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164 WOLFGANG SCHLAGER
4
Fig. A.6.— Power spectrum of a
gamma ray log. The log measures the
natural gamma radiation of the rock that
is largely a function of the rock’s clay
3 content. The variation of gamma radi-
ation therefore reflects the variation of
clay content in the stratigraphic column
and usually correlates with depositional
rhythms. First-order trend (dashed) indi-
2 cates power-law relation between power
log (power) erties of the underlying depositional
and frequency, suggesting fractal prop-
rhythms. Linear trend breaks down on
logging tool. After Tubman and Crane
1 the right near the limit of resolution of the
(1995), modified.
0
-1
log (frequency) cycles per ft -1 0
A)
2000 random numbers, mean = 0, s = 1 Fig. A.7.— A) Graph of random num-
bers with the characteristics of white
0 noise. B) Random walk generated by the
running sum of the numbers of A). There
is a distinct impression of a hierarchy of
cycles in B) but the pattern is different
for each set of random numbers and re-
B) serial sum of A) flects no ordering principle. After Harri-
son (2002).
0
Signal
-20
-40
0 Distance or Time 1200 1600 2000
