THE PALAEOCLIMATIC AND PALAEOGEOGRAPHIC SIGNIFICANCE OF THE CRETACEOUS RED-BED ICERAFTING DEPOSITS IN THE SONGLIAO BASIN,NORTHEASTERN CHINA

The authors in the present paper interprete the ice-rafting deposits to be originated from the melting of the sediment-laden ice blocks which were transported into seas or lakes. These deposits may occur in the low-latitude regions with higher elevations,where the climates are vertically zoned,or in the mountainous area of the high-latitude regions. The present paper has reported the ice-rafting deposits identified for the first time in the Cretaceous red beds of the Songliao Basin. These deposits appear as scattered or concentrated gravels in the Cretaceous red beds. The examination of the gravel compositions indicates that the principal source of detritus lay to the peripheral mountainous areas. In addition,the research results also show that the sporopollen assemblages consistmainly of the tropical and subtropical types,with minor amounts of Piceaepollenites and Cedripites,perhaps implying that there were greater height deviations around the Songliao Basin during the deposition of the Quantou Formation. The discovery of the Cretaceous ice-rafting deposits in the study area has important implications for the reconstruction of the palaeoclimates and palaeogeography of the Songliao Basin.