ORCID Profile
0000-0001-9066-7834
Current Organisation
University of Adelaide
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Publisher: CSIRO Publishing
Date: 2013
DOI: 10.1071/BT13197
Abstract: Although there is a broad knowledge of Cretaceous climate on a global scale, quantitative climate estimates for terrestrial localities are limited. One source of terrestrial palaeoproxies is foliar physiognomy. The use of foliar physiognomy to explore Cretaceous assemblages has been limited, and some of its potential sources of error have not been fully explored. Although museum collections house a wealth of material, collection bias toward particular taxa or preservation qualities of specimens further magnifies existing taphonomic bias to cold temperatures. As a result, specific collection for foliar physiognomy can be necessary. Here, we conduct three foliar physiognomic analyses on the early Late Cretaceous Lark Quarry flora and assess the results in the context of other proxies from the same formation. Our results suggest that the climate at the Cenomanian–Turonian boundary in central western Queensland was warm and had high precipitation (leaf-area analysis: 1321 mm + 413 mm – 315 mm mean annual precipitation leaf-margin analysis: 16.4°C mean annual temperature, 5.3°C binomial s le error climate leaf-analysis multivariate program: 16 ± 2°C for mean annual temperature, 9-month growth season, 1073 ± 483 mm growth-season precipitation). Our analysis also gave higher mean annual temperature estimates than did a previous analysis by climate leaf-analysis multivariate program, based on museum collections for the Winton Formation.
Publisher: Cambridge University Press (CUP)
Date: 22-02-2013
DOI: 10.1017/S001675681200091X
Abstract: Psephophorus polygonus Meyer, 1847, the first fossil leatherback turtle to be named, was described on the basis of shell ossicles from the middle Miocene (MN6–7/8?) of Slovakia. The whereabouts of this material is uncertain but a slab on display at the Naturhistorisches Museum Wien is considered the neotype. We rediscovered further type locality ossicles in four European institutions, re-evaluated their gross morphology and described for the first time their microstructure by comparing them with Dermochelys coriacea , the only living dermochelyid turtle. The gross morphology is congruent with that already described for P. polygonus , but with two significant exceptions: the ridged ossicles of P. polygonus may have a distinctly concave ventral surface as well as a tectiform shape in cross-section. They do not develop the external keel typical of many ossicles of D. coriacea . Both ridged and non-ridged ossicles of P. polygonus are characterized by compact diploe structures with an internal cortex consisting of a coarse fibrous meshwork, whereas the proportionately thinner ossicles of D. coriacea tend to lose the internal cortex, and thus their diploe, during ontogeny. The ossicles of both P. polygonus and D. coriacea differ from those of other lineages of amniotes whose carapace is composed of polygonal ossicles or platelets, in having growth centres situated at the plate centres just interior to the external bone surface and not within the cancellous core or closer to the internal compact layer. The new diagnosis of P. polygonus allows us to preliminarily re-evaluate the taxonomy of some of the Psephophorus- like species. Despite some macro- and micromorphological differences, it seems likely that Psephophorus was as cosmopolitan as extant Dermochelys and had a broadly similar ecology, with a possible difference concerning the e depth.
Publisher: Informa UK Limited
Date: 02-12-2010
Publisher: Elsevier BV
Date: 2015
Publisher: Copernicus GmbH
Date: 23-06-2022
Abstract: Abstract. Reconciling palaeodata with model simulations of the Pliocene climate is essential for understanding a world with atmospheric CO2 concentration near 400 ppmv (parts per million by volume). Both models and data indicate an lified warming of the high latitudes during the Pliocene however, terrestrial data suggest that Pliocene northern high-latitude temperatures were much higher than can be simulated by models. We focus on the mid-Pliocene warm period (mPWP) and show that understanding the northern high-latitude terrestrial temperatures is particularly difficult for the coldest months. Here the temperatures obtained from models and different proxies can vary by more than 20 ∘C. We refer to this mismatch as the “warm winter paradox”. Analysis suggests the warm winter paradox could be due to a number of factors including model structural uncertainty, proxy data not being strongly constrained by winter temperatures, uncertainties in data reconstruction methods, and the fact that the Pliocene northern high-latitude climate does not have a modern analogue. Refinements to model boundary conditions or proxy dating are unlikely to contribute significantly to the resolution of the warm winter paradox. For the Pliocene high-latitude terrestrial summer temperatures, models and different proxies are in good agreement. Those factors which cause uncertainty in winter temperatures are shown to be much less important for the summer. Until some of the uncertainties in winter high-latitude Pliocene temperatures can be reduced, we suggest a data–model comparison should focus on the summer. This is expected to give more meaningful and accurate results than a data–model comparison which focuses on the annual mean.
