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Paleocene Epoch

Paleocene Epoch

In geologic time , the Paleocene Epoch occurs during the Tertiary Period (also sometimes divided or referred to in terms of a Paleogene Period and a Neogene Period instead of a Tertiary Period) of the Cenozoic Era of the Phanerozoic Eon . The Paleocene Epoch is the earliest epoch in the Tertiary Period (in the alternative, the earliest epoch in the Paleogene Period).

The Paleocene Epoch spans the time between roughly 65 million years ago (mya) and 55 mya.

The Paleocene Epoch is further subdivided into (from earliest to most recent) Danian (65 mya to 61 mya) and Thanetian (61 mya to 55 mya) stages. The Eocene Epoch followed the Paleocene Epoch.

The onset of the Paleocene Epoch is marked by the K-T boundary or K-T event , a large mass extinction. Most scientists argue that the K-T extinction resulted fromor was initiated bya large asteroid impact in a submerged area off the Yucatan Peninsula of Mexico termed the Chicxulub crater. The impact caused widespread primary damage due to blast impact and firestorms. Post-impact damage to Earth's ecosystem occurred as dust, soot, and debris from the collision occluded the atmosphere to sunlight. The global darkening was sufficient to slow photosynthesis and the resulting climatic changes and widespread starvation resulted in extinction of the largest life forms with the greatest metabolic energy needs (e.g., the dinosaurs).

Other impact craters that date within the Paleocene Epoch include sites in Alberta, Canada and Marquez, Texas.

The Paleocene Epoch marks the rise of mammals as the dominant land species. During the Paleocene Epoch, climatic moderations reduced the evolutionary pressure of extreme swings in climate. Although a diversity of mammals had evolved and widely populated the changing continental land-masses long before the Paleocene Epoch, the reduction in predator species allowed land mammals to dominate and thriveeventually setting the stage from the evolution of homo sapiens (humans). Pine trees appeared during the Paleocene Epoch and avian species flourished and diversified.

See also Archean; Cambrian Period; Cretaceous Period; Dating methods; Devonian Period; Evolution, evidence of; Fossil record; Fossils and fossilization; Historical geology; Jurassic Period; Mesozoic Era; Miocene Epoch; Mississippian Period; Oligocene Epoch; Ordovician Period; Paleozoic Era; Pennsylvanian Period; Pleistocene Epoch; Pliocene Epoch; Precambrian; Proterozoic Era; Quaternary Period; Silurian Period; Supercontinents; Triassic Period

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Paleocene epoch

Paleocene epoch (pā´lēəsēn´), first epoch of the Tertiary period in the Cenozoic era of geologic time (see geologic timescale) between 60 to 66 million years ago. In W North America, the uplift of the Rocky Mts. that marked the end of the Mesozoic era continued throughout the Paleocene, and the Cretaceous inland seas gradually withdrew from the Great Plains area and central and SW California. In Montana and Wyoming the Fort Union shales and sandstones, laid down during this epoch, are noteworthy because they overlie undeformed upper Cretaceous sediments, thus recording the demise of the dinosaurs and the rise of mammals. The Paleocene mammals were mostly small herbivores similar to their Mesozoic ancestors. By mid-Paleocene, the ungulates, or hoofed mammals of mostly five-toed forms, became abundant. Prosimian primates (tree shrews and tarsiers) also increased in number. Except for part of N France, Europe was largely emergent (i.e., above water). During this epoch, the opening of the Norwegian Greenland Sea eventually resulted in a much more significant mixing of waters, creating the cold North Atlantic Deep waters. Greenland began separating from Europe as the northern mid-Atlantic Ridge formed. On the other side of the world, Antarctica and Australia had separated; India had completed its separation with Africa, resulting in an outpouring of basalts; and India, Africa, and Australia were about to collide with Eurasia. By the end of Paleocene time, N America's last large sea retreated to the Gulf of Mexico. Some of the fossil evidence from Paleocene sediments is difficult to explain; Alaska, for example, clearly had broad-leafed evergreen floras that typically grow in tropical forests. As the land has not changed significantly in latitude since the Paleocene, the evidence of these floras is a puzzle.

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"Paleocene epoch." The Columbia Encyclopedia, 6th ed.. . Encyclopedia.com. 24 Nov. 2017 <http://www.encyclopedia.com>.

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"Paleocene epoch." The Columbia Encyclopedia, 6th ed.. . Retrieved November 24, 2017 from Encyclopedia.com: http://www.encyclopedia.com/reference/encyclopedias-almanacs-transcripts-and-maps/paleocene-epoch