Marine and Petroleum Geology 19 (2002) 901–919 www.elsevier.com/locate/marpetgeo Middle Cretaceous to Eopleistocene Sequences on the New Siberian Islands: an approach to interpret offshore seismic M.K. Kos’ko*, G.V. Trufanov VN1Okeangeologia, 1 Angliisky Avenue, 190121 St Petersburg, Russian Federation Received 6 June 2000; received in revised form 10 June 2002; accepted 26 June 2002 Abstract The New Siberian Islands divide the Laptev Sea from the East Siberian Sea. The Archipelago comprises three island groups: De Long Islands, Anjou Islands, and Lyakhov Islands. The regional structural ensemble comprises De Long, Kotel’nyi, Faddeya and Lyakhov tectonic Domains. Aptian–Albian, Late Cretaceous, Palaeocene–Eocene, Oligocene–Miocene, and Pliocene–Eopleistocene tectono-stratigraphic and igneous sequences have been identified on the Islands. The succession of these sequences and their structural and compositional characters provide to distinguish specific stages in the tectonic history of the region showing alteration of regional tectonic environment through the middle Cretaceous and the Tertiary correlative to major North-East Eurasia, Arctic, and Global events. LS1, LS2, and LS3 major regional unconformities have been identified offshore by German geoscientists based on MCS data in the New Siberian Islands area. It is hypothesized in this paper that three offshore sedimentary cover units bounded by the unconformities correlate to the onshore sequences the following way: Unit I comprises Aptian–Albian and late Cretaceous Sequences, Unit II, Palaeocene–Eocene and Oligocene– Miocene Sequences, and Unit III comprises Pliocene–Eopleistocene Sequence and overlying Quaternary sediments. q 2002 Elsevier Science Ltd. All rights reserved. Keywords: Pliocene–Eopleistocene Sequence; Offshore seismic survey; Regional unconformities 1. Introduction basis of general global scale seismostratigraphic approaches, and extrapolations from neighboring onshore. The tectonic evolution of the New Siberian Islands in the There are no deep wells in the region to support the late Mesozoic and in the Tertiary has not been widely and interpretation. This paper is intended to contribute to the adequately discussed. The authors did geological mapping dating of seismostratigraphic units and deep reflectors on the New Siberian Islands in 1972–1977 as a part of the recorded by offshore seismic surveys within the New Ministry of Geology of the USSR regional geoscience Siberian Islands area on the assumption that the sequences research program. The resultant comprehensive geological established onshore extend offshore. The boundaries descriptions and maps were presented as regular publi- between the sequences are expected to form regional cations of the Ministry of Geology of the USSR (Kos’ko, disconformities mapable by seismic surveys within the Bondarenko, & Nepomiluev, 1985; Trufanov, Belousov, & sedimentary cover on the shelf. Three seismostratigraphic Neplmiluev, 1986). units are reliably distinguishable offshore based on the BGR A large amount of offshore seismic profiling has been MCS data (Franke & Hinz, 1999; Hinz et al., 1997). performed in the region recently (Drachev, Savostin, & TheseareUnitIborderedbyLS1andLS2regional Bruni, 1995a; Drachev, Savostin, Elistratov, & Bruni, unconformities, Unit II between unconformities LS2 and 1995b; Drachev, Savostin, Groshev, & Bruni, 1998; Franke LS3, and Unit III from LS3 up to sea bottom. Regional & Hinz, 1999; Hinz et al., 1997, 1998, Sekretov, 1998). The north-east Asia, circum Arctic, and global scale interpretation of the seismic data can be performed on the structural characters and tectonic events are reviewed in detail as an approach to dating the offshore * Corresponding author. seismostratigraphic units. 0264-8172/02/$ - see front matter q 2002 Elsevier Science Ltd. All rights reserved. PII: S0264-8172(02)00057-0 902 M.K. Kos’ko, G.V. Trufanov / Marine and Petroleum Geology 19 (2002) 901–919 Fig. 1. Location map. 2. Previous work and data Palaeozoic and Mesozoic strata and igneous rocks and on the structural pattern of the Islands collected in 1895–1902 The discovery and the geologic research in the New served the basic information on the geology of the New Siberian Islands have a long history discussed in many Siberian Islands till the middle fifties. publications (Gramberg & Pogrebitsky, 1984; Kos’lo et al., Regular geological mapping at 1:1 000 000 scale was 1985; Krasny & Putintsev, 1984; Samusin & Belousov, performed on the New Siberian Islands in 1955–1956 1985; Toll, 1899, 1904; Trufanov et al., 1986; Vitenburg, (Sorokov, Vol’nov, & Voitzekhovsky, 1961), and 1960; Vol’nov, Voitsekhovsky, Ivanov, Sorokov, & Yashin, 1:200 000 scale mapping was performed in 1972–1977. 