Upper Devonian and Lower Carboniferous Sequence Stratigraphy of South China

In South China four depositional sequences are recognized in the upper part of Upper Devonian and Tournaisian. They are named SQ0 SQ1, SQ2 and SQ3 in ascending order. SQ0 is Strunian (uppermost Devonian), and the other three Tournaisian in age. These four depositional sequences appear to correlate fairly well with the four sequence recognized in Europe, North America and other areas. This may suggest that these sequences are synchronous depos- its resulted from the eustatic changes. The present study on sequence stratigraphy, biostratigraphy and event stratigraphy indicates that in neritic facies areas of South China, the Devonian-Carboniferous boundary, matching the boundary between Siphonodella praesulcata zone and S. sulcata zone in pelagic facies areas, is not only higher than the top of the Cystophrentis zone, but also higher than the top of the Devonian-Carboniferous boundary event bed. In neritic facies areas, the Devonian-Carbonifrerous boundary is marked by the most distinct transgressive surface within the Cystophrentiseudouralina interval zone, i. e. at the base of the TST of the SQ1. This boundary coincides with the top surface of the event bed resulted from the eustatic fall, and approximately corresponds to the basal part of Rseudouralina assemblage zone.

On the Devonian-Carboniferous Boundary in Neritic Facies Areas of South China:A Viewpoint of Integrated StratigraPhy

Biostratigraphical data indicate that in the neritic facies areas of South China, the Devonian -Carboniferous boundary (DCB), matching the boundary between conodont Siphonodella praesulcata zone and S. sulcata zone, should be drawn between rugose coral Cystophrentis zone and Pseudouralina zone, i.e. the Cystophrentis\ Pseudouralina inter val-zone. The top of the sea level fall event bed near the DCB is lower than the boundary between S. praesulcata and S. sulcata zones, but higher than the top of the Cysto phrentis zone. Sequence stratigraphical study shows that the sea level fall event bed near the DCB constitutes the shelf margin system tract (SMST) of a depositional sequence (SQ1) in both neritic and pelagic facies areas. The top surfaces of SMST of SQ1 is slightly lower than the base of S. sulcata zone in the pelagic facies areas. In neritic facies areas of South China, therefore, the Devonian - Carboniferous boundary is marked by the most distinct transgressive surface within the Cystophrentis\ Pseudouralina interval-zone, i.e. the base of the TST of SQ1. This boundary coincides with the top surface of the event bed resulted from the eustatic fall, and approximately corresponds to the base of Pseudouralina assemblage zone.

Facies-succession and architecture of the third-order sequences and their stratigraphic framework of the Devonian in Yunnan-Guizhou-Guangxi area,South China

The Caledonian orogeny at the end of the Silurian resulted in great changes in the palaeogeography in the Yunnan-Guizhou-Guangxi area of South China; the continental area of the Early Paleozoic evolved into the extensive Dian-Qian-Gui Sea in the Late Paleo-zoic. Early in the Devonian, as a result of a major transgression, seawater encroached gradually from the south to the north and clastic facies were deposited. Carbonate deposition was then established in the Yunnan-Guizhou-Guangxi area, with a palaeogeography marked by attached platforms, isolated platforms and narrow basins. As a result of the Ziyun movement towards the end of the Devonian, the Upper Devonian strata are regressive and thin out from the open-sea to the land areas. A study of the nature and distribution of sedimentary facies in space and time recognises 13 third-order sequences in the Devonian strata in Yunnan-Guizhou-Guangxi area, and these form two second-order sequences. The strata of the Lower Devonian comprise 5 third-order sequences (SQ1 to SQ5 ), which are dominated by transgressive clastics. 4 third-order sequences (SQ6 to SQ9 ) in the Middle Devonian are characterized by alternations of transgressive clastics and highstand carbonates. In the Upper Devonian, carbonates constitute 4 third-order sequences (SQ10 to SQ13 ), which are generally marked by the transgressive limestones and highstand dolomites. On the basis of earlier biostratigraphic studies, sea-level changes represented by the third-order sequences with their different facies successions are explored, and the sequence stratigraphic framework is established. There-fore, the Devonian strata in the study area provide an example for further understanding of depositional trends within the sequence-stratigraphic framework.

Devonian Sequence Stratigraphy and Sea Level Change Cycles in South China

The Devonian is well developed in South China and has drawn a great attention from the geologists both at domestic and abroad. On the basis of study on the sequence stratigraphy in more than 10 sections in Guizhou, Guangxi, Longmenshan and Southern Qinling within South China we have identified 21 sequences and T-R cycles that correspond to third-order sea level changes. These sea level change cycles were controlled by autorhythm(Pragian,Eifelian), allorhythm(Lochkovian,Emsian,Givetian) and coupling rhythm mechanisms (frasian, Famennian and F-F boundary).

