geomorphological and sequence stratigraphic variability...

36
Geomorphological and sequence stratigraphic variability in wave-dominated, shoreface-shelf parasequences GARY J. HAMPSON* and JOEP E. A. STORMS  *Department of Earth Science and Engineering, Imperial College London, South Kensington Campus, London SW7 2AZ, UK (E-mail: [email protected])  Department of Applied Earth Sciences, Delft University of Technology, Mijnbouwstraat 120, 2628 RX, Delft, The Netherlands ABSTRACT Physical stratigraphy within shoreface-shelf parasequences contains a detailed, but virtually unstudied, record of shallow-marine processes over a range of historical and geological timescales. Using high-quality outcrop data sets, it is possible to reconstruct ancient shoreface-shelf morphology from clinoform surfaces, and to track the evolving morphology of the ancient shoreface-shelf. Our results suggest that shoreface-shelf morphology varied considerably in response to processes that operate over a range of timescales. (1) Individual clinoform surfaces form as a result of enhanced wave scour and/or sediment starvation, which may be driven by minor fluctuations in relative sea level, sediment supply and/or wave climate over short timescales (10 1 )10 3 years). These external controls cannot be distinguished in vertical facies successions, but may potentially be differentiated by the resulting clinoform geometries. (2) Clinoform geometry and distribution changes systematically within a single parasequence, reflecting the cycle in sea level and/or sediment supply that produced the parasequence (10 2 )10 5 years). These changes record steepening of the shoreface-shelf profile during early progradation and maintenance of a relatively uniform profile during late progradation. Modern shorefaces are not representative of this stratigraphic variability. (3) Clinoform geometries vary greatly between different parasequences as a result of variations in parasequence stacking pattern and relict shelf morphology during shore- face progradation (10 5 )10 8 years). These controls determine the external dimensions of the parasequence. Keywords Clinoform, facies model, parasequence, shelf, shoreface, shoreline trajectory. INTRODUCTION It is frequently difficult to reconcile modern shallow-marine processes with ancient stratigra- phy because of the vastly different timescales considered and the incompleteness of the strati- graphic record, particularly with regard to shore- face-shelf morphology. In this paper, we address this issue of comparison using geomorphological observations from high-quality outcrop data sets of ancient wave-dominated shoreface-shelf sys- tems. Our observations provide sufficient detail to reconstruct ancient shoreface-shelf morphology and to track the evolving morphology of the ancient shoreface-shelf within a detailed sequ- ence stratigraphic context. The aims of this work are: (1) to present a consistent conceptual frame- work that incorporates geomorphological and sequence stratigraphic variability in wave-dom- inated shoreface-shelf deposits and their modern counterparts; and (2) to examine the implications of this framework for current facies models and sequence stratigraphic paradigms. Shoreface-shelf systems in high wave and storm energy settings are commonly represented in the stratigraphic record by upward-coarsen- ing sandstone tongues that contain a distinctive vertical facies succession (i.e. the parasequences Sedimentology (2003) 50, 667–701 doi: 10.1046/j.1365-3091.2003.00570.x Ó 2003 International Association of Sedimentologists 667

Upload: truongkhue

Post on 05-Sep-2018

228 views

Category:

Documents


0 download

TRANSCRIPT

Page 1: Geomorphological and sequence stratigraphic variability …download.xuebalib.com/xuebalib.com.34933.pdf · Geomorphological and sequence stratigraphic variability ... facies model,

Geomorphological and sequence stratigraphic variabilityin wave-dominated, shoreface-shelf parasequences

GARY J. HAMPSON* and JOEP E. A. STORMS�*Department of Earth Science and Engineering, Imperial College London, South Kensington Campus,London SW7 2AZ, UK (E-mail: [email protected])�Department of Applied Earth Sciences, Delft University of Technology, Mijnbouwstraat 120,2628 RX, Delft, The Netherlands

ABSTRACT

Physical stratigraphy within shoreface-shelf parasequences contains a detailed,

but virtually unstudied, record of shallow-marine processes over a range of

historical and geological timescales. Using high-quality outcrop data sets, it is

possible to reconstruct ancient shoreface-shelf morphology from clinoform

surfaces, and to track the evolving morphology of the ancient shoreface-shelf.

Our results suggest that shoreface-shelf morphology varied considerably in

response to processes that operate over a range of timescales. (1) Individual

clinoform surfaces form as a result of enhanced wave scour and/or sediment

starvation, which may be driven by minor fluctuations in relative sea level,

sediment supply and/or wave climate over short timescales (101)103 years).

These external controls cannot be distinguished in vertical facies successions,

but may potentially be differentiated by the resulting clinoform geometries. (2)

Clinoform geometry and distribution changes systematically within a single

parasequence, reflecting the cycle in sea level and/or sediment supply that

produced the parasequence (102)105 years). These changes record steepening

of the shoreface-shelf profile during early progradation and maintenance of a

relatively uniform profile during late progradation. Modern shorefaces are not

representative of this stratigraphic variability. (3) Clinoform geometries

vary greatly between different parasequences as a result of variations in

parasequence stacking pattern and relict shelf morphology during shore-

face progradation (105)108 years). These controls determine the external

dimensions of the parasequence.

Keywords Clinoform, facies model, parasequence, shelf, shoreface, shorelinetrajectory.

INTRODUCTION

It is frequently difficult to reconcile modernshallow-marine processes with ancient stratigra-phy because of the vastly different timescalesconsidered and the incompleteness of the strati-graphic record, particularly with regard to shore-face-shelf morphology. In this paper, we addressthis issue of comparison using geomorphologicalobservations from high-quality outcrop data setsof ancient wave-dominated shoreface-shelf sys-tems. Our observations provide sufficient detail toreconstruct ancient shoreface-shelf morphologyand to track the evolving morphology of the

ancient shoreface-shelf within a detailed sequ-ence stratigraphic context. The aims of this workare: (1) to present a consistent conceptual frame-work that incorporates geomorphological andsequence stratigraphic variability in wave-dom-inated shoreface-shelf deposits and their moderncounterparts; and (2) to examine the implicationsof this framework for current facies models andsequence stratigraphic paradigms.

Shoreface-shelf systems in high wave andstorm energy settings are commonly representedin the stratigraphic record by upward-coarsen-ing sandstone tongues that contain a distinctivevertical facies succession (i.e. the parasequences

Sedimentology (2003) 50, 667–701 doi: 10.1046/j.1365-3091.2003.00570.x

� 2003 International Association of Sedimentologists 667

Page 2: Geomorphological and sequence stratigraphic variability …download.xuebalib.com/xuebalib.com.34933.pdf · Geomorphological and sequence stratigraphic variability ... facies model,

of Van Wagoner et al., 1990). Each sandstonetongue represents an episode of shorelineregression, and is capped by a thin transgressivesuccession that culminates in condensed marineshales (i.e. the flooding surfaces of Van Wagoneret al., 1990). Current facies models of theseshoreface-shelf sandstones emphasize their com-mon, generic features, but fail to address twokey geomorphological and stratigraphic issuesthat account for the variability between them.First, facies models focus on the relationshipbetween vertical facies successions and thedepth of fairweather and storm-wave base (e.g.Elliott, 1986; Walker & Plint, 1992), but do notdirectly relate these properties to ancient shore-face-shelf morphology. However, there is asignificant difference in scale between modernshorefaces, which are defined using nearshoremorphology, and their ancient counterparts,which are interpreted from vertical faciessuccessions using facies models (e.g. Clifton,2000; Fig. 1). Secondly, there is considerablevariability in the external dimensions (thicknessand width) of wave-dominated shoreface-shelfparasequences (Reynolds, 1999; Fig. 1). Thisvariability bears a strong relationship to the

sequence stratigraphic context of individualparasequences within larger progradational orretrogradational parasequence sets (Reynolds,1999; Fig. 1). Such stratigraphic variability can-not be accounted for by ‘static’ facies models(e.g. Elliott, 1986; Walker & Plint, 1992), butmay be explained instead by variations in theangle of shoreline migration (i.e. the shorelinetrajectory of Helland-Hansen & Martinsen, 1996)during different episodes of shoreline regression(e.g. Budding & Inglin, 1981). In this paper,these two aspects of parasequence variabilityare addressed via a consideration of nearshoremorphology and shoreline trajectory withindifferent shoreface-shelf parasequences. Twocase studies of parasequences with markedlydifferent dimensions (thickness and width) andsequence stratigraphic context are presented, inwhich the ancient shoreface-shelf profile andshoreline trajectory are reconstructed via analy-sis of detailed intraparasequence facies archi-tecture. These reconstructions are comparedwith similar data from modern and Holoceneshoreface-shelf sandbodies and with verticalfacies successions of the type emphasized incurrent facies models.

Highstand SystemsTract

ShelfMargin SystemsTract Transgressive Systems Tract

Lowstand Systems Tract

max

imum

wid

th(m

)

maximum thickness(m)

50 000

40

1:100

1:1000

30201000

40 000

30 000

20 000

10 000

'SC4'shoreface tongue

'K4'shoreface tongue

50

Holocene shoreface sands,TexasCoast, Gulf of Mexico

Fig. 1. Plot showing dimensions of ancient shoreface-shelf parasequences differentiated by their sequence strati-graphic context within different systems tracts (modified from Reynolds, 1999). The ‘SC4’ and ‘K4’ tongues describedin this paper are highlighted. Also shown is the range of Holocene shoreface sandbody dimensions along the TexasCoast, Gulf of Mexico (Rodriguez et al., 2001), where the height of the modern shoreface is defined using nearshoremorphology (after Clifton, 2000).

668 G. J. Hampson & J. E. A. Storms

� 2003 International Association of Sedimentologists, Sedimentology, 50, 667–701

Page 3: Geomorphological and sequence stratigraphic variability …download.xuebalib.com/xuebalib.com.34933.pdf · Geomorphological and sequence stratigraphic variability ... facies model,

Morphology, processes and facies modelsof wave-dominated shorefaces and shelves

The main morphological elements of a modernshoreface-shelf system are illustrated in Fig. 2.The foreshore is sculpted by the swash andbackwash of breaking waves, which producedistinctive planar-parallel and wedging lamina-tions (Clifton, 1969), and it dips steeply seawardat 2–3� (Fig. 2; Elliott, 1986; Walker & Plint,1992). The shoreface is characterized by day-to-day sand transport by fairweather waves and dipsseaward at � 0Æ1–0Æ3� (Fig. 2; Elliott, 1986; Cant,1991; Walker & Plint, 1992). Modern shorefacestend towards a concave-upward equilibriumprofile that reflects a balance between sedimentcalibre, active depositional processes and energylevel (Tanner, 1982; Walker & Plint, 1992). Thebase of the shoreface is identified as a break inslope at the base of the equilibrium profile(Clifton, 2000). The dominant fairweather deposi-tional processes on the shoreface involve along-shore and cross-shore sediment transport drivenby shoaling waves (Davis & Hayes, 1984; Walker &Plint, 1992). These processes result in onshoremovement of sand, which maintains the steep(0Æ1–0Æ3�) equilibrium profile, and the develop-ment of a distinctive series of bedforms fromlower to upper shoreface: symmetrical ripples,asymmetrical ripples and asymmetrical dunes(Clifton, 1976). The offshore shelf, where fair-weather waves do not impinge, dips seaward at� 0Æ01–0Æ03� (Fig. 2; Elliott, 1986; Cant, 1991;Walker & Plint, 1992). Deposition on the shelf iscontrolled by episodic storm-wave processes,which result in graded, waning flow beds char-

acterized by hummocky cross-stratification (Dott& Bourgeois, 1982; Walker & Plint, 1992), andother active shelf processes (e.g. tides). However,shelf morphology may be strongly influenced byinactive, relict processes.

The most significant short-term changes inshoreface-shelf profile occur during stormevents when wave base is lowered. This resultsin severe scouring of the shoreface, flattening ofthe shoreface profile and remobilization ofsediment (Hobday & Reading, 1972; Reineck &Singh, 1972; Walker & Plint, 1992). The remo-bilized sediment is transported offshore beyondstorm-wave base (Walker & Plint, 1992),reworked at the shoreface or transported intobackshore environments such as barrier-islandwashovers (Penland et al., 1985). It may takeseveral years for the equilibrium profile of theshoreface to be restored by fairweather waveprocesses after a major storm (e.g. Larson &Kraus, 1994; Lee et al., 1998), and storm-waveproducts may have a high preservation potentialon the shoreface (e.g. Clifton et al., 1971;Greenwood & Sherman, 1986). The preservationof storm-generated deposits above fairweatherwave base presents a challenge when interpret-ing the base of the shoreface in vertical faciessuccessions. As a result, different workers haveinterpreted the base of the shoreface at differentplaces in the same, idealized facies succession(Fig. 3): at the base of hummocky cross-stratifiedsandstone beds (Van Wagoner et al., 1990;Kamola & Van Wagoner, 1995), at the baseof amalgamated swaley-cross-stratified beds(Elliott, 1986; Walker & Plint, 1992) and at apebble lag that underlies trough and tabular

foreshore/beach(dip = 2-3˚)

(lithology: sandstone)

shoreface(dip = 0.1-0.3˚)

(lithology: sandstone)(common burrows:

Skolithos, Arenicolites,Diplocraterion, Ophiomorpha,

Thalassinoides)

inner shelf(dip = 0.03-0.1˚)

(lithology: sandstone and mudstone)(common burrows:

Phycodes, Rhizocorallium,Teichichnus, Terebellina)

mid to outer shelf(dip = 0.01-0.03˚)

(lithology: mudstone)(common burrows:

Phycosiphon, Zoophycos)

L/2

L

5-15 m

1000-2000 m

fairweather wave base

storm wave base

longshore bars

wav

es b

egin

to b

uild

up

spilli

ng b

reak

ers

Fig. 2. Schematic shoreface-shelf profile showing its main morphological elements (modified from Walker & Plint,1992).

Variability in wave-dominated, shoreface-shelf parasequences 669

� 2003 International Association of Sedimentologists, Sedimentology, 50, 667–701

Page 4: Geomorphological and sequence stratigraphic variability …download.xuebalib.com/xuebalib.com.34933.pdf · Geomorphological and sequence stratigraphic variability ... facies model,

cross-beds (Clifton, 2000). In this paper, we usethe terminology of Van Wagoner et al. (1990)and Kamola & Van Wagoner (1995), summarized

in Table 1, to describe shoreface-shelf faciessuccessions, because it can be applied mosteasily to vertical sections.

