鄂东南地区晚二叠世牙形石动物群研究

１牙形石的动物群特征本次发现于湖北大冶西畈李上二叠统中的牙形石经鉴定以Ｃｌａｒｋｉｎａｃｈａｎｇｘｉｎｇｅｎｓｉｓ和Ｃ．ｄｅｆｌｅｃｔａ为主,另外还有Ｃ．ｃａｒｉｎａｔａ,Ｃ．ｓｕｂｃａｒｉｎａｔａ,Ｃ．ｍｅｉｓｈａｎ＿ｅｎｓｉｓ,Ｈｉｎｄｅｏｄｕｓ...     

二叠-三叠纪之交牙形石生态新模式

通过对浙江长兴煤山剖面二叠－三叠系界线层沉积相分析及牙形石演化规律研究,提出了该时期Ｃｌａｒｋｉｎａ（Ｎｅｏｇｏｎｄｏｌｅｌａ）,Ｈｉｎｄｅｏｄｕｓ两类重要牙形石属的生态新模式．（１）Ｃｌａｒｋｉｎａ是一种底栖自由游泳生物,可出现于远岸浅海至盆地相较深水环境;（２）Ｈｉｎｄｅｏｄｕｓ是一种洋面浮游型生物,死亡之后可沉于海底的滨、浅海至深水盆地各种环境之中,并可渡过二叠－三叠纪之交海底缺氧事件这一难关,在早三叠世得到发展;因此,Ｈｉｎｄｅｏｄｕｓ可作为全球二叠－三叠系界线划分对比的可靠证据．     

华南二叠－三叠系的事件地层与生物地层界线

华南二叠－三叠系界线研究应严格区分事件地层界线与生物地层界线。“界线粘土”层的底界即为事件地层界线。生物地层界线定义不能与“混生层”或“过渡层”的概念连在一起。长兴煤山忠心大队剖面是最好的二叠－三叠系全球界线层型剖面点（ＧＳＳＰ）。二叠－三叠系生物地层界线定义为ＨｉｎｄｅｏｄｕｓｐａｒｖｕｓＭｏｒｐｈｏｔｙｐｅ１的首次出现,其位置就在长兴剖面界线层（混生层）２的内部,比事件地层界线高１５ｃｍ。ＨｉｎｄｅｏｄｕｓｐａｒｖｕｓＭｏｒｐｈｏｔｙｐｅ１的首次出现,即为长兴阶的顶界。     

华南二叠－三叠系的事件地层与生物地层界线

华南二叠－三叠系界线研究应严格区分事件地层界线与生物地层界线。“界线粘土”层的底界即为事件地层界线。生物地层界线定义不能与“混生层”或“过渡层”的概念连在一起。长兴煤山忠心大队剖面是最好的二叠－三叠系全球界线层型剖面点（ＧＳＳＰ）。二叠－三叠系生物地层界线定义为ＨｉｎｄｅｏｄｕｓｐａｒｖｕｓＭｏｒｐｈｏｔｙｐｅ１的首次出现,其位置就在长兴剖面界线层（混生层）２的内部,比事件地层界线高１５ｃｍ。ＨｉｎｄｅｏｄｕｓｐａｒｖｕｓＭｏｒｐｈｏｔｙｐｅ１的首次出现,即为长兴阶的顶界。     

西秦岭地区二叠—三叠系界线地层研究

在西秦岭地区南秦岭带广泛发育碳酸盐岩型二叠、三叠系。本文以选部益哇沟剖面为例，对该区界线地层进行研究，从岩石地层划分、生物地层划分以及地球化学元素最优分割研究出发，确定了二叠、三叠系界线点，证明牙形石Ｈｉｎｄｅｏｄｕｓｐａｒｖｕｓ可作为三叠系开始的标志，并且二叠、三叠系是连续的。沉积环境分析表明，三叠纪初期相对于二叠纪末发生了一次海侵。     

扬子台区二叠-三叠系界线层综合地层学研究

华南二叠－三叠系界线研究一直在地学界备受瞩目．目前被广泛接受的界线标准化石为牙形石Ｈｉｎｄｅｏｄｕｓｐａｒｖｕｓ,该化石的首现位置被定义为二叠－三叠系界线层型剖面点．然而在全球研究精度最高的４个候选层型剖面中,生物地层单位的对比问题尚存在分歧,从而影响了区域高精度地层对比框架的建立．在扬子台区丰富的资料及大量二叠－三叠系界线剖面进一步研究的基础上,发现许多剖面上二叠－三叠系界线处具有相似的岩石地层特征．其基本结构为粘土岩层、灰岩或泥灰岩层及粘土岩层沉积组合．从综合地层学角度的研究表明：该套沉积组合（界线层）在岩性特征、生物群总体面貌以及其他事件标志（如同位素年龄、磁性地层、地球化学特征等）上具有一定的对比意义．认为界线层应该是等时的地层单位,是扬子台区二叠－三叠系界线处重要的标志层组,并对这套地层进行了区域性对比．这套地层的发现大大提高了扬子台区二叠－三叠系界线处地层的对比精度．     

