Pliocene–Quaternary fluvial and aeolian records in the Souss Basin, southwest Morocco: A geomorphological model

The Souss Basin in SW Morocco is filled by Pliocene–Quaternary fluvial, fluvio-lacustrine and aeolian sediments, representing an excellent archive of palaeohydrology, palaeoclimate and the effects of crustal deformation. In general these sediments indicate stream-dominated alluvial systems, influenced by fluctuations in climate (humidity/aridity). Lakes developed within the basin around the Pliocene–Pleistocene transition and persisted into the Early Pleistocene. During this early period, relatively humid conditions are indicated by the dominance of coarse-grained sedimentation in the upper reaches of fluvial systems, the existence of large lakes and the considerable sediment thicknesses in the centre of the basin. Uplift of the surrounding mountain ranges contributed to piedmont formation by providing large amounts of coarse-grained material that accumulated at the lowland margin. Climatic deterioration in the Middle Pleistocene was accompanied by progressively more irregular and disrupted fluvial regimes. These trends were evident in the Late Pleistocene and became clearer after the mid-Holocene, with aeolian activity becoming the dominant sedimentary agent. Differences between upstream and downstream depositional regimes became marked: while coarse-grained sedimentation has characterized the upper reaches of wadi catchments, fine-grained sedimentation has prevailed downstream. Hiatuses in sedimentation throughout the Pliocene and Quaternary are marked by palaeosol horizons interbedded within the sedimentary sequences, indicating alternate vegetated (stable) and unvegetated (unstable/active) phases (biostasy and ‘rhexistasy’).     

The Jiddat al Harasis 073 strewn field,Sultanate of Oman

Abstract— The recently discovered Jiddat al Harasis (JaH) 073 strewn field is the largest found so far in the Sultanate of Oman, covering an area of 19 × 6 km. The 3463 single stones collected range in weight from 52.2 kg down to <1 g (total weight 600.8 kg) and show a pronounced mass sorting. The strewn field shape can be approximated by a NW‐SE‐oriented ellipsoid, indicating an atmospheric entry from SE at a low angle relative to the surface. The meteorite belongs to the L6 ordinary chondrite group and shows S4 average shock grade. Smaller stones generally show a higher weathering grade resulting in a spread from W2 and W4. Enhanced weathering of the stones causing fragmentation after the fall is observed in sandy depressions. Five ¹⁴C measurements on stones of variable size and weathering grade yielded ¹⁴C from 3.8 to 49.9 dpm/kg. Three samples give a ¹⁴C/ ¹⁰Be age consistent with about 14.4 ka. For two samples the cosmogenic, trapped, and radiogenic noble gases were measured. The ratio of the ⁴He and ⁴⁰Ar gas retention ages of 0.29 ± 0.10 and that of the ³He and ²¹Ne cosmic ray exposure ages of 0.36 ± 0.08 Ma indicate that JaH 073 experienced a complex exposure history and lost ⁴He and ⁴⁰Ar due to a major collision. Fragmentation statistics indicate a single major atmospheric disruption and an originally relatively spherical shape of the object. Assuming the material collected represents the majority of fallen mass, and 90–99% of the original weight was lost by ablation, the pre‐atmospheric minimum radius of the meteoroid with density 3.4 g cm^?3would have been at least 75 cm.     

Finite orbital angular momentum states and Laguerre–Gaussian potential in two-temperature electron plasmas

Electron-acoustic waves are studied with orbital angular momentum (OAM) in an unmagnetized collisionless uniform plasma, whose constituents are the Boltzmann hot electrons, inertial cold electrons and stationary ions. For this purpose, we employ the fluid equations to obtain a paraxial equation in terms of cold electron density perturbations, which admits both the Gaussian and Laguerre–Gaussian (LG) beam solutions. Furthermore, an approximate solution for the electrostatic potential problem is found, which also allows us to express the components of the electric field in terms of LG potential perturbations. Calculating the energy flux of the electron-acoustic waves, an OAM density for these waves is obtained. Numerically, it is found that the parameters, such as, azimuthal angle, radial and angular mode numbers, and the beam waist strongly modify the LG potential profiles associated with electron-acoustic waves. The present results should be helpful to study the trapping and transportation of plasma particles and energy as well as to understand the electron-acoustic mode excitations produced by the Raman backscattering of laser beams in a uniform plasma.     

Current-driven Alfvén waves in dusty magnetospheric plasmas

It is shown that the sheared flow of electrons and ions in the presence of heavy stationary dust gives rise to unstable Alfvén waves. The coupling of newly studied low frequency electrostatic current-driven mode with the electromagnetic Alfvén and drift waves is investigated. The instability conditions and the growth rates of both inertial and kinetic Alfvén waves are estimated. The theoretical model is applied to the night side boundary regions of Jupiter’s magnetosphere which contain positive dust. The growth rates increase with increase in sheared flow speed. In the nonlinear regime, both inertial and kinetic Alfvén waves form dipolar vortices whose speed and amplitude depend upon the magnitude of the zero-order current.     

An analysis of wave properties of isothermal plasma around Reissner-Nordström black hole

The 3+1 spacetime split is used in a preliminary investigation of waves propagating in a medium of isothermal plasma in the vicinity of event horizon of Reissner-Nordström planar analogue. The general relativistic magnetohydrodynamic equations for isothermal have been investigated there. The dispersion relations are obtained by using linear perturbation and Fourier analyze techniques for non-rotating and rotating, non-magnetized and magnetized environment. The wave number, phase velocity, group velocity etc. are shown to discuss the nature of the waves.     

