At the working site, there were plenty of recently extracted rocks to look at, with plenty of bone.
But there were also plenty left in the ground. Like this cluster of bat bone fragments.
And things that weren’t even mammalian, like this stromatolite.
But the prettiest things were the flowstone from now eroded caves. They had some impressive swirls.
Mercifully, the tour was not all walking but was broken up by more of Mike’s anecdotes. At one site he found a mother and child diprotodon skeleton, just metres apart. When the local residents found out about the fossils and how they must have died together, they called it the Madonna and Child of Riversleigh. There were also stories told at previously worked sites like Camel Sputum (named by Henk, another palaeontologist, when he was in a particularly bad mood), and other curiously named localities, which together formed a loose history of the dig at Riversleigh. At each site, we saw bones peering out of the limestone, and proving that the ‘richness of the sites’ quoted in numerous articles wasn’t just hearsay.
We didn’t just learn about fossils though. The geologists were hard at work, seeking out flowstone – evidence of cave systems – that could be used to date the sites.
We saw more of the landscape – spinifex and acacia mostly.
And more of the trecherous limestone – I had to watch out for all those holes.
At lunch, our spider expert dug out a hairy native tarantula from under some Spinifex – in the name of research, of course – which became the prime attraction at the dinner table that evening.
All of this was very interesting, but for a person whose idea of exercise is a walk to the corner shop and back, it was also exhausting. I was ready for a big nanny nap. I might have an interest in palaeontology, but a field palaeontologist I was not meant to be.
After our visit to ‘D’ site, we drove back a mile along the main road before entering a gate into what looked to me like a wilderness. Then setting the four wheel drive into gear, we bashed through plains of grass seven feet tall, ducked in and out of dry creek beds, and swerved around termite nests. It might have only been a fifteen minute ride, but to a four wheel drive novice passenger like me, it seemed like an endless, bumpy drive into nowhere. It was only later that I found out that there was science in the madness – we had followed a well-known track, which due to a bumper wet season was grossly overgrown. Aside from the natural impediments, there were also man-made impediments. Some of the gates that we drove through were so complex to open that it seemed like you needed a degree to do so successfully. I quickly realised that the Gulf country was rougher than I thought.
Eventually, we stopped at a limestone ridge called the Bite-Centennial Gallery. This site produced the first big finds after ‘D’ site.
Mike, our guide for the day, was one of the key palaeontologists behind the Riversleigh finds. He has returned here at least once a year for the last 36 years. You’d say that he was fountain of knowledge about the area, but he was also an amusing story teller.
At Bite-Centennial Gallery, he began by recounting the disturbing story behind the name (involving a drunken, biting cattleman, a distressed geologist, and a decapitated yabby), before we walked up the ridge, which for me was when the fun started.
I have never been a rock wallaby. I like being in the outdoors, but I’m more comfortable with gentle strolls along established paths than bush bashing across the wilderness. And worse still, an ankle injury six months before had made me more hesitant on my feet than usual. You can guess that my first hour at the Gallery was not terribly fun. Grasses constantly pricked my short legs, their seeds covered my trousers and top, and the razor-sharp limestone cut my hands when I touched them. This certainly was not what I was expecting.
I learned my lesson quickly though. The next day, I wore gaiters to the field, and my shins certainly thanked me for it.
Riversleigh in the Miocene wasn’t anything like the dry plains that we see today. Think the Daintree region of Far North Queensland, where the rainforest meets the sea, and you get an idea what the landscape was like 25 million years ago. At Riversleigh, you can even see some fossilised wave action.
As for the fauna, it was rather different. Aside from the big bird, there were big snakes, wombats, kangaroos, and crocodiles. The long-nosed animal is my old friend, the palorchestes, related to the koala.
The Riversleigh fossil sites are now under the management of national parks. Unfortunately, some people seem to disregard the rule of not taking anything without permission, hence the sign below.
