1) Diatom analysis for KHQ-14
A total of 138 diatom species, belong to 40 genera were identified in KHQ-14 (Fig.S7). KHQ-D1 is dominated by planktonic freshwater species (Aulacoseira spp.) and marine planktonic taxa (Actinocyclusspp. and Coscinodiscus spp.) indicate the marine inundation on a tidal flat environment, which is also influenced by freshwater from river or stream channel. KHQ-D2 is characterized by a reduction in freshwater, and increases in those indicative of marine and/or brackish species (C. stylorum and D. smithii ). The increased percentage of freshwater benthic species (Pinnularia spp.,Cymbella spp., etc) in KHQ-D3, suggest a shallow freshwater condition. KHQ-D3 is also characterized by the increased abundance of marine and/or brackish water species (including Actinoptychusspp., Coscinodiscus spp., C.stylorum , etc.). The mixture of diatom assemblages from different habitats combined with a large number of fragments (Fig. S6h) indicate a turbulence deposition, accompanied by strong hydrological condition.