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" virtually all sedimentary systems have stratigraphic disorder at come scale is probably a common feature of the fossil record " Fossils out of Sequences Cutler Palaios June 1990 on The conclusion of some scientists is that the Law of Superposition just doesn't work Shindewolf Comments on Some Stratigraphic Terms American Journal of Science June 1957 " Historical geology relies chiefly on paleontology the study of fossil organisms. The Law of Superposition makes logical sense but in practice it is the nature of the fossils found in the sedimentary layers that determine the relative ages of the rocks.
The theory of descent with modification trumps the empirical evidence of superposition.
The sedimentary layers with the simplest fossils are assumed to be older even if the sedimentary layer is found on top of a sedimentary layer that has fossils that are more complex and therefore assumed to be younger.
Fossils that are in violation of the law of superposition where the older fossil occurs above a younger fossil are said to be stratigraphically disordered.
An absolute age is one determined usually by mass-spectrometry where an isotope is measured and then an age can be calculated (a very very basic explanation).
Most commonly, the ancient factors of the rocks or objects are examined using the method called stratigraphy.Absolute age can be determined by using radiometric dating. Look at the diagram below and then answer this question: We can date the layers of volcanic ash using radiometric dating, but how can we determine the absolute age of fossil A?You have to date the volcanic layer above and below the fossil layer.Look at the diagram below representing layers of rocks and the fossils buried in them. (The bottom layer is circled)b) Explain how you know which layer is the oldest.(Hint: The Law of Superposition might help you.) According to the Law of Superposition newer rock layers form on top of already existing layers.
The layers on top could only be laid down on top of the bottom layer so must be younger.