摘要
四川盆地上三叠统须家河组可分为6段,整体表现为砂—泥间互的沉积结构,古气候是控制这种沉积结构的重要因素之一。文中利用孢粉分析法、黏土矿物分析法和特征元素分析法对全盆地6个采样点、6个层段的泥岩样品进行了系统分析,分别恢复了四川盆地晚三叠世须家河组各段地层沉积时期的古气候。研究表明,四川盆地晚三叠世须家河组沉积时期古气候特征为热带—亚热带背景下发生的温热交替、干湿更迭:须1段为海陆过渡相沉积,该时期温度高、湿度大,为炎热潮湿气候;须2段沉积时期,温度与须1段沉积时期持平或略低、湿度大幅降低,为温和干燥气候;须3段沉积时期,温度和湿度均比须2段沉积时期高,炎热潮湿,沼泽沉积发育;须4段沉积时期,温度升高、湿度略有降低,气候温和干旱;须5段沉积时期,温度和湿度均达到峰值,为整个须家河组沉积时期最炎热潮湿的阶段;须6段沉积时期,温度降至最低、湿度有所下降,气候温和干旱。
The Upper Triassic Xujiahe Formation in the Sichuan Basin can be divided into six members with a texture of interbeded sandstones and mudstones.Paleoclimate is one of the factors controlling the texture.Three methods named palynoflora,clay minerals,and eigen elements analyses were used to reconstruct the paleoclimate during the depositional period of the Xujiahe Formation.Mudstone samples of the six members were taken from six different areas through the entire basin,and then were analyzed to reconstruct the paleoclimate,respectively.The palynoflora indicated that the paleoclimate setting during the depositional period of the Xujiahe Formation was hot and humid within tropics-subtropics zone.With clay minerals analysis,the ratio of Kaolinite to Illite（K/I）was used to analyze the paleoclimate,which reduced the ambiguity.Using the ratio of calcium to magnesium（Ca/Mg）and strontium/barium（Sr/Ba）,the details of paleotemperature and paleomoisture（paleosalinity）were reconstructed.It indicates that the paleotemperature and paleomoisture during the depositional period of the Xujiahe Formation fluctuated regularly against the setting of tropics-subtropics.The Member 1 of the Xujiahe Formation was formed in a transitional facies when the paleoclimate was hot and humid.The Member 2 of the Xujiahe Formation was formed in a hot and arid climate.When the Member 3 of the Xujiahe Formation was formed,the temperature and moisture were all higher than the Member 2.It belonged to the swamp environment.After a short decrease of temperature and moisture in the Member 4,it became the hottest and wettest during the period when the Member 5 was formed.The temperature and moisture declined slightly when the Member 6 was formed,and the paleoclimate became warmer and more arid.
出处
《古地理学报》
CAS
CSCD
北大核心
2010年第4期415-424,共10页
Journal of Palaeogeography：Chinese Edition
基金
国家重点基础研究发展计划项目(973项目)(编号:2007CB209502)
中国石油勘探开发研究院中青年创新基金项目(编号:2009-B-10-04)联合资助
