Paleocene–Eocene Thermal Maximum

"PETM" redirects here. Not to be confused with PETN.

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 time period with a more than 5–8 °C global average temperature rise across the event.^[1][2] This climate event occurred at the time boundary of the Paleocene and Eocene geological epochs.^[3] The exact age and duration of the event is uncertain but it is estimated to have occurred around 55.5 million years ago (Ma).^[4]

Climate change during the last 65 million years as expressed by the oxygen isotope composition of benthic foraminifera. The Paleocene-Eocene thermal maximum (PETM) is characterized by a brief but prominent excursion, attributed to rapid warming. Note that the excursion is understated in this graph due to the smoothing of data.

The associated period of massive carbon release into the atmosphere has been estimated to have lasted from 20,000 to 50,000 years. The entire warm period lasted for about 200,000 years. Global temperatures increased by 5–8 °C.^[2]

The onset of the Paleocene–Eocene thermal maximum has been linked to volcanism^[1] and uplift associated with the North Atlantic Igneous Province, causing extreme changes in Earth's carbon cycle and a significant temperature rise.^[2][5][6] The period is marked by a prominent negative excursion in carbon stable isotope (δ¹³C) records from around the globe; more specifically, there was a large decrease in ¹³C/¹²C ratio of marine and terrestrial carbonates and organic carbon.^[2][7][8] Paired δ¹³C, δ¹¹B, and δ¹⁸O data suggest that ~12000 Gt of carbon (at least 44000 Gt CO₂e) were released over 50,000 years,^[5] averaging 0.24 Gt per year.

Stratigraphic sections of rock from this period reveal numerous other changes.^[2] Fossil records for many organisms show major turnovers. For example, in the marine realm, a mass extinction of benthic foraminifera, a global expansion of subtropical dinoflagellates, and an appearance of excursion, planktic foraminifera and calcareous nannofossils all occurred during the beginning stages of PETM. On land, modern mammal orders (including primates) suddenly appear in Europe and in North America.^[9]

Paleogene graphical timeline
This box: view talk edit
−65 — – −60 — – −55 — – −50 — – −45 — – −40 — – −35 — – −30 — – −25 — –	M Z C e n o z o i c Cretaceous P a l e o g e n e Neogene P a l e o c e n e E o c e n e O l i g o c e n e Danian Selandian Thanetian Ypresian Lutetian Bartonian Priabonian Rupelian Chattian	← PETM ← First Antarctic permanent ice-sheets^[10] ← K-Pg mass extinction
Subdivision of the Paleogene according to the ICS, as of 2021.^[11] Vertical axis scale: millions of years ago

Setting

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 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 CO₂ levels in the Eocene do not agree in absolute terms, all suggest that levels then were much higher than at present. In any case, there were no significant ice sheets during this time.^[12]

Earth surface temperatures increased by about 6 °C from the late Paleocene through the early Eocene.^[12] Superimposed on this long-term, gradual warming were at least two (and probably more) "hyperthermals". These can be defined as geologically brief (<200,000 year) events characterized by rapid global warming, major changes in the environment, and massive carbon addition. Though not the first within the Cenozoic,^[13] the PETM was the most extreme of these hyperthermals. Another hyperthermal clearly occurred at approximately 53.7 Ma, and is now called ETM-2 (also referred to as H-1, or the Elmo event). However, additional hyperthermals probably occurred 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).^[14] The number, nomenclature, absolute ages, and relative global impact of the Eocene hyperthermals are the source of considerable 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.

Global warming

 

A stacked record of temperatures and ice volume in the deep ocean through the Mesozoic and Cenozoic periods.
LPTM— Paleocene-Eocene thermal maximum
OAEs— oceanic anoxic events
MME— mid-Maastrichtian event

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).^[15] Estimates of the amount of average global temperature rise at the start of the PETM range from approximately 3 to 6 °C^[16] to between 5 and 8 °C.^[2] 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 δ¹⁸O of foraminifera shells, both those made in surface and deep ocean water. Because there was little or no polar ice in the early Paleogene, the shift in δ¹⁸O very probably signifies a rise in ocean temperature.^[17] The temperature rise is also supported by the spread of warmth-loving taxa to higher latitudes,^[18] changes in plant leaf shape and size,^[19] the Mg/Ca ratios of foraminifera,^[16] and the ratios of certain organic compounds, such as TEX^H₈₆.^[20]

Proxy data from Esplugafereda in northeastern Spain shows a rapid +8 °C temperature rise, in accordance with existing regional records of marine and terrestrial environments.^[21]

TEX^H₈₆ values indicate that the average sea surface temperature (SST) reached over 36 °C (97 °F) in 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.^[20] Oxygen isotope ratios from Tanzania suggest that tropical SSTs may have been even higher, exceeding 40 °C.^[22] Low latitude Indian Ocean Mg/Ca records show seawater at all depths warmed by ~4-5 °C.^[23] In the Pacific Ocean, tropical SSTs increased by about 4-5 °C.^[24] TEX^L₈₆ values from deposits in New Zealand, then located between 50°S and 60°S in the southwestern Pacific,^[25] 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 the boundary between the Selandian and Thanetian.^[26] The extreme warmth of the southwestern Pacific extended into the Australo-Antarctic Gulf.^[27] 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.^[28] In the North Sea, SSTs jumped by 10 °C, reaching highs of ~33 °C.^[29]

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.^[30] Moreover, temperatures increased during the PETM, as indicated by the brief presence of subtropical dinoflagellates,^[31] and a marked increase in TEX₈₆.^[32] 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 TEX₈₆ 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 the poles through an ice–albedo feedback.^[33] 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 was present in the late Paleocene.^[4]

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 the seafloor renders lower values than when formed. On the other hand, these and other temperature proxies (e.g., TEX₈₆) 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.

Carbon cycle disturbance

Clear evidence for massive addition of ¹³C-depleted carbon at the onset of the PETM comes from two observations. First, a prominent negative excursion in the carbon isotope composition (δ¹³C) 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.^[2]

The total mass of carbon injected to the ocean and atmosphere during the PETM remains 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.^[34][35] However, the shift in the δ¹³C 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‰.^[36][2][37] Carbonate dissolution also varies throughout different ocean basins. It was extreme in parts of the north and central Atlantic Ocean, but far less pronounced in the Pacific Ocean.^[35][38][39] With available information, estimates of the carbon addition range from about 2,000 to 7,000 gigatons.^[35][38][39]

Timing of carbon addition and warming

The timing of the PETM δ¹³C excursion is of considerable interest. This is because the total duration of the CIE, from the rapid drop in δ¹³C through the near recovery to initial conditions, relates to key parameters of our global carbon cycle, and because the onset provides insight to the source of ¹³C-depleted CO₂.

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 a constant sedimentation rate, the entire event, from onset though termination, was therefore estimated at 200,000 years.^[7] 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 ¹³C-depleted CO₂ 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.^[40] 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.^[41]

A ~200,000 year duration for the CIE is estimated from models of global carbon cycling.^[42]

Age constraints at several deep-sea sites have been independently examined using ³He 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 ³He records support a faster recovery to near initial conditions (<100,000 years) than predicted by flushing via weathering inputs and carbonate and organic outputs.^[43]

There is other evidence to suggest that warming predated the δ¹³C excursion by some 3,000 years.^[44]

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.^[45] Organic matter degradation by microbes has also been implicated as a source of skewing of carbon isotopic ratios in bulk organic matter.^[46]

Effects

Precipitation

 

Azolla floating ferns, fossils of this genus indicate subtropical weather at the North Pole

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.^[47] 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 the poles.^[48] 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.^[49] Very high precipitation is also evidenced in the Cambay Shale Formation of India by the deposition of thick lignitic seams as a consequence of increased soil erosion and organic matter burial.^[50] Precipitation rates in the North Sea likewise soared during the PETM.^[51] 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 a closed marsh to an open, eutrophic swamp with frequent algal blooms.^[52] Precipitation patterns became highly unstable along the New Jersey Shelf.^[53] In the Rocky Mountain Interior, precipitation locally declined, however,^[54] as the interior of North America became more seasonally arid.^[55] 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.^[56] Evidence from Forada in northeastern Italy suggests that arid and humid climatic intervals alternated over the course of the PETM concomitantly with precessional cycles in mid-latitudes, and that overall, net precipitation over the central-western Tethys decreased.^[57]

Ocean

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.^[47] The flux of freshwater entering the oceans increased drastically during the PETM, and continued for a time after the PETM's termination.^[58]

Anoxia

Main article: Anoxic event

The PETM generated the only oceanic anoxic event (OAE) of the Cenozoic.^[59] 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 the temperatures of the bottom water.^[38] However, many ocean basins remained bioturbated through the PETM.^[60] Iodine to calcium ratios suggest oxygen minimum zones in the oceans expanded vertically and possibly also laterally.^[61] Water column anoxia and euxinia was most prevalent in restricted oceanic basins, such as the Arctic and Tethys Oceans.^[62] Euxinia struck the epicontinental North Sea Basin as well,^[63] as shown by increases in sedimentary uranium, molybdenum, sulphur, and pyrite concentrations,^[64] along with the presence of sulphur-bound isorenieratane.^[63] The Gulf Coastal Plain was also affected by euxinia.^[65]

It is possible that during the PETM's early stages, anoxia helped to slow down warming through carbon drawdown via organic matter burial.^[66][67] A pronounced negative lithium isotope excursion in both marine carbonates and local weathering inputs suggests that weathering and erosion rates increased during the PETM, generating an increase in organic carbon burial, which acted as a negative feedback on the PETM's severe global warming.^[68]

Sea level

Main articles: Past sea level § Changes through geologic time, and Sea level rise

Along with the global lack of ice, the sea level would have risen due to thermal expansion.^[32] 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.^[32]

Currents

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 the deep oceans, enhancing further warming.^[69] The major biotic turnover among benthic foraminifera has been cited as evidence of a significant change in deep water circulation.^[70]

Acidification

Ocean acidification occurred during the PETM,^[71] causing the calcite compensation depth to shoal.^[72] The lysocline marks the depth at which carbonate starts to dissolve (above the lysocline, carbonate is oversaturated): today, this 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 CO₂ dissolved in the ocean. Adding CO₂ 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 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 the onset of the event. Acidification of deep waters, and the later spreading from the North Atlantic can explain spatial variations in carbonate dissolution.^[73] In parts of the southeast Atlantic, the lysocline rose by 2 km in just a few thousand years.^[60] Evidence from the tropical Pacific Ocean suggests a minimum lysocline shoaling of around 500 m at the time of this hyperthermal.^[74] Acidification may have increased 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.^[75] 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 the PETM.^[76] 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.^[77]

Life

Stoichiometric magnetite (Fe
₃O
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.^[78] 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, the result of dramatic changes in weathering and sedimentation rates, drove diversification of magnetite-forming organisms, likely including eukaryotes.^[79] Biogenic magnetites in animals have a crucial role in geomagnetic field navigation.^[80]

Ocean

The PETM is accompanied by significant changes in the diversity of calcareous nannofossils and benthic and planktonic foraminifera.^[81] A mass extinction of 35–50% of benthic foraminifera (especially in deeper waters) occurred over the course of ~1,000 years, with the group suffering more during the PETM than during the dinosaur-slaying K-T extinction.^[82][83][84] At the onset of the PETM, benthic foraminiferal diversity dropped by 30% in the Pacific Ocean,^[85] while at Zumaia in what is now Spain, 55% of benthic foraminifera went extinct over the course of the PETM,^[86] though this decline was not ubiquitous to all sites; Himalayan platform carbonates show no major change in assemblages of large benthic foraminifera at the onset of the PETM; their decline came about towards the end of the event.^[87] A decrease in diversity and migration away from the oppressively hot tropics indicates planktonic foraminifera were adversely affected as well.^[88] The Lilliput effect is observed in shallow water foraminifera,^[89] possibly as a response to decreased surficial water density or diminished nutrient availability.^[90] The nannoplankton genus Fasciculithus went extinct as a result of increased surface water oligotrophy;^[91] the genera Sphenolithus, Zygrhablithus, Octolithus suffered badly too.^[92] Contrarily, the dinoflagellate Apectodinium bloomed.^[93][94] The fitness of Apectodinium homomorphum stayed constant over the PETM while that of others declined.^[95]

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.^[96] 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 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 ^[97] and/or increased remineralization of organic matter in the water column, before it reached the benthic foraminifera on the sea floor.^[98] 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 CO₂ levels result in a decreased oceanic pH, which has a profound negative effect on corals.^[99] Experiments suggest it is also very harmful to calcifying plankton.^[100] However, the strong acids used to simulate the natural increase in acidity which would result from elevated CO₂ 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.^[101] No change in the distribution of calcareous nanoplankton such as the coccolithophores can be attributed to acidification during the PETM.^[101] Extinction rates among calcareous nannoplakton increased, but so did origination rates.^[102] Acidification did lead to an abundance of heavily calcified algae^[91] and weakly calcified forams.^[103] The calcareous nannofossil species Neochiastozygus junctus thrived; its success is attributable to enhanced surficial productivity caused by enhanced nutrient runoff.^[104] Eutrophication at the onset of the PETM precipitated a decline among K-strategist large foraminifera, though they rebounded during the post-PETM oligotrophy coevally with the demise of low-latitude corals.^[105]

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.^[106]

Land

Humid conditions caused migration of modern Asian mammals northward, dependent on the climatic belts. Uncertainty remains for the timing and tempo of migration.^[21]

The increase in mammalian abundance is intriguing. Increased global temperatures may have promoted dwarfing^{[107][108][109]} – which may have encouraged speciation. Major dwarfing occurred early in the PETM, with further dwarfing taking place during the middle of the hyperthermal.^[9] 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.^[110] 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.^[111][107]

The diversity of insect herbivory, as measured by the amount and diversity of damage to plants caused by insects, increased during the PETM in correlation with global warming.^[112] The ant genus Gesomyrmex radiated across Eurasia during the PETM.^[113] As with mammals, soil-dwelling invertebrates are observed to have dwarfed during the PETM.^[114]

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.^[115]

Geologic effects

Sediment deposition changed significantly at many outcrops and in many drill cores spanning this time interval.^[116] During the PETM, sediments are enriched with kaolinite from a detrital source due to denudation (initial processes such as volcanoes, earthquakes, and plate tectonics).^[117][118] Increased precipitation and enhanced erosion of older kaolinite-rich soils and sediments may have been responsible for this.^{[119][120][121]} Increased weathering from the enhanced runoff formed thick paleosoil enriched with carbonate nodules (Microcodium like), and this suggests a semi-arid climate.^[21] Unlike during lesser, more gradual hyperthermals, glauconite authigenesis was inhibited.^[122]

The sedimentological effects of the PETM lagged behind the carbon isotope shifts.^[123] In the Tremp-Graus Basin of northern Spain, fluvial systems grew and rates of deposition of alluvial sediments increased with a lag time of around 3,800 years after the PETM.^[124]

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.^[125]

Possible causes

Discriminating between different possible causes of 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"^[126]). 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. the carbon contained within the oceans and atmosphere, which can change on short timescales) underwent a −0.2 % to −0.3 % perturbation in δ¹³C, 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 the Paleogene as it is today – something which is very difficult to confirm.

