山地蚀源区的沉积类型及其相关概念的系统梳理与厘定

摘要

By systematically reviewing the research results of sedimentation types in exhumation prov-enance during recent decades to centuries at home and abroad,combined field study in modern sediments of Quaternary,based on whether sediments transport,transportation mechanism,sedimentation location, gradient and landform,etc.,the sedimentation types in exhumation provenance can be divided into eluvi-um,deluvium, colluvium, fluvial deposits in mountain-girt valley, pluvium, alluvium, etc.Various types have obvious differences in basic conception and connotation.Eluvium is sedimentation in-situ of the parent rock weathering product on the gentle landform (<3°).Deluvium is the deposits formed from parent rock weathering by sliding or rolling to the foot of the slopes under the impact of overland flow or gravity on the tilt landform (>3°,but no more than 30°).Colluvium is the deposits formed only under the impact of gravity by sliding or rolling to the foot of the slopes in the way of caving or fall or collapse on the steep landform (>30°).Fluvial deposits in mountain-girt valley form when eluvium,deluvium,colluvium are carried to valley or channel in mountains by overland flow.Pluvium forms during flood period when plenty of parent rock weathering products carried by intermountain flood current are located in mountain pass.Al-luvium forms during normal river flow period when plenty of parent rock weathering products carried by in-termountain flood current are located in mountain pass.In addition,gravity flow deposits such as land-slide,slump,debris flow,etc.,also exist in exhumation provenance.%通过对国内外近100多年来山地蚀源区沉积类型的研究成果系统梳理，结合第四系现代沉积的野外考察，根据沉积物是否发生搬运、搬运机制、沉积位置、沉积部位的坡度以及地貌特征等，将山地蚀源区沉积类型划分为残积物、坡积物、坠（崩／塌）积物、山间河流沉积物、洪积物和冲积物等6种类型，各种类型在基本概念及其内涵上存在明显差异。残积物是母岩风化的产物在较平缓的地貌上（＜3°）形成的原地堆积；坡积物是母岩风化后形成的产物在坡面流水或重力作用下沿着具有一定坡度（＞3°，但一般不超过30°）的斜坡滑动或滚动至斜坡坡脚（即山麓）形成的堆积物；坠积物是仅在重力作用下以坠落或崩落或崩塌的方式沿着较陡峭的坡地（＞30°）滑动或滚动至坡脚形成的沉积物；山区河流沉积物是残积物、坡积物和坠积物被坡面流水带到沟谷或山间河道中形成的沉积物；洪积物是洪水期山间洪流携带的大量母岩风化产物在出山口形成的沉积物；冲积物是平水期山间河流携带的大量母岩风化产物在出山口形成的沉积物。此外，山地蚀源区还存在滑坡、滑塌、泥石流等几种重力流沉积物。