Architectural-Element Analysis: A New Method of Facies Analysis Applied to Fluvial Deposits
Andrew D. Miall, 1985. "Architectural-Element Analysis: A New Method of Facies Analysis Applied to Fluvial Deposits", Recognition of Fluvial Depositional Systems and their Resource Potential, Romeo M. Flores, Frank G. Ethridge, Andrew D. Miall, William E. Galloway, Thomas D. Fouch
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The concept of the facies model has been the most powerful and successful tool devised by sedimentologists for classifying and explaining ancient sediments. At present there are at least a dozen formal fluvial facies models (Miall, 1980, 1981a), and many variants of these have been erected to explain specific ancient units. It has become clear that these models reflect fixed points on a continuum of variability. As discussed below, the continuum is, in fact, a multidimensional one because of the complexity of partly interdependent controls that govern fluvial sedimentation. A continuation of modelling studies along existing lines will simply result in a proliferation of arbitrary fixed points and a new approach is needed.
Friend (1983) proposed a classification of fluvial architecture based on a two-fold breakdown of the sediments into channel and interchannel sediments. Channels were further subdivided into fixed, mobile or sheet (i.e., non-channelized) types. Allen (1983) recognized “eight kinds of depositional features” or “internal architectural elements” in a study of a Devonian sandy braided stream deposit of the Welsh borders area. Ramos and Sopena (1983) defined five types of gravel and sand body in a Permo-Triassic unit in Spain.
These three studies contain the basis of a new architectural approach which, it is proposed here, can be applied to all fluvial deposits.
Facies models typically are constructed in the form of paleogeographic sketch maps, vertical profiles, block diagrams, or a combination of all three. These attempt to combine information on at least two scales: the assemblage of individual
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The understanding of fluvial environments and processes that operate within them as well as their products in the geological record is a recent development. During the past decade, facies analysis of fluvial rocks has been increasingly used to explore for and develop hydrocarbons, coal, uranium and metallic minerals. The rapid growth in the database on fluvial depositional systems coupled with the need to recognize the economic potential of their deposits has yielded numerous resources which deal with recognition and classification of the whole spectrum of fluvial systems, fluvial processes and their products, facies models of ancient fluvial deposits, and application of fluvial models to resource exploration and development. This notebook is an outgrowth of the burgeoning geological investigations of fluvial rocks and their associated potential. The notebook is divided into 11 chapters the cover methodology and classification of fluvial systems as well as modern and ancient deposits of alluvial fans, fan deltas, braided systems, meandering streams and anastomosed streams. In addition, application of facies modeling to exploration and development of hydrocarbons, coal and uranium is discussed for the Rocky Mountain region, Mid Continent, Gulf Coast and western China.