4.1. Precursor Event
Valet et al. (2012) showed a 90° change in VGP during reversed polarity
before the transition (Fig. 7c). According to this model, the precursor
prior to the magnetic reversal has a 2.5 kyr duration, and it occurs
~3.5 kyr before the actual transition (midpoint), which
has a 1 kyr duration (Fig. 7c). The model showed another 90° change as
the rebound with a 2.5 kyr duration after the transition (Fig. 7c).
Sagnotti et al. (2014) reported Valet et al.’s (2012) precursor with
140° change in VGP, 0.7 kyr duration, and 5 kyr prior to the actual
transition. In our VGP data (Fig. 7a), an ~75° change
between 13.6 and 11.8 cm depth shows a 2.6±0.2 kyr duration (according
to 0.7±0.2 cm/kyr average sedimentation rate estimation) that can be
interpreted as the precursor of the Matuyama-Brunhes magnetic reversal.
The pick point of the precursor (11.8 cm depth) is 4±0.2 kyr before the
actual transition (9.0 cm depth). The actual transition duration is
0.6±0.2 kyr between 9.2 and 8.8 cm. These values are consistent with
Valet et al.’s (2012) model and show the unique behavior of the Earth’s
magnetic field during the reversal time. The rebound after the
transition in the model is not seen in our data since a VGP change
between 7.1 and 3.2 cm is not enough to interpret it as the rebound.