Quaternary Uplift of Coral Terraces from Active Folding and Thrusting Along the Northern Coast of Timor-Leste

Emergent coral terraces along the northern coast of Timor-Leste, reveal differential vertical strain along the strike of the active Banda arc-continent collision complex. The number of major coral terraces in surveyed profiles increases from 2 to 25 along a coastal distance of 150 km from central to eastern Timor-Leste. Comparison of 8 separate terrace profiles with sea level curves predicts vertical displacement rates that increase eastward from <0.3 to 1.0-1.5 mm/year. This pattern is corroborated by U-series age analyses that document non-linear increases in vertical strain eastward with the uplift rates ranging from <.04 to 2.0 mm/year. U-series ages also indicates the occurrence of both erosional (regressional) and depositional terraces. Two profiles, dominated by erosional terraces, have associated local lower depositional terraces. The erosional terraces are more abundant, but yield apparent lower uplift rates in comparison with the depositional terraces. This occurrence questions the validity of uplift rates obtained by age analysis for the errosional terraces and/or aids in the conclusion that differential vertical strain not only exists with distance between profiles but with time for each profile. We associate active uplift with northward movement along retro- wedge thrust faults that are well documented in seismic reflection profiles adjacent to the north coast of Timor- Leste.