Eruption of large kimberlite field

Although the cause of the initial warming has been attributed to a massive injection of carbon (CO₂ and/or CH₄) 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 the carbon that triggered early warming in the form of exsolved magmatic CO₂. Calculations indicate that the estimated 900–1,100 Pg^[127] 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.^[128] The transfer of warm surface ocean water to intermediate depths led to thermal dissociation of seafloor methane hydrates, providing 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 CO₂ degassing during kimberlite emplacement is a plausible source of the CO₂ responsible for these sudden global warming events.

Volcanic activity

 

Satellite photo of Ardnamurchan – with clearly visible circular shape, which is the 'plumbings of an ancient volcano'

North Atlantic Igneous Province

One of the leading candidates for the cause of the observed carbon cycle disturbances and global warming 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.^[5] Mercury anomalies during the PETM point to massive volcanism during the event.^[129] On top of that, increases in ∆¹⁹⁹Hg show intense volcanism was concurrent with the beginning of the PETM.^[130] Osmium isotopic anomalies in Arctic Ocean sediments dating to the PETM have been interpreted as evidence of a volcanic cause of this hyperthermal.^[131]

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 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.^[132][133] This hydrothermal venting occurred at shallow depths, enhancing its ability to vent gases into the atmosphere and influence the global climate.^[134] Volcanic eruptions of a large magnitude can impact global climate, reducing 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 the stratosphere.^[135] Furthermore, phases of volcanic activity could have triggered the release of methane clathrates and other potential feedback loops.^[38][5][126] 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.^[136] The connection between the North Sea and the North Atlantic through the Faroe-Shetland Basin was severely restricted,^{[137][138][139]} as was its connection to it by way of the English Channel.^[136]

Later phases of NAIP volcanic activity may have caused the other hyperthermal events of the Early Eocene as well, such as ETM2.^[38]

Other volcanic activity

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.^[140]

Orbital forcing

The presence of later (smaller) warming events of 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.^[141] Cores from Howard's Tract, Maryland indicate the PETM occurred as a result of an extreme in axial precession during an orbital eccentricity maximum.^[142] The current warming period is expected to last another 50,000 years due to 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.^[143] 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.^[144]

Comet impact

One theory holds that a ¹²C-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 the thermal maximum.

A key feature and testable prediction of a comet impact is that it should produce virtually instantaneous environmental effects in the atmosphere and surface ocean with later repercussions in the deeper ocean.^[145] Even allowing for feedback processes, this would require at least 100 gigatons of extraterrestrial carbon.^[145] Such a catastrophic impact should have left its mark on the globe. A clay layer of 5-20m thickness on the coastal shelf of New Jersey contained unusual amounts of magnetite, but it was found to have formed 9-18 kyr too late for these magnetic particles to have been a result of a comet's impact, and the particles had a crystal structure which was a signature of magnetotactic bacteria rather than an extraterrestrial origin.^[146] However, recent analyses have shown that isolated particles of non-biogenic origin make up the majority of the magnetic particles in the clay sample.^[147]

A 2016 report in Science describes the discovery of impact ejecta from three marine P-E boundary sections from the Atlantic margin of the eastern U.S., indicating that an extraterrestrial impact occurred during the carbon isotope excursion at the P-E boundary.^[148][149] The silicate glass spherules found were identified as microtektites and microkrystites.^[148]

Burning of peat

The combustion of prodigious quantities of peat was once postulated, because there was probably a greater mass of carbon stored as living terrestrial biomass during the Paleocene than there is today since plants in fact grew more vigorously during the period of the PETM. This theory was refuted, because in order to produce the δ¹³C excursion observed, over 90 percent of the Earth's biomass would have to have been combusted. However, the Paleocene is also recognized as a time of significant peat accumulation worldwide. A comprehensive search failed to find evidence for the combustion of fossil organic matter, in the form of soot or similar particulate carbon.^[150]

Enhanced respiration

Respiration rates of organic matter increase when temperatures rise. One feedback mechanism proposed to explain the rapid rise in carbon dioxide levels is a sudden, speedy rise in terrestrial respiration rates concordant with global temperature rise initiated by any of the other causes of warming.^[151]

Methane clathrate release

Methane hydrate dissolution has been invoked as a highly plausible causal mechanism for the carbon isotope excursion and warming observed at the PETM.^[152] The most obvious feedback mechanism that could amplify the initial perturbation is that of methane clathrates. Under certain temperature and pressure conditions, methane – which is being produced continually by decomposing microbes in sea bottom sediments – is stable in a complex with water, which forms ice-like cages trapping the methane in solid form. As temperature rises, the pressure required to keep this clathrate configuration stable increases, so shallow clathrates dissociate, releasing methane gas to make its way into the atmosphere. Since biogenic clathrates have a δ¹³C signature of −60 ‰ (inorganic clathrates are the still rather large −40 ‰), relatively small masses can produce large δ¹³C excursions. Further, methane is a potent greenhouse gas as it is released into the atmosphere, so it causes warming, and as the ocean transports this warmth to the bottom sediments, it destabilizes more clathrates.^[34]

In order for the clathrate hypothesis to be applicable to PETM, the oceans must show signs of having been warmer slightly before the carbon isotope excursion, because it would take some time for the methane to become mixed into the system and δ¹³C-reduced carbon to be returned to the deep ocean sedimentary record. Up until the 2000s, the evidence suggested that the two peaks were in fact simultaneous, weakening the support for the methane theory. In 2002, a short gap between the initial warming and the δ¹³C excursion was detected.^[153] In 2007, chemical markers of surface temperature (TEX₈₆) had also indicated that warming occurred around 3,000 years before the carbon isotope excursion, although this did not seem to hold true for all cores.^[44] However, research in 2005 found no evidence of this time gap in the deeper (non-surface) waters.^[154] Moreover, the small apparent change in TEX₈₆ that precede the δ¹³C anomaly can easily (and more plausibly) be ascribed to local variability (especially on the Atlantic coastal plain, e.g. Sluijs, et al., 2007) as the TEX₈₆ paleo-thermometer is prone to significant biological effects. The δ¹⁸O of benthic or planktonic forams does not show any pre-warming in any of these localities, and in an ice-free world, it is generally a much more reliable indicator of past ocean temperatures. Analysis of these records reveals another interesting fact: planktonic (floating) forams record the shift to lighter isotope values earlier than benthic (bottom dwelling) forams.^[155] The lighter (lower δ¹³C) methanogenic carbon can only be incorporated into foraminifer shells after it has been oxidised. A gradual release of the gas would allow it to be oxidised in the deep ocean, which would make benthic foraminifera show lighter values earlier. The fact that the planktonic foraminifera are the first to show the signal suggests that the methane was released so rapidly that its oxidation used up all the oxygen at depth in the water column, allowing some methane to reach the atmosphere unoxidised, where atmospheric oxygen would react with it. This observation also allows us to constrain the duration of methane release to under around 10,000 years.^[153]

However, there are several major problems with the methane hydrate dissociation hypothesis. The most parsimonious interpretation for surface-water forams to show the δ¹³C excursion before their benthic counterparts (as in the Thomas et al. paper) is that the perturbation occurred from the top down, and not the bottom up. If the anomalous δ¹³C (in whatever form: CH₄ or CO₂) entered the atmospheric carbon reservoir first, and then diffused into the surface ocean waters, which mix with the deeper ocean waters over much longer time-scales, we would expect to observe the planktonics shifting toward lighter values before the benthics. Moreover, careful examination of the Thomas et al. data set shows that there is not a single intermediate planktonic foram value, implying that the perturbation and attendant δ¹³C anomaly happened over the lifespan of a single foram – much too fast for the nominal 10,000-year release needed for the methane hypothesis to work.^{[citation needed]}

An additional critique of the methane clathrate release hypothesis is that the warming effects of large-scale methane release would not be sustainable for more than a millennium. Thus, exponents of this line of criticism suggest that methane clathrate release could not have been the main driver of the PETM, which lasted for 50,000 to 200,000 years.^[156]

There has been some debate about whether there was a large enough amount of methane hydrate to be a major carbon source; a 2011 paper proposed that was the case.^[157] The present-day global methane hydrate reserve was once considered to be between 2,000 and 10,000 Gt C (billions of tons of carbon), but is now estimated between 1500 and 2000 Gt C.^[158] However, because the global ocean bottom temperatures were ~6 °C higher than today, which implies a much smaller volume of sediment hosting gas hydrate than today, the global amount of hydrate before the PETM has been thought to be much less than present-day estimates.^[156] In a 2006 study, scientists regarded the source of carbon for the PETM to be a mystery.^[159] A 2011 study, using numerical simulations suggests that enhanced organic carbon sedimentation and methanogenesis could have compensated for the smaller volume of hydrate stability.^[157] A 2016 study based on reconstructions of atmospheric CO₂ content during the PETM's carbon isotope excursions (CIE), using triple oxygen isotope analysis, suggests a massive release of seabed methane into the atmosphere as the driver of climatic changes. The authors also state that a massive release of methane hydrates through thermal dissociation of methane hydrate deposits has been the most convincing hypothesis for explaining the CIE ever since it was first identified, according to them.^[160] In 2019, a study suggested that there was a global warming of around 2 degrees several millennia before PETM, and that this warming had eventually destabilized methane hydrates and caused the increased carbon emission during PETM, as evidenced by the large increase in barium ocean concentrations (since PETM-era hydrate deposits would have been also been rich in barium, and would have released it upon their meltdown).^[161] In 2022, a foraminiferal records study had reinforced this conclusion, suggesting that the release of CO² before PETM was comparable to the current anthropogenic emissions in its rate and scope, to the point that that there was enough time for a recovery to background levels of warming and ocean acidification in the centuries to millennia between the so-called pre-onset excursion (POE) and the main event (carbon isotope excursion, or CIE).^[126] A 2021 paper had further indicated that while PETM began with a significant intensification of volcanic activity and that lower-intensity volcanic activity sustained elevated carbon dioxide levels, "at least one other carbon reservoir released significant greenhouse gases in response to initial warming".^[162]

It was estimated in 2001 that it would take around 2,300 years for an increased temperature to diffuse warmth into the sea bed to a depth sufficient to cause a release of clathrates, although the exact time-frame is highly dependent on a number of poorly constrained assumptions.^[163] Ocean warming due to flooding and pressure changes due to a sea-level drop may have caused clathrates to become unstable and release methane. This can take place over as short of a period as a few thousand years. The reverse process, that of fixing methane in clathrates, occurs over a larger scale of tens of thousands of years.^[164]

Ocean circulation

The large scale patterns of ocean circulation are important when considering how heat was transported through the oceans. Our understanding of these patterns is still in a preliminary stage. Models show that there are possible mechanisms to quickly transport heat to the shallow, clathrate-containing ocean shelves, given the right bathymetric profile, but the models cannot yet match the distribution of data we observe. "Warming accompanying a south-to-north switch in deepwater formation would produce sufficient warming to destabilize seafloor gas hydrates over most of the world ocean to a water depth of at least 1900 m." This destabilization could have resulted in the release of more than 2000 gigatons of methane gas from the clathrate zone of the ocean floor.^[165] The timing of changes in ocean circulation with respect to the shift in carbon isotope ratios has been argued to support the proposition that warmer deep water caused methane hydrate release.^[166] However, a different study found no evidence of a change in deep water formation, instead suggesting that deepened subtropical subduction rather than subtropical deep water formation occurred during the PETM.^[167]

Arctic freshwater input into the North Pacific could serve as a catalyst for methane hydrate destabilization, an event suggested as a precursor to the onset of the PETM.^[168]

Recovery

Climate proxies, such as ocean sediments (depositional rates) indicate a duration of ~83 ka, with ~33 ka in the early rapid phase and ~50 ka in a subsequent gradual phase.^[2]

