Figure 1. Location of the Leg 182 drill sites in the western Great Australian Bight.
Figure 2. Schematic North-South diagram from the Nullarbor Plain to the upper continental slope across the Eyre Terrace (along longitude 128°E), showing the distribution and internal relationships of seven Cenozoic sequences (unshaded) defined from seismic data, overlying Mesozoic synrift siliciclastic sequences, and Precambrian crystalline basement (after Feary and James, 1998). Vertical scales are approximate.
Figure 3. Lithostratigraphic summary of the western transect. Inset is schematic north-south diagram showing the location of the western transect sites.
Figure 4. Lithostratigraphic summary of the eastern transect. Inset is interpreted seismic line showing the location of the eastern transect sites.
Figure 5. Major biostratigraphic units, unconformities, and paleobathymetric units recorded at Leg 182 sites.
Figure 6. Age-depth plots of biostratigraphic datum levels, showing major hiatuses and estimated sedimentation rates. Datum controls are weaker in stratigraphically older sections, due partly to poor preservation and partly to the temperate nannofossil and foraminifer assemblages that contain few age-diagnostic species.
Figure 7. Summary of paleomagnetic data (inclination) and interpreted magnetostratigraphy for sites on the (A) eastern and (B) western shelf-slope transects of Leg 182. Cross symbols are long core measurements at 5–10 cm intervals, whereas discrete samples and lithified core fragments are shown as open symbols. The interpreted magnetostratigraphy is the same for Holes 1130A and 1130B.
Figure 8. Contour map of Cl– concentration at Sites 1127, 1131, and 1129 overlying the interpretation of the seismic line joining the three sites. Note that the concentrations of equal Cl– concentration crosscut the seismic sequences and appear to originate from a subhorizontal brine. Cl– concentrations are given in millimoles per liter (mM). Normal sea water concentration is 559 mM.
Figure 9. Concentration of methane (triangles), ethane (circles), and propane (diamonds) in headspace samples from Site 1129. Note the maximum in concentration of all three gaseous species occurs between 200 and 500 mbsf. This is particularly significant for the higher weight alkanes and suggests that they are not migrating from deeper in the section.
Figure 10. Concentration of dolomite at Sites 1127, 1131, and 1129. The highest sustained concentrations (10–15 wt%) occur at Sites 1129 and 1131, although samples with values as high as 35 wt% were measured at Site 1127. The dolomitization is principally associated with the Pleistocene sediments.
Figure 11. JNOC seismic line JA90-31 for the eastern drilling transect, overlain with spectral gamma radiation (right curve at each site), bulk density (left curve at Sites 1131 and 1129), and porosity (left curve at Site 1127) from the downhole logs. Because of high H2S in the drill hole at Site 1127, the nuclear source of the HLDS was not used. Thus, there are no bulk density estimates for this site. All data were converted to two-way traveltime using a linear interpolation of traveltime from the seafloor to the bottom of the drilled interval.