1. Buranga Leichardt Faults
Site 1
Site 2
Site 3
Mimosa Syncline
Surat
Triassic
BowenBasin
Permian
CattleCreek
Formation
PrecipiceSandstoneFreitagFormation
280Ma260Ma195Ma
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Study Area
Upper delta plain
Unit 1 – Brahmaputra Braided River, India
Unit 2 – Rhine-Meuse Delta - Avulsion
Anastomosing, Saskatchewan River ,
Canada
Unit 3 – Delta Mouth Bar
Unit 4 – Chenier Plain, Danube Delta, Romania
Modern Analogues – Bulimba Bluff Paleo-Depositional Environment
Zoophycos- bathyal zone 100 –
2000 m below sea level
Cruziana and Skolithos
(Diplocraterion) – sandy
shoreface up to 100 m below sea
Cruziana (Arenicolites) and
smaller Skolithos vertical burrows
0 – 10 m foreshore
Ichnofacies
The Freitag Formation is exposed at
Fairbairn Dam as a triangular shaped
outcrop, 30 m high by 200 m wide,
with its units easily discernible due to
changes in colour and essentially
planar contacts between beds (from
orange for sandstones to greys for
recessive siltstones). The outcrop is
located on the western margin of the
Bowen Basin (see map).
The Freitag Formation represents a
Permian aged paralic coastal to
shallow marine system which is
supported by its subsurface gamma
signature and isopach thickness (Left
images). The Freitag is a small,
coarsening up sequence and has
considerable lateral extent in the
subsurface. Its trace is similar to the
coarsening up sequence of a delta and
can be compared against the predicted
signature of a fluvial system. The
isopach map shows an elongated,
southward progradiing geometry,
which rapidly thins towards the south
and its margins. This is broadly
analogous to the mid and outer Great
Barrier Reef shelf thickness
distribution, and may indicate that
wave dominated processes were a
significant feature affecting deposition
of the Freitag Formation.
The stratigraphic column at a scale
1:50 (left) describes the sedimentary
rocks observed in the field. This is to
be read in conjunction with their
depositional environment
interpretation below:
The Cattle Creek group has several exposures in
the Springsure area. The outcrop of the Staircase
Sandstone was at a large road cutting south of
the town’s centre. Standing at approximately 14
m and 110 m long, this outcrop has six units. This
group represents the depositional environment
that resulted from a thermal relaxation event
with marine shelf activity (Mollan, R.G, 1969).
Evidence of deltaic style deposition is embodied
through the presence of herringbone cross-
stratification, Ophiamorpha burrows and trough
cross beds. The deltaic environment was overlain
by mudstone indicating a base level rise, which
deposited distal mudstone over the coarse
sandstone lobes.
1. Proximal Deltaic Lobe massive medium sandstone with
troughs, herringbone and ripple beds. Within the
nearshore, oxygenated waters (Ophiamorpha burrows).
Presence of soft-sediment deformation and escape
structures indicating rapid depositional event.
2. Deltaic Lobe with channel inlets: Pebble lags within
sigmoidal lenses have been attributed to rapidly
changing channels frequently being built and
abandoned within the delta.
3. Fluvial influenced Deltaic Lobe with unidirectional
paleocurrent: Over-steepened beds within dunes
represent the seaward migration within a major
estuarine channel.
4. Distal Deltaic Lobe: Paleocurrent shift indicating
another lobe ‘switch back’- similar direction to unit 3.
Contains wave ripples, siderite staining, clean quartz
which implies wave oscillation.
5. Sandy-Tidal flat: Laminated sandy mudstone with
siderite replacement and manganese staining.
Coarsening upward with sandstone pulses representing
high energy storm events.
6. Tidal Channel Inlet: Massive tabular body of finely
bedded pebbly sandstone with a sharp erosive contact.
Displays some ripples (or large dunes) and coarse
pebble lag.
KEY Learnings: The Staircase
Sandstone outcrop provides a
unique opportunity to observe
lateral features which
represent the changing
depositional environment of a
delta through time. It was
shown within this outcrop that
shifting paleocurrents are
indicative of deltaic lobe
switching similar to what can
be observed in the modern day
Mississippi River. A close
examination of ichnofacies also
allows for interpretation of
proximal-distal relationships
within each lobe. The
depositional sub-environment
of the outcrop are summarised
below:
KEY Learnings: Many modern day
environments are extremely complex:
varying in shape, size and lateral continuity
and can be difficult to compare to ancient
systems. The Freitag succession has been
interpreted in this filed guide to closely
resemble a coastal barrier tidal flat which
grades into an overlying estuary deposit at
the top of the outcrop. It preserves
excellent marine trace fossils and
sedimentary structures such as: Skolithos
burrows and trough -hummocky cross-
stratification with wave dominated ripples
in the sandstones. Maximum flooding
surfaces are also seen in the pebble to
cobble conglomerate lags with some
authors attributing their presence from a
marine transgression.
Mississippi River Delta Lobe Switching
Site2Site1
1. Barrier Island – Tidal Flat: Planar to sub-parallel laminated
micaceous/carbonaceous mudstone interbedded with fine sandstone sheets and
lenses, poorly sorted, quartz rich, lenticular to flaser gradational bedding with
ripple cross lamination.
