DEPOSITIONAL HISTORY AND PALEOGEOGRAPHY OF THE JURASSIC PLOVER FORMATION IN CALLIANCE AND BRECKNOCK FIELDS, BROWSE BASIN, NORTH WEST SHELF, AUSTRALIA FEDERICO TOVAGLIERI This thesis is presented for the degree of Doctor of Philosophy to The University of Western Australia School of Earth and Environment Submitted January 2013 Supervisors: Prof. Annette George W/Prof. Mike Dentith Dr Jennifer Wadsworth
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Depositional History anD paleogeograpHy of tHe Jurassic plover formation in calliance anD Brecknock fielDs, Browse Basin, nortH
west sHelf, australia
Federico Tovaglieri
This thesis is presentedfor the degree of
Doctor of Philosophy
to The University of Western AustraliaSchool of Earth and Environment
Submitted January 2013
Supervisors:
Prof. Annette GeorgeW/Prof. Mike Dentith
Dr Jennifer Wadsworth
i
Statement of candidate contribution
This thesis is my own original composition except where referenced. It contains no mate-
rial which was been accepted for the award of any degree or diploma in any university
and it is based on openfile data only. Part of Chapters 2, 4, 5 and 6 (with minor modifica-
tions to their present form) were included in the following paper submitted to Sedimentol-
ogy in May 2012 (currently under revision):
Tovaglieri F. and George A.D. (submitted) Stratigraphic architecture of an Early–Middle
Jurassic tidally influenced deltaic system: Browse Basin, Australian North West Shelf.
(I collected and analysed all the data and undertook the bulk of the interpretation, synthe-
sis and manuscript preparation (85%))
Part of Chapter 6, 7 and 8 (with minor modifications to their present form) will be in-
cluded in the following paper:
Tovaglieri F., Jones T., George A.D., Zwingmann H. (in preparation) Depositional His-
tory of the Early to Middle Jurassic deltaic reservoirs in Calliance and Brecknock fields
(Plover Formation), Browse Basin, North West Shelf, Australia.
(Data collection, analysis, interpretation and synthesis and manuscript preparation by me
(70%), Toby Jones (15), Annette D. George (10%) and Horst Zwingmann (5%))
Material presented in Appendix 4 represents an extract from the Honour Thesis of Mr.
Toby Jones (Jones, 2012) and it has been reproduced with the permission of the author.
Federico Tovaglieri
Candidate
Professor Annette D. George
Supervisor
University of Western Australia
January 2013
ii
iii
abStract
The Early to Middle Jurassic Plover Formation in the Browse Basin (Australian North
West Shelf) hosts reservoirs currently targeted for gas exploration and development. The
depositional history and paleogeographic evolution of the Plover Formation in the Cal-
liance and Brecknock fields has been established within a sequence-stratigraphic frame-
work through integrated sedimentological analysis of core and borehole image and wire-
line log analysis incorporating biostratigraphic and seismic data.
Seven siliciclastic and one volcano-sedimentary facies associations have been identified
through facies analysis of core and interpreted as fluvial channel-fill (FA0), tidally in-
fluenced channel- and tidal channel-fill complex (FA1-FA2), crevasse-splay and inter-
the internal stratigraphic architecture of these systems is critical to a proper assessment
of reservoir architecture and potential development of reservoir models. In the case of
the Plover Formation in the Browse Basin, relatively little has been published on its
stratigraphic architecture and evolution (e.g. Stephenson & Cadman, 1994; Blevin et
al.,1998; Keall & Smith, 2004; Ainsworth et al., 2008). Moreover, the relative scarcity
and uneven distribution of wells in the Browse Basin, with respect to its large size, means
that confident spatial correlation of the various sand bodies (i.e. potential reservoirs) has
been limited to date. A much better understanding of paleogeographic evolution during
deposition of the Plover Formation is, therefore, needed (Blevin et al., 1998; Longley et
al., 2002 ).
