Gravity anomalies in the KTB area and their structural interpretation with special regard to the granites of the northern Oberpfalz (Germany)

Abstract

 By fieldwork within the frame of the KTB project a new set of 1800 gravity data has become available. Prominent Bouguer anomalies are produced by the ZEV (high with −6 mGal), the Grafenwöhr block (low with −24 mGal) and the granites (low with −46 mGal). The vertical gradient map gives information about the near-surface structure. In addition, spectral analysis and upward continuation of the field data give information about depth extension of the granites and other units. The density structure of the crust is outlined by 3D interactive forward modeling. 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); and (c) the granites. The ZEV units are controled by the steeply inclined SE1 reflector as a tectonic element. The Falkenberg granite provides 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 crustal material below the granites and of the Erbendorf body remains unknown.