Sometimes archaeologists aren’t lucky enough to find clamshells or barnacle scars that can be radiocarbon dated. Thus, members of the Clam Garden Network have used optical dating as an alternative method of determining when a clam garden was constructed, and also to figure out how long it took for the sediment on the terrace to accumulate.
Excavating the trench.
hammering in the core
that Travis Gingerich is holding.
Christine (L) and Nicole Smith (R) record the location of the core to be dated.
Optical dating measures the last time quartz or feldspar minerals within the clam garden terrace or on the old beach below the garden, were exposed to sunlight (i.e., when they were buried). Based on this method, we know that some clam gardens were built between 1000 and 1700 years ago and that the sediments within the terrace accumulated slowly.