Evolution Characteristics and Stratigraphic Division of Quaternary Sedimentary in the South Wing of Yangtze River Delta, East China

Ming Wu,Zhongyang Lin

doi:10.4236/gep.2020.87014

Abstract

This paper discusses the sporo pollen assemblage, evolution of sedimentary environment, sedimentary facies and the lithotope characteristics revealed by boreholes since pliocene epoch by carrying out 14C dating, sporo pollen and micro-paleontological analysis of sediments in borehole BK01 (depth 237.80 m) in the southern flank of the Yangtze River Delta Plain. According to the results of this study, there are 17 species of foraminifera that have been identified as 11 genera, including 16 benthic foraminifera and 1 planktonic foraminifera；8 species of Ostracoda that have been identified as 8 genera; sporo pollen analysis shows that there are 37 types, including 18 species of woody plant pollen, 11 species of herbaceous plant pollen, 8 species of fern spores, of which, in the sporo pollen assemblage, woody plants have the highest content (about 85.1%), ferns spores have about 8.7%, and herbaceous plants have only 6.3%. Sedimentary environment records can be divided into 18 sporo pollen assemblage zones according to borehole lithology, sporo pollen assemblage and micropaleontology analysis. The results show that the BK01 bore strata from bottom to top can be divided into carbonaceous mudstone (Ech), Jiaxing Formation (N-Qp1j), Qiangang Formation (Qp2q) Dongpu Formation (Qp3d), Ningbo Formation (Qp3n) and Zhenhai Formation (Qhzh).

Highlights

With the change of global environment increasingly becoming an important issue of concern to the international community, the study of the evolution history of global climate and environment since Pleistocene has attracted much attention of scholars (Huang et al, 2018; Edwards, 2003)
This paper discusses the sporo pollen assemblage, evolution of sedimentary environment, sedimentary facies and the lithotope characteristics revealed by boreholes since pliocene epoch by carrying out 14C dating, sporo pollen and micro-paleontological analysis of sediments in borehole BK01 in the southern flank of the Yangtze River Delta Plain
The results show that the BK01 bore strata from bottom to top can be divided into carbonaceous mudstone (Ech), Jiaxing Formation (N-Qp1j), Qiangang Formation (Qp2q) Dongpu Formation (Qp3d), Ningbo Formation (Qp3n) and Zhenhai Formation (Qhzh)

Summary

Introduction

With the change of global environment increasingly becoming an important issue of concern to the international community, the study of the evolution history of global climate and environment since Pleistocene has attracted much attention of scholars (Huang et al, 2018; Edwards, 2003). Studying the sequence of sedimentary strata in the Yangtze River Delta since Pleistocene is of great significance to the study of the development history of sedimentation and the evolution of palaeogeographic environment in the Yangtze River Delta (Wang et al, 2008), and plays an unique role in studying the formation of alluvial plain and the change of palaeogeographic environment in the Yangtze River Delta in this geographical position on the southern wing of the Yangtze River Delta as a research hotspot in recent years (Fan et al, 2011; Chen et al, 2008; Yu et al, 2016) At present, it has made a lot of important achievements in the study of the changes of paleoclimate and sea level since the last glacial period in the Hangzhou Bay area (Wang et al, 2008; Li et al, 2011), which lays a foundation for the further study of sedimentary characteristics, stratigraphic sequence and paleoenvironment evolution since the Quaternary, especially the Holocene, and provides a detailed basis for the study of the evolution of the Yangtze River delta plain in the Quaternary (Lin et al, 2019a; Zhang, 2005; Yu et al, 2016; Miao et al, 2016; Liu et al, 2010). Through sampling and analysis of high resolution sporo pollen, foraminifera and ostracods in the sediment cores of borehole BK01, this paper studies the evolution characteristics of sedimentary facies and sedimentary environment in the plain area of the Yangtze River Delta, and carries out lithological stratification and stratigraphic division of boreholes by combining isotope dating data, which provides evidence for the division and comparison of Quaternary strata in the Yangtze River Delta, and provides basic information for the further research

Materials and Methods

Sporo Pollen Assemblage

Micropaleontology

Chronological Sequence

The Division of Quaternary Strata

Conclusion