Giant traces of Vendian animals

The Upper Vendian sequences exposed at the east-ern coast of the White Sea enclose low-topography impressions of four different patterns that are inter-preted as feeding traces of animals belonging to the type Proarticulata Fedonkin that became extinct in the Precambrian [1, 2]. Impressions with a maximum dimension of 4.3 m x ~15 cm (Fig. 1) and 2.5 m x ~35 cm (Fig. 2) were left by very large organisms. These traces occur on a common bedding surface that includes two different areas. The surface of the first area is flattened, whereas that of the second area is hummocky and complicated with different folds. Body impressions and traces of Proarticulata representatives occur only at the surface of the second area. The contact between areas with different surface patterns is sharp: the hummocky surface is slightly lower compared to the flattened one, and its margins are downwarped and submerged several centimeters into sediments grading into jointing sur-faces. Short linear and star-shaped folds on the hum-mocky surface can be deep. Like downwarped margins, they can form jointing surfaces crossing the bed. Some-times, trace impressions also appear to be submerged along these jointing surfaces (Fig. 1), although they preserve the trace patterns on the jointing surface. It seems that the surface of flattened areas resulted from erosion of the muddy bottom that immediately preceded the accumulation of the sandy substrate. The hummocky surface originated from some flat layer cov-ering the bottom that could break up, downwarp, get folded, and preserve the impressions. Most probably, such a layer was composed of a compact organic (algal-bacterial) film, which subsequently completely decomposed [3].