[meteorite-list] Platinum and other metals point to cosmic impact cause of Younger Dryas 13 kya: Robin Whittle: Rich Murray 2013.08.06
8:17 PM PST Tuesday 2013.08.06
to Meteorite-list
Here is a write-up:
of an article:
Large Pt anomaly in the Greenland ice core points to a cataclysm at the onset of Younger Dryas
Shichun Huang a,
Stein B. Jacobsen a
and Alan Zindler a
Abstract
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.
- Robin
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Platinum levels rose about 100 times...
Evidence for deposition of 10 million tonnes of impact spherules across four continents 12,800 y ago, James H. Wittke et al, PNAS: Rich Murray 2013.05.22
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