A new study of fossils in the Antarctic continent has concluded that plant and animal life on the continent was affected similarly by the mass extinction event that killed off the dinosaurs some 65-million years ago.
“Our research essentially shows that one day everything was fine — the Antarctic had a thriving and diverse marine community — and the next, it wasn’t,” says James Witts, PhD candidate at the University of Leeds School of Earth and Environment and lead author of the study. “Clearly, a very sudden and catastrophic event had occurred on Earth.”
Researchers completed a six-year excavation of over 6,000 marine fossils from the López de Bertodano Formation on Seymour Island, located roughly 2,000 km below the southernmost tip of South America, and identified a massive die-off of between 65 and 70 per cent of marine species at the end of the Cretaceous Period, coinciding precisely with the event that caused the massive and abrupt extinction of roughly three quarters of plant and animal species on the planet.
While researchers found evidence of the abrupt extinction of larger species such as sharks and marine reptiles, their study focused on the varieties of molluscs present at the time, concluding that of the 37 species alive before the extinction event known as the Cretaceous-Paleogene (K-Pg) mass extinction, only 12 survived it, contradicting previous research that suggested the Antarctic species die-off was a more gradual process.
“We show that the extinction was rapid and severe in Antarctica, with no significant biotic decline during the latest Cretaceous, contrary to previous studies,” say the study’s authors.
Scientists had earlier speculated that the K-Pg event likely had a less drastic effect on life near the north and south poles due to the already-extreme climactic conditions at the poles coupled with the large distance separating them from ground zero of the K-Pg event, thought to have been in the Gulf of Mexico at the Chicxulub crater.
Current consensus maintains that a 10- to 15-kilometre- wide comet or asteroid hit the Earth approximately 66 million years ago, causing a worldwide dust cloud that blocked out sunlight for perhaps an entire year, leading to the death of 75 per cent of plant and animal species, including the non-avian dinosaurs and all larger land animals. The K-Pg event marks the end of the Cretaceous and ushers in the Cenozoic Era, dubbed the “Age of Mammals” in recognition of the burst in diversity of mammal species that erupted in the 10 million years immediately following the K-Pg event.
A competing hypothesis holds that there were multiple, near simultaneous impacts, possibly from a broken up space rock, that landed at different parts of the planet and together contributed to the K-Pg event. Scientists point to craters in the Ukraine, the North Sea and Brazil as well as the Eagle Butte crater in Canada, south of Medicine Hat, Alberta, as potential impact sites.
Along with being the first to give evidence of a rapid, mass extinction in Antarctica, the research team assembled one of the largest collections of marine fossils from this period, ranging from small snails and clams to distant relatives of modern squid and octopi. “These Antarctic rocks contain a truly exceptional assemblage of fossils that have yielded new and surprising information about the evolution of life 66 million years ago,” says Professor Jane Francis from the British Antarctic Survey and co-author of the study. “Even the animals that lived at the ends of the Earth close to the South Pole were not safe from the devastating effects of the mass extinction at the end of the Cretaceous Period.”
The study is published in the journal Nature Communications.