In 1977, Be and Hudson wrote a significant article on the distribution of planktonic foraminifera in the Indian Ocean. They provided modern-day data on live collections for the entire ocean and established the ranges of salinities and temperatures for each of the 32 planktonic foraminifera based on 164 plankton tows. These authors also compared the live distribution of these foraminifera with the tests of the same species found on the sea floor in some 190 core tops, assuming they were of 'modern' age. More recent studies contributed to a discussion concerning the importance of seawater density on planktonic foraminifera distributions in the water column. These are discussed in detail. The Indian Ocean data are used to determine the range of water densities these foraminifera live in and an attempt is made here to determine the sea water densities the same foraminifera must have lived in during the Last Glacial Maximum (LGM) when surface seawater was at least 1 practical salinity unit higher as a result of a global sea level drop of some 125 m (compared with today), and oceanic temperatures had decreased significantly. Examination of planktonic foraminifera assemblages recovered from ten core tops and samples deposited during the LGM in the same cores from the Australian region in the Eastern Indian Ocean are used to evaluate if the distribution of those foraminifera had indeed been controlled by sea water density. In order to determine whether the Indian Ocean foraminifera at the LGM cores could live under high salinities, comparison is made with the distribution of live planktonic foraminifera in the Red Sea and the Gulf of Aden, as in these two 'restricted' areas salinity is extremely high due to intense evaporation. The contrasting foraminifera assemblages between modern and glacial conditions in all the Indian Ocean cores, with assumed density changes, clearly indicate that seawater density does not control the distribution of planktonic foraminifera. Instead, oceanic currents and oceanographic conditions such as nutrients and ephemeral upwelling as well as temperature changes, clearly affect the distribution of foraminifera when near-surface conditions change between interglacial and glacial conditions, especially concerning salinity. (c) 2025 Elsevier B.V. and Nanjing Institute of Geology and Palaeontology, CAS. This is an open access article under the CC BY license (http:// creativecommons.org/licenses/by/4.0/).

Living (Rose Bengal stained) benthic foraminifera were examined in multicore samples collected at depths ranging from 580 to 1,270 m from the Tasman Sea and southern margin of Australia. This study presents an initial overview of the deep-sea foraminifera living on these margins. Based on widely separated cores, there appears to be no correlation between foraminiferal abundance and species with ocean depth, seafloor grain size, oxygen availability, temperature, or particulate organic carbon. Although more work is needed, this study suggests environmental factors affect foraminiferal populations in a complex manner in the study area. The presence of species typical of shelf and shallow water environments in cores collected below 200 m water depth suggests a possible redistribution from shallower areas. In the ten samples from the 0-1 cm interval for the >150 mu m size fraction, 37 unique species were found. No more than four species overlapped across sites. Surprisingly, no significant correlations were observed egans, Uvigerina asperula, and Melonis affinis) and environmental parameters. Considerable environmental heterogeneity between sample sites, such as oxygen availability, grain size, and other factors associated with ocean circulation, is clearly evident. Based on observed assemblages, foraminiferal populations in the region appear influenced by dynamic and heterogeneous seafloor environments. This study serves as one of the few investigations of its kind to examine the ecology and diversity of contemporary deep-sea benthic foraminiferal communities along the southern and southeastern Australian margin, and highlights the potential ecological impacts of the heterogeneity and complexity of seafloor environments in the region. Additional work is necessary to further test and evaluate these hypotheses, and this research provides a foundation for future observations of living benthic foraminifera in the region.

