海面进退，海面升降，冰河变异...

The eustasy explanation put forward by Rona is also possible.罗纳提出的海面升降也是可能的....

eustasy的音标：eustasy的英式发音音标为：['ju:stəzɪ]eustasy的美式发音音标为：['justəzɪ]...