Pleistocene System

Pleistocene System, the most recent of the geological systems, including what are known as Superficial Deposits, resting sometimes conformably on the Crag, but generally unconformably on strata of any age, and containing molluscs all of which belong to living species. Some geologists remove them from the Tertiary under the name Quaternary, mainly because in them alone are found remains of man and his works. Two series are commonly distinguished: the Lower or Glacial, containing many extinct mammals and others now living in distant regions [Glacial Period, Boulder-Clay]; the Upper or Recent, containing few (if any) extinct mammals. Human remains or implements have been found in river-gravels, brick-earths, peat-mosses, lake-mud, cave-deposits, raised sea- and river-beaches, and shell-mounds or kitchen middens, associated with the extinct mammoth (q.v.), Machcerodus (q.v.), and Irish deer (Cervus Megaceros). The gigantic Kangaroos (Diprotodoni) of the Australian caves, and the sloths [Megatherium] and armadilloes [Glyptodon] in the river-deposits of Argentina, are probably as recent as the beds containing human remains in Europe.