Apparently, people have lifted huge slabs, without remorse before. ‘D’ Site is the only site in Riversleigh open to the public, and the first that was worked on. Back in 1976, a group of palaeontologists from the Queensland Museum came out to explore a tip-off they got from one of their colleagues, who found lots of bone in the limestone years before, but didn’t bother to pursue it further because he thought bones in limestone were impossible to extract.
This was what he saw.
Luckily, the QM paleos were more persistent, and they discovered lots of bone peeking out from the rock. And discovered more creatures from Miocene Australia (around 25 million years ago).
These bones are the leg bone of a dromornis – a giant bird that weight over 500kg, with a lethally big beak. So big and lethal in fact that the scientists nicknamed it the ‘Demon Duck of Doom’ (it might be distantly related to modern ducks).
Here it is fighting with a crocodile!
Let’s talk a bit about Riversleigh and where it is. Riversleigh is named after the property that it was on, Riversleigh Station. It’s about 280km by road, north west of Mount Isa, smack bang in the Gulf Country.
The landscape didn’t make much of an impression for me at first. It’s generally flat, with ridges of hills every now and then.
What makes the hills around Riversleigh different is that they are made of limestone – yes, we’re in karst country once again. You can tell by the grey-ish boulders on top of the hill.
The limestone here isn’t as old as the limestone around Wellington, NSW. It is much, much younger, from 50 to 5 million years. It’s formed because of the spring waters that are particularly rich in calcium carbonate. It seems to bind to the bones of animals, and fossilise them very well indeed.
Next, ‘D’ site, and its fossils.
Later in the day we travelled 15 minutes away to Dripstone, to look for more fossils, this time to take home.
We had to look a bit harder among the tall grass for them, but we did find a few things in the end. Like little stromatolites (they are small here, the little circular things).
Corals in different shapes than those at Wellington Caves.
And another block rich in crinoid stems.
There were also caves in the area, although the entrances are so small that no one was willing to climb in.
The limestone around Wellington is Devonian in age, around 390 million years ago. Back then, the area was still under water – a shallow sea. Dinosaurs weren’t to appear for at least another 150 million years. Plants were only starting to grow on land, and were probably very strange-looking. The only land animals were arthropods (insects, crustaceans, spiders) and lung fish with legs.
Most plant and animal life lived in the sea, and in the limestone, we saw a good cross-section of what was around in the ocean.
There were snails and other marine gastropods.
Giant stromatolites formed by micro-organisms (closely related to blue green algae). You can see the layers of sediment they formed.
Block of crinoid stems – remnants of ancient sea lilies.
But mostly, we saw lots and lots of coral. Yes, the ancestors of the coral that form the Great Barrier Reef.
They were literally all over the rocks in places.
The only thing we didn’t see (although there were plenty out there at the time) was fish. I guess I have to go to Canowindra one day to see Devonian fish in abundance.
Once you gathered together your pile of fossils, how do you know what you have? These students had a guide to what the bones and teeth of various animals looked like to help them.
And it’s also good to have a resident paleontologist nearby to help you identify things. These scientists have been studying bones and teeth of animals for over 30 years, so they know what they are talking about.
The students sorted their finds neatly into groups.
Some of them found some interesting things…
All this sorting helped the paleontologists catalogue what was in the pile, which told us the kinds of animals alive back then.
Looking at the white board at the end of the session, there were a lot of different finds that day.
It goes to show how diverse the fauna was back then – even more so that now, in a way.
That comes to the end of our walk through the Pleistocene age of one million years ago. I’ll be on a blog break for the next two weeks, and will be back with some Devonian fossils from around 400 million years ago!
It was interesting to see paleontologists (albeit students) in action. How do you extract the fossils from this?
When the mine was redug out in the 1990’s, it was already in dirt form, not in rock form. But how to sort the fossils from the dirt?
First you put a pile of ‘dirt’ in a sifter (the metal box).
Then you give it a good wash in the trough.
You lay out what’s left in the sun to dry.
And then collect it, ready for sorting.
Static and Silence 
