Some morphological variants of Palaeodictyon Heer
Abstract
O niektórych różnicach w morfologii Palaeodictyon Heer
Fragments of Palaeodictyon networks, preserved on the lower surfaces of sandstone layers in a Cretaceous flysch sequence exposed in the Biała Woda stream-section, near Szczawnica (Pieniny), frequently coincide with small- -scale elevations of the soles, which mark the areas of deepest current-scouring. The relationship between variations in network morphology and primary irregularities of the sandstone soles is such that the larger and more symmetrical meshes are commonly found on the crests of positive features of the soles, while smaller meshes showing relatively high degrees of departure from the commonly occurring hexagonal form tend to occur in hollows between the elevations. It is concluded that the Palaeodictyon networks were generated by a sediment-eating organism in a plane corresponding roughly to the present shale/sandstone interface, after the formation of current markings in the erosional upper surface of the bottom muds, and at a time later than the filling of these latter features during the deposition of the sandy part of the succeeding bed.
Fragments of Palaeodictyon networks, preserved on the lower surfaces of sandstone layers in a Cretaceous flysch sequence exposed in the Biała Woda stream-section, near Szczawnica (Pieniny), frequently coincide with small- -scale elevations of the soles, which mark the areas of deepest current-scouring. The relationship between variations in network morphology and primary irregularities of the sandstone soles is such that the larger and more symmetrical meshes are commonly found on the crests of positive features of the soles, while smaller meshes showing relatively high degrees of departure from the commonly occurring hexagonal form tend to occur in hollows between the elevations. It is concluded that the Palaeodictyon networks were generated by a sediment-eating organism in a plane corresponding roughly to the present shale/sandstone interface, after the formation of current markings in the erosional upper surface of the bottom muds, and at a time later than the filling of these latter features during the deposition of the sandy part of the succeeding bed.