Great Lyakhovsky Island

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Map showing the location of Lyakhovsky Islands

Great Lyakhovsky Island (Russian: Большой Ляховский: Bolshoy Lyakhovsky) is the largest of the Lyakhovsky Islands belonging to the New Siberian Islands archipelago in Laptev Sea in northern Russia. It has an area of 4,600 km², and a maximum altitude of 270 m (Emy Tas).

Great Lyakhovsky Island consists of highly folded and faulted Precambrian metamorphic rocks and turbidites; Mesozoic turbidites and igneous rocks; and Cenozoic sediments. Exposed in southeastern part of this island, the older Precambrian. Early Proterozoic, metamorphic rocks consist of schists and amphibolites. Small exposures of Late Proterozoic schistose, quartzose sandstones and phyllitic, sericite-quartz schist (turbidites) also occur in the southeastern part of Great Lyakhovsky Island. The bulk of this island consists of Late Jurassic to Early Cretaceous turbidites composed of interbedded fine-grained sandstones, thinly bedded siltstones, and argillites. The Precambrian and of Late Jurassic to Early Cretaceous rocks are intruded by Late Cretaceous granites and granodiorites (Fujita and Cook 1990, Kos’ko and Trufanov 2002, Kyz’michev et al. 2006).

A blanket of unconsolidated Cenozoic sediments blankets most of Great Lyakhovsky Island. These sediments include Paleocene to Eocene colluvial, alluvial, and deltaic gravels, sands, clays, and coals and Oligocene to Miocene alluvial, lacustrine, deltaic, and nearshore marine sands and clays that contain beds and lenses of gravel. Overlying these sediments are Pliocene to Pleistocene colluvial, alluvial, and nearshore marine sands, silts, and clays clays that contain occasional gravel layers. The nearshore marine sediments contain the shells of marine mollusks and pieces of lignitized wood. Thick permafrost characterized by massive ice wedges has developed in these sediments. Contrary to the interpretations of von Toll and earlier geologists, glacial deposits and ice are completely absent within Great Lyakhovsky Island ((Fujita and Cook 1990, Kos’ko and Trufanov 2002).

The vegetation of Great Lyakhovsky Island is a mixture of rush/grass, forb, cryptogam tundra, cryptogam herb barren, and sedge/grass,moss wetland. The rush/grass, forb, cryptogam tundra covers the bulk of Great Lyakhovsky Island. It consists mostly of very low-growing grasses, rushes, forbs, mosses, lichens, and liverworts. These plants typically cover about 40-80 percent of the surface of the ground. The soils are typically moist, fine-grained, and often hummocky. The cryptogam herb barren consists of dry to wet barren landscapes with scattered, herbs, lichens, mosses, and liverworts. Sedges, dwarf shrubs, and peaty mires are normally absent. These plants form a sparse (2-40%) and low-growing plant cover that often occurs as dark streaks on the otherwise barren lands, composed largely of bryophytes and cryptogamic crusts. Sedge/grass,moss wetlands, which occur on the northwest and southeast ends of Great Lyakhovsky Island, consist of wetland complexes dominated by sedges, grasses, and mosses. These wetlands occupy low, perennially wet parts of the landscape (CAVM Team 2003).

[edit] References

CAVM Team, 2003, [Circumpolar Arctic Vegetation Map]. Scale 1:7,500,000. Conservation of Arctic Flora and Fauna (CAFF) Map No. 1. U.S. Fish and Wildlife Service, Anchorage, Alaska.
Fujita, K., and D.B. Cook, 1990, The Arctic continental margin of eastern Siberia, in A. Grantz, L. Johnson, and J. F. Sweeney, eds., pp. 289-304, The Arctic Ocean Region. Geology of North America, vol L, Geological Society of America, Boulder, Colorado.
Kos’ko, M.K., and G.V. Trufanov, 2002, Middle Cretaceous to Eopleistocene Sequences on the New Siberian Islands: an approach to interpret offshore seismic. Marine and Petroleum Geology. vol. 19, no. 7, pp. 901–919.
Kyz’michev, A.B., A.V. Soloviev, V.E. Gonikberg, M.N. Shapiro, and O.V. Zamzhitskii, 2006, Mesozoic Syncollision Siliciclastic Sediments of the Bol’shoi Lyakhov Island (New Siberian Islands). Stratigraphy and Geological Correlation. vol. 14, no. 1, pp. 30–48.