220 / 2019-06-25 20:35:08

Recent steps towards a better understanding of the Jurassic climate of Gondwana by using stable isotope analyses of fossil shells

Gondwana,palaeoclimate,Jurassic,stable isotopes,water temperatures

Traditionally, the Jurassic climate has been described as warmer than today, relatively stable through time, and with weak latitudinal temperature gradients leading to a lack of polar glaciations. This simple view has been challenged in the last few decades by a series of articles, suggesting polar ice caps for at least short intervals in the Jurassic and larger temperature fluctuations. Much of the knowledge on Jurassic climate changes is based on water temperature reconstructions using stable isotope (δ18O) analyses of fossil hard parts. However, such research on temperature reconstructions is strongly dominated by European localities with data from other regions being scarce and scattered. Recently collected data from Gondwanan localities (Egypt, Madagascar, and Chile) show the large potential of stable isotope analyses in reaching a better understanding of the Jurassic world.
During the Middle to Late Jurassic, Egypt was situated at a near-equatorial latitude and the reconstructed water temperatures point to latitudinal temperature gradients as steep as today. During the same time interval, Madagascar (as a part of eastern Gondwana) drifted markedly southwards resulting in a prominent decrease in local water temperatures. These data illustrate the interdependence of palaeogeographic and palaeoclimatic developments over long time spans. While some temperature fluctuations are caused by local or regional processes, global climate changes can be identified, if they influenced regions distant from each other at the same time. An example for such a global event is the Late Pliensbachian Cooling Event, which has been recorded by several earlier studies in Europe, but can also be seen in stable isotope data from the Lower Jurassic of Chile.