Oligocene

system	series	step	≈ age ( mya )
higher	higher	higher	younger
Paleogene	Oligocene	Chattium	23.03 ⬍ 28.1
	Oligocene	Rupelium	28.1 ⬍ 33.9
	Eocene	Priobonium	33.9 ⬍ 38
		Bartonium	38 ⬍ 41.3
		lutetium	41.3 ⬍ 47.8
		Ypresium	47.8 ⬍ 56
	Paleocene	Thanetium	56 ⬍ 59.2
		Seelandium	59.2 ⬍ 61.6
		Danium	61.6 ⬍ 66
deeper	deeper	deeper	older

The Oligocene is in the Earth's history , a stratigraphic series (ie a time interval) within the system of the Paleogene , formerly of the Tertiary period . The beginning of the Oligocene is about 33.9 million years, it ended about 23.03 million years ago. The Oligocene was followed by the Miocene and preceded by the Eocene .

Naming and history

The name Oligocene (from Greek ὀλίγος = "little, little, weak" and καινός = "new, unusual") was proposed by Heinrich Ernst Beyrich in 1854.

Definition and GSSP

The beginning of the Oligocene (and thus also the Rupelium stage) is defined by the extinction of the foraminifera genus Hantkenina . The upper limit (and therefore the lower limit of the Miocene and Aquitaine ) is well defined by several events. It is characterized by the base of the magnetic polarity chronozone C6Cn.2n, the first appearance of the foraminifera species Paragloborotalia kugleri and the extinction of the calcareous nannoplankton species Reticulofenestra bisecta (base of the nannoplankton zone NN1). The GSSP (= global calibration point) for the base of the Oligocene (and the base of the Rupelium stage) is the Massignano profile in an abandoned quarry on the east side of the road from Ancona to Sirolo on the Adriatic coast near the village of Massignano (Ancona, Italy ).

Breakdown

The Oligocene is divided into two chronostratigraphic stages:

System : Paleogene (66–23.03 mya )
- Series : Oligocene (33.9–23.03 mya)
  - Level : Chattium (28.1-23.03 mya)
  - Level: Rupelium (33.9-28.1 mya)
- Series: Eocene (56–33.9 mya)
- Series: Paleocene (66–56 mya)

Other stage names are also used regionally and in older publications. For various reasons they were unsuitable as international levels and are only used regionally or have fallen out of use due to poor definition.

Geography and climate

Until the Eocene, there was still a relatively extensive remnant of the former southern major continent of Gondwana with the connected land areas of Australia , Antarctica and South America . At that time the circumpolar ocean current, which now flows clockwise around Antarctica, was not yet present. Instead, warmer seawater penetrated far south along the continental coastal areas and made the Antarctic climate much milder. In the Middle Eocene, about 45 million years ago, the final separation of Antarctica and Australia occurred, and during the transition to the Oligocene (34 mya) the land bridge to South America also broke. This led to the formation of the Drake Strait , which is now 480 nautical miles wide , and as a direct consequence of this, the Antarctic Circumpolar Current was created , which now thermally insulated Antarctica and probably - with the help of various feedbacks - gave the impetus for a worldwide cooling process. On a global level, the temperature of the oceans fell by 4 to 5 ° C down to the deeper layers, and the sea level fell by around 30 meters within a geologically very short period of time. What is striking in this context is the abrupt reduction in the atmospheric CO ₂ concentration. While this was still in the range of 700 to 1,000 ppm towards the end of the Eocene, this value decreased by around 40 percent (and was possibly even lower for a few millennia). The glaciation of the south polar mainland, which begins at a CO ₂ threshold of around 600 ppm , in the initial phase partly controlled by the cyclically changing earth orbit parameters and the resulting varying solar radiation , marks the beginning of the Cenozoic Ice Age . At the same time, the Arctic regions, and especially Greenland, also experienced a significant cooling. Among other things, finds of dropstones prove the temporary existence of Greenlandic continental ice.

Proto-Mediterranean and Paratethys, about 30 million years ago in the Rupelian , at the beginning of the main phase of the Alpidian orogeny .

