The fold structure is the strong effect of tectonic force on the rock formations.It makes up the Earth’s crust, which causes the rock formations to form a series of curved structures without losing continuity. In short, the bending of rock formations is called wrinkling. Folding phenomenon is the most obvious in layered rock formations and common geological structure on the Earth’s crust. Folds in rocks vary in size from microscopic crinkles to mountain-sized regional folds in satellite images.

　　The fold structure in this area is composed of Cambrian banded limestone formed more than 500 million years ago. The upwardly curved portion is called "anticline", and the downwardly curved portion is called "oblique".

Do I make myself clear?

　　Anticline is the type of incline where the two wings of the fold point upward while the center part bends downward. The core part is new stratum while the two wings are old stratum.

　　Syncline is the fold which bends upward. The stratum inclines outward from its center. The core part is old stratum while the two wings are new stratum.