Disjunct Lower Jurassic to Lowest Miocene Stratigraphic Units in the Matebian Overthrust Terrane, Timor-Leste, Northwestern Margin of Australian Continent

Abstract

Stratigraphic units, characterized by distinct rock types, ages and depositional environments, are described from one of the most geologically chaotic terranes on the present-day western Australian continental margin. The Matebian Overthrust Terrane in Timor-Leste has components interpreted to have been deposited (1) on the Early Jurassic northern margin of eastern Gondwana; (2) off the Late Cretaceous southern Sundaland margin of south-east Asia, probably in the vicinity of east Java–south Sulawesi; and (3) in an Eocene to earliest Miocene orogenic belt along the southern Sundaland margin. By the Early Miocene, the units were stitched together in a coherent terrane as evidenced by olistoliths, debris-slide conglomerates and detrital material in turbidites. During the Late Miocene the terrane rifted from the Sundaland margin, probably during the opening of the Banda Sea, and collided with Timor–Scott Plateau at the Australian continental margin, becoming incorporated in the Timor–Seram orogenic belt along this margin. The following stratigraphic units are described from the terrane: Perdido Limestone (Early Jurassic, Sinemurian–Pliensbachian, ~ 199–184 Ma; neritic deposit); Sagadati Argillite (new unit; Early Jurassic, Sinemurian–Pliensbachian, ~ 199–184 Ma; lower bathyal deposit adjacent continent margin); Tibalari Pelagite (new unit; early Late Cretaceous, mainly Cenomanian–Turonian, ~ 100–90 Ma; lower bathyal oceanic deposit); Lakamutu Mudstone (new unit; Middle Eocene, ~ 45–43 Ma; abyssal oceanic deposit near continent margin); Liloli Calcarenite (new unit; Middle Eocene; bathyal slope deposit adjacent continent margin); probable Barique Volcanics (probably Middle Eocene; submarine volcanics); Afalari Pelagite (new unit; mid Oligocene, ~ 30–28 Ma; lower bathyal oceanic deposit); Booi Limestone (Late Oligocene to earliest Miocene, ~ 27–20 Ma, neritic deposit); Atelari Mudstone (new unit; Late Oligocene to earliest Miocene, ~ 26–21 Ma, upper bathyal deposit). [Editor’s Note: Most of the content of this paper was originally archived as an unpublished supplementary file to Nano, J., Haig, D.W., Fraga, E., Soares, M., Barros, I.S., McCartain, E., Baillie, P., 2023. Debris-slides, olistoliths and turbidites: keys to understanding the tectonostratigraphic affinities of a terrane block in a young orogenic belt, Timor-Leste. Journal of the Geological Society, London, https://doi.org/10.1144/jgs2023-079 (https://doi.org/10.1144/jgs2023-079). It is here published with permission from this journal]