4.1. Precursor Event
Valet et al. (2012) showed a 90° change in VGP during reversed polarity
before the transition from reversed to normal polarity (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 (mid-point) which has a 1 kyr duration (Fig. 7c).
The model showed another 90° change as the rebound with 2.5 kyr duration
after the transition (Fig. 7c). Sagnotti et al. (2014) reported Valet et
al. (2012)’s precursor with 140° change in VGP, 0.7 kyr duration, and 5
kyr prior to the actual transition. In our VGP data (Fig. 7a), 75°
change between 13.6-11.8 cm depth shows 3 kyr duration (according to 0.6
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 4.6 kyr before the actual transition
(9.0 cm depth). The actual transition duration is 0.8 kyr between
9.2-8.8 cm. These values are consistent with the Valet et al. (2012)
model and show the unique behaviour of the Earth’s magnetic field during
the reversal time. The rebound after the transition in the model is not
seen in our study since VGP change between 7.1-3.2 cm is not enough to
interpret it as the rebound.