Geology Reference
In-Depth Information
Fig. 9.6.
Generalized distribution of microbialites in Mesozoic platforms and reefs.
Microbialites comprise non-laminar and
laminar types as well as microbial oncoids (see Sect. 4.2.4.1). Cement crusts refer to quantitatively frequent, microbially
induced marine carbonate cements. The Middle Triassic (predominantly Ladinian) and Late Triassic (predominantly Norian)
scenarios reflect case studies in the European western Tethys. The Late Jurassic scenario summarizes case studies in the
Tethys and in epicontinental settings. The Middle and Late Cretaceous sketch describes the distribution of microbialites in
the Tethys. Note similarities in the setting of microbial oncoids, but differences in the microbial contribution to reefs and mud
mounds. Modified and expanded from Leinfelder and Schmid (2000).
cavities or in borings (Sect. 9.3). The composition and
sequential order of encrustation patterns are important
microfacies criteria allowing the study of original eco-
logical relationships and the interactions and competi-
tion between encrusters to be studied, environmental
parameters, e.g. nutrient constraints to be estimated.
Encrusting organisms occur in all shallow- and deep-
marine settings, both in warm-water and cold-water en-
vironments.
Encrusting taxa act as binders and cementing organ-
isms, but also as constructors, and are often initial and
early colonizers.
Encrusters are commonly included in the binder
guild, but for many encrusting organisms a consider-
able guild overlap exists (Sect. 16.2.3.2). The domi-
nance of encrusters is used in limestone classifications
(Sect. 8.2).
Terminology:
Organisms living on a substrate can
be divided into epibenthic and endobenthic, depending
on whether they live above or below the substrate sur-
face. A simple nomenclature system was proposed by
Taylor and Wilson (2002) for marine plants and ani-
mals that encrust or bore natural hard substrates. The
