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Figure 1. The Lambert Glacier drainage basin, East Antarctica, showing the location of the Gamburtsev Mountains. Ice surface elevations are in meters (modified from Hambrey, 1991). Gl. = Glacier.
Figure 2. Model of trough mouth fan deposition. A. During periods of maximum ice advance, basal debris is delivered to the shelf edge and redistributed by sediment gravity flows and meltwater plumes. B. During interglacial conditions, the outer shelf is reworked by iceberg ploughing and biogenic input from the water column.
Figure 3. Bathymetric features of and ODP sites in Prydz Bay, Antarctica. Contours are in meters below sea level. The outer edge of the Amery Ice Shelf is shown for the years 1964 (black) and 1991 (green/gray).
Figure 4. Generalized map of circulation in the Prydz Bay region (modified from Smith et al., 1984). The direction of flow is indicated by arrows. Site 1165 is located on the margin of the Antarctic Divergence, a series of cyclonic gyres at the boundary between the Antarctic Circumpolar Current (ACC) and the Polar Current. These major currents move in opposite directions and extend into Antarctic deep water.
Figure 5. Pre-Mesozoic geology of the Lambert Glacier drainage basin and Prydz Bay region after Tingey (1982) and Federov (1982). Late Proterozoic metamorphism in the northern Prince Charles Mountains, Mac. Robertson Land, and Ingrid Christensen Coast are mostly granulite facies. The southern Prince Charles Mountains metasediments are generally chlorite grade in some outcrops displaying primary sedimentary structures. Not shown are Mesozoic and Eocene basic igneous dykes in the Beaver Lake area.
Figure 6. Structure contour map of the top of basement in Prydz Bay. Contours are in milliseconds two-way traveltime below sea level. A northeast-trending, faulted ridge separates the Prydz Bay Basin from the outer shelf.
Figure 7. Top Lower Cretaceous structure contour map (Surface PS.2B of Cooper et al., 1991a). Contours are in milliseconds two-way traveltime below sea level.
Figure 8. Sketch profile of seismic sequences drilled during Leg 119,
based on Line BMR 33-21. PS.1 is composed of Neogene topset and foreset
beds, PS.2A is Paleogene glacial and preglacial sediment, PS.2B is lower
Cretaceous nonmarine sediment, PS.4 is undated nonmarine red beds, and
PS.5 is basement.
Figure 9. Isopach map of postsurface PP12 sediments. Contours are in milliseconds two-way traveltime; dashed line indicates shelf edge. Deposition is concentrated in the Prydz Channel Fan with relatively thin subglacial sediment on Four Ladies Bank, several patches of diatom ooze in Svenner Channel, and a morainal bank on the western side of the bay. Elsewhere, post-PP12 sediments are present but are too thin to be resolved on seismic records.
Figure 10. A. Overview map of the primary Leg 188 drill sites with respect to port of origin (Fremantle) and final port (Hobart). B. Map of East Antarctic coastline between 50°E and 90°E, showing the location of Prydz Bay, Mac. Robertson Land, Antarctic stations, Leg 119 drill sites (light gray circles), and Leg 188 drill sites (dark gray circles).
Figure 11. Seismic reflection profile BMR 33-23P3 over Site 1166 showing lithostratigraphic units, ages, rock types, paleoenvironmental interpretation, the schematic section, and downhole-logging units. SP = shotpoints; TD = total depth.
Figure 12. Composite stratigraphic section for Site 1166 showing core recovery, a simplified summary of lithology, lithostratigraphic unit boundaries, and age. Gamma-ray and resistivity curves are derived from downhole logs along with minerals identified by XRD, which shows the percentage of the most abundant minerals. Note: Lithology patterns have been added to this figure.
Figure 13. Plots showing biostratigraphic age control and magnetostratigraphic polarity intervals for Site 1166. FO = first occurrence; LO = last occurrence. The inclinations obtained from split cores are compared with inclinations from stepwise-demagnetized discrete samples (red/gray squares). Polarity is shown on the log to the right. Black represents normal and white represents reverse polarity intervals.
Figure 14. Downhole wireline logs from Site 1165 showing density, porosity, resistivity, and sonic velocity curves, with the logging units marked. The core index property measurements of density and porosity and the lithostratigraphic units from core analysis are also shown. LWD = logging while drilling.
