Blocky corestones (X) set in grus and derived from subsurface weathering of sheet structure,
Paarlberg Quarry, near Cape Town, South Africa.
Disintegrated sheet structure (a) on midslope at Enchanted Rock, Llano, central Texas.
lower slopes are rounded. Such variations presumably reflect the availability of moisture at differ-
ent topographic levels. Comparatively few remnants remain on midslopes, where gradients are
sufficiently steep to cause blocks to slide down to lower levels, and those that remain consist of
disintegrated sheets in situ (Klaer, 1956) (Fig. 5.21).