Palaeogeographical Information Research Articles

A large-clawed theropod (Dinosauria: Tetanurae) from the Lower Cretaceous of Australia and the Gondwanan origin of megaraptorid theropods

Megaraptoridae comprises a clade of enigmatic Gondwanan theropods with characteristic hypertrophied claws on the first and second manual digits. The majority of megaraptorids are known from South America, although a single genus (Australovenator) plus additional indeterminate material is also known from Australia. This clade has a controversial placement among theropods, and recently has been interpreted alternatively as a carcharodontosaurian or a tyrannosauroid lineage. We describe new fragmentary but associated postcranial remains from the opal fields of Lightning Ridge (middle-Albian, Griman Creek Formation) in north-central New South Wales. The new unnamed taxon exhibits a number of unusual features that suggest the presence of a hitherto unrecognised Australian megaraptorid. From an Australian perspective, the Lightning Ridge taxon predates Australovenator by ca. 10Ma and is minimally coeval with megaraptoran material reported from the Eumeralla Formation of Victoria (but potentially 6.1–9.5Ma younger). It is also notable as the largest predatory dinosaur yet identified from Australia and is only the second theropod known from more than a single element. A Bayesian phylogenetic approach integrating morphological, stratigraphic and palaeogeographic information tested both the carcharodontosaurian and tyrannosauroid placements for Megaraptora. Regardless of the preferred placement among Tetanurae, rigorous palaeobiogeographic analyses support an Asian origin of Megaraptora in the latest Jurassic (about 150–135Ma), an Early Cretaceous (about 130–121Ma) divergence of the Gondwanan lineage leading to Megaraptoridae, and an Australian root for megaraptorid radiation. These results indicate that Australia's Cretaceous dinosaur fauna did not comprise simply of immigrant taxa but was a source for complex two-way interchange between Australia–Antarctica–South America leading to the evolution of at least one group of apex predatory dinosaurs in Gondwana.

Cryogenic Deformation Structures in Late Cenozoic Unconsolidated Sediments of the Tunka Depression in the Baikal Rift Zone

The Late Cenozoic alluvial deposits in the Tunka depression of the Baikal Rift Zone, Russia, contain wedge-shaped structures and involutions that provide valuable palaeogeographic information about the southern part of eastern Siberia. The structure of the unconsolidated host deposits, the shape and size of the deformation structures (wedge shaped, wave like or drop like) and the physical-mechanical properties of the sediments (particle size, density, porosity, water content and colour) point to a cryogenic origin of the deformation structures, as ice wedge pseudomorphs and cryoturbations, rather than an origin associated with seismic activity or sedimentation. The oldest pseudomorphs and cryoturbations developed during climate-warming periods of the subboreal climatic phase (3600–2600 years ago). Copyright © 2014 John Wiley & Sons, Ltd.

Phylogeny of the Saxifraga-associated species of Dichotrachelus (Insecta: Coleoptera: Curculionidae), with remarks on their radiation in the Alps

A phylogenetic analysis of the Saxifraga-associated species of Dichotrachelus was carried out based on morphological and, for some species, molecular data. The various methods implemented gave congruent results and yielded a significantly supported phylogenetic inference of the relationships among the species. Saxifraga-associated species form a monophyletic unit, and some species-groups were evidenced, distributed in the eastern, central and western Alps, respectively. Based on the phylogenetic inference, and taking into account palaeogeological and palaeogeographical information, a biogeographic scenario of the events that may have led to the present-day distribution is proposed.

Palaeomagnetic re-investigation of Early Permian rift basalts from the Baoshan Block, SW China: constraints on the site-of-origin of the Gondwana-derived eastern Cimmerian terranes

