Geol. Mag. 152 (3), 2015, pp. 480–491. c Cambridge University Press 2014 480 doi:10.1017/S0016756814000326 The Mesozoic–Cenozoic tectonic evolution of the New Siberian Islands, NE Russia ∗ CHRISTIAN BRANDES †, KARSTEN PIEPJOHN‡, DIETER FRANKE‡, NIKOLAY SOBOLEV§ & CHRISTOPH GAEDICKE‡ ∗ Institut für Geologie, Leibniz Universität Hannover, Callinstraße, 30167 Hannover, Germany ‡Bundesanstalt für Geowissenschaften und Rohstoffe (BGR), Stilleweg 2, 30655 Hannover, Germany §A.P. Karpinsky Russian Geological Research Institute (VSEGEI), Sredny av. 74, 199106 Saint-Petersburg, Russia (Received 27 December 2013; accepted 4 June 2014; first published online 25 September 2014) Abstract – On the New Siberian Islands the rocks of the east Russian Arctic shelf are exposed and allow an assessment of the structural evolution of the region. Tectonic fabrics provide evidence of three palaeo-shortening directions (NE–SW, WNW–ESE and NNW–SSE to NNE–SSW) and one set of palaeo-extension directions revealed a NE–SW to NNE–SSW direction. The contractional deformation is most likely the expression of the Cretaceous formation of the South Anyui fold–thrust belt. The NE–SW shortening is the most prominent tectonic phase in the study area. The WNW–ESE and NNW–SSE to NNE–SSW-oriented palaeo-shortening directions are also most likely related to fold belt formation; the latter might also have resulted from a bend in the suture zone. The younger Cenozoic NE–SW to NNE–SSW extensional direction is interpreted as a consequence of rifting in the Laptev Sea. Keywords: New Siberian Islands, De Long Islands, South Anyui suture zone, fold–thrust belt. 1. Introduction slip data. Such datasets deliver important information for understanding the regional geodynamic evolution In the last decades, several plate tectonic models have of the study area. In addition, understanding the ori- been developed to explain the evolution of the Arc- entation of faults and fractures is also important for tic region (e.g. Jones, 1980; Rowley & Lottes, 1988; hydrocarbon exploration (Gohram et al. 1979;Narr Miller et al. 2006; Shepard, Müller & Seton, 2013; 1991; Hennings, Olson & Thompson, 2000; Zahm & Vernikovsky et al. 2013a), but there are still many Hennings, 2009) and drilling campaigns (Dusseault open questions. Little is known so far about the struc- et al. 2004). The Laptev and East Siberian seas are tural evolution of the New Siberian Islands, which are regarded as an important hydrocarbon province (e.g. located in a key position on the east Russian Arctic Cramer & Franke, 2005; Khain, Polyakova & Filtova, shelf between the Laptev and the East Siberian seas 2009). Knowledge about the palaeo-shortening and (Fig. 1). This area is the western margin of the Alaska– palaeo-extension directions is crucial for exploration Chukotka microplate (e.g. Miller et al. 2006) and its campaigns, because the orientation of natural fractures structural evolution is important for understanding the and faults in sedimentary basins are systematically re- Mesozoic–Cenozoic tectonic evolution of the Arctic re- lated to the direction of the regional palaeostress field gion (Vernikovsky et al. 2013b). Studies have focused (Engelder & Geiser, 1980). Nevertheless, perturbations on the tectonics of the Laptev Sea region (Fujita, Cam- can occur that modify the local stress field (Homberg bray & Velbel, 1990; Drachev et al. 1998). Current et al. 1997). Faults and fractures also have an influence models largely depend on offshore reflection seismics on the subsurface fluid flow properties as they are dis- (Drachev et al. 1998; Franke, Hinz & Oncken, 2001; continuities in the rock mass that can affect the vertical Franke & Hinz, 2005, 2009). The onshore structural and lateral flow (Beaudoin et al. 2011, 2013). evolution of the New Siberian Islands has only been The aims of this study were to: (1) present an analysis analysed at selected locations (e.g. Kos’ko & Trufanov, of the outcrop-scale brittle fabrics of the New Siberian 2002; Kuzmichev & Pease, 2007; Kuzmichev, 2009) Islands; (2) derive the directions of tectonic deform- and knowledge is limited. There are no recent datasets ation of the eastern Laptev Sea and the western East from the De Long Islands available. To close this gap, Siberian Sea; and (3) connect the palaeo-shortening we present results of an onshore field-based structural and palaeo-extension directions with the geodynamic analysis carried out during the Circum-Arctic Struc- evolution of the NE Russian Arctic region. tural Events (CASE) 13 expedition in 2011, covering large parts of the New Siberian Islands including the De Long Islands. 