A Late Neoproterozoic age for a tonalite dyke in the Boisdale Hills, Cape Breton Island, Nova Scotia

A tonalite dyke in the Benacadie Brook Formation in the Boisdale Hills of central Cape Breton Island yielded a U-Pb (zircon) age of 564.5 ± 5.1 Ma, interpreted to be the age of intrusion. The age is identical within error to the U-Pb (zircon) age of 564 +3/-2 Ma previously reported for a granodiorite sample from the nearby Shunacadie Pluton. Based on geographic proximity and identical age, as well as petrological similarities, the tonalite dyke is interpreted to be comagmatic with the granodiorite. Although the new date does not provide further constraint on the age of the Benacadie Brook Formation, it affirms the importance of ca. 560 Ma plutonism in the Bras d'Or terrene of Cape Breton Island. RÉSUMÉ Un dyke de tonalite intrusive dans la formation de Benacadie Brook, dans les collines du centre de l’ile du Cap-Breton, a révèlé une datation au U-Pb (au zircon) de 564.5 ± 5.1 m.a. Cette datation est la même que celle obtenue au U-Pb (au zircon) de 564 +3/-2 m.a. signalee précéiemment pour un echantillon de granodiorite de la formation plutonique adjacente de Shunacadie. Compte tenu de la proximité g&jgraphique, du même âge et d'autres similitudes pétrologiques, ce dyke de tonalite est repute appartenir a la mfime province petrographique que la granodiorite. Bien que cette nouvelle datation ne donne pas d'autres précisions sur l’âge de la formation de Benacadie Brook, elle n'en établit pas moins I'importance de l'activité plutonique survenue dans le terrene du Bras d'Or sur l’ile du Cap-Breton il y a environ 560 m.a. Traduit par la rédactio

Note: U-Pb baddeleyite dating clarifies age of characteristic paleomagnetic remanence of Long Range dykes, southeastern Labrador

A second age of 615 Ma has been obtained for the Long Range dykes in Labrador. This age removes uncertainty, introduced by anomalous paleomagnetic results, that more than one age of dykes trending north-northeast is present in the region. It also establishes that the age of the primary magnetization of the Long Range dykes is 615 Ma. RÉSUMÉ On a obtenu un deuxième âge, fixé à 615 Ma, par rapport aux dykes de Long Range, au Labrador. Celui-ci élimine l'incertitude, qu'avaient amenée des résultats paléomagmétiques anomaux, au sujet de la présence de dykes de Long Range d'une direction nord-nord-est de plus d'un âge dans la région. On a en outre établi l'âge de la magnétisation originelle des dykes de Long Range à 615 Ma. [Traduit par la rédaction

A new U–Pb zircon age for an ash layer at the Bathonian–Callovian boundary, Argentina

A U–Pb zircon age of 164.64^0.2 Ma (95% confidence level) is reported for an ash bed, at the Bathonian–Callovian (late Middle Jurassic) boundary, determined by isotope dilution thermal ionisation mass spectrometry from individual, chemically abraded grains. The volcanic ash layer occurs within the Chacay Melehue Formation, Chacay Melehue section, Neuque´n Province, central west Argentina, above the last record of ammonites of the regional Lilloettia steinmanni Standard Zone, and, stratigraphically, where the first of those of the regional Eurycephalites vergarensis Standard Zone appears, generally referred to as the uppermost Bathonian and the lowermost Callovian, respectively. This ash layer represents the only known datable horizon worldwide that is directly related to a well-documented ammonite faunal succession at this boundary. The U–Pb zircon age is older than one previously reported for the same bed and closer to an estimation of 164.7^4Ma for the boundary based on the scaling durations of ammonite zones to their subzones in the sub-boreal standard zonation. The new age agrees better with the age model for the Oxfordian through Bathonian M-sequence magnetic anomalies in the Pacific and contributes to the radioisotopic age calibration of the Jurassic time scale.Facultad de Ciencias Naturales y Muse

Pohjois-Suomen varhaisproterotsooisen Näränkävaaran kerrosintruusion petrogeneesi, osa II: U-Pb ID-TIMS -ikä ja Sm-Nd-isotooppisystematiikka