A palaeomagnetic investigation was carried out on a series of rift basalts (Woniusi Formation) that accumulated on the Baoshan block (SW China) in the Early Permian, the aim being to provide quantitative palaeogeographical information on the eastern Cimmerian terrane as it detached from eastern Gondwana. Reliable data were obtained from four locations/28 individual cooling units, and when combined with the findings of an earlier study (three locations/19 sites) indicate that breakup occurred at 41.9°S (with errors, 34.2-51.2°S). Using this information, we fit Baoshan against Gondwana within a narrow longitudinal belt close to where northeast Greater India and northwest Australia were once in close proximity. Furthermore, we suggest that Sibumasu (Simao-Burma-Malyasia-Sumatra; the largest of the eastern Cimmerian blocks) lay directly to the east, offshore of Australia; Qiangtang and Lhasa almost certainly sat to the west (off northern Greater India-SE Arabia), but we are uncertain as to their exact configuration. Our findings are compared with several rather different models that have been published in recent years. The new palaeomagnetic constraint highlights the flexibility authors currently have in reconstructing the region, principally because of the overall lack of similar high-quality data from the various blocks. We explain how new data could resolve these ambiguities, thereby offering more robust explanations for eastern Gondwana's late Palaeozoic development.

An evaluation of new parsimony-based versus parametric inference methods in biogeography: a case study using the globally distributed plant family Sapindaceae

Aim Recently developed parametric methods in historical biogeography allow researchers to integrate temporal and palaeogeographical information into the reconstruction of biogeographical scenarios, thus overcoming a known bias of parsimony-based approaches. Here, we compare a parametric method, dispersal–extinction–cladogenesis (DEC), against a parsimony-based method, dispersal–vicariance analysis (DIVA), which does not incorporate branch lengths but accounts for phylogenetic uncertainty through a Bayesian empirical approach (Bayes-DIVA). We analyse the benefits and limitations of each method using the cosmopolitan plant family Sapindaceae as a case study. Location World-wide. Methods Phylogenetic relationships were estimated by Bayesian inference on a large dataset representing generic diversity within Sapindaceae. Lineage divergence times were estimated by penalized likelihood over a sample of trees from the posterior distribution of the phylogeny to account for dating uncertainty in biogeographical reconstructions. We compared biogeographical scenarios between Bayes-DIVA and two different DEC models: one with no geological constraints and another that employed a stratified palaeogeographical model in which dispersal rates were scaled according to area connectivity across four time slices, reflecting the changing continental configuration over the last 110 million years. Results Despite differences in the underlying biogeographical model, Bayes-DIVA and DEC inferred similar biogeographical scenarios. The main differences were: (1) in the timing of dispersal events – which in Bayes-DIVA sometimes conflicts with palaeogeographical information, and (2) in the lower frequency of terminal dispersal events inferred by DEC. Uncertainty in divergence time estimations influenced both the inference of ancestral ranges and the decisiveness with which an area can be assigned to a node. Main conclusions By considering lineage divergence times, the DEC method gives more accurate reconstructions that are in agreement with palaeogeographical evidence. In contrast, Bayes-DIVA showed the highest decisiveness in unequivocally reconstructing ancestral ranges, probably reflecting its ability to integrate phylogenetic uncertainty. Care should be taken in defining the palaeogeographical model in DEC because of the possibility of overestimating the frequency of extinction events, or of inferring ancestral ranges that are outside the extant species ranges, owing to dispersal constraints enforced by the model. The wide-spanning spatial and temporal model proposed here could prove useful for testing large-scale biogeographical patterns in plants.

