Download Geological Interpretive Signs

CLARE VALLEY ROCKS IS
A PROJECT THAT PROVIDES
INFORMATION ABOUT THE
ROCKS AND THE SOIL THAT
ARE THE EARTH BENEATH THE
CLARE VALLEY VINES.
OOK FOR OTHER INTERPRETIVE SITES
L
AROUND THE CLARE VALLEY.
PICK UP A CLARE VALLEY ROCKS
BROCHURE / MAP AT CELLAR DOORS.
YOU CAN SEE TYPICAL SOIL PROFILES
AT PARTICIPATING CELLAR DOORS AND
DISCOVER HOW DIFFERENT ROCKS
AND SOILS PLAY A ROLE IN THE WINE
YOU TASTE.
MINTARO SLATE AND
FLAGSTONE
Mintaro Slate is produced from what is believed to be the oldest continuously
operating quarry in Australia. The quarry is located 1.5 km west of the
Mintaro Township.
Among its many uses and qualities, the perfectly flat surface of Mintaro Slate
makes it ideal for billiard tables. Walter Lindrum, the Australian billiard player who
was world champion from 1932 to 1950, practiced at his Melbourne home on a
table made from a single slab of slate from Mintaro.
The Mintaro slate was discovered in the early 1850’s by a local farmer and
was used initially as a local building material as well as in the construction of
fermenting tanks at Clare Valley wineries, acid leaching tanks at the Kapunda
copper mines, cricket pitches, water troughs, switchboards and blackboards.
The Mintaro slate and flagstone are part of the Mintaro Shale Formation within
the Belair Subgroup (see map). They were deposited on the sea floor during
low energy conditions in the Adelaide Geosyncline about 800 million years ago.
They are grey, evenly bedded, finely laminated metasiltstones or slate with minor
dolomitic siltstone. Although the proportions of minerals vary from layer to layer,
overall mineral composition is:
MINERAL
%
Quartz
20 – 25
Plagioclase
20 – 25
Dolomite
15 – 20
Muscovite-sericite
15 – 20
Biotite
15 – 20
Calcite
1–3
At Mintaro, the natural jointing and fracturing are widely spaced and facilitate
the mining of large slabs. Remarkably uniform bedding, allows the slate to
split cleanly.
Many prominent buildings in Adelaide feature Mintaro Slate, including Parliament
House, St Francis Xavier Cathedral, South Australian Museum, Supreme Court,
Adelaide Town Hall, St Peters Cathedral and the Mortlock Library.
Acknowledgements: Government of South Australia and Jeff Olliver
[Olliver Geological Services]
(Clockwise from top): Mintaro Slate sawing yard, 1880. Hand-powered steel saws were fed with water
and abrasive sand to cut the slabs to size and shape. The sloping quarry floor is at the rear
(photo 32702).
Mintaro Slate Footings at St Peter’s Cathedral.
Mintaro Slate used as pavement material outside Adelaide Town Hall.
Source: MESA Journal 39
CLARE VALLEY ROCKS IS SPONSORED BY
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FOR MORE DETAILED INFORMATION ABOUT
CLARE VALLEY ROCKS PLEASE SCAN HERE
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CREATED & MANAGED BY
GEOLOGY MAP SOURCED FROM
CLARE VALLEY ROCKS IS
A PROJECT THAT PROVIDES
INFORMATION ABOUT THE
ROCKS AND THE SOIL THAT
ARE THE EARTH BENEATH THE
CLARE VALLEY VINES.
OOK FOR OTHER INTERPRETIVE SITES
L
AROUND THE CLARE VALLEY.
PICK UP A CLARE VALLEY ROCKS
BROCHURE / MAP AT CELLAR DOORS.
YOU CAN SEE TYPICAL SOIL PROFILES
AT PARTICIPATING CELLAR DOORS
AND DISCOVER HOW DIFFERENT ROCKS
AND SOILS PLAY A ROLE IN THE WINE
YOU TASTE.
