南昌市梅岭花岗岩石蛋地貌的特征与发育机制初探

摘要

梅岭主要以新元古代花岗岩为地质基础,在长期的构造抬升和风化侵蚀作用下,形成了以垄状山脊/锯状山脊和侵蚀沟谷为组合的地貌特征,其代表性地貌为大小不同和圆度各异的石块堆积,广泛分布于山顶、山谷和缓山坡上,对于其形成机制,过去常被认为是冰川遗迹或倒石堆.通过研究这些石块堆积的形态特征和分布规律,笔者认为属石蛋地貌,可分为裸露型石蛋地貌和埋藏型石蛋地貌.二者的广泛分布,表明梅岭处于花岗岩地貌演化的幼年期晚期—青年期早期阶段,发育机制与当地的地质构造背景和湿热气候环境密切相关,其中的裸露型石蛋主要与埋藏型石蛋剥露、裸露岩石的球状风化和倒石堆的球状风化有关,沟谷中的石蛋流主要形成于裸露岩石崩解破碎后顺坡滚动、土体崩塌导致埋藏型石蛋出露和顺坡滚动、洪水搬运、季节性冻融作用使岩石顺坡蠕动等方式的综合作用下.埋藏型石蛋主要是在花岗岩内部裂隙和节理的控制下,形成于温度和降水对不同深度花岗岩的差异性风化作用.%The Meiling Mountain is mainly composed of Upper-Proterozoic granite.After long-term tectonic uplift and weathering erosion,the mountain landscape is displaying jagged ridge or ridge combining with erosion valley,among which the representative landscape is stacked stone with different size and roundness,widely distributed at the peak,or in the valley and on the hillside.To its formation mechanism,previous studies used to consider it as glacial gravel or talus.Based on the distribution and characteristic of granitic rock,we considered it as granitic stone eggs,including buried stone eggs and exposed stone eggs.The wide distribution of stone eggs suggests that the granite landform evolution is at the stage of late juvenile to youth.The formation mechanism is closely related to the geological tectonic movement and hot-humid climate conditions within the areas.The exposed stone eggs mainly attribute to the exposure of buried stone egg,and spherical weathering of granite stone and talus,the stone eggs in the valley mainly derive from the combined interaction results of disintegration of exposed granite rock,outcropping of buried stone egg after soil collapse,flood carrying,seasonal freezing and thawing,as well as their rolling movement along the slope.,The buried stone eggs mainly attribute to the differential weathering at different depth within the granite by temperature and precipitation,under the control of the inner fracture and joint of the granite.