A period in Greek
history, starting with the Doric invasion
and the consequenting fall of the Mycenean culture
(though some historian claim that it was the other way around: the Doric
invasion was made possible due to the vacuum created by the fall of the Mycenean culture
), circa the 11th century BC, and ending with the emergence of Greek poleis
in The Archaic Era
circa the 8th century BC.
During that period of time we have no knowledge whatsoever of what occures in Greece and Asia Minor. There are no archaeological remains whatsoever, no written remains, no nothing!
In fact it seems as though the Mycenean writing (aka Linear B) was completely forgotten, and when writing reappears (not before the 7th century BC) it is already the Classic alphabeta.