Use of mode-converted waves in marine seismic data to investigate the lithology of the sub-bottom sediments in Isfjorden,Svalbard

The compression wavefield is efficiently converted to shear-wave energy at post-critical angles in areas of high impedance contrast at the sea floor. We have analysed mode-converted shear waves in a data set acquired with a hybrid marine/land geometry in Isfjorden, Svalbard. Through a kinematic 2D ray-tracing modellingV _p/V_s ratios for part of the uppermost 5km of the crust are obtained. Low values (V _p /V _s =1.65) are tentatively associated with the section of Devonian sandstones which appears to attain a minimum thickness of 1.5km below 3 km depth about 10km west of Kapp Thorden.     

Remarks on sequence stratigraphy and taphonomy of the Malvinokaffric shelly fauna during the KAČÁK Event in the Apucarana Sub-basin (Paraná Basin), Brazil

The Eifelian–Givetian (Middle Devonian) transition constituted an important paleoenvironmental event for the Malvinokaffric Realm in the Apucarana Sub-basin (Paraná Basin). This study highlights integration between taphonomy and sequence stratigraphy, and four depositional sequences are identified during the transition. In Sequence 1, the presence of a typical normal-sized Malvinokaffric fauna is recorded. In the transgressive systems tract (TST) of Sequence 2, no benthic fossils are present, and this is interpreted as a stratigraphic marker of an event of significant paleoenvironmental change (KA?ÁK Event). In Sequence 3, the TST has abundant bioclasts, which become rarer toward the top of the section, i.e., within the transgressive systems tract. The original habitat of this autochthonous to parautochthonous fauna was a low-energy environment between the fair weather wave base and the storm wave base of the Devonian epicontinental sea. In the highstand systems tract of this sequence, the presence of normal-sized Pennaia paulianna and lingulids demonstrates the return of more ambient conditions. Sequence 4 is of Carboniferous age. Its limit is a second-order sequence boundary recording a lowstand systems tract formed by a fluvial depositional system. The low diversity and the disappearance of taxa are not the result of a taphonomic bias, but reflect the post-KA?ÁK Event.     

Some comments on the low intensity Hα emission observed by J.-L. Leroy in the solar corona

Some comments are presented on the important observations of faint prominences made recently by Dr Jean-Louis Leroy at the Pic du Midi Observatory. The writer draws attention to the very probable connection with faintly luminous H obscuring prominences which appear sometimes as dark lanes and markings in ordinary prominences.     

Geographies of security and statehood in Norway’s ‘Battle of the North’

In this paper, we explore how ‘peak oil’ anxieties are woven into the spaces and practices of the state in Norway and the consequences of this for environmental justice and the public sphere more widely. We focus in particular on an ongoing struggle over access to hydrocarbon deposits in the Norwegian Arctic, the so-called ‘Battle of the North’. We use this dispute to highlight three wider theoretical points regarding (i) the continuing relevance of the state in the governing of nature-society relations, (ii) the increasingly fragmented and fluid nature of state space, and (iii) the significance of ‘security’ as a term around which social, economic and environmental tensions pivot. The paper concludes by reflecting on current efforts to prevent new oil activities in the north of Norway.     

Plane grating as polar heliostat in eclipse observations of the chromosphere and prominences with special application to studies of Doppler-widened Thomson-scattered Fraunhofer lines

Attention is drawn to a very simple instrumental arrangement for eclipse observations of the spectra of the chromosphere and prominences using a plane grating as polar heliostat and a short focus camera. A discussion is made of an infrared chromospheric spectrum showing traces of Thomson-scattered Ca ii absorption lines in the continuous spectrum. If the effect is real, it indicates a temperature of the order of 5000 K. A simple vector formula is presented describing various types of Doppler effects appearing in radiation scattered by moving particles.     

An Hα filament observed against the chromosphere at the limb

Observations are reported of an H filament clearly visible in the image of the chromosphere at the limb as well as in the H spectrum of the same part of the chromosphere. Observations of this kind may give valuable information about the absorption mechanism at work in filaments.