Palaeomagnetic determination of emplacement temperature of Vesuvius AD 79 pyroclastic deposits

Abstract

The city of Herculaneum was buried under 20 m of pyroclastic deposits during the AD 79 eruption of Vesuvius, whose crater is only 7 km to the east. These deposits have been interpreted as the deposits of mudflows or hot pyroclastic flows. Maury's studies of incinerated wood in Herculaneum demonstrate heating to at least 400° C. We have studied the variation of remanent magnetism with temperature for specimens taken from the deposits, including specimens of the matrix material and of embedded lithic fragments. We conclude that the temperature of the deposit at emplacement is unlikely to have been greater than 400° C, which further supports the interpretation of the pyroclastic deposits at Herculaneum as largely ignimbrites (hot pyroclastic flow deposits)