School of Geography, Earth and Atmospheric Sciences - Research Publications
Now showing items 1-36 of 222
Meso‐ and micro‐scale response to variation in cloudiness at three forested sites in the Maritime Continent
This study examines the relationships between the diurnal precipitation cycle, local morning insolation, and local and large-scale moisture availability using local radiative flux and precipitation observations from three forested tropical sites, together with ERA5 reanalysis data. Our results suggest that, away from the coast, there is a weak positive correlation between local morning insolation and the magnitude of the afternoon precipitation peak, and a weak negative relationship between locally observed surface moisture in the morning and the magnitude of the afternoon precipitation peak. There is little relationship between large-scale column moisture and the local afternoon precipitation peak. We examine analogous results in convection-permitting simulations. Results suggest that the simulated afternoon precipitation rate shows almost no dependence on surface radiative forcing or moisture availability, while the observed afternoon precipitation rate is dominated by radiative forcing. Simulated and observed satellite precipitation and cloud estimates for a single case study suggest a diversity of surface-flux–precipitation relationships amongst model configurations.
Seeking Justice through Interdisciplinary Environmental Education at Postgraduate Level: Lessons from Melbourne, Australia
(Universidad Autónoma de Madrid, 2018-05-18)
Masters degrees that offer a broad understanding of environmental issues have been taught in universities since the 1960s. As the problems, they address have increased in severity and become global in scale and reach, higher education offerings have flourished accordingly. Today, environmental Masters degrees offer a variety of specializations, are often embedded within university environmental institutes or centers, and they lead thousands of students into environmental careers, as activists, advocates, policymakers, technicians, resource managers, and researchers. They provide an opportunity to understand and critically debate mainstream concepts, like sustainability, the green economy, ecological resilience, environmental services, and good governance. The severity of environmental crises also requires a more radical curriculum: critiques of economic growth (including green growth), social and environmental justice, and the political ecology of unequal access to resources. In light of these complex demands and growing opportunities for environmental programs to address social and environmental justice, we discuss a unique and successful model for interdisciplinary environmental Masters teaching at a large Australian university that has juggled promotion of justice in its program along with meeting financial targets imposed by the neoliberal regime prevalent in Australia's underfunded higher education sector. The program has a distinctive approach to interdisciplinary learning, permitting a very wide range of student choice, and unified teaching efforts across ten Faculties. This has required agile administration, and strong defense of an unusual approach to the management of environmental pedagogy. The Master of Environment program illustrates how taught postgraduate programs can offer an alternative space for personal, institutional and environmental commitment to social and environmental justice.
Ethical choices behind quantifications of fair contributions under the Paris Agreement
(NATURE RESEARCH, 2021-04-01)
The Parties to the UNFCCC and Paris Agreement agreed to act on the basis of equity to protect the climate system. Equitable effort sharing is an irreducibly normative matter, yet some influential studies have sought to create quantitative indicators of equitable effort that claim to be value-neutral (despite evident biases). Many of these studies fail to clarify the ethical principles underlying their indicators, some mislabel approaches that favour wealthy nations as ‘equity approaches’ and some combine contradictory indicators into composites we call derivative benchmarks. This Perspective reviews influential climate effort-sharing assessments and presents guidelines for developing and adjudicating policy-relevant (but not ethically neutral) equity research.
Climate policy decision making in contexts of deep uncertainty-from optimisation to robustness
(ELSEVIER SCI LTD, 2021-06-01)
Integrated assessment models are often used to evaluate the role of different technologies in meeting global climate goals. Such models have been criticised for failing to address the deep uncertainties and plurality of values that are fundamental to energy transitions. One consequence is that model scenarios overwhelmingly depend on large-scale carbon dioxide removal to hold warming to below 2 °C. Here we propose an alternative approach using Scenario-Focused Decision Analysis (SFDA) as methods that embrace decision making under deep uncertainty. SFDA can accommodate a range of value sets and perspectives, and most importantly can integrate value-based decision-making in designing climate policy. We specifically consider Robust Decision Making (RDM) as an exemplar of SFDA for developing climate policy. We outline an iterative five-stage framework for RDM using the role of carbon dioxide removal in long-term mitigation pathways as an example. The five steps comprise (i) participatory definition of goals, values, potential policy options and uncertainties; (ii) modelling the performance of policy portfolios across a wide range of future scenarios; (iii) visualisation and identification of portfolio vulnerabilities; (iv) analysis of trade-offs; and (v) development of policy strategies. SFDA, and specifically RDM, provide untapped opportunities for diverse actors to explore alternative mitigation pathways and evaluate the robustness of climate policy choices through “deliberation with analysis”. In relation to carbon dioxide removal methods, RDM provides a framework for evaluating their potential for safely meeting climate goals in a societally acceptable manner.
