Millions of years old penguin bones from Seymour Island provide surprisingly precise insights into how the Antarctic climate once changed. Using a non-destructive X-ray method, researchers were able to reveal chemical traces in the fossils and thus trace the transition from a warm, humid Antarctic to a significantly cooler one.
Seymour Island, off the northern tip of the Antarctic Peninsula, is one of the most important fossil sites in Antarctica. The island’s rock strata preserve an exceptionally comprehensive history of penguins from the Eocene epoch. Some of the fossils date back around 55 million years, to a time when Antarctica was considerably warmer and wetter than it is today.
A research team from the China University of Geosciences in Beijing has now investigated whether the fossilised penguin bones contain information not only about the animals themselves, but also about the environment at that time. The results were published in the journal Fossil Record.
X-rays instead of destroyed fossils
As the valuable fossils are to remain as intact as possible, the scientists relied on micro-X-ray fluorescence, or µ-XRF for short. This technique involves scanning the surface of the bones with X-rays to visualise the distribution of various chemical elements. There is no need to cut samples out of the fossils.
The analyses revealed clear differences between bones from different geological periods. The older fossils in particular, dating back around 55 million years, contained significantly higher concentrations of titanium, silicon and potassium.
According to the researchers, these values are consistent with the warm and humid conditions of the early Eocene. At that time, intense weathering on land and heavy runoff transported large quantities of mineral material into the coastal waters. In more recent fossils from cooler periods, these chemical signatures were much weaker.
Bones reveal their environment
Iron, manganese and sulphur also left characteristic traces. These provide clues to the chemical conditions in the marine sediments in which the bones were buried after the animals’ deaths and eventually fossilised.
This makes the penguin fossils a kind of additional climate archive. Until now, past environmental conditions in Antarctica have been reconstructed primarily using sediment cores, rocks, microfossils and other geological indicators. The chemical composition of fossilised bones could complement these methods in future.
Seymour Island is particularly well-suited for this purpose. The La Meseta and Submeseta formations there contain one of the world’s richest sequences of Eocene penguin fossils. They document a crucial phase in Antarctic climate history, during which the region gradually cooled from relatively warm and humid conditions.
At that time, an astonishingly diverse penguin fauna also lived there. Among the known fossils are also representatives of giant extinct penguins, which significantly surpassed today’s emperor penguins in body size.
The new study thus shows that these ancient bones can tell us far more than just the story of their former owners. They also preserve chemical traces of an Antarctica that was a completely different world millions of years ago.
Rosamaria Kubny, PolarJournal