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206-425: The Paleocene–Eocene thermal maximum ( PETM ), alternatively ” Eocene thermal maximum 1 (ETM1) “ and formerly known as the " Initial Eocene " or “ Late Paleocene thermal maximum ", was a geologically brief time interval characterized by a 5–8 °C global average temperature rise and massive input of carbon into the ocean and atmosphere. The event began, now formally codified, at the precise time boundary between

412-457: A C-rich comet struck the earth and initiated the warming event. A cometary impact coincident with the P/E boundary can also help explain some enigmatic features associated with this event, such as the iridium anomaly at Zumaia , the abrupt appearance of a localized kaolinitic clay layer with abundant magnetic nanoparticles, and especially the nearly simultaneous onset of the carbon isotope excursion and

618-735: A climate similar to the Pacific Northwest . On the Alaska North Slope , Metasequoia was the dominant conifer. Much of the diversity represented migrants from nearer the equator. Deciduousness was dominant, probably to conserve energy by retroactively shedding leaves and retaining some energy rather than having them die from frostbite. In south-central Alaska, the Chickaloon Formation preserves peat-forming swamps dominated by taxodiaceous conifers and clastic floodplains occupied by angiosperm–conifer forests. At

824-591: A closed marsh to an open, eutrophic swamp with frequent algal blooms. Precipitation patterns became highly unstable along the New Jersey Shelf . In the Rocky Mountain Interior, precipitation locally declined, however, as the interior of North America became more seasonally arid. Along the central California coast, conditions also became drier overall, although precipitation did increase in the summer months. The drying of western North America

1030-450: A constant sedimentation rate, the entire event, from onset though termination, was therefore estimated at 200,000 years. Subsequently, it was noted that the CIE spanned 10 or 11 subtle cycles in various sediment properties, such as Fe content. Assuming these cycles represent precession , a similar but slightly longer age was calculated by Rohl et al. 2000. If a massive amount of C-depleted CO 2

1236-530: A decline among K-strategist large foraminifera, though they rebounded during the post-PETM oligotrophy coevally with the demise of low-latitude corals. A study published in May 2021 concluded that fish thrived in at least some tropical areas during the PETM, based on discovered fish fossils including Mene maculata at Ras Gharib , Egypt. Humid conditions caused migration of modern Asian mammals northward, dependent on

1442-468: A decreased oceanic pH , which has a profound negative effect on corals. Experiments suggest it is also very harmful to calcifying plankton. However, the strong acids used to simulate the natural increase in acidity which would result from elevated CO 2 concentrations may have given misleading results, and the most recent evidence is that coccolithophores ( E. huxleyi at least) become more , not less, calcified and abundant in acidic waters. No change in

1648-537: A defined deep-water thermocline (a warmer mass of water closer to the surface sitting on top of a colder mass nearer the bottom) persisting throughout the epoch. The Atlantic foraminifera indicate a general warming of sea surface temperature–with tropical taxa present in higher latitude areas–until the Late Paleocene when the thermocline became steeper and tropical foraminifera retreated back to lower latitudes. Early Paleocene atmospheric CO 2 levels at what

1854-622: A depth of about 1,000 m (3,300 ft). The Danian deposits are sequestered into the Aitzgorri Limestone Formation , and the Selandian and early Thanetian into the Itzurun Formation . The Itzurun Formation is divided into groups A and B corresponding to the two stages respectively. The two stages were ratified in 2008, and this area was chosen because of its completion, low risk of erosion, proximity to

2060-538: A floral and faunal turnover of species, with previously abundant species being replaced by previously uncommon ones. In the Paleocene, with a global average temperature of about 24–25 °C (75–77 °F), compared to 14 °C (57 °F) in more recent times, the Earth had a greenhouse climate without permanent ice sheets at the poles, like the preceding Mesozoic . As such, there were forests worldwide—including at

2266-546: A global scale, such as the Elmo horizon (aka ETM2 ), has led to the hypothesis that the events repeat on a regular basis, driven by maxima in the 400,000 and 100,000 year eccentricity cycles in the Earth's orbit . Cores from Howard's Tract, Maryland indicate the PETM occurred as a result of an extreme in axial precession during an orbital eccentricity maximum. The current warming period is expected to last another 50,000 years due to

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2472-618: A global value of around -3% to -4%. In addition, numerous smaller scale carbon isotope excursions are globally recorded on the falling limb of the larger negative δ C excursion. Although the PTo-E is not associated with a decrease in δ C analogous to the TOAE's, volcanism is nonetheless believed to have been responsible for its onset as well, with the carbon injection most likely having an isotopically heavy, mantle-derived origin. The Karoo-Ferrar magmatism released so much carbon dioxide that it disrupted

2678-463: A gradual grading back to grey). It is far more pronounced in North Atlantic cores than elsewhere, suggesting that acidification was more concentrated here, related to a greater rise in the level of the lysocline. Corrosive waters may have then spilled over into other regions of the world ocean from the North Atlantic. Model simulations show acidic water accumulation in the deep North Atlantic at

2884-419: A higher diversity ecological assemblage of lycophytes , conifers , seed ferns , and wet-adapted ferns is observed in the palaeobotanical and palynological record over the course of the TOAE. The coincidence of the zenith of Classopolis and the decline of seed ferns and spore producing plants with increased mercury loading implicates heavy metal poisoning as a key contributor to the floristic crisis during

3090-611: A higher rate than deciduous angiosperms as deciduous plants can become dormant in harsh conditions. In the Gulf Coast, angiosperms experienced another extinction event during the PETM, which they recovered quickly from in the Eocene through immigration from the Caribbean and Europe. During this time, the climate became warmer and wetter, and it is possible that angiosperms evolved to become stenotopic by this time, able to inhabit

3296-449: A lag time of around 3,800 years after the PETM. At some marine locations (mostly deep-marine), sedimentation rates must have decreased across the PETM, presumably because of carbonate dissolution on the seafloor; at other locations (mostly shallow-marine), sedimentation rates must have increased across the PETM, presumably because of enhanced delivery of riverine material during the event. Discriminating between different possible causes of

3502-680: A marked increase in TEX 86 . The latter record is intriguing, though, because it suggests a 6 °C (11 °F) rise from ~17 °C (63 °F) before the PETM to ~23 °C (73 °F) during the PETM. Assuming the TEX 86 record reflects summer temperatures, it still implies much warmer temperatures on the North Pole compared to the present day, but no significant latitudinal amplification relative to surrounding time. The above considerations are important because, in many global warming simulations, high latitude temperatures increase much more at

3708-416: A minimum in the eccentricity of the Earth's orbit. Orbital increase in insolation (and thus temperature) would force the system over a threshold and unleash positive feedbacks. The orbital forcing hypothesis has been challenged by a study finding the PETM to have coincided with a minimum in the ~400 kyr eccentricity cycle, inconsistent with a proposed orbital trigger for the hyperthermal. One theory holds that

3914-545: A mitigating factor that ameliorated to a degree the oppressively anoxic conditions that were widespread across much of the Tethys. The enhanced hydrological cycle during early Toarcian warming caused lakes to grow in size. During the anoxic event, the Sichuan Basin was transformed into a giant lake, which was believed to be approximately thrice as large as modern-day Lake Superior . Lacustrine sediments deposited as

4120-441: A narrow range of temperature and moisture; or, since the dominant floral ecosystem was a highly integrated and complex closed-canopy rainforest by the middle Paleocene, the plant ecosystems were more vulnerable to climate change . There is some evidence that, in the Gulf Coast, there was an extinction event in the late Paleocene preceding the PETM, which may have been due to the aforementioned vulnerability of complex rainforests, and

4326-404: A rapid +8 °C temperature rise, in accordance with existing regional records of marine and terrestrial environments. Southern California had a mean annual temperature of about 17 °C ± 4.4 °C. In Antarctica, at least part of the year saw minimum temperatures of 15 °C. TEX 86 values indicate that the average sea surface temperature (SST) reached over 36 °C (97 °F) in

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4532-664: A result of this lake's existence are represented by the Da’anzhai Member of the Ziliujing Formation . Roughly ~460 gigatons (Gt) of organic carbon and ~1,200 Gt of inorganic carbon were likely sequestered by this lake over the course of the TOAE. The TOAE and the Palaeocene-Eocene Thermal Maximum have been proposed as analogues to modern anthropogenic global warming based on the comparable quantity of greenhouse gases released into

4738-400: A role in the extinction of the calcifying foraminifera, and the higher temperatures would have increased metabolic rates, thus demanding a higher food supply. Such a higher food supply might not have materialized because warming and increased ocean stratification might have led to declining productivity, along with increased remineralization of organic matter in the water column before it reached

4944-424: A short time frame. The freezing temperatures probably reversed after three years and returned to normal within decades, sulfuric acid aerosols causing acid rain probably dissipated after 10 years, and dust from the impact blocking out sunlight and inhibiting photosynthesis would have lasted up to a year though potential global wildfires raging for several years would have released more particulates into

5150-721: A single formation (a stratotype ) identifying the lower boundary of the stage. In 1989, the ICS decided to split the Paleocene into three stages: the Danian, Selandian, and Thanetian. The Danian was first defined in 1847 by German-Swiss geologist Pierre Jean Édouard Desor based on the Danish chalks at Stevns Klint and Faxse , and was part of the Cretaceous, succeeded by the Tertiary Montian Stage. In 1982, after it

5356-503: A source of skewing of carbon isotopic ratios in bulk organic matter. The climate would also have become much wetter, with the increase in evaporation rates peaking in the tropics. Deuterium isotopes reveal that much more of this moisture was transported polewards than normal. Warm weather would have predominated as far north as the Polar basin. Finds of fossils of Azolla floating ferns in polar regions indicate subtropic temperatures at

5562-411: A sparse Pliensbachian marine vertebrate fossil record. The TOAE is suggested to have caused the extinction of various clades of dinosaurs, including coelophysids , dilophosaurids , and many basal sauropodomorph clades, as a consequence of the remodelling of terrestrial ecosystems caused by global climate change. Some heterodontosaurids and thyreophorans also perished in the extinction event. In