670 G. J. Hampson & J. E. A. Storms

� 2003 International Association of Sedimentologists, Sedimentology, 50, 667–701

Page 5: Geomorphological and sequence stratigraphic variability …download.xuebalib.com/xuebalib.com.34933.pdf · Geomorphological and sequence stratigraphic variability ... facies model,

DATA SETS AND METHODOLOGY

This paper presents data from two shoreface-shelfparasequences in the Campanian (Upper Creta-ceous) Blackhawk Formation, both of which arenearly continuously exposed in the Book Cliffs,Utah, USA (Figs 4 and 5). These parasequencesoccur within the Kenilworth Member (‘K4’ sho-reface tongue; Figs 5 and 6A) and the SpringCanyon Member (‘SC4’ shoreface tongue; Figs 5and 6B). The time represented by these parase-quences is poorly constrained. Sparse radiometricand palaeontological age data constrain depos-ition of the Blackhawk Formation to between 82Æ5and 79 Ma (Fouch et al., 1983), implying thateach member represents � 0Æ5–0Æ6 Myr, and thatindividual parasequences, including those des-cribed here, represent � 70–120 kyr. Shorelinesin the Blackhawk Formation have a depositionalstrike orientation varying between SSW–NNE(e.g. ‘SC4’ shoreface tongue; Fig. 4A and C) andSSE–NNW (e.g. ‘K4’ shoreface tongue; Fig. 4Aand B).

Both parasequences were studied using meas-ured, logged sections combined with detailedphotomontages and field sketches covering theirentire outcrop extent (Figs 4 and 6). Cliff-facephotomontages allow minor, intraparasequencestratigraphic discontinuities identified in meas-ured vertical sections to be traced laterally, wherethey define clinoforms (Hampson, 2000). Thisapproach has allowed the extents and geometriesof these clinoform surfaces, and the intraparase-quence facies architecture that they define, to bemeasured to a first approximation (relative tophotogrammetric techniques such as those des-cribed by Dueholm & Olsen, 1993). The precisionof the data presented here is limited by twofactors. First, some discontinuity-bounded unitsare too thin (< 50 cm) to be resolved sharply inthe photomontages. Secondly, accurate measuredthicknesses for the studied successions wereobtained only at localities with logged sections. T

able

1.

Su

mm

ary

of

facie

sass

ocia

tion

sin

the

stu

die

dp

ara

sequ

en

ces

(mod

ified

from

Van

Wagon

er

et

al.

,1990;K

am

ola

&V

an

Wagon

er,

1995;P

att

ison

,1995;

Taylo

r&

Lovell

,1995).

Lit

hofa

cie

sass

ocia

tion

Lit

holo

gy

an

dse

dim

en

tary

stru

ctu

res

Bio

turb

ati

on

Fore

shore

(FS

)U

pp

er

fin

e-g

rain

ed

san

dst

on

e.

Pla

nar-

para

llel

lam

inati

on

.A

bse

nt

Up

per

shore

face

(US

F)

Up

per

fin

e-

tolo

wer

med

ium

-gra

ined

san

dst

on

e.

Tro

ugh

an

dta

bu

lar

cro

ss-b

ed

s,m

inor

pla

nar

lam

inati

on

an

dsw

ale

ycro

ss-s

trati

ficati

on

Sp

ars

eto

mod

era

te(O

ph

iom

orp

ha,

Skoli

thos,

Cyli

nd

rich

nu

s,A

ren

icoli

tes)

Pro

xim

al

low

er

shore

face

(pL

SF

)A

malg

am

ate

dbed

sof

up

per

fin

e-g

rain

ed

san

dst

on

e.

Sw

ale

yan

dh

um

mocky

cro

ss-s

trati

ficati

on

,m

inor

wavy

lam

inati

on

an

dw

ave

rip

ple

cro

ss-l

am

inati

on

.

Mod

era

teto

inte

nse

(Op

hio

morp

ha,

Pala

eop

hycu

s,A

ren

icoli

tes,

Teic

hic

hn

us,

Th

ala

ssin

oid

es)

Dis

tal

low

er

shore

face

an

din

ner

shelf

/ram

p(d

LS

F)

Non

-am

alg

am

ate

dbed

sof

up

per

fin

e-g

rain

ed

san

dst

on

ew

ith

mu

dst

on

ean

dsi

ltst

on

ein

terb

ed

s.H

um

mocky

cro

ss-s

trati

ficati

on

,m

inor

wavy

lam

inati

on

an

dw

ave

rip

ple

cro

ss-l

am

inati

on

.

Mod

era

teto

inte

nse

(Op

hio

morp

ha,

Pla

noli

tes,

Pala

eop

hycu

s,T

ere

bell

ina,

Are

nic

oli

tes,

Teic

hic

hn

us,

Th

ala

ssin

oid

es)

Off

shore

shelf

/ra

mp

(OS

)M

ud

ston

ean

dsi

ltst

on

ew

ith

bed

sof

very

fin

e-

tou

pp

er

fin

e-g

rain

ed

san

dst

on

e.

Para

llel

lam

inati

on

,w

ave

an

dcu

rren

tri

pp

lecro

ss-l

am

inati

on

.

Inte

nse

(Pla

noli

tes,

Pala

eop

hycu

s,T

ere

bell

ina,

Teic

hic

hn

us,

Ch

on

dri

tes,

Helm

inth

op

sis)

Wave-i

nfl

uen

ced

delt

afr

on

t(D

F)

Up

per

fin

e-g

rain

ed

san

dst

on

ebed

sw

ith

mu

dst

on

ean

dsi

ltst

on

ein

terb

ed

s.B

ed

sth

icken

an

dam

alg

am

ate

up

ward

sth

rou

gh

the

success

ion

.P

lan

ar-

para

llel

lam

inati

on

,cli

mbin

gcu

rren

tri

pp

lecro

ss-l

am

inati

on

,w

ave

an

dcu

rren

tri

pp

lecro

ss-l

am

inati

on

.

Mod

era

te(O

ph

iom

orp

ha,

Cyli

nd

rich

nu

s,P

lan

oli

tes,

Pala

eop

hycu

s,R

oss

eli

a,

Con

ich

nu

s,T

eic

hic

hn

us,

Dip

locra

teri

on

,R

hiz

ocora

lliu

m,

Th

ala

ssin

oid

es)

Fig. 3. Idealized vertical facies succession through awave-dominated shoreface-shelf parasequence, high-lighting different interpretations of the morphologicalelements shown in Fig. 2 (after Elliott, 1986; VanWagoner et al., 1990; Walker & Plint, 1992; Kamola &Van Wagoner, 1995; Clifton, 2000). This paper uses thefacies association terminology of Van Wagoner et al.(1990) and Kamola & Van Wagoner (1995): offshoreshelf/ramp (OS), distal lower shoreface and inner shelf/ramp (dLSF), proximal lower shoreface (pLSF), uppershoreface (USF), foreshore (FS).

Variability in wave-dominated, shoreface-shelf parasequences 671

� 2003 International Association of Sedimentologists, Sedimentology, 50, 667–701

Page 6: Geomorphological and sequence stratigraphic variability …download.xuebalib.com/xuebalib.com.34933.pdf · Geomorphological and sequence stratigraphic variability ... facies model,

Elsewhere, the successions are exposed in inac-cessible, sheer cliff faces.

The two studied parasequences differ mark-edly in their thickness, their internal sedimen-

tological character and their sequence strati-graphic setting. The ‘SC4’ shoreface tongue hasa maximum thickness of 20 m, a dip extent of22 km (from landward to seaward pinch-outs of

A

B

C

672 G. J. Hampson & J. E. A. Storms

� 2003 International Association of Sedimentologists, Sedimentology, 50, 667–701

Page 7: Geomorphological and sequence stratigraphic variability …download.xuebalib.com/xuebalib.com.34933.pdf · Geomorphological and sequence stratigraphic variability ... facies model,

marine sandstone) and is documented to record‘normal regression’ within the early part of ahighstand systems tract (Fig. 1; Van Wagoneret al., 1990; Kamola & Van Wagoner, 1995). Thisparasequence is also interpreted to record atransition in shoreline type from wave-domi-nated shoreface to wave-influenced delta duringprogradation (Kamola & Van Wagoner, 1995).The ‘K4’ shoreface tongue has a maximumthickness of 45 m and a dip extent of 15 km(Fig. 1; Pattison, 1995; Taylor & Lovell, 1995;Hampson, 2000). This parasequence is documen-ted to record ‘forced regression’ of a wave-dominated shoreface (Pattison, 1995; Hampson,2000) and has been placed within the late part ofa highstand systems tract (Taylor & Lovell, 1995)and, alternatively, the late part of a highstandsystems tract to a lowstand systems tract (Patti-son, 1995; Hampson, 2000).

In order to reconstruct true spatial relation-ships in the study data sets, the clinoformgeometries and clinoform-defined facies architec-tures measured along cliff-face panels have beenprojected into the plane of regional depositionaldip (as defined by Kamola & Van Wagoner, 1995in the ‘SC4’ shoreface tongue and by Hampson,2000 in the ‘K4’ shoreface tongue; Fig. 4B and C).This procedure is relatively straightforward inthe ‘K4’ shoreface tongue and the palaeoland-ward portion of the ‘SC4’ shoreface tongue,which are characterized by linear, wave-domin-ated shorelines (Kamola & Van Wagoner, 1995;Taylor & Lovell, 1995; Hampson, 2000). Deposi-tional dip trends are more difficult to reconstructfor the wave-influenced deltaic shorelines of thepalaeoseaward portion of the ‘SC4’ shorefacetongue.

FACIES ASSOCIATIONS ANDCLINOFORM SURFACES

Intraparasequence facies architecture is definedby the facies associations present within theparasequence and by the dipping clinoform sur-faces to which intraparasequence facies distribu-tions are conditioned (e.g. Budding & Inglin,1981). These two components are describedbriefly below.

Facies associations: wave-dominatedshoreface-shelf and wave-influenced deltafront

The facies associations present within thetwo studied parasequences have been describedand interpreted in detail by previous workers(Howard & Frey, 1984; Van Wagoner et al.,1990; Kamola & Van Wagoner, 1995; Pattison,1995; Taylor & Lovell, 1995) and are sum-marized below. Five facies associations areinterpreted to represent wave-dominated shore-face-shelf deposits (e.g. Van Wagoner et al.,1990; Table 1): (1) interbedded rippled sand-stones and bioturbated mudstones, interpretedas offshore marine shelf/ramp (OS) deposits; (2)non-amalgamated hummocky cross-stratifiedsandstones, interpreted as distal lower shorefaceand inner shelf/ramp (dLSF) deposits; (3) amal-gamated hummocky and swaley cross-stratifiedsandstones, interpreted as proximal lower shore-face (pLSF) deposits; (4) cross-bedded sand-stones, interpreted as upper shoreface deposits(USF); and (5) planar-parallel-laminated sand-stones, interpreted as foreshore (FS) deposits.These five facies associations are arranged in adistinctive vertical succession of facies that isinterpreted to record an overall shallowing fromoffshore shelf/ramp deposits via distal andproximal lower shoreface deposits to uppershoreface and foreshore deposits (Figs 6, 7A–Dand 8).

An additional facies association in the ‘SC4’shoreface tongue is interpreted to represent wave-influenced delta front deposits (Kamola & VanWagoner, 1995; Table 1). This facies associationcomprises an upward-coarsening succession ofnon-amalgamated to amalgamated sandstonebeds, in which individual beds are characterizedby a distinctive vertical succession of structuresthat records deposition from waning, unidirec-tional currents: planar-parallel lamination over-lain by climbing or non-climbing current ripplecross-lamination (Figs 6B, 7E and 9). Bed tops are

Fig. 4. (A) Map of the Book Cliffs in east-central Utahshowing the location and extent of the two study areas.(B) Detailed maps of the first study area, which con-tains the ‘K4’ shoreface tongue, Kenilworth Member(Fig. 5). (C) Detailed maps of the second study area,which contains the ‘SC4’ shoreface tongue, SpringCanyon Member. The detailed maps of both areas showthe location of measured outcrop sections (includingthe logged sections illustrated in Figs 7, 8A and 9A),correlation panels (Fig. 6), photomontage-based cliff-face panels (Figs 12 and 13) and depositional strike anddip. Closed circles denote measured, logged sections.Open circles denote the location of prominent topo-graphic features that allow the mapped cliff line to betied directly to continuous photomontages of the cliffface (e.g. Fig. 10).

Variability in wave-dominated, shoreface-shelf parasequences 673

� 2003 International Association of Sedimentologists, Sedimentology, 50, 667–701

Page 8: Geomorphological and sequence stratigraphic variability …download.xuebalib.com/xuebalib.com.34933.pdf · Geomorphological and sequence stratigraphic variability ... facies model,

Fig

.5.

Su

mm

ary

stra

tigra

ph

iccro

ss-s

ecti

on

thro

ugh

the

Bla

ckh

aw

kF

orm

ati

on

(aft

er

Bals

ley,

1980;

Ham

pso

net

al.

,2001

an

dre

fere

nces

there

in).

Datu

mh

ori

zon

sare

regio

nall

yexte

nsi

ve

lith

ost

rati

gra

ph

icm

ark

ers

.D

ocu

men

ted

sequ

en

ce

bou

nd

ari

es

are

labell

ed

as

foll

ow

s:A

SB

,A

berd

een

sequ

en

ce

bou

nd

ary

;K

SB

,K

en

ilw

ort

hse

qu

en

ce

bou

nd

ary

;S

SB

,S

un

nysi

de

sequ

en

ce

bou

nd

ary

;G

SB

1–3,

Gra

ssy

sequ

en

ce

bou

nd

ari

es

1–3;

DS

B,

Dese

rtse

qu

en

ce

bou

nd

ary

;C

SB

,C

ast

legate

sequ

en

ce

bou

nd

ary

.S

hore

face

ton

gu

es

are

nu

mbere

dw

ith

inth

eS

pri

ng

Can

yon

(SC

1–7),

Aberd

een

(A1–4),

Ken

ilw

ort

h(K

1–5),

Su

nn

ysi

de

(S1–3)

an

dG

rass

yM

em

bers

(G1–4).

Th

etw

osh

ore

face

ton

gu

es

desc

ribed

ind

eta

ilin

this

pap

er

(‘S

C4’

an

d‘K

4’)

are

hig

hli

gh

ted

.

674 G. J. Hampson & J. E. A. Storms

� 2003 International Association of Sedimentologists, Sedimentology, 50, 667–701

Page 9: Geomorphological and sequence stratigraphic variability …download.xuebalib.com/xuebalib.com.34933.pdf · Geomorphological and sequence stratigraphic variability ... facies model,

A B

Fig

.6.

Corr

ela

tion

pan

els

thro

ugh

the

stu

die

dp

ara

sequ

en

ces:

(A)

the

‘K4’

ton

gu

ean

d(B

)th

e‘S

C4’

ton

gu

e,

show

ing

logged

secti

on

san

dgro

ssfa

cie

sd

istr

i-bu

tion

s.B

oth

pan

els

are

pro

jecte

din

toth

ep

lan

eof

regio

nal

dep

osi

tion

al

dip

for

each

para

sequ

en

ce

(Fig

.4).

Logged

secti

on

ssh

ow

nin

more

deta

ilin

Fig

.7

are

hig

hli

gh

ted

.T

he

corr

ela

tion

pan

els

do

not

rep

rese

nt

cli

nofo

rm-d

efi

ned

facie

sarc

hit

ectu

re,w

hic

his

show

nin

stead

inth

ep

hoto

mon

tage-b

ase

dli

ne

dra

win

gs

inF

igs

12

an

d13.

