An inclusive rock-magnetic and absolute paleointensity survey of the ~ 2-ka-old Xitle volcano (southerly Basin of Mexico) was undertaken to assess the faithfulness of the paleomagnetic log carried by fresh, widely exposed and well-preserved lava flows. Paleomagnetic samples from six lava flows were subjected to paleointensity analysis with a multi-method approach: the Thellier–Coe, IZZI, and multi-specimen methods. Overall mean flow PI values from flows 4–6 obtained by the Thellier-type methods used yielded 68.4 µT (σ = ± 5.6 µT), 63.9 µT (σ = ± 5.8 µT) and 61.5 µT (σ = ± 4.3 µT) for the TC, IZZI, and IZZI with CR correction methods, respectively. Although multi-specimen paleointensity results were, in general, lower than that obtained with the other methods for the same flows, that for Flow 5 (61.8 µT) was very similar to those obtained with the Thellier-type methods. Based on the results obtained, this lava flows sequence could correspond to two eruptive periods; one related with the Xitle volcano (flows 3–6), and another older (flows 1 and 2). The combined archeomagnetic dating of the different flows reinforces this hypothesis, as well as the multi-modal distribution for the age of the Xitle, proposed two decades ago. The application of stricter acceptance criteria and consideration of cooling-rate correction could slightly reduce the scattered observations. The multi-method approach employed under this study, combined with detailed rock-magnetic experiments, may definitively increase the accuracy of paleointensity determinations.
Las primeras exploraciones realizadas por el proyecto Arqueología de la Sierra de Manantlán, en el valle de Cuzalapa, al sur de Jalisco, arrojan datos sobre la ocupación prehispánica de esta región hasta ahora poco estudiada desde el punto de vista arqueológico. El hallazgo de varios sitios de arquitectura y manifestaciones gráfico-rupestres plantean la cuestión de la temporalidad de estos vestigios. Las condiciones complicadas para el trabajo de campo y la escasez de artefactos diagnósticos han dificultado la construcción de una cronología. El presente trabajo se inscribe dentro de las investigaciones de frontera entre la arqueología y geofísica (paleomagnetismo y arqueomagnetismo), para datar arqueomagnéticamente un piso de estructura sencilla en el sitio de La Palma. Aun tratándose de una datación aislada dentro del conjunto de evidencias registradas, este estudio permite ubicar tentativamente la ocupación del valle de Cuzalapa en el periodo Posclásico Temprano (900-1200 d.C.) y esbozar una primera interpretación de las dinámicas culturales posibles en el contexto extrarregional del desarrollo de la red Aztatlán.
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