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Refined age and geological context of two of Australia's most important Jurassic vertebrate taxa (Rhoetosaurus brownei and Siderops kehli), Queensland
Abstract
Australia’s Jurassic vertebrate fossil record remains extremely sparse with only two dinosaur taxa and two temnospondyl amphibians identified to date. Of these, the spectacular and extremely well-preserved giant amphibian, Siderops kehli, and the only known pre-Cretaceous sauropod in Australia, Rhoetosaurus brownei, are perhaps the most important. The age of both specimens, and the stratigraphic context of Rhoetosaurus brownei, are weakly constrained and imprecisely defined, limiting our understanding of their evolutionary relationships within a broader Gondwanan context. To clarify and contextualise the evolutionary relationships and ages of these two iconic Jurassic taxa, we used UPb detrital zircon geochronology to date the sandstone matrix from around the bones of the historic museum specimens. The robust maximum depositional age for Siderops was calculated at 176.6 Ma ± 2 Ma, indicating that it is no older than late Toarcian, which refines existing biostratigraphic estimates. The Rhoetosaurus maximum depositional age was determined to be 162.6 ± 1.1 Ma, no older than early Oxfordian, demonstrating that the fossils are younger than expected, and definitely recovered from the Walloon Coal Measures.
... The dating of detrital zircon, now routinely available through the application of laser ablation inductively coupled mass spectrometry (LA-ICPMS) offers the potential to redress this deficiency for both nonmarine and marine rocks, especially in tectonic settings subject to syndepositional volcanism (Cawood et al., 2012;Roberts et al., 2012;Hilbert-Wolf et al., 2017). Indeed, this technique has been shown to consistently improve temporal resolution in otherwise poorly dated successions, and been shown to significantly refine the chronostratigraphic constraints on well-established biozones (Tucker et al., 2013;Herriott et al., 2019;Owusu Agyemang et al., 2019;Todd et al., 2019). Recently, detrital zircon geochronology has been successfully employed in temporal recalibration of the Mesozoic Great Australian Superbasin system of eastern Australia (Tucker et al., 2013(Tucker et al., , 2016Wainman et al., 2015Wainman et al., , 2018aWainman et al., , 2018bBell et al., 2019;Todd et al., 2019). ...
... Indeed, this technique has been shown to consistently improve temporal resolution in otherwise poorly dated successions, and been shown to significantly refine the chronostratigraphic constraints on well-established biozones (Tucker et al., 2013;Herriott et al., 2019;Owusu Agyemang et al., 2019;Todd et al., 2019). Recently, detrital zircon geochronology has been successfully employed in temporal recalibration of the Mesozoic Great Australian Superbasin system of eastern Australia (Tucker et al., 2013(Tucker et al., , 2016Wainman et al., 2015Wainman et al., , 2018aWainman et al., , 2018bBell et al., 2019;Todd et al., 2019). More specifically, these studies have revised the depositional age assignments associated with the Jurassic-Cretaceous spore-pollen zonation schemes of Helby et al. (1987) and Price (1997), which are heavily utilised in eastern Australia. ...
... U-Pb CA-TIMS dating of tuff horizons from this interval provides the only precise chronostratigraphic control available for the Jurassic-basal Cretaceous system of eastern Australia (Wainman et al., 2015(Wainman et al., , 2018aCooling et al., 2020). Todd et al. (2019) utilised U-Pb LA-ICPMS detrital zircon dating of sandstones from the Surat Basin to demonstrate that maximum depositional ages (MDAs) derived from detrital zircons can be robust, and have proven consistent with the high-precision tuff ages for the same succession published by Wainman et al. (2015Wainman et al. ( , 2018a. ...
Sedimentary deposits of the Great Australian Superbasin, extensively developed across eastern Australia and covering almost a fifth of the continent, chronicle a rich record of palaeoenvironmental changes in northeastern Gondwana through the Jurassic and basal Cretaceous (Berriasian to Barremian). However, aside from the Surat Basin in the southeastern sector of the superbasin, little of this record has been examined closely. Likewise, the chronostratigraphy of the northern superbasin succession is poorly constrained. This study documents palaeoenvironmental and palaeogeographic records of the Carpentaria Basin at the northern extremity of the superbasin by integrating detailed sedimentary facies analysis with ichnology, palynology and U-Pb detrital zircon geochronology. This new geochronological data provides a refined age framework for the basin. At broad scale, the succession records the transition from a mixed paralic/fluviatile setting (Middle to Late Jurassic) to fully marine (Early Cretaceous) conditions. The depositional surface during basin accumulation stood close to sea level for which minor fluctuations induced a complex facies mosaic resulting in marked lithostratigraphic diachroneity for the basin fill. Two hitherto undocumented, discrete transgressive marine intervals, in the Middle Jurassic (Bajocian-Bathonian) and Late Jurassic (~Kimmeridgian-Tithonian) are identified. The former correlates with marine influence recorded in the Eromanga and Surat basins, and reflects extensive marine ingression from the north into the superbasin. The latter correlates with previously documented marine influence in the southeastern Carpentaria basin and the Surat Basin, indicating that a southeasterly-directed marine seaway existed across the Great Australian Superbasin during the Middle to Late Jurassic.
... The Evergreen Formation, however, contains scattered tuffs that have the potential for precise constraints on age. One maximum depositional age has been reported from detrital zircon dating of a sandstone outcropping on the north-eastern margin of the Surat Basin, which dates the topmost Evergreen Formation at 176.6 ± 2.0 Ma (Todd et al., 2019). The underlying Moolayember Formation of the Bowen Basin is believed to be Middle Triassic (APT3 zone; Playford et al., 1982;Price, 1997;Nicoll et al., 2015). ...
... On the eastern side of the Leichhardt-Burunga Fault (Chinchilla 4 and Kenya East GW7; Fig. 1B), one age from the middle of the J10-TS1 interval indicates deposition at approximately 186.9 ± 6.3 Ma while the MFS1 surface is apparently only 183. 9 ± 2.8 Ma old. The previously published 176.6 ± 2 Ma MDA from the Evergreen Formation outcropping at the north-eastern extre-mity of the Leichhardt-Burunga Fault (Todd et al., 2019) is consistent with this part of the basin being relatively younger. In Tipton 153 at the Surat and Clarence-Moreton Basin boundary, the MDAs are again older, comparable to the northwest. ...
A new view of the palaeogeography and tectonic evolution of eastern Gondwana during the late Mesozoic is emerging, driven largely by the detrital zircon record of sedimentary basins comprising the Great Australian Superbasin (GAS). The updated model suggests that a long-lived magmatic arc was present on the eastern margin of Australia, which is in stark contrast to some previous views that eastern Australia was situated well-inland of a plate boundary. However, the active magmatic arc model is derived from Late Jurassic-Cretaceous strata, with tectonic processes and sediment pathways operating in the Early Jurassic still poorly understood. The Lower Jurassic Precipice Sandstone in the Surat Basin – an important stratigraphic component of the GAS – affords an opportunity to fill such a knowledge gap. The Precipice Sandstone is also economically important due to its aquifer capacity and prospectively for CO2 sequestration. Previous work has hypothesized that the formation contains deposits sourced from multiple terranes, yet this has not been rigorously tested. In this study, we used detrital zircon geochronology, CA-TIMS dating, petrography, and palaeocurrent analysis to characterise the sedimentary provenance of the Precipice Sandstone and the overlying Evergreen Formation. Our analysis revealed mixed provenance with multiple source terranes within the Tasmanides. The bulk of sediment was derived from the Thomson Orogen, with a lesser contribution from the New England Orogen. We found no evidence for sediment derived from the Lachlan Orogen, despite a distinct northward palaeocurrent component. Syn-depositional volcanic material within the interval corroborates the notion of continued arc magmatism along the eastern Gondwana margin, which contributed sediment to the GAS throughout the Early Jurassic. Radiometric ages place the Precipice-Evergreen succession in the Sinemurian-Toarcian and suggest diachronous deposition across the basin. Despite pronounced variations in formation thickness, the Precipice Sandstone shows relatively uniform provenance across the basin, showing little evidence for multiple depocenters.
... The Evergreen Formation, however, contains scattered tuffs that have the potential for precise constraints on age. One maximum depositional age has been reported from detrital zircon dating of a sandstone outcropping on the north-eastern margin of the Surat Basin, which dates the topmost Evergreen Formation at 176.6 ± 2.0 Ma (Todd et al., 2019). The underlying Moolayember Formation of the Bowen Basin is believed to be Middle Triassic (APT3 zone; Playford et al., 1982;Price, 1997;Nicoll et al., 2015). ...
... On the eastern side of the Leichhardt-Burunga Fault (Chinchilla 4 and Kenya East GW7; Fig. 1B), one age from the middle of the J10-TS1 interval indicates deposition at approximately 186.9 ± 6.3 Ma while the MFS1 surface is apparently only 183. 9 ± 2.8 Ma old. The previously published 176.6 ± 2 Ma MDA from the Evergreen Formation outcropping at the north-eastern extre-mity of the Leichhardt-Burunga Fault (Todd et al., 2019) is consistent with this part of the basin being relatively younger. In Tipton 153 at the Surat and Clarence-Moreton Basin boundary, the MDAs are again older, comparable to the northwest. ...
... Samples were analysed by laser ablation inductively coupled mass spectrometry (LA-ICPMS). The analytical setup and instrument details can be found in Todd et al. (2019). Across all the samples, laser ablation was conducted using a 30 μm beam size. ...
... A discordance filter of 15% was applied, and those analyses with greater discordance were omitted from subsequent interpretations. Maximum depositional ages (MDAs) were determined (where possible) to better refine the age of units (see Tucker et al., 2013;Coutts et al., 2019;Todd et al., 2019) and compared with existing palynostratigraphic controls (Smart et al., 1971). MDAs were calculated by using the weighted mean age of the youngest concordant zircon cluster (in which n ≥ 3) where ages overlapped within 2σ error (see Dickinson and Gehrels, 2009). ...
