Posted on 07/03/2008 11:08:44 AM PDT by decimon
Simple Life Form May Have Existed
700 Million Years Earlier Than Previously Thought
Science Daily | July 8, 2008 | Curtin University
Posted on 07/11/2008 5:26:55 PM PDT by SunkenCiv
http://www.freerepublic.com/focus/chat/2044222/posts
Hmm, that cubic zirconium is often associated with dating? ;’)
http://www.freerepublic.com/tag/kirschvink/index
http://www.freerepublic.com/tag/joekirschvink/index
gotcha!
I tried reading up on that, very very complicated. I was wondering if zircons didn’t simply land here when the comet/meteor hit the earth...and that wouldn’t date the impact site, would it? But it seems that, although some extra-terrestrial object do contain zircons, when the body hits terra-firma, the zircons fracture.
And I’m really still no wiser...
bkmark
They are not the same as the Deccan. The Deccan traps are cretaceous flood basalts. These basins are Precambrian in age.
Cheers
Joe Meert
Dating of the zircons that are inherited into the sandstones (via erosion of nearby older rocks) can supply an age as follows. Suppose that there are rocks surrounding the basin that are well-dated. Suppose that there are rocks 1.6 billion years old, 1.1 billion years old and 800 million years old. If the basins are really 600 million years old, then the surrounding rocks would have eroded and supplied the mineral zircon (that is highly resistant to erosion) to the sandstone. When we looked in the sandstone, the youngest zircons we found were all older than 1 billion years. Thus, we concluded (along with some other confirming evidence) that the sediments were deposited around 1 billion years ago (they contained no 800 million year zircons from a nearby granite terrane.
Cheers
Joe Meert
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