Meteorite minerals offer clues to Ear...

Meteorite minerals offer clues to Earth extinctions, climate change

There are 2 comments on the MSNBC story from Sep 16, 2013, titled Meteorite minerals offer clues to Earth extinctions, climate change. In it, MSNBC reports that:

Scientists think a giant asteroid, which broke up long ago in the main asteroid belt between Mars and Jupiter, eventually made its way to Earth and led to the extinction of dinosaurs.

Join the discussion below, or Read more at MSNBC.

“Geologist [I'm Climate Change]”

Since: Mar 07

formerly Nuneaton

#1 Sep 18, 2013
Interesting article.

One item of note is that deposits from N. Mexico & Haiti long linked to Chixculub appear to be about 300,000 years earlier than the Chixculub impact.

The other item of note with these large impact spherules are that they are basaltic glass completely different to the average everyday rock @ the base of the crust under the chixculub crater.

The Chixculub ejecta also has a platinum group element anomaly which is absent from the Haiti & N. Mexico Spherule fallout beds.

Apparently the N.Mexico & Haiti impact glass has been devitrified & altered to smectite clay. It does however also contain spinel crystallised at higher melting point out of the glass during the airfall stage which should be quite easy to measure.

Also of interest is that core samples of the K-T impact clay appears to show in some areas a a part continental provenance with shocked quartz, Platinum group element anomaly, and microspherules.
Other core samples show a basaltic provenance of microspherules altered to smectite and generally an absence, or major reduction in the platinum group element anomaly.

Appears that 2 craters landing in 2 different similar geographic locality places @ 2 relatively closely spaced times have been sampled and stated to be the K-T boundary formation events.

The Chicxulub site being the latter event appears to be the crater responsible for the 6 months of dust shroud darkness as a result of it being a continental impact.
The Haiti, N.Mexico tektite strewn field crater appears to be a purely oceanic impact with local extinction of the marine life it landed on. The crater appears nowadays to be Gorgona island which was part of a basaltic plateau smashed into tectonic blocks with breccia and glassy spherules, and the scraped off onto the Colombian forearc.

Both Chixculub & Gorgona craters appear to be of similar size. The absence of mass extinction associated with Gorgona is likely a result of a local steam bath which snowed the dust out of the upper atmosphere resulting in it raining like hell & returning to daylight in a week or so after the impact.

The Danian impact (later but still in the same timeframe in earliest tertiary) also appears to have a platinum group element anomaly and likely also landed on a continent. It was smaller than Chixculub. A palaeo tsunami deposit in Brazil likely records a splash from the event but the crater site has not yet been revealed (either S. America or W. African continental shelf or interior basin).

Article is interesting as it may reveal that Platinum group element anomaly in some cases may be a signature of an impact onto old continental crust rather than a smashed up asteroid or comet. A chunk of the outer basalt shell of 4 Vesta for example will NOT carry an in house bolide hosted platinum group element abundance! It was not the only asteroid big enough to produce an iron core and outer basalt flows due to differentiation in early solar system history.

Will keep watching that space.

have a nice day: Ag
Guru

Colombo, Sri Lanka

#2 Sunday May 24
Adrian Godsafe MSc wrote:
Interesting article.
One item of note is that deposits from N. Mexico & Haiti long linked to Chixculub appear to be about 300,000 years earlier than the Chixculub impact.
The other item of note with these large impact spherules are that they are basaltic glass completely different to the average everyday rock @ the base of the crust under the chixculub crater.
The Chixculub ejecta also has a platinum group element anomaly which is absent from the Haiti & N. Mexico Spherule fallout beds.
Apparently the N.Mexico & Haiti impact glass has been devitrified & altered to smectite clay. It does however also contain spinel crystallised at higher melting point out of the glass during the airfall stage which should be quite easy to measure.
Also of interest is that core samples of the K-T impact clay appears to show in some areas a a part continental provenance with shocked quartz, Platinum group element anomaly, and microspherules.
Other core samples show a basaltic provenance of microspherules altered to smectite and generally an absence, or major reduction in the platinum group element anomaly.
Appears that 2 craters landing in 2 different similar geographic locality places @ 2 relatively closely spaced times have been sampled and stated to be the K-T boundary formation events.
The Chicxulub site being the latter event appears to be the crater responsible for the 6 months of dust shroud darkness as a result of it being a continental impact.
The Haiti, N.Mexico tektite strewn field crater appears to be a purely oceanic impact with local extinction of the marine life it landed on. The crater appears nowadays to be Gorgona island which was part of a basaltic plateau smashed into tectonic blocks with breccia and glassy spherules, and the scraped off onto the Colombian forearc.
Both Chixculub & Gorgona craters appear to be of similar size. The absence of mass extinction associated with Gorgona is likely a result of a local steam bath which snowed the dust out of the upper atmosphere resulting in it raining like hell & returning to daylight in a week or so after the impact.
The Danian impact (later but still in the same timeframe in earliest tertiary) also appears to have a platinum group element anomaly and likely also landed on a continent. It was smaller than Chixculub. A palaeo tsunami deposit in Brazil likely records a splash from the event but the crater site has not yet been revealed (either S. America or W. African continental shelf or interior basin).
Article is interesting as it may reveal that Platinum group element anomaly in some cases may be a signature of an impact onto old continental crust rather than a smashed up asteroid or comet. A chunk of the outer basalt shell of 4 Vesta for example will NOT carry an in house bolide hosted platinum group element abundance! It was not the only asteroid big enough to produce an iron core and outer basalt flows due to differentiation in early solar system history.
Will keep watching that space.
have a nice day: Ag

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