Debris-slides, olistoliths and turbidites: keys to understanding the tectonostratigraphic affinities of a terrane block in a young orogenic belt, Timor-Leste

Abstract

Timor lies at the centre of a rapidly evolving orogenic belt. The Matebian Range, one of its largest mountains, was previously mapped as Lower Miocene neritic Cablac Limestone and regarded as allochthonous (namely, Banda Terrane). New analyses have demonstrated a disjunct stratigraphy, extending from the Lower Jurassic to lowest Miocene and encompassing neritic to abyssal strata. Positioning each stratigraphic unit (six new) on a time v. bathymetry plot and identifying clast types in conglomerates and turbidites allows reconstruction of changes in provenance to depocentres through time. Terrane progression from the northern margin of Gondwana to the southern Sundaland margin (Asia) and then back to the NW margin of the Australian continent is indicated, involving progressive amalgamation and rifting and substantial episodes of uplift, particularly during the Middle Eocene and the Late Oligocene. The youngest unit (Late Oligocene–earliest Miocene) was deposited adjacent to a rapidly rising hinterland (southern Sundaland) very different from that on the coeval Australian margin. The study provides a model for the tectonostratigraphic reconstruction of limestone-dominated mountains in young orogenic belts and demonstrates the importance of using sedimentary clasts in mass-flow deposits to interpret ages and depositional environments of reworked material and to stitch together tectonostratigraphic pathways through time. Supplementary material: A description of stratigraphic units, including supplementary figures, a table and Appendices A and B, is available at https://doi.org/10.6084/m9.figshare.c.6852387