Quaternary stratigraphic sequence in Sanming area Fujian Province

In this study, we systematically studied Quaternary stratigraphic sequence of Sanming area, Fujian Province, to address several debated topics, including inconsistent division of Quaternary, imprecise chrono-stratigraphy and poor-studied river terraces. On the basis of intensive field surveys, the lithostratigraphy, optically stimulated luminescence (OSL) dating results and morphostratigraphic characteristic, the Quaternary deposits in Sanming area have been divided into three units: the Tong'an Formation, Longhai Formation and Xiaotao Formation. The Tong'an Formation, formed from Middle Pleistocene to early Late Pleistocene, consists of dark red sediments, which are fine grained in the upper part and argillaceous net-like gravels in the lower part, comprising terraces T3, T4, T5 and local alluvial fan. The Late Pleistocene Longhai Formation is divided into two parts: fine-grained or thin red earth in the upper part, and argillaceous sandy gravels in the lower part. The sediment's color shows brownish yellow to this formation. Most of the Longhai Formation comprise terrace T2 and alluvial fan, few bottom of terrace T1. The Holocene Xiaotao Formation is composed of grayish yellow and brownish gray sediments, which are fine grained in the upper part and sandy gravels in the lower part, comprising terrace T1 and flood plain. Moreover, terrace sequences of Sha River, Ba River and Wenchuan River have been established in order to comprehensively understand the Quaternary deposits in the study area.