Deformation characteristics of Cretaceous strata and its dynamic background, southwestern Fuzhou Basin, Jiangxi

The continental red clastic sedimentary rocks are exposed in the Tanqiu-Daifang area in the southwestern part of Fuzhou Basin.Zircon U-Pb dating sets the sedimentary lower limit of this formation at 109 Ma, confirming the previous understanding that it was classified as the Upper Cretaceous.Field observations show that there are two stages of compressional tectonic deformation developed in the Upper Cretaceous strata.The first stage of NNW-trending compression was mainly characterized by NEE-trending conjugate joints and flattened calcareous concretions.Systematic measurements of finite strain of calcareous concretions in the calcareous siltstone indicate the strain type was mainly flattening strain.The second stage of NE-trending compression was marked by the development of NW-trending thrusting fractures, which cut the first stage of deformations on a small scale.Combined with the tectonic evolution history of eastern China in the Mesozoic and Cenozoic, the dynamic backgrounds of these deformations are determined: the first stage NNW-trending compression may be related to the northward migration of Indian Plate and subsequent collision with the Eurasia Plate in the Early Paleogene; the second stage of NE-trending compression may be associated with the local compressive stress field derived from the dextral strike sliping of the Ganjiang fault zone, and its dynamic background may be the eastward escape of Tibetan Plateau caused by the collision between Indian and Eurasian plates during the middle to Late Paleogene.