Devonian Sea-Level Change Rhythms in South China and Coupling Relationships Among the Earth-spheres

Twenty orthosequences and their corresponding sea-level change (SLC) cycles have been recognized in the Devonian overlying the Caledonian unconformity, of which 9, 5.5 and 5.5 occurred in the Lower, Middle and Upper Devonian respectively. They can be grouped into 4 orthosequence sets, in which the maximum flooding surfaces lie in the sulcutus Zone (D12), perbonus Zone (D13), Middle and Upper varcus Zone (D22) and gigas Zone (D21) respectively. Four instant palaeogeographical reconstructions of South China have been made in the Emsian and Givetian. Devonian sea-level change rhythms of South China can be divided into 3 categories: the autorhythmic, the worldwide and regional allorhythmic, and the coupling-rhythmic. They developed respectively in the Famennian, Pragian, Eifelian, Lochkovian, Emsian, Givetian, Frasnian and the F / F (between the Frasnian and Famennian) event. The cause of the worldwide allorhythmic SLC of the Pragian and Eifelian under comparatively dry, warm and tranquil conditions may be related to the pulsating expanding and contracting of the oceanic basin volume or the earth volume pulsation, rather than the common glaciation and plate tectonism. The coupling-rhythmic SLC related to the F/ F event is a sensitive indicator of the interaction between terrestrial and extraterrestrial factors, and coordinated action among the earth-spheres.

Biostratigraphical significance of the Devonian Sinoleperditiini(Ostracoda)

The Tribe Sinoleperditiini (Ostracoda), which is mainly distributed in South China and its adjacent areas, is a single natural group of the Leperditiidae, characterized by the development of a trailing chevron muscle scar. This tribe is known only from the Devonian and ranges through most of the Devonian. The evolutionary trends within the Sinoleperditiini have been well documented and are exemplified by changes in the trailing chevron muscle scar. The main evolutionary change is a tendency of the trailing chevron muscle scar to extend ventrally through time, as demonstrated by the increasing ratio (th/ah) of the vertical height of the trailing chevron muscle scar (th) to that of the adductor muscle scar (ah). The recent discovery of a sinoleperditiine assemblage (th/ah values available) in the middle-upper Lower Emsian Shanglun Formation allows to propose a sinoleperditiine biostratigraphical sequence for the Devonian. This sequence contains 11 assemblages (th/ah value available for each assemblage), which cover all the 7 Devonian stages and some substages. This sequence is particularly useful for correlating and dating Devonian rocks in the littoral clastic, lagoonal and restricted or semirestricted car-bonate platform facies where these ostracodes are most abundant and other fossils are un-common.

Two Species of Zosterophyllum from South China and Dating of the Xujiachong Formation with a Biostratigraphic Method

ZosterophyUum longa sp. nov. is reported from the Lower Devonian Pingyipu Formation, Jiangyou District, northern Sichuan of China. This new plant has vertically elongate sporangia differing from all known species of Zosterophyllum, demonstrating morphological variations in Zosterophyllophytina. New materials of Zosterophyllum yunnanicum from the Lower Devonian Xujiachong Formation, Qujing District, eastern Yunnan of China show that fertile axes of this species are anisotomous or pseudomonopodial or K-shaped in branching. Sometimes fertile lateral axes are very short and bear an axillary axis at the dividing point. Distinct thickening occurs along the whole margin of a sporangium, with sporangial lobes undeveloped. The evolution of ZosterophyUum is tentatively discussed. A biostratigraphic method of Gerrienne and Streel is introduced and applied to dating of the Lower Devonian Xujiachong Formation, which is considered as of the late Pragian-early Emsian.