The most likely method of recovery involves an increase in biological productivity, transporting carbon to the deep ocean. This would be assisted by higher global temperatures and CO₂ levels, as well as an increased nutrient supply (which would result from higher continental weathering due to higher temperatures and rainfall; volcanoes may have provided further nutrients). Evidence for higher biological productivity comes in the form of bio-concentrated barium.^[169] However, this proxy may instead reflect the addition of barium dissolved in methane.^[170] Diversifications suggest that productivity increased in near-shore environments, which would have been warm and fertilized by run-off, outweighing the reduction in productivity in the deep oceans.^[103] Another pulse of NAIP volcanic activity may have also played a role in terminating the hyperthermal via a volcanic winter.^[171]

Comparison with today's climate change

Since at least 1997, the Paleocene–Eocene thermal maximum has been investigated in geoscience as an analog to understand the effects of global warming and of massive carbon inputs to the ocean and atmosphere,^[172] including ocean acidification.^[34] Humans today emit about 10 Gt of carbon (about 37 Gt CO2e) per year, and will have released a comparable amount in about 1,000 years at that rate. A main difference is that during the Paleocene–Eocene thermal maximum, the planet was ice-free, as the Drake Passage had not yet opened and the Central American Seaway had not yet closed.^[173] Although the PETM is now commonly held to be a "case study" for global warming and massive carbon emission,^[1][2][35] the cause, details, and overall significance of the event remain uncertain.^{[citation needed]}

Rate of carbon addition

Model simulations of peak carbon addition to the ocean–atmosphere system during the PETM give a probable range of 0.3–1.7 petagrams of carbon per year (Pg C/yr), which is much slower than the currently observed rate of carbon emissions. One petagram of carbon is equivalent to a gigaton of carbon (GtC); the current rate of carbon injection into the atmosphere is over 10 GtC/yr, a rate much greater than the carbon injection rate that occurred during the PETM.^[174] It has been suggested that today's methane emission regime from the ocean floor is potentially similar to that during the PETM.^[175] Because the modern rate of carbon release exceeds the PETM's, it is speculated the a PETM-like scenario is the best-case consequence of anthropogenic global warming, with a mass extinction of a magnitude similar to the Cretaceous-Palaeogene extinction event being a worst-case scenario.^[176]

Similarity of temperatures

Professor of Earth and planetary sciences James Zachos notes that IPCC projections for 2300 in the 'business-as-usual' scenario could "potentially bring global temperature to a level the planet has not seen in 50 million years" – during the early Eocene.^[177] Some have described the PETM as arguably the best ancient analog of modern climate change.^[178] Scientists have investigated effects of climate change on chemistry of the oceans by exploring oceanic changes during the PETM.^[179][180]

Tipping points

A study found that the PETM shows that substantial climate-shifting tipping points in the Earth system exist, which "can trigger release of additional carbon reservoirs and drive Earth's climate into a hotter state".^[181][126]

Climate sensitivity

Whether climate sensitivity was lower or higher during the PETM than today remains under debate. A 2022 study found that the Eurasian Epicontinental Sea acted as a major carbon sink during the PETM due to its high biological productivity and helped to slow and mitigate the warming, and that the existence of many large epicontinental seas at that time made the Earth's climate less sensitive to forcing by greenhouse gases relative to today, when much fewer epicontinental seas exist.^[182] Other research, however, suggests that climate sensitivity was higher during the PETM than today,^[183] meaning that sensitivity to greenhouse gas release increases the higher their concentration in the atmosphere.^[184]

See also

• Abrupt climate change
• Azolla event
• Canfield ocean
• Clathrate gun hypothesis
• Climate sensitivity
• Eocene
• Eocene Thermal Maximum 2
• Paleocene
• Paleogene
• Runaway greenhouse effect

