I think the Chiebukuro question can be straightforwardly translated using symbol as "What is the thing that is considered as the symbol of the disaster of the ice age?" This 象徴/symbol is used in the same manner as "The lion is a symbol of courage."
By indicator/sign/omen, do you mean "a precursor that happens before some bad event"? Then, no, that's not what 象徴 means. 象徴 never refers to something that portends an important event. Omen is usually translated as 予兆 or 前兆 in Japanese, but not 象徴.
By the way, I think the correct answer of this chiebukuro question should be "甲鱗のワーム/Scaled Wurm from Magic: The Gathering. In the Japanese version of the flavor text of this card, "they embodied the worst of the Ice Age" has been translated as 氷河期の災厄の象徴だった. Apparently 氷河期の災厄の象徴 is famous among Japanese MTG fans as a nickname of this creature. This user has asked some other MTG-related questions.