sandstone pebbles, basalt pebbles, and shell fragment, B, brown facies on upper rise (core 13, 8 to 10 cm) : coarse sand fraction showing clear

and iron-stained quartz and rock fragments, c, olive gray facies on slope (core 14, 10 to 12

cm) : very fine sand showing terrigenous fraction with abundant glauconite. D, tan facies on

lower rise (core 9A, 55 to 57 cm) coarse sand fraction showing biogenic assemblage with

abundant Foraminifera.

mineral: the darker glauconite exhibited better crystallinity, greater thermal stability, and a lower water

content; dark, well-rounded glauconite predominates

on the upper slope, while lighter, more poorly rounded

glauconite predominates on the lower slope. The two

populations represent (1) a detrital population of

dark, well-rounded grains weathering out of preRecent rocks cropping out, or formerly cropping out,

on the outer shelf and upper slope, and (2) a ubiquitous authigenic population associated with the foraminiferal slope sediments. The predominance of dark

glauconite in Nova Scotian margin samples suggests

that either the authigenic source is not as important

on the Nova Scotian slope, or that authigenic grains,

which Dill determined to be fragile relative to the

detrital group, have been selectively destroyed during

transport. Hubert and Neal (1967) in their study of

the North Atlantic petrologic province have also

noted a correlation between the abundance of very

fine glauconite and very fine quartz sand, and concluded that the two had been sorted during concurrent

transport.

Shell hash and Foraminifera are also significant

components of the coarse fraction (Figure 67). Either

component may comprise up to 70 percent (Figure

70) ; together as much as 90 percent. The two cate-
NUMBER 8 55

TABLE 2.—Relative abundance of light fraction components in slope and rise (HUD30) cores collected south of Sable Island Bank

Core

HUD-30-14

HUD-30-13

HUD-30-11

HUD-30-9B

HUD-30-9A

1

Xi

i i (X

ro

cO

CU

U

M

t

N U

4-1 CO

U Cu

cO co

O * r—1

CU

Pi P^H

CO

<U T3

fH Pi

O CO

70.62

66.38

55.58

20.43

26.18

CU

•eH

cO

4-1

CO

ko

M

9

16

13

4

4

CO

CO

1—1

CU

P&4

rO

acO

N

4-J

U

cO

3

o*

.73

.72

.28

.64

. 5 3

o

o) -l CO

4-1

xi G

CO CU

3"O I cO)

CU M

0.44

3.60

4.06

0.05

0.45

r!*5 CO

CJ 4-t

O Pi

U CU

c^0 caO

u u O m

0.93

5.92

2.08

0.70

1.76

CO

1—1

cO

uCU

Pi

•H

e

cO

CU

2.20

2.17

2.96

1.34

1.33

CO

4-1

CaU

B

to

to

M-ul

r-i

r-i

CU

xi

1.68

0.70

6.49

31.68

20.53

cO

U

M-<ul

•H

Pi

•H

i

o

2.85

2.47

8.10

39.80

44.64

CU

4J

c

oCJ

cO

iH

O

8.38

3.37

1.19

0.21

1.41

les

Pu

CO

M-l

O T)

CU

M 0 0

CU CO

g CU

!25 CO

5

8

11

5

11

gories are not completely exclusive of each other, in

that a significant portion of the shell hash consists of

comminuted foraminifers. Pelecypods, gastropods, bryozoans, and calcareous algae are also common in shellrich samples; diatoms, radiolarians, and chitinous or

otherwise noncalcareous fragments are also observed.

Fish vertebrae were occasionally observed in the very

coarse sand fraction.

A triangular plot of the major terrigenous "light"

components (Figure 66) indicates that most samples

have coarse fractions that are subarkosic in composition. The most quartzose sand fractions are those of

olive gray slope core HUD 30-14, and the most lithic

are sand fractions of brown continental rise core HUD

30-13. These variations may be attributed, at least in

part, to grain-size control as HUD 30-14 has the finest

sand fractions and HUD 30-13 the coarsest.

The transparent heavy mineral suite observed in

the five slope and rise HUD 30 cores (Figure 71) is

the same as that observed in the upper slope (Sc-)

cores (Figure 64). Heavy minerals in cores HUD 30-

14 (gray slope facies) and HUD 30-9 (light tan

lower rise facies) are very similar and can be distinguished from the brown facies of cores HUD 30-13

and HUD 30-11 on the upper rise. The former two

cores contain almost 50 percent (range 40 to 54 percent) hornblende, and approximately 6 to 9 percent

(range 4 to 17 percent) garnet and about the same

amount of epidote. The latter two core samples

(brown sediment type on the rise) contain less hornblende (range 18 to 35 percent) and epidote (range

1 to 12 percent), but relatively more garnet (5 to 39

percent). The upper rise core HUD 30-13 comprises

a high (> 23 percent) percentage of altered ("alterite") grains; core HUD 30-11 contains a somewhat

higher (> 11 percent) metamorphic suite (staurolite,

kyanite, etc.)

The heavy mineral suites of the slope and rise are

the same as those on Sable Island Bank although the

proportion of mineral types differs. On the bank the

relative percent of garnet generally exceeds that of

hornblende (James and Stanley 1968) while on the

slope and rise the relative percent of hornblende is invariably higher than garnet. This difference can probably be attributed to size sorting (e.g., generally finer

sediments on the slope than on the shelf would contain a

lower amount of garnet, an inherently large mineral).

Samples of Lamont-Doherty cores collected on

other parts of the outer margin south of Nova Scotia

also show a similar suite of minerals (Figure 72, Table
56 SMITHSONIAN CONTRIBUTIONS TO THE EARTH SCIENCES DSPA

R FE

L

0 80-

r

0 40-

A A

ft

A*5A

• •

A

A

• Q Q

a

o • o 0

0

4 6 8 10

%GLAUCONITE

12

20 30 40 50

%FORAMINIFERA

60

a

<

 80"

<

 60"

o

a: 401

O20-I

° HUD 30-9A

• HUD 30-9B

* HUD 30-11

• HUD 30-13

• HUD30-I4

2 6 10 14 18 22 26

% IRON-STAINED QUARTZ AND FELDSPAR

a:

(0

a

i

ixJ

Q

N

a:

o

Q

LLJTAI

N RONS

28-

24-

20-

16-

12-

8-

4-

•

A

0

a

0

o

+

Q +

A

«

. A

• A

A

A • A

A •

A

A

A

a

a

D

4 6 8 10

% ROCK FRAGMENTS

12

FIGURE 68.—Scatter plots of selected pairs of coarse fraction components in slope and rise

(HUD-30) cores.

3). In most of these samples, garnet plus hornblende

account for approximately half of the mineral suite.

In several cases, the amount of garnet exceeds that

of hornblende. The proportion is generally related to

grain size, i.e., higher amounts of garnet are generally

found in samples of coarser grain size.

Clay Mineralogy on the Outer Margin

Off Nova Scotia

Slope off Sable Island Bank

METHODS.—X-ray diffraction was used to identify

dominant clay mineral suites in the fine fraction of
NUMBER 8 57

REDDISH SANDSTONE

GRAY SANDSTONE

MISCELLANEOUS

CORE 13

MEDIUM TO VERY COARSE

SAND FRACTION

FIGURE 69.—Relative abundance of lithic fragments in coarse

fraction of samples of core HUD-13 collected on the rise

south of Sable Island Bank.

Red-stained quartz+feldspar-f

red and gray rock fragments

Non-stained quartz

+f«ldspor + glauconit«

Foraminifers + shell fragments

FIGURE 70.—Triangular plot of coarse fraction suites in

slope and rise (HUD-30) cores.

cores (Sc) on the slope off Sable Island Bank. Standard methods used are detailed in Silverberg (1965).

The scattering factors developed by Freas (1962)

have been used to determine approximately clay mineral (illite, kaolinite, montmorillonite) percentages.

Other minerals identified in the clay fraction are

chlorite, quartz and feldspar. The former was identified by the strong 101 reflection at 3.3A and by a

weaker 100 line at 4.3A. Feldspar was inferred from

the presence of one, and sometimes two, lines in the

range 3.16-3.21 A. An occasional shoulder along the

high angle side of the 7A reflection also suggested a

7.5A reflection of feldspar.

The most accurate method of analysis involves the

comparison of peak areas with those of internal standards or of prepared standard mixtures; in our case

the assumption has been made that the peak area

are proportional to the relative quantities of the components present (Johns, Grim, and Bradley 1954).

Before peak areas were measured, the background

level and the lower portions of each peak were

smoothed with French curves. Taking the average of

at least four planimeter readings, the areas of the 001

reflections about 14.2, 10.0, and 7.1A were recorded

for the untreated sample. Using the same background

line and peak widths, the areas of the 14A and the 7A

peaks were measured on glycolated and the HC1

treated samples, respectively.

Illite was measured as the area of the untreated

10A peak, chlorite the area of the glycolated 14A

peak, kaolinite the area of the HC1 treated 7A peak,

and montmorillonite, the difference in area of the

14A reflection before and after glycolization.

To determine the approximate composition, the

illite area was multiplied by three, the chlorite area

divided by three, and then the total corrected areas

added. The relative percentages of the various components were then computed and converted to parts

per ten of the total. The peak areas of different components are not directly comparable because of variations in the ability to scatter X-rays.

The decision to use the HC1 treated value of the

7A peak as the kaolinite contribution involves the

assumptions that all of the chlorite contribution is

removed by this treatment, and that the area is not

altered by acid attack on the kaolinite. An estimate

of the reproducibility of the procedure was made by

the examination of several slides sampled from the

same suspension. The diffractograms were virtually

identical, save for errors accountable by instrument

variation.

RESULTS.—Relative percentages of illite, chlorite,

montmorillonite, and kaolinite were obtained for eight

samples (Table 4). Illite is the dominant clay mineral,

making up as much as 88 percent of the Sc core samples (using Freas' scattering factors). Kaolinite ac-
58 SMITHSONIAN CONTRIBUTIONS TO THE EARTH SCIENCES

60* 59*

b cdefgh i

bed efgh i

DEPTH IN FATHOMS

60* 58*

FIGURE 71.—Relative percentages of transparent heavy minerals observed in core (HUD-30)

samples south of Sable Island Bank, a, hornblende, b, garnet; c, alterite; d, epidote; e, zircon

+ tourmaline + rutile; f, augite; g, hypersthene; h, metamorphic suite (staurolite, kyanite,

etc.); i, other minerals.

counts for 2 to 11 percent, montmorillonite 3 to 7

percent, and chlorite between 2 to 5 percent. These

percentages are only approximate.

