Archaeomagnetic results from mural paintings and pyroclastic rocks in Pompeii and Herculaneum

This work investigates the magnetic remanence associated with red pigments from murals at Pompeii and compares their directions to those of the pyroclastic rocks from the Vesuvius AD 79 eruption. The remanence of the murals is shown, using X-ray analyses, to be carried by haematite. Murals in Thermae Stabianae, known to have been painted a few years before AD 79, yield an archaeomagnetic direction (D = 1.2 degrees, I = 58.0 degrees; alpha(95) = 5.5 degrees) indistinguishable from that of a nearby kiln (D = 358.0 degrees, I = 59.1 degrees; alpha(95) = 1.7 degrees) (Evans and Mareschal, 1989) probably last used immediately prior to the eruption. The directions are also consistent with those of fine-grained pyroclastic rocks from the eruption (D = 351.2 degrees, I = 57.9 degrees; alpha(95) = 3.4 degrees) and lithic and the fragments embedded within them (D = 358.5 degrees, I = 60.4 degrees; alpha(95) = 8.5 degrees). Other paintings of the 1st century AD yield similar directions, with a lower statistical definition. This study shows that murals can retain their remanent magnetization for centuries and demonstrates the viability in principle of pictorial remanence as an archaeomagnetic tool. (C) 2000 Elsevier Science B.V. All rights reserved.