福建泰宁丹霞地貌中的洞穴类型及成因浅析

福建泰宁白垩纪红层盆地出露晚白垩世沙县组紫红色中一薄层粉砂岩、粉砂质泥岩和崇安组紫红色厚层砾岩、砂砾岩。红层发育北东，北北东向等多组不同走向断裂及节理。经外动力地质作用形成青年期丹霞地貌，崖壁上千姿百态的丹霞洞穴构成独特的微地貌景观。丹霞洞穴发育受岩性及节理、裂隙控制，崇安组粉砂岩、砂岩及含砾砂岩夹层是形成洞穴的主要层位，岩层的厚度及节理、裂隙控制洞穴产出的规模，风化剥蚀、流水侧蚀、大气降水及其水流侵蚀、重力崩塌是形成不同形态洞穴的主要外动力作用，洞穴的形成以一种外动力作用为主，或在发展过程中叠加了其它外动力作用，因而常为多种外动力综合作用的结果。

On Grotto Types and Their Origin of the Danxia Landform in Taining County of Fujian Province

The prunosus intermediate or thin-bedded siltstone,silty mudstone of Upper Cretaceous Shaxian Formation and prunus thick-bedded conglomerate and sandstone conglomerate of Upper Cretaceous Chongan Formation are widely distributed over the Cretaceous redbed basin in Taining County,Fujian Province.The northeastern trend or north-northeastern trend fractures and cleavages are well developed in the red beds.They take shapes of the young Danxia landform by the exogenic geological process and the all kinds of Danxia grottos on the rock walls compose of unique landscape of microtopography.The evolution of Danxia grottos is controlled by lithologic characters,cleavages and fissures.The siltstone and sandstone and pebbled sandstone interlayers of Upper Cretaceous Chongan Formation are the principal stratigraphic position of forming the caves.The scale of shaping grottos is regulated by the thickness of rock stratification,cleavagea and fissures.The weathering denudation,lateral erosion by running waters,the erosion by atmospheric water and water currents and landslip by gravitational force are the major exogenic process of making shapes of different grottos.The cavity development is often controlled by an exogenic process or is synchronously affected by another exogenic processes.Therefore,it is considered that the grotto evolvement in the surveyed area frequently results from the synthetic action of multifold external powers.