Sedimentology and stratigraphy of a transgressive ... for web/Documents for... · Sedimentology and stratigraphy of a transgressive, muddygravel beach: waterside beach, Bay of Fundy,

UNCORRECTEDPROOFSedimentology and stratigraphy of a transgressive, muddy

gravel beach: waterside beach, Bay of Fundy, Canada

SHAHIN E. DASHTGARD*, MURRAY K. GINGRAS* and KARL E. BUTLER�*Department of Earth and Atmospheric Sciences, 1-26 Earth Sciences Building, University of Alberta,Edmonton, AB, Canada T6E 2G3 (E-mail: [email protected])�Department of Geology, University of New Brunswick, PO Box 4400, Fredericton, NB, Canada E3B 5A3

ABSTRACT

Sediments exposed at low tide on the transgressive, hypertidal (>6 m tidal

range) Waterside Beach, New Brunswick, Canada permit the scrutiny of

sedimentary structures and textures that develop at water depths equivalent to

the upper and lower shoreface. Waterside Beach sediments are grouped into

eleven sedimentologically distinct deposits that represent three depositional

environments: (1) sandy foreshore and shoreface; (2) tidal-creek braid-plain

and delta; and, (3) wave-formed gravel and sand bars, and associated deposits.

The sandy foreshore and shoreface depositional environment encompasses the

backshore; moderately dipping beachface; and, a shallowly seaward-dipping

terrace of sandy middle and lower intertidal, and muddy sub-tidal sediments.

Intertidal sediments reworked and deposited by tidal creeks comprise the

tidal-creek braid plain and delta. Wave-formed sand and gravel bars and

associated deposits include: sediment sourced from low-amplitude, unstable

sand bars; gravel deposited from large (up to 5Æ5 m high, 800 m long),

landward-migrating gravel bars; and, zones of mud deposition developed on

the landward side of the gravel bars. The relationship between the gravel bars

and mud deposits, and between mud-laden sea water and beach gravels

provides mechanisms for the deposition of mud beds, and muddy clast- and

matrix-supported conglomerates in ancient conglomeratic successions.

Idealized sections are presented as analogues for ancient conglomerates

deposited in transgressive systems. Where tidal creeks do not influence

sedimentation on the beach, the preserved sequence consists of a gravel lag

overlain by increasingly finer-grained shoreface sediments. Conversely, where

tidal creeks debouch onto the beach, erosion of the underlying salt marsh

results in deposition of a thicker, more complex beach succession. The

thickness of this package is controlled by tidal range, sedimentation rate, and

rate of transgression. The tidal-creek influenced succession comprises

repeated sequences of: a thin mud bed overlain by muddy conglomerate,

sandy conglomerate, a coarse lag, and capped by trough cross-bedded sand and

gravel.

Keywords Beach, conglomerate, macrotidal, mud and gravel, muddy con-glomerate, sedimentology, stratigraphy, transgressive.

INTRODUCTION

Studies of modern, transgressive gravel beachesprovide important information regarding faciesrelationships and organization of ancient conglo-merates. In particular, determining sedimento-

logical and stratigraphic relationships on modernbeaches aids in predicting the extent, thickness,and morphology of conglomerates in the sub-surface. Waterside Beach is a transgressive,muddy gravel beach in the hypertidal Bay ofFundy. Because of the area’s extreme tidal range

S E D 7 7 3 B Dispatch: 1.2.06 Journal: SED CE: Hari

Journal Name Manuscript No. Author Received: No. of pages: 18 PE: Revathi

Sedimentology (2006) 1–18 doi: 10.1111/j.1365-3091.2006.00773.x

� 2006 The Authors. Journal compilation � 2006 International Association of Sedimentologists 1

UNCORRECTEDPROOF

(up to 12 m), foreshore (and shoreface equivalent)sediments are exceptionally well exposed atspring low tide. This provides an opportunity toassess the sedimentological characteristics ofconglomerates deposited at water depths equival-ent to the upper and lower shoreface (i.e. depos-ited because of shoaling, breaker, surf, and swashprocesses). In this paper: (1) sedimentologicallydistinct deposits are reported; (2) mechanisms fordepositing mud beds and muddy conglomerateson gravel beaches are described; and, (3) inferredstratigraphic successions of transgressive gravelbeaches are proposed.Sedimentological descriptions of modern,

wave-dominated gravel foreshores and back-shores are common in geological literature. Theoriginal model presented by Bluck (1967) recog-nized distinct, shore-parallel zones based onclast-shape selection. This shore-normal zonationis observed from gravel beaches around the world(Carr, 1969; Carr et al., 1970; Maejima, 1982; Hart& Plint, 1989; Postma & Nemec, 1990; Bartholomaet al., 1998; Bluck, 1999) and may be consideredtypical of high-energy, wave-dominated shore-lines with a limited fluvial- or marine-sedimentsupply. The above model, however, is limitedto a narrow (average 100–200 m wide) beach-normal zone that includes the steeply dippingbeachface (foreshore), berm, and backshore(Bluck, 1967; Carr et al., 1970; Kirk, 1980; Mae-jima, 1982; Postma & Nemec, 1990). Modernnearshore (shoreface) and more basinal conglo-merate facies have been described (Hart & Plint,1989), but are generally poorly understood.Shoreface conglomerate models are therefore,mainly derived from outcrop and core (Clifton,1981, 1988; Massari & Parea, 1988; Hart & Plint,1989, 2003; Caddell & Moslow, 2004; Zonneveld& Moslow, 2004). As a result, most moderndepositional models for conglomerates are acomposite of modern foreshore deposits, andancient shoreface and more basinal deposits(Bourgeois & Leithold, 1984).Shoreface conglomerates are broadly sub-

divided as transgressive and regressive (Wescott& Ethridge, 1982; Bourgeois & Leithold, 1984;Postma & Nemec, 1990). Transgressive conglom-erate successions encountered in the rock recordtend to lack backshore and foreshore deposits as aresult of erosion during transgression (Bourgeois& Leithold, 1984). Regressive (progradational)gravel beaches tend to be characterized byrepeating sequences of coarsening-upward con-glomerates with internal erosional surfaces (Bour-geois & Leithold, 1984), and by the preservation of

foreshore sediments (Clifton, 1981; Massari &Parea, 1988).Waterside Beach, New Brunswick, Canada is a

transgressive, muddy gravel beach in the hyper-tidal Bay of Fundy. It is considered that thestructures and morphology of the intertidaldeposits partly result from depositional processes(shoaling, breaker, surf, and swash zone pro-cesses) and water depths equivalent to the upperand lower shoreface. Examination of these mod-ern deposits, therefore, provides insights into thefacies and facies relationships of hydraulicallyreworked shoreface conglomerates.

Study area

Waterside Beach is located on the New Bruns-wick coastline of Chignecto Bay (Fig. 1). Orientednorthwest–southeast the beach is perpendicularto the dominant southwest winds (Amos &Asprey, 1979). During winter cyclones (mainlyNovember through January) it experiences peaksignificant wave heights of 3 m and wave periodsof 10 sec (Amos et al., 1991). Overall, mostsignificant waves heights (79%) are below1Æ25 m with periods of 7 sec or less (Amos et al.,1991). Waterside Beach experiences a mean tidalrange of 9 m. Vertical tidal range varies from 6 mduring neap tides to 12 m during spring tidesresulting in exposure of up to 1200 m of intertidalzone at low tide. Additionally, up to 650 m ofbeach sediments occur sub-tidally (Fig. 2). Thetoe of the beach is demarcated by a step that islocally steep (1�), but generally weakly defined.On the landward edge, backshore and beachfacedeposits abut either salt marsh or bedrock cliffs(Fig. 1C).At the northwest end of the beach, sand with

minor gravel is the dominant sediment; whereas,gravel is present near the mouth of Long MarshCreek (Figs 1B and 2). A maintained dike backsthe beach in the southeast (Fig. 1B and C). Thedike has significantly hindered transgression, yetdoes not appear to interrupt beach sedimentationpatterns in the intertidal and sub-tidal zones(Fig. 2).

