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DISPLAYING POSTS TAGGED: dinosaur dreaming (4)

Geology of the Flatrocks site

Author
by Lisa
Publish date
28 February 2012
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Comments (5)

Lisa works in the Public Programs Department at Melbourne Museum but also volunteers in the Palaeontology Department and has been on several fossil digs.

By the tenth day of the annual Dinosaur Dreaming dig we had already catalogued more than 140 fossils. To know where to dig in the first place we need to understand the geology of the area because the types of rock and how they have been laid down can give us much information about the palaeoenvironment. Dr Alan Tait, Adjunct Research Fellow in the Department of Geosciences at Monash University is currently researching the sedimentology of the Flatrocks site and kindly explained its geology to me.

Today the site known as Flatrocks is a rocky beach dominated by light grey sandstone but 120 million years ago during the Cretaceous, the environment was very different. Australia was once part of a supercontinent called Gondwana which also comprised Antarctica, South America, Africa, New Zealand and India.

Much of Gondwana had broken up by the Cretaceous and a rift had started to form between Australia and Antarctic. The types of rocks and fossils we find along the coastline in Inverloch today tell us the story of the rift valley and the animals and plants that lived there.

The cliff face near the Flatrocks site The cliff face near the Flatrocks site. The grey mudstone is the remains of a flood plain which was on the floor of the rift valley. The layer where we find most of our fossils lies above this and at the top is massive sandstone. To the left of the mudstone you can see a fault where the rock layers have shifted dramatically from their original horizontal deposition.
Image: Lisa Nink
Source: Museum Victoria

The fossil layer itself consists of the sedimentary rocks, grey sandstone and conglomerate that were deposited during flooding of the rift valley. The conglomerate pebbles are made of clay eroded from the flood plain soils during flooding. The sandstone is grey because it contains grains of volcanic rock eroded from active volcanos some distance away and washed into the rift valley. The sediments also include the fossilised remains of dead animals, plants and trees. The time between the floods was long enough for large trees to grow, perhaps at least 100 years, and the floods were catastrophic.

Cliff at Inverloch “The main fossil bearing layer (under the red line) consists of grey sandstone with coal throughout it. The layer is bounded by a layer of mudstone below and massive sandstone above.
Image: Lisa Nink
Source: Museum Victoria

There are many fossilised tree stumps on the shore platform. Some of these trees lie horizontally with their fossilised roots still attached and are believed to have been knocked over by the force of the floods and washed down the river. We also find fossil leaves of ferns, gingkoes and monkey puzzle-like trees that once grew as part of a forest within the rift valley.

Fossil tree trunk A fossil tree trunk. If you look closely you can even see the growth rings.
Image: Lisa Nink
Source: Museum Victoria
 

The coal in the fossil layer is the remains of decomposing plants that once grew in the valley. Fossilised grains of pollen from these plants have also been found and by identifying their species, we can date the sediments surrounding them.

A nearby dyke (a long straight crack in the rocks through which magma from deep below the Earth's crust travels upwards and cools) is made up of basaltic rock, another igneous rock type. The dyke is 99.5 million years old and cuts through the grey sandstone, meaning it formed after the sedimentary rocks had been deposited. 

volcanic dyke at Inverloch Dale Nelson stands upon the basaltic dyke near the Flatrocks site.
Image: Lisa Nink
Source: Museum Victoria
 

We also find minerals at the site, like pyrite and calcite.

Crystals found at dinosaur dig Minerals found at the fossil dig site, shown with objects often found in geologists' pockets, for scale. Left: Pyrite crystals | Right: Calcite crystals
Image: Lisa Nink
Source: Museum Victoria
 

Links:

Dinosaur Dreaming blog

Infosheet: Dinosaur Dreaming - the Inverloch fossil site

Video: Dinosaur Dreaming

Dinosaur Dreaming dig season opens

Author
by Lisa
Publish date
16 February 2012
Comments
Comments (1)

Lisa works in the Public Programs Department at Melbourne Museum but also volunteers in the Palaeontology Department and has been on several fossil digs.

