Structural Geology of Wrangel Island and Adjacent Russian Chukchi Sea Shelf

Vladimir Verzhbitsky

Wrangel Island represents the most uplifted part of Wrangel-Herald Arch – linear structural high of East Siberian-Chukchi Sea basement. The Island is mostly composed of intensively deformed Neoproterozoic metamorphic rocks and uncomfortably overlying folded and thrust faulted Silurian-Triassic sedimentary sequences. Upper Cretaceous(?)-Cenozoic sequence is outcropped rather locally and not involved in intensive Late Mesozoic (post-Triassic) compressional deformation. We believe that the latter was related to Chukotkan orogeny, caused by South Anyui ocean basin closure in Late Neocomian (Sokolov et al., 2002; 2009). Our field observations of 2006 confirmed rather uniform north-vergent low-angle thrust fault and fold structural pattern of the Island, complicated by NW-SE trending dextral strike-slip faults (Til’man et al, 1970; Byalobzhesky and Ivanov, 1971; Ganelin, 1989; Kos’ko et al., 1993, 2003). Our structural studies revealed no significant strike-slip constituent of general structural pattern, which was formed as a result of roughly N-S compression. The secondary N-S trending folds of S-dipping cleavage were found locally within the D-C black shale and most likely represent younger stage of compression. We also observed that folds in Silurian-Lower Devonian unit have ~ N-S strike, i.e. perpendicular to general structural trend. Taken together with existence of conglomerate units of Lower Carboniferous, it may point to Middle-Late Devonian tectonism coeval with Ellesmerian Orogeny of Arctic Alaska and Canadian Arctic Islands. This conclusion could also be considered as a supporting fact for rotational hypothesis of CA Basin opening. The latest normal faults and veins indicate post-collisional N-S to NE-SW extension (dextral transtension regime). Several recently published seismic lines (Verzhbitsky et al., 2010) show that normal faults cut the sharp seismic boundary interpreted as Mid-Brookian unconformity of North Chukchi Basin and Late Cretaceous-Paleocene peneplain of Wrangel Island. It points to Paleocene-Eocene time of major extension in the South Chukchi Basin and Wrangel Arch. The proposed earlier Permian-Triassic (Til’man et al, 1970; Sokolov et al., 2009; Miller et al., 2010) and Mid-Late Cretaceous (Natal’in et al., 1999) regional extensional episodes were likely masked by latest strong compressional events in Late Neocomian and Mid-Brookian time respectively. It appears that the tectonic basement of the South Chuckhi Basin is Neocomian. From the other hand the basement of North Chukchi Basin is likely Devonian and was formed as a result of Ellesmerian Orogeny, coeval with the basement of Arctic Alaska Petroleum Province and adjacent U.S.Chukchi shelf. The results of structural analysis of geological complexes of Wrangel Island should be used for petroleum exploration in Russian Chukchi Sea shelf, e.g. for seismic data interpretation, stratigraphic simulation and basin modeling of the South and North Chukchi sedimentary basins.

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