ICE-RAFTED DEPOSITS: PALAEOCLIMATIC AND PALAEOGEOGRAPHIC RECORDS

lce-rafted deposits as direct indicators for the existence, of palaeoglaciation are very useful for the reconstruction of palaeoclimate and palaeogeography. Up to now very few studies about these deposits have been done in China. The authors here give an overview on the recent advances in our basic understanding of the ice-rafted deposits and their applications to palaeoclimatic and palaeogeo-graphic studies, and then describe the Cretaceous ice-rafted deposits in the Songliao Basin, which were recognized for the first time by Prof. L.A. Frakes, Prof. Wang Dongpo and the authors.
In spite of being poor-studied on the whole, there are some criteria for identifying ice-rafted deposits, for example, the dropstone, cracks on grain surfaces, dramatic changes in grain size and the limited distribution in the strata.
By recognition of the ice-rafted deposits and comparison with those in modern environments, the authors have revised the reconstruction of the palaeogeography of the Songliao Basin during Early Cretaceous, which can reasonably explain the coexistence of warm climate sporo-pollens with the cold ones.