河谷外鼓

文章回顾了不同地质背景条件下的浅表河谷扰动。从广义上讲,“弓形坡和河谷外鼓”这个专用词在不列颠广泛用于描述浅表河谷扰动。在Ｒｕｔｌａｎｄ,Ｅｍｐｉｎｇｈａｍ存在一个绝好的实例,具备真实的弓形坡和河谷外鼓。相对薄的冠岩覆盖在相对厚的上里阿斯统粘土之上,向下直到拉脱面,这样一个组合,允许弓形坡和河谷外鼓特征得到最充分发育。它们特征包括（１）下面粘土层明显变薄,系粘土进入河谷外鼓位置结果;（２）覆盖在上面的冠岩同步弯曲,产生一个向河谷的弓形坡（Ｃ）,一个河谷边缘向斜（Ｙ）和一个对照外鼓侧翼的上拱（Ｕ）。

VALLEY BULGING

The paper reviews the superficial valley disturbances in various geological settings. The term "camber and valley bulging" has been used loosely in Britain to describesuperficial valley disturbances in a broad sense. There is an excellent example of true camber and valley bulging at Empingham, Rutland. The combination of relatively thin capping rocks overburden a considerable thickness of Upper Lias clay, down to the surface ofd6collement, allow of the fullest development of the camber characteristics and valley bulge features. These are: (1) marked thinning of the clay sub-stratum as a result of thetransfer of clay into the valley bulge; (2) sympathetic fie-curing of the superincumbentcapping rocks, producing a valleyward camber (C), a valley marginal syncline (Y) and anupturn (U) against the flanks of the bulge.