The ages of drift boulders are usually very difficult to be dated directly, and it is harder to know whether the boulders have been re-transported or rolled over since their formation.

冰川漂砾的形成年代通常难以直接测定，并且漂砾形成以后是否被再次搬运或者移动过，更是无法知道。

youdao

The ages of drift boulders are usually very difficult to be dated directly, and it is harder to know whether the boulders have been re-transported or rolled over since their formation.

冰川漂砾的形成年代通常难以直接测定，并且漂砾形成以后是否被再次搬运或者移动过，更是无法知道。

youdao