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Two major marine surveys off northern Papua New Guinea (PNG) earlier this year now suggest, when survivors' reports are taken into account, that last summer's disastrous tsunami there was caused by a sediment slump 25 km offshore. The slump was probably the result of seabed shaking from an earthquake. Not only was a sediment slump, or submarine landslide, responsible for the tsunami, according to the data, but the magnitude and wave‐height distribution of the tsunami along the coast were the result of focusing by local seabed morphology. The conclusions are based on new off‐shore bathymetry, remote operated vehicle (ROV) dive investigations, the time delay between the source earthquake and when the tsunami struck, computer simulation models, and earthquake aftershock distribution. The most critical evidence is in survivors' accounts of the timing of the tsunami relative to the initially felt earthquake and aftershock [see Davies, 1998a].

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Extensional transform zones (ETZs) are plate boundary segments of order 100 km long that strike at angles between 15° and 45° to the extension direction. They are characterized by neovolcanic/tectonic zones comprising overlapping en echelon volcanic systems and/or faults that trend 30°–75° to the extension direction, sometimes accompanied by a Riedel shear. Below these surficial en echelon structures the deformation is aseismic and ductile, and the plate boundary is probably continuous. ETZs occur in fast and slow spreading and rifting environments and may persist in a stable configuration for several million years. ETZs link oblique spreading segments to transform faults in the Manus and probably the Lau backarc basins. The Reykjanes Peninsula and Tjornes Fracture Zone in Iceland and the Mak'Arrasou in Afar are ETZs that link subaerial to submarine spreading or rifting segments. The Brawley and Cerro‐Prieto seismic zones appear to be ETZs in the Imperial and Mexicali valleys that link the San Andreas, Imperial, and Cerro‐Prieto transform faults. Experimental and analytical models of transtensional deformation in brittle‐ductile systems match many of the observed characteristics of ETZs and oblique spreading centers, including variably sigmoidal to straight en echelon faults that are not parallel to the extension direction. The contrasting fault patterns reflect the rheology of the models and lithosphere: they are more sigmoidal when the strain in the lower ductile layer is more focused, causing the axial faults to curve as they propagate toward parallelism with the less ductile rift margins. The angle (Ø) between the faults and the extension direction decreases with the angle (α) between the strike of the zone and the extension direction. ETZs occur in the range 15° ≤ α ≤ 45°, whereas oblique spreading centers have 45° < α < 90° and transform relay zones have 0° < α < 15°. Oblique fast spreading segments exhibit ridge‐parallel faults and volcanic systems (Ø = α), presumably reflecting locally rotated stress fields, whereas at oblique slow spreading centers, Ø is closer to orthogonal (α < Ø < 90°).

The presence of an archaeological site on Kosipe Sacre Coeur Mission was first noted in 1960, when axes and waisted blades were found by Father L. Willem during excavations for church foundations. Word of the site was sent to Mr W. Tomasetti, then Assistant District Officer, Department of Native Affairs, Tapini, and he informed White of it. Excavations were made there in June 1964 (White, 1965, 41–3; 1967). In 1966 the site was visited by Crook who collected further carbon and soil samples and in August 1967 White and Ruxton carried out further archaeological and geomorphological investigations. This report covers the entire history of excavations at the site.Kosipe lies about 135 kilometres north of Port Moresby and 20 kilometres north northwest of the Woitape Sub-District office, Central District, Papua, at 147° 16′ E, 8° 21′ S (fig. 1). The area around Kosipe has not yet been the object of a reconnaissance geological survey. Observations by Crook along the Woitape-Kosipe road, south of Kosipe and on the Kosipe-Tanipai track northwest of Kosipe along the Ivane River indicate that the oldest rocks are slates and other low grade metamorphics of unknown age with steeply dipping foliation. These are overlain, probably sub-horizontally, by several hundred feet of basic volcanics, probably largely basalt. The volcanics are probably of late Tertiary or early Quaternary age; they are strongly dissected and are not obviously related to any centres of extrusion.

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