Lower Cretaceous calcareous nannoplankton from the Neuquén Basin, Argentina

We present nannofossil analyses from five new sections of the Neuquén Basin, which together provide a relatively continuous stratigraphic succession ranging from Tithonian to Hauterivian (Vaca Muerta to Agrio Formations). The sections provide an opportunity to study nannofossils from a relatively little-studied area, which nevertheless represents an important marginal basin and a relict of the single, largest Mesozoic marine habitat, the Pacific Ocean. Our aims were, firstly, to generate biostratigraphic data in order to test existing ammonite-based age-models and, ultimately, to improve stratigraphic correlations between the Argentinian sections and global chronostratigraphic standards; and, secondly, to collect palaeogeographic information in order to improve our understanding of Mesozoic nannoplankton distributions and ecology. The sections yielded a continuous nannofossil succession, with assemblages of moderate preservation, abundance and diversity. Although many standard biostratigraphic index-species, of both Boreal and Tethyan affinities, were absent, we were able to use age-diagnostic taxa to provide a relatively robust stratigraphic framework (the first and last occurrences of Clepsilithus maculosus, Cruciellipsis cuvillieri, Eiffellithus primus, Eiffellithus windii, Eiffellithus striatus, Lithraphidites bollii and Nannoconus? ligius). Throughout the sections, there is remarkably good agreement between the correlation suggested by the nannofossils, based largely on globally distributed species, and ammonites, which are largely endemic to the basin. The Vaca Muerta and Upper Agrio Member correlations are identical, or within one or two ammonite zones. The Lower Agrio Member correlations are similarly close, but the occurrence of wide-canalled nannoconids suggests slightly younger, latest Valanginian to early Hauterivian, ages for much of the member. The Neuquén nannofossil assemblages are rather low in diversity and suggest that the basin supported a restricted nannoflora, dominated by shelf-adapted taxa ( Watznaueria, Micrantholithus, Nannoconus). Biogeographically distinctive taxa, whether Tethyan or Boreal-Austral, are limited to a few rare and sporadically distributed examples but two new species of Crucibiscutum may prove to be Austral in affinity. The presence of nannoconids consistently from the late Valanginian indicates the presence of a good, shallow-marine connection with Tethys via the Hispanic Corridor seaway, but their low abundance and rather sporadic occurrence suggests they were probably at the limits of their ecological ranges. Four new nannofossil species are described: Crucibiscutum trilensis, Crucibiscutum neuquenensis, Calculites suturus and Nannoconus quadricanalis.

‘Laramide’ events: Mid North Sea High (UK Quadrants 38 & 39)

The Mid North Sea High is a broad, approximately east-trending structural high that extends from the coast of the Scottish Borders region to the UK North Sea median line. Recently acquired seismic reflection profiles were used to map isopach patterns of the Chalk Group (Upper Cretaceous and lowermost Paleocene), of the combined Montrose and Moray groups (Paleocene and lowermost Eocene), and of the lower Stronsay Group (lower Eocene) in UK Quadrants 38 and 39, on the eastern Mid North Sea High. In an anomalous and undrilled part of this area, the Chalk Group thins over an area broadly centred on a long lived, buried, NNW-trending structural high with a core largely comprised of Devono-Carboniferous sediments. In contrast, the combined Montrose and Moray groups and the lower Stronsay Group sediments thicken over the buried high. We informally name the buried high the α Ridge. Signal processing techniques were applied to the original stack sections to help clarify the geometry of seismic reflections, especially from within the Chalk Group and Palaeogene successions of the anomalous zone, and to interpret deep erosion at the top of the Chalk Group that probably occurred in Danian times. The area of deeply eroded Chalk was subsequently buried beneath an anomalously thick Palaeogene succession. The area of eroded Chalk is more extensive than the α Ridge and extends northwards beyond the survey area. From a regional perspective, the processes that may have controlled the observed depositional pattern are discussed. It is considered whether rapidly changing tectonic stress may have caused local ‘Laramide’ (mid Paleocene–Danian) uplift and erosion of the α Ridge and its immediately surrounding area, swiftly followed by enhanced subsidence (inversion) and deposition in the mid Paleocene (Danian), or whether the stratal pattern is better explained by the infilling of a large erosional hollow; mechanisms involving the local halokinesis and/or dissolution of Zechstein salt are discounted. We conclude that additional seismic and palaeogeographical information is required to fully test the models proposed in this paper.

Rates of delta progradation during highstands: consequences for timing of deposition in deep-marine systems

Estimated times required for 24 modern river systems to form a shelf-edge delta range from 8.5 ka to 116.5 ka, depending on fluvial sediment supply, delta width, shelf volume and shelf transport rates. These values indicate that transport of sand into deep-marine systems is likely to be significant during third-order highstands of relative sea-level. Factors such as shelf transport dynamics may slow delta progradation while submarine canyons cutting the shelf may reduce the time before deep-marine deposition occurs. Interpreting ancient sand-rich deep-marine strata as lowstand deposits without sufficient palaeogeographic information may not therefore always be appropriate.