Although Jurassic-Early Cretaceous sedimentary systems were extensively developed on northeastern Gondwana, deciphering their paleogeography has been complicated by poor exposure and the lack of a robust chronostratigraphic framework. The southeastern margin of the Carpentaria Basin, northeastern Australia is one of the few regions where these sedimentary systems are extensively exposed. Employing a combination of facies analysis and new data from paleontology and detrital zircon geochronology, we present a temporally and environmentally refined paleogeographic framework for this region. A Late Jurassic, southeasterly directed marine incursion invaded northeastern Gondwana, extending inland across the Carpentaria Basin, as demonstrated by a thin (~ 30 m), marine influenced (fluvio-estuarine) stratigraphic succession capped by a sequence bounding ~30 myr paraconformity. The depositional hiatus marked the Late Jurassic-Early Cretaceous uplift of the Euroka Arch, with loss of sedimentary and fluvial connectivity between the Carpentaria Basin and adjoining Eromanga Basin. Subsequent deposition by low-accommodation fluvial systems resulted in a thin, fluviatile depositional package developing during the Early Cretaceous. Paleocurrent and provenance data indicate that the Middle to Late Jurassic (c. 170-160 Ma) fluvial systems predating the paraconformity extended from the Eromanga Basin to the south across the southeastern Carpentaria Basin, transporting sediment from distal sources in the Lachlan Orogen of southeastern Australia. Fluvial systems of the southeastern Carpentaria Basin post-dating the paraconformity and Euroka Arch uplift show a provenance shift to easterly sources in the Mossman Orogen and Kennedy Igneous Association. Previously unrecognized Jurassic-Early Cretaceous igneous activity provided a persistent source of sediment to the southeastern Carpentaria Basin succession due to reworking of air fall tuff from an active magmatic arc located on the continental margin of northeastern Gondwana.
... In Australia, the Jurassic non-marine sedimentary deposits are extensive (Turner et al. 2009;Jell 2013) however, thus far they have failed to produce much in the way of dinosaur body-fossils. The most complete is the partial skeleton of the gravisaurian sauropodomorph Rhoetosaurus brownei (QM F1659) from the Middle to Upper Jurassic (Callovian-Tithonian) Walloon Coal Measures (Surat Basin) near Roma (Longman 1926(Longman , 1927a(Longman , 1927bNair and Salisbury 2012;Jannel et al. 2019;Todd et al. 2019) but other specimens are much more fragmentary and their identification has been more problematic (Grant-Mackie et al. 2000). The distal tibia of Ozraptor subottai, from the Middle Jurrasic (Bajocian) Colalura Sandstone near Geraldton, Western Australia, initially described by Long and Molnar (1998) but variably reinterpreted as either an indeterminate avetheropod (=neotetanuran) (Holtz et al. 2004), an abelisauroid (Rauhut 2005;Agnolin et al. 2010), or just too incomplete for assignment (Carrano and Sampson 2008;Pol 2012). ...
... Recently, however, extensive, high-precision ID-TIMS U-Pb geochronology of volcanic tuffs from throughout the succession by Wainman et al. (2018aWainman et al. ( , 2018b has necessitated a recalibration of these spore-pollen zonations, placing deposition of the Walloon Coal Measures between lower Callovian and lower Tithonian of the Middle-Upper Jurassic (~165-151 Ma). An age that is consistent with this determination was also made for the type location of R. brownei by Todd et al. (2019). ...
Dinosaur tracks associated with coal-mines of the Middle to Upper Jurassic (Callovian–Tithonian) Walloon Coal Measures (Clarence–Morton Basin) have been reported on more than any other track-bearing formation in Australia, yet due to the brevity of ichnological information, remain poorly known. All these tracks were found in sediments directly above coal seams in the ceilings of subterranean mines. This style of mining ceased more than a quarter of a century ago, and with many of the original mines having been back-filled or closed, ichnological investigations are restricted to the study of museum specimens and archival photographs. Here, we consolidate data from the literature, present previously unpublished archival photographs, and show the 3D topography of all accessioned track specimens from the Walloon Coal Measures. We recognise eleven track-bearing sites, most of which produced large (length of 30–50 cm) and very large (length greater than 50 cm) sized theropod tracks, including Australia’s largest carnivorous dinosaur footprint (79 cm long). The domination of theropod tracks is unique among Australian dinosaur tracksites. In light of the absence of near coveal body-fossil candidates, the Walloon Coal Measures ichnofaunal assemblages fills significant gaps in our understanding of Australia's Jurassic dinosaur fauna.
... D) U-Pb Condordia plot and lower intercept age for the youngest zircon population. (Teledyne Analyte G2 193 nm Excimer Laser with HeLex II Sample Cell and a Thermo iCAPRQ ICP-MS) at the AAC at JCU with a 30 μm spot size used for all analyses following the methodology described in Todd et al. (2019). The primary standard GJ-1 (Jackson et al. 2004) and the secondary standards Plešovice (Sláma et al. 2008) and Penglai (Li et al. 2010) were used, and the data was processed using Iolite (https://iolitesoftware.com), with weighted mean ages calculated using Isoplot (Ludwig 2008). ...
The East Africa Rift System records a key interval in the evolution of modern African ecosystems, documenting significant floral changes and faunal dispersals in the context of environmental shifts. To date, Miocene- to-Pliocene data from eastern Africa have been derived primarily from richly fossiliferous rift basins along the far north of the Eastern Branch of the rift, with more limited windows emerging from the Malawi Rift and more recently, coastal Mozambique. Here, we present the first quantitative paleoclimate data for the Miocene–Pliocene transition from the Western Branch of the East African Rift System, based on analyses of paleosols from the Rukwa Rift Basin. Paleosols derived from the fossiliferous late Miocene–early Pliocene lower Lake Beds succession in southwestern Tanzania preserve a shallow lacustrine setting grading into a system of alluvial fans and braided rivers with abundant floodplain deposits. Paleoclimate reconstructions using bulk geochemistry and clay mineralogy reveal a highly seasonal, semiarid, mesic climate during the late Miocene, with increased moisture availability in the early Pliocene resulting in a shift to subhumid conditions. Stable-carbon-isotope composition of pedogenic carbonates document a woodland/bushland/shrubland paleoenvironment across the Miocene–Pliocene transition. Results support the presence of Pliocene subhumid to humid habitats, dominated by woody vegetation offering shade, food, and water for faunal dispersal along an inland corridor connecting northern segments of the East African Rift System with southern Africa.
... Nevertheless, the depositional ages from CA-TIMS tuff dating and MDAs from detrital zircon ages obtained in this study and by Ciesiolka (2019) represent significant progress and add resolution to the Surat Basin stratigraphic framework. This is the first geochronological dataset reported for the Precipice Sandstone and some of the first data available for the Evergreen Formation (after an MDA presented by Todd et al., 2019). The ages for the J10-MFS1 interval align with previous broad age constraints from biostratigraphy (Price, 1997) placing the Precipice Sandstone in the Sinemurian to Pliensbachian. ...
... Ablation was performed at 5 Hz and 2.5-3 J/cm 2 , with spot sizes varying with target species and grainsize between 20 mm and 50 mm. Full instrument conditions are outlined in Todd et al. (2019). ...
The Tommy Creek Domain is a complex, yet little studied, terrane in the Eastern Subprovince of the Mount Isa Province, northwest Queensland Australia. In this study, we take advantage of modern low-cost and rapid geochronology techniques to undertake an iterative dating approach integrated with detailed fieldwork to define the ages and extents of numerous lithologies and units of the Tommy Creek Domain. This includes some units not previously identified, lithologies previously grouped together based on field observations but now shown to have multiple distinct ages and dates not commonly represented in Mount Isan time–space plots. We identify an episode of felsic magmatism at ca 1640 Ma, and multimodal intrusions (ca 1615 Ma) immediately preceding the onset of the Isan Orogeny. A major rock package of the Tommy Creek Domain, the Milo beds, are characterised here as the youngest pre-Isan Orogeny sedimentary unit in the Eastern Subprovince (1660–1620 Ma), confirming that sedimentation and possibly rifting continued after deposition of the Soldiers Cap, Mount Albert and Kuridala groups (ca 1690–1650 Ma) before the onset of the Isan Orogeny (ca 1600 Ma). The Milo beds are thus age equivalent to the Mount Isa and McNamara groups of the Western Succession. There is evidence of a compositional shift in sedimentation coincident with the ca 1640 Ma Riversleigh Inversion event, previously only observed in the Western Subprovince in the Lawn Hill Platform. The application of geochronology as part of the mapping workflow can assist with differentiating geological units in terranes where field evidence is ambiguous and can aid in the focusing of objectives for field campaigns to enable the best possible interpretations to be made.
• KEY POINTS
• New ages constrain the Milo beds in the Tommy Creek Domain as the youngest stratigraphy in the Eastern Subprovince of the Mount Isa Province.
• The Milo beds are age equivalents of the McNamara and Mount Isa groups of the Western Subprovince of the inlier.
• Recognition of felsic and mafic intrusions with ca 1640 Ma and ca 1615 Ma ages.
• Evidence for Riversleigh Inversion event ca 1640 in the Eastern Subprovince.
... Only one of these two samples (2-25-19-9 from SBM16) yielded a population (n = 3+) of potential syndepositional zircons. Details about mineral separation and the U-Pb LA-ICP-MS methods following those of Todd et al. (2019) and Foley et al. (2021) are provided in the Supplemental Material. ...
A second K/Pg boundary interval in the northern sector of the Antarctic Peninsula on Vega Island has been proposed, yet current temporal resolution of these strata prohibits direct testing of this hypothesis. To not only test for the existence of a K/Pg boundary on Vega Island but also provide increased age resolution for the associated vertebrate fauna (e.g., marine reptiles, non-avian dinosaurs, and avian dinosaurs), the Vega Island succession was intensively re-sampled. Stratigraphic investigation of the Cape Lamb Member of the Snow Hill Island Formation, and in particular, the overlying Sandwich Bluff Member of the López de Bertodano Formation, was conducted using biostratigraphy, strontium isotope stratigraphy, magnetostratigraphy, and detrital zircon geochronology. These data indicate a Late Campanian−early Maastrichtian age for the Cape Lamb Member and present three possible correlations to the global polarity time scale (GPTS) for the overlying Sandwich Bluff Member. The most plausible correlation, which is consistent with biostratigraphy, detrital zircon geochronology, sequence stratigraphy, and all but one of the Sr-isotope ages, correlates the base of the section to C31N and the top of the section with C29N, which indicates that the K/Pg boundary passes through the top of the unit. A second, less plausible option conflicts with the biostratigraphy and depends on a series of poorly defined magnetic reversals in the upper part of the stratigraphy that also correlates the section between C31N and C29R and again indicates an inclusive K/Pg boundary interval. The least likely correlation, which depends on favoring only a single Sr-isotope age at the top of the section over biostratigraphy, correlates the section between C31N and C30N and is inconsistent with an included K/Pg boundary interval. Although our preferred correlation is well supported, we failed to identify an Ir-anomaly, spherules/impact ejecta, or other direct evidence typically used to define the precise position of a K/Pg boundary on Vega Island. This study does, however, confirm that Vegavis, from the base of the Sandwich Bluff Member, is the oldest (69.2−68.4 Ma) phylogenetically placed representative of the avian crown clade, and that marine vertebrates and non-avian dinosaurs persisted in Antarctica up to the terminal Cretaceous.
