Geophysical and Geochemical Datings
Copan : Obsidian Hydration, Archaeomagnetic and C-14 Dating
"It can be seen from this graph that while the obsidian hydration and archaeomagnetic estimates support each other, the C-14 estimates are erratic, and are consistently earlier than either obsidian hydration or archaeomagnetic estimates. The estimates compared in this graph come from the same contexts (i.e. from the same hearth, floor, or feature etc.) and therefore form a perfectly comparable set." (Wells, Fuls 2000:10)
"There was no agreement between the two methods, indicating either that the events were not contemporary or that one dating method produced inaccurate results. In this experiment the hydration dates are a better contextual match for the event than the 14-C date." (David Webster: Obsidian Hydration and 14C Dating at Copán, Honduras: Three Concordance Experiments)
Test of the Obsidian Hydration Data and the Dates of Monuments
"In Figure 1.3 the defeat of Copan by Quirigua, and the decentralization of the Ahaw's power after 9.16.0.0.0 are both correlated to appropriate fluctuations in obsidian usage and population -- if the traditional chronology [GMT] is shifted about 200 years later. The frequency of monument dedication matches with the frequency of obsidian hydration dates, again if the traditional chronology is shifted 200 years later." (Wells, Fuls 2000:11)