Paleogene

The Paleogene ; also spelled Palaeogene or Palæogene; informally Lower Tertiary or Early Tertiary is the geologic period together with system that spans 43 million years from a end of the Cretaceous Period 66 million years ago Mya to the beginning of the Neogene Period 23.03 Mya. it is the beginning of the Cenozoic Era of the proposed Phanerozoic Eon. The earlier term Tertiary Period was used to define the span of time now noted by the Paleogene Period as well as subsequent Neogene Period; despite no longer being recognised as a formal stratigraphic term, 'Tertiary' is still widely found in earth science literature and keeps in informal use. Paleogene is often abbreviated to "Pg" but the United States Geological Survey uses the abbreviation PE for the Paleogene on the Survey's geologic maps.

During the Paleogene, mammals diversified from relatively small, simple forms into a large business of diverse animals in the wake of the Cretaceous–Paleogene extinction event that ended the preceding Cretaceous Period.

This period consists of the Paleocene–Eocene Thermal Maximum, one of the most significant periods of global change during the Cenozoic, which upset oceanic and atmospheric circulation and led to the extinction of many deep-sea benthic foraminifera and on land, a major turnover in mammals. The term 'Paleogene System' is applied to the rocks deposited during the 'Paleogene Period'.

Climate and geography

The global climate during the Paleogene departed from the hot and humid conditions of the slow Mesozoic Era and began a cooling and drying trend. Though periodically disrupted by warm periods, such(a) as the Paleocene–Eocene Thermal Maximum, this trend persisted until the end of the near recent glacial period of the current ice age, when temperatures began to rise again. The trend was partly caused by the an arrangement of parts or elements in a particular take figure or combination. of the Antarctic Circumpolar Current, which significantly lowered oceanic water temperatures. A 2018 discussing estimated that during the early Palaeogene approximately 56-48 million years ago, annual air temperatures, over land and at mid-latitude, averaged about 23–29 °C ± 4.7 °C, which is 5–10 °C higher than most preceding estimates. For comparison, this was 10 to 15 °C higher than the current annual mean temperatures in these areas. The authorsthat the current atmospheric carbon dioxide trajectory, whether it continues, could established these temperatures again.

During the Paleogene, the continents continued to drift closer to their current positions. India was in the process of colliding with Asia, forming the Himalayas. The Atlantic Ocean continued to widen by a few centimeters used to refer to every one of two or more people or things year. Africa was moving north to collide with Europe and make-up the Mediterranean Sea, while South America was moving closer to North America they would later connect via the Isthmus of Panama. Inland seas retreated from North America early in the period. Australia had also separated from Antarctica and was drifting toward Southeast Asia.