The “dinosaur-skin” surface is the sole of  a turbidite. Guide books refer to it as flute casts, sedimentary structures that originate by a kind of erosion taking place just before the first layer of sand comes to rest from a turbid flow. In this moment, small eddies form and act, together with the sand grains, like minute glacier mills. Accordingly, each flute starts with a globular excavation, whose drawn-out tail on the downcurrent side marks the migration and eventual dissipation of the eddy. Flute structures were never observed on modern sea floors, because they become immediately buried under the sand that scoured them.

The present structures differ from typical flute casts. Instead of   resembling radishes, they have a brain-like appearance. Also unusual is their arrangement in stretches perpendicular to current direction. This kind of sedimentary structures could be called “mop casts”, because the individual depressions end in a rather sharp front on the down current side and thereby resemble the threads of a household mop. The difference is important for reconstructing the ancient current direction: the steep sides point up-current in flute casts, but down-current in a mop cast, as shown by crossbedding in the overlying sand.

The lower slab (# 32b, from same locality) shows not only a trackway, but also beautiful raindrop impressions. These, however, are seen only in the upper right corner, where the sand cover had been thin enough for the impacts to press through.