Charles Lyell Cenozoic/Earth age dating theory flaws?

Question

I know Charles Lyell is known for his Uniformitarianism theory, but what I'd like to ask everyone (especially geologists) about his dating method of the Cenozoic era (through the amount of evolution shown by marine mollusks in the various series of the Tertiary System).

How did he exactly come to conclusions that the Cenozoic era was 80 million years old?

Secondly, what's the flaw in his theory? (The Cenozoic era is actually just 65 m.y.old)

Sources/links that are helpful and relevant are highly appreciated. Thanks!

Answer 1

Charles Lyell didn't have any methods to date rocks using radiometric techniques - so 80 million years old was I suppose an educated guess, perhaps based on sedimentation rate and thickness of rocks. If it is true that he came up with 80 million years, that only goes to illustrate what an outstanding geologist Lyell was. To make things more difficult for Lyell, the Mesozoic/Cenozoic boundary does not occur in Britain (I think the nearest Mesozoic/Cenozoic boundary is in Italy).

Today we know that the Cenozoic began 65.5 million years ago (Cenozoic = Tertiary).

International Commission on Stratigraphy dates the geological column using Global Boundary Stratotype Sections and Points (GSSPs). GSSPs are carefully studied rock outcrops, where scientists agree that the age is correct and the boundary is obvious, lots of animals go extinct.

The Mesozoic/Cenozoic boundary is defined today as follows:

"The GSSP is located in northern Tunisia about 7km west of the town of El Kef .... The GSSP is located at a latitude of 36°09'13.2"N and a longitude of 8°38'54.8"E.

The GSSP is defined at the base of the boundary clay. It is overlain by a rusty red layer containing a peak of Ni-rich spinel, which is more concentrated than the iridium anomaly. This implies that all the sediments generated by the meteorite impact belong to the Danian. This millimeter thick layer, containing the evidence of the meteorite impact and other significant geochemical changes, coincides with a sudden catastrophic mass extinction event."

Molina, E., Alegret, L., Arenillas, I., Arz, J. A., Gallala, N., Hardenbol, J., von Salis, K., Steurbaut, E., Vandenberghe, N, and Zaghbib-Turki, D. 2006. The Global Boundary Stratotype Section and Point for the base of the Danian Stage (Paleocene, Paleogene, "Tertiary", Cenozoic) at El Kef, Tunisia: original definition and revision. Episodes 29/4, p. 263-278