"Preliminary definition. Concepts such as \"characteristic\" may be problematic."^^ . "pbuttigieg"^^ . . "2013-10-15T16:49:04Z"^^ . "A stratum is a layer which is composed of sedimentary rock or soil with internally consistent characteristics that distinguish it from other layers."^^ . "stratum"^^ . . "ENVO"^^ . "ENVO:01000282"^^ .