The Collaborative International Dictionary
Preglacial \Pre*gla"cial\, a. (Geol.) Prior to the glacial or drift period.
Douglas Harper's Etymology Dictionary
Wiktionary
a. Before an ice age (usually referring to the Pliocene)
Usage examples of "preglacial".
The purpose was to show definitively that eoliths were to be found not only on the surface but in situ, deep within the Pliocene preglacial gravels.
They had no idea of setting out in starships, as preglacial peoples might have done.
To the south, Mount Jumbo, bare of trees but furred over with brown weeds, lay like a sleeping mammoth left over from the preglacial times when dinosaurs roamed the tropical swamps of Montana and Wyoming.
Looking carefully over the field where the ice has operated, we note that, though at first sight the area appears to have lost all trace of its preglacial river topography, this aspect is due mainly to the irregular way in which the glacial waste is laid down.