Paleogene period - Kodaisanki (English spelling) Paleogene period

A geological period division, the first period of the Cenozoic Era, a general term for the Paleocene, Eocene, and Oligocene epochs. It refers to the period from approximately 66 million years ago to 23.03 million years ago. The strata formed during the Paleogene period are called the Paleogene System. The climate was relatively warm, the sediments were rich in limestone, and it was a time when the world's great mountain ranges, such as the Himalayas and the Alps, were transformed into mountain-building periods. There was no differentiation of biogeographical regions, and many organisms were distributed worldwide. There were very few species in common with modern organisms. In the plant kingdom, the development of angiosperms, which began to flourish in the Cretaceous Period of the Mesozoic Era, was notable. It was the period when the marine benthic large foraminifera Nummulites flourished, and is also called the Nummulite Period.

[Toshiyuki Yamaguchi August 19, 2015]

Source: Shogakukan Encyclopedia Nipponica About Encyclopedia Nipponica Information | Legend

地質時代の時代区分の一つで、新生代の最初の紀であり、暁新世(ぎょうしんせい)、始新世、漸新世の三つをあわせた時代の総称。およそ6600万年前から2303万年前までの時代をいう。古第三紀に形成された地層を古第三系という。気候は比較的温暖で、堆積(たいせき)物は石灰岩質に富む、ヒマラヤ―アルプスなど世界の大山脈が造山期へと転化した時期にあたる。生物地理区の分化はまだなく、生物は汎(はん)世界的に分布するものが多い。現生の生物と共通する種はきわめて少ない。植物界では、中生代白亜紀に繁栄し始めた被子植物の発展が目だつ。海生の底生大形有孔虫のヌムリテスNummulitesが繁栄した時代で、ヌムライト紀ともいう。

［山口寿之　2015年8月19日］

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