Search results

Filters

  • Journals
  • Authors
  • Keywords
  • Date
  • Type

Search results

Number of results: 7
items per page: 25 50 75
Sort by:

Abstract

Palaeomagnetic investigation of the Upper Carboniferous clastic Hyrnefjellet Formation from opposite limbs of the Hyrnefjellet Anticline in southern Spitsbergen (Svalbard Archipelago) uncovered two components of NRM. Direction C1 (D = 224.6°; I = –27.9°; κ = 22.40; α95% = 5.6°) is of prefolding origin and most probably of near-primary origin. High Tb spectra above 575°C indicate hematite as the carrier of C1. Acquisition of the C1 component may be related to an early diagenetic crystallization of hematite, not excluding a detrital origin of the NRM. A paleopole calculated for the C1 component (F = 23.3°N; L= 147.7°E) falls into the Late Devonian–Early Carboniferous sector of APWP for Baltica. This result suggests that Svalbard remained in the present day orientation with respect to Baltica since the Carboniferous time. A second component with intermediate unblocking temperatures, determined in the Hyrnefjellet Formation deposits, is labelled C2. Its mean orientation for in situ position is D = 11.2°; I = 69.2° (κ = 44.05; α95% = 6.3°), thus being similar to Late Mesozoic directions for Baltica. After 100% tectonic correction for tilting of anticline limbs and axis, the C2 component orientation is D = 265.7°; I = 59.7°, thus being distant from any directions for Baltica. Detailed analysis suggest that the C2 component is most probably of synfolding origin, and it was formed during the Tertiary Alpine Tectonic Event.
Go to article

Abstract

The fusulinid foraminifers of Schellwienia arctica (Schellwien, 1908) have been investigated from Polakkfjellet Mt., south Spitsbergen, and used as biostratigraphic marker for the latest Carboniferous earliest Permian strata of the Treskelodden Formation. A series of thin sections enable to investigate the internal structure and growth pattern of individual specimens. The observed variation of growth suggests dynamic environmental conditions at the investigated location and most likely over one-year long life span of this foraminifer.
Go to article

Abstract

A total number of 156 palaeomagnetic specimens of metacarbonates from 9 sites in Blomstrandhalvøya and Lovénøyane (Kongsfjorden, western Spitsbergen) and an additional 77 specimens of unmetamorphosed sediments infilling fractures (4 sites) within the Caledonian metamorphic basement of Blomstrandhalvøya were demagnetized. No relicts of pre-metamorphic magnetization were identified. The Natural Remanent Magnetization (NRM) pattern of metacarbonates is dominated by Caledonian (sensu lato) – Svalbardian and Late Mesozoic/Cenozoic secondary magnetic overprints carried by the pyrrhotite and magnetite/maghemite phases, respectively. The NRM of unmetamorphosed sediments infilling the karstic/tectonic fractures is dominated by hematite carrier. It revealed three stages of magnetization: Caledonian sensu lato, Carboniferous and Late Mesozoic/Cenozoic, which can be related to their initial fracturing, karstification and sedimentation or reactivation. As the majority of the palaeopoles calculated for the Kongsfjorden sites fit the 430 – 0 Ma sector of Laurussia reference path in an in situ orientation these results support the hypothesis that Blomstrandhalvøya and Lovénøyane escaped main Eurekan deformations. The potential rotation of the Kongsfjorden basement by any west dipping listric fault activity rotating the succession accompanying the opening of North Atlantic Ocean was not documented by the palaeomagnetic data presented here.
Go to article

Abstract

Rye is an important crop widely cultivated in Europe, but one of the hardest to improve due to its allogamy and self-incompatibility. The market for rye-based products is constantly growing thanks to the popularity of organic farming, feed production and diverse industry applications. To address these demands, new highly productive hybrid rye varieties are needed. Currently, full potential of heterosis in rye breeding is hard to reach due to the limited success in in vitro cultures. This review summarizes the progress in rye in vitro cultures and proposes novel approaches to overcome recalcitrance in this species.
Go to article

Abstract

Palaeomagnetic−petrographic−structural analyses of Proterozoic–Lower Palaeozoic metamorphosed carbonates from 12 locations within Oscar II Land (Western Spitsbergen) have been carried out to determine their usefulness in palaeogeographic reconstructions for Caledonian time. Structural analyses confirm that metacarbonates record several stages of deformation: D1, D2 ductile phases related to Caledonian metamorphism and a D3 brittle phase related to Late Cretaceous–Paleogene evolution of the West Spitsbergen Fold Belt. The latter is represented by thrust faults, localized folds with strain slip cleavages and late extensional collapse. Petrographic investigations reveal that Caledonian greenschist facies metamorphism was characterized by the high activity of H 2 O−CO 2 −rich fluids which promoted extensive recrystallization and within−rock spatial reorganization of sampled meta carbonates. Microscopic, SEM and microprobe analyses exclude the existence of any primary pre−metamorphic ferromagnetic minerals (primary−related to sedimentation and or early diagenesis) and point to metamorphic 4C superstructure (Fe 7 S 8 ) pyrrhotite as the main ferromagnetic carrier in investigated rocks. This is confirmed by the three−component isothermal remanent magnetization (IRM) procedures and the results of thermal demagnetizations. In 12 sites a total number of 72 independently oriented palaeomagnetic samples were collected from which 181 specimens were drilled and thermally demagnetized. Sampled metacarbonates are weakly magnetized (NRM <0.2mA/m). The statistically significant palaeomagnetic results were achieved only from 1 of 12 investigated sites. In one site situated in the Western overturned limb of the Holmesletfjellet Syncline intermediate unblocking temperatures – “pyrrhotite related” component WTSJ5M superimposed on the S1 Caledonian schistosity was recognized (D = 100.7 ° , I = −21.4 °a 95% = 5.5 ° , k = 58.23). Coincidence of WTSJ5M with Silurian–Devonian sector of the Baltica reference path after unfolding of the syncline by the angle of 130 ° suggests synfolding origin of this direction. Further, this suggests that Holmesletfjellet Syncline originated as an open fold and has been transformed into an overturned syncline during the Late Caledonian shortening or in the Late Cretaceous–Palaeogene time.
Go to article

Abstract

Hybrid filter material was obtained via modification of polypropylene (PP) nonwoven with nanosize zinc oxide particles of a high aspect ratio. Modification was conducted as a three-step process, a variant of hydrothermal method used for synthesis of nano-ZnO, adopted for coating three dimensional polymeric nonwoven filters. The process consisted of plasma treatment of nonwoven to increase its wettability, deposition of ZnO nanoparticles and low temperature hydrothermal growth of ZnO rods. The modified nonwovens were investigated by a high resolution scanning electron microscopy (HR-SEM). It has been found that the obtained hybrid filters offer a higher filtration efficiency, in particular for so called most penetrating particle sizes.
Go to article

This page uses 'cookies'. Learn more