Coconino Sandstone in Grand Canyon looks similar to the 160 m.y Navajo Sandstone in southern Utah) [see Photos 6a&b].Lithology is also a poor basis for correlation because different rock types can be deposited at the same time in adjacent areas because of different environments.
A good collection of index fossils in a rock layer allows a very precise assignment of relative age.
An “index fossil” in the realm of clothing fashion could be polyester leisure suits – they were widespread, and thankfully, only around for a brief time.
Grand Canyon contains many important geologic resources, including a vast fossil record ranging from Precambrian stromatolites to Ice Age mammal bones and dung found in caves; a potentially active volcanic field in the western Grand Canyon; a geologic history ranging more than 1.7 billion years; and the canyon landscape itself as the greatest example of arid land erosion.
There are two major categories of geologic dating techniques: relative dating and absolute age determinations .
Someone looking at a photograph with men dressed in leisure suits would be able to correlate that photo to others of the same time period in which men are wearing leisure suits.