Dynamic Evolution of the Northern Carnarvon Basin: An Integrated Kinematic Approach

The geological histories of passive margin basins are dominated by tectonically induced vertical and lateral motions that control sediment transport and the development and distribution of resource systems within the basins. However, the upward (uplift and exhumation), downward (burial and subsidence) and lateral (extension, rifting and potential inversion) motions are rarely analysed together. Exploration models built from basin evolution models that include only the vertical dimension may contain larger uncertainties than those that combine lateral and vertical motions. Based on a case study, our research suggests that the combination of analyses can improve the accuracy of basin evolution models and help optimise exploration models. 

Here, we present a case study for the basin evolution model for the Northern Carnarvon Basin that incorporates data from such a combined vertical and lateral motion analysis. Backstripping and decompaction techniques were used to analyse subsidence in more than 200 wells to build the basin’s subsidence and sediment evolution maps. These maps were then used to analyse lateral motions associated with the intraplate rift development in the region. In parallel, we analysed exhumation using compaction and vitrinite reflectance analysis techniques on porosity, sonic logs and paleotemperature data from 210 wells. Our combined analyses revealed seven critical periods of basin development from the Triassic to the present. The Triassic Period was dominated by thermal subsidence and sedimentation within the south-western parts. High subsidence (~ 90 m/Ma) and sedimentation were dominant in the Early and Mid-Jurassic, coinciding with the intraplate rifting of up to ~8 mm/yr, which produced the major sub-basins in the southern and southeastern parts of the basin. This was followed by Callovian exhumation that removed up to 1500 m of sediments from the western part of the basin. The Cretaceous was dominated by rifting and breakup-related subsidence, truncated by exhumation episodes that removed up to 1000 m of sediment thickness in the southeastern parts of the basin. In the Cenozoic, the basin experienced subduction-related tilting that exhumed the southern part while the northeastern parts subsided. Our study has shown that integrating the vertical and lateral motions presents a more accurate and complete basin evolution model with the potential for improving the optimisation of basin exploration.