Part 5. Plate boundary evolution in the New Guinea region: Plate model for late Cainozoic volcanism at the southern margin of the Bismarck Sea, Papua New Guinea

The area of southeastern Papua New Guinea includes three active microplates – the Trobriand, Woodlark, and Solomon Sea plates – that are being deformed by regional convergence between the much larger Pacific and Australian Plates. The landward extent of the plate boundary between the Trobriand and Australian Plates corresponds to the Owen-Stanley Fault Zone (OSFZ), an onland and continuous 510 km-long left-lateral strike-slip fault that forms a linear, intermontane valley within the elongate Owen-Stanley Range (OSR) and continues as a 250 km-long low-angle normal fault along the margins of Goodenough and Woodlark basins. GPS geodesy reveals that the Trobriand microplate has undergone rapid counter-clockwise rotation since the Late Miocene (8.4 Ma) and that this rotation about a nearby pole of rotation predicts transpressional deformation along the 250 km-long northwestern segment of the OSFZ, strike-slip motion along a 100 km-long central segment, and transtension along the 270 km-long ESE-trending southeastern segment of OSFZ. In order to illustrate the along-strike variations in neotectonic uplift resulting from the changing structure of the OSFZ, we delineated 3903 river segments in the northeastern side of the OSR drainage divide and derived river longitudinal profiles along each river segment. Normalized steepness indices (ksn) and knickpoint clusters are the highest and most concentrated, respectively, for the northwestern transpressional segment of the OSR, moderately high and concentrated along the southeastern segment of the OSR, and the lowest and least concentrated along the central strike-slip segment. These geomorphological indices indicate that most of the plate boundary uplift occurs along the transpressional and transtensional segments that are connected by the central strike-slip zone. Within this overall pattern of structural variation, abrupt changes in the azimuth of the OSFZ create more localized anomalies in the geomorphological indices.

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Part 6. Present plate boundary seismic, volcanic and kinematic processes: Time variations in recent volcanism and seismicity along convergent plate boundaries of the south Bismarck Sea, Papua New Guinea

Exploration Geophysics ◽

10.1071/eg975077a ◽

1975 ◽

Vol 6 (3) ◽

pp. 77

Author(s):

R.J.S. Cooke

Keyword(s):

Papua New Guinea ◽

Plate Boundary ◽

Volcanic Eruptions ◽

New Guinea ◽

Plate Boundaries ◽

Complete Arc ◽

Time Variations ◽

New Britain ◽

Western Half ◽

Eastern Half

A striking spatial and temporal clustering of volcanic eruptions has occurred in the Bismarck Volcanic Arc, Papua New Guinea, since late 1972. In the complete arc, six volcanoes have been active during this period, Long Island, Langila, Ulawan, Karkar, Manam, and Ritter Island. Ulawan is located in the eastern (New Britain) half of the arc. The other five are located consecutively in the western half of the arc; no definite historical eruptions are known from any other volcano in the sector containing them. This western half is distinguishable from the eastern half on petrological and geophysical grounds by Johnson (this Symposium). The only western volcanoes with historical eruptions but not active in this present phase, are in the Schouten Islands at the far western end of the arc; this sector is also petrologically distinguishable.

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