Foredeep submarine fans and forebulge deltas: orogenic oﬀ … · 2015-10-06 · Foredeep...

Foredeep submarine fans and forebulge deltas:orogenic off-loading in the underfilled Karoo Basin

O. Catuneanu a,*, P.J. Hancox b, B. Cairncross c, B.S. Rubidge d

a Department of Earth and Atmospheric Sciences, University of Alberta, 1-26 Earth Sciences Building, Edmonton, Alta., Canada T6G 2E3b Department of Geology, University of Witwatersrand, PO Wits, Johannesburg 2050, South Africa

c Department of Geology, Rand Afrikaans University, P.O. Box 524, Auckland Park, Johannesburg 2006, South Africad Bernard Price Institute for Palaeontological Research, University of Witwatersrand, PO Wits, Johannesburg 2050, South Africa

Received 5 February 2002; accepted 28 October 2002

Abstract

Third-order sequence stratigraphic analysis of the Early Permian marine to continental facies of the Karoo Basin provides a case

study for the sedimentation patterns which may develop in an underfilled foreland system that is controlled by a combination of

supra- and sublithospheric loads. The tectonic regime during the accumulation of the studied section was dominated by the flexural

rebound of the foreland system in response to orogenic quiescence in the Cape Fold Belt, which resulted in foredeep uplift and

forebulge subsidence. Coupled with flexural tectonics, additional accommodation was created by dynamic loading related to the

process of subduction underneath the basin. The long-wavelength dynamic loading led to the subsidence of the peripheral bulge

below base level, which allowed for sediment accumulation across the entire foreland system.

A succession of five basinwide regressive systems tracts accumulated during the Artinskian (�5 My), consisting of foredeep

submarine fans and correlative forebulge deltas. The progradation of submarine fans and deltaic systems was controlled by coeval

forced and normal regressions of the proximal and distal shorelines of the Ecca interior seaway respectively. The deposition of each

regressive systems tract was terminated by basinwide transgressive episodes, that may be related to periodic increases in the rates of

long-wavelength dynamic subsidence.

� 2003 Elsevier Science Ltd. All rights reserved.

Keywords: Underfilled foredeep; Forebulge; Flexural tectonics; Dynamic subsidence; Systems tracts

1. Introduction

This paper provides a case study for the sedimenta-

tion patterns that may develop in an underfilled retroarc

foreland system, under a unique combination of factorsthat control the dynamics of the basin and the amounts

of available accommodation. These factors refer to

flexural compensation in response to orogenic unload-

ing, dynamic subsidence related to subduction pro-

cesses, and eustatic fluctuations. The example is from

the Karoo Basin of South Africa (Fig. 1), and deals with

the nature and correlation of the marine to continental

facies of Early Permian age that are associated with theevolution of the Ecca interior seaway. This research

builds on previous work that already established the

large-scale (second-order) sequence stratigraphic

framework of the Karoo Supergroup, and the relation-

ship between the foreland stratigraphy and the orogenic

cycles of loading and unloading in the adjacent Cape

Fold Belt (Catuneanu et al., 1998). The objective of thispaper is to increase the resolution of sequence strati-

graphic analysis to the third-order level of cyclicity for

the Early Permian stage of orogenic unloading that af-

fected the evolution of the Ecca seaway in the Karoo

Basin. This stage of orogenic unloading followed the

second major paroxysm recorded in the Cape Fold Belt

(P2 in Fig. 2) (H€aalbich, 1992).

1.1. Geological background

The Late Carboniferous to Middle Jurassic KarooBasin forms one of the most complete stratigraphic

successions in the world that span this time interval

(Veevers et al., 1994). Along a dip-oriented profile, the

Journal of African Earth Sciences 35 (2002) 489–502

www.elsevier.com/locate/jafrearsci

* Corresponding author. Tel.: +1-780-492-6569; fax: +1-780-492-

7598.

E-mail address: [email protected] (O. Catuneanu).

0899-5362/03/$ - see front matter � 2003 Elsevier Science Ltd. All rights reserved.

PII: S0899-5362 (02 )00154-9

mail to: [email protected]

Karoo sedimentary fill displays a wedge-shaped geo-

metry, typical for foreland successions, with a maximum

preserved thickness in excess of 6 km adjacent to the

Cape Fold Belt (Rubidge, 1995). The sedimentary por-

tion of the basin fill includes glacial (Dwyka Group),

marine (Ecca Group), and nonmarine (Beaufort and

Stormberg groups) deposits, which are capped by the

volcanic Drakensberg Group that relates to the break-

Fig. 1. Geological map of the preserved Karoo Basin, showing the outcrop distribution of the main lithostratigraphic units of the Karoo Super-

group. The Adelaide and Tarkastad subgroups together form the Beaufort Group.

Fig. 2. Lithostratigraphy of the Ecca Group along a north–south transect through the basin (compiled information from Oelofsen, 1987; Millsteed,

1994; Rubidge, 1995; Visser, 1995; Scott, 1997; Berthold et al., 1999). The stratigraphic hinge line that separates the foredeep from the forebulge has

been previously mapped for consecutive time slices in the evolution of the basin (Catuneanu et al., 1998). All formations shown in this chart have

regional development, excepting for the Ripon, Fort Brown, and Waterford, which have other correlative formations to the west (see Fig. 5). P2, P3,

and P4 represent the second, third, and fourth tectonic paroxysms in the Cape Fold Belt (H€aalbich, 1983, 1992; H€aalbich et al., 1983; Gresse et al.,

1992; see text for details).

490 O. Catuneanu et al. / Journal of African Earth Sciences 35 (2002) 489–502

up of Gondwana (Smith et al., 1998; Fig. 1). The KarooBasin was transgressed by an interior seaway during the

deposition of the Dwyka and Ecca groups, which com-

pletely regressed from the limits of the preserved basin at

the end of Ecca time. The bathymetric conditions of this

interior seaway changed from deep marine (102 m),

during the Dwyka–lower Ecca interval, to shallow ma-

rine (101 m) during the upper Ecca time (Visser and

Loock, 1978).The stratigraphy of the Karoo Supergroup is mar-

kedly different between the southern (proximal) and

northern (distal) regions of the basin. These differences

reflect contrasting tectonic histories across the flexural

hinge line of the foreland system (Catuneanu et al.,

1998). A deep marine environment controlled the sedi-

mentation processes in the south, leading to the accu-

mulation of marine till with dropstones (Dwyka Group),basin floor pelagic sediments (Prince Albert and

Whitehill formations), and submarine fans (Collingham

and Ripon formations) (Fig. 2). Sedimentation in the

southern Karoo continued with shallow marine deposits

including shelf and marginal marine facies (Fort Brown

and Waterford formations, respectively; Fig. 2). Con-

comitant with the deposition in the south, sediment

aggradation took place in the northern region of theKaroo Basin as well, in nonmarine to shallow marine

environments. The Dwyka–Ecca distal stratigraphy is

represented by continental tillites (Dwyka Group),

shallow marine facies (Pietermaritzburg and Volkrust

formations), and coal-bearing fluvial-deltaic strata

(Vryheid formation; Fig. 2). The regression of the Ecca

seaway led to the establishment of a fully nonmarine

environment within the limits of the preserved KarooBasin, which resulted in the accumulation of the fluvio-

lacustrine Beaufort Group and the subsequent aggra-

dation of the fluvial and aeolian Stormberg strata

(Smith, 1990; Smith et al., 1993).

1.2. Tectonic setting

The Karoo Basin is a retroarc foreland system (de

Wit et al., 1988; Johnson, 1991; Catuneanu et al., 1998)

formed in front of the Cape Fold Belt in response to

crustal shortening brought about by the subduction of

the paleo-Pacific plate beneath the Gondwana plate(Lock, 1978, 1980; de Wit and Ransome, 1992; Py-

sklywec and Mitrovica, 1989). Catuneanu et al. (1998)

modeled the changes in accommodation in the Karoo

Basin as being controlled by the flexural response of the

lithosphere to orogenic cycles of loading and unloading.

