The fossil meteorites in question are Ordovician, L-chondrites that are
mineralogically equivalent to around 20% of modern L-chondrites. All are
presumed to have originated from a single asteroid collision event. Also
interesting is that modern L-chondrites in this family have exposure ages
close to the 480 million year old fossil meteorites. The suggestion is that
a large population of fragments was generated, and some of these were
injected into a fast track across Earth's orbit- something that has been
modeled and found possible by considering orbital resonances in the Asteroid
Belt caused by Jupiter.
Also interesting is that the period of increased meteorite flux 480 million
years ago corresponds to a simultaneous increase in global biodiversity.
There have been some interesting talks on this subject at recent meteoritics
conferences.
Chris
*****************************************
Chris L Peterson
Cloudbait Observatory
http://www.cloudbait.com
----- Original Message -----
From: "Yinan Wang" <veom...@gmail.com>
To: <Meteorite-list@meteoritecentral.com>
Sent: Monday, October 25, 2010 2:54 PM
Subject: Re: [meteorite-list] Finding fossil Meteorites
As a fossil collector, I can tell you that there are tons of
meteor-wrongs in sedimentary rock. The main reason is that a lot of
metallic concretions form in sedimentary rock diagenetically; hematite
nodules, iron phosphates, pyrite concretions, marcasite, etc.
So you would find good layers of limestone and then suddenly there's a
meteorite-shaped nodule... But you guys know how to ID meteorites.
For Count Deiro; here's a link to a geologic map of Nevada:
http://geology.about.com/od/maps/ig/stategeomaps/NVgeomap.htm
-Yinan
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