Implications of a new,biostratigraphically well-controlled,radio-isotopic age for the lower Telychian Stage of the Llandovery Series （Lower Silurian,Sweden）

Radio-isotopic analysis of single zircons from two early Telychian K-bentonites, one of which is among the most widespread Lower Paleozoic volcanic ash falls in north- ern Europe, yields overlapping weighted mean 206pb/238U ages of 438. 7± 1.0 Ma and 437.8 ± 0.5 Ma, respectively. The former age is from zircons of the Osmundsberg K-bentonite from the type locality at Osmundsberget in the Siljan area of central Sweden where it occurs in the lower part of the Spirograptus tur- riculatus Graptolite Zone and in the lower part of the Angochitina longicollis Chitinozoan Zone. Zircons giv- ing the latter age are from a bed previously identified as the Osmundsberg K-bentonite at the Kallholn Quarry in the same area. Based on new biostratigraphic data, the latter bed is now considered to be slightly younger than the Osmundsberg K-bentonite. The dated stratigraphic level of the ash layers is slightly younger than the base of the Telychian Stage and thus represents a minimum age for the Aeronian/Telychian Stage boundary. A U-Pb age of 〉 438 Ma for the base of this stage, however, is older and in conflict with estimates in the most recent compilation of the Silurian time scale. In view of the fact that only three radio-isotopic dates from the entire Llan- dovery have been previously accepted, this new and biostratigraphically exceptionally well-controlled radio-isotopic date fills an important gap in the Lower Silurian geochronology.     

Sources and transport of carbon and nitrogen in the River Sava watershed, a major tributary of the River Danube

Carbon and nitrogen dynamics were examined throughout the River Sava watershed, a major tributary of the River Danube, in 2005 and 2006. The River Sava exported 2.1 × 10¹¹ mol C/yr as dissolved inorganic carbon (DIC), and emitted 2.5 × 10¹⁰ mol C/yr as CO₂ to the atmosphere. Stable carbon isotope ratios indicate that up to 42% of DIC originated from carbonate weathering and 23% from degradation of organic matter. Loads of dissolved and particulate organic carbon increased with discharge and export rates were calculated to be 2.1 × 10¹⁰ mol C/yr and up to 4.1 × 10⁹ mol C/yr, respectively. Isotopic compositions (δ¹³C and δ¹⁵N) and C/N ratios indicated that soil organic matter was the dominant source of particulate organic matter for 59% of the samples. Eighteen percent of the samples were dominated by plankton, 12% by periodic inputs of fresh terrestrial plant detritus with C/N > 15, and about 11% of the samples were dominated by the contribution of aquatic vascular plants. Nitrate inputs were controlled by land use in the River Sava watershed. δ¹⁵N_NO3 values <6‰ were found in predominantly forested watersheds, while values >6‰ typically represented watersheds with a higher percentage of agricultural and/or urban land use. Elevated δ¹⁵N_NO3 values (up to +25.5‰) at some sites were probably due to the combined effects of low-flow and inputs from sewage and/or animal waste.     

Preliminary report on a dinosaur tracksite from Lower Cretaceous strata in Mount Lebanon

A dinosaur tracksite was discovered in Batha on the side of the road from Harissa to Ghosta (Keserwan, Lebanon). About ten trackways are exposed at the top of two beds of Lower Cretaceous limestones over an area of approximately 1000 m². These footprints were probably made by at least two dinosaur species, Sauropoda and either Theropoda or Ornithopoda. The site, which is the first record from Lebanon, should be protected to allow further scientific investigations.     

Geodynamic evolution of the Sabzevar zone,northern central Iranian micro-continent

Mineralogy and Petrology - The Northern Central Iranian Micro-continent (CIM) represents Neotethys-related oceanic crust remnants, emplaced due to convergence between CIM and Eurasia plates during...     