Figure 15. Representative examples of Formation MicroScanner (FMS) resistivity images from Hole 1166A, with lithologic descriptions, porosity, density, gamma ray, and caliper and resistivity curves from downhole logging. APLC = accelerator porosity sonde near-array limestone porosity corrected (decimal fraction); RHOM = corrected bulk density (g/cm3).
Figure 16. Conceptual diagrams for the setting of the Prydz Bay region from preglacial (scene 1) to the initiation of glaciation with marine transgressions (scenes 2, 3, and 4) to full glaciation with ice sheets on the overdeepened continental shelf (scene 5).
Figure 17. Seismic reflection profile AGSO 49/0901 over Site 1167. SP = shotpoints.
Figure 18. Site 1167 lithostratigraphic units, facies, and interpretation. In "Recovery" column, black = recovered; gray = not recovered.
Figure 19. Distribution and frequency of sandstone vs. granite/igneous lonestones in Hole 1167A. A shift from largely sandstone clasts to granite clasts occurs uphole at ~200 mbsf.
Figure 20. Plots showing magnetostratigraphy, magnetic susceptibility, and the ratio of anhysteretic and isothermal remanent magnetization (ARM/IRM) for Site 1167. The inclinations from split cores are compared with inclinations from stepwise-demagnetized discrete samples (red/gray squares). The horizontal lines and the labels on the magnetic susceptibility plot indicate intervals with different magnetic properties.
Figure 21. Plots of chloride and sulfate interstitial water values with depth at Site 1167.
Figure 22. Seismic reflection profiles across Site 1165. A. Regional profile across the Wild Drift. The regional horizon PP12 can be traced beneath the continental slope and is the base of the Prydz Bay Trough Mouth Fan. B. Profile recorded over the drill site by the JOIDES Resolution's water gun seismic system upon approach to the site. Lithostratigraphic units and lithology are also shown.
Figure 23. Composite stratigraphic section for Site 1165 showing core recovery, a simplified summary of lithology, lithostratigraphic unit boundaries, and age. Also shown are the distribution of lonestones and dispersed clasts, mineral abundances identified by XRD, the percentage of diatoms and sponge spicules from smear slides, and color reflectance. See Figure 12 for lithology and mineral legends. The bar graph shows the distribution of isolated lonestones (>5 mm) downhole. The vertical bars on the right side of the column show the distribution of dispersed grains and granules (<5 mm). X-ray diffraction shows the percentage of most abundant minerals. This graph was plotted using the methods of Forsberg et al. (1999). In the smear-slide graph, solid line = diatoms; dashed line = sponge spicules. The thin line in the color reflectance plot shows the reflectance percent downhole. The thick line is a 200-point moving average.
Figure 24. Magnetostratigraphy for Site 1165.
Figure 25. Age-depth plot for Site 1165 based on biostratigraphy and magnetostratigraphy. FO = first occurrence; LO = last occurrence.
Figure 26. Organic gases and carbon in Holes 1165B (open symbols) and 1165C (solid symbols). A. Concentrations of methane (C1), ethane (C2), and propane (C3) gases with depth. B. Percentage of organic carbon with depth.
Figure 27. Example of the cyclicity (at Milankovitch periodicities; see text) observed in Site 1165 cores, with spectra of spectrophotometer-lightness and gamma-ray (GRA) bulk density values. A. Three sections for Core 188-1165B-14H with core photo (left), model (center), and lightness curve. B. Lightness and bulk density values, with maximum entropy spectra showing peaks (in depth) at periods of 4.27, 1.55, 0.95, and 0.72 m, equivalent to approximate time intervals of 93.7, 41.5, 20.8, and 18.2 k.y. at a sedimentation rate of 3.8 to 4.1 cm/k.y.
Figure 28. Conceptual diagrams showing the long-term shift from temperate to cold conditions across the continental margin at Prydz Bay, from times of wet-based glaciers with fluvial systems to those of dry-based(?) ice sheets in maximum glacial-interglacial conditions. During the transition to cold times, short-term seaward-landward shifts in glaciers (double arrow) may explain the cyclic gray/green sedimentation patterns with Milankovitch periodicities (i.e., Site 1165; early Miocene and younger times).
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