Effect of Varying Crustal Thickness on CHAMP Geopotential Data

Summary

To determine the effect of crustal thickness variation on satellite-altitude geopotential anomalies we compared two regions of Europe with vastly different values, South and Central Finland and the Pannonian Basin. Crustal thickness exceeds 44 km in Finland and is less than 26 km in the Pannonian Basin. Heat-flow data indicate that the crust of the Pannonian Basin has a value nearly three times that of the Finnish Svecofennian Province. A positive CHAMP gravity anomaly (∼4 mGal) is quasi-coincidental with the CHAMP magnetic anomaly across the Pannonian Basin. CHAMP gravity data indicates a minimum of 3 mGal in southwest Finland. CHAMP magnetic data reveal elongated semicircular negative anomalies for both regions with South-Central Finland having larger amplitude (<−6 nT) than that over the Pannonian Basin, Hungary (<−5 nT). In this latter region subducted oceanic lithosphere has been proposed as the anomalous body. In the former the central part of the negative gravity anomaly covers the northern part of the Baltic Sea basin and Gulf of Finland and underlying two rapakivi provinces plus it coincides with an area of lower crustal thickness. The magnetic anomaly directly correlates with the crustal thickness and inversely with the heat flow and, hence, may be caused either by variation of concentration of magnetite or by the elevated Curie-isotherm of magnetite in the lower crust — upper mantle region.