Atrypid Brachiopods from the Upper Devonian Wangchengpo Formation (Frasnian) of southern Guizhou, China — Extinction Patterns in the Frasnian of South China

The Wangchengpo Frasnian section of Dushan County contains two atrypid brachiopod assemblages. The lower is characterized by the Atryparia （Costatrypa） dushanensis fauna that appears at the base of the Hejiazhai Member approximately in the falsiovalis to transitans conodont zones： the upper is characterized by the Radiatrypa yangi fauna, which appears in the Lujiazhai Member approximately correspondent with the hassi to Upper rhenana conodont zones. Atrypid brachiopods, together with other brachiopods from the Dushan section show that the Hejiazhai Member is of Frasnian age. Preliminary analyses of Frasnian atrypid brachiopods from sections of South China indicate that there are nine genera and subgenera including Atryparia （Costatrypa）, Kyrtatrypa, Spinatrypa, lsospinatrypa, Spinatrypina, lowatrypa, Desquamatia （Desquamatia）. Desquamatia （Seratrypa）, and Radiatr）pa. Atrypid species diversity did not change much through the Frasnian. On a regional scale in South China, most atrypid species went extinct prior to the Frasnian/Famennian boundary. At any specific locality or section, these atrypids became extinct about 20-40 m below the Frasnian/Famennian （F/F） boundary, within the linguiformis conodont Zone, marking this as the major extinction level. Three new atrypid species are described： Atryparia （Costatrypa） dushanensis, lowatrypa pseudobodini, and Radiatrypa yangi.     

泥盆系弗拉阶/法门阶之交事件沉积和海平面变化

在华南板块南部被动大陆边缘和西伯利亚板块南部活动大陆边缘弗拉阶/法门阶之交识别出7种物理事件相: 细粒钙屑浊积岩相、钙质角砾岩相、软变形灰岩相、含微球粒的粒泥灰岩相、凝灰质砾岩相、黑色页岩相和火山喷溢相.它们在法门阶下Palmatolepis triangularis带底部和/或上Palmatolepis rhenana带底部具有广泛的分布, 可能是两次陨击事件记录, 是良好的高分辨率年代地层对比标志.弗拉期/法门期之交的海平面变化不具有同步性和一致性, 可分辨出2种型式(阶跃型和渐进型) 和5种状态(弗拉期最末期下降→法门期最初期上升、弗拉期最末期上升→法门期最初期下降、弗拉期最末期上升→法门期最初期上升、弗拉期最末期下降→法门期最初期下降、弗拉期最末期与法门期最初期海平面变化不明显).弗拉阶/法门阶之交生物的阶梯状绝灭可能与从上Palmatolepis rhenana带底部至Palmatolepis crepida带不均匀分布的6次陨击事件密切相关.      

Reef Formations in the West Canada Basin and Their Oil and Gas Potential

Devonian reefs are widespread in the West Canada Basin in three regions: lower Givetian in the north (Elk Point subbasin), upper Givetian and middle Frasnian in the central part (framing of the Peace River Arch), and middle Frasnian (southern end of the basin). Each stage of reef formation ended with regression, and the last reefs terminated long before the Frasnian/Famennian biotic crisis and mass extinction. Reefs of this basin are petroliferous. Moreover, the structure of reservoirs is determined by the reef type, and the highest reservoir properties are related to bioherm varieties in reefs.     

广西象州中坪马鞍山剖面上泥盆统弗拉斯阶/法门阶(F/F)界线的研究

笔者在广西象州中坪马鞍山剖面上泥盆统“融县组”中部,首次发现了地层连续、岩性均一、牙形石带齐全的弗拉斯阶/法门阶界线层。这一界线层完全符合国际泥盆纪地层分会(SDS 1983)作出的关于划分弗拉斯阶/法门阶界线条件的决议。并与被誉为盆地相最佳剖面的西德Schmidt剖面(SDS Newsl.1986,no.1,Doc.C)的牙形石序列基本一致。无论是从岩石的均一性或是牙形石生物的连续性上,马鞍山剖面完全可与西德Schmidt剖面媲美,它是目前国内研究弗拉斯阶/法门阶界线的理想剖面之一。本文除了对这一界线进     

Patterns of cornulitid encrustation on the Late Devonian brachiopod shells from Russia

