Autor Thema: Neue Belege für die 'Younger Dryas impact' Hypothese  (Gelesen 1689 mal)

Offline karmaka

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Neue Belege für die 'Younger Dryas impact' Hypothese
« am: März 06, 2012, 06:59:53 vorm. »
Neue Belege für die 'Younger Dryas impact' Hypothese

Studie ergibt neue Hinweise auf einen großen Impakt vor 12900 Jahren.

http://www.ia.ucsb.edu/pa/display.aspx?pkey=2662

''New evidence from Central Mexico supporting the Younger Dryas extraterrestrial impact hypothesis,'' by Isabel Israde-Alcántara

http://www.pnas.org/content/early/2012/03/01/1110614109.abstract

Younger Dryas impact hypothesis:   http://en.wikipedia.org/wiki/Younger_Dryas_impact_hypothesis

 :hut:

Martin

Offline karmaka

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Das Ende einer Theorie zum Ende der Clovis Kultur?
« Antwort #1 am: Januar 30, 2013, 16:20:34 nachm. »
Das Ende einer weitverbreiteten Theorie zum Ende der Clovis-Kultur ?

https://share.sandia.gov/news/resources/news_releases/clovis_rebuttal/

http://www.agu.org/books/gm/v198/2012GM001209/2012GM001209.shtml

http://de.wikipedia.org/wiki/Clovis-Kultur


PS: Der Beitrag hätte vielleicht besser in diesen bestehenden thread gehört  :weissefahne::

http://www.jgr-apolda.eu/index.php?topic=7569.0

Lassen sich die beiden 'verschmelzen', lieber Admin oder Sheriff?

Beste Grüße

Martin
« Letzte Änderung: Januar 30, 2013, 16:42:12 nachm. von karmaka »

Offline MetGold

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Re: Neue Belege für die 'Younger Dryas impact' Hypothese
« Antwort #2 am: Januar 30, 2013, 17:21:10 nachm. »
 
erledigt!

Ich habe mal die unterschiedlichen Betreffs(Themennamen) gelassen! Wenn nicht erwünscht mich nochmal kontaktieren!


 :winken:   MetGold
Ein ereignisreicher Tag ist mehr als namenlose Jahre - (Spruch aus einem chinesischen Kalender)

Offline karmaka

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Re: Neue Belege für die 'Younger Dryas impact' Hypothese
« Antwort #3 am: Januar 30, 2013, 17:26:22 nachm. »
Vielen Dank!

Die unterschiedlichen Themennamen sollten wir so lassen, denn sie zeigen ganz gut die scheinbar kontroverse Natur dieses Sachverhalts.

 :hut:

Martin

Offline karmaka

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Re: Neue Belege für die 'Younger Dryas impact' Hypothese
« Antwort #4 am: Mai 21, 2013, 00:46:53 vorm. »
The Mammoth’s Lament: UC Research Shows How Cosmic Impact Sparked Devastating Climate Change

Research published in the Proceedings of the National Academy of Sciences finds evidence of a major cosmic event near the end of the Ice Age. The ensuing climate change forced many species to adapt or die.

LINK

Evidence for deposition of 10 million tonnes of impact spherules across four continents 12,800 y ago

Zitat
Abstract:

Airbursts/impacts by a fragmented comet or asteroid have been proposed at the Younger Dryas onset (12.80 ± 0.15 ka) based on identification of an assemblage of impact-related proxies, including microspherules, nanodiamonds, and iridium. Distributed across four continents at the Younger Dryas boundary (YDB), spherule peaks have been independently confirmed in eight studies, but unconfirmed in two others, resulting in continued dispute about their occurrence, distribution, and origin. To further address this dispute and better identify YDB spherules, we present results from one of the largest spherule investigations ever undertaken regarding spherule geochemistry, morphologies, origins, and processes of formation. We investigated 18 sites across North America, Europe, and the Middle East, performing nearly 700 analyses on spherules using energy dispersive X-ray spectroscopy for geochemical analyses and scanning electron microscopy for surface microstructural characterization. Twelve locations rank among the world’s premier end-Pleistocene archaeological sites, where the YDB marks a hiatus in human occupation or major changes in site use. Our results are consistent with melting of sediments to temperatures >2,200 °C by the thermal radiation and air shocks produced by passage of an extraterrestrial object through the atmosphere; they are inconsistent with volcanic, cosmic, anthropogenic, lightning, or authigenic sources. We also produced spherules from wood in the laboratory at >1,730 °C, indicating that impact-related incineration of biomass may have contributed to spherule production. At 12.8 ka, an estimated 10 million tonnes of spherules were distributed across ∼50 million square kilometers, similar to well-known impact strewnfields and consistent with a major cosmic impact event.

Quelle

Supporting information (PDF-LINK)
« Letzte Änderung: Mai 21, 2013, 01:06:36 vorm. von karmaka »

Offline karmaka

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Re: Neue Belege für die 'Younger Dryas impact' Hypothese
« Antwort #5 am: August 02, 2013, 09:44:54 vorm. »
Erhöhte Platinkonzentration in 12890 Jahre altem grönländischen Eiskern

Large Pt anomaly in the Greenland ice core points to a cataclysm at the onset of Younger Dryas

Michail I. Petaev, Shichun Huang, Stein B. Jacobsen, und Alan Zindler

10.1073/pnas.1303924110 PNAS July 22, 2013

Zitat
One explanation of the abrupt cooling episode known as the Younger Dryas (YD) is a cosmic impact or airburst at the YD boundary (YDB) that triggered cooling and resulted in other calamities, including the disappearance of the Clovis culture and the extinction of many large mammal species. We tested the YDB impact hypothesis by analyzing ice samples from the Greenland Ice Sheet Project 2 (GISP2) ice core across the Bølling-Allerød/YD boundary for major and trace elements. We found a large Pt anomaly at the YDB, not accompanied by a prominent Ir anomaly, with the Pt/Ir ratios at the Pt peak exceeding those in known terrestrial and extraterrestrial materials. Whereas the highly fractionated Pt/Ir ratio rules out mantle or chondritic sources of the Pt anomaly, it does not allow positive identification of the source. Circumstantial evidence such as very high, superchondritic Pt/Al ratios associated with the Pt anomaly and its timing, different from other major events recorded on the GISP2 ice core such as well-understood sulfate spikes caused by volcanic activity and the ammonium and nitrate spike due to the biomass destruction, hints for an extraterrestrial source of Pt. Such a source could have been a highly differentiated object like an Ir-poor iron meteorite that is unlikely to result in an airburst or trigger wide wildfires proposed by the YDB impact hypothesis.

LINK

Supporting information (PDF-LINK)

Offline karmaka

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Re: Neue Belege für die 'Younger Dryas impact' Hypothese
« Antwort #6 am: September 03, 2013, 00:19:18 vorm. »
Es gibt wieder etwas Neues zum Thema

Study Links Prehistoric Climate Shift, Cosmic Impact

LINK

Die andere Seite:

Zitat
'Fringe science'

Scientists on the other side of the impact theory debate are not so sure.

"At this point, the pro-impact literature is fringe science being promoted by a single journal," said Nicholas Pinter, a geologist at Southern Illinois University in Carbondale, who was not involved in the PNAS research.

Sharma's osmium isotope analysis of Younger Dryas sediments supports studies that show high concentrations of iridium (a meteorite impact marker) in Younger Dryas layers are erroneous, said Gregory Ravizza, a geologist at the University of Hawaii, also not involved in the research. Osmium and iridium concentrations tend to track each other — both will be high at the same spot, Ravizza said, casting doubt on Sharma's conclusions.

Quelle

 

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