Information about Eocene
The Eocene epoch (55.8 ± 0.2 - 33.9 ± 0.1 Ma) is a major division of the geologic timescale and the second epoch of the Palaeogene period in the Cenozoic era. The Eocene spans the time from the end of the Paleocene epoch to the beginning of the Oligocene epoch. The start of the Eocene is marked by the emergence of the first modern mammals. The end is set at a major extinction event called Grande Coupure (the "Great Break" in continuity), which may be related to the impact of one or more large bolides in Siberia and in what is now Chesapeake Bay. As with other geologic periods, the strata that define the start and end of the epoch are well identified,[1] though their exact dates are slightly uncertain.
The name Eocene comes from the Greek ἠώς (eos, dawn) and καινός (kainos, new) and refers to the "dawn" of modern ('new') mammalian fauna that appeared during the epoch.
The Ypresian and occasionally the Lutetian constitute the Lower, the Priabonian and sometimes the Bartonian the Upper subsection; alternatively, the Lutetian and Bartonian are united as the Middle Eocene.
The Eocene global climate was perhaps the most homogeneous of the Cenozoic; the temperature gradient from equator to pole was only half that of today's, and deep ocean currents were exceptionally warm.[2] The polar regions were much warmer than today, perhaps as mild as the modern-day Pacific Northwest; temperate forests extended right to the poles, while rainy tropical climates extended as far north as 45 degrees latitude. The difference was greatest in the temperate latitudes; the climate in the tropics however, was probably similar to today's.(Stanley, 508)
Climates remained warm through the rest of the Eocene, although slow global cooling triggered by the Azolla event, which eventually led to the Pleistocene glaciations, started as ocean currents around Antarctica formed.
At the beginning of the period, Australia and Antarctica remained connected, and warm equatorial currents mixed with colder Antarctic waters, distributing the heat around the world and keeping global temperatures high. But when Australia split from the southern continent around 45 mya, the warm equatorial currents were deflected away from Antarctica, and an isolated cold water channel developed between the two continents. The Antarctic region cooled down, and the ocean surrounding Antarctica began to freeze, sending cold water and icefloes north, reinforcing the cooling.
The northern supercontinent of Laurasia began to break up, as Europe, Greenland and North America drifted apart.
In western North America, mountain building started in the Eocene, and huge lakes formed in the high flat basins among uplifts, resulting in the deposition of the Green River Formation lagerstätte.
In Europe, the Tethys Sea finally vanished, while the uplift of the Alps isolated its final remnant, the Mediterranean, and created another shallow sea with island archipelagos to the north. Though the North Atlantic was opening, a land connection appears to have remained between North America and Europe since the faunas of the two regions are very similar.
India continued its journey away from Africa and began its collision with Asia, folding the Himalayas into existence.
It is hypothesized that the Eocene hothouse world was caused by runaway global warming from released methane clathrates deep in the oceans. The clathrates were buried beneath mud that was disturbed as the oceans warmed. Methane (CH4) has ten to twenty times the greenhouse gas effect of carbon dioxide (CO2).
Polar forests were quite extensive. Fossils and even preserved remains of trees such as swamp cypress and dawn redwood from the Eocene have been found in Ellesmere Island in the Canadian Arctic. The preserved remains found in the Canadian Arctic are not fossils, but actual pieces preserved in oxygen-poor water in the swampy forests of the time and then buried before they had the chance to decompose. Even at that time, Ellesmere Island was only a few degrees in latitude further south than it is today. Fossils of subtropical and even tropical trees and plants from the Eocene have also been found in Greenland and Alaska. Tropical rainforests grew as far north as the Pacific Northwest and Europe.
Palm trees were growing as far north as Alaska and northern Europe during the early Eocene, although they became less abundant as the climate cooled. Dawn redwoods were far more extensive as well.
Cooling began mid-period, and by the end of the Eocene continental interiors had begun to dry out, with forests thinning out considerably in some areas. The newly-evolved grasses were still confined to river banks and lake edges and had not yet expanded into plains and savannas.
The cooling also brought seasonal changes. Deciduous trees, better able to cope with large temperature changes, began to overtake evergreen tropical species. By the end of the period, deciduous forests covered large parts of the northern continents, including North America, Eurasia and the Arctic, and rainforests held on only in equatorial South America, Africa, India and Australia.
Antarctica, which began the Eocene fringed with a warm temperate to sub-tropical rainforest, became much colder as the period progressed; the heat-loving tropical flora was wiped out, and by the beginning of the Oligocene, the continent hosted deciduous forests and vast stretches of tundra.
