Large‐scale stratigraphic architecture, eustatic variation, and unsteady tectonism: A theoretical evaluation

Abstract

We incorporate a process‐based depositional model with basin subsidence models to predict stratigraphic records. This allows us to investigate the importance of subsidence geometry on coastal stratigraphy and thus to characterize and compare the stratigraphic architecture of two categories of tectonic basins. The models demonstrate that the correlation of stratigraphic sequences to eustatic cycles is not the same in passive margin basins as in foreland basins and that in a foreland basin, the record of episodic tectonism is distinct from that of eustatic sea level change. In the model, sediment transport is approximated by slope‐controlled diffusion; nonmarine transport is treated as more efficient diffusion than marine transport. Three different subsidence and sediment supply models are examined: a simple passive margin basin, a simple foreland basin, and then a foreland basin for which vertical motions are driven by thrust shortening that is compensated flexurally and for which sediment supply is related to relief. Predicted passive margin stratigraphies, for cases of varying eustatic sea level, are similar to those of natural basins and include progradational packages and subaerial unconformities, which are used to define sequence boundaries that form during sea level fall. We explore the timing relationships between stratigraphic features and a sinusoidal sea level history, showing that the phase relationship depends on subsidence, sediment flux, efficiency of sediment transport, and period and amplitude of sea level. When the basic geometry of the basin is inverted, placing the sediment supply on the side with maximum subsidence as is the case in foreland basins, the sequence character changes markedly: subaerial erosion does not generate unconformities. In the models of a dynamic foreland basin, sediment supply and subsidence are linked to the structure of the flanking thrust belt and are not necessarily constant. For steady thrusting and variable sea level, unconformities that define sequence boundaries form only on the distal or forebulge side of the basin, and the ages of the sequence boundaries correlate to limes of rising sea level. In cases of constant sea level but variable thrusting, subaerial unconformities are cut locally on both the proximal margin of the basin and the distal margin of the basin, yet the ages of the proximal margin and distal margin unconformities are out of phase in the tectonic cycle: erosion is most pronounced during quiescence on the proximal side and during thrusting on the distal side.

Clinoform development by advection‐diffusion of suspended sediment: Modeling and comparison to natural systems

“…Diffusion-based models of clinoform formation assume that sediment transport is a function of topographic slope [Kenyon and Turcotte, 1985;Flemings and Jordan, 1989;Jordan and Flemings, 1991;Thorne, 1995]. These models result in a clinoform geometry that resembles that in natural systems, but implicit in these models is the interpretation that sediment transport is a function of slope-driven processes, such as creep, sliding, and slumping [e.g., Kenyon and Turcotte, 1985].…”

Tectonic Implications of Stratigraphy Architecture in Distal Part of Foreland Basin, Southwestern Taiwan

“…The characteristics of the subsidence history and stratigraphy architecture strongly imply that the foreland basin evolution favors the tectonostratigraphic model proposed by Flemings and Jordan [40] and Jordan and Flemings [41]. In their models, unconformity within the foreland basin sequences might represent active thrusting in the mountainbuilding belt, during which forebulge migrates toward the thrust front and causes uplifting in the distal part of the basin, while the rapid subsidence represents the later stage and quiescence of thrusting, during which sequences prograde toward the distal part of the basin and onto the unconformity.…”

“…Generally speaking, in response to each episode of large-scale thrust faulting in the orogenic belt, the subsidence rate in a basin, which is related to the rates of advancement of the front of orogenic belt and change of orogenic wedge morphology, the sediment supply rate and the global sea level change rate would all together affect the tectonostratigraphic architecture, time-spatial distribution of lithofacies and the superimposed unconformities in the basin [39,40,41,42,45,46,47,48,49]. Some models suggest that timing of rapid subsidence at different locations in a foreland basin has different tectonic implication [40,41,43]. In a young and on-going mountain building belt, such as that in Taiwan, the geological records in the foreland basin and fold-and-thrust belt are still well preserved and can be utilized to study the tectonostratigraphy problems and to test validity of different models for the problems.…”

“…Lately, time lag between erosion in the mountain side and deposition in the basin has been put into consideration when investigating and simulating a model of foreland basin sequences [38,39,40,41,42,43]. In response to each episode of active thrust faulting, newly formed foreland basin by rapid subsidence would not be filled up with sediments in the early time; therefore, according to the theoretical model [4], the sediment-starved basin would be deep and narrow and accumulate deep water sediments in an " underfilled" state [39,40,41]. In the following stage, the orogenic wedge began to uplift and the consequential erosion provided the sediments to fill up the basin when the large-scale thrust faulting wane.…”

Biostratigraphy and Inoceramus survival across the Cenomanian–Turonian (Cretaceous) boundary in the Ram River section, Alberta, Canada

“…Numerical modelling of the relationship between foreland basin subsidence, sea-level and facies distributions (Jordan and Flemings 1991), has shown, in marine basins, that episodes of rapid subsidence resulted in the trapping of sand and gravel in the proximal foredeep, resulting in the vertical stacking of nearshore sandstone bodies close to the orogen. Only muddy sediment was transported, mainly through storm-related processes, to the more offshore part of the basin.…”