CLOS CLARE ENTRANCE
In this soil profile it is possible to see two distinct soil types. At the surface is a
rich, chocolate brown loam, which overlies calcareous shale, which forms part
of the Mintaro Shale Formation of the Belair Subgroup (see geology map).
At the boundary between the loam and the shale is a concentration of white
calcrete, which also fills in cracks and fractures in the shale. This calcrete is
produced when calcium carbonate is dissolved out of rocks and transported by
water to be re-deposited elsewhere. In some places here you can see plant roots
that have been replaced by this calcrete, which are called root casts.
The rich brown loam that sits on top of the shale is likely to have been eroded from
both the underlying shale and from other sources and then redeposited here by a
creek or river system, behind you.
A great perspective of the earth (ie the rich loamy soil overlying very carbonate rich rocks) beneath the
vines of the Florita Watervale Vineyard at Clos Clare.
Description and photography contributed by Dr Dave Kelsey, Mr Kieran Meaney and Ms Katherine Stoate School of Earth and Environmental Sciences, The University of Adelaide
Mick Roche - Stewardship Matters Pty Ltd
CLARE VALLEY ROCKS IS SPONSORED BY
CLAREVALLEYROCKS.COM.AU
FOR MORE DETAILED INFORMATION ABOUT
CLARE VALLEY ROCKS PLEASE SCAN HERE
OR VISIT OUR WEBSITE.
CREATED & MANAGED BY
GEOLOGY MAP SOURCED FROM
CLARE VALLEY ROCKS IS
A PROJECT THAT PROVIDES
INFORMATION ABOUT THE
ROCKS AND THE SOIL THAT
ARE THE EARTH BENEATH THE
CLARE VALLEY VINES.
OOK FOR OTHER INTERPRETIVE SITES
L
AROUND THE CLARE VALLEY.
PICK UP A CLARE VALLEY ROCKS
BROCHURE / MAP AT CELLAR DOORS.
YOU CAN SEE TYPICAL SOIL PROFILES
AT PARTICIPATING CELLAR DOORS
AND DISCOVER HOW DIFFERENT ROCKS
AND SOILS PLAY A ROLE IN THE WINE
YOU TASTE.
JIM BARRY WINES
CARPARK
These green, grey and white mudstones, siltstones, shales and sandstones were
deposited on the seafloor about 750 million years ago.
They form part of the Rhynie Sandstone Formation of the Emeroo Subgroup,
which are some of the oldest rocks in the Clare valley.
Mountain building events that happened here some 500 million years ago tilted
the once flat lying beds up to being nearly vertical. Small round pitting marks can
be observed on some surfaces here. These have been caused by small pockets of
water within the rock, chemically altering it and making it easier to erode and wash
away, creating this interesting surface texture.
The rich red brown soil overlying the mudstones is derived from weathering and
altering of the mudstone. The soil contains sand and clay, as this is what makes
up the rock, and allows for water drainage as well as retention. This is what
remains when all the white (carbonate rich) mudstones have been dissolved from
the mudstone and is called a residual soil.
The top of the ridge and underlying these mudstones is the more erosion resistant
sandstone member of the formation.
Some of the oldest sediments in the Clare Valley Region are preserved in this exposure.
Description and photography contributed by Dr Dave Kelsey, Mr Kieran Meaney and Ms Katherine Stoate School of Earth and Environmental Sciences, The University of Adelaide
Mick Roche - Stewardship Matters Pty Ltd
CLARE VALLEY ROCKS IS SPONSORED BY
CLAREVALLEYROCKS.COM.AU
FOR MORE DETAILED INFORMATION ABOUT
CLARE VALLEY ROCKS PLEASE SCAN HERE
OR VISIT OUR WEBSITE.
CREATED & MANAGED BY
GEOLOGY MAP SOURCED FROM
CLARE VALLEY ROCKS IS
A PROJECT THAT PROVIDES
INFORMATION ABOUT THE
ROCKS AND THE SOIL THAT
ARE THE EARTH BENEATH THE
CLARE VALLEY VINES.
