Page 7 - Carbonate Facies in Geologic History

Preface

Since 1950 geologists have learned more about the origin and lithification of
carbonate sediments than in all the previous years of the history of science. This
is true in all the diverse fields of carbonate geology: the study of Recent
environments, marine zoology and botany, organic geochemistry, trace element
and isotope geochemistry, mineralogy, microfacies of depositional environments,
and trace-fossil and sedimentary structure investigation. A synthesis of this new
knowledge is just beginning to be formulated.
The purpose of this volume is to introduce the advanced student and
petroleum explorationist principally to one important aspect of this study: to
some of the principles of carbonate geology which may serve to interpret the
depositional environments of ancient strata and to better define their sequences
and patterns.
Chapter I is a brief review of principles of carbonate sedimentation. (For a
full discussion of the mineralogy, geochemistry, and diagenesis of carbonates
along with a review of Holocene sediments, one may refer to Bathurst's (1971)
and Milliman's (1974) texts.) Chapter II reviews stratigraphic and paleotectonic
concepts and discusses a general model for carbonate deposition. Chapter III
offers an outline of carbonate petrography, concentrating on lithologic descrip-
tion for the purposes of environmental interpretation. For a further review of
this subject and excellent photomicrographs, Horowitz and Potter (1971) and
Majewske (1969) may be used.
The remainder of the book (Chapter IV-XII) attempts to synthesize a large
amount of descriptive data interpreting depositional patterns from numerous
examples of carbonate facies. From this, certain generalizations appear which
are mainly set out in Chapters II and XII (Summary). The approach has been
mainly inductive: let us look at the record of marine deposition of lime sediment,
see what is there and learn how to describe and interpret it. A dual approach is
recommended: to focus attention equally on stratigraphic relations and petro-
graphic study. Comparisons between certain patterns are made to facilitate the
sorting out of parameters deemed to be most important in their formation.
The inductive approach is always fraught with some difficulty. One is
reminded of Mark Twain's remark in Innocents Abroad, that despite his perusal
of thousands of European cathedrals dedicated to a collection of Saints, he could
not honestly admit to an appreciation of such architecture. He felt that he
should, perhaps, study another 97,000 or so before making up his mind about
their esthetic value. Have we looked at sufficient models for a proper synthesis?
The author's answer is obviously "we have made a start at it." The facies patterns
described are mostly all from the author's personal experience in European and
Middle East regions and from the midcontinent, western Canada, Rocky
Mountains, Appalachian and southwestern United States and Mexico. These