Re: Asteroid Impact Ended The Triassic

["Emma C. Rainforth" <emmar@ldeo.columbia.edu>]

Title: Re: Asteroid Impact Ended The Triassic

> > Still to be found is what would be a
> vast crater, said Olsen, [...]
>
> What about that Nature paper from 1997 about a possible Tr-J boundary
> crater
> chain throughout North America and Europe
> (ref later)?

Spray, J. G., S. P. Kelley and D. B. Rowley. 1998. Evidence for a late Triassic multiple impact event on Earth. Nature 392:171-173.

Unfortunately the ranges and error bars on their dates for the craters in this 'chain' span millions of years. So there is no evidence, at the present resolution of dating, that these craters are 'contemporaneous' with each other, let alone the TJ boundary. Oh, and if memory serves, they used Harland et al's 1990 date of 208 Ma for the TJ boundary, whereas it's presently put at 202 Ma.

Likewise Manicouagan (Hodych and Dunning 1992) is supposedly 213 Ma but again the error bars (largely due to difficulties with argon loss) span TENS of millions of years (not to mention those authors had to discard a good third of their results to GET '213'!). But, Manicouagan is being redated as we speak....

emma

Hodych, J. P. and G. R. Dunning. 1992. Did the Manicouagan impact trigger end-of-Triassic mass extinction? Geology 20:51-54.