References

1. Haynes, Laura L.; Hönisch, Bärbel (14 September 2020). "The seawater carbon inventory at the Paleocene–Eocene Thermal Maximum". Proceedings of the National Academy of Sciences of the United States of America. 117 (39): 24088–24095. Bibcode:2020PNAS..11724088H. doi:10.1073/pnas.2003197117. PMC 7533689. PMID 32929018.
2. McInherney, F.A.; Wing, S. (2011). "A perturbation of carbon cycle, climate, and biosphere with implications for the future". Annual Review of Earth and Planetary Sciences. 39: 489–516. Bibcode:2011AREPS..39..489M. doi:10.1146/annurev-earth-040610-133431. from the original on 2016-09-14. Retrieved 2016-02-03.
3. Westerhold, T..; Röhl, U.; Raffi, I.; Fornaciari, E.; Monechi, S.; Reale, V.; Bowles, J.; Evans, H. F. (2008). "Astronomical calibration of the Paleocene time" (PDF). Palaeogeography, Palaeoclimatology, Palaeoecology. 257 (4): 377–403. Bibcode:2008PPP...257..377W. doi:10.1016/j.palaeo.2007.09.016. (PDF) from the original on 2017-08-09. Retrieved 2019-07-06.
4. Bowen; et al. (2015). "Two massive, rapid releases of carbon during the onset of the Palaeocene–Eocene thermal maximum". Nature. 8 (1): 44–47. Bibcode:2015NatGe...8...44B. doi:10.1038/ngeo2316.
5. Gutjahr, Marcus; Ridgwell, Andy; Sexton, Philip F.; Anagnostou, Eleni; Pearson, Paul N.; Pälike, Heiko; Norris, Richard D.; Thomas, Ellen; Foster, Gavin L. (August 2017). "Very large release of mostly volcanic carbon during the Palaeocene–Eocene Thermal Maximum". Nature. 548 (7669): 573–577. Bibcode:2017Natur.548..573G. doi:10.1038/nature23646. ISSN 1476-4687. PMC 5582631. PMID 28858305.
6. Jones, S.M.; Hoggett, M.; Greene, S.E.; Jones, T.D. (2019). "Large Igneous Province thermogenic greenhouse gas flux could have initiated Paleocene-Eocene Thermal Maximum climate change". Nature Communications. 10 (1): 5547. Bibcode:2019NatCo..10.5547J. doi:10.1038/s41467-019-12957-1. PMC 6895149. PMID 31804460.
7. Kennett, J.P.; Stott, L.D. (1991). "Abrupt deep-sea warming, palaeoceanographic changes and benthic extinctions at the end of the Paleocene" (PDF). Nature. 353 (6341): 225–229. Bibcode:1991Natur.353..225K. doi:10.1038/353225a0. S2CID 35071922. (PDF) from the original on 2016-03-03. Retrieved 2020-01-08.
8. Koch, P.L.; Zachos, J.C.; Gingerich, P.D. (1992). "Correlation between isotope records in marine and continental carbon reservoirs near the Palaeocene/Eocene boundary". Nature. 358 (6384): 319–322. Bibcode:1992Natur.358..319K. doi:10.1038/358319a0. hdl:2027.42/62634. S2CID 4268991.
9. Van der Meulen, Bas; Gingerich, Philip D.; Lourens, Lucas J.; Meijer, Niels; Van Broekhuizen, Sjors; Van Ginneken, Sverre; Abels, Hemmo A. (15 March 2020). "Carbon isotope and mammal recovery from extreme greenhouse warming at the Paleocene–Eocene boundary in astronomically-calibrated fluvial strata, Bighorn Basin, Wyoming, USA". Earth and Planetary Science Letters. 534: 116044. Bibcode:2020E&PSL.53416044V. doi:10.1016/j.epsl.2019.116044. S2CID 212852180.
10. Zachos, J. C.; Kump, L. R. (2005). "Carbon cycle feedbacks and the initiation of Antarctic glaciation in the earliest Oligocene". Global and Planetary Change. 47 (1): 51–66. Bibcode:2005GPC....47...51Z. doi:10.1016/j.gloplacha.2005.01.001.
11. "International Chronostratigraphic Chart" (PDF). International Commission on Stratigraphy.
12. Zachos, J.C.; Dickens, G.R.; Zeebe, R.E. (2008). "An early Cenozoic perspective on greenhouse warming and carbon-cycle dynamics" (PDF). Nature. 451 (7176): 279–283. Bibcode:2008Natur.451..279Z. doi:10.1038/nature06588. PMID 18202643. S2CID 4360841. (PDF) from the original on 2008-07-05. Retrieved 2008-04-23.
13. Gilmour, Iain; Jolley, David; Kemp, David; Kelley, Simon; Gilmour, Mabs; Daly, Rob; Widdowson, Mike (1 September 2014). "The early Danian hyperthermal event at Boltysh (Ukraine): Relation to Cretaceous-Paleogene boundary events". In Keller, Gerta; Kerr, Andrew C. (eds.). Volcanism, Impacts, and Mass Extinctions: Causes and Effects. Geological Society of America. doi:10.1130/2014.2505(06). ISBN 9780813725055.
14. Thomas, Ellen; Boscolo-Galazzo, Flavia; Balestra, Barbara; Monechi, Simonetta; Donner, Barbara; Röhl, Ursula (1 July 2018). "Early Eocene Thermal Maximum 3: Biotic Response at Walvis Ridge (SE Atlantic Ocean)". Paleoceanography and Paleoclimatology. 33 (8): 862–883. Bibcode:2018PaPa...33..862T. doi:10.1029/2018PA003375. S2CID 133958051. Retrieved 22 November 2022.
15. Inglis, Gordon; et al. (2020). "Global mean surface temperature and climate sensitivity of the early Eocene Climatic Optimum (EECO), Paleocene–Eocene Thermal Maximum (PETM), and latest Paleocene". Climate of the Past. 16 (5): 1953–1968. Bibcode:2020CliPa..16.1953I. doi:10.5194/cp-16-1953-2020. S2CID 227178097.
16. Evans, David; Wade, Bridget S.; Henehan, Michael; Erez, Jonathan; Müller, Wolfgang (6 April 2016). "Revisiting carbonate chemistry controls on planktic foraminifera Mg / Ca: implications for sea surface temperature and hydrology shifts over the Paleocene–Eocene Thermal Maximum and Eocene–Oligocene transition". Climate of the Past. 12 (4): 819–835. Bibcode:2016CliPa..12..819E. doi:10.5194/cp-12-819-2016. Retrieved 5 April 2023.
17. Thomas, Ellen; Shackleton, Nicholas J. (1996). "The Paleocene-Eocene benthic foraminiferal extinction and stable isotope anomalies". Geological Society of London, Special Publications. 101 (1): 401–441. Bibcode:1996GSLSP.101..401T. doi:10.1144/GSL.SP.1996.101.01.20. S2CID 130770597. from the original on 2013-05-21. Retrieved 2013-04-21.
18. Speijer, Robert; Scheibner, Christian; Stassen, Peter; Morsi, Abdel-Mohsen M. (1 May 2012). "Response of marine ecosystems to deep-time global warming: a synthesis of biotic patterns across the Paleocene-Eocene thermal maximum (PETM)". Austrian Journal of Earth Sciences. 105 (1): 6–16. Retrieved 6 April 2023.
19. Wing, Scott L.; Harrington, Guy J.; Smith, Francesca A.; Bloch, Jonathan I.; Boyer, Douglas M.; Freeman, Katherine H. (11 November 2005). "Transient Floral Change and Rapid Global Warming at the Paleocene-Eocene Boundary". Science. 310 (5750): 993–996. Bibcode:2005Sci...310..993W. doi:10.1126/science.1116913. PMID 16284173. S2CID 7069772. Retrieved 6 April 2023.
20. Frieling, Joost; Gebhardt, Holger; Huber, Matthew; Adekeye, Olabisi A.; Akande, Samuel O.; Reichart, Gert-Jan; Middelburg, Jack J.; Schouten, Stefan; Sluijs, Appy (3 March 2017). "Extreme warmth and heat-stressed plankton in the tropics during the Paleocene-Eocene Thermal Maximum". Science Advances. 3 (3): e1600891. Bibcode:2017SciA....3E0891F. doi:10.1126/sciadv.1600891. PMC 5336354. PMID 28275727.
21. Thierry Adatte; Hassan Khozyem; Jorge E. Spangenberg; Bandana Samant & Gerta Keller (2014). "Response of terrestrial environment to the Paleocene-Eocene Thermal Maximum (PETM), new insights from India and NE Spain". Rendiconti della Società Geologica Italiana. 31: 5–6. doi:10.3301/ROL.2014.17.
22. Aze, T.; Pearson, P. N.; Dickson, A. J.; Badger, M. P. S.; Bown, P. R.; Pancost, Richard D.; Gibbs, S. J.; Huber, Brian T.; Leng, M. J.; Coe, A. L.; Cohen, A. S.; Foster, G. L. (1 September 2014). "Extreme warming of tropical waters during the Paleocene–Eocene Thermal Maximum". Geology. 42 (9): 739–742. Bibcode:2014Geo....42..739A. doi:10.1130/G35637.1. S2CID 216051165. Retrieved 6 April 2023.
23. Barnet, James S. K.; Harper, Dustin T.; LeVay, Leah J.; Edgar, Kirsty M.; Henehan, Michael J.; Babila, Tali L.; Ullmann, Clemens V.; Leng, Melanie J.; Kroon, Dick; Zachos, James C.; Littler, Kate (1 September 2020). "Coupled evolution of temperature and carbonate chemistry during the Paleocene–Eocene; new trace element records from the low latitude Indian Ocean". Earth and Planetary Science Letters. 545: 116414. doi:10.1016/j.epsl.2020.116414. S2CID 221369520. Retrieved 3 July 2023.
24. Zachos, James C.; Wara, Michael W.; Bohaty, Steven; Delaney, Margaret L.; Petrizzo, Maria Rose; Brill, Amanda; Bralower, Timothy J.; Premoli-Silva, Isabella (28 November 2003). "A Transient Rise in Tropical Sea Surface Temperature During the Paleocene-Eocene Thermal Maximum". Science. 302 (5650): 1551–1554. Bibcode:2003Sci...302.1551Z. doi:10.1126/science.1090110. PMID 14576441. S2CID 6582869.
25. Hollis, Christopher J.; Taylor, Kyle W. R.; Handley, Luke; Pancost, Richard D.; Huber, Matthew; Creech, John B.; Hines, Benjamin R.; Crouch, Erica M.; Morgans, Hugh E. G.; Crampton, James S.; Gibbs, Samantha; Pearson, Paul N.; Zachos, James C. (15 July 2013). "Erratum to "Early Paleogene temperature history of the Southwest Pacific Ocean: Reconciling proxies and models" [Earth Planet. Sci. Lett. 349 (2012) 53–66]". Earth and Planetary Science Letters. 374: 258–259. Bibcode:2013E&PSL.374..258H. doi:10.1016/j.epsl.2013.06.012. Retrieved 18 September 2022.
26. Hollis, Christopher J.; Taylor, Kyle W. R.; Handley, Luke; Pancost, Richard D.; Huber, Matthew; Creech, John B.; Hines, Benjamin R.; Crouch, Erica M.; Morgans, Hugh E. G.; Crampton, James S.; Gibbs, Samantha; Pearson, Paul N.; Zachos, James C. (1 October 2012). "Early Paleogene temperature history of the Southwest Pacific Ocean: Reconciling proxies and models". Earth and Planetary Science Letters. 349–350: 53–66. Bibcode:2012E&PSL.349...53H. doi:10.1016/j.epsl.2012.06.024. Retrieved 18 September 2022.
27. Frieling, J.; Bohaty, S. M.; Cramwinckel, M. J.; Gallagher, S. J.; Holdgate, G. R.; Reichgelt, T.; Peterse, F.; Pross, J.; Sluijs, A.; Bijl, P. K. (16 February 2023). "Revisiting the Geographical Extent of Exceptional Warmth in the Early Paleogene Southern Ocean". Paleoceanography and Paleoclimatology. 38 (3). doi:10.1029/2022PA004529. ISSN 2572-4517. Retrieved 4 September 2023.
28. Sluijs, Appy; Bijl, P. K.; Schouten, Stefan; Röhl, Ursula; Reichart, G.-J.; Brinkhuis, H. (26 January 2011). "Southern ocean warming, sea level and hydrological change during the Paleocene-Eocene thermal maximum". Climate of the Past. 7 (1): 47–61. doi:10.5194/cp-7-47-2011. Retrieved 19 May 2023.
29. Stokke, Ella W.; Jones, Morgan T.; Tierney, Jessica E.; Svensen, Henrik H.; Whiteside, Jessica H. (15 August 2020). "Temperature changes across the Paleocene-Eocene Thermal Maximum – a new high-resolution TEX86 temperature record from the Eastern North Sea Basin". Earth and Planetary Science Letters. 544: 116388. Bibcode:2020E&PSL.54416388S. doi:10.1016/j.epsl.2020.116388. hdl:10852/81373. S2CID 225387296. Retrieved 3 July 2023.
30. Moran, K.; Backman, J.; Pagani, others (2006). "The Cenozoic palaeoenvironment of the Arctic Ocean". Nature. 441 (7093): 601–605. Bibcode:2006Natur.441..601M. doi:10.1038/nature04800. hdl:11250/174276. PMID 16738653. S2CID 4424147.
31. the dinoflagellates Apectodinium spp.
32. Sluijs, A.; Schouten, S.; Pagani, M.; Woltering, M.; Brinkhuis, H.; Damsté, J.S.S.; Dickens, G.R.; Huber, M.; Reichart, G.J.; Stein, R.; et al. (2006). "Subtropical Arctic Ocean temperatures during the Palaeocene/Eocene thermal maximum" (PDF). Nature. 441 (7093): 610–613. Bibcode:2006Natur.441..610S. doi:10.1038/nature04668. hdl:11250/174280. PMID 16752441. S2CID 4412522.
33. Shellito, Cindy J.; Sloan, Lisa C.; Huber, Matthew (2003). "Climate model sensitivity to atmospheric CO₂ levels in the Early-Middle Paleogene". Palaeogeography, Palaeoclimatology, Palaeoecology. 193 (1): 113–123. Bibcode:2003PPP...193..113S. doi:10.1016/S0031-0182(02)00718-6.
34. Dickens, G.R.; Castillo, M.M.; Walker, J.C.G. (1997). "A blast of gas in the latest Paleocene; simulating first-order effects of massive dissociation of oceanic methane hydrate". Geology. 25 (3): 259–262. Bibcode:1997Geo....25..259D. doi:10.1130/0091-7613(1997)025<0259:abogit>2.3.co;2. PMID 11541226. S2CID 24020720.
35. Zeebe, R.; Zachos, J.C.; Dickens, G.R. (2009). "Carbon dioxide forcing alone insufficient to explain Palaeocene–Eocene Thermal Maximum warming". Nature Geoscience. 2 (8): 576–580. Bibcode:2009NatGe...2..576Z. CiteSeerX 10.1.1.704.7960. doi:10.1038/ngeo578.
36. Zhang, Qinghai; Wendler, Ines; Xu, Xiaoxia; Willems, Helmut; Ding, Lin (June 2017). "Structure and magnitude of the carbon isotope excursion during the Paleocene-Eocene thermal maximum". Gondwana Research. 46: 114–123. doi:10.1016/j.gr.2017.02.016. Retrieved 4 September 2023.
