Holocene Climate and Catchment Change Inferred from the Geochemistry of Lashmars Lagoon, Kangaroo Island (Karti), Southern Australia

49 Pages Posted: 17 Aug 2023

See all articles by Lucinda Cameron Duxbury

Lucinda Cameron Duxbury

The University of Adelaide

Lluka Yohanni Johns-Mead

affiliation not provided to SSRN

Haidee Cadd

University of Wollongong

Alexander Francke

Flinders University

Stefan C. Löhr

affiliation not provided to SSRN

Wallace Boone Law

affiliation not provided to SSRN

Linda Armbrecht

affiliation not provided to SSRN

Tony Hall

University of Adelaide

Atun Zawadzki

Government of the Commonwealth of Australia - Australian Nuclear Science and Technology Organisation

Geraldine Jacobsen

Government of the Commonwealth of Australia - Australian Nuclear Science and Technology Organisation

Patricia S. Gadd

Government of the Commonwealth of Australia - Australian Nuclear Science and Technology Organisation

David P. Child

Government of the Commonwealth of Australia - Australian Nuclear Science and Technology Organisation

Charles Maxson

affiliation not provided to SSRN

Zoë Amber Thomas

University of Southampton

Jonathan James Tyler

affiliation not provided to SSRN

Abstract

We present a continuous ~7,000-year sedimentary record from Lashmars Lagoon, Kangaroo Island (Karti), southern Australia, from a region heavily impacted by drought and bushfires in recent decades. Records such as this are vital to contextualise current climatic and environmental shifts, particularly regarding the interplay between hydroclimate and fire-related disturbances in this ecologically sensitive area. We use high-resolution µX-ray fluorescence core scanning, complemented by bulk organic geochemistry and X-ray diffraction mineralogy of catchment soil and lake sediments to reconstruct past climate and catchment processes. Phases of elevated sediment organic matter content (inferred from high Br and total organic carbon) suggest increased lake freshening and productivity, and coincide with increased chemical weathering (inferred from high Al/K and kaolinite/illite and feldspars), likely reflecting the influence of wetter climates. Conversely, periods of high Ca correlate with biogenic carbonate inputs typical of brackish conditions, which we attribute to drier climates or a marine influence. From 7.0 ka, at the mid-Holocene sea level highstand, until 5.7 ka, we suspect Lashmars Lagoon was under virtually continuous influence from the sea. At 5.7 ka, we interpret the abrupt increase in sediment total organic carbon to reflect the severance of the connection to the sea, allowing organic material to accumulate. This, coupled with evidence of high inferred chemical weathering, suggests the climate was relatively wet at the time. After 5.4 ka, our data point to the establishment of drier conditions until the commencement of wetter climates at 4.5 ka. From 2.5 ka, however, drier climates prevailed again until present. Notably, the climate changes recorded in the sedimentary sequence at Lashmars Lagoon seem to be linked to the strength of the Leeuwin Current, which brings warm tropical waters to southern Australia and may well have been an important driver of rainfall on Kangaroo Island (Karti) over the past ~7,000 years.

Keywords: Lake sediment, Itrax, X-Ray Diffraction (XRD), X-Ray Fluorescence (XRF), weathering, hydroclimate

Suggested Citation

Duxbury, Lucinda Cameron and Johns-Mead, Lluka Yohanni and Cadd, Haidee and Francke, Alexander and Löhr, Stefan C. and Law, Wallace Boone and Armbrecht, Linda and Hall, Philip Anthony and Zawadzki, Atun and Jacobsen, Geraldine and Gadd, Patricia S. and Child, David P. and Maxson, Charles and Thomas, Zoë Amber and Tyler, Jonathan James, Holocene Climate and Catchment Change Inferred from the Geochemistry of Lashmars Lagoon, Kangaroo Island (Karti), Southern Australia. Available at SSRN: https://ssrn.com/abstract=4544393 or http://dx.doi.org/10.2139/ssrn.4544393

Lucinda Cameron Duxbury (Contact Author)

The University of Adelaide ( email )

Adelaide, 5005
Australia

Lluka Yohanni Johns-Mead

affiliation not provided to SSRN ( email )

No Address Available

Haidee Cadd

University of Wollongong ( email )

Northfields Avenue
Wollongong, 2522
Australia

Alexander Francke

Flinders University ( email )

GPO Box 2100
Adelaide S.A. 5001, 5063
Australia

Stefan C. Löhr

affiliation not provided to SSRN ( email )

No Address Available

Wallace Boone Law

affiliation not provided to SSRN ( email )

No Address Available

Linda Armbrecht

affiliation not provided to SSRN ( email )

No Address Available

Philip Anthony Hall

University of Adelaide ( email )

Adelaide, 5005
Australia
+61479187848 (Phone)

Atun Zawadzki

Government of the Commonwealth of Australia - Australian Nuclear Science and Technology Organisation ( email )

Locked Bag 2001
Kirrawee DC
Sydney, NSW 2232
Australia

Geraldine Jacobsen

Government of the Commonwealth of Australia - Australian Nuclear Science and Technology Organisation ( email )

Locked Bag 2001
Kirrawee DC
Sydney, NSW 2232
Australia

Patricia S. Gadd

Government of the Commonwealth of Australia - Australian Nuclear Science and Technology Organisation ( email )

Locked Bag 2001
Kirrawee DC
Sydney, NSW 2232
Australia

David P. Child

Government of the Commonwealth of Australia - Australian Nuclear Science and Technology Organisation ( email )

Charles Maxson

affiliation not provided to SSRN ( email )

No Address Available

Zoë Amber Thomas

University of Southampton ( email )

Southampton Business School
Southampton
United Kingdom

Jonathan James Tyler

affiliation not provided to SSRN ( email )

No Address Available

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