Th

ed

ep

osi

tion

al

dip

exte

nt

of

these

ph

oto

mon

tages

ish

igh

ligh

ted

.

Variability in wave-dominated, shoreface-shelf parasequences 675

� 2003 International Association of Sedimentologists, Sedimentology, 50, 667–701

Page 10: Geomorphological and sequence stratigraphic variability …download.xuebalib.com/xuebalib.com.34933.pdf · Geomorphological and sequence stratigraphic variability ... facies model,

A

Fig. 7.

676 G. J. Hampson & J. E. A. Storms

� 2003 International Association of Sedimentologists, Sedimentology, 50, 667–701

Page 11: Geomorphological and sequence stratigraphic variability …download.xuebalib.com/xuebalib.com.34933.pdf · Geomorphological and sequence stratigraphic variability ... facies model,

reworked by wave ripples and bioturbation.These beds are interpreted to record episodicdeposition from unidirectional flows, most prob-

ably fed by river floods at the mouth of the deltadistributary. The upward thickening and upwardamalgamation of beds within the succession are

Fig. 7. Detailed sedimentary logs through the studied parasequences showing sedimentology, facies and sequencestratigraphic interpretations: (A) the ‘K4’ tongue at Middle Mountain measured section 1 (Figs 4B, 6A and 12A); (B)the ‘K4’ tongue at Middle Mountain measured section 3 (Figs 4B, 6A and 12A); (C) the ‘SC4’ tongue at Peerless Mine(Figs 4C, 6B and 8A); (D) the ‘SC4’ tongue in the northern face of Spring Canyon (Figs 4C, 6B and 12C); and (E) the‘SC4’ tongue in the eastern ‘Kenilworth Face’, at Kenilworth measured section 1 (Figs 4C, 6B, 9A, 11B and 13C).Minor stratigraphic discontinuities are highlighted here and discussed further in the text. Key as for Fig. 3.

Variability in wave-dominated, shoreface-shelf parasequences 677

� 2003 International Association of Sedimentologists, Sedimentology, 50, 667–701

Page 12: Geomorphological and sequence stratigraphic variability …download.xuebalib.com/xuebalib.com.34933.pdf · Geomorphological and sequence stratigraphic variability ... facies model,

interpreted to represent increasing proximity tothe distributary mouth, which was the source ofthe episodic unidirectional flows, during anoverall shallowing. Waning-flow beds character-

ized by climbing current ripple cross-laminationare also observed in the storm-dominated, prox-imal lower shoreface deposits of the ‘SC4’ tongue(Fig. 9C). Their occurrence implies that episodic

C

E

Fig. 7. Continued.

678 G. J. Hampson & J. E. A. Storms

� 2003 International Association of Sedimentologists, Sedimentology, 50, 667–701

Page 13: Geomorphological and sequence stratigraphic variability …download.xuebalib.com/xuebalib.com.34933.pdf · Geomorphological and sequence stratigraphic variability ... facies model,

D

Fig

.7.

Con

tin

ued

.

Variability in wave-dominated, shoreface-shelf parasequences 679

� 2003 International Association of Sedimentologists, Sedimentology, 50, 667–701

Page 14: Geomorphological and sequence stratigraphic variability …download.xuebalib.com/xuebalib.com.34933.pdf · Geomorphological and sequence stratigraphic variability ... facies model,

storm- and river-mouth-derived currents wereboth active during deposition of the ‘SC4’ tongue,and the latter may have played a more significantrole in intratongue facies architecture than hasbeen interpreted previously (Van Wagoner et al.,1990; Kamola & Van Wagoner, 1995).

The vertical successions described aboverepresent the progradation of depositional sys-tems in which all the facies components arelinked genetically (i.e. the parasequences of VanWagoner et al., 1990). These successions can besubdivided internally into smaller genetic faciessuccessions bounded by minor stratigraphic dis-continuities (i.e. the bedsets of Van Wagoneret al., 1990).

Clinoform surfaces defined by minor,intraparasequence stratigraphicdiscontinuities

Minor stratigraphic discontinuities are recog-nized in both the parasequences described in

this paper (e.g. Figs 7 and 10) and in similaroutcrop and subsurface data sets (Valasek, 1990;O’Byrne & Flint, 1995; Jennette & Riley, 1996).The discontinuities have greater genetic signifi-cance than simple bedding surfaces and corre-spond closely to the bedset boundaries of VanWagoner et al. (1990). These surfaces defineclinoforms that dip gently palaeoseaward(Fig. 11) and are interpreted as preserved rem-nants of the ancient shoreface-shelf profile (e.g.McCubbin, 1982; Hampson, 2000). The utility ofthe surfaces is twofold. First, the physical char-acter and geometry of the discontinuity surfacesrecords the response of the ancient shoreface-shelf profile to short-term processes that arecomparable to those observed and measured inmodern settings (estimated at 101)103 years;Table 2). Secondly, the spatial distribution ofthe discontinuities within a parasequenceprovides a record of the shoreline trajectoryduring intermediate-term regression (estimatedat 102)105 years).

A B

C

Fig. 8. Photographs of wave-dominated shoreface-shelf successions in the ‘SC4’ tongue. (A) The vertical successionat Peerless Mine (Figs 4C, 6B and 7C) contains several non-depositional discontinuities. (B) The upper two non-depositional discontinuities in this succession are marked by rooted surfaces within anomalously thick foreshore(FS) deposits (at 21Æ3 m and 22Æ0 m in Fig. 7C), and they record minor transgressions. (C) Non-depositional dis-continuities in proximal lower shoreface facies (pLSF) are typically marked by intense bioturbation (e.g. at 13Æ5 m inthe eastern measured section in the northern face of Spring Canyon, Fig. 7D).

680 G. J. Hampson & J. E. A. Storms

� 2003 International Association of Sedimentologists, Sedimentology, 50, 667–701

Page 15: Geomorphological and sequence stratigraphic variability …download.xuebalib.com/xuebalib.com.34933.pdf · Geomorphological and sequence stratigraphic variability ... facies model,

Non-depositional discontinuitiesNon-depositional discontinuities are observedin both wave-dominated shoreface successionsand wave-influenced delta front successions(Table 2). In the former, they are marked by anabrupt decrease in the thickness and amalgama-tion of storm-generated event beds within prox-imal and distal lower shoreface and offshoreshelf/ramp facies (Fig. 7A–D). In the latter, theyare marked by a similarly abrupt decrease in thethickness and amalgamation of river flood-gen-erated event beds within delta front facies(Figs 7E and 9A). In both types of succession,the discontinuities are also marked by anincrease in the intensity of bioturbation. Asthe surfaces are traced palaeolandward intomore proximal strata, where mudstones areabsent, they may be characterized only bymoderate to intense bioturbation (Fig. 8C, alsocompare the palaeoseaward section shown inFig. 7B with the palaeolandward section shownin Fig. 7A). Further palaeolandward, the surfa-ces become more cryptic in expression and maybe represented by bedding surfaces with nodistinctive characteristics in vertical section[e.g. the surface between Pattison’s (1995) bed-sets 8a and 8b cannot be identified clearly

palaeolandward of the section shown in Fig. 7A].In these proximal settings, however, some discon-tinuities are marked by an anomalous incursion ofmore distal facies; for example, an incursion ofamalgamated storm-generated event beds, repre-senting proximal lower shoreface facies, intoupper shoreface facies [e.g. the surface betweenPattison’s (1995) bedsets 8b and 8c in Fig. 7A]. Inthe ‘SC4’ tongue, several of these discontinuitiescan be traced to their palaeolandward limit, wherethey occur within anomalously thick (> 2 m)successions of foreshore deposits (Fig. 7C andD). Individual discontinuity surfaces may bemarked by rooted surfaces in these foreshoresuccessions (Figs 7C and 8A and B).

The physical characteristics of these surfacessuggest that they record episodes of reducedsedimentation, which produced more intensebioturbation, synchronous with a decrease insand supply and/or river flood frequency or stormwave energy, which suppressed bed amalgama-tion (Hampson, 2000). Thus, these surfaces mayhave formed by three mechanisms: (1) decreasesin storm or river flood event frequency; (2)changes to a less energetic wave/storm climate;and (3) minor rises in relative sea level (e.g. Dott &Bourgeois, 1982; Hampson, 2000; Storms, 2003).

A B

C

Fig. 9. Photographs of wave-influenced delta front successions in the ‘SC4’ tongue. (A) The vertical succession atKenilworth measured section 1 (Figs 4C, 6B and 7E) contains several non-depositional discontinuities that can betraced out to define clinoform surfaces (Fig. 11B). The transgressive surface at the top of this succession (B) is markedby a coarse-grained lag deposit (at 13Æ7 m in Fig. 7E). (C) Continuous successions of climbing asymmetrical ripplesoccurring within proximal lower shoreface facies (pLSF) of wave-dominated shoreface successions, such as that atGilson Gulch (Figs 4C and 6B), record deposition from sustained unidirectional currents. These successions mayindicate episodic deposition by river floods in an environment that is otherwise dominated by storm-wave processes.

Variability in wave-dominated, shoreface-shelf parasequences 681

� 2003 International Association of Sedimentologists, Sedimentology, 50, 667–701

Page 16: Geomorphological and sequence stratigraphic variability …download.xuebalib.com/xuebalib.com.34933.pdf · Geomorphological and sequence stratigraphic variability ... facies model,

A B C

Fig

.10.

Exam

ple

of

the

meth

od

olo

gy

use

dto

recon

stru

ct

deta

iled

,cli

nofo

rm-d

efi

ned

facie

sarc

hit

ectu

rein

the

stu

die

dp

ara

sequ

en

ces.

(A)

Ph

oto

mon

tage

of

the

‘SC

4’

ton

gu

ealo

ng

part

of

the

nort

hfa

ce

of

Sp

rin

gC

an

yon

(Fig

.4C

),an

nota

ted

tosh

ow

the

tran

sgre

ssiv

esu

rfaces

that

bou

nd

the

para

sequ

en

ce

an

dse

lecte

dd

iscon

tin

uit

ysu

rfaces

wit

hin

the

para

sequ

en

ce.

Th

ep

hoto

mon

tage

isori

en

ted

ap

pro

xim

ate

lyalo

ng

dep

osi

tion

al

stri

ke.

(B)

Lin

ed

raw

ing

of

the

ph

oto

mon

tage

hig

hli

gh

tin

gth

esa

me

surf

aces

an

dfa

cie

sd

istr

ibu

tion

s.(C

)S

imp

lifi

ed

an

dvert

icall

yexaggera

ted

lin

ed

raw

ing

from

the

ph

oto

mon

tage,in

the

form

at

of

the

cli

ff-

face

pan

els

show

nin

Fig

s12

an

d13.

682 G. J. Hampson & J. E. A. Storms

� 2003 International Association of Sedimentologists, Sedimentology, 50, 667–701

Page 17: Geomorphological and sequence stratigraphic variability …download.xuebalib.com/xuebalib.com.34933.pdf · Geomorphological and sequence stratigraphic variability ... facies model,

A B

Fig

.11.

Un

inte

rpre

ted

an

din

terp

rete

dp

hoto

mon

tages

show

ing

cli

nofo

rmsu

rfaces

inth

est

ud

ied

para

sequ

en

ces.

(A)

Non

-dep

osi

tion

al

an

dero

sion

al

dis

-con

tin

uit

ies

(labell

ed

‘nd

’an

d‘e

’re

specti

vely

)d

efi

nin

geast

ward

-dip

pin

gcli

nofo

rms

inw

ave-d

om

inate

dsh

ore

face

dep

osi

tsof

the

‘K4’

ton

gu

e,

alo

ng

the

sou

thern

face

of

Blu

eC

ast

leB

utt

e(F

ig.

4B

).(B

)N

on

-dep

osi

tion

al

dis

con

tin

uit

ies

(labell

ed

‘nd

’)d

efi

nin

gso

uth

ward

-dip

pin

gcli

nofo

rms

inw

ave-i

nfl

uen

ced

delt

afr

on

td

ep

osi

tsof

the

dis

tal

‘SC

4’

ton

gu

e,

at

Ken

ilw

ort

hm

easu

red

secti

on

1(F

igs

4C

,7E

an

d9A

).B

oth

ph

oto

mon

tages

are

ali

gn

ed

ap

pro

xim

ate

lyalo

ng

dep

osi

tion

al

dip

.

Variability in wave-dominated, shoreface-shelf parasequences 683

� 2003 International Association of Sedimentologists, Sedimentology, 50, 667–701

Page 18: Geomorphological and sequence stratigraphic variability …download.xuebalib.com/xuebalib.com.34933.pdf · Geomorphological and sequence stratigraphic variability ... facies model,

Each of these mechanisms is highly probablealong wave-dominated and wave-influencedshorelines, but distinguishing their products inthe stratigraphic record is not easy. Those dis-continuity surfaces in the palaeolandward, wave-dominated part of the ‘SC4’ tongue that can betraced into upper shoreface and foreshore depos-its (Figs 7D, 8A and B and 12B and C) and aremarked by rooted surfaces in the latter (Figs 7Cand 8B) are demonstrably associated with minortransgressions (mechanism 3 above). However,discontinuity surfaces that can only be identifiedand traced within lower shoreface and delta frontdeposits, where sandstone deposition occursexclusively via episodic storm and/or river floodevents, are equally attributable to each of thethree mechanisms. Each mechanism impliessubtle, geometrical changes in the shorefaceprofile and resulting clinoforms: (1) a decreasein sedimentation event frequency will result in nosignificant change in shoreface profile; (2) adecrease in wave energy, and resulting shallow-ing of fairweather wave base, will result in adecrease in the gradient of the shoreface profile,as a result of reduced onshore sand advection(Inman & Bagnold, 1963; Carey et al., 1999;Storms, 2003); and (3) a minor rise in relativesea level will not cause a change in shoreface-shelf profile geometry, although some transgres-sive reworking of upper shoreface and foreshoredeposits may occur if sediment supply rates arelow. These changes in clinoform geometry are notapparent in one-dimensional, vertical logged sec-tions and are discussed below in relation toobservations in the ‘SC4’ and ‘K4’ tongues.

Erosional discontinuitiesErosional discontinuities are observed in wave-dominated shoreface successions only (Table 2).They are marked in vertical sections throughproximal and distal lower shoreface and offshoreshelf/ramp facies by erosion, a discontinuous lagof wood fragments and plant debris and abruptincreases in storm-generated event bed amalga-mation, grain size and sand content (Fig. 7A). Thediscontinuities occur at the base of amalgamatedhummocky cross-stratified beds in units 30 cm to7 m thick that pass upward into non-amalgama-ted beds (Hampson, 2000). The surfaces may alsobe associated with steep-walled gutter casts and aGlossifungites ichnofacies. The discontinuitiesare traced palaeolandward into amalgamated,erosionally based sandstone beds in proximallower shoreface facies, where they become diffi-cult to identify.T

able

2.

