A guide to Phanerozoic cold polar climates from high-latitude ice-rafting in the Cretaceous
The high-latitude extent of warm-climate indicators at certain times in Earth history has been considered as evidence that the globe was ice-free for long intervals, despite theoretical considerations and results from numerical modelling experiments1,2 indicating that this was unlikely. One of the warmest periods, the Cretaceous, displays faunal and floral evidence for 'cool-temperate' to 'sub-tropical' conditions very near to the poles. However, our studies of Lower Cretaceous mudstones of central Australia that contain outsized exotic blocks have led to the conclusion that the blocks were emplaced by ice-rafting, implying that high-latitude ice was present at sea level. Strata of a similar origin of mid-Jurassic to mid-Cretaceous age occur on other continents that were positioned between 65° and 78° palaeolatitude. Indeed, there is a record of high-latitude ice-rafting throughout the Phanerozoic, suggesting that ice was present on Earth for much of its history, and that ice-free conditions could have been at most only episodic over the past 600 Myr.
- Pub Date:
- June 1988