Noteworthy is the uniformity of the clay mineral

suite in the different slope facies. The uniformity of

this assemblage within a representative slope core

(Sc-16) penetrating both olive gray and brown sediment types is illustrated in Figure 73. The consistency
NUMBER 8 59

73 76 82 247 21 2 2 1

HORNBLENDE

HYPERSTHENE

TOURMALINE

ZIRCON

16 U 23 13 1.9 2.1 10 a?

OPAQUE/NON-OPAQUE

FIGURE 72.—Variation in relative percentages of the more

abundant nonopaque heavy minerals from 12 LamontDoherty core samples collected south of Nova Scotia. Numbers at top refer to "laboratory code" in Table 1. Data

arranged with shallower (Nova Scotia Slope) core samples

at left to deep-water (Sohm Abyssal Plain) samples at right.

Opaque to nonopaque heavy mineral ratio is given at bottom.

Heavy mineral data is also listed in Table 3.

of the clay mineral suite on a regional basis is shown

in diffractograms of samples taken from different slope

cores (Figure 74). Differences determined in the semiquantitative study are slight and are well within

experimental errors of this technique.

Slope and Rise Traverse South of Sable Island Bank

METHODS.—Samples were selected for clay mineral

analysis from the top and base of each HUD 30 core

in order to evaluate the mineral suites present in sediment facies on the slope and rise along the traverse

south of Sable Island Bank. The results cited in the

following study were obtained by T. T. Davies (personal communication).

Samples were disaggregated and treated to remove

calcium carbonate and iron by the procedure described

by Biscaye (1965) which was modified from Jackson

(1956). The procedure fully described by Biscaye

(1965) was closely adhered to in both sample preparation and X-ray data treatment. Gravity settlement followed by controlled centrifugal sedimentation was

used to isolate the < 2 micron fraction which had

been saturated with calcium ions. Oriented clay precipitates were made on glass plates from equal density

clay slurries.

A Norelco X-ray diffraction apparatus was used

with a wide range goniometer and a proportional

counter using pulse height analysis and Copper K

radiation. An A.M.R. lithium fluoride monochromator

was used to reduce low angle scattering and produce

monochromatic K radiation. Each sample was scanned

at various speeds over the required angular ranges

in an untreated state, and after glycolation and heat

treatment to 250°C and 450°C.

The mineral phases identified from the diffraction

traces consist almost entirely of clay minerals identified as illite, chlorite, kaolinite, and montmorillonite.

Small quantities of quartz, feldspar, and amphibole

can be identified in each sample, but they do not

form a significant contribution to the sample mineralogy, and consequently they have been ignored in

the quantitative estimates of the mineral contents of

the samples.

The peak areas obtained from the various glycolated samples of the 10A illite, the 17A expanded

montmorillonite, and the chlorite and kaolinite peak

that occurs at approximately 7A were measured on the

diffractometer charts, after background smoothing.

The 3.54A kaolinite peaks could be separated on

charts obtained from the untreated samples. The

ratio of these peak areas was used to define the areal

contribution provided by each mineral to the 7A

glycolated peak (Biscaye 1965). Replicate areal measurements on the montmorillonite peak exhibited great

variation because the peak is located in a region of

rapidly changing background and because the poorly

crystalline mineral occurs in such small quality.

Two methods have been used in estimating the

relative abundance of the clay mineral phases in the

various samples. The relative abundance of two particular minerals is expressed as a simple ratio of their

analysis peaks. A semiquantitative estimate of the actual abundance of the clay minerals in the samples

has been made by using scattering factors and weighting the peak areas. The mineral concentration is then

expressed as a percentage of the sum of the weighted
60 SMITHSONIAN CONTRIBUTIONS TO THE EARTH SCIENCES

TABLE 3.—Relative percentages of heavy minerals in samples from the rise and

Sohm Abyssal Plain (Lamont-Doherty cores) south of Nova Scotia (see also Figure

72). Numbers at top refer to samples identified in the laboratory code column in

Table 2

Andalusite

Apatite

Augite

Chlorite

Clinozoisitt

Corundum

Diopside

Enstitite

Epidote

Garnet

Hornblende

(Blua-Green)

Hornblende

(Common)

Hypersthene

Kyanite

Monazite

Rutile

Silliroanite

Sphene

Spinel

Staiarolite

Topaz

Tourmaline

Tremolite

Zircon

Zoisite

Non-opaque

counted

H-73

0.3

0.3

12.0

4O5

3

0.3

1.3

2.9

28.0

10.1

15.4

13.0

0.3

0.8

0.3

0.7

1.6

2.0

1.3

4.2

1.3

309

H-76

1.1

2.0

9.1

3.5

2.4

2.4

22.0

4.0

18.9

4.9

1.1

2.0

1.6

0.2

3.1

1.5

0.9

2.9

1.5

14.5

0.4

455

H-82

0.6

4.8

7.6

1.6

1.7

5.1

23.9

5.4

13.6

6.5

0.6

0.6

1.6

2O8

3.1

0.3

2.5

2.5

14.9

0.3

354

H-247

2O2

3.7

8.2

3.7

3.0

15.7

4.1

7.1

7.5

0.7

0.4

0o4

0.7

2.6

0o7

0.4

10o8

1.9

11.6

230

H-21

2.8

1.8

2.1

11.1

1.0

4.5

18.1

5.6

7.8

2.4

4.9

1.8

1.4

3.8

4.9

8.0

0.7

3.1

2.8

8.3

3.1

287

H-22

1.7

2.6

2.9

6.9

1.4

4,3

4.9

20.0

7O2

8.3

1.4

2.6

1.1

0.6

0.6

3.1

9.2

0.1

8.9

2.3

7.5

1.1

349

H-l

2.9

2.6

3.2

3.9

0.3

0.6

1.0

1.3

37.2

5.8

3.5

6.4

1.6

1.3

1.0

1.3

1.3

2.6

2.3

1.6

7.1

0.3

10.4

0.6

310

H-2

1.9

1.5

5.6

7.1

0.1

0.1

28.9

7.2

3.7

6.6

4.2

0.1

0ol

6.7

2«8

3O3

0.1

12.4

7.5

0.1

217

H-3

2.2

7.2

3.8

2.7

1.2

1.8

20.9

11.7

7.0

2.2

2.2

1.2

0.7

1.7

5.5

1.0

0.8

0.7

5.0

1.4

18.8

0.3

598

H-63

0.3

0.9

4.5

11.9

2.7

3.3

25.3

3.9

8.9

4.5

0.3

0.3

2.1

2.7

5.1

0.3

2.4

2.7

17.3

0.6

335

H-193

1.4

7.4

8.6

4.1

2.7

17.2

4.5

10.3

4.8

4.0

1.4

0.3

0.3

8.6

3.8

23.2

291

H-192

5.4

11.5

1.7

0.3

25.3

5.7

10.2

1.7

1.0

0.3

0.3

0.7

2.0

12.5

4.0

17.4

298
NUMBER 8 61

D.3A 13.5 A ISA

CORE SC - 16

(Untreated Samples)

I/A ho A

FIGURE 73.—Nova Scotian slope core Sc-16, diffractograms of less than 2 micron fraction.

Numbers on right refer to depth (in cm) in core (see Figure 14).

14A

FIGURE 74.—Diffractograms of less than 2-micron fraction,

slope core samples (Sc-1, -4, -7, -9, and -10) collected on the

slope south of Sable Island Bank. Numbers following hyphen

on right refer to depth (in cm) in core (see Figure 14).

peak areas assuming that the clay minerals account

for 100 percent of the sample mineralogy. To retain

consistency with Biscaye's methods the following

weighting factors have been used: four times the

illite 10A peak, the area of the montmorillonite peak

and twice the area of the 7A peak which is divided

proportionally between kaolin and chlorite [Biscaye

(1965), following Johns, Grim, and Bradley (1954),

and Weaver (1961)].

RESULTS.—The peak area ratios and the constructed mineral percentage are listed in Table 4

together with the mean clay mineral estimates of

Sc core samples and values given by Biscaye for the

surface sample of a Lamont-Doherty core taken closest

to the samples collected for this study. Sample SAC96 was obtained at a depth of 440 m on the upper

slope (above core HUD 30-14). Although there is

considerable variation in the physical properties of

the sediment within a single core there is no significant

consistent variation in the clay mineral content. The

same suite of clay minerals characterizes each of the

core samples analyzed by Biscaye (1965) and Conolly

et al. (1967) from this geographic region. Conolly

et al. (1967, page 145) note a decrease in the percentage of kaolinite with time (from brown Pleistocene to gray Holocene facies) in the Gulf of St.
62 SMITHSONIAN CONTRIBUTIONS TO THE EARTH SCIENCES

TABLE 4.—Predominant clay minerals measured in samples from the slope and risk

south of Sable Island Bank. Percentages are only approximate. Results of Lamont'

Doherty core sample (164-47/5) studied by Biscaye (1965) are listed for comparison.

Location of sample SAC 96 is shown as station 96 in Figure 3

SAMPLE NUMBER

SAC 96

HUD-30-14 TOP

BASE

HUD-30-13 TOP

BASE

HUD-30-11 TOP

BASE

HUD-30-9A TOP

BASE

(1965)

BISCAYE SAMPLE

A164-47/5

41°43'N 59°W

RANGE OF VALUES

OF Sc-CORES

(Silverberg, 1965)

WEIGHTED PEAK AREA

WATER DEPTH

(METERS)

440

1326

2222

3795

4938

4720

(Depth

Limits)

600-1200

PERCENTAGE

KAOLIN CHLORITE

7

7

9

5

7

10

6

13

8

12

10-14

2-11

13

14

11

23

16

17

11

17

17

17

15-19

2-5

MONTMORILLONITE

1

7

7

2

2

5

1

3

1

8

9

3-7

ILLITE

79

73

73

71

75

69

82

68

74

63

50

80-88

PEAK AREA RATIOS

K^C

3.58A/3.54A

0.54

0.49

0.83

0.17

0.42

0.58

0.58

0.77

0.48

0.67

7A/10A

0.18

0.18

0.25

0.13

0.18

0.28

0.15

0.38

0.22

0.37

oK/Mo

7A/17A

3.52

0.49

0.69

1.37

1.53

0.95

21.00

2.00

6.25

0.76

NO PEAK AREAS REPORTED

C/I

7A/10A1

0.32

0.37

0.30

0.42

0.43

0.48

0.26

0.48

0.58

0.52

Lawrence region. Such a distinct change could not be

recognized in the area south of Sable Island Bank.

The upper slope (Sc) cores treated in the previous

section show a slightly different proportion of clay

minerals. This slight difference of clay mineral assemblages can be attributed to differences in sample

preparation, and particularly the method of discriminating chlorite from kaolinite by hydrochloric

acid leaching techniques. Further, differences are also

derived from a different set of weighting factors to

calculate mineral percentage concentration. The composition of sample SAC 96 collected just seaward of

the southern margin of Sable Island Bank is directly

comparable to that of the upper slope (Sc) cores.

