Identification of buried valleys using the BGR helicopter-borne geophysical system

A Study of four airborne electromagnetic data sets collected during the past decade by the BGR helicopter-borne geophysical system over various geological settings shows that such data sets indicate not only layered horizontal geological features but also vertically and laterally confined structures, such as buried valleys. Indicative geological markers comprise conductive cover layers, conductive fills in resistive bedrock, and incisions in a conductive host filled with resistive materials. In cases where the valleys are incised into a magnetic basement and refilled with non-magnetic material, the magnetic data records can also be used for identification and thickness estimates of the infill. From a hydrogeological point of view, buried valleys are becoming increasingly important as they host groundwater reserves, which are in many cases big enough to satisfy the future demand for fresh water. This paper describes two examples from the North-West German lowlands and another two from the Namib coastal plains, where the Kuiseb and the Omaruru ephemeral rivers reach the shore of the South Atlantic Ocean.