史密斯地层与非史密斯地层

国际地层指南中指出, 地层学应扩展为包括对构成地壳的所有岩石体的描述.所有各类岩石(沉积的、火成的、变质的、固结的和非固结的) 都属于地层学和地层分类的总体研究范畴.传统地层学主要针对沉积成因地层, 虽然拓展包括了一部分火山喷出岩, 如熔岩类、火山碎屑岩和火山灰等层状火山岩, 其形成的力学机制基本上是重力机制, 即向地心方向受重力作用逐渐累积.本文将重力机制下形成的地层及其适度扩展物(如沉积变质和沉积火山岩类) 称之为史密斯地层.现代地层学概念中, 形成地层的力学机制不仅仅是重力, 而且包括了热力(如蛇绿岩)、机械力或构造力(如混杂岩、构造岩等).非重力机制或非沉积成因的地层, 亦都有时空顺序, 其顺序服从各自的力学机制和成因, 但不服从史密斯地层的叠覆律; 这些非重力机制形成的地层不属于史密斯地层学的范畴, 本文称之为非史密斯地层.造山带混杂岩区主要依据构造力作用机制不同, 其非史密斯地层形成方式可区分为俯冲刮削拼贴式、俯冲折返拼贴式和仰冲推覆式等. 

Smith Strata and Non-Smith Strata

International Stratigraphic Guide pointed out that stratigraphy should be defined as the description of all rock bodies constituting the earth crust. Hence, all kinds of rocks, including sedimentary, igneous, metamorphic, solidified and unsolidified rocks, should be considered as research contents of stratigraphy. While traditional stratigraphy mainly studies strata by gravitative deposit, though including some parts of bedded volcanic rocks such as lava, pyroclastic rocks and volcanic ashes. Smith strata are regarded as the strata deposited in gravity, including related strata such as depositional metamorphic and volcanic rocks in this paper. Whereas in modern stratigraphy, the mechanic mechanism of strata origination includes not only gravity, but also thermal (ophiolite), mechanic and tectonic forces (orogenic mixtite and tectonite). In these above-mentioned non-gravitative conditions, the strata, formed with their own mechanisms but not with the overlap rules of Smith stratigraphy, are called non-Smith strata here. In the orogenic belt mélange regions, formations of non-Smith strata could be classified into subduct-scrape-match, subduct-return-match and subduct-overthrust types.