Dinosaur-age microfossils uncover Australia’s Late Jurassic Inland Sea

Dinosaur-age microfossils uncover Australia’s Late Jurassic Inland Sea

New evidence uncovered by researchers at the University of Adelaide suggests the ancient seas in Central Australia were briefly covered by sea water as far back as the Late Jurassic (Image Source: NOVA ScienceNow)

By Jessica Franze

In the heart of central Australia – a land of scarce water – comes a new discovery: prehistoric marine microfossils from the age of the dinosaurs.

There is widespread evidence, such as that of ancient opalised plesiosaurs, proving the existence of large inland Eromanga Sea one hundred million years ago in the Cretaceous period.

However, newly discovered microfossils, found in rocks approximately 150 million years old, suggest the area was briefly covered by sea water during the Late Jurassic when Australia was joined to Antarctica; 50 million years before its more famous cousin came into fruition.

Researchers at the University of Adelaide discovered the microfossils underneath rocks in the town of Roma in South-Western Queensland.

Researchers estimate that Roma was located at least 1000 km away from the ancient coastline (Image Source: ABC News).

Typically found on ancient and modern sea floors, these fossilised egg-like cysts are the remains from which dinoflagellates hatched.

Dinoflagellates are microscopic, single-celled organisms with a whip-like tail, famous for turning the sea red and giving people seafood poisoning.

Despite their classification as marine inhabitants, dinoflagellates have been found to adapt to slightly saline or even freshwater environments; a transition very few organisms have achieved.

Experts have compared this adaption to humans living on the moon without a spacesuit.

First author and Postdoctoral Fellow in the University of Adelaide’s Australian School of Petroleum Dr Carmine Wainman believes the microfossils were introduced by a rapid marine incursion into the heart of the Australian continent, and evolved quickly to adapt to the freshening environment as the short-lived sea quickly receded.

“We found organisms normally found in the sea in the interior of Australia,” Dr Wainman said.

“We have to ask how they got there…probably a result of rising sea levels during a time when greenhouse conditions prevailed.

“Previous research has always reported this area to be entirely non-marine during the Jurassic as it is thousands of kilometres from the nearest ancient coastline.

“This was a region commonly regarded to be home to ancient meandering rivers, floodplains, peat bogs and small shallow lakes.”

The Eromanga Sea as it spanned Australia in the Cretaceous period (Image Source: News.com.au.).

As described in the journal Palynology, the rock samples were taken from 250 metres below the earth’s surface, tested, then analysed, before being re-tested to eliminate false results.

“I checked the lab records and took additional samples to check the initial sample was not contaminated,” Dr Wainman said.

“I then had my colleagues look over the slide to make sure it was actually there.”

Dinoflagellate cysts in rocks found at 247.55 metres depth (Image Source: C.C. Wainman, University of Adelaide).

Formally printed in July 2019, Dr Wainman’s article is substantiated by more recent research that supports the case of brief marine incursions in the same region.

This research found evidence of marine life, including dinoflagellate cysts, in older rocks of similar character.

While the fossilised remains of spectacular marine creatures provide strong evidence for ancient seas in central Australia in the Cretaceous period, further investigations could uncover more about Australia’s ancient geography during the Jurassic period.

Dr Wainman’s findings are also significant in terms of hydrocarbon exploration.

As IFL Science writer Stephen Luntz reported, “shallow seas with the right rock formations can make for hydrocarbon deposits”.

However, Dr Wainman states that further investigations are needed to assess the impact of these ancient events on said resources around Roma.

Even so, Dr Wainman believes the findings are significant in helping to recognise ancient marine flooding events.

This information would allow scientists to better understand the evolution of Australia’s ancient geography.

“Inland Australia is now dry and hot, back then it was temperate and wet,” Dr Wainman said.

“If we find the same body of rock between one place and another, this could lead to new concepts that may assist in the search for hydrocarbons.”

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