... Resin pucks were then imaged using a scanning electron microscope with a cathodoluminescence detector (SEMCL) to determine locations for analyses. U -Pb geochronology was performed using LA-ICP-MS (Teledyne Analyte G2 193 nm Excimer Laser with HeLex II Sample Cell and a Thermo iCAPRQ ICP-MS) at the Advanced Analytical Centre at JCU with a 30 μm spot size used for all analyses following the tuning and ablation methodology described in Todd et al. (2019). The primary standard GJ-1 (Jackson et al., 2004) and the secondary standards Plešovice (Sláma et al., 2008) and91,500 (Wiedenbeck et al., 2004) were used following the updated ideal ages for each reference material in Horstwood et al. (2016) and the data was processed using Iolite (https://iolite-software.com/). ...
We describe the sedimentology, geochronology, and geochemistry of the Early Cretaceus Sao Khua Formation of the Khorat Basin, northeastern Thailand, and report a temporal range adjustment for its dinosaurian assemblage. Facies analysis and architectural studies reveal that sedimentation occurred within a floodplain setting fed by large meandering bedload-rich channels. Interfluve areas comprised freshwater lakes and emergent areas subject to pedogenic modification. Multiple paleosol types are identified and geochemistry is indicative of a stable humid subtropical climate regime. Based on radiometric dating of detrital zircons (via LA-ICP-MS), we interpret that the middle part of the Sao Khua Formation was deposited no later than 133.8 (±1.8) Ma (late Valanginian), and grain ages collected from the overlying lowermost Phu Phan Fm constrain sedimentation of the upper part of the Sao Khua Formation to no earlier than 132.4 (±2.0) Ma (early Hauterivian). In consideration of the Early Cretaceous regional tectonic framework, we interpret that youthful igneous zircon grains are derived from the adjacent South China-Vietnam South Borneo Volcanic Arc. We establish that the entombed dinosaur biota (including members of the Ornithomimosauria, Spinosauridae, Megaraptora, and Somphospondylia) is ~5–9 million years older than previously recognized and that these records are among the oldest known globally for these clades. Constraining the age of the Sao Khua Formation indicates that the shift from sauropod-dominated, ornithischian depauperate ecosystems of the Sao Khua Formation to iguanodontian-rich ecosystems of the Khok Kruat Formation occurred sometime between the early Hauterivian and Aptian on the Khorat Plateau.
... standard mineral separation methods, including random-grain representative selection of all morphologies, and analyzed for U and Pb isotopes by LA-ICP-MS at the Advanced Analytical Centre at James Cook University as outlined in Beveridge et al. (2020). A Teledyne Analyte G2193 nm Excimer Laser with HeLex II Sample Cell was used to ablate 25 μm pits in the zircons and liberated material was analyzed in a Thermo iCAP-RQ ICP-MS (see Todd et al., 2019 andHuang et al., 2021 for further details on laboratory procedures). Zircon mineral standards used included GJ1 (primary), and Plesovice and 91500 (secondary). ...
The Western Interior of North America preserves one of the most complete successions of Upper Cretaceous marine and non-marine strata in the world; among these, the Cenomanian-Campanian units of the Kaiparowits Plateau in southern Utah are a critical archive of terrestrial environments and biotas. Here we present new radioisotopic ages for the Campanian Wahweap Formation, along with lithostratigraphic revision, to improve the geological context of its fossil biota. The widely accepted informal stratigraphic subdivisions of the Wahweap Formation on the Kaiparowits Plateau are herein formalized and named the Last Chance Creek Member, Reynolds Point Member, Coyote Point Member, and Pardner Canyon Member (formerly the lower, middle, upper, and capping sandstone members respectively). Two high-precision U-Pb zircon ages were obtained from bentonites using CA-ID-TIMS, supported by five additional bentonite and detrital zircon LA-ICP-MS ages. Improved geochronology of the Star Seep bentonite from the base of the Reynolds Point Member via CA-ID-TIMS demonstrates that this important marker horizon is over a million years older than previously thought. A Bayesian age-stratigraphic model was constructed for the Wahweap Formation using the new geochronologic data, yielding statistically robust ages and associated uncertainties that quantifiably account for potential variations in sediment accumulation rate. The new chronostratigraphic framework places the lower and upper formation boundaries at 82.17 + 1.47/−0.63 Ma and 77.29 + 0.72/−0.62 Ma, respectively, thus constraining its age to the first half of the Campanian. Additionally, a holistic review of known vertebrate fossil localities from the Wahweap Formation was conducted to better understand their spatio-temporal distribution including revised ages for early members of iconic dinosaur lineages such as Tyrannosauridae, Hadrosauridae, and Centrosaurinae. Chrono- and lithostratigraphic refinement of the Wahweap Formation and its constituent biotic assemblages establishes an important reference for addressing questions of Campanian terrestrial paleoecology and macroevolution, including dinosaur endemism and diversification throughout western North America.
... If sandstone ages conform to the law of superposition (consistently younging in age up-strata) in many wells across a given basin, they may provide time-correlative surfaces for the construction of a chronostratigraphic framework. The feasibility of this technique is demonstrated for volcanogenic sandstone beds in the Upper Jurassic Birkhead Formation of the Eromanga Basin in Australia (Figs. 7 and 8) (Wainman et al., 2018b), and for sandstones in the coeval Upper Jurassic Walloon Coal Measures of the Surat Basin (Hentschel, 2018;Todd et al., 2019). Significant young zircon populations (19% of grains) have also been identified in fluvial Triassic to Cretaceous units from basins of the North West Shelf of Australia (Lewis and Sircombe, 2013) and could potentially be dated using CA-TIMS and correlated using this technique. ...
Correlation of ancient fluvial strata in the subsurface is challenging due to complex facies architectures and the lateral discontinuity of facies over short distances (>10 km). The complexity of the strata is due to the interplay of allogenic factors that determine the rate of creation of accommodation, sediment supply and ultimately fluvial architectures on regional scales. The application of commonly used stratigraphic techniques in such successions has allowed for improved regional correlations and an enhanced understanding of the evolution of basin fills. Lithostratigraphy, biostratigraphy, chemostratigraphy, magnetostratigraphy, event stratigraphy, sequence stratigraphy, pedostratigraphy, chronostratigraphy (in particular geochronology), cyclostratigraphy, and provenance stratigraphy are assessed, outlining their benefits, drawbacks and application using several case studies. Lithostratigraphy is highly discouraged as facies boundaries are often time-transgressive. On the contrary, chemostratigraphy, event stratigraphy and provenance stratigraphy show excellent potential for correlating ancient fluvial strata as key signatures can be recognised between different localities over distances greater than 25 km. The character and thickness of paleosols can also greatly enhance both sequence stratigraphic and pedostratigraphic correlations. The most promising correlation tool involves the use of chronostratigraphy (in particular geochronology). The high-precision radiometric dating of tuffs, or precisely dating the youngest zircon population in a sandstone sample using U–Pb CA-TIMS (when available) provides a precise and independent way to correlate fluvially-dominated strata unambiguously over large distances (>100 km). The integration of several techniques, such as sequence stratigraphy in conjunction with pedostratigraphy, is also recommended to construct a comprehensive stratigraphic framework for fluvially-dominated successions. The most appropriate correlation technique is dependent on several factors including budget, the purpose and scope of the study and whether the data come from outcrops or the subsurface. Improved correlations will enhance our understanding of ancient fluvial systems and their resource potential.
... Laser ablation inductively coupled plasma mass spectrometry (LA ICP MS) was conducted using a Teledyne Analyte G2193 nm Excimer Laser with HeLex II Sample Cell and a Thermo iCAP-RQ ICP-MS at the AAC (as per. Todd et al., 2019). All uranium-lead laser ablation ICP-MS data was reduced and handled in Iolite (iolite-software.com) and Isoplot (Ludwig, 2012) respectively. ...
Lithostratigraphic investigation of the richly fossiliferous Kaiparowits Formation in southern Utah reveals the presence of a previously unidentified stratigraphic unit herein named the Upper Valley Member. The 255-m-thick Upper Valley Member is latest Campanian to earliest Maastrichtian in age and records a significant sedimentological change in the Kaiparowits Formation. This change is illustrated in the member by a significant increase in near syn-sedimentary aged zircons, coincident with the introduction of white, volcaniclastic sandstones, as well as a paucity of Jurassic grains, which dominate the provenance of the rest of the formation. The source of the late Campanian volcaniclastic material, including near syn-sedimentary zircons, is most likely from nearby volcanic centers within the Laramide porphyry copper province to the south of the Kaiparowits Plateau in the Mogollon region. Measured sections reported here stratigraphically expand the Kaiparowits Formation to a total of 1005 m and find that the upper boundary of the formation is largely gradational with the overlying Canaan Peak Formation. Lithological changes documented in this study are interpreted to signify a sedimentological response to proximal magmatism and emerging uplifts within the Cordilleran foreland basin during early Laramide orogenesis, which resulted in paleo-drainage rearrangement in southern Laramidia in the latest Campanian. The fossil-bearing Upper Valley Member can be correlated regionally to the Kirtland, Tuscher and Bearpaw formations and other latest Campanian – and possibly early Maastrichtian – units across western North America and represents the capping member one of the most continuous terrestrial records of the Campanian biosphere found anywhere in the world.
In 2020, the Australasian palaeontological association Australasian Palaeontologists (AAP) joined the Australian government-supported Australian National Species List (auNSL) initiative to compile the first Australian Fossil National Species List (auFNSL) for the region. The goal is to assemble comprehensive systematic data on all vertebrate, invertebrate and plant fossil taxa described to date, and to present the information both within a continuously updated open-access online framework, and as a series of primary reference articles in AAP’s flagship journal Alcheringa. This paper spearheads these auFNSL Alcheringa publications with an annotated checklist of Australian Mesozoic tetrapods. Complete synonymy, type material, source locality, geological age and bibliographical information are provided for 111 species formally named as of 2022. In addition, chronostratigraphically arranged inventories of all documented Australian Mesozoic tetrapod fossil occurrences are presented with illustrations of significant, exceptionally preserved and/or diagnostic specimens. The most diverse order-level clades include temnospondyl amphibians (34 species), saurischian (13 species) and ornithischian (12 species) dinosaurs (excluding ichnotaxa), and plesiosaurian marine reptiles (11 species). However, numerous other groups collectively span the earliest Triassic (earliest Induan) to Late Cretaceous (late Maastrichtian) and incorporate antecedents of modern Australian lineages, such as chelonioid and chelid turtles and monotreme mammals. Although scarce in comparison to records from other continents, Australia’s Mesozoic tetrapod assemblages are globally important because they constitute higher-palaeolatitude faunas that evince terrestrial and marine ecosystem evolution near the ancient South Pole. The pace of research on these assemblages has also accelerated substantially over the last 20 years, and serves to promote fossil geoheritage as an asset for scientific, cultural and economic development. The auFNSL augments the accessibility and utility of these palaeontological resources and provides a foundation for ongoing exploration into Australia’s unique natural history.
