It is pided into two kinds by its transport agent:(1) raft dropstone,iceborg dropstone and season-ice dropstone;(2) nonraft dropstone,creature dropstone and other dropstone.
坠石是沉积时落入水体底部沉积物中的单个或集群状外来碎屑。
Discovery of dropstones in the Poindo Group, northern Lhasa, Tibet, China, and its significance.;
拉萨北部旁多群坠石沉积的发现及其意义