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The Middle Jurassic is the second epoch of the Jurassic Period. It lasted from 176 to 161 million years ago. In European lithostratigraphy, rocks of this Middle Jurassic age are called the Dogger.〔 ''A Geologic time scale 1989'', Walter Brian Harland, 1990, p.53, webpage: (Books-Google-eggC ). 〕〔 "A palynological investigation of the Dogger Formation (Middle Jurassic)", JB Riding, NERC.ac.uk, 2007, webpage: (nerc-65 ). 〕 This name in the past was also used to indicate the Middle Jurassic epoch itself, but is discouraged by the IUGS, to distinguish between rock units and units of geological time. ==Paleogeography== During the Middle Jurassic epoch, Pangaea began to separate into Laurasia and Gondwana, and the Atlantic Ocean formed. Tectonic activities are active on eastern Laurasia as the Cimmerian plate continues to collide with Laurasia's southern coast, completely closing the Paleo-Tethys Ocean. A subduction zone on the coast of western North America continues to create the Ancestral Rocky Mountains. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Middle Jurassic」の詳細全文を読む スポンサード リンク
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