该现象发生的原因是白垩纪中期的海平面上升和气候变化的影响。
The causes for the occurrence of this phenomenon are the influences of the sea-level rise and climatic change in the Mid Cretaceous.
白垩纪中期之前，也就是说大约1亿年前，开花植物很少见：裸子植物占据着地球的景观。
Before the mid-Cretaceous, 100 million years ago or so, flowering plants were scarce: conifers and their relations ruled the landscape.
藏南定日地区在白垩纪中期发育一套浅灰色深灰色的以钙质页岩、泥灰岩及微晶灰岩为主的浅海陆棚相沉积，岩石中除含较高的粘土矿物及陆源石英矿物颗粒以外，还含有十分丰富的有孔虫化石。
The Middle Cretaceous shallow sea sediments, represented by a series of light dark gray marine clastic and carbonate rocks, were well exposed along the Gongzha Section in Tingri, southern Tibet.
藏南定日地区在白垩纪中期发育一套浅灰色深灰色的以钙质页岩、泥灰岩及微晶灰岩为主的浅海陆棚相沉积，岩石中除含较高的粘土矿物及陆源石英矿物颗粒以外，还含有十分丰富的有孔虫化石。
The Middle Cretaceous shallow sea sediments, represented by a series of light dark gray marine clastic and carbonate rocks, were well exposed along the Gongzha Section in Tingri, southern Tibet.
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