Re: [dinosaur] Dating of dinosaur age during history

Norell et al. (1995) mentioned that in 1915 William Diller Matthew produced
a diagram that put the end of the Cretaceous at 3 million years ago, with
the whole Mesozoic lasting 9 million years. I've made perfunctory searches
occasionally but I've yet to find the diagram.-Justin

Norell, M. A., E. S. Gaffney, and L. Dingus. 1995. Discovering dinosaurs in
the American Museum of Natural History. Alfred A. Knopf, Inc., New York,
New York.

On Fri, Nov 22, 2019 at 12:55 PM [email protected] <[email protected]>
wrote:

> It's more complicated than that. It is the level of 'golden spike' at
> Fortune Head that is assumed to be 541.0+-1.0 Ma. The boundary is defined
> by the first occurence of _Treptichnus pedum_, which is not an organism by
> itself, for one, and actually occurs in older levels at type section (
> https://urldefense.proofpoint.com/v2/url?u=https-3A__doi.org_10.1017_S001675680100509X&d=DwIFaQ&c=clK7kQUTWtAVEOVIgvi0NU5BOUHhpN0H8p7CSfnc_gI&r=Ry_mO4IFaUmGof_Yl9MyZgecRCKHn5g4z1CYJgFW9SI&m=FjdGnDRT2LKfGH-Q9WvVLIz-e-P6BibT5DAeJu36pm8&s=05ckjtAImsOvqE0x8mBDHcBwjzOWwtwM-WSDTCFmuXU&e= 
> <https://urldefense.proofpoint.com/v2/url?u=https-3A__doi.org_10.1017_S001675680100509X&d=DwMFaQ&c=clK7kQUTWtAVEOVIgvi0NU5BOUHhpN0H8p7CSfnc_gI&r=Ry_mO4IFaUmGof_Yl9MyZgecRCKHn5g4z1CYJgFW9SI&m=JjaSkxJpIYFPxbrFYwOkiR2V_WOCBtMGgfhCYjgujk8&s=JvzUvqvtGiYecSIn3OYJtsW_I1JPXYBolPLCE_ikCAc&e=> ).
> The first occurence of similar ichnofossils at ~538.5-539 Ma in the section
> discussed by Linnemann et al. is connected with change in lithology. I
> think it would be reasonable to assume that the first occurence of a
> certain behaviour at a specific site has more to do with regional onset of
> conditions favourable for the tracemakers than with the actual, global
> evolutionary origin of this specific behaviour. In other words, the
> Precambrian/Cambrian as defined by ichnofossils may be diachronous.
>
> Dnia 22 listopada 2019 16:54 David Marjanovic <[email protected]>
> napisał(a):
>
> At this opportunity I'll mention that even the 2019-5 version is already
> outdated in at least one respect: the beginning of the Cambrian is given
> there as 541.0 ± 1.0 Ma ago, but really happened later, between two
> volcanic-ash beds dated to 538.58 ± 0.19 and 538.99 ± 0.21 Ma ago.
>
> Linnemann, U., Ovtcharova, M., Schaltegger, U., Gärtner, A., Hautmann, M.,
> Geyer, G., Vickers-Rich, P., Rich, T., Plessen, B., Hofmann, M., Zieger,
> J., Krause, R., Kriesfeld, L. and Smith, J. (2018, printed 2019) New high‐resolution
> age data from the Ediacaran–Cambrian boundary indicate rapid, ecologically
> driven onset of the Cambrian explosion. *Terra Nova* 31, 49–58. doi:
> 10.1111/ter.12368
> <https://urldefense.proofpoint.com/v2/url?u=https-3A__doi.org_10.1111_ter.12368&d=DwMBaQ&c=clK7kQUTWtAVEOVIgvi0NU5BOUHhpN0H8p7CSfnc_gI&r=Ry_mO4IFaUmGof_Yl9MyZgecRCKHn5g4z1CYJgFW9SI&m=GOz54pssGqhTNivBDHTkjZumNCitcgZmjLkI-t0JTXo&s=0dqpuYUYHxoLAjgcRInFAYOpJXfUKrRqe05O3xqTfFY&e=>
>
>
>

-- 
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