ИСТИНА

The analysis of the seismic reflection profiling and gravity data shows that the Moho in the ultradeep sedimentary basins is underlain not by mantle peridotites but by a layer of eclogites, ~15 km thick. Their formation from a less dense gabbroids in the lower crust was sufficient to produce the sediment loaded subsidence of 14 km in the absence of stretching. Mafic eclogites are considerably denser than mantle peridotites; however, having high P-wave velocities they are commonly placed under the Moho boundary. The same situation is typical of the North Caspian, South Caspian and North Chukchi basins ~20 km deep. As the North Barents basin, they are several kilometers deeper than it could be expected under the observed thickness of their consolidated crust.