104-412: Eeco or EECO may refer to Early Eocene Climatic Optimum , a warm period 50 million years ago Maruti Suzuki Eeco , an Indian microvan Topics referred to by the same term [REDACTED] This disambiguation page lists articles associated with the title Eeco . If an internal link led you here, you may wish to change the link to point directly to
208-458: A C-rich comet struck the earth and initiated the warming event. A cometary impact coincident with the P/E boundary can also help explain some enigmatic features associated with this event, such as the iridium anomaly at Zumaia , the abrupt appearance of a localized kaolinitic clay layer with abundant magnetic nanoparticles, and especially the nearly simultaneous onset of the carbon isotope excursion and
312-609: A mass extinction of benthic foraminifera , a global expansion of subtropical dinoflagellates , and an appearance of excursion taxa, including within planktic foraminifera planktic foraminifera and calcareous nannofossils , all occurred during the beginning stages of the PETM. On land, many modern mammal orders (including primates ) suddenly appear in Europe and in North America. The configuration of oceans and continents
416-452: A constant sedimentation rate, the entire event, from onset though termination, was therefore estimated at 200,000 years. Subsequently, it was noted that the CIE spanned 10 or 11 subtle cycles in various sediment properties, such as Fe content. Assuming these cycles represent precession , a similar but slightly longer age was calculated by Rohl et al. 2000. If a massive amount of C-depleted CO 2
520-481: A decline among K-strategist large foraminifera, though they rebounded during the post-PETM oligotrophy coevally with the demise of low-latitude corals. A study published in May 2021 concluded that fish thrived in at least some tropical areas during the PETM, based on discovered fish fossils including Mene maculata at Ras Gharib , Egypt. Humid conditions caused migration of modern Asian mammals northward, dependent on
624-471: A decreased oceanic pH , which has a profound negative effect on corals. Experiments suggest it is also very harmful to calcifying plankton. However, the strong acids used to simulate the natural increase in acidity which would result from elevated CO 2 concentrations may have given misleading results, and the most recent evidence is that coccolithophores ( E. huxleyi at least) become more , not less, calcified and abundant in acidic waters. No change in
728-548: A global scale, such as the Elmo horizon (aka ETM2 ), has led to the hypothesis that the events repeat on a regular basis, driven by maxima in the 400,000 and 100,000 year eccentricity cycles in the Earth's orbit . Cores from Howard's Tract, Maryland indicate the PETM occurred as a result of an extreme in axial precession during an orbital eccentricity maximum. The current warming period is expected to last another 50,000 years due to
832-463: A gradual grading back to grey). It is far more pronounced in North Atlantic cores than elsewhere, suggesting that acidification was more concentrated here, related to a greater rise in the level of the lysocline. Corrosive waters may have then spilled over into other regions of the world ocean from the North Atlantic. Model simulations show acidic water accumulation in the deep North Atlantic at
936-412: A high water flow between an arc of volcanic islands not conducive to swimming or rafting. Evidence also suggests that the creation of this land mass and the subsequent warm, wet weather over northern Europe resulted in the formation of a large Arctic ice cap and contributed to the current ice age . That warm currents can lead to glacier formation may seem counterintuitive, but heated air flowing over
1040-451: A lag time of around 3,800 years after the PETM. At some marine locations (mostly deep-marine), sedimentation rates must have decreased across the PETM, presumably because of carbonate dissolution on the seafloor; at other locations (mostly shallow-marine), sedimentation rates must have increased across the PETM, presumably because of enhanced delivery of riverine material during the event. Discriminating between different possible causes of
1144-494: A last definite temporary breach as recently as 2.45 Ma. The ocean sediments between the volcanoes on the isthmus seem to have been laid down as recently as 3.1 Ma and the exchange of organism gene pools between the two oceans appears to have continued until about 3 Ma as well. The largest exchange of animals over the land bridge only happened after this time, although some species had made the crossing earlier, perhaps by rafting or brief periods of connection separated by periods of
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#17327870954281248-417: A major change in the lithologic, biotic and geochemical composition of sediment in hundreds of records across Earth. Other hyperthermals clearly occurred at approximately 53.7 Ma (now called ETM-2 and also referred to as H-1, or the Elmo event) and at about 53.6 Ma (H-2), 53.3 (I-1), 53.2 (I-2) and 52.8 Ma (informally called K, X or ETM-3). The number, nomenclature, absolute ages, and relative global impact of
1352-681: A marked increase in TEX 86 . The latter record is intriguing, though, because it suggests a 6 °C (11 °F) rise from ~17 °C (63 °F) before the PETM to ~23 °C (73 °F) during the PETM. Assuming the TEX 86 record reflects summer temperatures, it still implies much warmer temperatures on the North Pole compared to the present day, but no significant latitudinal amplification relative to surrounding time. The above considerations are important because, in many global warming simulations, high latitude temperatures increase much more at
1456-470: A minimum in the eccentricity of the Earth's orbit. Orbital increase in insolation (and thus temperature) would force the system over a threshold and unleash positive feedbacks. The orbital forcing hypothesis has been challenged by a study finding the PETM to have coincided with a minimum in the ~400 kyr eccentricity cycle, inconsistent with a proposed orbital trigger for the hyperthermal. One theory holds that
