This atlas is designed primarily as a reference volume. Only a few users will have the endurance to read and digest the whole tome from cover to cover. Most will want to concentrate on certain chapters or certain specific geological relations, as illustrated in selected maps, cross-sections or other diagrams. Yes, individual figures are designed to be largely self-explanatory, and yes, individual chapters are intended to be relatively self-contained. But there are myriad qualities of the atlas that reflect larger concepts and more pervasive design criteria than first glance will readily allow users to grasp. The principal purposes of this first chapter are to introduce users to the geological parameters that predicate the overall scope and structure of the book, the standards and protocols that apply throughout, and the manifest assumptions and constraints - in short, to provide a guide to the use of the atlas as a reference work.
Readers interested in a larger perspective on the overall purpose and history of the atlas project are referred to the foreleaf pages, which set out basic project tenets and acknowledge the scores of individuals and institutions who participated, and to a series of published project reports (Mossop, 1986, 1988a, b, 1989, 1990, 1991; Mossop and Shetsen, 1987, 1988, 1989, 1990, 1991, 1992, 1993).
Of the 35 chapters in the atlas, 19 deal with designated stratigraphic divisions or 'slices,' some encompassing whole geological periods (e.g., Triassic), others concentrating on smaller but economically important stratigraphic units (e.g., Cretaceous Cardium Formation). The bounding surfaces between divisions are set either at major unconformities or at stratigraphically significant and widespread marker horizons. Definitions of the bounding surfaces are discussed in each chapter and are catalogued in detail in the electronic Atlas database.
As is true for the rest of the Atlas, each division chapter is dominated by illustrations. Some are discretionary in nature but most are standard. The standard illustrations include: index map, correlation chart, reference logs, structure map on the top bounding surface, gross division isopach map, subdivision isopach and lithofacies maps, and a series of regional or "master" cross sections along transect lines common to all chapters. The assumptions and constraints that apply to these standard figures are discussed under the heading Atlas Illustrations.
The text of each division chapter is intended to establish the basic geological context of the subject stratigraphic slice, to guide the reader in understanding and interpreting the illustrations, and to furnish references to the essential literature. Standard headings and contents in division chapters are discussed under Atlas Text.
Sixteen chapters are devoted to generic or thematic material. They are designed to address aspects of the general geological, geophysical, geochemical and geotechnical character of the strata. Some deal with discrete tectonic domains (Cordillera, Williston Basin/Sweetgrass Arch, Peace River Arch), some with basin processes such as hydrocarbon generation and heat flow, some with very specific topics like stress distribution and sequence stratigraphic applications, and others with very broad and general overview themes such as Phanerozoic basin development and the paleogeographic evolution of the cratonic platform and of the foreland basin. Two chapters, 1 and 35, address the use and scope of the Atlas itself and of the Atlas database. Three deal specifically with the economically important resources of the basin - oil and gas, coal, and minerals.
The theme chapters are much less structured than the stratigraphic division chapters, and their illustrations are much more discretionary. They are in effect review papers that summarize the state of knowledge and provide referenced access to the open literature.
Last modified: July 31, 2008