2. Anoxic swamp – marsh: jointed bright-banded black coal with sharp contacts
3. Tidal Channel Inlet: Massive, tabular, pebble-cobble polymict para-
conglomerate, quartz dominated, subrounded, poorly sorted with pervasive
pluck marks and coal/ carbonaceous mudstone sigmoid lenses with erosive and
sharp contacts
4. Inner- outer marine shelf: Thick trough cross bedded coarse to very coarse,
bioturbated quartz arenite sandstone with ripple cross beds, well sorted and
well rounded with ironstone and quartz granules throughout and glauconite.
This large unit pinches out.
5. Flood tidal delta - Tidal bar (ebb shield) : Manganese stained silty claystone
with wave ripples, subparallel lenticular and convolute bedding and flame
structures. Paleocurrent multidirectional
6. Flood tidal inlet: Very coarse, sandstone, low angle bi-directional planar and
trough/hummocks cross-beds, (quartz arenite –subarkose) with heavy
bioturbation at bottom and iron stone precipitation
7. Distributive channel – Estuary: highly porous, medium to coarse, thinly bedded
sandstone in laminated bedsets with mudstones 10-15 cm, with cobble sized
intraclasts of sandstone and pebbly gravel lenses. Paleocurrent average 268ºSW
to W
Left: Freitag Formation Isopach Map - thickness
distribution (m)
Below: Wireline Gamma Signatures of Delta and Fluvial
Settings & comparison to Freitag’s Gamma response.
Australia’s Great Barrier Reef – Modern Analogue
to the Freitag Formation
Site3
AncientDepositional
EnvironmentInterpretation
SchematicFreitag
Formation
1. Braided River: Coarse, porous, highly porous quatzose
sandstone with erosional scours, trough cross beds,
conglomerate, planar cross-stratification and ripple cross
stratification. Also contains rip up clasts and log fossil clasts
(derived from a high gradient hinterland). Unimodal
paleocurrent.
2. Anastomosing deranged river: coarse to medium pebbly
sandstone with large planar and low-angle cross-stratification
potentially representing the splitting of flow around a channel
bar, dune migration or from channel avulsion. More widely
varying paleocurrent N to NE (interpreted to be a result of
avulsion and related tectonic activity from the Buranga fault as-
well as from lower gradients offering greater resistance to flow)
3. Delta mouth bar – supratidal flat: coarsening upward
sandstones from laminated pro-delta clays (extremely
muscovite and calcite rich) to distributary channel and bar
sands interfingered with interdistributary muds. Presence of
Skolithos vertical burrows and an Ophiamorpha crab burrow
within lobe’s coarser centre and ripple beds towards the finer
grained sides of the lobe.
4. Coastal Chenier Plain: Mudflat/marsh with bioturbation
followed by a sharp-erosive washover unit of re-worked
medium sandstone with trace brackish fossils and shells
interbedded with fine siltstone, followed by beach ridge dunes
5. Evergreen Formation – meandering river and lake: Poorly
exposed and not extensively mapped - thin rippled lamination,
low angle cross beds, asymmetrical ripples, animal tracks and
shells. Interference ripples over large symmetrical ripples on
the top of the outcrop could indicate past anti-dunes,
The Jurassic aged Precipice Sandstone is the oldest
unit in the Surat Basin and is exposed across the
Carnarvon Ranges (see map). The section of outcrop
mapped, was along the walking trail up Bulimba Bluff
within the Carnarvon National Park (approx. 76 m
high)
The Precipice sandstone is separated into two
discrete units: the Precipice Upper and the Precipice
Lower. The Upper member is a lower quality reservoir
rock - composed of interbedded siltstone with
intermittent thin sandstone lenses. The Lower
member is a high quality reservoir rock characterised
by: high porosity/permeabilty with coarse grained,
pebbly quartz rich sandstone and conglomerate with
minor siltstone.
KEY Learnings: The isopach map shows this formation
thinning westward onto the Roma Shelf and
thickening on the basin ward side of the Triassic
thrust fault system (see map). The formation is at its
thickest along the Mimosa Syncline where it is
interpreted an ancient river system, as large as the
Ganges Brahmaputra in India, was directed along SE.
Authors suggest this river initially was sourced from
Antarctica (when Australia formed part of
Gondwana), across the Eromanga Basin and finally
changing course to the south in the Bowen Basin.
Abrupt thinning and cessation of the unit along the
north-eastern flank was likely a result of steepening
along the Burunga Fault.
The stratigraphic column at a scale 1:50 (left)
describes the sedimentary rocks observed in the
field. This is to be read in conjunction with their
depositional environment interpretation and
schematics below:
Zoomed in Precipice Formation Thickness (m)
MEGGIE DORAN AND MICHAEL KOWALCZYK, 2015 – ERTH3103/7411
The Bowen-Surat Basin fieldtrip uses a sedimentological approach to describe ancient
depositional environments from the Permo-Jurassic time period at a series of outcrops
including: 1.) Emerald, Fairbairn Dam, 2.) Springsure, Cattle Creek Formation and 3.)
Carnarvon Gorge, Bulimba Bluff. Environments observed range from coastal successions,
marine shoreface tidal sequences and fluvial successions. It was concluded that many
sedimentary features observed within outcrops could be compared to modern day analogues
such as: the Mississippi River, United States, Ganges Brahmaputra, India and Bribie Island,
Queensland. The Bowen Basin is of regional importance for coal seam gas and coal mining. As
approximately 60% of all fossil fuel reservoirs throughout the world are found within fluvial-
deltaic depositional settings, the interpretation of ancient clastic environments and
understanding their lateral distribution through the subsurface becomes crucial for industry
productivity. The below seismic image from QGC shows the Permo-Triassic Bowen Basin and
overlying Jurassic Surat Basin.
Merivale Fault System