Out-of-sequence thrusts and paleogeography of the Rhenodanubian Flysch Belt (Eastern Alps) revisited

The Oberstdorf nappe of the Western and the Laab nappe of the Eastern Rhenodanubian Flysch (ERF) were independently identified as out-of-sequence thrust units by facies studies (Mattern 1999) and zircon analyses (Trautwein et al. 2001a, b, c), respectively. A new look at both areas reveals mutual similarities and new evidence for the out-of-sequence concept. Paleocurrent and heavy mineral data make it possible to reconstruct the sediment influx directions. From the Barremian to the mid-Campanian, the western and eastern basin segments were fed with south-derived garnet and north-derived zircon/”ZTR” (i.e., zircon, tourmaline, and rutile). Because both out-of-sequence units are relatively rich in zircon/ZTR they must have occupied the northernmost basin position. In the Western Rhenodanubian Flysch segment, the Sigiswang nappe occupied the central and the Üntschen nappe the southernmost basin position. In the ERF segment the central basin is represented by the Greifenstein nappe and the southernmost basin by the Kahlenberg nappe. Both out-of-sequence units do not occur in the northernmost and tectonically lowest position in their respective nappe piles as they were thrust over the other nappes. The reconstructed basin positions of the thrust units are suggested by the observation of a gradient in heavy mineral content in the thrust units. This paleogeographic arrangement is least problematic and renders models with differently positioned thrust units, requiring debris-shedding intrabasinal ridges, as unnecessarily complicated. Instead, we suggest that gradual changes in heavy mineral composition existed in across-basin direction. Garnet may stem from the Central Gneiss Complex of the Tauern window and formerly exposed lateral equivalents, all representing the southern Mid-Penninic zone. We assign the Falknis/Tasna nappe and formerly exposed lateral equivalents to the northern Mid-Penninic zone which served as the zircon/ZTR source. Interpreting Ebbing’s (Ph.D. thesis, Freie Universität Berlin, pp 1-143, 2002; Fig. 6.10) density section, we suggest that Mid-Penninic crust exists beneath the Central Gneiss Complex. During the latest Cretaceous much garnet was also N-derived. This may reflect processes related to the consumption of the North Penninic basin.     

A traverse through the western Kunlun (Xinjiang,China): tentative geodynamic implications for the Paleozoic and Mesozoic

The northern part of the western Kunlun (southern margin of the Tarim basin) represents a Sinian rifted margin. To the south of this margin, the Sinian to Paleozoic Proto-Tethys Ocean formed. South-directed subduction of this ocean, beneath the continental southern Kunlun block during the Paleozoic, resulted in the collision between the northern and southern Kunlun blocks during the Devonian. The northern part of the Paleo-Tethys Ocean, located to the south of the southern Kunlun, was subducted to the north beneath the southern Kunlun during the Late Paleozoic to Early Mesozoic. This caused the formation of a subduction-accretion complex, including a sizeable accretionary wedge to the south of the southern Kunlun. A microcontinent (or oceanic plateau?), which we refer to as “Uygur terrane,” collided with the subduction complex during the Late Triassic. Both elements together represent the Kara-Kunlun. Final closure of the Paleo-Tethys Ocean took place during the Early Jurassic when the next southerly located continental block collided with the Kara-Kunlun area. From at least the Late Paleozoic to the Early Jurassic, the Tarim basin must be considered a back-arc region. The Kengxiwar lineament, which “connects” the Karakorum fault in the west and the Ruogiang-Xingxingxia/Altyn-Tagh fault zone in the east, shows signs of a polyphase strike-slip fault along which dextral and sinistral shearing occurred.     

