Lomonosov Ridge Composite Tectono-Sedimentary Element, Arctic Ocean

Abstract

Abstract The Lomonosov Ridge (LR) is a sliver of continental crust, a microcontinent that stretches across the Arctic Ocean and separates the Mesozoic Amerasia Basin from the Cenozoic Eurasia Basin. The LR is thought to have been separated from the northern Barents Sea–Kara Sea passive continental margin by continental rifting at about 56–53 Ma and the subsequent formation of the oceanic crust in the Eurasia Basin. Following the nomenclature of this volume, the sedimentary succession of the LR and nearby area forms a composite tectono-sedimentary element containing an assemblage of the following main tectono-sedimentary elements (TSEs): (1) an undefined group of pre-rift TSEs mostly composed of Mesozoic and poorly known Paleozoic successions; (2) the Cretaceous–Paleocene synrift TSE; and (3) the Eocene–Holocene post-rift TSE. The age of the LR's folded and metamorphosed basement can be inferred based on correlations to basement units of the northern Eurasian passive continental margin, which may include a variety of geological structures formed during Timanian, Caledonian, late Paleozoic and Mesozoic orogenic events. The pre-rift TSE includes the oldest and most poorly known offshore sedimentary succession in the Arctic region. The lithostratigraphic units of these basins were mainly characterized from a handful samples collected at the seafloor and by correlation with better known stratigraphy of the conjugate continental margin. The synrift TSE of Cretaceous–Paleocene age has been defined based on seismic data and samples of sedimentary rocks recovered during the Arctic Coring Expedition (ACEX), as well as from seismic facies correlation between the LR and the Podvodnikov–Makarov, Laptev and East Siberian Sea basins. The post-rift Cenozoic sedimentary record was documented by the ACEX well in the central part of the LR.