Non L Chondrite from Ordivician Found in Sweden

[AndyExton]

The burst of life in the Ordivician is thought to have been due to a meteorite storm around 470 million years ago. Many L Chondrites have been discovered in sedimentation relating to this age but a newly discovered type of meteorite has now been discovered in Sweden. The findings have been published in Earth and Planetary Science Letters but a New Scientist article appears http://www.newscientist.com/article/dn25817-swedish-space-rock-may-be-piece-of-early-life-puzzle.html?cmpid=RSS%7CNSNS%7C2012-GLOBAL%7Conline-news#.U7PyTZR3KpX.

The Journal can be found at http://www.sciencedirect.com/science/article/pii/S0012821X14003367. I have been able to download it but this was via my Open University Library access so not sure if others will be able to view.

Andy

[David Entwistle]

Thanks Andy,

An interesting paper. Can anyone check my maths and understanding?

The authors appear to have identified 100 meteorites which fell in an area of 20,000(?) square metres over a period of 1.5 million years.

I make that a rate of 3.33 x 10^-9 meteorites per square metre, per year.

So, given a similar fall rate, with an area of 3.28031 x 10^11 square meters, the combined area of England, Scotland, Wales, Northern Ireland and Ireland may expect to experience 1,093 meteorite falls in a year.

It would probably make collecting less of a challenge....

I find it hard to understand why this number of fossil meteorites are only evident in this one location.

[Barwellian]

In my experience in the desert on very old surfaces the individual meteorites break up due to weathering and spread apart over large distances...so if this had happened in that area and then further spreading happened due to other geological activity before they were incorporated into the rocks then they would not have to be lots of different falls. Do we know if they represented many different types or are most of them paired?....that would help to answer the question. On my last trip we found four completely different types within 50 yds of each other, so higher flux at that time and the above processes might explain the abundance in one location....just a thought.

G

[AndyExton]

HI David.

Yes your maths seem right to me having just checked.

Regards the finding of these fossil meteorites in only this location, as it is a working quarry the relevant aged rocks are exposed. From what I remember of my UK Geological history study, Ordovician geology is best viewed today in Shropshire (no Ordovician here on the Yorkshire coast - mostly Jurassic) . It may be a case that fossil meteorites are found in these exposures but not studied as they have been in Sweden. It would certainly be interesting to know.

Andy

[TDHughes]

I`m no maths connoisseur, but does it take into account the vertical variation. You mentioned 100 meteorites fell in an area of 20,000 square meters, not an area of cubic size. If each square meter is 3.33 x 10-9 It would be more realistic if this denoted a 20 meter high unit rather than a single plain. I may be way off.

Its an interesting topic. I wonder how many fossilised meteorites must be out there, in fact, most exceptional preservation methods for fossils suit the requirements of meteorites; anoxic conditions, rapid burial and diagenesis.

The main mass of Chelyabinsk was removed from the anoxic muds at the base of the lake. So I wonder what its fate could have been if it had remained. Just an idea any who.

[Barwellian]

With the new house I have been working on we have used a few hundred square meters of limestone and sandstone and could not help but think that over the years the many quarries providing such must have come across meteorites in the cutting and splitting....and probably scrapped them as they would be classed as blemishes in the matrix....I have been considering going back to the wholesalers stores and investigating further...I wonder what's in their scrap pile?

G

[AndyExton]

I have been considering going back to the wholesalers stores and investigating further...I wonder what's in their scrap pile?

G

It could certainly be worth an investigation!

[AndyExton]

Its an interesting topic. I wonder how many fossilised meteorites must be out there, in fact, most exceptional preservation methods for fossils suit the requirements of meteorites; anoxic conditions, rapid burial and diagenesis.

With the 4.5 billion years of Earth history it is scary to think how much space material is buried within the Earth's geology.

[Barwellian]

In that time Andy the whole lot is space material...including you and I...just a bit rearranged

[David Entwistle]

I`m no maths connoisseur, but does it take into account the vertical variation. You mentioned 100 meteorites fell in an area of 20,000 square meters, not an area of cubic size. If each square meter is 3.33 x 10-9 It would be more realistic if this denoted a 20 meter high unit rather than a single plain. I may be way off.

Hi TD,

I think I see where you are coming from.

My clunky sums are largely base on the image below and the statement that "The recovered meteorites fell over an area of 20,000 m^2 of the sea floor during ∼2 Ma". I make the total depth quarried 4.67m, so a volume of 20,000 x 4.67 = 93,400 m^3.