The weathered mantle or regolith is all the
weathered material lying above the unaltered or
fresh bedrock (see Ehlen 2005). It may include
lumps of fresh bedrock. Often the weathered
mantle or crust is differentiated into visible
horizons and is called a weathering profile
(Figure 7.3). The weathering front is the boundary
between fresh and weathered rock. The layer
immediately above the weathering front is
sometimes called saprock, which represents the
first stages of weathering. Above the saprock lies
saprolite; this is more weathered than saprock but
still retains most of the structures found in the
parent bedrock. Saprolite lies where it was formed,
undisturbed by mass movements or other erosive
agents. Deep weathering profiles, saprock, and
saprolite are common in the tropics. No satis -
factory name exists for the material lying above
the saprolite, where weathering is advanced and
the parent rock fabric is not distinguishable,
although the terms ‘mobile zone’, ‘zone of lost
fabric’, ‘residuum’, and ‘pedolith’ are all used (see
Taylor and Eggleton 2001, 160).