The main problem in understanding the origin of the Flysch is the explanation of the innumerable pelitic and psammitic layers, which alternate without transition zones. Characteristics of Flysch series, both in the Carpathians and elsewhere are the contrast in character between the pelitic and psammitic layers, the scarcity of organic remains, and the monotony and lateral persistence of lithology and structure within any one series. Although the general aspect, or “style” of Flysch series persists, individual beds are not persistent, and sedimentary rhythms are not present. Characteristic structures are graded bedding and “hieroglyphs” on the lower surfaces of psammitic strata. The hieroglyphs are explained as moulds of decayed algae, animal tracks, or mechanically produced flowmarkings, or diastrophic scratches and furrows; the latter are not true hieroglyphs. Accessories to Flysch series include bedded cherts, calcareous marl or limestone, conglomerates and exotic blocks. Flysch series are explained as the product of normal pelitic or pelagic sedimentation, interrupted by the periodic deposition of psammitic layers brought in by turbidity currents. Either oxidizing or reducing conditions may prevail in the basin of deposition, and in the Carpathian Flysch the rate of deposition is of the order of 1 inch per 1000 years; the psammitic layers have a mean thickness of 5 inches, and deposition of a layer took place, on the average, once every 4000 years. The turbidity-current theory implies that Flysch series were deposited in deep water.

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