浙江长兴地区二叠纪与三叠纪之交牙形石动物群及地层意义

本文把采自华南浙江长兴煤山二叠系与三叠系界线剖面的牙形石动物群从老至新分为三个带:1.Gondolella subcarinata-G·wangi组合带;2.G.changxingensis-G.deflecta组合带;3.Anchignathodus parvus带。将煤山剖面的二叠系与三叠系界线划在2、3组合带之间。并初步探讨了长兴地区长兴期至早格里斯巴赫期的牙形石分异度与沉积环境变迁。     

宁夏中卫县下河沿太原组生物地层─—兼论石炭—二叠系分界

本文将宁夏中卫县下河沿原上石炭统太原组划分为上、下二个段。太原组上段（剖面１８—３１层），含科以Ｐｓｅｕｄｏｓｃｈｗａｇｅｒｉｎａ带及Ｓｐｈａｅｒｏｓｃｈｗａｇｅｒｉｎａ带的属种为代表，牙形石Ｓｔｒｅｐｔｏｇ－ｎａｔｈｏｄｕｓ属为主，植物为东方鳞木类繁多，裸子植物花粉占优势。以上古生物面貌应属于早二叠世。太原组下段（剖面１—１７层），含科Ｍｅｄｏｃｒｉｓ，Ｐｓｅｕｄｏｓｔａｆｆｅｌｌａ，牙形石Ｉｄｏｇｎａｔｈｏｄｕｓｄｅｌｌｉｃａｔｕｓ，Ｉ．ｏｌａｖｌｆｏｒｍｉｓ等为主；植物以Ｎｅｕｒｏｐｔｅｒｉｓｐｓｅｕｄｏｖａｔａ及Ｓｐｈｅｒｏｐｈｙｌｌｕｍｏｂｌｏｎｇｉｆｏｒｌｉｕｍ最繁盛，其时代呈现浓厚晚石炭世特征。据上述情况，本区石炭—二叠系的界线应置于太原组上、下段之间，这条界线比我国传统的划界位置低一些，而与目前国际上普遍采用的界线已趋于一致。     

湖南桑植县仁村坪上二叠统—下三叠统底部菊石动物群序列及其区域对比

湖南桑植县仁村坪剖面二叠-三叠系界线地层连续,菊石动物化石丰富.根据该剖面上二叠统大隆组至下三叠统大冶组底部菊石动物群的分布,自下而上划分为4个菊石带:Araxoceras-Konglingites-Sanyangites带、Sinoceltites带、Pseudotirolites-Rotodiscoceras带和Hypophiceras-Ophiceras-Lytophiceras带.通过对该剖面菊石和牙形石生物地层及其与华南其他剖面的对比可知,Araxoceras-Konglingites-Sanyangites带与牙形石Neospathodus orientalis带同期,为吴家坪期晚期;Sinoceltites带与牙形石N.subcarinata-N.wangi带同期,为长兴期晚期;Pseudotirolites-Rotodiscoceras带与牙形石N.postwangi-N.changxingensis带和N.xiangsiensis-N.changxingensis带同期,为长兴期晚期;Hypophiceras-Ophiceras-Lytophiceras带与H.parvus、I.isarcica-I.staesche和N.planata 3个牙形石带同期,相当于印度期早期.根据仁村坪剖面菊石Hypophiceras-Ophiceras-Lytophiceras带底界的出现位置,将该剖面的二叠-三叠系界线确定在第27a层的中部.     

