Evolution of the Novaya Zemlya fold-and-thrust belt, Arctic Russia, and its significance for adjacent hydrocarbon basins

The Novaya Zemlya archipelago contains an overall west-vergent fold-and-thrust belt that separates two contrasting hydrocarbon basins. On the foreland side are the deep depressions of the South and North Barents basins, containing sediment thicknesses approaching 20 km, of which around half is Permo-Triassic. The timing and cause of subsidence in this basin system is unclear, and the pre-Permian history is obscured by the thick overlying succession. The Mesozoic succession of the South Barents Basin is host to the Shtokman gas condensate discovery. On the hinterland side is the South Kara Basin, an offshore continuation of the gas-bearing northern West Siberian Basin.

Much of the compressional deformation recorded in Novaya Zemlya appears to have been either partially synchronous with the onset of subsidence in adjacent basins or significantly later. Furthermore, there is evidence to suggest that the emergence of the fold-and-thrust belt in its current form has been influenced by Cenozoic exhumation. Development of the Novaya Zemlya fold-and-thrust belt could therefore be expected to have had a considerable effect on hydrocarbon systems in adjacent basins. Published models for the fold-and-thrust belt propose a wide range of mechanisms, geometries and timings, but none provide an explanation for all aspects of the geological evolution. Here we attempt to explain the tectonic development of Novaya Zemlya and its relationship with adjacent basins in a coherent regional geodynamic framework.

Two characteristics of Novaya Zemlya immediately stand out on any topographic map: the plan-view curvature (convex towards the Barents Shelf) and the ~600 km westward offset compared with the remainder of the Uralian Orogen. Any regional tectonic model developed for the Novaya Zemlya fold-and-thrust belt must therefore be able to explain these first-order features. However, although several previous studies have sought to explain the offset of Novaya Zemlya from the remainder of the Uralian Orogen, there has been no previous attempt to link the geometry of structures on the archipelago with a potential mechanism that explains their curvature in plan view. Using field observations, information on geological maps and interpretation of satellite imagery, we seek to demonstrate the link between structural geometries in Novaya Zemlya and the subsidence history of the adjacent eastern Barents Shelf. We find no evidence to support previous interpretations of the fold-and-thrust belt as an orocline (bending of an originally straight deformation belt) and conclude that the offset from the remainder of the Uralian Orogen is a primary feature that results from an original embayment on the margin of Baltica. The presence of this embayment played a critical role in the evolution of the hinterland basin system (West Siberian Basin/South Kara Basin), permitting extensional subsidence that is coeval with compression in Novaya Zemlya.