利用长江口现代潮滩沉积硅藻建立海平面转换函数的尝试

在高精度海平面定量重建研究中,有孔虫、硅藻等海洋微体古生物转换函数技术是近10余年随着计算机技术发展而快速兴起的一项新技术,已成为欧美地区研究海平面变化的不可或缺的定量手段之一,而其在中国沿海地区全新世海平面定量重建中的应用却屈指可数。以硅藻为例,详细介绍了建立其与海平面之间的转换函数的过程,包括现代表层样采集、统计学分析、误差的可能来源和减小误差的方法。通过在对崇明岛四滧港SY剖面潮滩表层样品的环境因子分析和对硅藻属种的CCA排序分析发现,高程对潮滩硅藻属种排序有着很高的解释贡献。随后通过WA和WA-PLS建立模型,四滧港SY剖面全样WA-PLS模型的相关系数(R²_Jack)达到0.9004,预期误差(RMSEP)为12.622,若不考虑潮上带样品SY1后的转换模型其精度更能达到±10cm。本研究以期带动此项技术在国内的发展,促进高精度海平面定量重建,从而能为沿海地区海岸带管理提供更详实、更具现实指导意义的地质记录。

An attempt on construction of diatom-based sea-level transfer functions in modern tidal flat at Yangtze River estuary

In the research on quantitative high-resolution sea-level reconstruction,microfossil-based transfer function is a newly and rapidly developed technique assisted by the development of computer technology in the past decade. It has become one of the indispensable methods in sea-level research in many western countries. However,its application to reconstructions of the Holocene relative sea-level history in Chinese coasts has been limited. This paper intends to introduce the method of the diatom(as an example)based sea-level transfer functions,including tidal flat sampling strategy,statistical analysis, possible prediction errors and reducing-error method. Through analyzing the tidal flat surface samples collected from SY section at Siyao port of Chongming Island and the CCA ordination of diatom species,it was concluded that the elevation is the most contributing factor for diatoms sorting among all the environmental parameters. Thus,a transfer function with weighted average(WA)and weighted average partial least squares(WA-PLS) was used. The correlation(R²_Jack)is 0.9 and the RMSEP is±12.6cm with all samples of SY section at Siyao port. The precision may be improved to ±10cm when the sample from a supratidal site(sample of SY1)is excluded. This research will push such quantitative methods forwards to a higher level in high-resolution sea-level reconstructions that can help produce high-quality geological records to aid coastal management of China.