Fig. 4.

Schematic illustration of events described in the text. (A) During the LGM the ice sheet and associated ice shelf extends across the outer continental shelf. A grounding zone wedge marks the LGM grounding line position. Subice shelf deposits contain rare foraminifera but lack diatoms and ¹⁰Be. Diatoms and ¹⁰Be in sediments indicate seasonally open marine conditions. (B) An initial episode of ice-shelf collapse and associated grounding line retreat on the outer, western continental shelf occurred shortly after the LGM. Ice-shelf breakup resulted in clusters of deep-keeled icebergs that cut linear furrows at the depth of the former grounding line (−560 m). As icebergs began to disperse they formed randomly oriented furrows. (C) Continuous retreat of the grounding line in the western Ross Sea is marked by marginal landforms that back-step continuously within troughs and onto banks. An ice shelf is grounded on banks and extends across the middle and inner continental shelves of the western and eastern Ross Sea until the late Holocene, when final breakup occurs. Illustration not to scale.