Extension across the Laptev Sea continental rifts constrained by gravity modeling

Abstract

The Laptev Shelf is the area where the Gakkel Ridge, an active oceanic spreading axis, approaches a continental edge, causing a specific structural style dominated by extensive rift structures. From the latest Cretaceous to the Pliocene, extension exerted on the Laptev Shelf created there several deep subsided rifts and high-standing basement blocks. To understand syn-rift basin geometries and sediment supply relationships across the Laptev Shelf, accurate extension estimates are essential. Therefore, we used 2-D gravity modeling and 3-D gravity inversion to constrain the amount of crustal stretching across the North America-Eurasia plate boundary in the Laptev Shelf. The latest Cretaceous-Cenozoic extension in that area is partitioned among two rift zones, the Laptev Rift System and the New Siberian Rift. These rifts were both overprinted on the Eurasian margin that had been stretched by 190-250 km before the Late Cretaceous. While the Laptev Rift System, connected to the Gakkel Ridge, reveals increasing extension toward the shelf edge (190-380 km), the New Siberian Rift is characterized by approximately uniform stretching along strike (110-125 km). The architecture of the Laptev Rift System shows that the finite extension of about 500 km is sufficient to entirely eliminate crystalline continental crust. In the most stretched rift segment, continental mantle is exhumed at the base of the Late Mesozoic basement. The example of the Laptev Rift System shows that extension driven by divergent plate movement is a sufficient cause to produce almost complete continental breakup without an increased heat input from the asthenospheric mantle.

Crustal architecture of the East Siberian Arctic Shelf and adjacent Arctic Ocean constrained by seismic data and gravity modeling results

“…In the Laptev Sea, the Late Cretaceous and early Cenozoic extension preceded the opening of the Eurasian oceanic basin and formed a vast rift system (Drachev et al, 1998;Franke et al, 2001;Drachev, 2011). As shown recently by Mazur et al (2015), Drachev and Shkarubo (2017) and Drachev et al (2017), the thinning of the continental crust beneath the U L ' may have resulted in a complete rupture of the continental crust and upper mantle exhumation.…”

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

“…However, by using seismically constrained boundaries and geologically reasonable densities for the modelled bodies down to the Moho, we are able to minimize the number of possible outcomes. The range of rock densities (Table 1) is adopted from a previous modelling study by Mazur et al (2015) as well as being calculated from seismic interval velocities using a Nafe-Drake formula (Ludwig et al 1970;Brocher 2005).…”

“…The first attempt to constrain the amount of crustal stretching across the LRS with the use of 2D gravity modelling and 3D gravity inversion was published by Mazur et al (2015). They showed that the amount of crustal extension in the central and northern parts of the Ust' Lena Rift Basin reached 430 and 500 km, respectively, and resulted in both the complete elimination of the continental crust and mantle exhumation beneath this hyperextended basin.…”

“…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).…”

Khatanga-Lomonosov fault zone: structure, tectonic position and geodynamics

“…Среди них прежде всего следует отметить проблему, связанную с объяснением отсутствия регулярных линейных магнитных аномалий в самом южном сегменте Евразийского бассейна. В некоторых публикациях практически весь набор кайнозойских магнитных аномалий по инерции произвольно протягивается до континентального склона Лаптевоморской окраины в попытке определить таким образом положение полюса Эйлера при открытии Евразийского бассейна [9]. В этой связи очевидно и то, что на подходе к южной оконечности бассейна в ряде мест линейные магнитные аномалии теряют субпараллельную ориентировку и смыкаются.…”