Impact of global disturbances on the evolution of life in the polar regions during the early Cenozoic PALEOPOLAR

Lead Research Organisation: University of Bristol
Department Name: Geographical Sciences

Abstract

The greenhouse world of the Late Cretaceous to mid-Paleogene (~100 - 40 million years ago) is of particular interest to earth scientists because there is good geological evidence to show that at this time tropical/subtropical conditions extended into Antarctica in the south and into the Arctic in the north. At this time the south polar ice cap was either much smaller or absent. Many modern groups of plants and animals have their evolutionary roots in this greenhouse world and it is possible that their expansion related directly to this prolonged period of global warmth. This greenhouse world was punctuated by a mass extinction event at 65Ma at the Cretaceous - Paleogene boundary (K-Pg). In addition, this warm world was interrupted by a series of abrupt extreme warming events, or hyperthermals, probably caused by the sudden release of massive amounts of CO2 into the atmosphere and oceans. The K-Pg mass extinction event probably had a much longer-lasting effect on global ecosystems than the more transient hyperthermals but we will test this idea by investigating the geological record from the polar regions, the regions on Earth most sensitive to environmental and climate change. Much of the geological record for this time interval for the polar regions comes from deep sea drill sites but the best onshore exposure is found on Seymour Island, Antarctica. We have recently investigated this locality in detail and now have a high resolution geological record from the end of the Cretaceous period, across the K-Pg boundary and into the mid-Paleogene period. Analysis of large collections of sediments and plant and invertebrate fossils will provide us with new information about climates on land and temperatures in shallow seas around Antarctica at that time. The fossils also allow us to reconstruct the composition of faunas and floras that lived in the polar regions and to determine how their diversity changed over time. We will produce a new palaeotemperature curve for the latest Cretaceous - mid-Paleogene interval in Antarctica, and will assess whether the hyperthermal events occurred so far south. By matching fossil diversity with the climate record we will assess the time taken for plants and animals to recover from the K-Pg mass extinction and investigate whether times of high biodiversity were linked to episodes of warming. For example, do sub-tropical plant fossils and an unusual marine fossil assemblage represent poleward incursions of warmth-loving biotas during a global warming event 55 million years ago, only to go extinct when cooler conditions returned? Some studies indicate that the K-Pg mass extinction reset the global evolutionary clock forever, with new species subsequently appearing at a much higher rate in the tropics than at the poles. We will test this important theory by adding our new Antarctic fossil data to a global database for the latest Cretaceous to the mid-Paleogene. Was the radiation of species through this interval really slower at the poles, and if so, why did the change in rates occur immediately after the K-Pg boundary? How does our record of palaeoclimate and biodiversity from Antarctica compare to that from the Arctic and from low latitude sites - were high latitude communities particularly sensitive to climate change and environmental disturbance, even in a greenhouse world? How did forests at the poles affect the climate system? Does our fossil record match the evolutionary history derived from modern marine faunas by molecular studies? By using a range of palaeoenvironmental indicators and analytical techniques (isotope geochemistry, sedimentary facies analysis, palaeobotany, palaeobiology, climate modelling) we will reconstruct the greenhouse world of the past and assess the impact of dramatic global events on the evolution of life, particularly in the polar regions.
 
Description We discovered that vegetation feedbaks can amplify the response of the climate system during the Cretaceous.
Exploitation Route The results have fed into work which has resulted in some joint academic publications.
Sectors Energy