A number of gastropod fossils were discovered in the 4th lithologic member of Guge Formation within Zanda basin of Tibet, with the identification of an assemblage of Adelinella regularis-Velutinopsi which comprises Adelinella regularis Yü, Velutinopsis spiralis Yü, Radix zandaensis sp. Nov and Hippeutis cf.minor (Ping). Based on the distribution characteristics of these gastropod fossils in southwest Tibet, the authors regards them as a biological assemblage located in the intermontane fault basin in northern Himalayas, between the Rhino fossils layer and Unio douglasiae Giiffithet Pidgeon-Unio tschiliensis Sturany layer and with a paleomagnetic age of late Pliocene-Early Pleistocene. Based on a comparison with the existing species of gastropod, the authors hold that the gastropod in the fossil strata in Zanda basin might have lived in a shallow littoral lake environment. The sporopollen reveals that the place where the gastropod in the fossil strata lived was an environment of warm and moist forest-grasslands. Hipparion in the lower gastropods fossil layer in Zanda basin indicates a warm and arid shrub-grassland environment. Consequently, the paleo-climate during the deposition of the Tuolin Formation and Guge Formation experienced a transition from a warm and dry environment to a warm and humid environment.%在西藏札达盆地古格组第四岩性段发现大量腹足类化石:Adelinella regularis Yü(规则小隐螺)、Velutinopsis spiralis Yü(旋纹似天鹅绒螺)、Radix zandaensis sp.nov.(札达萝卜螺)、Hippeutis cf.minor (Ping)(微小圆扁卷螺),称为小隐螺-似天鹅绒螺组合.根据这些腹足类化石在西藏西南部的分布特征,认为它们是分布于北喜马拉雅山间断陷盆地的一个腹足类组合,介于西藏犀类化石与杜氏珠蚌-河北珠蚌层之间,时代处于晚上新世-早更新世之间.对比现生种属研究认为,札达盆地腹足类应生活于近岸的浅湖环境.孢粉分析认为化石层形成时为温暖潮湿的森林-草原环境,化石层下部的三趾马生活在温暖而显干旱的灌丛草原环境,可知札达盆地由托林组至古格组,古气候经历了由温暖干旱向温暖潮湿的转变过程.
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