Middle Pleistocene time is assigned to Marine Isotope Stages (MIS) 19-6 and falls entirely within the Brunhes Normal Chron. Oxygen isotope excursions in marine sediment are interpreted as representing glacial-interglacial cycles because light isotopes are preferentially evaporated from the oceans and during glaciations may be stored long term in ice sheets. The magnitude of the marine isotope excursion is therefore interpreted as an indirect record of the volume of terrestrial ice sheets. Nevertheless, the presence, location, extent, and character of Middle Pleistocene ice sheets require independent documentation and verification.
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