Inequalities through the lens of science
(Cell Press, 2021-10-22)
Inequalities are ubiquitous in every society on Earth, and the COVID-2019 pandemic has exposed the marginalized communities that suffer the most. A warming planet will only magnify this gap. On the eve of the 26th session of the Conference of the Parties to the UNFCCC, this Voices asks: how can science inform and address inequalities?
Geology, geochemistry and depositional history of the Port Campbell Limestone on the eastern flank of the Otway Basin, southeastern Australia
(Taylor and Francis, 2021)
A fully cored sequence of Hesse Clay, Port Campbell Limestone and uppermost Gellibrand Marl in the onshore Otway Basin, southeastern Australia, offers new insight into the evolution of the middle Miocene Port Campbell Limestone. The Port Campbell Limestone comprises grey unconsolidated to semi-consolidated and rarely lithified bioclastic muddy carbonate sands in a stack of thin repetitive cycles within cycles of predominantly shoaling-upward character. A glauconitic band with a distinctive mollusc–echinoderm–bryozoan fauna provides a distinctive marker interval in the sequence. In mineralogy, the Port Campbell Limestone is predominantly calcite with traces of remnant aragonite in muddier low-permeability sands, and with dolomitic zones in permeable intervals. The small non-carbonate component of the Port Campbell Limestone is between 3 and 15 wt% and comprises quartz silt with minor clay, feldspar and mica. Dissolution overprints are prominent throughout the carbonate sequence. Three distinct geochemical signatures of provenance are evident in the Port Campbell Limestone sequence, including possible volcanogenic contributions with felsic sources. Foraminifera are common and generally well preserved. Foraminiferal data suggest a depositional transition from outer shelf conditions in the Gellibrand Marl at ca 15 Ma to middle shelf environments in the lower part of the Port Campbell Limestone during the Middle Miocene Climatic Optimum (MMCO) at ca 14.24 Ma. Shallowing after 14 Ma indicates variable paleodepths of <70 m during and following the end of the Middle Miocene Climatic Transition (MMCT) at ca 13.2 Ma when the sequence was emergent for a brief but undetermined period, corresponding with sharp changes in geochemical ratios. Observed cyclicity in these mid-shelfal, cold-water carbonates is strongly correlated with orbital forcings—eccentricity and obliquity. Sedimentation rates determined from cyclostratigraphic analysis indicate 4–6 cm/kyr at the end of the MMCO, diminishing to 1.5–3 cm/kyr during the MMCT and the subsequent accumulation of the Port Campbell Limestone.
Irrigator relations with water in the Sunraysia region, northwestern Victoria
Irrigated agriculture faces significant challenges under climate change, and may not be feasible in parts of the Murray–Darling Basin beyond 2050. Recent research into the cultural politics of water has paid limited attention to the water cultures and relations of irrigators in Minority World countries. We analyse the water relations of grape farm irrigators in the Sunraysia region of Victoria, using interviews and farm tours undertaken between 2014 and 2016. Findings are summarised under five themes: (1) the sociality of irrigation water, (2) temporal and spatial relations, (3) the risk of rain, (4) the micro-scale of water knowledge, and (5) environment as actor. These themes shed light on the diverse relations that constitute both environmental and irrigation water. Irrigators are embedded in these relations at multiple scales, local and distant, mediated by technology and infrastructure. The scale of our focus makes visible water and other environmental knowledge that often goes unnoticed in broader debates over irrigation. The concept of “the environment”, understood as an embodied actor in policy discourse and by irrigators, is an emergent trend that warrants ongoing research attention.
