![]() ![]() Using this principle it is quite simple to determine the relatively date of each strata by its position within a sedimentary sequence. In contrast, slow changes in environmental conditions would cause sediment to grade vertically from one type to the other.Īs previously discussed in chapter 5, the principle of superposition states that in an undisturbed sequence of sedimentary rocks the older rock is on the bottom. This change may have occurred over a relatively short period of time or after an extended period of nondeposition or erosion. As discussed in chapter 5, the features of sedimentary rocks are a direct result of their sedimentary environment and source, therefore, since sediment on either side of the bedding plane must be visibly different in composition/texture/color the bedding plane represents changes in environmental conditions. The rocks above and below bedding planes will differ in composition, texture, or color. The boundary between each strata is a surface known as the bedding plane where no bedding planes are found sedimentary rocks will grade from one texture to another. Although this branch of geology is primarily concerned with sedimentary rocks its principles are used to also understand any layered earth material such as igneous and metamorphic rocks.Īs we look at sedimentary rocks their most obvious features are their layers or stratification. Stratigraphy is the branch of geology that is concerned with the composition, origin, relationship, and age of sedimentary rocks. Completing the Puzzle:Rocks, Fossils, and Time ![]()
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