The increasing expansion of the ice caps and glaciers led to the fact that numerous shelf seas silted up, creating various new land connections. At the beginning of the Oligocene, for example, the Turgaistraße , which for millions of years formed the border between Asia and Europe as a flat sea , fell dry. The once flooded Ebro basin southwest of the Pyrenees also became mainland, which led to the complete connection of the Iberian Peninsula with Europe. Tectonic shifts caused the Tethys to be divided into the Mediterranean in the west and the Paratethys in the east. The Paratethys was located in the east of what is now Europe and was only temporarily connected to the Mediterranean and the Indian Ocean. The Mediterranean was open to the Atlantic. In addition, it is assumed that the Arctic Ocean , which was isolated for a long time, found a connection to the global ocean circulation after a transition phase as a brackish sea in the early Oligocene (≈ 32 mya) with the influx of salty North Atlantic water . The African continent remained largely isolated from Europe and Asia. This was only to change fundamentally in the Miocene. In addition, the folding of the Alps and the Rocky Mountains reached a climax.

For large parts of the later Oligocene, an average CO ₂ concentration in the range of 400 to 450 ppm is likely. 27.8 million years ago there was a period of around 3 million years with warmer temperatures, somewhat less pronounced than the climatic optimum of the Miocene, but strong enough to establish subtropical conditions even in mid-latitudes. However, these climate signals were rarely used, especially in the southern polar region. There are therefore many indications that the core area of the Antarctic ice sheet had already reached an extent at this time that was associated with reduced sensitivity to global climatic influences.

Around the time of the Oligocene-Miocene transition, a significant, but relatively short-term cooling phase began again, combined with further growth in the Antarctic ice cover and a corresponding lowering of the sea level.

Paleogeography in Central Europe

Paleogeography of Central Europe in the Lower Oligocene (Rupelian)

In Germany at the time of the Oligocene (about 30 million years ago) the North Sea extended to the Lower Rhine and the Kassel area (Hesse). Eastern Germany was flooded by the sea as far as the Harz Mountains and Leipzig (Saxony). Between the North Sea and the Tethys Residual Sea in what is now the Alpine region, a sea strait stretched around 300 kilometers and a maximum of 40 kilometers wide. It ran from Kassel over the Wetterau valley and the Upper Rhine Rift to Basel (Switzerland). At the northern end of the Upper Rhine Rift, between Odenwald, Spessart, Taunus, Hunsrück and Palatinate Bergland, there was an inland sea that was almost ten times the size of today's Lake Constance. Sharks , rays and manatees lived in this strait .

Fauna development

Europe

Early Oligocene

The dry fall of the Turgaistraße created a land connection between Europe and Asia at the beginning of the Oligocene. This enabled numerous animal forms to penetrate from the east to Europe, which, together with serious climatic changes, led to greater losses among the fauna native to Europe. About 60 percent of the European mammal species were affected. This exchange of fauna at the beginning of the Oligocene was first referred to by the Swiss paleontologist Hans Georg Stehlin in 1909 as the Grande Coupure ( "Great Gorge" ). Most of the Palaeotheria were among the victims of this faunal exchange . Only a few genera, such as Palaeotherium and Plagiolophus , survived the Grande Coupure . The primates also almost completely disappeared from Europe at that time. Only the genus Pseudoloris survived a little longer in today's Spain, but died out in the Oligocene, as did the Leptictida , the Apatemyids and the last Ischromyids with the genus Plesiarctomys . The extinction of numerous tree or forest inhabitants suggests that more open habitats continued to expand at the beginning of the Oligocene. In contrast, the marsupials in Europe survived without major losses.

Among the newcomers from Asia, the first rhinos in Europe stand out. These were represented in the Oligocene of Europe by the hornless Hyracodonts and Amynodonts as well as by the horned rhinos of the Diceratheriinae and the Menoceratherien . Among the Hyracodonts, the sheep-sized Eggysodon immigrated to Europe at the beginning of the Oligocene. The amynodonts were common in Europe from the beginning to the end of the epoch with Cadurcotherium . Other rhinos of the European Oligocene were Ronzotherium and Epiaceratherium . These animals founded the later successful strain of the Aceratheriinae . In the course of the Oligocene, the western parts of Europe were also reached by the Paraceratherium , the largest land-living mammal of all time, which was mainly found in Asia. In addition to the rhinos and their close relatives, another extremely successful group of odd-toed ungulates immigrated from Asia at the beginning of the Oligocene, the Chalicotheria . The first genus to reach Europe was Schizotherium .

