What causes this striped rock formation?
Frost heaving of the striped variety

As soil freezes it expands, this slowly pushes coarser material outwards, (since no ice forms in the stones just between them). This forms in bands of coarse and fine material like you see in your image.

The effect only becomes more exaggerated as the soil gets more and more sorted, since the finer material holds more water and thus expands more. This also means that even the smallest variation in particle size can get the process started. 

A variety of patterns can form; sloped ground is especially prone to this sort of striped frost sorting.

B and C in this image are examples from this paper. 


Additional source