37. Norris, R.D.; Röhl, U. (1999). "Carbon cycling and chronology of climate warming during the Palaeocene/Eocene transition". Nature. 401 (6755): 775–778. Bibcode:1999Natur.401..775N. doi:10.1038/44545. S2CID 4421998.
38. Panchuk, K.; Ridgwell, A.; Kump, L.R. (2008). "Sedimentary response to Paleocene-Eocene Thermal Maximum carbon release: A model-data comparison". Geology. 36 (4): 315–318. Bibcode:2008Geo....36..315P. doi:10.1130/G24474A.1.
39. Cui, Y.; Kump, L.R.; Ridgwell, A.J.; Charles, A.J.; Junium, C.K.; Diefendorf, A.F.; Freeman, K.H.; Urban, N.M.; Harding, I.C. (2011). "Slow release of fossil carbon during the Palaeocene-Eocene thermal maximum". Nature Geoscience. 4 (7): 481–485. Bibcode:2011NatGe...4..481C. doi:10.1038/ngeo1179.
40. Röhl, U.; Bralower, T.J.; Norris, R.D.; Wefer, G. (2000). "New chronology for the late Paleocene thermal maximum and its environmental implications". Geology. 28 (10): 927–930. Bibcode:2000Geo....28..927R. doi:10.1130/0091-7613(2000)28<927:NCFTLP>2.0.CO;2.
41. Röhl, Ursula; Westerhold, Thomas; Bralower, Timothy J.; Zachos, James C. (11 December 2007). "On the duration of the Paleocene-Eocene thermal maximum (PETM)". Geochemistry, Geophysics, Geosystems. 8 (12): 1–13. Bibcode:2007GGG.....812002R. doi:10.1029/2007GC001784. S2CID 53349725. Retrieved 8 April 2023.
42. Dickens, G.R. (2000). "Methane oxidation during the late Palaeocene thermal maximum". Bulletin de la Société Géologique de France. 171: 37–49.
43. Farley, K.A.; Eltgroth, S.F. (2003). "An alternative age model for the Paleocene—Eocene thermal maximum using extraterrestrial ³He". Earth and Planetary Science Letters. 208 (3–4): 135–148. Bibcode:2003E&PSL.208..135F. doi:10.1016/S0012-821X(03)00017-7.
44. Sluijs, A.; Brinkhuis, H.; Schouten, S.; Bohaty, S.M.; John, C.M.; Zachos, J.C.; Reichart, G.J.; Sinninghe Damste, J.S.; Crouch, E.M.; Dickens, G.R. (2007). "Environmental precursors to rapid light carbon injection at the Palaeocene/Eocene boundary". Nature. 450 (7173): 1218–21. Bibcode:2007Natur.450.1218S. doi:10.1038/nature06400. hdl:1874/31621. PMID 18097406. S2CID 4359625.
45. Baczynski, Allison A.; McInerney, Francesca A.; Wing, Scott L.; Kraus, Mary J.; Bloch, Jonathan I.; Boyer, Doug M.; Secord, Ross; Morse, Paul E.; Fricke, Henry J. (6 September 2013). "Chemostratigraphic implications of spatial variation in the Paleocene-Eocene Thermal Maximum carbon isotope excursion, SE Bighorn Basin, Wyoming". Geochemistry, Geophysics, Geosystems. 14 (10): 4133–4152. doi:10.1002/ggge.20265. S2CID 129964067. Retrieved 19 May 2023.
46. Baczynski, Allison A.; McInerney, Francesca A.; Wing, Scott L.; Kraus, Mary J.; Morse, Paul E.; Bloch, Jonathan I.; Chung, Angela H.; Freeman, Katherine H. (1 September 2016). "Distortion of carbon isotope excursion in bulk soil organic matter during the Paleocene-Eocene thermal maximum". Geological Society of America Bulletin. 128 (9–10): 1352–1366. doi:10.1130/B31389.1. Retrieved 19 May 2023.
47. Pagani, M.; Pedentchouk, N.; Huber, M.; Sluijs, A.; Schouten, S.; Brinkhuis, H.; Sinninghe Damsté, J.S.; Dickens, G.R.; Others (2006). "Arctic hydrology during global warming at the Palaeocene/Eocene thermal maximum". Nature. 442 (7103): 671–675. Bibcode:2006Natur.442..671P. doi:10.1038/nature05043. hdl:1874/22388. PMID 16906647. S2CID 96915252.
48. Speelman, E. N.; van Kempen, M. M. L.; Barke, J.; Brinkhuis, H.; Reichart, G. J.; Smolders, A. J. P.; Roelofs, J. G. M.; Sangeorgi, F.; de Leeuw, J. W.; Lotter, A. F.; Sinninghe Damest, J. S. (March 2009). "The Eocene Arctic Azolla bloom: environmental conditions, productivity and carbon drawdown". Geobiology. 7 (2): 155–170. Bibcode:2009Gbio....7..155S. doi:10.1111/j.1472-4669.2009.00195.x. PMID 19323694. S2CID 13206343. Retrieved 12 July 2019.
49. Xie, Yulong; Wu, Fuli; Fang, Xiaomin (January 2022). "A transient south subtropical forest ecosystem in central China driven by rapid global warming during the Paleocene-Eocene Thermal Maximum". Gondwana Research. 101: 192–202. Bibcode:2022GondR.101..192X. doi:10.1016/j.gr.2021.08.005. Retrieved 28 September 2022.
50. Samanta, A.; Bera, M. K.; Ghosh, Ruby; Bera, Subir; Filley, Timothy; Prade, Kanchan; Rathore, S. S.; Rai, Jyotsana; Sarkar, A. (1 October 2013). "Do the large carbon isotopic excursions in terrestrial organic matter across Paleocene–Eocene boundary in India indicate intensification of tropical precipitation?". Palaeogeography, Palaeoclimatology, Palaeoecology. 387: 91–103. Bibcode:2013PPP...387...91S. doi:10.1016/j.palaeo.2013.07.008. Retrieved 15 November 2022.
51. Walters, Gregory L.; Kemp, Simon J.; Hemingway, Jordon D.; Johnston, David T.; Hodell, David A. (22 December 2022). "Clay hydroxyl isotopes show an enhanced hydrologic cycle during the Paleocene-Eocene Thermal Maximum". Nature Communications. 13 (1): 7885. doi:10.1038/s41467-022-35545-2. PMC 9780225. PMID 36550174.
52. Garel, Sylvain; Schnyder, Johann; Jacob, Jérémy; Dupuis, Christian; Boussafir, Mohammed; Le Milbeau, Claude; Storme, Jean-Yves; Iakovleva, Alina I.; Yans, Johan; Baudin, François; Fléhoc, Christine; Quesnel, Florence (15 April 2013). "Paleohydrological and paleoenvironmental changes recorded in terrestrial sediments of the Paleocene–Eocene boundary (Normandy, France)". Palaeogeography, Palaeoclimatology, Palaeoecology. 376: 184–199. doi:10.1016/j.palaeo.2013.02.035. Retrieved 11 June 2023.
53. Sluijs, A.; Brinkhuis, H. (25 August 2009). "A dynamic climate and ecosystem state during the Paleocene-Eocene Thermal Maximum: inferences from dinoflagellate cyst assemblages on the New Jersey Shelf". Biogeosciences. 6 (8): 1755–1781. doi:10.5194/bg-6-1755-2009. ISSN 1726-4189. Retrieved 4 September 2023.
54. Beard, K. Christopher (11 March 2008). "The oldest North American primate and mammalian biogeography during the Paleocene–Eocene Thermal Maximum". Proceedings of the National Academy of Sciences of the United States of America. 105 (10): 3815–3818. Bibcode:2008PNAS..105.3815B. doi:10.1073/pnas.0710180105. PMC 2268774. PMID 18316721.
55. Baczynski, Allison A.; McInerney, Francesca A.; Wing, Scott L.; Kraus, Mary J.; Bloch, Jonathan I.; Secord, Ross (1 January 2017). "Constraining paleohydrologic change during the Paleocene-Eocene Thermal Maximum in the continental interior of North America". Palaeogeography, Palaeoclimatology, Palaeoecology. 465: 237–246. doi:10.1016/j.palaeo.2016.10.030. Retrieved 19 May 2023.
56. Handley, Luke; O'Halloran, Aiofe; Pearson, Paul N.; Hawkins, Elizabeth; Nicholas, Christopher J.; Schouten, Stefan; McMillan, Ian K.; Pancost, Richard D. (15 April 2012). "Changes in the hydrological cycle in tropical East Africa during the Paleocene–Eocene Thermal Maximum". Palaeogeography, Palaeoclimatology, Palaeoecology. 329–330: 10–21. Bibcode:2012PPP...329...10H. doi:10.1016/j.palaeo.2012.02.002. Retrieved 22 April 2023.
57. Giusberti, L.; Boscolo Galazzo, F.; Thomas, E. (9 February 2016). "Variability in climate and productivity during the Paleocene–Eocene Thermal Maximum in the western Tethys (Forada section)". Climate of the Past. 12 (2): 213–240. doi:10.5194/cp-12-213-2016. Retrieved 11 June 2023.
58. Bornemann, André; Norris, Richard D.; Lyman, Johnnie A.; D'haenens, Simon; Groeneveld, Jeroen; Röhl, Ursula; Farley, Kenneth A.; Speijer, Robert P. (15 May 2014). "Persistent environmental change after the Paleocene–Eocene Thermal Maximum in the eastern North Atlantic". Earth and Planetary Science Letters. 394: 70–81. doi:10.1016/j.epsl.2014.03.017. Retrieved 11 June 2023.
59. Singh, Bhart; Singh, Seema; Bhan, Uday (3 February 2022). "Oceanic anoxic events in the Earth's geological history and signature of such event in the Paleocene-Eocene Himalayan foreland basin sediment records of NW Himalaya, India". Arabian Journal of Geosciences. 15 (317). doi:10.1007/s12517-021-09180-y. Retrieved 15 August 2023.
60. Zachos, J.C.; Röhl, U.; Schellenberg, S.A.; Sluijs, A.; Hodell, D.A.; Kelly, D.C.; Thomas, E.; Nicolo, M.; Raffi, I.; Lourens, L.J.; et al. (2005). "Rapid Acidification of the Ocean During the Paleocene-Eocene Thermal Maximum" (PDF). Science. 308 (5728): 1611–1615. Bibcode:2005Sci...308.1611Z. doi:10.1126/science.1109004. hdl:1874/385806. PMID 15947184. S2CID 26909706. (PDF) from the original on 2008-09-10. Retrieved 2008-04-23.
61. Zhou, X.; Thomas, E.; Rickaby, R. E. M.; Winguth, A. M. E.; Lu, Z. (2014). "I/Ca evidence for global upper ocean deoxygenation during the Paleocene-Eocene Thermal Maximum (PETM)". Paleoceanography and Paleoclimatology. 29 (10): 964–975. Bibcode:2014PalOc..29..964Z. doi:10.1002/2014PA002702.
62. Carmichael, Matthew J.; Inglis, Gordon N.; Badger, Marcus P. S.; Naafs, B. David A.; Behrooz, Leila; Remmelzwaal, Serginio; Monteiro, Fanny M.; Rohrssen, Megan; Farnsworth, Alexander; Buss, Heather L.; Dickson, Alexander J.; Valdes, Paul J.; Lunt, Daniel J.; Pancost, Richard D. (October 2017). "Hydrological and associated biogeochemical consequences of rapid global warming during the Paleocene-Eocene Thermal Maximum". Global and Planetary Change. 157: 114–138. doi:10.1016/j.gloplacha.2017.07.014. hdl:1983/e0d75bfc-35b5-4fbe-886b-10e04049f9e3. S2CID 44193490. Retrieved 24 April 2023.
63. Schoon, Petra L.; Heilmann-Clausen, Claus; Schultz, Bo Pagh; Sinninghe Damsté, Jaap S.; Schouten, Stefan (January 2015). "Warming and environmental changes in the eastern North Sea Basin during the Palaeocene–Eocene Thermal Maximum as revealed by biomarker lipids". Organic Geochemistry. 78: 79–88. doi:10.1016/j.orggeochem.2014.11.003. Retrieved 24 April 2023.
64. Stokke, Ella W.; Jones, Morgan T.; Riber, Lars; Haflidason, Haflidi; Midtkandal, Ivar; Schultz, Bo Pagh; Svensen, Henrik H. (2021-10-01). "Rapid and sustained environmental responses to global warming: the Paleocene–Eocene Thermal Maximum in the eastern North Sea". Climate of the Past. 17 (5): 1989–2013. doi:10.5194/cp-17-1989-2021. ISSN 1814-9332.
65. Sluijs, Appy; Van Roij, L.; Harrington, G. J.; Schouten, Stefan; Sessa, J. A.; LeVay, L. J.; Reichart, G.-J.; Slomp, C. P. (25 July 2014). "Warming, euxinia and sea level rise during the Paleocene–Eocene Thermal Maximum on the Gulf Coastal Plain: implications for ocean oxygenation and nutrient cycling". Climate of the Past. 10 (4): 1421–1439. doi:10.5194/cp-10-1421-2014. Retrieved 3 July 2023.
66. Dickson, Alexander J.; Rees-Owen, Rhian L.; März, Christian; Coe, Angela L.; Cohen, Anthony S.; Pancost, Richard D.; Taylor, Kyle; Shcherbinina, Ekaterina (30 April 2014). "The spread of marine anoxia on the northern Tethys margin during the Paleocene-Eocene Thermal Maximum". Paleoceanography and Paleoclimatology. 29 (6): 471–488. doi:10.1002/2014PA002629. Retrieved 3 July 2023.
67. Sluijs, Appy; Röhl, Ursula; Schouten, Stefan; Brumsack, Hans-J.; Sangiorgi, Francesca; Sinninghe Damsté, Jaap S.; Brinkhuis, Henk (7 February 2008). "Arctic late Paleocene-early Eocene paleoenvironments with special emphasis on the Paleocene-Eocene thermal maximum (Lomonosov Ridge, Integrated Ocean Drilling Program Expedition 302): PALEOCENE-EOCENE ARCTIC ENVIRONMENTS". Paleoceanography and Paleoclimatology. 23 (1): n/a. doi:10.1029/2007PA001495.
68. Von Strandmann, Philip A. E. Pogge; Jones, Morgan T.; West, A. Joshua; Murphy, Melissa J.; Stokke, Ella W.; Tarbuck, Gary; Wilson, David J.; Pearce, Christopher R.; Schmidt, Daniela N. (15 October 2021). "Lithium isotope evidence for enhanced weathering and erosion during the Paleocene-Eocene Thermal Maximum". Science Advances. 7 (42): eabh4224. Bibcode:2021SciA....7.4224P. doi:10.1126/sciadv.abh4224. PMC 8519576. PMID 34652934.
69. Nunes, F.; Norris, R.D. (2006). "Abrupt reversal in ocean overturning during the Palaeocene/Eocene warm period". Nature. 439 (7072): 60–3. Bibcode:2006Natur.439...60N. doi:10.1038/nature04386. PMID 16397495. S2CID 4301227.
70. Pak, Dorothy K.; Miller, Kenneth J. (August 1992). "Paleocene to Eocene benthic foraminiferal isotopes and assemblages: Implications for deepwater circulation". Paleoceanography and Paleoclimatology. 7 (4): 405–422. Bibcode:1992PalOc...7..405P. doi:10.1029/92PA01234. Retrieved 7 April 2023.
71. Fantle, Matthew S.; Ridgwell, Andy (5 August 2020). "Towards an understanding of the Ca isotopic signal related to ocean acidification and alkalinity overshoots in the rock record". Chemical Geology. 547: 119672. doi:10.1016/j.chemgeo.2020.119672. S2CID 219461270. Retrieved 23 April 2023.
