Abstract

Organic-walled microfossils called “palynomorphs” are tiny fossils less than half a millimeter in size. They come from land plants (terrestrial spores and pollen) and marine algae (dinoflagellate cysts and acritarchs). They are very resistant to destruction and so are found in large numbers in rock sequences around the Antarctic margin. By studying their shape, abundance and distribution through these rock sequences, these terrestrial and marine palynomorphs can help unravel climate change and major environmental catastrophes in the geological past. One such event occurred at the end of the Cretaceous, 66 million years ago, when a major mass extinction caused the demise of dinosaurs and many other organisms. The highest latitude exposure of Cretaceous rocks in the Southern Hemisphere is on Seymour Island, in the James Ross Basin at the northeast tip of the Antarctic Peninsula. From here we have collected exceptionally well-preserved palynomorphs that are revealing a detailed picture of polar climates and vegetation that grew on Antarctica millions of years ago. At that time global climate was much warmer than today and Antarctica was covered in forests. Fossil spores and pollen show that southern beech and conifer forests, like those that live in Patagonia today, grew on lowlands on the volcanic arc that formed the spine of the Antarctic Peninsula. In the adjacent ocean, cold-water dinoflagellate cysts show that the ocean may have been cold enough for winter sea ice suggesting that the end of the Cretaceous there may have been glaciers in the interior of Antarctica. The palynomorphs also show that about two million years before the end of the Cretaceous the climate warmed considerably, possibly the result of massive volcanic eruptions in India. Did this climate change cause the extinction of dinosaurs on Antarctica?