Stratigraphic sequence and episodes of the ancient Huanghe Delta along the southwestern Bohai Bay since the LGM.

The sedimentary evolution of the ancient Huanghe (Yellow River) Delta in China is not well documented due to frequent river-avulsions and limited deep cores. In this paper, 22 cores with lengths of > 20 m at the coastal plain along the southwestern Bohai Bay were used. The sedimentary facies were determined by grain size and microfossil analysis, and Carbon-14 dating. The strata in the study area since the Last Glacial Maximum (LGM) are divided into lowstand system tract (LST), transgressive system tract (TST), highstand system tract (HST), and retrograding system tract (RST). The LST, which formed during the LGM to 10.8 ka BP, consists of hard mud layer, and overlying interfluvial lowland and flood plain deposits. The TST that formed during 10.8–8.5 ka BP, mainly include coastal marsh, onshore sand bars, and filled incised valleys. The HST that formed during 8.5–2.6 ka BP mainly includes flood plain, river channel, delta front, mouth bar and prodelta. The RST that formed after 2.6 ka BP mainly includes crevasse splay, interfluvial lowlands and distributary channel. About eight episodes of the ancient Huanghe (delta) are observed during the Holocene and the names of the deltas are given by corresponding location names of cheniers: (1) during 10.8–8.5 ka BP, around YS3 and NP1 cores, without formation of cheniers during the transgression, (2) during 8.5–7.4 ka BP, around YS1, YS4 and NP3 cores, the Dongsun-Shuiyicheng delta, (3) during 7.4–6.1 ka BP, around CK1 core, the Mashanzi delta, (4) during 6.9–5.7 ka BP, around GZ3 core, the Miaozhuang-zhaizhuang delta, (5) during 4.6–3.5 ka BP, around YS4 core, the Wuditai delta, (6) during 3.0–2.6 ka BP, around HH4 and HH1 cores, the Qikou delta, (7) during 2.6–1.9 ka BP, around YS7 and NP1 cores, the Nanpaihe delta, and (8) during 1034 BC–1099 BC, around Wangzidao and Dakouhe, the Wangzidao delta. [ABSTRACT FROM AUTHOR]