Several mafic-ultramafic layered intrusions were emplaced in the NE Fennoscandian Shield during a magmatic episode at 2.44 Ga. The Paleoproterozoic Näränkävaara layered intrusion, northern Finland, is one of the largest ultramafic bodies in the Fennoscandian Shield, with a surface area of 25 km x 5 km and a magmatic stratigraphic thickness of ~3 km. The intrusion comprises a 1.3 km-thick peridotitic–dioritic layered series (2436 ± 5 Ma) with two peridotitic reversals, and a 1.5–2 km thick basal dunite series mainly composed of olivine adcumulates (dated here). The intrusion has been studied since the 1960’s, but several questions regarding its structure and petrogenesis remain. The basal dunite shows several lithological features typical of komatiitic rather than intrusive olivine cumulates; namely, >1 km-thick “extreme” olivine adcumulates, some showing textures with bimodal grain sizes, oscillating variations in Mg# with stratigraphic height, and poikilitic chromite. With Archean greenstone belts nearby, it was previously hypothesized that the basal dunite series could represent an Archean komatiitic wall rock to the Paleoproterozoic layered series. However, our new U-Pb ID-TIMS baddeleyite age of 2441.7 ± 0.9 Ma for the basal dunite series shows that the basal dunite and layered series of the Näränkävaara intrusion are co-genetic. New whole-rock Sm-Nd isotope data from key stratigraphic units (initial εNd at 2440 Ma of -3.5 to -1.7) indicate that the intrusion was constructed from repeated emplacement of LREE-enriched high-MgO basaltic magmas that were mantle-derived and contaminated by crust, similarly to other Fennoscandian 2.44 Ga intrusions. The parental magmas show similar compositions regardless of stratigraphic position, suggesting that most wall rock contamination and homogenization had occurred before emplacement, with in situ contamination being a relatively minor process. The open-system features of the basal dunite suggest that it may have formed (at least partly) as a feeder channel cumulate, possibly related to the ~100 km long Koillismaa-Näränkävaara Layered Igneous Complex. The Näränkävaara parental magmas show variably depleted metal ratios and could have potential for orthomagmatic mineral deposits, given the availability of S-rich wall rocks.Peer reviewe

New age constraints on the Lower Jurassic Pliensbachian–Toarcian Boundary at Chacay Melehue (Neuquén Basin, Argentina)

The Pliensbachian–Toarcian boundary interval is characterized by a ~ 3‰ negative carbon-isotope excursion (CIE) in organic and inorganic marine and terrestrial archives from sections in Europe, such as Peniche (Portugal) and Hawsker Bottoms, Yorkshire (UK). A new high-resolution organic-carbon isotope record, illustrating the same chemostratigraphic feature, is presented from the Southern Hemisphere Arroyo Chacay Melehue section, Chos Malal, Argentina, corroborating the global significance of this disturbance to the carbon cycle. The negative carbon-isotope excursion, mercury and organic-matter enrichment are accompanied by high-resolution ammonite and nannofossil biostratigraphy together with U–Pb CA-ID-TIMS geochronology derived from intercalated volcanic ash beds. A new age of ~ 183.73 + 0.35/− 0.50 Ma for the Pliensbachian–Toarcian boundary, and 182.77 + 0.11/− 0.15 for the tenuicostatum–serpentinum zonal boundary, is assigned based on high-precision U–Pb zircon geochronology and a Bayesian Markov chain Monte Carlo (MCMC) stratigraphic age model

Comparative proteomics using 2-D gel electrophoresis and mass spectrometry as tools to dissect stimulons and regulons in bacteria with sequenced or partially sequenced genomes

We propose two-dimensional gel electrophoresis (2-DE) and mass spectrometry to define the protein components of regulons and stimulons in bacteria, including those organisms where genome sequencing is still in progress. The basic 2-DE protocol allows high resolution and reproducibility and enables the direct comparison of hundreds or even thousands of proteins simultaneously. To identify proteins that comprise stimulons and regulons, peptide mass fingerprint (PMF) with matrix-assisted laser desorption ionization/time-of-flight mass spectrometry (MALDI-TOF-MS) analysis is the first option and, if results from this tool are insufficient, complementary data obtained with electrospray ionization tandem-MS (ESI-MS/MS) may permit successful protein identification. ESI-MS/MS and MALDI-TOF-MS provide complementary data sets, and so a more comprehensive coverage of a proteome can be obtained using both techniques with the same sample, especially when few sequenced proteins of a particular organism exist or genome sequencing is still in progress

Clues to the Causes of Mass Extinctions in Earth History from U-Pb CA-ID-TIMS Geochronology

Mass extinctions in Earth history have repeatedly altered the course of evolution of life on our planet. The extent and rapid rate at which they occurred required processes that were global in scale and catastrophic in nature. Asteroid impacts and volcanic eruptions are cited as triggers of environmental change and subsequent biological turnover. Causal mechanisms remain enigmatic, partly due to a lack of precise and accurate ages to establish the timing and duration of events, and to limitations of interpreting existing ages due to inter-method and inter-laboratory bias. Two of the largest extinction events in the Phanerozoic were triggered by different processes. The Cretaceous-Paleogene (K-Pg) extinctions are widely accepted as due to the consequences of impact, yet the link between the K-Pg boundary layer and Chicxulub impact has been questioned. Shocked zircon from K-Pg ejecta in Spain and Italy are 550 ± 6 Ma (2 and show a correlation between intensity of shock metamorphism and discordance to the time of impact. The data are identical to those from Chicxulub and North American ejecta sites and together support a genetic association. Clarification of this link is essential to understanding the role of impact on end-Cretaceous climate and environment. The end-Permian extinctions are the most profound in the rock record and eruption of the Siberian Flood Volcanic rocks as the trigger is supported by U-Pb ID-TIMS ages. The ages indicate that the marine extinctions in China occurred early in the eruptive sequence prior to 251.99 ± 0.18 Ma (2 synchronous with emission of climate forcing gases. Continued environmental stress from eruption in the Noril’sk and Meymecha-Kotuy areas, may have promoted terrestrial extinctions in the Karoo Basin of South Africa and delayed recovery. The extent of environmental stress is related to the composition of target lithologies, the nature, quantity, and rate of emission of the volatile load, pre-existing oceanic and atmospheric conditions, and global plate configuration.Ph

