摘要
句容地区下奥陶统仑山组碳酸盐岩沉积主要由开阔台地和深水陆棚组成,仑山组层序1和层序2均由低位体系域和海侵体系域构成,反映两次海侵过程。根据δ13 C值、Sr/Ba值、1 000Sr/Ca值和V/Ni值反映的古盐度、古水深曲线,结合沉积环境变迁与体系域特征,绘制了仑山组海平面相对升降曲线。一级海平面相对升降曲线反映仑山组时期经历了一次海侵。二级海平面波动曲线显示海平面波动频繁,由两次海平面相对上升和一次海平面相对下降组成。仑山组样品碳、氧同位素组成受后期成岩作用影响较小,基本保留了原始海洋的同位素组成:δ13 C值为-0.8‰~2.3‰,均值为0.45‰;δ18 O值为-14.4‰^-9.3‰,均值为-10.2‰,主要集中在-10.0‰^-9.0‰的范围内。利用δ13 C和δ18 O值计算得到的Z值全部大于120,反映仑山组碳酸盐岩在海相环境中形成。
The Lower Ordovician carbonate sedimentation of Lunshan Formation in Jurong area is composed of an open platform and a deep-water shelf. The sequences 1 and 2, two transgression processes, are both composed of the low stand system and the transgressive system tracts. The relative sea-level lifting curves of Lushan Formation can be drawn based on the paleo-salinity and paleo-bathymetric curves reflected by the values of δ13 C, Sr/Ba, 1 000St/Ca and V/Ni, combined with the sedimentary environment change and system tract features. The Level I sea-level relative lifting curve reflects that Lunshan Formation underwent a transgression. The Level II sea-level curve shows that the sea-level fluctuated frequently. A fluctuation included two sea-level relative rises and one fall. The composition of oxygen and carbon isotope in Lunshan Formation was less affected by the late diagenesis, and it retained basically the original marine isotope composition. The δ13 C value falls between -0.8‰ and 2.3‰, and the mean is 0.45‰. The δ18O value falls between -14.4‰ and -9.3‰ and the mean is 10.2‰, mainly in the range of -10.0‰- -9.0‰. The Z values calculated from δ13 C and δ18O are all greater than 120, which reflects that the carbonate in Lunshan Formation formed in a marine environment.
出处
《吉林大学学报（地球科学版）》
EI
CAS
CSCD
北大核心
2017年第5期1458-1470,共13页
Journal of Jilin University：Earth Science Edition
基金
中国地质调查局项目(GZH200800503-WX02)
国家自然科学基金青年基金项目(41402087)
中国博士后科学基金项目(2013M530976)~~
关键词
句容
下奥陶统
仑山组
元素地球化学
碳氧同位素
海平面变化
Jurong
Lower Ordovician
Lunshan Formation
element geochemistry
oxygen and carbon isotope
sea-level change