2. Geological setting and previous work The palaeo-shortening and palaeo-extension direc- tions were derived from the trend of fold-axes and fault- The New Siberian Islands are located between the Laptev Sea and the East Siberian Sea (Fig. 1). They can †Author for correspondence: [email protected] be divided into three groups: the Lyakhov Islands in the Downloaded from https://www.cambridge.org/core. Technische Informationsbibliothek, on 14 Nov 2017 at 13:16:51, subject to the Cambridge Core terms of use, available at https://www.cambridge.org/core/terms. https://doi.org/10.1017/S0016756814000326 New Siberian Islands Mesozoic–Cenozoic tectonic evolution 481 De Long Islands 200 km Henrietta N Island Bennett Island Jeannette Island South based on Frank Anjou Islands Belkov Kotel´ny Anyui Island Zhokhov Island Island e et al. (2008)suture Bunge Land zone Vilkitsky Island Faddeyev Island Novaya Sibir South Anyui suture based on Natal´in et al. (1999) New Siberian Islands Laptev Sea Rift Lyakhov zone Stolbovoy Island Island Bol´shoi Lyakhov Island ? South Anyuiuzmichev suture (2009)zone Key based on K Quaternary volcanics Lower Cretaceous volcanics Carboniferous Oligocene to Quaternary Jurassic/Cretaceous Devonian Upper Eocene Jurassic Silurian Lower and Middle Eocene Triassic Ordovician Cretaceous Permian/Triassic Cambrian Figure 1. Geological map of the study area. Map is based on VSEGEI, Position of the South Anyui suture zone is modified after Natal’in et al. (1999), Franke et al. (2008) and Kuzmichev (2009). Globe is taken from NASA World Wind. south; the Anjou Islands in the centre; and the De Long Belkov Island (Kuzmichev & Pease, 2007) and on the Islands in the northeast (Kos’ko & Trufanov, 2002). structural style of parts of Kotel’ny Island and Novaya The Lyakhov and Anjou Islands represent a fold–thrust Sibir (Kos’ko et al. 1990; Kos’ko & Trufanov, 2002; belt that evolved during Jurassic–Cretaceous time and Kos’ko & Korago, 2009). These studies were limited in is interpreted to be continuous from NW Alaska over their regional extent however, and there are no recent northern Chukotka to the Laptev Sea area (Kos’ko & structural studies available for the De Long Islands. Trufanov, 2002; Bondarenko et al. 2003). The New The most recent work on the New Siberian Islands and Siberian Islands are regarded as a key area to under- the De Long Islands has a focus on palaeomagnetics stand the plate tectonic evolution of the Arctic region and biostratigraphy (Vernikovsky et al. 2013a, b). and the opening of the Amerasian Basin (Vernikovsky Sedimentary rocks of Cambrian–Cenozoic age are et al. 2013a, b). The offshore geology of the region exposed on the New Siberian Islands (Fig. 1). Igneous has been comprehensively analysed over the last 15 rocks are also present to a lesser extent. Ordovician years (Franke et al. 1998, 2008; Drachev et al. 1998; rocks are represented by shallow-water carbonates in Franke, Hinz & Oncken, 2001; Franke, Hinz & Reich- the northern part of Kotel’ny Island and by deepwater ert, 2004; Drachev, 2011). These studies focused on the clastics on Bennett and Henrietta Islands. Belkov Is- geodynamic evolution of the Late Cretaceous – Palaeo- land and the SW part of Kotel’ny Island are dominated gene Laptev Sea Rift, based on 2D-seismic reflection by Devonian–Carboniferous shales (Fig. 1). Triassic– lines. The onshore geology of the New Siberian Is- Cretaceous rocks are exposed in the central part of lands was the subject of different studies dealing with Kotel’ny Island. The Cretaceous rocks are widespread the structural geology of Bol’shoi Lyakhov Island and on the New Siberian Islands and vary from deepwater the nature of the South Anyui suture zone (Kyz’michev clastics (Bol’shoi Lyakhov Island, Stolbovoy Island) to et al. 2006; Kuzmichev, 2009). Additional work was sandstones (central Kotel’ny Island) to sands and soft carried out on the geochemistry of magmatic rocks of coals (Novaya Sibir). Downloaded from https://www.cambridge.org/core. Technische Informationsbibliothek, on 14 Nov 2017 at 13:16:51, subject to the Cambridge Core terms of use, available at https://www.cambridge.org/core/terms. https://doi.org/10.1017/S0016756814000326 482 C. BRANDES AND OTHERS a b fault plane slickenside c d figure 2D 1 m e f normal fault Figure 2. Outcrop photos and stereographic projections from the New Siberian Islands. (a) Strike-slip fault on Stolbovoy Island. The stereographic projection shows the orientation of the fault plane as a great circle and the slickenside striations as dots. (b) Serpentinite with slickenside on Bol’shoi Lyakhov Island. The great circle is the fault plane orientation and the dots indicate the plunge direction of the slickenside striations. (c) Fault-propagation fold on Novaya Sibir. (d) Detail of the fault-propagation fold. The structure was later cut by normal faults. The stereographic projection shows the fault planes as great circles. (e) Normal faults in Palaeogene sediments of northern Bunge Land. (f) Normal faults in Palaeozoic sedimentary rocks on Belkov Island. The stereographic projection shows the fault planes as great circles and the slickenside striations as dots. 3. Methods the basis for fault-slip analyses. We used the software In more than 40 outcrops across the New Siberian Is- FaultKin by R. Allmendinger to analyse the fault-slip lands, the orientations of beds, faults and fractures as data and to calculate P and T axes based on the approach well as slickensides on these surfaces were measured of Marrett & Allmendinger (1990).