Tectonics of the Laptev Shelf, Siberian Arctic

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).

Crustal architecture of the Laptev Rift System in the East Siberian Arctic based on 2D long-offset seismic profiles and gravity modelling

“…Therefore, the total width of the ULRB western flank is c. 195 km if measured along the projected strike of the TGS profile, and c. 195 km if measured along the projected strike of the MAGE A4 Profile. Positive gravity anomaly C corresponds to a zone of highly attenuated lower crust, as interpreted by Drachev and Shkarubo (2017). The total sediment thickness along the studied part of the western flank varies from c. 3 km or less on the top of horsts to c. 10 km at the transition to the axial rift zone.…”

“…Its width varies from 27 to 30 km, and sediment thickness reaches to 15 km. This zone is inferred to be underlain by either exhumed serpentinized mantle or exhumed and radically thinned lower crust (Drachev & Shkarubo 2017).…”

“…The total thickness of the rift sedimentary infill decreases from over 10 km in the deepest northern part to less than 1 km in The stratigraphy of the LRS is a highly speculative matter due to the complete lack of deep wells offshore and the very fragmentary and incomplete Upper Cretaceous and Cenozoic stratigraphic record preserved onshore. The most recent summary of the seismic stratigraphy of the Laptev Shelf has been published by Drachev and Shkarubo (2017), and for the purpose of this paper, we adopt stratigraphy from their publication. The sedimentary fill of the ULRB is comprised of three major seismic units ( The timing of crustal extension onset is also unclear.…”

“…In a recent publication, Drachev and Shkarubo (2017) attempted to illustrate the internal structure of the hyperextended Ust' Lena Rift Basin using long-offset MCS profiles by MAGE and TGS. Their model also suggests the presence of exhumed mantle in the axial zone of the rift.…”

“…In this paper, we attempt to verify the postulated mantle exhumation by comparing a synthetic gravity response from geological models built along three selected seismic profiles to the observed regional gravity data compiled by Getech (Mazur et al 2015). For this purpose, we have used the two interpreted two way travel time (TWT) seismic profiles published recently by Drachev and Shkarubo (2017), the MAGE A4 and TGS ARS10F04 Profiles, as well as one depth-converted Profile BGR 9701 published by Franke et al (2001).…”