Terrigenous deposition in marginal-marine areas
The overlapping and wedgeout relations of the sediments deposited in a marginal-marine embayment can be complex. Everywhere, however, the relations give an indication of the behavior of the surface of deposition — subsiding, rising, or stationary. Also, the relations reflect the nature of the tectonic movement, that is, gradual or cyclic. The rate of sediment supply relative to the rate of submergence or emergence of the depositional surface also may be determined. Table 2 is a summary of important variables affecting deposition in the marginal-marine environment.
The comparisons between supply of sediment and the rate of subsidence, as shown in Table 2 (Ala and Alb), are modified from Grabau (1913, p. 728, 734), who first recognized the interrelations of the two variables. This table also catalogs and systematizes the relation of the supply of sediment type to cyclic subsidence and emergence and to gradual emergence (A2, B1, B2). The existence of predictable cyclic sequences of strata was emphasized first by Wanless and Weller (1932) in coal-measure sections in the Eastern Interior basin. A review of the cyclic sequences of sediments deposited in marginal-marine environments reveals that the principle of cyclic sedimentation applies to deposits dating from earliest Paleozoic time to the Holocene. The extent to which cyclic sedimentation may be related either to cyclic tectonism (rising and lowering of sea bottom) or to cyclic changes in sea level
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.