TY - JOUR

T1 - New Zealand as a source of mineral dust to the atmosphere and ocean

AU - Koffman, Bess G.

AU - Goldstein, Steven L.

AU - Winckler, Gisela

AU - Borunda, Alejandra

AU - Kaplan, Michael R.

AU - Bolge, Louise

AU - Cai, Yue

AU - Recasens, Cristina

AU - Koffman, Tobias N. B.

AU - Vallelonga, Paul

PY - 2021/1/1

Y1 - 2021/1/1

N2 - The chemical and isotopic compositions of sediments and dust can be used to trace their provenance, providing insights into many Earth surface processes. During past glacial climates, much of the New Zealand (NZ) South Island was blanketed by erosive glacier systems that produced large volumes of sediment. We estimate the expansion of glacial outwash plains based on a sea level lowering of 130 m at the Last Glacial Maximum (LGM), and find that the Canterbury Plains in the central South Island likely expanded by 30,000 km(2), a nearly five-fold increase, while the Southland/southern Otago region may have extended southward to cover an additional similar to 45,000 km(2), an eight-fold increase of the coastal plain area. Considering NZ's extreme uplift and erosion rates (similar to 10 m kyr(-1)), the South Island, though limited in extent compared to larger Southern Hemisphere landmasses, may serve as an important dust source to the high-latitude atmosphere and ocean.To facilitate accurate tracing of the extent of aeolian and oceanic transport of NZ dust, this study presents major/trace element and Sr-Nd-Pb isotope ratios on sediments from the major present-day dust and sediment producing regions of the South Island. The sediment compositions strongly reflect the regional geology. For example, compared to the central South Island, Nd isotope ratios in the southern South Island are more variable and show younger crustal residence ages. The combined Sr-Nd-Pb isotopic ratios show that the central NZ South Island can be distinguished geochemically from many other Southern Hemisphere dust sources. Although isotopic similarities between the central NZ South Island and more northerly regions of South America, including Central Western Argentina and the PunaAltiplano Plateau, and Kati Thanda-Lake Eyre in Australia (based on new data in this study) hinder downstream source attribution, a key finding is that these isotopes successfully discriminate NZ from other locations in Australia, such as the Murray-Darling Basin, Northern Territory, and Western Australia, as well as southern Africa and regions of South America south of similar to 37 degrees S (Patagonia and Tierra del Fuego). A comparison of the NZ data with East Antarctic ice core dust samples indicates that NZ was not a significant dust supplier to East Antarctica; rather, the East Antarctic dust compositions can be explained by dust supplied by Patagonia, Tierra del Fuego, and Central Western Argentina in South America, and West Antarctic Rift System volcanism. In contrast, the compositions of marine sediments in the Pacific sector of the Southern Ocean are compatible with mixing of South and North Island NZ dust sources, consistent with NZ's role as an active dust supplier to the Southern Ocean. New data from Kati ThandaLake Eyre in Australia show that it may also be a contributor, if dust from this region is able to reach the Pacific sector independent of other Australian sources. (C) 2020 Elsevier Ltd. All rights reserved.

AB - The chemical and isotopic compositions of sediments and dust can be used to trace their provenance, providing insights into many Earth surface processes. During past glacial climates, much of the New Zealand (NZ) South Island was blanketed by erosive glacier systems that produced large volumes of sediment. We estimate the expansion of glacial outwash plains based on a sea level lowering of 130 m at the Last Glacial Maximum (LGM), and find that the Canterbury Plains in the central South Island likely expanded by 30,000 km(2), a nearly five-fold increase, while the Southland/southern Otago region may have extended southward to cover an additional similar to 45,000 km(2), an eight-fold increase of the coastal plain area. Considering NZ's extreme uplift and erosion rates (similar to 10 m kyr(-1)), the South Island, though limited in extent compared to larger Southern Hemisphere landmasses, may serve as an important dust source to the high-latitude atmosphere and ocean.To facilitate accurate tracing of the extent of aeolian and oceanic transport of NZ dust, this study presents major/trace element and Sr-Nd-Pb isotope ratios on sediments from the major present-day dust and sediment producing regions of the South Island. The sediment compositions strongly reflect the regional geology. For example, compared to the central South Island, Nd isotope ratios in the southern South Island are more variable and show younger crustal residence ages. The combined Sr-Nd-Pb isotopic ratios show that the central NZ South Island can be distinguished geochemically from many other Southern Hemisphere dust sources. Although isotopic similarities between the central NZ South Island and more northerly regions of South America, including Central Western Argentina and the PunaAltiplano Plateau, and Kati Thanda-Lake Eyre in Australia (based on new data in this study) hinder downstream source attribution, a key finding is that these isotopes successfully discriminate NZ from other locations in Australia, such as the Murray-Darling Basin, Northern Territory, and Western Australia, as well as southern Africa and regions of South America south of similar to 37 degrees S (Patagonia and Tierra del Fuego). A comparison of the NZ data with East Antarctic ice core dust samples indicates that NZ was not a significant dust supplier to East Antarctica; rather, the East Antarctic dust compositions can be explained by dust supplied by Patagonia, Tierra del Fuego, and Central Western Argentina in South America, and West Antarctic Rift System volcanism. In contrast, the compositions of marine sediments in the Pacific sector of the Southern Ocean are compatible with mixing of South and North Island NZ dust sources, consistent with NZ's role as an active dust supplier to the Southern Ocean. New data from Kati ThandaLake Eyre in Australia show that it may also be a contributor, if dust from this region is able to reach the Pacific sector independent of other Australian sources. (C) 2020 Elsevier Ltd. All rights reserved.

KW - Dust and sediment provenance

KW - Sr-Nd-Pb isotopes

KW - Rare earth elements

KW - New Zealand

KW - Australia

KW - Antarctica

KW - South Pacific

KW - LAST GLACIAL MAXIMUM

KW - TRACE-ELEMENT COMPOSITION

KW - DEEP-SEA SEDIMENTS

KW - C ICE-CORE

KW - EAST ANTARCTICA

KW - SOUTHERN ALPS

KW - ISOTOPIC COMPOSITIONS

KW - AR-40/AR-39 AGES

KW - NORTH-ATLANTIC

KW - DOME C

U2 - 10.1016/j.quascirev.2020.106659

DO - 10.1016/j.quascirev.2020.106659

M3 - Journal article

VL - 251

JO - Quaternary Science Reviews

JF - Quaternary Science Reviews

SN - 0277-3791

M1 - 106659

ER -