They further showed that the out of phase history of

base level changes between the foredeep and the fore-

bulge flexural provinces generated contrasting stratig-raphies with a timing that matches the dated

compressional events in the Cape Fold Belt (H€aalbich,1983, 1992; H€aalbich et al., 1983; Gresse et al., 1992).

Eight tectonic paroxysms have been documented in theCape Fold Belt, and dated using radiometric techniques

(H€aalbich, 1983, 1992; H€aalbich et al., 1983; Gresse et al.,

1992), three of which (P2–P4) are indicated in Fig. 2.

The ages of the orogenic paroxysms have been obtained

by dating the final phases of compression and meta-

morphism associated with each pulse of orogenic ac-

tivity (cooling age of metamorphic minerals), which

means that the dates indicate the end of active stages oftectonism. Orogenic paroxysms were followed by stages

of orogenic quiescence (unloading), which define eight

cycles of orogenic loading and unloading, during the

evolution of the Cape Fold Belt. Within each cycle, the

relative duration between the stages of loading and un-

loading was inferred based on the stratigraphic patterns

in the Karoo Basin (Catuneanu et al., 1998).

Pysklywec and Mitrovica (1989) propose that a sig-nificant component (up to 30%) of the proximal subsi-

dence, and all the distal subsidence, could be accounted

for by dynamic subsidence caused by the deflection of

the lithosphere due to mantle flow coupled to adjacent

subduction. Such a shallow dipping subducting slab

(30–40�) is also able to reconcile the long wavelength of

the basin subsidence as previously proposed by Lock

(1980).

1.3. Accommodation in retroarc foreland systems

Retroarc foreland systems form through the flexuraldeflection of the lithosphere in response to a combina-

tion of supra- and sublithospheric loads (Beaumont,

1981; Jordan, 1981; Mitrovica et al., 1989; Sinclair and

Allen, 1992; Beaumont et al., 1993; DeCelles and Giles,

1996; Catuneanu et al., 1999; Fig. 3). Supracrustal

loading by orogens leads to the partitioning of foreland

systems into flexural provinces, i.e., the foredeep, fore-

bulge, and back-bulge. Renewed thrusting (addition ofload) in the orogenic belt results in foredeep subsidence

and forebulge uplift, and the reverse occurs as the oro-

genic load is removed by erosion or extension. This

pattern of opposite vertical tectonics modifies the rela-

tive amounts of available accommodation in the two

flexural provinces, and may generate out of phase (re-

ciprocal) proximal to distal stratigraphies (Catuneanu

et al., 1997b, 1999, 2000; Catuneanu and Sweet, 1999).Coupled with flexural tectonics, additional accommo-

dation may be created or destroyed by the superimposed

effects of eustasy and dynamic (sublithospheric) loading.

The latter mechanism operates at regional scales, and

depends on the dynamics and geometry of the subduc-

tion processes underneath the basin (Mitrovica et al.,

1989; Gurnis, 1992; Holt and Stern, 1994; Catuneanu

et al., 1997a). The eustatic and tectonic controls on ac-commodation may generate sedimentary sequences and

unconformities over a wide range of timescales, both

over and under 106 yr (Peper et al., 1992; Burgess et al.,

O. Catuneanu et al. / Journal of African Earth Sciences 35 (2002) 489–502 491

1997; Miall, 1997). Stratigraphic evidence for the Karoo

Basin suggests that both flexural tectonics and dynamic

loading have contributed to the total amount of subsi-

dence (Catuneanu et al., 1998; Pysklywec and Mitrovica,

1989). The partitioning of the Karoo foreland system

into foredeep and forebulge settings was documented byCatuneanu et al. (1998) and the hinge line separating the

two flexural provinces was mapped for consecutive time

slices. This work showed that the hinge line migrated

along the dip in relation to the redistribution of load in

the Cape Fold Belt from the end of the Carboniferous to

the Triassic (Catuneanu et al., 1998).

The interplay of base level changes and sediment

supply controls the degree in which the available ac-commodation is consumed by sedimentation (Miall,

1997). This defines the underfilled, filled, and overfilled

stages in the evolution of the foreland system, in which

the depositional processes are dominated by deep ma-

rine, shallow marine, or fluvial sedimentation respec-

tively (Sinclair and Allen, 1992). In the case of the

Karoo Basin, the underfilled, filled, and overfilled pha-

ses correspond to the accumulation of the Dwyka–lowerEcca (deep marine), upper Ecca (shallow marine), and

Beaufort-‘‘Stormberg’’ (nonmarine) successions (Fig. 4).

1.4. Aim of research

This paper focuses on the submarine fans of the lowerEcca succession in the south of the Karoo Basin (Ripon

and correlative formations), and their deltaic to fluvial

correlatives in the north (Vryheid formation) (Fig. 2).

These deposits accumulated during the underfilled phase

of the Karoo foredeep, when water depths in the region

of 500 m were recorded along the proximal rim of the

basin (Visser and Loock, 1978). The submarine fans are

related to the foredeep of the Karoo foreland system,

and have been intensively studied as deep marine reser-

voir analogues for the petroleum industry (Bouma andWickens, 1991, 1994; Kingsley, 1977, 1981; Wickens,

1994; Scott, 1997; Scott and Bouma, 1998). Their cor-

relative marginal marine and fluvial facies to the north

are related to the flexural forebulge of the Karoo fore-

land system (Catuneanu et al., 1998), and have also been

the object of numerous studies due to their included

economic coalfields (Cadle et al., 1982, 1993; Cairncross,

1989; Cairncross and Cadle, 1987, 1988; Le Blanc Smith,1980). A paleogeographic reconstruction showing the

distribution of submarine fans and fluvio-deltaic envi-

ronments in relation to the proximal and distal shore-

lines of the Ecca interior seaway respectively, is

illustrated in Fig. 5.

The accumulation of the Ripon formation and cor-

relative deposits took place after the second tectonic

paroxysm in the Cape Fold Belt (P2 in Fig. 2), during astage of orogenic quiescence (Wickens, 1994; Scott and

Bouma, 1998). Our objective is to analyse the relative

contributions of the external controls on sedimentation

which may have led to the accumulation of the observed

facies during this particular tectonic regime.

2. Lithostratigraphy

The formations that define the stratigraphic objective

of this paper are presented in turn for the foredeep and

the forebulge flexural provinces of the foreland system.

Fig. 3. Tectonic mechanisms controlling accommodation in retroarc

foreland systems. Flexural tectonics is related to supracrustal loading

by orogens (Beaumont, 1981; Jordan, 1981; Beaumont et al., 1993).

Dynamic subsidence is triggered by sublithospheric loading, which in

turn is controlled by the process of subduction underneath the basin

(Mitrovica, 1989; Gurnis, 1992; Burgess et al., 1997). The composite

lithospheric deflection may be modified by basement tectonics, not

shown. The horizontal and vertical scales vary with the amount and

distribution of loads, and the rheology and thickness of the litho-

sphere.

Fig. 4. The underfilled, filled, and overfilled phases of the Karoo

Basin, as reflected by the foredeep facies.


2.1. Flexural foredeep

The deposition of submarine fans in the Karoo

foredeep took place within three discrete depozones, or

subbasins, separated by structural highs (Fig. 5). Thewestern (Tanqua) and central (Laingsburg) subbasins

are separated by the Baviaanshoek and Hex River-

Bontberg anticlines (Wickens, 1994; Cole et al., 1998;

Scott and Bouma, 1998). One other structural high is

postulated along the meridian 24�E, to explain the

lithostratigraphic differences between the Laingsburg

(central) and southern subbasins (Rubidge, 1995).