Entelodon , drawing by Heinrich Harder , ca.1920

The artifacts were less affected by the large fauna exchange at the beginning of the Oligocene. Numerous European families and genera made the transition to the Oligocene, such as the Dichobunids with Dichobune , Tapirulus and Diplobune . The Cainotheriidae also survived with the rabbit-sized form Plesiomeryx and the larger Caenomeryx . However, some lines also died out among the ungulates, such as the dacrytherids , xiphodontids and anoplotherids . The reason for this could have been the superiority of the gelocid ruminants , which in the Oligocene reached a large number of forms with forms such as Gelocus , Lophiomeryx and Bachitherium . The large anthracotheria , which produced huge, hippopotamus-sized forms with the genus Anthracotherium , were striking cloven-hoofs of the Oligocene . Others, such as Bothriodon , Elomeryx, and Methriotherium , were smaller and about the same size as today's pigs. In the Oligocene, the giant pig-like entelodons reached Europe for the first time with entelodons . The skull of these animals alone was up to 1 m long. In addition, the first close relatives of the pigs appeared with the genera Palaeochoerus and Doliochoerus .

Skull of Eusmilus

The predators among the mammals were also subject to a drastic change at the beginning of the European Oligocene. Only the archaic Creodonts were relatively little affected . Some forms, such as Pterodon , died out, but the representatives of the genus Hyaenodon were replaced by Asian species. The representatives of the order Carnivora ( predatory animals ) were subject to far greater changes . With Eusmilus, the first Nimravids appeared, cat-like predators who developed huge saber teeth. Another genus of the family, Nimravus , had smaller teeth. It appeared a little later, but also in the early Oligocene. Another member of the Nimravids was Quercylurus , the largest predator of its era. It reached the size of a bear and seems to have been a sole walker. Of the Arctoids , Cynodictis disappeared at the transition to the Oligocene and was replaced by Aphicyonodon . Among the smaller predators of the Eocene were animals that were reminiscent of today's civets, such as stenoplescitis and the closely related genus palaeoprinodon .

Among the small mammals, the first appearance of the lagomorpha (hare-like) in Europe is noticeable in the early Oligocene . Among the insectivores that were Moles ( Eotalpa ) and shrews dominant. The rodents were as in the Eocene mainly by Theridomyiden and Bilche represented (Gliridae). As new releases first modern families like Hustler, squirrels, beavers and today confined to North America were Aplodontia on. The croissants were represented by Palaeosciurus , for example , and the beavers by stenofiber . In addition, the Eomyids appeared for the first time , which were typical in the Oligocene and Miocene, but eventually died out. The most characteristic newcomer among the small mammals, however, was Atavocricetodon , the first representative of the burrowers (Cricetidae).

A European Oligocene crocodile was Hispanochampsa , also known as Diplocynodon muelleri .

Late Oligocene

Reconstruction of the rhinoceros genus Menoceras (late Oligocene / early Miocene)

The pronounced change in climatic conditions during the Oligocene led to the spread of arid areas, which presumably sealed the fall of the Palaeotheria with Plagiolophus , most of the Anthracotherids and the genus Entelodon in Europe. During the late Oligocene, the hyracodontic rhinos and the rhinoceros Ronzotherium also disappeared . In contrast, the Menoceratherien became dominant and the genera Menoceras and Protaceratherium emerged from the early Oligocene genus Epiceratherium . From this tribe of Menoceratherien the three rhinocerotine groups of rhinocerotines, anthracerotherines and teleoceratherines developed up to the early Miocene. The oldest known genus of the Aceratheria, Mesaceratherium , arose in the late Oligocene, as did Brachydiceratherium , the first genus of Teleoceratheria. Menoceras is considered an early rhinocerotheride . In addition, the first tapirs appeared in Europe in the late Oligocene . These belonged to the genus Protapirus , which apparently already had a proboscis, very similar to today's tapirs.

The diversification of the moschoidal ruminants was typical of the cloven-hoofed animals of the late Oligocene. These include the genera Prodremotherium and Bedenomeryx , which emerged from Gelocus . In contrast to this, they had longer legs and a modified cannon leg .

Among the small animals, the theridomyden rodents suffered severe losses. The surviving genera included Blainvillimys and Issidoromys , a genus that developed hypsodontic teeth. The dormice and the eomyids produced several new genera. Significantly more different forms, however, emerged under the Cricetides, which appeared in numerous new genera with complex molars. One of them, Melissiodon , survived into the early Miocene and seems to have been alive with trees .

