Correlation
Coefficient Matrices, a New Graphic Tool for
the Evaluation of
Biostratigraphic
Data
Robert L. Ravn
Sequence stratigraphy places both new emphasis and new demands on
biostratigraphic
control in depositional interpretation. Traditional methods of
evaluation and display of
biostratigraphic
data do not always adequately address
sequence stratigraphic issues. Micropaleontological populations reflect the
history of sediment deposition. Overall populations within a single depositional
sequence tend to be more similar to one another than do populations compared
across a sequence boundary. Populations of any two samples can be compared
mathematically using any of several simple formulae. The resultant figures, or
correlation
coefficients, represent an objective measurement of relative sample
similarity. The comparison of each sample in a single well against each other
sample pr duces a matrix of these
correlation
coefficient values, which often
displays vertical variations in similarity that reveal positions of possible
boundaries. These events may not always coincide with conspicuous
extinction/appearance events that have historically been used as the major
interpretive tool for the biostratigrapher.
Correlation
coefficient matrices offer several advantages for the evaluation
of
biostratigraphic
(and potentially other) data. They are visually intuitive.
They are strongly objective, being produced directly from the data, without
intervening subjective interpretation filters. They may be derived from any
presence/absence data set of adequate size, independent of taxonomy or other
interpretation, permitting direct visual comparison of data sets from different
sources, or even of different disciplines. They can be produced on a normal
desktop computer having moderate memory capacity, and they require only
inexpensive non-specialized software. Older data sets can yield valuable new
information using this method.
AAPG Search and Discovery Article #91020©1995 AAPG Annual Convention, Houston, Texas, May 5-8, 1995