Smithian Strata and Non-Smithian Strata

The International Stratigraphic Guide defined that all stratified or quasi~stratified rock bodies of the earth crust, including sedimentary, igneous, metamorphic, solidified and unsolidified ones, should be considered as research contents of stratigraphy. Traditional stratigraphy mainly involves strata formed under gravity mechanism, plus a few kinds of bedded volcanic rocks such as lava, pyroclastic rock and volcanic ash, as well as metamorphic sedimentary and volcano~sedimentary rocks. These traditional strata are regarded as Smithian strata in this paper. In modern stratigraphy, mechanism of strata formation includes not only gravity but also thermal (ophiolite), mechanic and tectonic forces (orogenic melange and tectonite). In these above~mentioned non~gravitative conditions, the strata, formed complying with their own mechanisms but not with the law of superposition of Smithian stratigraphy, are called non~Smithian strata here. In melange regions from orogenic belt, formations of non~Smithian strata could be classified into subduct~scrape~match, subduct~return~match, and subduct overthrust types.