The oldest known fossils of most of the modern mammal orders appear within a brief period during the early Eocene. At the beginning of the Eocene, several new mammal groups arrived in North America. These modern mammals, like artiodactyls, perissodactyls and primates, had features like long, thin legs, feet and hands capable of grasping, as well as differentiated teeth adapted for chewing. Dwarf forms reigned. All the members of the new mammal orders were small, under 10 kg; based on comparisons of tooth size, Eocene mammals were only 60% of the size of the primitive Paleocene mammals that had preceded them. They were also smaller than the mammals that followed them. It is assumed that the hot Eocene temperatures favored smaller animals that were better able to manage heat.
Both groups of modern ungulates (hoofed animals) became prevalent because of a major radiation between Europe and North America; along with carnivourous ungulates like Mesonyx. Early forms of many other modern mammalian orders appeared, including bats, proboscidians, primates, rodents and marsupials. Older primitive forms of mammals declined in variety and importance. Important Eocene land fauna fossil remains have been found in western North America, Europe, Patagonia, Egypt and southeast Asia. Marine fauna are best known from South Asia and the southeast United States.
Reptile fossils from this period, such as fossils of pythons and turtles, are abundant.
During the Eocene, plants and marine faunas became quite modern. Many modern bird orders first appeared in the Eocene.
Also some scientists believed that the first primates appeared around 55 Ma in the Ypresian era of the Eocene but however the molecular clock and new paleontological finds state that the first primates appeared much earlier around 90 Ma in the cretaceous era.
The Grande Coupure, or "great break" in continuity,[2] with a major European turnover in mammalian fauna about 33.5 Ma, marks the end of the last phase of Eocene assemblages, the Priabonian, and the arrival in Europe of Asian immigrants. The Grande Coupure is characterized by widespread extinctions and allopatric speciation in small isolated relict populations.[3] It was given its name in 1910 by the Swiss palaeontologist Hans Georg Stehlin,[4] to characterise the dramatic turnover of European mammalian fauna, which he placed at the Eocene-Oligocene boundary. A comparable turnover in Asian fauna has since been called the "Mongolian Remodelling".
The Grande Coupure marks a break between endemic European faunas before the break and mixed faunas with a strong Asian component afterwards. J.J. Hooker and his team summarized the break:
Whether this abrupt change was caused by climate change associated with the earliest polar glaciations[5] and a major fall in sea levels, or by competition with taxa dispersing from Asia, few argue for an isolated single cause. More spectacular causes are related to the impact of one or more large bolides in Siberia and in the Chesapeake Bay impact crater. Improved correlation of northwest European successions to global events (Hooker et al. 2004) confirms the Grande Coupure as occurring in the earliest Oligocene, with a hiatus of about 350 ka prior to the first record of post-Grande Coupure Asian immigrant taxa.
An element of the paradigm of the Grande Coupure was the apparent extinction of all European primates at the Coupure: the recent discovery[6] of a mouse-sized early Oligocene omomyid, reflecting the better survival chances of small mammals, further undercut the Grand Coupure paradigm.
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The name Eocene comes from the Greek ἠώς (eos, dawn) and καινός (kainos, new) and refers to the "dawn" of modern ('new') mammalian fauna that appeared during the epoch.
| Paleogene period | ||
|---|---|---|
| Paleocene epoch | Eocene epoch | Oligocene epoch |
| Danian | Selandian Thanetian | Ypresian | Lutetian Bartonian | Priabonian | Rupelian | Chattian |
Subdivisions
The Eocene epoch is usually broken into Early and Late, or - more usually - Early, Middle, and Late subdivisions. The corresponding rocks are referred to as Lower, Middle, and Upper Eocene. The Faunal stages from youngest to oldest are:| Priabonian | (37.2 ± 0.1 – 33.9 ± 0.1 Ma) |
| Bartonian | (40.4 ± 0.2 – 37.2 ± 0.1 Ma) |
| Lutetian | (48.6 ± 0.2 – 40.4 ± 0.2 Ma) |
| Ypresian | (55.8 ± 0.2 – 48.6 ± 0.2 Ma) |
The Ypresian and occasionally the Lutetian constitute the Lower, the Priabonian and sometimes the Bartonian the Upper subsection; alternatively, the Lutetian and Bartonian are united as the Middle Eocene.