We geochemically-fingerprinted a large set of sediments collected from potential source areas (PSAs) in southeastern and southcentral Australia and to compare these data with the record obtained from X-ray Fluorescence (XRF) scanning on a long deep-sea sediment core MD03-2607 obtained offshore Kangaroo Island, South Australia. The entire data set of samples collected on land as well as the downcore measurements were unmixed using the numerical end-member method AnalySize. In this approach, we successfully use the elements Al, Fe, K, Mn, S, Sr and Y to define end members. In addition, the on-land occurrences of the chemical ratios of Zr/Zn, Ti/Rb, Ti/Y and Zr/Rb are used to support the provenance of the chemical end-members. Three main PSA’s are defined: Murray River Basin (MRB), Darling River Basin (DRB) and Kati Thanda – Lake Eyre District (LED), of which the MRB is represented in two different chemical end members. The downcore contributions of these end members in the sediment core are consequently interpreted in terms of fluvial (MRB and DRB) versus aeolian (LED) input. Consequently, the downcore dominance of sediment-transport modes are interpreted in terms of river runoff versus aeolian input over the last 125 kyr. The downcore palaeoclimate proxies show a dominance of MRB during the interglacial intervals versus a dominance of both LED (dust) and DRB input during the glacial ones, suggesting increased seasonal contrasts during glacial austral winter. See: www.nioz.nl/dust

It is common practice nowadays to assess the presence of terrigenous (land-derived) sediments in deep-sea cores using bulk geochemical data, but the key issue is to identify the source of these sediments and the way they were transported to the core site in order to interpret their palaeoclimatic significance. Here, we demonstrate a new approach taken to geochemically-fingerprint a large set of sediments collected from potential source areas (PSAs) in southeastern and southcentral Australia and to compare these data with the record obtained from X-ray Fluorescence (XRF) scanning on a long deep-sea sediment core MD03-2607 obtained offshore Kangaroo Island, South Australia. The entire data set of samples collected on land as well as the downcore measurements were unmixed using the numerical end-member method AnalySize. We successfully use the elements Al, Fe, K, Mn, S, Sr and Y to define end members. In addition, the on-land occurrences of the chemical ratios of Zr/Zn, Ti/Rb, Ti/Y and Zr/Rb are used to support the provenance of the chemical end-members. Three main PSA's are defined: Murray River Basin (MRB), Darling River Basin (DRB) and Kati Thanda - Lake Eyre District (LED), of which the MRB is represented in two different chemical end members. The downcore contributions of these end members in the sediment core are consequently interpreted in terms of fluvial (MRB and DRB) versus aeolian (LED) input. We determined the origin of the terrigenous sediments recovered from the core for the last glacial-interglacial cycle, with implications for atmospheric circulation across southern Australia.

Context In total, 43 shallow waterbodies were sampled in 1983 in the vicinity of Casey Station and nearby islands in Antarctica. The following physico-chemical parameters were obtained: water and air temperature, pH, conductivity, dissolved oxygen, plus major and minor elements. Aims To identify the physico-chemical characteristics of these waters and determine their origin, and calculate their mineral saturation indices. Methods Waters were analysed using standard methods, including for some elements, flame-atomic absorption spectrometry, spectrophotometry, ion chromatography and gravimetric determination. Mineral saturation indices were calculated using the PHREEQ program. Key results Water salinities were generally low and in the range of 120–1200 mg L−1 (total dissolved solids, TDS), except for one site connected to the sea, and four slightly saline sites. The Na/Cl, Cl/Br and Ca/SO4 ratios of several waters were in the vicinity of seawater ratios, implying a contribution of marine aerosols. However, the Mg/Ca ratio of most waters departed from the seawater ratio, plus there was concordance between the molar ratios of (Na + K)/(Ca + Mg) of many of the waters sampled and those calculated from rock geochemical analyses from diverse lithologies. Such chemical ‘provincialism’ appears to be dictated by rock composition. Nitrate and phosphate concentrations were high in the vicinity of penguin rookeries. Conclusions Two sources of ions are identified, one as marine aerosols as shown by three sets of ratios (Na/Cl, Cl/Br and Ca/SO4) with known marine values, and the other from the weathering of local rocks as shown by (Na + K)/(Ca + Mg) of the lake waters compared to the same ratios for the surrounding rocks. Only a few waterbodies have saturation levels for several carbonate minerals (calcite, aragonite, dolomite and rhodochrosite). Implications Future work is recommended for monitoring the waterbodies surrounding Casey Station as a result of the increased atmospheric CO2 concentration that has occurred over the past 40 years, and likely also with the cessation of building activities around Casey Station.

