THE DELONG ISLANDS AND ARCTIC TECTONIC RECONSTUCTIONS

Geological ’piercing points’ are unique in space and time and provide the means to constrain tectonic reconstructions. The De Long Archipelago, Russian Arctic, may provide such a piercing point for Arctic reconstructions given the distinctive geology of some of its islands. A joint Russian (VSEGEI) – Swedish (SWEDARCTIC) expedition to the De Long Archipelago in September of 2013 allowed us to perform fieldwork on the De Long islands of Bennett, Henrietta, and Jeanetta. This was the first geological investigation of Jeanetta island since the expedition of M. Ermoleav in 1933.

The De Long Archipelago comprises five islands from <1 km² to >50km²in size: Bennett, Henrietta, Jeanetta, Zhakov, and Vilkitsky. We present results from Henrietta and Jeanetta Islands. Henrietta Island comprises clastic, volcanoclastic, and volcanogenic rocks (sandstone, siltstone, tuffaceous clastic sediment, gabbro, basaltic dikes, sills and flows). The rocks are folded and faulted, and have been inferred to be Carboniferous (foraminifera), late Devonian to Carboniferous (K-Ar ages), and Ordovician (Ar-Ar age) in age. Jeanetta Island consists of sandstone, shale, dikes and volcanogenic rocks. Their ages are unknown, but may be correlated with the rocks of Henrietta Island. The geology of the Henrietta and Jeanetta islands appears unique in the archipelago and, depending on their age/provenance, may provide a ’piercing point’ for Arctic tectonic reconstructions reflecting M’Clintockian, Caledonian, or Ellesmerian genesis.

The application of modern geochronological and geochemical techniques provides important information on the age and tectonic setting(s) of the studied rocks. Our preliminary U-Pb zircon results indicate that sandstones and volcaniclastics of Jeanetta are likely Precambrian in age and have U-Pb detrital zircon age peaks at 570 and 600 Ma. Results from clastic and volcaniclastic sediments from Henrietta at the base of the section indicate a Cambrian age. One sample has age peaks at 530, 545 and 615 Ma, with a large spread from c. 850-1726 Ma. The second sample (higher in the section) defined age peaks at 530 and 550 Ma, with a spread from c. 1040-1440. These data indicate i) an active volcanic margin, ii) a strong Timanian (peri-Baltican) signature, and iii) possible displacement of the DeLong archipelago.