2.1.1. Southern subbasin

The stratigraphic objective in the southern subbasin is

the Ripon formation. This succession was interpreted as

a submarine fan complex by Truswell and Ryan (1969)

and Kingsley (1977). The name Ripon formation was

proposed for these rocks by Johnson (1976). Kingsley

(1977, 1981) recognised three members which constitute

the Ripon formation in the Eastern Cape, namely thePluto�s Vale, Wonderfontein and Trumpeters members

(Fig. 6). The entire basal Pluto�s Vale Member consists

of rhythmic turbidite units of varying thickness. The

fine- to very fine-grained greywacke beds grade upwards

into siltstone and shale. Parts of Bouma sequences can

be recognised, but complete Bouma sequences are scarce

(Kingsley, 1977). The overlying Wonderfontein Member

consists mainly of olive-grey, massive to laminatedmudstones, which in places shows graded bedding. A 5

m thick greywacke sandstone unit is present halfway up

this mudstone, and in many places has slumping on its

upper surface. Overlying this unit is the Trumpeters

Member which forms another sequence of greywackes

and mudstones with turbidite features (Kingsley, 1977).

The average azimuthal paleocurrent direction for the

Pluto�s Vale Member is 343�, and that for the Won-derfontein and Trumpeters members is 339�.

2.1.2. Laingsburg subbasin

The sequence under study in the Laingsburg subbasin

is represented by the Vischkuil and Laingsburg forma-

tions (Fig. 6). The Vischkuil formation, which is be-

tween 200 and 400 m thick, overlies the Collingham

formation and consists of mudrocks alternating withsubordinate sandstones. The mudrocks represent basin-

plain suspension settling of clays, interrupted by spo-

radic influxes of muddy turbidity flows. The sandstones,

Fig. 5. Paleogeographic reconstruction of the environments established in relation to the Ecca interior seaway of the Karoo Basin during the

Artinskian (compiled information from Kingsley, 1977; Cadle et al., 1993; Wickens, 1994; Rubidge, 1995). The position of the stratigraphic hinge line

is mapped by Catuneanu et al. (1998). The distribution of the northern deltaic and fluvial facies is restricted to the forebulge region. The foredeep

accumulated submarine fan systems along the southern rim of the basin, and almost exclusively pelagic facies to the north. The average paleocurrent

directions of the gravity flows are towards north-northeast (Southern subbasin), east (Laingsburg subbasin), and northeast (Tanqua subbasin).


which increase in thickness and abundance upwards,represent more proximal turbidites (Wickens, 1994). The

presence of minor tuff beds in the shale indicates con-

tinued volcanic activity in the southern magmatic arc

region (Cole et al., 1998). Conformably overlying the

Vischkuil formation are the sandstone packages of the

Laingsburg formation, which are organized as a suc-

cession of submarine fan systems (Scott, 1997). Greater

compression on the southern branch of the Cape FoldBelt caused the Laingsburg subbasin to evolve into a

deeper, narrower depozone of a more typical foredeep

style (Scott and Bouma, 1998). The submarine fan sys-

tems all have paleocurrent directions toward the east

(Scott, 1997; Fig. 5).

2.1.3. Tanqua subbasin

The gravity flow deposits of the Tanqua subbasin are

represented by the Tierberg and Skoorsteenberg for-

mations (Wickens, 1994) (Fig. 6). The Tierberg forma-

tion consists of grey shale and subordinate thin siltstonelayers. Very fine-grained sandstone beds occur in its

uppermost part (Cole et al., 1998). Deposition of mud

from suspension was the dominant sedimentary process,and water depths most likely did not exceed 500 m

(Visser and Loock, 1978). This formation is overlain by

the approximately 400 m thick Skoorsteenberg forma-

tion, which is composed of five sandstone packages

separated by mudrock units (Wickens, 1994). The Sko-

orsteenberg formation represents a basin floor complex

with the sandstone packages having been deposited by

submarine fan systems. Palaeocurrent directions forfour of the five fans range from the south-southwest to

south, and from west to west-northwest for the other

(Scott and Bouma, 1998).

2.1.4. Regional correlation

The correlation of submarine fan systems across the

three foredeep subbasins (Fig. 6) is based on the work of

Kingsley (1977), Wickens (1994), Scott (1997), Cole et al.

(1998) and Scott and Bouma (1998). Five discrete

gravity flow events can be inferred to have manifested

across the entire Karoo foredeep, resulting in the suc-cession of submarine fan systems observed in each of the

three subbasins. The correlation of gravity flow deposits

Fig. 6. Lithostratigraphic correlation of the post-Collingham Ecca formations along the southern rim of the basin (compiled information from

Kingsley, 1977; Wickens, 1994; Scott, 1977; Scott and Bouma, 1998). The vertical profile for the Southern subbasin is the Peddie section of Kingsley

(1977). Note the inferred coeval progradation of the five submarine fan systems in the three separate subbasins, suggesting that sedimentation

processes were controlled by external factors at the regional scale of the basin.


is further constrained by the presence of the 30 m thick,low-density turbidites of the Collingham formation at

the base of the submarine fan complexes in all subba-

sins, which can therefore be used as a stratigraphic da-

tum. The Collingham formation is underlain by the

pelagic facies of the Whitehill formation (Fig. 2), which

can also be traced across the entire Karoo foredeep.

Furthermore, the three submarine fan complexes are

overlain by the age-equivalent shallow marine facies ofthe Fort Brown and Kookfontein formations (Cole

et al., 1998; Fig. 6). The coeval gravity flow deposits of

the Tanqua, Laingsburg, and Southern subbasins (i.e.,

Ripon and correlative formations; Fig. 6) are dated as

Artinskian, with possible extension into the Kungurian

(Visser, 1995; Scott, 1997; Fig. 2). This age is further

supported by the independent dating of the underlying

Whitehill pelagic facies as Late Sakmarian (Oelofsen,1987; Oelofsen and Araujo, 1987 in Wickens, 1994), and

also by the recent radiometric dating of the lower

Collingham formation from ash beds as 270� 1 My,

which confirms the Sakmarian age of the pre-Ripon

facies (M. de Wit and S. Bowring, pers. comm.; Fig. 2).

The contemporaneous formation and filling of the

foredeep subbasins was also recognized by Scott and

Bouma (1998). The correlation of submarine fan sys-tems along the strike of the foredeep (Fig. 6) suggests

that the gravity flow events were driven by basin-scale

allogenic mechanisms rather than local controls at the

subbasin scale.

Further to the north relative to the submarine fan

depozones (i.e., the area between the submarine fans and

the flexural hinge line in Fig. 5), the depositional envi-

ronment of the foredeep was less dynamic, being domi-nated by basin floor pelagic sedimentation (Zawada and

Cadle, 1988).

2.2. Flexural forebulge

In contrast with the deep marine conditions esta-

blished along the proximal rim of the foredeep during

the Artinskian, the forebulge region was dominated by

deltaic to fluvial sedimentation (Fig. 5). Van Vuuren and

Cole (1979) were amongst the first to refer to the cyclical

nature of the upward-fining and upward-coarsening

successions that typify the Vryheid formation, charac-teristics that are well-documented by Hobday (1973),

Cadle (1974) and Mathew (1974). These three authors

ascribed the cyclicity to stacked depositional sequences

originating from deltaic and fluvial processes (Hobday,

1978). The formation is thickest in Kwazulu–Natal

(Blignaut and Furter, 1940), and thins progressively

towards the west and south until pinching-out (Cadle

et al., 1993; Fig. 7).The distribution of the strata forming the Vryheid

formation resulted from a combination of influence of

the source areas, sedimentation patterns, basement geo-

logy, basin tectonics, and eustatic processes (Cadle et al.,

1982). Maximum subsidence took place in the east of the

preserved Karoo Basin (Whateley, 1980; Stavrakis,

1989; Cadle et al., 1982; Fig. 7), as shown by the isopachmap. The clastic influx into the basin was driven by

bedload dominated river systems, which provided sedi-

ment to the shoreline delta systems positioned further

basinward (Cadle and Cairncross, 1993).

