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The processes involved in the structural and stratigraphic evolution of the North West Shelf (NWS), one of the most productive and prospective hydrocarbon provinces in Australia, remain controversial. The complex structural characteristics of the NWS include large-scale extensional detachments, difference between amounts of crustal and lithospheric extension and prolonged episodes of thermal sagging after rifting episodes. It has been proposed that the succession of different extensional style mechanisms (Cambrian detachment faulting, broadly distributed Permo-Carboniferous extension and Late Triassic to Early Cretaceous localised rift development) are best described in terms of variation in deformation response of a lithosphere that has strengthened from one extensional episode to the next. However, previous models invoking large-scale detachments fail to explain changes in extensional styles and over-estimate the structural importance of relatively local detachments (e.g. Scholl Island Fault). Here, we hypothesize that an initially weak lithosphere would distribute deformation by ductile flow within the lower crust and that the interaction between crustal flow, thermal-evolution and sediment loading/unloading could explain some of the structural complexities recorded by the NWS. To test this hypothesis we run a series of fully coupled 3D thermo-mechanical numerical experiments that include realistic thermal and mechanical properties, as well as surface processes (erosion, sediments transport and sedimentation). This modeling approach aims to provide insights into the thermal and structural history of the NWS, and a better understanding of the complex interactions between tectonics and surface processes on the margin scale.

The fluvio-deltaic Triassic Mungaroo Formation, North West Shelf (NWS) of Australia, hosts vast resources of hydrocarbons. However, the mechanisms that generated its 4-6 km monotonous infill archit...

800-2400 km long transcontinental paleovalleys straddle the modern landscape of Western Australia (WA). These valleys formed following emergence of the Canning Basin at the end of the Lower Cretaceous, and reached their greatest development during Eocene time. They owe their preservation to limited erosion/burial and to an overall drying climate since the Upper Cretaceous. They represent the largest network of inactive valleys visible at the Earth’s surface. These valleys debouch at their downstream ends into well-dated depocentres and paleo-shorelines, which provide age constraints and firm milestones of their temporal and spatial evolution. Drainage network evolution and valley long profiles constrain the timing of long (~1000 km) to intermediate wavelength (~200 km) variations in uplift and subsidence rates over the continental interior. We use these data to decipher the respective contributions of regional tectonics and dynamic topography to the evolution of the Northwest Shelf. Upon emergence uplift determined the shape of the initial drainage that started to drain the emerging landmass. Later, a changing field of surface uplift triggered drainage rearrangements in the early Cenozoic. Rearrangement resulted in piecemeal rerouting of water and sediments towards the North West Shelf. Increasing aridity during the Neogene contributed to the tectonic defeat of some of these rivers. We use the Badlands surface model developed by the Basin Genesis Hub to quantify sediment and water delivery to the North West Shelf during the lifespan of the drainage. Further, there is some debate regarding the chronology of aridification in the continental interior. We use the modelling to derive the first quantitative estimates of the water balance to see if numeric water balance assessments can reconcile discrepant sets of paleoclimatic proxies.

The landscape of Papua New Guinea is very young, shaped by Plio-Quaternary tectonic events. Tectonic uplift rates exceed 400 m/Myr and rainfall exceeds 10 m/yr. Uplift and rainfall combine to generate very high erosion rates. The Gulf of Papua is the ultimate sink for a very large terrigenous flux of ~ 365˙106 t/yr stemming from the southern New Guinean mainland and from the Papuan Peninsula. Sediment cores indicate sediment accumulation rates of 0.12-0.8 mm/yr in the deep-sea basin since the Late Pleistocene. Rock types and erosion rates determine the nature and burial rate of the sediments delivered to the basin. Understanding their evolution through space and time helps predict the petrological stratigraphy of the basin. We use Badlands, a surface process numerical model developed by the Basin Genesis Hub, which simulates sediment erosion, routing and deposition, in order to simulate present-day fluxes and assess their evolution in the past. To reproduce landscape evolution in deep time we need to constrain the erodibility of the source areas. To achieve this we calibrate the model over the present-day landscape, using the present-day topography, rainfall patterns, distribution of source rocks, recent surface uplift field, and estimates of Late Quaternary sediment fluxes. Relative uplift along the southern flank of the Papuan Peninsula is constrained by the elevation of remnants of extensive late Miocene volcanics and by the modern elevation of contemporary low-lying surfaces. They reveal an uplift rate that increases from 0 m/Myr at the coastline to 440 m/Myr in the headwaters.

Rift settings preserve high-fidelity records of their depositional history in response to multiple processes, such as climate change that significantly influences the sediment input, and tectonic deformation which contributes to accommodation generation or consuming. Integrated studies of geomorphology, thermochronology, analog experiments and numerical modelling improved our understanding of the rifting processes and associated structural evolution. However, the interplay between climate change, sediment transport from eroding highland to rift basins and rift-related deformation is poorly understood. We present a forward numerical scheme that couples surface process with thermo-mechanical modelling on a rift setting. In the coupling numerical framework, a 2D (potentially 3D) lithospheric scale model is set up. The erosion, sediment transport and deposition are controlled by surface processes with the boundary conditions of climate force (precipitation) and erosion coefficient. The resulting sediment volumes are transferred to the thermo-mechanical system, which has significant effect of crustal deformation. The produced tectonic uplift or subsidence then contributes to the change of surface topography and thus the sediment routing. We focus on investigating the climatic controls on source dynamics, sediment transport, and the deposition in both marine and nonmarine environments. We then quantify the influence of sediment accumulation on crustal deformation and rift evolution. The resulting stratigraphic architecture will be analyzed through evolving stratal stacking patterns and shoreline trajectories to explore the feedbacks between erosion/deposition patterns and the rift structural. We will then apply our modelling to typical rifting examples such as East Africa rift system.

Surface process dynamics play an important role in sedimentary basin evolution. It affects hydrologic and carbon cycling, which are particularly difficult to simulate because of their complex inter...