Conditions of sedimentation in the Hauterivian-Cenomanian sea basin of the Sikhote-Alin and Lower Amur Region
Close orientations of mechanoglyphs and oblique bedding in the Hauterivian-Cenomanian sediments of the Amur-Zhuravlyovka and Tumnin turbidite complexes have been obtained. They suggest similar hydrodynamic conditions of sedimentation. These deposits are assemblages of gravitational flows, and in a lesser degree, bottom currents and background sedimentation. Sediments of the Zhuravlyovka trough accumulated in the north-western margin of the paleocontinent in immediate proximity to the foot of its continental slope. The available data on the orientations of mechanoglyphs and oblique bedding suggest the existence of large-scale vortex of constant bottom currents. The direction of the bottom current along the feeding province (the extreme outer branch of the vortex) was north-eastern. Away from the foot the direction of the bottom current changed to north, and then to west. The fragmental material on the continental slope was transported from south-east to north-west into the deep parts of the basin. In the zone of the foot of continental slope turbidity flows interacted with bottom currents. Sandy turbidites accumulated from the deviated meridional turbidity flows; and sandy argillite and silty argillite cyclites, from the most weakened sublatitudinal flows. In pauses between turbidity flows contourites and background sediments formed under circulation conditions.