Jurassic geodynamic history of the Sikhote-Alin-Priamurye region

In the Sikhote-Alin-Priamurye area of southeastern Russia, folded and faulted fragments of sedimentary and less common volcanic rocks comprise tectonostratigraphic units (complexes) that are imbricated. Sections of coherent, correlative strata composed of chert, siliceous mudstone, mudstone, siltstone, and sandstone within the tectonic stacks distinguish subterranes that are grouped into a suite of regional terranes. Among the ubiquitously imbricated strata, the age of deformed units ranges from Middle Paleozoic up to Late Jurassic–Early Cretaceous (Tithonian–­Berriasian). Chaotic units (mélange) that are represented by siltstone and sandy siltstone matrix containing different-sized and different-aged lumps, blocks, and fragments of cherts, limestone, sandstones, basalt, and gabbro are Callovian to Tithonian in age. Accretion-like processes brought together fragments of a Paleozoic oceanic plateau and abyssal plain fragments of different ages during Middle and Late Jurassic time. The transition from chert to clastic sections tracks the approach of the oceanic strata to sources of detritus presumably close to a continental margin. Paleozoic oceanic rocks began to receive clastic inputs by the Pliensbachian, and Oxfordian chert approached the margin by the Kimmmeridgian. The terrane rocks do not record high-pressure metamorphism nor are they correlative with nearby volcanic “arc” rocks. The absence of these features, commonly associated with subduction at plate margins, may indicate that the rocks have been isolated, presumably by strike-slip faulting, as suggested by mapping