5768-468: A transition from icehouse to greenhouse conditions further retarded ocean circulation, aiding the establishment of anoxic conditions. Geochemical evidence from what was then the northwestern European epicontinental sea suggests that a shift from cooler, more saline water conditions to warmer, fresher conditions prompted the development of significant density stratification of the water column and induced anoxia. Extensive organic carbon burial induced by anoxia

5974-437: Is also evidence this occurred again 300,000 years later in the early Thanetian dubbed MPBE-2. Respectively, about 83 and 132 gigatons of methane-derived carbon were ejected into the atmosphere, which suggests a 2–3 °C (3.6–5.4 °F) rise in temperature, and likely caused heightened seasonality and less stable environmental conditions. It may have also caused an increase of grass in some areas. From 59.7 to 58.1 Ma, during

6180-468: Is at about 4 km, comparable to the median depth of the oceans. This depth depends on (among other things) temperature and the amount of CO 2 dissolved in the ocean. Adding CO 2 initially raises the lysocline, resulting in the dissolution of deep water carbonates. This deep-water acidification can be observed in ocean cores, which show (where bioturbation has not destroyed the signal) an abrupt change from grey carbonate ooze to red clays (followed by

6386-537: Is controversial, but most likely about 2,500 years. This carbon also interfered with the carbon cycle and caused ocean acidification, and potentially altered and slowed down ocean currents, the latter leading to the expansion of oxygen minimum zones (OMZs) in the deep sea. In surface water, OMZs could have also been caused from the formation of strong thermoclines preventing oxygen inflow, and higher temperatures equated to higher productivity leading to higher oxygen usurpation. Further, expanding OMZs could have caused

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6592-435: Is explained by the northward shift of low-level jets and atmospheric rivers. East African sites display evidence of aridity punctuated by seasonal episodes of potent precipitation, revealing the global climate during the PETM not to be universally humid. The proto-Mediterranean coastlines of the western Tethys became drier. Evidence from Forada in northeastern Italy suggests that arid and humid climatic intervals alternated over

6798-435: Is now Castle Rock , Colorado, were calculated to be between 352 and 1,110 parts per million (ppm), with a median of 616 ppm. Based on this and estimated plant-gas exchange rates and global surface temperatures, the climate sensitivity was calculated to be +3 °C when CO 2 levels doubled, compared to 7 °C following the formation of ice at the poles. CO 2 levels alone may have been insufficient in maintaining

7004-556: Is now the Mediterranean Sea tropical. South-central North America had a humid, monsoonal climate along its coastal plain, but conditions were drier to the west and at higher altitudes. Svalbard was temperate, having a mean temperature of 19.2 ± 2.49 °C during its warmest month and 1.7 ± 3.24 °С during its coldest. Global deep water temperatures in the Paleocene likely ranged from 8–12 °C (46–54 °F), compared to 0–3 °C (32–37 °F) in modern day. Based on

7210-450: Is other evidence to suggest that warming predated the δ C excursion by some 3,000 years. Some authors have suggested that the magnitude of the CIE may be underestimated due to local processes in many sites causing a large proportion of allochthonous sediments to accumulate in their sedimentary rocks, contaminating and offsetting isotopic values derived from them. Organic matter degradation by microbes has also been implicated as

7416-601: Is rapidly injected into the modern ocean or atmosphere and projected into the future, a ~200,000 year CIE results because of slow flushing through quasi steady-state inputs (weathering and volcanism) and outputs (carbonate and organic) of carbon. A different study, based on a revised orbital chronology and data from sediment cores in the South Atlantic and the Southern Ocean, calculated a slightly shorter duration of about 170,000 years. A ~200,000 year duration for

7622-416: Is used as a biostratigraphic marker defining the PETM. The fitness of Apectodinium homomorphum stayed constant over the PETM while that of others declined. Radiolarians grew in size over the PETM. Colonial corals, sensitive to rising temperatures, declined during the PETM, being replaced by larger benthic foraminifera. Aragonitic corals were greatly hampered in their ability to grow by the acidification of

7828-494: Is volcanic activity associated with the North Atlantic Igneous Province (NAIP), which is believed to have released more than 10,000 gigatons of carbon during the PETM based on the relatively isotopically heavy values of the initial carbon addition. Mercury anomalies during the PETM point to massive volcanism during the event. On top of that, increases in ∆Hg show intense volcanism was concurrent with

8034-548: Is why the GSSP was moved to Zumaia. Today, the beginning of the Selandian is marked by the appearances of the nannofossils Fasciculithus tympaniformis , Neochiastozygus perfectus , and Chiasmolithus edentulus , though some foraminifera are used by various authors. The Thanetian was first proposed by Swiss geologist Eugène Renevier , in 1873; he included the south England Thanet , Woolwich , and Reading formations. In 1880, French geologist Gustave Frédéric Dollfus narrowed

8240-605: The Ancient Greek παλαιός palaiós meaning "old" and the Eocene Epoch (which succeeds the Paleocene), translating to "the old part of the Eocene". The epoch is bracketed by two major events in Earth's history. The K–Pg extinction event , brought on by an asteroid impact ( Chicxulub impact ) and possibly volcanism ( Deccan Traps ), marked the beginning of the Paleocene and killed off 75% of species, most famously

8446-756: The Antarctic Peninsula . In the Paleocene, the waterways between the Arctic Ocean and the North Atlantic were somewhat restricted, so North Atlantic Deep Water (NADW) and the Atlantic Meridional Overturning Circulation (AMOC)—which circulates cold water from the Arctic towards the equator—had not yet formed, and so deep water formation probably did not occur in the North Atlantic. The Arctic and Atlantic would not be connected by sufficiently deep waters until

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8652-826: The Caribbean Plate ), which had formed from the Galápagos hotspot in the Pacific in the latest Cretaceous, was moving eastward as the North American and South American plates were getting pushed in the opposite direction due to the opening of the Atlantic ( strike-slip tectonics ). This motion would eventually uplift the Isthmus of Panama by 2.6 mya. The Caribbean Plate continued moving until about 50 mya when it reached its current position. The components of

8858-593: The Cleveland , West Netherlands, and South German Basins. Valdorbia, a site in the Umbria-Marche Apennines, also exhibited euxinia during the anoxic event. There is less evidence of euxinia outside the northwestern Tethys, and it likely only occurred transiently in basins in Panthalassa and the southwestern Tethys. Due to the clockwise circulation of the oceanic gyre in the western Tethys and

9064-826: The Cretaceous Period and the Mesozoic Era , and initiated the Cenozoic Era and the Paleogene Period. It is divided into three ages : the Danian spanning 66 to 61.6 million years ago (mya), the Selandian spanning 61.6 to 59.2 mya, and the Thanetian spanning 59.2 to 56 mya. It is succeeded by the Eocene. The K–Pg boundary is clearly defined in the fossil record in numerous places around

9270-549: The Holarctic region (comprising most of the Northern Hemisphere) was mainly early members of Ginkgo , Metasequoia , Glyptostrobus , Macginitiea , Platanus , Carya , Ampelopsis , and Cercidiphyllum . Patterns in plant recovery varied significantly with latitude , climate, and altitude. For example, what is now Castle Rock, Colorado featured a rich rainforest only 1.4 million years after

9476-517: The Karoo-Ferrar Large Igneous Province is generally attributed to have caused the surge in atmospheric carbon dioxide levels. Argon-argon dating of Karoo-Ferrar rhyolites points to a link between Karoo-Ferrar volcanism and the extinction event, a conclusion reinforced by uranium-lead dating and palaeomagnetism. Occurring during a broader, gradual positive carbon isotope excursion as measured by δ C values,

9682-517: The Pacific and Atlantic Oceans . The Drake Passage , which now separates South America and Antarctica , was closed, and this perhaps prevented thermal isolation of Antarctica. The Arctic was also more restricted. Although various proxies for past atmospheric CO 2 concentrations across the Cenozoic do not agree in absolute terms, all suggest that levels in the early Paleogene before and after

9888-531: The Paleocene and Eocene geological epochs . The exact age and duration of the PETM remain uncertain, but it occurred around 55.8 million years ago (Ma) and lasted about 200 thousand years (Ka). The PETM arguably represents our best past analogue for which to understand how global warming and the carbon cycle operate in a greenhouse world. The time interval is marked by a prominent negative excursion in carbon stable isotope ( δ C ) records from around

10094-480: The Paleocene–Eocene thermal maximum , a short period of intense warming and ocean acidification brought about by the release of carbon en masse into the atmosphere and ocean systems, which led to a mass extinction of 30–50% of benthic foraminifera –planktonic species which are used as bioindicators of the health of a marine ecosystem—one of the largest in the Cenozoic. This event happened around 55.8 mya, and

10300-503: The Paleogene as it is today – something which is very difficult to confirm. Although the cause of the initial warming has been attributed to a massive injection of carbon (CO 2 and/or CH 4 ) into the atmosphere, the source of the carbon has yet to be found. The emplacement of a large cluster of kimberlite pipes at ~56 Ma in the Lac de Gras region of northern Canada may have provided

10506-753: The Quaternary from the Tertiary in 1829; and Scottish geologist Charles Lyell (ignoring the Quaternary) had divided the Tertiary Epoch into the Eocene , Miocene , Pliocene , and New Pliocene ( Holocene ) Periods in 1833. British geologist John Phillips had proposed the Cenozoic in 1840 in place of the Tertiary, and Austrian paleontologist Moritz Hörnes had introduced the Paleogene for

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10712-530: The Transantarctic Mountains . The poles probably had a cool temperate climate; northern Antarctica, Australia, the southern tip of South America, what is now the US and Canada, eastern Siberia, and Europe warm temperate; middle South America, southern and northern Africa, South India, Middle America, and China arid; and northern South America, central Africa, North India, middle Siberia, and what

10918-435: The elegantulum subzone of the serpentinum ammonite zone, during a marked, pronounced warming interval. The TOAE lasted for approximately 500,000 years, though a range of estimates from 200,000 to 1,000,000 years have also been given. The PTo-E primarily affected shallow water biota, while the TOAE was the more severe event for organisms living in deep water. Geological, isotopic, and palaeobotanical evidence suggests

