GRAVITY-ANOMALIES IN THE KTB AREA AND THEIR STRUCTURAL INTERPRETATIONWITH SPECIAL REGARD TO THE GRANITES OF THE NORTHERN OBERPFALZ (GERMANY)

By fieldwork within the frame of the KTB project a new set of 1800 gra vity data has become available. Prominent Bouguer anomalies are produc ed by the ZEV (high with - 6 mGal), the Grafenwohr block (low with - 2 4 mGal) and the granites (low with - 46 mGal). The vertical gradient m ap gives information about the near-surface structure. In addition, sp ectral analysis and upward continuation of the field data give informa tion about depth extension of the granites and other units. The densit y structure of the crust is outlined by 3D interactive forward modelin g. Regional anomalies are caused by the Erbendorf body and the dipping Moho. Local and dominating anomalies have different sources: (a) the foreland sediments with an underlying deep structure (possibly of ZEV material), (b) the ZEV metamorphic units (gneisses and metabasites); a nd (c) the granites. The ZEV units are controled by the steeply inclin ed SEI reflector as a tectonic element. The Falkenberg granite provide s two thirds of the total granitic volume and its depth reaches 6.5 km , whereas other granites reach depths of 2-3 km. The nature of the cru stal material below the granites and of the Erbendorf body remains unk nown.