OOK FOR OTHER INTERPRETIVE SITES
L
AROUND THE CLARE VALLEY.
PICK UP A CLARE VALLEY ROCKS
BROCHURE / MAP AT CELLAR DOORS.
YOU CAN SEE TYPICAL SOIL PROFILES
AT PARTICIPATING CELLAR DOORS
AND DISCOVER HOW DIFFERENT ROCKS
AND SOILS PLAY A ROLE IN THE WINE
YOU TASTE.
CLARE RAILWAY STATION
These rocks are sedimentary sandstones which contain layers of shale or
mudstone that were deposited in a marine environment at around 750 Million
years ago. They are part of the Watervale Sandstone Member of the Bungarider
Subgroup within the Burra Group (see geology map). At around 500 million years
ago this area was folded, tilting these originally horizontal layers into the near
vertical orientation that you see here.
The rock is predominantly sandstone, but there are thin layers where sandstone
is inter-layered with mudstone. These thin layers are buckled, and have eroded
to form this spectacular feature here, where the harder, more resistant sandstone
forms ‘hills’ and the softer, more easily eroded mudstone forms ‘valleys’.
This small scale feature can be related to the large fold structure that defines the
Clare Valley. Ridges in the Clare Valley region tend to be made of more erosionresistant sandstone/quartzite, whereas the valleys are underlain by softer rock
types such as mudstone and dolomite.
Rain penetrates into rock via bedding planes and fractures, and plants are able to
access the groundwater in times of dry by accessing/penetrating the fractures and
bedding planes.
(From top): Elongate quartz nodules.
Description and photography contributed by Dr Dave Kelsey, Mr Kieran Meaney and Ms Katherine Stoate School of Earth and Environmental Sciences, The University of Adelaide
Mick Roche - Stewardship Matters Pty Ltd
Watervale Sandstone cliff face.
CLARE VALLEY ROCKS IS SPONSORED BY
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FOR MORE DETAILED INFORMATION ABOUT
CLARE VALLEY ROCKS PLEASE SCAN HERE
OR VISIT OUR WEBSITE.
CREATED & MANAGED BY
GEOLOGY MAP SOURCED FROM
CLARE VALLEY ROCKS IS
A PROJECT THAT PROVIDES
INFORMATION ABOUT THE
ROCKS AND THE SOIL THAT
ARE THE EARTH BENEATH THE
CLARE VALLEY VINES.
OOK FOR OTHER INTERPRETIVE SITES
L
AROUND THE CLARE VALLEY.
PICK UP A CLARE VALLEY ROCKS
BROCHURE / MAP AT CELLAR DOORS.
YOU CAN SEE TYPICAL SOIL PROFILES
AT PARTICIPATING CELLAR DOORS
AND DISCOVER HOW DIFFERENT ROCKS
AND SOILS PLAY A ROLE IN THE WINE
YOU TASTE.
GREENWOOD ROAD
CROSSING THE
RIESLING TRAIL
The rocks exposed in this old rail cutting are grey to black dolomitic siltstones
that are part of the Saddleworth Formation in the Bungarider Subgroup (see
geology map). The layering that can be seen is called sedimentary bedding, and
the thickness of the beds here ranges from a few millimetres to a few centimetres.
Such thin sedimentary beds indicate that the rock was deposited in a quiet
(marine) environment that allowed the settling out of fine/small sized particles.
This could have been deep water or shallow water in a restricted depositional
setting (like an estuary). This rock was deposited as horizontal layers of sediment
approximately 750 million years ago in a shallow sea that extended from
Antarctica up into central Australia.
About 500 million years ago, once the sediment had been buried by the deposition
of more sediment, the rocks were rotated into the tilted orientation that you can
see here. This rotation of the layering in the sedimentary rock is related to folding
that can be seen at a much larger scale to define the shape of the Clare Valley.