Preliminary Characterisation of New Glass Reference Materials (GSA-1G, GSC-1G, GSD-1G and GSE-1G) by Laser Ablation-Inductively Coupled Plasma-Mass Spectrometry Using 193 nm, 213 nm and 266 nm Wavelengths

New glass reference materials GSA-1G, GSC-1G, GSD-1G and GSE-1G have been characterised using a prototype solid state laser ablation system capable of producing wavelengths of 193 nm, 213 nm and 266 nm. This system allowed comparison of the effects of different laser wavelengths under nearly identical ablation and ICP operating conditions. The wavelengths 213 nm and 266 nm were also used at higher energy densities to evaluate the influence of energy density on quantitative analysis. In addition, the glass reference materials were analysed using commercially available 266 nm Nd:YAG and 193 nm ArF excimer lasers. Laser ablation analysis was carried out using both single spot and scanning mode ablation. Using laser ablation ICP-MS, concentrations of fifty-eight elements were determined with external calibration to the NIST SRM 610 glass reference material. Instead of applying the more common internal standardisation procedure, the total concentration of all element oxide concentrations was normalised to 100%. Major element concentrations were compared with those determined by electron microprobe. In addition to NIST SRM 610 for external calibration, USGS BCR-2G was used as a more closely matrix-matched reference material in order to compare the effect of matrix-matched and non matrix-matched calibration on quantitative analysis. The results show that the various laser wavelengths and energy densities applied produced similar results, with the exception of scanning mode ablation at 266 nm without matrix-matched calibration where deviations up to 60% from the average were found. However, results acquired using a scanning mode with a matrix-matched calibration agreed with results obtained by spot analysis. The increased abundance of large particles produced when using a scanning ablation mode with NIST SRM 610, is responsible for elemental fractionation effects caused by incomplete vaporisation of large particles in the ICP.     

Continental strike-slip rifts and their stratigraphic signature: application to the Bangong/Nujiang zone (Tibet) and the South Penninic zone (Alps)

Our literature studies show that the thermal regime along continental strike-slip rifts is inconspicuous and that they are "low-volcanicity rifts" at best. Along with that, young continental strike-slip rifts exhibit no signs of major thermally controlled doming. We suggest that the larger the strike-slip component of a rift is, the less likely major thermal doming is causally associated with the rift zone. Since vertical lithosphere movements are reflected in the stratigraphic record of a rifted area, different rift modes (strike-slip, dip-slip) may be distinguished by analyzing the relevant sequences. Two ancient and especially suitable strike-slip rift margins in Tethyan mountain belts, the Bangong/Nujiang zone of Tibet and the South Penninic zone of the Alps, were analyzed with regard to their uplift history. The results confirm recent regional rift models which indicate in both cases that rifting was dominated by strike-slip. The stratigraphic approach may provide significant clues as to the mode of paleorifting when structural data are unavailable.     

Monte Carlo modeling of neutral gas and dust in the coma of Comet 1P/Halley

The neutral gas environment of a comet is largely influenced by dissociation of parent molecules created at the surface of the comet and collisions of all the involved species. We compare the results from a kinetic model of the neutral cometary environment with measurements from the Neutral Mass Spectrometer and the Dust Impact Detection System onboard the Giotto spacecraft taken during the fly-by at Comet 1P/Halley in 1986. We also show that our model is in good agreement with contemporaneous measurements obtained by the International Ultraviolet Explorer, sounding rocket experiments, and various ground based observations.The model solves the Boltzmann equation with a Direct Simulation Monte Carlo technique (Tenishev, V., Combi, M., Davidsson, B. [2008]. Astrophys. J. 685, 659-677) by tracking trajectories of gas molecules and dust grains under the influence of the comet’s weak gravity field with momentum exchange among particles modeled in a probabilistic manner. The cometary nucleus is considered to be the source of dust and the parent species (in our model: H₂O, CO, H₂CO, CO₂, CH₃OH, C₂H₆, C₂H₄, C₂H₂, HCN, NH₃, and CH₄) in the coma. Subsequently our model also tracks the corresponding dissociation products (H, H₂, O, OH, C, CH, CH₂, CH₃, N, NH, NH₂, C₂, C₂H, C₂H₅, CN, and HCO) from the comet’s surface all the way out to 10⁶ km.As a result we are able to further constrain cometary the gas production rates of CO (13%), CO₂ (2.5%), and H₂CO (1.5%) relative to water without invoking unknown extended sources.     

