Abstract The New Siberian Islands are affected by a number of Mesozoic tectonic events. The oldest event (D1a) is characterized by NW-directed thrusting within the South Anyui Suture Zone combined with north–south-trending sinistral strike-slip in the foreland during the Early Cretaceous. This compressional deformation was followed by dextral transpression along north–south-trending faults, which resulted in NE–SW shortening in the Kotelny Fold Zone (D1b). The dextral deformation can be related to a north–south-trending boundary fault zone west of the New Siberian Islands, which probably represented the Laptev Sea segment of the Amerasia Basin Transform Fault in pre-Aptian–Albian times. The presence of a transform fault west of the islands may be an explanation for the long and narrow sliver of continental lithosphere of the Lomonosov Ridge and the sudden termination of the South Anyui Suture Zone against the present Laptev Sea Rift System. The intrusion of magmatic rocks 114 myr ago was followed by NW–SE-trending sinistral strike-slip faults of unknown origin (D2). In the Late Cretaceous–Paleocene, east–west extension (D3) west of the New Siberian Islands initiated the development of the Laptev Sea Rift System, which continues until today and is largely related to the development of the Eurasian Basin.

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).