72. Kitch, Gabriella Dawn (December 2021). "Calcium isotope composition of Morozovella over the late Paleocene–early Eocene". Identifying and Constraining Biocalcification Stress from Geologic Ocean Acidification Events (PhD). Northwestern University. ProQuest 2617262217. Retrieved 4 September 2023.
73. Kaitlin Alexander; Katrin J. Meissner & Timothy J. Bralower (11 May 2015). "Sudden spreading of corrosive bottom water during the Palaeocene–Eocene Thermal Maximum". Nature Geoscience. 8 (6): 458–461. Bibcode:2015NatGe...8..458A. doi:10.1038/ngeo2430.
74. Colosimo, A. B.; Bralower, T. J.; Zachos, James C. (June 2006). "Evidence for Lysocline Shoaling at the Paleocene/Eocene Thermal Maximum on Shatsky Rise, Northwest Pacific". In Bralower, T. J.; Silva, I. Premoli; Malone, M. J. (eds.). Proceedings of the Ocean Drilling Program, 198 Scientific Results. Vol. 198. Ocean Drilling Program. doi:10.2973/odp.proc.sr.198.112.2006.
75. Ma, Zhongwu; Gray, Ellen; Thomas, Ellen; Murphy, Brandon; Zachos, James C.; Paytan, Adina (13 April 2014). "Carbon sequestration during the Palaeocene–Eocene Thermal Maximum by an efficient biological pump". Nature Geoscience. 7 (1): 382–388. Bibcode:2014NatGe...7..382M. doi:10.1038/ngeo2139. Retrieved 27 April 2023.
76. Luo, Yiming; Boudreau, Bernard P.; Dickens, Gerald R.; Sluijs, Appy; Middelburg, Jack J. (1 November 2016). "An alternative model for CaCO3 over-shooting during the PETM: Biological carbonate compensation". Earth and Planetary Science Letters. 453: 223–233. doi:10.1016/j.epsl.2016.08.012. Retrieved 4 September 2023.
77. Kelly, D. Clay; Zachos, James C.; Bralower, Timothy J.; Schellenberg, Stephen A. (17 December 2005). "Enhanced terrestrial weathering/runoff and surface ocean carbonate production during the recovery stages of the Paleocene-Eocene thermal maximum". Paleoceanography and Paleoclimatology. 20 (4): 1–11. Bibcode:2005PalOc..20.4023K. doi:10.1029/2005PA001163.
78. Peter C. Lippert (2008). "Big discovery for biogenic magnetite". Proceedings of the National Academy of Sciences of the United States of America. 105 (46): 17595–17596. Bibcode:2008PNAS..10517595L. doi:10.1073/pnas.0809839105. PMC 2584755. PMID 19008352.
79. Schumann; et al. (2008). "Gigantism in unique biogenic magnetite at the Paleocene–Eocene Thermal Maximum". Proceedings of the National Academy of Sciences of the United States of America. 105 (46): 17648–17653. Bibcode:2008PNAS..10517648S. doi:10.1073/pnas.0803634105. PMC 2584680. PMID 18936486.
80. O. Strbak; P. Kopcansky; I. Frollo (2011). "Biogenic Magnetite in Humans and New Magnetic Resonance Hazard Questions" (PDF). Measurement Science Review. 11 (3): 85. Bibcode:2011MeScR..11...85S. doi:10.2478/v10048-011-0014-1. S2CID 36212768. (PDF) from the original on 2016-03-04. Retrieved 2015-05-28.
81. Al-Ameer, Abdullah O.; Mahfouz, Kamel H.; El-Sheikh, Islam; Metwally, Amr A. (August 2022). "Nature of the Paleocene/Eocene boundary (the Dababiya Quarry Member) at El-Ballas area, Qena region, Egypt". Journal of African Earth Sciences. 192: 104569. doi:10.1016/j.jafrearsci.2022.104569. Retrieved 4 September 2023.
82. Thomas E (1989). "Development of Cenozoic deep-sea benthic foraminiferal faunas in Antarctic waters". Geological Society of London, Special Publications. 47 (1): 283–296. Bibcode:1989GSLSP..47..283T. doi:10.1144/GSL.SP.1989.047.01.21. S2CID 37660762.
83. Thomas E (1990). "Late Cretaceous–early Eocene mass extinctions in the deep sea". Global Catastrophes in Earth History; an Interdisciplinary Conference on Impacts, Volcanism, and Mass Mortality. GSA Special Papers. Vol. 247. pp. 481–495. doi:10.1130/SPE247-p481. ISBN 0-8137-2247-0.
84. Thomas, E. (1998). "The biogeography of the late Paleocene benthic foraminiferal extinction". In Aubry, M.-P.; Lucas, S.; Berggren, W. A. (eds.). Late Paleocene-early Eocene Biotic and Climatic Events in the Marine and Terrestrial Records. Columbia University Press. pp. 214–243.
85. Takeda, Kotaro; Kaiho, Kunio (3 August 2007). "Faunal turnovers in central Pacific benthic foraminifera during the Paleocene–Eocene thermal maximum". Palaeogeography, Palaeoclimatology, Palaeoecology. 251 (2): 175–197. doi:10.1016/j.palaeo.2007.02.026. Retrieved 3 July 2023.
86. Alegret, Laia; Ortiz, Silvia; Orue-Extebarria, Xabier; Bernaola, Gilen; Baceta, Juan I.; Monechi, Simonetta; Apellaniz, Estibaliz; Pujalte, Victoriano (1 May 2009). "THE PALEOCENE–EOCENE THERMAL MAXIMUM: NEW DATA ON MICROFOSSIL TURNOVER AT THE ZUMAIA SECTION, SPAIN". PALAIOS. 24 (5): 318–328. doi:10.2110/palo.2008.p08-057r. hdl:2158/372896. Retrieved 15 August 2023.
87. Li, Juan; Hu, Xiumian; Zachos, James C.; Garzanti, Eduardo; BouDagher-Fadel, Marcelle (November 2020). "Sea level, biotic and carbon-isotope response to the Paleocene–Eocene thermal maximum in Tibetan Himalayan platform carbonates". Global and Planetary Change. 194: 103316. Bibcode:2020GPC...19403316L. doi:10.1016/j.gloplacha.2020.103316. S2CID 222117770. Retrieved 17 April 2023.
88. Hupp, Brittany N.; Kelly, D. Clay; Williams, John W. (22 February 2022). "Isotopic filtering reveals high sensitivity of planktic calcifiers to Paleocene–Eocene thermal maximum warming and acidification". Proceedings of the National Academy of Sciences of the United States of America. 119 (9): 1–7. doi:10.1073/pnas.2115561119. PMC 8892336. PMID 35193977. S2CID 247057304.
89. Khanolkar, Sonal; Saraswati, Pratul Kumar (1 July 2015). "Ecological Response of Shallow-Marine Foraminifera to Early Eocene Warming in Equatorial India". The Journal of Foraminiferal Research. 45 (3): 293–304. doi:10.2113/gsjfr.45.3.293. ISSN 0096-1191. Retrieved 4 September 2023.
90. Alegret, L.; Ortiz, S.; Arenillas, I.; Molina, E. (1 September 2010). "What happens when the ocean is overheated? The foraminiferal response across the Paleocene-Eocene Thermal Maximum at the Alamedilla section (Spain)". Geological Society of America Bulletin. 122 (9–10): 1616–1624. doi:10.1130/B30055.1. ISSN 0016-7606. Retrieved 4 September 2023.
91. Bralower, Timothy J. (31 May 2002). "Evidence of surface water oligotrophy during the Paleocene-Eocene thermal maximum: Nanofossil assemblage data from Ocean Drilling Program Site 690, Maud Rise, Weddell Sea". Paleoceanography and Paleoclimatology. 17 (2): 13-1–13-12. Bibcode:2002PalOc..17.1023B. doi:10.1029/2001PA000662.
92. Agnini, Claudia; Fornaciari, Eliana; Rio, Domenico; Tateo, Fabio; Backman, Jan; Giusberti, Luca (April 2007). "Responses of calcareous nannofossil assemblages, mineralogy and geochemistry to the environmental perturbations across the Paleocene/Eocene boundary in the Venetian Pre-Alps". Marine Micropaleontology. 63 (1–2): 19–38. doi:10.1016/j.marmicro.2006.10.002.
93. Gupta, Smita; Kumar, Kishor (January 2019). "Precursors of the Paleocene–Eocene Thermal Maximum (PETM) in the Subathu Group, NW sub-Himalaya, India". Journal of Asian Earth Sciences. 169: 21–46. doi:10.1016/j.jseaes.2018.05.027. Retrieved 4 September 2023.
94. Crouch, Erica M.; Dickens, Gerald R.; Brinkhuis, Henk; Aubry, Marie-Pierre; Hollis, Christopher J.; Rogers, Karyne M.; Visscher, Henk (25 May 2003). "The Apectodinium acme and terrestrial discharge during the Paleocene–Eocene thermal maximum: new palynological, geochemical and calcareous nannoplankton observations at Tawanui, New Zealand". Palaeogeography, Palaeoclimatology, Palaeoecology. 194 (4): 387–403. doi:10.1016/S0031-0182(03)00334-1. Retrieved 4 September 2023.
95. Sluijs, Appy; van Roij, Linda; Frieling, Joost; Laks, Jelmer; Reichart, Gert-Jan (29 November 2017). "Single-species dinoflagellate cyst carbon isotope ecology across the Paleocene-Eocene Thermal Maximum". Geology. 46 (1): 79–82. doi:10.1130/G39598.1. ISSN 0091-7613. Retrieved 4 September 2023.
96. Thomas, E. (2007). "Cenozoic mass extinctions in the deep sea: What perturbs the largest habitat on Earth?". In Monechi, S.; Coccioni, R.; Rampino, M. (eds.). Large Ecosystem Perturbations: Causes and Consequences. GSA Special Papers. Vol. 424. pp. 1–24. doi:10.1130/2007.2424(01). ISBN 9780813724249.
97. Winguth A, Thomas E, Winguth C (2012). "Global decline in ocean ventilation, oxygenation and productivity during the Paleocene-Eocene Thermal Maximum – Implications for the benthic extinction". Geology. 40 (3): 263–266. Bibcode:2012Geo....40..263W. doi:10.1130/G32529.1.
98. Ma Z, Gray E, Thomas E, Murphy B, Zachos JC, Paytan A (2014). "Carbon sequestration during the Paleocene-Eocene Thermal maximum by an efficient biological pump". Nature Geoscience. 7 (5): 382–388. Bibcode:2014NatGe...7..382M. doi:10.1038/NGEO2139.
99. Langdon, C.; Takahashi, T.; Sweeney, C.; Chipman, D.; Goddard, J.; Marubini, F.; Aceves, H.; Barnett, H.; Atkinson, M.J. (2000). "Effect of calcium carbonate saturation state on the calcification rate of an experimental coral reef". Global Biogeochemical Cycles. 14 (2): 639–654. Bibcode:2000GBioC..14..639L. doi:10.1029/1999GB001195. S2CID 128987509.
100. Riebesell, U.; Zondervan, I.; Rost, B.; Tortell, P.D.; Zeebe, R.E.; Morel, F.M.M. (2000). "Reduced calcification of marine plankton in response to increased atmospheric CO₂" (PDF). Nature. 407 (6802): 364–367. Bibcode:2000Natur.407..364R. doi:10.1038/35030078. PMID 11014189. S2CID 4426501.
101. Iglesias-Rodriguez, M. Debora; Halloran, Paul R.; Rickaby, Rosalind E. M.; Hall, Ian R.; Colmenero-Hidalgo, Elena; Gittins, John R.; Green, Darryl R. H.; Tyrrell, Toby; Gibbs, Samantha J.; von Dassow, Peter; Rehm, Eric; Armbrust, E. Virginia; Boessenkool, Karin P. (April 2008). "Phytoplankton Calcification in a High-CO₂ World". Science. 320 (5874): 336–40. Bibcode:2008Sci...320..336I. doi:10.1126/science.1154122. PMID 18420926. S2CID 206511068.
102. Gibbs, Samantha J.; Bown, Paul R.; Sessa, Jocelyn A.; Bralower, Timothy J.; Wilson, Paul A. (15 December 2006). "Nannoplankton Extinction and Origination Across the Paleocene-Eocene Thermal Maximum". Science. 314 (5806): 1770–1173. Bibcode:2006Sci...314.1770G. doi:10.1126/science.1133902. PMID 17170303. S2CID 41286627. Retrieved 16 April 2023.
103. Kelly, D.C.; Bralower, T.J.; Zachos, J.C. (1998). "Evolutionary consequences of the latest Paleocene thermal maximum for tropical planktonic foraminifera". Palaeogeography, Palaeoclimatology, Palaeoecology. 141 (1): 139–161. Bibcode:1998PPP...141..139K. doi:10.1016/S0031-0182(98)00017-0.
104. He, Tianchen; Kemp, David B.; Li, Juan; Ruhl, Micha (March 2023). "Paleoenvironmental changes across the Mesozoic–Paleogene hyperthermal events". Global and Planetary Change. 222: 104058. doi:10.1016/j.gloplacha.2023.104058. S2CID 256760820.
105. Scheibner, C.; Speijer, R. P.; Marzou, A. M. (1 June 2005). "Turnover of larger foraminifera during the Paleocene-Eocene Thermal Maximum and paleoclimatic control on the evolution of platform ecosystems". Geology. 33 (6): 493–496. doi:10.1130/G21237.1. Retrieved 15 August 2023.
106. Sanaa El-Sayed; et al. (2021). "Diverse marine fish assemblages inhabited the paleotropics during the Paleocene-Eocene thermal maximum". Geology. 49 (8): 993–998. Bibcode:2021Geo....49..993E. doi:10.1130/G48549.1. S2CID 236585231.
107. Gingerich, P.D. (2003). "Mammalian responses to climate change at the Paleocene-Eocene boundary: Polecat Bench record in the northern Bighorn Basin, Wyoming" (PDF). In Wing, Scott L. (ed.). Causes and Consequences of Globally Warm Climates in the Early Paleogene. GSA Special Papers. Vol. 369. Geological Society of America. pp. 463–78. doi:10.1130/0-8137-2369-8.463. ISBN 978-0-8137-2369-3.
108. D'Ambrosia, Abigail R.; Clyde, William C.; Fricke, Henry C.; Gingerich, Philip D.; Abels, Hemmo A. (15 March 2017). "Repetitive mammalian dwarfing during ancient greenhouse warming events". Science Advances. 3 (3): e1601430. Bibcode:2017SciA....3E1430D. doi:10.1126/sciadv.1601430. PMC 5351980. PMID 28345031.
109. Secord, R.; Bloch, J. I.; Chester, S. G. B.; Boyer, D. M.; Wood, A. R.; Wing, S. L.; Kraus, M. J.; McInerney, F. A.; Krigbaum, J. (2012). "Evolution of the Earliest Horses Driven by Climate Change in the Paleocene-Eocene Thermal Maximum". Science. 335 (6071): 959–962. Bibcode:2012Sci...335..959S. doi:10.1126/science.1213859. PMID 22363006. S2CID 4603597. from the original on 2019-02-05. Retrieved 2018-12-23.