Late Cretaceous Peruvian eggshells and their relationships with Laurasian and eastern Gondwanian material : Vianey-Liaud M., Hirsch K., Sahni A. & Sige B., Geobios, 1997, 30/1, (75–90)

Megaraptoridae comprises a clade of enigmatic Gondwanan theropods with characteristic hypertrophied claws on the first and second manual digits. The majority of megaraptorids are known from South America, although a single genus (Australovenator) plus additional indeterminate material is also known from Australia. This clade has a controversial placement among theropods, and recently has been interpreted alternatively as a carcharodontosaurian or a tyrannosauroid lineage. We describe new fragmentary but associated postcranial remains from the opal fields of Lightning Ridge (middle-Albian, Griman Creek Formation) in north-central New South Wales. The new unnamed taxon exhibits a number of unusual features that suggest the presence of a hitherto unrecognised Australian megaraptorid. From an Australian perspective, the Lightning Ridge taxon predates Australovenator by ca. 10 Ma and is minimally coeval with megaraptoran material reported from the Eumeralla Formation of Victoria (but potentially 6.1–9.5 Ma younger). It is also notable as the largest predatory dinosaur yet identified from Australia and is only the second theropod known from more than a single element. A Bayesian phylogenetic approach integrating morphological, stratigraphic and palaeogeographic information tested both the carcharodontosaurian and tyrannosauroid placements for Megaraptora. Regardless of the preferred placement among Tetanurae, rigorous palaeobiogeographic analyses support an Asian origin of Megaraptora in the latest Jurassic (about 150–135 Ma), an Early Cretaceous (about 130–121 Ma) divergence of the Gondwanan lineage leading to Megaraptoridae, and an Australian root for megaraptorid radiation. These results indicate that Australia's Cretaceous dinosaur fauna did not comprise simply of immigrant taxa but was a source for complex two-way interchange between Australia–Antarctica–South America leading to the evolution of at least one group of apex predatory dinosaurs in Gondwana.

Statistical analysis of palaeomagnetic inclination data

Palaeomagnetic studies on bore core or on tectonically disturbed localities often lose declination information, but the inclination still offers important palaeogeographic information. While the arithmetic mean of inclinations, Ī, is a biased estimator, the bias is negligible with shallow data. Using co-inclination ¯θ=90°−|Ī| and precision K*=1/variance, we find that the arithmetic mean and associated 95 per cent confidence interval are acceptable estimates when . When inclination is steep and /or precision low, numerical methods must be applied. We develop the likelihood function for θ and K and offer an efficient method to find its maximum, (^θ,^κ), and to calculate the confidence interval. When , the confidence interval is asymmetric about the mean. When sites are collected from several rigid blocks, the relative declinations within each block can be useful. Using ‘block-rotation Fisher analysis’, better inclination estimates with tighter confidence intervals can be made, even on very steep data. We describe how to apply these methods to an inclination-only fold test. The techniques are illustrated on real data and are tested extensively using numerical simulations.

Holocene tides of The Wash, U.K.: The influence of water-depth and coastline-shape changes on the record of sea-level change

Tidal simulations are conducted using a numerical model to investigate the relative influence of water depth and coastline shape changes on the Holocene tides of The Wash. Tidal input to this model is obtained by running a nested series of models commencing with a model of the northeast Atlantic. Results of both types of simulations are compared with those of other simulations incorporating all the palaeogeographic information available on both past water depths and coastline shapes around The Wash. The model employs six harmonic tidal constituents to obtain mean high water of spring tides (MHWST) altitudes. The Wash was a depositional embayment during the Holocene and results of model simulations are compared with sea-level indicators in the stratigraphy which record past MHWST altitudes. Tidal simulations for water depths reduced by 2, 5 and 10 m compared with present sea levels generally give lower tidal amplitudes around The Wash than found at present. MHWST altitudes simulating the coastline shape for 3000, 4000 and 5000 yrs B.P. utilising present water depths show similar patterns of tidal changes to those obtained from the palaeogeographic simulations. However, reduced water-depth tidal simulations accord more closely with the palaeogeographic simulation results in terms of the magnitude of changes to MHWST altitudes than the palaeocoastline simulations. This is due to the fact that the rise in mean sea level during the Holocene is far greater than any change in the amplitude of tides in The Wash. Palaeogeographic simulation model results for MHWST agree, within experimental errors, with sea-level curve altitudes. Reasons for discrepancies include inaccuracies in model parameters or measurement errors in obtaining MHWST altitudes from the stratigraphy. Overall, tidal heights increase with sea-level rise towards the present day. Alterations to coastline shape and non-uniform water-depth changes (for example, due to sediment movements or coastal defence schemes), must be taken into consideration when assessing changes to the tidal regime for different sea levels in coastal embayments in order to determine both the pattern and magnitude of tidal changes. This applies to both past and possible future tidal simulations.

