a Map of the distribution and base elevations of Fm A and C gravel remnants and potential equivalents in the Middle and Upper Glatt valley and in the Hochrhein valley. Line A–A′ connects the lowest documented base elevations (black circles) of Fm C which are plotted in inset b. b Profile A–A′ plots the base elevations of the Aathal Gravel (for locations see a) and Fm C along the Glatt valley. Assuming a straight base surface, Fm C in the Lower Glatt valley plots directly on the down-valley extension of this base surface (dashed regression line: projection), whereas base elevation points of Fm H plot below it. This observation may give some support to the interpretation that Fm C is an equivalent of the Aathal Gravel (see text). A vertical uncertainty of ± 5 m is included. Best linear fit suggests a slope of 0.35% for the base surface. Base elevations of Fm C marked with * have not been considered as no other tie points are available. These points occur over bedrock along the valley sides and are thus likely to lie above the deepest channel base.