11124-475: The mirabile subzone of the tenuicostatum ammonite zone, coinciding with a slight drop in oxygen concentrations and the beginning of warming following a late Pliensbachian cool period. This first pulse, occurring near the Pliensbachian-Toarcian boundary, is referred to as the PTo-E. The TOAE itself occurred near the tenuicostatum – serpentinum ammonite biozonal boundary, specifically in

11330-847: The opening of the North Atlantic Ocean and seafloor spreading , the divergence of the Greenland Plate from the North American Plate , and, climatically, the PETM by dissociating methane clathrate crystals on the seafloor resulting in the mass release of carbon. North and South America remained separated by the Central American Seaway , though an island arc (the South Central American Arc) had already formed about 73 mya. The Caribbean Large Igneous Province (now

11536-496: The water column . Though the temperature in the latest Danian varied at about the same magnitude, this event coincides with an increase of carbon. About 60.5 mya at the Danian/Selandian boundary, there is evidence of anoxia spreading out into coastal waters, and a drop in sea levels which is most likely explained as an increase in temperature and evaporation, as there was no ice at the poles to lock up water. During

11742-584: The Østerrende Clay . The beginning of this stage was defined by the end of carbonate rock deposition from an open ocean environment in the North Sea region (which had been going on for the previous 40 million years). The Selandian deposits in this area are directly overlain by the Eocene Fur Formation —the Thanetian was not represented here—and this discontinuity in the deposition record

11948-682: The Americas had not yet joined, the Indian Plate had begun its collision with Asia, and the North Atlantic Igneous Province was forming in the third-largest magmatic event of the last 150 million years. In the oceans, the thermohaline circulation probably was much different from what it is today, with downwellings occurring in the North Pacific rather than the North Atlantic, and water density mainly being controlled by salinity rather than temperature. The K–Pg extinction event caused

12154-616: The CIE is estimated from models of global carbon cycling. Age constraints at several deep-sea sites have been independently examined using He contents, assuming the flux of this cosmogenic nuclide is roughly constant over short time periods. This approach also suggests a rapid onset for the PETM CIE (<20,000 years). However, the He records support a faster recovery to near initial conditions (<100,000 years) than predicted by flushing via weathering inputs and carbonate and organic outputs. There

12360-549: The Cambay Shale Formation of India by the deposition of thick lignitic seams as a consequence of increased soil erosion and organic matter burial. Precipitation rates in the North Sea likewise soared during the PETM. In Cap d'Ailly, in present-day Normandy , a transient dry spell occurred just before the negative CIE, after which much moister conditions predominated, with the local environment transitioning from

12566-448: The Cretaceous, had receded. Between about 60.5 and 54.5 mya, there was heightened volcanic activity in the North Atlantic region—the third largest magmatic event in the last 150 million years—creating the North Atlantic Igneous Province . The proto- Iceland hotspot is sometimes cited as being responsible for the initial volcanism, though rifting and resulting volcanism have also contributed. This volcanism may have contributed to

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12772-439: The Cretaceous, tropical or subtropical , and the poles were temperate , with an average global temperature of roughly 24–25 °C (75–77 °F). For comparison, the average global temperature for the period between 1951 and 1980 was 14 °C (57 °F). The latitudinal temperature gradient was approximately 0.24 °C per degree of latitude. The poles also lacked ice caps, though some alpine glaciation did occur in

12978-465: The Early Toarcian diversity collapse. Belemnite richness in the northwestern Tethys dropped during the PTo-E but slightly increased across the TOAE. Belemnites underwent a major change in habitat preference from cold, deep waters to warm, shallow waters. Their average rostrum size also increased, though this trend heavily varied depending on the lineage of belemnites. The Toarcian extinction

13184-635: The Eocene and Neogene for the Miocene and Pliocene in 1853. After decades of inconsistent usage, the newly formed International Commission on Stratigraphy (ICS), in 1969, standardized stratigraphy based on the prevailing opinions in Europe: the Cenozoic Era subdivided into the Tertiary and Quaternary sub-eras, and the Tertiary subdivided into the Paleogene and Neogene Periods. In 1978, the Paleogene

13390-639: The Eocene hyperthermals remain a source of current research. Whether they only occurred during the long-term warming, and whether they are causally related to apparently similar events in older intervals of the geological record (e.g. the Toarcian turnover of the Jurassic ) are open issues. A study in 2020 estimated the global mean surface temperature (GMST) with 66% confidence during the latest Paleocene (c. 57 Ma) as 22.3–28.3 °C (72.1–82.9 °F), PETM (56 Ma) as 27.2–34.5 °C (81.0–94.1 °F) and Early Eocene Climatic Optimum (EECO) (53.3 to 49.1 Ma) as 23.2–29.7 °C (73.8–85.5 °F). Estimates of

13596-425: The Eocene". The Eocene, in turn, is derived from Ancient Greek eo— eos ἠώς meaning "dawn", and—cene kainos καινός meaning "new" or "recent", as the epoch saw the dawn of recent, or modern, life. Paleocene did not come into broad usage until around 1920. In North America and mainland Europe, the standard spelling is "Paleocene", whereas it is "Palaeocene" in the UK. Geologist T. C. R. Pulvertaft has argued that

13802-420: The Hispanic Corridor into European seas after the extinction event, aided in their dispersal by higher sea levels. The TOAE had minor effects on marine reptiles, in stark contrast to the major impact it had on many clades of marine invertebrates. In fact, in the Southwest German Basin, ichthyosaur diversity was higher after the extinction interval, although this may be in part a sampling artefact resulting from

14008-433: The Indian Subcontinent acted as a diversity hub from which mammalian lineages radiated into Africa and the continents of the Northern Hemisphere. Multiple Eurasian mammal orders invaded North America, but because niche space was not saturated, these had little effect on overall community structure. The diversity of insect herbivory, as measured by the amount and diversity of damage to plants caused by insects, increased during

14214-418: The Indian Subcontinent. In the Tarim Sea, sea levels rose by 20-50 metres. At the start of the PETM, the ocean circulation patterns changed radically in the course of under 5,000 years. Global-scale current directions reversed due to a shift in overturning from the Southern Hemisphere to Northern Hemisphere. This "backwards" flow persisted for 40,000 years. Such a change would transport warm water to

14420-563: The Kerguelen Plateau, nannoplankton productivity sharply declined at the onset of the negative δ C excursion but was elevated in its aftermath. The nannoplankton genus Fasciculithus went extinct, most likely as a result of increased surface water oligotrophy; the genera Sphenolithus , Zygrhablithus , Octolithus suffered badly too. Samples from the tropical Atlantic show that overall, dinocyst abundance diminished sharply. Contrarily, thermophilic dinoflagellates bloomed, particularly Apectodinium . This acme in Apectodinium abundance

14626-408: The K–Pg boundary, the largest the Mexican Chicxulub crater whose impact was a major precipitator of the K–Pg extinction, and also the Ukrainian Boltysh crater , dated to 65.4 mya the Canadian Eagle Butte crater (though it may be younger), the Vista Alegre crater (though this may date to about 115 mya ). Silicate glass spherules along the Atlantic coast of the U.S. indicate a meteor impact in

14832-535: The K–Pg extinction event, every land animal over 25 kg (55 lb) was wiped out, leaving open several niches at the beginning of the epoch. Toarcian turnover Occurring during the supergreenhouse climate of the Early Toarcian Thermal Maximum (ETTM), the Early Toarcian extinction was associated with large igneous province volcanism, which elevated global temperatures, acidified

15038-542: The Late Cretaceous became dominant trees in Patagonia, before going extinct. Some plant communities, such as those in eastern North America, were already experiencing an extinction event in the late Maastrichtian, particularly in the 1 million years before the K–Pg extinction event. The "disaster plants" that refilled the emptied landscape crowded out many Cretaceous plants, and resultantly, many went extinct by

15244-410: The Miocene about 24–17 mya. There is evidence that some plants and animals could migrate between India and Asia during the Paleocene, possibly via intermediary island arcs. In the modern thermohaline circulation , warm tropical water becomes colder and saltier at the poles and sinks ( downwelling or deep water formation) that occurs at the North Atlantic near the North Pole and the Southern Ocean near

15450-728: The Northern Component Waters by Greenland in the Eocene—the predecessor of the AMOC—may have caused an intense warming in the North Hemisphere and cooling in the Southern, as well as an increase in deep water temperatures. In the PETM, it is possible deep water formation occurred in saltier tropical waters and moved polewards, which would increase global surface temperatures by warming the poles. Also, Antarctica

15656-410: The PETM comes from two observations. First, a prominent negative excursion in the carbon isotope composition ( δ C ) of carbon-bearing phases characterizes the PETM in numerous (>130) widespread locations from a range of environments. Second, carbonate dissolution marks the PETM in sections from the deep sea. The total mass of carbon injected to the ocean and atmosphere during the PETM remains

15862-569: The PETM in correlation with global warming. The ant genus Gesomyrmex radiated across Eurasia during the PETM. As with mammals, soil-dwelling invertebrates are observed to have dwarfed during the PETM. A profound change in terrestrial vegetation across the globe is associated with the PETM. Across all regions, floras from the latest Palaeocene are highly distinct from those of the PETM and the Early Eocene. The Arctic became dominated by palms and broadleaf forests. The Gulf coast of central Texas

16068-407: The PETM is difficult. Temperatures were rising globally at a steady pace, and a mechanism must be invoked to produce an instantaneous spike which may have been accentuated or catalyzed by positive feedback (or activation of "tipping or points"). The biggest aid in disentangling these factors comes from a consideration of the carbon isotope mass balance. We know the entire exogenic carbon cycle (i.e.