Methods

Fieldwork on Waterside Beach was undertaken in2003 and 2004. Beach-normal and beach-paralleltransects were conducted to establish beachzonation and morphology. Line-and-level meas-urements were used to document changes inslope and to establish major changes in morphol-

2 S.E. Dashtgard, M.K. Gingras and K.E. Butler

� 2006 The Authors. Journal compilation � 2006 International Association of Sedimentologists, Sedimentology, 1–18

UNCORRECTEDPROOF

ogy. In total, 5Æ6 km of line-and-level measure-ments were taken in the shore-normal directionand 1Æ1 km in the alongshore direction. Stationswere then erected at intervals in both directions.In areas where sediment distribution was hetero-geneous, additional stations were established tocharacterize the sedimentological characteristicsof each zone. At each station, sedimentary struc-tures were recorded from the surface and from

trenches dug mainly perpendicular to deposi-tional strike. Box cores were collected at moststations for X-ray imaging.High-resolution, single-channel seismic pro-

files were acquired in 2003 and 2004. Thesesurveys were used to map out the toe of the beach(Fig. 2), but otherwise are not presented in thispaper. In 2005, a grab-sampling program wasundertaken to sample sub-tidal beach and off-shore sediments. Samples collected during thisprogram are incorporated into the grain-size dataand are used to map out the horizontal distribu-tion of sediments in the sub-tidal zone (Fig. 2).Grain-size distribution on Waterside Beach was

determined using one of three techniques: (1) gridsampling, (2) bulk-sample dry sieving, and (3) X-ray absorption. (1) Grid sampling (Wolman, 1954;Rice & Church, 1996; Hoey, 2004) was employedfor deposits with significant quantities of cobble-and boulder-sized clasts. This method involvedestablishing a 5 m · 5 m or 10 m · 10 m grid inan area considered representative of a deposit,and measuring the b-axis of clasts (>4 mm)encountered every 0Æ5 or 1 m across the grid(Wolman, 1954; Church et al., 1987). A matrixsample of sediment <4 mm was then collectedfrom each grid and sieved to accurately determinethe grain-size distribution of the matrix. (2) Threehundred and fifteen kilograms of sediment (60samples) was collected for dry sieving. In thefield, samples were dried, sieved, and weighedand the coarse fraction (particle diameter >1/)discarded. Representative sub-samples wereextracted from the remaining sample and drysieved in the laboratory in one phi-size incre-ments to the sand-silt break (4/). Grain-sizestatistics included in this paper are reported forall grab samples, and for intertidal samples wherethe total sample mass is equal too or greater than100 times the mass of the largest clast observed.This is smaller than sample sizes suggested byChurch et al. (1987) and Hoey (2004); but stillprovides reasonable grain-size information forcomparison between deposits (Hoey, 2004). (3)Silt and clay fractions of samples with a signifi-cant fine-grained component (>2% silt and clay)were determined by X-ray absorption on a Micro-metrics Sedigraph 5100.Mean grain size (/), sorting (r), and skewness

(Sk) were calculated by graphical analysis (Folk &Ward, 1957) and the method of moments (Krum-bein & Pettijohn, 1938; Boggs, 1995). Reportedmean grain-size values are arithmetic meansderived by the method of moments using milli-metre values. For ease of comparison these values

65′ 63′

63′65′67′ W

44′ N

46′

44′

NOVA SCOTIA

U.S.A.

P.E.I.

Saint John

Moncton

Halifax

ATLANTIC OCEAN

BAY OF FUNDY

Chignecto BayStudy Area

0 50 100

kilometers

NEWBRUNSWICK

A

Waterside Beach

CHIGNECTO BAY

kilometers

0 1 2 3 Capeenrage

Dennis Beach

Dike

B

915

Beach

Salt Marsh

Long MarshCreek

500 m

C

Fig. 1. Location map of the study area. (A) Location ofthe Bay of Fundy in Canada, and Waterside Beach inthe Bay of Fundy. (B) Diagram of Waterside Beach. (C)Airphoto of Waterside Beach in 1996.

Sedimentology, stratigraphy of muddy gravel beaches 3


UNCORRECTEDPROOF

Fig. 2. Sediment distribution maps from 2003 and 2004 and profiles of Waterside Beach. Note the significant dif-ferences in the size of the mud zone (D11), bar locations (D8), and tidal-creek braid plain (D6) from 2003 to 2004. Alllithologies on the 2003 map correspond to deposits described in Tables 1 and 2 except for the cross-hatch pattern,which demarcates a rock platform of Palaeozoic bedrock exposed in the intertidal zone. P1 and P2 indicate thelocations of profiles 1 and 2. Points 1 and 2 are referred to in the text. The thick, dashed line on the 2004 mapindicates the approximate edge of salt-marsh sediments exposed or buried shallowly on Waterside Beach. Betweenthe two lines the beach is deeply incised into the salt marsh.



UNCORRECTEDPROOF

are converted to the phi scale. Sorting andskewness values are derived from graphical ana-lysis of phi-scale, cumulative grain-size curvesallowing for easy comparison of the WatersideBeach sediments to standard sorting and skew-ness scales (Folk & Ward, 1957; Boggs, 1995;Hoey, 2004). Reported values are an average of allsamples in each deposit (D1 to D11; Tables 1 and2), but do not encompass the full range of meangrain sizes, sorting, and skewness measurements.These values offer a means for easy comparison ofsediment properties between deposits.In situ sediment samples were collected and

imaged using X-ray radiography. Samples werecollected with a 22Æ5 cm · 15 cm · 7Æ5 cm stain-less-steel box core as described in Bouma (1969).From this, a 22Æ5 cm · 14 cm · 2 cm thick slabwas extracted and X-rayed to assess sedimentaryand biogenic sedimentary structures. By combi-ning grain-size data, X-ray images, photos, fielddescriptions, and GPS measurements, sedimentdistribution maps were generated for the back-shore, intertidal, and sub-tidal zones of WatersideBeach (Fig. 2).

RESULTS

Sediment source

Sediment deposited on Waterside Beach is de-rived from three main sources. Mud is sourcedfrom the bay; sand from the outcrops surroundingWaterside Beach; and, gravel and sand fromreworking of glacial deposits exposed sub-tidally.Sediment sourced from the Bay of Fundy isprimarily fine-grained, comprising silt and clayderived from erosion of the seafloor and Palaeo-zoic cliffs surrounding Chignecto Bay (Amos &Asprey, 1979; Amos, 1987; Amos et al., 1991). Inparticular, Amos (1987) reports that suspendedparticulate matter in upper Chignecto Bay com-prises 70–90% silt with approximately 10–20%clay and minor sand. This grain-size distributionis similar (but slightly more silt-rich) to those ofmud deposits (D5 and D11) on Waterside Beach,which yield an average grain-size distribution(and range) of 4% (1–7%) sand, 58% (50–66%)silt, and 38% (28–48%) clay.Erosion of Palaeozoic and Triassic outcrops

fringing Waterside Beach and Long Marsh Creekpresent a second major source of sediment. Theseoutcrops predominantly comprise siltstone andsandstone with recessive shale beds (Amos &Asprey, 1979; Plint, 1986; Amos, 1987; St. Peter,

1996; McLeod & Johnson, 1999). Blocks erodedfrom the cliffs are friable and disaggregate intocomponent grains and clasts. This is manifestedas a decrease in outcrop-derived gravel aggregatesaway from the cliffs and abrasion platformsfringing the beach. It is considered that theoutcrops provide a significant volume of sand tothe beach, but are only a minor contributor ofgravel. A second major source of sand and themain source of gravel are glacial deposits exposedsub-tidally. These sediments are considered to beglacial based on their sedimentological character,mineralogy, and from reconstructed glacial flowmaps presented by Rampton et al. (1984). Thedistribution of the deposits is seismically mappedand the composition determined by grab samp-ling. They are exposed immediately seaward ofthe beach in the southeast, but are covered bybeach sediments in the northwest.

Beach sedimentology

Beach and shoreface sediments are subdividedinto eleven zones (D1 to D11), which representsedimentologically distinct deposits observed inthe sub-tidal, intertidal, and supratidal zones ofWaterside Beach. Sediment textures and struc-tures observed in each deposit are summarized inTables 1 and 2 and Figs 3–5. The deposits arebroadly divided into three categories: (1) sandyforeshore and shoreface (D1 to D5); (2) tidal-creekbraid-plain and delta (D6 and D7); and, (3) wave-formed gravel and sand bars, and associateddeposits (D8 to D11). The relationship betweenthese deposits is complex and their boundariesare commonly gradational. Nevertheless, thedeposit interrelationships are tractable, therebypermitting the development of a characteristicfacies model.

Deposits 1 through 5Deposits 1 to 5 encompass sandy foreshore andshoreface sediments (Table 1; Figs 2 and 3). Theyform a shore-normal continuum of sedimentsdeposited from the backshore (D1) to the sub-tidal zone (D5). Below the moderately dippingbeachface (D2), deposits 3 to 5 occur as a laterallyextensive, shallowly seaward-dipping terrace(Fig. 2). The intertidal component of the terraceis referred to as a low-tide terrace (Masselink &Short, 1993) and is the equivalent of the foreshoreand upper shoreface. The sub-tidal componentrepresents the lower shoreface. Terrace sedimentsexposed at low tide are submerged up to 12 mduring high tide. Consequently, sedimentation



UNCORRECTEDPROOF

Table

1.

Summary

table

ofsedim

entary

deposits

1to

5atW

atersideBeach.

