How are these layered rocks formed?

In the early days, people always thought that it was sedimentary rocks, that is, layers of rocks were deposited, so it was layered. Most of the rocks are formed by volcanic magma, and even near Zhu Feng, layered rocks can be seen. Shale structure can be seen in most mountains even in the mountains, and layered structure can be seen in many granites. Obviously, sedimentary rocks are difficult to explain all shale. Recently, geologists put forward a new explanation, that is, the testimony of the ice age. An ordinary granite mountain formed by volcanic eruption will be covered with ice and snow during the ice age. In the small ice age, there were hundreds of meters and thousands of meters of ice sheets, and even more than ten kilometers of ice sheets during the big ice age to compress the mountain. After the ice age, the snow melted and the mountain recovered until the next ice age, and so on. The mountain has been compressed and relaxed many times, forming a shale structure.