3-D seismic chronostratigraphy of reefs and drifts in the Browse Basin, NW Australia

Abstract

Abstract In its subsurface, the Browse Basin on the Australian Northwest Shelf accommodates one of the largest Miocene–Pliocene carbonate platform provinces on Earth. This study presents a comprehensive three-dimensional (3-D) documentation and investigation of the Neogene Browse Basin carbonates based on the analysis of 15 3-D seismic reflection volumes covering ca. 33,000 km2 and 22 industry boreholes. Eight basin-wide seismic marker horizons tied to Sr isotope and biostratigraphic data provide a robust 3-D chronostratigraphic framework that (1) newly documents the occurrence of Miocene to recent carbonate systems in vast inboard basin areas; (2) presents the 3-D distribution and dynamic development of carbonate platforms through time constrained by absolute ages; and (3) supports the detailed 3-D interpretation of Miocene to recent depositional processes and key stratigraphic controls. Around 18.6 Ma, the extent of all Browse Basin carbonate platforms was ca. 8600 km2, rising to >10,000 km2 between 15.6 Ma and 12 Ma. By ca. 9.7 Ma, the total platform extent had decreased to ca. 5700 km2, waning to <2800 km2 in the Pliocene. The observed reef demise is less abrupt than previously thought and comprises two steps, with the first in the late Miocene on the outer shelf and the second in the Pliocene on the middle and inner shelf. The Miocene outer-shelf platform demise coincided with (1) strong subsidence that outpaced sedimentation, (2) an increase in NW–SE-oriented tidal current activity, (3) the development of NNE–SSW-oriented bottom currents, and (4) the onset of drift sedimentation. The Pliocene demise of middle-shelf reefs coincided with (1) an increase of clastic sediment input from land and (2) stalling of the Indonesian Throughflow around 3.7 Ma. The basin-wide, 3-D seismic chronostratigraphic analysis presented supports a re-evaluation of the key controls for Miocene and Pliocene reef growth and decay on the NW Shelf and highlights the complexity of interacting global, regional, and local processes and peculiarities in carbonate platform development.