Magnetic dating of Holocene volcanic rocks: case of the lava flows around Pátzcuaro Lake (Michoacán-Guanajuato volcanic field)

Abstract

Archaeomagnetic dating is based on the fact that baked clays often contain small amounts of magnetic minerals that under certain conditions, can record the direction and intensity of the Earth magnetic field in the past. When the reference secular variation (SV) curve is well established for a given geographical area, the archaeomagnetic analyzes provide an accurate dating of the last heating of the studied artifacts. In this paper we apply this dating method to recent lava flows formed during the past 14,000 years using the geomagnetic field prediction model SHADIF14K. The full vector (declination, inclination and absolute geomagnetic intensity) values are satisfactorily compared with previous dating using radiometric methods (14C) for 3 out of 4 analyzed lavas around Patzcuaro Lake and belonging to the Michoacán-Guanajuato volcanic field. A single lava flow shows a reverse magnetic polarity and was probably formed during the short geomagnetic event Lashamp between 40 and 45 ka.