Sequence stratigraphic framework and application to the Precambrian

Abstract

Sequence stratigraphy highlights stratal stacking patterns and changes thereof within a time frame. Each stratal stacking pattern defines a particular genetic type of deposit with a unique geometry and sediment dispersal pattern within the basin. Common genetic types of deposit are referred to as ‘forced regressive’, ‘lowstand normal regressive’, ‘transgressive’, and ‘highstand normal regressive’. These genetic units are the basic building blocks of the sequence stratigraphic framework at any scale of observation, and are bounded by sequence stratigraphic surfaces. 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. Depending on the scale of observation, sequences and sequence stratigraphic surfaces may be ascribed to different hierarchical orders.

The concept of accommodation, which defines the space available for sediments to fill, is central to sequence stratigraphy. Changes in accommodation are in part controlled by regional to local tectonism, and therefore are location specific. The construction of accommodation curves is based on Wheeler diagrams, the preserved thickness of sequences, and the paleodepositional environment. Accommodation curves may or may not correlate between different sedimentary basins, or even between different sub-basins of the same sedimentary basin, depending on the interplay of local versus global controls on sedimentation. The offset between the accommodation curves that characterize different depozones tends to increase for cycles of increasingly lower rank.

While the workflow and principles of sequence stratigraphy remain the same irrespective of the age of strata under analysis, the differences and similarities between the Phanerozoic and the Precambrian rock record provide significant clues to improving our approach to the application of the sequence stratigraphic method.