A Revision to the U.S. Southwest Archaeomagnetic Master Curve

The pre-AD 585 extension of the U.S. Southwest archaeomagnetic reference curve

“…In keeping with previous studies in the U.S. Southwest (e.g., Eighmy, 1991;LaBelle and Eighmy, 1997;Lengyel and Eighmy, 2002;Sternberg and McGuire, 1990b), this study used the moving window method developed by Sternberg (1982Sternberg ( , 1989Sternberg and McGuire, 1990a) to fit a smooth temporal curve to the dataset. This approach uses a running average to smooth the archaeomagnetic dataset into a sequential series of mean VGPs that define the regional reference curve.…”

“…A variety of methods are available for smoothing archaeomagnetic datasets into regional dating curves, including several that employ running averages (Sternberg, 1982(Sternberg, , 1989Le Goff et al, 2002; e.g., Batt, 1997;Lengyel and Eighmy, 2002) and a more recent approach that uses Bayesian modeling to fit a spherical spline to the data ; e.g., Lanos, 2005, 2006;Zananiri et al, 2007). In keeping with previous studies in the U.S. Southwest (e.g., Eighmy, 1991;LaBelle and Eighmy, 1997;Lengyel and Eighmy, 2002;Sternberg and McGuire, 1990b), this study used the moving window method developed by Sternberg (1982Sternberg ( , 1989Sternberg and McGuire, 1990a) to fit a smooth temporal curve to the dataset.…”

“…For clarity, it should be noted that the two curves, SWCV595 and SWCV2000, are based on the same dataset but depict slightly different paths of secular variation. The curve SWCV595 is a statistically calculated curve constructed through Sternberg's moving windows method, whereas SWCV2000 is a modification of that curve that corrects for specific shortcomings of the averaging calculations (see Lengyel and Eighmy, 2002 for a full discussion).…”

“…Two of the tree-ring dated samples were reported by Cox and Blinman (1999) and are new to the Southwest archaeomagnetic dataset. The remaining 13 tree-ring dated samples are included in the SWCV595/2000 reference curve dataset (Eighmy and LaBelle, 1995) and contribute to the earliest three mean VGPs calculated for those curves (LaBelle and Eighmy, 1997;Lengyel and Eighmy, 2002).…”

“…However, as the scope of archaeological research has shifted to include earlier periods of occupation in this region, the temporal restrictions of the existing archaeomagnetic reference curve have hampered efforts to date these sites. Currently, the most commonly used reference curves for the U.S. Southwest, SWCV595 (LaBelle and Eighmy, 1997) and SWCV2000 (Lengyel and Eighmy, 2002), cover the temporal period between AD 585 and the present. A number of projects in central and southern Arizona, however, have focused on archaeological features and sites that were utilized before AD 585.…”