【作者】 张宁；

【导师】 夏文臣；

【作者基本信息】 中国地质大学 ， 矿物学、岩石学、矿床学， 2004， 博士

【摘要】 在连续沉积厚度大、时限长的广西钦州地区板城泥盆-二叠纪硅质岩系中，精确划分生物地层单位、建立全球可对比的化石带和地层界限剖面是一项有重要科学意义的研究课题。近10年来，我国的生物地层学家做了大量的放射虫地层研究，先后建立了弗拉斯阶的Helenifore laticlavium动物群和法门阶的Holoecisicus foremanae动物群(王玉净等，2000；Wang et al, 2003, )同时还报道了下石炭统的放射虫化石带(吴浩若等，1994；冯庆来等，1997)。但是，与碳酸盐岩系的牙形石地层研究成果相比(Klarpper et al., 1987, 1993; Paproth, 1991; Zieglar and Sandberg, 1990)，放射虫分带性的研究程度相对较低，诸多重要科学问题尚未解决，如：泥盆—石炭纪放射虫动物群的演化谱系和谱系带尚未建立、在层型界限点附近未定义出相应的放射虫标志带等。这些科学问题未能解决的主要原因在于：在牙形石带与放射虫带之间没有建立起一个能有效对比的桥梁。 新世纪开始时，笔者在研究广西钦州地区板城晚泥盆-早石炭世放射虫动物群演化与硅质岩沉积环境的关系时(Zhang and Xia, 2002)在多个层位发现了与放射虫共生的牙形石，这一发现让笔者很自然的联想到：若在该剖面深入研究，重叠建立放射虫和牙形石化石带或许能在二者之间建立起一个有效对比的桥梁!受此启发，笔者再次精测了所研究过的剖面。野外工作中根据硅质岩的颜色、混入物的含量和单层厚变化划分出了228个岩性层，在每个分层标定了层号和顶、底界标记，共采样567件。利用设备完善的微体生物实验室系统处理和鉴定了放射虫和牙形石，对中—晚泥盆统和下石炭统的放射虫进行了谱系带的划分，同时发现了更多的牙形石。在此基础上，又特意在吉维特阶—弗拉斯阶、弗拉斯阶—法门阶以及泥盆系—石炭系界面附近以5-10 cm间距加密采样，依据国际地层指南关于建立层型剖面的要求(Hedberg, 1976, 1994)，进行了高分辨率的放射虫和牙形石生物地层研究。实验室内再次进行两种微体化石的处理和鉴定工作，同时通过各种渠道收集和追踪相关参考文献160余篇，最新中外文献截止到2003年底。幅系统描述了19个属55个重的放射虫化石、5个属15个种的牙形石化石，通过编图和与国内外层型剖面对比研究，完成了本博士学位论文。 其主要成果是：在中泥盆统上部至下石炭统，建立了17个放射虫谱系带，分别在G-F、F-F和D-C三个重要地层界面附近建立了可与全球层型剖面对比的牙形石带，按国际地层指南的要求在硅质岩剖面中鉴别了三个生物地层界限点，厘定了鉴别每个界面的首现放射虫分子和放射虫带；同时，结合硅质岩REE地球化学的分析结果，讨论了导致晚泥盆世放射虫动物群衰减的Hangenberg事件的多幕性。 1)在法国南部黑山东南的St. Nazaire-de-Ladarez de Col du Puech de Ia Suque全球层型(GSSP)剖面上，中—上泥盆统界面(弗拉斯阶底界面)定义在牙形石Ancyrodella rotundiloba(Bryant)的首现层位(相当于牙形石带Polygnathus asymmetricus之底)(Klarpper et al.，1987:099，2003)。在中国广西六景剖面则以Ancy厂odella仰t胡d1’1oba early form的首现将中一上泥盆统界限定义在谷闭组底界之上1.80米处(于干等，2000;江大勇等，2000)。此界限位于牙形石下加sodaxz’sfa了sJ口阳1z’s带之底。笔者在板城硅质岩剖面的SE23一19层中获得了牙形石加so内x了sfa了sz’ova1z’‘Sandberg，Ziegler&Bultynek和藏。阳ljs(Ziegler&Klarpper)，在其上14 em处的SE24一35层还获得了肋叹人℃delja rot二d1’Joba(Bryant)和袱a双于沥叨etrlca(Bisehoff&Ziegler)、袱。阳1z’s(Ziegler&KlarPPer)。在SE23一19层之下，笔者曾多次采样和逐层处理微体化石，仅仅只在SE23一34层获得少量放射虫St丁g功口胡人earost少lush了Strjc“osa(Aitchoson)和Tr.二tusta Hinde，因此首次出现从fajsjo二115的SE23一19层之底为falsiovalis带的底界面。而将中一上泥盆统界限定在肋以了口dellarotundz’1oba首现的SE24一35层之底。此界限确定之后，其附近的放射虫谱系带就有了明确的时代归属。 2)上泥盆统法门阶的底界位于生物大灭绝层(上KellwaSSer horizon层)之上，上Kellwasser事件导致了牙形石AncyrodeJla属、必a厂介口成刀刁属、菊石Gephuro。eratidae科的面刀la tj tes属与Beloceratidae科的灭绝。层型剖面(GSSP)位于法国南部黑山 (Mon七agne Noir)塞申农(Cessnon)Coumia。采石场(099，2003，Klarpper et al.，1993)，以牙形石Pal功ot口了ePjs tr ja刀圳larl Sannemann的首现定义卜F界面。层型剖面被通过后，全球不少地区又在上K。11wasser层位也发现与Pal功otolePjs tr ja裂卿larjs十分相似的牙形石分子(Sehulke，1999:over and Repetski，2000)，由此看来，人为性通过的层型剖面界限点仍存面临着客观的挑战。本论文以硅质岩相F一F剖面为研究对象，系统研究牙形石、放射虫谱系演化与硅质岩REE地球化学参数变化的祸合关系，在相当于上Kellwasser的层位鉴定出了下triangularis带。此带内无论是牙形石还是放射虫动物群都表现出弗拉斯末期分子多幕式衰减一灭绝同时与法门早期的先?更多还原

