Sequence Stratigraphy as a “Concrete” Stratigraphic - SEPM Strata

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systems tract (TST) bounded by the sequence boundary below and the MFS above and a regressive systems tract (RST) bound by the MFS below and the sequence boundary above (Fig. 8b). Carbonate Sequence Stratigraphy The main concepts of sequence stratigraphy, which primarily concern the delineation and correlation of stratigraphic surfaces formed through the interaction of variations in sediment supply with base level change, were developed on the basis of either models (e.g. Posamentier et al, 1988) or empirical observations (e.g. Galloway, 1989) involving siliciclastic depositional systems. Given this, and the fact that, in comparison to siliciclastics systems, carbonate sedimentary systems react much differently to changes in base level (Schlager, 1991), it is reasonable to ask if siliciclastic-derived, sequence stratigraphic concepts can also be applied to carbonate strata. The basic question is, “Are the sequence stratigraphic surfaces which are generated in siliciclastic strata during changes in base level also generated in a carbonate depositional regime?” The answer to the above question is an emphatic yes as has been demonstrated by a multitude of articles on carbonate sequence stratigraphy. Thus, the same sequence stratigraphic surfaces are used to define specific types of sequence stratigraphic units and to build a quasi-chronostratigraphic correlation framework in both carbonates and siliciclastics. There is no doubt the geometries of the various sequence stratigraphic units developed in carbonates differ substantially from their counterparts in siliciclastics due to the different responses of the two sediment types to base level changes. However, such geometrical differences have no bearing on the question of whether the basic concepts of sequence stratigraphy are equally applicable to both sediment types. The evolution of sequence stratigraphic methods and terminology, as applied to carbonates, proceeded in tandem with that of siliciclastics. The same model-driven and data-driven approaches have been applied and the same spectrum of different sequence boundary types and system tract schemes is in the literature. All the comments regarding 28
the history of sequence stratigraphy and the problems which have developed apply to carbonates just as well as they do to siliciclastics. Schlager (2005) provides a useful review of the evolving application of sequence stratigraphy to carbonate strata since 1977. What tends to set carbonate sequence stratigraphy apart is the distinct nature of some of the sequence stratigraphic surfaces. Carbonate sediments, like siliciclastics, are deposited in both ramp and platform//basin settings. The sequence stratigraphic surfaces which are developed in a carbonate ramp setting have similar characteristics to those developed in siliciclastics strata (Schlager, 2005). However, because of the major differences in the response of carbonate sedimentation to base level changes as compared to siliciclastics, sequence stratigraphic surfaces developed in a carbonate platform/basin setting have somewhat different attributes than those of siliciclastics. For example, a maximum regressive surface in a siliciclastic setting (high sediment supply during late stage base level fall) has very different attributes than a maximum regressive surface in a carbonate platform/basin setting (minimal sediment supply during late stage base level fall). Consequently, when the surfaces are described in a following section, the attributes of each are discussed for both carbonate and siliciclastic settings. Summary There are currently four very different approaches to sequence analysis in siliciclastic and carbonate strata, two based on the deductive Jervey Model and two based on empirical data. Not surprisingly there is considerable ongoing debate concerning which ones are scientifically valid and of practical value and which are not (e.g. Embry, 2002; Catuneanu, 2006). In the sections below, we describe all the various types of surfaces that have been proposed by both the inductive and deductive approaches and evaluate each for its suitability to be used as a bounding surface for the units of sequence stratigraphy, sequences and systems tracts. Sequence Stratigraphic Surfaces 29
Page 1 and 2: Sequence Stratigraphy as a “Concr
Page 3 and 4: deposited during a specific interva
Page 5 and 6: As Hedberg (1959, p.674) put it “
Page 7 and 8: “two distinct intellectual approa
Page 9 and 10: The Early Years Sequence stratigrap
Page 11 and 12: 11
Page 13 and 14: encompassed unconformities on the b
Page 15 and 16: Subaerial Unconformity or Unconform
Page 17 and 18: asinward, and a constant sediment s
Page 19 and 20: (maximum flooding surface) by the T
Page 21 and 22: the significant differences between
Page 23 and 24: 23
Page 25 and 26: Sequence HST TST LST SR NON-MARINE
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Page 31 and 32: surface should also have solid theo
Page 33 and 34: and in some situations it may be co
Page 35 and 36: estuarine or marine strata which fi
Page 37 and 38: ecord, including some of those used
Page 39 and 40: The MRS is interpreted to form when
Page 41 and 42: the MFS marks a change from decreas
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Page 45 and 46: such modelling was done. Helland-Ha
Page 47 and 48: Marine-Flooding Surface A marine-fl
Page 49 and 50: instances. However in cases where s
Page 51 and 52: Sequence Introduction - We see the
Page 53 and 54: stratigraphic unit bounded by subae
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Page 57 and 58: sequence. The determination of the
Page 59 and 60: transgressive surface) are stratigr
Page 61 and 62: In summary, we recommend that a dep
Page 63 and 64: 63
Page 65 and 66: Lowstand Systems Tract (sensu Posam
Page 67 and 68: Highstand Systems Tract (HST) - The
Page 69 and 70: discussing how one might draw a con
Page 71 and 72: one (Fig. 12). Given this, a parase
Page 73 and 74: 2006). Notably two very different m
Page 75 and 76: 75
Page 77 and 78: amounts of erosion and significant
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79
Page 81 and 82:
tracts would not need informal name
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Siliciclastic Ramp We have chosen t
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85
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87
Page 89 and 90:
thus divided into 3rd order sequenc
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(MRS) at the base of slope channels
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overlying RST. Like the previous ex
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16) That, in the future, any new ty
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References Barrell, J., 1917, Rhyth
Page 99 and 100:
Embry, A.F., in press, Correlating
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Mitchum, R, Vail, P. and Thompson,
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Sloss, L., Krumbein, W. and Dapples
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Sequence Stratigraphy as a “Concrete” Stratigraphic - SEPM Strata

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