geologia: Paleocene–Eocene thermal maximum

Evidence: 100 • authority: 72

The Paleocene–Eocene thermal maximum (PETM), alternatively Eocene thermal maximum 1 (ETM1) and formerly known as the Initial Eocene or Late Paleocene thermal maximum, was a geologically brief time interval characterized by a 5–8 °C (9–14 °F) 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 PETM lasted about 200,000 years, and occurred about 56 million years ago. The PETM arguably represents our best past analogue by which to understand how global warming and the carbon cycle operate in a greenhouse world. The time interval is…

Evidence: 56 • authority: 92

Widespread terrestrial ecosystem disruption at the onset of the Paleocene-Eocene Thermal Maximum.. The Paleocene-Eocene Thermal Maximum (PETM, ~56 Mya) interval was marked by massive 13 C-depleted carbon emissions into the ocean/atmosphere system, manifested as a negative carbon isotope excursion (CIE) in sedimentary components, and ~5 °C global average warming. Episodes of hydrological perturbations and soil-erosion have been widely documented for the PETM but their link with vegetation- and carbon cycle changes remain poorly constrained. Here, we present organic microfossil evidence showing a strong increase in fern-dominated pioneer vegetation that replaced coniferous forests on the marg…

Evidence: 51 • authority: 72

The Eocene (IPA: EE-ə-seen, EE-oh-) is a geological epoch that began about 56 million years ago (Ma). It is the second epoch of the Paleogene Period in the modern Cenozoic Era. The end point of the Eocene is the Eocene-Oligocene transition (EOT), between 33.9 and 33.4 Ma. Precise boundaries between the epochs are sometimes given at 33.9 or 33.7 Ma. The Eocene spans the time from the end of the Paleocene Epoch to the beginning of the Oligocene Epoch. The start of the Eocene is marked by a brief period in which the concentration of the carbon isotope 13C in the atmosphere was exceptionally low in comparison with the more common isotope 12C. The average temperature of Earth at the beginning of…

Evidence: 45 • authority: 92

Recognition of two potential warming events in the Paleocene terrestrial record of North America and associated mammalian responses.. Numerous early Cenozoic transient warming events ("hyperthermals") have been recognized in the marine record, but few have been located in fossiliferous terrestrial strata. Locating warming events is critical for understanding how terrestrial animals and plants responded to past climate change. We recognize two carbon isotope excursions (CIEs) in lower Paleocene (Danian) strata of the San Juan Basin, New Mexico, United States, based on sustained decreases in carbon isotope values in bulk organic carbon. The upper excursion correlates closely with the Latest D…

Evidence: 37 • authority: 88

Diagenetic Attenuation of Carbon Isotope Excursion Recorded by Planktic Foraminifers During the Paleocene‐Eocene Thermal Maximum. Abstract Earth surface temperatures warmed by ~5 °C during an ancient (~56 Ma) global warming event referred to as the Paleocene‐Eocene thermal maximum (PETM). A hallmark of the PETM is a carbon isotope excursion (CIE) signaling the release of massive amounts of 13 C‐depleted carbon into the ocean‐atmosphere system, but substrate‐specific differences in the CIE magnitude are a source of uncertainty for estimating the mass of carbon emitted. Here we report that secondary ion mass spectrometry (SIMS)‐based in situ measurements of δ 13 C in minute (7 μm) domains of…

Evidence: 33 • authority: 88

Supplemental Material: Larger benthic foraminiferal turnover and carbon isotope excursion during the Paleocene–Eocene Thermal Maximum in the Southern Himalayan carbonate platform (Eastern Neo-Tethys Ocean, Pakistan). Stable isotope datasets (δ13C and δ18O) from the Jandran and Sanjawi sections, along with supporting figures illustrating isotopic cross-plots and correlations, and tables of matrix micrite and bulk carbonate values.<p></p>

Evidence: 33 • authority: 88

Supplemental Material: Larger benthic foraminiferal turnover and carbon isotope excursion during the Paleocene–Eocene Thermal Maximum in the Southern Himalayan carbonate platform (Eastern Neo-Tethys Ocean, Pakistan). Stable isotope datasets (δ13C and δ18O) from the Jandran and Sanjawi sections, along with supporting figures illustrating isotopic cross-plots and correlations, and tables of matrix micrite and bulk carbonate values.<p></p>

Evidence: 33 • authority: 92

Changes in continental weathering regimes inhibited global marine deoxygenation during the Paleocene-Eocene thermal maximum.. The moderate impact of rapid global warming on oceanic redox and biodiversity during the Paleocene-Eocene thermal maximum (PETM; ~55.9 Ma) contrasts with other hyperthermal events in Earth's history, and remains mostly unexplained. Here, we use lithium isotope (δ 7 Li) proxy and Earth system model simulations to reconstruct continental weathering regimes during the PETM. Negative δ 7 Li excursions of 3-4‰ in shallow-marine carbonates suggests globally increased erosion rates and decreased weathering intensities. Further, large negative δ 7 Li excursions of 4-5‰ in si…

Evidence: 23 • authority: 72

The clathrate gun hypothesis is a proposed explanation for the periods of rapid warming during the Quaternary. The hypothesis is that changes in fluxes in upper intermediate waters in the ocean caused temperature fluctuations that alternately accumulated and occasionally released methane clathrate on upper continental slopes. This would have had an immediate impact on the global temperature, as methane is a much more powerful greenhouse gas than carbon dioxide. Despite its atmospheric lifetime of around 12 years, methane's global warming potential is 72 times greater than that of carbon dioxide over 20 years, and 25 times over 100 years (33 when accounting for aerosol interactions). It is f…