藏南江孜地区古近纪甲查拉组孢粉组合及古环境分析

PALEOGENE PALYNOLOGICAL ASSEMBLAGES AND PALEOENVIRONMENTAL ANALYSIS FROM GYACHALA FORMATION IN THE GYANGZI AREA,SOUTHERN TIBET,CHINA

甲查拉组位于藏南特提斯喜马拉雅北带的江孜盆地,是江孜地区的最高海相地层,被视为新特提斯洋关闭时代的主要证据。通过对甲查拉组剖面的孢粉分析,自下而上划分为3个孢粉组合带:1 Ulmipollenites minor+Ulmoideipites-Myricipites组合带;2 Quercoidites-Caryapollenites组合带;3 Abiespollenites-Betulaceoipollenites+Betulaepollenites组合带。甲查拉组孢粉植物群揭示出其沉积自晚古新世开始,其沉积结束可能延续到早渐新世。推测晚古新世—早始新世为温暖湿润的暖温带或亚热带气候,始新世中晚期为温暖、潮湿的亚热带气候,早渐新世为温和湿润的暖温带气候。

Gyachala Formation is located in the Gyangzi basin of the northern subzone of Tethys-Himalaya, southern Tibet, China. It is the latest marine sequence in the Gyangzi area and regarded as the main evidence of the close of Neotethyan Ocean. This paper includes a systematic analysis on the palynological assemblages of the Gyachala Formation in the Gyangzi area, southern Tibet. From the bottom to the top there are three zones at the Gyachala section： （1） Ulmipollenites minor ＋Ulmoideipites-Myricipites Zone; （2） Quercoidites-Caryapollenites Zone; （3） Abiespollenites-Betulaceoipollenite -}- Betulaepollenites Zone. Based on the analysis of the palynological assemblages of the Gyaehala Formation, we recognized that the Gyachala Formation was deposited from the Late Paleocene to the Early Oli- gocene. The palynological assemblages of the Late Paleocene--Early Eocene show a warm-temperate or subtropical climate condition. The Middle-Late Eocene palynological assemblage presents a warm and humid subtropical climate condition. The Early Oligocene assemblage of the Gyachala Formation reflects a warm-temperate climate condition.