ABSTRACT Non-marine dinoflagellate fossil of middle cretaceous is very rare in the world.

中白垩世非海相沟鞭藻化石在世界上极为罕见。

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The subsidence of Sunjiawan episode in Middle Cretaceous are further transferred eastward, and the half-graben defined by the fault F1 was formed.

中白垩世孙宗湾组的沉陷进一步向东侧移，形成了以F1断层为盆缘断层的半地堑；

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Both the Pacific plate and the Siberian block slowed down in the early Cretaceous, and almost stopped in the middle Cretaceous with the rapid decrease of abnormal heat in the mantle below.

进入早白垩世晚期至晚白垩世早期，由于双重俯冲带中西侧俯冲作用带基本停止活动，而本区地慢热能的快速衰减则控制盆地的构造热演化；

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Scientists say it formed when high sea levels flooded the middle of North America, splitting the continent in two for millions of years during the late Cretaceous period.

VOA: special.2010.10.05