Published March 15, 2023 | Version v1
Conference paper Open

Landscape and basin evolution modelling elucidates sediment supply and accommodation relationships in the Cretaceous Crayfish Sub-group of the Otway Basin

  • 1. University of Sydney, m.boyd@sydney.edu.au
  • 2. University of Sydney, tristan.salles@sydney.edu.au
  • 3. University of Sydney, sara.moronpolanco@sydney.edu.au

Description

In the Otway Basin, the early Cretaceous Crayfish Sub-group infills syn-rift half grabens and has produced petroleum and commercial volumes of CO2. Naturally occurring Hydrogen has also been recorded in historic exploration wells. Previous work focusing on the depositional environment and tectonostratigraphic evolution within the depocenters indicates that variations in accommodation and sediment supply strongly influences the stratigraphic architecture of the Crayfish Sub-group. To evaluate this influence, we use a landscape and basin evolution numerical model (Badlands). First, we generate a series of simulations with varied tectonic, climate and erodibility parameters using a design of experiments method. From these, we select scenarios with a correspondence between the modelled and observed stratigraphy of the Crayfish Sub-group at specified well locations. We then propose that the observed stratigraphy of the Otway Basin Crayfish Sub-group can be explained by sediment supply variations caused by the evolution of the surrounding landscape across four phases which are: Phase 1: Limited sediment supply as the drainage systems start to develop in response to the rift formation. Phase 2: Sediment supply peaks as high erosion in the steep rift escarpment proximal to the depocenters increases sediment volumes delivered to the depocenters. Phase 3: Relatively high sediment supply continues thanks to an efficient connection between upstream region and the depocenter. Phase 4: Differential sediment supply controlled by a distal and a proximal source. Sediment from the distal escarpment is supplied at a constant rate and buffered within the landscape, while proximal, high sediment supply pulses are generated when the proximal rift escarpments steepen. By extending and quantifying existing conceptual models that link stratigraphy to sediment supply and accommodation, this work demonstrates how source-to-sink models enhance our understanding of the complex stratigraphy taking place within rift systems.

Notes

Open-Access Online Publication: May 29, 2023

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