Australian Beasts

Australian Beasts

Bluff Downs - Fossil Sites - Australian Beasts - ABC Science

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Bluff Downs

The open woodlands of north Queensland's Cape York Peninsula are probably little changed from conditions that were established there 4 million years ago. That's the world frozen in a snapshot of time at Bluff Downs, north of Charters Towers.

The end of Australia's isolation began around 4 million years ago. As the continent drifted further north it began to collide with the plates of south-east Asia, pushing up the island chain that we now know as Indonesia and New Guinea. This provided a series of stepping stones between the two continents, allowing terrestrial mammals to disperse across what had previously been an impenetrable sea.

At Bluff Downs we start to see the mixture of mammal types that today we recognise as typically Australian. There are several marsupials that would be familiar to any modern naturalist, such as the bandicoot Perameles. This little root snuffler from Bluff Downs is pretty much identical to bandicoots as we know them today.

A less familiar marsupial was the cow-sized Euryzygoma. It had huge cheek bones that may have supported enormous cheek pouches where leaves could be held and munched before swallowing.

There were also crocodiles, turtles and snakes, many of which would be at home in the area today. However, some, like the giant water python Liasis, while still having living relatives, was definitely a creature of the past. It grew to lengths of 10 metres, a size that could have worried all but the largest animals living at Bluff Downs.

All sites have their surprises and Bluff Downs has Phoenicopterus, a flamingo that lived in the waterways. Fossils of flamingos have been found in other sites across Australia including older localities in South Australia. And Pliocene sites such as Bluff Downs are the earliest records of rodents in Australia.

Apart from the abundance of many strange creatures in the Bluff Downs landscape, the other major change that a time-travelling visitor to the area would notice is the volcanos. Four million years ago basaltic volcanos similar to those of modern Hawai‘i spewed streams of lava across the north Queensland landscape.

One of these flows now entombs the fossil beds of Bluff Downs beneath metres of impossibly hard basalt rock. As well as protecting the site from erosion for four million years, this basalt has also provided the feldspars needed to take accurate radiometric dates for the deposit. This layer of once molten rock is both the protector of the Bluff Downs site as well as its chronicler.

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