Re: [dinosaur] Dating of dinosaur age during history

The 3 Ma date for the end of the Cretaceous was due to the influence of Lord Kelvin's time scale. He found that since there was no new way of energy warming the interior of the Earth it must be continuously cooling, and by his calculations it was something like 90 million years old at most. Subdividing this duration by the relative thickness of the different strata of the various time periods gave a duration of only about 3 million years for the Cenozoic.

Famously the solution to both the missing internal heat for the Earth AND the method by which numerical ages of units could accurately be estimated was the same: natural radioactive decay.

On Sun, Nov 24, 2019 at 2:37 AM Justin Tweet <thescelosaurus@gmail.com> wrote:

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 dawidmazurek@wp.pl <dawidmazurek@wp.pl> 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 (Âhttps://doi.org/10.1017/S001675680100509XÂ). 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 <david.marjanovic@gmx.at> napisaÅ(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At this opportunity I'll mention that even the 2019-5 version is already outdated in at least one respect: the beginning of the Cambrian is given there as 541.0ÂÂ 1.0 Ma ago, but really happened later, between two volcanic-ash beds dated to 538.58ÂÂ 0.19 and 538.99ÂÂ 0.21 Ma ago.
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Linnemann, U., Ovtcharova, M., Schaltegger, U., GÃrtner, 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 highâresolution age data from the EdiacaranâCambrian boundary indicate rapid, ecologically driven onset of the Cambrian explosion. Terra Nova 31, 49â58. doi: 10.1111/ter.12368

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Justin Tweet
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