The continuous record offered by deep-sea sediments has been extensively used to constrain shifting continental and oceanographic conditions. Yet, past fluctuations in deep-sea benthic conditions and bottom-currents are in numerous parts of the globe scarcely documented, one such example being the South Australian margin. Indeed, though variations in surface water masses and continental aeolian dust and river outflow are well documented in the area, little is known about benthic environments and their dynamics during the last interglacial-glacial cycle. We focus here on benthic foraminiferal assemblages sampled from a sediment core recovered at 2420 m depth from a small plateau south of Kangaroo Island within the underwater Murray Canyons Group (South Australian margin). Benthic foraminiferal assemblages show a distinct separation between interglacial and glacial periods over the last 94 ka, and indicate that the benthic environment was well-ventilated and oligotrophic during glacial periods, whilst being rather marked by reduced oxygenation associated to higher food input during the Holocene and Marine Isotope Stage 5a-c. We demonstrate that autochtonous deep-sea benthic foraminiferal communities neither respond to changes in the Murray River's discharges, nor do they follow variations in aeolian dust input from South Australia. Instead, the deep-sea and the terrestrial realm appear decoupled. Moreover, our obser-vations suggest that bottom-water slope currents were stronger during the Holocene and Marine Isotope Stage 5a-c. We propose that this strengthening was triggered by an intensification of the poleward-circulating deep eastern boundary current transporting carbon-rich Indian Deep Water. In contrast, glacial seafloor conditions, especially during the Last Glacial Maximum, may reflect a greater influence and a shoaling of oxygen-rich Antarctic Bottom Water of South Australia. This bottom-water shift would follow the northward displacement of the Subtropical and Subantarctic Fronts and coincide with a withering influence of the Leeuwin Current within surface waters.

The timing and cause of megafaunal extinctions are an enduring focus of research interest and debate. Despite the developments in the analysis of coprophilous fungal spores (CFS), the proxy for reconstructing past megaherbivore changes, the environmental consequences of this fauna loss remain understudied. This is partly due to the general obscurity of such a signal in pollen records, as well as limitations in disentangling human and extinction ecological impact, and the lack of spatial information of megafauna changes in site-level sedimentary records. In Australia, the debate centres on the possibility that habitat loss through climate change, vegetation-fire change, human intervention, or a combination of these factors led to the extinction of some large animals during the Late Pleistocene. Pollen and plant isotope studies have also demonstrated that vegetation-fire responses following the Late Pleistocene megafaunal extinctions were characterized by increased vegetation density and fire activity due to reduced grazing/browsing pressure. Here, we use a well-dated marine sedimentary core record from the Murray Darling Basin in southern Australia and apply palynological and functional palaeoecological approaches to reconstruct the Late Pleistocene megafaunal abundance changes, the timing and potential cause of extinction across the basin and investigate if extinction was associated with any signal of trait-based vegetation changes. We infer megafaunal abundance changes from the abundance of CFS and compare this with climatic proxies from the same core. We then link modern observations of fruit, seed and fire response traits of plant genera within the basin to the fossil pollen record to reconstruct palaeo vegetation community traits and determine if extinction was associated with any changes in plant community trait composition. Closely-spaced 14C dates obtained from planktonic foraminifera and δ18O tie points place a major decline in CFS, and thus the timing of extinction, within the basin at ∼43.3 ka. While climate-driven environmental changes largely controlled megafaunal presence, human arrival and frequent landscape burning are considered the most likely primary cause of extinction or, at the very least, megafauna decline in the Murray Darling Basin. We also found that the proposed period of megafaunal decline was also accompanied and followed by a decline in the prevalence of plants with larger seeds and fruits that were likely to have been once dispersed by megaherbivores. Our study supports the idea of a human-driven megafaunal extinction in mainland Australia and that the extinction caused changes in vegetation due to reduced plant dispersal and herbivory. However, high fire activity primarily linked to these vegetation changes was not observed, as humans were already practicing landscape burning before the period of megafaunal extinction and likely continued to do so afterward.