DepositDescription

Sedim

entTexture

Sedim

entary

Structures

Depositionalenvironment&

Contacts

Major

Minor

D1

Weakly

bedded,rooted

well-sortedsand

Wellsorted,coarseskewed

m.g.sand(1Æ21/;0Æ49r;

)0Æ17Sk(10))

Weakly

definedbedding,

Commondisc-shaped

cobblesnearcontact

withD2

Backsh

ore

dunecomplexand

wash

overfan

GradationalcontactwithD2

D2

Moderately

seaward-dipping,

interbeddedpebbly

sand&gravel

Moderately

well

sorted,

very

coarseskewed

c.g.sand(0Æ58/;0Æ80r;

)0Æ38Sk(4))

Very-poorlysortedgravel

()2Æ81/;2Æ16r;)0Æ02Sk(1))

Moderately

seaward

dipping(3–5�),

planar-parallelbedsof

pebbly

sand&

gravel

TroughXB

(landward

dip)

&common

disc-shapedcbls

nearcontactwithD1

Beachface/foresh

ore

Gradational

contactwithD1;sh

arp

withD3,6

D3

Troughcross-bedded,

WR&CR

cross-

laminatedpebbly

sand

Moderately

well

sorted,m.g.sand

(1Æ22/;0Æ62r;

)0Æ09Sk(14))

Beachcusp

s,TroughXB

(landward

&seaward

dip),

WRto

CR(landward

&seaward

dip)

cross-laminated,

PB,Gravellenses,

Scatteredpebbles,

Bubble

sand

InterbeddedW

Rmuddysand

LTT/upperto

middle

shoreface

equivalentSharp

contactwith

D2,6,8;gradationalwithD4,7,9;

InterbeddedwithD11

D4

Flaserbedded,W

R&

CR

cross-laminated

sand

Moderately

well

sortedf.g.sand

(2Æ41/;0Æ60r;

0Æ1

Sk(4))

Current-modifiedW

R,

Discontinuous,

lunate

mudlenses

(upto

2cm

thick),

PB,Discontinuous

gravellenses,

Scatteredpebbles

LTT/m

iddle

tolowersh

oreface

equivalentTransitionalbetw

een

D3&D5Gradationalcontact

withD3,5,7,9

D5

Clayeysiltandsilty

sand

Clayeysilt(6Æ01/,2Æ3%

sand,

52Æ2%

silt,45Æ5%

clay(2))Very

poorlysorted,siltyv.f.g.

sand(3Æ28/;2Æ23r;

0Æ06Sk(2))

Scatteredpebbles,

sandlenses

ST/lowersh

orefaceequivalent

GradationalcontactwithD4,7,9

Thevaluesin

brackets

afterskewness

valuesindicate

thenumberofsamplesincludedin

thereportedvaluesandastarnextto

thenumberindicatesgrid-by-

numbersampling.Abbreviationsare

usedin

this

table

forwaveripples(W

R),currentripples(CR),planebeds(PB),cross-bedding(X

B),andforgrain

size:fine-

(f.g.),medium-(m

.g.),coarse-(c.g.),and

very

coarse-(v.c.g.)

grained

sand.Underdepositionalenvironments,LTT

represents

low-tideterraceand

ST

for

sub-tidalterrace.



UNCORRECTEDPROOF

Table

2.

Summary

table

ofsedim

entary

deposits

6to

11.

DepositDescription

Sedim

entTexture

Sedim

entary

Structures

Depositionalenvironment&Contacts

Major

Minor

D6

Plane-&

trough

cross-bedded

sand&gravel

Heterogeneousgrain-size

distribution()3Æ65to

0Æ97

/(generallydecreases

offsh

ore);0Æ69to

2Æ22r;

)0Æ15to

0Æ42Sk(3))

PB,TroughXB

(landward

dip),

CR&W

Rsand

TroughXB

(seaward

dip),

Mudlayers

inW

Rtroughs,

GravelW

R

LTT/tidal-creekbraid

plain

Sharp

contactwithD2,3;

gradationalwithD4,7,9,10

InterbeddedwithD8,10,11

D7

Offsh

ore

fining,

sandygravelto

f.g.sand

Heterogenousgrain-size

distribution()1Æ14/;1Æ40r;

0Æ42Skgradesoffsh

ore

to2Æ15/;0Æ60r;

0Æ09Sk(4))

Unknown

Unknown

ST/tidal-creeksand‘delta’

Sharp

contactwithD8,10;


InterbeddedwithD6,8,10,11

D8

Shallowly

tosteeply,

landward-dipping

sand&gravelbeds

Very-pooly

sortedgravel

()3Æ26/;2Æ05r;0Æ04Sk(4))

Steeply

(upto

29�)

tosh

allowly,

landward-dipping

interbedsofgravel

&pebbly

sand,Trough

XB(landward

dip)

Interbeddedsh

allow,

seaward-dippinggravel

&pebbly

sand

LTT

&ST/w

ave-generated

gravelbars

Sharp

contactwith

D3,4,5,6,7,9,11;gradational

withD10

InterbeddedwithD5,6,7,9,10,11

D9

Interbedded,trough

cross-beddedPB

sand&gravellysand

Poorlysorted,very

coarse

skewedv.c.g.sand

()0Æ48/;1Æ24r;

)0Æ32Sk(4))

TroughXB

(dom.

landward

dip)gravelly

sand,PBsand,W

R,CR

Thin,discontinuous

mudlaminae

LTT

&ST/w

ave-generatedsandbars

Sharp

contactwithD6,8,10;



D10

Very

shallowly

seaward

dipping,extremely

poorlysortedgravel

Very-poorlysorted,very

fine

skewedgravel()5Æ93/;

2Æ47r;0Æ48Sk(2*))

Shallowly

(<1�)

seaward-dippinggravel,

PBsandbetw

eenclasts

WR&CR

sand&

mud

LTT

&ST/gravellag

(deflationofD8)

Sharp

contactwith

D5,6,7,8,9,11;Interbedded

withD5,6,7,8,9,11

D11

Wavyto

lenticular

bedded,wavy-parallel

laminatedclayeysilt&

WRmuddysand

Clayeysilt(5Æ60/,4Æ7%

sand,59Æ5%

silt,35Æ7%

clay(6))

Poorlysortedsand(1Æ29/;

1Æ57r;0Æ08Sk,7Æ4%

mud(2))

Wavy-parallellaminated

mud,InterbeddedW

R&

PBsand&pebbly

sand,

Scatteredpebblesand

gravellenses

Mudcracks,

Flame

structures,

Runzelm

arkken

LTT/m

ud

Sharp

contactwith

D6,7,8,10;gradationalwithD8


Abbreviationsare

thesameasin

Table

1.



UNCORRECTEDPROOF

and sediment transport on the terrace (D3 to D5)is almost completely dominated by shoalingwaves. Swash-backwash and surf-zone processesdominate deposition on the beachface (D2).Deposit 1 is well-sorted, medium-grained aeo-

lian sand (Table 1) situated in the backshore(Profile 1, Fig. 2). The basal contact of D1 (under-lain by D2) is gradational and marked by layers ofdisc-shaped cobbles. Deposit 2 tends to be verypoorly sorted with interbedded, moderately well-sorted sands. All beds dip 3 to 5� seawards.Deposit 2 is analogous to narrow beachface–foreshore deposits reported from gravel, andmixed sand and gravel beaches (McLean & Kirk,1969; Kirk, 1980; Clifton, 1981; Bourgeois &Leithold, 1984; Forbes & Taylor, 1987; Massari &Parea, 1988). Deposit 2 differs from those nar-rower, more gravel-rich beaches in that it lacks animbricate disc zone or well-defined clast segrega-tion. The toesets of D2 are marked by roundedcobbles and pebbles that accumulate at the baseof the foreshore during storms (Bluck, 1967,1999). These sediments overlie a wave-scouredsurface cut into salt-marsh deposits that isexcavated during transgression (Dashtgard &Gingras, 2005). Deposit 3 sands onlap the cobble

toesets of D2 and are derived from onshore-directed currents developed under fair-weatherconditions (Table 1; Roy et al., 1994; Reading &Collinson, 1996). Along depositional strike at thetop of D3, sand is distributed into low-amplitudebars spaced equidistantly (�100–200 m). Grainsize and sorting of bar sediments is ideal fortrapping air; hence, these zones tend to bedominated by bubble sand (i.e. air trapped insand; Fig. 3A) in the upper 0Æ1 to 0Æ15 m. Runoffzones dominated by silty sand and silt depositionoccur between the bars. Mud deposited in thesezones may be up to 5 cm thick, but is typicallyeroded when the bars shift position. High-energywave conditions are manifested as onshore-direc-ted trough cross-beds in D3 (Fig. 3A), gravellayers at the base of scours (Fig. 3B), and bygravel-dune foresets.Deposit 4 encompasses sediment deposited

below the mean-tide low-water level and is atransitional zone between D3 and D5 (i.e. equiv-alent to the middle shoreface). This zone isdominated by wave-ripples with silt infillingripple troughs. The silt deposits are generallythin, lunate, and discontinuous, but may exceed6 cm in thickness. Throughout D3 and D4, wave-

A B C

5 cm 5 cm 5 cm

Fig. 3. X-ray images of D3, D4, and D6. All images are taken from box cores oriented beach-normal (seawarddirection to the right). (A) Example of landward-dipping trough cross-beds overlain by seaward-dipping current-ripple laminae in D3. Trough cross-bedding is enhanced by air bubbles (dark holes) developed along bedding planes.(B) Deposit 4 dominated by wave- and current-ripple laminae, and plane-bedded sand. Dark laminae indicate moremud-rich sediments and light laminae more sand-rich. Note the gravel-lined scour near the base of the image (blackarrow) and pervasive bioturbation (white arrows). (C) Plane-bedded sandy gravel of D6. The lighter beds are gravel-rich versus the grey, sandier beds. Black spots are pores spaces.



