| Prydz Bay is the largest bay in East Antarctica, it lies in the Indian sector of Southern Ocean. To south, it connects Lambert-Amery Ice Shelf which is a key area to understand the East Antarctic Ice Sheet dynamic and reveal the interactions between sea and ice. In the thesis surface sediments of Prydz Bay and sediment core P4-01 gained from continental slope of the bay awere analysized, we disscussed the characteristic of grain size, minerals and their implications to sediment provenance; the evolution of nearly 520 kyr paleoceanographyic features in the northern continental slope of the bay were also discussed, and several conclusions were as drawn as follows:(1) Constrained by water depth/topography, currents and icebergs, sediment environment differes beyween different sectors of the bay. The shelf area can be subdivided into two sectors. In sector Ⅰ, including Fram Bank, area in front of Amery Ice Shelf, Cape Darnley(Burton Basin) and Four Ladies Bank, sediment contains more gravel, sand and Ice Rafted Detritus. Sediment supply is obviously influenced by Amery Ice Shelf and tidal glaciers, currents, icebergs, and their transport routine in the bay. In sector Ⅱ, including Amery Basin, Prydz Channel and Svenner Channel, sediments contain more silt, while sand and gravel content is less, and sedimentation is influenced by water depth, currents. Particularly, sediment in Amery Basin, center of Prydz Bay Gyre, contains more fine particles and is well sorted. Sedimentation is affected by bottom currents, Antarctic Slope Current, gravity flow, material exchanges between continental shelf and continental slope and icebergs.(2) Heavy mineral contents of surface sediments show a decreasing trend from east to west in the bay. Higher amphibole content in sediments of Four Ladies Bank may derive from the orthogneiss, which contains more amphibole in Princess Elizabeth II Land; and the outcrops in Prince Charles Mountains, which is mainly amphibole facies gneiss, suggest sediment in front of Amery Ice Shelf partly derive from the transport of Lambert-Amery Ice Shelf system. In Fram Bank, amphibole content is higher than the sum of that in Four Ladies Bank, Svenner Channel and areas in front of Amery Ice Shelf. This indicates that it may be glacialgenic from the Mac. Robertson Land, where charnockite intrusions were widely spreaded. In the near coast areas, rutile, monazite and zoisite are constrained in Four Ladies Bank,it may derive from the high-grade metamorphic gneiss in Vestfold Hills. While these three minreals in Amery Basin and Prydz Channel may be attributed to the influence of Prydz Bay Gyre, which transports icebergs into these areas. Tourmaline and cinnabar were only found in sediments near the Fram Bank, they may derive from the charnockite intrusions in Mac. Robertson. Sediments in front of Amery Ice Shelf contains much higher magnetite than any other areas in the bay, this is due to the contribution of dertitus supply from Lambert-Amery Ice Shelf system. In northern areas of the bay, heavy mineral composition in sediments is in accordance with the mineral composition of bedrocks in Lambert Graben.(3) Clay mineral compositions in different sectors of the bay shows little difference in single mineral content and illite chemisty. Average smectite content in sediments in Four Ladies Bank is higher and the illite chemistry is low, which suggests that these clay may derive from tidal glaciers in Princess Elizabeth Land. In areas in front of Amery Ice Shelf, average smectite content is the highest in the area, this is due to the supply of Lambert-Amery Ice Shelf system; average smectite content in Svenner Channel is lower than the former two sectors, but the intermediate illite chemistry indicates clay in the channel is influenced by Lambert-Amery Ice Shelf system and Princess Elizabeth Land. In Fram Bank and area near Cape Darnley, the relative high average content of smectite and kaolinite can be attribute to the influence of tidal glaciers in Mac.Robertson Land. While in Amery Basin and Prydz Channel, clay mineral composition indicates the influence of Prydz Bay Gyre, which mixes the fine clay from Four Ladies Bank, Fram Bank and areas in front of Amery Ice Shelf. In plegic-hemiplegic areas, northern sector of the study area, clay mineral conposition is similar to the clay mineral composition in continental slope, this suggests that sediment in the deep sea areas are the result of interactions from continental shelf and continental slope.(4) Grain size, color reflectance data, heavy minerals, clay minerals and δ18O and δ13C of planktonic foraminifera N.Pachyderma were analyzed to reveal the dynamics of sea-ice interactions in the past approximately 520 kyr. Sample station, P4-01, is in the Antarctic Divergence, where the Circumpolar Deep Water/Modified Circumpolar Deep Water(CDW/MCDW) upwells and influenced by shelf waters. Thus the δ18O and δ13C of planktonic foraminifera N.Pachyderma is influenced by sea surface temperature, water masses, sea-ice and ice shelf, etc. Sea surface temperature was >0.5℃ during most times of the past 520 kyr, and even rised up to 3℃ during MIS 7. During glacials, the δ18O is lower, the average sea surface temperature decreases and the ice shelf expanded, thus the seasonal sea-ice coverage moves north which leads to the norward of the ACC. The Ice-Rafted Dertitus content in Glacia-Interglacials is determined by the position of 0℃ isotherm. Our sample station is near the isotherm. Thus Ice-Rafted Detritus content is much higher during interglacials, including MIS1, MIS3, MIS5, MIS7, MIS9, MIS11 and MIS13. This suggests that the warming environment led to the retreat of ice sheet/ice shelf, and more icebergs calved from ice shelf/tidal glaciers, and transport the dertitus into Southern Ocean. The Sortable Silt and clay content varies cyclically and suggests that bottom current is weakened during glacials, which is helpful to the sedimentation of clay; During interglacials, the main axis of Antarctic Circumpolar Current moves south, this strengthened the interactions between shelf water and continental waters, and result in a strengthened bottom current, which strenghened the transportation and selective effect of bottom current. Clay minerals in the core sediment mainly derive from continental shelf. The northward and southward movement of water masses, currents, and varied iceberg volume in the sea during glacial-interglacials result in the clay mineral composition and illite chemistry fluctuating greatly. |
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