Finally, many studies highlighted similarities in the stratigraphic evolution of
large deltaic systems developed during rifting (e.g. Ravnås & Steel, 1998; Lambiase &
Morley, 1999; Young et al., 2002). This means that the knowledge gained from a thorough
study of a large system like that of the Plover Formation has the potential to be useful to
better understand the evolution of other synrift deltaic systems of interest in petroleum
exploration.
1.2 Location of study area
The Browse Basin lies entirely offshore in the southern Timor Sea region, over an
area of approximately 140,000 km2 (Hocking et al., 1994; Baillie et al., 1994 Struckmeyer
et al., 1998; Fig. 1.1). Major regions surrounding the Browse Basin are the Kimberley
Craton to the east and the Argo Abyssal Plain to the west (Fig. 1.2). The basin is contiguous
with the Rowley Sub-basin to the southwest (Fig. 1.1) and with the Ashmore Platform,
Vulcan Sub-basin and Londonderry High of the Bonaparte Basin to the northeast (Fig.
1.2).
Internal subdivision of the Browse Basin (Fig. 1.2) is based on the terminology
introduced by Willis (1988), Elliot (1990), O’Brien et al. (1993), Hocking et al. (1994),
Symonds et al. (1994) and Struckmeyer et al. (1998). The southeastern boundary of the
basin is defined by a series of shallow basement elements, namely the Prudhoe Terrace,
Chapter 1 - Introduction 3
Figure 1.1 The North West Shelf of Australia illustrating the location and extent of the Northern Carnarvon, Roebuck, Offshore Canning, Browse and Bonaparte Basins (from Mantle & Riding, 2012). Rw: location of Rowley Sub-basin.
and Yampi and Leveque Shelves. The central Browse Basin has two major depocentres,
the Caswell and Barcoo sub-basins (Fig. 1.2). The outboard, deep water part of the basin
is the Scott Plateau, underlain by the Scott and Seringapatam Sub-basins, the boundaries
of which are poorly understood but probably extend to the Timor Trough (Struckmeyer
et al., 1998).
The Caswell Sub-basin is the major depocentre of the Browse Basin and is
separated to the south from the Barcoo Sub-basin by a major NNE-trending structural
zone, the Buffon-Brecknock-Scott Reef anticlinal trend (Struckmeyer et al., 1998; Fig.
1.2). The Carboniferous to Holocene stratigraphic succession in the Caswell Sub-basin
is ~15 km thick with up to 1.5 km of Early to Middle Jurassic strata (Struckmeyer et al.,
1998).
The study focuses on the Plover Formation of the Calliance and Brecknock fields
located in the Caswell Sub-basin on the Brecknock-Scott Reef Trend (Fig. 1.2). The study
area is approximately 400 km northwest of Broome and 40 km south-southwest of Scott
Rw
Introduction - Chapter 14
Figure 1.2 Simplified map of the Browse Basin showing major sub-basins (from Geoscience Australia, 2011; after Struckmeyer et al., 1998). Basin is bounded by Kimberley Craton, by structural elements of the Bonaparte Basin to the north and by Rowley and Oobagooma Sub-basins of the Roebuck and Offshore Canning Basins respectively to the south.
Chapter 1 - Introduction 5
Reef, on the edge of the Australian continental shelf (Fig. 1.2).
Brecknock and Calliance fields consist of four wells each and are operated by
Woodside Energy Limited and their joint venture partners (Fig. 1.3). Brecknock field was
discovered in 1979, with the well Brecknock-1, whereas Calliance field was discovered
in 2000 after drilling of Brecknock South-1. The Plover Formation was the main target
and was intersected in both fields at a depth varying from 3830 to 3900 m below Rotary
Table (mRT) (Tab1e 1.1).
Seismic data show that the target structures for both fields are faulted anticlines.