Arc-continent collision in Southeast Asia during the Neogene may have driven global cooling through chemical weathering of freshly exposed ophiolites resulting in atmospheric CO 2 removal. Yet, little is known about the cause-and-effect relationships between erosion and the long-term evolution of tectonics and climate in this region. Here, we present an 8-million-year record of seawater chemistry and sediment provenance from the eastern Indian Ocean, near the outflow of Indonesian Throughflow waters. Using geochemical analyses of foraminiferal shells and grain size–specific detrital fractions, we show that erosion and chemical weathering of ophiolitic rocks markedly increased after 4 million years (Ma), coincident with widespread island emergence and gradual strengthening of Pacific zonal sea-surface temperature gradients. Together with supportive evidence for enhanced mafic weathering at that time from re-analysis of the seawater 87 Sr/ 86 Sr curve, this finding suggests that island uplift and hydroclimate change in the western Pacific contributed to maintaining high atmospheric CO 2 consumption throughout the late Neogene.

210 Pb and 137 Cs dating of bulk sediments obtained from the alpine Blue Lake, located in the Snowy Mountains of southeastern Australia, was applied here to date recent lacustrine sediments. In addition, the presence of Pinus pollen (a taxon introduced in Australia about 150 years ago) down to a sediment depth of 56 cm in the core is used to obtain a chronology for the upper part of the core. Accelerated Mass Spectrometry radiocarbon dates obtained from organic muds from the same core do not agree with the chronology constructed using the three other dating techniques. In addition, optically stimulated luminescence (OSL) dating of single quartz grains, from sediment-core samples collected from the same lake, was applied to date recent lacustrine sediments. The optical age of 185 ± 20 years for a sample at 60–62 cm depth, and 470 ± 50 years at 116–118 cm depth are well over 1000 years younger than the ages inferred from radiocarbon dates. We therefore infer that the ‘old’ radiocarbon ages result from carbon stored for considerable time within the catchment prior to its transport and deposition on the lake floor. As plant decomposition occurs at much slower rates in high altitude environments, these results bring into question the veracity of previously published radiocarbon dates from Blue Lake and alpine lake sediments in general. The deposition ages inferred from the 210 Pb- 137 Cs and OSL dating, and the first appearance of Pinus pollen, indicate that for the 100-year period after European settlement (from the mid 1800s to early 1900s) the sediment-accumulation rate increased by a factor of about 2, from 0.19 ± 0.01 cm yr −1 to 0.35 ± 0.02 cm yr −1 . In the 1900s the accumulation rate increased further to 0.60 cm yr −1 . The accumulation rate was particularly rapid in the 20-year period from 1940–1960, reaching a rate 18 times higher than the pre-European rate in the mid-1950s. The increase in sedimentation rate is attributed to changes in land use resulting from European activities in the lake catchment, primarily through sheep and cattle grazing in the Blue Lake catchment.

The morphology and development of several submarine canyons offshore southeast South Australia and western Victoria are described. The existence of three of those canyons had been foreshadowed in 1963 by N. Boutakoff, who thought them to be linked to ancient courses of the Glenelg River. These canyons occur on the outer continental shelf where their heads are situated in depths shallower than 1000 m. Sinuous channels are visible within two of the canyon heads, indicating that water and sediment may still travel downslope and cause erosion, and thus are geologically recent. Several other canyons are also documented and named. Two canyons are confined to depths below 3000 m; they may be much older and seem not to be linked to ancient river courses. They are also oblique to the upper canyons. The other characteristic feature of the area is the presence of numerous undersea slides. These occur at three specific depths (similar to 1200, similar to 1500 and similar to 1800 m) and are coincident with stratigraphic horizons in which continental groundwater flows have been identified in adjacent exploratory oil and gas wells drilled into the continental shelf. Sapping of groundwater may likely have occurred during very wet periods inland. We suggest that these undersea slides could be the first step in the formation of deep-sea canyons that are not necessarily linked to ancient river courses. We also postulate that the 'sliding' of large piles of sediment down the continental slope has tsunamigenic potential and may have occurred during significant wet climate on land.

