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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

ISSN号：1000-0550
期刊名称：《沉积学报》
时间：0
分类：P512.2[天文地球—地质学]
作者机构：[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
相关基金：国家自然科学基金项目（批准号：40839903,40921062,40972002）和国家理科基地资金共同资助.致谢李永涛副教授提供磁化率测试方面的帮助;本课题组夏文臣教授和张宁教授提供牙形石生物地层资料和层序地层划分资料,胡庆、向字和陈桂凡在研究过程中提供帮助;审稿专家和编辑对本文提出宝贵修改意见,在此一并致谢.

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, magnetic susceptibility , geochemistry , palynology , paleoclimate , Permian-Triassic boundary , South Chi-na

中文摘要：

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。

英文摘要：

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.

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