The northern-most occurrence of Sauropoda in South America was collected in the 1940s from Early–Middle Jurassic-aged continental sediments on the western flank of the Serranía del Perijá in Colombia. Relocation of the site and re-preparation of the specimen, a well-preserved dorsal vertebra, provide important information about the initial diversification of sauropods at low latitudes. The specimen possesses autapomorphies and a unique combination of character states (e.g., divided centropostzygapophyseal lamina, strongly dorsally arched postzygapophyseal facets) that diagnose it as the new genus and species Perijasaurus lapaz. A medium-sized early eusauropod, Perijasaurus inhabited tropical lowland forested areas around the Toarcian–Aalenian boundary. Our phylogenetic analysis recovers Perijasaurus near the base of Eusauropoda, in an unresolved position near Cetiosaurus, Patagosaurus and kin (Bagualia, Spinophorosaurus, Nebulasaurus), and more deeply nested eusauropods. The phylogenetic position of Perijasaurus bolsters the idea that eusauropods achieved a broad geographic distribution during the Early–Middle Jurassic, before the deeper fragmentation of Pangea and after the Toarcian faunal turnover documented at high southern latitudes. Perijasaurus and other basally diverging sauropods display an intermediate level of bone weight reduction in the axial column that represents an antecedent to the more highly developed pneumatic system characterizing Neosauropoda.
The Great Artesian Basin (GAB) in eastern Australia is one of the most productive complex aquifers on Earth, covering a large portion of the continent. Yet stratigraphic correlation within and among constituent basins of the GAB remain poorly constrained. This has significant implications for resource estimation and management. In this study and for the first time, palynostratigraphic and zircon geochronologic data are integrated from the Lower Jurassic Precipice Sandstone and Evergreen Formation in the Surat Basin–a component of the GAB. The goal was to better constrain the depositional ages as a starting point for calibrating stratigraphy across the GAB. The results showed that the Precipice Sandstone and Evergreen Formation are highly diachronous, as are their sequence stratigraphic subdivisions. We provisionally revise the stratigraphic framework based on the integration of age information to show that the “lower” Precipice Sandstone (lowstand systems tract) ranges from Hettangian to Pliensbachian, the “upper” Precipice Sandstone (transgressive systems tract) extends from Sinemurian to Pliensbachian, the Evergreen Formation varies from Pliensbachian to Aalenian within which the Boxvale Sandstone varies from Pliensbachian to Toarcian and the Westgrove Ironstone member ranges from Pliensbachian to Aalenian. Additionally, the data allow us to provisionally assign the APJ1 to APJ2 palynozone boundary to ∼190 Ma, the APJ3.2 to APJ3.3 boundary to ∼180 Ma, and to constrain the APJ2.2.2 palynozone to span 184.80 ± 0.20 Ma. This new age-context for the Precipice Sandstone and Evergreen Formation will be useful for future workers correlating strata between constituent basins of the GAB, as well as New Zealand and the broader Gondwana palaeocontinent.
The Nambour Basin provides the easternmost record of Jurassic sedimentation for Australia. U-Pb detrital zircon age spectra constrain basin infill as Early-Middle Jurassic (ca. 195-163 Ma). Early Jurassic samples are dominated by 650–500 Ma detrital zircon sourced from the Lachlan Orogen of southeastern Australia. Distal Jurassic upland associated with this orogen was generated by epeiric uplift. Sediment sourced from it was transported northwards and eastwards into the Nambour Basin as corroborated by basinal paleocurrent data. In contrast, Devonian to Triassic detrital zircon from the New England Orogen, which abuts the Nambour Basin margin, are scarce. Topographic relief across this orogen generated by the Permo-Triassic (ca.260-230 Ma) Hunter Bowen Orogeny, had been largely eliminated by the Early Jurassic. Dominant Jurassic detrital zircon for one sample of this age, combined with related paleocurrent data and the absence of a Jurassic zircon source in eastern Australia, reflects an easterly Jurassic igneous assemblage now located on submerged northern Zealandia. The detrital zircon data presented herein constrains tectonic interpretations proposed for Jurassic east Gondwana, continental margin sedimentary assemblages in New Caledonia and New Zealand. Documentation of continental epeiric uplift from detrital zircon age data obtained from basin fill has potential yet to be explored.
Supplementary material: Tables S1 and S2 are available at https://doi.org/10.6084/m9.figshare.c.5988017
The Great Australian Superbasin, incorporating the Great Artesian Basin, is host to one of the largest artesian groundwater systems on Earth. However, despite the crucial nature of this resource to Australian agriculture, industry and rural communities, key aquifer units remain poorly studied, apart from the exposed eastern/southeastern portions of the superbasin. In this study, maximum depositional age (MDA) estimations for stratigraphic units, derived from detrital zircon U–Pb geochronology, were undertaken across the Carpentaria and northern Eromanga basins, representing the northern Queensland sector of the Great Australian Superbasin. The objective was to better constrain the ages of key aquifer and aquitard units, thereby facilitating improved stratigraphic correlations and future hydrogeological modelling. Age dating of detrital zircon significantly enhances the confidence, accuracy and precision of age assignments based solely on palynology, especially in continental facies. Furthermore, the provision of MDA estimates permits confident correlation of endemic Australian spore-pollen zonations (used to date continental strata), and dinocyst zonations (used to date marine strata) to the international time-scale. Results indicate that calculated MDAs are commonly either equivalent to, or appreciably younger than, stratigraphic age estimates based on palynostratigraphy. Therefore, several of the most economically strategic aquifer units in the superbasin have been revised upwards in geological time. Similar geochronological campaigns are required in the central, western and southern superbasin to facilitate both high-resolution correlation of key aquifer units across the superbasin and the detailed tracking of the Jurassic to Early Cretaceous paleogeographic evolution of eastern Australia.
• Key points
• U–Pb detrital zircon maximum depositional age (MDA) constraints generated are applied to the Jurassic–Cretaceous stratigraphy of the northern Great Australian Superbasin.
• MDA estimates facilitate robust correlation of endemic Australian palynostratigraphic zones to the international time-scale, reducing chronostratigraphic uncertainty.
• Several of the key aquifer units across the northern superbasin (e.g. Hooray Sandstone) yield MDA estimates younger than age assignments based on palynostratigraphy and have been revised upwards in geological time.
• Several units yield divergent MDA estimates, suggesting either unit diachroneity or miscorrelation, indicating that the chronostratigraphic framework of the northern superbasin (and the superbasin at large) warrants further examination.
During the Early Cretaceous, Australia was flooded by the epicontinental Eromanga Sea, deposits of which occur across the Great Australian Superbasin. However, the mid‐Cretaceous retreat of this shallow sea, and the resultant palaeogeographic and sediment distribution patterns, are poorly understood. This study chronicles the Eromanga Sea’s northward regression through the Carpentaria Basin as captured in the sedimentary record of the Normanton Formation. We achieve this by integrating sedimentary facies analysis of cores from across the Carpentaria Basin with palynology, sandstone petrography and U‐Pb detrital zircon geochronology. Results indicate that the Normanton Formation was deposited between ca. 100 and 96 Ma, and that it represents a large, northward‐prograding, likely river‐dominated delta, system. The unit’s volcanoclastic nature is exhibited through abundant lithic volcanics and devitrified glass, with a prominent, near‐depositional detrital zircon population attributed to a proximal continental magmatic arc‐derived source hypothesised to parallel the eastern seaboard of Australia at this time. The Normanton Formation is temporally correlative with the lower‐middle portions of the similarly volcanoclastic Winton Formation in the Eromanga Basin, which drained southwards into the Cenomanian‐Santonian Ceduna River Delta system. However, Normanton Formation strata display subtly different provenance signatures and drainage patterns, indicating input from similar, but likely more northern source terrains than much of the contemporaneous Winton Formation. These sediments were unlikely recycled southwards into the Ceduna Delta like those of the Winton Formation; rather they drained northward following the retreat of the Eromanga Sea through the Carpentaria Basin, indicating a Cretaceous drainage divide between two river systems, with distinct northern and southern drainage catchments. The mid‐Cretaceous palaeogeography of eastern Australia is analogous to that of the Late Cretaceous Western Interior Seaway of North America, in which the retreat of a shallow epicontinental sea is marked by the rapid deposition and progradation of multiple large, geographically distinct clastic wedges.
Middle Jurassic sauropod taxa are poorly known, due to a stratigraphic bias of localities yielding body fossils. One such locality is Cerro Cóndor North, Cañadón Asfalto Formation, Patagonia, Argentina, dated to latest Early–Middle Jurassic. From this locality, the holotype of Patagosaurus fariasi Bonaparte 1986 is revised. The material consists of the axial skeleton, the pelvic girdle, and the right femur. Patagosaurus is mainly characterised by a combination of features mainly identified on the axial skeleton, including the following: 1) cervical centra with low Elongation Index; 2) high projection of the postzygodiapophyseal lamina; 3) deep anterior pleurocoels that are sometimes compartmentalized in cervicals; 4) high projection of the neural arch and spine in dorsal vertebrae and anterior(most) caudal vertebrae; 5) deep pneumatic foramina in posterior dorsals which connect into an internal pneumatic chamber; and 6) anterior caudal vertebrae with ‘saddle’ shaped neural spines. Diagnostic features on the appendicular skeleton include: 1) a transversely wide and anteroposteriorly short femur; 2) a medial placement of the fourth trochanter on the femur; and 3) an anteroposteriorly elongated ilium with a rounded dorsal rim, with hook-shaped anterior lobe. The characters that are diagnostic for Patagosaurus are discussed, and the osteology of Patagosaurus is compared to that of Early and Middle Jurassic (eu)sauropods from both Laurasia and Gondwana.