The Plover Formation in Calliance field is approximately 200-450 m thick, whereas in
Brecknock field it is approximately 50-130 m thick. In Calliance field, Calliance-1 is the
only well that intersects the entire thickness of the Plover Formation. The other wells
(Calliance-2, Calliance-3 and Brecknock South) reach different depths within the lower
part of the formation. In contrast, in Brecknock field all the wells reach and penetrate
the Triassic strata (>20 m). No core was taken in Brecknock-1 and Brecknock South,
whereas in Brecknock-2 and -3 core stops before reaching the top of the Formation. Core
from Brecknock -4 encompasses the whole Formation thickness, although in this well
the uppermost part of the Formation is truncated by a fault. Cores from Calliance wells
encompass only the upper 167-226 m of the Formation, leaving the lower part uncored.
1.3 Objective and aims
A detailed study of the stratigraphy and sedimentology of the Plover Formation
in two Browse Basin fields is the focus of this thesis. The objective is to establish the
depositional history and paleogeographic evolution of the Jurassic deltaic system on the
Brecknock-Scott Reef Trend, on the western margin of the Caswell Sub-basin. Integration
of datasets such as core, image and wireline log data and seismic data represents a
key factor in this project. To fulfil the project objective, the following aims have been
identified.
1. Detailed logging of drill cores to identify stacking patterns and key stratal
surfaces, and to characterize the igneous and volcaniclastic intervals.
Introduction - Chapter 16
WA-275-P
WA-28-R
WA-275-P WA-28-R
WA-397-PWA-31-R
WA-396-P
WA-29-R
WA-32-R
TR/5
Calliance-3Calliance-1
Calliance-2Brecknock S.
Brecknock-2
Brecknock-1
Brecknock-3
Brecknock-4
Snarf-1
0 10 20 km121°30'0˝E 122°0'0˝E
121°30'0˝E 122°0'0˝E
14°30'0˝S
14°30'0˝S
N
LegendBlocks
Gas fields
Figure 1.3 Map of the study area showing the location of the wells in the Calliance and Brecknock fields.
2. Facies analysis to establish the lateral extent and vertical evolution of the
siliciclastic facies associations and interpret depositional environments.
3. Detailed image logs analysis and interpretation to determine large scale stacking
patterns, paleocurrent directions as well as correlations and to interpret facies
associations in uncored part of the wells.
4. Petrographic analysis on selected samples in order to determine compositional
variation and to establish likely source terrains.
5. Integration of all sedimentological and image data sets with seismic and
biostratigraphic data available and development of a depositional model and
palaeogeographic maps, highlighting the lateral and vertical distribution of
reservoir sands.
Chapter 1 - Introduction 7
1.4 Materials and Methods
This study integrates sedimentological analysis of drillcore (providing direct
physical information) and interpretation of borehole image log (BHI) which enables
broader interpretation of uncored intervals in wells (e.g. Bourke, 1992; Bal et al., 2002;
Xu et al., 2009; Prosser et al., 1999; Donselaar & Schmidt, 2005). Similar studies that
integrate image logs with other geological and geophysical datasets have been undertaken
and the importance of image logs as a powerful interpretation tool has been highlighted
(e.g. Russel et al., 2002; Khan et al., 2004; Prioul & Jocker, 2009; Lacazette, 2009).
However, the complexity of image signal can easily lead to over- or mis-interpretation
(e.g. Xu, 2007; Slatt & Davis, 2010) and effective interpretation of image facies in
uncored wells remains problematic. Seven wells in the Calliance and Brecknock fields
of the Browse Basin have good quality BHI through a significant thickness of Plover
Formation (Table 1.1). These data provide an excellent opportunity to investigate the
value of image log analysis and its application to uncored intervals through definition of
image facies and image associations directly comparable to those defined from core.
Integration of well data with biostratigraphic and seismic data is also used in
this study to strengthen the interpretation and to extend the correlation between fields.
