Seasonally laminated late Quaternary Antarctic sediments

Quaternary diatom-rich laminated sediments, found in Antarctic inner shelf depressions, contain high-resolution records of climate change. Diatom assemblages and sediment fabric of four laminated intervals were examined with a scanning electron microscope (using backscattered and secondary electron imagery) and light microscope in this study. Deglacial Palmer Deep laminated sediments (western Antarctic Peninsula) are composed of alternating biogenic diatom ooze and diatom-bearing terrigenous laminae. These laminae are interpreted as spring and summer signals respectively, with negligible winter deposition. Sub-seasonal species specific sub-laminae are observed repeatedly through the summer laminae. Tidal cycles, high storm intensities and / or intrusion of Circumpolar Deep Water onto the continental shelf create variation in shelf waters, enhancing species specific productivity through the summer. Post-glacial Mertz Ninnis Trough laminated sediments (East Antarctic Margin) are composed of five lamina and one sub-lamina types. During deposition the Mertz Glacier Polynya was active and Adelie Land Bottom Water formation was strong. Mid-Holocene Mertz Ninnis Trough laminated sediments are composed of five lamina types. Sea ice cover and sea ice formation was reduced relative to post-glacial times. The Mertz Glacier Polynya was not as active as in the post-glacial and Adelie Land Bottom Water formation was lower. Late-Holocene Durmont d'Urville Trough laminated sediments (East Antarctic Margin) are composed of eight lamina and one sub-lamina types. Sea ice cover was extensive and persistent in the late-Holocene. Warmer periods occurred during the transition from mid-Holocene Climatic Optimum to cooler late-Holocene climatic conditions. The types of lamina and sub-lamina formed in all four laminated intervals are controlled by seasonal sea ice cover, nutrient levels and light levels, which are in turn influenced by climate and oceanography. The Western Antarctic Peninsula and East Antarctic Margin laminated sediments give an insight into oceanographic responses to climatic change and variation through the Quaternary around the Antarctic margin