下扬子南京地区早寒武世幕府山组海平面相对升降的地球化学和碳、氧同位素记录

本文对南京地区早寒武世幕府山组沉积环境及地球化学特征进行了研究，利用元素地球化学和碳、氧同位素特征对古盐度、古水深及古环境的记录，分析幕府山组时期发生的海平面相对升降。结果表明：下扬子南京地区下寒武统幕府山组Mg²⁺/Ca²⁺值与古水深呈负相关，Sr/Ba值、1000Sr/Ca值和V/Ni值与古盐度、古水深呈正相关，Sr/Ba值、1000Sr/Ca值和V/Ni值反映的古盐度、古水深曲线可以指示海平面相对升降。幕府山组样品碳、氧同位素保留了原始海洋的同位素组成：δ¹³C_PDB值分布于0.8‰~3.5‰之间，均值为2.55‰；δ¹⁸O_PDB值分布于-6.9‰~-2.2‰之间，均值为-4.18‰。幕府山组样品的δ¹³C_PDB值大小可以反映海平面的相对升降，两者呈正相关。根据Sr/Ba值、1000Sr/Ca值、V/Ni值、δ¹³C_PDB值和沉积环境演化，绘制了幕府山组海平面相对升降曲线。幕府山组经历了一次海侵-海退旋回，海平面相对升降曲线反映了幕府山组海平面波动频繁，由3次海平面相对上升和3次海平面相对下降组成。

Geochemical and Carbon and Oxygen Isotope Records of Relative Sea-Level Change of Mufushan Formation in Early Cambrian in Nanjing,Lower Yangtze Region

This research is to study the sedimentary environment and geochemical characteristics of the Early Cambrian Mufushan Formation in Nanjing area. The relative sea level rise and fall of the Mufushan Formation is analyzed by using element geochemistry, isotopic characteristics of carbon and oxygen, records of paleo-salinity, paleo-water depth, and paleo-environment. The Mg²⁺/Ca²⁺ values of the Mufushan Formation has a negative correlation with the paleo-bathymetry. The values of Sr/Ba, 1000Sr/Ca and V/Ni show positive correlation with the paleo-salinity and paleo-water depth. The curves of paleo-salinity and paleo-water depth reflected by the values of Sr/Ba, 1000Sr/Ca and V/Ni indicate the cyclicity of the sea-level changes. The oxygen and carbon isotopes of the Mufushan Formation samples retain the original marine isotope composition. The δ¹³C_PDB values distribute between 0.8‰ and 3.5‰,with the mean of 2.55‰. The δ¹⁸O_PDB values distribute between -6.9‰ and -2.2‰,with the mean of -4.18‰. The δ¹³C_PDB values of the Mufushan Formation samples reflect the relative sea-level lift. Based on the values of Sr/Ba, 1000Sr/Ca, V/Ni,δ¹³C_PDB and the evolution of the sedimentary environment, the curves of relative sea-level lift of the Mufushan Formation are drawn. The Mufushan Formation underwent a transgressive-regressive cycle. The relative sea-level lift curve shows that the sea-level fluctuated frequently in the Mufushan period. The fluctuation is composed by three relative sea-level rises and three declines.