110. Solé, Floréal; Morse, Paul E.; Bloch, Jonathan I.; Gingerich, Philip D.; Smith, Thierry (July 2021). "New specimens of the mesonychid Dissacus praenuntius from the early Eocene of Wyoming and evaluation of body size through the PETM in North America". Geobios. 66–67: 103–118. Bibcode:2021Geobi..66..103S. doi:10.1016/j.geobios.2021.02.005. S2CID 234877826. Retrieved 3 January 2023.
111. Bowen, Gabriel J.; Clyde, William C.; Koch, Paul L.; Ting, Suyin; Alroy, John; Tsubamoto, Takehisa; Wang, Yuanqing; Wang, Yuan (15 March 2002). "Mammalian Dispersal at the Paleocene/Eocene Boundary". Science. 295 (5562): 2062–2065. Bibcode:2002Sci...295.2062B. doi:10.1126/science.1068700. PMID 11896275. S2CID 10729711. Retrieved 15 April 2023.
112. Currano, Ellen C.; Wilf, Peter; Wild, Scott L.; Labandeira, Conrad C.; Lovecock, Elizabeth C.; Royer, Dana L. (12 February 2008). "Sharply increased insect herbivory during the Paleocene–Eocene Thermal Maximum". Proceedings of the National Academy of Sciences of the United States of America. 105 (6): 1960–1964. doi:10.1073/pnas.0708646105. PMC 2538865. PMID 18268338.
113. Aria, Cédric; Jouault, Corentin; Perrichot, Vincent; Nel, André (2 February 2023). "The megathermal ant genus Gesomyrmex (Formicidae: Formicinae), palaeoindicator of wide latitudinal biome homogeneity during the PETM". Geological Magazine. 160 (1): 187–197. Bibcode:2023GeoM..160..187A. doi:10.1017/S0016756822001248. S2CID 256564242. Retrieved 11 April 2023.
114. Smith, Jon J.; Hasiotis, Stephen T.; Kraus, Mary J.; Woody, Daniel T. (20 October 2009). "Transient dwarfism of soil fauna during the Paleocene–Eocene Thermal Maximum". Proceedings of the National Academy of Sciences of the United States of America. 106 (42): 17655–17660. doi:10.1073/pnas.0909674106. PMC 2757401. PMID 19805060.
115. Korasidis, Vera A.; Wing, Scott L.; Shields, Christine A.; Kiehl, Jeffrey T. (9 April 2022). "Global Changes in Terrestrial Vegetation and Continental Climate During the Paleocene-Eocene Thermal Maximum". Paleoceanography and Paleoclimatology. 37 (4): 1–21. doi:10.1029/2021PA004325. S2CID 248074524.
116. Clyde, William C.; Gingerich, Philip D.; Wing, S. L.; Röhl, Ursula; Westerhold, T.; Bowen, G.; Johnson, K.; Baczynski, A. A.; Diefendorf, A.; McInerney, F.; Schnurrenberger, D.; Noren, A.; Brady, K. (5 November 2013). "Bighorn Basin Coring Project (BBCP): a continental perspective on early Paleogene hyperthermals". Scientific Drilling. 16: 21–31. Bibcode:2013SciDr..16...21C. doi:10.5194/sd-16-21-2013. Retrieved 30 December 2022.
117. Bolle, Marie-Pierre; Pardo, Alfonso; Adatte, Thierry; Tantawy, Abdel Aziz; Hinrichs, kai-Uwe; Von Salis, Katharina; Burns, Steve (6 August 2009). "Climatic evolution on the southern and northern margins of the Tethys from the Paleocene to the early Eocene". GFF. 122 (1): 31–32. doi:10.1080/11035890001221031. Retrieved 15 August 2023.
118. Clechenko, Elizabeth R.; kelly, D. Clay; Harrington, Guy J.; Stiles, Cynthia A. (1 March 2007). "Terrestrial records of a regional weathering profile at the Paleocene-Eocene boundary in the Williston Basin of North Dakota". Geological Society of America Bulletin. 119 (3–4): 428–442. doi:10.1130/B26010.1. Retrieved 15 August 2023.
119. Wang, Chaowen; Adriaens, Rieko; Hong, Hanlie; Elsen, Jan; Vandenberghe, Noël; Lourens, Lucas J.; Gingerich, Philip D.; Abels, Hemmo A. (1 July 2017). "Clay mineralogical constraints on weathering in response to early Eocene hyperthermal events in the Bighorn Basin, Wyoming (Western Interior, USA)". Geological Society of America Bulletin. 129 (7–8): 997–1011. doi:10.1130/B31515.1. Retrieved 15 August 2023.
120. John, Cédric M.; Banerjee, Neil R.; Longstaffe, Fred John; Sica, Cheyenne; Law, Kimberley R.; Zachos, James C. (1 July 2012). "Clay assemblage and oxygen isotopic constraints on the weathering response to the Paleocene-Eocene thermal maximum, East Coast of North America". Geology. 40 (7): 591–594. doi:10.1130/G32785.1. Retrieved 15 August 2023.
121. Mason, T. G.; Bybell, Laurel M.; Mason, D. B. (July 2000). "Stratigraphic and climatic implications of clay mineral changes around the Paleocene/Eocene boundary of the northeastern US margin". Sedimentary Geology. 134 (1–2): 65–92. doi:10.1016/S0037-0738(00)00014-2. Retrieved 15 August 2023.
122. Choudhury, Tathagata Roy; Khanolkar, Sonal; Banerjee, Santanu (July 2022). "Glauconite authigenesis during the warm climatic events of Paleogene: Case studies from shallow marine sections of Western India". Global and Planetary Change. 214: 103857. doi:10.1016/j.gloplacha.2022.103857. S2CID 249329384. Retrieved 3 July 2023.
123. Manners, Hayley R.; Grimes, Stephen T.; Sutton, Paul A.; Domingo, Laura; Leng, Melanie J.; Twitchett, Richard J.; Hart, Malcolm B.; Jones, Tom Dunkley; Pancost, Richard D.; Duller, Robert; Lopez-Martinez, Nieves (15 August 2013). "Magnitude and profile of organic carbon isotope records from the Paleocene–Eocene Thermal Maximum: Evidence from northern Spain". Earth and Planetary Science Letters. 376: 220–230. doi:10.1016/j.epsl.2013.06.016. Retrieved 15 August 2023.
124. Pujalte, Victoriano; Schmitz, Birger; Payros, Aitor (1 March 2022). "A rapid sedimentary response to the Paleocene-Eocene Thermal Maximum hydrological change: New data from alluvial units of the Tremp-Graus Basin (Spanish Pyrenees)". Palaeogeography, Palaeoclimatology, Palaeoecology. 589: 110818. Bibcode:2022PPP...589k0818P. doi:10.1016/j.palaeo.2021.110818. hdl:10810/57467. Retrieved 16 January 2023.
125. Giusberti, L.; Rio, D.; Agnini, C.; Backman, J.; Fornaciari, E.; Tateo, F.; Oddone, M. (2007). "Mode and tempo of the Paleocene-Eocene thermal maximum in an expanded section from the Venetian pre-Alps". Geological Society of America Bulletin. 119 (3–4): 391–412. Bibcode:2007GSAB..119..391G. doi:10.1130/B25994.1.
126. Kender, Sev; Bogus, Kara; Pedersen, Gunver K.; Dybkjær, Karen; Mather, Tamsin A.; Mariani, Erica; Ridgwell, Andy; Riding, James B.; Wagner, Thomas; Hesselbo, Stephen P.; Leng, Melanie J. (31 August 2021). "Paleocene/Eocene carbon feedbacks triggered by volcanic activity". Nature Communications. 12 (1): 5186. Bibcode:2021NatCo..12.5186K. doi:10.1038/s41467-021-25536-0. hdl:10871/126942. ISSN 2041-1723. PMC 8408262. PMID 34465785.
127. Carozza, D. A.; Mysak, L. A.; Schmidt, G. A. (2011). "Methane and environmental change during the Paleocene-Eocene thermal maximum (PETM): Modeling the PETM onset as a two-stage event". Geophysical Research Letters. 38 (5): L05702. Bibcode:2011GeoRL..38.5702C. doi:10.1029/2010GL046038. S2CID 129460348.
128. Patterson, M. V.; Francis, D. (2013). "Kimberlite eruptions as triggers for early Cenozoic hyperthermals". Geochemistry, Geophysics, Geosystems. 14 (2): 448–456. Bibcode:2013GGG....14..448P. doi:10.1002/ggge.20054.
129. Jones, Morgan T.; Percival, Lawrence M. E.; Stokke, Ella W.; Frieling, Joost; Mather, Tamsin A.; Riber, Lars; Schubert, Brian A.; Schultz, Bo; Tegner, Christian; Planke, Sverre; Svensen, Henrik H. (6 February 2019). "Mercury anomalies across the Palaeocene–Eocene Thermal Maximum". Climate of the Past. 15 (1): 217–236. doi:10.5194/cp-15-217-2019. ISSN 1814-9332. Retrieved 3 November 2023.
130. Jin, Simin; Kemp, David B.; Yin, Runsheng; Sun, Ruyang; Shen, Jun; Jolley, David W.; Vieira, Manuel; Huang, Chunju (15 January 2023). "Mercury isotope evidence for protracted North Atlantic magmatism during the Paleocene-Eocene Thermal Maximum". Earth and Planetary Science Letters. 602: 117926. doi:10.1016/j.epsl.2022.117926. S2CID 254215843. Retrieved 3 July 2023.
131. Dickson, Alexander J.; Cohen, Anthony S.; Coe, Angela L.; Davies, Marc; Shcherbinina, Ekaterina A.; Gavrilov, Yuri O. (15 November 2015). "Evidence for weathering and volcanism during the PETM from Arctic Ocean and Peri-Tethys osmium isotope records". Palaeogeography, Palaeoclimatology, Palaeoecology. 438: 300–307. doi:10.1016/j.palaeo.2015.08.019. Retrieved 11 June 2023.
132. Svensen, H.; Planke, S.; Malthe-Sørenssen, A.; Jamtveit, B.; Myklebust, R.; Eidem, T.; Rey, S. S. (2004). "Release of methane from a volcanic basin as a mechanism for initial Eocene global warming". Nature. 429 (6991): 542–545. Bibcode:2004Natur.429..542S. doi:10.1038/nature02566. PMID 15175747. S2CID 4419088.
133. Storey, M.; Duncan, R.A.; Swisher III, C.C. (2007). "Paleocene-Eocene Thermal Maximum and the Opening of the Northeast Atlantic". Science. 316 (5824): 587–9. Bibcode:2007Sci...316..587S. doi:10.1126/science.1135274. PMID 17463286. S2CID 6145117.
134. Berndt, Christian; Planke, Sverre; Alvarez Zarikian, Carlos A.; Frieling, Joost; Jones, Morgan T.; Millett, John M.; Brinkhuis, Henk; Bünz, Stefan; Svensen, Henrik H.; Longman, Jack; Scherer, Reed P.; Karstens, Jens; Manton, Ben; Nelissen, Mei; Reed, Brandon (3 August 2023). "Shallow-water hydrothermal venting linked to the Palaeocene–Eocene Thermal Maximum". Nature Geoscience. 16 (9): 803–809. doi:10.1038/s41561-023-01246-8. ISSN 1752-0908. Retrieved 3 November 2023.
135. Jason Wolfe (5 September 2000). "Volcanoes and Climate Change". Earth Observatory. NASA. from the original on 11 July 2017. Retrieved 19 February 2009.
136. Jones, Morgan T.; Stokke, Ella W.; Rooney, Alan D.; Frieling, Joost; Pogge von Strandmann, Philip A. E.; Wilson, David J.; Svensen, Henrik H.; Planke, Sverre; Adatte, Thierry; Thibault, Nicolas; Vickers, Madeleine L.; Mather, Tamsin A.; Tegner, Christian; Zuchuat, Valentin; Schultz, Bo P. (8 July 2023). "Tracing North Atlantic volcanism and seaway connectivity across the Paleocene–Eocene Thermal Maximum (PETM)". Climate of the Past. 19 (8): 1623–1652. doi:10.5194/cp-19-1623-2023. ISSN 1814-9332. Retrieved 3 November 2023.
137. Hartley, Ross A.; Roberts, Gareth G.; White, Nicky; Richardson, Chris (10 July 2011). "Transient convective uplift of an ancient buried landscape". Nature Geoscience. 4 (8): 562–565. doi:10.1038/ngeo1191. ISSN 1752-0908. Retrieved 3 November 2023.
138. White, Nicky; Lovell, Bryan (26 June 1997). "Measuring the pulse of a plume with the sedimentary record". Nature. 387 (6636): 888–891. doi:10.1038/43151. ISSN 1476-4687. Retrieved 3 November 2023.
139. Champion, M. E. Shaw; White, N. J.; Jones, S. M.; Lovell, J. P. B. (9 January 2008). "Quantifying transient mantle convective uplift: An example from the Faroe‐Shetland basin". Tectonics. 27 (1): 1–18. doi:10.1029/2007TC002106. ISSN 0278-7407. Retrieved 3 November 2023.
140. Bralower, T.J.; Thomas, D.J.; Zachos, J.C.; Hirschmann, M.M.; Röhl, U.; Sigurdsson, H.; Thomas, E.; Whitney, D.L. (1997). "High-resolution records of the late Paleocene thermal maximum and circum-Caribbean volcanism: Is there a causal link?". Geology. 25 (11): 963–966. Bibcode:1997Geo....25..963B. doi:10.1130/0091-7613(1997)025<0963:HRROTL>2.3.CO;2.
141. Piedrahita, Victor A.; Galeotti, Simone; Zhao, Xiang; Roberts, Andrew P.; Rohling, Eelco J.; Heslop, David; Florindo, Fabio; Grant, Katharine M.; Rodríguez-Sanz, Laura; Reghellin, Daniele; Zeebe, Richard E. (15 November 2022). "Orbital phasing of the Paleocene-Eocene Thermal Maximum". Earth and Planetary Science Letters. 598: 117839. Bibcode:2022E&PSL.59817839P. doi:10.1016/j.epsl.2022.117839. S2CID 252730173. Retrieved 22 November 2022.
142. Lee, Mingsong; Bralower, Timothy J.; Kump, Lee R.; Self-Trail, Jean M.; Zachos, James C.; Rush, William D.; Robinson, Marci M. (24 September 2022). "Astrochronology of the Paleocene-Eocene Thermal Maximum on the Atlantic Coastal Plain". Nature Communications. 13 (1): 5618. Bibcode:2022NatCo..13.5618L. doi:10.1038/s41467-022-33390-x. PMC 9509358. PMID 36153313.
143. Lourens, L.J.; Sluijs, A.; Kroon, D.; Zachos, J.C.; Thomas, E.; Röhl, U.; Bowles, J.; Raffi, I. (2005). "Astronomical pacing of late Palaeocene to early Eocene global warming events". Nature. 435 (7045): 1083–1087. Bibcode:2005Natur.435.1083L. doi:10.1038/nature03814. hdl:1874/11299. PMID 15944716. S2CID 2139892.
144. Cramer, Benjamin S.; Wright, James D.; Kent, Dennis V.; Aubry, Marie-Pierre (18 December 2003). "Orbital climate forcing of δ13C excursions in the late Paleocene–early Eocene (chrons C24n–C25n)". Paleoceanography and Paleoclimatology. 18 (4): 1097. Bibcode:2003PalOc..18.1097C. doi:10.1029/2003PA000909. Retrieved 16 April 2023.
