by Mikhail ALEKSEEV, Dr. Sc. (Geol. & Mineral.), Chief Researcher at the Geological Institute of the Russian Academy of Sciences; Valentina DRUSHCHITS, Cand. Sc. (Geogr.), Senior Researcher at the same Institute
Large-scale search is on all over the world for natural resources in sea-shelf areas. Our country is no exception either: by the close of the 20th century we had discovered oil, gas and placer deposits in seas of the Arctic and Pacific Oceans. A large body of materials collected on this part of Eurasia has facilitated the exploration work there.
Many works by our scientists and field experts show it abundantly clear that exploration of sea shelves in Russia's North and Far East is of immense scientific, economic and ecological significance.* The total area of our economic zone there is above 6,000,000 km2 . Nearly all of it lies in typical sea-shelf areas where major hydrocarbon deposits have been discovered and feasibility studies carried out into the geology and geophysics of field work, alongside exploratory parametric drilling and data evaluation toward detection of placer formations.
The idea of compiling the atlas "Geology and Mineral Resources of the Russian Shelf Areas" was suggested way back in the early 1980s by the Shelf Working Group of the Commission on World Ocean Problems (Presidium of the Russian Academy of Sciences). To begin with, it decided to update the materials on Eurasia's continental shelves. For years and years our expeditions working in coastal and sea-water areas had been amassing this body of information. By the end of the 12th century they had collected vast data arrays both in this country and abroad on the structure and stratigraphy of shelf areas, and on the composition of sediments there. After long and circumstantial discussions the Shelf Working Group under Dr. M. N. Alekseev proposed the idea that this immense volume of data should be systematized in the form of a paleographic atlas. This idea won support from Yuri M. Pushcharovsky and Igor S. Gramberg, both members of the national Academy of Sciences.
This very atlas - "Eurasian Shelf Areas in the Mesozoic and Cenozoic" - compiled though it was in
* See: N. Bogdanov, "Russia's Shelf, Its Riches", Science in Russia, No. 4, 2003; S. Golubchikov, "Arctic Shelf, Russia's Chief Reserve", Science in Russia, No. 1, 2000; I. Gramberg et al., "Continental Shelf: Russia's Last Fuel-and-Power Reserve", Science in Russia, No. 1, 1998. - Ed.
this country, was published in Great Britain in 1991. It allowed to visualize the evolution of this continent's submarine margins in time and in space. The atlas was drawn up on the territorial principle, that is its maps were prepared for every marginal and inner sea according to certain geologic periods - from the Triassic to the Mesoholocene (6,000 years ago). All in all, the atlas comprised 129 maps supplemented with a bilingual monograph, in Russian and English.
However, the ever growing attention to shelf natural resources called for further in-depth studies into the geomorphologic and tectonic characteristics of the shelf s external boundary so as to define the zone of our country's economic interests. Hence the felt need for a new atlas with information on mineral resources of Russia's shelf areas as well as data on the occurrence of mineral deposits, on their exploration and mining environments. The research team that had compiled the first atlas was all set to continue its work. However, the situation changed for the worse in the meantime with no wherewithal to finance an undertaking like that. Still and all, the research collective did not give up hope and went on with the preparatory work of data analysis and evaluation. Again, the ideas of the Working Group, now within the RAS Scientific Council on World Ocean Problems, got support from Acad. Yu. M. Pushcharovsky and Acad. I. S. Gramberg.
Involved in the new atlas project were experts of many Russian agencies and institutions: Russian Academy of Sciences, Ministry of Natural Resources, Ministry of Education and Science, Moscow State University, among other bodies, with the RAS Geological institute as the head organization. This project was included into the subprogram "Exploration of the Nature of the World Ocean" within the framework of the federal goal-oriented program "World Ocean", and it got financial support from the federal budget.
