揭西石肚溪河谷壶穴的形态与成因

Morphological Characteristics and Origin of Potholes in the Shiduxi River, Jiexi

揭西石肚溪壶穴的成因此前曾引起广东地学界的争鸣。为了对该问题提供更多新的证据材料,详细测量了该河流河谷232处壶穴的形态特征并进行统计分析。结果表明:壶穴的大小、深度和形态等在河床纵剖面上的分布没有明显规律;椭圆形和长条形壶穴较为多见;壶穴基本沿节理发育,且长轴走向与主节理即河谷的走向一致;部分壶穴内壁和底部分别可见擦痕和碎屑。壶穴的形成发育受河床基岩岩性、地质构造、河床比降、流水作用等多种因素影响,尤其是节理的控制作用非常明显。壶穴为山区河床上流水侵蚀的产物,与冰川作用无关。壶穴在河床具有一定比降、河水流速较快、适量节理发育的山区石质河床中出现是很正常的现象。

There were debates about the origin of the potholes in the Shiduxi River, Jiexi, in Geoscience community of Guangdong. In order to get more new evidence for that issue, the authors investigated the potholes in the river with new measuring and statistical methods proposed in recent years. The morphological characteristics of 232 potholes were measured in detail and were statistically analyzed. Results show that the potholes are distributed across the streambed profile without clear regularity in size, depth and shape. Most of the potholes are elliptical or elongate, and develop along the rock joints. The strikes of the potholes are consistent with the main joint and the valley trend. In some of the potholes, striation and debris can be respectively seen on their walls and bottoms. Origin and development of pothole are influenced by multiple factors such as lithology and geological structure of streambed rock, gradient and fluvial action. Joints play a particularly important role on pothole origin and development. Potholes are created by runoff erosion and are irrelevant to glaciation. They commonly develop in the rocky streambed of mountain rivers with certain gradient, rapid-flow stream and appropriate joints.