1560-408: A rapid +8 °C temperature rise, in accordance with existing regional records of marine and terrestrial environments. Southern California had a mean annual temperature of about 17 °C ± 4.4 °C. In Antarctica, at least part of the year saw minimum temperatures of 15 °C. TEX 86 values indicate that the average sea surface temperature (SST) reached over 36 °C (97 °F) in
1664-401: A role in the extinction of the calcifying foraminifera, and the higher temperatures would have increased metabolic rates, thus demanding a higher food supply. Such a higher food supply might not have materialized because warming and increased ocean stratification might have led to declining productivity, along with increased remineralization of organic matter in the water column before it reached
1768-505: A source of skewing of carbon isotopic ratios in bulk organic matter. The climate would also have become much wetter, with the increase in evaporation rates peaking in the tropics. Deuterium isotopes reveal that much more of this moisture was transported polewards than normal. Warm weather would have predominated as far north as the Polar basin. Finds of fossils of Azolla floating ferns in polar regions indicate subtropic temperatures at
1872-547: A year, and the settlement was abandoned twice. The California Gold Rush , starting in 1849, brought a large increase in the transportation of people from the Atlantic to the Pacific. Steamships brought gold diggers from eastern U.S. ports, who trekked across the isthmus by foot, horse, and later rail. On the Pacific side, they boarded Pacific Mail Steamship Company vessels headed for San Francisco . Ferdinand de Lesseps ,
1976-531: 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. Precipitation rates in the North Sea likewise soared during the PETM. In Cap d'Ailly, in present-day Normandy , a transient dry spell occurred just before the negative CIE, after which much moister conditions predominated, with
2080-468: Is at about 4 km, comparable to the median depth of the oceans. This depth depends on (among other things) temperature and the amount of CO 2 dissolved in the ocean. Adding CO 2 initially raises the lysocline, resulting in the dissolution of deep water carbonates. This deep-water acidification can be observed in ocean cores, which show (where bioturbation has not destroyed the signal) an abrupt change from grey carbonate ooze to red clays (followed by
2184-555: Is likely that instead of islands, a full isthmus between the North and South American continents had already formed where the Central American Seaway had been previously. A genomic study of army ants also suggests that the isthmus emerged millions of years earlier than had long been thought. The Isthmus of Panama is not the only part of central America that has been low lying in the last tens of million years. This means
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#17327870954282288-453: Is other evidence to suggest that warming predated the δ C excursion by some 3,000 years. Some authors have suggested that the magnitude of the CIE may be underestimated due to local processes in many sites causing a large proportion of allochthonous sediments to accumulate in their sedimentary rocks, contaminating and offsetting isotopic values derived from them. Organic matter degradation by microbes has also been implicated as
2392-603: Is rapidly injected into the modern ocean or atmosphere and projected into the future, a ~200,000 year CIE results because of slow flushing through quasi steady-state inputs (weathering and volcanism) and outputs (carbonate and organic) of carbon. A different study, based on a revised orbital chronology and data from sediment cores in the South Atlantic and the Southern Ocean, calculated a slightly shorter duration of about 170,000 years. A ~200,000 year duration for
2496-400: Is used as a biostratigraphic marker defining the PETM. The fitness of Apectodinium homomorphum stayed constant over the PETM while that of others declined. Radiolarians grew in size over the PETM. Colonial corals, sensitive to rising temperatures, declined during the PETM, being replaced by larger benthic foraminifera. Aragonitic corals were greatly hampered in their ability to grow by
2600-498: Is volcanic activity associated with the North Atlantic Igneous Province (NAIP), which is believed to have released more than 10,000 gigatons of carbon during the PETM based on the relatively isotopically heavy values of the initial carbon addition. Mercury anomalies during the PETM point to massive volcanism during the event. On top of that, increases in ∆ Hg show intense volcanism was concurrent with
2704-593: The Atlantic and Pacific Oceans and causing the creation of the Gulf Stream , as first suggested in 1910 by Henry Fairfield Osborn . Osborn based the proposal on the fossil record of mammals in Central America, a conclusion that would provide a foundation for Alfred Wegener when he proposed the theory of continental drift in 1912. Some recent studies suggest an earlier formation of the isthmus than
2808-503: The Paleogene as it is today – something which is very difficult to confirm. Although the cause of the initial warming has been attributed to a massive injection of carbon (CO 2 and/or CH 4 ) into the atmosphere, the source of the carbon has yet to be found. The emplacement of a large cluster of kimberlite pipes at ~56 Ma in the Lac de Gras region of northern Canada may have provided
2912-490: The carbon cycle operate in a greenhouse world. The time interval is marked by a prominent negative excursion in carbon stable isotope ( δ C ) records from around the globe; more specifically, a large decrease in the C/ C ratio of marine and terrestrial carbonates and organic carbon has been found and correlated across hundreds of locations. The magnitude and timing of the PETM ( δ C ) excursion, which attest to
