Marine sediment record from the East Antarctic margin reveals dynamics of ice sheet recession

Abstract

The Antarctic shelf is traversed by large-scale troughs developed
\nby glacial erosion. Swath bathymetric, lithologic, and
\nchronologic data from jumbo piston cores from four sites along
\nthe East Antarctic margin (Iceberg Alley, the Nielsen Basin, the
\nSvenner Channel, and the Mertz-Ninnis Trough) are used to
\ndemonstrate that these cross-shelf features controlled development
\nof calving bay reentrants in the Antarctic ice sheet during
\ndeglaciation. At all sites except the Mertz-Ninnis Trough, the
\ntransition between the Last Glacial Maximum and the Holocene
\nis characterized by varved couplets deposited during a
\nshort interval of extremely high primary productivity in a fjordlike
\nsetting. Nearly monospecific layers of the diatom Chaetoceros
\nalternate with slightly more terrigenous layers containing
\na mixed diatom assemblage. We propose that springtime
\ndiatom blooms dominated by Chaetoceros were generated
\nwithin well-stratified and restricted surface waters of calving
\nbays that were influenced by the input of iron-rich meltwater.
\nIntervening post-bloom summer-fall laminae were formed
\nthrough the downward flux of terrigenous material sourced
\nfrom melting glacial ice combined with mixed diatom assemblages.
\nRadiocarbon-based chronologies that constrain the timing
\nof deposition of the varved sediments within calving bay
\nreentrants along the East Antarctic margin place deglaciation
\nbetween ca. 10,500–11,500 cal yr B.P., post-dating Meltwater
\nPulse 1A (14,200 cal yr B.P.) and indicating that retreat of ice
\nfrom the East Antarctic margin was not the major contributor to
\nthis pulse of meltwater.