Reconstructing the Southwest Pacific
The relatively recent tectonic processes in the southwest Pacific are commonly used as an analogue for understanding the evolution of fossil orogenic systems, such as the northern Appalachians and British Caledonides, Central Asian Orogenic Belt and Arabian-Nubian shield, eastern Australian Tasmanides, and Western Alps. This comparison arises from the recognition that complex tectonic interactions may occur over short geological timescales (few millions of years), involving, for example, plate sub-rotations, multiple collisional events of discrete terranes, simultaneous development of extensional and contractional tectonics, and rapid changes in plate kinematics. Naturally, reconstructing such temporal and spatial changes in ancient orogenic belts is a challenging task due to the partial preservation of diagnostic tectono-magmatic features and the limited temporal resolution.
This research examines the tectonic evolution of the Papua New Guinea and the Southwest Pacific region. Papua New Guinea, in particular, is significant because it represents a complex plate boundary zone between the Pacific and Australian plates, situated between the obliquely converging Ontong Java Plateau and the Australian continent.
The reconstructions integrate and draw from existing datasets of seafloor magnetic isochrons, paleomagnetic data, seismic tomography models, and additional geological and geophysical observations from numerous multidisciplinary studies. Tectonic reconstructions such as this demonstrate how near and far-field changes in subduction dynamics can have a profound influence on microplate geometries and the tectono-magmatic evolution of long- and short-lived plate boundaries over time. In particular, the video below highlights the extremely different geometries between the initiation of microplate interaction at ca. 6 Ma and the markedly different final tectonic relationships that are recognized today.
Video from Holm et al., 2016, Earth Science Reviews