武夷山脉西北麓丹霞地貌特征及成因分析

Features and genesis analysis of Danxia landscape in the northwest foothills of the Wuyi Mountains

武夷山脉西北麓地区白垩纪至古近纪时发生强烈的断裂构造活动,沿区域断裂带形成了一系列红层盆地,并沉积了一套红色陆相碎屑岩,包括从北东到南西分布的信江、南城、南丰、宁都、石城、瑞金、会昌等盆地。这些盆地明显受NNE向断裂所控制,除北侧的信江盆地规模稍大外,其余均为小型断陷盆地。新生代以来随着华南区域隆起,盆地内红层抬升,在构造、河流等内、外动力地质作用下形成了众多丹霞地貌。由于红层岩性、构造及河流侵蚀强度的差异性,在不同盆地形成了不同形态的丹霞地貌,其经历的演化阶段也不尽相同。野外地质地貌调查及对比研究表明,该地区丹霞地貌景观按照形态特征可分为山峰类、陡崖类、崩塌体类、峡谷类、洞穴类及其他类六种类型;面积高程积分法和多级缓冲区分析表明,该地区丹霞地貌演化具有从北东向南西年轻化趋势,其成因与红层、断裂活动、河流发育等条件的空间差异具有相关性,它们共同构成了武夷山脉西北麓丹霞地貌的成景系统。

Intense faulting tectonic activity occurred in the Cretaceous to Paleogene period in the northwest foothills area of the Wuyi Mountains,forming a series of red-faulted basins along the regional fracture zones and depositing a set of red terrestrial clastic rocks,which include Xinjiang,Nancheng,Nanfeng,Ningdu,Shicheng,Ruijin and Huichang basins distributed from the north-east to the south-west.These basins are obviously controlled by NNE-oriented faults,and all of them are small fracture basins except for the slightly larger Xinjiang basin in the north.With the swell of the South China region since the Cenozoic,the red strata in the basin was uplifted,and numerous Danxia landscapes were formed under the geological effects of internal and external dynamics such as tectonics and rivers.Due to the differences of the lithology,tectonics and river erosion intensity of the red strata,diverse forms of Danxia landscapes have been formed in different basins and undergone various evolutionary stages.Field geological and geomorphological investigation and comparative studies show that the Danxia landscapes in the area can be divided into six types according to morphological features:peaks,steep cliffs,collapse bodies,canyons,caves and others.Indicated by the area elevation integration and multi-level buffer zone analysis,the evolution of Danxia landscapes in this area show a trend of getting younger from north-east to south-west,and its genesis is correlated with the spatial differences under the conditions of red strata,fault activities and river development,which together constitute the formation system of Danxia landscapes in the northwest foothills of the Wuyi Mountains.