The principle of lateral continuity states that layers of sediment initially extend laterally in all directions unless obstructed by a physical object or topography.
The principle of cross-cutting relationships states that whatever cuts across or intrudes into the layers of strata is younger than the layers of strata.
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.
Isotopic age dating would not give the age of the sediment deposition or lithification, but rather the age of the source rocks.
He calculated the modern rate of salt delivery to the oceans, and suggested that the present salinity of ocean water would take at least 100 million years to develop.
In the 1860's, English physicist Lord Kelvin disagreed with Charles Lyells proposition that the earth behaves in a uniform, unchanging manner.
For example, isotopes with very long half lives are no good for dating rocks younger than about 100 million years.