The Neogene larger foraminiferal sequence in the Australian and New Zealand regions, and its relevance to the East Indies Letter Stage Classification

In northern Australia, Neogene larger foraminifera range from the Late Oligocene into the earliest Middle Miocene, and are restricted to the late Early Miocene in southern Australia. In contrast, these forms range over a longer interval in New Zealand, from Late Oligocene to mid-Middle Miocene. Even though correlation with the Letter Stages lower T e to lower T f can be achieved, the usefulness of these stages to southeastern Australia and New Zealand is reduced because of the lower diversity of faunas in this area, compared with areas nearer the equator. The association of good planktic foraminiferal faunas with the larger foraminifera further reduces the usefulness of the Letter Stage correlations because finer correlations can be achieved using planktic forms. The presence of larger foraminifera gives considerable environmental and palaeogeographic information.

West African and North American transgressional maxima and the dispersal of benthic organisms

Abstract The information currently available for dating the mid-Cretaceous (Albian-Coniacian) transgressions of the Gulf of Guinea in relation to the Western Interior of the United States is reviewed. The North American transgressions T5 (Late Albian), T6 (Late Cenomanian-Early Turonian) and T7 (Late Turonian-Coniacian) are represented in Nigeria, and T6 and T7 in Niger Republic; the North American Greenhorn (T6) and Nigerian Ezeaku (T6) cycles are the most extensive of the three. The biogeographical distributions of molluscs and ostracods are reappraised in the light of available palaeontological and geological information. Distributional patterns of pelecypods and gastropods along the western African seaboard are similarto what pertains today, thus implying that the palaeogeographical information they can supply is restricted. Ostracods present a different distributional display, which may reflect their physiological reaction to depth and sediment-type. Essential to the interpretation of the dispersal of fossil benthic organisms is the estimation of palaeobathymetrical conditions; an example using the occurrence in time of peralkaline intrusives is considered.

Palaeoenvironment and palaeogeography of Miocene marls from southeast Sicily and the Maltese Islands

Tortonian marls and clays are extensively developed in southeast Sicily. Macrofaunas are sparsely distributed in these strata except for a new section at Musenna Hill in the Vittoria-Scoglitti area. This section, together with two other coastal sequences of about the same age, are described for the first time. Their abundant faunas are recorded, ecological requirements for these faunas are considered and some attempt is made to place them into the known Sicilian Miocene Stratigraphy. The Musenna Hill section shows a particularly close relationship to the upper part of the Miocene Blue Clay Formation of the Maltese Islands, both from the viewpoint of sediment and macrofauna. The Maltese faunas are recorded in detail for the first time and ecological and palaeogeographical information is considered. An attempt at an overall regional palaeoenvironmental reconstruction is made for the Maltese and southeast Sicilian parts of the central Mediterranean for Tortonian times.

Intérêt paléobotanique et stratigraphique de l'étude palynologique des séries Jurassiques et crétacées du Sahara

The study of organic microfossils makes it possible to evaluate the periods during which the principal secondary vegetal taxa have differentiated, bloomed and regressed in the Sahara. Corresponding to these different periods, characteristic associations of species or predominant groups have a stratigraphic value as they occasionally extend over a great part of the Sahara. Jurassic and Cretaceous sediments are analysed, using samples from boreholes in the Tunisian and Algerian Sahara. The particular conditions of sedimentation (continental, lagunar or marine) have favoured the fossilisation of a great variety of plant microfossils, and “microorganontes” of marine or lagunar affinity. The study of these organic microfossils provides palaeobotanical, stratigraphical and palaeogeographical information about the Jurassic and Lower Cretaceous of one part of the African continent.