1970). Major geoscientific information was obtained as a The maps and accompanying explanatory notes were result of a few projects. The first was the 1895–1896 published and are available (Kos’lo et al., 1985; Samusin expedition headed by Bunge (1887). A participant of the & Belousov, 1985; Trufanov et al., 1986). The 1:200 000 project,Toll investigated fossil ice and Quaternary strata on mapping was accompanied by drilling aimed to penetrate Bol’shoi Lyakhov Island and studied a section of coal loose sediments. The depth of the majority of the drill holes bearing deposits of Cape Utes Derevyannykh Gor on was up to 200 m. The 1:200 000 mapping was also Novaya Sibir’ Island. The next project was a multi- supported by specific biostratigraphic, paleontological and disciplinary research performed by a team of the Russian lithological research. Cassiterite placers were discovered Polar Expedition on the yacht ‘Zarya’ in 1900–1902 headed and explored on Bol’shoi Lyakhov Island. The prospecting by Toll. Coal bearing deposits on Bennett Island were and exploration involved a large amount of drilling discovered by Toll and were first mentioned in his brief including reference drilling. The cores were documented posthumous report of (1904). Toll and his three companions in detail and much analytical lithological, mineralogical, perished on their way from Bennett Island to the Anjou and paleontological research was performed. The results Islands. The report along with sample collection including were summarized in a monograph by Dorofeev, Blago- early Paleozoic Trilobites was found by a rescue party veschensky, Smirnov, and Ushakov (1999). The present day headed by Kolchak in 1903 (Kolchak, 1904; 1906). knowledge of the geology of the archipelago is, therefore, Scientific results of the Russian Polar Expedition were based on the results of a series of regional and industrial published by Vollosovich (1902, 1905).Dataonthe projects, and some minor specific scientific projects. M.K. Kos’ko, G.V. Trufanov / Marine and Petroleum Geology 19 (2002) 901–919 903 Fig. 2. Geological map of the New Siberian Islands. From the Geological Map of Russia (Sokolov, 1990/1992) amended and simplified. 3. Regional geologic background gently dipping thrust sheets through undisturbed horizontal layering. The New Siberian Islands are located between The De Long Islands area is believed by many Russian 135825.50 –158824.60 east and 73811.20 –77807.40 north geoscientists to be a fragment of a former Hyperborean (Fig. 1). The Islands separate the Laptev Sea from the Platform (Khain, Koronovsky, & Yasamanov, 1997; East Siberian Sea. The archipelago comprises three Shatsky, 1935) with early Palaeozoic basement (Eghia- island groups. Starting from the north these are the De zarov, 1977). The Anjou Islands and Lyakhov Islands are Long Islands, the Anjou Islands, and the Lyakhov located within a late Mesozoic fold belt, extending here Islands. from Alaska and Chukotka. The last orogeny in the fold belt The bedrock geology exposed on the islands is variable took place in the early Cretaceous. It was manifested by in composition, age, and structural style (Fig. 2). Strata from folding, faulting, and thrusting, emplacement of granites, the Cambrian through Recent are known here. Sediment and the formation of foredeep and intermontane basins. types include clastics, pelites, and carbonates deposited Some of those features are well known on the islands. The under nonmarine, shallow marine and deep marine environ- Anjou Islands represent an outer, moderately deformed zone ments. Magmatic rocks are mafics, ultramafics, granites and of the fold belt. Intense thrusting, tectonic piling, and intermediate and alkaline types from early Palaeozoic to fragments of an ophiolitic sequence have been documented Recent in age. Structural styles range from tectonic piling of on the Lyakhov Islands. It allows projection of the former 904 M.K. Kos’ko, G.V. Trufanov / Marine and Petroleum Geology 19 (2002) 901–919 sedimentary cover with locally outcropping Cretaceous sediments and Jurassic siliciclastics penetrated by shallow drill holes. It is hypothesized that the sedimentary cover overlies a composite basement comprising blocks of deepseated carbonates (Avetisov, 1982) stitched by inten- sely deformed siliciclastics and intruded by igneous bodies. Jurassic strata have been deformed. Cretaceous and Tertiary layers locally display complex folding and faulting on the general background of undisturbed layering. Stratigraphic and facies variability in the Cretaceous–Tertiary sedimen- tary cover within the Domain is shown in Fig. 4. The Lyakhov Domain is variable in structural style, age of exposed bedrock and in manifestation of the igneous activity. The south-eastern part of the Bol’shoi Lyakhov Island is a