Su

mm

ary

of

min

or

stra

tigra

ph

icd

iscon

tin

uit

ysu

rfaces

inth

est

ud

ied

para

sequ

en

ces.

Su

rface

Recogn

itio

ncri

teri

aG

eom

etr

y,

exte

nt

Gen

esi

s

Non

-dep

osi

tion

al

dis

con

tin

uit

y(1

)A

bru

pt

decre

ase

ineven

tbed

thic

kn

ess

an

dam

alg

am

ati

on

(OS

,d

LS

F,

pL

SF

,D

Ffa

cie

s);

(2)

Incre

ase

inbio

turb

ati

on

inte

nsi

ty(O

S,

dL

SF

,p

LS

F,

DF

facie

s);

(3)

An

om

alo

us

facie

sin

terfi

ngeri

ng

(pL

SF

,U

SF

,F

Sfa

cie

s)

Gen

tly

dip

pin

g,

con

cave-u

pw

ard

cli

nofo

rms

(Fig

.12A

,B

an

dD

)H

iatu

sin

sed

imen

tati

on

:(1

)d

ecre

ase

inst

orm

or

river

flood

even

tfr

equ

en

cy;

(2)

ch

an

ges

toa

less

en

erg

eti

cw

ave/s

torm

cli

mate

;(3

)m

inor

rise

inre

lati

ve

sea

level

Ero

sion

al

dis

con

tin

uit

y(1

)A

bru

pt

incre

ase

sin

storm

-gen

era

ted

even

tbed

am

alg

am

ati

on

,gra

insi

ze

an

dsa

nd

con

ten

t(d

LS

F,

pL

SF

facie

s);

(2)

Dis

con

tin

uou

sla

gof

wood

fragm

en

tsan

dp

lan

td

ebri

s;(3

)S

teep

-wall

ed

gu

tter

cast

san

dG

loss

ifu

ngit

es

ich

nofa

cie

s.

Gen

tly

dip

pin

g,

con

cave-u

pw

ard

cli

nofo

rms

(Fig

.12C

)E

nh

an

ced

storm

-wave

scou

r:(1

)ch

an

ge

toa

more

en

erg

eti

cw

ave/s

torm

cli

mate

;(2

)m

inor

fall

inre

lati

ve

sea

level

684 G. J. Hampson & J. E. A. Storms

� 2003 International Association of Sedimentologists, Sedimentology, 50, 667–701

Page 19: Geomorphological and sequence stratigraphic variability …download.xuebalib.com/xuebalib.com.34933.pdf · Geomorphological and sequence stratigraphic variability ... facies model,

Fig

.12.

An

nota

ted

cli

ff-f

ace

pan

els

thro

ugh

wave-d

om

inate

dsh

ore

face

dep

osi

tsin

the

stu

die

dp

ara

sequ

en

ces,

base

don

measu

red

secti

on

s(e

.g.F

igs

6an

d7A

–D

)an

dp

hoto

mon

tages

(e.g

.F

igs

10

an

d11A

).T

he

pan

els

are

pro

jecte

din

toth

ep

lan

eof

regio

nal

dep

osi

tion

al

dip

for

each

para

sequ

en

ce

(Fig

.4).

Tra

nsg

ress

ive

surf

aces

an

dse

lecte

dm

inor,

intr

ap

ara

sequ

en

ce

stra

tigra

ph

icd

iscon

tin

uit

ies,

wh

ich

defi

ne

cli

nofo

rms,

are

labell

ed

.T

he

min

or

stra

tigra

ph

icd

iscon

tin

uit

ies

are

dip

pin

g,

thro

ugh

goin

gsu

rfaces

that

can

be

traced

up

-dip

an

dd

ow

n-d

ipbetw

een

facie

sass

ocia

tion

s,alt

hou

gh

they

coin

cid

elo

call

yw

ith

facie

sass

ocia

tion

bou

nd

ari

es

over

part

of

their

len

gth

.P

an

els

are

from

the

foll

ow

ing

para

sequ

en

ces

(Fig

s4

an

d6):

(A)

the

‘K4’to

ngu

ealo

ng

the

sou

thern

face

of

Mid

dle

Mou

nta

inan

dG

un

nis

on

Bu

tte;

(B)

the

‘SC

4’

ton

gu

ealo

ng

the

nort

hern

face

of

Wil

dcat

Can

yon

;an

d(C

)th

e‘S

C4’

ton

gu

ealo

ng

the

nort

hern

face

of

Sp

rin

gC

an

yon

.N

ote

that

(A)

issh

ow

nat

half

the

hori

zon

tal

an

dvert

ical

scale

of

(B)

an

d(C

).K

ey

as

for

Fig

.10.

Variability in wave-dominated, shoreface-shelf parasequences 685

� 2003 International Association of Sedimentologists, Sedimentology, 50, 667–701

Page 20: Geomorphological and sequence stratigraphic variability …download.xuebalib.com/xuebalib.com.34933.pdf · Geomorphological and sequence stratigraphic variability ... facies model,

Fig

.13.

An

nota

ted

cli

ff-f

ace

pan

els

thro

ugh

wave-i

nfl

uen

ced

delt

afr

on

td

ep

osi

tsin

the

‘SC

4’

ton

gu

e,

base

don

measu

red

secti

on

s(e

.g.

Fig

.7E

)an

dp

hoto

-m

on

tages

(e.g

.F

igs

10

an

d11B

).T

he

pan

els

are

pro

jecte

din

toth

ep

lan

es

of

regio

nal

dep

osi

tion

al

dip

an

dst

rike

(Fig

.4).

Tra

nsg

ress

ive

surf

aces

an

dse

lecte

dm

inor,

non

-dep

osi

tion

al

dis

con

tin

uit

ies,

wh

ich

defi

ne

cli

nofo

rms,

are

labell

ed

.D

ipp

an

els

are

locate

das

foll

ow

s(F

igs

4C

an

d6B

):(A

)alo

ng

the

nort

hern

face

of

Pan

ther

Can

yon

;(B

)alo

ng

the

‘Mart

inF

ace’;

an

d(C

)alo

ng

the

‘Help

er

Face’

an

d‘K

en

ilw

ort

hF

ace’.

Str

ike

pan

els

are

locate

das

foll

ow

s(F

ig.

4):

(D)

alo

ng

the

east

ern

face

of

Help

er

Can

yon

;(E

)alo

ng

the

west

ern

‘Ken

ilw

ort

hF

ace’;

an

d(F

an

dG

),east

of

Ken

ilw

ort

h.

Key

as

for

Fig

.10.

686 G. J. Hampson & J. E. A. Storms

� 2003 International Association of Sedimentologists, Sedimentology, 50, 667–701

Page 21: Geomorphological and sequence stratigraphic variability …download.xuebalib.com/xuebalib.com.34933.pdf · Geomorphological and sequence stratigraphic variability ... facies model,

These discontinuities are characterized byerosion, a discrete increase in sand supply andan increase in storm wave energy, whichenhanced bed amalgamation. In combination,these features suggest a lowering of storm wavebase. Gutter casts and Glossifungites ichnofaciesassociated with some of the discontinuitiesrecord scouring and burrowing into a partlylithified substrate (MacEachern et al., 1992) thatmay have been exhumed by erosion at thediscontinuity surface. These surfaces, recordinga lowering of storm wave base, may have formedby two mechanisms: (1) changes to a moreenergetic wave/storm climate; and (2) minorfalls in relative sea level (e.g. Dott & Bourgeois,1982; Storms, 2003). Distinguishing the productsof these two mechanisms in the stratigraphicrecord is difficult, particularly where the dis-continuity surfaces can only be traced withinlower shoreface and inner shelf deposits (e.g. inthe ‘K4’ tongue, Figs 7A and 12A). The formermechanism implies no relative change in waterdepth, but would be associated with a steepen-ing of the shoreface profile, as a result of anincrease in advective, onshore sand transport(Inman & Bagnold, 1963; Carey et al., 1999;Storms, 2003). The geometry of the shorefaceprofile produced via the latter mechanism isdependent on the shoreline trajectory and theshelf geometry. Where the forced-regressiveshoreline trajectory is steeper than the localshelf dip, the shoreface profile would steepen,because of increased wave stress on the sea-bedand a resulting increase in advective, onshoresand transport (Carey et al., 1999). Where theforced-regressive shoreline trajectory is equal to,or less than, the local shelf dip, the shorefaceprofile would maintain its previous equilibriumgeometry (Inman & Bagnold, 1963). Thesechanges in shoreface profile are discussed laterin relation to clinoform geometry in the ‘SC4’and ‘K4’ tongues.

CLINOFORM GEOMETRY ANDSHOREFACE-SHELF PROFILE

When traced laterally, the discontinuity surfacesdescribed above are observed to define clinoformsthat are interpreted as preserved remnants of theancient shoreface-shelf profile (Figs 7D and 11–13). Thus, the ancient shoreface-shelf profile canbe reconstructed directly from clinoform dips,subject to constraints imposed by data quality anddata distribution.

Assumptions

Clinoform geometry and intraparasequence faciesarchitecture in both ‘SC4’ and ‘K4’ tongues arereconstructed using three assumptions: (1) localclinoform dip is parallel to regional depositionaldip; (2) coal seams and transgressive surfaces atthe base and top of the shoreface-shelf parase-quences are used as local stratigraphic data; and(3) clinoform geometry is not significantly alteredby post-depositional compaction.

Depositional dipThe assumption that local clinoform dip is par-allel to regional depositional dip appears to bejustified in wave-dominated shoreface deposits,which are characterized by long, linear shorelines(e.g. McCubbin, 1982; Elliott, 1986; Walker &Plint, 1992). For example, in the ‘K4’ tongue,Hampson’s (2000) study of intraparasequencefacies architecture interprets a local palaeoshore-line orientation that is entirely consistent withTaylor & Lovell’s (1995) regional reconstructionof palaeoshoreline trends. This assumption is notjustified in wave-influenced delta deposits,which are characterized by more complex, lobateshoreline trends (e.g. Bhattacharya & Walker,1992). Near the seaward pinch-out of the ‘SC4’tongue, clinoform surfaces define lobes with amean dip to the south-south-west (Fig. 13E–G),implying a local palaeoshoreline orientation thatis perpendicular to the regional palaeoshorelinetrend (Fig. 4C).

Datum surfacesIn this study, the base of the Sowbelly CoalSeam is used as a datum in the landwardportion of the ‘SC4’ tongue (Fig. 12B and C),and a transgressive surface at the top of thetongue is used as a datum in its seaward portion(Fig. 13). Similarly, transgressive surfaces at thebase and top of the ‘K4’ tongue are used as localstratigraphic data (Fig. 12A). However, none ofthese data represent a smooth, palaeohorizontalsurface. For example, the base of the SowbellyCoal Seam is a composite, time-transgressivesurface that can be traced down-dip into rootedsurfaces within foreshore sandstones (e.g. thenon-depositional discontinuity surfaces at21Æ4 m and 22Æ0 m in Fig. 7C). Although thebase of the coal seam most probably approxi-mates palaeohorizontal over short distances(< 1 km), such that clinoform geometry relat-ive to this surface may be reconstructedwith reasonable confidence, a more complex

Variability in wave-dominated, shoreface-shelf parasequences 687

� 2003 International Association of Sedimentologists, Sedimentology, 50, 667–701

Page 22: Geomorphological and sequence stratigraphic variability …download.xuebalib.com/xuebalib.com.34933.pdf · Geomorphological and sequence stratigraphic variability ... facies model,

treatment of the coal seam is needed over largerdistances (> 1 km) in order to reconstructintraparasequence facies architecture. Similarproblems are encountered for the transgressivesurfaces used as local stratigraphic data. Thereis some degree of erosion associated with eachof these transgressive surfaces (e.g. the ravine-ment surfaces marked by lag deposits at 45Æ3 min Fig. 7A and 13Æ7 m in Figs 7E and 8A and B),and the transgressive surface at the top of the‘K4’ tongue is onlapped in its palaeoseawardpart by hummocky cross-stratified sandstonebeds. In combination, these observations suggestthat the transgressive surfaces had a very gentle(<< 1�) palaeoseaward dip, comparable to amodern shelf, with minor erosional topographyproduced by wave ravinement. Consequently,clinoform dips reconstructed relative to thesetransgressive-surface data are apparent dips thatslightly and systematically underestimate truedip relative to an (imaginary) horizontal datum.

Post-depositional compactionThe studied parasequences are uniform in thick-ness, have a quartz-rich mineralogy and uniformlithological composition over most of their extent,implying that they have undergone little differen-tial compaction internally and, hence, clinoformgeometries have not been significantly modified.Differential compaction may play an importantrole in modifying clinoform dips near the pinch-out of the parasequences, where there is an abruptlateral transition from sandstone-dominatedfacies to mudstone-dominated facies. Becausepeat compacts by a factor of approximately sevenduring the transition to coal (Ryer & Langer, 1980),there may be significant differential compactionassociated with abrupt lateral thickness variationsin the Sowbelly Coal Seam, above the ‘SC4’tongue. The most abrupt thickness changes inthe Sowbelly Coal Seam occur near its down-dippinch-out (Kamola & Van Wagoner, 1995).

Reconstruction of shoreface-shelf profile

In the ‘SC4’ tongue, clinoform dips have beencollated for well-preserved, non-depositionaldiscontinuities in wave-dominated shorefacedeposits (i.e. in the landward portion of thetongue; Figs 12B and C and 14A) and in wave-influenced delta front deposits (i.e. near theseaward pinch-out of the tongue; Figs 13 and14B). Similar collations of data are presented fornon-depositional discontinuities and erosionaldiscontinuities in wave-dominated shoreface

deposits in the ‘K4 tongue’ (Fig. 14C and D;Hampson, 2000).

Although each clinoform has a unique geom-etry, all display a concave-upward geometry inwhich the shoreface-shelf or delta front dipdecreases progressively offshore (Fig. 14). Abruptbreaks in slope and convex-upward geometriesalong sections of some clinoform surfaces areartifacts of data collection and geometrical recon-struction. The former are the result of using one-dimensional, vertical sections at photomontagetie-points to reconstruct two-dimensional clino-form geometries (Fig. 10). The latter are inter-preted to reflect protuberances from the cliff line,which impose minor along-strike variability onclinoform geometries reconstructed from panelsaligned along local depositional dip (Figs 12 and13D–G).

