SLOPE DEPOSITS AND WATER PATHS IN A SPRING CATCHMENT, FRANKENWALD, BAVARIA, GERMANY

The spring catchment under study is underlain by shale, on which sever al layers of slope sediments (cover-beds) are deposited. The upper of these layers contain eolian fines mixed into shale-derived debris, whi ch latter material entirely comprises the basal cover-bed. Due to its dislocation by solifluction, the shale debris has a tegular structure. This leads to hydraulic anisotropy, particularly where no fine earth occurs. Thus, water that seeps into such material is forced to flow la terally while vertical movement is impeded. The basal cover-bed theref ore hosts a deep aquifer. Only during major discharge events, excess h ydrostatic pressure makes water flow into upper parts of the soils, be ing mixed with surficially interflowing water. Most of the time, howev er, there are two levels of water flow at different depths with differ ent dwelling times, which finding is supported by probably geogenic su lphur isotopes in the deeply flowing water that are different from pre cipitation water.