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Circum-Pacific and Caribbean Orogens |
Geophysics Department, Imperial College, Prince Consort Road, London SW7
New Guinea, which forms the northern and most recently deformed margin of the Australasian continental block, can be divided into a central trapezoidal nucleus and western and eastern peninsular areas which are respectively transitional to the complex Indonesian and Melanesian archipelagos. The eastern peninsular area is described in this article, the central-western area in the following article by Hermes.
Although usually regarded as a single orogen, differences exist between other paired metamorphic belts of the Western Pacific and central New Guinea, which in width of intermontane depressions, elevation of central and coastal mountains and distribution of ultramafic rocks and metamorphic assemblages appears to have closer affinities with central California. In terms of plate tectonic theory the central and western parts of the island are anomalous since although a high degree of crustal shortening can be deduced from study of the movements of the major plates (Le Pichon 1968), vulcanism is absent.
Segment: the Moresby segment described here is 500 km long with a median width of about 800 km, and includes parts of the Papuan Peninsula and New Britain, as well as entirely marine zones. Eastern limits to the segment in the land zones have been selected to exclude areas of increased complexity; in New Britain the Gazelle Peninsula has participated in tectonism associated with the Solomon Islands trend, while the east of the Papuan Peninsula has been subjected to N-S extension probably associated with the formation of new oceanic crust in the Woodlark Basin. These movements appear to Woodlark
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