Using the collated data (Fig. 14), mean shore-face-shelf and delta front profiles have beenconstructed for clinoforms defined by non-depo-sitional discontinuities in the ‘SC4’ tongue(Fig. 15A and B). The delta front profile (Fig. 15B)is constructed from panels that are orientedperpendicular to the regional depositional dip(Fig. 13E–G). There is significant variance aboutboth these mean profiles (Fig. 14). Hampson(2000) used the same method to construct meanprofiles for non-depositional discontinuities anderosional discontinuities in wave-dominated sho-reface deposits in the ‘K4’ tongue (Fig. 15C andD). These mean shoreface-shelf profiles wereinterpreted as equilibrium profiles, because thepopulations of non-depositional and erosionaldiscontinuities in the ‘K4’ tongue possess dis-tinctive clinoform geometries (Hampson, 2000).The validity of this interpretation and its impli-cations are discussed later. The approach of usingmean profiles is appropriate given the inaccur-acies associated with data set collection, but itdoes not allow the geometries of individualclinoforms to be evaluated in detail. For example,we cannot distinguish discrete populations ofnon-depositional discontinuities with shallowerdips, which may have formed as a result ofchanges to a less energetic wave/storm climate,from those with steeper dips, which may haveformed by decreases in sedimentation eventfrequency or rises in sea level (Inman & Bagnold,1963; Carey et al., 1999; Storms, 2003).

Variability in shoreface-shelf profile

Each of the four mean clinoform profiles recon-structed for the ‘SC4’ and ‘K4’ tongues has a

688 G. J. Hampson & J. E. A. Storms

� 2003 International Association of Sedimentologists, Sedimentology, 50, 667–701

Page 23: Geomorphological and sequence stratigraphic variability …download.xuebalib.com/xuebalib.com.34933.pdf · Geomorphological and sequence stratigraphic variability ... facies model,

pLS

FU

SF

dLS

FF

S

nond

epos

ition

al d

isco

ntin

uitie

s (w

ave-

dom

inat

ed s

hore

face

, 'S

C4'

tong

ue)

gradient = 0.037 ± 0.013clinoform dip = 1.4-2.9˚ (n = 12)

gradient = 0.024 ± 0.010clinoform dip = 0.8-1.9˚(n = 13)

gradient = 0.015 ± 0.007clinoform dip = 0.5-1.3˚(n = 12)

gradient = 0.010 ± 0.006clinoform dip = 0.2-0.9˚ (n = 5)

A

0 m

510

vert

ical

exa

gger

atio

n x5

0

nond

epos

ition

al d

isco

ntin

uitie

s (w

ave-

influ

ence

d de

lta fr

ont,

'SC

4' to

ngue

)D

F

grad

ient

= 0

.016

± 0

.011

clin

ofor

m d

ip =

0.3

-1.5

˚ (n

= 5

2)

B

gradient = 0.0082 ± 0.0043clinoform dip angle = 0.22-0.72(n = 33)

gradient = 0.0139 ± 0.0027clinoform dip angle = 0.64-0.95˚(n = 3)

gradient = 0.0145clinoform dip angle = 0.83˚(n = 1)

pLS

FU

SF

dLS

F

eros

iona

l dis

cont

inui

ties

(wav

e-do

min

ated

sho

refa

ce, '

K4'

tong

ue)

grad

ient

= 0

.005

6 ±

0.0

045

clin

ofor

m d

ip a

ngle

= 0

.06-

0.58

˚(n

= 4

)

grad

ient

= 0

.002

9 ±

0.0

025

clin

ofor

m d

ip a

ngle

= 0

.02-

0.31

(n =

4)

dLS

F

nond

epos

ition

al d

isco

ntin

uitie

s(w

ave-

dom

inat

ed s

hore

face

, 'K

4' to

ngue

)pL

SF

C

D

Fig

.14.

Coll

ate

dcli

nofo

rmd

ips

inth

e‘S

C4’

an

d‘K

4’

shore

face

ton

gu

es.

Data

are

deri

ved

from

(A)

non

-dep

osi

tion

al

dis

con

tin

uit

ies

inw

ave-d

om

inate

dsh

ore

face

dep

osi

tsin

the

lan

dw

ard

port

ion

of

the

‘SC

4’to

ngu

e(F

ig.

12C

);(B

)n

on

-dep

osi

tion

al

dis

con

tin

uit

ies

inw

ave-i

nfl

uen

ced

delt

afr

on

td

ep

osi

tsn

ear

the

seaw

ard

pin

ch

-ou

tof

the

‘SC

4’

ton

gu

e(F

ig.

13D

–G

);(C

)ero

sion

al

dis

con

tin

uit

ies

inw

ave-d

om

inate

dsh

ore

face

dep

osi

tsin

the

cen

tral

port

ion

of

the

‘K4’

ton

gu

e(e

.g.

Fig

.12A

;‘z

on

es

IVan

dV

I’of

Ham

pso

n(2

000);

an

d(D

)n

on

-dep

osi

tion

al

dis

con

tin

uit

ies

inw

ave-d

om

inate

dsh

ore

face

dep

osi

tsn

ear

the

seaw

ard

pin

ch

-ou

tof

the

‘K4’

ton

gu

e(F

ig.

12A

;‘z

on

eV

III’

of

Ham

pso

n(2

000).

Bold

lin

es

show

obse

rved

dis

con

tin

uit

ies,

an

dth

inli

nes

show

pro

jecti

on

sof

obse

rved

dis

con

tin

uit

ies

tocorr

esp

on

din

gfa

cie

sch

an

ges

inu

pp

er

shore

face

(US

F)

or

dis

tal

low

er

shore

face

(dL

SF

)d

ep

osi

ts.

Abru

pt

bre

aks

incli

nofo

rmsl

op

ean

dcon

vex-u

pw

ard

geom

etr

ies

are

art

ifacts

of

data

coll

ecti

on

an

dgeom

etr

ical

recon

stru

cti

on

.M

ean

cli

nofo

rmgra

die

nts

an

dst

an

dard

devia

tion

sfr

om

these

valu

es

are

show

n,an

dth

era

nge

of

cli

nofo

rmd

ipan

gle

sis

for

on

est

an

dard

devia

tion

from

the

mean

gra

die

nts

.It

shou

ldbe

note

dth

at

man

yof

the

coll

ate

dd

ata

sets

are

too

small

toass

ess

rigoro

usl

yby

stati

stic

al

mean

s.

Variability in wave-dominated, shoreface-shelf parasequences 689

� 2003 International Association of Sedimentologists, Sedimentology, 50, 667–701

Page 24: Geomorphological and sequence stratigraphic variability …download.xuebalib.com/xuebalib.com.34933.pdf · Geomorphological and sequence stratigraphic variability ... facies model,

0 m

510

0 m

1000

500

vert

ical

exa

gger

atio

n x5

0

coas

tal p

lain

= 0

.02˚

sea

leve

l

pLSF =

0.1

-0.6

˚

dLSF =

0.0

2-0.

shor

efac

e an

d in

ner

shel

f/ram

pof

fsho

re s

helf/

ram

p =

0.0

1-0.

FS = 2

-3˚

DN

on

dep

osi

tio

nal

dis

con

tin

uit

y in

wav

e-d

om

inat

ed s

ho

refa

ce-s

hel

f ('K

4' t

on

gu

e)

coas

tal p

lain

= 0

.02˚

offs

hore

she

lf/ra

mp

= 0

.01-

0.3˚

shor

efac

e an

din

ner

shel

f/ram

p

sea

leve

l

FS = 1

.4-2

.9˚

AN

on

dep

osi

tio

nal

dis

con

tin

uit

y in

wav

e-d

om

inat

edsh

ore

face

-sh

elf

('SC

4' t

on

gu

e)

BN

on

dep

osi

tio

nal

dis

con

tin

uit

y in

wav

e-in

flu

ence

dd

elta

fro

nt

('SC

4' t

on

gu

e)

coas

tal p

lain

= 0

.02

˚

offs

hore

she

lf/ra

mp

= 0

.01-

0.3˚

delta

fron

t

sea

leve

l

shor

efac

e an

d in

ner

shel

f/ram

p

coas

tal p

lain

= 0

.02˚

offs

hore

she

lf/ra

mp

= 0

.01-

0.3˚

FS = 2

-3˚

sea

leve

l

USF = 0

.8˚

pLSF =

0.2

-0.7

˚

dLSF =

0.6

-1.0

˚

CE

rosi

on

al d

isco

nti

nu

ity

in w

ave-

do

min

ated

sh

ore

face

-sh

elf

('K4'

to

ng

ue)

USF = 0

.8-1

.9˚

pLSF =

0.5

-1.3

˚

dLSF =

0.2

-0.9

˚

DF = 0

.3-1

.5˚

USF = 0

.5-0

.9˚

Fig

.15.

Sch

em

ati

cequ

ilib

riu

msh

ore

face-s

helf

pro

file

sfo

rth

e‘S

C4’an

d‘K

4’sh

ore

face

ton

gu

es,

wit

hsl

op

es

deri

ved

from

data

show

nin

Fig

s12–14.P

rofi

les

are

for

cli

nofo

rms

defi

ned

by

(A)

non

-dep

osi

tion

al

dis

con

tin

uit

ies

inw

ave-d

om

inate

dsh

ore

face

dep

osi

tsin

the

lan

dw

ard

port

ion

of

the

‘SC

4’

ton

gu

e;

(B)

non

-d

ep

osi

tion

al

dis

con

tin

uit

ies

inw

ave-i

nfl

uen

ced

delt

afr

on

td

ep

osi

tsn

ear

the

seaw

ard

pin

ch

-ou

tof

the

‘SC

4’

ton

gu

e;

(C)

ero

sion

al

dis

con

tin

uit

ies

inw

ave-

dom

inate

dsh

ore

face

dep

osi

tsin

the

cen

tral

port

ion

of

the

‘K4’to

ngu

e;an

d(D

)n

on

-dep

osi

tion

al

dis

con

tin

uit

ies

inw

ave-d

om

inate

dsh

ore

face

dep

osi

tsn

ear

the

seaw

ard

pin

ch

-ou

tof

the

‘K4’to

ngu

e.R

econ

stru

cti

on

sof

equ

ilib

riu

mp

rofi

lein

the

‘K4’to

ngu

econ

tain

dip

valu

es

for

fore

shore

an

doff

shore

shelf

/ram

pd

eri

ved

from

the

lite

ratu

re(E

llio

tt,

1986;

Can

t,1991;

Walk

er

&P

lin

t,1992).

690 G. J. Hampson & J. E. A. Storms

� 2003 International Association of Sedimentologists, Sedimentology, 50, 667–701

Page 25: Geomorphological and sequence stratigraphic variability …download.xuebalib.com/xuebalib.com.34933.pdf · Geomorphological and sequence stratigraphic variability ... facies model,

concave-upward geometry that contains no majorbreak(s) in slope (Fig. 15). There is some variab-ility between them.

Shoreface-shelf gradientThere is little difference in gradient betweenshoreface-shelf profiles (Fig. 15A) and wave-influenced delta front profiles (Fig. 15B) recon-structed from non-depositional discontinuity sur-faces in the ‘SC4’ tongue. The uniform, butrelatively steep, gradient of the ‘SC4’ shoreface-shelf and delta front profiles (Fig. 15A and B) isattributed to the importance of river-flood proces-ses, rather than storm processes, in supplyingsand to the distal part of both profiles (e.g.Fig. 9C). In the ‘K4’ tongue, where storm-waveprocesses controlled sand transport to the distalpart of the profile and where the shelf depth wasgreater, the lower shoreface had a consistentlyshallower gradient (Fig. 15C and D). Non-deposi-tional discontinuities in the ‘K4’ tongue(Fig. 15D) are also consistently shallower andmore gently dipping than corresponding ero-sional discontinuities (Fig. 15C). There is nochange in sediment calibre associated with thetwo discontinuity types. Instead, the shallower,more gently dipping geometries of the non-depo-sitional discontinuities are likely to reflect shore-face advance into shallower water, a decrease instorm-wave energy and/or a decrease in the rate ofsediment supply (e.g. Inman & Bagnold, 1963;Storms, 2003).

Shoreface-shelf depthShoreface-shelf profiles reconstructed from the‘SC4’ tongue are consistently less deep than thosereconstructed from the ‘K4’ tongue (Fig. 15). Therelative depths of these profiles indicate that the‘SC4’ shoreface was developed on a considerablyshallower shelf than the ‘K4’ shoreface. Indeed,the entire ‘SC4’ shoreface profile (Fig. 15A) isdirectly comparable in thickness, and gradient, tothe upper shoreface component of the ‘K4’ sho-reface-shelf profile (Fig. 15C and D). This differ-ence in palaeoshelf depth may account for theoccurrence of a thin (< 7 m) upper shorefacecomponent of the shoreface-shelf profile in the‘SC4’ tongue (Fig. 15A), because some fairwea-ther wave energy may have been absorbed asthese waves travelled across the shallower shelfto the ‘SC4’ shoreface. The greater shelf depthsassociated with the ‘K4’ tongue may have resultedin less attenuation of fairweather wave energyand a thicker (15–20 m) upper shoreface compo-nent of the shoreface-shelf profile (Fig. 15C and

D). Alternatively, the two tongues may have beendeposited when different wave-climate condi-tions prevailed in the Utah Bight of the WesternInterior Seaway, reflecting subtle changes inclimate or palaeogeography.

CLINOFORM DISTRIBUTION ANDSHORELINE TRAJECTORY

Minor stratigraphic discontinuities marked byclinoforms are not distributed with uniform spa-cing in the studied parasequences, and the phys-ical character and geometry of the clinoformsurfaces also varies within each parasequence(Figs 12 and 13). In order to analyse these varia-tions in an appropriate context, it is necessary toreconstruct the detailed, intraparasequence shore-line trajectory (sensu Helland-Hansen & Martin-sen, 1996).

Assumptions

In addition to the assumptions used to recon-struct shoreface-shelf profiles from clinoformsurfaces, two further assumptions have beenused to reconstruct shoreline trajectories in the‘SC4’ and ‘K4’ tongues: (1) local stratigraphicdata are assumed to have had an appropriatedepositional dip; and (2) each type of clinoformsurface identified in the two parasequences isassumed to possess the mean geometry shown inFig. 15.

Depositional dip of datum surfacesVarious transgressive surfaces and the base of theSowbelly Coal Seam are used as local stratigraph-ic data for the reconstruction of clinoform geom-etries (Fig. 16A and C). The transgressive surfacesare generally flat but characterized by minorerosion and onlap, implying that they are waveravinement surfaces across the palaeoshelf, withan inferred depositional dip of 0Æ02� in a seawarddirection (Fig. 16B, D and E; after Elliott, 1986;Cant, 1991; Walker & Plint, 1992). Two recon-structions are presented for the Sowbelly CoalSeam, assuming that either the base (Fig. 16D) orthe top (Fig. 16E) of the seam had a palaeosea-ward dip of 0Æ02� during deposition (Fig. 16D),typical for a coastal plain (Elliott, 1986; Cant,1991; Walker & Plint, 1992). The latter recon-struction is more consistent with our observationthat the base of the seam is a composite, time-transgressive surface that can be traced down-dipinto rooted surfaces within foreshore sandstones

Variability in wave-dominated, shoreface-shelf parasequences 691

� 2003 International Association of Sedimentologists, Sedimentology, 50, 667–701

Page 26: Geomorphological and sequence stratigraphic variability …download.xuebalib.com/xuebalib.com.34933.pdf · Geomorphological and sequence stratigraphic variability ... facies model,

(e.g. the non-depositional discontinuity surfacesat 21Æ4 m and 22Æ0 m in Fig. 7C). Both recon-structions include decompaction of the coal seamby a factor of seven (Ryer & Langer, 1980).

