From Sedimentary Structures to Facies Models: Example from Fluvial Environments
Published:January 01, 1975
1975. "From Sedimentary Structures to Facies Models: Example from Fluvial Environments", Depositional Environments as Interpreted from Primary Sedimentary Structures and Stratification Sequences, J. C. Harms, J. B. Southard, D. R. Spearing, R. G. Walker
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In this section, our basic objective is to show how an understanding of the physical significance of sedimentary structures discussed in preceding chapters can be used in combination to make deductions about the succession of depositional processes and environments involved in a local sequence of rocks, and the ways in which generalized facies models can be formulated. We will work from individual structures, and small groups of structures, showing how the basic “building blocks” of a stratigraphic sequence can be identified and interpreted. We will then discuss the arrangement of the building blocks into specific sequences, and show how a large number of specific sequences can be combined and distilled into a general facies model. Using the fluvial environment as an example, we will examine the range of fluvial facies models that have been proposed, and finally we will attempt interpretations of the models in two contrasting ways--hydrodynamic, as discussed in Chapters 2 and 3, and also in terms of channel morphology.
It is clearly impossible to make a coherent detailed interpretation of a thick stratigraphic sequence (tens or hundreds of meters) without in some way subdividing it into homogeneous pieces--the basic “building blocks” of the sequence. Subdivision into similar parts requires familiarity with the range of descriptive features present in the entire section, and upon:
The degree of detail required for the particular purpose of the study.
The abundance, variety, and type of descriptive features contained in the rock.
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Depositional Environments as Interpreted from Primary Sedimentary Structures and Stratification Sequences
The focus of these notes is on the use of primary sedimentary structures and stratification sequence as tools for interpretation of depositional environment of clastic sediments, emphasizing advances in understanding that the authors judge to be important. To accomplish the primary objective, several topics have been selected. Experimental flume studies are summarized with emphasis on work which extends the understanding of distribution of bed forms over increased ranges of grain size, flow depths, or velocity. Studies of modern and ancient sedimentary sequences are used to illustrate and interpret environments of deposition. Fluvial sediments are reviewed to show how experimentally derived generalizations are applied or qualified to interpret natural environments.