Upper Devonian brachiopods from the Central Devonian Field, Russia have been investigated with respect to encrustation patterns of cornulitids. These Palaeozoic encrusters were very characteristic component of shelly substrates during the Devonian and may serve as valuable objects for palaeoecological studies, especially those concerning the encrusters-host relationships. On the basis of rich material, it has been shown that cornulitid abundance significantly increased in the lower Famennian. Their disparity also increased from one morphotype (robust) present in the upper Frasnian to two distinct morphotypes (robust and slender, presumably representing two different species) in the lower Famennian. The analysis of the spatial occurrence of cornulitids on two dominant lower Famennian brachiopod species (Cyrtospirifer zadonicus and Ripidiorhynchus huotinus) showed, that these encrusters preferred the marginal parts of the shells. This, together with a dominant directional growth of cornulitids toward the commissure, indicates that cornulitids benefited from food brought by feeding currents produced by the brachiopod’s lophophore. The unequivocal evidence for syn vivo association of the cornulitids and their brachiopod hosts is the presence of distinct shell malformations caused by cornulitid growth affecting the host’s shell-secreting epithelium, preserved on some lower Famennian specimens. Interestingly, these malformations were caused by a slender cornulitid morphotype only. Thus, it is evident that during food gathering from the inhalant currents, this cornulitid species exerted a distinct, negative effect on the brachiopod – a deviation of its shell growth. In this case, we may consider this particular cornulitid species as ectoparasite rather than commensal with respect to its host.     

新疆巴楚地区的“Icriodus de formatus”（牙形刺）与巴楚组和东河塘组的时代

新疆巴楚小海子剖面发现的牙形刺被有关作者鉴定为Icriodus de formatus Han，并将弗拉斯阶-法门阶界线置于巴楚组中段底部，认为东河塘组的时代为弗拉斯期或更老。但巴楚小海子剖面的牙形刺不是Icriodus de formatus，泥盆系-石炭系的界线应划在巴楚组中段下部之内，东河塘组的时代很可能是法门期的。     

滇西保山地区晚泥盆世至早石炭世早期牙形石生物相

一、绪言保山地区是滇西泥盆系和下石炭统出露的主要地区之一,以前已有不少报道。近年来,由于该地区特殊的大地构造位置,引起了国内外广大地质工作者的密切注意,因而对泥盆石炭纪地层及其古生物的研究也更加深入。保山地区的上泥盆统目前暂分为何元寨组和整合其上的大寨门组,前者底部尚属中泥盆统(龚大明等,待刊)。下石炭统下部称鱼洞组。何元寨组在其命名剖面施甸何元寨主要是一套中层灰岩和泥灰岩,厚约220m,腕足、珊瑚、层孔及苔藓动物丰富,向东北至大寨门、由     

广西弗拉阶—法门阶之交碳同位素与分子地层对比研究

对广西 7条碳酸盐台地、斜坡和盆地相剖面的碳同位素与分子地层的对比研究表明 ,在牙形石生物地层带或偏心率轨道旋回层建立的等时地层格架内 ,跨越弗拉阶—法门阶 (F—F)之交的碳同位素组成在 1 4Ma内不具一致性 ,表现为正偏、负偏和无偏 3种模式。主要的分子化石包括正构烷烃、类异戊二烯烃、萜类、甾类 ;其母体生物源主要为海源浮游植物、浮游动物、底栖非光合作用的菌类和陆源高等植物。其中浮游植物和浮游动物是构成F—F事件期碳酸盐台地、斜坡和盆地相生物量的主体。分子地层参数及其与碳同位素的关系显示 ,F—F之交广西海域高温、高盐、缺氧、多风 ;Pr Ph与δ1 3C曲线的变化表现为负相关。地层的加积方式 (加积、进积和退积 )、堆积速率、缺氧程度、分子化石类型和丰度是影响广西F—F之交碳同位素组成变化的主要因素。退积序列、快速堆积、缺氧程度和有机质埋藏量增加通常对应δ1 3C值增加。由于分子地层参数能提供生物与环境这两大直接影响碳同位素组成的量化信息 ,因此 ,碳同位素与分子地层的对比研究对正确解释碳同位素的特征和成因具有重要意义     

Microbial mounds prior to the Frasnian‐Famennian mass extinctions,Hantang, Guilin,South China