16274-660: The PETM to ~40 °C. In the eastern Tethys, SSTs rose by 3 to 5 °C. Low latitude Indian Ocean Mg/Ca records show seawater at all depths warmed by about 4-5 °C. In the Pacific Ocean, tropical SSTs increased by about 4-5 °C. TEX 86 values from deposits in New Zealand, then located between 50°S and 60°S in the southwestern Pacific, indicate SSTs of 26 °C (79 °F) to 28 °C (82 °F), an increase of over 10 °C (18 °F) from an average of 13 °C (55 °F) to 16 °C (61 °F) at

16480-516: The PETM were much higher than at present-day. In any case, significant terrestrial ice sheets and sea-ice did not exist during the late Paleocene through early Eocene Earth surface temperatures gradually increased by about 6 °C from the late Paleocene through the early Eocene. Superimposed on this long-term, gradual warming were at least three (and probably more) "hyperthermals". These can be defined as geologically brief (<200,000 year) events characterized by rapid global warming, major changes in

16686-498: The PETM, and continued for a time after the PETM's termination. The PETM generated the only oceanic anoxic event (OAE) of the Cenozoic. Oxygen depletion was achieved through a combination of elevated seawater temperatures, water column stratification, and oxidation of methane released from undersea clathrates. In parts of the oceans, especially the North Atlantic Ocean, bioturbation was absent. This may be due to bottom-water anoxia or due to changing ocean circulation patterns changing

16892-468: The PETM, generating an increase in organic carbon burial, which acted as a negative feedback on the PETM's severe global warming. Along with the global lack of ice, the sea level would have risen due to thermal expansion. Evidence for this can be found in the shifting palynomorph assemblages of the Arctic Ocean, which reflect a relative decrease in terrestrial organic material compared to marine organic matter. A significant marine transgression took place in

17098-707: The PETM. As a consequence of coccolithophorid blooms enabled by enhanced runoff, carbonate was removed from seawater as the Earth recovered from the negative carbon isotope excursion, thus acting to ameliorate ocean acidification. Stoichiometric magnetite ( Fe 3 O 4 ) particles were obtained from PETM-age marine sediments. The study from 2008 found elongate prism and spearhead crystal morphologies, considered unlike any magnetite crystals previously reported, and are potentially of biogenic origin. These biogenic magnetite crystals show unique gigantism, and probably are of aquatic origin. The study suggests that development of thick suboxic zones with high iron bioavailability,

17304-410: The PTo-E and TOAE. In northeastern Panthalassa, in what is now British Columbia , euxinia dominated anoxic bottom waters. The early stages of the TOAE were accompanied by a decrease in the acidity of seawater following a substantial decrease prior to the TOAE. Seawater pH then dropped close to the middle of the event, strongly acidifying the oceans. The sudden decline of carbonate production during

17510-412: The Paleocene, especially at the end, in tandem with the increasing global temperature. At the North Pole, woody angiosperms had become the dominant plants, a reversal from the Cretaceous where herbs proliferated. The Iceberg Bay Formation on Ellesmere Island , Nunavut (latitude 75 – 80 ° N) shows remains of a late Paleocene dawn redwood forest, the canopy reaching around 32 m (105 ft), and

17716-531: The South Pole, due to the increasing isolation of Antarctica, many plant taxa were endemic to the continent instead of migrating down. Patagonian flora may have originated in Antarctica. The climate was much cooler than in the Late Cretaceous, though frost probably was not common in at least coastal areas. East Antarctica was likely warm and humid. Because of this, evergreen forests could proliferate as, in

17922-402: The TOAE is preceded by a global negative δ C excursion recognised in fossil wood, organic carbon, and carbonate carbon in the tenuicostatum ammonite zone of northwestern Europe, with this negative δ C shift being the result of volcanic discharge of light carbon. The global ubiquity of this negative δ C excursion has been called into question, however, due to its absence in certain deposits from

18128-402: The TOAE is widely believed to be the result of this abrupt episode of ocean acidification . Additionally, the enhanced recycling of phosphorus back into seawater as a result of high temperatures and low seawater pH inhibited its mineralisation into apatite, helping contribute to oceanic anoxia. The abundance of phosphorus in marine environments created a positive feedback loop whose consequence

18334-434: The TOAE, as shown by a positive δ S excursion in carbonate-associated sulphate occurs synchronously with the positive δ C excursion in carbonate carbon during the falciferum ammonite zone. This positive δ S excursion has been attributed to the depletion of isotopically light sulphur in the marine sulphate reservoir that resulted from microbial sulphur reduction in anoxic waters. Similar positive δ S excursions corresponding to

18540-466: The TOAE. Carbonate platforms collapsed during both the PTo-E and the TOAE. Enhanced continental weathering and nutrient runoff was the dominant driver of carbonate platform decline in the PTo-E, while the biggest culprits during the TOAE were heightened storm activity and a decrease in the pH of seawater. The recovery from the mass extinction among benthos commenced with the recolonisation of barren locales by opportunistic pioneer taxa. Benthic recovery

18746-445: The TOAE. Concentrations of phosphorus, magnesium, and manganese rose in the oceans. A -0.5% excursion in δ Ca provides further evidence of increased continental weathering. Osmium isotope ratios confirm further still a major increase in weathering. The enhanced continental weathering in turn led to increased eutrophication that helped drive the anoxic event in the oceans. Continual transport of continentally weathered nutrients into

18952-694: The TOAE; the increase in clastic sedimentation was synchronous with excursions in Os/ Os, Sr/ Sr, and δ Ca. Additionally, the Toarcian was punctuated by intervals of extensive kaolinite enrichment. These kaolinites correspond to negative oxygen isotope excursions and high Mg/Ca ratios and are thus reflective of climatic warming events that characterised much of the Toarcian. Likewise, illitic/smectitic clays were also common during this hyperthermal perturbation. The Intertropical Convergence Zone (ITCZ) migrated southwards across southern Gondwana, turning much of

19158-845: The Thanetian is best correlated with the C26r/C26n reversal. Several economically important coal deposits formed during the Paleocene, such as the sub-bituminous Fort Union Formation in the Powder River Basin of Wyoming and Montana, which produces 43% of American coal; the Wilcox Group in Texas, the richest deposits of the Gulf Coastal Plain ; and the Cerrejón mine in Colombia, the largest open-pit mine in

19364-431: The Toarcian mass extinction. Poisoning by mercury, along with chromium, copper, cadmium, arsenic, and lead is speculated to be responsible for heightened rates of spore malformation and dwarfism concomitant with enrichments in all these toxic metals. The TOAE was associated with widespread phosphatisation of marine fossils believed to result from the warming-induced increase in weathering that increased phosphate flux into

19570-681: The Turgai route connecting Europe with Asia (which were otherwise separated by the Turgai Strait at this time). The Laramide orogeny , which began in the Late Cretaceous, continued to uplift the Rocky Mountains ; it ended at the end of the Paleocene. Because of this and a drop in sea levels resulting from tectonic activity, the Western Interior Seaway , which had divided the continent of North America for much of

19776-570: The West Siberian Sea, SSTs climbed to ~27 °C. Certainly, the central Arctic Ocean was ice-free before, during, and after the PETM. This can be ascertained from the composition of sediment cores recovered during the Arctic Coring Expedition (ACEX) at 87°N on Lomonosov Ridge . Moreover, temperatures increased during the PETM, as indicated by the brief presence of subtropical dinoflagellates ( Apectodinium spp. }, and

19982-466: The abrupt warming interval associated with the TOAE. This global warming, driven by rising atmospheric carbon dioxide, was the mainspring of the early Toarcian environmental crisis. Carbon dioxide levels rose from about 500 ppm to about 1,000 ppm. Seawater warmed by anywhere between 3 °C and 7 °C, depending on latitude. At the height of this supergreenhouse interval, global sea surface temperatures (SSTs) averaged about 21 °C. The eruption of

20188-438: The absence of frost and a low probability of leaves dying, it was more energy efficient to retain leaves than to regrow them every year. One possibility is that the interior of the continent favored deciduous trees, though prevailing continental climates may have produced winters warm enough to support evergreen forests. As in the Cretaceous, podocarpaceous conifers, Nothofagus , and Proteaceae angiosperms were common. In

20394-474: The algae Discoaster and a diversification of Heliolithus , though the best correlation is in terms of paleomagnetism . A chron is the occurrence of a geomagnetic reversal —when the North and South poles switch polarities . Chron 1 (C1n) is defined as modern day to about 780,000 years ago, and the n denotes "normal" as in the polarity of today, and an r "reverse" for the opposite polarity. The beginning of

20600-410: The amount of average global temperature rise at the start of the PETM range from approximately 3 to 6 °C to between 5 and 8 °C. This warming was superimposed on "long-term" early Paleogene warming , and is based on several lines of evidence. There is a prominent (>1 ‰ ) negative excursion in the δ O of foraminifera shells, both those made in surface and deep ocean water. Because there

20806-487: The amount of solar radiation reaching the Earth's surface, lowering temperatures in the troposphere, and changing atmospheric circulation patterns. Large-scale volcanic activity may last only a few days, but the massive outpouring of gases and ash can influence climate patterns for years. Sulfuric gases convert to sulfate aerosols, sub-micron droplets containing about 75 percent sulfuric acid. Following eruptions, these aerosol particles can linger as long as three to four years in

21012-650: The approximate time intervals corresponding to the PTo-E and TOAE have likewise been invoked as tell-tale evidence of the ecological calamity's cause being a large igneous province, although some researchers attribute these elevated mercury levels to increased terrigenous flux. There is evidence that the motion of the African Plate suddenly changed in velocity, shifting from mostly northward movement to southward movement. Such shifts in plate motion are associated with similar large igneous provinces emplaced in other time intervals. A 2019 geochronological study found that

21218-700: The atmosphere. Carbon release via metamorphic heating of coal has been criticised as a major driver of the environmental perturbation, however, on the basis that coal transects themselves do not show the δ C excursions that would be expected if significant quantities of thermogenic methane were released, suggesting that much of the degassed emissions were either condensed as pyrolytic carbon or trapped as coalbed methane. In addition, possible associated release of deep sea methane clathrates has been potentially implicated as yet another cause of global warming. Episodic melting of methane clathrates dictated by Milankovitch cycles has been put forward as an explanation fitting

