Geology Reference
In-Depth Information
6.2 Frequency Analysis of
Microfacies Data
• Grain-size ranges in combination with geochemi-
cal data offer a possibility to characterize marble types
and to recognize the provenance of antique marbles (e.g.
Benea et al. 1993).
Thin sections of carbonate rocks exhibit marked dif-
ferences in the frequency of grains, matrix, cements,
and pores. The value of microfacies for interpreting an-
cient depositional environments, discussing controls on
distributional patterns of organisms, and understand-
ing diagenesis and porosity relies strongly on quantita-
tive data. Compositional studies of modern and ancient
carbonates illustrate that the abundance of different
grain types (called constituent composition by Gins-
burg 1956) is of particular significance for reconstruct-
ing depositional systems. Sect. 6.2.1 reviews the meth-
ods commonly used in determining the relative fre-
quency of constituent particles and groundmass by
counting, estimating image analysis and other meth-
ods. The advantages of multivariate and semiquan-
titative methods applied to frequency data are discussed
in Sect. 6.3.
Basics: Grainsize analysis
Burger, H., Skala, W. (1976): Comparison of sieve and thin-
section techniques by a Monte Carlo model. - Computers
and Geosciences,
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Carozzi, A.V. (1988): Carbonate rock depositional models. A
microfacies approach. - 604 pp., Englewood Cliffs
(Prentice Hall)
Folk, R.L. (1966): A review of grain size parameters. - Sedi-
mentology,
6
, 73-93
Folk, R.L., Robles, R. (1964): Carbonate sands of Isla Perez,
Alacran reef complex, Yucatan. - J. Geol.,
72
, 255-292
Folk, L.R., Ward, W. (1957): Brazos river bar: A study in the
significance of grain size parameters. - J. Sed. Petrol.,
27
,
3-26
Friedman, G.M. (1958): Determination of sieve-size distri-
bution from thin-section data for sedimentary petrological
studies. - J. Geol.,
66
, 394-416
Friedman, G.M. (1962): Comparison of moment measures
for sieving and thin-section data in sedimentary petrologi-
cal studies. - J. Sed. Petrol.,
32
, 15-35
Friedman, G.M. (1979): Address of the retiring president of
the International Association of Sedimentologists: Differ-
ences in size distributions of populations of particles among
sands of various origin. - Sedimentology,
26
, 3-32
Hötzl, H. (1966): Zur Kenntnis der Tressenstein-Kalke (Ober-
Jura, Nördliche Kalkalpen). - Neues Jahrbuch für Geologie
und Paläontologie, Abhandlungen,
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, 281-310
Longiaru, S. (1987): Visual comparators for estimating the
degree of sorting from plane and thin sections. - J. Sed.
Petrol.,
57
, 792-794
McManus, J. (1988): Grain size determination and interpre-
tation. - In: Tucker, M. (ed.): Techniques in sedimentol-
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sieve transformation of granulometric data. - Acta Geolo-
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, 117-146
Piller, W.E, Mansour, A.M. (1990): The northern Bay of
Safaga (Red Sea, Egypt): an actuopaleontological approach.
II. Sediment analysis and sedimentary facies. - Beiträge
zur Paläontologie von Österreich,
16
, 1-102
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as a geological tool. - J. Sed. Petrol.,
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, 830-847
Pye, K. (ed., 1994): Sediment transport and depositional pro-
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Rizzini, A. (1968): Sedimentological representation of grain
sizes. - Memoria della Società Geologica Italiana,
7
, 65-89
Syvitski, J.P.M. (ed., 1991): Principles, methods and appli-
cation of particle size analysis. - 368 pp., Cambridge (Cam-
bridge University Press)
Visher, G.S. (1969): Grain size distribution and depositional
processes. - J. Sed. Petrol.,
39
, 1074-1106
Zanke, U. (1982): Grundlagen der Sedimentbewegung. -
402 pp., Berlin (Springer)
Further reading
: K106
6.2.1 Methods of Frequency Analyses
The raw data for frequency analyses are derived from
the study of thin sections, peels or microphotographs.
The use of digital images or flatbed color scanners al-
lowing overall and detailed views and measures of thin
sections is particularly recommended for limestones
which differ strongly in the distribution and frequency
ranges of constituents (e.g. reef or slope carbonates).
6.2.1.1 Counting
Frequently used methods
Four methods of determining frequency (modal
analysis) are commonly used: point-, line-, ribbon- and
area-counting. These procedures are illustrated sche-
matically in Fig. 6.7. Point counting is an area mea-
sure. Ribbon and area counting are number frequency
measures. Both point counting and area counting mea-
sure the relative proportions of grains of different size,
but in point counting where an area proportion rather
than a number frequency is measured, the relative pro-
portion of the coarser grains is emphasized relative to
the finer ones.
(1) In
point counting
(Fig. 6.7A), the most widely
used method, a regular two-dimensional grid is used,
and every grain (or matrix and cement) which falls un-
der a grid point is counted. The estimated volume of a
particle type is proportional to the counted number of
