Sequence Stratigraphy: Methodology and Nomenclature

Abstract

Abstract. The recurrence of the same types of sequence stratigraphic surface through geologic time defines cycles of change in accommodation or sediment supply, which correspond to sequences in the rock record. These cycles may be symmetrical or asymmetrical, and may or may not include all types of systems tracts that may be expected within a fully developed sequence. Depending on the scale of observation, sequences and their bounding surfaces may be ascribed to different hierarchical orders. Stratal stacking patterns combine to define trends in geometric character that include upstepping, forestepping, backstepping and downstepping, expressing three types of shoreline shift: forced regression (forestepping and downstepping at the shoreline), normal regression (forestepping and upstepping at the shoreline) and transgression (backstepping at the shoreline). Stacking patterns that are independent of shoreline trajectories may also be defined on the basis of changes in depositional style that can be correlated regionally. All stratal stacking patterns reflect the interplay of the same two fundamental variables, namely accommodation (the space available for potential sediment accumulation) and sediment supply. Deposits defined by specific stratal stacking patterns form the basic constituents of any sequence stratigraphic unit, from sequence to systems tract and parasequence. Changes in stratal stacking patterns define the position and timing of key sequence stratigraphic surfaces. Precisely which surfaces are selected as sequence boundaries varies as a function of which surfaces are best expressed within the context of the depositional setting and the preservation of facies relationships and stratal stacking patterns in that succession. The high degree of variability in the expression of sequence stratigraphic units and bounding surfaces in the rock record means ideally that the methodology used to analyze their depositional setting should be flexible from one sequence stratigraphic approach to another. Construction of this framework ensures the success of the method in terms of its objectives to provide a process-based understanding of the stratigraphic architecture. The purpose of this paper is to emphasize a standard but flexible methodology that remains objective.

Sedimentological study of the Nikolčice Formation - evidence of the Middle Jurassic transgression onto the Bohemian Massif (subsurface data)

“…The thick ness of the NF in these bore holes var ies greatly, be ing be tween 8 m and 81 m. An up wards shallowing/coars en ing suc ces sion typ i cally re veals progradation. Such a re peat ing prograding suc ces sion ter mi nated by a flooding sur face is in the ter mi nol ogy of se quence stra tig ra phy described as a parasequence or parasequence set (Catuneanu et al, 2011). Ev i dence of sev eral prograding parasequences, with thick nesses be tween a few metres and ~20 m, is com mon in these bore holes.…”

Forced regressive wedge in the Mesoproterozoic Koldaha Shale, Vindhyan basin, Son valley, central India

“…However local and regional tectonic activity can also play a significant role in creation of accommodation space and hence in determining the stacking pattern. The term 'sequence' has been redefined by Catuneanu et al (2011) as 'a cycle of change in accommodation or sediment supply'. Changes in accommodation are typically of allogenic origin (i.e., eustasy and tectonics, although additional space can also be created by compaction and sediment loading), whereas changes in sediment supply can be either of allogenic (e.g., climatic) or autogenic (e.g., fluvial channel avulsion, delta lobe switching and abandonment, efficiency of longshore sediment transport) origin .…”

Tubular tempestites from Jurassic mudstones of southern Poland

“…The ho ri zons with tu bu lar tempestites are used in se quence stra tigra phy anal y sis, as they of ten ac com pany omis sion sur faces, record ing syndepositional ero sion and re duced sed i men ta tion rate. These pro cesses are char ac ter is tic of an ini tial stage of trans gres sion and transgressive sys tem tract, dur ing which terrigenous sed i ment is mostly trapped in the coastal zone, and the shal low ma rine en vi ron ment be comes starved of sed i ment (Catuneanu et al, 2011).…”