Global cooling inferred from dropstones in the Cretaceous: Fact or wishful thinking?

Traditionally, the Cretaceous has been considered as a long period of global warmth, a 'greenhouse' world. This view has been challenged in recent years by several lines of evidence; palaeobotany, stable isotopes, and palaeoclimatic modelling in particular. However, although these data demonstrate that cooling is likely, the only first-hand evidence which demonstrates the presence of substantial ice build-up in Cretaceous high palaeolatititudes are dropstones. These outsized or exotic clasts set in a fine-grained sediment are often interpreted as a direct result of ice rafting. The reliability of this dropstone evidence and particularly its validity is questioned in demonstrating ice age interludes within the Cretaceous greenhouse.