Plate 123

Load structures: plan view (load casts)

We can see here, on the base of a sandstone bed, that load structures are equidimensional in the horizontal plane; they are organized in polygonal cells as in typical convecting fluids (compare, for example, with the "granular" surface of the solar photosphere), the main difference being that density contrasts are not temperature-dependent in sediments. Some alignments of cells are also visible, giving the pattern a brainlike aspect. It is possible, in fact, that the load-induced polygons mask previous elongated structures made by a current (the deposit is a turbidite). I could also dare say that the supposed current went from the upper left to the lower right.

Pietraforte Formation (Cretaceous), northern Apennines; this is one of the deep-water siliciclastic "flysch" of the Mesozoic Tethys paleo-ocean.