Abstract
The study of geomagnetic excursions is key for understanding the behavior of the magnetic field of the Earth. In this paper, we present the geomagnetic record in a 2.29-m-long continuous core sampled in a flowstone in Liguria (Italy) and dated to the Lower Brunhes. The cored flowstone developed from Marine Isotopic Stage (MIS) 13 to MIS 7, according to 21 U-series dates. The mean growth rate is closely related to glacial and interglacial isotopic stages. Magnetic remanence was measured using u-channel and deconvolved. Four geomagnetic excursions were recorded at the same location, in a single flowstone, during interglacial MIS 11 and 13; Basura 1, 2, 3 and 4, at depths of 213 cm, 181, 160 and 92 cm, respectively. Due to the uncertainties of U-Th dating, the timing of the three events, namely Basura 1, 2 and 3 overlaps. The Basura 4 is well-dated to 417 + −7/8 ka and is clearly distinguishable from the others. It should therefore be considered as a possible excursion.
Highlights
Geomagnetic excursions are short worldwide episodes of intermediate polarity of the Earth’s magnetic field[1], beyond the range of secular variation[2,3,4,5]
The studied record is a 2.29-m-long continuous core, drilled from a calcitic flowstone which grew on the cave floor, the growth record of which has been was constrained by twenty-one U-Th dates
The paleomagnetic study of core BF2 revealed a record of several geomagnetic events during the Lower Brunhes period
Summary
Geomagnetic excursions are short worldwide episodes of intermediate polarity of the Earth’s magnetic field[1], beyond the range of secular variation[2,3,4,5]. They are recorded in almost all types of rocks, the inventory of geomagnetic excursions in the Lower Brunhes, before 200 ka, has not yet been clearly established. The construction of a reliable inventory of excursions depends on the convergence of lava, sediment and speleothem records with their independent dating methods. The area contains abundant Paleolithic sites recording evidence of human occupation during the Middle and Upper Pleistocene[21,22]
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