风化壳是岩石表层由风化作用形成的残余物质所组成的薄壳。此处，夹在地层中的地质历史时期形成的风化壳称为古风化壳。Weathering crust refers to the thin crust at the rock surface composed of remnant matters formed by weathering. At this site the weathering crust interlayer between the strata was formed in the geological history, thus called the ancient weathering crust.