The stratigraphy of the Vryheid formation is des-

cribed by a succession of five coarsening-upward se-

quences which display a remarkable lateral continuity

across the entire distal region of the Karoo Basin (Cadleet al., 1982; Figs. 7 and 8). In a complete succession each

of the five coarsening-upward sequences starts with fine-

grained marine facies, which grade upwards into coarser

delta front and delta plain-fluvial facies. Several coal

seams occur in the Vryheid formation, and are associ-

ated predominantly with the coarser-grained fluvial fa-

cies at the top of each sequence (Fig. 8). These coal

seams can be traced laterally across the entire area ofoccurrence of the Vryheid formation. Research on

the Karoo coalfields (Le Blanc Smith, 1980; Cairn-

cross, 1986; Winter et al., 1987; Taverner-Smith et al.,

1988; Cadle, 1995) recognize the repetitive process

Fig. 7. Isopach map of the Vryheid formation, suggesting the patterns

of subsidence of the forebulge region (modified from Cadle et al.,

1982). The depocenter of forebulge sedimentation appears to be lo-

cated in the north-eastern part of the preserved basin. The generalized

vertical profile of the Vryheid formation is illustrated on the top-left

side of the diagram, showing a succession of five coarsening-upward

deltaic sequences. This profile is representative for the Vryheid for-

mation across the entire area of occurrence due to the remarkable

lateral continuity of the five progradational sequences. The thickness

of this succession varies according to the isopach map. The southern

limit of the Vryheid facies coincides with the location of the strati-

graphic hinge line (Fig. 5).


of basinward migration of coarse-grained (gravel-bed

braided) fluvial systems feeding into deltaic depositionalsystems. These periods were followed by stages of rising

water tables, favorable for peat accumulation. Further

deepening of the basin waters led to the flooding of the

peat swamps, which became covered with fine, trans-

gressive clastic material. A shifting balance between

sedimentation and the rates of base level rise is therefore

most likely to explain the cyclic nature of the Vryheid

formation. The transgressive units which occur at thebase of each coarsening-upward sequence are some of

the most widespread and laterally continuous beds in

the Vryheid formation in this northern part of the basin.

Such units form good markers for stratigraphic corre-

lation, and may be exemplified by the bioturbatedmudstones and siltstones above the no. 2 coal seam and

the bioturbated, glauconite-bearing argillites above the

no. 4 and no. 5 coal seams (Cadle et al., 1982, 1993;

Cairncross, 1986) (Fig. 8). The very good lateral conti-

nuity of the Vryheid sequences and coal beds suggests

uniform depositional conditions across the entire fore-

bulge region, with no partitioning into subbasins.

The Vryheid formation is dated as Artinskian, withpossible extension into the Kungurian (McLachlan and

Anderson, 1973; Loock and Visser, 1985; MacRae,

1988; Visser, 1990; Aitken, 1994, 1998; Millsteed, 1994).

3. Sequence stratigraphy

The sequence stratigraphic nomenclature used in this

paper is illustrated in Fig. 9. The various types of se-

quences, systems tracts and bounding surfaces are de-

fined in relation to the relative sea-level (combined effect

of tectonics and eustasy) and transgressive–regressive(T–R) (combined effect of relative sea-level and sediment

supply) curves.

3.1. Cyclicity of foredeep facies

The Ripon and correlative formations are built by a

relatively conformable succession of five submarine fansystems that may be correlated along the strike of the

basin (Figs. 5 and 6). Each submarine fan system dis-

plays a coarsening-upward trend that reflects the pro-

gradation of the system during times of base level fall

(Posamentier et al., 1992; Hunt and Tucker, 1992). The

lifespan of each submarine fan complex was terminated

by stages of abrupt water deepening and transgression

across the foredeep, which inhibited the manifestation ofmajor gravity flow events (Galloway, 1989; Embry,

1995). During such stages, the depositional regime

changed from gravity flow to fine-grained pelagic sedi-

mentation. The sharp contacts between turbidites and

the overlying pelagic facies suggest abrupt shifts from

forced regressions to subsequent transgressions, which

did not allow for the accumulation of any significant

normal regressive lowstand deposits. At the other end ofthe cycle, the contacts between pelagic and overlying

submarine fan facies are generally marked by scour

surfaces cut by the earliest gravity flows of each fan

complex (basal surface of forced regression, Hunt and

Tucker, 1992; Fig. 9). Below each basal surface of forced

regression, the pelagic deposits are undifferentiated and

attributed here to the transgressive systems tracts. The

lack of any recognizable normal regressive deposits(lowstand and highstand systems tracts; Fig. 9) allows to

interpret the submarine fan complexes as regressive

systems tracts.

Fig. 8. Stratigraphic column for the north-eastern part of the Vryheid

formation (modified from Cadle et al., 1982). The succession consists

of five T–R sequences, each of them including a transgressive and a

regressive systems tract. The transgressive systems tracts are related to

the marine flooding of the forebulge area, whereas the regressive sys-

tems tracts reflect normal regressions of the distal Ecca shoreline in

relation to fluvial-deltaic progradation. The marine facies are mainly

represented by fine-grained shelf sediments. The deltaic facies consist

of cross-laminated and cross-bedded sandstones. The fluvial facies

occur at the top of the T–R sequences, being represented by cross-

stratified gravels. Abbreviations: Fl––horizontally-laminated fine-

grained sediments; Sr––ripple cross-laminated sandstone; Sp––planar

cross-bedded sandstone; St––trough cross-bedded sandstone; Gx––

cross-bedded gravel; b––bioturbation; TST––transgressive systems

tract; RST––regressive systems tract; MFS––maximum flooding sur-

face; MRS––maximum regressive surface.


In this interpretation, the Ripon and correlative

successions are composed of five T–R sequences, each

comprising a relatively thin basal transgressive systemstract overlain by a much thicker regressive systems tract.

The former includes deeper water, fine-grained pelagic

sediments, whereas the latter includes the actual sub-

marine fans. The two systems tracts are bounded by the

maximum regressive surface (top of submarine fan fa-

cies, which replaces the correlative conformity in the

absence of a lowstand systems tract; Fig. 9) and by the

maximum flooding surface (top of pelagic facies, whichis reworked by the basal surface of forced regression in

the absence of a highstand systems tract; Fig. 9).

3.2. Cyclicity of forebulge facies

The Vryheid formation is also built by a succession of

five T–R sequences, as illustrated in Fig. 8. A number of

marker horizons, including glauconitic sandstones and

coal seams, can be traced across the entire forebulge

region (Cadle et al., 1982, 1993). The vertical profile isdominated by coarsening-upward trends which relate to

the gradual progradation of fluvio-deltaic systems. Each

T–R sequence includes a generally thinner (less than

10 m thick) transgressive systems tract overlain by a

much thicker (tens of meters range) regressive systems

tract. The transgressive systems tracts represent periodic

floodings of the forebulge region, when the entire

northern part of the Karoo Basin was transgressed fromsouth to north by a shallow marine environment. Each

transgressive episode was followed by normal regres-

sions of the shoreline in the northern part of the basin,

in a southerly direction, during which the progradation

and aggradation of fluvio-deltaic systems took place.

Fig. 5 illustrates one of the regressive stages in theevolution of the Vryheid formation. The periodic change

in the direction of the shoreline shift between the

transgressive and regressive stages is likely related to the

interplay between sediment supply and varying rates of

base level rise.