Mean clinoform geometriesIn order to simplify our reconstructions of shore-line trajectory and to extrapolate them into areasof poor exposure (Fig. 16), we have used the

A

B

C

D

E

692 G. J. Hampson & J. E. A. Storms

� 2003 International Association of Sedimentologists, Sedimentology, 50, 667–701

Page 27: Geomorphological and sequence stratigraphic variability …download.xuebalib.com/xuebalib.com.34933.pdf · Geomorphological and sequence stratigraphic variability ... facies model,

mean shoreface-shelf and delta front profilesshown in Fig. 15 as a proxy for the uniqueshoreface-shelf profiles represented by eachclinoform surface. This simplification assumesthat the mean profiles possess an equilibriumgeometry about which the individual clinoformsrepresent temporary variations. The validity ofthis interpretation and its implications are dis-cussed later.

Reconstruction of shoreline trajectory

Using these assumptions, shoreline trajectory isreconstructed for both ‘SC4’ and ‘K4’ tongues insimple, two-dimensional transects along deposi-tional dip (Fig. 16). Within the ‘K4’ tongue, thedistribution of clinoform surfaces is interpreted toreflect subtle changes in progradation and aggra-dation rates of the shoreface-shelf profile, andthus shoreline trajectory (Fig. 16A and B). Inparticular, forced regressive shoreline trajectoriesare marked by the amalgamation of erosionaldiscontinuity clinoform surfaces into regressivesurfaces of marine erosion (Hampson, 2000;Hampson et al., 2001). Variations in shorelinetrajectory can be mapped in three dimensions inthe ‘K4’ tongue to define linear zones parallel tothe palaeoshoreline trend in which there is eithera forced regressive trajectory or a normal regres-sive trajectory (Fig. 17A; Hampson, 2000).

Similarly detailed variations in shoreline tra-jectory are not evident in the ‘SC4’ tongue,although they may be obscured by the effects ofdecompacting the Sowbelly Coal Seam (Fig. 16C–E). Instead, major changes in intraparasequencefacies architecture are related to increased flu-vio-deltaic influence near the seaward pinch-out

of the tongue (Kamola & Van Wagoner, 1995),as reflected in plan-view changes in the palae-oshoreline trend (Fig. 17B). Using the base of theSowbelly Coal Seam as a palaeo-coastal plaindatum surface (Fig. 16D) produces a near-hori-zontal geometry to the transgressive surfaces atthe base of the tongue, and thus presents a morelikely reconstruction of shoreline trajectory dur-ing progradation in the ‘SC4’ tongue. However,the top of the Sowbelly Coal Seam is interpretedto have been near-horizontal during transgressionat the end of ‘SC4’ tongue deposition (as por-trayed in Fig. 16E), because it is overlain by awidespread, shallow lagoon (Van Wagoner et al.,1990; Kamola & Van Wagoner, 1995). It is there-fore inferred that significant early decompactionof the Sowbelly Coal Seam occurred duringprogradation and/or early transgression of the‘SC4’ shoreline.

Shoreline trajectory and variability inshoreface-shelf profile

In the ‘SC4’ and ‘K4’ tongues, several key obser-vations outlined below suggest that the dip of theshoreface-shelf profile was gentle during trans-gression, steepened during the first 1–2 km ofprogradation and remained steep during subse-quent progradation (Fig. 16). The dip of theshoreface-shelf profile decreased at the turn-around from progradation to transgression. Thus,significant variations in shoreface-shelf profileappear to be caused by changes between regres-sion and transgression, rather than variations inshoreline trajectory during progradation.

Landward pinch-out of shoreface tonguesAt the landward pinch-out of a shoreface-shelftongue, its basal transgressive surface records theshoreface-shelf profile immediately before shore-face progradation (Nummedal & Swift, 1987;Olsen et al., 1999). The landward pinch-out ofthe ‘K4’ tongue is obscured by erosion at anoverlying sequence boundary (Pattison, 1995;Taylor & Lovell, 1995), whereas the landwardpinch-out of the ‘SC4’ tongue is only exposed ininaccessible vertical cliff faces in Wildcat Canyon(Fig. 4C). Our reconstructions of the latter fromphotomontages suggest that the basal transgres-sive surface of the ‘SC4’ tongue is significantlymore gently dipping than the mean clinoformgeometry within either tongue (Fig. 16B, D andE). This discrepancy suggests that the shoreface-shelf profile must have steepened significantlyduring the first 1–2 km of progradation. Olsen

Fig. 16. Reconstructions of shoreline trajectory insimple, two-dimensional transects along deposition-al dip for the ‘SC4’ and ‘K4’ shoreface tongues. (A)Observed facies architecture in the ‘K4’ tongue is usedto reconstruct progradational shoreline trajectory (B)via imposing a depositional dip on local transgressivesurface data and via the use of mean shoreface-shelfprofiles as a proxy for observed clinoform surfaces(Fig. 15C and D). (C) Observed facies architecture inthe ‘SC4’ tongue is used to reconstruct progradationalshoreline trajectory (D) via imposing a depositional dipon local base-coal and transgressive surface data andvia the use of mean shoreface-shelf profiles as a proxyfor observed clinoform surfaces (Fig. 15A and B). (E)An alternative reconstruction for the ‘SC4’ tongue usesthe top of the Sowbelly Coal as a datum and is appro-priate for reconstructing transgressive shoreline tra-jectory and geomorphology at the end of deposition ofthe ‘SC4’ tongue. Key for (A) and (C) as for Fig. 12.

Variability in wave-dominated, shoreface-shelf parasequences 693

� 2003 International Association of Sedimentologists, Sedimentology, 50, 667–701

Page 28: Geomorphological and sequence stratigraphic variability …download.xuebalib.com/xuebalib.com.34933.pdf · Geomorphological and sequence stratigraphic variability ... facies model,

0m

iles

12

0ki

lom

eter

s1

23

N

B

mea

sure

d se

ctio

nsph

otom

onta

ge ti

e po

ints

dow

n-di

p te

rmin

atio

nof

upp

er s

hore

face

dep

osit

s

n=10

n=9

n=5

n=3

n=9

n=3

n=5

n=1

n=2

long

shor

e sa

nd tr

ansp

ort

appr

oxim

ate

prog

rada

tion

dire

ctio

nof

wav

e-in

fluen

ced

delta

com

ple

x(lo

ngsh

ore

sand

tran

spor

t?)

appr

oxim

ate

pala

eoge

ogra

phy

ofw

ave-

influ

ence

d de

lta fr

ont c

ompl

ex

N.R

.?

N.R

.?

N.R

.?

0m

iles

1

2

0ki

lom

eter

s1

2m

easu

red

sect

ions

phot

omon

tage

tie

poin

ts

N

dow

n-di

p te

rmin

atio

nof

upp

er s

hore

face

dep

osit

s

A

n=1

n=2

N.R

.

F.R

.

long

shor

e sa

nd tr

ansp

ort

N.R

.

N.R

.

F.R

.

F.R

.

F.R

.

n=1

wav

e-rip

ple

cres

ts, d

LSF

and

DF

fac

ies

(n =

num

ber

of r

eadi

ngs)

n=1

trou

gh a

nd ta

bula

r cr

oss-

beds

, US

F fa

cies

(n =

num

ber

of r

eadi

ngs)

Pal

aeoc

urre

nt k

ey

'nor

mal

' reg

ress

ive

shor

elin

e tr

ajec

tory

(ris

ing

rela

tive

sea-

leve

l)N

.R.

appr

oxim

ate

shor

elin

e or

ient

atio

n

Pal

aeog

eogr

aphy

key

'forc

ed' r

egre

ssiv

e sh

orel

ine

traj

ecto

ry(f

allin

g re

lativ

e se

a-le

vel)

F.R

.

up-d

ip te

rmin

atio

nof

mar

ine

depo

sits

N.R

.

3

Fig

.17.

Pala

eogeogra

ph

icre

con

stru

cti

on

sof

vari

able

shore

lin

etr

aje

cto

ryin

the

‘SC

4’

an

d‘K

4’

shore

face

ton

gu

es.

(A)

Th

e‘K

4’to

ngu

econ

tain

sli

near

zon

es

of

alt

ern

ati

ng

forc

ed

regre

ssiv

ean

dn

orm

al

regre

ssiv

esh

ore

lin

etr

aje

cto

ry(s

how

nin

cro

ss-s

ecti

on

inF

ig.

16B

)th

at

are

para

llel

toth

elo

cal

pala

eosh

ore

lin

etr

en

d.

Th

ela

tera

lcon

tin

uit

yof

these

zon

es

iscon

sist

en

tw

ith

asi

mp

le,li

near

wave-d

om

inate

dsh

ore

lin

ew

ith

litt

lealo

ng-s

trik

evari

ati

on

inse

dim

en

tsu

pp

ly.(B

)T

he

‘SC

4’

ton

gu

eis

inte

rpre

ted

tocon

tain

an

orm

al

regre

ssiv

esh

ore

lin

etr

aje

cto

ryth

rou

gh

ou

t(F

ig.

16D

),bu

tit

sse

aw

ard

part

isd

om

inate

dby

alo

bate

,d

elt

aic

pala

eosh

ore

lin

etr

en

d.L

on

gsh

ore

cu

rren

tsd

om

inate

pala

eocu

rren

tori

en

tati

on

sin

wave-d

om

inate

du

pp

er

shore

face

(US

F)

dep

osi

tsan

dap

pear

tocon

trol

wave-

infl

uen

ced

delt

alo

be

geom

etr

y.

694 G. J. Hampson & J. E. A. Storms

� 2003 International Association of Sedimentologists, Sedimentology, 50, 667–701

Page 29: Geomorphological and sequence stratigraphic variability …download.xuebalib.com/xuebalib.com.34933.pdf · Geomorphological and sequence stratigraphic variability ... facies model,

et al. (1999) documented similar steepening ofthe shoreface-shelf profile during early prograda-tion near the landward pinch-out of two shorefacetongues in the Cretaceous Cliff House Sandstone,Colorado.

Main body of shoreface tonguesThe clinoform geometry within both ton-gues remains relatively constant between theirlandward and seaward pinch-outs (portrayedschematically in Fig. 16B, D and E). The wave-dominated shoreface component of the ‘SC4’tongue contains only non-depositional disconti-nuities that exhibit a limited variance in clino-form geometry (Figs 12B and C, 14 and 15A).Except for its seaward pinch-out, the ‘K4’ tonguecontains only erosional discontinuities with alimited variance in clinoform geometry (Figs 12Aand 15C).

Seaward pinch-out of shoreface tonguesAt the seaward pinch-out of the ‘K4’ tongue, theshoreface-shelf profile became shallower and hada gentler dip (Fig. 16B), coincident with a changein the physical character of clinoform surfacesfrom erosional discontinuities (Figs 12A and 15C)to non-depositional discontinuities (Figs 12A and15D). The seaward pinch-out of the ‘SC4’ tongueis more difficult to interpret, because it is associ-ated with complex palaeogeographies (Fig. 17B).However, the basal transgressive surface of the‘SC5’ tongue (Fig. 16D and E) may be reconstruc-ted as a proxy for the shoreface-shelf profileduring transgression at the end of ‘SC4’ tonguedeposition. The geometry of this surface is wellconstrained by preservation of flood-tidal deltadeposits at the landward pinch-out of the ‘SC5’tongue (Van Wagoner et al., 1990; Kamola & VanWagoner, 1995). The foreshore (FS) and uppershoreface (USF) components of the shoreface-shelf profile recorded by the transgressive surfaceare comparable in height to those interpreted inthe ‘SC4’ tongue (Fig. 15A), although the dip ofthis part of the profile is not constrained by ourobservations. The lower shoreface component ofthe shoreface-shelf profile recorded by the trans-gressive surface is much thinner than thoseinterpreted for the ‘SC4’ tongue (Fig. 15A), andis interpreted to have a more gentle dip, corres-ponding to the top of the decompacted SowbellyCoal Seam (Fig. 16D and E). Thus, it appears that,in both ‘SC4’ and ‘K4’ tongues, the shoreface-shelf profile became shallower and more gentlydipping at the tongues’ seaward pinch-out and/orduring subsequent transgression.

DISCUSSION: DYNAMIC CHANGESIN SHOREFACE-SHELF PROFILE

The observations and interpretations presentedabove suggest that the stratigraphic record con-tains considerable evidence for variability in theshoreface-shelf profile. Spatial variability reflectsalong-strike changes in depositional process andpalaeogeography that are inherent in any shore-line (e.g. Rodriguez et al., 2001). For example, thedistribution of wave-influenced delta front depos-its in the ‘SC4’ tongue (Fig. 17B) most probablyrecords switching of distributary channel loca-tion. The origin of temporal variability and itsimplications for current models of shorefacebehaviour are discussed below (Fig. 18).

Equilibrium profile

Modern shorefaces tend towards an equilibriumprofile (sensu Tanner, 1982; Walker & Plint, 1992)that forms in response to fairweather waveprocesses of low magnitude and high frequency.However, most shoreface-shelf deposits recordstorm-wave processes of high magnitude and lowfrequency, which are preferentially preserved inthe stratigraphic record (Dott, 1982; Dott &Bourgeois, 1982; Niedoroda et al., 1989; Stormset al., 2002; Storms, 2003). Thus, the portion of theshoreface-shelf profile above fairweather wavebase may maintain an equilibrium profile, whereasthat below fairweather wave base is widely inter-preted to respond over longer timescales to epi-sodic storm waves (e.g. De Vroeg et al., 1988; Stive& De Vriend, 1995; Fig. 18). Therefore, the conceptof equilibrium profile is most applicable to theupper parts of the shoreface-shelf profile (abovefairweather wave base) where the timescale ofintrinsic, dynamic response is fast relative tochanges in extrinsic controls such as sea level,sediment supply and wave climate (Stive & DeVriend, 1995; Fig. 20). Supporting evidence forthis view may occur at the seaward pinch-out ofthe ‘K4’ tongue, where clinoform surfaces changefrom steeply dipping erosional discontinuities togently dipping non-depositional discontinuities(Figs 12A and 16B). The associated change inshoreface-shelf profile geometry is most pro-nounced in the lower part of the profile (corres-ponding to pLSF and dLSF facies in Fig. 15C andD), which may have been unable to re-equilibrateto storm-wave climate as shoreline trajectory and/or sediment supply changed.