The upper Paleozoic–lower Mesozoic strata in the northeastern Galilee Basin are important for their hydrocarbon and groundwater potential; however, despite numerous previous investigations, the nature of this stratigraphic interval remains enigmatic. This study integrates lithostratigraphy, palynology and U–Pb zircon geochronology of well-exposed Permian and Triassic sedimentary rocks and nearby stratigraphic cores from the Hughenden district to determine their maximum depositional ages and then revises the stratigraphy where necessary. The newly defined Galah Tuff Bed was discovered at the top of the Betts Creek beds in Porcupine Gorge and was dated at 251.9 ± 3 Ma. This provides an important age constraint for the Betts Creek beds and is a tie-point for correlations with coeval units in the adjacent Bowen Basin and the Sydney and Gunnedah basins to the southeast. The Galah Tuff Bed is interpreted to correlate with the Yarrabee Tuff in the Bowen Basin. Unconformably overlying the Betts Creek beds is a newly recognised stratigraphic unit, defined herein as the Porcupine Gorge Formation. Detrital zircon maximum depositional ages and palynology indicate a significant depositional hiatus of up to 20 million years between the Betts Creek beds and Porcupine Gorge Formation. The hiatus indicates that the lower part of the Porcupine Gorge Formation is at least upper Middle Triassic, whereas the upper part of the unit extends into the Late Triassic. This age also constrains the overlying Warang Sandstone, which is considerably younger locally than previously reported and is likely diachronous across the northeastern Galilee Basin.
• KEY POINTS
• An integrated lithostratigraphy, palynology and U–Pb detrital zircon geochronology methodology is applied to the Permian–Triassic succession the northeastern Galilee Basin.
• Two new stratigraphic units were recognised: the upper Permian Galah Tuff Bed (251.9 ± 3 Ma) and the late Middle–Late Triassic Porcupine Gorge Formation (238.7 ± 3 Ma).
• The Galah Tuff Bed, correlative of the Yarrabee Tuff in the Bowen Basin, is evidence for widespread volcanism in the late Permian.
• The age of the Porcupine Gorge Formation indicates diachroneity of the Triassic succession in the Galilee Basin, warranting further examination.
The Upper Cretaceous 'upper' Winton Formation of Queensland, Australia is world famous for hosting Dinosaur Stampede National Monument at Lark Quarry Conservation Park, a somewhat controversial tracksite that preserves thousands of tridactyl dinosaur tracks attributed to ornithopods and theropods. Herein, we describe the Snake Creek Tracksite, a new vertebrate ichnoassemblage from the 'upper' Winton Formation, originally situated on Karoola Station but now relocated to the Australian Age of Dinosaurs Museum of Natural History. This site preserves the first sauropod tracks reported from eastern Australia, a small number of theropod and ornithopod tracks, the first fossilised crocodyliform and ?turtle tracks reported from Australia, and possible lungfish and actinopterygian feeding traces. The sauropod trackways are wide-gauge, with manus tracks bearing an ungual impression on digit I, and anteriorly tapered pes tracks with straight or concave forward posterior margins. These tracks support the hypothesis that at least one sauropod taxon from the 'upper' Winton Formation retained a pollex claw (previously hypothesised for Diamantinasaurus matildae based on body fossils). Many of the crocodyliform trackways indicate underwater walking. The Snake Creek Tracksite reconciles the sauropod-, crocodyliform-, turtle-, and lungfish-dominated body fossil record of the 'upper' Winton Formation with its heretofore ornithopod-and theropod-dominated ichnofossil record.
The Callide Basin Lower Jurassic units had been noted two decades ago as having preserved dinosaur ichnites, however, none had been shown or described at that time. The current study is the first to describe a dinosaur track from this region, a fossil collected over a decade ago from an overburden dump from the Callide Mine (Dunn Creek mine area). The track morphologically resembles those of a large Anomoepus-like ‘Anomoepid’ and confirms previously unsubstantiated reports of ornithischian tracks at the location. The tracksite represents the third Early Jurassic dinosaur fossil site in Australia. All of these are tracksites restricted to Central Queensland with the Biloela track the only known Australian Jurassic dinosaur print preserved as a concave epirelief (impression). The find contrasts with earlier statements that the open-pit mining practices make the discovery of dinosaur tracks unlikely. Instead, the extraction of overburden rock has the potential of re-discovering additional fossil track-bearing strata. It is hoped that there will be further discoveries made within the region.
Wainman, C.C., Hannaford, C., Mantle, D. & McCabe, P.J., April.2018. Utilizing U–Pb CA-TIMS dating to calibrate the Middle to Late Jurassic spore-pollen zonation of the Surat Basin, Australia to the geological time-scale. Alcheringa XX, xx-xx.
Spore-pollen palynostratigraphy is commonly used to subdivide and correlate Jurassic continental successions in eastern Australia and thus aid the construction of geological models for the petroleum and coal industries. However, the current spore-pollen framework has only been tenuously calibrated to the geological time-scale. Age determinations are reliant on indirect correlations of ammonite and dinoflagellate assemblages from New Zealand, the North West Shelf of Australia and Southeast Asia to the standard European stages. New uranium-lead chemical abrasion thermal ionization mass spectrometry (U–Pb CA-TIMS) dates from 19 tuff beds in the Middle–Upper Jurassic Injune Creek Group of the Surat Basin enables regional spore-pollen palynostratigraphic zones to be precisely dated for the first time. These results show the base of the APJ4.2 and APJ4.3 subzones are similar in age to previous estimates (Middle Jurassic, Bathonian) from indirect palynostratigraphic correlation. However, the base of the APJ5 Zone and the APJ6.1 Subzone may be somewhat younger than previously estimated, possibly by as much as 2.5 and 4.2 Myrs, respectively. The continued utilization of U–Pb CA-TIMS dates will further refine the absolute ages of these zones, improve the inter- and intra-basinal correlation of Middle–Upper Jurassic strata in eastern Australian basins and greatly enhance intercontinental correlations.
Carmine Christopher Wainman [carmine.wainman@adelaide.edu.au] and Peter James McCabe [peter.mccabe@adelaide,edu.au] Australian School of Petroleum, University of Adelaide, SA, 5005, Australia; Carey Hannaford [carey.hannaford@mgpalaeo.com.au] and Daniel Mantle [dan.mantle@mgpalaeo.com.au] MGPalaeo Pty Ltd, 5 Arvida Street, Malaga, WA, 6090, WA, Australia.
U-Pb geochronology and Lu-Hf isotope analysis of detrital zircon from the mid-Cretaceous Winton and Mackunda Formations in the Eromanga Basin were employed to investigate regional provenance patterns in order to better understand the tectonic setting and paleogeography of eastern Australia during the late Mesozoic. A suite of Mesozoicaged zircon populations recovered from these formations suggests that volcanism along the eastern margin of Australia was relatively continuous from the Triassic (252 Ma) to at least the mid-Cretaceous (ca. 92 Ma). Cretaceous- age zircon populations dominate the provenance record, and a distinct up-section younging trend in Cretaceous grain ages indicates that deposition was largely synchronous with ongoing volcanism to the east. Lu-Hf isotopic data suggest that these zircon populations were sourced from igneous rocks of a mixed juvenile and crustal source, similar to Lu-Hf isotopic systematics for eastern Australian zircons from Pennsylvanian-Permian igneous assemblages (307-252 Ma), for which an active convergent margin association is well established. An extensive Cretaceous volcanic terrain, now limited to the Whitsunday Igneous Association, was once located along the northeastern margin of Australia. Results from this study support the hypothesis that the Whitsunday igneous association was the main source of Cretaceous sediment to the Eromanga Basin, and likely for sediment transported across the continent southward and into the Ceduna Delta system offshore South Australia. The Whitsunday igneous association has been interpreted as a siliceous large igneous province associated with the onset of rifting in the region and linked to opening of the Tasman and Coral Seas. Yet, in this study, we document a relatively continuous Late Triassic to Late Cretaceous (240-92 Ma) age range for detrital zircons from the Mackunda and Winton Formations, consistent with relatively uninterrupted magmatic activity along the continental margin until ca. 92 Ma (earliest Turonian). Furthermore, zircon grains across this age spectrum exhibit dominantly positive to strongly positive εHf(t) values, between +4 and +12, consistent with values known for zircon suites from older magmatic arc rocks of eastern Australia. Although these data do not support a conclusive interpretation, they are consistent with an east Australian magmatic arc related to westward subduction of paleo-Pacific oceanic crust beneath eastern Australia enduring into the Cretaceous, as distinct from extensional siliceous large igneous province magmatism unrelated to subduction and generated by rupture of continental crust.
Late Jurassic dinosaur faunas from the Southern Hemisphere are still poorly known, and it thus remains unclear whether or not the famous Tendaguru fauna (Kimmeridgian–Tithonian, Tanzania) represents a typical Gondwanan dinosaur assemblage of that time. In South America, only the Oxfordian–Kimmeridgian Cañadón Calcáreo Formation of Chubut Province, Argentina, has yielded more than isolated Late Jurassic dinosaur remains so far. Here we report fragmentary remains of a dipolodocid sauropod from this unit, representing the first record of this family from the Late Jurassic of South America. Incorporating the basal macronarian Tehuelchesaurus, an unidentified brachiosaurid, the dicraeosaurid Brachytrachelopan, and the diplodocid described here, the taxonomic composition of the sauropod fauna from the Cañadón Calcáreo Formation is remarkably similar to that of the Tendaguru Formation, but also to roughly contemporaneous faunas in North America and Europe. The diverse non-neosauropodan sauropod fauna known from the early Middle Jurassic (Aalenian–Bajocian) of the same depositional basin within Chubut Province is congruent with the dominance of non-neosauropodan sauropods in continental faunas globally to at least the Bathonian. These assemblages suggest a rapid faunal turnover within sauropod faunas in the late Middle Jurassic-earliest Late Jurassic at least in western Pangea, through which basal eusauropods were replaced by diplodocoid and macronarian neosauropods. Taking paleogeographical reconstructions into account, this faunal replacement might have taken place in a surprisingly short time interval of maximally five million years close to the end of the Middle Jurassic.SUPPLEMENTAL DATA—Supplemental materials are available for this article for free at www.tandfonline.com/UJVP
The middle–upper Cretaceous Ceduna River system traversed continental Australia from the NE coast to the centre of the southern coast. At its mouth, it formed a vast delta system that is similar in scale to the Niger delta of West Africa. The delta system is composed of two main lobes that represent different phases of delta construction. A recent hypothesis has challenged the traditional idea that both lobes of the delta were derived from a transcontinental river system by suggesting that the upper lobe (Santonian–Maastrichtian) is instead derived from a restricted catchment within southern Australia. Hafnium isotopic data presented here fingerprint the original source of the upper delta lobe zircons to NE Australia, with data comparing well with similar U-Pb and Lu-Hf isotopic data from the Lachlan Orogen, the New England Orogen, the eastern Musgraves Province and the northern Flinders Ranges. These data do not preclude a model where the lobe is derived from recycled Eromanga Basin sediments during a phase of Late Cretaceous inland Australian uplift, but when coupled with reconnaissance low-temperature thermochronometry from the region of the Ceduna River course indicating widespread Triassic–Jurassic exhumation, and comparisons with detrital zircon data from the Winton Formation upstream of any proposed uplift, we suggest that both lobes of the Ceduna Delta are likely to be derived from a transcontinental Ceduna River.