3016-498: The opossum , armadillo , and porcupine all trace back to ancestors that came across the land bridge from South America. Likewise, bears, cats, dogs, horses, llamas, and raccoons all made the trek south across the isthmus. As the connecting bridge between two vast land masses, the Panamanian biosphere is filled with overlapping fauna and flora from both North and South America. There are, for example, over 978 species of birds in
3120-668: The " Initial Eocene " or “ Late Paleocene thermal maximum ", was a geologically brief time interval characterized by a 5–8 °C global average temperature rise and massive input of carbon into the ocean and atmosphere. The event began, now formally codified, at the precise time boundary between the Paleocene and Eocene geological epochs . The exact age and duration of the PETM remain uncertain, but it occurred around 55.8 million years ago (Ma) and lasted about 200 thousand years (Ka). The PETM arguably represents our best past analogue for which to understand how global warming and
3224-619: The CIE is estimated from models of global carbon cycling. Age constraints at several deep-sea sites have been independently examined using He contents, assuming the flux of this cosmogenic nuclide is roughly constant over short time periods. This approach also suggests a rapid onset for the PETM CIE (<20,000 years). However, the He records support a faster recovery to near initial conditions (<100,000 years) than predicted by flushing via weathering inputs and carbonate and organic outputs. There
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3328-630: The Caribbean side and destroyed the city . The town was relocated some kilometers to the west at a small peninsula. The ruins of the old town, Panamá Viejo , are preserved and were declared a UNESCO World Heritage Site in 1997. The local Indigenous population, known as the Cueva , experienced genocidal effects from European colonization of the Isthmus. A regional slave trade in Indigenous peoples
3432-695: The Early Eocene. The Arctic became dominated by palms and broadleaf forests. The Gulf coast of central Texas was covered in tropical rainforests and tropical seasonal forests. Sediment deposition changed significantly at many outcrops and in many drill cores spanning this time interval. During the PETM, sediments are enriched with kaolinite from a detrital source due to denudation (initial processes such as volcanoes , earthquakes , and plate tectonics ). Increased precipitation and enhanced erosion of older kaolinite-rich soils and sediments may have been responsible for this. Increased weathering from
3536-803: The Eocene hyperthermals remain a source of current research. Whether they only occurred during the long-term warming, and whether they are causally related to apparently similar events in older intervals of the geological record (e.g. the Toarcian turnover of the Jurassic ) are open issues. A study in 2020 estimated the global mean surface temperature (GMST) with 66% confidence during the latest Paleocene (c. 57 Ma) as 22.3–28.3 °C (72.1–82.9 °F), PETM (56 Ma) as 27.2–34.5 °C (81.0–94.1 °F) and Early Eocene Climatic Optimum (EECO) (53.3 to 49.1 Ma) as 23.2–29.7 °C (73.8–85.5 °F). Estimates of
3640-577: The Indian Subcontinent acted as a diversity hub from which mammalian lineages radiated into Africa and the continents of the Northern Hemisphere. Multiple Eurasian mammal orders invaded North America, but because niche space was not saturated, these had little effect on overall community structure. The diversity of insect herbivory, as measured by the amount and diversity of damage to plants caused by insects, increased during
3744-547: The Indian Subcontinent. In the Tarim Sea, sea levels rose by 20-50 metres. At the start of the PETM, the ocean circulation patterns changed radically in the course of under 5,000 years. Global-scale current directions reversed due to a shift in overturning from the Southern Hemisphere to Northern Hemisphere. This "backwards" flow persisted for 40,000 years. Such a change would transport warm water to
3848-701: The Kerguelen Plateau, nannoplankton productivity sharply declined at the onset of the negative δ C excursion but was elevated in its aftermath. The nannoplankton genus Fasciculithus went extinct, most likely as a result of increased surface water oligotrophy; the genera Sphenolithus , Zygrhablithus , Octolithus suffered badly too. Samples from the tropical Atlantic show that overall, dinocyst abundance diminished sharply. Contrarily, thermophilic dinoflagellates bloomed, particularly Apectodinium . This acme in Apectodinium abundance
3952-711: The Kuna or Guna Indians . Scotland tried to establish a settlement in 1698 through the Darien scheme which was ultimately unsuccessful. The scheme was backed largely by investors of the Kingdom of Scotland in order to gain wealth and influence by establishing New Caledonia, a colony in the Darién Gap in the late 1690s. The plan was for the colony, located on the Gulf of Darién , to establish and manage an overland route to connect
4056-413: The PETM comes from two observations. First, a prominent negative excursion in the carbon isotope composition ( δ C ) of carbon-bearing phases characterizes the PETM in numerous (>130) widespread locations from a range of environments. Second, carbonate dissolution marks the PETM in sections from the deep sea. The total mass of carbon injected to the ocean and atmosphere during the PETM remains
4160-401: The PETM in correlation with global warming. The ant genus Gesomyrmex radiated across Eurasia during the PETM. As with mammals, soil-dwelling invertebrates are observed to have dwarfed during the PETM. A profound change in terrestrial vegetation across the globe is associated with the PETM. Across all regions, floras from the latest Palaeocene are highly distinct from those of the PETM and
4264-408: The PETM is difficult. Temperatures were rising globally at a steady pace, and a mechanism must be invoked to produce an instantaneous spike which may have been accentuated or catalyzed by positive feedback (or activation of "tipping or points" ). The biggest aid in disentangling these factors comes from a consideration of the carbon isotope mass balance. We know the entire exogenic carbon cycle (i.e.
