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are used in assessing paleo-waterdepth and differenti-
ating high-energy and low-energy environments of Pa-
leozoic and Mesozoic reefs, assuming that growth form
types are predominantly related to adaption to the physi-
cal environment. Major limitations to this concept were
discussed by Stearn (1982), who stresses that variations
in shape are the result of interactions between various
environmental factors and genetically controlled growth
patterns of the organisms. Nevertheless, some useful
generalizations concerning the relationships between
organism growth forms and hydrodynamic controls are
possible (Fig. 12.2).
carbonate admixtures) and fossils (types, abundance and
associations). In addition, sedimentary structures are
important for augmenting the interpretation of textural
data. The term 'clastic particle' is used for (carbonate)
grains that have been mechanically transported by wave
action.
A crucial point of this concept is the distinction be-
tween sedimentary particles that have been transported
and those that have not. The authors offer a list of crite-
ria that may infer the existence of agitated water envi-
ronments or at least some transportation:
Angular or rounded fragments of partially endured
sediment or of preexisting rock (intraclasts and ex-
traclasts).
Relations between water energy and nutrient supply
The distribution of sponges and suspension-feeding
bivalves is limited by turbidity, those of crinoids and
blastoids by the energy conditions of the environment.
These limitations cause different nutrient supplies and
potentially different distribution patterns. See Ausich
(1983) for an example.
Distinctly rounded fragments of fossils.
Poorly sorted matrix, e.g. sand grains within a fine-
grained matrix (can also be caused by bioturbation).
Carbonate grains mixed with terrigenous clastics
(e.g. detrital quartz) of the same size.
Mixtures of ecologically incompatible biota (e.g.
dasycladacean algae in crinoidal limestones).
12.1.1.2 Classifying LowEnergy and High
Energy Environments
Ooids (excluding 'quiet-water ooids'!).
Wave-resistant colonial organisms in place (not al-
ways decisive, because of the adaption of growth
forms to dominating water energy; see Fig. 12.2).
All limestone classifications based on texture and
focusing on the relative abundance of matrix and grains
are at least in part genetic (see Sect. 8.3). The basic
subdivisions are oriented to interpretative, energy lev-
els' distinguishing between sediments deposited in quiet
waters ('low-energy' sediments) and turbulent waters
('high-energy' sediments). The basic philosophy behind
these classifications is that differences in water energy
should be reflected in sediment texture and biota. This
rather simple dual differentiation does not consider the
broad variations in wave- and current-controlled sedi-
mentation patterns and resulting depositional textures.
Environmental and depositional interpretations based
solely on Dunham's or Folk's rock types may, there-
fore, be misleading. The Energy Index Classification
discussed below offers a better possibility for recog-
nizing depositional conditions controlled by low or high
water energy conditions.
Sedimentary structures (e.g. small scale cross-bed-
ding, imbrication).
Basic classification: Plumley et al. (1962) distin-
guished five major limestone categories I to V, repre-
senting a grading spectrum from quiet water to strongly
agitated water deposits. The arbitrary boundaries be-
tween these types are determined by semiquantitative
and qualitative textural criteria. Each major limestone
type is subdivided into three subtypes (I-1, I-2, I-3).
These subtypes indicate genetic similarities among
limestones with different textural criteria, and genetic
differences among limestones with similar textural cri-
teria.
Type I represents the end of the spectrum with mini-
mum water agitation. The principal feature of these
quiet-water limestones is the lack of recognizable trans-
ported particles. Subtype I-1 (Pl. 44/1) is characterized
by conspicuous argillaceous admixtures. Subtypes I-2
(Pl. 45/2) and I-3 (Pl. 119/1) are relatively pure car-
bonates (< 15% clay). Subtype I-2 is essentially non-
fossiliferous; subtype I-3 corresponds to a fossilifer-
ous limestone. Fossil assemblages are simple and con-
sist of many individuals but few species. Fossils are
not transported and not rounded; many fossils are un-
broken.
Energy Index Classification
Differences in water energy are reflected by a lime-
stone classification proposed by Plumley et al. (1962).
It is based on the inferred degree of water agitation in
the depositional environment. Textural and composi-
tional data are used in grouping limestones into genetic
categories. Textural criteria include size, sorting and
roundness of grains, and the nature of the matrix. Com-
positional data refer to mineralogy (carbonate and non-
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