Rock types such as shale and siltstones are fissile – this means that they quite
readily break and fracture into pieces, commonly breaking along the sedimentary
bedding planes. The high abundance of fractures and ‘split’ bedding planes in this
siltstone means that rain water can easily penetrate to deeper depths and reach
the water table. In (prolonged) times of little or no rain, plants growing on rock
types such as this have ready supply/access to groundwater.
Right near the top of the siltstone is a thin layer of calcrete, which is then overlain
by a thin soil horizon in which the grape vines are planted.
(From top) : A “boudin” of coarser grained and more massive sandstone overlain and underlain by finer
grained and thinner beds of siltstone.
Description and photography contributed by Dr Dave Kelsey, Mr Kieran Meaney and Ms Katherine Stoate School of Earth and Environmental Sciences, The University of Adelaide
Mick Roche - Stewardship Matters Pty Ltd
Steep east dipping siltstone with only a thin soil horizon in which the vines are grown.
CLARE VALLEY ROCKS IS SPONSORED BY
CLAREVALLEYROCKS.COM.AU
FOR MORE DETAILED INFORMATION ABOUT
CLARE VALLEY ROCKS PLEASE SCAN HERE
OR VISIT OUR WEBSITE.
CREATED & MANAGED BY
GEOLOGY MAP SOURCED FROM
CLARE VALLEY ROCKS IS
A PROJECT THAT PROVIDES
INFORMATION ABOUT THE
ROCKS AND THE SOIL THAT
ARE THE EARTH BENEATH THE
CLARE VALLEY VINES.
OOK FOR OTHER INTERPRETIVE SITES
L
AROUND THE CLARE VALLEY.
PICK UP A CLARE VALLEY ROCKS
BROCHURE / MAP AT CELLAR DOORS.
YOU CAN SEE TYPICAL SOIL PROFILES
AT PARTICIPATING CELLAR DOORS
AND DISCOVER HOW DIFFERENT ROCKS
AND SOILS PLAY A ROLE IN THE WINE
YOU TASTE.
JOLLY’S ROAD CROSSING
The sedimentary rock type here is quartzite/sandstone, which is part of the
Watervale Sandstone Formation in the Bungarider Subgroup (see geology map).
The layering that can be seen is called sedimentary bedding, and the thickness
of the beds here ranges from about 5 cm to 50 cm or so. This rock was deposited
as horizontal layers of sediment approximately 750 million years ago in a
shallow sea that extended from Antarctica up into central Australia. About 500
million years ago, once the sediment had been buried by the deposition of more
sediment, the rocks were rotated into the near-vertical orientation that you can see
here. This rotation of the layering in the sedimentary rock is related to folding that
can be seen at a much larger scale to define the shape of the Clare Valley
(on geology map).
There are some places in this sandstone/quartzite where you can see 750 million
year old marine ripples, similar to what you see at the beach today. The ripples
can be identified as the sedimentary bed has one curved side (the ripple) and one
flat/straight side. The ripples tend to be preserved in layers where there is some
muddier rock (mudstone/shale) inter-layered with the sandstone.
(From top): “Slickenslides” in quartz result from rock movement above and below.
Thin beds of siltstone in between the sandstone.
Description and photography contributed by Dr Dave Kelsey, Mr Kieran Meaney and Ms Katherine Stoate School of Earth and Environmental Sciences, The University of Adelaide
Mick Roche - Stewardship Matters Pty Ltd
CLARE VALLEY ROCKS IS SPONSORED BY
CLAREVALLEYROCKS.COM.AU
FOR MORE DETAILED INFORMATION ABOUT
CLARE VALLEY ROCKS PLEASE SCAN HERE
OR VISIT OUR WEBSITE.
