苏北盆地湖沼沉积记录的30～17cal ka BP期间的气候变化

Climate Change Records of Lacustrine Deposits of Subei Basin in Eastern China,30-17 cal ka BP

以苏北盆地里下河地区获取的SG钻孔沉积岩心为研究对象,进行了AMS14C年代、粒度、Rb和Sr含量分析。结果表明,苏北盆地湖沼沉积的粒度分布和Rb/Sr比值能够很好地指示东亚季风区的气候变化。根据粒度和Rb/Sr比值的变化,可将苏北盆地30~17cal ka BP期间的气候变化划分为3个阶段。在30.3~25.9cal ka BP期间,降雨量相对增多,气候相对湿润;25.9~18.3cal ka BP期间,降雨量减少,气候相对干旱;18.3~17.1cal ka BP期间,降雨量又明显增加,气候相对湿润,期间还可能存在变干突变。SG钻孔沉积岩心的环境代用指标与西峰黄土平均粒径、葫芦洞石笋氧同位素有着很好的可比性,并且SG钻孔沉积岩心的黏土含量趋势线与北半球30°N六月的太阳辐射强度曲线极为相似,这表明苏北盆地的气候受太阳辐射驱动下的东亚季风系统影响明显。

Giant karst fracture-cavity reservoirs develop in the Ordovician shallow of T738 region of Tahe Oilfield. This paper studies the sedimentary and karst characteristics of the reservoir sections in the area based on high resolution 3-D seismic data, core andlogging,data and the seismic attributes extraction. The paper also analyzes the main karst stages and the controlling factors of the reservoir and then proposes a model of karstification development. The result shows that .the major reservoir sections are the Middle Ordovician Yijianfang Formation and the Lower-Middle Ordovician Yingshan Formation. Nearly layered cave or caverns and fractures provide the main space for the reserves. The cave , fracture and primary pores in grain limestone were generally developed with a relatively small scale during the Episode I of the mid- Caledonian. With plenty of karst water supply, fractures and caves provide an advantageous path, while down-cutting rivers and fractures work as a discharge channel. An evolutionary model of bedded karstifica- tion is proposed to provide a theoretical reference for futher cave reservoir prediction and exploration prac- tice.