Re: All kinds of odd observat...

[Tompaleo@xxxxxxx]

>> IRIDIUM
> > 
 >> Terry also queries the relevance of iridium.  This is now 
 >> recorded from over a hundred sites in the K-T boundary rocks >>from
 >> all continents and from deep-sea cores.  Even though Alvarez et
 >> al. only had th ree sites for their original paper they guessed
 >> right that it would turn out to be world-wide.

>True.  However the interesting thing is that at *some* sites there
>appear to be several iridium spike, rather than just one.  (This
>is variable from site to site, but still notworthy).

'Multiple Iridium spikes" need also be taken in the context of the
depositional history of the stratum in question. I believe at least one (Hell
Creek?? I forget where ) had more than one Ir spike but can be explained by
the fact that the formation was created by a fluvial stream complex. In such
a  highly variable depositional setting, not only fossils can be reworked but
so can the geochemical signature of an impact.

                                       Regards,
                                       Thomas R. Lipka
                                       Paleontological/Geological Studies