Siliceous-volcanogenic complexes of western Sikhote Alin: Their stratigraphy and origin

摘要

New age and structural data are reported for the siliceous-volcanogenic complexes developed in the lower reaches of the Ussuri River. These complexes, which were previously treated as one stratigraphic unit, are subdivided into the Snarsky tectonostratigraphic complex (end of the Middle Jurassic-Middle Aptian) and the basaltic sequence (supposedly, Campanian-Maastrichtian). The Snarsky Complex is made up of basic volcanics, cherts, siliceous-clayey rocks, as well as subordinate limestones, sandstones, and conglomerates. Its distinctive features are the large amounts of genetically diverse basalts, the abundance of volcanomictic and pyroclastic material in siliceous-clayey rocks, the absence of fragmental rocks typical of the continental convergent zone, and the facies heterogeneity of the deposits. The complex is considered to be the southwestern continuation of the Kiselevka-Manoma terrane. Its origin is presumably related to the tectonic piling of genetically heterogeneous assemblages. The basaltic sequence includes basalts, basaltic andesites, their tuffs, and tuff conglomerates. The tuff conglomerates contain numerous fragments of granites and garnet-bearing felsic volcanics. The sequence was formed on the crystalline paleocontinental basement in the Late Cretaceous.