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Figure 4. Sediment accumulation rate (SAR, cma‘) and mass accumulation rate (MAR, g cm” a’) of samples versus water depth in the northern Pandora Trough. The SAR and MAR decrease with increasing distance from the shelf and increasing water depth.

Figure 4 Sediment accumulation rate (SAR, cma‘) and mass accumulation rate (MAR, g cm” a’) of samples versus water depth in the northern Pandora Trough. The SAR and MAR decrease with increasing distance from the shelf and increasing water depth.

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Figure 1. Map of the Gulf of Papua (GOP) region showing the continental slope, major basins, and reefs. The hashed line on the inner shelf is the 60 m isobath showing the extent of prograding clinoform. Black dots show locations of multicores examined in this study, whereas gray squares and white triangles show locations of cores examined by Walsh and Nittrouer [2003] and Brunskill et al. [2003], respectively. Bathymetric contour interval is 200 m; the 100 m contour is also shown.
Figure 1. Map of the Gulf of Papua (GOP) region showing the continental slope, major basins, and reefs. The hashed line on the inner shelf is the 60 m isobath showing the extent of prograding clinoform. Black dots show locations of multicores examined in this study, whereas gray squares and white triangles show locations of cores examined by Walsh and Nittrouer [2003] and Brunskill et al. [2003], respectively. Bathymetric contour interval is 200 m; the 100 m contour is also shown.
Figure 2a. Cores from the northern Pandora Trough. Excess apy activity (dpm gt: decay per minute per gram) is plotted on the x axis, and depth is plotted on the y axis. Solid lines represent best fit through the data points. Core locations are shown in Figure 1, and water depths are given in Table 1.
Figure 2a. Cores from the northern Pandora Trough. Excess apy activity (dpm gt: decay per minute per gram) is plotted on the x axis, and depth is plotted on the y axis. Solid lines represent best fit through the data points. Core locations are shown in Figure 1, and water depths are given in Table 1.
Figure 2b. Same as Figure 2a except for cores from the Ashmore Trough and southwestern Pandora basin
Figure 2b. Same as Figure 2a except for cores from the Ashmore Trough and southwestern Pandora basin
Figure 2c. Same as Figure 2a except for cores from the Moresby Trough channel.
Figure 2c. Same as Figure 2a except for cores from the Moresby Trough channel.
“Supported *!°Pb = 7!°Pbotat — 7! °PBexcess- >The theoretical flux is the sum of atmospheric fallout (0.3 dpm cm™? a~') and ??°Ra water column production from GEOSECS western Pacific data [Chung and Craig, 1980]. “Ratio of core-derived flux (dpm cm~* a7') estimated from measured 7!°Pbexcess inventory (dpm cm~”) to theoretical flux (dpm cm~ a7’) given as R. “Lead 210-derived apparent sediment accumulation rates calculated by least squares fit of the analytical solution to the equation, assuming accumulation is dominant over bioturbation (D, = 0). These accumulation rates, therefore, represent a maximum estimate. °MAR (gem a!) = (1 — @) p, SAR (cma_') where @ is the average porosity for the entire length of each core, and p, is the density of sediment grains (assumed to be 2.65 g cm *). ‘SAR and MAR from Walsh and Nittrouer [2003]. MAR from Brunskill et al. [2003]. Table 1. Excess *!°Pb Surface Activities, Supported Activities, Measured Inventories, Estimated Fluxes, and Upper Limits for Sedimen Accumulation Rates
“Supported *!°Pb = 7!°Pbotat — 7! °PBexcess- >The theoretical flux is the sum of atmospheric fallout (0.3 dpm cm™? a~') and ??°Ra water column production from GEOSECS western Pacific data [Chung and Craig, 1980]. “Ratio of core-derived flux (dpm cm~* a7') estimated from measured 7!°Pbexcess inventory (dpm cm~”) to theoretical flux (dpm cm~ a7’) given as R. “Lead 210-derived apparent sediment accumulation rates calculated by least squares fit of the analytical solution to the equation, assuming accumulation is dominant over bioturbation (D, = 0). These accumulation rates, therefore, represent a maximum estimate. °MAR (gem a!) = (1 — @) p, SAR (cma_') where @ is the average porosity for the entire length of each core, and p, is the density of sediment grains (assumed to be 2.65 g cm *). ‘SAR and MAR from Walsh and Nittrouer [2003]. MAR from Brunskill et al. [2003]. Table 1. Excess *!°Pb Surface Activities, Supported Activities, Measured Inventories, Estimated Fluxes, and Upper Limits for Sedimen Accumulation Rates
Figure 3. X-radiographs from multicores show sedimen- tary structure of seabed from GOP (scale in centimeters). (left) Core (MV-14; water depth of 760 m) from Ashmore Trough showing bioturbation and absence of any physical structures. This is typical of biogenic fabric observed in X- radiographs of most cores. (right) Core (MV-24; water depth of 2102 m) taken from the Moresby Trough showing possible turbidite layers partially destroyed by bioturbation.
