Lithospheric density structure study by isostatic modelling of the European geoid

Abstract

We deal with modelling of the geoid undulations for the European Plate by use of topographic and Moho data. Two models assuming linear density stratification in the lithosphere (constant contrast model CCM, constant gradient model CGM) and isostatic balance of the lithosphere were used for calculating the undulation in the flat layer approximation. The results show that the constant contrast model is able to describe the entire oceanic lithosphere, as it indicates the amplitude of thermal density change is in good agreement with the cooling plate model estimation. The constant gradient model gives reliable estimations of the lithosphere properties only in smaller regions of relatively uniform conditions like the Interior of the East European Craton. For continental and oceanic regions the resulting values of the density gradient have some average meaning and they are in interpretable correspondence with characteristic mantle heat flow. In the entire area, both models show strong confusion giving not intermediate and unrealistic lithosphere characterization, which is a result of essential differences of thermal constitution, differences in average crustal density and mineral differences of the lower lithosphere, occurring between the two major tectonic provinces (oceanic and continental). The convention of equivalent linear reduction was discussed extensively and applied as an adequate method of lithosphere thickness estimation. This approach leads to thickness determination similar to other methods (seismic, petrological and thermal). The two concepts allow for the construction of LAB (transitional zone between the lithosphere and asthenosphere) depth maps from topographic and Moho data.