11:00 AM - 1:00 PM
[MIS03-P04] Holocene relative sea-level change in Lake Oyako-Ike, Soya coast, East Antarctica
Accelerated melting of the Antarctic ice sheet (AIS) is one of the major contributors to global sea-level rise. To better constrain future climatic and environmental consequences, it is important to understand the history and mechanisms of AIS melting and associated sea-level changes. Since the Last Glacial Maximum, regional sea-level reconstructions are a critical component of these efforts to resolve past fluctuations in ice sheets and global sea-level.
Regional sea-level reconstructions have previously been attempted across the Skarvsnes area of Lützow-Holm Bay, East Antarctica (Takano et al., 2012; Verleyen et al., 2017). However, the results were not consistent, making it difficult to provide firm constraints on the past AIS in this region. Therefore, this study examines new evidence for relative sea-level changes from Lake Oyako-Ike, Skarvsnes, through sedimentological and microfossil (ostracod) analyses of a sediment core collected in 2017–2018 by the 59th Japanese Antarctic Research Expedition (JARE 59).
A total of 17 ostracod species were identified in 50 samples from the core, corresponding to the time interval between 8500 and 2200 cal BP. Cluster analysis (Q-mode) of the ostracod assemblages revealed four biofacies. Paleoenvironmental changes interpreted from those ostracod assemblages, lithology, and calibrated 14C ages, can be summarized as follows. Before ca. 8500 cal BP, the study site was covered by an ice sheet, and hence uninhabitable (or inaccessible) to ostracods. From 8500 to 6700 cal BP, the study site occupied a coastal environment characterized by seaweed. This changed to a shallow marine setting (water depths ca. 20–30 m) with muddy substrates and proximality to seaweed beds, probably recording marine transgression. After 4200 cal BP, there was a change to a higher energy, open marine paleoenvironment with sandy substrates (again at water depths of ca. 20–30 m). Ostracods corresponding to the interval 3800–2200 cal BP are poorly preserved, suggesting agitation and reworking by wave action or tidal currents. Above an organic-rich layer dated at 2200 cal BP, ostracods disappear entirely, implying paleoenvironmental isolation from seawater.
A modern analog technique was used to construct a relative sea-level curve based on the ostracod assemblages. The result is lower than the relative sea-level curve previously inferred for Skarvsnes (Verleyen et al., 2017) but higher than glacial-isostatic adjustment models, and thus provides an important data point for a future revision and refinement of these models.
Regional sea-level reconstructions have previously been attempted across the Skarvsnes area of Lützow-Holm Bay, East Antarctica (Takano et al., 2012; Verleyen et al., 2017). However, the results were not consistent, making it difficult to provide firm constraints on the past AIS in this region. Therefore, this study examines new evidence for relative sea-level changes from Lake Oyako-Ike, Skarvsnes, through sedimentological and microfossil (ostracod) analyses of a sediment core collected in 2017–2018 by the 59th Japanese Antarctic Research Expedition (JARE 59).
A total of 17 ostracod species were identified in 50 samples from the core, corresponding to the time interval between 8500 and 2200 cal BP. Cluster analysis (Q-mode) of the ostracod assemblages revealed four biofacies. Paleoenvironmental changes interpreted from those ostracod assemblages, lithology, and calibrated 14C ages, can be summarized as follows. Before ca. 8500 cal BP, the study site was covered by an ice sheet, and hence uninhabitable (or inaccessible) to ostracods. From 8500 to 6700 cal BP, the study site occupied a coastal environment characterized by seaweed. This changed to a shallow marine setting (water depths ca. 20–30 m) with muddy substrates and proximality to seaweed beds, probably recording marine transgression. After 4200 cal BP, there was a change to a higher energy, open marine paleoenvironment with sandy substrates (again at water depths of ca. 20–30 m). Ostracods corresponding to the interval 3800–2200 cal BP are poorly preserved, suggesting agitation and reworking by wave action or tidal currents. Above an organic-rich layer dated at 2200 cal BP, ostracods disappear entirely, implying paleoenvironmental isolation from seawater.
A modern analog technique was used to construct a relative sea-level curve based on the ostracod assemblages. The result is lower than the relative sea-level curve previously inferred for Skarvsnes (Verleyen et al., 2017) but higher than glacial-isostatic adjustment models, and thus provides an important data point for a future revision and refinement of these models.