: Chigutisauridae is the longest-lived trematosaurian clade (from early Triassic to early Cretaceous). They were reported in Argentina, Australia, India and South Africa. This contribution reports a putative chigutisaurid specimen in the Carnian of southern Brazil (Santa Maria Formation, Paraná Basin). The material comprises two skull fragments, a mandibular fragment, a clavicular blade and a humerus. Ontogenetic features point to an early development stage of the specimen. The presence of a long, straight and pointed tabular horn, which runs parallel to the skull midline towards its tip, and a distinctive projection in the posterior border of the postparietal indicates a close relationship of the Brazilian chigutisaurid with the Indian Compsocerops cosgriffi. Three distinctive and combined characters suggest that the Brazilian chigutisaurid is a distinctive specimen: the presence of an alar process of the jugal in the ventral margin of the orbit; jugal does not extend well beyond the anterior margin of the orbit; and tabular does not contact the parietal. These characters could justify the erection of a new taxon; however, they might reflect its immature ontogenetic stage as well. Accordingly, we attribute this new specimen to Compsocerops sp. Argentinean and Indian occurrences are dated as Norian, so the presence of a Carnian chigutisaurid in southern Brazil indicates that western Gondwana chigutisaurids have first occupied the Paraná Basin and later migrated towards west (to Argentina) and east (India). However, the presence of ghost chigutisaurid taxa cannot be dismissed, because their long temporal range contrasts with their still short (in comparison with other temnospondyl groups) geographic distribution. Hence, they might have been more geographically widespread than their fossil record suggests.
The Late Cretaceous Ceduna Delta is the largest deltaic system on the Australian continent, yet its source is unknown. Apatite fission-track data reveal widespread Late Cretaceous exhumation across the southern Australian margin. New detrital zircon analysis of 786 grains from the Gnarlyknots-1 well, which penetrated the offshore delta top, show that the upper part of the delta (Santonian–Maastrichtian) was sourced largely from recycled Permian to Early Cretaceous cover and underlying basement eroded from the margin, proximal to the basin. This challenges the widely accepted model involving distal provenance of >2000 km from the eastern margin of Australia.
Supplementary material
The 2D seismic reflection data, results for detrital zircon LA-ICP-MS and zircon fission-track analyses, including the LA-ICP-MS method, and a list of sample intervals and ages are available at www.geolsoc.org.uk/SUP18582 .
Titanosauriforms represent a diverse and globally distributed clade of neosauropod dinosaurs, but their inter‐relationships remain poorly understood. Here we redescribe Lusotitan atalaiensis from the Late Jurassic Lourinhã Formation of Portugal, a taxon previously referred to Brachiosaurus. The lectotype includes cervical, dorsal, and caudal vertebrae, and elements from the forelimb, hindlimb, and pelvic girdle. Lusotitan is a valid taxon and can be diagnosed by six autapomorphies, including the presence of elongate postzygapophyses that project well beyond the posterior margin of the neural arch in anterior‐to‐middle caudal vertebrae. A new phylogenetic analysis, focused on elucidating the evolutionary relationships of basal titanosauriforms, is presented, comprising 63 taxa scored for 279 characters. Many of these characters are heavily revised or novel to our study, and a number of ingroup taxa have never previously been incorporated into a phylogenetic analysis. We treated quantitative characters as discrete and continuous data in two parallel analyses, and explored the effect of implied weighting. Although we recovered monophyletic brachiosaurid and somphospondylan sister clades within Titanosauriformes, their compositions were affected by alternative treatments of quantitative data and, especially, by the weighting of such data. This suggests that the treatment of quantitative data is important and the wrong decisions might lead to incorrect tree topologies. In particular, the diversity of Titanosauria was greatly increased by the use of implied weights. Our results support the generic separation of the contemporaneous taxa Brachiosaurus, Giraffatitan, and Lusotitan, with the latter recovered as either a brachiosaurid or the sister taxon to Titanosauriformes. Although Janenschia was recovered as a basal macronarian, outside Titanosauria, the sympatric Australodocus provides body fossil evidence for the pre‐Cretaceous origin of titanosaurs. We recovered evidence for a sauropod with close affinities to the Chinese taxon Mamenchisaurus in the Late Jurassic Tendaguru beds of Africa, and present new information demonstrating the wider distribution of caudal pneumaticity within Titanosauria. The earliest known titanosauriform body fossils are from the late Oxfordian (Late Jurassic), although trackway evidence indicates a Middle Jurassic origin. Diversity increased throughout the Late Jurassic, and titanosauriforms did not undergo a severe extinction across the Jurassic/Cretaceous boundary, in contrast to diplodocids and non‐neosauropods. Titanosauriform diversity increased in the Barremian and Aptian–Albian as a result of radiations of derived somphospondylans and lithostrotians, respectively, but there was a severe drop (up to 40%) in species numbers at, or near, the Albian/Cenomanian boundary, representing a faunal turnover whereby basal titanosauriforms were replaced by derived titanosaurs, although this transition occurred in a spatiotemporally staggered fashion. © 2013 The Linnean Society of London
Remains of a fossil amphibian have been recovered from an ironstone layer in the Upper Evergreen Formation, dated as late Liassic, of southeast Queensland. Extraction of the skeleton from the very hard matrix has presented a number of problems which are discussed. The find is an almost complete skull and mandible connected to an articulated postcranial skeleton which is missing only some ribs, the right hind leg and the distal portions of the other limbs and tail. The remains are those of a temnospondyl labyrinthodont described as a new genus and species of the family Chigutisauridae. The new form is notable for its very large size (total length estimated to be in excess of 2.5 m), relatively large marginal dentition, with unique lance-shaped tooth tips, the presence of minute denticles associated with the palate and mandible, a well developed atlas showing a strong link with the axis, neorhachitomous vertebrae that lack ossified pleurocentra and have low, heavily built neural spines, a neck region and a narrow dermal pectoral girdle associated with unreduced limbs. The discovery of this chigutisaur provides the first unequivocal evidence that labyrinthodonts survived beyond the end of the Triassic. The status of two previously described doubtful Jurassic forms is reviewed. Austropelor Longman, 1941, from the Early Jurassic Marburg Sandstone of southeast Queensland, is confirmed as a fragment of temnospondyl lower jaw, probably attributable to the superfamily Brachyopoidea, and there is no longer any reason to consider the earlier suggestion that it is a reworked Triassic fossil. Cyrtura Jaekel, 1904, from the Late Jurassic Solnhofen Shale of Germany, is considered not to be a labyrinthodont, but its exact relationships are uncertain. The unsatisfactory nature of the higher taxonomy of the Temnospondyli is noted. The superfamily Brachyopoidea is reviewed and the family Kourerpetontidae is removed from it, membership of the superfamily thereby being restricted to the Brachyopidae (Late Permian to Middle Triassic) and Chigutisauridae (Early Triassic to Early Jurassic). Diagnoses for the superfamily and its two included families are provided. The relationships of the better characterized members of the two families are examined and a phylogeny based on shared derived character states is proposed. The analysis of relationships indicates that Brachyops allos Howie, 1972 shares few of the characters diagnostic of the type of Brachyops (B. laticeps Owen, 1855), and a new genus is proposed. The diversity of Australia's brachyopoids, including the presence of the most primitive and earliest-known members of each of the included families, suggests that the superfamily originated in Australia.
The Winton Formation provides an important snapshot of Australia's late Mesozoic terrestrial biota, boasting a vertebrate fauna that includes dinosaurs, crocodyliforms, aquatic squamates, turtles, lungfish and teleost fishes, and a flora that has previously been considered to include some of the world's earliest known flowering plants. Despite its significance, poor age control has thus far prevented precise regional and global correlations, limiting the depth of paleobiogeographic assessments. The goal of this study was to use U–Pb isotope dating of detrital zircons by laser ablation to refine the depositional age range of selected horizons within the Winton Formation. We applied this technique, with refined instrumental tuning protocols, to systematically investigate detrital zircon grain ages for five samples from different stratigraphic levels and vertebrate-bearing fossil locations throughout the Winton Formation. Seven different metrics for interpreting the maximum depositional age of each of the detrital zircon samples were compared and our results suggest that sedimentation of the Winton Formation commenced no earlier than latest Albian (~103.0–100.5 Ma) and that deposition of the upper vertebrate fossil-rich portion of the section began roughly near or after the Cenomanian–Turonian boundary (93.9 Ma), demonstrating that the formation and its important flora and fauna were deposited primarily during the Late Cretaceous. These results provide a significant advancement in understanding the age of the Winton Formation's flora and fauna, and will help to contextualize Australia's Late Cretaceous terrestrial biota within a broader Gondwanan framework.
We report on three large volume Early Cretaceous volcanic and sedimentary provinces: the Whitsunday Volcanic Province and Great Artesian Basin system, both of northeastern Australia, and the Otway/Gippsland basin system along the southeastern margin of Australia. The Whitsunday Volcanic Province is part of a mafic to silicic, high-K calc-alkaline pyroclastic volcanic belt that extends for more than 900 km along the central and southern Queensland coast. Estimated extrusive volumes are >105 km3. Volcanic and intrusive activity shows a broad range of ages from 132 to 95 Ma, but ages are dominated by an event between ∼120 and 105 Ma. Contemporaneous with volcanism in the Whitsunday Volcanic Province, sedimentary basins in interior and eastern Queensland were receiving large volumes (>106 km3) of volcanogenic sediment. The Otway and Gippsland basins 1500 km to the south, were initiated by the break-up of Antarctica and Australia. These basins contain >4×105 km3 of Aptian–Albian extrabasinal volcanogenic sediment supplied from the east. This volcanogenic sedimentation post-dates rift-related volcanism within the basin system. These three provinces are each significant for: (1) the accumulation of large volumes of volcanic and/or coeval volcanic-derived material; (2) the compositional similarity between phenocryst and detrital plagioclase, augite and hornblende; and (3) age data recording a major volcanic episode between 125 and 105 Ma. A causal relationship between volcanism in the Whitsunday Volcanic Province and volcaniclastic sedimentation in the Otway/Gippsland and Great Artesian basin systems is therefore suggested. We propose these provinces record volcanism related to the break-up of eastern continental Gondwana and the formation of the modern eastern Australian passive margin. The scale and volume of volcanic products, coupled temporally with emplacements of oceanic plateaux in the Southwest Pacific, demonstrate that this volcanic event along the present eastern Australian plate margin should be considered as another Early Cretaceous large igneous province.
