Geochemical and microbiological characteristics of sediments near the Malenky mud volcano (Lake Baikal, Russia), with evidence of Archaea intermediate between the marine anaerobic methanotrophs ANME-2 and ANME-3

Detailed lithological, biogeochemical and molecular biological analyses of core sediments collected in 2002–2006 from the vicinity of the Malenky mud volcano, Lake Baikal, reveal considerable spatial variations in pore water chemical composition, with total concentrations of dissolved salts varying from 0.1 to 1.8‰. Values of methane δ¹³С in the sediments suggest a biogenic origin (δ¹³С_min. ?61.3‰, δ¹³С_max. ?72.9‰). Rates of sulphate reduction varied from 0.001 to 0.7 nmol cm^?3 day^?1, of autotrophic methanogenesis from 0.01 to 2.98 nmol CH₄ cm^?3 day^?1, and of anaerobic oxidation of methane from 0 to 12.3 nmol cm^?3 day^?1. These results indicate that methanogenic processes dominate in gas hydrate-bearing sediments of Lake Baikal. Based on clone libraries of 16S rRNA genes amplified with Bacteria- and Archaea-specific primers, investigation of microbial diversity in gas hydrate-bearing sediments revealed bacterial 16S rRNA clones classified as Deltaproteobacteria, Gammaproteobacteria, Chloroflexi and OP11. Archaeal clone sequences are related to the Crenarchaeota and Euryarchaeota. Baikal sequences of Archaea form a distinct cluster occupying an intermediate position between the marine groups ANME-2 and ANME-3 of anaerobic methanotrophs.     

Fast-changing processes in a medium subject to loading as detected by resistivity measurements

Making measurements of electric resistivity at 16 s intervals, the authors noticed fast changes of this parameter prior to the occurrence of the main fracture. The changes are superposed on bay pulsations of increasing amplitude and decreasing period. This finding opens prospects for a wider use of an electric resistivity method and proves the high quality of automatic instruments, in particular their high resolution. It also gives evidence for the occurrence of short-period precursors in the fracture zone while the main fracture is being formed.     

Response to the paper by H. Zia,B. Lecampion “Explicit versus implicit front advancing schemes for the simulation of hydraulic fracture growth” (Int. J. Numer. Anal. Methods Geomech., 2019, 43 (6), 1300–1315)

The response presents three comments, which (i) explain theoretical background for the success of the explicit front advancing scheme by Zia and Lecampion (comment 1), (ii) suggest possible extensions (comment 2), and (iii) pay attention on expected limitations of the scheme to be checked by the authors in numerical experiments (comment 3). The response does not intend to present novel results: it is entirely based on known results published in the references cited.     

Discussion: “Xenoliths in ultrapotassic volcanic rocks in the Lhasa block: direct evidence for crust–mantle mixing and metamorphism in the deep crust” by Wang et al. 2016 (Contributions to Mineralogy and Petrology) 171:62

Wang et al. (Contrib Mineral Petrol 171:62, 2016a) present data on composition of xenolith from Southern Tibet and conclude that ulrapotassic melts from the region formed by melting mantle, and complex interaction with a crustal component. In this discussion we demonstrate that numerous observations presented by Wang et al. (2016a) can be explained by partial melting of crust followed by interaction between that melt and the mantle. We show that this model can explain the variability of magmas in such suits without evoking occurrence of coincidental, unrelated events. Moreover we demonstrate that our model of a crustal origin of the proto-shoshonite melts is now supported by independent lines of evidence such as geochemistry of restites after high- and ultrahigh- pressure melting and melt inclusion studies.     

Choice of conodont Idiognathodus simulator （sensu stricto） as the event marker for the base of the global Gzhelian Stage （Upper Pennsylvanian Series,Carboniferous System）

We propose that the level at which the conodont species Idiognathodus simulator （Ellison 1941） （sensu stricto） first appears be selected to mark the base of the Gzhelian Stage, because we believe that this is the optimal level by which this boundary can be correlated. This taxon has a short range and a wide distribution, as shown by correlation of glacial-eustatic cyclothems across the Kasimovian-Gzhelian boundary interval among Midcontinent North America and the Moscow and Donets basins of eastern Europe, based on scale of the cyclothems along with several aspects of biostrati- graphy. Outside of these areas, I. simulator （sensu stricto） is known also from other parts of the U.S., and is reported from the southern Urals and south-central China in its expected position between other widespread taxa. Its first appearance is consistent with the current ammonoid placement of the boundary （first appearance of Shumardites cuyleri）, and it is also compatible with certain aspects of the distribution of Eurasian fusulinid faunas （e.g., lectotype ofRauserites rossicus）.     

