Dating obsidian arrowheads
While this period coincides with decreased signs of human activity in those areas, the new research seems to show increased activity around Twentynine Palms.This raises questions about whether ancient hunter-gatherers migrated from the colder, drier northern Great Basin to what’s now the Mojave Desert, beginning around 7,000 years ago.Near a dry lakebed, or playa, by the western border of the base, for example, archaeologists in 2000 found at least 19 points fashioned in the Western Stemmed Tradition at various sites in the area, as well as more than 14 so-called Pinto points, whose triangular style has been found around the Great Basin at sites dating back 6,000 to 8,500 years.Estimating the ages of these artifacts is challenging, Byerly noted, because the dynamics of the local geology has caused deposits from different periods to mix together.Test excavations at a rocky blister of lava turned up 8,830 artifacts, discovered in several layers that together span up to 9,800 years of human occupation.
Energy absorbed from ionizing radiation frees electrons to move through the crystal lattice and some are trapped at imperfections.
When an archeologist has identified the source of the obsidian from which an artifact is made, he or she may be able to date the artifact using the obsidian hydration technique.
This technique of dating obsidian artifacts measures the microscopic amount of water absorbed on freshly broken surfaces.
“As a probable example of a Clovis form, there is no reason to suspect that the specimen is not contemporaneous with dated Clovis components,” he said.
Elsewhere on the base, the review of previously unpublished research showed that dozens of other distinctive stone points had also been uncovered, dating back as much as 9,000 years.
The principle behind obsidian hydration dating is simple—the longer the artifact surface has been exposed, the thicker the hydration band will be.