• The Korean Journal of Petroleum Geology
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• v.5 no.1_2 s.6
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• pp.36-47
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• 1997

This study presents multi-variable sequence model for a broader application of sequence concept proposed by Exxon group. The concept of the multi-variable model is based on the fact that internal organization and boundary type of the sequences are determined by three varying factors including 3rd-order cycles of eustasy, and tectonic movement and sediment influx with 2nd-order changes. Instead of Exxon group's systems tracts, this model adopts parasequence sets as the fundamental building blocks of the sequence, because they are descriptive stratigraphic units simply defined by internal stacking pattern, reflecting interactions of accommodation and sediment influx. Seven sequence types which vary in number and type of internal parasequence sets are formulated as associations of four types of accommodation development and three grades of sediment influx. In the southwestern margin of Ulleung Basin, the multi-variable sequence analysis of shelf-slope sequence shows systematic changes in stratal patterns and the numbs, of constituent parasequence sets (i.e. sequence type). These changes are interpreted to reflect temporal and spatial changes in type and rate of tectonic movement and sediment influx, as a result of back-arc opening and closing. During the back-arc opening, rapid subsidence, continuous rise of relative sea level, and high sediment influx gave rise to sequences dominantly of single progradational parasequence set. In the early stage of back-arc closing accompanied by local contractional deformation, different types of sequences contemporaneously formed depending on the spatial changes in tectonically-controlled accommodation and influx rates. During the subsequent slow back-arc subsidence, rise-dominated relative sea-level cycle was coupled with moderate to high sedimentation rate to have resulted in sequences consisting of $2~3$ parasequence sets.

• Economic and Environmental Geology
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• v.44 no.6
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• pp.503-511
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• 2011

The Upper Devonian Grosmont Formation in northern Alberta, Canada, underlies the erosion unconformity that formed between the Cretaceous and Upper Devonian. The formation is divided into four units on the basis of intercalated shales and showing a typical shelf environment of shallowing-upward. It was possible to separate four units(LG~UG3), considering the seismic interpretation attributes of polarity, continuity, frequency/spacing and amplitude and showing the reflection characteristics of the medium-high amplitude, medium-low frequency, good continuity, and subparallel reflection events. The formation can be interpreted as shelf or platform, based on in-situ core data. However, it is difficult, only with reflection attributes and features, to recognize the boundaries and sedimentary environment of parasequence. Therefore, we try to interprete by parasequence set in this study. The parasequence set was formed by erosion unconformity with systems tracts. The erosion unconformity can be recognized by facies data and karst, erosional surface. Grosmont carbonate deposits ranging from platform and shelf to shelf slope are; by wedge-shaped strata of characterized by complex sigmoid-oblique progradational configurations, reflecting a depositional history of upbuilding and outbuilding in response to sea-level changes. Most of the sedimentary units is interpreted as platforms under regression and lowstand environments that support is evidences. In particular, shale layer at the basal part of the highstand systems tracts represents the regressive to lowstand of sea level.