Relative dating of geological features
They then go further by interpreting the formation of each feature to be the consequence of a speciﬁc geologic event.
Examples of geologic events include: Deposition of sedimentary beds; erosion of the land surface; intrusion or extrusion of igneous rocks; deformation (folding and/or faulting); and episodes of metamorphism.
If sediments were deposited on a steep slope, they would likely slide downslope before they could be buried and lithified.
Canal digging provided fresh exposures of bedrock, which previously had been covered by vegetation.
From these data, we can deﬁne the range of speciﬁc fossils in the sequence, meaning the interval in the sequence in which the fossils occur.
The sequence contains a deﬁnable succession of fossils (A, B, C, D, E, F), that the range in which a particular species occurs may overlap with the range of other species, and that once a species vanishes, it does not reappear higher in the sequence.
For example, a conglomerate containing pebbles of basalt is younger than the basalt, and a sill containing fragments of sandstone must be younger than the sandstone.
Geologists apply geologic principles to determine the relative ages of rocks, structures, and other geologic features at a given location.