Calcareous concretions in the upper Cretaceous Tangbian formation is the product of climate change of the late Cretaceous in Guixi basin

which were show reddish

spherical

ellipsoidal and dumb-bell shape

densely and hard structural

surrounded by shale and the size of 15-100 mm at outcrop sections. Lots of micrite calcite few sparry calcite under the microscope. The carbonate composition accounting for about 75% in the total component

while the terrigenous clasts composition accounting for 25%. Metasomatism and erosion phenomenon in the surface of Quartz and Feldspar obviously

show that the rocks have experienced strong recrystallization in the later.