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The Paleocene ( or ; symbol Pε ) or Palaeocene, the "old recent", is a geologic epoch that lasted from about . It is the first epoch of the Paleogene Period in the modern Cenozoic Era. As with many geologic periods, the strata that define the epoch's beginning and end are well identified, but the exact ages remain uncertain. The Paleocene Epoch brackets two major events in Earth's history. It started with the mass extinction event at the end of the Cretaceous, known as the Cretaceous–Paleogene (K–Pg) boundary. This was a time marked by the demise of non-avian dinosaurs, giant marine reptiles and much other fauna and flora. The die-off of the dinosaurs left unfilled ecological niches worldwide. It ended with the Paleocene–Eocene Thermal Maximum. This was a geologically brief (~0.2 million year) interval characterized by extreme changes in climate and carbon cycling. The name "Paleocene" comes from Greek and refers to the "old(er)" (, ''palaios'') "new" (, ''kainos'') fauna that arose during the epoch.〔(【引用サイトリンク】url=http://www.etymonline.com/index.php?term=Paleocene&allowed_in_frame=0 )〕 ==Boundaries and subdivisions== The K–Pg boundary that marks the separation between Cretaceous and Paleocene is visible in the geological record of much of the Earth by a discontinuity in the fossil fauna, with high iridium levels. There is also fossil evidence of abrupt changes in flora and fauna. There is some evidence that a substantial but very short-lived climatic change may have happened in the very early decades of the Paleocene. There are several theories about the cause of the K–Pg extinction event, with most evidence supporting the impact of a 10 km diameter asteroid forming the buried Chicxulub crater on the coast of Yucatan, Mexico. The end of the Paleocene (~55.8 Ma) was also marked by a time of major change, one of the most significant periods of global change during the Cenozoic. The Paleocene–Eocene Thermal Maximum upset oceanic and atmospheric circulation and led to the extinction of numerous deep-sea benthic foraminifera and a major turnover in mammals on land. The Paleocene is divided into three stages, the Danian, the Selandian and the Thanetian, as shown in the table above. Additionally, the Paleocene is divided into six Mammal Paleogene zones. 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「Paleocene」の詳細全文を読む スポンサード リンク
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