UNCORRECTEDPROOF

and current-ripple laminae are developed underfair-weather conditions (Fig. 3A and B). Wheninitially exposed by the falling tide, the terrace iscovered by wave-ripples, probably resulting from

shoaling-waves (Wright et al., 1982; Masselink &Short, 1993; Masselink, 1993). With continuedexposure, sheet-like surface drainage reworksmany of the wave ripples into offshore-directed

A

D8

D11

D6

B CD6

D11

5 cm

DD11

D8

E

D8

D8

Fig. 4. Photos of D6 to D11. (A) Panoramic view of the relationship between the 5Æ5 m high gravel bar (D8), braidedchannel of Long Marsh Creek (D6), and zone of mud deposition (D11). Panoramic taken from the top of the gravel barlooking east, the bay is to the right of the photo and land to the left. (B) Example of interbedded D6 and D11. The mudlayer is 0Æ04 m thick and the scale is 0Æ15 m long. (C) Trench excavated normal to the beach on the backside of thegravel bar in photo A (D8). The dashed white lines highlight steeply landward-dipping gravel beds overlain byshallowly seaward-dipping gravel. Scale is 0Æ15 m long. (D) Photo of a trench excavated normal to the beach in thezone of mud deposition (D11) on photo A. Note the mud-coated gravel within the upper 0Æ15 m of sediment andsteeply landward-dipping sand and gravel beds (D8) preserved below mud beds (D11). (E) Image of a beach-normaltrench excavated approximately 1 m above the base of the gravel bar in photo A on its stoss face. All gravel clasts0Æ10 m below the bar surface are coated in mud. Scale is 0Æ15 m long.

COLOUR

FIG

.Sedimentology, stratigraphy of muddy gravel beaches 9


UNCORRECTEDPROOF

current ripples resulting in preservation of ebb-current modified wave-ripples (Fig. 3B).Deposit 5 is the lowest most unit of the terrace

and only occurs sub-tidally. It is considered theequivalent of the lower shoreface (Fig. 2). Thiszone is dominated by clayey silt and silty very-fine grained sand deposition (Table 1) with inter-bedded thin pebbly sand lenses. The offshorepinchout of D5 corresponds to the toe of theshoreface, and is demarcated by a weakly definedstep and a decrease in the slope of the seafloor.

Deposits 6 and 7Deposits 6 and 7 comprise plane and troughcross-bedded sand and gravel deposited as aresult of tidal-creek processes active on the low-tide terrace at low tide. Water transported up thecreeks at high tide (particularly spring high tide)flood the salt marsh and drain into two tidallakes, 2 and 10 km landward of the beach. Duringthe falling tide, bay waters drain off the marshand out of the lakes at a relatively constant rate –maintaining a relatively steady flow rate withinthe creeks throughout falling- and low-tide. Tidal-creek waters winnow fine gravel and sand fromupper terrace deposits and transports it to thelower intertidal and sub-tidal zones. As a result,upper and middle terrace sediments exhibitimproved sorting and a general shift towardscoarsely skewed sediment. The tidal creeks alsoredistribute low-tide terrace sediments into creek-parallel sand and gravel beds. These depositsform a braided outwash plain with a very hetero-geneous distribution of grain size, sorting, andskewness (D6, Table 2). The hydraulic energy of abraid channel determines whether gravel, sand ormud is actively deposited and the thickness ofthat deposit. Moreover, sedimentary structuresobserved in a particular area of the braid plain are

related to sediment grain size and hydraulicenergy. High-energy streams (active channels)are erosive and remove up to pebble-sized clastsfrom the underlying deposit. In moderate-energychannels, sand and gravel is deposited as planebeds (Fig. 3C) with intermittent steeply dippingforesets of stream-parallel and stream-normalchannel bars. Grain-size distribution is hetero-geneous; however, there is an overall decrease ingrain size offshore (Table 2). At the seaward endof D6, sand and fine gravel winnowed out ofupper and middle terrace deposits is deposited asa sand ‘delta’ (D7). The delta extends from thelower intertidal seaward to the toe of the shore-face (Fig. 2) where it develops a pronounced (1�)step. This sediment is likely the source for thelandward-migrating sand dunes and bars ofdeposit 9.

Deposits 8 through 11Deposits 8 to 11 are reworked by high-energywaves.Deposit 8 encompasses sediment laiddownas large (up to 800 m long), landward-migratinggravel bars (Figs 2 and 4A). In Fig. 4A, the gravelbar on the right of the photo comprises a 5Æ5 mhighlee face and 6Æ7 m high stoss face (Profile 2, Fig. 2).Overall, the bars are composed of steeply land-ward-dipping foresets of very-poorly sorted graveland sand (Table 2; Figs 2, 4C, E and 6). Sedimentmigrates up the stoss face of the large bars andavalanches down the lee slope forming foresetsthat dip up to 29� (Figs 2, 4C, E and 6). Interbeddedwith these sediments are better sorted, coarselyskewed gravels representing hydraulicallywinnowed surface sediment.The Waterside gravel bars develop in the

shallow sub-tidal zone (lower shoreface) andincrease in volume as they migrate onshore.Measurements of bar migration indicates that

A B

5 cm 5 cm

Co Co

P WR

Fig. 5. (A) X-ray image of the wavy-parallel laminated clayey silt (dark layers) and silty sand (light layers) of D9,overlying gravelly sand. U-shaped Corophium volutator burrows (Co) are prevalent throughout the mud. (B) X-rayimage of D9 showing the variability in the lithology of the deposit. Dark layers are clayey silt, dark grey areas sandymud, and light layers are gravelly sand. Note the large pebble (P), Corophium volutator burrows (Co) and waveripples (WR).



UNCORRECTEDPROOF

mudvf f m c vc gn

lpb

lcb

lmud

vf f m c vc gnl

pbl

cbl

0

1

2

3

D2

D3

D4

0

1

2

3

4

5

6

7

8

D8

D6

D11

D8

D10D11

D6

D11

D10

D8

D6

D8

D11

D9/D7

Strip log 2A

D5 D5

mudvf f m c vc gn

lpb

lcb

l

0

1

D2

D4

Strip log 1B

D5

Strip log 1A

mudvf f m c vc gn

lpb

lcb

l

0

1

D2

Strip log 1C

D5

Muddy gravel

Sandy gravel

Mud (clayey silt & sandy silt)

Gravel Weak or possible bedding / laminae

Visible bedding / laminae

Wave- and current-ripple laminae

Trough cross-bedding

Wave-scoured contact

Planar-parallel bedding (plane beds, steeply andshallowly dipping beds)

Salt marsh with roots

Gravel lag

mudvf f m c vc gn

lpb

lcb

l

0

1

2

3

D8

D6

D7 / D9

D5

mudvf f m c vc gn

lpb

lcb

l

0

1

2

D8

D5

Strip log 2B

Strip log 2C

Fig. 6. Idealized sections that may be expected if Waterside Beach is preserved in the rock record. Strip logs 1A, 1B,and 1C refer to sections for point 1, and strip logs 2A, 2B, and 2C for point 2 (2003 map, Fig. 2). The logs arediscussed extensively in the text. Lithology is not indicated on the strip log unless it differs from the indicatedlithology type (i.e. gravel beds in a sand unit). The vertical bars and D’s on the right side of each log refer to thevertical distribution of each deposit type in the section. Scale is in metres.