This approach has been proven valuable in other studies aimed to establish a sequence-
stratigraphic framework as a basis for paleogeographic reconstruction (e.g. Krassay &
Totterdel, 2003; Snedden & Sarg, 2008).
An important aspect considered was the quality of the data available, with
particular reference to image logs and cored intervals. Open file data from Department
of Mines and Petroleum (DMP) were used in this project. These include core photos and
well completions reports.
1.4.1 Core description and facies analysis
Descriptions of cored intervals in Calliance-1, Calliance-2 and Calliance-3 and
Brecknock-2, Brecknock -3 and Brecknock -4 (732 m total length) were undertaken at
Department of Mines and Petroleum Core Library, in Carlisle, Perth, using a logging
scale of 1:50 and WellCAD® software to record observations. Side-wall core were
Introduction - Chapter 18
examined where core was not available (Brecknock-1). Core was logged to document
sedimentological and ichnological features and then, facies analysis and identification
of important stratal surfaces was carried out. Facies analysis has been used to interpret
depositional environments for reconstruction of the deltaic system. Particular attention
has been paid to identification of unconformities and other important stratal surfaces for
intra- and inter-field correlations between wells in a field and between fields.
1.4.2 Image log analysis
Good to excellent quality borehole image (BHI) logs from Calliance and
Brecknock wells, provided by Woodside Energy Limited (WEL), were analysed in order
to extend facies analysis to uncored part of the wells via identification of image facies
and to extract paleocurrent information. Image analysis was performed on Fullbore
Formation MicroImager (FMI) logs from Brecknock-2, -3, -4, Calliance-1, -2, and -3, and
on a Formation MicroScanner (FMS) log from Brecknock South. Following conventional
Core and wireline log data were used to calibrate the statically normalised image
logs. Identification of image lithology was undertaken on the basis of direct observation
on core and defined by the signatures of a number of wireline logs. Where cored material
was not available, log responses were used to discriminate lithology. Identification of
image fabric, i.e. the spatial arrangement and orientation of the elements or ‘features’
of a borehole image (Bal at al., 2002), may be locally subjective (e.g. Slatt and Davis,
2010) so broad classes of features have been used in this study to minimise potential
over-interpretation. The magnetometer data from the FMI orientation sonde was useful
for identifying magnetic anomalies associated with igneous rock types.
Bedding surfaces, cross-bedding and other planar features visible in borehole
images were manually picked, classified and interpreted using Recall® software. Structural
tilt has been determined by analysing dips from imaged mudstone intervals as the best
Chapter 1 - Introduction 9
Tabl
e 1.
1 O
verv
iew
of C
allia
nce
and
Bre
ckno
ck w
ells
and
dat
a av
aila
ble
for t
he p
rese
nt st
udy.
A m
ore
com
preh
ensi
ve ta
ble
is p
rese
nted
in A
ppen
dix
1. A
bbre
viat
ions
: mRT
, m
eter
s bel
ow ro
tary
tabl
e; F
MI,
Fullb
ore
Mic
roIm
ager
; FM
S, F
orm
atio
n M
icro
Sca
nner
.
Wel
lC
allia
nce
3C
allia
nce
1C
allia
nce
2Br
eckn
ock
Sout
hBr
eckn
ock-
1Br
eckn
ock-
2Br
eckn
ock-
3Br
eckn
ock-
4La
titud
e (d
eg)
-14.
5310
278
-14.
5394
083
-14.
5739
625
-14.
6050
649
-14.
4355
692
-14.
4446
5-1
4.39
4408
3-1
4.36
28Lo
ngitu
de (d
eg)
121.
4981
389
121.
5533
083
121.
5789
275
121.
6403
1612
1.67
3773
112
1.64
2261
112
1.64
3558
312
1.65
94To
tal m
easu
red
dept
h (m
RT)
4262
4178
4188
4008
4300
3872
3948
3971
TD u
nit
Low
er P
love
r Fm
.Tr
iass
icLo
wer
Plo
ver F
m.
