Page 33 - Carbonate Facies in Geologic History

Chapter II

The Stratigraphy of Carbonate Deposits

The basic processes of carbonate sedimentation result in certain stratigraphic
relations and in predictable facies patterns which are widespread in the geologic
record. These patterns recur in a variety of tectonic settings. This Chapter consid-
ers these interrelations and also treats correlation problems in carbonate strata
and the techniques for recognition of approximate "time planes" in shelf and
shelf-margin areas. The Chapter contains many of the basic premises from which
the author formulates stratigraphic and petrologic interpretations. Later Chap-
ters furnish considerable basic data and offer numerous examples of facies pat-
terns in a variety of tectonic settings, all of which serve to test some of the
stratigraphic ideas set forth below. A summary Chapter repeats most of these
generalizations.

Definitions

Recent rapid growth in understanding the formative processes of carbonate
buildup has resulted in redundancy and confusion of terminology used in describ-
ing and interpreting such sedimentary bodies. The number of scholarly papers,
including a review of the term "reef' alone, probably exceeds twenty. Therefore,
rather than reviewing further the evolution of terms and concepts, only definitions
of common expressions are given. The terms below are those now widely em-
ployed-even though some of those defining composition and genesis are some-
what overlapping. Several preliminary observations are worthwhile: (1) It is im-
portant to separate expressions describing shape of carbonate bodies from those
describing their internal composition-the latter necessarily intermingle concepts
of genesis. (2) Distinction must be made between names for discrete smaller scale
limestone bodies and large regional configurations formed by carbonates (e.g.,
"Bank" has been used in two ways). (3) The term "reef' has evolved rapidly and
geologists have modified and restricted its meaning. This has caused confusion to
the extent that the term should be used always with a modifier to designate its
meaning (Heckel, 1974).

General Definitions

Carbonate buildup: A body of locally formed (laterally restricted) carbonate
sediment which possesses topographic relief. This is a general and useful term
because it carries no inference about internal composition (Fig. II-I).