Publisher: Society for Sedimentary Geology
Date: 12-06-2014
Publisher: Coquina Press
Date: 2021
DOI: 10.26879/1121
Publisher: Copernicus GmbH
Date: 12-06-2018
Publisher: Tree-Ring Society
Date: 07-08-2019
Publisher: Copernicus GmbH
Date: 15-07-2022
DOI: 10.5194/EGUSPHERE-GC10-PLIOCENE-61
Abstract: & & The Pliocene Model Intercomparison Project (PlioMIP) is one of the most successful MIPs in palaeoclimatology. Over two phases since 2008, PlioMIP has co-ordinated the experimental design and publication strategy of the community, which has included an increasing number of climate models and modelling groups from around the world. It has engaged with the palaeo-data community in order to foster new data synthesis, supporting the construction of new model boundary conditions as well as to facilitate new data/model comparisons.& & & & Given the long implementation period for a new phase it is necessary to define the broad parameters of PlioMIP3 now. Here we present different potential components of a new science plan. This incorporates feedback gained from PlioMIP participants following the online PlioMIP2 showcase event in 2021.& & & & PlioMIP3 will continue to have balanced scientific portfolio across both Pliocene for Pliocene and Pliocene for Future agendas. It will continue to carefully consider the competing demands of the overall effort required to complete experiments, and to be a part of the project, versus having the ability to introduce new and existing elements to enhance scientific exploration and understanding of the Pliocene.& & & & We propose the retention of the PlioMIP2 core experiment (Eoi400), but an extension to Core requirements to include either (or both) an experiment focussed on the Early Pliocene, or an alternative Eoi400 simulation. These additions will (a) allow an intercomparison of Early and Late Pliocene warm intervals and help build research connections and synergies with the MioMIP project, and (b) through removal of some of the largest palaeogeographic differences introduced between the PlioMIP2 and 1 (the closure of the Bering Strait and Canadian Archipelago and the exposure of the Sahul and Sunda Shelves), create a time slice simulation for 3.205 Ma (MIS KM5c) with minimal palaeogeographic variations from the modern. This will enhance the palaeo to future scientific connection, and enable an exploration of the significance of palaeogeographic uncertainties on climate simulations.& & & & In addition, we propose a number of optional experiments across 2 tiers of additional activity that incorporate simulations designed to enhance our understanding of Climate Sensitivity, as well as incorporating the radiative forcing potentially stemming from non-CO& sub& & /sub& greenhouse gases. For the first time, we have introduced orbital sensitivity experiments into the science plan examining both Northern Hemisphere minimum and maximum insolation forcing, as well as a specific simulation using dynamic vegetation models. Finally, we have proposed an experiment designed to examine the potential significance of East Antarctic Ice Sheet boundary condition uncertainty, which would help inform a new phase of the Pliocene Ice Sheet Model Intercomparison Project. & & &
Publisher: Elsevier BV
Date: 2019
Publisher: University of New Brunswick Libraries - UNB
Date: 20-04-2017
DOI: 10.12789/GEOCANJ.2017.44.116
