What is stratigraphy?
Stratigraphy refers to the layering of the soil. Alternating periods of soil deposition from the environment (for example, from a flood) and deposition from humans due to occupation create layer cakes of stratigraphy. As when baking a cake, the bottom layer is the oldest or was laid down first, and the topmost layer was laid down last. Therefore, artifacts are sealed in their order of occurrence during each occupation. Artifact styles change through time, much as the general style and shape of modern day automobiles have changed through the decades. This sequence of changes is preserved in well-stratified sites. Therefore, when the layers of stratigraphy are dated, the objects within them become diagnostic time markers. This is useful when artifacts are found at sites without good stratification. For example, the different styles of projectile points through time is well documented, and if several projectile points of one specific style are found at a site without good stratigraphy, th