The key stratigraphic surfaces that delineate the

transgressive and regressive systems tracts are the maxi-

mum regressive surfaces and the maximum floodingsurfaces (Fig. 8). The maximum regressive surfaces

bound the T–R sequences, marking the timing of the

maximum regressions of the distal shoreline of the Ecca

seaway. These surfaces are found at the top of the

coarsening-upward prograding facies. The maximum

flooding surfaces correspond to the timing of maximum

marine transgressions, and are found at the top of fine-

grained shelf facies.

3.3. Regional correlation

The resolution of the available time control only al-

lows for stratigraphic correlations at the formation level

(Fig. 2). The only two lines of correlation constrained by

biostratigraphic evidence are shown in Fig. 10 at the

base and top of the studied successions. The position of

these horizons indicate coeval transgressions for the

earliest foredeep and forebulge T–R sequences, as wellas coeval deposition of the latest foredeep submarine

fans and forebulge deltaic deposits. This suggests that

the proximal and distal shorelines of the Ecca seaway

Fig. 9. Types of sequences, bounding surfaces and systems tracts defined in relation to the base level and T–R curves (from Catuneanu, 2002).

Abbreviations: TST––transgressive systems tract; RST––regressive systems tract; LST––lowstand systems tract; HST––highstand systems tract;

FSST––falling stage systems tract; SU––subaerial unconformity; c.c.––correlative conformity; MRS––maximum regressive surface; MFS––maxi-

mum flooding surface; BSFR––basal surface of forced regression; (A)––positive accommodation; NR––normal (sediment supply-driven) regression;

FR––forced (base level fall-driven) regression.


(Fig. 5) may have experienced similar types of shore-

line shifts, i.e., coeval transgressions and coeval regres-sions.

Higher-frequency sequence stratigraphic correlations

can be further inferred within the studied interval. The

Artinskian (�Kungurian) foredeep and forebulge suc-

cessions both include five sequences of stacked subma-

rine fans and deltas respectively. We suggest a direct

correlation of these five sequences along the dip of the

Karoo foreland system, as illustrated in Fig. 10. Thisinterpretation assumes periodic episodes of basinwide

flooding of the Karoo Basin, separated by periods of

time of coeval forced and normal regressions of the

proximal and distal shorelines of the Ecca interior sea-

way respectively. The proposed correlation is based on

the following arguments:

(i) Chemical, petrographic, and microprobe analyses

of the sandstones in the submarine fan systems indicatethey were derived from the same distant source areas,

during times of tectonic quiescence and denudation in

the Cape Fold Belt (Wickens, 1994; Scott, 1997; Scott

and Bouma, 1998). Such times of tectonic quiescence

correspond to a stage of erosional orogenic unloading,

which is expected to result in the isostatic rebound of the

foredeep compensated by flexural subsidence of the

forebulge (Beaumont et al., 1993). This tectonic regimetranslates into proximal base level fall coeval with distal

base level rise, which supports the correlation between

proximal forced regressions (gravity flows) and distal

normal regressions (deltaic facies). The normal regres-

sions require sedimentation rates higher than the rates

of base level rise, which is a likely scenario given the low

rates of forebulge flexural subsidence.(ii) Basinwide transgressions require the manifesta-

tion of long wavelength controls on accommodation,

such as global (eustatic) sea-level rise, or regional scale

dynamic subsidence. Both these mechanisms are known

to have been operative during Ecca times (Cadle et al.,

1993; Pysklywec and Mitrovica, 1989), which allows for

the correlation of proximal and distal transgressive

systems tracts.An alternative interpretation would be to correlate

the proximal transgressive facies (pelagic sediments)

with the distal normal regressive deposits (deltaic facies),

and implicitly the proximal forced regressive deposits

(submarine fans) with the distal transgressive facies.

This is an unlikely scenario for a stage of tectonic qui-

escence, which involves a flexural regime of foredeep

uplift and forebulge subsidence. In order to have proxi-mal transgressions, the rates of flexural uplift must be

outpaced by the rates of long-wavelength base level rise.

In turn this infers even higher rates of distal relative sea-

level rise, as the long-wavelength base level rise is com-

plemented by flexural subsidence. The interplay of

flexural and long-wavelength controls results in more

accommodation being created in the distal region of the

foreland system, which implies that the distal shorelineis more likely to be the subject of transgressive, rather

than normal regressive, shifts.

The end members of the five regional sequences in

Fig. 10 are the foredeep submarine fans and the fore-

bulge deltas. Each of these sequences represent higher-

Fig. 10. Regional correlation between the foredeep submarine fan systems and the forebulge deltaic sequences. Both successions are dated as

Artinskian, with possible extension into the Kungurian. No higher resolution time control is available, but a one-to-one correlation between the five

submarine fan systems and the five deltaic sequences is proposed on theoretical grounds (see text for details).


frequency subdivisions of the second-order cyclothemsidentified in previous research (Catuneanu et al., 1998),

and are therefore interpreted here as third-order se-

quences. Considering the 5 My duration of the Artins-

kian (Fig. 2), the average timespan of these third-order

sequences is 1 My.

4. Discussion

The key element of this case study is the background

regime of tectonic quiescence during which the accu-

mulation of submarine fans and their correlative Vry-

heid deposits took place (Wickens, 1994; Scott, 1997;

Scott and Bouma, 1998). This fits well into the succes-

sion of tectonic paroxysms of H€aalbich (1983, 1992),

H€aalbich et al. (1983) and Gresse et al. (1992). The ac-cumulation of the submarine fan-deltaic sequences took

place during the quiescence time which separated the

second and third tectonic paroxysms in the Cape Fold

Belt (Fig. 2). This means that the duration of the third

tectonic paroxysm was of 5 My or less, which is inagreement with the fact that stages of orogenic thrusting

and loading tend to be much shorter relative to the

stages of orogenic quiescence (Catuneanu et al., 1997b).

In our case, considering the 20 My interval that sepa-

rates the tectonic paroxysms P2 and P3 (Fig. 2), the

inferred ratio between the post-P2 quiescence stage and

the pre-P3 loading stage is at least 3:1 (15 My or more

versus 5 My or less respectively).Superimposed on this background flexural regime of

foredeep rebound and forebulge subsidence, eustatic

fluctuations in sea-level and/or fluctuations in the rates

of long-wavelength dynamic subsidence modified the

amounts of available accommodation across the basin.

Both eustasy and dynamic subsidence may undergo

changes in rates and magnitudes at the observed time-

scales of 105–106 yr (Gurnis et al., 1996; Burgess et al.,1997; Miall, 1997), which could explain the interpreted

basinwide transgressive facies. We thus infer that the

coeval proximal forced regressions and distal normal

regressions are the result of long-term flexural tectonics,

Fig. 11. Conceptual model for the deposition of the observed transgressive and regressive facies. The two block diagrams illustrate a full cycle

leading to the sedimentation of each one of the five third-order sequences. The same flexural background of orogenic unloading operated in both

cases, but fluctuations in the rates of long-wavelength base level rise (dynamic subsidence and/or eustasy) led to cyclic changes in the relative im-

portance between the two controls on accommodation. Diagram (1) shows a foreland system dominated by flexural tectonics. The coeval forced and

normal regressions of the proximal and distal shorelines of the Ecca seaway account for the accumulation of gravity flow and deltaic facies. Diagram

(2) illustrates the periods of time when flexural tectonics was outpaced by increased rates of long-wavelength base level rise. The basinwide rise in base

level inhibited the major gravity flow events, leading to pelagic sedimentation in the foredeep, and triggered the flooding of the forebulge region.


and that this regime was periodically interrupted bypulses of basinwide drowning and transgressions in re-

lation to the higher-frequency fluctuations of eustasy

and/or dynamic loading. Such fluctuations in the

amount of dynamic loading are related to changes in the

angle and velocity of subduction underneath the retro-

arc foreland system (Mitrovica et al., 1989; Gurnis,

1992; Holt and Stern, 1994).