Clay Mineral Suite in the Source Area

The similarity of the clay mineral suites in all deepwater samples in this area indicates a common provenance of the clay fraction for the olive gray and

brown facies. The color difference reflects different

oxidation states of iron, and not differences of clay

mineral suites, in the two sediment types.

In an earlier section we indicated that Carboniferous, Triassic, and Pleistocene deposits in New Brunswick and Nova Scotia served as the predominant source

of red material of late Quaternary age on the outer

Nova Scotian margin. Red and gray Pleistocene and

Triassic units along the northern shore of the Minas

Basin in the vicinty of Five Islands, Nova Scotia, were

sampled in the summer of 1968. The clay mineral

suites in this area (Table 5) are similar to those on

the slope and rise (Table 4). The similarity of the

olive gray and brown facies clay mineral suite on the

upper continental slope (Sc cores) and that of Triassic units on shore is particularly noteworthy.

Foraminifera and Stratigraphy of Surficial

Continental Margin Sediments

Foraminifera in 40 samples of Nova Scotia Slope

cores (Sc) were examined (F. Medioli, Dalhousie

University, personal communication). Twenty-two

samples were obtained from slope (Sc) cores in which

a total of 31 species are identified (Table 6). Foraminifera represented by only a few individuals are
NUMBER 8 63

TABLE 5.—Clay mineral composition (weighted peak area percentage method after

Biscaye 1965) of Pleistocene and Triassic samples collected near Five Islands, on

the mainland of Nova Scotia

Pleistocene

Gray mud

Brown Sandy mud

Reddish-brown mud

Triassic

Red mudstone

Gray mudstone

Red siltstone

Gray siltstone

Kaolin

12

9

9

1

1

3

1

Chlorite

32

22

25

5

5

8

5

Montmorillonite

3

5

4

3

17

7

13

Illite

53

64

63

91

77

82

81

not listed. All the species reported are living in the

North Atlantic region at the present time.

Deep-sea Quaternary chronology is commonly reflected by variations in selected colder and warmer

water foraminifers. Forms such a Globigerina pachyderma, Elphidium arcticum, and Nonion laboradoricum are indicative of a cold water environment. Attempts to base a chronology on the coiling directions

of Globigerina pachyderma were without success.

Planktonic: benthonic ratios show several significant changes within a single core. The top and bottom of core Sc-16 have relatively high ratios, with

maxima at 80 and 240 cm (Figure 75). High planktonic numbers can imply an actual increase in abundance of planktonic forms, such as might accompany

a rise in sea level, or it can indicate a relative reduction in benthonic forms.

A study of the distribution of individual species

provides useful stratigraphic information. In core

Sc-16 a total of 29 species were observed (numbers 1-29 on Table 5). A change in the planktonicbentonic ratio occurs at the boundary between the

brown and olive gray facies at a depth of about 209

cm from the top of the core. It is noteworthy, however, that the major faunal assemblage change occurs

at a depth of approximately 80 cm within the upper

olive gray facies. Within a section about 70 cm thick,

Rank/ BerthRatio

Q

Planktonic

"BO

200

Benthonic

%E 4 2 0 (sequence as listed m table 6 )

FIGURE 75.—Distribution of Foraminifera in core Sc-16

(see Table 6).
64 SMITHSONIAN CONTRIBUTIONS TO THE EARTH SCIENCES

TABLE 6.—Foraminifera in Nova Scotian Slope core Sc-16 (see Figure 75)

PLANKTONIC FORMS

1. Glbbigerina pachyderma (Ehrenberg)

2. Globlgerina bulloides d'Orb.

3. Globigerina inflata d'Orb.

4. Globorotalla menardil (d'Orb.)

5. Globorotalla truncatulinoldes (d'Orb.)

6. Globlgerlnoides rubra (d'Orb.)

BENTHONIC FORMS

7. Sphaeroidina bulloides d'Orb.

8. Nonion labradoricum (Dawson)

9. Cassidulina norcrossi Cush.

10. Cibicldes lobatulus (Walker & Jacob)

11. Virgullna complanata Egger

12. Elphidium arctlcum (Parker & Jones)

13. Eponides umbonatus (Reuss)

14. Globobulimina auricolata (Bailey)

15. Cassidulina subglobasa Brady

16. Bulimina marginata d'Orb.

17. Bolivina subspinescens Cush.

18. Bulimina aculeata d'Orb.

19. Pullenia bulloides (d'Orb.)

20. Epistomina elegans (d'Orb.)

21. Karreriella brady (Cush.)

22. Uvigerina sp. A - after Cush.

23. Pullenia quinqueloba (Reuss)

24. Reophax atlantica (Cush.)

25. Virgulina fusiformis (Williamson)

26. Buccella frigida (Cush.)

27. Augulogerina augulosa (Williamson)

28• Bulimina exilis Brady

29. Cassidulina neocarinata Thalmann

30. Elphidium incertum (Williamson)

31. Quinqueloculina seminulum Lin.

8 forms disappear and 11 species first appear; 3 other

species make their appearance within a slightly

broader range (see Figure 75).

This faunal change corresponds with the position

of the upper plantonic to benthonic maximum. It also

corresponds with the position of the change from

cold to warmer water conditions reported by Heezen

and Drake (1964) in a similar core sequence (olive

gray facies above brown facies) taken in the Laurentian Channel. Other cores collected on the continental

rise off Nova Scotia show this faunal boundary at

a depth of about 50 to 75 cm (Ericson et al. 1961);

the faunal change is believed to coincide with the

period of glacial retreat and rapid rise in sea level

at the end of Wisconsin glaciation.

Gonolly (1965) has reported a date of 24,000 B. P.

for the upper part of the brown sediment (which in

core Sc-16 occurs at a depth of 209 centimeters). The

top of the brown layer may be as young as 15,000

years old (Gonolly et al. 1967). Heezen and Drake

(1964) do not indicate any evidence for a marked

climatic change across the gray-brown contact. We

thus believe that a position of the Holocene-Pleistocene

boundary at a depth of approximately 80 cm (within

the olive gray facies) on the slope of Nova Scotia is

probably correct. The change in dominant species of

planktonic Foraminifera has been noted in Atlantic

and Caribbean cores and is estimated to have occurred

about 11,000 years B.P. (Broecker et al. 1960, Ericson

et al. 1964). If the faunal change in core Sc-16 cor-
NUMBER 8 65

responds to this climatic event, then a sedimentation

rate of 7 to 8 cm per 1000 years can be postulated for

the upper 80 cm Holocene section of olive gray sediments south of Sable Island Bank. This rate is somewhat lower than the average rate of 10 cm per 1000

years during Tertiary to Quaternary time calculated

for the slope off eastern North American (Uchupi and

Emery 1967).

A survey of Foraminifera in both olive gray slope

(HUD 30-14) and brown upper rise (HUD 30-13

and 11) cores show a dominance of cold water forms.

In contrast with these assemblages, the lower rise cores

(HUD 30-9A and B) show an alternation of cold and

warm water forms. This latter observation probably

reflects the effect of meandering of warm Gulf Stream

water masses transporting forms indigenous to the

Sargasso Sea back and forth above the Nova Scotian

rise (Cifelli and Smith 1970, and others).

Interpreting Sedimentary Sequences

and Stratigraphy

Slope and Upper Rise Fades

Petrologic investigations detailed in the previous

sections serve to define a trio of mappable sediment

types that occur on the continental slope and upper

rise south of Sable Island Bank. The distribution of

these three facies, as determined by textural, mineralogical, and X-radiographic examinations of cored

surficial and upper sediment sections, is patchy (Figure

18). The three dominant sediment types on the slope

and upper rise are summarized below.

BROWN SEDIMENT TYPE.—This is an easily distinguishable brown pebble-sand-mud admixture (see

cores HUD 30-13 and 11, Figure 15) whose provenance, as determined by the clay and coarse fraction

minerolagy, is primarily Paleozoic and Triassic source

areas in the Canadian Maritime Provinces of the

north and northwest. The sand and coarser fraction in

this facies is relatively important (as much as 50 percent pebbles) and is distinguished by an important

"unstable terrigenous assemblage" consisting of redstained quartz and feldspar; reddish and gray rock

fragments and abundant heavy minerals (see logs of

cores HUD 30-13 and 11, Figure. 76B). The coarse

fraction also contains red sandstone and shale grains

and occasional basalt fragments in the reddish brown

mud (also noted by Marlowe 1964, and Conolly et al.

1967). It has been postulated on the basis of seismic

evidence that a Triassic trough may once have been

exposed on the Nova Scotian Shelf (Officer and Ewing

1954). It is more probable, however [as suggested by

Marlowe (1964), Silverberg (1965), Conolly et al.

(1967), James and Stanley (1968), and Stanley and

Cok (1968)], that deposits of Carboniferous and

Triassic age were eroded in the New BrunswickPrince Edward Island-Nova Scotian area, and served

as the predominant source of red sandstone and basalt

fragments on the outer margin.

The angular and fissile nature of red shale fragments would suggest that this sediment was not transported very far. Evaluation of geological conditions in

this region, however, indicate another conclusion:

material, although angular, was in fact carried as

much as several hundred kilometers from source areas.

Transport by glacial and berg ice (ice-rafting) is a

process which would best explain the angularity of the

fragments.

The brown facies, the lowermost deposit penetrated

in cores, is pre-Holocene in age. It crops out most

commonly at or near intervalley highs and ridges, and

floors much of the lower slope and rise. Faunal

evidence indicates that the brown facies was being

deposited during the height of the Wisconsin glaciation to perhaps as recently as 15,000 or even 13,000

years B.P. (Conolly et al. 1967). The PleistoceneHolocene boundary at about 11,000 years B.P., also

based on faunal evidence, is placed at 80 cm in Core

Sc-16, suggesting an average sedimentation rate of

about 7 to 10 cm per 1000 years during the Holocene.

On the basis of this rate, the age of the top of the

brown facies, lying at a depth of approximately 200

cm, may be as old as 20,000 years B.P. on the upper

continental slope.