CREATED & MANAGED BY
GEOLOGY MAP SOURCED FROM
CLARE VALLEY ROCKS IS
A PROJECT THAT PROVIDES
INFORMATION ABOUT THE
ROCKS AND THE SOIL THAT
ARE THE EARTH BENEATH THE
CLARE VALLEY VINES.
OOK FOR OTHER INTERPRETIVE SITES
L
AROUND THE CLARE VALLEY.
PICK UP A CLARE VALLEY ROCKS
BROCHURE / MAP AT CELLAR DOORS.
YOU CAN SEE TYPICAL SOIL PROFILES
AT PARTICIPATING CELLAR DOORS
AND DISCOVER HOW DIFFERENT ROCKS
AND SOILS PLAY A ROLE IN THE WINE
YOU TASTE.
WATERLOO
HOMESTEAD
In this soil profile you can see a red-brown loam, which overlies a grey, dolomitic
siltstone. This siltstone is part of the Saddleworth Formation of the Bungarider
Subgroup (see geology map).
The siltstones are altered by weathering and by water dissolving and removing
certain elements, such as calcium, which get redeposited elsewhere in the
soil profile. Although they are very weathered, it is still possible to see the
original sedimentary bedding from when this rock was originally deposited,
around 750 million years ago.
At the boundary between these two soils a concentration of calcrete can be
observed, which reflects water pooling in the soil at the boundary and depositing
dissolved elements. Calcrete can also be seen as nodules and concretions in both
soil types which shows how water moves through the profile.
In some places near the top of the profile it is possible to see plant roots that have
been replaced by calcrete, creating a type of fossil called root casts.
Classic “Terra Rossa soil overlying “limestone” profile of the southern part of the Clare Valley.
Description and photography contributed by Dr Dave Kelsey, Mr Kieran Meaney and Ms Katherine Stoate School of Earth and Environmental Sciences, The University of Adelaide
Mick Roche - Stewardship Matters Pty Ltd
CLARE VALLEY ROCKS IS SPONSORED BY
CLAREVALLEYROCKS.COM.AU
FOR MORE DETAILED INFORMATION ABOUT
CLARE VALLEY ROCKS PLEASE SCAN HERE
OR VISIT OUR WEBSITE.
CREATED & MANAGED BY
GEOLOGY MAP SOURCED FROM
CLARE VALLEY ROCKS IS
A PROJECT THAT PROVIDES
INFORMATION ABOUT THE
ROCKS AND THE SOIL THAT
ARE THE EARTH BENEATH THE
CLARE VALLEY VINES.
OOK FOR OTHER INTERPRETIVE SITES
L
AROUND THE CLARE VALLEY.
PICK UP A CLARE VALLEY ROCKS
BROCHURE / MAP AT CELLAR DOORS.
YOU CAN SEE TYPICAL SOIL PROFILES
AT PARTICIPATING CELLAR DOORS
AND DISCOVER HOW DIFFERENT ROCKS
AND SOILS PLAY A ROLE IN THE WINE
YOU TASTE.
NEAGLES ROCK
LOOKOUT
The Neagles Rock lookout is part of the Skillogalee Dolomite, silicified adjacent
to the Clare-Spalding Fault (see geology map and cross section). This very major
structure is the most significant structural discontinuity in the Clare Valley or,
indeed, in the whole of the Mid-North.
Silicification adjacent to major faults is common in the Skillogalee in many part of
the Mid-North, and often the silicified zones are extensively brecciated and may
be recemented with more silica and iron oxides.
Although Neagles Rock is the most prominent siliceous outcrop, there are many
occurrences of totally silicified dolomite all along the Clare-Spalding Fault;
often they are just float (ie loose, scattered rocks) in paddocks.
Looking south is a view of the Skillogalee Valley. Underlying this valley is the
Skillogalee Dolomite (a formation within the Mundallio Subgroup). The dolomite,
being relatively soft, erodes a lot quicker that the sandstones and quartzites that
make up the ridges on either side – thus, resulting in a valley.
A spectacular view looking south along the Skillogalee Valley can be seen from the top of the lookout.