The indirect response of an aquatic ecosystem to long-term climate-driven terrestrial vegetation in a subalpine temperate lake
Aim To assess whether climate directly influences aquatic ecosystem dynamics in the temperate landscape of Tasmania or whether the effects of long‐term climatic change are mediated through the terrestrial environment (indirect climate influence). Location Paddy's Lake is located at 1065 m a.s.l. in temperate north‐west Tasmania, a continental island south‐east of mainland Australia (41°15–43°25′ S; 145°00–148°15′ E). Methods We developed a new 13,400 year (13.4 kyr) palaeoecological dataset of lake sediment subfossil cladocerans (aquatic grazers), bulk organic sediment carbon (C%) and nitrogen (N%) and δ13C and δ15N stable isotopes. Comparison of this new data was made with a recently published pollen, geochemistry and charcoal records from Paddy's Lake. Results Low cladoceran diversity at Paddy's Lake is consistent with other temperate Southern Hemisphere lakes. The bulk sediment δ15N values demonstrate a significant lagged negative response to pollen accumulation rate (pollen AR). Compositional shifts of dominant cladoceran taxa (Bosmina meridionalis and Alona guttata) occur following changes in both pollen AR and pollen (vegetation) composition throughout the 13.4 kyr record at Paddy's Lake. The δ15N values demonstrate a significant positive lagged relationship to the oligotrophic:eutrophic cladoceran ratio. Main conclusions Long‐term changes in cladoceran composition lag changes in both pollen AR and terrestrial vegetation composition. We interpret pollen AR as reflecting climate‐driven changes in terrestrial vegetation productivity and conclude that climate‐driven shifts in vegetation are the principal driver of the cladoceran community during the last ca. 13.4 kyr. The significant negative lagged relationship between pollen AR and δ15N reflects the primary control of vegetation productivity over within‐lake nutrient status. Thus, we conclude that the effects of long‐term climate change on aquatic ecosystem dynamics at our site are indirect and mediated by the terrestrial environment. Vegetation productivity controls organic soil development and has a direct influence over lake trophic status via changes in the delivery of terrestrial organic matter into the lake.
Exhumed lateral margins and increasing flow confinement of a submarine landslide complex
Submarine landslides, including the basal shear surfaces along which they fail, and their subsequent infill, are commonly observed in modern seabed and seismic reflection data sets; their resultant relief impacts sediment routing and storage patterns on continental margins. Here, three stacked submarine landslides are documented from the Permian Ecca Group, Laingsburg depocentre, Karoo Basin, South Africa, including two superimposed lateral margins. The stratigraphic framework includes measured sections and correlated surfaces along a 3 km long, 150 m high outcrop. Two stacked 2·0 to 4·5 km wide and 90 m and 60 m deep erosion surfaces are recognized, with lateral gradients of 8° and 4°, respectively. The aim of this study was to understand the evolution of a submarine landslide complex, including: evolution of basal shear surfaces/zones; variation of infill confinement; and location of the submarine landslides in the context of basin-scale sedimentation and degradation rates. Three stages of formation are identified: (i) failure of submarine landslide 1, with deposition of unconfined remobilized deposits; (ii) failure of submarine landslide 2, forming basal shear surface/zone 1, with infill of remobilized deposits and weakly confined turbidites; and (iii) failure of submarine landslide 3, forming basal shear surface/zone 2, with infill of remobilized deposits and confined turbidites, transitioning stratigraphically to unconfined deposits. The expression of basal shear varies laterally, from metres thick zones in silt-rich strata to sharp stepped surfaces in sand-rich strata. Faulting and rotation of overlying bedding suggest that the shear surfaces/zones were dynamic. Stacking of landslides resulted from multi-phase slope failure, increasing down-dip topography and confinement of infilling deposits. The failure slope was probably a low supply tilted basin margin evidenced by megaclast entrainment from underlying basin-floor successions and the lack of channel systems. This study develops a generic model of landslide infill, as a function of sedimentation and degradation rates, which can be applied globally.
