Plio-Pleistocene evolution of Bohai Basin (East Asia): demise of Bohai Paleolake and transition to marine environment.

Xiaoke Qiang,Qiang Xie,Qiao Su,Yanping Chen,Guangquan Chen,Hongjun Yu,Lizhu Tian,Huafeng Qin,Chenglong Deng,Rixiang Zhu,Liang Yi,Xingyong Xu,Xuefa Shi,Junyi Ge,Xingyu Jiang

doi:10.1038/srep29403

Abstract

The Bohai Basin was transformed to an inner shelf sea hundreds of thousands years ago. This youngest land-sea transition participated in the significant modification of the distribution of fresh water, sediment fluxes and climate in East Asia, and played an important role in the origin of the Asian marginal seas. Here we present the results of a magnetostratigraphic investigation and propose a conceptual model for the land-sea transition. Our findings indicate that the transition probably started several million years ago, from a fluvial system during the late Miocene and early Pliocene, to a lacustrine environment between the late Pliocene and Middle Pleistocene, and finally to a marine system in the late Pleistocene. Comparison of our results with previous research suggests that the Bohai Paleolake was initiated from the late Pliocene, was fully developed prior to ~1.0 Ma, and terminated around the late Middle Pleistocene. The Miaodao Islands formed the eastern “barrier” of the basin and since the Pliocene or earlier they played a significant role in blocking the lake water and sediments. They deformed from ~1.0 Ma, subsided significantly at ~0.3 Ma and completely by ~0.1 Ma, resulting in the maturation of the basin as an inner shelf sea.

Highlights

As a result of the Cenozoic deformation of the Asian continent and subduction of the Pacific plate, a series of marginal seas, from the Bering Sea in the north to the Banda Sea in the south, were separated from the Asian continent[1]
Since very few geochronological frameworks have been established for the pre-Bohai Sea interval, the Bohai Paleolake (BHPL) prior to 260 ka[15] was discussed mainly from a sedimentological perspective[6,9,11,18,19,20], and there are no reports examining the timing of the formation of the BHPL and its long-term evolution
A high-stability characteristic remanent magnetization (ChRM) component was separated between 20 mT and 50 mT or between 300 °C and 585 °C with maximum angular deviation (MAD) values of ≤15°

Summary

Introduction

As a result of the Cenozoic deformation of the Asian continent and subduction of the Pacific plate, a series of marginal seas, from the Bering Sea in the north to the Banda Sea in the south, were separated from the Asian continent[1]. The basins were constrained by three major paleo-uplifts, similar to a three-order dam system. A classical study based on 71 coastal cores[10] proposed that there were three transgressions in the western Bohai Sea, which can be correlated to the late Pleistocene (since 130 ka). 9 further divided the three major transgressions into seven sea-level events based on Borehole BC-1 from the Bozhong basin (Fig. 1). 17 re-dated the three major transgression events proposed by Zhao et al ref. The present study uses magnetostratigraphy to date three sedimentary sequences (Boreholes BH1, BH2 and HLL02) from the southern Bohai Sea, spanning the Pliocene to the Pleistocene Epochs (Figs 2 and 3). A chronostratigraphic framework is established for the Bohai basin since the Pliocene by combining the sedimentary characteristics and geochronological information from three new boreholes and integrating the findings with those of previous works. Since there were several periods of lake development during the Meso-Cenozoic[9,20], this study concentrates on the final period of lake development, spanning the interval from its probable origin in the late Miocene to its transformation to an inner continental shelf environment in the late Quaternary

Methods

Results

Conclusion