The block diagrams in Fig. 11 illustrate palaeogeo-graphic reconstructions of the foredeep and forebulge

environments during the regressive and transgressive

phases of each sequence. Fig. 11(1) shows the coeval

deposition of submarine fans (forced regressive shore-

line) and deltaic systems (normal regressive shoreline)

during the flexural regime of orogenic unloading that

dominated the Artinskian. Fig. 11(2) accounts for the

periods of time in which the rates of long-wavelengthbase level rise outpaced the background effects of flex-

ural tectonics. Such stages resulted in the drowning of

the foreland system, with the development of pelagic

facies in the foredeep and shallow marine transgressive

facies over the forebulge. It is important to note that

sediment aggradation took place across the entire fore-

land system during both regressive and transgressive

phases due to the fact that the flexural forebulge had notopographic expression, being placed below the base

level. Such a ‘‘missing’’ peripheral bulge has also been

documented in the Western Canada Basin, and is an

evidence for the manifestation of long-wavelength dy-

namic subsidence (Catuneanu et al., 1997a).

The importance of the external controls on sedi-

mentation is further supported by the in-phase accu-

mulation of submarine fans across the syn-depositionalstructural highs, within the three separate subbasins

(Fig. 6). The five inferred third-order sequences can be

traced across the flexural hinge line of the foreland

system, within both the foredeep and the forebulge

provinces (Fig. 10), which also supports the importance

of the external controls on accommodation and sedi-

mentation.

The accumulation of submarine fans in the Karooforedeep represents the last stage of the underfilled

phase in the evolution of the Karoo Basin. The succes-

sion of foredeep Ecca facies started with the basin floor

pelagic sediments of the Prince Albert and Whitehill

formations, which were gradually prograded by the

submarine fan systems of the Collingham, Ripon and

correlative formations. The contact between the Ripon

and Fort Brown formations, and their correlatives to thewest, marks the debut of the filled phase of the Karoo

Basin, which was dominated by the shelf and shallower

marine facies of the Fort Brown/Kookfontein and

Waterford formations. The final regression of the Ecca

seaway, represented in the stratigraphy by the Ecca-

Beaufort contact, marks the debut of the overfilled

phase in the evolution of the Karoo Basin (Fig. 4).

5. Conclusions

(1) Five third-order T–R sequences of Artinskian age

accumulated during a period of time of �5 My within

the Karoo foreland system. These sequences can be

mapped across the flexural hinge line of the basin, both

within the foredeep and the forebulge regions. Each T–

R sequence is composed of one transgressive and one

regressive systems tract.(2) The regressive systems tracts include foredeep

submarine fans and forebulge deltas. They accumulated

in relation to the flexural regime of orogenic unloading

in the Cape Fold Belt, which resulted in foredeep uplift

and forebulge subsidence. This tectonic regime deter-

mined the manifestation of coeval forced and normal

regressions of the proximal and distal shorelines of the

Ecca interior seaway respectively.(3) Coupled with flexural tectonics, additional ac-

commodation for sediment accumulation was created by

long-wavelength dynamic subsidence. As a consequence

of dynamic loading, the peripheral bulge of the foreland

system subsided below the base level, allowing for sedi-

ment accumulation across the entire foreland system.

(4) The transgressive systems tracts of each T–R se-

quence are related to periods of time of overall drown-ing of the foreland system in relation to increased rates

of long-wavelength base level rise. The transgressive

facies are represented by pelagic sediments in the fore-

deep, and shallow marine strata in the forebulge region.

(5) This case study may illustrate a predictable asso-

ciation of facies for the underfilled phase of any retroarc

foreland system in which accommodation is controlled

by both orogenic and sublithospheric loading. Themiddle portions of all studied T–R sequences are almost

exclusively composed of pelagic facies (potential source

rocks), which grade laterally into foredeep and forebulge

reservoirs (turbidites and deltaic facies respectively).

Acknowledgements

OC acknowledges financial support from the Uni-

versity of Alberta and NSERC Canada, while PJH and

BSR acknowledge support from the NRF and the

University of the Witwatersrand. We wish to thank P.G.

Eriksson and J.J. Veevers for their comments which

helped to improve earlier versions of this manuscript.

References

Aitken, G.R., 1994. Permian palynomorphs from the Number 5 Seam,

Ecca group, Witbank/Highveld Coalfields, South Africa. Palaeont.

Afr. 31, pp. 97–109.

Aitken, G.R., 1998. A palynological and palaeoenvironmental analysis

of Permian and early Triassic sediments of the Ecca and Beaufort

groups, northern Karoo basin, South Africa. PhD thesis (unpubl.),


University of the Witwatersrand, Johannesburg, South Africa, 499

pp.

Beaumont, C., 1981. Foreland basins. Geophys. J. Roy. Astronom.

Soc. 65, 291–329.

Beaumont, C., Quinlan, G.M., Stockmal, G.S., 1993. The evolution of

the western interior basin: causes, consequences and unsolved

problems. In: Caldwell, W.G.E., Kauffman, E.G. (Eds.), Evolution

of the Western Interior Basin. Geol. Assoc. Canada, Special Paper

39, pp. 97–117.

Berthold, B., Stollhofen, H., Lorenz, V., Armstrong, R., 1999. The

geochronology and significance of ash-fall tuffs in the glaciogenic

Carboniferous-Permian Dwyka Group of Namibia and South

Africa. J. Afr. Earth Sci. 29 (1), 33–49.

Blignaut, J.J., Furter, F.J.J., 1940. The northern Natal Coalfield (area

1). The Vryheid-Paulpietersburg area. Coal Mem. Geol. Surv. S.

Afr. 1, 336.

Bouma, A.M., Wickens, H. de V., 1991. Permian passive margin

submarine fan complex, karoo basin, South Africa: possible model

to Gulf of Mexico. Gulf Coast Assoc. Geol. Soc. Trans. 41, 30–42.

Bouma, A.M., Wickens, H. de V., 1994. Tanqua Karoo, ancient

analog for fine-grained submarine fans. In: Weimer, P., Bouma

A.M., Perkins, B.F. (Eds.), Submarine Fan and Turbedite Systems:

Sequence Stratigraphy, Reservoir Architecture, and Production

Characteristics. Gulf of Mexico and international: Proceedings,

15th Annual GCSSEPM Conference, pp. 23–34.

Burgess, P.M., Gurnis, M., Moresi, L., 1997. Formation of sequences

in the cratonic interior of North America by interaction between

mantle, eustatic, and stratigraphic processes. GSA Bull. 108 (12),

1515–1535.

Cadle, A.B., 1974. A subsurface sedimentological investigation of parts

of the Ecca and Beaufort Groups in the north-eastern Karoo Basin.

M.Sc. thesis (unpubl.), University of Natal, Pietermaritzburg, 144

pp.

Cadle, A.B., 1995. Depositional systems of the Permian Vryheid

formation Highveld Coalfield, South Africa. Their relationship to

coal seam occurrence and distribution. PhD thesis (unpubl.),

University of the Witwatersrand, Johannesburg, 316 pp.

Cadle, A.B., Cairncross, B., 1993. A sandy, bed-load dominated fluvial

system deposited by lateral-accretion: Permian Karoo Sequence,

South Africa. Sediment. Geol. 85, 435–455.

Cadle, A.B., Hobday, D.K., Smyth, M., van Rensburg, W.C.J., 1982.

Coal exploration, economics and assessment. Lecture notes to

accompany a short course. Geology Department, University of the

Witwatersrand, Johannesburg, pp. I-1–IV-30.

Cadle, A.B., Cairncross, B., Christie, A.D.M., Roberts, D.L., 1993.

The Karoo basin of South Africa: type basin for coal-bearing

deposits of southern Africa. Int. J. Coal Geol. 23, 117–157.

