Uppal Raod, Hyderabad – 500 606, email: abhey_bansal@ngri.res.in (ARB), director@ngri.res.in (VPD), gerald.gabriel@liaghannover.de (GG) P-129 Depth to the bottom of magnetic sources in Germany – analysis of anomalies of the Earth’s magnetic total field A.R. Bansal 1* , G. Gabriel 2 and V. P. Dimri 1 1. National Geophysical Research Institute, Council of Scientific and Industrial Research 2. Leibniz Institute for Applied Geophysics Summary The depth to the bottom of magnetic sources (DBMS) is calculated from 31 overlapping blocks in Germany using Centoid method. The depth to the top of magnetic bodies varies from 1.49 km to 5.25 km in the region. The centroid depth and DBMS varies from 9.82 to 19.03 km and 19.9 to 33.98 km, respectively. The deeper DBMS are found corresponding to the North German Basin having lower heat flow values in the region. The inverse relation between the heat flow and DBMS is found. In general Moho depth is deeper than the DBMS except for the blocks 24, 25, 27 and 28 lying in the lower heat flow region of North German Basin. The thermal conductivity values in the region varies from 2.4 to 4.0 Wm -1 °C -1 based on the constant temperature at the DBMS. Introduction The DBMS is an important parameter to understand the temperature distribution in the crust and the rheology of the Earth’s lithosphere (Ravat et al., 2007). Some authors assume that the DBMS is equivalent to the Curie point depth of the magnetic minerals, where rocks loose their ferromagnetic properties due to an increase of the temperature in the crust. Curie temperature depends strongly on the magnetic minerals and in general 580 °C is considered as Curie temperature in the continental crust (e.g. Ross et al. 2006). As the basal depth of the magnetic sources can be caused by contrasts in lithology also, the DBMS and Curie point depths might not coincide. To avoid the complication of the Curie point depth and the DBMS, we are using the DBMS in our study for greater transparency, as depths are derived from aeromagnetic data. Nevertheless, the DBMS can be used as a proxy for temperature at depth and therefore to estimate heat flow density and geothermal gradient. Nevertheless, the more precise and direct way to measure heat flow is geophysical logging in boreholes (Pollack et al., 1993). So far these measurements are very sparse and often insufficient to define the regional thermal structures. Ravat et al. (2007) presented a comparison of different spectral methods for computing the DBMS, e.g. the spectral peak method (Spector & Grant, 1970), forward modeling of the spectral peak (Finn & Ravat, 2004), centroid method (Bhattacharyya & Leu 1975, 1977), and power-law correction method or scaling spectral method (Pilkington and Todoeschuck, 1993; Maus and Dimri,