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of carbonate rocks to be quantitatively collected (Muge
et al. 1997; Lebrun et al. 1999): Depositional textures,
e.g. the degree of bioturbation (Magwood and Ekdale
1994; Francus 2001), the relationship between micro-
facies of heterogeneous limestones and their suitabil-
ity as building stones (Fronteau and Paicheler 1999),
or the intensity of the skeletonization of frame-build-
ing reef organisms (Bernecker and Weidlich 1994).
Image analysis can be used to characterize the geom-
etry and frequency of porosity in carbonate rocks from
random thin sections (Anselmetti et al. 1998; White et
al. 1998; Frykman 1992). Frequency counting based
on digital image analysis is a common method. The
results correspond rather nicely to frequency measure-
ments based on pointcounting in thin sections (Dorobek
et al. 1987).
embrace fossils which can be identified in thin sections
only at gross taxonomic levels (e.g. echinoderms, bra-
chiopods, rugose corals, dasyclad algae), at group lev-
els (e.g. small very thin-shelled ostracods vs. large os-
tracods with homogeneous microstructure), or, rarely
even at generic taxonomic levels. PFD differs from di-
versity based on taxonomic richness primarily in the
broader level of taxonomic identification. Consideration
of fossil diversity in thin sections yields a good first
approximation to simple taxonomic diversity and is,
therefore, often used as a rule of thumb measure of en-
vironmental conditions, although this method can be
dangerous if no other supporting data exist. PFD can
be determined just by counting the number of fossil
types, but statistically based comparisons of samples
require percentage data produced by area, point or rib-
bon counting.
6.2.1.4 Constituent Ranking, Diversity and
Maturity
Compositional maturity
The extent to which a grain-rich carbonate sediment
approaches the constituent end-members (composi-
tional maturity: Smosna 1987) reflects the complexity
of the processes that operate on carbonate sediments.
End-members are synsedimentary clasts, ooids, skel-
etal grains, peloids, micrite, and terrigenous minerals.
The proportions of samples consisting of these end-
members give some indications of major depositional
controls. A grainstone composed almost totally of oo-
ids and no other grain types may reflect conditions
which are most favorable for the accumulation of oo-
ids. A mixed grainstone with various skeletal grains and
some ooids points to poor conditions for autochtho-
nous ooid formation, but good and varying conditions
favoring the occurrence of diverse biota.
The relative frequency of grain types, the diversity of
grain types and the dominance of specific grain cat-
egories carry environmental signals which should be
considered in microfacies studies (see Box 11.1): These
approaches are based on identificating the relative
amount of grains rather than purely numeric data.
Constituent ranking
This technique requires ranking grains according to
visual estimates of their volumetric importance. The
most important constituent is coded as rank 1, the sec-
ond most important as rank 2, and so on. Rank 4 in-
cludes all grains present but those of lesser importance
than 3. The ranking is independent of the proportions
of matrix or cement and thus expresses relationships
between grains. Shifts in ranking indicate gradual en-
vironmental changes particularly within defined units
(e.g. Waulsortian carbonate mud mounds: Lees et al.
1985) containing various and diverse grains. A statisti-
cal treatment of ranking data using presence/absence
data and looking for relay conditions assists in recog-
nizing natural transitions between qualitatively defined
microfacies types (Sect. 14.4).
6.2.1.5 Integrated Frequency Studies of Reef
Carbonates
The complexity and variability of reef carbonates re-
quires studying abundance and distribution of biota on
different scales. Field methods used in modern reefs to
describe ecological zonation or monitoring changes in
the diversity include plotting techniques using quad-
rats (arranged randomly or in belts) as sampling and
counting areas (corresponding to area or ribbon count-
ing), as well as plotless techniques utilizing line tran-
sects with defined lengths or grids (corresponding to
line- and point-counting). Quadrat-belt methods exhibit
the most complete data sets with respect to taxonomic
diversity, size and growth form of reefbuilders, and cov-
erage (Sullivan and Chiappone 1992; Vogt 1995; Segal
and Castro 2001).
Petrographic Fossil Diversity
In analyzing ancient environments fossil diversity
is generally regarded to be most significant. Diversity
measures based on microfacies data are not identical
with those of the usual paleoecological studies. Petro-
graphic fossil diversity (PFD) is defined as the total
number of all dissimilar fossil types observed in thin
sections (Smosna and Warshauer 1978). Fossil types
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