Consedimentation tectonites in the Paleozoic of Sikhote Alin

Carboniferous and Permian terrigenous sediments in the basin of the Iman, Vaka and Ulakhe rivers show features known as tectonites — lens structures in conglomerate-type rocks, elongated pebbles and so on. These features and other considerations indicate that the central and eastern parts of the main Sikhote-Alin anticlinorium was experiencing contemporaneous differential movements. Competent beds of sandstones and flints form lenses, ovals and sometimes shapeless blocks embedded in incompetent siltstones and clay shales. Competent beds range greatly in thickness; fragments indicate most ranged from 1–5 cm with some beds 1–5 m. Most of the enclosing sequences are 100–300 m thick. Disposition of fragments indicates clearly the lines of the original beds. Direction of displacement is parallel to the plane of the layer. Elongation of fragments is in the direction of transport. Latest papers show a tendency to assign these tectonites a consedimentation origin; they are believed to be products of endogenous forces acting on consolidated sediments. The term hydrotectonite is used when morphologically similar products are formed under water through the joint action of forces both tectonic and otherwise. Two such structures are illustrated and their origin considered. Effects of dewatering are also discussed. Epochs favorable to hydrotectonites are rapid sinking a geosyncline when inclination of the floor increases and when earth tremors are common, in combination with rapid sedimentation. High tectonic activity in the Sikhote Alin syncline, based on hydrotectonites, may correlate with numerous magmatic effects in the adjacent Khanda central massif.—W.D. Lowry