宁夏红寺堡盆地隐伏古隆起成因机制及其对区域沙漠化的影响

Origin of the Latent Palaeohigh in Hongsibu Basin of Ningxia,China and Its Effect on the Regional Desertification

目前对于青藏高原东北缘活动构造研究多集中于活动断裂带的活动性,而对夹持于其间的沉积盆地构造格架及活动性研究甚少。以夹持于烟筒山断裂与牛首山—罗山断裂之间的宁夏红寺堡盆地为研究对象,采用重力资料重处理解译、音频大地电磁测深(AMT)和地震勘探相结合,揭示红寺堡盆地隐伏构造特征,并进一步采用盆山一体化思路分析隐伏构造的成因机制及其对区域沙漠化的控制作用。结果表明:青藏高原在中新世末发生强烈的NE向推挤、扩展和隆升,红寺堡盆地由坳陷盆地转变为挠曲盆地;在青藏高原NE向扩展的影响下,烟筒山断裂发生强烈的逆冲作用,古生代—中生代基底逆冲于古近系—新近系之上,受构造变形影响的最新地层为中新统彰恩堡组;红寺堡盆地内的隐伏古隆起呈NW—SE向,与烟筒山构造带具有相同的构造动力学背景,受青藏高原NE向扩展影响形成于中新世末,并且至今仍具有活动性;隐伏古隆起周缘断裂的活动破坏了地表稳定性、蓄水能力和地表植被,导致区域沙漠化呈现有规律的NW—SE向带状展布。该研究成果对于宁夏红寺堡盆地区域稳定性评价及沙漠化的综合治理具有现实指导意义。

Arc-shaped tectonic belt in the northeastern margin of Qinghai-Tibet Plateau consists of Haiyuan fault, Xiangshan-Tianjingshan fault, Yantongshan fault, Niushoushan-L uoshan fault and intermontane basins between these faults. Former’s researches about the active tectonic in the northeastern margin of Qinghai-Tibet Plateau mainly focus on the active activities of fault zones while the tectonic framework and activities in the intermontane basins are rarely known. Gravity anomalies interpretation, AMT and seismic prospecting in Hongsibu Basin of Ningxia between Yantongshan fault and Niushoushan-Luoshan fault were carried out, and the structural characteristics of the latent palaeohigh in this basin were revealed. Moreover, the origin of the latent palaeohigh and controlling factors of the desertification in Hongsibu Basin were discussed based on the theory of the coupling system between basin and range. The results show that the intense northeastward pushing, extension and uplift in the northeastern margin of Qinghai-Tibet Plateau occur at the end of Miocene;as a result, Hongsibu Basin is transformed from depression basin to flex basin;besides that, Paleozoic-Mesozoic basement thrust above Eogene-Neogene sedimentary stratum, and the latest strata which involve in the tectonic deformation is Miocene Zhang’enbao Formation;NW-SE trending latent paleohigh in Hongsibu Basin has the same tectonic background with Yantongshan tectonic zone;under the effect of the northeastern extention of Qinghai-Tibet Plateau, the latent paleohigh develops at the end of Miocene and is still active until now;the active movements of faults around the latent paleohigh destroy the stability, water storage capacity and surface vegetation, and the regional desertification around the latent paleohigh distributes in bands with NW-SE trending.The research is of great significance to the evaluation of the regional stability and comprehensive treatment of the desertification in Hongsibu Basin of Ningxia.