UNCORRECTEDPROOF

annual landward migration along the bar front isvariable, ranging from 0 to over 50 m year)1

(Maps 2003 and 2004, Fig. 2). At the landwardlimit of the beach the bars either accrete to thebeachface (D2) or infill the tidal creeks (Strip logs2A, 2B, and 2C, Fig. 6). Small bars (<2 m high)tend to be washed out by storm waves in theintertidal zone whereas large bars are moreresilient and migrate landward during storms.Under fair-weather conditions, migration of thelarge bars is minimal and is restricted to small,low-amplitude, mixed sand and gravel dunes thatmigrate up and over the stoss face of the bar.In sandy systems, bar-forms similar to, but

smaller than, the Waterside bars are common andhave been the subject of numerous studies (King& Williams, 1949; McCave & Geiser, 1978; Green-wood & Davidson-Arnott, 1979; Kroon & Masse-link, 2002; Anthony et al., 2004; Yang et al.,2005). Initially, these intertidal bars were consid-ered to form as a result of swash processes anddestroyed by surf processes (King & Williams,1949; King, 1972). However, recent work byKroon & Masselink (2002) shows that onshorebar-migration results mainly from surf-zone pro-cesses and that swash processes play a secondaryrole. The Waterside bars may then be consideredintertidal bars that are akin to sub-tidal, innersurf-zone bars (Sunamura & Takeda, 1984; Kroon& Masselink, 2002).Deposit 9 refers to sediment deposited from

sandy, low amplitude (<1 m) bars with gentlydipping lee and stoss slopes. D9 bars are com-posed of poorly sorted sand and gravel, but tendto be predominantly gravelly sand (Table 2;Fig. 6). The increased sand content is partly theresult of wave reworking of D7 sand-delta sedi-ments in the lower intertidal and sub-tidal zones(Fig. 2). Sedimentary structures are dominated bytrough cross-bedding (dipping in all directions)and plane beds that form as a result of waterflowing over and off the bar forms. These bars arehighly unstable and are akin to the Type 2 barsreported by Greenwood & Davidson-Arnott(1979). They are also considered to result fromsimilar processes (Kroon & Masselink, 2002;Anthony et al., 2004) as the larger gravel bars(D8) and may be considered analogous to sub-tidal, inner surf-zone bars as well.Deposit 10 is a wave-winnowed pebble and

cobble lag (Fig. 2) deposited to seaward of thelandward-migrating gravel bars (D8). The upperlayer of D10 is wave-reworked into weaklydefined horizontal to gently seaward-dippingbeds (Fig. 6). Hydraulic winnowing of the pri-

mary deposit (D8) removes most fines and con-centrates large pebbles and cobbles on the beachsurface. Secondary infilling of interstitial poreswith sand (D9) and mud (D5 and D11) results inan increased proportion of fines, hence the fineskew and very-poor sorting (Table 2). Deposit 10may occur from the top of the low-tide terrace(foreshore) to the base of the shoreface (Fig. 2).The development of large gravel bars (D8) is

both an important mechanism for gravel transportand deposition, and is necessary for the occur-rence of extensive mud deposition landward ofthe bars (Fig. 2). The gravel bars dissipate andreflect wave-energy resulting in the developmentof quiescent zones dominated by clayey siltdeposition (Figs 2, 4A and 5). Below a thresholdbar-height (�1Æ5 m) mud deposition is negligible.With increased height the mud zone extendslandward (Fig. 2). This mud is deposited on topof the existing sediment (Figs 2 and 4A, B) andpinches or swells in response to the antecedenttopography (Fig. 6). In abandoned channel lows(D6) or depressions in the underlying surface,mud deposits (D11) are commonly 0Æ15 to 0Æ2 mthick. Mud up to 0Æ4 m thick has been observed.On topographic highs, mud thickness rarelyexceeds 0Æ07 m. The clayey silt is wavy parallellaminated (Fig. 5A) to wave-ripple laminated(Fig. 5B) and is commonly interbedded with sandand sandy gravel beds deposited during storms orby ice (Fig. 5B).

DISCUSSION

Muddy conglomerates and mud beds inconglomerates

Understanding the relationship between the muddeposits (D11), channel deposits (D6), gravel bars(D8), and lag deposits (D10) on Waterside Beachprovides a mechanism for mud deposition inconglomeratic systems and for the formation ofmuddy conglomerates. Landward of the gravelbars, mud is deposited as thin layers on top ofbraided-channel bars and in abandoned channelsof D6 (Figs 4A, B and 5). Initially, the mud issoupy and easily resuspended by low-energyhydraulic currents. Subsequent desiccation,dewatering, and/or bacterial (or algal) bindingrenders it firm – forming resistant mud beds.An example of this is shown in Fig. 4B wherea 0Æ04 m thick mud bed is interbedded withbraided-channel gravel-bar deposits of D6. Mud-dy clast- and matrix-supported conglomerates



UNCORRECTEDPROOF

develop in front of the landward-migrating gravelbars (D8). Gravel transported up the seaward(stoss) side of the bar avalanches down thelandward (lee) face and either accumulates onthe face or in the mud at the base of the bar. Thearea directly in front of the bar is not affected bywave- or tidal-energy; hence, the mud is noteroded during bar migration. Gravel avalanchingdown the lee face either rests on top of the mud orsinks into it resulting in mud infilling the spacesbetween gravel clasts. This relationship is repre-sented on Strip log 2A (Fig. 6) by muddy gravel inthe basal portion of each D8 deposit.Muddy conglomerates also develop when mud-

rich sea water seeps through the beach sediments(Fig. 4D and E). Figure 4D is an example ofmuddy gravel that occurs below the zone ofmud deposition. Mud-laden sea water percolatingdown through the gravel rapidly loses velocitybelow the surface resulting in mud deposition inthe near-surface beach sediment. The mud tendsto coat grains instead of infilling the pore spaces.Figure 4E depicts muddy gravels encountered ina trench approximately 1 m above the low-tideterrace on the stoss side of a gravel bar (D8). Inthis case, mud-laden sea water passing throughthe gravel bar coats sand and gravel clasts withmud. In both cases muddy gravels are developed,although the depth (relative to the beach surface)at which they occur differs. Below the zone ofmud deposition (D11, Fig. 2) muddy gravelsoccur in the near-surface sediment (upper0Æ15 m) and overly mud-free sand and gravel.Within the gravel bars, muddy gravels occurbelow the upper 0Æ1 to 0Æ15 m resulting fromwave winnowing of the near-surface sediment.The two mechanisms presented for the develop-

ment of muddy, matrix- and clast-supported con-glomerates and for the deposition of mud beds inconglomerates provide a means to assess environ-mental conditions of the palaeo-depositionalenvironment that otherwise may not be discerna-ble. The latter mechanism (requiring gravel depos-its and mud-laden sea water) suggests that theoccurrence of muddy conglomerates is a goodindicator that seawater at the time of conglomeratedeposition was muddy. The first mechanismnecessitates bar formation and migration, whichis dependent on the location of the bars relative tothe beach and on the local tidal range. Intertidalbars exhibit characteristics that are distinct to anintertidal environment and thus, may be distin-guished from their sub-tidal equivalents. Primar-ily, the height of intertidal bars is restricted by tidalrange where bar height cannot exceed the maxi-

mum tide height. This in turn, controls the occur-rence of mud deposits on the landward side of thegravel bars. Short (<1Æ5 m high) bars tend not topermit the development of mud beds. Sub-tidalgravel bars are not restricted by tidal range andmayoccur in microtidal to hypertidal settings.Intertidal bars are sub-aerially exposed twice a

day, resulting in dewatering, desiccation, andalgal binding of the mud beds that developlandward of the bars. In a sub-tidal environmentdewatering and possibly algal binding may alsorender mud beds firm, but is less likely too occur.Moreover, bar migration rates are likely to behigher in a sub-tidal setting as a result ofprolonged exposure to surf-zone processes. Con-sequently, the occurrence of mud beds in aconglomeratic succession may indicate an inter-tidal environment and upper mesotidal to hyper-tidal conditions. The occurrence of muddyconglomerates however, is less restrictive andmay either indicate sub-tidally formed gravelbars, intertidal bars or mud-laden sea water. Ifbedding is apparent in a muddy conglomerate itmost likely developed from mud-laden sea waterseeping through the gravel; whereas, a lack ofbedding may be more indicative of bar migrationover soupy mud deposits in either a sub-tidal orintertidal setting.

Transgressive muddy gravel beach sequences

Waterside Beach occurs in a hypertidal settingwhere the dominance of wave-processes willresult in a facies architecture that correspondsto that of a transgressive gravel beach. Figure 6illustrates six idealized successions that can bepredicted if continued transgression resulted inburial and preservation of Waterside Beach in therock record. Strip logs 1A, 1B, and 1C (Fig. 6)relate to point 1, and strip logs 2A, 2B, and 2Crelate to point 2 on Map 2003, Fig. 2. Thestratigraphic successions presented for points 1and 2 represent end members of the possiblestratigraphic relationships that exist on WatersideBeach. Strip logs 1A and 2A are complete trans-gressive sequences that may either be encoun-tered in systems with high sedimentation rates orthat may develop at or near the maximum trans-gressive shoreline. Strip logs 1B and 2B presentthe expected preserved succession that may beencountered in areas with moderate sedimenta-tion, or at the early or late stages of transgression.Strip logs 1C and 2C show sedimentary succes-sions that will develop in rapidly transgressingsystems. Continued transgression of present day



UNCORRECTEDPROOF

Waterside Beach should result in preservation ofa succession that resembles either strip logs 1Band 2B or 1C and 2C.The (extreme) difference in thickness between

sequences constructed for points 1 and 2 is due toerosion of the salt marsh at the mouth ofLong Marsh Creek (LMC; Fig. 2). This in turn,is controlled by tidal range, where the cross-sectional area of a tidal-inlet throat (i.e. whereLMC debouches onto the beach) is related to thetidal prism (French, 1993; Pye & French, 1993;Allen, 1997, 2000). On the hypertidal WatersideBeach the tidal prism is large; hence the cross-sectional area of LMC is also large (8Æ2 m deep,54 m wide; Dashtgard & Gingras, 2005). Depthmeasurements taken from the beach and withinmarsh indicate that at the landward end of thebeach (seaward limit of the marsh), LMC is filledwith 4Æ5 m of gravel and sand derived from thebeach, and is presently filling in a landwarddirection. Seaward of LMC, the erosional profileof underlying salt-marsh sediments flares later-ally and vertically (as a cone opening seawards)from the mouth of the creek to beyond the outeredges of the gravel bars (Map 2004, Fig. 2).Within this cone the beach and shoreface depositis much thicker; thus, the successions presentedin strip logs 2A, 2B, and 2C (i.e. near tidal-channel complex) are nearly three times thickerthan those in strip logs 1A, 1B, and 1C respect-ively (i.e. ambient beach; Fig. 6).