Climate
Marking the start of the Eocene, the planet heated up in one of the most rapid (in geologic terms) and extreme global warming events recorded in geologic history, called the Paleocene-Eocene Thermal Maximum or Initial Eocene Thermal Maximum (PETM or IETM). This was an episode of rapid and intense warming (up to 7°C at high latitudes) that lasted less than 100,000 years [1]. The Thermal Maximum provoked a sharp extinction event that distinguishes Eocene fauna from the ecosystems of the Paleocene.The Eocene global climate was perhaps the most homogeneous of the Cenozoic; the temperature gradient from equator to pole was only half that of today's, and deep ocean currents were exceptionally warm.[2] The polar regions were much warmer than today, perhaps as mild as the modern-day Pacific Northwest; temperate forests extended right to the poles, while rainy tropical climates extended as far north as 45 degrees latitude. The difference was greatest in the temperate latitudes; the climate in the tropics however, was probably similar to today's.(Stanley, 508)
Climates remained warm through the rest of the Eocene, although slow global cooling triggered by the Azolla event, which eventually led to the Pleistocene glaciations, started as ocean currents around Antarctica formed.
){kind=small} | An editor is concerned that statements of fact in this article may be misleading. Please see the discussion on the talk page. |
Paleogeography
During the Eocene, the continents continued to drift toward their present positions.At the beginning of the period, Australia and Antarctica remained connected, and warm equatorial currents mixed with colder Antarctic waters, distributing the heat around the world and keeping global temperatures high. But when Australia split from the southern continent around 45 mya, the warm equatorial currents were deflected away from Antarctica, and an isolated cold water channel developed between the two continents. The Antarctic region cooled down, and the ocean surrounding Antarctica began to freeze, sending cold water and icefloes north, reinforcing the cooling.
The northern supercontinent of Laurasia began to break up, as Europe, Greenland and North America drifted apart.
In western North America, mountain building started in the Eocene, and huge lakes formed in the high flat basins among uplifts, resulting in the deposition of the Green River Formation lagerstätte.
In Europe, the Tethys Sea finally vanished, while the uplift of the Alps isolated its final remnant, the Mediterranean, and created another shallow sea with island archipelagos to the north. Though the North Atlantic was opening, a land connection appears to have remained between North America and Europe since the faunas of the two regions are very similar.
India continued its journey away from Africa and began its collision with Asia, folding the Himalayas into existence.
It is hypothesized that the Eocene hothouse world was caused by runaway global warming from released methane clathrates deep in the oceans. The clathrates were buried beneath mud that was disturbed as the oceans warmed. Methane (CH4) has ten to twenty times the greenhouse gas effect of carbon dioxide (CO2).
Flora
At the beginning of the Eocene, the high temperatures and warm oceans created a moist, balmy environment, with forests spreading throughout the earth from pole to pole. Apart from the driest deserts, Earth must have been entirely covered in forests.Polar forests were quite extensive. Fossils and even preserved remains of trees such as swamp cypress and dawn redwood from the Eocene have been found in Ellesmere Island in the Canadian Arctic. The preserved remains found in the Canadian Arctic are not fossils, but actual pieces preserved in oxygen-poor water in the swampy forests of the time and then buried before they had the chance to decompose. Even at that time, Ellesmere Island was only a few degrees in latitude further south than it is today. Fossils of subtropical and even tropical trees and plants from the Eocene have also been found in Greenland and Alaska. Tropical rainforests grew as far north as the Pacific Northwest and Europe.
Palm trees were growing as far north as Alaska and northern Europe during the early Eocene, although they became less abundant as the climate cooled. Dawn redwoods were far more extensive as well.
Cooling began mid-period, and by the end of the Eocene continental interiors had begun to dry out, with forests thinning out considerably in some areas. The newly-evolved grasses were still confined to river banks and lake edges and had not yet expanded into plains and savannas.
The cooling also brought seasonal changes. Deciduous trees, better able to cope with large temperature changes, began to overtake evergreen tropical species. By the end of the period, deciduous forests covered large parts of the northern continents, including North America, Eurasia and the Arctic, and rainforests held on only in equatorial South America, Africa, India and Australia.
Antarctica, which began the Eocene fringed with a warm temperate to sub-tropical rainforest, became much colder as the period progressed; the heat-loving tropical flora was wiped out, and by the beginning of the Oligocene, the continent hosted deciduous forests and vast stretches of tundra.
