平顺老马岭岩溶陷落柱的发现及形成时段探讨

Discover and formation time of karst collapse pillar in Laomaling,Pingshun County

岩溶陷落柱是华北煤系中大量赋存的一种危害矿井生产的灾害地质现象,探求岩溶陷落柱的形成时段是进一步研究其运动学过程、导水性及分布规律的基础。野外调查发现,山西省平顺县老马岭1 450m的分水岭上发育一赋存在奥陶系灰岩中的岩溶陷落柱。基于老马岭岩溶陷落柱柱体剖面揭示的形态学特征、流域构造地貌与岩溶水系统演化的表生过程模式及之前对太原西山岩溶陷落柱群形态特征的统计结果,发现平顺河流域岩溶地貌演化经历了2期夷平面与1期宽谷面,其间构造活跃期山顶面平均剥蚀速率分别为19.2,45.3,220.0m/Ma;得出岩溶陷落柱发育于构造稳定、岩溶水侧蚀作用加强的夷平面形成时期;类比证实了奥陶系灰岩顶面横截面积为40m×60m的老马岭岩溶陷落柱完全可以塌透上覆176.5m厚的地层。进而从陷落柱柱体岩块最大塌落距、发育的地貌部位及前人对夷平面时间的研究成果,探求出老马岭岩溶陷落柱形成时段为42~25Ma间的甸子梁夷平面发育时期,同时也表明老马岭岩溶陷落柱可作为本区甸子梁期夷平面存在的重要标志。

Karst collapse pillar,which widely exists in coal measure strata of North China,is one kind of geologic hazard and is harmful to mine exploitation.So exploring the forming time of the collapse pillar is significant for further study on its kinetic process,transmissibility and distribution characteristics.A karst collapse pillar which developed in Ordovician limestone was found through field investigation at watershed with the altitude of 1 450 min Pingshun Laomaling.Based on the morphological feature revealed by collapse pillar profile,the supergene evolution process mode of tectonic landform in drainage area and karst water system,adding to our previous statistical results of morphological characteristics for Karst collapse pillar forest in Xishan,Taiyuan,it was found that the karst landform evolution in Pingshun River drainage area undergwent two-period planation surfaces and one-period strath surface,and average denudation rate of summit surface in tectonic activity stage was respectively 19.2,45.3and 220.0m/Ma;And the Karst collapse pillar was found to developed in the period of planation surface formation with stable tectonics and intensively lateral erosionfrom karst water;It has been confirmed that Karst collapse pillar developing in Ordovician with cross sectional area of 40m×60m,can absolutely collapse throughout its above strata with the thick of 176.5m.According to the maximum collapse distance,the developing landform position and the previous results about planation surface,it was found that the karst collapse pillar in Laomaling developed in the stage of Dianzilian planation surface from 42 to 25Ma,which meant that karst collapse pillar in Laomaling could be an important sign for the existence of Dianziliang planation surface.