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were being drilled. This regular sampling effect was previously explained in
Sect.
9.1.2
. In general, events with equal observed depths in a well record are coeval
but their exact superpositional relationship cannot be established. However, it can be
seen from Fig.
9.23
that the regular sampling effect is relatively minor in the large-
scale RASC applications used for example.
RASC & CASC Version 20 allows application of many other statistical tests.
Of special interest are the so-called normality tests by means of which the location
of each event in each well can be checked to see that it is not a statistical outlier.
9.4 Automated Stratigraphic Correlation
The first RASC-CASC studies were carried out for wells on the Labrador Shelf,
Grand Banks (offshore Newfoundland) and the Scotian Shelf (Gradstein and
Agterberg
1982
). Some results for these wells were already presented in this chapter
(Fig.
9.17
, dataset B). Scaling and correlation results for this same dataset and
Foraminifera from Jurassic to Lower Cretaceous rocks on the Grand Banks will be
reviewed in this section. Shaw's (
1964
) topic uses first and last occurrences of
trilobites and some other fauna in the Cambrian Riley Formation of Texas for
example (for detailed data, see Shaw's 129-page appendix). His Riley Composite
Standard (RST) results will be compared with a subjective zonation originally
proposed by Palmer (
1954
) and RASC-CASC results. Finally, large-scale biostrat-
igraphic zonation and correlations for a Cretaceous Greenland-Norway Seaway
microfossil data base (Kaminski and Gradstein
2005
) also will be briefly reviewed.
9.4.1 NW Atlantic Margin and Grand Banks
Foraminifera Examples
Figure
9.24
(afterWilliamson
1987
) shows a RASC scaling diagrambased on 21wells
drilled into the Upper Jurassic and Lower Cretaceous on the northern Grand Banks,
offshore Newfoundland. Eleven zones from Kimmeridgian to Cenomanian primarily
were based on last occurrences of Foraminifera. Lowest occurrences of events were
not used. Index taxa including several with last occurrences included as unique events
were used to construct the regional stratigraphic zonation. This was a 4/3 RASC run
meaning that events used for statistical calculations were found in at least four wells
and pairs of events in at least three wells. Some of the relatively large interfossil
(or interevent) distances coincide with major sedimentary changes or breaks that
separate the majority of events below from those occurring above it. For example,
the large interfossil distance between zones X (Tithonian) and IX (Valanginian) is
mainly due to intermediate non-marine or very shallow marine facies probably or
Berriasian age, which has a paucity of microfossils. This break may be associated with
a condensed limestone sequence believed to cause seismic marker 1 and to be related
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