陕西省丹霞地貌景观特征、空间分布与形成机理初探

Characteristics, spatial distribution and formation mechanism of Danxialandform in Shaanxi Province

陕西省共有丹霞地貌54处,分布在鄂尔多斯盆地渭北隆起和伊陕斜坡。正、负丹霞地貌兼具,沿西南—东北方向呈现明显的区域分异规律;风成沙漠相砂岩丹霞分布面积最广,以狭缝型沟谷丹霞、波浪型丹霞、彩色丘陵为特色,多数处于发育青年期。运用最邻近点指数法、核密度分析法研究得出,陕西省丹霞地貌分布的空间结构类型为凝聚型,出现2个高密度区(延安甘泉—志丹—安塞—富县丹霞片区和榆林靖边丹霞片区)、1个中密度区(照金—旬邑—彬县丹霞片区)和2个低密度区(宝鸡九龙山片区、神木公格沟—府谷莲花辿片区)。从形成机理看,鄂尔多斯盆地中生代沉积奠定了丹霞地貌的物质基础,燕山晚期以来的地势格局控制着正、负地貌的分布,节理和裂隙特征对丹霞地貌景观格局起关键性作用,水蚀、风蚀等为主导营力塑造出丹霞地貌景观形态。

There are more than 54 spots of Danxia landforms in Shaanxi Province,northwest China,which are distributed in the Weibei Uplift and Yishan Slope of the Ordos Basin.In terms of landscape,both positive and negative Danxia landforms have considerable regional differentiation from southwest to northeast of the province.The sandstones of aeolian desert facies with mainly near horizontal or gently inclined Danxia occurrences are the most widely distributed.They are characterized by gully Danxia,wave Danxia,and colored hills,and most of them are in their early stage.The spatial structure type of Danxia landform distribution in Shaanxi Province is condensed,with two high-density areas(Ganquan-Zhidan-Ansai-Fuxian Danxia area and Yulin Jingbian Danxia area),one medium-density area(Zhaojin-Xunyi-Binxian Danxia area),and two low-density areas(Baoji Jiulongshan area and Fugu Lianhuachan area)according to the nearest neighbor index and nuclear density analysis methods.From the viewpoint of the formation mechanism,Mesozoic sedimentation in the Ordos Basin laid the material foundation for the Danxia landform,regional tectonic evolution controls the distribution of positive and negative landforms,and characteristics of joints and fissures are critical in the landscape pattern of the Danxia landform,and water and wind erosions are the leading forces shaping the landscape form of the Danxia landform.