Pollen-derived biomes in the Eastern Mediterranean-Black Sea-Caspian-Corridor
AIM: To evaluate the biomization technique for reconstructing past vegetation in the Eastern Mediterraneanâ Black Seaâ Caspianâ Corridor using an extensive modern pollen data set and comparing reconstructions to potential vegetation and observed land cover data. LOCATION: The region between 28â 48Â°N and 22â 62Â°E. METHODS: We apply the biomization technique to 1,387 modern pollen samples, representing 1,107 entities, to reconstruct the distribution of 13 broad vegetation categories (biomes). We assess the results using estimates of potential natural vegetation from the European Vegetation Map and the Physicoâ Geographic Atlas of the World. We test whether anthropogenic disturbance affects reconstruction quality using land use information from the Global Land Cover data set. RESULTS: The biomization scheme successfully predicts the broadscale patterns of vegetation across the region, including changes with elevation. The technique discriminates deserts from shrublands, the prevalence of woodlands in moister lowland sites, and the presence of temperate and mixed forests at higher elevations. Quantitative assessment of the reconstructions is less satisfactory: the biome is predicted correctly at 44% of the sites in Europe and 33% of the sites overall. The low success rate is not a reflection of anthropogenic impacts: only 33% of the samples are correctly assigned after the removal of sites in anthropogenically altered environments. Open vegetation is less successfully predicted (33%) than forest types (73%), reflecting the underâ representation of herbaceous taxa in pollen assemblages and the impact of longâ distance pollen transport into open environments. Samples from small basins (<1Â kmÂ²) are more likely to be reconstructed accurately, with 58% of the sites in Europe and 66% of all sites correctly predicted, probably because they sample an appropriate pollen source area to reflect regional vegetation patterns in relatively heterogeneous landscapes. While methodological biases exist, the low confidence of the quantitative comparisons should not be overâ emphasized because the target maps themselves are not accurate representations of vegetation patterns in this region. MAIN CONCLUSIONS: The biomization scheme yields reasonable reconstructions of the broadscale vegetation patterns in the Eastern Mediterraneanâ Black Seaâ Caspianâ Corridor, particularly if appropriateâ sized sampling sites are used. Our results indicate biomization could be used to reconstruct changing patterns of vegetation in response to past climate changes in this region.
Evolution of sandstone peak-forest landscapes - insights from quantifying erosional processes with cosmogenic nuclides
(John Wiley and Sons, 2018-03-15)
The sandstone peak-forest landscape in Zhangjiajie UNESCO Global Geopark of Hunan Province, China, is characterized by >3000 vertical pillars and peak walls of up to 350 m height, representing a spectacular example of sandstone landform variety. Few studies have addressed the mechanisms and timescales of the longer-term evolution of this landscape, and have focused on fluvial incision. We use in situ cosmogenic nuclides combined with GIS analysis to investigate the erosional processes contributing to the formation of pillars and peak-forests, and discuss their relative roles in the formation and decay of the landscape. Model maximum-limiting bedrock erosion rates are the highest along the narrow fluvial channels and valleys at the base of the sandstone pillars (~83–122 mm kyr−1), and lowest on the peak wall tops (~2.5 mm kyr−1). Erosion rates are highly variable and intermediate along vertical sandstone peak walls and pillars (~30 to 84 mm kyr−1). Catchment-wide denudation rates from river sediment vary between ~26 and 96 mm kyr−1 and are generally consistent with vertical wall retreat rates. This highlights the importance of wall retreat for overall erosion in the sandstone peak-forest. In combination with GIS-derived erosional volumes, our results suggest that the peak-forest formation in Zhangjiajie commenced in the Pliocene, and that the general evolution of the landscape followed our sequential refined model: (i) slow lowering rates following initial uplift; (ii) fast plateau dissection by headward knickpoint propagation along joints and faults followed by; (iii) increasing contribution of wall retreat in the well-developed pillars and peak-forests and a gradual decrease in overall denudation rates, leading to; (iv) the final consumption of pillars and peak-forests. Our study provides an approach for quantifying the complex interplay between multiple geomorphic processes as required to assess the evolutionary pathways of other sandstone peak-forest landscapes across the globe.