Cairncross, B., 1986. Depositional environments of the Permian

Vryheid formation in the east Witbank Coalfield: a framework

for coal seam stratigraphy, occurrence and distribution. PhD thesis

(unpubl.), University of the Witwatersrand, Johannesburg. 232 pp.

Cairncross, B., 1989. Paleodepositional environments and tectono-

sedimentary controls of postglacial Permian coals, Karoo basin,

South Africa. Int. J. Coal Geol. 12, 365–380.

Cairncross, B., Cadle, A.B., 1987. A genetic stratigraphy for the

Permian coal-bearingVryheid formation in the east Witbank

Coalfield, South Africa. S. Afr. J. Geol. 90 (3), 219–230.

Cairncross, B., Cadle, A.B., 1988. Depositional palaeoenvironments of

the coal-bearing Vryheid formation in the east Witbank Coalfield,

South Africa. S. Afr. J. Geol. 91 (1), 1–17.

Catuneanu, O., 2002. Sequence stratigraphy of clastic systems:

concepts, merits, and pitfalls. J. Afr. Earth Sci. 35, 1–43.

Catuneanu, O., Sweet, A.R., 1999. Maastrichtian–Paleocene foreland

basin stratigraphies, Western Canada: a reciprocal sequence

architecture. Can. J. Earth Sci. 36, 685–703.

Catuneanu, O., Beaumont, C., Waschbusch, P., 1997a. Interplay of

static loads and subduction dynamics in foreland basins: reciprocal

stratigraphies and the ‘‘missing’’ peripheral bulge. Geology 25 (12),

1087–1090.

Catuneanu, O., Sweet, A.R., Miall, A.D., 1997b. Reciprocal architec-

ture of bearpaw T–R sequences, uppermost cretaceous, Western

Canada Sedimentary Basin. Bull. Can. Petrol. Geol. 45 (1), 75–94.

Catuneanu, O., Hancox, P.J., Rubidge, B.S., 1998. Reciprocal flexural

behaviour and contrasting stratigraphies: a new basin development

model for the Karoo retroarc foreland system, South Africa. Basin

Res. 10, 417–439.

Catuneanu, O., Sweet, A.R., Miall, A.D., 1999. Concept and styles of

reciprocal stratigraphies: Western Canada foreland basin. Terra

Nova 11, 1–8.

Catuneanu, O., Sweet, A.R., Miall, A.D., 2000. Reciprocal stratigra-

phy of the Campanian–Paleocene Western Interior of North

America. Sediment. Geol. 134 (3–4), 235–255.

Cole,D.,Wickens,H. de V., Viljoen, J., 1998. LowerKaroo supergroup:

glacial, basinal and terrestrial environments in the southwestern

part of the main Karoo basin. Guidebook 10th Gondwana

Conference. University of Cape Town, South Africa, 77 pp.

DeCelles, P.G., Giles, K.A., 1996. Foreland basin systems. Basin Res.

8, 105–123.

de Wit, M.J., Jeffery, M., Nicolaysen, L.O.N., Bergh, H., 1988.

Explanatory notes on the Geologic Map of Gondwana. American

Association Petroleum Geol., Tulsa.

de Wit, M.J., Ransome, I.G.D., 1992. Regional inversion tectonics

along the southern margin of Gondwana. In: de Wit, M.J.,

Ransome, I.G.D. (Eds.), Inversion Tectonics of the Cape Fold

Belt, Karoo and Cretaceous Basins of Southern Africa. Balkema,

Rotterdam, pp. 15–21.

Embry, A.F., 1995. Sequence boundaries and sequence hierarchies:

problems and proposals. In: Steel, R.J., Felt, V.L., Johannessen,

E.P., Mathieu, C., (Eds.), Sequence Stratigraphy on the Northwest

European Margin. Norwegian Petroleum Society (NPF), Special

Publication 5, pp. 1–11.

Galloway, W.E., 1989. Genetic stratigraphic sequences in basin

analysis. I. Architecture and genesis of flooding-surface bounded

depositional units. Am. Assoc. Petrol. Geologists Bull. 73, 125–142.

Gresse, P.G., Theron, J.N., Fitch, F.J., Miller, J.A., 1992. Tectonic

inversion and radiometric resetting of the basement in the Cape

Fold Belt. In: de Wit, M.J., Ransome, I.G.D. (Eds.), Inversion

Tectonics of the Cape Fold Belt, Karoo and Cretaceous Basins of

Southern Africa. Balkema, Rotterdam, pp. 217–228.

Gurnis, M., 1992. Rapid continental subsidence following the initia-

tion and evolution of subduction. Science 255, 1556–1558.

Gurnis, M., Eloy, C., Zhong, S., 1996. Free-surface formulation of

mantle convection: implications for subduction zone observables.

Geophys. J. Int. 127, 719–727.

H€aalbich, I.W., 1983. A tectonogenesis of the Cape Fold Belt (CFB). In:

S€oohnge, A.P.G., H€aalbich, I.W. (Eds.), Geodynamics of the Cape

Fold Belt. Geol. Soc. S. Afr., vol. 12, pp. 165–175.

H€aalbich, I.W., 1992. The Cape Fold Belt Orogeny: State of the art

1970s–1980s. In: de Wit, M.J., Ransome, I.G.D. (Eds.), Inversion

Tectonics of the Cape Fold belt, Karoo and Cretaceous Basins of

Southern Africa. Balkema, Rotterdam, pp. 141–158.

H€aalbich, I.W., Fitch, F.J., Miller, J.A., 1983. Dating the Cape

Orogeny. In: S€oohnge, A.P.G., H€aalbich, I.W., (Eds.), Geodynamics

of the Cape Fold Belt. Special Publications of the Geological

Society of South Africa, vol. 12, pp. 149–164.

Hobday, D.K., 1973. Middle Ecca deltaic deposits in the Muden–

Tugela Ferry area of Natal. Trans. Geol. Soc. S. Afr. 76, 309–318.

Hobday, D.K., 1978. Fluvial deposits of the Ecca and Beaufort

Groups in the eastern Karoo basin, southern Africa. In: Miall,

A.D. (Ed.), Fluvial Sedimentology. Can. Soc. Petrol. Geol. Mem.,

vol. 5, pp. 413–429.

Holt, W.E., Stern, T.A., 1994. Subduction, platform subsidence and

foreland thrust loading: the late Tertiary development of Taranaki

basin, New Zealand. Tectonics 13, 1068–1092.


Hunt, D., Tucker, M.E., 1992. Stranded parasequences and the forced

regressive wedge systems tract: deposition during base-level fall.

Sediment. Geol. 81, 1–9.

Johnson, M.R., 1976. Stratigraphy and sedimentology of the Cape and

Karoo sequences in the Eastern Cape Province. PhD thesis

(unpubl.), Rhodes University, Grahamstown, South Africa, 336 pp.

Johnson, M.R., 1991. Sandstone petrography, provenance and plate

tectonic setting in Gondwana context of the south-eastern Cape

Karoo Basin. S. Afr. J. Geol. 94 (2/3), 137–154.

Jordan, T.E., 1981. Thrust loads and foreland basin evolution,

Cretaceous western United States. Bull. Am. Assoc. Petrol.

Geolog. 65, 2506–2520.

Kingsley, C.S., 1977. Stratigraphy and sedimentology of the Ecca

Group in the eastern Cape Province, South Africa. PhD thesis

(unpubl.), University of Port Elizabeth, Port Elizabeth, South

Africa, 290 pp.

Kingsley, C.S., 1981. A composite submarine fan-delta-fluvial model

for the Ecca and lower Beaufort Groups of Permian age in the

Eastern Cape Province. Trans. Geol. Soc. S. Afr. 84, 27–40.

Le Blanc Smith, G., 1980. Genetic stratigraphy for the Witbank

Coalfield. Trans. Geol. Soc. S. Afr. 83 (3), 313–326.