Simulation of full-waveform log in saturated cracked formations using Hudson's approach

We study the propagation of elastic waves that are generated in a fluid‐filled borehole surrounded by a cracked transversely isotropic medium. In the model studied the anisotropy and borehole axes coincide. To obtain the effective elastic moduli of a cracked medium we have applied Hudson's theory that enables the determination of the overall properties as a function of the crack orientation in relation to the symmetry axis of the anisotropic medium. This theory takes into account the hydrodynamic mechanism of the elastic‐wave attenuation caused by fluid filtration from the cracks into a porous matrix. We have simulated the full waveforms generated by an impulse source of finite length placed on the borehole axis. The kinematic and dynamic parameters of the compressional, shear and Stoneley waves as functions of the matrix permeability, crack orientation and porosity were studied. The modelling results demonstrated the influence of the crack‐system parameters (orientation and porosity) on the velocities and amplitudes of all wave types. The horizontally orientated cracks result in maximal decrease of the elastic‐wave parameters (velocities and amplitudes). Based on the fact that the shear‐ and Stoneley‐wave velocities in a transversely isotropic medium are determined by different shear moduli, we demonstrate the feasibility of the acoustic log to identify formations with close to horizontal crack orientations.     

Analytical solution for the electric potential in arbitrary anisotropic layered media applying the set of Hankel transforms of integer order

The analytical solution and algorithm for simulating the electric potential in an arbitrarily anisotropic multilayered medium produced by a point DC source is here proposed. The solution is presented as a combination of Hankel transforms of integer order and Fourier transforms based on the analytical recurrent equations obtained for the potential spectrum. For the conversion of the potential spectrum into the space domain, we have applied the algorithm of the Fast Fourier Transform for logarithmically spaced points. A comparison of the modelling results with the power‐series solution for two‐layered anisotropic structures demonstrated the high accuracy and computing‐time efficiency of the method proposed. The results of the apparent‐resistivity calculation for both traditional pole‐pole and tensor arrays above three‐layered sequence with an azimuthally anisotropic second layer are presented. The numerical simulations show that both arrays have the same sensitivity to the anisotropy parameters. This sensitivity depends significantly on the resistivity ratio between anisotropic and adjacent layers and increases for the models with a conductive second layer.     

Toward a disaster risk assessment and mapping in the virtual geographic environment of Armenia

This paper presents the results of a research aiming natural and technological hazard, and risk assessment and mapping in Web-based holistic geographic environment, and the implementation of the Sendai Framework for Disaster Risk Reduction 2015–2030 in Armenia. A common spatial multi-criteria evaluation method was used for natural and technological hazard, risk and population vulnerability assessments. The virtual geographic environment developed by the authors during the previous period of investigations was upgraded and used for the implementation of this research. It involves the following components: 1. geodatabase, 2. modeling and simulation, 3. interface for digital mapping, 4. metadata, 5. Web–based network service for collaboration. Moreover, the country specific natural and technological hazard, risk and population vulnerability assessment methods were developed, implemented, and appropriate digital maps were created.     

The Berelekh Mammoth “Graveyard”: New Chronological and Stratigraphical Data from the 2009 Field Season

To clarify unanswered questions of site formation, geology and the archaeology of the Berelekh geoarchaeological complex, a special survey was undertaken in 2009 of the area surrounding the site. Several geological units have been revealed. By establishing the spatial and temporal relationship of these deposits—as well as their age—we have reconstructed the formation history of the Berelekh bone bed. The mammoth bone deposit belongs to a paleochannel. Radiocarbon dating of mammoth remains at Berelekh demonstrates rapid accumulation during the Bølling warming. Human involvement in its formation is, at best, questionable, since there is no real overlap between the radiocarbon dates associated with past human activity, and those of the mammoth bone bed. This study confirms that humans used mammoth bone remains after the bone bed was deposited. Culturally, the Berelekh “site” does not have any relationship to the so‐called “Dyuktai culture.” Instead, the Berelekh archaeological finds (side notched stone pendants) show certain similarities to non‐microblade terminal Pleistocene assemblages found from Yenisei to Kamchatka. Additionally, the Berelekh complex presents a clear analogy with lithics found in Eastern Beringia. Teardrop‐shaped incomplete bifaces found in the assemblage are comparable to the Chindadn points of Alaska. The nature of this “Chindadn connection” is intriguing but it is the only visible cultural link between Western and Eastern Beringia.     

Low-Level Atmospheric Jets And Inversions Over The Western Weddell Sea

For four months in the fall and earlywinter of 1992, as Ice Station Weddell (ISW) driftednorthward through the ice-covered western Weddell Sea,ice station personnel profiled the atmosphericboundary layer (ABL) with radiosondes. These showedthat the ABL was virtually always stably stratifiedduring this season: 96% of the soundings found anear-surface inversion layer. Forty-four percent ofthese inversions were surface-based. Eighty percentof the soundings that yielded unambiguous windprofiles showed an atmospheric jet with speeds as highas 14 m s^-1 in a core below an altitude of 425 m. This paper documents the features of these inversionsand low-level jets. Because the inversion statistics,in particular, are like those reported in and aroundthe Arctic Ocean, similar local processes seem tocontrol the ABL over sea ice regions in bothhemispheres. A simple two-layer model, in which anelevated layer becomes frictionally decoupled from thesurface, does well in explaining the ISW jetstatistics. This model also implies a new geostrophicdrag parameterization for sea-ice regions that dependson the magnitude of the geostrophic wind, the 10-mdrag coefficient C_DN10, and the ABL height, butnot explicitly on any stratification parameter.