东濮凹陷沙三段盐岩成因

东濮凹陷沙三段（Es3）发育盐岩和膏盐岩，岩心观察见有冲刷面、泥裂、波痕等浅水和暴露标志，地震剖面显示有低位楔、削截面、下超等湖岸线进退现象，说明Es3沉积期古湖泊水体深度变化大。高水位期沉积深灰色、暗色泥岩与少量重力流砂体，低水位期沉积盐岩、膏岩，发育低位三角洲与扇三角洲沉积．纵向形成深湖泥岩与蒸发岩、低位砂岩的频繁互层。分析认为，盐岩为浅水成因，盐源为周边隆起的中、下奥陶统。这一认识不同于过去“高山深盆”、“深水成盐”和“海相成因”的观点，将给东濮凹陷沉积古地理、古环境研究带来新的认识。图6表3参13

Origin of 3rd Member salt rock of Shahejie Formation in Dongpu Sag

In Dongpu Sag,red sediments can be found within the salt-gypsum developed in 3~(rd) Member of Shahejie Formation(Es_(3)). Shallow-water and exposed signs are also found as scour surfaces,mud cracks and ripple marks in the cores.Lakeshore on-off signs of lowstand wedge,truncation and downlap are recognized from seismic profiles.These indicate that the water depth of paleolake changed during the deposition of Es_(3).Deep-grey and dark mudstones and a few gravity sandbodies developed in the highstand period, while salt rock,gypsum rock,lowstand deltas and fan deltas developed in the lowstand period.As a result,deep lake mudstones are interbedded with evaporites and lowstand sandbodies.The paper argues that the salt rocks are deposited in shallow water,the salt comes from the Lower-Middle Ordovician series of the surrounding uplifts.This argument is different from the past theories of "high mountain deep lake","salt deposited in deep water" and "salt deposited in marine facies".