The relationship between the nature of margins and the subduction of oceanic plateaus: Insights from variations in the forearc basement and sediments along the New Guinea Trench in the West Pacific

Abstract

The generation of erosive and accretionary margins has yet to be determined. Here, we explore the variations in the forearc structures of the New Guinea Trench (NGT) based on the latest high-quality multichannel seismic profiles perpendicular or subparallel to the New Guinea Trench axis. Our results reveal that for the domain of the oceanic crust subducted beneath the NGT (O-NGT), the thickness of the sedimentary strata decreases from the forearc sedimentary basin to the forearc slope. The basement is generally characterized by homogeneous intra-basement reflections, and few discontinuous, prominent layered reflections in the basement are identified. On the forearc slope, arcward-dipping fault-plane reflections have been identified within the basement, and an abrupt topographic decrease occurs in the eastern part of the forearc basement uplift. Widespread sedimentary sequences are identified as the present, transparent and horizontal seismic reflections with high continuities and low amplitudes. The sedimentary sequences show a large lateral variation of thickness and present folded features near the seaward-dipping faults due to the development of slump bodies. However, the sedimentary sequences in the forearc slope of the domain of the oceanic plateau subducted beneath the NGT (P-NGT) are obviously thicker than those of the O-NGT and present folded features. The stratigraphic thickness from the forearc sedimentary basin to the forearc slope clearly increases. Our initial results initially indicate that the NGT might constitute an internal reverse polarity subduction zone that changes from an erosive margin in the O-NGT to an accretionary margin in the P-NGT.