Influence of the Upper Mantle Convection Cell and Related Pacific Plate Subduction on Arctic Tectonics in the Late Cretaceous-Cenozoic

摘要

The article considers the history of seafloor spreading of the Eurasian Basin. The sharp decline in the spreading rate in the Eocene about 46 Ma was revealed, which is recorded in the distribution of linear magnetic anomalies. This jump in velocity is explained by a geodynamic model, but not by the northward movement of Greenland. The geodynamic processes of the Pacific subduction zone generate the upper mantle convection cell with return flow that drags the continental lithosphere of the Arctic toward this zone. The geodynamic mechanism is confirmed by seismic tomographic mantle sections of the northeastern margin of Asia and by a numerical model of upper mantle convection in the active continental margin. The plate tectonics and kinematics of the Eurasian Basin are namely influenced by the activity of the upper mantle convection return cell, which is controlled by the flow volume and ultimately by the velocity and directions of the subduction vectors of lithospheric material of the Kula and Pacific plates in the subduction zone. In the Middle Cretaceous-Middle Eocene, the return cell was active for about 73 Ma, since the Kula and Pacific plates are moving north and subducting orthogonally under the Central Arctic. After geodynamic reorganization in the Middle Eocene about 47.5 Ma, the oceanic plates in the Pacific began to move northwest. As a result, supply of Pacific Ocean lithospheric material to the Arctic convective return cell virtually ceased. Shortly after the reorganization, seafloor, spreading of the Eurasian Basin decelerated about 46 Ma to an ultraslow regime. The main tectonic and geodynamic consequences of applying the proposed geodynamic model for the Arctic in the Late Cretaceous-Cenozoic are considered.