Features of thrust nappe structure in northern South Yellow Sea

In marine formations of the northern South Yellow Sea,thrust nappe took place from NW to SE on Cambrian bottom,Silurian top(or Caledonian tectonic surface) and Upper Permian Longtan Formation coal strata.The thrust nappe structure spread from the Qianliyan Uplift to the southern margin of Laoshan Uplift,mainly in NE or EW direction.According to thrust nappe scale and basement involvement extent,the thrust nappe structure was divided into 3 belts from north to south:root,middle and front.The root located in the Qianliyan Uplift where a huge pre-Sinian thrust(overthrust) napped on the Paleozoic.The middle zone was from the Yantai Depression to the middle of Laoshan Uplift.In this region,imbricate thrusts were found in the Upper Paleozoic.The front zone located in the south of Laoshan Uplift,where detachment structures were found in the Longtan and Qinglong Formations.Analyses of seismic data indicated that thrust nappe movements in the northern South Yellow Sea mainly took place from Indosinian to the early Yanshanian.