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4368-666: The PETM to ~40 °C. In the eastern Tethys, SSTs rose by 3 to 5 °C. Low latitude Indian Ocean Mg/Ca records show seawater at all depths warmed by about 4-5 °C. In the Pacific Ocean, tropical SSTs increased by about 4-5 °C. TEX 86 values from deposits in New Zealand, then located between 50°S and 60°S in the southwestern Pacific, indicate SSTs of 26 °C (79 °F) to 28 °C (82 °F), an increase of over 10 °C (18 °F) from an average of 13 °C (55 °F) to 16 °C (61 °F) at
4472-629: The PETM, and continued for a time after the PETM's termination. The PETM generated the only oceanic anoxic event (OAE) of the Cenozoic. Oxygen depletion was achieved through a combination of elevated seawater temperatures, water column stratification, and oxidation of methane released from undersea clathrates. In parts of the oceans, especially the North Atlantic Ocean, bioturbation was absent. This may be due to bottom-water anoxia or due to changing ocean circulation patterns changing
4576-531: The PETM, generating an increase in organic carbon burial, which acted as a negative feedback on the PETM's severe global warming. Along with the global lack of ice, the sea level would have risen due to thermal expansion. Evidence for this can be found in the shifting palynomorph assemblages of the Arctic Ocean, which reflect a relative decrease in terrestrial organic material compared to marine organic matter. A significant marine transgression took place in
4680-710: The PETM. As a consequence of coccolithophorid blooms enabled by enhanced runoff, carbonate was removed from seawater as the Earth recovered from the negative carbon isotope excursion, thus acting to ameliorate ocean acidification. Stoichiometric magnetite ( Fe 3 O 4 ) particles were obtained from PETM-age marine sediments. The study from 2008 found elongate prism and spearhead crystal morphologies, considered unlike any magnetite crystals previously reported, and are potentially of biogenic origin. These biogenic magnetite crystals show unique gigantism, and probably are of aquatic origin. The study suggests that development of thick suboxic zones with high iron bioavailability,
4784-464: The Pacific Ocean on 25 September, 1513, then called the "South Sea" as it was on the south side of the Isthmus. Balboa had heard of a second ocean on the other side of the Isthmus from natives while sailing along the Caribbean coast. In 1519 the town of Panamá was founded near a small indigenous settlement on the Pacific coast. In 1671 the Welsh privateer Henry Morgan crossed the Isthmus of Panamá from
4888-405: The Pacific and Atlantic Oceans. The backers knew that the first sighting of the Pacific Ocean by Vasco Núñez de Balboa was after crossing the isthmus through Darién . The expedition also claimed sovereignty over "Crab Isle" (modern day Vieques, Puerto Rico ) in 1698, yet sovereignty was short-lived. The attempt at settling the area did not go well; more than 80 percent of participants died within
4992-572: The West Siberian Sea, SSTs climbed to ~27 °C. Certainly, the central Arctic Ocean was ice-free before, during, and after the PETM. This can be ascertained from the composition of sediment cores recovered during the Arctic Coring Expedition (ACEX) at 87°N on Lomonosov Ridge . Moreover, temperatures increased during the PETM, as indicated by the brief presence of subtropical dinoflagellates ( Apectodinium spp. }, and
5096-539: The acidification of the ocean and eutrophication in surficial waters. Overall, coral framework-building capacity was greatly diminished. The deep-sea extinctions are difficult to explain, because many species of benthic foraminifera in the deep-sea are cosmopolitan, and can find refugia against local extinction. General hypotheses such as a temperature-related reduction in oxygen availability, or increased corrosion due to carbonate undersaturated deep waters, are insufficient as explanations. Acidification may also have played
5200-414: The amount of average global temperature rise at the start of the PETM range from approximately 3 to 6 °C to between 5 and 8 °C. This warming was superimposed on "long-term" early Paleogene warming , and is based on several lines of evidence. There is a prominent (>1 ‰ ) negative excursion in the δ O of foraminifera shells, both those made in surface and deep ocean water. Because there
5304-487: The amount of solar radiation reaching the Earth's surface, lowering temperatures in the troposphere, and changing atmospheric circulation patterns. Large-scale volcanic activity may last only a few days, but the massive outpouring of gases and ash can influence climate patterns for years. Sulfuric gases convert to sulfate aerosols, sub-micron droplets containing about 75 percent sulfuric acid. Following eruptions, these aerosol particles can linger as long as three to four years in
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#17327870954285408-406: The beginning of the PETM. Osmium isotopic anomalies in Arctic Ocean sediments dating to the PETM have been interpreted as evidence of a volcanic cause of this hyperthermal. Intrusions of hot magma into carbon-rich sediments may have triggered the degassing of isotopically light methane in sufficient volumes to cause global warming and the observed isotope anomaly. This hypothesis is documented by
5512-408: The benthic foraminifera on the sea floor. The only factor global in extent was an increase in temperature. Regional extinctions in the North Atlantic can be attributed to increased deep-sea anoxia, which could be due to the slowdown of overturning ocean currents, or the release and rapid oxidation of large amounts of methane. In shallower waters, it's undeniable that increased CO 2 levels result in