Strip logs 1A, 1B, and 1CAssuming Waterside Beach is preserved in therock record, strip logs 1A, 1B, and 1C (Fig. 6) areidealized sections of the sedimentary successionthat may be expected at point 1 (Map 2003,Fig. 2). The three sections are presented to illus-trate variations in the preserved succession thatcan occur under varying rates of transgressionand/or sedimentation. In general, a completesedimentological record will be relatively thinand dominated by middle to lower terrace depos-its representing mainly shoaling-wave (shoreface)processes. In transgressive systems, backshoreand beachface deposits are normally eroded(Bourgeois & Leithold, 1984; Nemec & Steel,1984); whereas, shoreface and offshore faciestend to be preserved (Roy et al., 1994; Reading &Collinson, 1996). This is likely to be the case forWaterside Beach with the vertically significant,but laterally restricted D1 and D2 deposits (Profile1, Fig. 2) having a limited to nil chance ofpreservation. The rest of the succession consistsof a deepening-upward trend.

Strip logs 1A, 1B, and 1C depict the faciesevolution on top of a wave-scoured contact(wave-ravinement surface) cut into underlyingsalt-marsh deposits that develops during trans-gression (Fig. 6). This contact is in turn overlainby a thin transgressive lag that is sedimento-logically similar to the transgressive lag describedby Massari & Parea (1988) and Clifton (1981). Thelag comprises toeset sediments of D2 that arepartly wave-reworked resulting in destruction ofbedding (Fig. 6). Above the lag, the rates oftransgression and sedimentation controls thethickness of the preserved succession and thedeposit relationships observed.Three scenarios are presented for the expected

preserved succession at point 1 (Map 2003,Fig. 2). In strip log 1A, the lag (D2) is sharplyoverlain by D3, then D4, and finally D5 sedimentsthat form a continuum of decreasing grain sizeupward in the succession. This trend is accom-panied by an increase in mud deposition andripple cross-lamination, and a decrease in troughcross-bedding and gravel content. Strip log 1Billustrates the case of moderate sedimentationrates relative to transgression resulting in in-creased erosion of the low-tide terrace deposits(foreshore and upper shoreface) and deposition ofmiddle and lower shoreface sediments (D4 andD5) sediments on top of the gravel lag (Fig. 6).Finally, strip log 1C presents a succession that islikely to develop in a rapidly transgressive settingwith low sedimentation. In this scenario, theentire foreshore and upper shoreface sequence isremoved (D2 to D4), with lower shoreface sedi-ments (D5) overlying the gravel lag (Fig. 6).Because the beach has an abundant source ofsand and gravel (i.e. glacial deposits exposed sub-tidally) and experiences relatively rapid trans-gression, it is considered that either strip log 1Bor 1C (Fig. 6) represents the most likely succes-sion that will be preserved if Waterside Beachpasses into the rock record.

Strip logs 2A, 2B, and 2CStrip logs 2A, 2B, and 2C (Fig. 6) depict a muchthicker beach and shoreface sequence that may beexpected at point 2 (Map 2003, Fig. 2). Asdiscussed above, erosion of the salt marsh ismuch more pronounced near the mouth of LongMarsh Creek and extends seaward as a cone ofrelatively deeply incised beach sediment (Map2004, Fig. 2). The complete sequences are avertical representation of the complex strati-graphic relationships between deposits 6 to 11observed on the beach surface (Fig. 2). The depo-



UNCORRECTEDPROOF

sitional conditions – rates of transgression andsedimentation – for strip logs 2A, 2B, and 2C arethe same as those for strip logs 1A, 1B, and 1Crespectively.The base of the successions is demarcated by

a tidally scoured contact cut into salt-marshdeposits (Strip logs 2A, 2B, and 2C, Fig. 6). Instrip log 2A, this surface is directly overlain bya 3 m thick unit of gravel bar (D8) then channel(D6) deposits representing the initial fillingepisode of LMC by gravel-bar sediments. Theupper part of the bar sediments are hydraulic-ally reworked by tidal-creek waters to form D6.From 3 m to nearly 5 m is a typical sedimentarypackage for this succession. Mud deposition(D11) occurs on top of the channel sediments(D6) as a result of gravel-bar formation. Down-ward percolating sea water coats sand andgravel clasts in the sediment immediately belowthe mud beds resulting in the development ofmuddy gravel. Subsequent landward migrationof the bar, deposits a thick bedset of steeplydipping sand and gravel (D8) on top of themud. The basal third of the bar deposit isdominated by muddy gravel as a result of mudbeing forced into the pore spaces betweengravel clasts. The surface sediments of the bar-deposited bedset (D8) are hydraulically win-nowed and reworked by waves into weaklydeveloped seaward-dipping plane beds (D10).Once the bar reaches the beachface or is washedout by waves, braided drainage channels ofLMC are re-established on the low-tide terraceforming channel-bar deposits (D6). This sedi-mentation cycle is repeated vertically (Fig. 6).After the last bar, channel, and mud unit (atapproximately 7Æ5 m), the D10 beds are sharplyoverlain by either low-relief sand-bar (D9) orsand-delta (D7) sediments representing the low-ermost intertidal and sub-tidal zones (Strip log2A, Fig. 6).Strip logs 2B and 2C (Fig. 6) depict the same

sequence as in 2A, but under varying rates oftransgression and/or sedimentation. Similar tostrip log 1A, strip log 2A should be preserved ina setting with high sedimentation rates and slowtransgression, such as at or near the maximumtransgressive shoreline. Strip log 2B will bepreserved where sedimentation rates are highenough to result in some aggradation duringtransgression. This results in erosion of theforeshore by transgressive wave ravinement,and partial preservation of middle and lowershoreface sediments (D4 and D5; Strip log 2B,Fig. 6). Strip log 2C illustrates a sequence that

will be preserved when sedimentation rates aremuch lower than transgression rates. Transgres-sive wave ravinement removes most of theintertidal (foreshore and upper shoreface) andsub-tidal (middle and upper lower shoreface)deposits. Lower shoreface muds then accumulateon top of the wave-scoured sediments. Theresultant package therefore, consists of foreshoreand upper shoreface sediments that infilled thetidal creeks, decapitated by wave ravinement,and capped by lower shoreface muds (Strip log2C, Fig. 6).

Application to the rock record

The sedimentological relationships and theoret-ical stratigraphy of Waterside Beach providesimportant information for facies and facies rela-tionships of transgressive gravel-, muddy gravel-,and mixed sand and gravel-beaches preserved inthe rock record. Firstly, it is observed that archi-tecture, thickness, and extent of transgressivegravel-beach deposits are significantly influencedby the occurrence and size of associated tidalcreeks. The size of these creeks is a function of thetidal prism (French, 1993; Pye & French, 1993;Allen, 1997, 2000). The successions in strip logs2A, 2B, and 2C are very thick reflecting thehypertidal nature of Waterside Beach. The thick-ness of these units will decrease with a reductionin tidal range; hence, the thick deposits observedin these strip logs are applicable to upper meso-tidal to hypertidal settings. Strip logs 1A, 1B, and1C depict much thinner sedimentary successionstypical of beach and shoreface sediments depos-ited outside the zone of tidal-creek influence(Fig. 2). The thickness of these deposits is con-trolled by the rate of sedimentation, transgres-sion, and by wave action, and is independent oftidal range. Strip logs 1A, 1B, and 1C are there-fore, applicable to transgressive gravel, muddygravel, and mixed sand and gravel successions inany tidal setting.Secondly, sedimentation rate versus trangres-

sion rate controls the thickness and architectureof the preserved succession. In rapidly trans-gressing systems and/or those with limited sedi-ment supply, the preserved succession tends tobe thin, either manifested as a gravel lag (Strip log1C, Fig. 6) or as a thin (<2 m thick) shore-normalgravel deposit where tidal creeks debouch ontothe beach (Strip log 2C, Fig. 6). In both cases thesuccessions are capped by lower shoreface siltysand and clayey silt deposits. This depositionalsetting is similar to described transgressive beach



UNCORRECTEDPROOF

successions and the transgressive components ofprogradational deposits, which tend to be thin(commonly manifested as a wave-winnowed,gravel lag) and grade quickly upward into off-shore, muddy marine facies (Clifton, 1981; Bour-geois & Leithold, 1984; Massari & Parea, 1988). Abeach and shoreface succession that results froma rapidly transgressing shoreline with a limitedsediment supply represents one end member ofpossible successions that may occur. The otherend member is illustrated in strip logs 1A and 2A(Fig. 6), which are the expected successionswhen the sedimentation rate is high relative tothe transgression rate. These deposits tend to bemuch thicker and occur at or near the maximumtransgressive shoreline.The stratigraphic successions depicted in strip

logs 2A, 2B, and 2C (Fig. 6) develop over anerosional surface into salt-marsh deposits scouredby Long Marsh Creek and enhanced by waveaction on the beach (Map 2004, Fig. 2). Conse-quently, the zone of thick beach deposits devel-ops perpendicular to the strike of the beach andmay be mistaken for fluvial or estuarine deposits.This is a significant problem in rapidly trans-gressing systems where the beach tends to bemanifested as a thin gravel lag and the tidal-creekinfluenced deposit as a shore-normal gravel unitup to 2 m thick (Strip logs 1C and 2C, Fig. 6). Theoriginal depositional environment may be ascer-tained if sedimentary structures, such as steeplylandward-dipping gravel beds (D8), horizontalmud beds (D11), and muddy conglomerates (D8)are observed.