依牙形刺论Gallowayinella()的时代和长兴阶的底界

类Ｇａｌｏｗａｙｉｎｅｌａ长期以来被当作长兴阶的带化石，是长兴阶底界的标志。江西上高七宝山剖面表明Ｇａｌｏｗａｙｉｎｅｌａ富集层并非像以往认为的那样是稳定的一层，在此剖面上至少有二层：下层在Ｃｌａｒｋｉｎａｌｅｖｅｎｉ带之下，其上下均有典型的吴家坪期的菊石（Ｋｏｎｇｌｉｎｇｉｔｅｓ等）；上层与吴家坪期的牙形刺Ｃｌａｒｋｉｎａｏｒｉｅｎｔａｌｉｓ，Ｃ．ｇｕａｎｇｙｕａｎｅｎｓｉｓ，Ｃ．ｄｅｍｉｃｏｒｎｉｓ，Ｃ．ｌｉａｎｇｓｈａｎｅｎｓｉｓ共存。这一事实表明Ｇａｌｏｗａｙｉｎｅｌａｍｅｉｔｉｅｎｅｎｓｉｓ是吴家坪期的而不是长兴期的。为此建议，长兴阶的底界不用类定义，而以牙形刺Ｃｌａｒｋｉｎａｓｕｂｃａｒｉｎａｔａ和／或Ｃ．ｗａｎｇｉ的首次出现为准。     

Conodont biostratigraphy across the Permian–Triassic boundary at the Dawen section, Great Bank of Guizhou, Guizhou Province, South China: Implications for the Late Permian extinction and correlation with Meishan

Several continuous Permian–Triassic boundary (PTB) sections are well exposed in the interior of the Great Bank of Guizhou (GBG) on the east limb of the Bianyang syncline, Luodian County, Guizhou Province, South China. Fourteen conodont taxa are identified, including Clarkina kazi, Clarkina lehrmanni n. sp., Clarkina taylorae, Clarkina zhejiangensis, Hindeodus eurypyge, Hindeodus inflatus, Hindeodus sxlatidentatus, Hindeodus parvus erectus, Hindeodus parvus parvus, Hindeodus postparvus, Hindeodus praeparvus, Hindeodus typicalis, Isarcicella staeschei, and Merrillina ultima based on a detailed study of the Permian-Triassic interval at the Dawen section. The first occurrence (FO) of H. parvus parvus in the lower Daye Formation, at about 7.45 m above the contact surface between the Upper Permian skeletal packstone and a calcimicrobial framestone unit, is correlated with the Permian–Triassic boundary; the occurrence of H. eurypyge, H. praeparvus and M. ultima immediately below and H. postparvus above the interval supports this interpretation. A morphometric analysis of 31 Hindeodus specimens helped distinguish H. parvus erectus from H. parvus parvus and H. postparvus. Correlation with the Meishan section (PTB GSSP) using both conodont biostratigraphy and carbon isotopes, indicates that the major extinction at the two localities is simultaneous and coincides with the top of the skeletal packstone at Dawen. The contact between the skeletal packstone and the calcimicrobialite is very irregular and has previously been interpreted as a dissolution surface and correlated with a surface in the lower part of bed 27 at Meishan. Our results confirm this interpretation and reveal that the dissolution event postdated the extinction.     

鄂西地区上二叠统的牙形石及其分带意义

湖北恩施天桥剖面发育有完好的二叠系大隆组下段硅质岩层。对其下伏吴家坪组灰岩及上覆大隆组上段灰岩中牙形石的研究表明,吴家坪组灰岩自下而上可分为Clarkina postbitteri postbitteri带、Clarkina dukouensis带、Clarkina asymmetrica带以及Clarkina guangyuanensis—Clarkina transcaucasica带,属吴家坪阶中下部牙形石带;大隆组上段灰岩可划分出两个牙形石带,即Clarkina subcarinata—Clarkina wangi带和Clarkina changxingensis changxingensis—Clarkina deflecta带,为长兴阶底部牙形石带。认为鄂西地区大隆组下段硅质岩的时代应归属于二叠纪吴家坪中期至长兴早期。     

Comment on"First Record of Hindeodus-Isarcicella Population in Lower Triassic of Slovenia"by Tea Kolar-Jurkovek and Bogdan Jurkovek in Palaeogeography,Palaeoclimatology,Palaeoecology,252:72-81

Some conodonts described by Tea Kolar-Jurkovsek and Bogdan Jurkovsek(2007)from the Permian-Triassic boundary section in the Ziri area of western Slovenia are revised in this paper.One specimen that they assigned to Hindeodus parvus is tentatively regarded as Hindeodus cf.scalaris Wu 2005.Two specimens that they assigned to Isarcicella sp.A is changed to Hindeodus parvus.One specimen that they described as Isarcicella lobata Perri and Farabegoli is changed to Hindeodus crenatus Wu(2006).One specimen that ...     