In Europe, the great Nimravids, such as Eusmilus , Nimravus, and Quercylurus, disappeared among the predators during the late Oligocene . However, this appears to have been a local process. The Creodonts were also in decline. The last ones disappeared in Europe with Hyaenodon at the end of the Oligocene. In Africa, however, they survived longer and even made their way back to Europe for a short time in the Miocene. In return, the predators (Carnivora) continued to spread. Various other predators such as Haplogale , Stenogale and Proailurus developed from the genera Stenolescitis and Palaeoprionodon . Proailurus was about the size of an ocelot and is considered the first genus of cats . In addition, the amphicyonids spread . These were predators that looked like a hybrid of dogs and bears. The first forms of the Oligocene were quite small unspecialized genera such as Pseudocyonopsis and Cynelos , whose teeth were reminiscent of today's dogs. Another genus, Ysengrinia , had specialized carnivore teeth. Later amphicyonids reached the dimensions of tigers and may have hunted similarly. However, they were probably slower but more persistent. At the same time as the first amphicyonids, the first bears appeared with Cephalogale . This genus seems to have developed from the early Oligocene Amphicyonodon . With different genres and the spread in the late Oligocene mustelidae .

Asia

The largest land animal of the Asian Oligocene and at the same time the largest land mammal of all time was Paraceratherium , a huge hornless animal , related to the rhinoceros , up to 5 m shoulder height. The skull alone measured 1.3 m. The adult males are believed to have weighed around 15 tons. In addition, the amynodonts, as hornless rhinos of the Oligocene, were typical of Asia.

North America

Skull of the Oligocene horse Miohippus

Cat-like predators of the North American Oligocene were Hoplophoneus and Nimravus . Dogs in particular were characteristic of the predatory fauna of the Oligocene in North America . Hesperocyon was a surviving genus from the Eocene and appears to have been the only canid with a consistent fossil record in the early Oligocene. From this form the three subfamilies of dogs, the Hesperocyoninae , the Borophaginae and the Caninae, which still exist today, were formed in the course of the Oligocene . The Hesperocyoninae are initially represented by Mesocyon , Enhydrocyon and Osbornodon , the first genus of Borophaginae is Otarocyon . The caninae are only known from a lower jaw fragment, which is believed to have come from an ancestor of the genus Leptocyon . Later in the Oligocene, larger dogs emerged from the Hesperocyonine tribe, some of which reached the size of small wolves. These were Sunkahetanka , Philotrox , Enhydrocyon and Paraenhydrocyon . While the Hesperocyoninae were the dominant dogs in the Oligocene, the Borophaginae were still rather small at that time. They were represented by Archaeocyon , Cynarctoides and Phlaocyon . The Caninae were represented by Leptocyon . In the later Oligocene, the canids in North America reached a diversity of 25 species that was never reached again. Other late Oligocene mammals of North America included Protoceras , the oreodontid Leptauchenia , and the horse Miohippus .

Africa

Arsinoitherium

The land connection between Africa and Eurasia was not yet fully developed in the Oligocene. Until the Miocene, the continent preserved a very peculiar mammal fauna with distinctive elements. The dominant larger herbivores of Oligocene Africa were the hyrax . They developed a wide variety of shapes, including some very large shapes. The artifacts were still sparse in the Oligocene of Africa. However, large forms such as the anthracotheria were already found. The trunk animals were much smaller and only remotely resembled today's elephants. At that time, the trunk animals were still limited to their native Africa. In addition, there was another group of animals, the Embrithopoda , which produced large herbivores. Its most famous representative, the mighty arsinoitherium , is vaguely reminiscent of a rhinoceros. However, it had two paired horns on its forehead and was not related to the rhinos that were already living on other continents at the same time. The Hyaenodontidae were large carnivores . However, they are relatively rare in the fossil record of Oligocene Africa. The primates were represented by Apidium in the Oligocene of Africa .

Oligocene outcrops and sites in Germany

Marine fossil deposits

Doberg near Bünde

Doberg frets

The Doberg near Bünde is not a mountain, but a former mining area for marine sediments (limestone marl) from the Oligocene Sea. Numerous fossil finds can be viewed in the Doberg Museum in Bünde.

Kassel sea sand

The sediments of the Kassel sea sand deposited under marine conditions in the Kassel area with their outcrops belong to the classic geological sites of the Oligocene in Germany. There are still noteworthy collections in the Natural History Museum in the Ottoneum in Kassel . A large part of the old collection of the Natural History Museum was burned in a bomb attack in 1943.