Description and photography contributed by Dr Dave Kelsey, Mr Kieran Meaney and Ms Katherine Stoate School of Earth and Environmental Sciences, The University of Adelaide
Mick Roche - Stewardship Matters Pty Ltd
CLARE VALLEY ROCKS IS SPONSORED BY
CLAREVALLEYROCKS.COM.AU
FOR MORE DETAILED INFORMATION ABOUT
CLARE VALLEY ROCKS PLEASE SCAN HERE
OR VISIT OUR WEBSITE.
CREATED & MANAGED BY
GEOLOGY MAP SOURCED FROM
CLARE VALLEY ROCKS IS
A PROJECT THAT PROVIDES
INFORMATION ABOUT THE
ROCKS AND THE SOIL THAT
ARE THE EARTH BENEATH THE
CLARE VALLEY VINES.
OOK FOR OTHER INTERPRETIVE SITES
L
AROUND THE CLARE VALLEY.
PICK UP A CLARE VALLEY ROCKS
BROCHURE / MAP AT CELLAR DOORS.
YOU CAN SEE TYPICAL SOIL PROFILES
AT PARTICIPATING CELLAR DOORS
AND DISCOVER HOW DIFFERENT ROCKS
AND SOILS PLAY A ROLE IN THE WINE
YOU TASTE.
QUARRY HILL LOOKOUT
This lookout is situated on a north-south trending ridge of relatively erosionresistant quartzite. It is called the Gilbert Range Quartzite which is part of the
Belair Sub-group, which in turn is part of the Burra Group (see geology map).
This sandstone was deposited approximately 750 million years ago in a shallow
marine environment that extended from Antarctica to central Australia.
About 500 million years ago, once the sand had been buried and converted
to rock, folding and tilting of the sandstone occurred. Folding of this layer of
sandstone that you are standing on can be seen by looking across the valley to
the next north-south trending ridge to the east (middle distance away). That ridge
is the same layer as what you are standing on here!
You are standing on the western limb of a giant fold that is about 500 million years
old! The size of the fold can be appreciated on the geological map. The fold axis
runs north south down the valley in front of you.
This ancient fold defines the shape of the Clare Valley. The different rock types that
make up the Clare Valley (sandstones, mudstones, dolomites, limestones) have
different capabilities in terms of retaining or allowing the flow of water through
them. Rock types that are good at retaining water, such as clay-rich mudstones,
are good to grow grape vines on because they have a source of water that can be
utilised by the vines in times of little or no rain.
Quarry Hill - Looking across the Polish Hill River Valley - the true centre of the Clare Valley Fold Axis.
Description and photography contributed by Dr Dave Kelsey, Mr Kieran Meaney and Ms Katherine Stoate School of Earth and Environmental Sciences, The University of Adelaide
Mick Roche - Stewardship Matters Pty Ltd
CLARE VALLEY ROCKS IS SPONSORED BY
CLAREVALLEYROCKS.COM.AU
FOR MORE DETAILED INFORMATION ABOUT
CLARE VALLEY ROCKS PLEASE SCAN HERE
OR VISIT OUR WEBSITE.
CREATED & MANAGED BY
GEOLOGY MAP SOURCED FROM
CLARE VALLEY ROCKS IS
A PROJECT THAT PROVIDES
INFORMATION ABOUT THE
ROCKS AND THE SOIL THAT
ARE THE EARTH BENEATH THE
CLARE VALLEY VINES.
OOK FOR OTHER INTERPRETIVE SITES
L
AROUND THE CLARE VALLEY.
PICK UP A CLARE VALLEY ROCKS
BROCHURE / MAP AT CELLAR DOORS.
YOU CAN SEE TYPICAL SOIL PROFILES
AT PARTICIPATING CELLAR DOORS
AND DISCOVER HOW DIFFERENT ROCKS
AND SOILS PLAY A ROLE IN THE WINE
YOU TASTE.
