大理苍山世界地质公园第四纪冰碛物特征及年代测定

云南大理苍山世界地质公园具有较高的美学价值与地学科研价值,在地学研究领域中苍山又被称为点苍山。本次研究的主要区域是点苍山玉局峰北坡和点苍山西北部的罗坪山大小海子地区,本文对点苍山玉局峰北坡冰碛物和罗坪山第四纪沉积物进行了光释光年代测定,讨论了光释光测年方法在点苍山地区第四纪冰碛物测年中的适用性,测得玉局峰北坡搬运距离较远的三条冰碛垄的年龄为(31.68±3.22)~(28.01±1.95)ka BP,属于末次冰期。对罗坪山地区第四纪沉积物进行石英砂扫描电镜分析,观察到大小海子附近第四纪沉积物石英砂表面具有一定的冰川成因特征,推断罗坪山大小海子地区曾发育过第四纪冰川作用,通过光释光测年得到大小海子附近冰川沉积物年代为(136.36±10.16)ka BP,相当于倒数第二次冰期。结合前人研究,推断点苍山地区也具有发育倒数第二次冰期的可能性。

Quaternary Glacial Deposits Features and Its OSL Dating in Mt. Cangshan Global Geopark of Dali, Yunnan Province

Rich and diverse types of geoheritage resources are distributed in Mt. Cangshan Global Geopark of Dali, Mt. Cangshan is known as Diancang Mountain in geosciences. In this study, the authors applied Optically Stimulated Luminescence (OSL) dating and Scanning Electron Microscopy (SEM) analysis to the Quaternary sediments on the north slope of the Yuju peak and the Luoping Mountain, investigated the applicability of OSL dating to glacial deposits and made a comparison between the deposits in these areas. OSL dating results indicate that the three lateral moraines on the Diancang Mountain was formed in (31.68±3.22)~(28.01±1.95) ka BP, SEM analysis of the quartz grains of Quaternary sediments of Luoping Mountain indicates that there are certain glacial characteristics, and OSL dating results with (136.36±10.16) ka BP shows that it belongs to the Penultimate Glaciation. Combining this work with previous studies, the authors infer that there exists certain possibility that the Diancang Mountain developed the Penulti-mate Glaciation.