On the D́ust content of nearby galaxies

By inspection of photographs of the Hubble Atlas of Galaxies the frequency distribution of the sizes of dark cloud complexes in the four nearby galaxies NGC 3031, 5128, 5194 and 5457 is derived and the total amount of dust in these systems is estimated. The frequency distribution of the clouds is nearly the same in all the considered galaxies and may be approximated by n(R) ∼ e^−kR, k ≈︂ 0.050 pc⁻¹. The total amount of dust yields to roughly 10⁶M⊙.     

The K-band Hubble diagram of submillimetre galaxies and hyperluminous galaxies

We present the K -band Hubble diagrams ( K – z relations) of submillimetre-selected galaxies and hyperluminous galaxies (HLIRGs). We report the discovery of a remarkably tight K – z relation of HLIRGs, indistinguishable from that of the most luminous radio galaxies. Like radio galaxies, the HLIRG K – z relation at   z ≲ 3  is consistent with a passively evolving ∼3 L _* instantaneous starburst starting from a redshift of   z ∼ 10  . In contrast, many submillimetre-selected galaxies are ≳2 mag fainter, and the population has a much larger dispersion. We argue that dust obscuration and/or a larger mass range may be responsible for this scatter. The galaxies so far proved to be hyperluminous may have been biased towards higher AGN bolometric contributions than submillimetre-selected galaxies due to the 60-μm selection of some, so the location on the K – z relation may be related to the presence of the most massive active galactic nucleus. Alternatively, a particular host galaxy mass range may be responsible for both extreme star formation and the most massive active nuclei.     

Forest cover change assessment in conflict-affected areas of northwest Pakistan: the case of swat and shangla districts

This study examines the spatial and temporal forest cover changes in Swat and Shangla districts to understand the deforestation pattern in context of the recent security conflict in these districts. We used multi-resolution satellite images to assess the long term deforestation from 2001 to 2009 and also to identify episodic forest cutting areas appeared during the conflict period of Oct. 2007 - Oct. 2008. There are only 58 ha of deforestation identified during the conflict period while 1268 ha of gross annual deforestation were assessed during last eight years. Most of the deforestation patches persist around the administrative boundaries at sub-district levels (tehsils) which can be attributed to ambiguity in unclear jurisdiction between the forest official. The results highlight that the forest cutting appeared in Swat and Shangla during the conflict period is not as significant when compared with the long term deforestation pattern in the area. On the one side the results of the study are supportive to the picture that emerges from international studies which report high rate of deforestation in the country and on the other side it negates any relation between the security situation and the increasing deforestation in the north western Pakistan. The study concludes that deforestation assessments require verification by independent sources of data, such as satellite imagery to improve our understanding of deforestation processes.     

Fisher Matrix-based Predictions for Measuring the <Emphasis Type="Italic">z</Emphasis> = 3.35 Binned 21-cm Power Spectrum using the Ooty Wide Field Array (OWFA)

We use the Fisher matrix formalism to predict the prospects of measuring the redshifted 21-cm power spectrum in different k-bins using observations with the upcoming Ooty Wide Field Array (OWFA) which will operate at 326.5 MHz. This corresponds to neutral hydrogen (HI) at z = 3.35, and a measurement of the 21-cm power spectrum provides a unique method to probe the large-scale structures at this redshift. Our analysis indicates that a 5σ detection of the binned power spectrum is possible in the k range 0.05 ≤ k ≤ 0.3 Mpc^?1 with 1000 hours of observation. We find that the signal- to-noise ratio (SNR) peaks in the k range 0.1?0.2 Mpc^?1 where a 10σ detection is possible with 2000 hours of observations. Our analysis also indicates that it is not very advantageous to observe beyond 1000 h in a single field-of-view as the SNR increases rather slowly beyond this in many of the small k-bins. The entire analysis reported here assumes that the foregrounds have been completely removed.     

Geochemical and oxygen isotope perspective of a new R chondrite Dhofar 1671: Affinity with ordinary chondrites

Dhofar 1671 is a relatively new meteorite that previous studies suggest belongs to the Rumuruti chondrite class. Major and REE compositions are generally in agreement with average values of the R chondrites (RCs). Moderately volatile elements such as Se and Zn abundances are lower than the R chondrite values that are similar to those in ordinary chondrites (OCs). Porphyritic olivine pyroxene (POP), radial pyroxene (RP), and barred olivine (BO) chondrules are embedded in a proportionately equal volume of matrix, one of the characteristic features of RCs. Microprobe analyses demonstrate compositional zoning in chondrule and matrix olivines showing Fa‐poor interior and Fa‐rich outer zones. Precise oxygen isotope data for chondrules and matrix obtained by laser‐assisted fluorination show a genetic isotopic relationship between OCs and RCs. On the basis of our data, we propose a strong affinity between these groups and suggest that OC chondrule precursors could have interacted with a ¹⁷O‐rich matrix to form RC chondrules (i.e., ?¹⁷O shifts from ~1‰ to ~3‰). These interactions could have occurred at the same time as “exotic” clasts in brecciated samples formed such as NWA 10214 (LL3–6), Parnallee (LL3), PCA91241 (R3.8–6), and Dhofar 1671 (R3.6). We also infer that the source of the oxidation and ¹⁷O enrichment is the matrix, which may have been enriched in ¹⁷O‐rich water. The abundance of matrix in RCs relative to OCs, ensured that these rocks would be apparently more oxidized and appreciably ¹⁷O‐enriched. In situ analysis of Dhofar 1671 is recommended to further strengthen the link between OCs and RCs.