Revision of the Pleistocene Daotang Formation in northern Hainan Island, China

On the basis of the latest data of 1:250000 regional geological mapping of the Qionghai County Sheet, the authors redefine the Quaternary Daotang Formation in the "Lithostratigraphy of Hainan Province". A sedimentary unconformity and an overlap unconformity are recognized between the previously established First Member and Second Member in the orthostratotype of the original Daotang Formation, thus dividing the original Daotang Formation into two formation rank lithostratigraphic units. According to the naming principle of lithostratigraphic units, the First Member of the original Daotang Formation below the overlap unconformity is assigned to the newly established Duowen Formation, while the Second, Third and Fourth members in the upper part of the original Daotang Formation above the overlap unconformity are assigned to the newly defined Daotang Formation and defined as the Lower, Middle and Upper members of the revised Daotang Formation respectively. The age of the redefined Daotang Formation is mid-late Pleistocene.