沉积地层中坠石的成因及其研究意义

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，按其搬运载体不同可分为：（１）冰筏成因坠石：冰山作用形成的坠石和季节性冰体形成的坠石；（２）非冰筏成因坠石；动物植成因坠石和其它成因坠石。坠石是寒冷气候的标志，其形成时的气候具有多解性。

The Origin and Studying Significance of Dropstone in Stratigraphy

Dropstone is extraneous clasts occurring as isolited or clustur body,which drops into the sediment of waterfloor. It is divided into two kinds by its transport agent:(1) raft dropstone,iceborg dropstone and season-ice dropstone;(2) nonraft dropstone,creature dropstone and other dropstone.As the climate of the dropestone formed is variou,thus dropstone is the indicator of cold climate.Ice-berg dropstone is always the indicator of cool climate,because ice period is of globa.The stratum including same period iceberg dropstone can be the key bed for stratigraphic correlation. As the period forming iceberg dropstone is correspond with the age of sea-level decline curve,itrepresents the expression of the correlative conformity of the sequence boundar