Onshore hydrocarbon exploration in Timor Leste has resumed after a 50-year gap from the last well by Timor Oil in 1972 to Timor Resources' recent drilling in the Suai Sub-Basin. Encouragement from the new wells is providing incentive to conduct further exploration, including targeting a deeper 'sub-decollement' play, first proposed in the 1970s. The play concept depends on the model applied to explain crustal shortening during the continental collision that created Timor. There is debate over the mechanism and over the true nature of the metamorphic rocks outcropping north of the Suai Sub-Basin. Does the Lolotoi Metamorphic Complex (LMC) represent an allochthonous unit below which is an un-metamorphosed prospective section, or is it composed of uplifted Australian continental margin material? New data acquired by Timor Resources is used to update the regional model and present support for the former concept, which at the time of writing, is being tested by drilling. The paper presents recently acquired seismic cross-sections, 2D gravity modelling results and data from the recent wells. The new data is used to support the concept that the LMC is the remanent of an allochthonous unit thrust from the north whose base is a major decollement. It is proposed that the allochthon sits above a complex of over-thrusted Australian Continental margin blocks including a deeper decollement that pre-dates the active decollement and associated accretionary wedge, visible today at the base of the Timor Trough. Building on work by previous authors, we show the rationale for a deep sub-decollement test in the Suai Sub-Basin of southern Timor Leste.

Open-Access Online Publication: May 29, 2023