Reconstructions of ocean oxygenation are critical for understanding the role of respired carbon storage in regulating atmospheric CO 2 . Independent sediment redox proxies are essential to assess such reconstructions. Here, we present a long magnetofossil record from the eastern Indian Ocean in which we observe coeval magnetic hardening and enrichment of larger, more elongated, and less oxidized magnetofossils during glacials compared to interglacials over the last ~900 ka. Our multi-proxy records of redox-sensitive magnetofossils, trace element concentrations, and benthic foraminiferal Δδ 13 C consistently suggest a recurrence of lower O 2 in the glacial Indian Ocean over the last 21 marine isotope stages, as has been reported for the Atlantic and Pacific across the last glaciation. Consistent multi-proxy documentation of this repeated oxygen decline strongly supports the hypothesis that increased Indian Ocean glacial carbon storage played a significant role in atmospheric CO 2 cycling and climate change over recent glacial/interglacial timescales.

Close examination of key and well-dated Holocene sites, both on land and at sea in the Australian region indicates that at the very beginning of the Holocene, as a result of strong westerlies, there must have been a continuous positive Southern Annular Mode (SAM). Following from that, the entire region switched to a negative SAM scenario and, during that time, the westerlies must have retreated further south. Afterwards, a period of time spaning ∼8200 to ∼5500 years ago temperatures were higher than today. We refer to it as the Holocene Hyspithermal. Coincident to this period, lake levels and postulated rainfall were extraordinarily high and vegetation spectra in places very different compared to today. The extent of this period varies by a few centuries between sites, but this may result from the level of resolution and also appears to be controlled by latitude. There is also clear indication that the influence of the westerlies was reduced over Australia during those two and a half millennia. Nevertheless, air temperatures recognised in Antarctic ice cores are at the opposite to those recognised in Australia. In addition, during the Australian Holocene Hypsithermal, CO2 levels were at their lowest in Antarctic ice cores. Climatic conditions then progressively deteriorated everywhere a bit after ∼6000 years BP until recent times as ENSO signals with alternating El Niño and La Niña conditions across the entire Pacific region as already described by Perner et al. (2018) based on the same cores studied here. Brief mention is also made to the presence of humans in SE Australia during the Holocene. It seems that human activities changed well after the period of high temperatures and rainfall, with more sedentary activities along the major rivers, with an enhancement of food production in organized settings suggestive of villages.

Details of the post-embryonic development of two Notodromadidae species, Notodromas trulla Smith Kamiya, 2014 and Newnhamia fenestrata King, 1855, (subfamily Notodromadinae) are provided, and compared with previous ontogenetic studies on other podocopid families and superfamilies. The ontogenetic development is generally similar to other families, consisting of eight free-living juvenile stages and one adult stage, but the first instar, with a leg-like mandible, resembles that of the Cyprididae, rather than other families. From the A-7 instar onwards, the ventral margin of the carapace is a flattened ovoid, and the dorsolateral eye cups are separated, resembling those of the adults, suggesting that a neustonic lifestyle, similar to that of the adults, is embraced from a very early age. In addition to the ventral margin, other apomorphies of the Notodromadinae include spur-like protrusions on the walking legs of juveniles, which become reduced in adults, and features of the mandibles, probably related to neustonic feeding. Overall, Ne. fenestrata has more plesiomorphic features than No. trulla, and most differences between the two species are related to sexually selected characters, such as different sexually dimorphic features of the antennae. This suggests that sexual selection has been the main evolutionary driving force causing morphological divergence in the subfamily. The two taxa, one from Japan (No. trulla), the other Australia (Ne. fenestrata), have perhaps been separated since the breakup of Pangaea, which started in the Middle Jurassic. This suggests that despite the long geographical isolation, many aspects of ostracod anatomy have remained unchanged over long periods of time. On reviewing the taxonomy of the family, we conclude that monophyly needs to be confirmed with further work, and the subfamily Notodromadinae can be divided into two groups: the Notodromas-group and the Newnhamia-group.

