Late Pleistocene Catastrophic Landslide from the Balaganchik Ridge: Evidence from the Mitoga 2 Reference Section (Western Kamchatka)

Lithology and Mineral Resources - A new reference section of the Okhotsk seaside of Kamchatka in the Mitoga 2 River area is studied and dated for the first time (14C and 230Th/U). Sedimentary...     

On the seismic hazard of the Bolshoi Sochi region

In connection with the intensive development of the northeastern part of the Black Sea, at present a number of serious technical, scientific, and ecological problems have arisen. As the constructions being raised are of large sizes and they are designed for a long period of use, the probability of their damage by natural phenomena significantly increases. First of all, these are phenomena connected with seismotectonic activity. In the present paper, the current concepts about the regional tectonic structure are considered. Moreover, a detailed analysis of the seismic activity in the Bolshoi Sochi region and the adjacent regions is conducted in the historical perspective. The basic results of the marine seismic research carried out by the Institute of Oceanology of the Russian Academy of Sciences on the shelf and the continental slope of the northeastern part of the Black Sea during the period of 1998–2001 are presented. On the basis of the scheme of the general seismic zoning developed by the International Expert Group for the Caucasian Region, a scheme of the seismic hazard in the Bolshoi Sochi region has been constructed. For the specific zones of the region, the values of the seismic hazard characteristics—the maximum shocks and accelerations and the periods of oscillations under maximum seismic effect—have been calculated. Some ideas concerning the integrated modernization of the system for seismological observations in this region, including the deployment of autonomous bottom seismographs and automatic seismographs in almost inaccessible places, are proposed.     

Submarine landslide structures in neopleistocene deposits on the western slope of the Derbent basin of the Caspian Sea

In the autumn of 2004, during cruise 19 of R/V Rift, an “SES-2000 standard” super high-resolution narrow-beam parametric profiler was applied for studies of the fine structure of the uppermost sediments for the first time in the Caspian Sea. In this paper, we discuss the latitudinal seismoacoustic profile across the western slope of the Derbent Basin in the region of the Russian part of the Yalama-Samur hydrocarbon field. In the upper part of the slope, in the Neopleistocene deposits, a series of overthrust covers with a step-wise structure of displacement surfaces (duplexes) was revealed. They seem to have been formed by gravity processes. We also suggest the existence of a “pushed wedge” type of structure of landslide origin formed by the Bakinian-Khvalynian deposits intruding into the overlying Holocene sediments. Sufficiently distinct signs of disintegration of the bottom sediments and landslide-slumping processes were distinguished within the Eopleictocene deposits on the steepest lower part of the slope. The data of seismoacoustic profiling indicate that submarine landslide processes proceeded on the western slope of the Derbent Basin during the Neopleistocene-Holocene, which may have retained their activity up to present. These facts should be considered when designing engineering constructions over the Yalama-Samur structure.     

Contourites and Gravitites on the Rio Grande Rise,Southwest Atlantic Ocean (Seismoacoustic Data)

Morphology of the Rio Grande Rise and the acoustic structure of different types of deposits in its uppermost sedimentary cover were discussed based on high-resolution seismoacoustic profiling of cruises #32 (2010) and #52 (2016) of R/V Akademik Ioffe. Slopes of the Rio Grande Rise are composed mainly of landslide deposits and gravitites, but contourite sedimentation is possible on its southern slope. Contourite sedimentary waves and, probably, small drifts are identified in the Cruzeiro do Sul Trough at the top of the Rio Grande Rise. Mixed gravitite–contourite sedimentary systems seem to be located at the foot of northern and southern slopes. The downslope density flows and the Antarctic Bottom Water (AABW) contourite current are responsible for the formation of these features.     

Seismic Evidences of Contourites on the Rio Grande Rise,Southwest Atlantic

Doklady Earth Sciences - Several features probably formed by contour bottom currents were recognized on the Rio Grande Rise by high-resolution seismic survey in the transatlantic profiles of the...     

Methane anomaly in the waters of the Anapa shelf and its possible relation to oil-and-gas bearing structures

The results of gas geochemical and seismoacoustic measurements obtained in the course of the expedition for the studies of gas seepages at the Anapa shelf of the Black Sea are presented. According to the data of the gas survey in the surface waters of the Anapa shelf, a large methane anomaly was discovered and mapped. The correlation of the anomaly with the bottom sources located over the Pionerskaya structure is proved. The geological structure of the area studied is analyzed. The data set allowed us to positively characterize the prospects of the oil-and-gas content of the Anapa shelf interiors and of the Pionerskaya structure proper.     

Slump structures in quaternary slope sediments of the northern Derbent Basin (Caspian Sea)

During Cruise 20–3 of the R/V Rift (April, 2006), the area that includes the shelf and slope of the Derbent Basin in the northern Middle Caspian was studied using the continuous seismoacoustic profiling method. In accordance with the previous standpoint, two Pleistocene deltaic complexes formed in the Enotaevian and Mangyshlakian time are defined in this area. The seismoacoustic records obtained for the northern slope of the Derbent Basin demonstrate the development of specific rootless exogenic-gravitational fold structures in the upper (～150–200 m) Quaternary part of the sedimentary sequence. The Quaternary section encloses angular unconformities indicating the pulsating mode of gravitational processes in the northern slope of the basin. South-dipping gravitational normal faults (and/or normal fault-related flexures) displacing the bottom surface and uppermost sedimentary layers (with vertical amplitudes up to 5–6 m) were defined in the southern part of the study area. Several impulses of the submarine slump structures predated and accompanied the deposition of the upper deltaic sequence (Mangyshlakian), although their most intense formation took place later during the Novocaspian (Holocene) time. Thus, the structural analysis of the seismoacoustic data revealed intense development of different-origin and different-age gravitational structures within the Quaternary sediments in the northern slope of the Derbent Basin. These results should be taken into consideration when designing, building, and operating submarine constructions in order to prevent potential natural hazards and reduce their consequences.     

Mosaic of Deformed Tectonic Blocks in the Central Basin of the Indian Ocean

Doklady Earth Sciences - A detailed map of the seafloor relief of a unique area of the intraplate lithosphere deformation in the Central Basin of the Indian Ocean was constructed for the first...     

Contourites in the Derbent Basin,Caspian Sea (Geophysical Data)

Doklady Earth Sciences - A high resolution seismic survey carried out by the Shirshov Institute of Oceanology, Russian Academy of Sciences in 2004–2012 near the foot of the continental slopes...