21424-507: The atmosphere. For the following half million years, the carbon isotope gradient—a difference in the C / C ratio between surface and deep ocean water, causing carbon to cycle into the deep sea—may have shut down. This, termed a "Strangelove ocean", indicates low oceanic productivity ; resultant decreased phytoplankton activity may have led to a reduction in cloud seeds and, thus, marine cloud brightening , causing global temperatures to increase by 6 °C ( CLAW hypothesis ). Following

21630-404: The beginning of the PETM. Osmium isotopic anomalies in Arctic Ocean sediments dating to the PETM have been interpreted as evidence of a volcanic cause of this hyperthermal. Intrusions of hot magma into carbon-rich sediments may have triggered the degassing of isotopically light methane in sufficient volumes to cause global warming and the observed isotope anomaly. This hypothesis is documented by

21836-518: The beginning stages of the PETM. On land, many modern mammal orders (including primates ) suddenly appear in Europe and in North America. The configuration of oceans and continents was somewhat different during the early Paleogene relative to the present day. The Panama Isthmus did not yet connect North America and South America , and this allowed direct low-latitude circulation between

22042-407: The benthic foraminifera on the sea floor. The only factor global in extent was an increase in temperature. Regional extinctions in the North Atlantic can be attributed to increased deep-sea anoxia, which could be due to the slowdown of overturning ocean currents, or the release and rapid oxidation of large amounts of methane. In shallower waters, it's undeniable that increased CO 2 levels result in

22248-597: The boundary between the Selandian and Thanetian . The extreme warmth of the southwestern Pacific extended into the Australo-Antarctic Gulf. Sediment core samples from the East Tasman Plateau , then located at a palaeolatitude of ~65 °S, show an increase in SSTs from ~26 °C to ~33 °C during the PETM. In the North Sea, SSTs jumped by 10 °C, reaching highs of ~33 °C, while in

22454-605: The boundary; for example, in the Williston Basin of North Dakota, an estimated 1/3 to 3/5 of plant species went extinct. The K–Pg extinction event ushered in a floral turnover; for example, the once commonplace Araucariaceae conifers were almost fully replaced by Podocarpaceae conifers, and the Cheirolepidiaceae , a group of conifers that had dominated during most of the Mesozoic but had become rare during

22660-406: The carbon contained within the oceans and atmosphere, which can change on short timescales) underwent a −0.2 % to −0.3 % perturbation in δ C , and by considering the isotopic signatures of other carbon reserves, can consider what mass of the reserve would be necessary to produce this effect. The assumption underpinning this approach is that the mass of exogenic carbon was the same in

22866-417: The carbon cycle disruption. It has also been hypothesised that the release of cryospheric methane trapped in permafrost amplified the warming and its detrimental effects on marine life. Obliquity-paced carbon isotope excursions have been interpreted as some researchers as reflective of permafrost decline and consequent greenhouse gas release. The TOAE is believed to be the second largest anoxic event of

23072-548: The carbon that triggered early warming in the form of exsolved magmatic CO 2 . Calculations indicate that the estimated 900–1,100 Pg of carbon required for the initial approximately 3 °C of ocean water warming associated with the Paleocene-Eocene thermal maximum could have been released during the emplacement of a large kimberlite cluster. The transfer of warm surface ocean water to intermediate depths led to thermal dissociation of seafloor methane hydrates, providing

23278-427: The climatic belts. Uncertainty remains for the timing and tempo of migration. Terrestrial animals suffered mass mortality due to toxigenic cyanobacterial blooms enkindled by the extreme heat. The increase in mammalian abundance is intriguing. Increased global temperatures may have promoted dwarfing – which may have encouraged speciation. Major dwarfing occurred early in the PETM, with further dwarfing taking place during

23484-695: The country. Paleocene coal has been mined extensively in Svalbard , Norway, since near the beginning of the 20th century, and late Paleocene and early Eocene coal is widely distributed across the Canadian Arctic Archipelago and northern Siberia. In the North Sea, Paleocene-derived natural gas reserves, when they were discovered, totaled approximately 2.23 trillion m (7.89 trillion ft ), and oil in place 13.54 billion barrels. Important phosphate deposits—predominantly of francolite —near Métlaoui , Tunisia were formed from

23690-429: The course of the PETM concomitantly with precessional cycles in mid-latitudes, and that overall, net precipitation over the central-western Tethys Ocean decreased. The amount of freshwater in the Arctic Ocean increased, in part due to Northern Hemisphere rainfall patterns, fueled by poleward storm track migrations under global warming conditions. The flux of freshwater entering the oceans increased drastically during

23896-479: The course of ~1,000 years, with the group suffering more during the PETM than during the dinosaur-slaying K-T extinction . At the onset of the PETM, benthic foraminiferal diversity dropped by 30% in the Pacific Ocean, while at Zumaia in what is now Spain, 55% of benthic foraminifera went extinct over the course of the PETM, though this decline was not ubiquitous to all sites; Himalayan platform carbonates show no major change in assemblages of large benthic foraminifera at

24102-404: The dark forest floor, and epiphytism where a plant grows on another plant in response to less space on the forest floor. Despite increasing density—which could act as fuel—wildfires decreased in frequency from the Cretaceous to the early Eocene as the atmospheric oxygen levels decreased to modern day levels, though they may have been more intense. There was a major die-off of plant species over

24308-408: The deep oceans, enhancing further warming. The major biotic turnover among benthic foraminifera has been cited as evidence of a significant change in deep water circulation. Ocean acidification occurred during the PETM, causing the calcite compensation depth to shoal. The lysocline marks the depth at which carbonate starts to dissolve (above the lysocline, carbonate is oversaturated): today, this

24514-472: The definition to just the Thanet Formation. The Thanetian begins a little after the mid-Paleocene biotic event —a short-lived climatic event caused by an increase in methane —recorded at Itzurun as a dark 1 m (3.3 ft) interval from a reduction of calcium carbonate . At Itzurun, it begins about 29 m (95 ft) above the base of the Selandian, and is marked by the first appearance of

24720-504: The distribution of calcareous nannoplankton such as the coccolithophores can be attributed to acidification during the PETM. Nor was the abundance of calcareous nannoplankton controlled by changes in acidity, with local variations in nutrient availability and temperature playing much greater roles; diversity changes in calcareous nannoplankton in the Southern Ocean and at the Equator were most affected by temperature changes, whereas in much of

24926-482: The early to middle Eocene. There is evidence of deep water formation in the North Pacific to at least a depth of about 2,900 m (9,500 ft). The elevated global deep water temperatures in the Paleocene may have been too warm for thermohaline circulation to be predominately heat driven. It is possible that the greenhouse climate shifted precipitation patterns, such that the Southern Hemisphere

25132-529: The ecosystem may have been disrupted by only a small change in climate. The warm Paleocene climate, much like that of the Cretaceous , allowed for diverse polar forests. Whereas precipitation is a major factor in plant diversity nearer the equator, polar plants had to adapt to varying light availability ( polar nights and midnight suns ) and temperatures. Because of this, plants from both poles independently evolved some similar characteristics, such as broad leaves. Plant diversity at both poles increased throughout

25338-415: The efficiency of transport of photic zone water into the ocean depths, thus partially acting as a negative feedback that retarded the rate of atmospheric carbon dioxide buildup. Also, diminished biocalcification inhibited the removal of alkalinity from the deep ocean, causing an overshoot of calcium carbonate deposition once net calcium carbonate production resumed, helping restore the ocean to its state before

25544-684: The emplacement of the Karoo-Ferrar large igneous province and the TOAE were not causally linked, and simply happened to occur rather close in time, contradicting mainstream interpretations of the TOAE. The authors of the study conclude that the timeline of the TOAE does not match up with the course of activity of the Karoo-Ferrar magmatic event. The large igneous province also intruded into coal seams, releasing even more carbon dioxide and methane than it otherwise would have. Magmatic sills are also known to have intruded into shales rich in organic carbon, causing additional venting of carbon dioxide into

25750-508: The enhanced runoff formed thick paleosoil enriched with carbonate nodules ( Microcodium like), and this suggests a semi-arid climate . Unlike during lesser, more gradual hyperthermals, glauconite authigenesis was inhibited. The sedimentological effects of the PETM lagged behind the carbon isotope shifts. In the Tremp-Graus Basin of northern Spain, fluvial systems grew and rates of deposition of alluvial sediments increased with

25956-568: The environment, and massive carbon addition. Though not the first within the Cenozoic , the PETM was the most extreme hyperthermal, and stands out as a major change in the lithologic, biotic and geochemical composition of sediment in hundreds of records across Earth. Other hyperthermals clearly occurred at approximately 53.7 Ma (now called ETM-2 and also referred to as H-1, or the Elmo event) and at about 53.6 Ma (H-2), 53.3 (I-1), 53.2 (I-2) and 52.8 Ma (informally called K, X or ETM-3). The number, nomenclature, absolute ages, and relative global impact of

26162-486: The event, probably due to a rain shadow effect causing regular monsoon seasons. Conversely, low plant diversity and a lack of specialization in insects in the Colombian Cerrejón Formation , dated to 58 mya, indicates the ecosystem was still recovering from the K–Pg extinction event 7 million years later. Flowering plants ( angiosperms ), which had become dominant among forest taxa by

26368-539: The extreme disruptions in the aftermath of the K-Pg extinction event, the relatively cool, though still greenhouse, conditions of the Late Cretaceous–Early Palaeogene Cool Interval (LKEPCI) that began in the Late Cretaceous continued. The Dan –C2 Event 65.2 mya in the early Danian spanned about 100,000 years, and was characterized by an increase in carbon, particularly in the deep sea. Since

26574-535: The former southern supercontinent Gondwanaland in the Southern Hemisphere continued to drift apart, but Antarctica was still connected to South America and Australia. Africa was heading north towards Europe, and the Indian subcontinent towards Asia, which would eventually close the Tethys Ocean . The Indian and Eurasian Plates began colliding in the Paleocene, with uplift (and a land connection) beginning in

