Lamina, Laminaset, Bed, Bedset
1990. "Lamina, Laminaset, Bed, Bedset", Siliciclastic Sequence Stratigraphy in Well Logs, Cores, and Outcrops: Concepts for High-Resolution Correlation of Time and Facies, J. C. Van Wagoner, R. M. Mitchum, K. M. Campion, V. D. Rahmanian
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Campbell (1967) identified laminae, larninasets, beds, and bedsets as the components of a sedimentary body; we recognize these stratal units as the building blocks of parasequences. General characteristics of these units are given in Table 1; definitions and more detailed characteristics are given in Table 2. Figure 1shows these types of strata from delta-front turbiditesin cores, outcrops, and well logs from the Panther Tongue of late Santonian age (Fouch et al., 1983) in east-central Utah. Because treatment of these units is not our major thrust, Campbell's (1967) paper is recommended for additional detail.
The four types of stratal units listed above are genetically similar; they differ primarily in the interval of time for formation and in the areal extent of the bounding surfaces. The surfaces bounding the unit sare defmed by (1) changes in texture, (2) stratal terminations, and (3) paraconformities (Dunbar and Rogers, 1957) marked by burrow, root, or soil zones. Figure 2 illustrates these criteria at the scale of the bed. The bounding surfaces are slightly erosional to non depositional and separate younger from older strata. The lateral continuity of the bounding surfaces varies from square inches for some lamina sets to thousands of square miles for some beds or bedsets. The surfaces form relatively rapidly, ranging from seconds to thousands of years, and so are essentially synchronous over their areal extents (Campbell, 1967). In addition, the time interval represented by the surfaces bounding these layers probably is much greater than the time interval represented by the layers themselves.
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Siliciclastic Sequence Stratigraphy in Well Logs, Cores, and Outcrops: Concepts for High-Resolution Correlation of Time and Facies
Application of sequence-stratigraphic analysis depends on the recognition of a hierarchy of stratal units including beds, bedsets, parasequences, parasequence sets, and sequences bounded by chronostratigraphically significant surfaces of erosion, nondeposition, or their correlative surfaces. This method of stratigraphic analysis contrasts with the use of transgressive and regressive cycles of strata for regional correlation of time and facies. Transgressive and regressive cycles have been used for regional correlation for at least 50 years. Recently, proponents of transgressive and regressive cycles, referred to as T-R units, for regional correlation have included Ryer (1983), Busch and Rollins (1984), Busch et al. (1985), and Galloway (1989a). Galloway (1989a) introduced the “genetic stratigraphic sequence,” which is a regressive depositional unit bounded by transgressive surfaces. Although he did not define it specifically, he described it as “a package of sediments recording a significant episode of basin-margin outbuilding and basin filling, bounded by periods of widespread basin margin flooding.”