With respect to more ancient glacial periods, several geologists are convinced, from direct evidence, that such occurred during the miocene and eocene formations, not to mention still more ancient formations.
Antzinagoko glaziaraldiei dagokienez, zenbait geologo komentziturik daude, zuzeneko frogez, glaziaraldiok Miozeno eta Eozenoko formazioetan gertatu zirela, formazio are lehenagoakoak ez aipatzearren.