【Abstract】 It is an important scientific problem to divide in detail the biostratigraphic zones and to establish the global comparable radiolarian zones in the Middle Devonian to Lower Carboniferous pelagic chert sequences with the thick in thickness and longer in duration at Bancheng near Qinzhong city of Guangxi, South China. During the decade geologists have much studied on the radiolarian stratigraphy, and a Helenifore laticlavium fauna for Frasnian Stage, a Holoecisicus foremanae fauna for Famennian Stage was determined by Wang et al. (Wang et al., 2000, 2003). Wu et al. (1994) have reported radiolarians from the Lower Carboniferous (Wu et al., 1994). However, how to correlate the radiolarian zones from pelagic chert sequence with the conodont zones from limestone sequence, as well as to identify the stratotype points of the Givetian-Frasnian, Frasnian-Famennian and Devonian-Carboniferous boundaries that is necessary to understand.When author recovered the radiolarians using the 5% solution of HF acid, some conodont elements ware found together with radiolarians from the chert samples in Bancheng section, therefore an idea to trance the G-F, F-F and D-C boundary in the pelagic chert sequence by both conodont and radiolarian zonations. Introduced under the professor Xia Wenchen, I measured in detail this section again in 2000. Two hundreds and twenty eight chert beds were distinguished according to variation of color, lithology and thickness, each bed was marked using paint, and 567 samples were took for recovering radiolarians and conodonts. For two years, I treated all off samples and traced these three boundaries again and again, Finally, three global comparable conodont and radiolarian sections are established respectively near the G-F, F-F and D-C boundaries by high-resolution stratigraphy. These results have exactly indicated the points of the G-F, F-F and D-C boundaries in the Bancheng chert section, and identified three radiolarian first appearance data for identifying respectively the G-F, F-F and D-C boundaries. Also seventeen radiolarian phylozones are established in range from the upper Givetian Stage to Visean Stage.The GSSP of the Mid-Upper Devonian (G-F) boundary was defined by the FAD of the conodont Ancyrodella rotundiloba (Bryant) at the GSSP in Col du Puech de la Suqus section of southeastern St. Nazaire-de-Ladarez, Montagne Noir, South France in 1986 (Klarpper et al., 1987; Ogg, 2003). This boundary was determined at the 1.80 meter level above the base of Gubi Formation in Liujing section, Guangxi, South China by the first appearance of Ancyrodella rotundiloba (Bryant) early form (Yu, et al., 2000; Jiang et al., 2000). Author has recovered conodonts Mesotaxis falsiovalis Sandberg, Ziegler & Bultynck 和 M. ovalis (Ziegler & Klarpper) from the chert bed of SE23-19 in the Bancheng section, and Mesodaxis asymmetricus (Bisehoff & Zieg!er） M ovalis (Ziegler & Klarpper) and Anryrodella rotundiloba Bryant from the chert bed of SE24-35 that is 1.40 m above the bed of SE23-19. Never conodont was found from the beds underlain the SE23-19, except the radiolarian Stigmosphearostylus hystricuosa (Aitchoson) and Tr. vetusta Hinde were recovered only from the chert bed of SE 23-34 in the Bancheng section. Therefore, I propose that the conodont falsiovalis Zone could begin with thefirst appearance of Mesotaxis falsiovalis, that is determined at the base of bed SE 23-19 in the Bacheng section. The G-F boundary is defined nat the base of the bed SE 23-35 by the first appearance of Ancyrodella rotundiloba Bryant. By this result, the ages of radiolarian zones above the G-F boundary should be exactly identified.The Frasnian-Famennian boundary is located at the top of a massive extinction horizon (upper Kellwasser horizon) that punctuated the conodont Ancyrodella and Ozarkdina genus, as we as the Geniatites genus of Gephuroceratidae and Beloceratidae of Ammonoidea. The GSSP of F-F boundary was defined at the base of bed 32a in the upper Coniatites section, Cessenon, Montagne Noir, South Frabce by the first appearance of Palma更多还原