【摘要】 武江在坪石段共保留下6级基座阶地。坪石的多级基座阶地是在与粤北金鸡岭夷平面同期发育的准平原基础上,由河流的阶段性下切所形成。本区由于受以掀斜运动为特征的新构造运动的影响,阶地所在的西南岸台地区抬升速率约为0.073m/ka,大于金鸡岭夷平面0.066m/ka的抬升速率,致使武江在坪石段不断向东北方向摆动,沿途形成了多级基座阶地。在湿热气候条件下,尤其是在基座上覆富含有机质的河漫滩相沉积物的"储酸池"效应作用下,阶地基座发生了强烈的化学风化。该风化基座具有双层夷平结构,与我国南方覆盖型岩溶的双层夷平结构在成因上具有一致性。更多还原

【Abstract】 Total six classes of rock-based alluvial terraces are discovered in the Pingshi section of the Wujiang River,North of Guangdong Province.Those rock-based alluvial terraces and the Jinjiling Planation Surface are all originated from the same peneplain that was formed in the Ternary Period when the geomorphic processes progressed its eventual stage.The alluvial terrace is formed when the river intermittently incised into the bedrocks.Influenced by the new tectonic movement that characterized by inclined lifting,the Wujiang River at Pingshi section moved towards northeast and formed many classes of rock-based alluvial terraces on the way.Under the humid and tropical circumstance,especially with the promotion of the effect of "a pool stored the acid" of the fine alluvial sediment up to the bedrocks that is abundant in organic matter,the bedrocks are deeply chemically weathered.The weathered rock-based alluvial terrace is characterized with the double surface of leveling,which is identical in cause of formation to those developed in the karst region of the southern China.更多还原