145. Kent, D.V.; Cramer, B.S.; Lanci, L.; Wang, D.; Wright, J.D.; Van Der Voo, R. (2003). "A case for a comet impact trigger for the Paleocene/Eocene thermal maximum and carbon isotope excursion". Earth and Planetary Science Letters. 211 (1–2): 13–26. Bibcode:2003E&PSL.211...13K. doi:10.1016/S0012-821X(03)00188-2.
146. Kopp, R.E.; Raub, T.; Schumann, D.; Vali, H.; Smirnov, A.V.; Kirschvink, J.L. (2007). "Magnetofossil spike during the Paleocene-Eocene thermal maximum: Ferromagnetic resonance, rock magnetic, and electron microscopy evidence from Ancora, New Jersey, United States". Paleoceanography and Paleoclimatology. 22 (4): PA4103. Bibcode:2007PalOc..22.4103K. doi:10.1029/2007PA001473.
147. Wang, H.; Kent, Dennis V.; Jackson, Michael J. (2012). "Evidence for abundant isolated magnetic nanoparticles at the Paleocene–Eocene boundary". Proceedings of the National Academy of Sciences of the United States of America. 110 (2): 425–430. Bibcode:2013PNAS..110..425W. doi:10.1073/pnas.1205308110. PMC 3545797. PMID 23267095.
148. Schaller, M. F.; Fung, M. K.; Wright, J. D.; Katz, M. E.; Kent, D. V. (2016). "Impact ejecta at the Paleocene-Eocene boundary". Science. 354 (6309): 225–229. Bibcode:2016Sci...354..225S. doi:10.1126/science.aaf5466. ISSN 0036-8075. PMID 27738171. S2CID 30852592.
149. Timmer, John (2016-10-13). "Researchers push argument that comet caused ancient climate change". Ars Technica. from the original on 2016-10-13. Retrieved 2016-10-13.
150. Moore, E; Kurtz, Andrew C. (2008). "Black carbon in Paleocene-Eocene boundary sediments: A test of biomass combustion as the PETM trigger". Palaeogeography, Palaeoclimatology, Palaeoecology. 267 (1–2): 147–152. Bibcode:2008PPP...267..147M. doi:10.1016/j.palaeo.2008.06.010.
151. Bowen, Gabriel J. (October 2013). "Up in smoke: A role for organic carbon feedbacks in Paleogene hyperthermals". Global and Planetary Change. 109: 18–29. doi:10.1016/j.gloplacha.2013.07.001. Retrieved 19 May 2023.
152. Dickens, G. R. (5 August 2011). "Down the Rabbit Hole: toward appropriate discussion of methane release from gas hydrate systems during the Paleocene-Eocene thermal maximum and other past hyperthermal events". Climate of the Past. 7 (3): 831–846. Bibcode:2011CliPa...7..831D. doi:10.5194/cp-7-831-2011. S2CID 55252499. Retrieved 11 April 2023.
153. Thomas, D.J.; Zachos, J.C.; Bralower, T.J.; Thomas, E.; Bohaty, S. (2002). . Geology. 30 (12): 1067–1070. Bibcode:2002Geo....30.1067T. doi:10.1130/0091-7613(2002)030<1067:WTFFTF>2.0.CO;2. Archived from the original on 2019-01-08. Retrieved 2018-12-23.
154. Tripati, A.; Elderfield, H. (2005). "Deep-Sea Temperature and Circulation Changes at the Paleocene-Eocene Thermal Maximum". Science. 308 (5730): 1894–1898. Bibcode:2005Sci...308.1894T. doi:10.1126/science.1109202. PMID 15976299. S2CID 38935414.
155. Kelly, D. Clay (28 December 2002). "Response of Antarctic (ODP Site 690) planktonic foraminifera to the Paleocene–Eocene thermal maximum: Faunal evidence for ocean/climate change". Paleoceanography and Paleoclimatology. 17 (4): 23-1–23-13. Bibcode:2002PalOc..17.1071K. doi:10.1029/2002PA000761.
156. Higgins, John A.; Schrag, Daniel P. (30 May 2006). "Beyond methane: Towards a theory for the Paleocene–Eocene Thermal Maximum". Earth and Planetary Science Letters. 245 (3–4): 523–537. Bibcode:2006E&PSL.245..523H. doi:10.1016/j.epsl.2006.03.009. Retrieved 6 April 2023.
157. Gu, Guangsheng; Dickens, G.R.; Bhatnagar, G.; Colwell, F.S.; Hirasaki, G.J.; Chapman, W.G. (2011). "Abundant Early Palaeogene marine gas hydrates despite warm deep-ocean temperatures". Nature Geoscience. 4 (12): 848–851. Bibcode:2011NatGe...4..848G. doi:10.1038/ngeo1301.
158. Fox-Kemper, B.; Hewitt, H.T.; Xiao, C.; Aðalgeirsdóttir, G.; Drijfhout, S.S.; Edwards, T.L.; Golledge, N.R.; Hemer, M.; Kopp, R.E.; Krinner, G.; Mix, A. (2021). Masson-Delmotte, V.; Zhai, P.; Pirani, A.; Connors, S.L.; Péan, C.; Berger, S.; Caud, N.; Chen, Y.; Goldfarb, L. (eds.). "Chapter 5: Global Carbon and other Biogeochemical Cycles and Feedbacks" (PDF). Climate Change 2021: The Physical Science Basis. Contribution of Working Group I to the Sixth Assessment Report of the Intergovernmental Panel on Climate Change. Cambridge University Press, Cambridge, UK and New York, NY, USA: 80. doi:10.1017/9781009157896.011.
159. Pagani, Mark; Caldeira, K.; Archer, D.; Zachos, J.C. (8 December 2006). "An Ancient Carbon Mystery". Science. 314 (5805): 1556–7. doi:10.1126/science.1136110. PMID 17158314. S2CID 128375931.
160. Gehler; et al. (2015). "Temperature and atmospheric CO2 concentration estimates through the PETM using triple oxygen isotope analysis of mammalian bioapatite". Proceedings of the National Academy of Sciences of the United States of America. 113 (8): 7739–7744. Bibcode:2016PNAS..113.7739G. doi:10.1073/pnas.1518116113. PMC 4948332. PMID 27354522.
161. Frieling, J.; Peterse, F.; Lunt, D. J.; Bohaty, S. M.; Sinninghe Damsté, J. S.; Reichart, G. -J.; Sluijs, A. (18 March 2019). "Widespread Warming Before and Elevated Barium Burial During the Paleocene-Eocene Thermal Maximum: Evidence for Methane Hydrate Release?". Paleoceanography and Paleoclimatology. 34 (4): 546–566. Bibcode:2019PaPa...34..546F. doi:10.1029/2018PA003425. PMC 6582550. PMID 31245790.
162. Babila, Tali L.; Penman, Donald E.; Standish, Christopher D.; Doubrawa, Monika; Bralower, Timothy J.; Robinson, Marci M.; Self-Trail, Jean M.; Speijer, Robert P.; Stassen, Peter; Foster, Gavin L.; Zachos, James C. (16 March 2022). "Surface ocean warming and acidification driven by rapid carbon release precedes Paleocene-Eocene Thermal Maximum". Science Advances. 8 (11): eabg1025. Bibcode:2022SciA....8G1025B. doi:10.1126/sciadv.abg1025. PMC 8926327. PMID 35294237. S2CID 247498325.
163. Katz, M.E.; Cramer, B.S.; Mountain, G.S.; Katz, S.; Miller, K.G. (2001). (PDF). Paleoceanography and Paleoclimatology. 16 (6): 667. Bibcode:2001PalOc..16..549K. CiteSeerX 10.1.1.173.2201. doi:10.1029/2000PA000615. Archived from the original (PDF) on 2008-05-13. Retrieved 2008-02-28.
164. MacDonald, Gordon J. (1990). "Role of methane clathrates in past and future climates". Climatic Change. 16 (3): 247–281. Bibcode:1990ClCh...16..247M. doi:10.1007/BF00144504. S2CID 153361540.
165. Bice, K.L.; Marotzke, J. (2002). "Could changing ocean circulation have destabilized methane hydrate at the Paleocene/Eocene boundary" (PDF). Paleoceanography and Paleoclimatology. 17 (2): 1018. Bibcode:2002PalOc..17.1018B. doi:10.1029/2001PA000678. hdl:11858/00-001M-0000-0014-3AC0-A. (PDF) from the original on 2012-04-19. Retrieved 2019-09-01.
166. Tripati, Aradhna K.; Elderfield, Henry (14 February 2004). "Abrupt hydrographic changes in the equatorial Pacific and subtropical Atlantic from foraminiferal Mg/Ca indicate greenhouse origin for the thermal maximum at the Paleocene-Eocene Boundary". Geochemistry, Geophysics, Geosystems. 5 (2): 1–11. Bibcode:2004GGG.....5.2006T. doi:10.1029/2003GC000631. S2CID 129878181.
167. Bice, Karen L.; Marotzke, Jochem (15 June 2001). "Numerical evidence against reversed thermohaline circulation in the warm Paleocene/Eocene ocean". Journal of Geophysical Research. 106 (C6): 11529–11542. Bibcode:2001JGR...10611529B. doi:10.1029/2000JC000561. hdl:11858/00-001M-0000-0014-3AC6-D. Retrieved 7 April 2023.
168. Cope, Jesse Tiner (2009). On The Sensitivity Of Ocean Circulation To Arctic Freshwater Pulses During The Paleocene/Eocene Thermal Maximum (Masters thesis). University of Texas Arlington. hdl:10106/2004. Retrieved 2013-08-07.
169. Bains, S.; Norris, R.D.; Corfield, R.M.; Faul, K.L. (2000). "Termination of global warmth at the Palaeocene/Eocene boundary through productivity feedback". Nature. 407 (6801): 171–4. Bibcode:2000Natur.407..171B. doi:10.1038/35025035. PMID 11001051. S2CID 4419536. Retrieved 6 April 2023.
170. Dickens, G. R.; Fewless, T.; Thomas, E.; Bralower, T. J. (2003). "Excess barite accumulation during the Paleocene-Eocene thermal Maximum: Massive input of dissolved barium from seafloor gas hydrate reservoirs". Special Paper 369: Causes and consequences of globally warm climates in the early Paleogene. Vol. 369. p. 11. doi:10.1130/0-8137-2369-8.11. ISBN 978-0-8137-2369-3. S2CID 132420227.
171. Stokke, Ella W.; Jones, Morgan T.; Tierney, Jessica E.; Svensen, Henrik H.; Whiteside, Jessica H. (15 August 2020). "Temperature changes across the Paleocene-Eocene Thermal Maximum – a new high-resolution TEX86 temperature record from the Eastern North Sea Basin". Earth and Planetary Science Letters. 544: 116388. Bibcode:2020E&PSL.54416388S. doi:10.1016/j.epsl.2020.116388. hdl:10852/81373. S2CID 225387296. Retrieved 6 April 2023.
172. Kiehl, Jeffrey T.; Shields, Christine A.; Snyder, Mark A.; Zachos, James C.; Rothstein, Mathew (3 September 2018). "Greenhouse- and orbital-forced climate extremes during the early Eocene". Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences. 376 (2130): 1–24. doi:10.1098/rsta.2017.0085. PMC 6127382. PMID 30177566.
173. "PETM Weirdness". RealClimate. 2009. from the original on 2016-02-12. Retrieved 2016-02-03.
174. Ying Cui; Lee R. Kump; Andy J. Ridgwell; Adam J. Charles; Christopher K. Junium; Aaron F. Diefendorf; Katherine H. Freeman; Nathan M. Urban & Ian C. Harding (2011). "Slow release of fossil carbon during the Palaeocene–Eocene Thermal Maximum". Nature Geoscience. 4 (7): 481–485. Bibcode:2011NatGe...4..481C. doi:10.1038/ngeo1179.
175. Ruppel and Kessler (2017). "The interaction of climate change and methane hydrates". Reviews of Geophysics. 55 (1): 126–168. Bibcode:2017RvGeo..55..126R. doi:10.1002/2016RG000534.
176. Keller, Gerta; Mateo, Paula; Punekar, Jahnavi; Khozyem, Hassan; Gertsch, Brian; Spangenberg, Jorge E.; Bitchong, Andre Mbabi; Adatte, Thierry (April 2018). "Environmental changes during the Cretaceous-Paleogene mass extinction and Paleocene-Eocene Thermal Maximum: Implications for the Anthropocene". Gondwana Research. 56: 69–89. doi:10.1016/j.gr.2017.12.002.
177. "High-fidelity record of Earth's climate history puts current changes in context". phys.org. Retrieved 26 September 2021.
178. "Ancient Climate Events: Paleocene Eocene Thermal Maximum | EARTH 103: Earth in the Future". www.e-education.psu.edu. Retrieved 26 September 2021.
179. "Scientists draw new connections between climate change and warming oceans". phys.org. University of Toronto. Retrieved 26 September 2021.
180. Yao, Weiqi; Paytan, Adina; Wortmann, Ulrich G. (24 August 2018). "Large-scale ocean deoxygenation during the Paleocene-Eocene Thermal Maximum". Science. 361 (6404): 804–806. Bibcode:2018Sci...361..804Y. doi:10.1126/science.aar8658. PMID 30026315.
181. "'Tipping points' in Earth's system triggered rapid climate change 55 million years ago, research shows". phys.org. Retrieved 21 September 2021.
182. Kaya, Mustafa Y.; Dupont-Nivet, Guillaume; Frieling, Joost; Fioroni, Chiara; Rohrmann, Alexander; Altıner, Sevinç Özkan; Vardar, Ezgi; Tanyaş, Hakan; Mamtimin, Mehmut; Zhaojie, Guo (31 May 2022). "The Eurasian epicontinental sea was an important carbon sink during the Palaeocene-Eocene thermal maximum". Communications Earth & Environment. 3 (1): 1–10. Bibcode:2022ComEE...3..124K. doi:10.1038/s43247-022-00451-4. S2CID 249184616. Retrieved 4 September 2023.
183. Shaffer, Gary; Huber, Matthew; Rondanelli, Roberto; Pepke Pedersen, Jens Olaf (23 June 2016). "Deep time evidence for climate sensitivity increase with warming". Geophysical Research Letters. 43 (12): 6538–6545. doi:10.1002/2016GL069243. ISSN 0094-8276. Retrieved 4 September 2023.
184. Tierney, Jessica E.; Zhu, Jiang; Li, Mingsong; Ridgwell, Andy; Hakim, Gregory J.; Poulsen, Christopher J.; Whiteford, Ross D. M.; Rae, James W. B.; Kump, Lee R. (10 October 2022). "Spatial patterns of climate change across the Paleocene–Eocene Thermal Maximum". Proceedings of the National Academy of Sciences of the United States of America. 119 (42): e2205326119. doi:10.1073/pnas.2205326119. PMC 9586325. PMID 36215472.

Further reading

• Jardine, Phil (2011). "Paleocene–Eocene Thermal Maximum". Palaeontology Online. 1 (5): 1–7.

External links

• BBC Radio 4, In Our Time, The Paleocene–Eocene Thermal Maximum, 16 March 2017
• Global Warming 56 Million Years Ago: What it Means for Us (Video)