New Record of Dust Input and Provenance During Glacial Periods in Western Australia Shelf (IODP Expedition 356, Site U1461) from the Middle to Late Pleistocene

Abstract

International Ocean Discovery Program (IODP) Expedition 356 Site U1461 represents one of the few records from the North West Australian shelf that provides information about aridity fluctuations in Australia during the Quaternary. A combination of chronostratigraphic indicators revealed the (partial) preservation of two major glaciations (Marine Isotope Stage (MIS) 2 and MIS 12) in the sedimentary record. The faunal content (mainly benthic foraminifera, corals and bryozoans) was analyzed to estimate paleo-environments and paleo-depths in order to determine if these sediments have been remobilized by reworking processes. Despite the occurrence of a depositional hiatus (including MIS 5d to MIS 9-time interval), the excellent preservation of faunal content suggests that the preserved sediment is in situ. The geochemical composition of the sediments (Nd and major elements) indicates that during MIS 12 riverine input was likely reduced because of enhanced aridity, and the sediment provenance (mainly atmospheric dust) is likely in the central (Lake Eyre) or eastern (Murray Darling Basin) parts of the Australian continent. MIS 2 is confirmed to be one of the driest periods recorded in Australia but with mixed dust sources from the eastern and western parts of the continent. More humid conditions followed the glacial maximum, which might correspond to the peak of the Indian-Australian Summer Monsoon.

Climate and sea‐level controlling internal architecture of a Quaternary carbonate ramp (Northwest Shelf of Australia)

“…Skeletal grains typically include large benthic foraminifera, molluscs (bivalve shells and gastropods), bryozoans and echinoid fragments. Benthic foraminifera mainly include the species Asterorotalia gaimardii , Parrellina verriculata and Elphidium craticulatum (Courtillat et al ., 2020).…”

“…The age model of the top 70 m (CCSF‐A) of Site U1461 is based on a combination of radiocarbon ages, biostratigraphic datums and oxygen isotope data (Gallagher et al ., 2017b; Hallenberger et al ., 2019; Ishiwa et al ., 2019b; Courtillat et al ., 2020). These datasets were previously compiled into a comprehensive chronological profile (Courtillat et al ., 2020), which is in large parts adopted for this research (Fig. 2).…”

“…The material used for radiocarbon dating includes planktonic foraminifera and macrofossils, all of which were cleaned and screened for cementation prior to measurement (Hallenberger et al ., 2019; Ishiwa et al ., 2019b). In older strata (>40 ka), ages are determined based on cocco‐lithophorid biostratigraphic datums and oxygen isotope data of planktonic foraminifera (Gallagher et al ., 2017b; Courtillat et al ., 2020). Nannofossil biostratigraphy includes the first occurrence of Emiliania huxleyi (18.65 m) and the last occurrence of Pseudoemiliania lacunosa (60.73 m).…”

“…2). For this study, the borehole specific depth scale (CSF-A) of Courtillat et al (2020) was converted to a composite depth scale (CCSF-A), which accounts for differences in depth between holes (Gallagher et al, 2017b).…”

Southern Ocean Ecosystem Response to Last Glacial Maximum Boundary Conditions

“…It has been previously hypothesized that enhanced aeolian iron input into HNLC regions during the LGM could have increased NPP and EP in these regions (Martin, 1990). However, there are significant uncertainties associated with the regional magnitude of dust fluxes during the LGM, particularly in the Southern Ocean (Albani et al, 2014(Albani et al, , 2016Courtillat et al, 2020;Lambert et al, 2015;Lamy et al, 2014;Ohgaito et al, 2018;Mahowald et al, 2006;). Comparing these different estimates with lithogenic fluxes from marine sediment cores suggests that the best agreement is obtained for the LGM-lamb dust mask (Lambert et al, 2015), due to the increase in dust deposition in the south Pacific region.…”