CONCLUSIONS

Waterside Beach deposit can be subdivided intoeleven sedimentologically distinct deposits thatrepresent three main depositional environments:(1) sandy foreshore and shoreface; (2) tidal-creekbraid-plain and delta; and, (3) wave-depositedgravel and sand bars, and associated deposits.Sandy foreshore and shoreface deposits encom-pass aeolian-deposited sand of the backshore(D1), moderately seaward-dipping (3–5�) mixedsand and gravel of the beachface (D2), and ashallowly seaward-dipping terrace comprisingintertidal sand (D3) and silty sand (D4), andsub-tidal silty sand and clayey silt deposits (D5).Deposit 6 includes terrace sediments reworked ordeposited by tidal creeks. Sand and fine gravelremoved from the upper and middle intertidal isdeposited in the lower intertidal and sub-tidal

components of the terrace forming a sand ‘delta’(D7). This sediment is then transported onshoreby waves as unstable, low-amplitude sandy barsof D9. Deposits 8 and 10 represent gravel depos-ited by large, landward-migrating gravel bars (upto 5Æ5 m high, 800 m long). These bars form andmigrate in response to surf-zone processes (Kroon& Masselink, 2002) and are considered sub-tidal(shoreface) features exposed as a result of theextreme tidal range. D11 represents the zones ofmud deposition developed on the landward sideof large gravel bars.The occurrence of mud beds in a conglo-

meratic succession is most indicative of uppermesotidal to hypertidal conditions at the time ofdeposition, and may indicate sub-aerial exposureof mud beds resulting in dewatering, desicca-tion, and algal binding of the mud. Muddy,clast- and matrix-supported conglomerates maydevelop from sub-tidally formed gravel bars,intertidal bars or mud-laden sea water. If bed-ding is apparent in a muddy conglomerate itmore likely develops from mud-laden sea waterseeping through the gravel. A lack of beddingmay be more indicative of bar migration oversoupy mud deposits in either a sub-tidal orintertidal setting.The thickness and preservation of transgressive

gravel beaches is dependent on tidal regime,sedimentation rate, and transgression rate. Inareas where tidal creeks do not influence sedi-mentation on the beach, a preserved sequencewill be thin, consisting of an upward-deepening(fining) profile (Strip logs 1A, 1B, and 1C, Fig. 6).Conversely, where tidal creeks do occur landwardof the beach, the beach sequence tends to bemuch thicker (Strip log 2A, 2B, and 2C, Fig. 6).The thickness of the succession is largely con-trolled by the occurrence and size of tidal creeks,which is proportional to the tidal prism. AtWaterside Beach, the tidal prism is large, thusthe preserved succession is thick. The thicknessof the preserved succession is also stronglyinfluenced by the rates of sedimentation andtransgression. Where sedimentation is low andtransgression rapid, the preserved deposits arethin – comprising either a thin conglomerate lag(Strip log 1C, Fig. 6) or a thin (<2 m thick) gravelunit oriented shore-normally (Strip log 2C,Fig. 6). These successions would typically becapped by lower shoreface mud. At or near themaximum transgressive shoreline or in transgres-sive settings with high sedimentation rates thepreserved gravel deposits are predicted to bemuch thicker (Strip logs 1A and 2A, Fig. 6).



UNCORRECTEDPROOF

ACKNOWLEDGEMENTS

Special thanks to Tyler Hauck and Andrew Cookfor assistance in the field and laboratory; toRichardo White and Peter Simpkin for theirefforts in acquiring and processing the seismicdata; and, to Russell Parrott from the GeologicalSurvey of Canada, Atlantic Division for makingthe grab sampling program possible. Thanks to DrGuy Plint and two anonymous reviewers whosereviews aided in improving this paper. Fundingof the research program under which this datawas collected is generously provided by theNatural Sciences and Engineering ResearchCouncil (NSERC), BP Canada, ConocoPhillipsHouston, Devon Energy, Nexen Energy, PetroCanada, Talisman Energy, and Imperial Oil.

REFERENCES

Allen, J.R.L. (1997) Simulation models of salt-marsh morpho-

dynamics: some implications for high-intertidal sediment

couplets related to sea level change.Sed. Geol., 113, 211–223.Allen, J.R.L. (2000) Morphodynamics of Holocene salt mar-

shes: a review sketch from the Atlantic and Southern North

Sea coasts of Europe. Quatern. Sci. Rev., 19, 1155–1231.Amos, C.L. (1987) Fine-grained sediment transport in Chig-

necto Bay, Bay of Fundy, Canada. Cont. Shelf Res., 7, 1295–1300.

Amos, C.L. and Asprey, K.W. (1979) Geophysical and Sedi-

mentary Studies in the Chignecto Bay System, Bay of Fundy– A Progress Report. Current Research Paper 79–1B,

pp. 245–252. Geological Survey of Canada, Ottawa.

Amos, C.L., Tee, K.T. and Zaitlin, B.A. (1991) The post-glacial

evolution of Chignecto Bay, Bay of Fundy, and its modern

environment of deposition. In: Clastic Tidal Sedimentology

(Eds D.G. Smith, G.E. Reinson, B.A. Zaitlin and R.A. Rah-

mani), Memoir 16, pp. 59–89. Canadian Society of Petro-

leum Geologists, Calgary, AB, Canada.

Anthony, E.J., Levoy, F. and Monfort, O. (2004) Morpho-

dynamics of intertidal bars on a megatidal beach, Merli-

mont, Northern France. Mar. Geol., 208, 73–100.Bartholoma, A., Ibbeken, H. and Schleyer, R. (1998) Modifi-

cation of gravel during longshore transport (Bianco Beach,

Calabria, southern Italy). J. Sed. Res., 68, 138–147.Bluck, B.J. (1967) Sedimentation of beach gravels: examples

from south Wales. J. Sed. Petrol., 37, 128–156.Bluck, B.J. (1999) Clast assembling, bed-forms, and structure

in gravel beaches. Trans. Roy. Soc. Edinb. Earth Sci., 89,291–323.

Boggs, S. Jr. (1995) Principles of Sedimentology and Strati-

graphy, 2nd edn. Prentice-Hall, New Jersey, 774 pp.

Bouma, A.H. (1969) Methods for the Study of SedimentaryStructures. John Wiley & Sons, New York, 458 pp.

Bourgeois, J. and Leithold, E.L. (1984) Wave-worked con-

glomerates – depositional processes and criteria for recog-

nition. In: Sedimentology of Gravels and Conglomerates(Eds E.H. Koster and R.J. Steel), Memoir 10, pp. 331–343.

Canadian Society of Petroleum Geologists, Calgary, AB,

Canada.

Caddell, E.M. andMoslow, T.F. (2004) Outcrop sedimentology

and stratal architecture of the Lower Albian Falher C sub-

Member, Spirit River Formation, Bullmoose Mountain,

northeastern British Columbia. Bull. Can. Petrol. Geol., 52,4–22.

Carr, A.P. (1969) Size grading along a pebble beach: Chesil

Beach, England. J. Sed. Petrol., 39, 297–311.Carr, A.P., Gleason, R. and King, A. (1970) Significance of

pebble size and shape in sorting by waves. Sed. Geol., 4, 89–101.

Church, M.A., McLean, D.G. and Wolcott, J.F. (1987) River

bed gravels: sampling and analysis. In: Sediment Transport

in Gravel-Bed Rivers (Eds C.R. Thorne, J.C. Bathurst and

R.D. Hey), pp. 43–79. John Wiley & Sons, Chichester, UK.

Clifton, H.E. (1981) Progradational sequences in Miocene

shoreline deposits, southeastern Caliente range, California.

J. Sed. Petrol., 51, 165–184.Clifton, H.E. (1988) Sedimentologic approaches to paleobathy-

metry, with applications to the Merced Formation of central

California. Palaios, 3, 507–522.Dashtgard, S.E. and Gingras, M.K. (2005) Facies architecture

and ichnology of recent salt-marsh deposits: Waterside

Marsh, New Brunswick, Canada. J. Sed. Res., 75, 594–605.Folk, R.L. and Ward, W.C. (1957) Brazos River bar: a study in

the significance of grain size parameters. J. Sed. Petrol., 27,3–26.