OLIVE GRAY SEDIMENT TYPE.—The olive gray facies

covers upper reaches of The Gully Canyon, the Gully

Trough, and valley axes on the upper to midcontinental slope. It does not cover the rise and mid and

lower part of The Gully Canyon. Silt is the predominant textural fraction (see Core HUD 30-14,

Figure 76A). Sand and pebble layers are proportionately less common than in the brown facies. The

mineral components of fine- and coarse-grained fractions are almost identical with those of the older

brown facies and their provenance is presumed to be

the same. It is note worth, however, that the proportion

of "stable terrigenous assemblage" (clear and unstained

quartz, feldspar, and glauconite) tends to be con-
66 SMITHSONIAN CONTRIBUTIONS TO THE EARTH SCIENCES

SLOPE

(Olive Gray Facies)

HUD 30-14

20 40 60 80 100%

UPPER RISE

(Brown Fades)

HUD 30-13

20 40 60 80 100%

MID RISE

(Brown Facies)

HUD 30-11

0 20 40 60 80 100%

LOWER RISE

(Light Tan Facies)

HUD 30-9B

20 40 60 80 100%

[ ' | Sand (and coarser) fraction.

| 1 Silt fraction

H H | Clay fraction

HUD 30-9A

20 40 60 80 100%

HUD 30-14 HUD 30-13

2? 40 «> 80

HUD 30-11 HUD 30-9B

"Stable terrigenous assemblage1

HUD 30-9A

Clear quartz 8feldspar, glauconite

,,,. .. . . HI 1 Red-stained quartz Bfeldspar; reddish rock

Unstable terrigenous assemblage | | f^ments,gray rockfrogments,heavy minerals

"Biogenic assemblage" Foraminifers, shell fragments

FIGURE 76.—A, Percent of sand, silt, and clay in slope and rise (HUD) cores, B, Percent of

the coarse fraction suites (stable terrigenous, unstable terrigenous and biogenic assemblages)

in the same cores.

siderably higher in the olive gray facies than in the

brown facies (core HUD 30-14, Figure 76B).

Bioturbate structures are also more common in this

facies. The Pleistocene-Holocene boundary lies within

the olive gray sediment type, and presumably sedimentation of the olive gray facies on the upper to mid

slope has continued until recent time.

SURFICIAL SAND SEDIMENT TYPE.—The uppermost

member of the trio, only locally present on the slope,

is particularly common in depressions. It consists of

thin sand laminae composed of light and heavy

minerals similar to those of the underlying olive gray

and brown facies. The composition is also similar to

sand covering adjacent Sable Island Bank. Its position
NUMBER 8 67

in cores clearly suggests that it is the youngest of the

three slope facies and is recent (probably within

historic time) in age.

Lower Continental Rise Facies

LIGHT TAN CONTINENTAL RISE SEDIMENT TYPE.—On

the lower continental rise a fourth sediment type is

apparent. A light tan, soft to stiff mud consists of silt

and clay (cores HUD 30-9A and 9B, Figure 76A)

and is equivalent in age to the olive gray facies on the

upper and mid slope. It blankets most of the outer

margin from the lower rise to the abyssal plain. This

facies contains less sand than either the olive gray or

brown facies (Figure 76A), and its composition is

distinct: the coarser fraction is dominated by a

"biogenic assemblage" consisting of Foraminifera and

shell fragments, with subordinate amounts of the stable

and unstable terrigenous assemblages described above

(cores HUD 39-9B and -9A, Figure 76B; see also

Figure 70). In addition to disseminated terrigenous

constituents, occasional layers of terrigenous sand are

noted in rise cores; these become more frequent below

one meter from the top of the core. This terrigenous

sand is, in fact, a fifth sediment type, but it is practical

to consider it together with the light tan mud and

biogenic sand. This sequence of biogenic with intercalated terrigenous strata is referred to as the lower

rise hemipelagic facies. The coarse horizon observed

at a depth of about 80 cm (core HUD 30-9A, Figure

76) may correspond to the brown-olive gray sediment

boundary noted in some slope cores (see Sc-16 for instance at 210 cm, Figure 38). Coarser sediment below

80 cm on the lower rise may have been deposited at the

time of the last maximum lowering of sea level at some

period between 20,000 and 15,000 years B.P. A sedimentation rate of about 4 to 5 cm per 1000 years is

estimated for deposition of fine-grained facies in this

environment, or approximately half of the estimated

sedimentation rate on the continental slope. A somewhat lower rate of 3.4 cm per 1000 years was calculated for lower rise cores to the southwest (Emery

etal. 1970, page 95).

SAND AND SILT STRATA IN DEEP-SEA CORES.—Sand

and silt strata referred to above as a fifth sediment

type are frequently encountered in cores on the lower

rise and the Sohm Abyssal Plain (Figure 17). These

coarse units, accounting for as much as 50 percent of

the core sections penetrated, are graded or laminated

or both. Insufficient core coverage does not allow

core-to-core correlation of these coarse layers. However, our preliminary survey suggests that sands grade

into silts in a seaward direction. The composition of

the sand-sized fraction is similar to that of outer shelf

sand, and consists of both stable and unstable terrigenous assemblages. These coarse intrusions, some of

them clearly turbidites, are believed to have accumulated much more rapidly than the clay- and silt-rich

strata with which they are interbedded.

Sediment Dispersal and Spillover

on Shelf-Edge Banks

Introduction

The broad shallow banks sited along the outer shelf

have played a unique role in the sediment dispersal

system of the Nova Scotian continental margin. They

have served as reservoirs for sediment received under

one set of conditions (glacial, glaciofluvial, and glacioaeolian) and subsequently released under a second set

of conditions (marine littoral conditions, and deeper

marine wave- and tide- agitated environments).

The varying role of the banks are reflected in the

sedimentary record of the more distal depositional

environments of this sediment dispersal system, as

will be demonstrated in the following three sections.

Sedimentation During Subaerial Exposure

During the maximum low eustatic stand of the sea in

Wisconsin time, sea level was believed to be 110 to

120 m lower [approximately 17,500 to 20,000 years

B.P. according to Curray (1965), and closer to 15,000

years B.P. according to Milliman and Emery (1968)].

During this stage the coast coincided closely with the

shelf-break, as determined by a study of terraces

(Stanley et al. 1968, and others).

Pleistocene ice tongues approached Banquereau

Bank and Sable Island Bank but apparently were unable to override them (Stanley and Cok 1968). Hence

the bank surfaces received enormous volumes of outwash during periods of maximum glacial advances

(see Figure 12). Some of this material accumulated as

a thickening outwash plain which locally underwent

aeolian modification (James and Stanley 1968,

Medioli et al. 1967). Fluvial processes resulted in

deposition of mud to pebble-size material on bank
68 SMITHSONIAN CONTRIBUTIONS TO THE EARTH SCIENCES

surfaces, and local pockets of gravel (Figure 29)

encountered on Sable Island Bank are probably relict

from this phase. Much of the material, however, must

have been bypassed to the shoreline where it became

available for deposition on the slope and beyond.

The coastal margin was dissected with deep bays

formed by the heads of the large canyons (Sable Island

Canyon and The Gully Canyon, for example) which

indent the outer shelf. These embayments undoubtedly served as outlets for meltwater. In some

cases they may have contained heavily stratified water

bodies with well-developed estuarine circulation, capable of serving as hydraulic traps for accumulating fine

sediment (Postma 1967). During peaks of outwash

aggradation, the resulting estuarine clay deposits

would be loaded by rapidly growing intra-estuary

deltas of coarse sediment (Swift and Borns 1967).

Transfer of all sediment-size grades from the bank tops

onto the steep bank margins was probably accelerated

during those phases when ice tongues migrated closest

to the outer banks.

The seaward edge of Sable Island Bank, serving as

the coast, received the brunt of erosion by surface

waves, and if meltwater had sufficiently stratified

coastal waters then possibly by breaking internal waves.

The relatively steep slope (5° or more) of the outer

bank margin meant that storm waves were not damped

by a shallow shelf and that the coast was under intensive attack. Slumping of the heterogeneous coastal

material would be expected and would provide a large

volume of sediment for transfer downslope.

Sedimentation During and Subsequent to Inundation

In late Pleistocene time sea level began to rise first

slowly and then more rapidly (Emery 1968, his figure

15). The transgressing surf would have stripped sediment from the retreating shore face and would have

released this material on the adjacent shelf floor for

resedimentation by marine currents (Swift 1968). This

resedimentation process has resulted in a second set of

petrographic attributes being overprinted on the

original textures. Most obviously, the finer fractions

(silt and clay, have been winnowed out leaving a clean

sand lag whose pebbly admixture reflects the original

periglacial origin (see Figures 8, 9). Such hybrid

sediments have been designated palimpsest (Swift et al.

1971). Processes resulting in the modification of texture have been more effective on the outer banks than

in the deeper central shelf physiographic province.

After water deepened over the banks, the blanket

of palimpsest sand continued to undergo textural

modification and transport according to a new and

well-defined system of sediment dispersal. This system

has been best studied on Sable Island Bank where its

elements include Sable Island, the emerged crest of the

bank, and the surrounding submarine bank surface.

Sable Island consists of two parallel beach-dune

ridges which, with the rise of sea level, have converged

toward the crest of the bank until they are contiguous.

This sediment reservoir exchanges material with the

adjacent shallow sea floor according to a seasonal cycle

whereby sediment is accreted to the island in summer

by marine processes and is later deflated by strong

winter winds (James and Stanley 1967).

The island was initiated by convergence of the dune

ridges in late Pleistocene-early Holocene time (Medioli et al. 1967), but it is presently maintained as a

dynamic system of water and sediment circulation.

The island and surrounding bank would, in fact, appear to be a circulating sand cell of the type described

by Van Veen (1936) from the floor of the southern

bight of the North Sea. The distribution of large-scale

sand waves indicates a clockwise circulation of residual tidal and wave-driven currents (James and Stanley 1968). Large sand waves are present between 10

and 70 m depth, both north and south of Sable Island

and on the western part of the bank. Smaller sand

waves, averaging 6 to 7 m in height (Figure 77) and

having wave lengths from 300 to 1000 m, are most

abundant south of Sable Island. Their asymmetry indicates a predominant wave migration from east to

west, while north of the island, sand wave asymmetry

indicates migration from west to east. A sequence of

lines trending north-south across the submerged bar

west of the island shows that sand waves in that sector are migrating northward (Figure 78). The east bar

of Sable Island (Figure 77) has been likened to an

asymmetric sand wave with a steeper northern face

suggesting predominant movement of sand toward

the north just east of the island (Figure 79).

Smaller scale structures, such as asymmetric ripple

marks as observed on most bottom photographs of

Sable Island Bank (Figure 80), show vectorial properties that are much more variable than those of sand

waves. Regional pattern of these ripples conforms in
NUMBER 8 69

EAST

SABLE

BAR

ISLAND

BATHYMETRY

from

RCA. DEPTH SOUNDER

FIGURE 77.—Diagram showing submarine topography in the vicinity of the east terminal bar

of Sable Island based on records obtained with an RCA depth sounder. The northern face is

steeper than the more gently southern slope (based on data obtained in May 1965).

a general way to the sand-wave circulation pattern:

ripples off the west end of the island indicate predominantly northward and eastward transport, and

those off the east end show southward and westward

flow; those on the northern part of the bank migrate

west and north. One station (78) at the southern

margin of the bank near the head of Sable Island

Canyon shows a predominant southerly (or off-bank)

transport.

