GEOLOGICAL BACKGROUND TO SEARCH UNDERWATER ACCUMULATIONS OF MAMMOTH IVORY BY SONAR IN THE RUSSIAN ARCTIC

Currently, the need for substantial increase in the base of actually recoverable resources of fossil mammoth ivory (FMI) — of the Mammuthus primigenius ivory (Blumenbach, 1799), is determined by intensified interest of domestic and foreign markets in this unique type of natural raw material. Accumulations of mammoth ivory are exogenous formations of the placer class, classified as boulder type placers, formed on the residual-denudation principle exclusively under conditions of the Arctic permafrost zone degradation. An analysis of their localization conditions allows the authors to identify several morphogenetic (geological and commercial) types of placers of the coastal-marine and continental genesis. The ivory is recovered (up to 30-50 tons annually) in the territory of Northern Yakutia from placers located on land, including the beach area.
Significant prospects for increasing the FMI resource base are associated with the study and exploitation of predicted underwater placers: bottom coastal-marine deposits in the shallow waters of the eastern Arctic Seas, and lacustrine placers formed in thermokarst lakes that are very common to the territory of Northern Yakutia. Bottom placers are under water, which excludes the possibility of their direct visual observation, especially resource estimation and processing by traditional methods.
Sonar detection is the most effective method of searching and identifying mammoth ivory and their fragments in underwater conditions. The technical basis are sensitive side-scan sonars (SSS) with an operating frequency between 500 and 1200 kHz and more, capable of operating in shallow waters. The mammoth tusks are small objects and their identification is possible only by morphology. This fact determines the necessity of using equipment with a high operating frequency.

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