Abstract: This short summary presents selected results of an ongoing investigation into the feedbacks that contribute to lified Arctic warming. The consequences of warming for Arctic bio ersity and landscape response to global warmth are currently being interpreted. Arctic North American records of large-scale landscape and paleoenvironmental change during the Pliocene are exquisitely preserved and locked in permafrost, providing an opportunity for paleoenvironmental and faunal reconstruction with unprecedented quality and resolution. During a period of mean global temperatures only ~2.5°C above modern, the Pliocene molecular, isotopic, tree-ring, paleofaunal, and paleofloral records indicate that the high Arctic mean annual temperature was 11°C–19°C above modern values, pointing to a much shallower latitudinal temperature gradient than exists today. It appears that the intense Neogene warming caused thawing and weathering to liberate sediment and create a continuous and thick ( .5 km in places) clastic wedge from at least Banks Island to Meighen Island to form a coastal plain that provided a highway for camels and other mammals to migrate and evolve in the high Arctic. In this summary we highlight the opportunities that exist for research on these and related topics with the PoLAR-FIT community.RÉSUMÉCe bref résumé présente les résultats choisis d'une enquête en cours sur les déclencheurs qui contribuent à l’ lification du réchauffement de l'Arctique. Les conséquences du réchauffement sur la bio ersité arctique et de la réponse du paysage au réchauffement climatique sont en cours d’être interprété. Des dossiers nord-américains de paysage à grande échelle et le changement paléoenvironnementales durant le Pliocène sont exceptionnellement préservés et scellées dans un état de congélation qui fournissant une occasion pour la reconstruction paléoenvironnementale et faunistique avec une qualité et une résolution sans précédent. Pendent une période de réchauffement global seulement ~2,5°C au-dessus de moderne les dossiers, moléculaire, isotopique, annaux de croissance, paléofaunistique et paléovégétation indiquent que l'Arctique a connu une augmentation de la température annuelle moyenne de 11°C–19°C au-dessus de moderne, en montrant un inferieur gradient de température latitudinal qu'aujourd'hui. Il semble que le réchauffement intense pendent le Néogène a provoqué la décongélation et erosion pour libérer les sédiments et créer une plaine côtière continuel et épaisse ( 2,5 km dans lieux) qui a fourni une route pour les chameaux et autres mammifères pour migrer et évoluer dans l’Haut-Arctique. Dans ce résumé, nous soulignons les opportunités qui existent pour la recherche sur ces sujets et les sujets connexes avec la communauté PoLAR-FIT.
Publisher: PeerJ
Date: 07-09-2018
DOI: 10.7717/PEERJ.5513
Abstract: The Winton Formation is increasingly recognised as an important source of information about the Cretaceous of Australia, and, more broadly, the palaeobiogeographic history of eastern Gondwana. With more precise dating and stratigraphic controls starting to provide temporal context to the geological and palaeontological understanding of this formation, it is timely to reassess the palaeoenvironment in which it was deposited. This new understanding helps to further differentiate the upper, most-studied portion of the formation (Cenomanian–Turonian) from the lower portions (Albian–Cenomanian), allowing a coherent picture of the ecosystem to emerge. Temperatures during the deposition of the Upper Cretaceous portion of the Winton Formation were warm, with high, seasonal rainfall, but not as extreme as the modern monsoon. The landscape was heterogeneous, a freshwater alluvial plain bestrode by low energy, meandering rivers, minor lakes and mires. Infrequent, scouring flood events were part of a multi-year cycle of drier and wetter years. The heavily vegetated flood plains supported abundant large herbivores. This was the final infilling of the great Eromanga Basin.