5616-657: The boundary between the Selandian and Thanetian . The extreme warmth of the southwestern Pacific extended into the Australo-Antarctic Gulf. Sediment core samples from the East Tasman Plateau , then located at a palaeolatitude of ~65 °S, show an increase in SSTs from ~26 °C to ~33 °C during the PETM. In the North Sea, SSTs jumped by 10 °C, reaching highs of ~33 °C, while in
5720-407: The carbon contained within the oceans and atmosphere, which can change on short timescales) underwent a −0.2 % to −0.3 % perturbation in δ C , and by considering the isotopic signatures of other carbon reserves, can consider what mass of the reserve would be necessary to produce this effect. The assumption underpinning this approach is that the mass of exogenic carbon was the same in
5824-550: The carbon that triggered early warming in the form of exsolved magmatic CO 2 . Calculations indicate that the estimated 900–1,100 Pg of carbon required for the initial approximately 3 °C of ocean water warming associated with the Paleocene-Eocene thermal maximum could have been released during the emplacement of a large kimberlite cluster. The transfer of warm surface ocean water to intermediate depths led to thermal dissociation of seafloor methane hydrates, providing
5928-659: The cities of Panama, Nombre de Dios, and Nata combined. During the Spanish colonization of Peru , the Isthmus developed into an important port of trade and became an administrative center for the conquests of both South and wider Central America. Silver and gold from the viceroyalty of Peru were transported overland across the isthmus by the Spanish Silver Train to Porto Bello , where Spanish treasure fleets shipped them to Seville and Cádiz from 1707. Lionel Wafer spent four years between 1680 and 1684 among
6032-432: The climatic belts. Uncertainty remains for the timing and tempo of migration. Terrestrial animals suffered mass mortality due to toxigenic cyanobacterial blooms enkindled by the extreme heat. The increase in mammalian abundance is intriguing. Increased global temperatures may have promoted dwarfing – which may have encouraged speciation. Major dwarfing occurred early in the PETM, with further dwarfing taking place during
6136-548: The continents of North and South America, allowing the waters of the Pacific and Atlantic Oceans to mix freely. Beneath the surface, two plates of the Earth's crust were slowly colliding, forcing the Cocos Plate to slide under the Caribbean Plate . The pressure and heat caused by this collision led to the formation of underwater volcanoes , some of which grew large enough to form islands . Meanwhile, movement of
6240-431: The course of the PETM concomitantly with precessional cycles in mid-latitudes, and that overall, net precipitation over the central-western Tethys Ocean decreased. The amount of freshwater in the Arctic Ocean increased, in part due to Northern Hemisphere rainfall patterns, fueled by poleward storm track migrations under global warming conditions. The flux of freshwater entering the oceans increased drastically during
6344-484: The course of ~1,000 years, with the group suffering more during the PETM than during the dinosaur-slaying K-T extinction . At the onset of the PETM, benthic foraminiferal diversity dropped by 30% in the Pacific Ocean, while at Zumaia in what is now Spain, 55% of benthic foraminifera went extinct over the course of the PETM, though this decline was not ubiquitous to all sites; Himalayan platform carbonates show no major change in assemblages of large benthic foraminifera at
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#17327870954286448-481: The date of first closure and final closure of the Central American Seaway before it was artificially reopened to a degree by the Panama Canal is likely to remain controversial. Some experts have proposed 15 Ma as the date of first closure, while others suggest that final closure might be more recent based on genetic drift data of black mangroves along the Atlantic and Pacific coasts. The process of formation of
6552-413: The deep oceans, enhancing further warming. The major biotic turnover among benthic foraminifera has been cited as evidence of a significant change in deep water circulation. Ocean acidification occurred during the PETM, causing the calcite compensation depth to shoal. The lysocline marks the depth at which carbonate starts to dissolve (above the lysocline, carbonate is oversaturated): today, this
6656-796: The developer of the Suez Canal , started a Panama Canal Company in 1880 that went bankrupt in 1889 in the Panama scandals . In 1902–1904, the United States forced Colombia to grant independence to the Department of the Isthmus , bought the remaining assets of the Panama Canal Company, and finished the canal in 1914. A significant body of water (referred to as the Central American Seaway ) once separated
6760-506: The distribution of calcareous nannoplankton such as the coccolithophores can be attributed to acidification during the PETM. Nor was the abundance of calcareous nannoplankton controlled by changes in acidity, with local variations in nutrient availability and temperature playing much greater roles; diversity changes in calcareous nannoplankton in the Southern Ocean and at the Equator were most affected by temperature changes, whereas in much of
6864-543: The early modern era. The remains of a variety of paleolithic fauna that were found in the Canal Zone in 2007 include bear-dogs , miniature horses, rhinos, camels, early relatives of modern hippos, and at least one species of chalicothere . The first humans to inhabit the isthmus were Paleo-Indians , who probably arrived between 18 and 15 kya . Since then, the isthmus has been inhabited by Indigenous peoples who have continually developed and adapted to life on
