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Contrasting Extensional Basin Styles and Sedimentary Fill Across the Eastern Russian Arctic Shelf as Imaged in Crustal-Scale PSDM Reflection Data

Abstract

The Siberian Arctic Shelf is one of the broadest continental shelves on Earth containing the Laptev, East Siberian and Chukchi Seas across an area of 3×106 km2. More than 13,000 line km of reflection data in the Laptev, East Siberian, and Chukchi Seas forms the basis for the interpretation east of the New Siberian Islands covering the North Chukchi-Vilkitski and New Siberian Sea Rift basins. The basement offshore (acoustic basement) is interpreted as an extension of onshore geology, which is dominated by Phanerozoic fold belts and their associated volcanic and plutonic complexes, and suture assemblages. These surveys and potential field data image a number of late Mesozoic and Cenozoic basins with at least 7.5 to 10 km of sedimentary fill. In the North Chukchi Basin as much as 20 km of sedimentary fill lies above acoustic basement. The entire shelf is overlain by a post-rift prograding succession. These basins have contrasting structural styles, even though they are connected and collectively relate to the opening of the Arctic Ocean. In the west, the East Siberian Sea Rift is comprised of arrays of tilted fault blocks rooting in a mid-crustal detachment system, underlain by a master fault at or near Moho level. It covers an area equivalent in size to the entire North Sea. In contrast, the North Chukchi Basin is a deep, gently-structured basin detached at Moho level and floored by oceanic crust, or possibly by serpentinized mantle. These basins exhibit contrasting styles of stratigraphic fill, related to the tectonics underlying their creation. For example, late-stage (post-rift) architecture in the North Chukchi Basin shows Tertiary shelf margin progradation traversing over 400 km northward over vertically accreting, Late Cretaceous high-accommodation aggradational sedimentation. In contrast, the East Siberian Sea Rift exhibits more conventional rift basin architecture, with tilted fault blocks bounded by deep troughs and potential large hydrocarbon fetch areas, similar to the North Sea. These basins contain the potential for reservoir development in shelf margin, lowstand systems, sub-unconformity regional stratigraphic traps, and within horst-graben systems typical of Neogene rifts. A mega-regional total sediment (above acoustic basement) isopach map over the large area illustrates that several other large gravity lows are present and suggests substantial potential for additional prospective basins.