tag:blogger.com,1999:blog-5519292617097628087.post3676204507533718556..comments2024-01-02T16:09:12.886-07:00Comments on Chinleana: The TR-J Terrestrial Extinction Actually Early Jurassic?Bill Parkerhttp://www.blogger.com/profile/05941940882532354219noreply@blogger.comBlogger5125tag:blogger.com,1999:blog-5519292617097628087.post-82817622656248862102008-09-09T17:19:00.000-07:002008-09-09T17:19:00.000-07:00Bill - you are definitely correct. We have alot t...Bill - you are definitely correct. We have alot to learn about the precise age and correlation of various Chinle Formation units. In fact, I would say that is the case for most early Mesozoic terrestrial assemblages around the world.220myahttps://www.blogger.com/profile/06403919493457640549noreply@blogger.comtag:blogger.com,1999:blog-5519292617097628087.post-80733275477541199772008-09-08T19:31:00.000-07:002008-09-08T19:31:00.000-07:00Thanks for the excellent comments. Will and 220mya...Thanks for the excellent comments. Will and 220mya are correct, this is all very tentative, something I quickly concluded after reading Adam Yate's post and contemplating the Zeigler and Geissman abstract. However, the point is that when all of these units are the future focus of more detailed research (especially geochronological) we may get some surprising results.Bill Parkerhttps://www.blogger.com/profile/05941940882532354219noreply@blogger.comtag:blogger.com,1999:blog-5519292617097628087.post-56715103157240346722008-09-08T18:55:00.000-07:002008-09-08T18:55:00.000-07:00I think the Zeigler & Geissman data is very in...I think the Zeigler & Geissman data is very interesting, but it only demonstrates that the a variety of uppermost Chinle units are not correlative. Vertebrate biostratigraphy is simply not precise enough to correlate magnetostratigraphic records.<BR/><BR/>You can always slide magnetostratigraphic records up and down relative to each other and come up with a best fit that looks good. But this is mostly subjective unless you have precise geochronologic constraints to tie them together. The thicknesses of each chron are largely meaningless unless you can correct for basin fill rates for every record.220myahttps://www.blogger.com/profile/06403919493457640549noreply@blogger.comtag:blogger.com,1999:blog-5519292617097628087.post-90943567886125194982008-09-08T14:39:00.000-07:002008-09-08T14:39:00.000-07:00Soooo...what-if the opposite? The Tr-J Mass Extin...Soooo...what-if the opposite? The Tr-J Mass Extinction was more of a nonevent? It could be that there were multiple places that faunal turnover at different rates and at different times. Didn't they JUST find a bunch of dinosauromorphs that survived much later than they thought at Ghost Ranch (Hayden Quarry) supposedly late triassic locale?<BR/><BR/>That would run contrary to the biostrategraphic approach, but...I have to wonder. Or perhaps we were witnessing a gradual faunal turnover, but because of sampling biases, we thought we had a mass extinction on our hands?<BR/><BR/>Your explanation is more parsimonious, but...just something to test.Will Bairdhttps://www.blogger.com/profile/07562404098136557872noreply@blogger.comtag:blogger.com,1999:blog-5519292617097628087.post-11574884806402628892008-09-08T07:53:00.000-07:002008-09-08T07:53:00.000-07:00Perhaps this mass extinction was also partly respo...Perhaps this mass extinction was also partly responsible for the rise of eurypod thyreophorans and neornithischians. :-)Nickhttps://www.blogger.com/profile/08718847558790015112noreply@blogger.com