Mainz Basin

The Mainz Basin, which became a sediment trap as a bulge (Mainzer Bucht) in the Upper Rhine Rift, is the most famous region for finding marine Oligocene fossils in Germany. Exhibits show u. a. the local history museum in Alzey , the natural history museum in Mainz , the paleontological museum Nierstein and the museum Wiesbaden . On the coast in the westernmost part of the basin near Steinhardt near Bad Sobernheim in the Nahe valley, fossil-bearing barite concretions formed, which became known as Steinhardt peas . The Bad Sobernheim Local History Museum has a larger collection of around 500 exhibits.

Sülstorf layers

Sternberger Cake, Stadtmuseum Berlin, Geological Collection: SM-2012-4234

The mostly reddish brown Sternberg rock , also known as Sternberg cake , named after the small Mecklenburg town of Sternberg , was shifted from the Mecklenburg subsurface to the surface as debris by the glaciers of the Ice Age . The Sternberg local history museum houses an extensive collection of rocks from this local bedload, in which around 600 species of plants and animals have been identified so far.

Limnian fossil sites

Kunkskopf Lake

The Kunkskopf lake south of Burgbrohl about 3.5 km north of the Laacher See was a freshwater lake of the late Oligocene with Upper Oligocene sediments (black pelites), which Wilhelm Ahrens made famous in 1929. The State Office for the Preservation of Monuments in Rhineland-Palatinate carried out paleontological excavations at this site in 1998 and 1999. So far, fossil leaves, seeds, frogs, fish, bird feathers and insects have been found at the site.

Rotterdam lake

The Rotter See ( Rott fossil deposit ) is a limnic deposit of fossils from the Oligocene near the present-day Rott district of the city of Hennef, which has been known outside of Germany since the beginning of the 19th century, because of the wealth and the exceptionally good conservation of fossil plants and animals ) . Up until 1997, 250 plant species, 630 insect species and 20 amphibian and reptile species were described in around 470 publications dealing with the fossil deposit or the individual fossils themselves.

Stöffel Lake

According to previous knowledge, the Stöffel Lake near Enspel in the Westerwald was a freshwater lake assigned to the Late Oligocene, the fine layers of which were protected by a basalt cover and were investigated by targeted excavations from 1990 to 2015. So far, around 36,000 different fossils have been recovered, prepared and inventoried. The enspelmaus Eomys quercyi Storch , Engesser & Wuttke , found in 1992 , is the oldest evidence of gliding in rodents to date. The fossil was previously only known from isolated tooth finds from France. Against this background, the tertiary and industrial adventure park Stöffel was established as an open-air museum and part of the Westerwald-Lahn-Taunus Geopark.

Sieveless lake

The Siebloser See ( Sieblos fossil deposit ) was a forest-surrounded freshwater lake with a bank zone rich in vegetation, the sediments of which, on the other hand, are a few million years older with an age of around 33 million years (early Oligocene) and the fauna and flora of this site thus evolve before the fossils from Stöffel-See as well as those from the Rotter See. The collection from the Sieblos Museum in Poppenhausen (Wasserkuppe) comprises around 2600 exhibits and can also be viewed directly in the archive after prior registration. The former Ernst Hassencamp collection went to the Geological-Paleontological Institute in Würzburg and is now part of the Bavarian State Collection for Paleontology and Geology .

Munzenberger leaf sandstone

The Münzenberg sandstone in the Wetterau (Hesse) in the quarry on the northeastern outskirts of Munzenberg opens up the youngest (= latest) Oligocene sediments in pink to deep red-brown colors, overlaid by mighty Miocene conglomerates. The collection of the palaeobotanical section of the Senckenberg Research Institute at the Frankfurt site includes a large number of plant remains from the "Münzenberg sandstone or quartzite".

Rockenberg in the Wetterau

Rockenberger Sandrose (front)

In a nature reserve in the Höll on the northern outskirts of Rockenberg , Oligocene sands are exposed, some of which have hardened into stable sedimentary quartzites through silica precipitation. The Sand Rose Museum in the Untertor in Büdingen shows impressive sand roses made from these sands, which are also known in literature as Rockenberger Röschen .

