Relative dating cross cutting
The boundary between the two represents a time gap of nearly 300 million years.[SE ]Figure 8.9 The four types of unconformities: (a) a nonconformity between non-sedimentary rock and sedimentary rock, (b) an angular unconformity, (c) a disconformity between layers of sedimentary rock, where the older rock has been eroded but not tilted, and (d) a paraconformity where there is a long period (millions of years) of non-deposition between two parallel layers.So, let's imagine for a second that you have a 3-layered cake. So, by definition, the oldest layer of cake would be chocolate, as it was put there first. Now all of a sudden the big tower of cookies running through the middle of your cake is the youngest feature, as the other three layers in order for it to be there.Your 3 layers will consist of a chocolate cake, a vanilla cake, and a cheesecake, because you're crazy and your cake doesn't have to conform to standards. On your plate, you put the chocolate cake on bottom, or the first layer. Then vanilla and cheesecake are the second and third oldest, respectively. Now that I've gotten you all hungry for cake and cookies let's talk about rocks instead.The Proterozoic rocks of the Grand Canyon Group have been tilted and then eroded to a flat surface prior to deposition of the younger Paleozoic rocks.The difference in time between the youngest of the Proterozoic rocks and the oldest of the Paleozoic rocks is close to 300 million years.These strata make up much of the famous prominent rock formations in widely spaced protected areas such as Capitol Reef National Park and Canyonlands National Park.From top to bottom: Rounded tan domes of the Navajo Sandstone, layered red Kayenta Formation, cliff-forming, vertically jointed, red Wingate Sandstone, slope-forming, purplish Chinle Formation, layered, lighter-red Moenkopi Formation, and white, layered Cutler Formation sandstone.
There are a few simple rules for doing this, some of which we’ve already looked at in Chapter 6.(The near-vertical stripes are blasting drill holes.The image is about 7 m across.) [SE photo] An unconformity represents an interruption in the process of deposition of sedimentary rocks.Photo from Glen Canyon National Recreation Area, Utah.Relative dating is the science of determining the relative order of past events (i.e., the age of an object in comparison to another), without necessarily determining their absolute age (i.e. In geology, rock or superficial deposits, fossils and lithologies can be used to correlate one stratigraphic column with another.
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For example, the principle of superposition states that sedimentary layers are deposited in sequence, and, unless the entire sequence has been turned over by tectonic processes or disrupted by faulting, the layers at the bottom are older than those at the top.