Late Frasnian mounds of the Yunghsien Formation, Guilin, South China, developed as part of the Guilin platform, mostly in reef‐flat and platform margin settings. Microbial mounds in platform margin settings at Hantang, about 10 km west of Guilin, contain Frasnian biota, such as Stachyodes and Kuangxiastraea and, thus, occur below the Frasnian‐Famennian mass extinction boundary. Platform margin facies were dominated by microbes, algae and receptaculitids. Massive corals and stromatoporoids are not common and rarely show reef‐building functions as they did in Givetian time. The margin mounds are composed of brachiopod‐receptaculitid cementstone, and a variety of boundstones that contain Rothpletzella, Renalcis, thrombolite and stromatolite. Other microbial communities include Girvanella, Izhella, Ortonella and Wetheredella. Solenoporoid algae are abundant locally. Zebra structures and neptunian dykes are well‐developed at some intervals. Pervasive early cementation played an important role in lithification of the microbial boundstones and rudstones. Frasnian reefs of many regions of the world were constructed by stromatoporoids and corals, although a shift to calcimicrobe‐dominated frameworks occurred before the Famennian. However, the exact ages of many Frasnian margin outcrops are poorly constrained owing to difficulties dating shallow carbonate facies. The Hantang mounds represent a microbe‐dominated reef‐building community with rare skeletal reef builders, consistent with major Late Devonian changes in reef composition, diversity and guild structure occurring before the end of the Frasnian. A similar transition occurred in the Canning Basin of Western Australia, but coeval successions in North America, Western Europe and the northern Urals are either less well‐known or represent different bathymetric settings. The transition in reef‐building style below the Frasnian‐Famennian boundary is documented here in the two best exposed successions on two continents, which may have been global. Set in the larger context of Late Devonian and Mississippian microbial reef‐building, the Hantang mounds help to demonstrate that controls on microbial reef communities differed from those on larger skeletal reef biota. Calcimicrobes replaced stromatoporoids as major reef builders before the Frasnian‐Famennian extinction event, and increasing stromatoporoid diversity towards the end of the Famennian did not result in a resurgence of skeletal reef frameworks. Calcimicrobes dominated margin facies through the Famennian, but declined near the Devonian‐Carboniferous boundary. Stromatolite and thrombolite facies, which occurred behind the mound margin at Hantang, rose to dominate Mississippian shallow‐water reef frameworks with only a minor resurgence of the important Frasnian calcimicrobe Renalcis in the Visean when well‐skeletonized organisms (corals) also became volumetrically significant frame builders again.     

Palynostratigraphy of the Zorritas Formation,Antofagasta region,Chile: Insights on the Devonian/Carboniferous boundary in western Gondwana

The Middle Member of the Zorritas Formation in the Antofagasta region of northern Chile, yielded terrestrial and marine palynomorph assemblages which span the Devonian/Carboniferous boundary. The assemblages show a clear predominance of terrestrial palynomorphs with 70 miospore species, 18 marine phytoplankton species, two non-marine algae and one chitinozoan species, all coming from 15 productive levels. Palynomorphs are poorly preserved and most of them are reworked. Three palynological associations are recognized based on miospores. These are assigned to the Tournaisian–Visean, Tournaisian and probable latest Famennian. Age assignments are discussed in the frame of the spore zonal schemes established for Euramerica and western Gondwana. The stratigraphical distribution of spores allows the identification of the probable position of the Devonian/Carboniferous boundary within the Zorritas Formation. This system boundary is proposed for the first time in Palaeozoic sedimentary rocks of northern Chile. The presence of Gondwanan typical miospore species indicates affinities with this palaeocontinent even though the Tournaisian and Tournaisian–Visean miospore associations support the cosmopolitanism already suggested for the early Carboniferous flora. The significant number of reworked palynomorphs together with the sedimentological analysis of the studied sections, suggest that these deposits were severely impacted by the climatic change and major sea level fluctuations. Similar conditions were recorded in coeval western Gondwana basins.     

Frasnian–Famennian crisis in the Malaguide Complex (Betic Cordillera,Spain)

Devonian sediments of the Malaguide Complex potentially could include the Frasnian–Famennian boundary, one of the five greatest Phanerozoic biotic crises. Conodont biofacies and microfacies of carbonate clasts from a pebbly mudstone underlying Tournaisian radiolarites allows identification, for the first time in the Malaguide Complex, of Devonian shallow marine environments laterally grading to deeper realms. The clasts yielded Frasnian conodont associations of the falsiovalis to rhenana biozones, with six biofacies that reveal different environmental conditions in their source areas. Source sediments were dismantled and redeposited within the pebbly mudstone, whose origin is tentatively related to one of the events that are associated worldwide with the Frasnian–Famennian crisis. The latter is recorded, in two equivalent Malaguide pelagic successions, by stratigraphic discontinuities, and it was, probably, tectonically and/or eustatically controlled, as in other Alpine‐Mediterranean Paleotethyan margins.     