Potential natural vegetation and pre-anthropic pollen records on the Azores Islands in a Macaronesian context
This paper discusses the concept of potential natural vegetation (PNV) in the light of the pollen records available to date for the Macaronesian biogeographical region, with emphasis on the Azores Islands. The classical debate on the convenience or not of the PNV concept has been recently revived in the Canary Islands, where pollen records of pre‐anthropic vegetation seemed to strongly disagree with the existing PNV reconstructions. Contrastingly, more recent PNV model outputs from the Azores Islands show outstanding parallelisms with pre‐anthropic pollen records, at least in qualitative terms. We suggest the development of more detailed quantitative studies to compare these methodologies as an opportunity for improving the performance of both. PNV modelling may benefit by incorporating empirical data on past vegetation useful for calibration and validation purposes, whereas palynology may improve past reconstructions by minimizing interpretative biases linked to differential pollen production, dispersal and preservation.
Early angiosperm diversification in the Albian of southeast Australia: implications for flowering plant radiation across eastern Gondwana
This study provides the first record of the high diversity and abundance of Victoria's earliest angiosperms from outcrops in the non-marine upper Eumeralla Formation of the Otway Basin. The biostratigraphic schemes established for the Albian of Australia are re-evaluated using more reliable and widespread index species, resulting in the construction of a high-resolution Albian biostratigraphy in the Otway Basin. New localities in the uppermost outcrop of the Eumerella Formation contain spore–pollen assemblages that cannot be placed in the existing scheme and a new Upper Phimopollenites pannosus Subzone is recognised. The correlation of the P. pannosus Zone to the geochronological timescale was re-assessed and shows that it is 103–101.51 Ma, giving a late Albian age. In contrast to previous studies that record low diversity angiosperm assemblages in the Albian, this study identifies twenty-three angiosperm species, including one new species, Tricolpites tortuous. The high diversity and abundance of angiosperm pollen in the Otway Basin provides further evidence that angiosperms probably migrated into eastern Gondwana via South America and Antarctica.
The origin of lithotype cycles in Oligo-Miocene brown coals from Australia and Germany
(ELSEVIER SCIENCE BV, 2016-09-01)
Brown coal colour lithotype cycles range from 10 to 30 m thick in Oligo-Miocene coals of the Latrobe Valley, Gippsland Basin, Australia. Similar colour lithotype cycles occur in the Lusatia German Miocene brown coals. In both the Latrobe Valley and Germany, the cycles often display well-developed colour-lightening-upward trends as defined by new colourimetry measurement. The typical lithotype cycle boundary is abrupt between light below and dark lithotype above. Geological, geochemical, palynological and macrofossil evidence is consistent with a relative drying (terrestrialisation) upward depositional model for each cycle, and the overlying dark lithotype represents renewed peat accretion. The dark lithotype may include charcoal near the cycle base, explained by the fire-prone and highly flammable nature of the herbaceous/reed wetlands. In both the German and Australian coals, wetter (darker) lithotypes are characterized by a gymnosperm paleoflora, while drier (lighter) lithotypes are characterized by angiosperms. In the German (Rhenish) Miocene brown coal exposed in large open cut mines at Garzweiler and Hambach, a 1.0 m spaced sampling and colourimetry measurement program shows lightening-upwards cycles for the Morken seam, Frimmersdorf-A seam, Frimmersdorf-B seam and for the Garzweiler-II seam. At Hambach where the 60 m thick ‘Main Seam’ includes amalgamations of Frimmersdorf-A, Frimmersdorf-B and Garzweiler-I, II & III seams, the lightening-upwards trends, provides a means of stratigraphic subdivision. The palaeogeographic setting for Latrobe Valley and German brown coals is similar – in Latrobe Valley the seams split and thin to the east into marine facies. In the Rhenish and Lusatia brown coals they also split and thin to the north into marine facies. The two Rhenish mines at Hambach and Garzweiler respectively typify end members of this palaeogeography – the Hambach mine is located in a distal location where sulphur content is negligible; the Garzweiler mine is located in a proximal location to the marine boundary where sulphur content is higher. The colourimetry and facies succession suggest German brown coal deposition followed a similar cyclic depositional succession to the Latrobe Valley, and that this succession may be fundamental in all thick coal seams.
