Abstract The Laptev Sea in the Siberian Arctic represents a unique tectonic junction of an active spreading ridge, the Gakkel Ridge in the Eurasian oceanic basin, with the Siberian Arctic continental margin. New long-offset seismic profiles acquired in recent years provide a reliable basis for deciphering the structural and seismic stratigraphic characteristics of the Laptev Rift System. The tectonic development of the Laptev Shelf represents a sequence of four phases controlled by relative plate movements: (1) intense brittle normal faulting (an initial rifting or stretching phase) affected the entire shelf in the Late Cretaceous(?)–Paleocene(?); (2) a thinning/exhumation phase resulted in exhumation of the lower continental crust and probably upper mantle in the western part of the rift system – this phase is inferred to have occurred during the Late Paleocene to Early Eocene, preceding and accompanying continental break-up in the Eurasia Basin; (3) a stalled rift phase characterized by either a dramatically reduced rate of extension, or a non-extension/compression regime controlled by major reorganization of the plate movements – the onset of this fourth phase is inferred to coincide with the initiation of seafloor spreading in the southern Eurasia Basin at around 53–50 Ma; and (4) reactivation of the rifting in the mid-Miocene (a second rift phase).

Abstract A total of 143 sedimentary successions that contain, or may be prospective for, hydrocarbons were identified in the Arctic Region north of 58–64°N and mapped in four quadrants at a scale of 1:11 000 000. Eighteen of these successions (12.6%) occur in the Arctic Ocean Basin, 25 (17.5%) in the passive and sheared continental margins of the Arctic Basin and 100 (70.0%) on the Circum-Arctic continents of which one (<1%) lies in the active margin of the Pacific Rim. Each succession was assigned to one of 13 tectono-stratigraphic and morphologic classes and coloured accordingly on the map. The thickness of each succession and that of any underlying sedimentary section down to economic basement, where known, are shown on the map by isopachs. Major structural or tectonic features associated with the creation of the successions, or with the enhancement or degradation of their hydrocarbon potential, are also shown. Forty-four (30.8%) of the successions are known to contain hydrocarbon accumulations, 64 (44.8%) are sufficiently thick to have generated hydrocarbons and 35 (24.5%) may be too thin to be prospective.

Abstract The paper summarizes the results of geological and geophysical studies of the Siberian Arctic Shelf (Laptev, East Siberian and Chukchi seas), which is one of the largest continental shelves on Earth. This region consists of as many as 22 significant sedimentary basins of variable age and genesis which are expected to bear significant undiscovered volumes of hydrocarbons. Two major groups of the basins are identified based on the age of the underlying crustal basement: (1) post-Hauterivian/Barremian basins resting on the Late Mesozoic folded basement; and (2) older (Late Palaeozoic to Early Mesozoic?) basins preserved outboard of the Late Mesozoic deformational front in the northern part of the East Siberian and Chukchi seas. At least two significant tectonic events caused the overall tectonic pattern of the shelf as well as formation and structural styles of its individual crustal domains and the sedimentary basins: (1) Late Mesozoic convergence and subsequent collision of the Arctic Alaska–Chukchi Microplate with the Verkhoyansk–Kolyma/Omolon margin of the North Asia Continent around 130–125 Ma (the Verkhoyansk–Brookian compressional event); and (2) a series of Cretaceous and Cenozoic extensional events related to the origin of the Arctic oceanic basins. Based on 2D regional multichannel seismic reflection data constrained by onshore geology, plate tectonic models and inter-regional correlations, as well as on gravity and magnetic grids, the structural styles, lithostratigraphy and possible hydrocarbon systems of the offshore sedimentary basins are considered.