Derivation of Photosynthetically Available Radiation from METEOSAT data in the German Bight with Neural Nets

Two different models, a Physical Model and a Neural Net (NN), are used for the derivation of the Photosynthetically Available Radiation (PAR) from METEOSAT data in the German Bight; advantages and disadvantages of both models are discussed. The use of a NN for derivation of PAR should be preferred to the Physical Model because by construction, a NN can take the various processes determining PAR on a surface much better into account than a non-statistical model relying on averaged relations.

Interdecadal modulation of the relationship between ENSO,IPO and precipitation: insights from tree rings in Australia

Australian climate-proxy reconstructions based on tree rings from tropical and subtropical forests have not been achieved so far due to the rarity of species producing anatomically distinct annual growth rings. Our study identifies the Australian Red Cedar (Toona ciliata) as one of the most promising tree species for tree-ring research in Australasia because this species exhibits distinct annual tree rings, a prerequisite for high quality tropical dendroclimatology. Based on these preliminary studies, we were able, for the first time in subtropical and tropical Australia, to develop a statistically robust, precisely dated and annually resolved chronology back to AD1854. We show that the variability in ring widths of T. ciliata is mainly dependent on annual precipitation. The developed proxy data series contains both high- and low-frequency climate signals which can be associated with the El Niño Southern Oscillation (ENSO) and the Interdecadal Pacific Oscillation (IPO). A comparison of different data sets (Brisbane precipitation, tree rings, coral luminescence record from the Great Barrier Reef, ENSO and IPO) revealed non-stationary correlation patterns throughout the twentieth century but little instability between the new tree-ring chronology and Brisbane precipitation.     

Composition and sediment dispersal pattern of the Upper Triassic flysch in the eastern Himalayas,China: significance to provenance and basin analysis

International Journal of Earth Sciences - The paleogeography and basin type of Upper Triassic flysch (Langjiexue Group) in the eastern Himalayan Orogen are disputed. In order to shed new light on...     

Suturing of the Proto- and Paleo-Tethys oceans in the western Kunlun (Xinjiang, China)

The Proto-Tethys Ocean between the North and South Kunlun began to form during the Sinian. Remnants of this ocean are preserved at the Oytag-Kudi suture. The presence of Paleozoic arc batholiths in the northern South Kunlun and their absence in the North Kunlun indicates southward subduction of the Proto-Tethys Ocean beneath the South Kunlun. Opposite subduction polarity can be demonstrated for the Late Paleozoic to mid-Mesozoic when the southerly located Paleo-Tethys Ocean was consumed beneath the South Kunlun and generated a Late Carboniferous to mid-Jurassic magmatic arc in the southern South Kunlun. Arc magmatism affected the southern South Kunlun and the large Kara-Kunlun accretionary prism (a suture sensu lato) which formed as a result of Paleo-Tethys’ consumption. The dextral shear sense of ductile faults which are located at the margins of the arc batholiths, and which parallel the South Kunlun/Kara-Kunlun boundary, suggests oblique plate convergence with a dextral component. Different lines of evidence encourage us to interpret the Proto-Tethys ophiolites of the Oytag-Kudi zone as at least partly derived from an oceanic back-arc basin. In contrast, we assume that Paleo-Tethys was a large ocean basin which was eliminated directly at the southern margin of the South Kunlun where no oceanic back-arc region existed.     

Editorial: Reflections from Ireland

Responses of governance systems to change in coastal and marine ecosystems vary from country to country around the globe. Lessons can be learned from country specific case studies, as national governments strive to adapt and respond to issues of concern. This short paper highlights the benefits of a country-specific, special edition of Marine Policy, with a focus on Ireland. Despite the uniqueness of socio-ecological setting, many of the issues faced by policy makers in Ireland, such as the reconciliation of economic development and conservation needs, are shared elsewhere. This special edition was produced at the end of the ‘Celtic Tiger’ in Ireland. As a result, it reflects an era when economic development was very much a priority. The same period represented an unparalleled investment in marine science since the foundation of the State in 1922. Despite this, the papers in the Special Edition point to varying degrees of progress in policy integration and implementation. Papers covering a range of sectors (fisheries, ocean energy, conservation and fisheries) and disciplines (economics, science and management) will be of interest to academics, policy makers, students and practitioners of marine policy.