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SUMMARY Distribution and growth history of isolated carbonate build-ups (ICBs) is controlled by complex interplay between various tectonic, eustatic, and oceanographic parameters. Quaternary ICBs in the Timor Sea (NW Australia) are located in tropical waters, and at present they form clusters of ~150 build-ups, developing 2 to 85 km from the edge of a wide continental shelf. The tectonic evolution of the Timor Sea lead to regional changes in the oceanography and flexural deformation of the NW Bonaparte Basin, which in turn had a major impact on the evolution of ICBs. Flexure-induced fault activity produced structural topography for the growth of ICBs over ‘highs’, while oceanic current through Timor Trough provided warm and nutrient-rich water. Our results demonstrate that, despite potentially good conditions for carbonate production, ICBs did not form until the Mid Pleistocene (ca. 0.582-0.8 Ma BP). This age corresponds to the onset of repeated, high-amplitude (+120 m) sea level fluctuations with rapid deglacial rises and slow falls. Thus, we infer that the NW Australia ICBs formed due to: (1) structural shaping of the margin; (2) oceanographic changes, and; most importantly, (3) onset of repeated short-term transgressions reactivating the carbonate production along isolated highs. The distribution and growth of ICBs could be useful to understand the evolution of ancient ICBs that formed along very wide shelves and epeiric seas.

The North-western Bonaparte Basin offers a very good opportunity to understand the nature of oblique extension system, where Neogene flexure-induced extension was superimposed obliquely to the Mesozoic rift-related structures. The Mesozoic trends strongly control the distribution and style of the younger Neogene structures, both at regional and local scale. The younger Neogene activity produced a new set of NE trending, right-stepping en echelon faults and reactivated the older faults. In addition, episodes of stratigraphic growth provide critical evidence regarding the timing of fault activity. Results demonstrate that, in the study area, main fault activity occurred in several pulses during the latest Miocene to Late Pleistocene. These episodes of fault activity correspond to recently constrained regional tectonic events i.e., the initial collision of the Australian Plate with the Banda Arc, the episodes of uplift of the Timor Island and the timing of lithospheric flexure.