GEOL 1010 Lecture Notes - Lecture 16: Relative Dating, Uniformitarianism, Archean
8 Nov 2016
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Relative geologic age dating: uniformitarianism principle that the processes operating today also operated in the past. Determines which rock came first, which came next, etc. It doesn"t tell you how old a rock is in years: key elements in relative dating. Original horizontality: sediment beds are deposited horizontally (thus folding, faulting, tilting, must occur later) Superposition: in a stack of sedimentary layers the top layer is the youngest and the bottom layer is the oldest. Cross-cutting relationships: younger features cut across older ones. A rock must exist before it can be cut by something else. A fault is younger than the rocks that it cuts through. Inclusions: a rock containing an inclusion (fragment of another rock) must be younger than the inclusion. Correlation of rock layers: how we determine if layers separated by large distances formed at the same time. We compare the rock layers from place to place.
