Three-dimensional (3-D) ground-penetrating radar (georadar) mapping of
fers new opportunities for determining the geometries and facies of su
rficial sedimentary units. To investigate the potential of this high-r
esolution technique and at the same time study the architecture of Qua
ternary glaciofluvial deposits, georadar data have been collected on a
dense grid established across a sequence of braided-river gravels and
sands in northeastern Switzerland, Results of this survey are strikin
g 3-D images that provide many more details and much more reliable inf
ormation on the heterogeneities of the shallow underground than are af
forded by conventional georadar profile data, Continuous subhorizontal
and oblique reflections can be traced throughout vertical sections an
d horizontal slices of the georadar data block to a depth of similar t
o 15 m. Clearly defined are the dominant flow direction of the ancient
braided-river system, the boundaries between different sedimentary fa
cies, and the level of the ground-water table, Trough-fill sediments a
nd subhorizontal channel deposits observed on 7-m-high quarry walls ca
n be followed confidently in the subsurface. The orientation, shape, a
nd size of the troughs and the strike and dip of the cross-bedding are
all well resolved.