HOLOCENE STRATA OF THE QINGSHUI RIVER VALLEY AT TONGXIN COUNTY, NINGXIA

A Holocene impact layer is widely developed in the Qingshui River basin, Ningxia, forming terraces II—III. It is mainly represented by a layer of silty soil and sandy loam with gravels. It contains abundant sporopollen, tolalling more than 90 genera and species. From below upward three sporopollen assemblages have been established. Regional correlation indicates that chronostratigraphically it is equivalent to the Lower, Middle and Upper Holocene. The paleoclimate went through the evolution from cold and dry through warm and slightly dry to dry.