Low
er P
love
r Fm
.Tr
iass
icTr
iass
icTr
iass
icTr
iass
icPl
over
Fm
. thi
ckne
ss
(m)
>443
.636
5.5
270.
615
6.3
166
128.
1743
.65
52.5
9
Cor
ed P
love
r Fm
. (t
hick
ness
- m
)22
6.67
193.
3516
7.63
none
none
121.
439
.47
52.5
9
Imag
e lo
g ty
peFM
IFM
IFM
IFM
Sno
neFM
IFM
IFM
IIm
aged
Plo
ver F
m.
(thi
ckne
ss -
m)
443.
636
5.5
270.
615
6.3
166
128.
1743
.65
52.5
9
Wel
l log
sw
irelin
ew
irelin
ew
irelin
ew
irelin
ew
irelin
ew
irelin
ew
irelin
ew
irelin
e
Introduction - Chapter 110
indicators of deposition on an approximately horizontal surface. Abnormally steep dip
values were subtracted where required to correct post-depostional deformation. Structural
tilt correction was needed only for the lower part of Calliance-3, where 2.7° (dip) and
250° (azimuth) were subtracted to the interval from 4036 m to 4259 m. Dips of cross-beds
>5º from imaged sandstone intervals from each well have been used to generate statistical
plots, e.g. rose plots and azimuth vector plots (walkout plots), to determine mean azimuths
and, subsequently, unimodal, bimodal/bipolar or polymodal data distributions.
1.4.3 Petrographic analysis
Petrographic analysis of selected sandstones was undertaken to describe detrital
composition and to determine sediment provenance. Existing sandstone thin sections
from wells (held by WA Department of Mines and Petroleum) were examined using
conventional petrological microscopy (Nikon 50i polarising microscope with Nikon
camera attachment and image capture software).
1.4.4 Seismic analysis
Forty-four 2D seismic reflection lines from Brecknock 3D MSS (1997) and
Brecknock South 3D MSS (1999) surveys, covering an area of 1800 Km2, were collected
from Woodside Energy Limited and analysed using Kingdom Suite®. Seismic interpretation
was used to identify larger scale stratal geometry and highlight the paleotopography at the
time of Plover deposition. Depth structure maps and isochore maps were constructed and
used as a base for the paleogeographic maps.
1.4.5 Biostratigraphy
Biostratigraphic data from the wells is provided in well completion reports on
WAPIMS. Data were incorporated in this study to build correlations based on coeval
ages of strata. The biostratigraphic zonations adopted is based on Helby et al. (2004),
Partridge (2006) and Riding et al. (2010).
Chapter 1 - Introduction 11
1.5 Thesis organization
Following this introductory chapter, Chapter 2 presents a summary of the regional
geological framework. Chapter 3 presents a sedimentological overview of the core material
and petrographic results on selected thin sections. It also represents an introduction to
Chapter 4, which presents the results of the facies analysis of the cored intervals. The
results of image log analysis are presented in Chapter 5. Interpretations derived from
integration of results in previous chapters with biostratigraphic data are used to construct
the sequence-stratigraphic framework for the Plover Formation in the study area. Chapter
7 contains the results of the analysis of seismic data and is followed, in Chapter 8, by the
proposed depositional model and related paleogeographic maps for key time intervals.
Finally, Chapter 9 presents the conclusions of this study and recommendations for future
work.
13
Chapter 2 - regional Setting
2.1 Introduction
The Browse Basin formed as an intracratonic basin during the Late Carboniferous
to Early Permian in response to rifting and formation of the Westralian Superbasin (Yeates
et al., 1987; Longley et al., 2002). It remained a discrete basin until the end of the Early
Cretaceous when its western margin subsided (Willis, 1988; Symonds et al., 1994). The
whole basin was then overlain by widespread deposition of transgressive sediments during
Figure 2.1 Simplified structural map of the Browse Basin showing major sub-basins (Caswell,Barcoo, Scott and Seringapatam) and Paleozoic and Jurassic normal faults (modifiedfrom Kennard et al., 2004). Basin is bounded by Kimberley Craton and by structural elementsoftheBonaparteBasin(grey)tothenorth.BSRT:Brecknock-ScottReefTrend.Rectangles on faults indicate downthrown direction. Study area outlined by yellow box.
