Productivity events of the marine diatom Thalassiosira tumida (Janisch) Hasle recorded in deglacial varves from the East Antarctic Margin
During the last deglaciation calving bay reentrants formed over several deep inner shelf basins around Antarctica as the ice sheets retreated. Marine diatoms flourished in spring and summer within the bays, providing exceptionally high silica flux rates to the basins on an annual basis. As a result,...
| Published in: | Marine Micropaleontology |
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| Main Authors: | , , |
| Format: | Article in Journal/Newspaper |
| Language: | unknown |
| Published: |
2006
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| Subjects: | |
| Online Access: | https://orca.cardiff.ac.uk/id/eprint/9466/ https://doi.org/10.1016/j.marmicro.2006.02.009 |
| Summary: | During the last deglaciation calving bay reentrants formed over several deep inner shelf basins around Antarctica as the ice sheets retreated. Marine diatoms flourished in spring and summer within the bays, providing exceptionally high silica flux rates to the basins on an annual basis. As a result, several hundred years of the late deglaciation are archived in many of these deep basins as continuously laminated diatom-rich marine sediments. The laminae are excellently preserved and offer a unique opportunity to study deglacial processes over the Antarctic shelf at very high resolution (subseasonal to seasonal at best). Annual palaeoenvironments from these sediments have been recently reconstructed. However, finer sedimentary detail is also apparent by the preservation of sublaminae of single diatom species, which represent discrete productivity events (blooms). In this paper, we focus on Thalassiosira tumida (Janisch) Hasle sublaminae preserved in the ∼5 m thick deglacial laminated sequence of NBP01-01 Jumbo Piston Core (JPC) 43B from Iceberg Alley (∼67°S, 63°E) on the Mac.Robertson Shelf, East Antarctic Margin. These T. tumida sublaminae are distinctive, occur several times throughout the deglacial sequence and are always preserved within summer laminae. Importantly they carry ecological and paleoceanographic information for deglacial Iceberg Alley and possibly the entire East Antarctic Margin.We describe and illustrate the T. tumida sublaminae using scanning electron microscope backscattered electron imagery of highly polished thin sections and secondary electron imagery of sublamina fracture surfaces. T. tumida sublaminae range in thickness from 0.57 to 21.07 mm (mean=5.12; σ=4.49) and are defined as discrete sedimentary intervals within a summer lamination where T. tumida is the dominant diatom species (abundanceN50%; but frequentlyN80%) or is very abundant (abundance 40% to 49%). Based on the stratigraphic position of these sublaminae in the annual/seasonal succession and on published morphological, ... |
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