Radial Dispersal and Sediment Spill-Over

While bed-forms indicate primarily a clockwise system of sediment transport, textural and mineralogical

patterns on the bank surface (James and Stanley

1968) reflect a net long-term process of radial dispersal off the banks into the adjacent lows. Transport

patterns are clearly marked as orthogonals to isopleths

of mineralogy, mean grain size, sorting, and skewness.

In general, on Sable Island Bank, sediment is being
70

O-i-O

SMITHSONIAN CONTRIBUTIONS TO THE EARTH SCIENCES

60 58 ff

M40-

BOTTOM PROFILES ALONG SAMPLE STATIONS

SCALE 52.1 : I

SABLE ISLANO BANK

FIGURE 78.—Bathymetric profiles of the surface of Sable Island Bank plotted from PDR and

RCA depth sounder records. Sand waves and related bed-forms are shown to depths of 70 m.

Note the northward set of sand waves along selected portions of profiles.

transported from central areas of relatively coarse,

coarse-skewed sand to marginal areas of relatively fine,

fine-skewed sand. These marginal areas tend to be

less sorted than the zones where unmixing and transport is most intensive. Sediment-yielding lag deposits

are richer in the heavier, coarser, heavy minerals

(opaques, garnet); sediment-receiving areas are richer

in the lighter heavy minerals (hornblende, kyanite, and

tourmaline). The intensity of iron-staining of relict

quartz is assumed to be inversely proportioned to the

intensity of abrasion during modern transport; areas

of stain-free quartz are areas indicated by other criteria to be areas of active sediment unmixing and

transport. A pattern of erosion, transport, and deposition on Sable Island Bank emerges upon integration

of all data (Figure 81).

Thus, the present cyclical movement results in a net

loss of sediment from the bank surface by transfer of

sand-size material off Sable Island Bank. This transfer

of silt and sand by bottom currents from the outermost shelf across the shelf-break and onto the upper

slope and beyond is here designated as spillover.

There appears to be several large areas of sand

spillover: south and southwest of Sable Island, from

the outer shelf onto upper slope; north of the island,

from the bank margin into the Gully Trough; and

east of the bank, into The Gully Canyon. Details of

sediment spillover into The Gully Canyon have been

presented elsewhere (Stanley 1967). Relatively clean

palimpsest sands are noted draping onto both east and

west canyon walls (Stanley 1967, his figure 3B), presumably from the adjacent bank surfaces. Further evidence of spillover in the shelf-break area occurs south

of the bank. Here, also, sand drapes from the outer

shelf onto the upper slope (Figure 29), and cores in

the area penetrate a surficial sand layer above older

muds.
NUMBER 8 71

SABLE ISLAND BANK

NEARSHORE BOTTOM PROFILES

L-tO

NAUTICAL MILES

9

FIGURE 79.—Bathymetric profiles of the surface of Sable Island Bank. Profiles are oriented

roughly parallel with Sable Island. Asymmetric sand waves appear to progress westward on

southern side and eastward on northern side of island. Net movement north of the island is

directed eastward, except between stations 38 and 46 which appears to be a zone of confluence.

Quaternary Progradation on the Nova Scotian

Outer Margin: A Summary

Introduction

The shift in sediment dispersal processes and patterns

on the Nova Scotian banks through late Quaternary

time has resulted in a corresponding sequence of depositional events on the slope and rise. The consanguinous nature of these two sedimentary provinces is

clearly indicated by the similarity of mineral suites

noted repeatedly in preceding sections of this study.

Thus the late Quaternary history of the study area

has been one of progradation: the seaward extension

of the shelf edge, slope, and rise by sediment accumulation. Seismic study of the continental margin off

Nova Scotia has led Uchupi and coworkers (Uchupi

and Emery 1967, Uchupi 1969, Emery et al. 1970,

Uchupi, 1970) to estimate 5 kilometers of progradation, although they do not clearly indicate the stratigraphic horizon from which this progradation was

initiated. These workers can distinguish among such

gross lithostructural units as seaward dipping strata,

slumps and slides, turbidites, and pelagic deposits. On

the other hand, our data based primarily on cores

provides much higher resolution of the thinner uppermost section of Wisconsin to recent age. The time sequence of events which generated the progradation

and the resulting stratigraphic sequences, illustrated in

Figures 82 and 83, are evaluated below.

Brown Sediment Time

During Pleistocene time, large volumes of fine to

coarse reddish-brown, fluvioglacial material carried

south to the coast was rapidly transferred to the adjacent slope below the strandline (Figure 82A). The

high and rapidly varying rate of sediment input and

short distance to the upper slope would have been

capable of generating stratified sequences of muds,

sands, and gravels, but would not have been capable
72 SMITHSONIAN CONTRIBUTIONS TO THE EARTH SCIENCES

•C

«

* Q J3

•s

CO

O
NUMBER 8 73

ACTIVE SEDIMENT

MOVEMENT ,

ACTIVE SEDIMENT

TRANSPORT

DEPOSITION

FIGURE 81—Interpretation of bottom circulation pattern on Sable Island Bank showing areas

of dominant sediment transport and deposition (after James and Stanley 1968).

of effecting large-scale horizontal size fractionation on

the slope. The resulting heterogeneous sediment pile,

precariously poised on a relatively steep submarine

slope, would have been prone to fail by slumping.

That mass-gravity processes have been in large part

responsible for the scalloped topography of the region

south of Sable Island Bank has been shown by bottom

profiles (Pratt 1967) and subbottom profiles (Uchupi

1969, Emery et al. 1970) which reveal large slide

blocks on the lower slope and rise. These studies indicate that most of the dissected topography presently

observed is clearly of relict origin. When slumping

actually began is not clearly established, but seismic

studies show that gravitational sliding was effective

during much of the Tertiary, and has certainly antedated the glacial stages. However, it is reasonable to

suspect that in this region, as elsewhere, the rate and

scale of slumping must have become considerably accelerated during the Pleistocene, especially during

those periods when low sea-level stands resulted in the

exposure of much of the shelf (Stanley and Silverberg

1969). The relatively nondissected slope south of

Western Bank (Figure 6) may not have received as

much sediment as in regions to the east (south of what

is now Sable Island) and, consequently, may have

been less prone to slumping.

During this time of heightened sedimentation, mass

gravity processes were also intensified in canyon heads.

The attack of open ocean storm waves on the unconsolidated emerging coastline would have released large

volumes of sand and gravel to littoral drift systems

intercepted by canyon heads. Periodic flushing of these

depressions would have further contributed to slope

and rise sedimentation as attested by the presence of

sand layers in rise and abyssal plain cores. Turbidity

currents or turbid-layer flows (Moore 1969) channelized by the canyon system would have had a higher

probability of reaching base-of-slope environments.

Such far-traveled material would indeed have the opportunity to undergo horizontal size sorting as indicated by the general decrease in grain size between
74 SMITHSONIAN CONTRIBUTIONS TO THE EARTH SCIENCES

N N W SABLE ISLAND

6ULLV THOUGH

 BAN K

OUTWASH PLAIN

 6 6 WTH0 M

 TERRACE

£ SUSPENDED SEDIMENT

SSE

Maximum late-Wisconsin

Low stand of sea level

20,000 to 18,000 years aP

PRO-GLACIAL

SUBMERGENCE STREAMS CUT OFF

OF BANK BEGINS J f

GLACIER RETREAT

Rapid rise in sea level during perio

approx. 17,000-15,000 years B. P.

HOLOCENE (GREY-GREEN) SEDIMENTS

Climatic change at approx.

11,000 years B.R

SPILL-OVER SABLE ISLAND

SEDIMENTS \ SEDIMENTS

HEMI PELAGIC WEDGE

FIGURE 82.—Interpretation of late Quaternary to recent sedimentary progradation on the Nova

Scotian continental margin south of Sable Island Bank (Stanley and Silverberg (1969).
NUMBER 8 75

cores HUD-13 and HUD-11, respectively, on the upper and lower rise.

In addition to mass gravity movement on the bottom, the seaward diffusion of fines (clay, silt, and possibly fine sand) would have been a second major

process during this time of heightened periglacial sedimentation. The meltwater runoff was heavily loaded

with fines, and received in addition material resuspended by wave attack on the coast. The intensified "estuarine" circulation of the coastal water mass would

have carried turbid surficial water far out to sea so

that the suspended fines would have rained out over

the slope and rise, perhaps even over the Sohm Abyssal Plain. Such fine sediment fallout on the upper

slope may have generated near-bottom, nepheloid,

suspension-rich layers which, in turn, would have settled seaward across the rise.

In addition to the general seaward movement of

suspended sediment entrained in surficial meltwater,

masses of coarse material were carried seaward by floe

ice and calving glacier ice. This is attested by the presence of pebble clusters within cores from the brown

facies, and gravel patches seen in sea-floor photographs

(Brundage et al. 1967).

Gray Sediment Time

As the sea level rose over the banks and the bank sediment dispersal system shifted from a subaerial glacial

regime to a regime of submarine reworking, the character of sediment accumulating on the slope and rise

underwent a change (Figure 82B) . The mineral suites

of slope and rise sediments accumulating during this

transition remained qualitatively constant, although

the relative proportions shifted in some cases. An obvious difference, however, was the color of material

accumulating during and subsequent to submergence

of the banks. This study has shown that color change

does not reflect a change in provenance, but simply

a change in the rate of sedimentation, such that sediment passed through the sediment-water interface

sufficiently slowly that it was reduced (Hinze and

Meischner 1968). This slower rate of sediment accumulation is also demonstrated by the greater intensity

of bioturbation and increase in benthonic Foraminifera as noted in cores of this facies.

Most processes of sediment dispersal discussed for

brown sediment time continued, but at reduced rates.

Contorted stratification in cores, and local exposure of

Pleistocene strata normally under gray sediment, suggests that slumping continued as a dominant process

on the slope in gray sediment time. The presence of

interbedded, brecciated, reddish-brown Pleistocene

and younger gray sediment in the upper sections of

cores is evidence that slumping has, in fact, continued

to the present time. Is the triggering mechanism tectonic or sedimentological in origin? This continental

margin is generally considered to be a relatively stable

one, although recent earthquake activity is known to

have affected the outer continental margin east of

Sable Island Bank, particularly off Newfoundland

(Heezen and Drake 1964). Although earthquakes or

other movements could thus effectively trigger the

sudden downslope movement of sediment, the sediment regime in this environment is sufficient in itself

to account for slumping. The rate of sedimentation on

the upper and mid sectors of the slope, for instance,

though reduced, has continued to be relatively high

since the beginning of the post-Pleistocene rise in sea

level. Estimated average rates, based on an evaluation

of the total thickness of the olive gray facies (1 to

over 5 m total thickness), range from 5 to 25 cm per

1000 years.