6968-416: The efficiency of transport of photic zone water into the ocean depths, thus partially acting as a negative feedback that retarded the rate of atmospheric carbon dioxide buildup. Also, diminished biocalcification inhibited the removal of alkalinity from the deep ocean, causing an overshoot of calcium carbonate deposition once net calcium carbonate production resumed, helping restore the ocean to its state before
7072-511: The enhanced runoff formed thick paleosoil enriched with carbonate nodules ( Microcodium like), and this suggests a semi-arid climate . Unlike during lesser, more gradual hyperthermals, glauconite authigenesis was inhibited. The sedimentological effects of the PETM lagged behind the carbon isotope shifts. In the Tremp-Graus Basin of northern Spain, fluvial systems grew and rates of deposition of alluvial sediments increased with
7176-546: The intended article. Retrieved from " https://en.wikipedia.org/w/index.php?title=Eeco&oldid=1219845609 " Category : Disambiguation pages Hidden categories: Pages with broken anchors Short description is different from Wikidata All article disambiguation pages All disambiguation pages Paleocene%E2%80%93Eocene Thermal Maximum#Timing of carbon addition and warming The Paleocene–Eocene thermal maximum ( PETM ), alternatively ” Eocene thermal maximum 1 (ETM1) “ and formerly known as
7280-485: The interchange of terrestrial life. The formation of the isthmus fundamentally changed the system of inter-ocean circulation of warm and cold currents, which caused the northern polar ice cap to form. The creation of the Gulf Stream and the Atlantic system of weather and currents would eventually serve as the environmental engine of the " triangle trade " routes that were the basis of the Atlantic World system in
7384-549: The isotopically depleted carbon that produced the carbon isotopic excursion. The coeval ages of two other kimberlite clusters in the Lac de Gras field and two other early Cenozoic hyperthermals indicate that CO 2 degassing during kimberlite emplacement is a plausible source of the CO 2 responsible for these sudden global warming events. One of the leading candidates for the cause of the observed carbon cycle disturbances and global warming
7488-498: The isthmus and its implications is geologically and ecologically more nuanced. There is isotopic and carbonate deposition rate evidence that deep water connections below 1,800 m (5,900 ft) were broken between the Atlantic and Pacific by between 12 and 9.2 Ma. However exchange of surface water so as to maintain western Atlantic salinity at eastern Pacific values continued until about 4.6 Ma with current Caribbean values being reached by about 4.2 Ma although there seems to have been
7592-552: The isthmus. The Monagrillo archeological site contains ceramics dating from 2500-1200 BCE, some of the earliest examples of ceramics in Central America. This site also contains evidence of one of the earliest sites of maize agriculture in the region. The Monagrillo site evolved into a variety of thriving cultural traditions, identified by archeologists as the Gran Coclé culture area. Indigenous peoples in Panama have been connected to
7696-483: The late Paleocene through the early Eocene. Superimposed on this long-term, gradual warming were at least three (and probably more) "hyperthermals". These can be defined as geologically brief (<200,000 year) events characterized by rapid global warming, major changes in the environment, and massive carbon addition. Though not the first within the Cenozoic , the PETM was the most extreme hyperthermal, and stands out as
7800-581: The local environment transitioning from a closed marsh to an open, eutrophic swamp with frequent algal blooms. Precipitation patterns became highly unstable along the New Jersey Shelf . In the Rocky Mountain Interior, precipitation locally declined, however, as the interior of North America became more seasonally arid. Along the central California coast, conditions also became drier overall, although precipitation did increase in
7904-415: The massive past carbon release to our ocean and atmosphere, and the source of this carbon remain topics of considerable current geoscience research. What has become clear over the last few decades: Stratigraphic sections across the PETM reveal numerous changes beyond warming and carbon emission. Consistent with an Epoch boundary, Fossil records of many organisms show major turnovers. In the marine realm,
8008-406: The middle of the hyperthermal. The dwarfing of various mammal lineages led to further dwarfing in other mammals whose reduction in body size was not directly induced by the PETM. Many major mammalian clades – including hyaenodontids , artiodactyls , perissodactyls , and primates – appeared and spread around the globe 13,000 to 22,000 years after the initiation of the PETM. It is possible that
8112-554: The onset of the PETM; their decline came about towards the end of the event. A decrease in diversity and migration away from the oppressively hot tropics indicates planktonic foraminifera were adversely affected as well. The Lilliput effect is observed in shallow water foraminifera, possibly as a response to decreased surficial water density or diminished nutrient availability. Populations of planktonic foraminifera bearing photosymbionts increased. Extinction rates among calcareous nannoplankton increased, but so did origination rates. In
