The ice age paleo-channel Ellerbeker Rinne an integrated 3D gravity study

Abstract

In the framework of a joint field work with partners of the Landesamt fur Landwirtschaft, Umwelt und landliche Raume (LLUR, the former LANU; Flintbek, Germany) and the Leibniz-Institut fur Angewandte Geophysik (LIAG; Hannover, Germany) gravity measurements have been conducted in July 2005 by members of a student course Geophysical field exercise in the area of the Ellerbek paleo-channel near Tangstedt. At approximately 450 stations complete Bouguer anomalies have been calculated. The error of gravity anomaly accounts for 2 x 10(-7) m/s(2) (max.) to -8 x 10(-7) m/s(2) (min.). The gravity field of the region is affected by a strong regional gravity field, which is caused by salt structures. Therefore, a regional field was calculated which based on a regional survey of the State Geodetic Survey. It was subtracted from the Bouguer field and a slightly negative residual field (-1.0 to -1.5 x 10(-5) m/s(2)) resulted in the area of the Ellerbek paleo-channel. It was analysed and interpreted by curvature algorithms, Euler deconvolution and 3D modelling. Euler deconvolution and curvature result in a depth of max. 400 m for this part of the Ellerbek paleo-channel; clusters of Euler source points were also calculated for depths of 130 m and 220 m which points to rather inhomogeneous infill of the channel. The compiled 3D density model was constrained by the seismic profile P3 of LIAG and borehole information. The model explains the positive anomaly north of Tangstedt (> 1.5 x 10(-5) m/s(2)) With a high density body (Geschiebemergel; boulder clay) of 300 kg/m(3) density contrast to the sedimentary infill of the paleo-channel which has its bottom at 200 m depth.