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Xenoceratops foremostensis gen. et. sp. nov., a new centrosaurine ceratopsid from the Foremost Formation (Campanian) of Alberta, is described based on frill material from at least three adult-sized individuals collected from a low-density bone bed. The material can be assigned to Centrosaurinae based on features of the preserved squamosal. Although the parietals are incomplete, the shape of the diagnostic parietal can be inferred from several overlapping serial elements. The parietal of the new taxon shares with all other centrosaurines, except Centrosaurus apertus, spike-like ornamentation at the posterolateral (P3) locus under traditional coding methods. At approximately 78 Ma, it is the oldest known Canadian ceratopsid, approximately 0.5 Ma older than Albertaceratops from the lower Oldman Formation of Canada and approximately 1.0 Ma younger than Diabloceratops from the Wahweap Formation of Utah. A phylogenetic analysis resolves the new taxon as the basalmost centrosaurine and places Centrosaurus brinkmani as the sister taxon to Styracosaurus albertensis. The type species of Centrosaurus brinkmani is moved to a new genus. Xenoceratops foremostensis gen. et. sp. nov., un nouveau ceratopside centrosaurine de la Formation de Foremost (Campanien) d'Alberta, est decrit a la lumiere de materiel de collerette provenant d'au moins trois individus de taille adulte recueilli dans un lit a ossements de faible densite. Le materiel peut etre affecte aux Centrosaurines a la lumiere de caracteristiques des os squamosaux preserves. Bien que les os parietaux soient incomplets, la forme du parietal diagnostique peut etre inferee a la lumiere de plusieurs elements en serie superposes. Le parietal du nouveau taxon a en commun avec ceux de tous les autres centrosaurines, a l'exception de Centrosaurus apertus, une ornementation d'aspect epineux de la bordure posterolaterale (P3), selon les methodes de codage traditionnelles. Datant d'environ 78 Ma, il s'agit du plus ancien ceratopside canadien connu, precedant d'environ 0.5 Ma Albertaceratops, de la partie inferieure de la Formation d'Oldman du Canada, et d'environ 1.0 Ma Diabloceratops, de la Formation de Wahweap de l'Utah. L'analyse phylogenetique etablit que le nouveau taxon est le centrosaurine le plus basal et situe Centrosaurus brinkmani comme taxon-frere de Styracosaurus albertensis. L'espece type de C. brinkmani est reaffectee a un nouveau genre. [Traduit par la Redaction], Introduction Ceratopsidae is the most speciose clade of dinosaurs known from the Late Cretaceous of Laramidia. The fossil-rich Belly River and Edmonton groups of Alberta, Canada, alone have produced at [...]

To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.earscirev.2008.11.004 Byline: G.J.H. McCall Keywords: impact structures; craters; shock metamorphism; geophysical investigations; biotic extinctions Abstract: The author, who investigated the Wolfe Creek, Australia, in 1962 and edited two Benchmark Sets of Readings on Meteorite Craters and possible Astroblemes in 1977 and 1979, reviews the state of knowledge at the present time. The text is concerned with terrestrial impact structures, geological features, without any consideration of extraterrestrial analogues. A handful of definitive publications are drawn on to present the story of terrestrial impact in a single article. The text covers historical aspects (briefly); the effect of target variations; the paucity of human observation of such large-scale events; distinction from volcanic (endogenous) structures; modification by geological processes; the transience of the crater initially formed on the target, and its subsequent modifications; the global geographic distribution of the 174 structures now listed (of which a number are dubious attributions); their distribution in geological time (many ages being known only known to wide limits, maximum or minimum values); their size distribution; calculations of impact frequencies; shock effects; processes on impact; the stages of formation; impact into shallow marine and deep sea targets; impacts on ice (about which little is known); and finally the input of impact into biotic extinctions. In this last lengthy section, the summaries of the conclusions of scientists researching impact on Earth and palaeontologists researching biotic impact are set side by side. It is concluded that, if the recent foraminiferal evidence obtained by Gerta Keller and associates is taken at its face value, the case of impact as a sole agent in extinction is non-existent: biotic extinction is clearly a complex process involving a number of causes, in some cases it was staggered in time, and different sets of organisms responded quite differently and surprisingly, even in the same extinction event. Extraterrestrial impact may have been one of the causes in some cases, but it may have been regional rather than global in its effects. We may never know how much input it had into the record of biotic extinction on Earth? An enormous amount of new knowledge has arisen from detailed studies of this new family of remarkable geological structures. Author Affiliation: Western Australian Museum, 44 Robert Franklin Way, South Cerney, Glos., England GL7 5UD, United Kingdom Article History: Received 3 March 2008; Accepted 12 November 2008

