Published Online First on December 12, 2013 © 2014 The Geological Society of London The Banda Arc of Timor-Leste and eastern Indonesia (Fig. 1) repre-

sents one of the youngest arc–continent collision zones, yet the age of onset of collision remains disputed, in part because quantitative geo-chronological data are limited. A number of observations point to the onset of collision coincident with the c. 3 Ma cessation of volcanism north of Timor-Leste (Hall 1996; Elburg et al. 2005). An earlier onset of collision has been suggested by some workers to account for the depositional age (c. 5.7–3.3 Ma) of post-orogenic strata (e.g. Haig 2012) and the late Miocene (c. 8 Ma) cooling ages from the Aileu Complex (Fig. 2) of northern Timor-Leste (Berry & McDougall 1986; Charlton et al. 1991; Harris et al. 2000; Keep & Haig 2010). Crucial to this debate is the question of the provenance of the Aileu Complex protoliths and, specifically, whether the sediment was derived from the continental margin of northern Australia or elsewhere. The Aileu Complex comprises an extensive succession of mostly terrigenous sedimentary rocks exposed along the north coast of Timor-Leste (Fig. 2). Owing to the absence of diagnostic faunal assemblages, the biostratigraphic affinity of the Aileu Complex is unclear. Both Australian (Harris et al. 2000; Charlton 2002) and Asian (Carter et al. 1976; Barber et al. 1977) provenances have been suggested. To better understand the source of the Aileu Complex protoliths, and the evolution of the Banda Arc, this paper presents two new geo-chronological datasets. The first dataset comprises detrital zircon U–Pb ages from Aileu Complex metasediments. These data provide constraints on the provenance and depositional age of the complex. Together with zircon morphological data, the new results also allow evaluation of the degree of sediment recycling and transport distances. The second dataset comprises new 40Ar/39Ar cooling ages from meta-morphic hornblende separated from mafic rocks of the Aileu Complex. These data provide cooling ages from regional metamorphism observed in the Aileu Complex and, together with existing 40Ar/39Ar data (Berry & McDougall 1986), constrain the timing of orogenesis