Summary of Northeast Asia geodynamics and tectonics*

The New Siberian Islands comprise De Long Islands, Anjou Islands, and Lyakhov Islands. Early Paleozoic, Mesozoic and Cenozoic sediments and igneous rocks are known on the De Long Islands. Cambrian slate, siltstone, mudstone and silicified limestone occur on Bennett Island. Ordovician volcanogenic turbidites, lavas, and small intrusions of andesite-basalt, basalt, dolerite, and porphyritic diorite were mapped on Henrietta Island. The igneous rocks are of calc-alkaline island arc series. The Ordovician age of the sequence was defined radiometrically. Early Paleozoic strata were faulted and folded presumably in the Caledonian time. Early Cretaceous sandstone and mudstone are known on Bennett Island. They are overlain by a 106–124 Ma basalt unit. Cenozoic volcanics are widespread on the De Long Islands. Zhokhov Island is an eroded stratovolcano. The volcanics are mostly of picrite-olivine type and limburgite. Radiometric dating indicates Miocene to Recent ages for Cenozoic volcanism. On the Anjou islands Lower-Middle Paleozoic strata consist of carbonates, siliciclastics, and clay. A Northwest-southeast syn-sedimentary facies zonation has been reconstructed. Upper Paleozoic strata are marine carbonate, clay and siliciclastic facies. Mudstone and clay predominate in the Triassic to Upper Jurassic section. Aptian-Albian coal bearing deposits uconformably overlap lower strata indicating Early Cretaceous tectonism. Upper Cretaceous units are mostly clay and siltstone with brown coal strata resting on Early Cretaceous weathered rhyolite. Cenozoic marine and nonmarine silisiclastics and clay rest upon the older units with a transgressive unconformity including a weathering profile in the older rocks. Manifestations of Paleozoic and Triassic mafic and Cretaceous acidic magmatism are also found on these islands. The pre-Cretaceous structure of the Anjou islands is of a block and fold type Late Cimmerian in age followed by faulting in Cenozoic time. The Lyakhov islands are located at the western end of the Late Cimmerian South Anyui suture. Sequences of variable age, composition, and structural styles are known on the Lyakhov Islands. These include an ancient metamorphic sequence, Late Paleozoic ophiolitic sequence, Late Mesozoic turbidite sequence, Cretaceous granites, and Cenozoic sediments. Fold and thrust imbricate structures have been mapped on southern Bol'shoi Lyakhov Island. North-northwestern vergent thrusts transect the Island and project offshore. Open folds of Jurassic–Early Cretaceous strata are characteristic of Stolbovoi and Malyi Lyakhov islands. Geology of the New Siberian Islands supports the concept of a circum Arctic Phanerozoic fold belt. The belt is comprised of Caledonian, Ellesmerian, Early Cimmerian and Late Cimmerian fold systems, manifested in many places on the mainland and on islands around the Arctic Ocean. Knowledge of the geology of the New Siberian Islands has been used to interpret anomalous gravity and magnetic field maps an