###

A new study has upended the previously accepted theory regarding the preservation of fossils in the Yixian Formation, an ancient geological formation in northeast China’s Liaoning Province that dates back 120 to 130 million years. Renowned for its perfectly preserved fossils, including those of insects, plants, shells, fish, and feathered dinosaurs, the Yixian Formation has long been likened to a "Chinese Pompeii."

For over two decades, scientists believed these fossils were the result of sudden volcanic activity that buried the organisms, akin to the volcanic disaster that struck Pompeii more than 2,000 years ago. Prior studies proposed that multiple volcanic events over a million years led to these exceptional preservations. However, the new study refutes this explanation, revealing that the fossils were preserved during a period of less than 93,000 years, without any volcanic activity.

According to Paul Olsen, a paleontologist at Columbia Climate School's Lamont-Doherty Earth Observatory and coauthor of the study, this new finding sheds light on an important human tendency to attribute extraordinary events to unfamiliar phenomena when simpler explanations are often more accurate. "These fossils are just a snapshot of everyday deaths in normal conditions over a relatively brief time," Olsen explains.

The study highlights that the dinosaurs and other animals found in the Yixian Formation were not obliterated by violent volcanic activity. Instead, many of the creatures were likely preserved due to the collapse of their burrows during rainy periods. Analysis of rock cores reveals coarse grains surrounding the fossils, while finer grains appear immediately around and within the skeletons. This indicates that after the organisms' soft tissues decayed, fine grains seeped in to fill these voids, preserving the bones.

Researchers also observed that the animals were not in distressed positions typically associated with volcanic disasters, such as those seen in Pompeii. Instead, many were found in relaxed postures, with their arms and tails tucked in as if they were sleeping. A dinosaur described in 2020 was even named Changmiania liaoningensis, meaning "Eternal Sleeper from Liaoning."

Scott MacLennan, the study's lead author from South Africa's University of the Witwatersrand, utilized the CA-ID-TIMS method, a precise technique for measuring radioactive uranium-to-lead ratios in zircon grains from the surrounding rocks and fossils, to determine their age. His findings consistently pointed to 125.8 million years ago, tightly clustering around a span of fewer than 93,000 years.

Olsen posits that similar fossil discoveries could be awaiting in other parts of the world, where environments mirrored those of the Yixian Formation. He cites locations such as a rock quarry on the North Carolina-Virginia border, sites in Connecticut, and a former quarry in North Bergen, New Jersey, which have previously yielded remarkably well-preserved fossils and hold potential for further discoveries.

The full study, titled "Extremely rapid, yet noncatastrophic, preservation of the flattened-feathered and 3D dinosaurs of the Early Cretaceous of China," was published in the Proceedings of the National Academy of Sciences and is available for further exploration.