During compression, platy minerals align at right angles to the maximum direction of compression. These minerals create a plane of weakness called cleavage which is often highlighted by preferential weathering.
In these turbidites, the mudstones exhibit vertical cleavage. The massive sandstones, with their rounded grains, won't have cleavage as the grains can't rotate to reduce exposure to the stress field. Sandy-mudstones show weak cleavage. This is often deflected from the orientation of least-strain as the presence of the sand grains create a more massive and resistant rock.
The image below shows the deflection of cleavage through turbidites in Chewton, Victoria.
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