26780-487: The globe; more specifically, a large decrease in the C/ C ratio of marine and terrestrial carbonates and organic carbon has been found and correlated across hundreds of locations. The magnitude and timing of the PETM ( δ C ) excursion, which attest to the massive past carbon release to our ocean and atmosphere, and the source of this carbon remain topics of considerable current geoscience research. What has become clear over

26986-453: The greenhouse climate, and some positive feedbacks must have been active, such as some combination of cloud, aerosol, or vegetation related processes. A 2019 study identified changes in orbital eccentricity as the dominant drivers of climate between the late Cretaceous and the early Eocene. The effects of the meteor impact and volcanism 66 mya and the climate across the K–Pg boundary were likely fleeting, and climate reverted to normal in

27192-459: The imprint of the 9 Myr long-term carbon cycle that was otherwise steady and stable during the Jurassic and Early Cretaceous. The values of Os/ Os rose from ~0.40 to ~0.53 during the PTo-E and from ~0.42 to ~0.68 during the TOAE, and many scholars conclude this change in osmium isotope ratios evidences the responsibility of this large igneous province for the biotic crises. Mercury anomalies from

27398-549: The isotopically depleted carbon that produced the carbon isotopic excursion. The coeval ages of two other kimberlite clusters in the Lac de Gras field and two other early Cenozoic hyperthermals indicate that CO 2 degassing during kimberlite emplacement is a plausible source of the CO 2 responsible for these sudden global warming events. One of the leading candidates for the cause of the observed carbon cycle disturbances and global warming

27604-562: The last 300 Ma, and possibly the largest of the Phanerozoic. A positive δ C excursion, likely resulting from the mass burial of organic carbon during the anoxic event, is known from the falciferum ammonite zone, chemostratigraphically identifying the TOAE. Large igneous province resulted in increased silicate weathering and an acceleration of the hydrological cycle , as shown by a increased amount of terrestrially derived organic matter found in sedimentary rocks of marine origin during

27810-490: The last few decades: Stratigraphic sections across the PETM reveal numerous changes beyond warming and carbon emission. Consistent with an Epoch boundary, Fossil records of many organisms show major turnovers. In the marine realm, a mass extinction of benthic foraminifera , a global expansion of subtropical dinoflagellates , and an appearance of excursion taxa, including within planktic foraminifera planktic foraminifera and calcareous nannofossils , all occurred during

28016-482: The late Danian, there was a warming event and evidence of ocean acidification associated with an increase in carbon; at this time, there was major seafloor spreading in the Atlantic and volcanic activity along the southeast margin of Greenland. The Latest Danian Event, also known as the Top Chron C27n Event, lasted about 200,000 years and resulted in a 1.6–2.8 °C increase in temperatures throughout

28222-871: The late Paleocene to the early Eocene. Impact craters formed in the Paleocene include: the Connolly Basin crater in Western Australia less than 60 mya, the Texan Marquez crater 58 mya, the Greenlandic Hiawatha Glacier crater 58 mya, and possibly the Jordan Jabel Waqf as Suwwan crater which dates to between 56 and 37 mya. Vanadium -rich osbornite from the Isle of Skye , Scotland, dating to 60 mya may be impact ejecta . Craters were also formed near

28428-414: The late Pliensbachian was an icehouse period. These ice sheets are believed to have been thin and stretched into lower latitudes, making them extremely sensitive to temperature changes. A warming trend lasting from the latest Pliensbachian to the earliest Toarcian was interrupted by a "cold snap" in the middle polymorphum zone, equivalent to the tenuicostatum ammonite zone, which was then followed by

28634-491: The late Selandian and early Thanetian, organic carbon burial resulted in a period of climatic cooling, sea level fall and transient ice growth. This interval saw the highest δ O values of the epoch. The Paleocene–Eocene Thermal Maximum was an approximately 200,000-year-long event where the global average temperature rose by some 5 to 8 °C (9 to 14 °F), and mid-latitude and polar areas may have exceeded modern tropical temperatures of 24–29 °C (75–84 °F). This

28840-478: The latter spelling is incorrect because this would imply either a translation of "old recent" or a derivation from "pala" and "Eocene", which would be incorrect because the prefix palæo- uses the ligature æ instead of "a" and "e" individually, so only both characters or neither should be dropped, not just one. The Paleocene Epoch is the 10 million year time interval directly after the K–Pg extinction event , which ended

29046-404: The methane released from ocean sediments was rapidly sequestered, buffering its ability to act as a major positive feedback, and that methane clathrate dissociation occurred too late to have had an appreciable causal impact on the extinction event. Hypothetical release of methane clathrates extremely depleted in heavy carbon isotopes has furthermore been considered unnecessary as an explanation for

29252-562: The mid- Maastrichtian , more and more carbon had been sequestered in the deep sea possibly due to a global cooling trend and increased circulation into the deep sea. The Dan–C2 event may represent a release of this carbon after deep sea temperatures rose to a certain threshold, as warmer water can dissolve less carbon. Alternatively, the cause of the Dan-C2 event may have been a pulse of Deccan Traps volcanism. Savanna may have temporarily displaced forestland in this interval. Around 62.2 mya in

29458-573: The mid-Palaeocene biotic event (MPBE), also known as the Early Late Palaeocene Event (ELPE), around 59 Ma (roughly 50,000 years before the Selandian/Thanetian boundary), the temperature spiked probably due to a mass release of the deep sea methane hydrate into the atmosphere and ocean systems. Carbon was probably output for 10–11,000 years, and the aftereffects likely subsided around 52–53,000 years later. There

29664-399: The middle Cretaceous 110–90 mya, continued to develop and proliferate, more so to take advantage of the recently emptied niches and an increase in rainfall. Along with them coevolved the insects that fed on these plants and pollinated them. Predation by insects was especially high during the PETM. Many fruit-bearing plants appeared in the Paleocene in particular, probably to take advantage of

29870-432: The middle Paleocene. The strata immediately overlaying the K–Pg extinction event are especially rich in fern fossils. Ferns are often the first species to colonize areas damaged by forest fires , so this " fern spike " may mark the recovery of the biosphere following the impact (which caused blazing fires worldwide). The diversifying herb flora of the early Paleocene either represent pioneer species which re-colonized

30076-401: The middle of the hyperthermal. The dwarfing of various mammal lineages led to further dwarfing in other mammals whose reduction in body size was not directly induced by the PETM. Many major mammalian clades – including hyaenodontids , artiodactyls , perissodactyls , and primates – appeared and spread around the globe 13,000 to 22,000 years after the initiation of the PETM. It is possible that

30282-415: The most dire crises in their evolutionary history. Brachiopod taxa of large size declined significantly in abundance. Uniquely, the brachiopod genus Soaresirhynchia thrived during the later stages of the TOAE due to its low metabolic rate and slow rate of growth, making it a disaster taxon . The species S. bouchardi is known to have been a pioneer species that colonised areas denuded of brachiopods in

30488-604: The newly evolving birds and mammals for seed dispersal . In what is now the Gulf Coast , angiosperm diversity increased slowly in the early Paleocene, and more rapidly in the middle and late Paleocene. This may have been because the effects of the K–Pg extinction event were still to some extent felt in the early Paleocene, the early Paleocene may not have had as many open niches, early angiosperms may not have been able to evolve at such an accelerated rate as later angiosperms, low diversity equates to lower evolution rates, or there

30694-679: The non-avian dinosaurs. The end of the epoch was marked by the Paleocene–Eocene Thermal Maximum (PETM), which was a major climatic event wherein about 2,500–4,500 gigatons of carbon were released into the atmosphere and ocean systems, causing a spike in global temperatures and ocean acidification . In the Paleocene, the continents of the Northern Hemisphere were still connected via some land bridges ; and South America, Antarctica, and Australia had not completely separated yet. The Rocky Mountains were being uplifted,

30900-423: The northwestern Tethyan region. Ostracods also suffered a major diversity loss, with almost all ostracod clades’ distributions during the time interval corresponding to the serpentinum zone shifting towards higher latitudes to escape intolerably hot conditions near the Equator. Bivalves likewise experienced a significant turnover. The decline of bivalves exhibiting high endemism with narrow geographic ranges

31106-440: The observed shifts in the carbon isotope record. Other studies contradict and reject the methane hydrate hypothesis, however, concluding that the isotopic record is too incomplete to conclusively attribute the isotopic excursion to methane hydrate dissociation, that carbon isotope ratios in belemnites and bulk carbonates are incongruent with the isotopic signature expected from a massive release of methane clathrates, that much of

31312-515: The ocean and eutrophication in surficial waters. Overall, coral framework-building capacity was greatly diminished. The deep-sea extinctions are difficult to explain, because many species of benthic foraminifera in the deep-sea are cosmopolitan, and can find refugia against local extinction. General hypotheses such as a temperature-related reduction in oxygen availability, or increased corrosion due to carbonate undersaturated deep waters, are insufficient as explanations. Acidification may also have played

31518-468: The ocean enabled high levels of primary productivity to be maintained over the course of the TOAE. Rising sea levels contributed to ocean deoxygenation; as rising sea levels inundated low-lying lands, organic plant matter was transported outwards into the ocean. An alternate model for the development of anoxia is that epicontinental seaways became salinity stratified with strong haloclines , chemoclines , and thermoclines . This caused mineralised carbon on

31724-585: The ocean. This produced exquisitely preserved lagerstätten across the world, such as Ya Ha Tinda, Strawberry Bank, and the Posidonia Shale . As is common during anoxic events, black shale deposition was widespread during the deoxygenation events of the Toarcian. Toarcian anoxia was responsible for the deposition of commercially extracted oil shales, particularly in China. Enhanced hydrological cycling caused clastic sedimentation to accelerate during

31930-476: The oceans, and prompted the development of anoxia, leading to severe biodiversity loss. The biogeochemical crisis is documented by a high amplitude negative carbon isotope excursions, as well as black shale deposition. The Early Toarcian extinction event occurred in two distinct pulses, with the first event being classified by some authors as its own event unrelated to the more extreme second event. The first, more recently identified pulse occurred during