RIESLING TRAIL –
WHITE HUT CROSSING
This coarse grained quartzite was originally deposited in a high energy, shallow
marine environment around 750 million years ago. It is part of the Leasingham
Quartzite member of the Belair Sub-group of the Burra Group sediments
(see geology map). The layering that can be seen is called sedimentary bedding,
and the thickness of the beds here ranges from about 10cm to 50cm.
If you look closely, some of the layers preserve ripples similar to what you might
expect to see at the beach today!
At around 500 million years ago the rocks in this area were folded, causing the
originally horizontal layers to be tilted up into their current orientation –
dipping steeply to the east.
Fractures are near vertical here allowing rainwater to seep into the rock to become
groundwater, and plants such as grape vines can access this ground water by
sending their roots down along fractures and bedding planes. The natural porosity
of sandstone is also quite high, meaning that water can (potentially) pass through
the sandstone at depth.
On some surfaces you can see some smooth quartz veins with lines on them.
Geologists call these ‘Slickenslides’.
These lines indicate that a slab of rock that once lay above what you can see now
slid over this rock, forming these striations/lines in the quartz. These lines are
oriented approximately east-west, and so the sliding of rocks over one another
might be related to the large-scale folding of rocks that can be seen to define the
shape of the Clare Valley.
(From top): Quartz vein with slickenslides.
Recent quartz veining is fractures that cross cut the bedrock.
Description and photography contributed by Dr Dave Kelsey, Mr Kieran Meaney and Ms Katherine Stoate School of Earth and Environmental Sciences, The University of Adelaide
Mick Roche - Stewardship Matters Pty Ltd
CLARE VALLEY ROCKS IS SPONSORED BY
CLAREVALLEYROCKS.COM.AU
FOR MORE DETAILED INFORMATION ABOUT
CLARE VALLEY ROCKS PLEASE SCAN HERE
OR VISIT OUR WEBSITE.
CREATED & MANAGED BY
GEOLOGY MAP SOURCED FROM
CLARE VALLEY ROCKS IS
A PROJECT THAT PROVIDES
INFORMATION ABOUT THE
ROCKS AND THE SOIL THAT
ARE THE EARTH BENEATH THE
CLARE VALLEY VINES.
OOK FOR OTHER INTERPRETIVE SITES
L
AROUND THE CLARE VALLEY.
PICK UP A CLARE VALLEY ROCKS
BROCHURE / MAP AT CELLAR DOORS.
YOU CAN SEE TYPICAL SOIL PROFILES
AT PARTICIPATING CELLAR DOORS
AND DISCOVER HOW DIFFERENT ROCKS
AND SOILS PLAY A ROLE IN THE WINE
YOU TASTE.
SPRING GULLY
CONSERVATION PARK
From this lookout it is possible to see all the way to the Gulf St. Vincent. This point
is on the western most edge of the large fold that is seen on the geological map.
Near-vertically oriented layers of sedimentary rock can be seen in the hillside
across the steep valley immediately south. These were once sediments that
were deposited horizontally about 750 million years ago in a shallow marine
environment. They are sandstones and siltstones of the Rhynie Sandstone
Formation of the Emeroo Subgroup (see geology map) and are some of the
oldest rocks in the Clare Valley.
The tilting or folding of the layers to vertical occurred as a result of two processes.
One occurred about 500 million years ago and caused the large fold that defines
the shape of the Clare Valley to form. The second is much more recent and
involved the Mt Lofty-Flinders Ranges (including Clare Valley region) to be pushed
up higher than the Adelaide plains. The transition between the hills of the Clare
Valley region you can see here immediately in front of you and the flat plains out
to the west is marked by the presence of a fault line that runs in a north-south
direction. This fault line has been active in the last 5 million years and continues
to be periodically active to this day, very slowly moving the hills up relative to
the plains. The east-west oriented forces that are required to push the Mt LoftyFlinders Ranges up along north-south fault lines originate many thousands of
kilometres to the east – in the vicinity of New Zealand, where the Australian
tectonic plate is being rammed from the east by the largest tectonic plate on
Earth, the Pacific plate.
