Tectonics and Geodynamics of the New Guinea Region Since the Triassic
The New Guinea margin has experienced a complex geodynamic evolution as it is situated at the junction between the Tethyan and (proto-) Pacific tectonic domains. The chronology and nature of basin opening and closure, as well as the timing and style of collisions is critical for understanding the genesis of ore and hydrocarbon resources in the region. Detailed regional plate reconstructions in this area are difficult because no seafloor spreading histories are preserved, while remnants of multiple generations of back-arc and intra-oceanic subduction systems are dismembered along many suture zones in remote parts of New Guinea. We present a new plate tectonic reconstruction since the Triassic for this region, implemented in the open-source and cross-platform GPlates (www.gplates.org) software. This digital plate motion model is accompanied by new synthetic seafloor spreading histories consistent with block motions, as well as an evolving network of plate boundary topologies in 1 Myr intervals. The regional model is embedded in a new global model with an updated and optimised absolute reference frame with improvements to Pacific plate motions, and particularly significant updates to the eastern Tethyan reconstructions. These digital models allow us to extract the velocity field and the nature of plate boundary evolution, that we couple to High Performance Computing forward numerical models of mantle flow in CitcomS (https://geodynamics.org/cig/software/citcoms/). The mantle convection is driven by the plate motions on the surface, and heating at the core-mantle boundary, capturing mantle evolution and a prediction of the mantle structure at present day. These models also allow us to extract the dynamic topography resulting from mantle flow, which has a time-evolving amplitude of several hundred meters. Our plate reconstructions incorporate long-lived Andean style subduction along the New Guinea margin during the (Permian? -) Triassic, transitioning to back-arc opening from slab roll-back in the Mid Jurassic. This event detached the Sepik terrane, with seafloor spreading initiated by ~170-160 Ma in the Sepik back-arc basin. The spatial origin of the Sepik terrane along the margin remains unknown, hence we implement a simplified model. In addition, the roll-back and arc evolution likely represent the origin of the Philippine Arc. North-dipping subduction along the Sepik terrane initiated in the mid to Late Cretaceous. Previous testing of end-member models of the Sepik terrane accretion indicates a collision in the early Eocene, but this process was likely diachronous along the margin.
AAPG Datapages/Search and Discovery Article #90371 © 2020 AAPG Asia Pacific Region, The 1st AAPG/EAGE PNG Geosciences Conference, PNG’s Oil and Gas Industry: Maturing Through Exploration and Production, Port Moresby, Papua New Guinea, February 25-27, 2020