From the early to late Pliocene, a northward-thinning turbidite succession accumulated on rifted crust of the western Woodlark Basin offshore Papua New Guinea. The source of detritus was to the north and west, resulting in oblique to longitudinal supply into the propagating rift. Formation MicroScanner (FMS) microresistivity images collected in three boreholes along a north-south transect (Holes 1118A, 1109D, and 1115C) were used to construct bed-by-bed sedimentary sections through the turbidite succession, which consists of variable proportions of mud and graded sand and silt turbidites. In all holes, the number of sand and silt turbidite beds decreases exponentially with increasing bed thickness, and there is a significant "tail" of relatively thick beds. Plots in log-log space of the number of beds thicker than T, vs. T, consist of one or two straight-line segments, except for deviations at low values of T near the FMS tool resolution limit. Each straight-line segment suggests a power-law relationship of the form Y = nT(-beta), with beta in the range of 1.5-5.5. It is proposed that the underlying control on this pattern is the widely observed power-law distribution of earthquakes.At times, the rate of addition of new sand and silt turbidites to Sites 1118 and 1109 was ~1000-1500 beds/106 yr, whereas Site 1115 never received more than ~450 beds/106 yr. Site 1118, nearest the axis of the rift basin, had the longest history of high-frequency turbidite deposition (~1500 beds/106 yr, equivalent to a recurrence interval of 670 yr). Turbidite recurrence intervals are approximately one order of magnitude longer than the recurrence intervals of >=7-magnitude earthquakes in this region, suggesting that factors other than the availability of seismic triggers are required to generate turbidity currents. The lower frequency of deposition of sand and silt turbidites north of the axis of the rift, when compared to the turbidite frequency at axial Site 1118, is ascribed to a combination of lateral and distal fining, so that many flows responsible for graded beds of sand and silt at Site 1118 only deposited mud at Sites 1109 and 1115. This mud was subsequently disturbed by burrowing in areas of slow accumulation.

Supplement to: Awadallah, Sherif A M; Hiscott, Richard N; Bidgood, Michael; Crowther, Timothy E (2001): Turbidite facies and bed-thickness characteristics inferred from microresistivity (FMS) images of lower to upper Pliocene rift-basin deposits, Woodlark Basin, offshore Papua New Guinea. In: Huchon, P; Taylor, B; Klaus, A (eds.) Proceedings of the Ocean Drilling Program, Scientific Results, College Station, TX (Ocean Drilling Program), 180, 1-30