A varve is a sedimentary bed, or sequence of beds, deposited in a body of still water within a years time.
Counting and correlation of varves have been used to measure the age of Pleistocene glacial deposits.
Sedimentary rocks- Sedimentary rocks are generally not datable using isotopic methods because the grains in sedimentary rocks may come from many different rocks of different ages.
When this happens in a mineral, the two departing nuclei leave behind a trail of destruction in the crystal lattice. Fission track dating is ideal for samples from recent times back to 100,000,000 years.
Beyond 100,000,000 years, the density of the tracks becomes so great (saturated) that they cannot be counted reliably.
Lyell's extreme form of uniformitarianism would have required a perfect balance between heat production and heat loss.
Kelvin argued that this was physically impossible (the concept is akin to a perpetual motion machine).
The quantitative approach is admirable, but Buffon's assumptions are flawed. Silicate minerals have lower heat conductivity than steels and are better insulators leading to slower cooling rates.