With the retreat of the ice, outwash was no longer

supplied but littoral sands concentrated by coastal

erosion were still available for redistribution. Initially,

their volume does not appear to have been as great as

during the preceding brown sediment period. These

sands continued to be trapped in canyon heads and

depressions on the upper slope and discharged from

these lows as turbidity currents.

Suspended fines were no longer provided by meltwater, but surf and sea floor erosion of the outer banks

provided an alternate source. In addition, far-traveled

fines were now being bypassed from recently submerged portions of the central shelf landward of the

outer banks (Curray 1965, his figure 3) and transported onto the slope. Ice-rafting would have progressively diminished throughout gray sediment time

as the ice sheet withdrew from the Maritimes.

Because of the diminished input of sediment and

also because of the reduction in freshwater runoff with

concomitant reduction of "estuarine" circulation, suspended sediment settled primarily on the slope. Such

material as has bypassed the slope by means of turbidity currents (Erickson et al. 1952 and 1961, Gorsline et al. 1968, Piper 1970), turbid layer flows (Moore

1969), and/or nepheloid layers (Stanley 1970) accu-
76 SMITHSONIAN CONTRIBUTIONS TO THE EARTH SCIENCES

mulated beyond the base of the slope. Biogenic materials primarily in the form of planktonic foraminiferal

tests sedimented in parts from the overlying Gulf

Stream formed a prominent admixture of this terrigenous influx. The resulting hemipelagic wedge appears to thicken seaward within the area of study. Its

light tan color is more a consequence of slow transport and attendant oxidation as in the case of abyssal

red clays, rather than an inherited pigment as in the

case of the brown sediment type. The sands of this

facies may be diverted into two populations on the

basis of sedimentary structures and textural parameters. One group displaying graded bedding is distinguished as the "typical" turbidite unit, the other nongraded in origin may have been deposited by reworking of turbidite sediments by marine currents.

Between the thin gray sediment prism of the slope

and seaward thickening wedge of tan hemipelagic

sediments on the lower rise there is a window through

which is exposed the older brown sediments. This sector may be a one of nondeposition as a consequence

of the southwestward flowing Western Boundary Undercurrent (Heezen et al. 1966, Schneider et al. 1967).

These authors have suggested that the red sediments

of the rise are a modern rather than a relict facies;

that they are eroded from the St. Lawrence region and

swept south parallel to the contours. However, our

cores (HUD-30-11 and 13) are anomalously coarse

and contain pebbly horizons within the uppermost 10

cm. Since modern icebergs only rarely proceed south

to Newfoundland, such pebbles were most probably

transported by Pleistocene ice.

The change in microfauna noted within the olive

gray facies, also noted by others in this region (Ericson

et al. 1961), coincides with a change in climate at

about 11,000 to 10,000 years B.P. as recorded elsewhere

in the North Atlantic (Broeker et al. 1960, Ericson

et al. 1964). See c, figure 82.

Surftcial Sand Time

As the banks continued to submerge and the development of the blanket of winnowed sand and sandy

gravel approached completion, less and less fines were

generated by littoral and sea floor erosion on the

banks. Rates of fine sediment deposition on the adjacent slope decreased yet further, and spillover sands,

emplaced during occasional storms, became a progressively more prominent part of the upper- to midslope section (Figure 82D.) A number of the slope

(Sc) cores are capped by relatively clean sands of this

type that may have been emplaced in historic times.

Shelf sands draped thus over gullies and depressions

of the upper slope appear to be intermittently activated as turbidity currents, which may bypass the slope

and appear as coarse horizons within the top of baseof-slope facies (see Lamont-Doherty cores, Figure 17,

and hypothetical core d, Figure 83). Channelizing in

canyons appears to be one important method of bypassing as attested by the presence of sand in The

Gully Canyon axis (Stanley 1967) and levees bordering submarine valleys (Hurley 1964, Pratt 1968).

As early as 1952 Ericson and coworkers called attention to sands of shallow water origin on the ocean

floor of the Western North Atlantic and attributed

their presence to turbidity current action. More recent

studies of the textures of Atlantic deep-sea sands (Hubert 1964) and of ocean floor current indicators (Heezen et al. 1966, Schneider et al. 1967) have suggested

that ocean bottom currents may also be of primary

importance in the transport of deep-sea sands. Although many of these deep-sea sand layers are, in fact,

current laminated and display a low clay content, it is

believed that most sands were nonetheless originally

emplaced by turbidity currents (Kuenen 1967) and

subsequently received their secondary structure and

texture through reworking by bottom currents (Stanley 1970, his figure 12). Our study supports the contention of others (Hubert and Neal 1967, and others) that

mineralogic dispersal patterns formed during Quaternary progradation of the western North Atlantic continental margin reflect predominantly a downslope

movement of sediment normal to the continental margin with a minor contour-parallel component.

Acknowledgments

This study, like most modern oceanographic investigations, is the result of a multi-author cooperative venture. We are indebted to a number of organizations

for their generous backing, including financial aid,

ship-time, materials, and facilities provided, which

made this investigation possible: Bedford Institute of

Oceanography, Dalhousie University (Institute of

Oceanography), Lamont-Doherty Geological Observatory of Columbia University, and the Smithsonian

Institution. Sampling was conducted on the CSS

Hudson, CSS Kapuskasing, and CNAV Sackville: the
NUMBER 8 77

= 0 Wave- and tide-generated currents on Sable Island Bank.

>> Postulated dominant bottom current activity on rise.

——•—*- Resedimentation processes (mass gravity

creep,etc.) on slope andjji

(Vertical scale greatly exaggerated)

Holocene :Reworked relict (fluvio-glacial) relatively clean

sediments on Sable Island Bank; spill-over sandy

units on slope and rise.

Holocene:Gray-green silty clay prograding on slope.

Largely Holocene:lightgray-brown(hemipelagic) silty-clayon rise.

Largely Pleistocene: Brown-reddish brown pebble-sandsilt-clay admixture (glacio-marine) prograding on slope arise.

Pre-quaternary units.

FIGURE 83.—Interpretation of late Quaternary sedimentary fades distribution on the Nova

Scotian continental margin south of Sable Island Bank. This schema of the upper sediment

sections on the slope and rise also shows postulated dispersal patterns and stratigraphy as based on

observations made in this study.

Captains; officers, and men of these ships are thanked

for support so efficiently given in the work at sea.

We acknowledge with gratitude the many persons

with whom we have had an opportunity to discuss the

various problems raised in this study and, in particular,

our many colleagues who have made special contributions to this undertaking: Dr. A. E. Gok, Adelphi

University, and Mr. G. Drapeau, Bedford Institute,

with whom we shared pleasant and productive hours

at sea and in the laboratory. Dr. Cok kindly identified heavy minerals from slope cores. We are also

indebted to Dr. T. T. Davies, University of South

Carolina, who kindly provided data on selected clay

mineral suites in slope and rise cores, Dr. J. I. Marlowe, Miami Dade Junior College (formerly with

Bedford Institute of Oceanography), for generously

sharing his Gully Canyon cores with us, and Dr. F.

Medioli, Dalhousie University, for identifying Foraminifera in selected slope and rise cores collected off

Sable Island Bank. We thank Mrs. A. E. Cok and Mr.

H. Sheng for help in processing core and rise samples,

and Mr. L. Isham for drafting and modifying a number of figures. Drs. A. E. Cok and J. I. Marlowe critically read the manuscript.

Support for continued coordination of this project,

including travel and preparation of the manuscript,

has been provided to one of us (D.J.S.) by the Smithsonian Institution Research Foundation grants No.

235320 (FY 1970) and No. 436330 (FY 1971).

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1966a. A Modified Woods Hole Rapid Sediment Analyser.

Journal of Sedimentary Petrology, 36:403-414.

1966b. Glacial History of the Gulf of Maine (abstract).

Program Annual Meeting of the American Association for the Advancement of Science, Section E,

page 32.

Schneider, E. D., P. J. Fox, C. D. Hollister, H. D. Needham,

and B. C. Heezen

1967. Further Evidence of Contour Currents in the

Western North Atlantic. Earth and Planetary

Science Letters, 2:351-359.

Shepard, F. P.

1931. Glacial Troughs of the Continental Shelves. The

Journal of Geology, 39:345-360.

1954. Nomenclature Based on Sand-Silt-Clay Ratios.

Journal of Sedimentary Petrology, 24:151—158.

1963. Submarine Geology (second edition). New York,

Harper and Row, 557 pages.

Shepard, F. P., and J. R. Curray

1967. Carbon-14 Determination of Sea Level Changes

in Stable Areas. In Progress in Oceanography

(B. C. Heezen, editor). Pages 283-291. Pergamon

Press, Oxford.

Shepard, F. P., and R. F. Dill

1966. Submarine Canyons and Other Sea Valleys.

Rand McNally and Company, Chicago. 381 pages.

Shepard, F. P., J. M. Trefethen, and G. V. Cohee

1934. Origin of Georges Bank. The Geological Society

of America Bulletin, 45:281-302.

Silverberg, N.

1965. Reconnaissance of the Upper Continental Slope

off Sable Island Bank, Nova Scotia. M.Sc. thesis,

Dalhousie University, Halifax. 79 pages.
NUMBER 8 81

Stanley, D. J.

1967. Comparing Patterns of Sedimentation in Some

Modern and Ancient Submarine Canyons. Earth

and Planetary Science Letters, 3:371-380.

1968. Reworking of Glacial Sediments in the North West

Arm, a Fjord-like Inlet on the Southeast Coast of

Nova Scotia. Journal of Sedimentary Petrology,

38:1224-1241.

1970. Flyschoid Sedimentation on the Outer Atlantic

Margin Off Northeast North America. In Flysch

Sedimentology in North America (J. Lajoie, editor), Geological Association of Canada Special

Paper, 7:179-210.

Stanley, D. J., and L. R. Blanchard

1967. Scanning of Long Unsplit Cores by X-radiography.

Deep-Sea Research, 14:379-380.

Stanley, D. J., and A. E. Cok

1968. Sediment Transport by Ice on the Nova Scotian

Shelf. Ocean Sciences and Engineering of the

Atlantic Shelf, Philadelphia, Marine Technological

Society, Delaware Valley Section, pages 109-125.

Stanley, D. J., G. Drapeau, and A. E. Cok

1968. Submerged Terraces on the Nova Scotian Shelf.

Zeitschrift fur Geomorphologie, Supplement, 7:

85-94.

Stanley, D. J., and N. Silverberg

1969. Recent Slumping on the Continental Slope off

Sable Island Bank, Southeast Canada. Earth and

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1936. Geology and Paleontology of the Georges Bank

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America Bulletin, 47:367-410.

Sutton, R. G.

1964. Use of Sedimentary Parameters in the Differentiation of North Atlantic Shelf, Slope, and Abyssal

Plain Sands (abstract). Program 1964 Annual

Meeting of the Geological Society of America,

page 202.

