Quantitative Stratigraphy, Splining and Geologic Time Scales - Geomathematics: Theoretical Foundations, Applications and Future Developments - page 334

Fig. 9.19 Estimation of distance ʔ AB between events A and B from relative frequency of

inconsistencies p (D AB 0) when A is a marker horizon with zero variance.

The variance of the distance between A and B is equal to the variance of B. Consequently, marker
horizons receive more weight than biostratigraphic events when the RASC scaled optimum
sequence is calculated (Source: Agterberg 1990 , Fig. 6.11)

0) ¼ 1 p (D AB

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Fig. 9.20 Simple example
to illustrate application of
unique event option. A
unique event was observed
in a single section where it
coincided with the event S,
stratigraphically below A
and above the events B, B 0
and B 00 . Cumulative RASC
distances of the latter five
events are shown along the
scale on the left . First, the
positions of S, A and B were
averaged to obtain first
approximation for position
of the unique event. Second
approximation was based on
the RASC distances of all
events within the range R
(Source: Agterberg 1990 ,
Fig. 6.12)

The ranked optimum sequence for the current example can be used to determine
first-order depth differences measured by subtracting the depth of an observed event
from the depth of the event below it in a well. This option is part of depth-scaling
routines later added to the RASC/CASC program (Agterberg et al. 2007 ). A first-order