DEPENDENCE OF THE OCEAN DEPTH ON THE AGE OF THE SEA-FLOOR IN THE NORTH-ATLANTIC IN CONNECTION WITH HISTORY OF CONTINENTAL BREAK-UP

The dependence of subsidence rates variations on various factors is sh own on the example of the North Atlantic. Formation of the largest sca le depth anomalies correlating with the large scale geode anomalies is caused by the heterogeneity of the upper mantle and sometimes even th e lower mantle. Intermediate scale depth anomalies (from 500 to 2000 k m in diameter) are mostly associated with the hotspots. Analysis of th e subsidence rates change along the MAR taking into account the hotspo ts influence, shows that in many regions subsidence rates on the oppos ite flanks of the ridge differ substantially, i.e. subsidence is asymm etric. Subsidence rates and even the polarity of the asymmetry change abruptly on major transform boundaries, which were important in the pa leorift system structure. Asymmetric structure and periodical change o f the polarity of asymmetry were characteristic for the paleorift syst em of the Atlantic, moreover change of the polarity of asymmetry also took place on major transform boundaries. We suggest that the observed asymmetry of the subsidence rates on MAR may be inherited from the ea rly stages of opening of the Atlantic and possibly is caused by the as ymmetry of the asphenospheric rise.