The National Science Foundation's Continental Dynamics Program has awarded a five-year, $3.595 million grant to Syracuse University, Columbia University, the University of California-Santa Barbara and the University of Texas at Austin for the investigation into very young, ultrahigh-pressure metamorphic (UHP) rocks exposed on islands near the eastern tip of Papua New Guinea. SU is taking the lead on this major research initiative with the objective of discovering how these UHP rocks are being naturally exhumed to the Earth's surface from depths of about 100 kilometers. This is a fundamental geologic process that remains poorly understood, but in eastern Papua New Guinea this process is active today. This research will allow for a greater understanding of the natural hazards that exist at plate boundaries, such as faults, earthquakes and volcanoes, and more insight into why and how the Earth changes.
SU College of Arts and Sciences faculty members Suzanne Baldwin, professor of earth sciences; Paul Fitzgerald, associate professor of earth sciences; and Laura Webb, assistant research professor of earth sciences, are the principal investigators and leaders of the collaborative research team that will begin work in Papua New Guinea this January.
"The Woodlark Rift of Papua New Guinea is one of the few sites in the world where the continental crust is being ripped apart, and new oceanic crust is forming at the same time," Baldwin says. "A significant portion of the world's population lives on active plate boundaries. We need to understand how the crust deforms over time to better understand potential geologic hazards at the local level."
The subduction of the Earth's crust to mantle depths produces high-pressure (HP) rocks
and UHP rocks at convergent plate boundaries. How these rocks return to the Earth's surface -- often at plate tectonic rates -- remains an outstanding question of first-order importance to continental dynamics and plate tectonics. This five-year, multidisciplinary, collaborative study involving a team of earth scientists from the United States, New Zealand, Papua New Guinea, Canada, Germany and Australia aims to resolve how the world's youngest high-pressure and UHP rocks have been brought to the surface.
Typical convergent margins, where dense oceanic crust is subducted and recycled back into the Earth's mantle, are common, and are best known for producing large earthquakes, such as the 2004 magnitude nine Sumatran earthquake, and large volcanoes, such as Mount St. Helen's in the Cascade Range of the western United States. Convergent plate margins where buoyant continental crust is subducted to mantle depths to produce HP rocks (at 70 kilometer depth) and UHP rocks (at 100 kilometer depth), before these rocks are exhumed back to the surface, are rare, and most evidence for these preserved in the rock record are several hundred million years old. However, in eastern Papua New Guinea -- along an active plate boundary -- exhumation of the world's youngest HP and UHP rocks is occurring today. There, exhumation occurs between the Australian and the Woodlark plates, where a seafloor spreading system is propagating westward and progressively changing a convergent plate boundary to a divergent plate boundary. In effect, a former convergent margin is unzipping, and in the process HP and UHP rocks are being exhumed to the surface.
Within this framework, this National Science Foundation-funded project will employ a range of methodologies that can contribute to piecing together the UHP exhumation history and the tectonic evolution. Efforts spearheaded by SU will integrate field studies with geology, thermochronology, petrology and geochemistry. These efforts will be complemented by passive seismic data acquisition to image the crust and mantle beneath the area where partially exhumed HP/UHP rocks may occur at depth. In addition, GPS work and geodynamic modeling are included.
Fitzgerald and Baldwin are SU's husband-and-wife team of geologists, and they, along with Webb, have collected rock samples in some of the most remote regions of the world, including Antarctica, Mongolia, Alaska and the rugged, tropical islands off the coast of Papua New Guinea.