Fauna
)
Mesonyx, a carnivorous ungulate
Both groups of modern ungulates (hoofed animals) became prevalent because of a major radiation between Europe and North America; along with carnivourous ungulates like Mesonyx. Early forms of many other modern mammalian orders appeared, including bats, proboscidians, primates, rodents and marsupials. Older primitive forms of mammals declined in variety and importance. Important Eocene land fauna fossil remains have been found in western North America, Europe, Patagonia, Egypt and southeast Asia. Marine fauna are best known from South Asia and the southeast United States.
Reptile fossils from this period, such as fossils of pythons and turtles, are abundant.
During the Eocene, plants and marine faunas became quite modern. Many modern bird orders first appeared in the Eocene.
Also some scientists believed that the first primates appeared around 55 Ma in the Ypresian era of the Eocene but however the molecular clock and new paleontological finds state that the first primates appeared much earlier around 90 Ma in the cretaceous era.
Oceans
The Eocene oceans were warm and teeming with fish and other sea life. The first Carcharinid sharks appeared, as did early marine mammals, including Basilosaurus, an early species of whale that is thought to be descended from land animals, the hoofed predators called mesonychids, of which Mesonyx was a member. The first sirenians, relatives of the elephants, also appeared at this time.Grande Coupure
)
The "end Eocene" event.
The Grande Coupure marks a break between endemic European faunas before the break and mixed faunas with a strong Asian component afterwards. J.J. Hooker and his team summarized the break:
- "Pre-Grande Coupure faunas are dominated by the perissodactyl family Palaeotheriidae (distant horse relatives), six families of artiodactyls (cloven-hoofed mammals) (Anoplotheriidae, Xiphodontidae, Choeropotamidae, Cebochoeridae, Dichobunidae and Amphimerycidae), the rodent family Pseudosciuridae, the primate families Omomyidae and Adapidae, and the archontan family Nyctitheriidae.
- "Post-Grande Coupure faunas include the true rhinos (family Rhinocerotidae), three artiodactyl families (Entelodontidae, Anthracotheriidae and Gelocidae) related respectively to pigs, hippos and ruminants, the rodent families Eomyidae, Cricetidae (hamsters) and Castoridae (beavers), and the lipotyphlan family Erinaceidae (hedgehogs). The speciose genus Palaeotherium plus Anoplotherium and the families Xiphodontidae and Amphimerycidae were observed to disappear completely.
- "Only the marsupial family Herpetotheriidae, the artiodactyl family Cainotheriidae, and the rodent families Theridomyidae and Gliridae (dormice) crossed the faunal divide undiminished." (Hooker et al. 2004)
Whether this abrupt change was caused by climate change associated with the earliest polar glaciations[5] and a major fall in sea levels, or by competition with taxa dispersing from Asia, few argue for an isolated single cause. More spectacular causes are related to the impact of one or more large bolides in Siberia and in the Chesapeake Bay impact crater. Improved correlation of northwest European successions to global events (Hooker et al. 2004) confirms the Grande Coupure as occurring in the earliest Oligocene, with a hiatus of about 350 ka prior to the first record of post-Grande Coupure Asian immigrant taxa.
An element of the paradigm of the Grande Coupure was the apparent extinction of all European primates at the Coupure: the recent discovery[6] of a mouse-sized early Oligocene omomyid, reflecting the better survival chances of small mammals, further undercut the Grand Coupure paradigm.
See also
- Green River Formation in western North America
- List of fossil sites (with link directory)
- London Clay
- Messel Pit in Germany
Notes
1. ^ The extinction of the Hantkeninidae, a planktonic family of foraminifera became became generally accepted as marking the Eocene-Oligocene boundary; in 1998 Massignano in Umbria, central Italy, was designated the Global Boundary Stratotype Section and Point (GSSP).
2. ^ also termed the MP 21 event.
3. ^ Called "dispersal-generated origination" in Hooker et al. 2004
4. ^ H.G. Stehlen, 1910. "Remarques sur les faunules de Mammifères des couches eocenes et oligocenes du Bassin de Paris," in Bulletin de la Société Géologique de France, 4'.9, pp 488-520.
5. ^ A major cooling event preceded the Grande Coupure, based on pollen studies in the Paris Basin conducted by Chateauneuf (J.J. Chateauneuf, 1980. "Palynostratigraphie et paleoclimatologie de l'Éocene superieur et de l'Oligocene du Bassin de Paris (France)" in Mémoires du Bureau de Recherches Géologiques et Minières, 116 1980).