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1968. Coastal Erosion and Transgressive Stratigraphy.

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1967. A Raised Fluviomarine Outwash Terrace, North

Shore of the Minas Basin, Nova Scotia. The

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Swift, D. J. P., D. J. Stanley, and J. R. Curray

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Uchupi, E.

1968. Atlantic Continental Shelf and Slope of the United

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1967. Structure of Continental Margin off Atlantic

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1894. The Fishing Banks between Cape Cod and Newfoundland. American Journal of Science, 47:

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1960. Stratigraphic Principles and Practice. Harper and

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Appendix

Description of Cores Collected South of the Nova Scotian Shelf by the LamontDoherty Geological Observatory of Columbia University (locality number refers

to core locations shown in Figure 17)

Locality No. 1

Lamont No. Al64-46

Depth: 2610 fm (4773m;

Unit Position(cm)

Lat. 41° 20'N

Long. 59° 00' W

Core Length: 245 cm

Description

9

10

11

12

13

14

0-9

9-18

18-33

33-42

42-48

48-66

66-95

95-101

101-120

120-128

128-145

145-170

170-221

221-245

Gray lutite with silt laminae

Gray foram lutite grading down to pink

lutite at base

Gray foram sand

Red silty lutite

Brown silt

Interbedded red lutite and brown silt

Grayish red lutite grading down to red

lutite at base. Mottling 80-90 cm

Red lutite with gray mottling

Red lutite with silt laminae

Brownish gray lutite grading down to

pale red lutite at base

Interbedded red lutite and brown silt

Brownish gray lutite grading down to

mottled red lutite at base

Interbedded red lutite and laminated

silts

Mottled gray silty lutite with gray silt

at base

Locality No. 2

Lamont No. A164-47

Depth: 2580 fm (4718m)

Unit

1

2

3

4

5

6

7

8

Position (cm)

0-3

3-4

4-19

19-31

31-37

37-43

43-48

48-49

Lat. 49° 45' N

Long. 59° 00' W

Core Length: 70 cm

Description

Gray lutite

Brown silt

Gray lutite grading down to pale pink

mottled lutite at base

Brown silt grading down to foram-rich

sand

Gray foram-rich lutite grading down to

red-gray laminated lutite

Brown silt

Red lutite

Gray, silty lutite

Locality No. 2

9 49-52

10

11

52-58

58-70

Red lutite with 3 mm light gray lutite

at base

Interbedded brown silt and red silty

lutite

Interbedded silt and brownish gray silty

lutite (flowage)

Locality No. 3

Lamont No. A164-48

Depth: 2530 fm (4627m)

Unit

1

2

3

4

5

6

7

8

Position(cm)

0-15

15-18

18-40

40-230

230-250

258-272

272-400

400-450

Lat. 41 ° 30' N

Long. 59° 50' W

Core Length: 490 cm

Description

450-490

Gray silty lutite grading down to red

mottled silty lutite

Brown foram-rich silt, laminated at top

Gray silty lutite grading down to red

mottled lutite. Forams abundant

Brown silt interbedded with red and

gray lutites

Gray silty lutite grading down to red

silty lutite with brown silt at base

Red lutite

Red lutite with brown silt laminae

Gray lutite grading down to red lutite

with silt laminae

Red lutite (flowage)

Locality No. 4

Lamont No. A164-49

Depth: 510 fm (933m]

Unit Position (cm)

0-146

Lat. 42° 50'N

Long. 61° 35' W

Core Length: 473 cm

Description

1

146-148

148-160

160-267

267-473

Brown silty lutite with forams. Faint

mottling at 40 cm; sand at 60 cm

and large burrows at 65-70 cm

Pale red silty lutite

Brown silty lutite with silt at 151-153 cm

Pale red silty lutite with sand 163-165 cm

Brown silty lutite with pebbles at 305

cm and 340 cm

82
NUMBER 8 83

Locality No. 5

Lamont No. A164-54

Depth: 1230 fm (2250m)

Unit Position(cm)

Lat. 42° 05'N

Long. 63° 25' W

Core Length: 441 cm

Description

1 0-70 Pale brown silty lutite

2 70-170 Brown silty lutite. Mottled 90-120 cm

Burrows 130-170 cm

3 170-441 Pink silty lutite with pebbles throughout

Locality No. 6

Lamont No. A164-55

Depth: 1820 fm (3329m;

Unit Position(cm)

1 0-47

47-203

203-325

Lat. 41°45'N

Long. 63° 00' W

Core Length: 325 cm

Description

Pale brown silty lutite with forams and

burrows

Brown pebbly lutite

Pale brown lutite with a few silt laminae

Locality No. 7

Lamont No. A173-8

Depth: 1490 fm (2725m)

Unit Position(cm)

0-60

60-510

510-615

615-1025

Lat. 43° 40'N

Long. 58° 45' W

Core Length: 1025 cm

Description

Gray, laminated, silty lutite

Grayish brown silty lutite interbedded

with silt and fine-grained sand

Gray sand

Interbedded gray sand and brownish

gray laminated silty lutite

Locality No. 8

Lamont No. A173-9

Depth: 1775 fm (3246m)

Unit Position(cm)

Lat. 43° 30'N

Long. 58° 30' W

Core Length: 374 cm

Description

0-12

12-16

16-315

315-374

Reddish gray sandy silt

Reddish gray silty lutite

Interbedded gray sandy silt and brownish gray laminated silty lutite

Fine-grained bedded sand. No grading

noted

Locality No. 9

Lamont No. A173-10

Depth: 900 fm (1646m)

Lat. 43° 15'N

Long. 60° 30' W

Core Length: 440 cm

Unit Position (cm) Description

1 0-90 Brown silty lutite with beds of red pebbly lutite at 16-20 cm

Locality No. 9

2 90-440 Pale red silty lutite with thin beds of

dark gray silty lutite

Locality No. 10

Lamont No. A173-11

Depth: 1426 fm (2608m)

Unit Position(cm)

Lat. 40° 00' N

Long. 60° 30' W

Core Length: 188 cm

Description

0-30

30-34

34-188

Interbedded red and gray lutite

Gray clayey silt

Gray silty lutite

Locality No. 11

Lamont No. A173-12

Depth: 1150 fm (2103m)

Unit Position(cm)

0-135

135-212

212-870

Lat. 42° 15'N

Long. 63° 30' W

Sore Lenth: 870 cm

Description

Brown silty lutite with forams

Pale red silty lutite. Bright red blebs in

upper 5 cm

Brown silty lutite with a few pebbles,

granules and forams

Locality No. 12

Lamont No. A173-13

Depth: 1600 fm (2926m)

Unit Position(cm)

0-76

76-90

90-128

128-185

185-450

Lat. 42° 15'N

Long. 63° 25' W

Core Length: 450 cm

Description

Pale pinkish brown silty lutite with

forams

Pink silty and sandy lutite with gray

mottling

Brown silty lutite with forams, sand, and

granules

Pink lutite

Brown silty lutite with scattered granules

and pebbles

Locality No. 13

Lamont No. Al 73-14

Depth: 1410 fm (2578m)

Lat. 41° 55'N

Long. 64° 35' W

Core Length: 370 cm

Unit

1

2

3

4

Position(cm)

0-22

22-26

26-40

40-65

Brownish

age)

Pale red

Interlami

lutite

Pale red

Description

gray sandy lutite

silty lutite

nated brown and

silty lutite

(some

gray

flowsilty
84

Locality No. 13

5 65-110 Same as 26-40 cm

6 110-123 Same as 40-65 cm

7 123-245 Interlaminated red and gray silty lutite

8 245-370 Flowage

SMITHSONIAN CONTRIBUTIONS TO THE EARTH SCIENCES

Locality No. 14

Lamont No. G25-10

Depth: 910 fm (1664m)

Lat.43°50'N

Long. 59° 00' W

Core Length: 30 cm

Unit Position (cm) Description

1 0-30 Brown silty lutite. No bedding noted

Locality No. 18

Lamont No. KM 1-7

Depth: 450 fm (823m)

Lat. 43°35'N

Long. 60° 05' W

Core Length: 310 cm

Unit

1

2

3

4

5

Position (cm)

0-78

78-121

121-150

150-250

250-310

Description

Gray silty lutite. Pebbles and shells at

72 cm

Brown clayey silt with scattered shell

fragments

Interbedded brownish gray silty lutite

and silt

Gray silty lutite grading to brownish

gray clayey silt at base

Reddish brown clayey silt

Locality No. 15

Lamont No. KM 1-2

Depth: 750 fm (1372m)

Unit Position(cm)

1 0-475

Lat. 43° 10' N

Long. 60° 15' W

Core Length: 475 cm

Description

Brownish gray clayey and sandy silt.

Forams rare; pelecypod valves in upper 10 cm.

Locality No. 16

Lamont No. KM 1-5

Depth: 136 fm (249m)

Unit Position(cm)

Lat. 43° 35'N

Long. 59° 20' W

Core Length: 122 cm

Description

1 0-122 Brown silty sand with fragments of red

silt scattered throughout

Locality No. 17

Lamont No. KM 1-6

Depth: 310 fm (567m)

Unit

1

2

3

4

5

6

7

8

Position(cm)

0-53

53-65

65-123

123-147

147-151

151-158

158-164

164-300

Lat. 43° 35' N

Long. 59° 30'W

Core Length: 300 cm

Description

Brown clayey silt with fragments of red

lutite

Interbedded gray silt and laminated

lutite

Interbedded pink and brownish gray,

clayey, granular silt (some flowage)

Brown silt

Brown silt interbedded with gray and

pink lutite

Brown silt

Same as 147-151 cm

Brown granular lutite grading down to

a brown clayey, pebbly silt

Locality No. 19

Lamont No. SP 12-1

Depth: 700 fm (1280m)

Unit

1

2

3

4

5

6

Position (cm)

0-55

55-72

72-126

126-135

135-155

155-345

Lat. 43° 20'N

Long. 59° 55' W

Core Length: 345 cm

Description

Brownish gray silty lutite. Burrows 36-45

cm

Pink to brownish gray pebbly lutite (some

flowage)

Interbedded pink and brown silty lutite

with a few burrows and granules

Brownish gray silty lutite

Interbedded pink and brown silty lutite

Red pebbly lutite

Locality No. 20

Lamont No. SP 12-2

Depth: 680 fm (1244m)

Unit Position(cm)

1 0-95

2 95-240

Lat. 43° 20'N

Long. 60° 15' W

Core Length: 240 cm

Description

Gray silty lutite grading down to brownish red granular silt at bottom. Burrows abundant.

Pale red granular lutite. Bedding faint

but distinct. Granules at 98-110 cm

and 205-40 cm

Locality No. 21

Lamont No. SP 12-3

Depth: 1300 fm (2377m)

Unit Position(cm)

1 0-75

Lat. 43° 05' N

Long. 59° 55' W

Core Length: 215 cm

Description

Pale brownish gray silty lutite grading

down to brownish red lutite at base.

