古海蚀与相似地形的区别:形态与成因——以广东黄圃海蚀遗迹为例

Difference Between Ancient Marine Eroded Landforms and Those with Similar Features:Morphology and Origination——An Example at Huangpu Town, Guangdong Province, China

对比黄圃镇海蚀遗迹与其它非海蚀成因相似地形,得出其形态特征差异:海蚀槽穴同时切过软硬相间的岩石,仅出现在某一水平面;片流和风化作用形成的凹槽与结构面或岩层完全平行而且连续延伸,出现在整个山坡面上,凹槽前无平台;河流侧蚀作用在同一水平面上,不能同时形成凹槽和平台;河流溶蚀作用也是水平的,在石灰岩河岸侧壁形成凹槽,槽上有突出屋檐,无平台;波浪作用不强的石灰岩海岸也可形成凹槽和突出屋檐,但无海蚀平台;只有波浪作用才能同时形成(海蚀)平台和(海蚀)凹穴。

The origin and the age of many ancient marine eroded landforms in the coastal areas of Guangdong cannot be determined due largely to no sediments kept with or within the landforms. Arguments about the origin for the marine eroded landforms are, therefore, often raised by the fact that non-marine eroded landforms also have similar morphological features. The difference between marine and non-marine eroded landforms is originally caused by the different erosion processes resulting in the different morphological features, although, some of which are similar. The focus of this study is trying to highlight a number of such differences important for distinguishing marine eroded landforms from non-marine ones. Ancient marine landforms found at Huangpu. Town is one with typical marine eroded features. In this article, morphological features of the ancient marine landforms at Huangpu were compared to those with similar features but formed from non-marine origin. The difference among those feature and their origins are analyzed based on the principles of dynamical geomorphology. The comparison indicates ： （ 1 ） Ancient marine notches or caves associated with marine benches only appeared at a same horizontal level such as the hill foot that was a formal sea-level, and could cut off both hard and soft rock layers along this level. （2） Differential weathering or erosion by sheet flows on a hill slope with structural difference would produce notch-like features or grooves along the soft rock layers or the structural weaknesses of the slope, no matter they were horizontal or not. The notch like features could develop all the way from the top to the foot of the hill slope but without any benches formed in front of the grooves. （3） The lateral erosion of a river is also horizontal but could not produce notches and benches at the same time. （4） The dissolution process of river water was also horizontal, by which horizontal grooves were formed in limestone river banks at the height of the water surface. A prominent roof could often formed over the groove but no benches formed in front of it because of more dissolution under the water than in the air. （5） By the same reason, marine notches without marine platforms or benches developed on limestone coasts with short fetches. （6） The width of the marine bench apparently increased with greater wave energy.