Our recent ice sheet reconstruction, PaleoMIST 1.0, was created on the basis of using near-field (i.e., ice sheet proximal) geological constraints.This was done so that it would be independent of far-field relative sea level observations, that are subject to uncertainties in the global distribution of ice, and deep sea proxy based global mean sea level reconstructions, which have large uncertainties due to temperature and salinity effects.We do not disagree with the interpretation of the farfield data highlighted by Yokoyama et al., but emphasise that near-field constraints should be the starting point for reconstructing ice sheets.We thank Yokoyama et al. for the opportunity to further discuss our ice sheet and paleotopography reconstruction, PaleoMIST 1.0 1 and acknowledge their extensive work acquiring sea level proxy data.Yokoyama et al. state: community efforts have led to better understanding of the GMSL (e.g., PALSEA).We agree, and this is why we provided a comparison of our modelled sea level against scrutinised paleo relative sea level proxies for over 150 regions 2 , primarily taken from databases assembled by the HOLSEA project 3 .We focused on including datasets that we used to reduce the misfit with modelled near-field relative sea level in North America 4,5 and Europe 6-8 .We included a far-field dataset from southeastern Asia 9 and selected locations in tropical regions based on a database of coral relative sea level proxies 10 , including Tahiti and the Huon Peninsula.This modeldata comparison was used to justify the Earth model used in our reconstruction.No standardised database exists for the LGM, so we entered data from a few well known far-field areas to test if the ice sheet volume in our reconstruction was reasonable.This was neither claimed nor meant to be a comprehensive review, and we unintentionally missed adding some data from the Bonaparte Gulf 11 .We do dispute the

A palynological record spanning the last glacial-interglacial period was derived from high-resolution, deep-sea core MD03-2607, located near Kangaroo Island in South Australia. The core site lies opposite the mouth of the River Murray that, together with the Darling River, drains the extensive (similar to 1.6 x 10(6) km(2)) Murray-Darling Basin (MDB). The record comprises 120 samples and is compared with detailed records of sea-surface temperature (SST), the C-3/C-4 plant ratio obtained from the delta C-13 of n-alkanes from leaf waxes, the fluvial clay fraction and its neodymium isotopic composition, airborne dust and the biomass-burning component levuglosan. The chronology of the core is robust; it is built on 24 radiocarbon dates derived from planktic foraminifera, 16 optically stimulated luminescence dates, plus 12 tie points linked to the astronomically tuned marine isotopic record. Algal remains are found in nearly all samples supporting our postulation that the palynoflora is predominantly waterborne. Major findings are that the gymnosperm Callitris, together with high percentages of herb pollen (mostly C-3 plants), is predominant during cold, arid phases, whereas Eucalyptus, is predominant during warmer and wetter periods. High charcoal concentration coincides with high percentages of Eucalyptus, mostly during wet and warm periods. Using the geochemistry of the core's fluvial sediments, it has been possible to identify when water-transported palynoflora and charcoal originated from the Murray sub-basin (consisting of the River Murray and its main tributaries but not from central or western South Australia). During those periods, rainfall principally originated from the southeastern Indian Ocean. When the Darling sub-basin was the main source of the palynoflora, rainfall must have instead originated from northern Australia. The eolian dust record from the core shows that the dust signal generally coincides with the increased values in herb pollen, in particular during the Last Glacial Maximum (LGM) when, in addition to high herb percentages, Callitris representation also increased. This dry landscape taxon likely colonised the then-exposed Lacepede Shelf during this period of extreme low sea-level. There is a good correspondence between SST and mean annual precipitation reconstructed from the pollen counts. During warm phases in the ocean, Eucalyptus was the dominant tree taxon, especially for the entirety of Marine Isotope Stages (MIS) 5, plus MIS 3 and MIS 1. Charcoal levels were particularly low during the dry phases MIS 4 and 2, and even more so during the LGM.

