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South Georgia marine productivity over the past 15 ka and implications for glacial evolution

Wilkin, Jack T. R.; Kender, Sev; Dejardin, Rowan; Allen, Claire S.; Peck, Victoria L.; Swann, George E. A.; McClymont, Erin L.; Scourse, James D.; Littler, Kate; Leng, Melanie J.

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Authors

Jack T. R. Wilkin

Sev Kender

Rowan Dejardin

Claire S. Allen

Victoria L. Peck

George E. A. Swann

James D. Scourse

Kate Littler

Melanie J. Leng



Abstract

The subantarctic islands of South Georgia are located in the Southern Ocean, and they may be sensitive to future climate warming. However, due to a lack of well-dated subantarctic palaeoclimate archives, there is still uncertainty about South Georgia’s response to past climate change. Here, we reconstruct primary productivity changes and infer Holocene glacial evolution by analysing two marine gravity cores: one near Cumberland Bay on the inner South Georgia shelf (GC673: ca. 9.5 to 0.3cal.kyrBP) and one offshore of Royal Bay on the mid-shelf (GC666: ca. 15.2cal.kyrBP to present). We identify three distinct benthic foraminiferal assemblages characterised by the dominance of Miliammina earlandi, Fursenkoina fusiformis, and Cassidulinoides parkerianus that are considered alongside foraminiferal stable isotopes and the organic carbon and biogenic silica accumulation rates of the host sediment. The M. earlandi assemblage is prevalent during intervals of dissolution in GC666 and reduced productivity in GC673. The F. fusiformis assemblage coincides with enhanced productivity in both cores. Our multiproxy analysis provides evidence that the latest Pleistocene to earliest Holocene (ca. 15.2 to 10.5cal.kyrBP) was a period of high productivity associated with increased glacial meltwater discharge. The mid–late Holocene (ca. 8 to 1cal.kyrBP), coinciding with a fall in sedimentation rates and lower productivity, was likely a period of reduced glacial extent but with several short-lived episodes of increased productivity from minor glacial readvances. The latest Holocene (from ca. 1cal.kyrBP) saw an increase in productivity and glacial advance associated with cooling temperatures and increased precipitation which may have been influenced by changes in the southwesterly winds over South Georgia. We interpret the elevated relative abundance of F. fusiformis as a proxy for increased primary productivity which, at proximal site GC673, was forced by terrestrial runoff associated with the spring–summer melting of glaciers in Cumberland Bay. Our study refines the glacial history of South Georgia and provides a more complete record of mid–late Holocene glacial readvances with robust chronology. Our results suggest that South Georgia glaciers were sensitive to modest climate changes within the Holocene.

Journal Article Type Article
Acceptance Date May 2, 2024
Online Publication Date Jun 18, 2024
Publication Date Jun 18, 2024
Deposit Date Jun 27, 2024
Publicly Available Date Jun 28, 2024
Journal Journal of Micropalaeontology
Print ISSN 0262-821X
Publisher Copernicus Publications
Peer Reviewed Peer Reviewed
Volume 43
Issue 1
Pages 165-186
DOI https://doi.org/10.5194/jm-43-165-2024
Public URL https://durham-repository.worktribe.com/output/2504501

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