6. ^ Meike Kohler and Salvador Moya-Sola, "A finding of Oligocene primates on the European continent," in Proceedings of the National Academy of Sciences of the United States 96.25 (Dec. 7, 1999), pp 14664-14667
2. ^ also termed the MP 21 event.
3. ^ Called "dispersal-generated origination" in Hooker et al. 2004
4. ^ H.G. Stehlen, 1910. "Remarques sur les faunules de Mammifères des couches eocenes et oligocenes du Bassin de Paris," in Bulletin de la Société Géologique de France, 4'.9, pp 488-520.
5. ^ A major cooling event preceded the Grande Coupure, based on pollen studies in the Paris Basin conducted by Chateauneuf (J.J. Chateauneuf, 1980. "Palynostratigraphie et paleoclimatologie de l'Éocene superieur et de l'Oligocene du Bassin de Paris (France)" in Mémoires du Bureau de Recherches Géologiques et Minières, 116 1980).
6. ^ Meike Kohler and Salvador Moya-Sola, "A finding of Oligocene primates on the European continent," in Proceedings of the National Academy of Sciences of the United States 96.25 (Dec. 7, 1999), pp 14664-14667
References
- Ogg, Jim; June, 2004, Overview of Global Boundary Stratotype Sections and Points (GSSP's) http://www.stratigraphy.org/gssp.htm Accessed April 30, 2006.
- Stanley, Steven M. Earth System History. New York: W.H. Freeman and Company, 1999. ISBN 0-7167-2882-6
- J.J. Hooker M.E. Collinson and N.P. Sille, 2004. "Eocene–Oligocene mammalian faunal turnover in the Hampshire Basin, UK: calibration to the global time scale and the major cooling event" in Journal of the Geological Society 161.2, pp 161-172 (on-line text)
External links
- PaleoMap Project
- Paleos Eocene page
- PBS Deep Time: Eocene
- Eocene Fossils
- Eocene and Oligocene Fossils
- Eocene Primate, Carnegie Museum of Natural History
- The UPenn Fossil Forest Project, focusing on the Eocene polar forests in Ellesmere Island, Canada
- Basilosaurus Primitive Eocene Whales
- Eocene Whale Origins
- Detailed maps of Tertiary Western North America
- Map of Eocene Earth
The geological time scale is used by geologists and other scientists to describe the timing and relationships between events that have occurred during the history of Earth.
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Annum is a Latin noun meaning year. It is the accusative singular of the second declension masculine noun annus (nominative), anni (genitive) [1] .
As a unit of time, it is defined as exactly 365.
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As a unit of time, it is defined as exactly 365.
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The geological time scale is used by geologists and other scientists to describe the timing and relationships between events that have occurred during the history of Earth.
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The Paleogene (alternatively Palaeogene) period is a unit of geologic time that began 65.5 ± 0.3 and ended 23.03 ± 0.05 million years ago and comprises the first part of the Cenozoic era.
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A geologic period is a subdivision of geologic time that divides an era into smaller timeframes. The equivalent term used to demarcate rock layers and the fossil record is the system; thus the rocks of the Devonian System were laid down during the Devonian Period.
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The Cenozoic Era (IPA pronunciation: [ˌsiːnəˈzəʊɪk]); sometimes Caenozoic Era or Cainozoic Era (in the United Kingdom), meaning "new life" (Greek
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The Paleocene, "early dawn of the recent", is a geologic epoch that lasted from 65.5 ± 0.3 Ma to 55.8 ± 0.2 Ma (million years ago). It is the first epoch of the Palaeogene Period in the modern Cenozoic era.
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The Oligocene epoch is a geologic period that extends from about 33.9 million to 23 million years before the present. As with other older geologic periods, the rock beds that define the period are well identified but the exact dates of the start and end of the period are slightly
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Mammalia
Linnaeus, 1758
Subclasses & Infraclasses
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Linnaeus, 1758
Subclasses & Infraclasses
- Subclass †Allotheria*
- Subclass Prototheria
- Subclass Theria
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An extinction event (also known as: mass extinction; extinction-level event, ELE) is a sharp decrease in the number of species in a relatively short period of time...... Click the link for more information.
The Popigai crater in Siberia, Russia is tied with Manicouagan Reservoir as the 4th largest impact crater on Earth. A large bolide impact created the 100-kilometer diameter crater about 35 million years ago during the late Eocene epoch.
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Chesapeake Bay impact crater was formed by a bolide that impacted the eastern shore of North America about 35.5 million years ago, in the late Eocene epoch. It is one of the best-preserved "wet-target" or marine impact craters, and the second largest impact crater in the U.S.