华南泥盆纪分形类豆石分类一新族Sinoleperditiini

在华南，迄今只在泥盆纪地层中发现豆石介类（ｌｅｐｅｒｄｉｔｉｉｄｓ）。由于它们均具有下垂“Ｖ”字型肌痕且此肌痕随时间的推移不断向下延伸，被考虑是豆石介类中一独立的演化支系，并归一新族：Ｓｉｎｏｌｅｐｅｒｄｉｔｉｉｎｉ。此族，在华南地区含２属和６亚属：Ｓｉｎｏｌｅｐｅｒｄｉｔｉａ（Ｓｉｎｏｌｅｐｅｒｄｉｔｉａ）Ｗａｎｇ，１９８９，Ｓ．（Ｐｓｅｕｄｏｂｒｉａｒｔｉｎａ）ｓｕｂｇｅｎ．ｎｏｖ．，Ｓ．（Ｙａｏｓｕｏｌｅｐｒｄｉｔｉａ）ｓｕｂｇｅｎ．ｎｏｖ，Ｐａｒａｍｏｅｌｌｅｒｉｔｉａ（Ｐａｒａｌａｐｅｒｄｉｔｉａ）Ｓｕｎ，１９７８，Ｐ．（Ｐａｒａｍｏｅｌｌｅｒｉｔｉａ）Ｗａｎｇ，１９７６和Ｐ．（Ｂｒｅｖｉｌａｐｅｒｄｉｔｉａ）ｓｕｂｇｅｎ．ｎｏｖ．。重点探讨了此族的起源，演化型式及趋势和绝灭。指出“Ｖ”字型或下垂“Ｖ”字型肌的功能与闭壳肌可能是异曲同功，起闭壳作用；放射和横向条纹可能是闭壳肌和下垂“Ｖ”字型肌频繁收缩所致而不是血管束的痕迹，并可能具有排泻作用；ＤａｌｅｌｉｎａＳｕｎ，１９７８是ＰａｒａｌｅｐｅｒｄｉｔｉａＳｕｎ，１９７８的同物异名；ＰａｒａｅｏｌｏｐｅｒｄｉｔｉａＡｄａｃｈｉｅｔＩｇｏ。

黔桂地区泥盆纪层序地层和台内裂陷槽的形成演化

黔桂地区是泥盆纪时期南华海盆内裂陷活动作用初始且十分显著的地区。本文结合区域构造和盆地格局分析，通过典型剖面研究，将黔桂稳定型滨岸一台地相区的泥盆系划分为２１个３级海平面变化控制的层序。根据南丹罗富、大厂裂陷槽盆地泥盆系层序地层研究和与相邻稳定型泥盆系层序地层对比及层序地层格架分析，揭示了裂陷槽盆地的形成演化过程。指出构造幕式沉降是裂陷槽盆地层序发育和层序构成的主控因素。

黔桂地区泥盆系层序地层格架及相对海平面变化

志留纪末期的加里东运动 ,使黔桂地区的古地理格局发生了重大变化 ,早古生代的滇黔桂古陆演变为晚古生代的滇黔桂海。泥盆纪初期 ,海水由南而北逐渐海侵超覆 ,在泥盆系的底部形成一套海侵碎屑岩系地层 ;早泥盆世晚期的大规模海侵事件造成了明显的相分异 ,在习称的滇黔桂盆地中发育了若干孤立碳酸盐台地 ,这种“台—盆—丘—槽”的格局一直延续到晚泥盆世早期 ;而泥盆纪末期的紫云运动所造成的地壳抬升 ,又使晚泥盆世地层产生海退尖灭。因此 ,该地区的泥盆系构成一个二级构造层序 ,其中包含 13个三级沉积层序。在前人大量生物地层学研究的基础上 ,追索和对比不同沉积背景中的三级沉积层序的相序组构特征以及由其所代表的相对海平面变化 ,即可建立黔桂地区泥盆系的层序地层格架。层序地层格架较为充分地表现出三级沉积层序的两大特征——空间上相序的有序性和时间上环境变化的同步性 ,同时也明显地显示出地层记录中的两种相变面和两种穿时性。

华南泥盆纪海平面变化节律及圈层耦合关系

在加里东不整合面之上的华南纪盆系中，可识别出２０个正层序和相对应的海平面变化旋回，其中下泥盆统９个，中泥盆弦５．５个，上泥盆统５．５个。它们可归并为４个正层序组，最大海泛面分别位于ｓｕｌｃａｔｕｓ带，ｐｅｒｂｏｎｕｓ带（Ｄ＾３１），中、上ｖａｒｃｕｓ带（Ｄ＾２２）和ｇｉｇａｓ带。

华南板块泥盆纪层序地层及海平面变化

华南板块在泥盆纪时期属东亚古特提斯泛大洋中华夏古陆群的一部分，它和冈瓦那大陆与北方大陆群（北美、东欧、西伯利亚等）处于不同的构造背景下。华南泥盆系分布广泛、发育齐全，可以作为东亚泥盆系的典型地区。本文根据华南黔桂、龙门山及南秦岭泥盆系１０余条部面层序地层划分和对比，识别出２１个与二级海平面变化响应的层序和Ｔ—Ｒ旋回，并与Ｊｏｈｎｓｏｎ（１９８５，１９９２）和Ｒｏｓｓ（１９８８）以欧美大陆为代表的泥盆纪的Ｔ—Ｒ旋回进行了对比，并讨论二者之间的异同及其控制因素。

