PRELIMINARY ARCHAEOMAGNETIC DIRECTIONS OBTAINED FROM FIRST MILLENNIAL CE SITES FROM SAN JOSÉ DE MORO, PERU

The Earth’s magnetic field can vary greatly on the surface over millennial time scales. Observations of geomagnetic field behavior over the first millennia CE are biased towards the Northern Hemisphere. The lack of Southern Hemisphere data greatly limits the ability for geomagnetic models to accurately predict geomagnetic behavior on a global scale. Robust regional secular variation model exist for Northern Hemisphere locations however, the ability to use these data to answer question regarding Southern Hemisphere field behavior is greatly limited. Robust secular variation models are uniquely capable of resolving fine-scale chronologic question within an established stratigraphic framework.

The newly established Yale University Archaeology Laboratory – Archaeomagnetic Laboratory is dedicated to increasing the number of observations of magnetic field behavior obtained from Southern Hemisphere sites. We present preliminary archaeomagnetic directional data obtained from first millennia CE sites from San José de Moro, coastal Peru. San José de Moro is an ideal place for an archaeomagnetic investigation because long-term excavations have produced a highly detailed sequence spanning much of the first and second millennium CE. A total of fifty-one independent horizons of archaeomagnetic samples were collected from burnt architectural elements (floors, plasters, hearths, etc.). We present preliminary results from six of these sites obtained from archaeological material classified as Middle Moche (CE 400-600). Samples were treated with stepwise alternating field demagnetization and yield virtual geomagnetic pole positions of about 200° N and 80° S with typical alpha95 values between 3° and 7°. Virtual geomagnetic poles positions through time are used to create secular variation curves. Secular variation curves provide an independent age constraint to aid in deciphering the timing of socially significant events preserved in the archaeological records. Future research efforts will focus on obtaining both direction and intensity values from this and other Peruvian Archaeology sites.