The interest in the mineral resources of Russia's shelf areas is spurred by several factors. First, major deposits of many different minerals have been discovered there. Second, with the Soviet Union's disintegration some of these deposits, both explored and indicated, happened to be outside the Russian Federation, and thus it became necessary to look for new raw material deposits elsewhere. Third, under certain conditions the mining of offshore deposits is more profitable economically than on dry land. Fourth, there are cogent examples of fairly intensive extraction of seashore placers and shelf deposits of oil and gas in other countries. And last, private investors have debunked the old mind stereotype about the rigors of the Far North and the Far East forbidding the proper survey and extraction work.
However, bare data on mineral resources alone are of no use without information on their geo- and ecoenvironments in sea-shelf and contiguous territories. This is true of feasibility studies, and research and development work alike: geoecologic and cartographic data are a must before one gets down to commercial mining. Accommodation modular platforms for offshore drilling are designed and built with due account of the ice and hydrology situation. On the other hand, works in shelf areas are up to mandatory state ecological examination to ensure the use of ecologically safe drilling technologies and effective waste disposal. The "must list" also provides for organizational and technical steps toward prevention or elimination of emergencies, including a system of oil spillage disposal, possible environmental impacts, risk factors and the like. Therefore atlas maps should draw upon diverse geologic and geoecologic information. And so, our new atlas lists data on the geology, ecology and mineral resources of the Barents, Laptev, East Siberian, Chukchi, Bering, Caspian, Black and Baltic Seas as well the Seas of Okhotsk and Japan.
The issue of sea-shelf boundaries gains in scope and significance with the further expansion of geologic exploration offshore. Within the limits of its national jurisdiction zones a coastal state is the owner of its natural resources, and that is why special attention is attached to the definition of the very notion of "shelf area". Geologic data are quite indispensable here.
Now by shelf area we understand a plainland strip of a continent's underwater (submarine) margin adjacent to continental coasts and characterized by a common geological structure with the coastal land. Shelf areas vary in width from several kilometers to 1,200 to 1,500 km. A shelf s edge my lie at different depths, from 50 to 200 m, and occasionally-as deep as 1.5 to 2 km. Thus, two geological criteria are used for pinpointing the outer boundary of a submarine margin: the first one is based on the change of a sedimentary cover's thickness within the limits of the external boundary of a continental margin, while the other-on the structural geologic unity of the sea floor and the continent (the geologic past is considered here as well).
Our new atlas was produced by the NAUCHNY MIR (Scientific World) Publishing House in 2004; its editor-in-chief is Dr. M. N. Alekseev (who edited the previous atlas, too). It is a logical follow-up of the paleographic atlas and updates it essentially, comprising nearly 98 different sheets (maps) (scale from 1:8,500,000 to 1:200,000) and providing an insight into processes implicated in the formation of useful minerals as well as natural conditions and risk factors involved in their prospecting and mining.
This work is in two parts - the atlas proper and the monograph appended to it with the description of the materials indicated on the maps and published in Russian and English (the English text is an abridged version of the Russian). Both the atlas and the monograph are predicated on the theme principle and consist of four chapters: Hydrocarbons, Hard Mineral Resources, Geology, and Geoecology of Russian Marginal Seas.
Sea of Okhotsk oil and gas prospects.
Gas hydrate environments in the water areas of the Eastern Arctic.
The atlas offers maps on the structure and geological position of oil-and-gas areas. Russia continues to lead the world in the total output of hydrocarbons-our country has as much as 13 percent of the world's oil reserves (it mines 15 percent of the world total) and more than 36 percent of natural gas (output, 27 percent of the world total).
Geologic and geophysical studies of shelf and adjacent coastal areas have made it possible to determine general regularities for the occurrence of hydrocarbon deposits. We have good evidence on the location of inferred hydrocarbon deposits. Prepared expressly for our atlas were the first maps on the presence of oil and gas in the Eastern Arctic, the Bering and the Okhotsk Seas.
Gas hydrates are a promising kind of hydrocarbons discovered not so long ago. They are ice-like mixtures of gas and water formed under high pressure and at low temperatures; the gas molecules are located within a volumetric lattice formed by water molecules. Gas hydrates are usually detected at low depths. Japan (Nankai trough) and India are already mining them. Experts stress the importance of gas-hydrate environments: we know that this raw material can clog pipelines and interfere with the steady performance of offshore modular drilling platforms and the drilling process proper. In arctic areas gas hydrates were formed due to gas migration in rocks, water-saturated to some extent and crystallized within permafrost.
