#oldasthehills

Old as… ?: Dating Archaeological Sites

Knowing the date of an archaeological site is one of the things that makes it most interesting – when were people here?

Two main types of dating are applied to archaeological sites when possible– relative and absolute dating. Relative dating puts sites or artifacts “in order” by simply determining if one event happened before or after another. A common example of relative dating in Alberta is by using Mazama Ash. About 7600 years ago, Alberta was blanketed in ash after the Mazama volcanic eruption. This ash is still sometimes found today in stratigraphic profiles, buried under other deposits of sediment. When this ash is encountered it can be used as a time marker. Anything below it is older than 7600 years and anything found above it is younger than 7600 years.

Example of a buried volcanic ash (also known as tephra) found during archaeological excavation. The ash is the lightest coloured layer in the profile, between 25 and 35 cm below the surface (between the 1 and 3 on the tape measure).

Relative dates can also be obtained using artifact styles. Projectile points are one of the most common types of artifacts used to relatively date sites. Spearpoints represent the oldest projectile point technology and indicate that the site falls within the “Early Prehistoric Period” (11,200-7,500 calendar years before present), dartpoints are representative of the “Middle Prehistoric Period” (7,500-1,350 calendar years before present) and arrowpoints represent the emergence of the use of bow and arrow in the “Late Prehistoric Period” (1,350-250 calendar years before present). Dates can be further refined within each general time period based on the spear, dart or arrow style.

Absolute dating is more specific than relative dating and provides a more exact date (with standard deviation) of when the site or artifact was used. There are several methods of absolute dating but one of the most common methods used by archaeologists is radiocarbon dating. Radiocarbon dating can be used on organic material such as bone or charcoal. A radiocarbon date can be obtained by measuring the amount of (more…)