WEATHERING AND DENUDATION RATES OF LIMESTONES AND FORMATIVE PROCESSES OF KARST LANDFORMS

这项研究试图利用方解石中原位产生的宇宙源的36&gt；Cl来量化裸露碳酸盐岩表面的长期地表剥蚀作用。碳酸盐样本是从日本亚热带到亚北极地区几个非冰川喀斯特地区裸露的尖顶上5厘米处采集的。用同位素稀释法测定方解石中天然氯和36&lt；36&gt；Cl的浓度。核素浓度约为10^5~10^6个原子g^-1~gt；，在作用于岩溶表面的化学和物理过程的10^5年的时间尺度上，转换成平均的总剥蚀率。剥蚀率为20-60 mm，在日本中部最低。这一趋势表明，在剥蚀过程中，化学(溶解)和物理(霜冻破碎)过程的相对重要性发生了变化，这取决于特定地点的因素，如平均温度、年降水量和冻融强度。

This study attempted to quantify long-term subaerial denudation of bare carbonate rock surfaces by using in situ-produced cosmogenic ^<36>Cl in calcite. Carbonate samples were collected from the topmost 5cm of exposed pinnacles at several non-glaciated karst areas in subtropical to subarctic regions in Japan. Concentrations of natural Cl and ^<36>Cl in calcite were determined by accelerator mass spectrometry with isotope dilution with ^<35>Cl-enriched carrier spike. The nuclide concentrations were of the order of 10^5-10^6 atom g^<-1>, and converted to total denudation rates averaged over a 10^5 yr-timescale of chemical and physical processes acting on the karst surfaces. The denudation rates were 20-60mm kyr<-1>, being lowest in the central part of Japan. This tendency indicates the alternation of relative importance of chemical (dissolution) and physical (frost shattering) processes in denudation, depending on site-specific factors such as mean temperature, annual precipitation, and freeze-thawing intensity.