Rhoetosaurus brownei is the only known named pre-Cretaceous sauropod from Australia. It is therefore a
potentially important taxon for understanding global paleobiogeographic and phylogenetic patterns among early sauropods. Despite its obvious significance, Rhoetosaurus has been too poorly understood to be included in most recent analyses of early sauropod evolution. With this in mind, we evaluated the osteology and phylogeny of undescribed materials of Rhoetosaurus, in order to attempt to close the gap in this understanding. The lower hind limb of Rhoetosaurus highlights a plethora of differences from other sauropods, supporting the distinctiveness of Rhoetosaurus even in the absence of other materials. Some unique traits include prominent crests and sulci on the tibia medially, a narrow metatarsal articular bridge, and pedal claws with an accessory groove or fossa. The pes plesiomorphically retains four claws where most sauropods have three, and bears superficial similarity to that of Shunosaurus. Preliminary cladistic analysis confirms that Rhoetosaurus is a non-neosauropod gravisaurian, although weak support for the most parsimonious topology suggests further findings are required to improve upon incompleteness in the character data. Examination of alternative phylogenetic hypotheses rules out a close relationship between Rhoetosaurus and East Asian Jurassic sauropods, and indicates a closer examination of the potential relationships between Rhoetosaurus and other contemporaneous Middle Jurassic Gondwanan sauropods is necessary.
Strata of Jurassic age occur extensively across onshore Australia, but they are predominantly of non-marine origin. Marine Jurassic strata have only limited onshore exposure in northwestern and central-western Australia, with thick marine sequences lying offshore on the North West Shelf. The richest petroleum province in Australia is located at the shelf’s southern end, where the Dingo Claystone represents an important source rock for oil and gas. By and large, non-marine deposits, including economic coals, are distributed in the eastern states. Jurassic stage boundaries, in the main, are poorly constrained with respect to the Australian sedimentary succession. New work on microfossils, plants, fish, and zircon dating is providing a basis for improved correlation across Australian basins, with overseas successions, and recent international IUGS geologic timescales.
Iolite is a non-commercial software package developed to aid in the processing of inorganic mass spectrometric data, with a strong emphasis on visualisation versus time of acquisition. The goal of the software is to provide a powerful framework for data processing and interpretation, while giving users the ability to implement their own data reduction protocols. It is intended to be highly interactive, providing the user with a complete overview of the data at all stages of processing, and allowing the freedom to change parameters and reprocess data at any point. The program presents a variety of windows for the selection and viewing of data versus time, as well as features for the generation of X-Y plots, summary reports and export of data. In addition, it is capable of generating X-Y images from laser ablation rasters, and combining information from up to four separate elemental concentrations (intensities of red, green and blue, and the z-axis) in a false-colour three-dimensional image. By virtue of its underlying computing environment—Igor Pro—Iolite is capable of processing very large datasets (i.e., millions of timeslices) rapidly, and is thus ideal for the interrogation of multi-hour sessions of laser ablation data that can not be easily manipulated in conventional spreadsheet applications, for example. It is also well suited to multi-day sessions of solution-mode inductively-coupled plasma mass spectrometer (ICPMS) or thermal ionisation mass spectrometer (TIMS) data. A strong emphasis is placed on the interpolation of parameters that vary with time by a variety of user selectable methods including smoothed cubic splines. Data are processed on a timeslice-by-timeslice basis, allowing outlier rejection and calculation of statistics to be employed directly on calculated results. This approach can reduce the risk of processing biases associated with the manipulation of integrated datasets, while also allowing the implementation of more complex data reduction methods.
Over the last few decades our understanding of what Australia was like during the Mesozoic Era has changed radically. A rush of new fossil discoveries, together with cutting-edge analytical techniques, has created a much more detailed picture of ancient life and environments from the great southern continent. Giant dinosaurs, bizarre sea monsters and some of the earliest ancestors of Australia’s unique modern animals and plants all occur in rocks of Mesozoic age. Ancient geographical positioning of Australia close to the southern polar circle and mounting geological evidence for near freezing temperatures also make it one of the most unusual and globally significant sources of fossils from the age of dinosaurs. This book provides the first comprehensive overview of current research on Australian Mesozoic faunas and floras, with a balanced coverage of the many technical papers, conference abstracts and unpublished material housed in current collections. It is a primary reference for researchers in the fields of palaeontology, geology and biology, senior undergraduate and postgraduate students, secondary level teachers, as well as fossil collectors and anyone interested in natural history. Dinosaurs in Australia is fully illustrated in colour with original artworks and 12 reconstructions of key animals. It has a foreword by Tim Flannery and is the ideal book for anybody seeking to know more about Australia’s amazing age of dinosaurs.
The Late Jurassic Tendaguru Formation of Tanzania, southeastern Africa, records a rich sauropod fauna, including the diplodocoids Dicraeosaurus and Tornieria, and the brachiosaurid titanosauriform Giraffatitan. However, the taxonomic affinities of other sympatric sauropod taxa are poorly understood. Here, we critically reassess and redescribe these problematic taxa, and present the largest phylogenetic analysis for sauropods (117 taxa scored for 542 characters) to explore their placement in Eusauropoda. Janenschia robusta has played a prominent role in discussions of titanosaur origins, with various authors referring at least some remains to Titanosauria, a clade otherwise known only from the Cretaceous. Redescription of the holotype of Janenschia, and all referable remains, supports its validity and placement as a nonneosauropod eusauropod. It forms a clade with Haestasaurus from the earliest Cretaceous of the UK, and the Middle/Late Jurassic Chinese sauropod Bellusaurus. Phylogenetic analysis and CT scans of the internal pneumatic tissue structure of Australodocus bohetii tentatively support a non-titanosaurian somphospondylan identification, making it the only known pre-Cretaceous representative of that clade. New information on the internal pneumatic tissue structure of the dorsal vertebrae of the enigmatic Tendaguria tanzaniensis, coupled with a full redescription, results in its novel placement as a turiasaur. Tendaguria is the sister taxon of Moabosaurus, from the Early Cretaceous of North America, and is the first turiasaur recognized from Gondwana. A previously referred caudal sequence cannot be assigned to Janenschia and displays several features that indicate a close relationship with Middle–Late Jurassic East Asian mamenchisaurids. It can be diagnosed by six autapomorphies, so we erect the new taxon Wamweracaudia keranjei gen. et sp. nov. The presence of a mamenchisaurid in the Late Jurassic of southern Gondwana indicates an earlier and more widespread diversification of this clade than previously realized, prior to the geographic isolation of East Asia. Our revised phylogenetic dataset sheds light on the evolutionary history of Eusauropoda, including supporting a basal diplodocoid placement for Haplocanthosaurus, and elucidating the interrelationships of rebbachisaurids. The Tendaguru Formation shares representatives of nearly all sauropod lineages with Middle Jurassic–earliest Cretaceous global faunas, but displays a greater range of diversity than any of those faunas considered individually. Biogeographic analysis indicates that the Tendaguru sauropod fauna was assembled as a result of three main phenomena during the late Early and/or Middle Jurassic: (1) invasions from Euramerica (brachiosaurids, turiasaurs); (2) endemism in west Gondwana (dicraeosaurids, diplodocids); and (3) regional extinctions that restricted the ranges of once widespread groups (mamenchisaurids, the Janenschia lineage). Multiple dispersals across the Central Gondwanan Desert are required to explain the distributions of Jurassic sauropods, suggesting that this geographic feature was at most a filter barrier that became easier to cross during the late Middle Jurassic.
To better predict the architecture of reservoirs and the location of undiscovered resources in fluvial-dominated strata, a sound chronostratigraphic framework is needed. This study reassesses the stratigraphic framework of petroleum-bearing Jurassic fluviolacustrine successions in the Eromanga, Surat, and Clarence-Moreton Basins of eastern Australia. Correlation of the strata is challenging because of the heterolithic facies, the absence of conventional stratigraphic marker beds, and the longevity of palynostratigraphic zones. The abundance of laterally discontinuous volcanic air-fall tuffs and volcanogenic sandstones across the Jurassic of eastern Australia allows for the construction of a new, regional chronostratigraphic framework. High-precision U-Pb zircon chemical abrasion-thermal ionization mass spectrometry (CA-TIMS) dates ranging from 168.07 - 0.07 Ma to 149.08 - 0.06 Ma were obtained from 31 samples from 13 wells across 3 basins. Five chronostratigraphic datums were defined and extrapolated to 677 wells within a time interval of 420 ka or less over hundreds of kilometers across eastern Australia. The new chronostratigraphic framework reveals inaccuracies in picking lithostratigraphic units based on lithology and wire-line log characteristics and shows coal-bearing facies of the Walloon Coal Measures to be two episodes of coal (peat) accumulation separated by an unconformity. The study also demonstrates the feasibility of extending chronostratigraphic datums to neighboring basins without tuff beds by dating the youngest zircon in volcanogenic sandstones by U-Pb CA-TIMS following laser ablation-inductively coupled plasma mass spectrometry analysis. The dates provide a substantial revision to the Middle to Upper Jurassic stratigraphy of eastern Australia. The use of precise U-Pb CA-TIMS dates should help elucidate the lithofacies architecture of nonmarine successions in other basins and assist in petroleum development. Copyright © 2018. The American Association of Petroleum Geologists. All rights reserved.
