Application of airborne transient electromagnetic (SkyTEM) technique for buried valley detection in part of Hadsten, Aarhus County, Denmark

Buried valleys of Quaternary age in Denmark are complex structures filled predominantly with glacio-lacustrine clay, silt, meltwater sand and gravel. These valleys are important target for groundwater exploration as they are potentially good aquifers. Most of the Danish aquifer consists of Quaternary sand and gravel deposited in valleys eroded and buried in the Tertiary clay basement. The resistivity of the impermeable Tertiary clay lies between 5 - 20 ?m, moraines clay are 25 - 60 ?m and sandy/gravel are from 60 - 200 ?m. SkyTEM has the ability to effectively differentiate between these lithologies based on their range of resistivity values. In addition, SkyTEM has been proven to have an excellent depth penetration exceeding 200 m. A 1-D inversion was carried out for all the sounding data to obtain resistivity values which were then plotted as contour maps at selected depth intervals. A 3-D image of the subsurface was created by stacking these maps at different depths. The study identified buried valleys located at the southern and northern part of the survey at a depth of 155 and 40 m, and thickness of up to 140 m and 30 m, respectively