Foraminiferal assemblages from ice-proximal paleo-settings in the Whales Deep Basin, eastern Ross Sea, Antarctica

Abstract

Reconstructions of Ross Sea paleoenvironments based on foraminifera are hindered by the dearth of actualistic data, especially from below the Ross Ice Shelf. To fill this gap, we used a recently developed well-resolved deglaciation record from the Whales Deep Basin of the eastern Ross Sea to understand the ecological affinities of different foraminiferal assemblages. During open-water conditions similar to the present, two benthic foraminiferal communities are strongly dominated by agglutinated species. However, in the underlying sediments that represent sub-ice-shelf and grounding-zone proximal settings on the outer continental shelf, we identified five different assemblages of calcareous foraminifera. By Antarctic margin standards, these calcareous assemblages are periodically truly abundant. Along with assemblages dominated by benthic calcareous species that are well known from many Antarctic settings, i.e., Globocassidulina biora, Trifarina earlandi, and Astrononion echolsi, two important assemblages are dominated by a heretofore undescribed pustulose morphotype of G. biora and poorly known spinose morphotype of T. earlandi. Based on our correlations to the deglacial record, these two assemblages live near the grounding line or in environments with especially intense bottom water currents. As grounded and floating ice retreated south to the middle continental shelf, these later sub-ice-shelf and grounding-zone proximal settings were largely devoid of calcareous foraminifera and instead were inhabited by agglutinated taxa. This improved understanding of foraminiferal assemblage distributions from a variety of environments within the eastern Ross Sea may contribute to better use of foraminiferal data to investigate the evolution of environmental changes in grounding-line proximal environments.