The Winton Formation of central Queensland is recognized as a quintessential source of mid-Cretaceous terrestrial faunas and floras in Australia. However, sedimentological investigations linking fossil assemblages and palaeoenvironments across this unit remain limited. The intent of this study was to interpret depositional environments and improve stratigraphic correlations between multiple fossil localities within the preserved Winton Formation in the Eromanga Basin, including Isisford, Lark Quarry, and Bladensburg National Park. Twenty-three facies and six repeated facies associations were documented, indicating a mosaic of marginal marine to inland alluvial depositional environments. These developed synchronously with the final regression of the Eromanga Seaway from central Australia during the late Albian-early Turonian. Investigations of regional- and local-scale structural features and outcrop, core and well analysis were combined with detrital zircon provenance signatures to help correlate stratigraphy and vertebrate faunas across the basin. Significant palaeoenvironmental differences exist between the lower and upper portions of the preserved Winton Formation, warranting informal subdivisions; a lower tidally influenced fluvial-deltaic member and an upper inland alluvial member. This work further demonstrates that the Isisford fauna is part of the lower member of the preserved Winton Formation; whereas, fossil localities around Winton, including Lark Quarry and Bladensburg National Park, are part of the upper member of the Winton Formation. These results permit a more meaningful framework for both regional and global comparisons of the Winton flora and fauna.
Over 190 partial and complete dinosaur prints which include six trackways are preserved in the ceilings of a disused clay mine near Mount Morgan central eastern Queensland, Australia. These represent the best record of Early Jurassic dinosaur footprints thus far discovered within Australia. Anomoepus dominates with other morphologies present including, Grallator, cf. Eubrontes, and Skartopus and several indeterminate prints. Only one possible manus print was observed. All preserved tracks are short walking tracks.
Cranial and postcranial remains from the Early Cretaceous (Aptian) of southeastern Australia appear to be from the last known members of the labyrinthodont Amphibia and to belong to the temnospondyl superfamily Brachyopoidea. Koolasuchus cleelandi n. gen. n.sp. lived well beyond the documented time of labyrinthodonts elsewhere in the world, perhaps protected by a polar "safe area" that excluded such competitors as the modern crocodiles. These late occurring Australian temnospondyls are always associated with coarser grained facies.
The Jurassic Walloon Coal Measures of the Surat Basin were previously estimated to be of Middle Jurassic age, ranging from Aalenian to Callovian, based on an uncalibrated eastern Australian biostratigraphic framework. New U–Pb dates of 162.55 ± 0.05 Ma and 158.86 ± 0.04 Ma obtained from zircons in ash-fall volcanic tuffs now place the Walloon Coal Measures of the Surat Basin in the Upper Jurassic Oxfordian. The new dates have several implications for the interpretation of the Jurassic strata in the Surat Basin. First-order subsidence rates of 61 m/Myr for the Walloon Coal Measures are more akin to those of foreland basins than the previously assumed intracratonic setting. The dates also imply deposition of the Walloon coals in substantially higher latitudes than previously assumed and that they accumulated as peats in mires that experienced more than three months’ continual darkness each winter. Zircon dating of tuffs and associated geochemistry should assist with the correlation of the laterally impersistent coals, fluvial sandstone and mudstone of the Walloon Coal Measures, which are currently difficult to correlate over distances of more than a few kilometres. Dating of the palynostratigraphic zones APJ4.2 to APJ5 (Aequitriradites norrisii Association Zone to Murospora florida Association Zone) will also need to be recalibrated.
This chapter examines the evolutionary relationships of sauropods using cladistic analysis. It also describes in the detail their paleobiology, taphonomy, and paleoecology. Sauropod dinosaurs include the largest terrestrial animals ever to have existed. At present, Sauropoda comprises twenty-two genera. Sauropods have small skulls in relation to their body size, extremely elongate necks and tails, columnar limbs, and stout, barrel-shaped bodies. Sauropod remains have been recovered from all continents except Antarctica. They are found in mass accumulations (bone beds) in the Morrison Formation of the western United States, in the Tendaguru Beds of East Africa, in the Kota Formation of India, in the Lower Shaximiao Formation of the Sichuan Basin in China, and in the Cañodon Asfalto Formation of Patagonia.
The Middle Jurassic Walloon Subgroup is a prolific coal seam gas (CSG) resource in the Surat Basin, Queensland. Sedimentary framework models constrain stochastic reservoir models of the geological heterogeneity, but there is limited basin analysis information in the public domain. Here we present a regionally consistent stratigraphic framework model for the Walloon CSG play in the eastern Surat Basin. Lithostratigraphic correlation of open-file industry and government wireline logs supports the interpretation of six subunits in the eastern Surat Basin (oldest–youngest: Durabilla Formation; Taroom Coal Measures; Tangalooma Sandstone; and Juandah Coal Measures, informally divided into three members named the lower Juandah Coal Measures, Juandah sandstone and upper Juandah Coal Measures). Important findings are that subunits within the Walloon Subgroup do not correlate along the entire CSG play area; in many places, the overlying Springbok Sandstone (Upper Jurassic) has incised to the lower Juandah Coal Measures level, removing the upper coal seam groups. The Walloon Subgroup thins to the south through a combination of depositional thinning and truncation. Lithofacies analysis and isopach maps support deposition in a southerly prograding fluvial system or clastic wedge. This stratigraphic and depositional interpretation informs models for hydrogeological studies of the Walloon Subgroup and underpins a regional assessment of controls on microbial methane distribution.
Jurassic plesiosaur fossils are exceptionally rare in Australia and currently restricted to a single fragmentary skeleton (Sinemurian, Razorback beds, Queensland), some articulated vertebrae (lower Toarcian, Evergreen Formation, Queensland) and a few isolated bones and teeth (Aalenian–Bajocian, Champion Bay Group, Western Australia). These remains are attributable to either indeterminate plesiosaurs, or more specifically to pliosauroids and plesiosauroids, and occur within a variety of fluviatile‐lacustrine to coastal marine depositional settings. Although hampered by their incompleteness, Australia’s Jurassic plesiosaurs are significant because they include some of the most ancient occurrences from nonmarine strata, and Gondwanan marine reptiles of a similar age are otherwise very sparsely known.
The Early–mid Cretaceous marks the confluence of three major continental-scale events in eastern Gondwana:
(1) the emplacement of a Silicic Large Igneous Province (LIP) near the continental margin;
(2) the volcaniclastic fill, transgression and regression of a major epicontinental seaway developed over at least a quarter of the Australian continent; and
(3) epeirogenic uplift, exhumation and continental rupturing culminating in the opening of the Tasman Basin c. 84 Ma.
The Whitsunday Silicic LIP event had widespread impact, producing both substantial extrusive volumes of dominantly silicic pyroclastic material and coeval first-cycle volcanogenic sediment that accumulated within many eastern Australian sedimentary basins, and principally in the Great Australian Basin system (>2 Mkm3 combined volume). The final pulse of volcanism and volcanogenic sedimentation at c. 105–95 Ma coincided with epicontinental seaway regression, which shows a lack of correspondence with the global sea-level curve, and alternatively records a wider, continental-scale effect of volcanism and rift tectonism. Widespread igneous underplating related to this LIP event is evident from high paleogeothermal gradients and regional hydrothermal fluid flow detectable in the shallow crust and over a broad region. Enhanced CO2 fluxing through sedimentary basins also records indirectly, large-scale, LIP-related mafic underplating. A discrete episode of rapid crustal cooling and exhumation began c. 100–90 Ma along the length of the eastern Australian margin, related to an enhanced phase of continental rifting that was largely amagmatic, and probably a switch from wide–more narrow rift modes.
Along-margin variations in detachment fault architecture produced narrow (SE Australia) and wide continental margins with marginal, submerged continental plateaux (NE Australia). Long-lived NE-trending cross-orogen lineaments controlled the switch from narrow to wide continental margin geometries.
Remains of plesiosaurs (aquatic reptiles of the suborder Plesiosauria,
order Sauropterygia) are known from Cretaceous sediments in every
continent1, including Antarctica2. Jurassic
plesiosaurs, by contrast, seem to have had a more restricted
distribution, and are virtually unknown outside the Northern Hemisphere.
We report here the discovery of two plesiosaur specimens in the Lower
Jurassic of the eastern part of the Surat Basin, Queensland. These are
the earliest adequate examples of plesiosaurs to be discovered in the
Gondwana continents, and they greatly extend the known geographical
range of early sauropterygians.
Natural casts of seven small footprints have been identified on a single weathered block derived from the Precipice Sandstone (Lower Jurassic) of the Carnarvon Gorge, southeastern Queensland. The footprints are attributed to ornithopod dinosaurs and are referred to the ichnogenus Anomoepus. They appear to be most similar to the ichnospecies Anomoepus gracillimus, originally defined on footprints from the Lower Jurassic of the northeastern United States. This identification is consistent with the presumed age of the Precipice Sandstone, since Anomoepus or closely related ichnotaxa are common in Lower Jurassic sediments of the United States, Europe and southern Africa but have never been identified with certainty in Triassic sediments. The tracks described here were made by at least four dinosaurs, all estimated to have been about 30 cm high at the hip and less than 1·3 m in total length. In their general appearance these animals probably resembled the small plant-eating dinosaur Fabrosaurus (Lesothosaurus), from the Lower Jurassic of southern Africa. Tracks of two animals provide estimates of walking speeds between 0·68 and 0·80 m/s (2·4 and 2·9 km/h). These footprints are the earliest evidence for the existence of ornithischian dinosaurs in Australia.
We test the research strategy of using youngest U–Pb ages of detrital zircons to constrain the maximum depositional ages of strata containing the zircon grains by comparing U–Pb ages of detrital zircons in 58 samples of Mesozoic sandstone from the Colorado Plateau and adjacent areas with depositional ages known independently from biostratigraphy. Our analysis confirms the validity of the research strategy but indicates that results vary somewhat depending upon how youngest grain age is specified. We use four alternate measures of youngest age which vary from least to most statistically robust as follows: (a) youngest single grain age, (b) youngest graphical age peak controlled by more than one grain age; (c) mean age of the youngest two or more grains that overlap in age at 1σ, (d) mean age of the youngest three or more grains that overlap in age at 2σ. We also calculated the “youngest detrital zircon age” generated by Isoplot 2008 but do not recommend that model age as a youngest-age measure. In general, the youngest-age measures based on multiple grain ages are more consistently compatible with depositional ages, but the youngest single grain ages are compatible with depositional age for > 90% of samples, and lie within 5 Ma of depositional age for ~60% of samples. Selected minor discrepancies between youngest grain age and depositional age may reflect stratigraphic miscorrelations rather than errors in U–Pb geochronology.
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The Surat and Bowen Basins
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A palynological zonation of the Australian Mesozoic
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Jurassic spores and pollen grains from the Surat Basin
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A giant dinosaur from Durham Downs
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A Queensland fossil amphibian
- H A Longman
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Late Early to Late Jurassic palynology, biostratigraphy and palaeogeography of the Roma Shelf area
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Ornithischian dinosaurs in Australia
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