Web links

German Stratigraphic Commission, Manfred Menning (Hrsg.): Stratigraphische Tisch von Deutschland 2002 . Potsdam 2002, ISBN 3-00-010197-7 (1 sheet, Stratigraphie.de [PDF; 6.6 MB ]).
Commission for the paleontological and stratigraphic research of Austria of the Austrian Academy of Sciences (Ed.): The Stratigraphic Table of Austria (sedimentary layer sequences). Vienna 2004 (PDF; 376 kB)
International Chronostratigraphic Chart 2020/01
World map for the Oligocene (Blakey)
Oligocene microfossils: more than 300 images of foraminifera

literature

Peter Prinz-Grimm: Subtropical life in a long, narrow sea. 18 Tertiary: Oligocene. In: Peter Rothe , Volker Storch and Claudia von See (eds.): Traces of life in the stone. Excursions into the geological history of Central Europe. Wiley / VCH 2014, pp. 199–207
Fritz F. Steininger, MP Aubry, WA Berggren, M. Biolzi, AM Borsetti, JE Cartlidge, F. Cati, R. Corfield, R. Gelati, S. Iaccarino, C. Napoleone, F. Ottner, F. Rögl, R Roetzel, S. Spezzaferri, F. Tateo, G. Villa, D. Zevenboom: The Global Stratotype Section and Point (GSSP) for the base of the Neogene . In: Episodes . tape 20 (1) , 1997, ISSN 0705-3797 , pp. 23-28 .
Isabella Premoli-Silva, David G. Jenkins: Decision on the Eocene-Oligocene boundary stratotype . In: Episodes . tape 16 (3) , 1993, ISSN 0705-3797 , pp. 379-382 .

Individual evidence

↑ Ernst Beyrich: About the position of the Hessian tertiary educations . In: Report on the negotiations of the Royal Prussian Academy of Sciences in Berlin that are suitable for publication, Berlin 1854, p. 664 ( digitized version )
↑ Mark Pagani, Matthew Huber, Zhonghui Liu, Steven M. Bohaty, Jorijntje Henderiks, Willem Sijp, Srinath Krishnan, Robert M. DeConton: The Role of Carbon Dioxide During the Onset of Antarctic Glaciation . (PDF) In: Science . 334, No. 6060, December 2011, pp. 1261-1264. doi : 10.1126 / science.1203909 .
↑ Simone Galeotti, Robert DeConto, Timothy Naish, Paolo Stocchi, Fabio Florindo, Mark Pagani, Peter Barrett, Steven M. Bohaty, Luca Lanci, David Pollard, Sonia Sandroni, Franco M. Talarico, James C. Zachos: Antarctic Ice Sheet variability across the Eocene-Oligocene boundary climate transition . (PDF) In: Science . 352, No. 6281, April 2016, pp. 76-80. doi : 10.1126 / science.aab0669 .
↑ James Hansen, Makiko Sato, Gary Russell, Pushker Kharecha: Climate sensitivity, sea level and atmospheric carbon dioxide . (PDF) In: Philosophical Transactions A (The Royal Society) . 371, No. 2001, October 2013. doi : 10.1098 / rsta.2012.0294 .
↑ James S. Eldrett, Ian C. Harding, Paul A. Wilson, Emily Butler, Andrew P. Roberts: Continental ice in Greenland during the Eocene and Oligocene . (PDF) In: Nature . 446, March 2007, pp. 176-179. doi : 10.1038 / nature05591 .
↑ Aradhna Tripati, Dennis Darby: Evidence for ephemeral middle Eocene to early Oligocene Greenland glacial ice and pan-Arctic sea ice . (PDF) In: Nature Communications . March 9, 2018. doi : 10.1038 / s41467-018-03180-5 .
↑ Michael Starkz, Wilfried Jokat, Gregor Knorr, Gerrit Lohmann: Threshold in North Atlantic-Arctic Ocean circulation controlled by the subsidence of the Greenland-Scotland Ridge . In: Nature Communications (online) . June 8, 2017. doi : 10.1038 / ncomms15681 .
↑ ^a ^b ^c ^d ^e ^f ^g ^h Jordi Augusti: Mammoths, Sabertooths and Hominids 65 Million Years of Mammalian Evolution in Europe . Columbia University Press, 2002, ISBN 0-231-11640-3 .
↑ Stefan M. Schmid, Daniel Bernoulli, Bernhard Fügenschuh, Liviu Matenco, Senecio Schefer, Ralf Schuster, Matthias Tischler, Kamil Ustaszewski: The Alpine-Carpathian-Dinaridic orogenic system: correlation and evolution of tectonic units . (PDF) In: Swiss Journal of Geosciences . 101, March 2008, pp. 139-183. doi : 10.1007 / s00015-008-1247-3 .
↑ Michaela Grein, Christoph Oehm, Wilfried Konrad, Torsten Utescher, Lutz Kunzmann, Anita Roth-Nebelsick: Atmospheric CO ₂ from the late Oligocene to early Miocene based on photosynthesis data and fossil leaf characteristics . (PDF) In: Palaeogeography, Palaeoclimatology, Palaeoecology . 374, March 2013, pp. 41–51. doi : 10.1016 / j.palaeo.2012.12.025 .
^ ^A ^b D. W. Hauptvogel, SF Pekar, V. Pinca: Evidence for a heavily glaciated Antarctica during the late Oligocene “warming” (27.8-24.5 Ma): Stable isotope records from ODP Site 690 . In: Paleoceanography and Paleoclimatology . 32, No. 4, April 2017, pp. 384-396. doi : 10.1002 / 2016PA002972 .
↑ Helen M. Beddow, Diederik Liebrand, Appy Sluijs, Bridget S. Wade, Lucas J. Louren: Global change across the Oligocene-Miocene transition: High-resolution stable isotope records from IODP Site U1334 (equatorial Pacific Ocean) . (PDF) In: Paleoceanography (AGU Publications) . 31, No. 1, January 2016, pp. 81-97. doi : 10.1002 / 2015PA002820 .
^ A. Turner, M. Antón: The big cats and their fossil relatives. Columbia University Press, New York 1997, ISBN 0-231-10229-1 .
↑ Xiaoming Wang, Richard H. Tedford, Mauricio Antón: Dogs, their fossil relative & evolutionary history . Columbia University Press, New York 2008, ISBN 978-0-231-13528-3 .
^ Alan Turner, Mauricio Anton: Evolving Eden: An Illustrated Guide to the Evolution of the African Large Mammal Fauna . Columbia University Press, 2004, ISBN 0-231-11944-5 .

