THE STRUCTURE AND HISTORY OF ABYSSAL HILLS OF THE NORTH-WESTERN PACIFIC PLATE FROM CONTINUOUS SEISMIC PROFILING AND STRATIGRAPHIC DATA

The abyssal hills of the North-Western Pacific plate are characterized on the basis of the continuous seismic profiling and stratigraphic data on the Meso–Cenozoic sedimentary trappean cover, and the relative ages of the hills are estimated. The study revealed the dominating occurrence of asymmetric tectonic and relatively symmetric injection hills of the Late Cenozoic age with no signs of volcanic activity. The tectonic hills are mainly associated with faults in the eastern allochthone, a result of gradual shearing of all layers of the oceanic crust. The injection hills are related to rootless granite protrusions from the lower layer of the crust (probably, granitized, primary sedimentary strata of the epicontinental ocean). Several hills are of combined tectonic and injective origin and have features inherited from the previous peneplanation era. The paper also describes the characteristics of several hills of other genesis.