江汉盆地江陵凹陷南缘古新统沙市组四段含盐岩系沉积特征及其沉积环境意义

通过钻井岩心观察及室内测试分析等方法,对江汉盆地江陵凹陷南缘古新统沙市组四段含盐岩系的沉积特征进行了研究.该时期研究区盐湖的特点是:成盐多期次、沉积连续、淡化—成化周期性交替,因而成为恢复古气候和古环境的重要研究对象.该区沙市组四段盐层间的层段由非砂岩组成,主要由单层厚度为几毫米至几十厘米、累积厚度达几十厘米至几米的含...

Sedimentary characteristics and its environmental significance of salt-bearing strata of the Member 4 of Paleocene Shashi Formation in southern margin of Jiangling Depression, Jianghan Basin

Based on drilling core and experimental analyses,the authors studied the sedimentary characteristics of salt-bearing strata of the Member 4 of Paleocene Shashi Formation in southern margin of Jiangling Depression of Jianghan Basin.The sedimentation of salt lake is characterized by multi-period,continuous and periodically alternating of fresh and salt water.Therefore,it has become the important research focus to study palaeoclimate and palaeoenvironment.The salt-bearing strata of the Member 4 of Shashi Formation in southern margin of Jiangling Depression is composed of non-sandstone,mainly peperite of evaporate mineral,carbonate mineral,terrigenous clay and fine detrital mineral.The layer thickness can be a few millimeter to a few dozen centimeters.The accumulated bed thickness is up to a few dozen centimeters to a few meters.Through comparison analysis of Fe,Mn,Al,Ca,Mg,Co,Ni,V,Cu content and Sr/Ba,Mg/Ca,V/(V+Ni),Ni/Co,Cu/Zn ratio,the sedimentary characteristics and sedimentary environment of salt-bearing strata are studied systematically.It shows that the lake environment in the Yanjian Member of Shashi Formation is perennial relative deep delamination salt lake,which can be classified as brackish-water lake,semi-salt-water lake,salt-water lake and brine lake.The lake depth becomes shallow from downward to upward.Primary glauberite,typically warm facies saline minerals,is widely developed in this formation.The Fe2O3/FeO ratio represents drought climate.This feature reveals that the Paleocene Shashi Formation in southern margin of Jiangling Depression of Jianghan Basin is characterized by a drought and warm palaeoclimate.