PALYNOMORPH ASSEMBLAGES,ORIGIN AND PALAEOENVIRONMENTAL SIGNIFICANCE OF THE UPPER MOST HARD CLAY IN THE DELTAIC AREA OF THE CHANGJIANG RIVER
从孢粉、藻类化石组合看长江三角洲第一硬质粘土层的成因及其古环境意义

Several layers of dark green or yellowish brown hard clay have been found in the Late Quaternary strata in the south margin of the Deltaic area of the Changjiang River, which can be used as marked layers for the stratigraphical correlation in the region due to their typical characteristics and widespread distribution. No important pollen and phytoplankton assemblages can be used to distinguish the depositional environment and type of vegetation in the developing period of the Hard Clay. Therefore it is unlikely to assemble the evidence to reach to a conclusion on the origin of the hard clay based on the known flora assemblages. A large amount of palynomorphs has been found to use to reconstruct the palaeoenvironment from the uppermost of the Hard Clay in the Deltaic area of the Changjiang River during the Late Pleistocene. The high contents of microfossil evidence, freshwater algae, indicate that the formation of Hard Clay is freshwater sediments. Whereas low content of Dinoflagellate in the palynological assemblages shows that the area might be influenced by the sea water when the Hard Clay was deposited. The sporo pollen assemblages of Gramineae Cyperaceae Quercus (deciduous trees) Pinus , Gramineae Quercus Pinus Artemisia and Cyperaceae Quercus Typha indicate that meadows were developed on the lowland plain being close to the areas where mixed broadleaved and conifer forests were developed non the mountainous area.