32136-566: The onset of TOAE are known from pyrites in the Sakahogi and Sakuraguchi-dani localities in Japan, with the Sakahogi site displaying a less extreme but still significant pyritic positive δ S excursion during the PTo-E. Euxinia is further evidenced by enhanced pyrite burial in Zázrivá, Slovakia, enhanced molybdenum burial totalling about 41 Gt of molybdenum, and δ Mo excursions observed in sites in

32342-548: The onset of the PETM; their decline came about towards the end of the event. A decrease in diversity and migration away from the oppressively hot tropics indicates planktonic foraminifera were adversely affected as well. The Lilliput effect is observed in shallow water foraminifera, possibly as a response to decreased surficial water density or diminished nutrient availability. Populations of planktonic foraminifera bearing photosymbionts increased. Extinction rates among calcareous nannoplankton increased, but so did origination rates. In

32548-418: The onset of the event. Acidification of deep waters, and the later spreading from the North Atlantic can explain spatial variations in carbonate dissolution. In parts of the southeast Atlantic, the lysocline rose by 2 km in just a few thousand years. Evidence from the tropical Pacific Ocean suggests a minimum lysocline shoaling of around 500 m at the time of this hyperthermal. Acidification may have increased

32754-694: The onset provides insight to the source of C -depleted CO 2 . The total duration of the CIE can be estimated in several ways. The iconic sediment interval for examining and dating the PETM is a core recovered in 1987 by the Ocean Drilling Program at Hole 690B at Maud Rise in the South Atlantic Ocean. At this location, the PETM CIE, from start to end, spans about 2 m. Long-term age constraints, through biostratigraphy and magnetostratigraphy , suggest an average Paleogene sedimentation rate of about 1.23 cm/1,000yrs. Assuming

32960-434: The original areas the stages were defined, accessibility, and the protected status of the area due to its geological significance. The Selandian was first proposed by Danish geologist Alfred Rosenkrantz in 1924 based on a section of fossil-rich glauconitic marls overlain by gray clay which unconformably overlies Danian chalk and limestone . The area is now subdivided into the Æbelø Formation , Holmehus Formation , and

33166-402: The poles through an ice–albedo feedback . It may be the case, however, that during the PETM, this feedback was largely absent because of limited polar ice, so temperatures on the Equator and at the poles increased similarly. Notable is the absence of documented greater warming in polar regions compared to other regions. This implies a non-existing ice-albedo feedback, suggesting no sea or land ice

33372-419: The poles. Central China during the PETM hosted dense subtropical forests as a result of the significant increase in rates of precipitation in the region, with average temperatures between 21 °C and 24 °C and mean annual precipitation ranging from 1,396 to 1,997 mm. Similarly, Central Asia became wetter as proto-monsoonal rainfall penetrated farther inland. Very high precipitation is also evidenced in

33578-515: The poles—but they had low species richness in regards to plant life, and were populated by mainly small creatures that were rapidly evolving to take advantage of the recently emptied Earth. Though some animals attained great size, most remained rather small. The forests grew quite dense in the general absence of large herbivores. Mammals proliferated in the Paleocene, and the earliest placental and marsupial mammals are recorded from this time, but most Paleocene taxa have ambiguous affinities . In

33784-405: The presence of extensive intrusive sill complexes and thousands of kilometer-sized hydrothermal vent complexes in sedimentary basins on the mid-Norwegian margin and west of Shetland. This hydrothermal venting occurred at shallow depths, enhancing its ability to vent gases into the atmosphere and influence the global climate. Volcanic eruptions of a large magnitude can impact global climate, reducing

33990-685: The presence of sulphur-bound isorenieratane. The Gulf Coastal Plain was also affected by euxinia. The Atlantic Coastal Plain , well oxygenated during the Late Palaeocene, became highly dysoxic during the PETM. The tropical surface oceans, in contrast, remained oxygenated over the course of the hyperthermal event. It is possible that during the PETM's early stages, anoxia helped to slow down warming through carbon drawdown via organic matter burial. A pronounced negative lithium isotope excursion in both marine carbonates and local weathering inputs suggests that weathering and erosion rates increased during

34196-444: The proliferation of sulfate-reducing microorganisms which create highly toxic hydrogen sulfide H 2 S as a waste product. During the event, the volume of sulfidic water may have been 10–20% of total ocean volume, in comparison to today's 1%. This may have also caused chemocline upwellings along continents and the dispersal of H 2 S into the atmosphere. During the PETM there was a temporary dwarfing of mammals apparently caused by

34402-610: The proposal was officially published in 2006. The Selandian and Thanetian are both defined in Itzurun beach by the Basque town of Zumaia , 43°18′02″N 2°15′34″W  /  43.3006°N 2.2594°W  / 43.3006; -2.2594 , as the area is a continuous early Santonian to early Eocene sea cliff outcrop . The Paleocene section is an essentially complete, exposed record 165 m (541 ft) thick, mainly composed of alternating hemipelagic sediments deposited at

34608-404: The recently emptied landscape, or a response to the increased amount of shade provided in a forested landscape. Lycopods , ferns, and angiosperm shrubs may have been important components of the Paleocene understory . In general, the forests of the Paleocene were species-poor, and diversity did not fully recover until the end of the Paleocene. For example, the floral diversity of what is now

34814-675: The region at the PETM. During the Paleocene, the continents continued to drift toward their present positions. In the Northern Hemisphere, the former components of Laurasia (North America and Eurasia) were, at times, connected via land bridges: Beringia (at 65.5 and 58 mya) between North America and East Asia, the De Geer route (from 71 to 63 mya) between Greenland and Scandinavia , the Thulean route (at 57 and 55.8 mya) between North America and Western Europe via Greenland, and

35020-633: The region more arid. This aridification was interrupted, however, in the spinatus ammonite biozone and across the Pliensbachian-Toarcian boundary itself. The large rise in sea levels resulting from the intense global warming led to the formation of the Laurasian Seaway, which enabled the flow of cool water low in salt content to flow into the Tethys Ocean from the Arctic Ocean . The opening of this seaway may have potentially acted as

35226-408: The rest of the open ocean, changes in nutrient availability were their dominant drivers. Acidification did lead to an abundance of heavily calcified algae and weakly calcified forams. The calcareous nannofossil species Neochiastozygus junctus thrived; its success is attributable to enhanced surficial productivity caused by enhanced nutrient runoff. Eutrophication at the onset of the PETM precipitated

35432-472: The result of dramatic changes in weathering and sedimentation rates, drove diversification of magnetite-forming organisms, likely including eukaryotes. Biogenic magnetites in animals have a crucial role in geomagnetic field navigation. The PETM is accompanied by significant changes in the diversity of calcareous nannofossils and benthic and planktonic foraminifera. A mass extinction of 35–50% of benthic foraminifera (especially in deeper waters) occurred over

35638-458: The rough, uneven bathymetry in the northward limb of this gyre, oxic bottom waters had relatively few impediments to diffuse into the southwestern Tethys, which spared it from the far greater prevalence of anoxia and euxinia that characterised the northern Tethys. The Panthalassan deep water site of Sakahogi was mainly anoxic-ferruginous across the interval spanning the late Pliensbachian to the TOAE, but transient sulphidic conditions did occur during

35844-823: The same is true in the North Dakotan Almont/Beicegel Creek —such as Ochnaceae , Cyclocarya , and Ginkgo cranei —indicating the same floral families have characterized South American rainforests and the American Western Interior since the Paleocene. The extinction of large herbivorous dinosaurs may have allowed the forests to grow quite dense, and there is little evidence of wide open plains. Plants evolved several techniques to cope with high plant density, such as buttressing to better absorb nutrients and compete with other plants, increased height to reach sunlight, larger diaspore in seeds to provide added nutrition on

36050-406: The seafloor renders lower values than when formed. On the other hand, these and other temperature proxies (e.g., TEX 86 ) are impacted at high latitudes because of seasonality; that is, the "temperature recorder" is biased toward summer, and therefore higher values, when the production of carbonate and organic carbon occurred. Clear evidence for massive addition of C-depleted carbon at the onset of

36256-437: The seafloor to be recycled back into the photic zone, driving widespread primary productivity and in turn anoxia. The freshening of the Arctic Ocean by way of melting of Northern Hemisphere ice caps was a likely trigger of such stratification and a slowdown of global thermohaline circulation. Stratification also occurred due to the freshening of surface water caused by an enhanced water cycle. Rising seawater temperatures amidst

36462-574: The seas, ray-finned fish rose to dominate open ocean and recovering reef ecosystems. The word "Paleocene" was first used by French paleobotanist and geologist Wilhelm Philipp Schimper in 1874 while describing deposits near Paris (spelled "Paléocène" in his treatise). By this time, Italian geologist Giovanni Arduino had divided the history of life on Earth into the Primary ( Paleozoic ), Secondary ( Mesozoic ), and Tertiary in 1759; French geologist Jules Desnoyers had proposed splitting off

36668-515: The source of debate. In theory, it can be estimated from the magnitude of the negative carbon isotope excursion (CIE), the amount of carbonate dissolution on the seafloor, or ideally both. However, the shift in the δ C across the PETM depends on the location and the carbon-bearing phase analyzed. In some records of bulk carbonate, it is about 2‰ (per mil); in some records of terrestrial carbonate or organic matter it exceeds 6‰. Carbonate dissolution also varies throughout different ocean basins. It

36874-482: The stratosphere. Furthermore, phases of volcanic activity could have triggered the release of methane clathrates and other potential feedback loops. NAIP volcanism influenced the climatic changes of the time not only through the addition of greenhouse gases but also by changing the bathymetry of the North Atlantic. The connection between the North Sea and the North Atlantic through the Faroe-Shetland Basin

37080-513: The temperatures of the bottom water. However, many ocean basins remained bioturbated through the PETM. Iodine to calcium ratios suggest oxygen minimum zones in the oceans expanded vertically and possibly also laterally. Water column anoxia and euxinia was most prevalent in restricted oceanic basins, such as the Arctic and Tethys Oceans. Euxinia struck the epicontinental North Sea Basin as well, as shown by increases in sedimentary uranium , molybdenum , sulphur , and pyrite concentrations, along with

