Sedimentary controls on the sequence stratigraphic architecture in intra-cratonic basins: An example from the Lower Permian Shanxi Formation, Ordos Basin, northern China

- Intra-cratonic basin has the retrogradational sequence stratigraphic pattern.
- The observed cyclothemic sequences were simulated by numerical simulation.
- Sediment accumulation can control stratigraphic architecture of intra-cratonic basin.

Intra-cratonic basins are characterized by stable tectonic regimes, closed depositional systems, finite sizes of receiving basins and extremely low morphological gradients. This paper examines the effect of sediment accumulation on the sequence stratigraphic architecture and quantitatively evaluates its controls on the development of intra-cratonic sedimentary sequences using numerical modelling. A well documented intra-cratonic sedimentary sequence, the Lower Permian Shanxi Formation in the Ordos Basin, northern China, was used to illustrate a sequence stratigraphic model developed for intra-cratonic sedimentary basins. The studied sequence is characterized by a typical backstepping or source-ward retrogradation. A 2-D simulation software (SEDPAK) and a 3-D simulation software (SEDSIM) were used to model the intra-cratonic sequence. The modelling results indicated that sediment accumulation alone can produce the classical retrogradational stratigraphic stacking patterns. The sediment accumulation can (1) increase the retrogradational range of the original retrogradational stacking sequences, (2) change an original aggradational stacking sequence to a retrogradational stacking one, and (3) decrease the progradational range of an original progradational stacking sequence, or (4) even change an original progradational stacking sequence to a retrogradational stacking sequence. Understanding the relationship between the sediment accumulation and the stratigraphic development in an intra-cratonic basin is essential for interpreting the sequence stratigraphic framework and stacking patterns, and for predicting the distribution of potential reservoir sand-bodies within such basins. This work enriches the classic sequence stratigraphic models by providing a new model for intra-continental basins, and offers new insight on hydrocarbon exploration in intra-cratonic basins.