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Paleocene-Eocene Comet impact
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Comet impact 'linked' to rise of mammals

Dennis Kent, from Rutgers University, a co-author of the new study, thinks the glass found in sediment cores drilled along the New Jersey coast could have come from a 10km-wide comet slamming into the Atlantic Ocean.
This could be behind the mysterious release of CO2, and other greenhouse gases, which warmed the planet very rapidly 55.6 million years ago. During this event, global temperatures rose by about 6C in less than 1,000 years.

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RE: Palaeocene-Eocene Thermal Maximum
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Did a cosmic crash heat up Earth 56 million years ago?

Researchers have found evidence that a comet or space rock smashed into Earth 56 million years ago, perhaps setting off a massive warming that began around that time.
It's a suggestion that is causing much debate among scientists, many of whom question the link. Researchers study the mysterious ancient warming to better understand current man-made climate change and Earth's future.
About 56 million years ago Earth warmed by about 9 to 14 degrees (5 to 8 degrees Celsius) and then returned to normal, all in about 100,000 years. This helped lead to some extinctions and the rise of mammals. Theories about the cause have pointed to increased carbon in the atmosphere from many erupting volcanoes; a Greenland volcano that cooked a huge coal deposit; and sudden methane releases from underwater. But a new study in the journal Science suggests a link to a cosmic crash.

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Paleocene-Eocene impact
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Title: Widespread wildfires at the Paleocene Eocene boundary: Evidence from abundant charcoal preserved in the thick Marlboro Clay
Author: FUNG, Megan K., SCHALLER, Morgan F., HOFF, Christopher M., KATZ, Miriam E. and WRIGHT, James D

The overall warming trend of the late Paleocene through early Eocene was punctuated by a prominent, short-lived warming event known as the Paleocene-Eocene Thermal Maximum (PETM; ~56 Ma): a 5-8C global warming associated with a negative carbon isotope excursion (CIE). The PETM was accompanied by the rapid expansion of terrestrial plants and mammals, acceleration of the hydrologic cycle, ocean acidification, and the extinction of 40-60% of deep-sea benthic foraminifera. The backdrop for these climatic and biotic changes is a massive injection of isotopically light carbon into the ocean-atmosphere system, creating a negative 13C excursion in both marine and terrestrial settings. The source and magnitude of the 13C-depleted carbon that generated the CIE is still debated. However, the recent discovery of silicate glass impact ejecta (microtektites and microkrystites) in the onset of the CIE indicates that the Paleocene-Eocene (P-E) boundary transition was coincident with an extraterrestrial impact. Here, we present the discovery of charcoal-rich sediments from three Atlantic Coastal Plain paleo-continental shelf sites (Medford, Wilson Lake B, and Millville) where primary impact ejecta was recently identified at the P-E boundary. Peak charcoal abundances occur immediately above the spherule layer and charcoal content decreases upsection. The individual microscopic black carbon shards (~100 m long) contain 60-85 wt % carbon and show the remains of charred plant features, such as cellular textures and side wall pits. We infer that the thermal anomalies resulting from the impact and ejecta fallout probably ignited widespread wildfires, evidence for which has been documented previously from other P-E sections globally. Post-wildfire changes in soil infiltration dramatically increase runoff and erosion, resulting in substantial soil loss. Burnt terrestrial plant matter and eroded forest soils would have been transported to the shelves in a massive deluge of sediment, and is probably responsible for the thick Marlboro Clay whose base is coincident with the onset of the CIE.

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RE: Palaeocene-Eocene Thermal Maximum
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Dire climate warning locked in ancient rocks

Carbon is pouring into Earth's atmosphere ten times faster today than during a dramatic event 56 million years ago that raised Earth's temperature by at least five degrees Celsius (nine degrees Fahrenheit), according to a study released Sunday.
That's not good news, geologists say, because the Palaeocene-Eocene Thermal Maximum, or PETM, might have been a pre-historic dress rehearsal for a future climate change event that could be more abrupt and more damaging.

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Carbon release to atmosphere 10 times faster than in the past

The rate of release of carbon into the atmosphere today is nearly 10 times as fast as during the Palaeocene-Eocene Thermal Maximum (PETM), 55.9 million years ago, the best analogy we have for current global warming, according to an international team of geologists. Rate matters and this current rapid change may not allow sufficient time for the biological environment to adjust.
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