Geoscience Reference
In-Depth Information
0
BRUNHES
P
L
E
I
S
T
O
C
E
N
E
NORMAL
CHRON
0.78
1
Jaramillo
Cobb Mt
MATUYAMA
REVERSED
Olduvai
CHRON
2
Reunion
2.60
GAUSS
P
L
I
O
C
E
N
E
3
Kaena
NORMAL
Mammoth
CHRON
3.58
4
GILBERT
Cochiti
REVERSED
Nunivak
CHRON
Sidufjall
5
Normal polarity
Reversed polarity
Figure 6.2. Geomagnetic time scale for the last 5 million years. (Modified from
Williams et al.,
1998
, fig. A4, and Walker,
2005
, fig. 7.9.)
6.4.3 Dating based on marine isotope stages and orbital
(Milankovitch) variations
Initial attempts at devising a chronology based on recurrent expansion and contraction
of ice caps during the late Cenozoic, particularly the Quaternary, were doomed from
the outset because the terrestrial record of glacial-interglacial cycles is so incomplete
(Williams et al.,
1998
). However, with the advent of stable oxygen isotope analysis