Cyclic floral succession and fire in a Cenozoic wetland/peatland system
The cyclic succession of brown coals in the Latrobe Valley, Gippsland Basin, Australia, records an exceptional floral and charcoal record from the Late Oligocene to Middle Miocene. New palynological, geological and charcoal data are consistent with existing colourimetry, carbon isotope, and organic geochemical and palaeobotanical data, indicating that the repeated lithotype cycles represent relative drying (terrestrialization). Based on this detailed palynological study, the vegetation succession within the Latrobe Valley peatlands is interpreted to have begun with a fire-prone emergent marsh of bulrushes (Typhaceae), which grades landward into a fire-prone meadow marsh of rushes (Restionaceae), heaths (Ericaceae) and coral-ferns (Gleicheniaceae). This marsh environment then developed into a forested bog, with gymnosperms (e.g. the Podocarpaceae Dacrycarpus and Dacrydium) as the dominant trees, until an ombrogenous forest bog developed, predominantly consisting of angiosperms (e.g. Nothofagus, Quintinia). The similarity between vegetation successions in New Zealand and the lightening-upwards cycles from the Latrobe Valley coals suggests that New Zealand's modern vegetation communities represent a floral analogue for the successions preserved in the Latrobe Valley coals. High abundances of micro and macro charcoal recorded in the darker lithotypes, within the lithotype cycles of the M1B and M2A seams, suggest that the Latrobe Valley peatlands were subject to repeated fires during the Late Oligocene to Early Miocene.
Oligo-Miocene peatland ecosystems of the Gippsland Basin and modern analogues
(ELSEVIER SCIENCE BV, 2017-02-01)
A detailed examination of the brown coal facies preserved in the Latrobe Valley Morwell 1B seam indicates that the type of peat-forming environment and the associated hydrological regime are the main factors influencing the development of lithotypes in brown coal deposits. New palynological data from the Morwell 1B seam suggests that each respective lithotype in the lightening-upwards lithotype cycles was deposited in a particular depositional environment that was characterised by a distinct floral community. The laminated dark lithotype represents a fire-prone emergent marsh that grew on the margins of a coastal lagoon and/or freshwater swamp. This facies grades into the dark lithotype, representing the transition from a meadow marsh to a periodically flooded ombrogenous forested bog. The medium and lighter lithotypes are interpreted as being deposited in an angiosperm-dominated ombrogenous forest bog that was intolerant of fire. These peat-forming environments are interpreted as being largely controlled by moisture and relative depth to water table. Each environment produces distinct lithotypes and lightening-upwards cycles are interpreted as terrestrialization cycles. As the peat grew upwards and above the water table, less moist conditions prevailed and lighter lithotypes were produced. The observed change in colour, from darker to lighter lithotypes, results from the environment evolving from anaerobic/inundated to less anaerobic/less moist settings via terrestrialization. The thin and laterally extensive light and pale lithotypes that top the cycles are interpreted to represent a residual layer of concentrated, oxidation resistant peat-forming elements that result from intense weathering and aerobic degradation of the peats. At a generic level, modern lowland bogs of South Westland in New Zealand have remarkably similar floral/ecological gradients to those of the Oligo-Miocene Morwell 1B brown coal cycles in Australia. This suggests that modern New Zealand bogs can be used as floral/ecological analogues in order to better understand these Oligo-Miocene peatland environments.
