QUOTE (tdemko @ Jan 8 2006, 01:55 PM)
Yes, Myran...post edited...thanks!
For all of the non-geologists out there, the traditional methods for processing rocks for datable zircons is a very time- and work-intensive task, with much hands-on and microscope work (including final picking and separating very small grains with tweezers, needles, and brush hairs). Even in the best cases, zircon and sanidine crystals that may provide reliable absolute age dates of crystallization are a very small percentage of rock volume.
Jarosite in the Opportunity-analyzed Meridiani deposits seems to be quite common in some beds, and processing for datable separates may prove to be much simpler...
I will be perusing the terrestrial literature for some examples of jarosite dating...I can post results/key references, if anyone is interested...
Hehe, that tweezer picking image is precisely the one I had in mind when I posted a comment in another topic about the difficulty of building a robotic age-dating lab. I too, would like to learn more about the jarosite method.
QUOTE (Bill Harris @ Jan 8 2006, 02:10 PM)
And we need to come up with stratigraphic markers so we can figure out where we are in the section.
Yes, post anything you find.
--Bill
Thinking about marker beds, we really don't have anything solid in the way of such things, do we? We only have a tiny section from Eagle crater, and a larger one from Endurance. The closest thing to a marker I have seen is the Wellington contact observed at the base of Burns Cliff. That is the break between the high-angle bedding and the lower angle stuff. Considering the relatively short section we have seen, it would be hard to imagine we could call that a marker one could be confident in regionally. Unless we come across an ash bed that was deposited in a geological instant, we probably have to pray that the Opster hobbles up to Victoria for a closer look at deeper strata.