Geochronology and lithogeochemistry of granitoid rocks from the central part of the Central plutonic belt, New Brunswick, Canada: implications for Sn-W-Mo exploration

The central part of the Central plutonic belt in New Brunswick is underlain by numerous plutons of calc-alkaline, foliated and unfoliated granite that intrude Cambrian to Early Ordovician metasedimentary rocks. U-Pb (zircon) dating demonstrates that granites range in age from Middle Ordovician to Late Devonian, although most are late Silurian to Early Devonian. An age of 467 ± 7 Ma has been obtained on the foliated McKiel Lake Granite, whereas unfoliated intrusions yield ages of 423.2 ± 3.2 Ma (Bogan Brook Granodiorite), 420.7 +1.8/-2.0 Ma (Nashwaak Granite), 419.0 ± 0.5 Ma (Redstone Mountain Granite), 416.1 ± 0.5 Ma (Beadle Mountain Granite), 415.8 ± 0.3 Ma (Juniper Barren Granite), 409.7 ± 0.5 Ma (Lost Lake Granite), and 380.6 ± 0.3 Ma (Burnthill Granite). All plutons exhibit mixed arc-like and within-plate geochemical signatures, although the Redstone Mountain and Burnthill granites are dominantly of within-plate type. Trace element data reveal a close overall geochemical similarity between Ordovician and Silurian – Devonian plutons, indicating that all were generated by partial melting of the same crustal source. Late Silurian to Early Devonian plutons mainly comprise biotite and/or muscovite-bearing, peraluminous granite and are considered prospective for granophile-element mineralization. All plutons contain Sn well in excess of the granite global average abundance, and several contain average tin values comparable to productive stanniferous granites elsewhere. The Burnthill, Lost Lake, Beadle Mountain, and Nashwaak granites are geochemically most evolved and enriched in Sn and W. The Burnthill Granite in particular has experienced late-stage hydrothermal processes that have resulted in local enrichments of these elements

First high-precision U–Pb CA–ID–TIMS age for the Battle Formation (Upper Cretaceous), Red Deer River valley, Alberta, Canada: implications for ages, correlations, and dinosaur biostratigraphy of the Scollard, Frenchman, and Hell Creek formations

The Battle Formation (BFm) is a widespread Upper Cretaceous marker horizon in western Canada that records a time of low sediment-input and marks the boundary between the Edmontonian and Lancian land-vertebrate ages. Here, we present the first high-precision U-Pb CA-ID-TIMS age of 66.936 ± 0.047/0.060/0.140 Ma for the Battle bentonite, an altered vitric ash in the upper portion of the BFm at Knudsen’s Farm in the Red Deer River valley of Alberta. This age supersedes those previously reported, confirms that rates of sediment accumulation for the formation were very low (~1.40 cm/ka), and allows us to interpolate an age range of ~66.88–67.20 Ma for the BFm. Our data also provide a maximum age of ~66.88 Ma for the base of the overlying Scollard Formation, a dinosaur-rich unit. We combine our age data with calibrated magneto- and palynostratigraphic data to assess chronostratigraphic correlations among the Scollard Formation (K-ScF) of Alberta, the Frenchman Formation (FFm) of Saskatchewan, and the Hell Creek Formation (HCF) in eastern Montana. Whereas the combined data support previous interpretations that equate the age ranges of the K-ScF, FFm, and the upper one-third of the HCF in eastern Montana, they also indicate that all of the lower one-third (L3) and part of the middle one-third (M3) of the HCF in Montana are chronostratigraphically equivalent to all or part of the sub-BFm unconformity and the BFm in Alberta. Accordingly, a minimum age of ~67.20 Ma is assessed for the base of the Hell Creek Formation in its type area.The accepted manuscript in pdf format is listed with the files at the bottom of this page. The presentation of the authors' names and (or) special characters in the title of the manuscript may differ slightly between what is listed on this page and what is listed in the pdf file of the accepted manuscript; that in the pdf file of the accepted manuscript is what was submitted by the author