Cambrian Deposits on Bennett Island (the De Long Islands): A Continuation of the Siberian Platform

Maria Danukalova

Bennett Island was discovered by George W. De Long team in 1881 and up to now was poorly studied. The island is composed of Cambrian and Ordovician marine sediments and Lower Cretaceous basalts. Here we provide new information on Cambrian deposits of Bennett Island obtained during fieldwork in 2011. Cambrian sequence consists of four lithological units. 1. Shale, siltstone and storm-generated sandstone beds with hummocky and swaley cross-stratification (Lower Cambrian, Atdabanian; 100 m). 2. Shallow-marine shale with rare limestone beds and concretions (upper Lower – lower Middle Cambrian, Amgan; 160 m). 3. Lagoonal greenish shale with pink nodular limestones (Middle Cambrian, Mayan – lowermost Upper Cambrian; 130 m). 4. Relatively shallow-water black shales (Upper Cambrian; at least 100 m). Indicated age is based on the numerous trilobites found on different levels. Our investigations reveal no evidence for oceanic basin separated Bennett Is. from the Siberian platform in Cambrian time. Most of Early Cambrian trilobites in our collection and part of Middle and Upper Cambrian ones are known only from Siberia. Four Cambrian units in Bennett succession are similar in age (though show some different lithology) in comparison to four formations of the northern Siberian platform. The Cambrian sediments exposed on Bennett Island were formed at the same Siberian shelf. At that time most of Siberian craton was a carbonate platform while its recent NE part including Bennett Is. demonstrate siliciclastic sedimentation due to proximity of some land that lied to the NE from it. This conclusion contradicts commonly held view that Bennett Is. and surrounding shelf belongs to one of exotic Arctic terranes and confirms opinion of E. Toll (1902 y.) that the island is a continuation of the Siberian platform.

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