The Significance of Peatland Aggradation in Modern and Ancient Environments
(Society for Sedimentary Geology (SEPM), 2017-10-19)
Peats are commonly used in paleoenvironmental and paleoclimatic studies but detailed sedimentological and facies models for peatlands are poorly developed relative to other sedimentary settings. A comparison of the palynology and charcoal abundances in modern and ancient Cenozoic peats (i.e., brown coals) demonstrates that, in a single cycle, their respective flora commonly evolves from inundated wetland assemblages to more elevated and well-drained forest. The repetitive nature of this pattern suggests that the changing floral compositions result from changes in substrate wetness during peatland aggradation in high rainfall settings. In this scenario, floristic changes within the peat are suggested to represent peatland facies that were controlled by the local peat-forming environment. We suggest that peatland aggradation is an important process that may ubiquitously control the floral and environmental changes documented in modern and Holocene ombrogenous peats, brown coal lithotype cycles, and perhaps black coal dulling-upwards cycles.
Palaeoenvironments and palaeocommunities from Lower Cretaceous high latitude sites, Otway Basin, southeastern Australia
(ELSEVIER SCIENCE BV, 2018-05-01)
Lower Cretaceous (Barremian to Albian) fossil plant assemblages are preserved in sediments of the Otway Group, Otway Basin, and contemporaneous Strzelecki Group, Gippsland Basin, southeastern Australia. Detailed lithofacies and biofacies analyses of terrestrial strata within the upper Eumeralla Formation (Albian), Otway Group, allow fine-scale interpretation of braided fluvial and paludal depositional environments throughout the succession. The previously described flora is re-assessed in light of changes in depositional style and plant communities to describe six Albian biofacies. Forests in the highlands are dominated by Araucariaceae conifers, which turn over to Podocarpaceae and Cheirolepidiaceae forests on the dry, raised areas in the lowlands. Ferns and angiosperms inhabit the moist floodplains and water ferns and lycophytes dwell in the ox-bow lakes. Significant changes occur between floral communities characteristic of riparian, levee and floodbasin settings through the Early Cretaceous. Albian floras are characterized by the dominance of broad-leafed araucarian conifers, an understory of diverse ferns and a dearth of seedferns and angiosperms. There is a notable absence of macrofossil ginkgoaleans in the Eumeralla Formation, although they reappear in younger (Turonian) deposits in southeastern Australia, but angiosperms are extremely scarce as macrofossils compared to the diversity recently recorded in the pollen record. Abundant charcoal demonstrates that fire continued to be a significant environmental factor at high latitudes during the middle to late Albian. The discovery of dinoflagellate species supports an earlier marine incursion and increased coastal environments, probably inhabited by cheirolepids, across the Otway Basin. Palaeontological, palynological and sedimentological data has provided a synthesis of the region's warm, high-latitude, palaeoclimatic setting in the Albian stage of the Early Cretaceous when compared to the cooler Barremian to Aptian.
New age controls on Oligocene and Miocene sediments in southeastern Australia
(ELSEVIER SCIENCE BV, 2018-09-01)
The Cenozoic spore-pollen zonation scheme of southeastern Australia is used to constrain the ages of marine and terrestrial strata throughout Australasia. New palynological, strontium isotope and foraminiferal data from the Torquay and Gippsland basins in southeastern Australia are here used to revise and chronologically calibrate the Oligocene and Miocene portions of this scheme. The revised age assigned to the Upper Nothofagidites asperus/Lower Proteacidites tuberculatus zonal boundary is 30.5–31.2 Ma, the Lower/Middle P. tuberculatus zonal boundary is 23.03 Ma, the Middle/Upper P. tuberculatus zonal boundary is approximately 21.1 Ma and the Upper P. tuberculatus/Triporopollenites bellus zonal boundary is 17.54 Ma. This revision confirms that a near-continuous Early Miocene neritic sequence is present in the Torquay Basin. The new ages also suggest that the timing of coal seam deposition in the Latrobe Valley was episodic, rather than continuous as has previously been interpreted. We propose that abrupt changes in moisture content across seam boundaries are associated with stratigraphic gaps. The new age controls facilitate more accurate comparisons of time-equivalent paleobotanical material throughout the southern hemisphere. The refinements presented will improve future Cenozoic paleoclimatic and paleobotanical reconstructions concerning Australia, New Zealand, South America and Antarctica.