New <Superscript>40</Superscript>Ar/<Superscript>39</Superscript>Ar age constraints on cooling and unroofing history of the metamorphic host rocks (and igneous intrusion associates) from the Bulfat Complex (Bulfat area), NE-Iraq

The Northern Zagros Suture Zone (NZSZ), formed as a result of the collision between Arabian and Sanandaj-Sirjan microplate, is considered as part of the Zagros orogenic belt. NZSZ is marked by two allochthonous thrust sheets in upward stacking order: lower and upper allochthon. The Bulfat complex is a part of the upper allochthon or “Ophiolite-bearing terrane” of Albian-Cenomenion age (97–105 Ma). Voluminous highly sheared serpentinites associated with ophiolites occur within this upper allochthon. In addition, the Gemo-Qandil Group is characterized by gabbroic to dioritic Bulfat intrusion with a crystallization age spanning from ~45 to ~?40 Ma, as well as extensive metapelites with contact to the Walash-Naupurdam metavolcanic rocks. Due to the deformation in the Sanandaj-Sirjan Zone along the eastern side of the Iraqi segment of NZSZ, the Gemo-Qandil Group was regionally metamorphosed during late Cretaceous (~?80 Ma). This tectono-compressional dynamics ultimately caused an oscillatory deformation against Arabian continental margin deposits as well. During these events, gabbro-diorite intrusion with high-grade contact metamorphic aureoles occurred near Bulfat. Thus, there is an overlap between regional and contact metamorphic conditions in the area. The earlier metamorphic characteristic can be seen only in places where the latter contact influence was insignificant. Generally, this can only observed at a distance of more than 2.5 km from the contact. According to petrographic details and field observations, the thermally metamorphosed metapelitic units of the metasediment have been completely assimilated, with only some streaks of biotite and relicts of initial foliation. They strongly resemble amphibolite-grade slices from the regional metamorphic rocks in the region. Metapelitic samples far from the intrusion give similar biotite cooling ages as the intrusive rocks. Thus, they may be affected by the same thermal event. ⁴⁰Ar/³⁹Ar dating of biotite in metapelite rocks of Bulfat by step-wise heating with laser gave average weighted isotopic ages of 34.78?±?0.06 Ma. This is interpreted as crystallization/recrystallization age of biotite possibly representing the time of cooling and uplift history of the Bulfat intrusion. Cooling and exhumation rates for the Bulfat gabbro-diorite rocks were estimated as ~?400 °C/Ma and ~?3.3 mm/year respectively. According to petrographic details, field observations and Ar/Ar dating concerning the contact metamorphism near Bulfat due to the gabbro-diorite intrusion, no significant deformation is visible during exhumation processes after the Paleogene tectono-thermal event, indicating that isotopic ages of 34.78?±?0.06 Ma could mark the timing of termination of the island arc activity in the Ophiolite-bearing terrane (upper allochthon).     

InSAR datum connection using GNSS-augmented radar transponders

Deformation estimates from Interferometric Synthetic Aperture Radar (InSAR) are relative: they form a ‘free’ network referred to an arbitrary datum, e.g. by assuming a reference point in the image to be stable. However, some applications require ‘absolute’ InSAR estimates, i.e. expressed in a well-defined terrestrial reference frame, e.g. to compare InSAR results with those of other techniques. We propose a methodology based on collocated InSAR and Global Navigation Satellite System (GNSS) measurements, achieved by rigidly attaching phase-stable millimetre-precision compact active radar transponders to GNSS antennas. We demonstrate this concept through a simulated example and practical case studies in the Netherlands.     

Numerical modelling of multiphase immiscible flow in double‐porosity featured groundwater systems

A numerical model describing the flow of multiphase, immiscible fluids in a deformable, double‐porosity featured soil has been developed. The model is focused on the modelling of the secondary porosity features in soil, which is more relevant to groundwater contamination problems. The non‐linear saturation and relative permeabilities were expressed as functions of the capillary pressures. The governing partial differential equations in terms of soil displacement and fluid pressures were solved numerically. Galerkin's weighted‐residual finite element method was employed to obtain the spatial discretization whereas temporal discretization was achieved using a fully implicit scheme. The model was verified against established, peer‐reviewed works, and the assumption that the immiscible fluids (non‐aqueous phase liquids) will flow preferentially through the secondary porosity features in soil was validated. Copyright © 2011 John Wiley & Sons, Ltd.