Last weekend hailed the beginning of the annual Dinosaur Dreaming dig season at Inverloch in Victoria. The crew will spend the next three weeks searching for the fossils of animals including dinosaurs, mammals, turtles, freshwater plesiosaurs, fish and pterosaurs that lived on and around the floodplain and in the forests that existed in the area 120 million years ago.

We can only access the dig site while the tide is out far enough to expose the shore platform, and before we can start hunting for fossils we need to prepare the site. First we remove the sand with shovels, which is often a bit of a smelly job due to the bits of rotting seaweed that have washed into the hole (the name we give to the part of the site which is being worked at any given time) with the tide.

Preparing the fossil site dig Left: The crew removes sand, boulders and seaweed from on top of the rock layers. Right: John Wilkins and Dean Wright remove one of many large boulders from the dig site using a boulder extraction contraption John invented and built for us.
Image: Lisa Nink
Source: Museum Victoria
 

Next we use large chisels, crowbars and large drills to remove the overlying layer of sandstone. Once we have access to the fossil layer we can begin searching.

Some of the crew use large chisels and sledgehammers to remove large chunks of the fossil layer and the rest of the crew sit further up on the shore breaking these large rocks into walnut sized pieces in search of fossils.

Breaking rocks to find fossils Left: Travis Park uses a sledgehammer and chisel to remove a large chunk of fossil-bearing rock. Right: Gerry Kool uses a much smaller hammer and chisel to break down chunks of rock in search of fossils.
Image: Lisa Nink
Source: Museum Victoria
 

While the main aim of the dig is to find fossils, there is much more we can learn about the site. Dean Wright, a surveyor, and Doris Seegats-Villiers, a PhD candidate at Monash University, used a Leica Total Station to collect data which will be used to map geological features such as the different rock layers and fault lines. Dean plans to overlay this data onto a 3D map of the site he made last year and this information will assist scientists to better understand the geology of the site.

measuring geology of fossil site Dean Wright and Doris Seegats-Villiers taking data points which Dean will use to create a geologic map of the Flatrocks site.
Image: Lisa Nink
Source: Museum Victoria
 

Some of the interesting bones we have found so far this season:

dinosaur bones found at Inverloch Left: A cross-section through a dinosaur limb bone. Right: A cross-section through a dinosaur toe bone.
Image: Lisa Nink
Source: Museum Victoria
 

Links:

Dinosaur Dreaming blog

Infosheet: Dinosaur Dreaming - the Inverloch fossil site

Video: Dinosaur Dreaming

How to dig for dinosaurs

Author
by Lisa
Publish date
19 December 2011
Comments
Comments (7)

Lisa works in the Public Programs Department at Melbourne Museum but also volunteers in the Palaeontology Department and has been on several fossil digs.

Have you ever wondered what it would be like to go on a dinosaur dig? Recently I went on a fossil-hunting adventure with a crew of 12 Museum Victoria staff and volunteers at a site called Eric the Red West in Cape Otway National Park.

120 million years ago this part of Australia was a river valley surrounded by forest. When the valley flooded, the remains of dinosaurs, small mammals, pterosaurs and forest plants (which became the coal that we see in the rock) were washed into the river. Eventually some of these bones, as well as those of animals such as fish and turtles that were living in the river, became covered by sand and mud. Over time the sediment became the grey sandstone that is exposed on beach today.

palaeontology fieldwork The crew heads down to the site.
Image: Lisa Nink
Source: Museum Victoria
 

When we first arrived on site we unloaded all of our gear and took it down onto the beach. Before we started any digging we prospected along the beach for fossils that were naturally exposed through weathering of the rock.