Argus-1
Buffon-1
Regional setting - Chapter 214
Figure 2.2 Schematic cross-sections (not to scale) illustratingmajor basin-forming events in theBrowse Basin (from Struckmeyer et al., 1998): A. Upper Carboniferous to Lower Permian extension (Upper Permian basin geometry); B. Upper Permian to Middle Triassic thermal subsidence (Middle Triassic basin geometry); C. Upper Triassic inversion (Hettangian basin geometry); D. Early to Middle Jurassic extension (Callovian basin geometry). BSRT:Brecknock-ScottReetTrend.Faultsshownarerepresentativeofmajornortheast-trending fault systems of the basin.
C
B
A
Plover Fm.
Faults
Basement
Nome Fm.
Triassic strata
Paleozoic strata
DBSRT
Chapter 2 - Regional setting 15
the Cretaceous. Since the Cenozoic carbonate strata have prograded over the entire region
to form the present continental shelf (Willis, 1988).
Thischapterprovidesanoverviewof thetectono-stratigraphicevolutionof the
Browse Basin and the Early to Middle Jurassic paleoclimate. The Jurassic depositional
MK - MangkalihatPM - Paternoster-MeratusPNG - Papua New GuineaSK - Sikuleh (Western Sumatra)T - TimorWS - West Sulawesi
C
B
A
Figure 2.3 Late Triassic to Middle Jurassic geodynamic evolution of Gondwana (from Jablonsky & Saitta, 2004). This time interval is characterised by rifting of microplates from Gondwanan Supercontinent. After rifting in Early Jurassic, Mangkalihat microplate migrates northwards (in map C it is not shown because outside of the map area).
Chapter 2 - Regional setting 17
the eastern edge of the Scott Plateau, but movement on the outer Scott Plateau followed
Age of Event Geodynamic Event Browse tectonic regime
Important regional surfaces relevant to this study
Rifting of SE Asia, Sibumasu and Qiangtang micro-plates from Gonwana- Initiation of the Westralian Superbasin.
Fitzroy Movement.
Movement of Sibu-masu and Qiantang microplates.
Riftng of Mangkalihat microplate from Gondwana.
Riftng of Argo micro-plate from Gondwana
Rifting of Greater India from Gond-wana.
NW-SE directed rifting and generation of NE-trending structural grain of the Browse Basin.
N-S transpression; reactivation and inversion of Paleozoic faults. Formation of major anticlinal and synclinal trends.
Relative tectonic quiescence.
Post-inversion subsidence and extensive faulting (NE-trending). Reactivation of older faults.
Faulting (NE-trending). Reactiva-tion of older faults.
Post-rift sag and relative tectonic quiescence.
Middle Miocene to Recent
Collision and subduc-tion of Australian plate under Asian plate in the Banda Arc.
Compression; reactivation and inversion of older faults. Generation of Brecknock and Calliance structures.
Early Cretaceous to Miocene
Rifting of India and Australia from Gondwana.
Thermal subsidence and relative tectonic quiescence.
Trmid/TRC1
JH
JP1/JS
JC
JO/MU
KV
Ktur
TRR
Table 2.1 Tectonic event history and associated tectonic regime for the Browse Basin based on Struckmeyer et al. (1998) and Jablonski & Saitta (2004). Key stratigraphic surfaces with sequencestratigraphicsignificancearealsohighlighted(red:sequenceboundary;green:Transgressive surface of erosion).
