Fundamental concepts related to sediments of marginal-marine area
In Figures 1–10, a sand-mud line is shown. It was pointed out that this line represents the maximum depth of wave agitation. It is also the depth above which marginal-marine sand is deposited and below which silts and clays accumulate. The intensity of wave energy varies greatly. Dunbar and Rodgers (1957, p. 130) stated that, “The depth of wave action falls almost to zero in calm weather and may rise to 300 feet or more during heavy storms. It varies from day to day with the passing storms, and from season to season as the prevailing weather changes. Currents generated by the winds likewise vary, and they commonly change direction with the shifting winds.” Thus, the sand-mud line fluctuates in its vertical depth below the surface of the water. Lohse (1955, p. 99) pointed out that the surface wind is the principal agent controlling non-tidal currents, surface waves, and the coastal-drifting processes in the northwest Gulf of Mexico. He made a distinction “… between prevailing winds, which blow most of the time, and predominant winds, which expend a greater amount of energy and usually do the greater amount of geologic work.” The predominant winds, through the waves they generate, distribute the sediments and shape “… the bays, lagoons, barriers, passes, and sand-sheet in southwest Texas.”
Figures & Tables
Though Memoir 21 was first published in 1974, the concepts and illustrations are timeless for those interested in stratigraphic exploration for sandstone reservoirs. Quickly the reader will note the same relationships in sequence stratigraphy recognized by the author. For university earth science majors and less experienced members of the energy industry, the CD is presented as a reference work. The concepts of depositional control on the distribution of sandstone reservoirs is critical to understand no matter the terminology used. With the kind permission of Dr. Daniel A. Busch, this memoir now can become part of your exploration library.