贵州安顺新民二叠系—三叠系界线剖面磁化率变化及古气候环境意义  

Variations of the Magnetic Susceptibility across the P-T Boundary at Xinmin Section in Anshun,Guizhou and Their Paleoclimatic Implications

作　　者：徐国真[1] 冯凡斌[1] 雷勇[1] 沈俊[1] 冯庆来[1] 

机构地区：[1]中国地质大学地质过程与矿产资源国家重点实验室,武汉430074

出　　处：《沉积学报》2012年第5期817-824,共8页Acta Sedimentologica Sinica

基　　金：国家自然科学基金项目(批准号:40839903;40921062;40972002);国家理科基地资金共同资助

摘　　要：贵州安顺新民二叠系—三叠系界线剖面磁化率测试结果表明,该剖面二叠系磁化率整体偏低(平均6.4×10-8m3/kg),界线之上磁化率快速增加并相对稳定在1.3×10-7m3/kg附近,与华南其他二叠系—三叠系剖面磁化率变化趋势相同;与陆源孢粉丰度、TiO2曲线的同步变化趋势表明,新民剖面磁化率主要来自陆源物质。结合磁化率、地球化学指标的变化特征,将源区P—T之交古气候划分为3个阶段:阶段Ⅰ(1-2层中部)为化学风化作用较强的温暖潮湿的气候条件;阶段Ⅱ(2层上部-P—T界线)整体处于较强化学风化作用条件下温热潮湿的气候环境,变化较为频繁,表现为温润/湿热交替;阶段Ⅲ(P—T界线之上)物理风化加强,化学风化明显减弱,经短暂"过渡段",气候总体转变为干热的条件。Magnetic susceptibility results from Xinmin section in An-shun, Guizhou indicate that the Permian Dalong Formation is with low values（6.4 x 10-8 m3/kg in average） and that their values increase significantly across the P-T boundary and are high, about 1.3 ~ 10.7 m3/kg, in the Triassic Luolou Formation, which shows the same variation trend with that across other P-T boundary sections in South China. A good positive correlation with both terrestrial sporopollen abundance and TiO2 variations proves that terrestrial influx attributes most of the magnetic susceptibility at Xinmin section. 3 paleoclimatic stages in the source area were figured out based on the variations of magnetic suscep- tibility and geochemical climatic proxies： Stage I （bed 1 to the middle of bed 2） is characterized by a warm/humid climate with strong chemical weathering; while a hot/humid climate with stronger chemical weathering dominates stage I1 （top of bed 2 to the P-T boundary）, the climate condition change rapidly between much milder climate and humid climate; after a short transitional period, the climate in stage m （above the P-T boundary） turns into a relatively hot/ dry climate with obvious much stronger physical weathering and weaker chemical weathering.

关 键 词：磁化率 地球化学 孢粉 古气候 二叠纪—三叠纪之交 华南 

分 类 号：P512.2[天文地球—地质学]