The most extensive studies of gas hydrates were carried out in Russia back in the 1960s at the Messoyakh deposit in the northern part of West Siberian Lowlands. Although the initial data on its high recovery potential proved overstated somewhat, the interest in gas-hydrate resources keeps rising. In arctic shelf zones and in sea bottom sediments elsewhere gas hydrates may evolve as a cementing substance and thus trap free gas.
Our atlas is the first to show that structurally similar deposits of hydrocarbons, gas hydrates among them, may be found in water areas of the East Siberian and Chukchi Seas. Just as interesting in this respect are also the Laptev and Kara Seas.
The second chapter-"Hard Mineral Resources" - is in two parts dealing with placer minerageny (presence of metal) and coals. The maps of the first one are drawn up for key chronological stages (stratoisochrons) of the geologic evolution of the Arctic and Far Eastern shelf areas, with their paleography borrowed from the old paleographic atlas, though the relevant information was used for the first time in placer minerageny maps. The informative content of such maps is enhanced owing to the lists of discovered deposits and inset maps indicating the profiles and locations of major deposits or those characteristic of the region concerned.
Laptev and East Siberian Seas. Placer minerageny (Early Eocene).
The drawing up of paleographic maps according to chronostratigraphic profiles (stratoisochrons) touches on the intricate problem of the placers age. These maps indicate it by landscape environments contemporaneous with the formative processes of corresponding deposits. The use of stratoisochrons opens up a new perspective on the geologic position of placers of marine genesis in West Siberia. They were formed in the Eocene as the Tethys and Arctic Oceans merged into one ocean (about 50 million years ago). The coastal line of this giant Oligocene oceanic lake allows to delineate the area of coeval placers. The paleography of the main Quaternary glacial and interglacial periods shows the character of the ice cover and its implication in the formation of placers in the Western Arctic.
Eighteen placer zones composed of 42 districts are identified in the shelf areas of the Arctic and the Far East. These include-according to their prevalent specialization-several major provinces: Western Arctic (minerals of titanium, iron, zirconium, rare-earths, diamonds, amber); Central Arctic (the eastern part of the Kara Sea basin and the Laptev Sea: gold, diamonds); Eastern Arctic (gold, tin); Far East (gold, chromite, platinum* as well as minerals of titanium, iron and zirconium).
Placer deposits areas in the Eastern Arctic (dating from the early Eocene to the Neo-Pleistocene, or 55 million to 800 thousand years ago) are significantly larger than similar and younger formations that appeared less than 800,000 years ago, i.e. between the Neo-Pleistocene and Holocene periods. The wealth of early Cenozoic placers (65 million years ago) is due to favorable natural conditions, such as the warm temperate and sufficiently wet climate, and major tectonic shifts. A substantial role was also played by the shifts of individual crustal blocks during the late Neogene and Quaternary periods within what is now the eastern arctic shelf area.** The placers dating to the early Cenozoic turned to be conserved within permafrost rocks in the late Cenozoic under the effect of the polar accumulation of sediments when the shelf dried up every now and then. This protected them from destruction and redepo-sition. The ancient placers stripped by active erosion and thermal abrasion served as additional sources of alimentation for younger placers.
In the shelves and coastal zones of the Far East the scope of placer formation in the Neo-Pleistocene and Holocene depended on a blend of climatic, sedimentologic and hydrodynamic factors. The volume of ore mineral placers is especially large.
As to coal deposits, their inferred resources are esti-
* See: A. Kremenetsky, "Rare Metals: Russia's Strategic Wealth", Science in Russia, No. 3, 1999; N. Laverov, V. Distler, "Platinum: Our Strategic Wealth", Science in Russia, No. 4, 1999. - Ed.
** The boundary between the Neogene and Quaternary periods is now dated 1.8 mn years ago. - Ed.
Recent tectonics and active faults of the Russian Arctic.
mated at something like 740 billion tons, though unfortunately the level of their exploration is very low. This is explained by scant data on regions of complex geologic structure in active continental margins (islands, coastal land areas and water areas of marginal seas).
