Modelling fluvial, aeolian and lacustrine response to differential rates of accommodation generation in developing rift and salt basins

Background. Many rift and salt basins exhibit stratigraphic fills that record complex development in response to subsidence histories that varied spatio-temporally. For example, the presence of intraformational unconformities within the fill of such basins demonstrates differential tilting of the land surface at the time of accumulation. Thickening of accumulated successions in depocentres demonstrates differential patterns of subsidence and accommodation generation. In regions that experienced continental sedimentation, such styles of basin development can be shown to have exerted a primary control on fluvial, aeolian and lacustrine system behaviour, and style of accumulation and long-term preservation of the developing successions. Stratigraphic numerical modelling provides an opportunity to demonstrate how tectonic and halokinetic controls on basin development may be recorded in and deciphered from the preserved stratigraphic expression of the fill of rift and salt basins, respectively.
Aim and objectives. This project will use a combined field-based and numerical modelling approach to investigate the following aspects of tectono-sedimentary basin development: (i) the role of syn-sedimentary tectonic movement on basin-bounding faults in influencing patterns of fluvial, aeolian and lacustrine sedimentation and system behaviour (e.g. style of fluvial channel-body lateral accretion, avulsion frequency, and rate of incision) in actively developing rift basins; (ii) the role of salt mini-basin subsidence and associated salt-wall uplift in determining the nature of sediment infill in basins developing in halokinetic provinces. Specific research objectives are as follows: (i) to determine the nature of feedback between on-going sedimentation, loading and basin subsidence; (ii) to establish sedimentological and stratigraphic criteria for prediction of the complex 4D spatio-temporal development of basin fills.
Methodology. The research will involve the development of a numerical forward stratigraphic model to test how a variety of styles and rates of deformation will influence both the fluvial system planform morphology and the preserved architecture of the resulting stratigraphic succession. Lateral tilting of the ground surface is known to systematically cause rivers to locally aggrade, incise and migrate laterally as they seek out zones of unfilled accommodation associated with differential basin subsidence. Understanding patterns of vertical and lateral fluvial channel-body stacking resulting from different styles of fault movement or salt deformation has major implications for better predicting subsurface reservoir properties in hydrocarbon provinces. The numerical stratigraphic model to be developed as part of this research will be used to account for fluvial, aeolian and lacustrine system behaviour in a range of currently tectonically active settings including, for example, the Madison and South Fork rivers of Montana, which have recently incised and migrated laterally in response to the 1956 Hebgen earthquake. The numerical modelling software to be developed will be applied to account for the stacking of sand-prone fluvial channel elements and associated aeolian and lacustrine elements in ancient outcrop successions developing in sedimentary basins such as those of the Gulf of Corinth region, Greece and the Salt Anticline Region, South East Utah. Results will be applied to predict sand-body architecture and connectivity in a range of hydrocarbon reservoirs developed in rift and salt basins.
Results from this research will be in the form of a predictive model whereby the response of continental (fluvial, aeolian and lacustrine) systems to faulting in rift-basin settings and salt-wall uplift and mini-basin subsidence in salt-basin settings can be used to document and quantify styles of system response to basin development in a manner not currently possible. As such, this research will enable rates of fluvial channel-belt lateral migration, rates of fluvial incision and associated rates of erosion to be determined for a variety of possible scenarios. Further, it will enable the development of criteria for the prediction of how and when aeolian and lacustrine accumulations will likely be preserved in such settings. A major outcome of this research will be the development of a workflow for the recognition and interpretation of fluvial, aeolian and lacustrine architectural elements in rift-basin and salt-basin settings and development of a predictive database for the characterization (including geometry, dimensions and relationship to one another) of such elements in basins subject to a range of styles of accommodation generation.