School of Geography, Earth and Atmospheric Sciences - Research Publications

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    Global Changes in Terrestrial Vegetation and Continental Climate During the Paleocene-Eocene Thermal Maximum
    Korasidis, VA ; Wing, SL ; Shields, CA ; Kiehl, JT (AMER GEOPHYSICAL UNION, 2022-04-01)
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    Early angiosperm diversification in the Albian of southeast Australia: implications for flowering plant radiation across eastern Gondwana
    Korasidis, VA ; Wagstaff, BE ; Gallagher, SJ ; Duddy, IR ; Tosolini, A-MP ; Cantrill, DJ ; Norvick, MS (ELSEVIER, 2016-09-01)
    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.
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    The origin of lithotype cycles in Oligo-Miocene brown coals from Australia and Germany
    Holdgate, G ; Wallace, M ; O'Connor, M ; Korasidis, V ; Lieven, U (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.
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    Cyclic floral succession and fire in a Cenozoic wetland/peatland system
    Korasidis, VA ; Wallace, MW ; Wagstaff, BE ; Holdgate, GR ; Tosolini, A-MP ; Jansen, B (ELSEVIER, 2016-11-01)
    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.
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    Oligo-Miocene peatland ecosystems of the Gippsland Basin and modern analogues
    Korasidis, VA ; Wallace, MW ; Wagstaff, BE ; Holdgate, GR (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.
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    The Significance of Peatland Aggradation in Modern and Ancient Environments
    Korasidis, VA ; Wallace, MW ; Jansen, B (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.
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    Palaeoenvironments and palaeocommunities from Lower Cretaceous high latitude sites, Otway Basin, southeastern Australia
    Tosolini, A-MP ; Korasidis, VA ; Wagstaff, BE ; Cantrill, DJ ; Gallagher, SJ ; Norvick, MS (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.
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    New age controls on Oligocene and Miocene sediments in southeastern Australia
    Korasidis, VA ; Wallace, MW ; Wagstaff, BE ; Gallagher, SJ ; McCaffrey, JC ; Allan, T ; Rastogi, S ; Fletcher, M-S (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.
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    Terrestrial cooling record through the Eocene-Oligocene transition of Australia
    Korasidis, VA ; Wallace, MW ; Wagstaff, BE ; Hill, RS (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.
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    Depositional setting for Eocene seat earths and related facies of the Gippsland Basin, Australia
    Korasidis, VA ; Wallace, MW ; Dickinson, JA ; Hoffman, N (ELSEVIER, 2019-07-15)
    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.