The square miles of Nilpena burn beneath an outback sky…

kmd9
Monday 5 August 2019
“Sunset over the Flinders Ranges seen from Nilpena”

“On an outback cattle station, next to the Flinder’s Ranges, the square miles of Nilpena burn beneath an outback sky..” – Nilpena Station by John O’Dea, a brilliant local musician

During the first summer of my Laidlaw Research Scholarship, I was in St Andrews researching two specimens of Ediacaran fossils (Palaeopascichnus and Corumbella). The Ediacaran fauna is a fantastically weird and enigmatic group of life that existed near 10 times as long ago as the extinction of the dinosaurs. They reputably represent some of the earliest animals and show the first evidence of motility (Dickinsonia) and sexual reproduction (Funisia). I was looking in particular at their geochemistry to try and establish what sort of creatures these enigmatic fossils were.

This year I was over 10,000 miles away at Nilpena Station in the outback of South Australia. While Ediacara proper, just north of Nilpena and the rest of the Flinders lie looted and stripped of their ancient fossils, Nilpena Station remains an Aladdin’s cave thanks to the protection of owners Ross and Jane Fargher. Nilpena is so special as unlike other sites, swathes of ancient sea floor are carefully excavated and piece by piece laid out in situ rather than individual specimens being carted off to museums.

“Nilpena fossil bed”

Back in the Ediacaran, pond scum-like microbial mats coated the sea floor until a storm came through depositing a load of sand smothering the surface. A new mat would then develop upon this bed of sand. 560 million years later, these mats allow the sandstone beds to be pried apart, without the need of any finer muddy layer as well as preserving the ancient ripples. The storms also buried whatever life was present on the mat at that moment in time, casting them on the bed above. Sometimes the effect of the storm can be seen in the strained holdfasts of fronds (Aspidella) or structures where the fronds have been yanked out (“mop”) as well as in folded and lifted Dickinsonia.

Over a 20-year period, 33 beds have been excavated from Nilpena. Each of these is very distinct in its assemblage of fossils, from the dense panoply that is “Alice’s Restaurant Bed” (named after the Arlo Guthrie song that goes “..you can get anything you want at Alice’s Restaurant..” through Aspidella dominated beds to the comparatively empty “Duck Bed” (but it is uncannily bird-like in shape). As whole beds are excavated rather than individual specimens, ecological studies are possible. Research into the spatial distributions of certain taxa, their environmental associations and the associations between taxa have opened a window to this peculiar world. Bed scale studies also allows you to distinguish whether differences in the appearance of fossils represent different organisms or just different preservation (taphonomy).

“Dickinsonia (L) and Andiva (R) on Alice’s Restaurant Bed”

During my time at Nilpena I assisted Prof Mary Droser and her students from the University of California, Riverside in their work. Armed with the tools of the trade (dishbrushes, dental picks, silly putty, paint-scrapers, shovels and blu-tack), I helped clean, log, move, excavate and 3D model the Nilpena beds. But how does this link to the geochemistry of the Ediacaran specimens I looked at last summer? Nilpena also had Paleopascichnids. The Ediacara member lies just above the Wonoka, where the Palaeopascichnids I have been studying were collected from. However rather than the dark “Wi-Fi symbol” appearance of the Wonoka, they are wrinkly sumo wrestler like things due to the difference in preservation. This exemplifies one of the key lessons of Nilpena. The antiquity of the fossils and variability in preservation means that conclusions must be drawn with great caution, and only for the strongest patterns. The Ediacaran, due to its bizarre nature has attracted some equally bizarre theories where such caution has been thrown to the wind. With regards to my geochemical analyses, such caution is key. My time at Nilpena station has also helped me to contextualize what I was doing. Last summer I was only able to study two types of fossils, at Nilpena there are 11 genera on Alice’s Restaurant Bed alone.

“Kangaroos spotted on our way to the field site, image courtesy of Philip Boan”

In the coming days I will be analysing the results of maps of elemental concentrations in the fossils that I obtained from LA-ICP-MS out at Trinity College, Dublin in March. Armed with what I’ve seen and discussion I’ve had at Nilpena, I can’t wait to see what they might reveal.

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