Magnetic properties and archeointensity determination on Pre-Columbian pottery from Chiapas, Mesoamerica

As part of the effort to establish an archeointensity variation curve for Mesoamerica, 13 archeologically well-identified pottery samples belonging to the Ocozocoautla site (Chiapas) were Studied. Analyzed samples consist of 'ofrenda type' pottery fragments found in several caves. Three archeological intervals are involved: 450100 B.C., 200-550 A.D. and 550-900 A.D. The Thellier method in its modified form was applied to small fragments previously embedded in salt pellets. Raw intensity values were further corrected for cooling rate effects. The common time-consuming TRM anisotropy correction protocol was substituted by an alternative approach during the paleointensity experiments. Forty-two specimens, belonging to six samples, yielded high-quality Thellier determinations. The NRM fraction f used for paleointensity determination ranges between 0.42 to 0.99, and the quality factor q (Coe et al., 1978) varies from 4 to 59, being normally greater than 5. These results correspond to data of good quality. The mean archeointensity values per pottery fragments range from 14.6 +/- 1.5 to 59.5 +/- 13.8 mu T, while the corresponding virtual axial dipole moments range from 2.5 +/- 0.3 to 10.0 +/- 2.4 x 10(22) A m(2). These new data, although not numerous, are of high quality and definitively contribute to the Mesoamerican, still insipient, archeointensity database.