青藏高原若尔盖盆地更新世介形类瘤饰探讨  

ON THE NODAL ORNAMENTATION OF PLEISTOCENE OSTRACODA FROM THE ZOIGE BASIN,EASTERN QINGHAI-XIZANG(TIBETAN)PLATEAU

作　　者：勾韵娴[1] 彭金兰[1] 

机构地区：[1]中国科学院南京地质古生物研究所,南京210008

出　　处：《微体古生物学报》2011年第1期7-21,共15页Acta Micropalaeontologica Sinica

摘　　要：RM孔位于青藏高原东部边缘若尔盖盆地内,孔深310.46m,埋深底界为90万年,取芯率90%,是迄今青藏高原最深的全取芯井,也是青藏高原介形类分析最详细的深井。由此井沉积物分析获得各层段的介形类组合,具分异度低,但丰度高的特点。笔者在上世纪90年代中期,对RM孔介形类做了初步研究。本文选择了RM孔中较具代表意义的非海相多型性种Ilyocypris echinataHuang,Li mnocythere inopinata(Baird)和Cytherissalacustris(Sars)瘤的成因问题,试做初步探讨。在上述三种壳饰特征,特别是瘤的特征及其分布情况研究的基础上,选择几个国内和国外不同地区、不同时代和现代沉积环境的同种标本进行对比研究。RM孔中L.inopinata和C.lacustris壳面瘤的分布模式与国内不同区域和不同时代的同种标本是完全相同的;与国外不同区域、不同时代同种标本壳面瘤的分布模式,亦有很好的对应关系。但C.lacustris壳面瘤在个体发育过程中,其强度和数量都有变化。RM孔中的I.echinata与青藏高原其它地区同种的化石和现代标本瘤的分布模式相比亦很吻合。较长时间以来,介形类研究者对非海相多型性种壳面中空瘤的起因问题持两种观点:一种观点认为瘤是由基因决定的,即瘤的出现与否受基因控制,因而属于基因型;另一种观点则认为瘤的出现是由外因诱发的,故称为表型,外因是指环境因素的影响。本文研究结果显示,I.echinata,L.inopinata和Cytherissa lacustris壳面瘤的分布位置有惊人的稳定性,因此推测:它们壳面上的瘤,似有由基因控制的可能性。Core RM（310.46 m-long,dated 900ka BP at bottom）is situated in the Zoige Basin,eastern Qinghai-Xizang（Tibetan）Plateau,having the core recovery of 90%,and becomes the deepest whole-cored well in the plateau up to date.Core RM is also a deep one with the most intensive ostracod analyses.The ostracod assemblages obtained from different beds of Core RM show the characteristic of high abundance,but low diversity.The present paper focuses on the nodal ornamentation in representative nonmarine polymorphic species from Core RM,i.e.Ilyocypris echinata Huang,Limnocythere inopinata（Baird）and Cytherissa lacustris（Sars）.By comparing the noded L.inopinata and C.lacustris with their respective conspecifics in different areas,horizons and environments from China and abroad,it is discovered,that the positions of nodes in these two species are well correspondent with those of their conspecifics.However,the nodes of C.lacustris from Core RM have great ontogenic variations on the strength and numbers.The strength of nodes in this species ranges from strongly noded via intermediately to basically unnoded valve surface,while the number of its nodes is also gradually reduced in the process of ontogeny.The position of nodes in I.echinata from the Core RM coincides with that of the fossil and recent specimens of its conspecifics from other regions in Qinghai-Xizang（Tibetan）Plateau.It is noted that,when the nodes occur everywhere in above three species,they always adhere to fixed position on the valve surface.These present observations showed a surprisingly stable pattern in the position of nodes in these species.Therefore,we are inclined to consider that the nodes of the studied species seems to be of genotypic origin.

关 键 词：介形类 瘤饰 更新世 RM孔 若尔盖盆地 青藏高原 

分 类 号：Q915[天文地球—古生物学与地层学]