[meteorite-list] Platinum & other metals point to cosmic impact cause of Younger Dryas 13kya

From: Robin Whittle <rw_at_meteoritecentral.com>
Date: Wed, 07 Aug 2013 13:17:34 +1000
Message-ID: <5201BC4E.10200_at_firstpr.com.au>

Here is a write-up:

http://phys.org/news/2013-08-evidence-cosmic-impact-younger-dryas.html

of an article:

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

    Michail I. Petaeva, Shichun Huanga, Stein B. Jacobsena and
    Alan Zindlera

    http://www.pnas.org/content/110/32/12917


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 B?lling-Aller?d/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.

http://en.wikipedia.org/wiki/Clovis_culture

 - Robin
Received on Tue 06 Aug 2013 11:17:34 PM PDT