AbstractNorthern and southern hemispheric influences—particularly changes in Southern Hemisphere westerly winds (SSW) and Southern Ocean ventilation—triggered the stepwise atmospheric CO2increase that accompanied the last deglaciation. One approach for gaining potential insights into past changes in SWW/CO2upwelling is to reconstruct the positions of the northern oceanic fronts associated with the Antarctic Circumpolar Current. Using two deep-sea cores located ~600 km apart off the southern coast of Australia, we detail oceanic changes from ~23 to 6 ka using foraminifer faunal and biomarker alkenone records. Our results indicate a tight coupling between hydrographic and related frontal displacements offshore South Australia (and by analogy, possibly the entire Southern Ocean) and Northern Hemisphere (NH) climate that may help confirm previous hypotheses that the westerlies play a critical role in modulating CO2uptake and release from the Southern Ocean on millennial and potentially even centennial timescales. The intensity and extent of the northward displacements of the Subtropical Front following well-known NH cold events seem to decrease with progressing NH ice sheet deglaciation and parallel a weakening NH temperature response and amplitude of Intertropical Convergence Zone shifts. In addition, an exceptional poleward shift of Southern Hemisphere fronts occurs during the NH Heinrich Stadial 1. This event was likely facilitated by the NH ice maximum and acted as a coup-de-grâce for glacial ocean stratification and its high CO2capacitance. Thus, through its influence on the global atmosphere and on ocean mixing, “excessive” NH glaciation could have triggered its own demise by facilitating the destratification of the glacial ocean CO2state.

Clay mineral-bearing mudstones are a prominent component of ancient fluvial-lacustrine deposits, 100s of meters thick, documented by the Mars Science Laboratory (MSL) rover, in Gale crater, Mars. Most of the clay minerals documented by MSL are hypothesized to have formed in situ, at or close to the time of deposition ∼3.5 Ga ago, by aqueous alteration of basaltic detritus. Here we study the mechanisms, controls, and timescales of clay mineral authigenesis in a series of lakes with a wide range of water chemistries from the Western Volcanic District, Victoria, SE Australia, as an analog to the Gale crater mudstones. X-ray diffraction (XRD) analysis reveals that the sediments of most of the Western Volcanic District lakes studied contain mixtures of kaolinite, illite, mixed-layer illite-smectite (I-S), and dioctahedral smectite clay minerals. Comparisons of this mineral assemblage with regional soils and creek bedload material confirm previous assertions of significant inputs of detrital clay minerals into the lakes. A trioctahedral clay mineral phase is also detected, making up to 39 wt.% of bulk sediments. The abundance of trioctahedral clay minerals correlates with contemporary lake hydrology and proxies for past lake water Mg concentration. This indicates in situ formation of trioctahedral clay minerals by the uptake of Mg and Si from lake waters and pore fluids at rates determined by local physico-chemical conditions. Examination of crater lake sediments, where detrital clay mineral input is minimized, demonstrate that neoformed trioctahedral clay minerals are poorly crystalline trioctahedral smectites. Neoformation of trioctahedral smectites also occurs in lakes where detrital clay minerals are more abundant. However, an additional authigenic transformation process is indicated by the proportions of Mg and Si added to detrital clay minerals as well as evidence for the uptake of K from lake waters. The transformation process probably involved the incorporation of Mg into the octahedral sheets of detrital clay minerals, leading to irreversible uptake of K into interlayer sites (illitization). The distribution of trioctahedral smectites and radiocarbon ages from sediment cores show that clay mineral authigenesis occurred before sediment consolidation, on timescales of years to 100s of years. These results support syndepositional interpretations of analogous Mg-rich clay minerals documented by MSL, and their use as proxies for chemical conditions in ancient Gale lakes. In comparison with the Western Volcanic District lakes, clay mineral-bearing lacustrine mudstones from Gale crater exhibit only modest chemical weathering of basaltic detrital materials and rarely contain carbonate minerals in quantities detectable by XRD. These observations highlight significant differences in weathering regimes and regolith mineralogy on ancient Mars that could be linked to lake catchment geomorphology, climate, atmospheric CO2 content, and the absence of biotic processes on Mars.

