The erosional and weathering response to arc–continent collision in New Guinea

Abstract

Arc–continent collision is a fundamental stage in the plate-tectonic cycle that allows the continental crust to grow and can influence global climate through chemical weathering. Collision between Australia and the oceanic North Coast Range–New Britain Arc began in the Middle Miocene, resulting in uplift of the modern New Guinea Highlands. The temporal evolution of this collision and its erosional and weathering impacts is reconstructed here using sedimentary archives from the Gulf of Papua. Sr and Nd isotopes show dominant erosion from igneous arc-ophiolite crust, accounting for c. 40–70% of the total flux in the Early Miocene, and rising to c. 80–90% at 8 Ma, before falling again to 72–83% by the present day. Greater erosion from Australia-derived units accelerated in the Pliocene, like the classic Taiwan collision but with greater erosion from arc rather than continental units. Chemical alteration of the sediment increased through time, especially since c. 5 Ma, consistent with increasing kaolinite indicative of more tropical weathering. Erosion was focused in the high topography where mafic arc units are preferentially exposed. Comparison of sediment with bedrock compositions implies that the source terrains have been more efficient at removing CO2 from the atmosphere compared with Himalayan drainages.