Earth Sciences 1022A/B Lecture Notes - Lecture 8: Erosion Surface, Irreversible Process, Batholith
27 Apr 2019
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Document Summary
Features such as faults (cracks along which movement has occurred) and igneous intrusions are cut into/across pre-existing rock bodies. Based on this principle, the law of cross-cutting relationships states that a fault or intrusive igneous body must be younger than the rock through which it has cut. This fault (and associated movement) is younger than the strata that it has cut into and displaced. These felsic dykes (igneous intrusions) are younger than the mafic volcanic rocks into which they have been intruded. Thus, individual fossil species represent finite periods of time and occur in a specific sequence. The law of fossil succession states that fossils occur in a consistent vertical order in sedimentary rocks all over the world. Thus, relative age of slices of time represented in rock strata can be determined from the fossil content of rocks. Fossils that are particularly useful for this purpose are called index fossils. The rate of sediment deposition is not uniform through time.