Temporal changes in external controls such asrelative sea level, wave climate and sediment

Variability in wave-dominated, shoreface-shelf parasequences 695

� 2003 International Association of Sedimentologists, Sedimentology, 50, 667–701

Page 30: Geomorphological and sequence stratigraphic variability …download.xuebalib.com/xuebalib.com.34933.pdf · Geomorphological and sequence stratigraphic variability ... facies model,

calibre will alter the geometry of the equilibriumprofile (e.g. Storms et al., 2002; Storms, 2003).Such variability is likely to occur over geologicaltimescales, for example in response to minor,climatically driven cycles in sediment supply andwave climate (102)104 years; Fig. 18), and mayproduce clinoform surfaces characterized by ero-sional or non-depositional discontinuities.

The ‘Bruun rule’

The ‘Bruun rule’ (Bruun, 1962), which hasbeen used widely in coastal engineering studies,implies that the shoreface-shelf profile maintainsa constant, equilibrium geometry during trans-gression. The rule has since been applied ingeometric models of stratigraphic architecturethat include both regressive and transgressiveshorelines (e.g. Cant, 1991; Nummedal et al.,1993). Our interpretation that the shoreface-shelfprofile varies markedly between episodes oftransgression and regression questions the appli-cability of the ‘Bruun rule’ in such modellingstudies.

Landward pinch-out of shoreface tonguesSteepening of the shoreface-shelf profile duringearly progradation is interpreted in several geo-logical data sets (Van der Valk, 1992; Olsen et al.,1999; ‘SC4’ and ‘K4’ tongues described in thispaper) and is reproduced in numerical massbalance models (Stive & De Vriend, 1995) andprocess response models (Storms et al., 2002).Steepening is interpreted to result from progra-dation of the shoreface-shelf profile into deeper

water as a result of coeval aggradation of theprofile and/or seaward-dipping shelf geometry.As the shoreface-shelf profile advanced intodeeper water, where wave energy was less attenu-ated, an increasing amount of wave energyreached the shoreface, which steepened in re-sponse (Olsen et al., 1999).

Main body of shoreface tonguesThe shoreface-shelf profile is interpreted to havevaried little during the main progradation historyof the ‘SC4’ and ‘K4’ tongues. A similar pattern isnoted in Holocene progradational shoreface-shelfsuccessions (Fig. 19). In all cases, shelf depthremained relatively uniform, implying that therewas little change in the attenuation of waveenergy as the shoreface advanced. Observedvariability in the shoreface-shelf profile may beattributed to minor changes in wave climate andsediment calibre supplied by longshore drift.

Seaward pinch-out of shoreface tonguesThe shoreface-shelf profile in the ‘SC4’ tongue isinterpreted to have been shallower and moregently dipping during transgression (Fig. 16D andE). This is attributed to a reduction in water depthas the shoreface-shelf profile retreated acrossthe underlying progradational deposits, whichattenuated wave energy and caused a decrease inthe profile dip. Attenuation would have beenmore pronounced for the larger storms thatsculpted the lower part of the shoreface-shelfprofile. Also, low sediment supply and/or rapidshoreline retreat may have produced a flattened,disequilibrium shoreface-shelf profile, partic-

100

101

102

103

104

105

106

107

108

10-1

10-2

time

scal

e (y

ears

)

10-3

indi

vidu

al s

torm

eve

nt

ret

urn

perio

d of

sto

rm e

vent

s(v

arie

s w

ith s

torm

mag

nitu

de)

min

or c

ycle

s in

wav

e cl

imat

e

min

or c

ycle

s in

rel

ativ

e s

ea-le

vel (

6th

orde

r?)

depositionalprocesses

analytical techniquesand models

depositionalproducts

cyc

les

in r

elat

ive

sea

-leve

l (5t

h or

der?

)

sho

refa

ce to

ngue

(sho

refa

ce-s

helf

para

sequ

ence

)

indi

vidu

al s

torm

-eve

nt b

ed

clin

ofor

m/d

isco

ntin

uity

-bou

nded

unit

("be

dset

", "

clin

othe

m")

clin

ofor

m s

urfa

ce(d

isco

ntin

uity

sur

face

)

"Bru

un R

ule

"(c

oast

al e

ngin

eerin

g) sequ

ence

stra

tigra

phy

seas

onal

cha

nges

inst

orm

inte

nsity

phys

ical

and

num

eric

al m

odel

s(in

divi

dual

sto

rm e

vent

)

num

eric

al m

odel

s(in

tra-

tong

ue fa

cies

arc

hite

ctur

e)

min

or c

ycle

s in

sedi

men

t sup

ply

Fig. 18. Schematic illustration ofthe timescales represented by (1)key depositional processes in wave-dominated shorefaces and shelves;(2) depositional products preservedwithin facies successions; and (3)analytical techniques and modelsused to study and predict shallow-marine stratigraphy. Note that thetimescales represented by the de-positional products within a singleshoreface-shelf parasequence spaneight orders of magnitude(10)3)105 years).

696 G. J. Hampson & J. E. A. Storms

� 2003 International Association of Sedimentologists, Sedimentology, 50, 667–701

Page 31: Geomorphological and sequence stratigraphic variability …download.xuebalib.com/xuebalib.com.34933.pdf · Geomorphological and sequence stratigraphic variability ... facies model,

AB

D

C

E

F

Fig

.19.

Com

pari

son

sof

shore

face-s

helf

pro

file

an

dsh

ore

lin

etr

aje

cto

ryin

an

um

ber

of

wave-d

om

inate

d,H

olo

cen

esh

ore

lin

ed

ep

osi

ts:(A

)cen

tral

Holl

an

dcoast

(aft

er

Van

der

Valk

,1992;S

tive

&D

eV

rien

d,1995);

(B)

Galv

est

on

Isla

nd

,T

exas

coast

,U

SA

(aft

er

Bern

ard

et

al.

,1970;M

cC

ubbin

,1982);

(C)

Wil

lap

aB

ay

barr

ier

isla

nd

,W

ash

ingto

n,U

SA

(aft

er

Sm

ith

et

al.

,1999);

an

d(D

)N

ayari

tst

ran

dp

lain

,M

exic

o(a

fter

Cu

rray

et

al.

,1969).

Th

ecen

tral

Holl

an

dcoast

was

pro

gra

dati

on

al

betw

een

ap

pro

xim

ate

ly5000

an

d2000

years

BP

an

dis

now

un

derg

oin

gtr

an

sgre

ssio

n(V

an

der

Valk

,1992).

Cli

nofo

rmsu

rfaces

inth

eW

illa

pa

Bay

barr

ier

isla

nd

are

mark

ed

by

heavy

min

era

lcon

cen

trati

on

s(S

mit

het

al.

,1999).

Cli

nofo

rmsu

rfaces

inth

eN

ayari

tst

ran

dp

lain

dep

osi

tsare

tran

sgre

ssiv

era

vin

em

en

tsu

rfaces

that

pu

nctu

ate

overa

llst

ran

dp

lain

pro

gra

dati

on

(Cu

rray

et

al.

,1969).

Th

etw

op

ara

sequ

en

ces

dis

cu

ssed

inth

isp

ap

er

are

als

osh

ow

nfo

rcom

pari

son

:(E

)th

e‘S

C4’

ton

gu

e,

Sp

rin

gC

an

yon

Mem

ber

(Fig

.16D

);an

d(F

)th

e‘K

4’

ton

gu

e,

Ken

ilw

ort

hM

em

ber

(Fig

.16B

).K

ey

as

for

Fig

.16.

Variability in wave-dominated, shoreface-shelf parasequences 697

� 2003 International Association of Sedimentologists, Sedimentology, 50, 667–701

Page 32: Geomorphological and sequence stratigraphic variability …download.xuebalib.com/xuebalib.com.34933.pdf · Geomorphological and sequence stratigraphic variability ... facies model,

ularly in the lower, storm-generated part (e.g.Inman & Bagnold, 1963).

Our interpretations suggest that the ‘Bruun rule’is applicable only when an equilibrium profile ismaintained during periods of uniform shorelinetrajectory across portions of the shelf with littleantecedent topography. These conditions may bemet over the short timescales considered in coastalengineering studies (100)103 years; Fig. 18), butthey are unlikely to prevail over the timescalesconsidered in numerical models of sequence-scalestratigraphy (105)108 years; Figs 18 and 19).Thus, numerical models that assume the geome-tries implied by the ‘Bruun rule’ are unlikely toreproduce accurately the detailed morphology oftransgressive surfaces or the parasequence-scalestratigraphy that they define (Olsen et al., 1999).In particular, they may overestimate the depth oftransgressive ravinement.

Variability between modern shorefaces andancient shoreface-shelf parasequences

The interpretation that shoreface-shelf profilevaries with shoreline trajectory and shelf mor-phology, in addition to sediment calibre andwave energy, provides a mechanism to explainthe discrepancy in scale between modern shore-faces and ancient shoreface-shelf parasequences(Fig. 1). Most well-studied modern shorefacesare developed on the inner shelf in relativelyshallow water (e.g. Holocene shoreface depositsof the Central Holland Coast, Galveston Island,Willapa Bay and Nayarit shoreface in Fig. 19;Curray et al., 1969; Bernard et al., 1970; McCub-bin, 1982; Van der Valk, 1992; Stive & DeVriend, 1995; Smith et al., 1999) and conse-quently are relatively thin compared with an-cient shoreface-shelf parasequences (Fig. 1).These modern shorefaces are in the early stagesof progradation, and we infer that they willbecome higher and steeper as they advance intodeeper water on the middle to outer shelf. Inaddition, progradational shoreface-shelf profilesin the two studied parasequences do not containprominent breaks in slope at either fairweatheror storm-wave base, but grade seawards to thedip of the inner shelf. Their smooth geometryimplies that the profiles were developed oversufficiently long timescales to enable near-equi-librium geometries to form in response to storm-wave climate. Modern shoreface-shelf profiles,which developed during transgression and earlyprogradation, exhibit a break in slope at, or nearto, fairweather wave base (e.g. Clifton, 2000).

The lower part of these profiles is interpreted tobe in disequilibrium with storm-wave climateand/or sediment supply.

Differences between ancient shoreface-shelfparasequences can also be explained by variationsin shoreline trajectory and shelf morphology. Forexample, the ‘K4’ tongue is interpreted to havebeen deposited in relatively deep water, seawardof the antecedent shelf topography generated byunderlying shoreface-shelf parasequences (‘K1’–‘K3’ tongues in Fig. 5). Consequently, this para-sequence attains an anomalously large thickness(Figs 1 and 19), despite evidence for a forcedregressive shoreline trajectory during its depos-ition (Fig. 16B; Pattison, 1995; Hampson, 2000).Other unusually thick parasequences in the BookCliffs succession overlie major flooding surfacesassociated with the generation of large amounts ofaccommodation across the entire shelf (e.g. the‘A1’ and ‘K1’ tongues in Fig. 5; fig. 12A inReynolds, 1999). In contrast, the wave-dominatedportion of the ‘SC4’ tongue was deposited directlyabove the antecedent shelf topography generatedby underlying shoreface-shelf parasequences(‘SC2’–‘SC3’ tongues in Fig. 5), and it is signifi-cantly thinner than the ‘K4’ tongue (Figs 1 and19). Differences in parasequence thickness relatedto stacking patterns within larger parasequencesets are predictable, because they reflect system-atic variations in the generation of shelfal accom-modation (Reynolds, 1999). Antecedent shelftopography is likely to cause anomalous thicken-ing of parasequences that extend a significantdistance palaeoseaward of their precursors (e.g.the ‘K4’ tongue; Fig. 5).

IMPLICATIONS FOR FACIES ANDSEQUENCE STRATIGRAPHIC MODELS

Shoreface-shelf stratigraphy at intraparasequencescale is considerably more complex than repre-sented in current facies and sequence stratigraph-ic models (Fig. 20).

• Although modern shoreface systems are idealnatural laboratories for the study of wave andstorm processes, they are not fully representativeof ancient shoreface-shelf parasequences. Modernshorefaces are invariably developed on the innershelf and record only the early stages of progra-dation. Ancient shoreface-shelf parasequencesrecord the dynamic response of the shorefaceprofile to prolonged progradation and subsequenttransgression.

698 G. J. Hampson & J. E. A. Storms

� 2003 International Association of Sedimentologists, Sedimentology, 50, 667–701

Page 33: Geomorphological and sequence stratigraphic variability …download.xuebalib.com/xuebalib.com.34933.pdf · Geomorphological and sequence stratigraphic variability ... facies model,

• The geometry and physical character of theshoreface-shelf profile varies over several time-scales. (1) Over short geological timescales(102)104 years), erosional and non-depositionaldiscontinuities are produced along the profile as aresult of minor cycles in relative sea level, waveclimate and/or sediment supply. (2) Over inter-mediate geological timescales (103)105 years), thegeometry of the shoreface-shelf profile varies withshoreline trajectory in a single parasequence, suchthat it steepens during early progradation,remains steep and relatively constant during lateprogradation, and becomes shallower and moregently dipping during transgression. These chan-ges in shoreline trajectory are controlled by sho-reface advance into deeper water and shorefaceretreat into shallower water, and are modulated byrelative sea level and/or sediment supply. (3) Overlong geological timescales (105)108 years), be-tween-parasequence variations in shoreface-shelfprofile most likely reflect changes in long-termrelative sea level, shelf morphology, sedimentcalibre and wave energy in the basin.

• Vertical facies successions lack geometricaldata on the shoreface-shelf profile and shorelinetrajectory. Consequently, such successions do notallow the construction of geometrically robust

facies models, and neither do they allow adetailed sea-level history to be reconstructed. Keygeometrical attributes within parasequences maybe measured at well-exposed outcrops, allowingshoreface-shelf profile and shoreline trajectory tobe carefully reconstructed. In the absence of veryhigh-resolution seismic data, accurate recon-struction of geometrical attributes in the subsur-face is likely to prove extremely difficult, even infields with high well density. As a result, con-fident prediction of parasequence dimensions(e.g. location of their landward and seawardpinch-outs) and detailed internal heterogeneity(e.g. clinoform dip angle) is limited. Genericpredictive models at this level of detail may beachieved via the comparative study of well-exposed parasequences at outcrop, combinedwith process-response numerical models, usingthe former to calibrate the latter.

ACKNOWLEDGEMENTS

G.J.H. would like to thank Diane Kamola for anintroduction to the Spring Canyon Member,Andalex Resources for access to Panther Canyon,and John Howell for insightful discussions. The

100 101 102 103 104 105 106 107 10810-110-2

time scale (years)

10-3

minor cycles inwave climate

minor cycles in relative sea-level (6th order?)

minor cycles insediment supply clinoform surface

(discontinuity surface)

disequilibriumshoreface-shelf profile?

equilibriumshoreface-shelf profile?

minor cycles in relative sea-level (6th order?)

minor cycles insediment supply

intra-parasequenceshoreline trajectory

(clinoform distribution,"bedsets", clinothems")

cycles in relative sea-level (5th order?)

maintenance of equilibriumprofile ("Bruun Rule")

breakdown ofequilibrium profile

parasequence

cycles in relative sea-level (5th order?)

sediment supply

cycles in relativesea-level (4th order ?)

shelf morphology

sediment supply parasequence stacking

stra

tigra

phic

hie

rarc

hy

Fig. 20. Hierarchy of stratigraphicunits at intraparasequence andparasequence scales. The timescalesof formation and driving processesfor these units are suggested, andthe inferred applicability of theequilibrium profile concept (for theentire shoreface-shelf) and the‘Bruun rule’ are shown.

