Development of the Leeuwin Current on the northwest shelf of Australia through the Pliocene-Pleistocene period

Terrestrial Material Input to the Northwest Shelf of Australia Through the Pliocene‐Pleistocene Period and Its Implications on Continental Climates

“…In terms of the ratio-based proxy, C 31Alk /C 28-30Str values vary from 0.008 to 1.84 (Figure 2e) and show a general decreasing trend between 5 and 0.8 Ma (r 2 = 0.65, n = 159, p < 0.05). At some well-recognized cooling and ITF weakening periods through the Pliocene-Pleistocene period, including 1.7-1.5, 2.7-2.5, and 3.8-3.5 Ma, C 31Alk /C 28-30Str values also slightly decreased (Figure 2, Auer et al, 2019Auer et al, , 2020De Vleeschouwer et al, 2018He et al, 2021;Petrick et al, 2019;Smith et al, 2020). Compared with those between 5 and 0.8 Ma, the C 31Alk /C 28-30Str values show no obvious decreasing or increasing trend between 0.8 and 0 Ma.…”

“…Site U1461 is located on the northwest shelf of Australia (20°12′51″S, 115°03′56″E, water depth of 126 m, Figure 1), ∼100 km northwest of the Barrow Island. Age-depth model for sedimentary cores at Site U1461 was built by integrating datums from biostratigraphy, micropaleontology, lithological property, and 14 C dates distributed from the top 950 m (Figure S1, see details in He et al, 2021).…”

“…By contrast, the decreasing C 31Alk /C 28-30Str values seem to mimic the long-term ITF constriction trend (Figure 2, Christensen et al, 2017). Also at periods with weak ITF conditions including 1.7-1.5, 2.7-2.5, and 3.7-3.4 Ma, the C 31Alk /C 28-30Str record also suggests decreased vegetational OC input (Figure 2, Auer et al, 2019Auer et al, , 2020Christensen et al, 2017;De Vleeschouwer et al, 2019;He et al, 2021;Petrick et al, 2019;Smith et al, 2020). Therefore, the decrease of the vegetational OC input between 5 and 0.8 Ma might be largely due to less discharge and less vegetation coverage in drier phases under the restricted ITF condition.…”

“…Also, a GDGT-based temperature record at Site U1460 suggests cooling and weak ITF conditions at ∼0.65 Ma and ∼1.55 Ma, which were caused by lowering sea level and regional tectonic changes (Petrick et al, 2019). Temperature and primary productivity records at Site U1461 suggested prevailing warm, low-salinity, nutrient-deficient surface water, and thus a stronger LC under the restricted ITF after ∼1.2 Ma, tentatively suggesting a complex relation between the LC and the ITF (He et al, 2021). During the mid-to late Pleistocene with the weak ITF and the strong LC, a generally drier conditions in northwestern and southeastern Australia were recognized (McLaren & Wallace, 2010;Sniderman, 2011;Sniderman et al, 2016;Stuut et al, 2019).…”

“…Theoretically, sea level, vegetation coverage, and riverine discharge could be the major controllers on vegetational OC input. The global sea level started to de-HE AND WANG 10.1029/2021GL092745 4 of 9 Gray shadings indicate weak Indonesian Throughflow (ITF) events, including 0.8-0.6, 1.7-1.5, 2.7-2.5, and 3.7-3.4 Ma (Auer et al, 2019(Auer et al, , 2020Christensen et al, 2017;De Vleeschouwer et al, 2019;He et al, 2021;Petrick et al, 2019;Smith et al, 2020). crease after ∼3 Ma, moving Site U1461 closer to the shoreline (Figure 3d, De Boer et al, 2010).…”