In 1929, they found a charred log near Show Low, Arizona, that connected the two patterns.It was now possible to assign a calendar date to archaeological sites in the American southwest for over 1000 years.Seriation is thought to be the first application of statistics in archaeology. The most famous seriation study was probably Deetz and Dethlefsen's study Death's Head, Cherub, Urn and Willow, on changing styles on gravestones in New England cemeteries.
Determining calendar rates using dendrochronology is a matter of matching known patterns of light and dark rings to those recorded by Douglass and his successors.
Dendrochronology has been extended in the American southwest to 322 BC, by adding increasingly older archaeological samples to the record.
Stratigraphy is the oldest of the relative dating methods that archaeologists use to date things.
Stratigraphy is based on the law of superposition--like a layer cake, the lowest layers must have been formed first.
First used, and likely invented by archaeologist Sir William Flinders-Petrie in 1899, seriation (or sequence dating) is based on the idea that artifacts change over time.
Like tail fins on a Cadillac, artifact styles and characteristics change over time, coming into fashion, then fading in popularity. The standard graphical result of seriation is a series of "battleship curves," which are horizontal bars representing percentages plotted on a vertical axis.Plotting several curves can allow the archaeologist to develop a relative chronology for an entire site or group of sites.For detailed information about how seriation works, see Seriation: A Step by Step Description.In 1901, Douglass began investigating tree ring growth as an indicator of solar cycles.Douglass believed that solar flares affected climate, and hence the amount of growth a tree might gain in a given year.Since the turn of the century, several methods to measure elapsed time have been discovered.