STRUCTURAL DEFORMATION, EXHUMATION AND UPLIFT OF THE TIMOR FOLD-THRUST BELT

Abstract

The island of Timor is an ideal location to study several important mountain-building processes. Timor's unique plate tectonic configuration and fortuitous exposure of various lithologies allows us to examine processes of uplift and exhumation during early orogenic development, constrain magnitudes of subduction of continental crust, document feedbacks between surface processes and tectonics, and evaluate processes controlling along-strike variation in mountain belts.

In this dissertation I integrate structural mapping, balanced cross sections, low-temperature thermochronology and associated thermal modeling, micropaleontology, and river network analyses into a history of the development of the Timor fold-thrust belt. Thermochronology and micropaleontology reveal extreme heterogeneity in uplift and exhumation across small spatial scales. Before synorogenic basins experienced demonstrable uplift from >1 km below sea level at 3.35-3.0 Ma, other areas a few tens of kilometers away were emergent and exhuming rapidly. Recent exhumation rates highlight similar spatial variability, with exhumation rates in local regions faster than 3 mm/yr concurrent with regions of very low exhumation rates and modern deposition. Structural mapping, combined with this thermochronology and micropaleontology, have revealed the style of deformation that has built the Timor orogen. Balanced cross-sections incorporating these constraints suggest that at least 199-229 km of the buoyant Australian continental margin has been subducted below the forearc of the Banda volcanic arc. The topology of the river network on Timor allows us to relate long-term structural and exhumation data to modern surface uplift patterns, revealing that tectonic processes have driven changes in drainage basin organization and that surface processes have influenced the position and activity of subsurface faults. Lastly, a comprehensive comparison of correlative datasets collected several hundred kilometers apart reveal that, despite extreme short-wavelength heterogeneity, the first-order characteristics of the Timor orogen are remarkably consistent along strike, influencing our understanding of the mechanisms that control orogen morphology.