Relative dating is used to determine the age of a fossil by looking at its position in layers of sedimentary rocks, whose age may have already been determined. Relative dating is used to determine the relative age of rocks. Sedimentary Rocks. Sedimentary rocks are not the only way to determine relative age. The principal of cross-cutting relationships can determine relative ages. If you are talking about sedimentary rock, and the idea of relative dating, then the younger rock would be on top closer the the surface.
How Do Scientists Determine the Age of Dinosaur Bones?
Dating Sedimentary Rock - How Do Scientists Determine the Age of Dinosaur Bones? | HowStuffWorks
The most obvious feature of sedimentary rock is its layering. This feature is produced by changes in deposition over time. With this in mind geologist have long known that the deeper a sedimentary rock layer is the older it is, but how old? Although there might be some mineral differences due to the difference in source rock, most sedimentary rock deposited year after year look very similar to one another. This means that a quartz sandstone deposited million years ago will look very similar to a quartz sandstone deposited 50 years ago.
Why are sedimentary rocks important to relative dating?
Relative dating is the science of determining the relative order of past events i. In geology, rock or superficial deposits , fossils and lithologies can be used to correlate one stratigraphic column with another. Prior to the discovery of radiometric dating in the early 20th century, which provided a means of absolute dating , archaeologists and geologists used relative dating to determine ages of materials. Though relative dating can only determine the sequential order in which a series of events occurred, not when they occurred, it remains a useful technique.
The simplest and most intuitive way of dating geological features is to look at the relationships between them. 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. The principle of inclusions states that any rock fragments that are included in rock must be older than the rock in which they are included. For example, a xenolith in an igneous rock or a clast in sedimentary rock must be older than the rock that includes it Figure 8. The principle of cross-cutting relationships states that any geological feature that cuts across, or disrupts another feature must be younger than the feature that is disrupted.