Forbes, D.L. and Taylor, R.B. (1987) Coarse-grained beach

sedimentation under paraglacial conditions, Canadian

Atlantic Coast. In: Glaciated Coasts (Eds D.M. FitzGerald

and P.S. Rosen), pp. 51–86. Academic Press, San Diego,

USA.

French, J.R. (1993) Numerical simulation of vertical marsh

growth and adjustment to accelerated sea-level rise, north

Norfolk, U.K. Earth Surf. Proc. Land., 18, 63–81.Greenwood, B. and Davidson-Arnott, R.G.D. (1979) Sedi-

mentation and equilibrium in wave-formed bars: a review

and case study. Can. J. Earth Sci., 16, 312–332.Hart, B.S. and Plint, A.G. (1989) Gravelly shoreface deposits: a

comparison of modern and ancient facies sequences. Sedi-

mentology, 36, 551–557.Hart, B.S. and Plint, A.G. (2003) Stratigraphy and sedimen-

tology of shoreface and fluvial conglomerates: insights from

the Cardium Formation in NW Alberta and adjacent British

Columbia. Bull. Can. Petrol. Geol., 51, 437–464.Hoey, T.B. (2004) The size of sedimentary particles. In: A

Practical Guide to the Study of Glacial Sediments (Eds

D.J.A. Evans and D.I. Benn), pp. 52–77. Arnold Publishers,

London, UK.

King, C.A.M. (1972) Beaches and Coasts. Edward Arnold,

London, UK, 570 pp.

King, C.A.M. and Williams, W.W. (1949) The formation and

movement of sand bars by wave action. Geogr. J., 113, 70–85.

Kirk, R.M. (1980) Mixed sand and gravel beaches: morphology,

processes and sediments. Prog. Phys. Geogr., 4, 189–210.Kroon, A. and Masselink, G. (2002) Morphodynamics of

intertidal bar morphology on a macrotidal beach under low-

energy wave conditions, North Lincolnshire, England. Mar.

Geol., 190, 591–608.Krumbein, W.C. and Pettijohn, F.J. (1938) Manual of Sedi-

mentary Petrology. Appleton-Century Crofts, New York, 549

pp.

Maejima, W. (1982) Texture and stratification of gravelly

beach sediments, Enju Beach, Kii Peninsula, Japan. J. Geo-

sci. Osaka City Univ., 25, 35–51.



UNCORRECTEDPROOF

Massari, F. and Parea, G.C. (1988) Progradational gravel beachsequences in a moderate- to high-energy, microtidal marine

environment. Sedimentology, 35, 881–913.Masselink, G. (1993) Simulating the effects of tides on beach

morphodynamics. J. Coastal Res. Spec. Issue, 15, 180–197.Masselink, G. and Short, A.D. (1993) The effect of tidal range

on beach morphodynamics and morphology: a conceptual

beach model. J. Coast. Res., 9, 785–800.McCave, I.N. and Geiser, A.C. (1978) Megaripples, ridges and

runnels on intertidal flats of the Wash, England. Sedimen-

tology, 26, 353–369.McLean, R.F. and Kirk, R.M. (1969) Relationships between

grain size, size-sorting, and foreshore slope on mixed sand-

shingle beaches. NZ J. Geol. Geophys., 12, 138–155.McLeod, M.J. and Johnson, S.C. (1999) Bedrock geological

compilation of the Alma map area (NTS 21 H/14), Albert

County, New Brunswick. Plate 99–25. New Brunswick

Department of Natural Resources and Energy, Minerals and

Energy Division.

Nemec, W. and Steel, R.J. (1984) Alluvial and coastal con-

glomerates: their significant features and some comments on

gravelly mass-flow deposits. In: Sedimentology of Gravelsand Conglomerates (Eds E.H. Koster and R.J. Steel), Memoir

10, pp. 1–31. Canadian Society of Petroleum Geologists,

Calgary, AB, Canada.

Plint, A.G. (1986) Slump blocks, intraformational conglomer-

ates and associated erosional structures in Pennsylvanian

fluvial strata of eastern Canada. Sedimentology, 33, 387–

399.

Postma, G. and Nemec, W. (1990) Regressive and transgressive

sequences in a raised Holocene gravelly beach, southwest-

ern Crete. Sedimentology, 37, 907–920.Pye, K. and French, P.W. (1993) Erosion and Acretion Pro-

cesses on British Salt Marshes. Cambridge Environmental

Research Consultants, Cambridge, UK.

Rampton, V.N., Gauthier, R.C., Thibault, J. and Seaman, A.A.(1984) Quaternary Geology of New Brunswick, Memoir 416.

Geological Survey of Canada, Ottawa.

Reading, H.G. and Collinson, J.D. (1996) Clastic coasts. In:

Sedimentary Environments; Processes, Facies and Strati-

graphy, 3rd edn (Ed. H.G. Reading), pp. 154–231. Blackwell

Science, Oxford, UK.

Rice, S. and Church, M.A. (1996) Sampling surficial fluvial

gravels: the precision of size distribution percentile esti-

mates. J. Sed. Res., 66, 654–665.Roy, P.S., Cowell, P.J., Ferland, M.A. and Thom, B.G. (1994)

Wave-dominated coasts. In: Coastal Evolution: Late Qua-

ternary Shoreline Morphodynamics (Eds R.W.G. Carter and

C.D. Woodroffe), pp. 121–186. Cambridge University Press,

Cambridge, UK.

St. Peter, C. (1996) Carboniferous Geology of the Waterside-

Midway Area (NTS 21 H/10f), Albert County, New Bruns-

wick. Plate 96–51C. New Brunswick Department of Natural

Resources and Energy, Minerals and Energy Division.

Sunamura, T. and Takeda, I. (1984) Landward migration of

inner bars. Mar. Geol., 60, 63–78.Wescott, W.A. and Ethridge, F.G. (1982) Bathymetry and

sediment dispersal dynamics along the Yallahs fan delta

front, Jamaica. Mar. Geol., 46, 245–260.Wolman, M.G. (1954) A method for sampling coarse river-bed

material. Trans. Am. Geophys. Union, 35, 951–956.Wright, L.D., Nielsen, P., Short, A.D. and Green, M.O. (1982)

Morphodynamics of a macrotidal beach. Mar. Geol., 50, 97–128.

Yang, B.C., Dalrymple, R.W. and Chun, S.S. (2005) Sedi-

mentation on a wave-dominated, open-coast tidal flat,

south-western Korea: a summer tidal flat – winter shoreface.

Sedimentology, 52, 235–252.Zonneveld, J.-P. and Moslow, T.F. (2004) Exploration poten-

tial of the Falher G shoreface conglomerate trend: evidence

from outcrop. Bull. Can. Petrol. Geol., 52, 23–38.

Manuscript received 31 May 2005; revision accepted 13December 2005



Marginal mark

Stet

New matter followed by

New letter or new word

under character

e.g.

over character e.g.

and/or

and/or

MARKED PROOFÐÐÐÐÐÐÐÐÐÐÐÐÐÐÐÐÐÐÐÐÐÐÐÐÐÐÐÐÐÐÐÐÐÐÐÐÐÐÐÐÐÐÐÐÐÐÐÐÐÐÐÐÐÐÐÐÐÐÐÐÐÐÐÐÐÐÐÐÐÐÐÐÐÐÐÐÐÐÐÐ

Please correct and return this setÐÐÐÐÐÐÐÐÐÐÐÐÐÐÐÐÐÐÐÐÐÐÐÐÐÐÐÐÐÐÐÐÐÐÐÐÐÐÐÐÐÐÐÐÐÐÐÐÐÐÐÐÐÐÐÐÐÐÐÐÐÐÐÐÐÐÐÐÐÐÐÐÐÐÐÐÐÐÐÐ

Textual mark

under matter to remain

through matter to be deleted

through matter to be deleted

through letter or through

word

under matter to be changed





Encircle matter to be changed

(As above)

through character or where

required

(As above)

(As above)

(As above)

(As above)

(As above)

(As above)

linking letters

between letters affected

between words affected

between letters affected

between words affected

Instruction to printer

Leave unchanged

Insert in text the matter

indicated in the margin

Delete

Delete and close up

Substitute character or

substitute part of one or

more word(s)

Change to italics

Change to capitals

Change to small capitals

Change to bold type

Change to bold italic

Change to lower case

Change italic to upright type

Insert `superior' character

Insert `inferior' character

Insert full stop

Insert comma

Insert single quotation marks

Insert double quotation

marks

Insert hyphen

Start new paragraph

No new paragraph

Transpose

Close up

Insert space between letters

Insert space between words

Reduce space between letters

Reduce space between words

Please use the proof correction marks shown below for all alterations and corrections. Ifyou wish to return your proof by fax you should ensure that all amendments are writtenclearly in dark ink and are made well within the page margins.