CONCLUSIONS

1. Microresistivity (FMS) images collected along a transect of three ODP drill sites in the western Woodlark Basin confirm and complement shipboard descriptions of the thin-bedded turbidite succession that accumulated from the late early Pliocene to early late Pliocene (3.9-1.8 Ma). Based mainly on sand-bed and silt-bed thicknesses, as well as percentages of interbedded mud, the FMS images have been divided into three microresistivity facies. Only Facies C contains clusters of thick sand beds; it is confined to the southern Site 1118.
2. Thickness distributions of turbidite beds are broadly exponential (many thin beds and few thick beds) but also approximate power-law distributions with either one or two linear segments (i.e., one or two values for different ranges of bed thickness). These patterns can be interpreted to result from partial confinement of less voluminous flows in the rift basin, perhaps because of subtle seabed topography and/or channels. Broad conformity with a power-law model is consistent with triggering of turbidity currents by earthquakes in the tectonically active rift.
3. Frequencies of turbidites reach ~930 beds/m.y. at Sites 1109 and 1118 in the period 3.6-3.45 Ma (beginning somewhat early at Site 1109). Subsequently, frequencies drop at Sites 1109 and 1115 but remain unchanged at Site 1118 until ~2.6 Ma. This apparent higher rate of arrival of turbidity currents closest to the basin axis may indicate (a) greater trapping of bottom-hugging gravity flows in the morphologically deeper axial trough or (b) frequent deposition of only mud from distal turbidity currents once they had traveled beyond the axial zone of the rift.