Comment on "First Record of Hindeodus-Isarcicella Population in Lower Triassic of Slovenia" by Tea Kolar-Jurkovsek and Bogdan Jurkov(s)ek in Palaeogeography, Palaeoclimatology, Palaeoecology, 252:72-81

Some conodonts described by Tea Kolar-Jurkovsek and Bogdan Jurkovsek (2007) from the Permian-Triassic boundary section in the Ziri area of western Slovenia are revised in this paper. One specimen that they assigned to Hindeodus parvus is tentatively regarded as Hindeodus cf. scalaris Wu 2005. Two specimens that they assigned to IsarciceUa sp. A is changed to Hindeodus parvus. One specimen that they described as IsarciceUa lobata Perri and Farabegoli is changed to Hindeodus crenatus Wu (2006). One specimen that they assigned to lsarcicella turgida (Kozur, Mostler and Rahimi-Yazd) is changed to Hindeodus cf. parvus. Since these revisions, the three conodont zones that they defined have been correspondingly revised. Their first zone may belong to Hindeodus parvus zone, but it is not certain. Their second zone is changed to the Hindeodus parvus zone, and their third one remains as is.     

Comment on “First Record of Hindeodus–Isarcicella Population in Lower Triassic of Slovenia” by Tea Kolar-Jurkov?ek and Bogdan Jurkov?ek in Palaeogeography, Palaeoclimatology, Palaeoecology, 252: 72–81

Some conodonts described by Tea Kolar-Jurkovsek and Bogdan Jurkovsek (2007) from the Permian-Triassic boundary section in the ?iri area of western Slovenia are revised in this paper. One specimen that they assigned to Hindeodus parvus is tentatively regarded as Hindeodus cf. scalaris Wu 2005. Two specimens that they assigned to Isarcicella sp. A is changed to Hindeodus parvus. One specimen that they described as Isarcicella lobata Perri and Farabegoli is changed to Hindeodus crenatus Wu (2006). One specimen that they assigned to Isarcicella turgida (Kozur, Mostler and Rahimi-Yazd) is changed to Hindeodus cf. parvus. Since these revisions, the three conodont zones that they defined have been correspondingly revised. Their first zone may belong to Hindeodus parvus zone, but it is not certain. Their second zone is changed to the Hindeodus parvus zone, and their third one remains as is.     

湖南嘉禾大窝岭剖面吴家坪阶-长兴阶界线牙形石生物地层及一次碳同位素负偏

吴家坪阶-长兴阶界线位于这两次生物大灭绝事件之间,科学界对该界线附近是否发生重大地质事件仍然知之甚少,有关该时期的环境变化、碳循环的研究也不深入.嘉禾大窝岭剖面牙形石生物地层以及碳同位素变化的研究,为进一步探讨吴家坪期-长兴期附近的生物及环境事件提供基础材料.晚二叠世时以深水盆地相沉积为主的大窝岭剖面位于湖南省嘉禾县袁家镇附近.该剖面大隆组出露较好,岩性主要为硅质岩、硅质灰岩、灰岩以及泥岩.在大隆组中共识别出牙形石1属3种(含一个未定种):Clarkina wangi,C. deflecta,C. sp.,并识别出牙形石C. wangi带和C. changxingensis-C. deflecta组合带.根据C. wangi的首现,将大窝岭剖面的吴家坪阶-长兴阶界线(Wuchiapingian-Changhsingian boundary,简称WCB)置于第11层底部.该剖面全岩无机碳同位素数据显示在13~15层发生了一次快速的负偏,从2.18‰负偏到-1.39‰,负偏值近3.50‰,可与浙江煤山及四川上寺等剖面进行很好的对比,揭示这次碳同位素负偏在华南区域上可具对比性.      

鄂东伍家冲剖面乐平世牙形石生物地层及大隆组的时代

大隆组是华南地区乐平世一种重要的较深水沉积.为进一步探讨大隆组沉积的时空分布,选择对鄂东伍家冲剖面吴家坪组和大隆组重点进行了牙形石生物地层研究,此次研究共鉴定出牙形石1属5种,均为Clarkina,并由老到新识别出4个牙形石带:C.guangyuanensis带、C.transcaucasica带、C.orientalis带及C.wangi带.根据牙形石C.wangi的首现,将伍家冲剖面的吴家坪阶-长兴阶界线(Wuchiapingian-Changhsingian boundary,简称WCB)置于第18层底部.根据菊石Ophiceras的首现将伍家冲剖面的二叠系-三叠系界线(Permian-Triassic boundary,简称PTB)置于第20层顶部,仅高于WCB界线0.72 m.牙形石生物地层指示伍家冲剖面大隆组的主体为吴家坪期沉积产物.数个长兴期牙形石带的缺失和极短的长兴阶表明,该剖面长兴阶中上部可能因沉积间断存在缺失.