37286-471: The thermal maximum. Paleocene The Paleocene ( IPA : / ˈ p æ l i . ə s iː n , - i . oʊ -, ˈ p eɪ l i -/ PAL -ee-ə-seen, -⁠ee-oh-, PAY -lee- ), or Palaeocene , is a geological epoch that lasted from about 66 to 56 million years ago (mya). It is the first epoch of the Paleogene Period in the modern Cenozoic Era . The name is a combination of

37492-657: The time, such as the Bächental bituminous marls, though its occurrence in areas like Greece has been cited as evidence of its global nature. The negative δ C shift is also known from the Arabian Peninsula , the Ordos Basin , and the Neuquén Basin . The negative δ C excursion has been found to be up to -8% in bulk organic and carbonate carbon, although analysis of compound specific biomarkers suggests

37698-467: The tropics during the PETM, enough to cause heat stress even in organisms resistant to extreme thermal stress, such as dinoflagellates, of which a significant number of species went extinct. Oxygen isotope ratios from Tanzania suggest that tropical SSTs may have been even higher, exceeding 40 °C. Ocean Drilling Program Site 1209 from the tropical western Pacific shows an increase in SST from 34 °C before

37904-471: The upper limit, average sea surface temperatures (SSTs) at 60° N and S would have been the same as deep sea temperatures, at 30° N and S about 23 °C (73 °F), and at the equator about 28 °C (82 °F). In the Danish Palaeocene sea, SSTs were cooler than those of the preceding Late Cretaceous and the succeeding Eocene. The Paleocene foraminifera assemblage globally indicates

38110-498: The upward excursion in temperature. The warm, wet climate supported tropical and subtropical forests worldwide, mainly populated by conifers and broad-leafed trees. In Patagonia, the landscape supported tropical rainforests , cloud rainforests , mangrove forests , swamp forests , savannas , and sclerophyllous forests. In the Colombian Cerrejón Formation , fossil flora belong to the same families as modern day flora—such as palm trees , legumes , aroids , and malvales —and

38316-405: The wake of the extinction event, many derived clades of ornithischians, sauropods, and theropods emerged, with most of these post-extinction clades greatly increasing in size relative to dinosaurs before the TOAE. Eusauropods were propelled to ecological dominance after their survival of the Toarcian cataclysm. Megalosaurids experienced a diversification event in the latter part of the Toarcian that

38522-599: The world by a high- iridium band, as well as discontinuities with fossil flora and fauna. It is generally thought that a 10 to 15 km (6 to 9 mi) wide asteroid impact, forming the Chicxulub Crater in the Yucatán Peninsula in the Gulf of Mexico , and Deccan Trap volcanism caused a cataclysmic event at the boundary resulting in the extinction of 75% of all species. The Paleocene ended with

38728-419: Was a negative feedback loop retarding the otherwise pronounced warming and may have caused global cooling in the aftermath of the TOAE. In anoxic and euxinic marine basins in Europe, organic carbon burial rates increased by ~500%. Furthermore, anoxia was not limited to oceans; large lakes also experienced oxygen depletion and black shale deposition. Euxinia occurred in the northwestern Tethys Ocean during

38934-514: Was covered in tropical rainforests and tropical seasonal forests. Sediment deposition changed significantly at many outcrops and in many drill cores spanning this time interval. During the PETM, sediments are enriched with kaolinite from a detrital source due to denudation (initial processes such as volcanoes , earthquakes , and plate tectonics ). Increased precipitation and enhanced erosion of older kaolinite-rich soils and sediments may have been responsible for this. Increased weathering from

39140-455: Was due to an ejection of 2,500–4,500 gigatons of carbon into the atmosphere, most commonly explained as the perturbation and release of methane clathrate deposits in the North Atlantic from tectonic activity and resultant increase in bottom water temperatures. Other proposed hypotheses include methane release from the heating of organic matter at the seafloor rather than methane clathrates, or melting permafrost . The duration of carbon output

39346-487: Was extreme in parts of the north and central Atlantic Ocean, but far less pronounced in the Pacific Ocean. With available information, estimates of the carbon addition range from about 2,000 to 7,000 gigatons. The timing of the PETM δ C excursion is of considerable interest. This is because the total duration of the CIE, from the rapid drop in δ C through the near recovery to initial conditions, relates to key parameters of our global carbon cycle, and because

39552-426: Was little or no polar ice in the early Paleogene, the shift in δ O very probably signifies a rise in ocean temperature. The temperature rise is also supported by the spread of warmth-loving taxa to higher latitudes, changes in plant leaf shape and size, the Mg/Ca ratios of foraminifera, and the ratios of certain organic compounds , such as TEX 86 . Proxy data from Esplugafereda in northeastern Spain shows

39758-530: Was not a major contributor to the greenhouse climate, and deep water temperatures more likely change as a response to global temperature change rather than affecting it. In the Arctic, coastal upwelling may have been largely temperature and wind-driven. In summer, the land surface temperature was probably higher than oceanic temperature, and the opposite was true in the winter, which is consistent with monsoon seasons in Asia. Open-ocean upwelling may have also been possible. The Paleocene climate was, much like in

39964-429: Was not much angiosperm migration into the region in the early Paleocene. Over the K–Pg extinction event, angiosperms had a higher extinction rate than gymnosperms (which include conifers, cycads , and relatives) and pteridophytes (ferns, horsetails , and relatives); zoophilous angiosperms (those that relied on animals for pollination) had a higher rate than anemophilous angiosperms; and evergreen angiosperms had

40170-440: Was officially defined as the Paleocene, Eocene, and Oligocene Epochs; and the Neogene as the Miocene and Pliocene Epochs. In 1989, Tertiary and Quaternary were removed from the time scale due to the arbitrary nature of their boundary, but Quaternary was reinstated in 2009. The term "Paleocene" is a portmanteau combination of the Ancient Greek palaios παλαιός meaning "old", and the word "Eocene", and so means "the old part of

40376-439: Was one of the most significant periods of global change during the Cenozoic. Geologists divide the rocks of the Paleocene into a stratigraphic set of smaller rock units called stages , each formed during corresponding time intervals called ages. Stages can be defined globally or regionally. For global stratigraphic correlation, the ICS ratify global stages based on a Global Boundary Stratotype Section and Point (GSSP) from

40582-432: Was particularly severe. At Ya Ha Tinda, a replacement of the pre-TOAE bivalve assemblage by a smaller, post-TOAE assemblage occurred, while in the Cleveland Basin , the inoceramid Pseudomytiloides dubius experienced the Lilliput effect . Ammonoids , having already experienced a major morphological bottleneck thanks to the Gibbosus Event, about a million years before the Toarcian extinction, suffered further losses in

40788-519: Was possibly a post-extinction radiation that filled niches vacated by the mass death of the Early Toarcian extinction. Insects may have experienced blooms as fish moved en masse to surface waters to escape anoxia and then died in droves due to limited resources. The volcanogenic extinction event initially impacted terrestrial ecosystems more severely than marine ones. A shift towards a low diversity assemblage of cheirolepid conifers, cycads , and Cerebropollenites -producers adapted for high aridity from

40994-455: Was present in the late Paleocene. Precise limits on the global temperature rise during the PETM and whether this varied significantly with latitude remain open issues. Oxygen isotope and Mg/Ca of carbonate shells precipitated in surface waters of the ocean are commonly used measurements for reconstructing past temperature; however, both paleotemperature proxies can be compromised at low latitude locations, because re-crystallization of carbonate on

41200-440: Was severely restricted, as was its connection to it by way of the English Channel . Later phases of NAIP volcanic activity may have caused the other hyperthermal events of the Early Eocene as well, such as ETM2. It has also been suggested that volcanic activity around the Caribbean may have disrupted the circulation of oceanic currents, amplifying the magnitude of climate change. The presence of later (smaller) warming events of

41406-417: Was shown that the Danian and the Montian are the same, the ICS decided to define the Danian as starting with the K–Pg boundary, thus ending the practice of including the Danian in the Cretaceous. In 1991, the GSSP was defined as a well-preserved section in the El Haria Formation near El Kef , Tunisia, 36°09′13″N 8°38′55″E  /  36.1537°N 8.6486°E  / 36.1537; 8.6486 , and

41612-403: Was slow and sluggish, being regularly set back thanks to recurrent episodes of oxygen depletion, which continued for hundreds of thousands of years after the main extinction interval. Evidence from the Cleveland Basin suggests it took ~7 Myr for the marine benthos to recover, on par with the Permian-Triassic extinction event . Many marine invertebrate taxa found in South America migrated through

41818-425: Was still connected to South America and Australia, and, because of this, the Antarctic Circumpolar Current —which traps cold water around the continent and prevents warm equatorial water from entering—had not yet formed. Its formation may have been related in the freezing of the continent. Warm coastal upwellings at the poles would have inhibited permanent ice cover. Conversely, it is possible deep water circulation

42024-405: Was the further exacerbation of eutrophication and anoxia. The extreme and rapid global warming at the start of the Toarcian promoted intensification of tropical storms across the globe. The extinction event associated with the TOAE primarily affected marine life as a result the collapse of the carbonate factory. Brachiopods were particularly severely hit, with the TOAE representing one of

42230-582: Was unbelievably catastrophic for corals ; 90.9% of all Tethyan coral species and 49% of all genera were wiped out. Calcareous nannoplankton that lived in the deep photic zone suffered, with the decrease in abundance of the taxon Mitrolithus jansae used as an indicator of shoaling of the oxygen minimum zone in the Tethys and the Hispanic Corridor. Other affected invertebrate groups included echinoderms , radiolarians , dinoflagellates , and foraminifera . Trace fossils , an indicator of bioturbation and ecological diversity, became highly undiverse following

42436-436: Was wetter than the Northern, or the Southern experienced less evaporation than the Northern. In either case, this would have made the Northern more saline than the Southern, creating a density difference and a downwelling in the North Pacific traveling southward. Deep water formation may have also occurred in the South Atlantic. It is largely unknown how global currents could have affected global temperature. The formation of

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