Fine‐Scale Forward Modelling of a Devonian Patch Reef, Canning Basin, Western Australia

Abstract

Although factors that control the distribution of carbonate sediments are relatively well understood, their interaction in producing known geometries remains poorly known. A fine-scale forward model was developed to analyse the controls on decimetre-scale heterogeneity and carbonate facies distribution within larger-scale sediment bodies. The model was tested on a Frasnian (Late Devonian) patch reef, part of the so-called Glenister Knolls reef complex in the Canning Basin, Western Australia. The evolution of Glenister Knolls was digitally reconstructed using digital surveying technologies that resulted in a high-resolution dataset containing geological information from centimetrescale to outcrop dimensions. The three-dimensional digital outcrop model of Glenister Knolls was used to evaluate predictions from the fine-scale forward modelling results.The fine-scale forward model is based on a stochastic cellular automaton that simulates the spatial distribution of carbonate facies through time. The modelled carbonate facies is based on two main factors, stromatoporoid growth and sediment transport, and it successfully predicts the distribution of the basic elements -reef fabric and sediment -that compose the patch reef. The fine-scale forward model also successfully reproduces all major depositional relationships observed in the field such as backstepping, downlapping and interfingering contacts. The external structure of the reef is very sensitive to subsidence and production rates, since these directly influence accommodation space so constraining the vertical growth of the patch reef. However, the internal structure predicted by this model does not seem to be affected by one specific parameter, and displays the same sensitivity to other parameters, such as current intensity and wave amplitude.

The intrinsic effect of shape on the retrogradation motif and timing of drowning of carbonate patch reef systems (Lower Frasnian, Bugle Gap, Canning Basin, Western Australia)

“…As detailed in the previous sections, traditional field observations defined the depositional history and stratigraphic evolution of the Glenister Knolls patch reefs and the southern tip of the Laidlaw Range platform. In order to enable digital outcrop modelling and precise quantification of the Lower Frasnian carbonate system, surveying and digital mapping techniques were deployed (Hasler et al. , 2008).…”

“…In this study, high‐resolution GPS surveying was used to delineate and examine spatially aggrading, retrograding and drowning patterns observed in Lower Frasnian reef complexes of the Canning Basin of Western Australia (Hasler et al. , 2008).…”