8216-421: The onset of the event. Acidification of deep waters, and the later spreading from the North Atlantic can explain spatial variations in carbonate dissolution. In parts of the southeast Atlantic, the lysocline rose by 2 km in just a few thousand years. Evidence from the tropical Pacific Ocean suggests a minimum lysocline shoaling of around 500 m at the time of this hyperthermal. Acidification may have increased
8320-695: The onset provides insight to the source of C -depleted CO 2 . The total duration of the CIE can be estimated in several ways. The iconic sediment interval for examining and dating the PETM is a core recovered in 1987 by the Ocean Drilling Program at Hole 690B at Maud Rise in the South Atlantic Ocean. At this location, the PETM CIE, from start to end, spans about 2 m. Long-term age constraints, through biostratigraphy and magnetostratigraphy , suggest an average Paleogene sedimentation rate of about 1.23 cm/1,000yrs. Assuming
8424-403: The poles through an ice–albedo feedback . It may be the case, however, that during the PETM, this feedback was largely absent because of limited polar ice, so temperatures on the Equator and at the poles increased similarly. Notable is the absence of documented greater warming in polar regions compared to other regions. This implies a non-existing ice-albedo feedback, suggesting no sea or land ice
8528-401: The poles. Central China during the PETM hosted dense subtropical forests as a result of the significant increase in rates of precipitation in the region, with average temperatures between 21 °C and 24 °C and mean annual precipitation ranging from 1,396 to 1,997 mm. Similarly, Central Asia became wetter as proto-monsoonal rainfall penetrated farther inland. Very high precipitation
8632-409: The presence of extensive intrusive sill complexes and thousands of kilometer-sized hydrothermal vent complexes in sedimentary basins on the mid-Norwegian margin and west of Shetland. This hydrothermal venting occurred at shallow depths, enhancing its ability to vent gases into the atmosphere and influence the global climate. Volcanic eruptions of a large magnitude can impact global climate, reducing
8736-691: The presence of sulphur-bound isorenieratane. The Gulf Coastal Plain was also affected by euxinia. The Atlantic Coastal Plain , well oxygenated during the Late Palaeocene, became highly dysoxic during the PETM. The tropical surface oceans, in contrast, remained oxygenated over the course of the hyperthermal event. It is possible that during the PETM's early stages, anoxia helped to slow down warming through carbon drawdown via organic matter burial. A pronounced negative lithium isotope excursion in both marine carbonates and local weathering inputs suggests that weathering and erosion rates increased during
8840-457: The recognized age of 3 Ma, potentially stretching as far back as 19 Ma. The Isthmus of Panama has always been a place of global significance. Its formation as a geological feature had several biological and climatic effects that resonated on a planetary scale. The separation of the oceans increased marine biodiversity on both sides, and the connection between the American continents allowed for
8944-413: The rest of the open ocean, changes in nutrient availability were their dominant drivers. Acidification did lead to an abundance of heavily calcified algae and weakly calcified forams. The calcareous nannofossil species Neochiastozygus junctus thrived; its success is attributable to enhanced surficial productivity caused by enhanced nutrient runoff. Eutrophication at the onset of the PETM precipitated
9048-475: The result of dramatic changes in weathering and sedimentation rates, drove diversification of magnetite-forming organisms, likely including eukaryotes. Biogenic magnetites in animals have a crucial role in geomagnetic field navigation. The PETM is accompanied by significant changes in the diversity of calcareous nannofossils and benthic and planktonic foraminifera. A mass extinction of 35–50% of benthic foraminifera (especially in deeper waters) occurred over
9152-407: The seafloor renders lower values than when formed. On the other hand, these and other temperature proxies (e.g., TEX 86 ) are impacted at high latitudes because of seasonality; that is, the "temperature recorder" is biased toward summer, and therefore higher values, when the production of carbonate and organic carbon occurred. Clear evidence for massive addition of C-depleted carbon at the onset of
9256-521: The source of debate. In theory, it can be estimated from the magnitude of the negative carbon isotope excursion (CIE), the amount of carbonate dissolution on the seafloor, or ideally both. However, the shift in the δ C across the PETM depends on the location and the carbon-bearing phase analyzed. In some records of bulk carbonate, it is about 2‰ (per mil); in some records of terrestrial carbonate or organic matter it exceeds 6‰. Carbonate dissolution also varies throughout different ocean basins. It
9360-487: The stratosphere. Furthermore, phases of volcanic activity could have triggered the release of methane clathrates and other potential feedback loops. NAIP volcanism influenced the climatic changes of the time not only through the addition of greenhouse gases but also by changing the bathymetry of the North Atlantic. The connection between the North Sea and the North Atlantic through the Faroe-Shetland Basin
9464-494: The summer months. The drying of western North America is explained by the northward shift of low-level jets and atmospheric rivers. East African sites display evidence of aridity punctuated by seasonal episodes of potent precipitation, revealing the global climate during the PETM not to be universally humid. The proto-Mediterranean coastlines of the western Tethys became drier. Evidence from Forada in northeastern Italy suggests that arid and humid climatic intervals alternated over