Figure 3. X-radiographs from multicores show sedimen- tary structure of seabed from GOP (scale in centimeters). (left) Core (MV-14; water depth of 760 m) from Ashmore Trough showing bioturbation and absence of any physical structures. This is typical of biogenic fabric observed in X- radiographs of most cores. (right) Core (MV-24; water depth of 2102 m) taken from the Moresby Trough showing possible turbidite layers partially destroyed by bioturbation.
Figure 5. Excess 7!°Pb inventory versus water depth in the northern Pandora Trough shelf break and slope region in GOP. [38] We did not measure ~~° column from the study area. water column inventory of 7*° from GEOSECS Station 263 Ra activities in the water Consequently, we estimate Ra based on measurements ocated at 16°40’S; 167°05’W in the southwestern Pacific, integrated over the depth range at each core location. The pro increases to a maximum a file of **°Ra at this station bove 1500 m water depth, decreases below 2000 m, and activity of *’°Ra ranges between 6.0 + 0.7 and 27.3 surface to 2500 m water depth + 0.6 dpm 100 kg! from [Chung and Craig, 1980]. Water column generation of *'° as the product of 7*°Ra water Pb from 7*°Ra is calculated column inventory and the ?1°Pb decay constant (assuming negligible loss of the intermediate decay product 7*?Rn).
Figure 5. Excess 7!°Pb inventory versus water depth in the northern Pandora Trough shelf break and slope region in GOP. [38] We did not measure ~~° column from the study area. water column inventory of 7*° from GEOSECS Station 263 Ra activities in the water Consequently, we estimate Ra based on measurements ocated at 16°40’S; 167°05’W in the southwestern Pacific, integrated over the depth range at each core location. The pro increases to a maximum a file of **°Ra at this station bove 1500 m water depth, decreases below 2000 m, and activity of *’°Ra ranges between 6.0 + 0.7 and 27.3 surface to 2500 m water depth + 0.6 dpm 100 kg! from [Chung and Craig, 1980]. Water column generation of *'° as the product of 7*°Ra water Pb from 7*°Ra is calculated column inventory and the ?1°Pb decay constant (assuming negligible loss of the intermediate decay product 7*?Rn).
Figure 6. Map of calcium carbonate concentrations (% by mass) from core tops after Febo et al. [2006]. Lowest carbonate concentrations occur in the region with the highest sediment accumulation rates and most enriched *!°Pb inventories (i.e., northernmost continental slope).
Figure 6. Map of calcium carbonate concentrations (% by mass) from core tops after Febo et al. [2006]. Lowest carbonate concentrations occur in the region with the highest sediment accumulation rates and most enriched *!°Pb inventories (i.e., northernmost continental slope).
Figure 7. Pandora Trough sediment budget using MAR values divided into four regions. MAR values decrease with increasing water depth and reflect hemipelagic sedimentation seaward of the upper slope.
Figure 7. Pandora Trough sediment budget using MAR values divided into four regions. MAR values decrease with increasing water depth and reflect hemipelagic sedimentation seaward of the upper slope.
Figure 8. Map of relative enrichment in excess *'°Pb inventories from equation (4) and Table 1, showing submarine channel network derived from DEM analysis (channel network data from Patterson et al. [2006] with permission). The largest dots indicate highest relative levels of *!°Pb enrichment, primarily on the shelf edge and upper slope of the northeast GOP. Patterns of 7!°Pb enrichment and channel networks outline important sediment transport pathways from the shelf edge to deep basins.
Figure 8. Map of relative enrichment in excess *'°Pb inventories from equation (4) and Table 1, showing submarine channel network derived from DEM analysis (channel network data from Patterson et al. [2006] with permission). The largest dots indicate highest relative levels of *!°Pb enrichment, primarily on the shelf edge and upper slope of the northeast GOP. Patterns of 7!°Pb enrichment and channel networks outline important sediment transport pathways from the shelf edge to deep basins.
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GeologyOceanographySedimentary RockTurbidity current
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