华南浅海相泥盆系吉维特阶和弗拉阶四射珊瑚组合特征

中泥盆世吉维特晚期(更精确的说是在中吉维特期末)发生的生物更替事件使大量的头贝、全部的泡沫珊瑚亚目以及大多数的绳珊瑚科和内板珊瑚科惨遭灭绝。晚泥盆世弗拉期出现了许多新生分子,诸如Micto-phyllum,Wapitiphyllum,Pseudozaphrentis,Peneckiella等。根据珊瑚的不同组合特征可以鉴别出它们的地质时代。华南自上而下可划分出4个四射珊瑚组合,分别为上泥盆统弗拉阶(Frasnian):4)Disphyllum-Wapitiphyl-lum组合(牙形类gigas或rhenana带和hassi-jamieae带),3)Mictophyllum-Pseudozaphrentis组合(牙形类asymmetricus带);中泥盆统吉维特阶(Givetian):2)Endophyllum-Sunophyllum组合(牙形类varcus带的中部和下部之上段),1)Stringophyllum-Paramixogonaria组合(牙形类hemiansatus带-varcus带最下部)。

华南上泥盆统和下石炭统层序地层学

本文把华南法门阶上部和杜内阶分为４个层序，自下而上依次命名为ＳＱ０、ＳＱ１、ＳＱ２和ＳＱ３。其中ＳＱ０属斯图年阶（Ｓｔｒｕｎｉａｎ）（泥盆系最顶部），其余３个层序归杜内阶。这４个层序可以与欧美等地同期的层序进行对比，表明当时的海平面升降变化及其由此而产生的沉积层序具有全球的一致性。层序地层学、生物地层学和事件地层学综合研究表明，华南浅海相区与Ｓｉｐｈｏｎｏｄｅｌａｐｒａｅｓｕｌｃａｔａ－Ｓ．ｓｕｌｃａｔａ界线一致的泥盆－石炭系界线不仅高于Ｃｙｓｔｏｐｈｒｅｎｔｉｓ带顶界，而且还应高于引起Ｃｙｓｔｏｐｈｒｅｎｔｉｓ绝灭的海退事件层的顶界。因此建议以Ｃｙｓｔｏｐｈｒｅｎｔｉｓ－Ｐｓｅｕｄｏｕｒａｌｉｎａ间隔带中最明显的一个海进面，即ＳＱ１的海进体系域的底界作为华南浅海相区泥盆－石炭系界线。这条界线与泥盆－石炭纪之交海退事件层的顶界正好一致。

华南中泥盆世艾菲尔期浅海相四射珊瑚的组合特征和古生物地理区系

虽然在华南中泥盆世艾菲尔期(Eifelian)较深水或斜坡相地层中产有许多国际标准的牙形类带化石,但在广阔的浅海相地层中却很难寻觅到其踪影。华南浅海相沉积地区是否缺失艾菲尔阶?在野外众多剖面的实地考察中表明,从下泥盆统埃姆斯阶到中泥盆统吉维特阶都是连续沉积,中间并没有发现地层的缺失或间断现象。浅海相的艾菲尔阶与其上覆的吉维特阶和下伏的埃姆斯阶都是连续沉积,说明可能是由于海水太浅,不太适合那些国际标准分子的生存而已。艾菲尔期中期末发生一次生物灭绝事件(Mid-Eifelian event),favositids,heliolitids和许多古老类型的珊瑚在地球上灭绝。华南艾菲尔期四射珊瑚可以划分成下、上两个完全不同的组合:1)Utara-tuiasinen sis-Sociop hyllum minor组合(牙形类partitus带—costatus带);2)Columnaria spinosa-Dendrostella praerhenana组合(牙形类australis带—kocklianus带)。

华南泥盆系法门阶浅海相四射珊瑚的组合序列

晚泥盆世弗拉期末F-F的生物灭绝事件,导致珊瑚以及许多浅海底栖生物灭绝,几乎整个法门期珊瑚群都处于残存阶段,华南地区目前只在湖南的个别地方发现少量的Smithiphyllum。直到法门期末珊瑚和其它一些造礁底栖生物开始复苏,出现了不少与典型泥盆纪珊瑚存在很大差别的新分子。华南泥盆纪最晚期(Strunian)的珊瑚可划分成上、下两个组合:上部Cystophrentis组合;下部Eocaninophyllum组合。泥盆—石炭纪之交的另一次生物灭绝事件,使新生的泥盆纪最晚期的珊瑚又遭灭绝。

华南泥盆系层序地层与岩石、年代地层界线间相关性探讨

以广西六景，象州大乐，桂林塘家湾及贵州独山与贵阳东北郊乌当剖面为例，在已有的地层，古生物，沉积相研究的基础上，开展了层序地层学研究，通过这项研究，认为那高岭组与莲花山组的界线是一年代地层，岩石地层及层序地层合一的界面；论证了大乐冲面应堂组的古琶段与贵州独山剖面的龙洞水组属于下泥盆统的可行性，总结了吉维特阶与艾菲尔阶间多处存在沉积间断面或沉积停滞面的客观事实。