Figure from:Sequence Stratigraphy

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Figure 2 Conceptual cross sections in relation to depth (A) and geological time (B) showing stratal geometry, the distribution of siliciclastic facies, and standard nomenclature for unconformity- bounded depositional sequences in a basin with a shelf-slope break (modified from Vail 1987 and Vail et al 1991, specifically to include offiap). Systems tracts: SMST, shelf margin; HST, highstand, TST, transgressive; LST, lowstand. Sequence boundaries: sb2, type 2; sbi, type 1. Other abbreviations: iss, interval of sediment starvation (condensed section and maximum flooding surface of Vail 1987); ts, transgressive surface (top lowstand surface and top shelf-margin surface of Vail et al 1991); iv, incised valley; isw, lowstand progading wedge; sf, slope fan; bff, basin floor fan. Note that in the seismic stratigraphic literature, the term submarine “fan” includes a range of urbidite systems and sediment-gravity-flow deposits that are not necessarily fan-shaped, prominence of associated facies discontinuities, and whether or not lowstand deposits (LST in Figure 2) are present in the adjacent basin. This particular view of stratigraphy is best suited to the study of siliciclastic sedimentation at a dif- ferentially subsiding passive continental margin with a well-defined shelf-slope break, and under conditions of fluctuating sea level. As with any sedimentary model], it represents a distillation of case studies and inductive reasoning, and modifications are therefore needed for individual examples, for other deposi- tional settings, and as concepts evolve (Posamentier & James 1993).

Figure 3 (A) Simplified stratigraphic cross section of the upper part of San Andres Formation (Permian) in the Guadalupe Mountains, New Mexico. (B) Schematic representation of the broader stratigraphic context of the San Andres Formation at the scale of conventional seismic reflection data. Individual high-order sequences within sequences uSA4 (numbered 1-12) and uSA5 (num- bered 13-14) are characterized by stratal onlap and offlap and are themselves oblique to a still lower-order sequence boundary at the top of the San Andres Formation. The datum for cross section A is the base of the Hayes sandstone of the Grayburg Formation. Also shown in B are the names of other associated lithostratigraphic units. (Modified from Sonnenfeld & Cross 1993.)

Figure 4 Simplified stratigraphic cross section and lithostratigraphic nomenclature for mid- to upper Cretaceous strata in the Book Cliffs, eastern Utah and western Colorado (A; from Nummedal & Remy 1989), with a detail of the Albian sequence stratigraphy (Dakota Group) of north-central Colorado (B; from Weimer 1984 and RJ Weimer, personal communication, 1988). A detail of the Desert Member of the Blackhawk Formation and Castlegate Sandstone (box in A) is illustrated in Figure 5. The base of the foreland-basin succession is marked approximately by a regional sequence boundary at or near the base of the Dakota Sandstone (in A) and at or near the base of the Muddy (or J) Sandstone of the Dakota Group (in B). FC refers to the Fort Collins Member, a portion of the Muddy Sandstone that locally underlies the sequence boundary.

Figure 5 Stratigraphic cross section of the Desert Member of the Blackhawk Formation and Castlegate Sandstone showing depositional facies and sequence geometry (simplified from Van Wagoner et al 1991, Nummedal & Cole 1994). See Figure 4 for location. The two sequence boundaries illustrated are characterized up-dip (west) by well-developed incised valleys. The Desert sequence boundary passes down-dip (eastward) in the vicinity of Sagers Canyon into a marine flood- ing surface that was probably modified by ravinement during transgression. A similar transition is observed in the Castlegate Sandstone as it is traced farther eastward. Note the presence of offlap- ping parasequences beneath each sequence boundary. Abbreviations for generalized paleoenviron- ments: BF, braided fluvial; SF/E, sinuous fluvial/estuarine; FS, foreshore; USF, upper shoreface; LSF, lower shoreface; OT, offshore transition. Systems tracts (modified from the interpretations of Van Wagoner et al 1991 and Nummedal & Cole 1994): HST, highstand; TST, transgressive. Some uncertainty exists about the location of the interval of maximum flooding in the Desert sequence ow- ing to the difficulty of interpreting parasequence stacking trends in thin sections: It is at or slightly above the dashed line labeled Ravinement Surface (D Nummedal, personal communication, 1994). necessary to call upon rapid eustatic change for which there is no plausible

‘igure 7 Interpreted and uninterpreted versions of a seismic reflection profile (line NF79-08) from the Jeanne d’ Arc basin, offshore astern Canada (from Driscoll et al 1995). The profile is oriented north-northeast, oblique to the curvilinear Mercury border fault, which trikes approximately eastward at its intersection with the Nantilus transfer zone. Annu. Rev. Earth. Planet. Sci. 1995.23:451-478. Downloaded from arjoumals.annualreviews.o1 by Columbia University on 09/17/05. For personal use only.