Variability in wave-dominated, shoreface-shelf parasequences 699

� 2003 International Association of Sedimentologists, Sedimentology, 50, 667–701

Page 34: Geomorphological and sequence stratigraphic variability …download.xuebalib.com/xuebalib.com.34933.pdf · Geomorphological and sequence stratigraphic variability ... facies model,

‘K4’ tongue study was funded by Shell UK Expro.The authors are grateful to Tina Olsen for herconstructive review, and to Chris Fielding andPeter Haughton for editorial comments.

REFERENCES

Balsley, J.K. (1980) Cretaceous Wave-Dominated Delta Sys-

tems, Book Cliffs, East-central Utah. AAPG Continuing

Education Course Field Guide, 163 pp.

Bernard, H.A., Major, C.F., Parrott, B.S. and LeBlanc, R.J.(1970) Recent Sediments of Southeast Texas: a Field Guide

to the Brazos Alluvial and Deltaic Plains and the GalvestonBarrier Island Complex. University of Texas Bureau of

Economic Geology, Guidebook 11, 132 pp.

Bhattacharya, J.P. and Walker, R.G. (1992) Deltas. In: Facies

Models; Response to Sea-Level Change (Eds R.G. Walker

and N.P. James), pp. 157–177. Geological Association of

Canada, St John’s, Newfoundland.

Bruun, P. (1962) Sea-level rise as a cause of shore erosion.

J. Waterw. Harbours Div. Am. Soc. Civil Eng., 88, 117–130.

Budding, M.C. and Inglin, H.F. (1981) A reservoir geological

model of the Brent Sands in southern Cormorant. In: Pet-

roleum Geology of the Continental Shelf of NW Europe (Eds

G.D. Hobson and V. Illing), pp. 326–334. Institute of Petro-

leum, London.

Cant, D.J. (1991) Geometric modelling of facies migration:

theoretical development of facies successions and local

unconformities. Basin Res., 3, 51–62.

Carey, J.S., Swift, D.J.P., Steckler, M., Reed, C.W. and

Niedoroda, A. (1999) High-resolution sequence strati-

graphic modelling 2: effects of sedimentation process. In:

Numerical Experiments in Stratigraphy: Recent Advances

in Stratigraphic and Sedimentologic Computer Simulations

(Eds J.W. Harbaugh, W.L. Watney, E.C. Rankey, R. Slinger-

land, R.H. Goldstein and E.K. Franseen), SEPM Spec. Publ.,

62, 151–164.

Clifton, H.E. (1969) Beach lamination: nature and origin. Mar.

Geol., 7, 553–559.

Clifton, H.E. (1976) Wave-formed sedimentary structures – a

conceptual model. In: Beach and Nearshore Sedimentation

(Eds R.A. Davis and R.L. Ethington), SEPM Spec. Publ., 24,126–148.

Clifton, H.E. (2000) Shoreface myths and misconceptions.

Programme for AAPG Annual Convention 2000 (abstract),

Tulsa, A29.

Clifton, H.E., Hunter, R.E. and Phillips, R.L. (1971) Deposi-

tional structures and processes in the non-barred, high-

energy nearshore. J. Sed. Petrol., 41, 651–670.

Curray, J.R., Emmel, F.J. and Crampton, P.J.S. (1969) Holo-

cene history of a strand plain, lagoonal coast, Nayarit,

Mexico. In: Coastal Lagoons – a Symposium (Eds A.A.

Castanares and F.B. Phleger), pp. 63–100. Universidad

Nacional Autonoma, Mexico.

Davis, R.A. and Hayes, M.O. (1984) What is a wave-dominated

coast? Mar. Geol., 60, 313–329.

De Vroeg, J.H., Smit, E.S.P. and Bakker, W.T. (1988) Coastal

genesis. In: Proceedings of the 21st International Conference

on Coastal Engineering, pp. 2825–2839. American Society

of Civil Engineers, New York.

Dott, R.H. (1982) Episodic sedimentation – how normal is

average? how rare is rare? does it matter? J. Sed. Petrol., 53,5–23.

Dott, R.H. and Bourgeois, J. (1982) Hummocky stratification:

significance of its variable bedding sequences. Bull. Geol.

Soc. Am., 93, 663–680.

Dueholm, K.S. and Olsen, T. (1993) Reservoir analog studies

using multimodel photogrammetry: a new tool for the pet-

roleum industry. AAPG Bull., 77, 2023–2031.

Elliott, T. (1986) Clastic shorelines. In: Sedimentary Environ-

ments and Facies (Ed. H.G. Reading), pp. 143–177. Black-

well Scientific Publications, Oxford.

Fouch, T.D., Lawton, T.F., Nichols, D.J., Cashion, W.B. and

Cobban, W.A. (1983) Patterns and timing of synorogenic

sedimentation in Upper Cretaceous rocks of central and

northeast Utah. In: Mesozoic Paleogeography of the West-

Central United States (Eds M.W. Reynolds and E.D. Dolly),

pp. 305–336. SEPM, Rocky Mountain Section, Denver, CO.

Greenwood, B. and Sherman, D.J. (1986) Hummocky cross

stratification in the surf zone: flow parameters and bedding

genesis. Sedimentology, 33, 33–45.

Hampson, G.J. (2000) Discontinuity surfaces, clinoforms, and

facies architecture in a wave-dominated, shoreface-shelf

parasequence. J. Sed. Res., 70, 325–340.

Hampson, G.J., Burgess, P.M. and Howell, J.A. (2001) Shore-

face tongue geometry constrains history of relative sea-level

fall: examples from late Cretaceous strata in the Book Cliffs

area, Utah. Terra Nova, 13, 188–196.

Helland-Hansen, W. and Martinsen, O.J. (1996) Shoreline

trajectories and sequences: description of variable deposi-

tional-dip scenarios. J. Sed. Res., B66, 670–688.

Hobday, D.K. and Reading, H.G. (1972) Fair weather versus

storm processes in shallow marine sand bar sequences in

the late Precambrian of Finnmark, North Norway. J. Sed.

Petrol., 42, 318–324.

Howard, J.D. and Frey, R.W. (1984) Characteristic trace fossils

in nearshore to offshore sequences, Upper Cretaceous of

east-central Utah. Can. J. Earth Sci., 21, 200–219.

Inman, D.L. and Bagnold, R.A. (1963) Littoral processes. In:

The Sea, Vol. 3 (Ed. M.N. Hill), pp. 529–553. Wiley-Inter-

science, New York.

Jennette, D.C. and Riley, C.O. (1996) Influence of relative sea-

level on facies and reservoir geometry of the Middle Jurassic

lower Brent Group, UK North Viking Graben. In: HighResolution Sequence Stratigraphy: Innovations and Appli-

cations (Eds J.F. Aitken and J.A. Howell), Geol. Soc. London

Spec. Publ., 104, 87–113.

Kamola, D.L. and Van Wagoner, J.C. (1995) Stratigraphy and

facies architecture of parasequences with examples from the

Spring Canyon Member, Blackhawk Formation, Utah. In:

Sequence Stratigraphy of Foreland Basin Deposits: Outcropand Subsurface Examples from the Cretaceous of North

America (Eds J.C. Van Wagoner and G.T. Bertram), AAPG

Mem., 64, 27–54.

Larson, M. and Kraus, N.C. (1994) Temporal and spatial scales

of beach profile change, Duck, North Carolina. Mar. Geol.,

117, 75–94.

Lee, G., Nicholls, R.J. and Birkemeier, W.S. (1998) Storm-

driven variability of the nearshore-profile at Duck, North

Carolina, USA, 1981–91. Mar. Geol., 148, 163–177.

McCubbin, D.G. (1982) Barrier-island and strand-plain facies.

In: Sandstone Depositional Environments (Eds P.A. Scholle

and D. Spearing), AAPG Mem., 31, 247–279.

MacEachern, J.A., Raychaudhuri, I. and Pemberton, S.G.(1992) Stratigraphic applications of the Glossifungites

ichnofacies: delineating discontinuities in the rock record.

In: Applications of Ichnology to Petroleum Exploration

(Ed. S.G. Pemberton), SEPM Core Workshop, 17, 169–198.

700 G. J. Hampson & J. E. A. Storms

� 2003 International Association of Sedimentologists, Sedimentology, 50, 667–701

Page 35: Geomorphological and sequence stratigraphic variability …download.xuebalib.com/xuebalib.com.34933.pdf · Geomorphological and sequence stratigraphic variability ... facies model,

Niedoroda, A.W., Swift, D.J.P. and Thorne, J.A. (1989) Mod-

elling shelf storm beds: controls of bed thickness and bed-

ding sequence. In: Shelf Sedimentation, Shelf Sequences

and Related Hydrocarbon Accumulation (Eds R.A. Morton

and D. Nummedal), pp. 15–39. Proceedings of the Gulf

Coast Section SEPM 7th Annual Research Conference.

Nummedal, D. and Swift, D.J.P. (1987) Transgressive strati-

graphy at sequence-bounding unconformities: some princi-

ples derived from Holocene and Cretaceous examples. In:

Sea-Level Fluctuation and Coastal Evolution (Eds D. Num-

medal, O.H. Pilkey and J.D. Howard), SEPM Spec. Publ., 41,241–260.

Nummedal, D., Riley, G.W. and Templett, P.L. (1993) High-

resolution sequence architecture: a chronostratigraphic

model based on equilibrium profile studies. In: SequenceStratigraphy and Facies Associations (Eds H.W. Posamen-

tier, C.P. Summerhayes, B.U. Haq and G.P. Allen), Int.

Assoc. Sedimentol. Spec. Publ., 18, 55–68.

O’Byrne, C.J. and Flint, S.S. (1995) Sequence, parasequence,

and intra-parasequence architecture of the Grassy Member,

Blackhawk Formation, Book Cliffs, Utah, USA In: Sequence

Stratigraphy of Foreland Basin Deposits: Outcrop andSubsurface Examples from the Cretaceous of North America

(Eds J.C. Van Wagoner and G.T. Bertram), AAPG Mem., 64,225–255.

Olsen, T.R., Mellere, D. and Olsen, T. (1999) Facies architec-

ture and geometry of landward-stepping shoreface tongues:

the Upper Cretaceous Cliff House Sandstone (Mancos Can-

yon, south-west Colorado). Sedimentology, 46, 603–626.

Pattison, S.A.J. (1995) Sequence stratigraphic significance of

sharp-based lowstand shoreface deposits, Kenilworth

Member, Book Cliffs, Utah. AAPG Bull., 79, 444–462.

Penland, S., Suter, J.R. and Boyd, R. (1985) Barrier island arcs

along abandoned Mississippi River deltas. Mar. Geol., 63,197–233.

Reineck, H.E. and Singh, I.B. (1972) Genesis of laminated sand

and graded rhythmites in storm-sand layers of shelf mud.

Sedimentology, 18, 123–128.

Reynolds, A.D. (1999) Dimensions of paralic sandstone bod-

ies. AAPG Bull., 83, 211–229.

Rodriguez, A.B., Fassell, M.L. and Anderson, J.B. (2001) Var-

iations in shoreface progradation and ravinement along the

Texas coast, Gulf of Mexico. Sedimentology, 48, 837–853.

Ryer, T.A. and Langer, A.W. (1980) Thickness change in-

volved in the peat-to-coal transformation for a bituminous

coal of Cretaceous age in central Utah. J. Sed. Petrol., 50,987–992.

Smith, D.G., Meyers, R.A. and Jol, H.M. (1999) Sedimentology

of an upper-mesotidal (3.7 m) Holocene barrier, Willapa

Bay, SW Washington, USA. J. Sed. Res., 69, 1290–1296.

Stive, M.J.F. and De Vriend, H.J. (1995) Modelling shoreface

profile evolution. Mar. Geol., 126, 235–248.

Storms, J.E.A. (2003) Event-based stratigraphic simulation of

wave-dominated shallow-marine environments. Mar. Geol.,

(in press).

Storms, J.E.A., Weltje, G.J., Van Dijke, J.J., Geel, C.R. and

Kroonenberg, S.B. (2002) Process-response modelling of

wave-dominated coastal systems: simulating evolution and

stratigraphy on geological timescales. J. Sed. Res., 72, 226–

239.

Tanner, W.F. (1982) Equilibrium shoreline. In: The Encyclo-

pedia of Beaches and Coastal Environments (Ed. M.L.

Schwartz), pp. 391–392. Hutchinson-Ross, Stroudsberg.

Taylor, D.R. and Lovell, R.W.W. (1995) High-frequency

sequence stratigraphy and paleogeography of the Kenil-

worth Member, Blackhawk Formation, Book Cliffs, Utah,

USA In: Sequence Stratigraphy of Foreland Basin Deposits:Outcrop and Subsurface Examples from the Cretaceous of

North America (Eds J.C. Van Wagoner and G.T. Bertram),

AAPG Mem., 64, 257–275.

Valasek, D.W. (1990) Compartmentalization of shoreface

sequences in the Cretaceous Gallup Sandstone west of

Shiprock, New Mexico: implications for reservoir quality

and continuity (Abstract). AAPG Bull., 74, 784.

Van der Valk, L. (1992) Mid- and late-Holocene evolution inthe beach barrier area of the western Netherlands. UnPubl.

PhD Thesis, Free University of Amsterdam, 235 pp.

Van Wagoner, J.C., Mitchum, R.M., Campion, K.M. and

Rahmanian, V.D. (1990) Siliciclastic sequence stratigraphy

in well logs, cores, and outcrops. AAPG Methods in

Exploration, 7, 55 pp.

Walker, R.G. and Plint, A.G. (1992) Wave and storm-domin-

ated shallow marine systems. In: Facies Models: Response

to Sea-Level Change (Eds R.G. Walker and N.P. James),

pp. 219–238. Geological Association of Canada, St John’s,

Newfoundland.

Manuscript received 11 December 2001;revision accepted 12 March 2003.

Variability in wave-dominated, shoreface-shelf parasequences 701

� 2003 International Association of Sedimentologists, Sedimentology, 50, 667–701

Page 36: Geomorphological and sequence stratigraphic variability …download.xuebalib.com/xuebalib.com.34933.pdf · Geomorphological and sequence stratigraphic variability ... facies model,

本文献由“学霸图书馆-文献云下载”收集自网络,仅供学习交流使用。

学霸图书馆(www.xuebalib.com)是一个“整合众多图书馆数据库资源,

提供一站式文献检索和下载服务”的24 小时在线不限IP

图书馆。

图书馆致力于便利、促进学习与科研,提供最强文献下载服务。

图书馆导航:

图书馆首页 文献云下载 图书馆入口 外文数据库大全 疑难文献辅助工具