Publisher: American Geophysical Union (AGU)
Date: 26-08-2019
DOI: 10.1029/2019GL083960
Publisher: Elsevier BV
Date: 09-2014
Publisher: Copernicus GmbH
Date: 17-01-2022
Publisher: Frontiers Media SA
Date: 31-03-2017
Publisher: Informa UK Limited
Date: 29-05-2014
Publisher: Geological Society of America
Date: 08-09-2021
Abstract: Meighen Island, in the Canadian Arctic Archipelago, is one of the most important localities for study of the late Neogene Beaufort Formation because of the presence of marine sediments interbedded with terrestrial fossiliferous sands. The stratigraphic succession, fossils from the marine beds, correlation with reconstructions of sea level, and paleomagnetic data from the Bjaere Bay region of the island suggest that the Beaufort Formation on Meighen Island was likely deposited either at 3.2–2.9 Ma or during two intervals at ca. 4.5 Ma and 3.4 Ma. The exposed Beaufort Formation on Meighen Island probably encompasses at least one warm interval and eustatic sea-level highstand of the Pliocene. Fossils of plants and arthropods are abundant in the alluvial sands exposed in the Bjaere Bay region. The lower part of the sequence (Unit A), beneath the muddy marine sequence (Unit B), contains plant taxa that have not been seen above the marine beds. Sediments below the marine beds are dominated more by fossils of trees, whereas the organic debris from above marine beds contains many fossils of plants, insects, and mites characteristic of open treeless sites. Regional tree line probably occurred on Meighen Island during deposition of the upper sediments, which implies a mean July climate at least 9 °C warmer than at present. When the marine sediments were deposited, nearshore water temperatures probably did not fall below 0 °C hence, the Arctic Ocean probably lacked perennial ice cover. This confirms recent modeling experiments exploring the causes of Arctic lification of temperature that have found the removal of sea ice to be a key factor in resolving previous proxy-model mismatches.
Publisher: Elsevier BV
Date: 12-2021
Publisher: Copernicus GmbH
Date: 12-06-2018
DOI: 10.5194/CP-2018-60
Abstract: Abstract. The mid-Pliocene is a valuable time interval for understanding the mechanisms that determine equilibrium climate at current CO2 concentrations. One intriguing, but not fully understood, feature of the early to mid-Pliocene climate is the lified arctic temperature response. Current models underestimate the degree of warming in the Pliocene Arctic and validation of proposed feedbacks is limited by scarce terrestrial records of climate and environment, as well as discrepancies in current CO2 proxy reconstructions. Here we reconstruct the CO2 and summer temperature from a re-dated 3.9 +1.5/−0.5 Ma sub-fossil fen-peat deposit on west-central Ellesmere Island, Canada, and investigate fire as a potential feedback to Arctic lification of warming during the mid-Pliocene. Average CO2 was determined using isotope ratios of mosses to be 440 ± 50 ppm. The estimate for average mean summer temperature is 15.4 ± 0.8 °C using specific bacterial membrane lipids, i.e. branched glycerol dialkyl glycerol tetraethers. Macro-charcoal was present in all s les from this Pliocene section with notably higher charcoal concentration in the upper part of the sequence. This change in charcoal was synchronous with a change in vegetation that saw fire promoting taxa increase in abundance. Paleovegetation reconstructions are consistent with warm summer temperatures, relatively low summer precipitation and an incidence of fire comparable to fire adapted boreal forests of North America, or potentially central Siberia. To our knowledge, this study represents the furthest northern evidence of fire during the Pliocene and highlights the important role of forest fire in the ecology and climatic processes of the Pliocene High Arctic. The results provide evidence that terrestrial fossil localities in the Pliocene High Arctic were probably formed during warm intervals that coincided with relatively high CO2 concentrations that supported productive biotic communities. This study indicates that interactions between paleovegetation and paleoclimate were mediated by fire in the High Arctic during the Pliocene, even though CO2 concentrations were only ~ 30 ppm higher than modern.
Publisher: Elsevier BV
Date: 05-2021
Publisher: Copernicus GmbH
Date: 19-06-2019
Abstract: Abstract. The mid-Pliocene is a valuable time interval for investigating equilibrium climate at current atmospheric CO2 concentrations because atmospheric CO2 concentrations are thought to have been comparable to the current day and yet the climate and distribution of ecosystems were quite different. One intriguing, but not fully understood, feature of the early to mid-Pliocene climate is the lified Arctic temperature response and its impact on Arctic ecosystems. Only the most recent models appear to correctly estimate the degree of warming in the Pliocene Arctic and validation of the currently proposed feedbacks is limited by scarce terrestrial records of climate and environment. Here we reconstruct the summer temperature and fire regime from a subfossil fen-peat deposit on west–central Ellesmere Island, Canada, that has been chronologically constrained using cosmogenic nuclide burial dating to 3.9+1.5/-0.5 Ma. The estimate for average mean summer temperature is 15.4±0.8 ∘C using specific bacterial membrane lipids, i.e., branched glycerol dialkyl glycerol tetraethers. This is above the proposed threshold that predicts a substantial increase in wildfire in the modern high latitudes. Macro-charcoal was present in all s les from this Pliocene section with notably higher charcoal concentration in the upper part of the sequence. This change in charcoal was synchronous with a change in vegetation that included an increase in abundance of fire-promoting Pinus and Picea. Paleo-vegetation reconstructions are consistent with warm summer temperatures, relatively low summer precipitation and an incidence of fire comparable to fire-adapted boreal forests of North America and central Siberia. To our knowledge, this site provides the northernmost evidence of fire during the Pliocene. It suggests that ecosystem productivity was greater than in the present day, providing fuel for wildfires, and that the climate was conducive to the ignition of fire during this period. The results reveal that interactions between paleo-vegetation and paleoclimate were mediated by fire in the High Arctic during the Pliocene, even though CO2 concentrations were similar to modern values.