9568-572: The temperatures of the bottom water. However, many ocean basins remained bioturbated through the PETM. Iodine to calcium ratios suggest oxygen minimum zones in the oceans expanded vertically and possibly also laterally. Water column anoxia and euxinia was most prevalent in restricted oceanic basins, such as the Arctic and Tethys Oceans. Euxinia struck the epicontinental North Sea Basin as well, as shown by increases in sedimentary uranium , molybdenum , sulphur , and pyrite concentrations, along with
9672-604: The thermal maximum. Panama Isthmus The Isthmus of Panama ( Spanish : Istmo de Panamá ) is the narrow strip of land that lies between the Caribbean Sea and the Pacific Ocean , linking North and South America . It contains the country of Panama and the Panama Canal . Like many isthmuses , it is a location of great geopolitical and strategic importance. The isthmus is thought to have been finally formed around 3 million years ago ( Ma ), separating
9776-469: The tropics during the PETM, enough to cause heat stress even in organisms resistant to extreme thermal stress, such as dinoflagellates, of which a significant number of species went extinct. Oxygen isotope ratios from Tanzania suggest that tropical SSTs may have been even higher, exceeding 40 °C. Ocean Drilling Program Site 1209 from the tropical western Pacific shows an increase in SST from 34 °C before
9880-538: The two tectonic plates was also pushing up the sea floor, eventually forcing some areas above sea level. Over time, massive amounts of sediment from North and South America filled the gaps between the newly forming islands. Over millions of years, the sediment deposits added to the islands until the gap was completely filled. However, an article in Science magazine stated that zircon crystals in middle Miocene bedrock from northern Colombia indicated that by 10 Ma, it
9984-487: The warm Gulf Stream can hold more moisture. The result is increased precipitation that contributes to snow pack. The formation of the Isthmus of Panama also played a major role in biodiversity on the planet. The bridge made it easier for animals and plants to migrate between the two continents. This event is known in paleontology as the Great American Interchange . For instance, in North America,
10088-507: The wider regional networks of exchange and diffusion for as long as they have inhabited the isthmus, evident in the presence of Coclé gold work being found as far away as Chichin Itza in the Yucatan. By 1501, when Europeans first arrived, the isthmus was inhabited widely by Chibchan- and Chocoan -speaking peoples. Vasco Núñez de Balboa , a Spanish conquistador, was the first European to reach
10192-453: Was also more restricted. Although various proxies for past atmospheric CO 2 concentrations across the Cenozoic do not agree in absolute terms, all suggest that levels in the early Paleogene before and after the PETM were much higher than at present-day. In any case, significant terrestrial ice sheets and sea-ice did not exist during the late Paleocene through early Eocene Earth surface temperatures gradually increased by about 6 °C from
10296-419: Was carried out by the colonizing forces in the early 16th century across Central America from Panama to Nicaragua. Deadly working conditions, wars of conquest, and the destruction of Indigenous communities and infrastructure resulted in the complete destruction and dispersal of Indigenous peoples from the most heavily colonized parts of the Isthmus. By 1550, less than three hundred Indigenous people were counted in
10400-492: Was extreme in parts of the north and central Atlantic Ocean, but far less pronounced in the Pacific Ocean. With available information, estimates of the carbon addition range from about 2,000 to 7,000 gigatons. The timing of the PETM δ C excursion is of considerable interest. This is because the total duration of the CIE, from the rapid drop in δ C through the near recovery to initial conditions, relates to key parameters of our global carbon cycle, and because
10504-485: Was little or no polar ice in the early Paleogene, the shift in δ O very probably signifies a rise in ocean temperature. The temperature rise is also supported by the spread of warmth-loving taxa to higher latitudes, changes in plant leaf shape and size, the Mg/Ca ratios of foraminifera, and the ratios of certain organic compounds , such as TEX 86 . Proxy data from Esplugafereda in northeastern Spain shows
10608-456: Was present in the late Paleocene. Precise limits on the global temperature rise during the PETM and whether this varied significantly with latitude remain open issues. Oxygen isotope and Mg/Ca of carbonate shells precipitated in surface waters of the ocean are commonly used measurements for reconstructing past temperature; however, both paleotemperature proxies can be compromised at low latitude locations, because re-crystallization of carbonate on
10712-510: Was severely restricted, as was its connection to it by way of the English Channel . Later phases of NAIP volcanic activity may have caused the other hyperthermal events of the Early Eocene as well, such as ETM2. It has also been suggested that volcanic activity around the Caribbean may have disrupted the circulation of oceanic currents, amplifying the magnitude of climate change. The presence of later (smaller) warming events of
10816-465: 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
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