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- West Papua, Papua, and Papua New Guinea make up the island of New Guinea
- The northern region of Papua lies on the Maoke plate. The Solomon Sea lies on the Solomon Sea plate.
- The northern and eastern regions of Papua New Guinea, and the region south of the Solomon Sea all lie on the Woodlark plate.
The Solomon Sea (SS) plate is oceanic crustal plate remnant. The northern part of the SS plate subducts under the South Bismarck, which led to the formation of the New Britain trench. (Bird, 2003) Estimates of convergence at the New Britain Trench vary between 92 and 125 mm/yr. (Tregoning and Lambeck, 1998)
The southwest part of SS plate subducts under the Woodlark (WL) plate, which led to the formation of the Trobriand Trough. Subduction at the Trobriand Trough is estimated to be between rates of 6-20mm/yr. (Tregoning and Lambeck, 1998) The Trobriand Trough connects to northeast trending transform fault on northwest margin of Woodlark rise. Because the SS plate is experiencing subduction from two of its boundaries, it is slowly disappearing.
The Trobriand Trough subduction zone has only seven volcanoes and few intermediate-depth earthquakes, and it is much more slow-moving than New Britain Trench, which means that the Solomon Sea plate is moving in a northerly direction.
The Solomon Sea Plate mainly developed during late Oligocene. 60-40 Mya. Physical characteristics of Solomon Sea Basin lithosphere, such as flexural rigidity, heat flow, water depth and sediment thickness, were reviewed, in order for this age to be determined. (Honza et. al, 1987)
The Maoke (MO) plate is bounded by three plates. It has convergent boundary with Woodlark Plate on eastern side, a transform boundary with Australian plate on the south, and another transform boundary with Bird’s Head plate on the west. (Bird, 2003)
The Woodlark (WL) plate has a convergent boundary with the Caroline plate along its northern boundary, where subduction occurs. Subduction also occurs on its southern border, where the Australian plate is converging into the Woodlark plate. (Bird, 2003)
However, the trench between the Australian and Woodlark plates is slow moving compared to the trench between the Caroline plate and Woodlark plate, and so, seafloor spreading is occurring in Woodlark basin, between the Woodlark plate and the Australian Plate. (Wallace, 2004)
The southwest part of SS plate subducts under the Woodlark (WL) plate, which led to the formation of the Trobriand Trough. Subduction at the Trobriand Trough is estimated to be between rates of 6-20mm/yr. (Tregoning and Lambeck, 1998) The Trobriand Trough connects to northeast trending transform fault on northwest margin of Woodlark rise. Because the SS plate is experiencing subduction from two of its boundaries, it is slowly disappearing.
The Trobriand Trough subduction zone has only seven volcanoes and few intermediate-depth earthquakes, and it is much more slow-moving than New Britain Trench, which means that the Solomon Sea plate is moving in a northerly direction.
The Solomon Sea Plate mainly developed during late Oligocene. 60-40 Mya. Physical characteristics of Solomon Sea Basin lithosphere, such as flexural rigidity, heat flow, water depth and sediment thickness, were reviewed, in order for this age to be determined. (Honza et. al, 1987)
The Maoke (MO) plate is bounded by three plates. It has convergent boundary with Woodlark Plate on eastern side, a transform boundary with Australian plate on the south, and another transform boundary with Bird’s Head plate on the west. (Bird, 2003)
The Woodlark (WL) plate has a convergent boundary with the Caroline plate along its northern boundary, where subduction occurs. Subduction also occurs on its southern border, where the Australian plate is converging into the Woodlark plate. (Bird, 2003)
However, the trench between the Australian and Woodlark plates is slow moving compared to the trench between the Caroline plate and Woodlark plate, and so, seafloor spreading is occurring in Woodlark basin, between the Woodlark plate and the Australian Plate. (Wallace, 2004)
From Figure 4, it can be seen that each of Maoke plates and Woodlark plates have a few different types of geology on them.
The northern part of both of these plates is comprised of Neogene to Quaternary sediments, while the southern parts are occupied by limestone. Both plates also contain Paleogene to mid-Miocene arc type volcanics, ophiolite, dioritic intrusions, and Mesozoic and Cenozoic metamorphic rocks, with the Woodlark plate having more of these than the Maoke plate. In addition to the geology mentioned above, the Woodlark plate also comprises of small amounts of Quaternary volcanics, floor basalts from the Cretaceous and mid-Eocene, and Miocene volcanics and sediments. (Davies, 2012) The Solomon Sea plate is an oceanic plate, and it is comprised of basalt, overlain by oceanic sediments. |
References:
Bird, Peter. “An Updated Digital Model of Plate Boundaries.” Geochemistry, Geophysics, Geosystems 4.3 (2003). Web. 9 Jan. 2014.
Honza, E. et al. “Plate Boundaries and Evolution of the Solomon Sea Region.” Geo-Marine Letters 7.3 (1987): 161–168. Web. 15 Jan. 2014.
Davies, HL. “The Geology of New Guinea—The Cordilleran Margin of the Australian Continent.” … Newsmagazine of the International Union of Geological … 35.1 (2012): 87–102. Web. 15 Jan. 2014.
Wallace, Laura M. “GPS and Seismological Constraints on Active Tectonics and Arc-Continent Collision in Papua New Guinea: Implications for Mechanics of Microplate Rotations in a Plate Boundary Zone.” Journal of Geophysical Research 109.B5 (2004): B05404. Web. 15 Jan. 2014.
Tregoning, P, and K Lambeck. “Estimation of Current Plate Motions in Papua New Guinea from Global Positioning System Observations.” … : Solid Earth (1978– … (1998): n. pag. Web. 15 Jan. 2014.
Bird, Peter. “An Updated Digital Model of Plate Boundaries.” Geochemistry, Geophysics, Geosystems 4.3 (2003). Web. 9 Jan. 2014.
Honza, E. et al. “Plate Boundaries and Evolution of the Solomon Sea Region.” Geo-Marine Letters 7.3 (1987): 161–168. Web. 15 Jan. 2014.
Davies, HL. “The Geology of New Guinea—The Cordilleran Margin of the Australian Continent.” … Newsmagazine of the International Union of Geological … 35.1 (2012): 87–102. Web. 15 Jan. 2014.
Wallace, Laura M. “GPS and Seismological Constraints on Active Tectonics and Arc-Continent Collision in Papua New Guinea: Implications for Mechanics of Microplate Rotations in a Plate Boundary Zone.” Journal of Geophysical Research 109.B5 (2004): B05404. Web. 15 Jan. 2014.
Tregoning, P, and K Lambeck. “Estimation of Current Plate Motions in Papua New Guinea from Global Positioning System Observations.” … : Solid Earth (1978– … (1998): n. pag. Web. 15 Jan. 2014.