To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.earscirev.2008.09.001 Byline: Renato Posenato Keywords: biostratigraphy; magnetostratigraphy; carbon isotopes; Early Triassic; Dolomites; Southern Alps Abstract: The Dolomites (Southern Alps, Italy) are a reference-area for research on the end-Permian mass extinction and its Early Triassic aftermath. The effects on shallow marine benthic biota are recorded in the Werfen Formation, a thick mixed carbonate-siliciclastic sedimentary succession. Only in its lower (Griesbachian) and upper (Spathian) parts, this formation is bio-chronologically constrained by means of conodonts and ammonoids, whilst no significant bioevent occurs in its middle part. This represents an impediment to the biochronologic recognition of the Induan/Olenekian boundary (IOB). The Bulla/Pufels (Val Gardena) succession is a key-section for the P/T boundary and Early Triassic for global correlation due to the abundance of studies on biostratigraphy (mostly on conodonts), magnetostratigraphy and chemostratigraphy carried out there by stratigraphers of various nationalities. Recent chemostratigraphic studies have permitted the recognition of some carbon isotope positive peaks, the strongest of which is considered to approximate the IOB. However, various authors have reached different conclusions on the position of the maximum peak and thus on the IOB location. This leads to important stratigraphic consequences for the calibration of conodont biostratigraphy. The critical revision of the traditional stratigraphic units (litho- and biostratigraphy), under-evaluated in most of the recent literature, and magneto-, chemo- and sequence stratigraphic units allowed herein an integrated stratigraphic scale for the Bulla/Pufels section to be proposed. This contribution highlights the mid Early Triassic Dolomites record for regional and global correlations. The most significant results attained herein regard the different lithostratigraphic subdivisions of the middle Werfen Formation and its consequences on the position of the IOB with respect to the conodont and bivalve biostratigraphy and sequence stratigraphic units. The upper part of the section is attributed herein to the Gastropod Oolite Member, which is represented by the lithozone A, a predominant supratidal episode, and the lower part of the subtidal lithozone B. Between the lithozones A and B, a sequence boundary of 3th order (Sc2/Sc3) is located. The maximum carbon isotope excursion is near this boundary, which therefore approximates the IOB in the Dolomites. This proposal suggests a Dienerian age for the FO of the conodont Pachycladina obliqua, which occurs about 60 m below the stage boundary. No significant biotic event, either for molluscs or conodonts, occurred across this stage boundary. Author Affiliation: Dipartimento di Scienze della Terra, Universita di Ferrara, Via Saragat 1, 44100 Ferrara, Italy Article History: Received 13 March 2008; Accepted 23 September 2008

Abstract In 2006 volcanic glass deposits on Vanua Lava and Gaua Islands were re-visited and systematically sampled. Twenty-nine source samples were analysed using EDXA-SEM and LA-ICP-MS with a focus on [...]

Abstract: Pre-Mesozoic rocks are exposed on the southeastern third of Grand Manan Island and adjacent offshore islands in the Bay of Fundy. U-Pb (zircon) ages reported here demonstrate that most [...]

Earth is the only known planet with subduction zones and plate tectonics, and this fact demonstrates that special conditions are required for this mode of planetary heat loss. Sinking of cold, dense lithosphere in subduction zones is the principal plate-driving force, so plate tectonics could not have begun until Earth cooled sufficiently to allow lithosphere to collapse into the underlying asthenosphere. Direct geologic evidence for when the modern episode of subduction tectonics began focuses on the first appearance of ophiolitic graveyards, blueschist facies metamorphic rocks, and ultrahigh-pressure metamorphic terranes. Ophiolites manifest two modes of lithospheric motion expected from subduction tectonics: seafloor spreading and obduction. High-pressure, low-temperature metamorphic blueschists and ultrahigh-pressure terranes indicate subduction and exhumation of oceanic and continental crust, respectively. These lines of evidence indicate that the modern style of subduction tectonics began in Neoproterozoic time. This revolution in the functioning of the solid Earth may have driven wild fluctuations in Earth's climate, described under the 'snowball Earth' hypothesis. These conclusions may be controversial, but suggest fruitful avenues for research in geodynamics and paleoclimate. Keywords: plate tectonics, Neoproterozoic, ophiolites, blueschist, ultrahigh-pressure metamorphism, subduction.