From empirical considerations to absolute ages: How geomagnetic field variation may date Teotihuacan mural paintings

Teotihuacan, the most important city of the Americas during the Classic period, developed a deep and complex civilization without any written histories. This millennial culture mostly used pictorial forms of visual communication expressed in numerous mural paintings. Thus, the knowledge of the absolute chronology of some of the most important mural arts is of great importance. Here, we report a comprehensive magnetic survey on two major murals of Palace of Quetzalcoatl, which represent an initial stage of the Teotihuacan archaeology. The magnetic mineralogy of sampled murals is dominated by both magnetite and hematite grains. The contribution of hematite, however, seems to be minor in the Pictorial Remanent Magnetization. Characteristic remanence was successfully isolated for 11 out of 16 analyzed samples belonging to both paintings. Archaeomagnetic dating was achieved using magnetic inclination and declination, yielding an interval between 312 CE and 409 CE as the best estimate of the time of painting of the murals. This study reinforces the early hypothesis that, red color mural paintings may be considered a complementary source of information about the secular variation of the Earth's Magnetic Field.