Publisher: Copernicus GmbH
Date: 17-01-2022
DOI: 10.5194/CP-2021-186
Abstract: Abstract. Reconciling palaeodata with model simulations of the Pliocene climate is essential for understanding a world with atmospheric CO2 concentration near 400 parts per million by volume. Both models and data indicate an lified warming of the high latitudes during the Pliocene, however terrestrial data suggests Pliocene high latitude temperatures were much higher than can be simulated by models. Here we show that understanding the Pliocene high latitude terrestrial temperatures is particularly difficult for the coldest months, where the temperatures obtained from models and different proxies can vary by more than 20 °C. We refer to this mismatch as the ‘warm winter paradox’. Analysis suggests the warm winter paradox could be due to a number of factors including: model structural uncertainty, proxy data not being strongly constrained by winter temperatures, uncertainties on data reconstruction methods and also that the Pliocene high latitude climate does not have a modern analogue. Refinements to model boundary conditions or proxy dating are unlikely to contribute significantly to the resolution of the warm winter paradox. For the Pliocene, high latitude, terrestrial, summer temperatures, models and different proxies are in good agreement. Those factors which cause uncertainty on winter temperatures are shown to be much less important for the summer. Until some of the uncertainties on winter, high latitude, Pliocene temperatures can be reduced, we suggest a data-model comparison should focus on the summer. This is expected to give more meaningful and accurate results than a data-model comparison which focuses on the annual mean.
Publisher: Elsevier BV
Date: 05-2017
Publisher: Copernicus GmbH
Date: 15-05-2023
DOI: 10.5194/EGUSPHERE-EGU23-13521
Abstract: Cloud has profound impacts on climate, thus accurate cloud simulation is critical for accurate climate modelling. As the greatest source of uncertainty in such models, cloud drives discrepancies in the prediction of future climate. Cloud simulations are validated against recent observations however, these records do not capture the climate space we are entering this century, limiting our ability to test model accuracy under near future conditions.The best analogue for the 21st Century climate trajectory comes from the Pliocene. Reconstructions of Pliocene cloud regimes would provide critical validation data for climate model performance with respect to cloud. However, despite the wealth ways to reconstruct other climate variables, no method has been developed for reconstructing cloud in deep time.We are working towards proxies capable of reconstructing past cloud, with the goal of establishing a global cloud database for the Pliocene. Our initial results demonstrate the relationship between vegetation and large-scale patterns in cloud in the modern, and tests the model derived from the modern data against palaeoclimate model vegetation and cloud.
Location: United Kingdom of Great Britain and Northern Ireland
Start Date: 2019
End Date: 2021
Funder: Chinese Academy of Sciences
View Funded ActivityStart Date: 2019
End Date: 2021
Funder: Department of Education and Training, Australian Governement
View Funded ActivityStart Date: 2019
End Date: 2021
Funder: National Geographic Society
View Funded ActivityStart Date: 2009
End Date: 2014
Funder: Department of Education and Training
View Funded ActivityStart Date: 2022
End Date: 2022
Funder: Alan Turing Institute
View Funded ActivityStart Date: 2021
End Date: 2023
Funder: European Commission
View Funded Activity