Prospecting and fossil finds Left: Lesley Kool and Mary Walters in search of fossils weathering out of the rock. | Right: Part of a dinosaur limb bone.
Image: Lisa Nink
Source: Museum Victoria
 

Next it was time to bring out the heavier equipment to remove rock and search for fossils that were still buried. We used large rock saws, small electric saws, sledgehammers and chisels to remove large chunks of the fossil-bearing rock.

tools to remove rock Travis removes sand from the rock with a shovel and Gerry removes chunks of rock with a sledge hammer and chisel.
Image: Liza Nink
Source: Museum Victoria
 

Removing fossils with tools. Left: David Pickering uses a small electric saw to delicately remove a fossil. | Right: Dr Erich Fitzgerald uses a larger rock saw to not so delicately (but precisely) remove a fossil.
Image: Lisa Nink
Source: Museum Victoria
 

When large chunks of rock have were removed and checked for fossils, the rest of the crew used smaller hammers and chisels to carefully break the rock down to sugar-cube sized pieces in search of tiny fossils.

Searching for fossils Left: David Pickering uses a hand lens to inspect a newly exposed fossil. | Right: Astrid patiently chisels away at rock in search of delicate fossils.
Image: Lisa Nink
Source: Museum Victoria
 

And we were well rewarded for our efforts:

Dr Erich Fitzgerald points to a fossil fish jaw Dr Erich Fitzgerald points to a fossil fish jaw he has just discovered in the rock.
Image: Lisa Nink
Source: Museum Victoria
 

Despite the rain and cold it was a wonderful experience. My friends and colleagues often ask me, 'doesn't it get boring breaking rocks on a beach all day?' but it never does. You never know when the next strike of your hammer and chisel may reveal a new fossil that hasn't seen the light of day for 120 million years. You never know, it may even be a completely new species.

You can see some of the fossils that have been found along Victoria's coastline in 600 Million Years: Victoria evolves at Melbourne Museum.

Links:

Dinosaur Dreaming Blog

MV Blog: Dinosaur Dreaming Dig

Infosheet: Inverloch fossil site

Dinosaur Dreaming

Author
by Priscilla
Publish date
22 February 2011
Comments
Comments (2)

Priscilla is a Program Coordinator for Life Sciences and works on education programs at Melbourne Museum. She has been a regular dinosaur digger for over 10 years!

I'm often asked what it's like at a dinosaur dig. The romantic view most people have, fuelled by films like Jurassic Park, is that we simply sweep away the sand with a brush, use high-tech gadgets to locate the exact location of the bones, and get flown to tropical islands with Jeff Goldblum.

Over 100 years ago the first dinosaur fossil, the Cape Paterson Claw, was found on the coast of Victoria at a site known as Eagles Nest. Nothing much else was found until two young palaeontologists in the making, Tim Flannery and John Long, spent their youth searching the rocks along the coast of Victoria, eventually finding more fossil booty. Their finds have led to decades of dinosaur digs along the coast of Victoria.

From Cape Otway to Inverloch, the Cretaceous-aged sandstone rocks have been blasted, bashed and bored to reveal what life was like 120 million years ago in Victoria. Each year the work at the Dinosaur Dreaming Dig, which is a joint project between Museum Victoria and Monash University, recruits numerous volunteers who spend hours breaking rock. Over the years, the same volunteers return, making the whole experience more like a giant family gathering at Christmas. Uncle Norman, Mother Lesley, Sister Alanna, and Grandma Mary are all there. Gerry and his rock, Doris and her eggnog, Mike and his poems, Nick and his telescope, Nicole and her berry crumble are all part of the experience.

And yes, there are the dinosaur bones. Each year some 800 new bones are found and catalogued. Just like a Christmas stocking, you never know what you are going to find inside each rock – will it be the discovery that changes theories of evolution or another disappointment? Yet despite so many fruitless ‘stocking openings’, I and many others are lured back. After so many years of digging, amazing fossils have been found. Many of these incredible specimens are now on display in 600 Million Years: Victoria evolves. Hopefully, this clip gives you some insight into just how we find them...

Watch this video with a transcript

Links:

Dinosaur Dreaming: the Inverloch Fossil Site infosheet

Fossil collecting sites in Victoria infosheet

Dinosaur Walk

Dinosaur Dreaming blog

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