--> Abstract: Tectonics and Paleostress Field Pattern of the New Siberian Islands and De Long Islands: Insights into the NE Russian Arctic Shelf, by Christian Brandes; #90177 (2013)

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Tectonics and Paleostress Field Pattern of the New Siberian Islands and De Long Islands: Insights into the NE Russian Arctic Shelf

Christian Brandes

The Laptev and East Siberian Sea are potential future hydrocarbon provinces, but the knowledge about the structural style of the NE Russian shelf is very limited. During the CASE 13 expedition in 2011 we analysed the structural geology of the New Siberian Islands and De Long Islands, which are located in a key position between the Laptev and the East Siberian Sea. Structural data was derived from Stolbovoy, Belkovsky Island, Kotelny, Bunge Land, Great Lyakhovsky Island, Novaya Sibir, Bennett, Zhokov and Henrietta Island. Special focus was the reconstruction of the regional paleostress field. The paleostress data shows that there are two major compressional horizontal paleostress directions and one extensional. The NNE-SSW directed contractional phase is very pronounced and recorded in rocks on Great Lyakhovsky, Stolbovoy, Belkovsky and Kotelny. On Great Lyakhovsky this compressional paleostress direction rotates from NNE-SSW to a NNW-SSE orientation. Outcrops at the coast of Belkovsky imply that this contractional phase seems to be more N-S directed in the western part of the study area. A second set of fabrics, exposed in the center of Kotelny and on Bennett Island indicates a WNW-ESE directed compressional horizontal paleostress. Evidence for a NNE-SSW extension was found on Zhokov and Novaya Sibir. Outcrops on Novaya Sibir show that normal faults cut through fault-related folds, so the extension is younger than the contraction. This is supported by observations made on Zhokov, where the same extension direction is recorded in Quaternary magmatic rocks. Different sets of strike-slip faults are developed. Many of them fit into the NNE-SSW directed compressional stress regime as on Kotelny, Stolbovoy and Great Lyakhovsky. Most of the observed paleostress direction can be linked to regional geodynamic processes. The NNE-SSW compression is the prominent tectonic phase and most likely related to the closure of the South Anyui Ocean. The younger NNE-SSW extension is probably a consequence of the rifting in the Laptev Sea. The strike-slip faults on Belkovsky are different. From a kinematic point of view, they are difficult to explain with a NNE-SSW contraction. A reasonable explanation would be also a relation to the Laptev Rift. These strike-slip movements could be tip line effects of normal faults. The WNW-ESE directed compressional paleostress vectors could represent an individual deformation phase, but from our data set, there is no clear evidence that this phase is significantly older than the NNE-SSW compression. Further potential explanations for the two different compressional paleostress directions could be local stress field perturbation along fold structures, or the pattern might be related to changes in the parameters of the South Anyui subduction zone, from normal to a more oblique convergence.

AAPG Search and Discovery Article #90177©3P Arctic, Polar Petroleum Potential Conference & Exhibition, Stavanger, Norway, October 15-18, 2013