Continental Slopes of the West Africa Region: A Unique Treasure of Hydrocarbons

The West African region embraces a number of coastal sedimentary basins, which continued in deep-water areas of the Atlantic Ocean. It includes the following oil-and-gas-bearing basins: the Gulf of Guinea, the Kwanza–Cameroonian, and the Namibian. The sedimentary cover of the basins of this passive margin is represented by Mesozoic–Cenozoic deposits. The composition of sediments accumulated in them is quite specific and surprisingly units over the vast areas. The tectonic structure of the majority of the continental margins of West Africa makes possible to refer them to the margins of epiplatform orogenic belts. The existence of two systems of linear troughs—internal and external—on the passive margins at the early stages of continent–ocean transition zones relates deep-water hydrocarbon deposits to internal troughs filled by younger sediments: the alluvial fans of submarine rivers and landslide fronts with prograde formations (turbidites, debris flows, etc.). Late Cretaceous and Middle Paleogene clay formations played the role of source beds in the region, so-called “black clays.” An analysis of over 200 hydrocarbon fields, mainly petroleum, discovered in the past 10–15 years in the region revealed a clear tendency of these fields occurring in a productive zone of oil pools extending in a sea depth interval of 400–3000 m on the continental slope and possibly to 4000 m at the continental rise. Moreover, all discovered fields have been estimated in terms of reserves from large to giant. It is also noteworthy that within the shallow of this region, which includes the shelf and the coastal plain, only a number of small, insignificant oil and gas pays have been discovered. The main of oil and gas bearing potential prospects are related to deposits in the middle and lower parts of the continental slope and possibly adjacent areas of the continental rise. In the long term, the drilling objectives will be both postsalt and presalt deep-water oil-and-gas fields.     

Morphostructural Analysis and Seabed Shelf Typing

Analysis of the morphometric characteristics from a study of the Barents Sea seabed has shown that the existing troughs are consistent with geodynamic conclusions, allowing morphological typing into structural slopes and reconstruction of their origin. Thus, the Norwegian–Mezenskaya rift system and Svyataya Anna and Victoria troughs were formed due to stretching of the lithosphere. The South Barents and Medvezinsko- Edzinskaya depressions formed at the generation stage of lithospheric plates due to the collision of several island arcs between outliers of the ancient oceanic crust. The choice of the geomorphic method for studying the seabed is because the science of geomorphology comprehensively studies bottom relief (morphology), its origin, and age. Adequate reconstruction of the causal relationships of exogenous and endogenous processes aids in substantiating the prediction of probable catastrophic seabed events. The results of mathematical calculations have confirmed the geodynamic conclusions within the Barents Sea region.     

Numerical simulation and spectral analysis of the November 15, 2006, tsunami in the Kurile-Kamchatka region

Numerical simulation of the earthquake and tsunami of November 15, 2006, and the spectral analysis of the distribution of the wave fields in the basin made it possible to analyze in detail the tsunami generation by a seismic source and the pattern of the wave propagation through the Bussol Strait, as well as to estimate the influence of this strait on the further propagation of the waves in the basin of the Sea of Okhotsk and the near-field zones of the Kurile and Japanese Islands.     

The Kuril Earthquakes and tsunamis of November 15, 2006, and January 13, 2007: Observations,analysis, and numerical modeling

Major earthquakes occurred in the region of the Central Kuril Islands on November 15, 2006 (M _w = 8.3) and January 13, 2007 (M _w = 8.1). These earthquakes generated strong tsunamis recorded throughout the entire Pacific Ocean. The first was the strongest trans-Pacific tsunami of the past 42 years (since the Alaska tsunami in 1964). The high probability of a strong earthquake (M _w ≥ 8.5) and associated destructive tsunami occurring in this region was predicted earlier. The most probable earthquake source region was investigated and possible scenarios for the tsunami generation were modeled. Investigations of the events that occurred on November 15, 2006, and January 13, 2007, enabled us to estimate the validity of the forecast and compare the parameters of the forecasted and observed earthquakes and tsunamis. In this paper, we discuss the concept of “seismic gaps,” which formed the basis for the forecast of these events, and put forward further assumptions about the expected seismic activity in the region. We investigate the efficiency of the tsunami warning services and estimate the statistical parameters for the observed tsunami waves that struck the Far Eastern coast of Russia and Northern Japan. The propagation and transformation of the 2006 and 2007 tsunamis are studied using numerical hydrodynamic modeling. The spatial characteristics of the two events are compared.     

Bitumoids of Holocene Sediments in the Barents Sea

Doklady Earth Sciences - The results of studying the content, composition, and distribution of chloroform bitumoids (CBs) in the Holocene sediments of the Barents Sea (cruise 68 of the R/V Akademik...     

Role of Brazil’s Continental Slopes in Being Provided with Hydrocarbon Resources

Oceanology - Abstract—Analysis more of 80 hydrocarbon fields, mainly oil-producing, in the deepwater part of the Santos, Campos and Espirito Santo basins reveal the tendency of these large...     

New data on the subaerial low-center-polygonal relief and factors controlling its transformation and current state on the East Siberian Shelf

The problem of the current state of subaerial morphosculptures on the periglacial East Siberian Shelf is still debatable due to the lack of in situ data. Therefore, any new information contributes to the knowledge of the evolution of the Arctic environment. In view of this, a complex of interdisciplinary oceanological studies was carried out in the southeastern part of the Laptev Sea. Using a side-scan sonar, images of the bottom surface were made, which show the shape of low-center-polygonal relief of the part of the modern coastal lowland area in the coastal zone near the area under study. Possible factors controlling the state of this morphosculpture within the East Siberian Shelf area of interest are considered.     

New Data on Seismotectonics of the Laptev Sea from Observations by Ocean Bottom Seismographs

Doklady Earth Sciences - The results of new local seismic observations in the Laptev Sea obtained using ocean bottom seismographs were compared with actual data from global and regional earthquake...     

Regularities of Hydrocarbon Distribution in the Deepwater Part of the West African Margin

It is revealing a clear tendency of the fields layered in producing belt of oil-pays, extending in the limit of the sea depth from 400 m to 3000 m at the continental slope and possibly 4000 m at the continental rise.