This is a structurally, the most complex area of the Clare Valley.
(From top): The view to the west across the plains show that the Clare Valley is an uplifted plateau
comprising a series of ridges and valleys. On the western horizon are the Hummocks Range at the
apex of Gulf St Vincent.
Description and photography contributed by Dr Dave Kelsey, Mr Kieran Meaney and Ms Katherine Stoate School of Earth and Environmental Sciences, The University of Adelaide
Mick Roche - Stewardship Matters Pty Ltd
Complexly faulted NeoProterozoic sediments - the oldest in the Clare region.
CLARE VALLEY ROCKS IS SPONSORED BY
CLAREVALLEYROCKS.COM.AU
FOR MORE DETAILED INFORMATION ABOUT
CLARE VALLEY ROCKS PLEASE SCAN HERE
OR VISIT OUR WEBSITE.
CREATED & MANAGED BY
GEOLOGY MAP SOURCED FROM
CLARE VALLEY ROCKS IS
A PROJECT THAT PROVIDES
INFORMATION ABOUT THE
ROCKS AND THE SOIL THAT
ARE THE EARTH BENEATH THE
CLARE VALLEY VINES.
OOK FOR OTHER INTERPRETIVE SITES
L
AROUND THE CLARE VALLEY.
PICK UP A CLARE VALLEY ROCKS
BROCHURE / MAP AT CELLAR DOORS.
YOU CAN SEE TYPICAL SOIL PROFILES
AT PARTICIPATING CELLAR DOORS
AND DISCOVER HOW DIFFERENT ROCKS
AND SOILS PLAY A ROLE IN THE WINE
YOU TASTE.
FRACTURED ROCK –
A SOURCE OF
GROUNDWATER IN
THE CLARE VALLEY
The sediments (sandstone and siltstones) in this cliff face, were originally
deposited horizontally in a shallow marine basin approximately 750 million
years ago.
They form part of the Watervale Sandstone, a formation within the Bungarider
Subgroup (see geology map).
These sediments were then buried by the deposition of more sediments on top
of them, and the resulting pressure from the overlying sediments eventually
converted these sediments into rock. About 250 million years after they were
deposited, these sediments – now rock – were folded into the vertical orientation
you can see here. The folding can be seen at a much larger scale to defining the
shape of the Clare Valley (see geology map). Each layer you can see here is called
a sedimentary bed. Colour differences in the layers represent different types of
sedimentary rocks (e.g. sandstone vs siltstone). Different types of sedimentary
rock have different amounts of porosity, which means that some rocks allow for
efficient flow of water through them whereas other types don’t.
Extensive fracturing of these rocks also allows for better water movement. This
can be easily observed in the staining and bleaching of certain elements from
around fractures. Dark rust-red coloured patches in the rocks show where water
has flowed and deposited iron oxide (rust) along fractures, as well as bleached
white areas where iron and other elements have been removed by water.
Fractured rock aquifer style, as seen at Clare Valley Woolworths supermarket carpark.
While these fractures occur in any orientation, the stained and bleached
fractures are most commonly vertical, indicating water was flowing vertically
through these rocks.
The combination of fractures in the rocks and porosity allows water to get into
rocks and the water table, and also allows plants such as grape vines to access/
suck up water from below. Tree roots can be seen here to be penetrating along
fractures as they try to access groundwater.
Elsewhere in the Clare Valley, where this fractured sandstone occurs much deeper,
holes are drilled down to the sandstone, in order to access the groundwater
trapped in the fractures and the water is pumped to the surface.
Description and photography contributed by Dr Dave Kelsey, Mr Kieran Meaney and Ms Katherine Stoate School of Earth and Environmental Sciences, The University of Adelaide
Mick Roche - Stewardship Matters Pty Ltd
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