The Lyakhov-South Anyui Suture and Basement Composition of the Laptev Sea

Dieter Franke, Christian Reichert, Volkmar Damm, and Karsten Piepjohn
BGR - Fed. Inst. Geosciences and Nat. Res., Hannover, Germany

The existence of an Anyui Ocean in Paleozoic and Mesozoic time is widely accepted. The closure of this oceanic basin is manifest in western Chukotka by Mesozoic terrigenous turbidites and fragments of both Paleozoic and Mesozoic ophiolites, the South Anyui suture. However, the suture zone, and especially its western flank is not yet clearly defined and many structural details are not understood.

We identify distinct buried folds, about 50 km wide, offshore at ~150°E on multichannel seismic data acquired in the 1990th around the New Siberian Islands. These structures fit well the proposed trend of the South Anyui suture and we interpret the folds as expression of the closure of the Anyui oceanic basin. Stepping westward from this position along a couple of MCS lines running south of the New Siberian Islands, we found negligible indications for folding or faulting in the basement. The only exception is one location in between Kotel’nyi and Malyi Lyakhov islands where a deep reaching (?)wrench fault is distinct that may be linked with a major NW-trending fault on Kotel’nyi Island.

In the eastern Laptev Sea we identify symmetrical anticlines in the basement which are in width, depth, shape and reflection characteristics analogous to the folds identified in the basement of the East Siberian Shelf. We suppose that these structures likely form the western flank of the South Anyui suture. The suture thus trends E-W along the shoreline south of the New Siberian Islands and in northern direction to the west of the New Siberian Islands.

This implies that all the New Siberian Islands are terranes which were accreted to NE Siberia. The presence of Paleozoic and Mesozoic carbonates and clastic rocks with a thickness of 6-10 km which are reported for the western New Siberian Islands is limited to the NE of the suture. The acoustic basement south of the suture remains unclear.

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