Geology Reference
In-Depth Information
Basics: Standard microfacies
Bonham-Carter, G.F., Gradstein, F.M., D'Iorio, M.A. (1986):
Distribution of Cenozoic foraminifera from the northwest-
ern Atlantic margin analyzed by correspondence analysis.
- Computer and Geoscience,
12
, 621-635
Carozzi, A.V. (1989): Carbonate rock depositional models. A
microfacies approach. - 604 pp., Englewood Cliffs
(Prentice Hall)
Cheetham, A.H., Hazel, E.J. (1969): Binary (presence-ab-
sence) similarity coefficients. - Journal of Paleontology,
43
, 1130-1136
Flügel, E. (1972): Mikrofazielle Untersuchungen in der
alpinen Trias: Methoden und Probleme. - Mitteilungen
der Gesellschaft der Geologie- und Bergbaustudenten in
Österreich,
21
, 6-64
Hennebert, M., Lees, A. (1985): Optimized similarity matri-
ces applied to the study of carbonate rocks. - Geological
Journal,
20
, 123-131
Hennebert, M., Lees, A. (1991): Environmental gradients in
carbonate sediments and rocks detected by correspondence
analysis: examples from the Recent of Norway and the
Dinantian of southwest England. - Sedimentology,
38
,
623-642
Koopman, B.J., Lees, A., Piessens, P., Sarnthein, M. (1979):
Skeletal carbonate sands and wind-derived silty marls off
the Sahara coast: Baie de Lévrier, Arguin platform, Mau-
ritania. - Meteor Forschungsergebnisse, C,
30
, 15-57
Spence, G.H., Tucker, M. (1999): Modelling carbonate micro-
facies in the context of high-frequency dynamic relative
sea-level and environmental changes. - Journal of Sedi-
mentary Research,
69
, 947-961
Wilson, J.L. (1975): Carbonate facies in geologic history. -
471 pp., Berlin (Springer)
Further reading
: K148, K190
Fig. 14.31.
Microfacies relays.
A:
Traditional microfacies
types based on the abundance of grain types are generally
considered as discrete units caused by a discontinuous
distribution of the grain types across depositional environ-
ments or within a stratigraphic section. Differences in grain
abundance are used to distinguish facies which seem to be
genetically unrelated.
B:
The relay method shows the
distribution and relative abundance of grain types formed in
response to a unidirectional environmental gradient, e.g.
water depth or decreasing water energy in shallowing-upward
sequences. After Spence and Tucker (1999).
Relays reflecting environmentally controlled com-
positional changes document the effects of relative
third-order sea-level fluctuations and can, therefore,
successfully be used in identifying system tracts and
hidden sequence boundaries and evaluating microfacies
types (Spence and Tucker 1999; Fig. 14.31).
Ordination methods use coefficients giving a mea-
sure of similarity in sample composition or in grain
distributions. Relays are detected using computer-op-
timized similarity coefficient matrices (e.g. the Jaccard
similarity coefficient) based on presence/absence com-
positional data or applying correspondence analysis
techniques (Hennebert and Lees 1985). The latter
method can consider absolute frequencies, relative fre-
quencies (percentages), ranked values (e.g. low, me-
dium, high) and binary data (presence/absence) as well.
Fig. 14.32.
Exercise:
Try to determine the SMF Type for this
sample using the Guide in Sect. 14.3.6. How old is the
limestone (see Chap. 10) and from which environment does
it come? Answers can be found in the Appendix.
