辽宁南部石炭-二叠系界线处同位素分析

Stable isotopic shift near boundary of the Carboniferous and Permian in the southern Liaoning Province of China

辽宁南部大连金州湾剖面位于东北与华南、华北的交界区域,为海相海陆交互相沉积剖面,是我国北方为数不多的以海相沉积为主的剖面。在剖面第28层中发现的与华北地区早二叠世虫筳类化石相当的Sphaeroschwagerina Rugosofusulina带附近发现了沉积碳酸盐岩内大幅度的碳同位素组成正向波动,可以进行大区域的石炭二叠系界线划分对比。该期氧同位素组成亦有大幅度正向波动,是石炭纪后期至二叠纪早期全球冰期的反映,有利于沉积有机质的保存和烃源岩的发育。

The Jinzhou Bay Section located in Dalian of the southern Liaoning Province is near the boundary between north and south China plate with marine and continental-oceanic sediments. It is one of the main marine deposits in North China. The obvious carbon isotopic composition shift was discovered in the No.28 layer nearby the Sphaeroschwagerina-Rugosofusulina zone that is equivalent to the Fusulinida zone of the Early Permian in North China. The shift could be a tool for widely dividing and correlating the boundaries of the Carboniferous and Permian. Meanwhile, the oxygen isotopic shift discovered in the same episode suggests the glaciations existing during the Later Carboniferous and Early Permian, which would be favorable for preventing sedimentary organic matters and development of oil and gas source rocks at that time.