[1] Ernst Beyrich: About the position of the Hessian tertiary educations . In: Report on the negotiations of the Royal Prussian Academy of Sciences in Berlin that are suitable for publication, Berlin 1854, p. 664 ( digitized version )

[10.1126/science.1203909-2] Mark Pagani, Matthew Huber, Zhonghui Liu, Steven M. Bohaty, Jorijntje Henderiks, Willem Sijp, Srinath Krishnan, Robert M. DeConton: The Role of Carbon Dioxide During the Onset of Antarctic Glaciation . (PDF) In: Science . 334, No. 6060, December 2011, pp. 1261-1264. doi : 10.1126 / science.1203909 .

[10.1126/science.aab0669-3] Simone Galeotti, Robert DeConto, Timothy Naish, Paolo Stocchi, Fabio Florindo, Mark Pagani, Peter Barrett, Steven M. Bohaty, Luca Lanci, David Pollard, Sonia Sandroni, Franco M. Talarico, James C. Zachos: Antarctic Ice Sheet variability across the Eocene-Oligocene boundary climate transition . (PDF) In: Science . 352, No. 6281, April 2016, pp. 76-80. doi : 10.1126 / science.aab0669 .

[10.1098/rsta.2012.0294-4] James Hansen, Makiko Sato, Gary Russell, Pushker Kharecha: Climate sensitivity, sea level and atmospheric carbon dioxide . (PDF) In: Philosophical Transactions A (The Royal Society) . 371, No. 2001, October 2013. doi : 10.1098 / rsta.2012.0294 .

[10.1038/nature05591-5] James S. Eldrett, Ian C. Harding, Paul A. Wilson, Emily Butler, Andrew P. Roberts: Continental ice in Greenland during the Eocene and Oligocene . (PDF) In: Nature . 446, March 2007, pp. 176-179. doi : 10.1038 / nature05591 .

[10.1038/s41467-018-03180-5-6] Aradhna Tripati, Dennis Darby: Evidence for ephemeral middle Eocene to early Oligocene Greenland glacial ice and pan-Arctic sea ice . (PDF) In: Nature Communications . March 9, 2018. doi : 10.1038 / s41467-018-03180-5 .

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