Lock, B.E., 1978. The Cape Fold Belt of South Africa; tectonic control

of sedimentation. Geol. Ass. (London). Proc. 89, 263–281.

Lock, B.E., 1980. Flat-plate subduction and the Cape Fold Belt of

South Africa. Geology 8, 35–39.

Loock, J.C., Visser, J.N.J., 1985. South Africa. In: Martinez Diaz, C.

(Ed.), The Carboniferous of the world. II. Australia, Indian

subcontinent, South Africa, South America, and North Africa.

Instituto Geologico y Minero de Espana, Madrid, pp. 167–174.

MacRae, C.S., 1988. Palynostratigraphic correlation between the

Lower Karoo sequence of the Waterberg and Pafuri coal-bearing

basins and the Hammanskraal plant and macrofossil locality,

Republic of South Africa. Mem. Geol. Surv. S. Afr. 5, 1–21.

Mathew, D., 1974. A statistical and palaeoenvironmental analysis of

the Ecca Group in northern Natal. M.Sc. thesis (unpubl.),

University of Natal, Pieternaritzburg, 158 pp.

Mc Lachlan, I.R., Anderson, A., 1973. A review of the evidence of

marine conditions in Southern Africa during Dwyka times.

Palaeont. Afr. 15, 37–64.

Miall, A.D., 1997. The Geology of Stratigraphic Sequences. Springer,

Berlin, pp. 433.

Millsteed, B.D., 1994. Palynological evidence for the age of the

Permian Karoo coal deposits near Vereeniging, northern Orange

Free State, South Africa. S. Afr. J. Geol. 97 (1), 15–20.

Mitrovica, J.X., Beaumont, C., Jarvis, G.T., 1989. Tilting of conti-

nental interiors by the dynamical effects of subduction. Tectonics 8,

1079–1094.

Oelofsen, B.W., 1987. The biostratigraphy and fossils of the Whitehill

and Irai Sahle formations of the Karoo and Parana Basins. In:

McKenzie, G.D. (Ed.), Gondwana Six: Stratigraphy, Sedimentol-

ogy, and Palaeontology. Geophys. Monogr. Ameri. Geophys.

Union., vol. 41, pp. 131–138.

Peper, T., Beekman, F., Cloetingh, S., 1992. Consequences of thrusting

and intraplate stress fluctuations for vertical motions in foreland

basins and peripheral areas. Geophys. J. Int. 111, 104–126.

Posamentier, H.W., Allen, G.P., James, D.P., Resson, M., 1992.

Forced regressions in a sequence stratigraphic framework: con-

cepts, examples, and exploration significance. AAPG Bull. 76,

1687–1709.

Pysklywec, R.N., Mitrovica, J.X., 1989. The role of subduction-

induced subsidence in the evolution of the Karoo Basin. J. Geol.

107, 155–164.

Rubidge, B.S., 1995. Biostratigraphy of the Beaufort Group (Karoo

Supergroup). South African Committee for Stratigraphy, Bio-

stratigraphic series no. 1. Council for Geoscience, Pretoria, 46 pp.

Scott, E.D., 1997. Tectonics and sedimentation: the evolution, tectonic

influences and correlation of the Tanqua and Laingsburg sub-

basins, southwest Karoo Basin, South Africa. Unpublished PhD

Dissertation, Lousiana State University, 234 pp.

Scott, E.D., Bouma, A., 1998. Influence of tectonics on basin shape

and deep water sedimentary fill characteristics: Tanqua and

Laingsburg subbasins, southwest Karoo Basin. In: Almond, J.,

Anderson, J., Booth, P., Chinsamy-Turan, A., Cole, D., de Wit,

M.J., Rubidge, B.S., Smith, R., van beven Donker, J., Storey, B.C.

(Eds.), Gondwana 10: Event stratigraphy of Gondwana (Ab-

stracts). J. Afr. Earth Sci. 27 (1A), 174.

Sinclair, H.D., Allen, P.A., 1992. Vertical versus horizontal motions in

the Alpine orogenic wedge: stratigraphic response in the foreland

basin. Basin Res. 4, 215–232.

Smith, R.M.H., 1990. A review of stratigraphy and sedimentary

environments of the Karoo basin of South Africa. J. Afr. Earth Sci.

10, 117–137.

Smith, R.M.H., Eriksson, P.G., Botha, W.J., 1993. A review of

stratigraphy and sedimentary environments of the Karoo basins of

southern Africa. J. Afr. Earth Sci. 16, 143–169.

Smith, R.M.H., Turner, B.R., Hancox, P.J., Rubidge, B.R., Catu-

neanu, O., 1998. Trans-Karoo II: 100 million years of changing

terrestrial environments in the main Karoo Basin. Guidebook

Gondwana-10 International Conference, University of Cape Town,

South Africa, 117 pp.

Stavrakis, N., 1989. Sedimentology of Karoo coal-measures in the

Eastern Transvaal. PhD thesis (unpubl.), University of Strathclyde,

Scotland, 201 pp.

Taverner-Smith, R., Mason, T.R., Cristie, A.D.M., Roberts, A.M.,

van der Spuy, A., 1988. Sedimentary models for coal formation in

the Vryheid formation, northern. Natal. Bull. Geol. Surv. S. Afr.

94, 1–46.

Truswell, J.F., Ryan, P.J., 1969. A flysch facies in the lower Ecca

Group of the southern Karoo and a portion of the Transkei. Trans.

Geol. Soc. S. Afr. 72, 151–158.

Van Vuuren, C.J., Cole, D.I., 1979. The stratigraphy and depositional

environments of the Ecca Group in the northern part of the Karoo

basin. Geol. Soc. S. Afr. Spec. Pub. 6, 103–111.

Veevers, J.J., Cole, D.I., Cowan, E.J., 1994. Southern Africa: Karoo

Basin and Cape Fold Belt. In: Veevers, J.J., Powell, C.Mc.A.

(Eds.), Permian-Triassic Pangean Basins and foldbelts along the

Panthalassan margin of Gondwanaland. Geological Society of

America Memoir 184, pp. 223–279.

Visser, J.N.J., 1990. The age of the late Palaeozoic deposits in southern

Africa. S. Afr. J. Geol. 93, 366–375.

Visser, J.N.J., 1995. Post-glacial Permian stratigraphy and geography

of southern and central Africa: boundary conditions for climatic

modelling. Palaeogeog., Palaeoclimatol., Palaeoecol. 118, 213–

243.

Visser, J.N.J., Loock, J.C., 1978. Water depth in the main Karoo Basin

in South Africa during Permian sedimentation. Trans. Geol. Soc. S.

Afr. 81, 185–191.

Whateley, M.G.K., 1980. Deltaic and fluvial deposits of the Ecca

Group, Nongoma Graben, northern Zululand. Trans. Geol. Soc. S.

Afr. 83 (3), 345–351.

Wickens, H. de V., 1994. Basin floor fan building turbidites of the

southwestern Karoo Basin, Ecca Group, South Africa. Unpub-

lished PhD thesis, University of Port Elizabeth, South Africa, 233

pp.

Winter, M.F., Cairncross, B., Cadle, A.B., 1987. A genetic stratigraphy

for the Vryheid formation in the northern Highveld Coalfield,

South Africa. S. Afr. J. Geol. 90 (4), 333–343.

Zawada, P.K., Cadle, A.B., 1988. Position of the Ecca-Beaufort

contact in the southwestern Orange Free State: an evaluation of

four possible alternatives. S. Afr. J. Geol. 91, 49–56.


Foredeep submarine fans and forebulge deltas: orogenic oﬀ … · 2015-10-06 · Foredeep...

Documents

Transcript of Foredeep submarine fans and forebulge deltas: orogenic oﬀ … · 2015-10-06 · Foredeep...