The year 2020 marked the 200th anniversary of European settlers first encountering the 'noble expanse of water' of Lake George in New South Wales. Since 1820, unofficial observations and official measurements of the lake's water-level have been recorded almost continuously by various individuals, research teams, government departments and private companies. The lake's recent hydrographic history has been characterised by periods of flood and drought, which correspond with the prevailing climate conditions of SE Australia. This is the longest water-level record of its sort in the Southern Hemisphere and hence of great scientific and historic value. Here, we have compiled all available historic water-level data for Lake George, referenced them to common datums and presented a methodology for continuing the record using satellite imagery in lieu of on-site measurements.

A review is provided of first-documented occurrences of dust transport within Australia for the last century, but which later on were considerably improved as a result of access to satellite observations and extensive ground observations. This was followed by the use of the HYSPLIT tracking models that enabled people to determine the major sources of dust in Australia. As a result of several important studies, the Lake Eyre Basin in central Australia is now considered to be the main source of dust entrainment, although other regions do contribute to dust production. This is followed by examination of the occurrence over the last few decades of dust transport and deposition within Australia and across the Tasman Sea, with dust being deposited even as far as New Zealand. After that, consideration is given to the deposition of dust not only at sea around Australia but also in New Zealand during the Holocene and Late Quaternary. As a consequence of these observations, a shift in the direction of dust plumes exiting Australia is noted. For example, during the Last Glacial Maximum (LGM), a substantial northerly shift of the Trans-Tasman dust plume is recorded and this coincides with stronger westerlies and an equatorward shift of oceanic fronts such as the Intertropical Convergence and Subpolar and Antarctic Fronts that were located closer to Australia compared to today. Strengthening of the winds during the LGM may have prevented dust plumes from travelling over the southern part of the Tasman Sea, even perhaps reaching Antarctica. Examination of the dust components in cores in the western Pacific Ocean would address this question. The second part of the paper examines the geochemical fingerprints of dusts from Australia, South America and those recovered from Antarctic ice cores. Examination of atmospheric conditions that prevailed in the Southern Ocean around Antarctica during a major dust storm event that occurred in Australia in October 2002 helps identify how dust can be entrained around cold fronts and eventually reach the Antarctic mainland. Once again, it appears that Australian dust did travel as far as Antarctica more frequently during the Holocene, than prior to that time. New Zealand as a dust source to some Antarctic sites is also discussed. Examination of the isotopic fingerprints in Antarctic ice cores point to South America being the main source of dust during the Last Glacial Maximum and previous glacial periods, with intermittent occurrences likely to have come from Australia and New Zealand as well. It is postulated that Australian dust plumes did travel mostly over the Tasman Sea, and eventually over the western Pacific Ocean during the LGM, and frequently less so towards Tasmania and the Southern Ocean as a result of the strengthening of the westerlies and their northward shift. It transpires that the dust flux from Australia was much higher during the glacial periods. It appears also that the dust plumes that traverse the eastern Indian Ocean remained unchanged during the LGM. Finally, this paper concludes by identifying that there is a need to either obtain larger dust samples from ice cores, or use more elaborate analytical techniques to combine more than two isotopes to fingerprint the origin of dusts recovered in ice cores. Perhaps a combination of not only isotopes, but also rare earth elements and major elements would eventually provide a better definition of atmospheric circulation in the Southern Hemisphere for comparison between glacial and interglacial periods.