Terrestrial cooling record through the Eocene-Oligocene transition of Australia
(ELSEVIER SCIENCE BV, 2019-02-01)
A new mid-latitude terrestrial climate proxy record is presented for southeastern Australia. The Middle Eocene to Middle Miocene palynofloral and δ13C record of the Latrobe Group, Gippsland Basin, details that the climate of southeastern Australia, paleolatitude 60–50°S, supported the growth of highly diverse subtropical to cool-temperate rainforests. These forests are characterized by mesothermal to microthermal floral elements that are here interpreted as subtropical (Malvacipollis subtilis and Cupanieidites orthoteichus dominated palynofloras), warm-temperate (Beaupreadites elegansiformis and Phyllocladus mawsonii dominated palynofloras) and cool-temperate (Nothofagus spp. and Dacrycarpidites australiensis dominated palynofloras) rainforests. The palynofloral record of the Latrobe Group indicates that mean annual temperatures were between 20 and 24 °C during the Middle Eocene resulting in subtropical rainforests, between 14 and 20 °C for the late Middle Eocene to earliest (i.e. pre-Oi1) Oligocene resulting in warm-temperate rainforests, between 10 and 14 °C for the late Early Oligocene to Early Miocene resulting in cool-temperate rainforests and between 14 and 20 °C in the Middle Miocene, facilitating the resurgence of warm-temperate rainforest floras. Rainfall was also likely in excess of 1500 mm throughout the Middle Eocene to the Middle Miocene in southeastern Australia. The climatic trends preserved within this mid-latitude terrestrial record relate to global Cenozoic cooling, the exception being the Middle Miocene records, which instead relate to the Middle Miocene Climatic Optimum. In the mid-latitude Gippsland Basin, cooling appears to have begun in the Middle Eocene. Correlation of our palynoflora with records from Antarctica and New Zealand, in addition to benthic δ18O records, reaffirms that the Latrobe Group coals provide a long-term, largely authochthonous mid-latitude floral record that directly relates to global climatic evolution through the Cenozoic. Our new mid-latitude terrestrial record provides critical insight into the validation of Eocene-Oligocene climate models and improves our understanding of mid-latitude terrestrial ecosystem responses to increased carbon dioxide forcing. The correlation between the δ13C values of the Yallourn and Morwell coal seams to benthic δ13C records also highlights that a relationship exists between the terrestrial and marine benthic δ13C record.
Depositional setting for Eocene seat earths and related facies of the Gippsland Basin, Australia
The origin of seat earths (i.e. underclays, seat rocks, fire clays) has been investigated using sedimentological, palynological and mineralogical analysis of clastic-coal successions from the Eocene Traralgon Formation of the Gippsland Basin, Australia. The seat earths of the Latrobe Group are massive, a light grey to white colour, contain abundant slickensided fracture surfaces and isolated organic matter, and mineralogically consist of abundant kaolinite and lesser amounts of 2 M illite. From palynological evidence, the seat earths have paleoenvironments that grade from a fire-prone heath-fern meadow marsh (i.e. Gleicheniaceae and Epacridaceae dominant), to fire-tolerant shrubs and small trees (i.e. Cyatheaceae, Schizaeaceae and Proteaceae dominant) that fringe raised peatland rainforests. The palynological data also indicate a non-marine origin for the kaolinitic mudstones. The non-marine seat earths were deposited over a foundation of intertidal sediments (containing lenticular, wavy and flaser bedding, tidal rhythmites, extensive burrowing and a diverse assemblage of marine-influenced dinoflagellates). The upward increase in kaolinite, slickensides and rootlets within the seat earth indicates this clay was kaolinitized by pedogenic processes (i.e. weathering by organically derived humic/fulvic acids) prior to and throughout peat formation. The presence of well-preserved and abundant spore-pollen in the kaolinitic mudstones also suggests that the seat earths were deposited in an acidic and relatively reducing setting. The stratigraphic transition from tidal siltstone, to mudstone (seat earth) to coal in ascending order is interpreted as a shallowing-upwards succession. The seat earths of the Gippsland Basin were therefore deposited as a precursor non-marine facies (mostly meadow-marsh) grading into an ombrogenous coal facies, thereby explaining the intimate association between coals and seat earths globally.