From reefs to drift: Miocene/Pliocene sedimentary change in the Browse Basin, NW Australia
Final Report Abstract
The Miocene to Pliocene sedimentary succession of the Browse Basin, Australian Northwest Shelf (NWS), records a paleo-environmental change from tropical reef growth to drift sedimentation. This research project focused on the comprehensive three-dimensional (3D) documentation and investigation of this change based on the analysis of 15 3D seismic-reflection volumes covering ca. 33000 km² of the Browse Basin and 22 industry boreholes. 3D seismic-horizon interpretation tied to Sr-isotope and biostratigraphic data provided a robust 3D chronostratigraphic framework that i) newly documented the occurrence of Miocene to recent carbonate systems in vast inboard basin areas; ii) presented the 3D distribution and dynamic development of carbonate platforms through time constrained by absolute ages; and iii) supported the detailed 3D interpretation of Miocene to recent depositional processes and key stratigraphic controls. Newly documented Miocene to Pliocene carbonate build-ups and platforms are located on the middle shelf along the Adele-Heywood fault trend 30-80 km inboard of an extensive belt of well-known Miocene outer-shelf reefs. Around 18.6 Ma, the extent of all shelf platforms was ca. 8600 km², rising to > 10000 km² between 15.6 and 12 Ma. By ca. 9.7 Ma total platform extent had however decreased to ca. 5700 km², waning to < 2800 km² in the Pliocene. The observed reef demise is less abrupt than previously thought and happened in two steps, firstly in the late Miocene on the outer shelf, secondly in the Pliocene on the middle shelf. The Miocene outer-shelf platform demise coincided with strong subsidence outpacing sedimentation, an increase in NW-SE-oriented tidal current activity, the development of NNE-SSW-oriented bottom currents and the onset of drift sedimentation. The Pliocene demise of middle-shelf reefs coincided with an increase of clastic sediment input from land and stalling of the Indonesian Throughflow around 3.7 Ma. The new basin-wide 3D seismic-chronostratigraphic data presented support a re-evaluation of the key controls for Miocene and Pliocene reef growth and decay on the NWS, highlighting the complexity of interacting global, regional and local processes and peculiarities for carbonate sedimentation.
Publications
- 2018. From Reefs to Drifts: Miocene/Pliocene sedimentary change in the Browse Basin, NW Australia. In: GeoBonn 2018 Bonn, 2018-09-02 - 2018-09-06, 2018
Thronberens, S., Back, S., Reuning, L., Bourget, J.
- 2018. Mineralogy of ditch cuttings from wells Abalone-1, Brewster-1, Heywood-1, Leveque-1 and Rob Roy-1. Geoscience Australia Approval No. 00593, Technical Report
Thronberens, S., Wollenberg, U.
- 2019. Miocene to Pliocene reef demise or survival in the Browse Basin, NW Australia. In: 16th International Meeting of Carbonate Sedimentologists Bathurst Meeting Mallorca, Palma de Mallorca, 2019-07-09 - 2019-07-11, 2019
Thronberens, S., Back, S., Reuning, L., Bourget, J.
- 2020. Basin subsidence and Miocene/Pliocene sedimentary change in the Browse Basin, NW Australia. In: Abstracts & presentations: EGU General Assembly 2020, EGU2020-21627
Thronberens, S., Back, S., Reuning, L., Bourget, J.
(See online at https://doi.org/10.5194/egusphere-egu2020-21627)
