食盐析出实验对盐湖盆地沉积研究的启示

Enlightenment from Salt Precipitation Experiment to the Researching on Saline Lacustrine Basin Sedimentology

将物理模拟实验结果与地震、岩芯资料相结合,对东濮凹陷盐岩沉积的古地理位置、成因机制提出新的认识。研究认为:洼陷带的边缘、中央隆起带等浅水部位是盐岩沉积较早的部位,可以沉积厚度大、粒度小的单盐层,而靠近湖盆中心,矿物结晶时间充分,沉积的盐岩粒度大,单盐层厚度可大可小,甚至可以缺失,盐岩沉积的古地理位置受古盐度影响明显;盐湖盆地绝大多部分地区,湖水有一定深度时便已形成湖底盐层,湖水变浅时盐层已具备一定厚度,保证了其下部泥页岩的还原环境,盐岩沉积后基本保持了原有的构造形态,其上可以再次接受泥页岩沉积;湖盆边缘的渗滤带在湖水退去以后仍可以沉积盐岩,该处盐层最薄、粒度细小,下部地层常见氧化环境标志。

Combined the results of the physical simulation experiment with the seismic and core information,a new understanding about the tectonic position,paleogeographic position of salt sediment and the genetic mechanism were proposed in Dongpu Depression. The research suggested that the sedimentation of salt was earlier in shallow parts such as the edge of the lake basin sag and the central uplift belt,the salt layer were thick,the particle size of salt rock was small while the size was large and with a thin or absent layer near the center of the lake basin; a single salt layer with large thickness and small particle size may be deposited,while near the center of the lake basin,there are enough time for the mineral to crystallize,salt rock with large particle was deposited,and the thickness of a single salt layer can be very flexible,or can even be absent. The paleogeographic position of salt rock sediment were obviously impacted by paleosalinity. The salt layer at the bottom of the lake has already formed in certain depth in most areas of the saline lake basin,and has a certain thickness when lakes become shallower,that ensures the reducing environment of the lower part of the shale,and the basic original structure was kept after the salt sediment,the upper can again accept shale deposition; The salt rock can still deposit after the lake receded in the leakage zone at the edge of the lake basin,there salt layer is thinnest,small particle size,symbol of redox environment were commonly in sight in the lower strata.