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50
50
20
20
10
10
5
5
SERIES 4
SERIES 6
S
1
S
1
2
2
1.0
1.0
SILT
0.5
0.5
C
2
0.2
0.2
C
8
C
3
C
4
C
9
C
5
95%
C
7
0.1
C
6
0.1
CLAY
0.05
0.05
5%
0.1
0.2
0.3
0.4
0.5
0.02
0.02
50 20
10
5
3.33
2.5
2
50 20
10
5
3.33
2.5
2
10
10
5
5
2
2
1.0
1.0
SERIES 8
SERIES 7
S
1
0.5
0.5
S
1
0.2
0.2
S
2
S
3
0.1
0.1
0.05
0.05
0.02
0.02
50 20
10
5
3.33
2.5
2
50 20
10
5
3.33
2.5
2
PERIOD IN YEARS
Fig. 6.5 Power spectra with
m
ΒΌ
50 for four longest series (
n >
250); Frequency scale is shown
in spectrum for series 4 only. Confidence belts also are shown (Source: Agterberg and Banerjee
1969
, Fig. 5)
slightly larger than 0.05. This probably reflects the 22-year and 11-year sunspot
cycles that have been found in varves elsewhere in the world (Schove
1983
; Berry
1987
) and in other laminated sediments, e.g. in marl-limestone couplets belonging
to the Late Campanian
Radotruncana calcarata
Zone (Wagreich et al.
2012
).
Sunspot cycles have variable duration but, on average, they last 11 years. The
22-year cycle is due to alternation of stronger and weaker 11-year cycles.
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