Answer:
The R horizon or "bedrock" is de rock layer made of organic matter and some minerals. It is located at the base of the soil profile.
Step-by-step explanation:
The R horizon is a largely comprise continuos mass of hard rock part of the soil profile, which is the layer parallel to the soil surface. Other upper parts are (in down-up order): C horizon (Substratum - non-indurated poorly weathered or unweathered rocks), B horizon (subsoil - iron oxides and clay minerals accumulate as a result of weathering), A (surface - mineral soil with most organic matter accumulated and soil life) and O (organic matter - plant residues). They differ from the layers above and beneath in physical, chemical and biological characteristics. Being defined in many cases by obviuos physical features, manly colour and texture.