Figure 2.4 Jurassic lithostratigraphic framework of the Browse Basin. Geological Time Scale from Gradstein et al. (2012); Spore-Pollen Zonation SE Standard from Partridge (2006);Dynoflagellataecystbiozones fromRidinget al. (2010). Key surfaces from Jablonski & Saitta (2004) and Struckmeyer et al. (1998): red surfaces are sequence boundaries; and green surfaces are transgressive surfaces of erosion. Climate from van Aarssen et al. (2000). Error on absolute ages ±0.2 to 1.4 Ma. The biostratigraphy of Browse Basin is basedonspore-pollenanddinoflagellataebiozones(e.g.Ridinget al., 2010). Compared to other organisms used in biostratigraphy, the biozonation based on these two taxa proved to be the most reliable, with spore/pollen offering the only continuous fossil record available over the entire region (Apthorpe, 1994).
2.6 Jurassic paleoclimate of the Browse Basin
The paleolatitude of the Browse Basin during the Early to Middle Jurassic was
likelytohavebeenaround35°S(Scoteseet al., 1999; Rees et al., 2000; Metcalfe, 2011).
OnthebasisofdistributionofJurassic fossil leaves, thispaleolatitude in thesouthern
hemisphere is equated with a warm temperate climate (e.g. Rees et al., 2000).
A review of Australian paleoclimatic evidence by Parrish et al. (1996) and
t al.,2002).Synriftstrataarecolouredinpaleblue.TRC1:Norianunconformity;
JP1:Sinem
uriantransgressivesu
rface;JC
:Calloviantransgressivesurface;JO
:OxfordianM
ainUnconformity;K
:Berriasian;K
V:Valanginian;K
A:A
ptian;KC:
Cenom
anian;T:E
arlyPaleogene;TE:M
iddlePaleogene;TO:L
atePaleogene;TM2:EarlyM
iocene;TM1:LateMiocene.W
elllocationsaresh
ownonFig.1.2.
NW
SE
Chapter 2 - Regional setting 23
Figure 2.6 Lithostratigraphic correlation chart for Jurassic Formations of theBonaparte, Browseand Carnarvon Basins, matched against the chronostratigraphic scale of Gradstein et al. (2012)andOgget al.(2008).FromTurneret al. (2009).
the Yampi Shelf (Stevenson & Cadman, 1994; Blevin et al., 1998).
Sandstones, mudstones and minor carbonate rocks constitute the main rock types
ofthePloverFormation(Willis,1988;Blevinet al., 1998; Keall & Smith, 2004). The broad
depositional environment proposed is a large, tidally influenced to tidally dominated,
sandy delta fed by rivers draining uplifted areas to the east of the basin (e.g. Precambrian
Kimberley Craton; Longley et al., 2002; Ainsworth et al., 2008). Igneous rocks are
present at several stratigraphic levels within the formation and have been interpreted as
volcanic units and subvolcanic intrusions related to synrift volcanism associated with a
majorvolcanicprovince(Symondset al., 1998; Blevin et al., 1998; Struckmeyer et al.,
Regional setting - Chapter 224
1998).
Informal subdivision of the Plover Formation in theBrowseBasin into lower
Figure 2.7 PaleogeographicmapsoftheCaswellSub-basinfromStevensonandCadman(1994;mapsAandB)andLongleyet al. (2002; maps C and D). A. Early Jurassic (Hettangian to Toarcian); B.MiddleJurassic(AaleniantoBathonian).NotethepostulatedpeninsulaconnectingLombardina-1(L)tothestudyarea;C. Early to Middle Jurassic (Sinemurian to Callovian) Plover deltaic system according to Longley et al.(2002).Notetheabsenceofemersedlandtothewestinthisinterpretation (compared to A and B). Grey arrow indicates direction of delta progradation; D.UpliftandwidespreaderosionovermostoftheCaswellSub-basinwhichtookplaceintheCallovian.Red-circled‘V’locatespotentialvolcanicvents.Orangeboxindicatesthestudyarea.Reddotsarewells.