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A geologic period is a subdivision of geologic time that divides an era into smaller timeframes. The equivalent term used to demarcate rock layers and the fossil record is the system; thus the rocks of the Devonian System were laid down during the Devonian Period.
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stratum (plural: strata) is a layer of rock or soil with internally consistent characteristics that distinguishes it from contiguous layers. Each layer is generally one of a number of parallel layers that lie one upon another, laid down by natural forces.
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The Paleogene (alternatively Palaeogene) period is a unit of geologic time that began 65.5 ± 0.3 and ended 23.03 ± 0.05 million years ago and comprises the first part of the Cenozoic era.
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The Paleocene, "early dawn of the recent", is a geologic epoch that lasted from 65.5 ± 0.3 Ma to 55.8 ± 0.2 Ma (million years ago). It is the first epoch of the Palaeogene Period in the modern Cenozoic era.
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The Oligocene epoch is a geologic period that extends from about 33.9 million to 23 million years before the present. As with other older geologic periods, the rock beds that define the period are well identified but the exact dates of the start and end of the period are slightly
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The Danian (also known as the Montian) is the first stage of the Paleocene Epoch, making up the Early Paleocene sub-epoch. The beginning of the stage is defined by the Cretaceous-Tertiary extinction event 65.5 ± 0.3 Ma (million years ago). The stage ended 61.7 ± 0.
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Selandian or Middle Paleocene is a stage of the Paleocene Epoch. It spans the time between 61.7 ± 0.2 Ma and 58.7 ± 0.2 Ma (million years ago).
Paleogene period
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References
- GeoWhen Database - Selandian
Paleogene period
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The Thanetian (also known as the Landenian or Heersian) is the last stage of the Paleocene Epoch, corresponding to the Late Paleocene sub-epoch. It spans the time between 58.7 ± 0.2 Ma and 55.8 ± 0.2 Ma (million years ago).
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The Ypresian is the first stage of the Eocene Epoch and usually corresponds to the Early Eocene subepoch, though sometimes the Lutetian is included therein.
It spans the time between 55.8 ± 0.2 Ma and 48.6 ± 0.2 Ma (million years ago).
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It spans the time between 55.8 ± 0.2 Ma and 48.6 ± 0.2 Ma (million years ago).
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The Lutetian is a stage of the Eocene Epoch. It spans the time between 48.6 ± 0.2 Ma and 40.4 ± 0.2 Ma (million years ago).
It is usually united with the Bartonian to form the Middle Eocene subepoch.
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It is usually united with the Bartonian to form the Middle Eocene subepoch.
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The Bartonian (also known as the Auversian) is a stage of the middle Eocene Epoch. It spans the time between 40.4 ± 0.2 Ma and 37.2 ± 0.2 Ma (million years ago).
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See Also
- List of fossil sites (with link directory)
References
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The Priabonian (also known as Jacksonian or Runangan) is the final stage of the Eocene Epoch. It spans the time between 37.2 ± 0.1 Ma and 33.9 ± 0.1 Ma (million years ago).
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The Rupelian (also known as Stampian, Tongrian, Latdorfian, Vicksburgian, or Early Oligocene) is the first of two stages of the Oligocene Epoch. It spans the time between 33.9 ± 0.1 Ma and 28.4 ± 0.1 Ma (million years ago).
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The Chattian (also known as Chickasawhayan or Late Oligocene) is the second and final of two stages of the Oligocene Epoch. It spans the time between 28.4 ± 0.1 Ma and 23.03 ± 0.05 Ma (million years ago).
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Faunal stages are subdivisions of rock layers used primarily by paleontologists who study fossils rather than by geologists who study rock formations. Typically, a faunal stage will consist of a series of rocks that contain similar fossils.
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The Priabonian (also known as Jacksonian or Runangan) is the final stage of the Eocene Epoch. It spans the time between 37.2 ± 0.1 Ma and 33.9 ± 0.1 Ma (million years ago).
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Annum is a Latin noun meaning year. It is the accusative singular of the second declension masculine noun annus (nominative), anni (genitive) [1] .
As a unit of time, it is defined as exactly 365.
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As a unit of time, it is defined as exactly 365.
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The Bartonian (also known as the Auversian) is a stage of the middle Eocene Epoch. It spans the time between 40.4 ± 0.2 Ma and 37.2 ± 0.2 Ma (million years ago).
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See Also
- List of fossil sites (with link directory)
References
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