The oldest tenor of coal is related to profiles of the Permian age, though the best coal-bearing deposits are confined to the Cretaceous rocks. Drawn up for the atlas for the first time are maps of coal-bearing deposits in the shelf areas of the Barents, Kara and Laptev Seas as well as in the western part of the East Siberian Sea.
The section "Geology" of our new atlas comprises most different maps, including those on geophysics and recent sediments. By bringing all these maps together we sought to present a complete picture of formative conditions for mineral deposits.
The extent of exploration of Russia's marginal seas is rather different. For the Western Arctic, apart from seismic profile shooting, biostratigraphic and drilling data, there are arrays of geochemical tests, heat flow and radiation measurements. The degree of geological exploration of the shelf area declines dramatically if we move eastward, and the amount of information is quite low where the Eastern Arctic and the Far Eastern seas are concerned.
The geologic maps of the atlas illustrate processes concomitant to the initial stages of orogeny and genesis of mineral deposits. Therefore our atlas includes maps reconstructing the formative history of Russia's continental margin. There is also a map on recent tectonics and active faults of the arctic continental margin. It shows the position of the shelf edge of this vast region, and it is the first to indicate the faults of the late Neo-Pleistocene and Holocene, and earthquake hypocenters. Proceeding from all these data, we can conclude that activation of neotectonic processes here may have a negative impact on the operating facilities-or those at the gestation stage-of the oil and gas industry and pipelines-in fact, on any exploratory work within the shelf and coastal zone.
Our new atlas is remarkable in more ways than one. Aside from pinpointing a broad spectrum of mineral resources, it presents a set of geoecological maps characterizing prospecting, development and extraction environments. This is why we have divided the last chapter, "Geoecology of Russian Marginal Seas", into two parts. The first one contains maps on the situation in the coastal zone, and the other-in the shelf area.
Drawn up on the basis of interaction among 19 indicators of hazardous natural processes, the map on natural risks of Russia's coastal areas allows to single out territories with a different risk factor pertaining to their exploration and development. This section of the atlas
Barents and Kara Seas. Radionuclide pollution of bottom sediments.
also offers a map on radionuclides pollution of Russia's coastal zone.
This map shows in particular that radionuclide pollution is determined by three groups of factors: the nature of pollution sources themselves; meteorological and hydrogeological conditions; and landscape and geo-chemical environments. Geochemical barriers are playing an important part either in changing or in preserving the landscape geoecological characteristics if the landscape is subjected to anthropogenic effects; such barriers evolve as natural regulators capable of eliminating different groups of pollutants from technogenic effluents and/or accumulating such pollutants. And last, we offer a map on radionuclides pollution of bottom sediments in the Barents and Kara Seas. This region is among the best studied ones and, consequently, most exploited.
The maps dealing with landscape-geochemical environments as a background of radionuclide pollution sources and their distribution allow to identify the presence of radionuclides depending on a variety of factors: geochemical characteristics of radionuclides; modes of their transportation; pollution sources; characteristics of bottom sediments and their sorption capacity; redox potential; oxidation process intensity in surflcial sediments. Radioactive pollution anomalies in marine surficial sediments are usually the result of redistribution of radionuclides coming from various sources. The cause is in the presence of natural, local and regional geochemical barriers. Our ecomaps may prove to be useful for small-scale targeted designing of economic activities in the arctic and shelf areas of the Russian Far East.
The publication of our two atlases-"Eurasian Shelf Areas in the Mesozoic and Cenozoic", and "Geology and Mineral Resources of the Russian Shelf Areas" - apparently closes the age of extensive and long-term basic research into this problem of the 20th century. Our materials describe the structure and development stages of Russia's shelf areas and shed light on the chronological and structural regularities for the location of mineral resources there.
These two atlases are still in the focus of interest in this and other countries. Both describe the paleographic, geologic, and resource-related situation in the Far North, along the Northern Sea Route, and in the Far East, and are a tangible contribution of Russian scientists to Russia's economic progress and to the world practice of geological research in general.
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