Burrows 15-60 cm
NUMBER 8

Locality No. 21

2 75-215 Interbedded pale red and brown silty

lutite

3 below 215 Brown silty lutite (flowage)

Locality No. 22

LamontNo. SP12-4

Depth: 1310 fm (2395m)

Locality No. 25

Lamont No. V7-63

Depth: 220 fm (402m)

Lat. 43° 10'N

Long. 59° 45' W

Gore Length: 360 cm

Unit

1

2

3

4

Position(cm)

0-78

78-172

172-182

182-210

85

Lat. 43° 00'N

Long. 61° 55'W

Core Length: 210 cm

Description

Brownish gray silty lutite grading to

clayey silt at base

Brownish gray silty lutite (some flowage)

Gray fine-grained silt

Light brown silty clay (flowage)

Unit Position(cm) Description

1 0-303

303-308

308-350

350-360

Pale brown lutite grading down to reddish brown silty lutite at base. Burrows at 76 cm; pebbles at 85 cm;

forams in upper 40 cms

Red clayey silt

Brown granular lutite with a few forams

Pale red silty lutite

Locality No. 23

Lamont No. V 2-4

Depth: 2000 (?) fm (3658m)

Unit Position(cm)

Lat. 43° 15' N

Long. 56° 00' W

Core Length: 390 cm

Description

0-53

53-390

Red silty lutite

Red lutite with widely spaced silt laminae. No flowage

Locality No. 24

Lamont No. V7-38

Depth: 2508 fm (4587m)

Unit Position(cm)

Lat. 39° 30'N

Long. 64° 55' W

Core Length: 490 cm

Description

0-8

8-11

11-40

4 40-80

5 80-84

6 84-130

9

10

11

12

13

14

15

16

17

130-140

140-142

142-158

158-160

160-195

195-300

300-400

400-415

415-435

435-447

447-490

Gray silty lutite with forams

Red lutite with fragments of gray silt

Gray silty lutite grading down to red

silty lutite

Brown silty lutite

Gray silt

Two beds of gray lutite grading down to

red lutite with silt at base of each

Gray lutite

Silt

Gray lutite grading down to pink lutite

Silt

Brownish gray lutite

Silt interbedded with gray silty lutites

Brown silty lutite

Red lutite with beds of granules

Light brown silty lutite

Foram sand

Silts interbedded with brown silty lutite^

Locality No. 26

Lamont No. V7-68

Depth: 2143 fm (4102m)

Unit Position(cm)

Lat. 40° 45'N

Long. 64° 40'W

Core Length: 245 cm

Description

1

2

3

0-17

17-54

54-245

Brown silty sand with forams

Pink mottled lutite with forams

Sand grading to granules at 60 cm, grading to pebbles with cobbles at base.

Reversal of grading at 210 cm

Locality No. 27

Lamont No. V7-69

Depth: 1600 fm (2926m)

Unit Position(cm)

Lat. 40° 55' N

Long. 65° 35'W

Core Length: 612 cm

Description

1 0-20

20-110

110-127

127-186

186-210

210-260

7 260-345

8 345-450

9 450-612

Brownish gray clayey foram silt grading

down to red silt at base. Mottling in

lower part

Brownish gray clayey silt with sand and

granules

Red lutite and brown silt (flowage)

Brownish gray clayey silt grading down

to red silty clay. Isolated pebbles

throughout

Brownish gray clayey silt

Red and brown clayey silt interbedded

with silt laminae

Brownish gray clayey silt with granules

Same as 210-260 cm

Silt interbedded with brownish gray silty

lutite

Locality No. 28

Lamont No. V7-7O

Depth: 700 fm (1280m)

Lat. 41° 55'N

Long. 64° 30' W

Core Length: 560 cm

Unit Position(cm) Description

1 0—60 Brown sandy and clayey silt with burrows
86 SMITHSONIAN CONTRIBUTIONS TO THE EARTH SCIENCES

Locality No. 28

2

3

4

5

6

7

8

9

10

11

60-67

67-162

162-167

167-190

190-194

194-285

285-290

290-320

320-330

330-560

Red sandy and clayey silt with foram

laminae

Brown granular, clayey silt interbedded

with layers of shells and granules

Red sandy silt

Brown sandy, clayey silt grading down to

reddish brown silt at base

Laminated silt

Reddish brown granular, clayey silt with

scattered small pebbles

Red sandy silt

Brown sandy, clayey silt

Sand laminae

Brown sandy, clayey silt with thin beds

of sand and gravel

Locality No. 29

LamontNo. V16-213

Depth: 2065 fm (3777m)

Lat.41°40'N

Long. 62°55'W

Gore Length: 980 cm

Unit Position(cm) Description

1 0—40 Light brown foram lutite

Locality No. 29

2 40-280

3 280-409

4 409-870

5 870-980

Lutite, pale red to red at base, with

silt laminae

Light brown silty lutite interbedded with

light brown silt

Interbedded red lutite, brownish gray

lutite and silt

Flow-in

Locality No. 30

LamontNo. VI7-209

Depth: 2453 fm (4486m)

Unit Position (cm)

Lat. 40° 25' N

Long. 63° 15' W

Core Length: 415 cm

Description

1

2

3

4

5

0-38

38-140

140-209

209-244

244-415

Light brown silty foram lutite

Brown silty lutite with laminated silt

beds

Graded bed with silt at top, sand

throughout except for granular bed at

base

Red lutite

Interbedded light brown lutite and laminated silt
Index

Abrasions, 33, 54

Banquereau Bank,

physiography, 3

sediments, 31, 37, 40, 43

Bioturbate structures, 19-22, 66, 75

Boulder concentration, 12, 14

Brown sediment facies,

cores in, 17

Foraminifera, 62-65

mineralogical composition, 49, 51, 57-59

on rise, 65

on slope, 31, 32, 65

structures, 21, 22

Browns Bank, 3

Canyon heads as bays, 68

Channelized transportation in canyons, 73, 75, 76

Circulating sand cell, 68, 70

Clay minerals, 37, 56-62

Clean sand facies,

cores in, 17

mineralogical composition, 49

on slope, 31, 66

structures, 19

Color of sediments,

changes in time, 75

green, 37

red, 37, 51

tan, 75

Current-produced structures, 19, 23, 24, 33

Diamictite, 12

Emerald Bank, 3

Facies on outer margin, 17-19, 65-67

Glacial erosion, 1, 9, 14

Glacial moraines, 12

Gulf Stream, 76

Gully Trough,

sediments on, 26, 36-40

topography, 3, 6

Heavy mineral suites,

Banquereau Bank, 41

Gully Trough, 38, 40

Nova Scotian Rise, 55, 56

Nova Scotian Slope, 49, 50

Sable Island Bank, 33, 55

The Gully Canyon, 41-43

Ice flow, 13, 14, 16, 75

Ice rafting, 14, 16, 19, 65, 75

Ice transport, Nova Scotian Shelf, 9, 14, 67

Kapuskasing Canyon, 7

Le Have Bank, 3

Lag deposits, 38, 70

Laurentian Channel, 2, 53

Lower rise hemipelagic facies, 67

Microfaunal changes, 76

Middle Bank, 3, 38

Nepheloid layers, 75

Northeast Channel, 2

Nova Scotian Rise,

composition of sediments, 50-56, 59-62

cores on, 17

facies, 17, 32, 33

Nova Scotian Shelf,

ice cover, 9

lakes on, 9

physiographic provinces, 3

physiography, 2, 3

rock outcrops, 14, 36

previous studies, 1

sediment composition, 13-16

Nova Scotian Slope,

cores collected on, 16, 17

facies, 17, 31, 32

mineralogical composition, 43-50, 57-62

sediment distribution, 31

topography, 6-9

Olive gray sediment facies,

cores in, 17

Foraminifera, 62-65

mineralogical composition, 49, 57-59

on rise, 32, 65

on slope, 31, 32, 65

structures, 19, 21

Organic structures in cores, 19-22

Palimpsest sediments, 2, 68, 70

Planktonic: benthonic foraminiferal ratio, 63, 64

Pleistocene-Holocene boundary, 66, 68

Progradation on Nova Scotian margin,

brown sediment facies, 71-75

clean sand facies, 76

Holocene time, 75

modern time, 76

olive gray sediment facies, 75, 76

Wisconsin time, 71

Provenance, 13, 14, 36, 38, 43, 51, 53, 62, 65

Quartz,

clear, 37, 50

green-stained, 37

stained, 14, 33, 37, 40, 43, 50

Relict sediments, 2, 10, 38, 40, 68, 76

Reworking of sediments, 11, 38, 40, 54

87
88 SMITHSONIAN CONTRIBUTIONS TO THE EARTH SCIENCES

Ripple marks, 68

Rise (see Nova Scotian Rise)

Sable Island, 2, 3, 25, 68

Sable Island Bank,

as barrier to ice, 9

as source of sediments, 9

Sable Island Bank,

circulating sand cell, 68, 69, 70

outwash plain, 67, 75

physiography, 3

sediments on, 24-26, 33, 36

surface gradients, 3

Sable Island Canyon, 7, 68

Sackville Canyon, 7

Sand waves, 68

Sea level oscillations, 1, 9, 11, 67, 68, 73, 75

Sediment dispersal, 2

Sediment distribution, Nova Scotian Shelf, 9-13

Sediment-water interface, 75

Sedimentary structures, 19-22

Sedimentation rates, 22, 65, 67, 75

Shelf (see Nova Scotian Shelf)

Shelfbreak, 6, 7, 67, 68, 70

Slope (see Nova Scotian Slope)

Slumping, 9, 33, 68, 73, 75

Sohm Abyssal Plain,

sediment sequences, 22-24

topography, 7

Sorting, 11, 12

Spillover, 67, 69-70, 76

Stable terrigenous assemblage, 65-66

Stratigraphy,

based on Foraminifera, 62-65

based on sedimentary sequence, 65-67

Submarine valleys, 7, 76

Suspension, 73, 75

Tan-light brown facies,

composition, 65

cores in, 17

on rise, 33

Terraces, 9, 67

Textural facies, Nova Scotian Shelf, 9-13

The Gully Canyon,

rock outcrops, 43

sediment distribution, 28, 31, 40-43

sediment facies, 17

topography, 3-4

Till, 13, 53

Till texture, 10

Turbidites, 19, 23, 33, 67, 76

Turbidity currents, 23, 73, 75, 76

Unstable terrigenous assemblage, 65

Weathering, 38, 43

Western Bank, 3, 9, 73

Western Boundary Undercurrent, 76

Winnowing, 11, 76

X-radiography, 19

* U.S. GOVERNMENT PRINTING OFFICE: 1972- 184- 3ia/3