Middle to Late Devonian basin evolution in the Rügen area,NE Germany

The Middle to lower Upper Devonian succession of the Rügen Depression in NE Germany consists of largely clastic sediments, whereas the Upper Devonian deposits are mixed carbonate and clastic. Petrographic and geochemical data suggest that the sediments were deposited in a cratonic or recycled setting. Deposition was largely confined to a fault-bounded basin, located between two structural highs. During the Devonian, the Rügen area underwent evolution from a continental and marginal marine area during the Eifelian-early Frasnian to a deeper marine environment during the late Frasnian-early Famennian. By the latest Famennian, an open-shelf carbonate-facies environment was established.     

Reef Formation during Mass Extinction Events: Frasnian—Famennian and Devonian—Carboniferous Boundaries

An analysis of the development of Late Devonian reefs in a number of regions worldwide shows that reef formation decreased gradually and discontinuously during the second half of the Frasnian and was completely terminated in some places. These events were associated with regression stages. The final Frasnian regression and Kellwasser event, which led to the biotic crisis, resulted, first, in the quantitative reduction of reef formation in the Famennian and, second, in the change of the frame reef formation by the formation of microbial mud mounds in the Famennian.     

Famennian microbial reef facies, Napier and Oscar Ranges, Canning Basin, western Australia

Following the Frasnian–Famennian mass extinction, which eliminated most skeletal reef-building fauna, the early Famennian reefs of the Canning Basin were constructed primarily by reef-framework microbial communities. In the Napier and Oscar Ranges, the Famennian reef complexes had high-energy, reef-flat depositional environments on a reef-rimmed platform that transitioned into low-energy, deep-water reefs growing in excess of 50 m below sea level. High-energy, reef-flat depositional environments contain doming fenestral stromatolites that grade into porous thrombolites and are associated with coarse-grained sandstones and grainstones. The reef-margin subfacies contains mounds of microdigitate thrombolites, which are more delicate than the reef-flat thrombolites and locally contain abundant red algae, Girvanella, renalcids and sediment-filled tubes. Within the thrombolites, the red algae are in upright growth positions, suggesting that the thrombolites are largely composed of carbonate that precipitated in situ. Reefal-slope environments are dominated by Wetheredella and Rothpletzella with locally abundant Girvanella, renalcids and Uralinella. In reefal-slope strata, delicate fans and microdigitate stromatolites of Wetheredella and Rothpletzella are often oriented horizontal or diagonal to bedding and are interpreted as syndepositionally toppled over. Most mesoscale microbial community structures contain several species of microbial fossils, and no single microbial species appears to have controlled the morphology of the community structure. Therefore, the depositional environment must have determined the distribution and morphology of the stromatolites, thrombolites and other microbial community structures. The adaptability of microbial communities to various reef environments allowed them to fill ecological niches opportunistically after the Frasnian–Famennian mass extinction.     

西藏泥盆纪海相红层的分布与时代

在作者及前人对西藏地区泥盆纪地层学、古生物学等资料研究的基础上,作者对该区泥盆纪海相红层进行了初步的系统整理。共识别出6层(套)海相红层,它们是:早泥盆世扎西岗组海相红层(洛赫柯夫阶—布拉格阶)(XDRB1)和春节桥组上部海相红层(埃姆斯阶)(XDRB2),中泥盆世海通组海相红层(艾费尔阶)(XDRB3)和丁宗隆组底部海相红层(吉维阶)(XDRB4),晚泥盆世查果罗玛组(下部)海相红层(弗拉斯阶)(XDRB5)和羌格组顶部海相红层(法门阶)(XDRB6)。所有海相红层均形成于近岸或浅水碳酸盐岩台地环境,因此,属于浅水-半深水陆棚红层,此外,还讨论了中国南方泥盆纪海相红层的分布及全球法门期海相红层广布事件。     

Zircon dating of Devonian‐Carboniferous rocks from the Bombala area,New South Wales

Zircons from two igneous and two sedimentary units in the Bombala area of southeastern New South Wales have been examined by the sensitive high resolution ion microprobe (SHRIMP) to establish a timeframe in which to interpret these rocks. Previous studies have correlated these rocks with Late Devonian units of the south coast, solely upon the basis of stratigraphy and lithology as palaeontological evidence was absent. The two igneous units are the Hospital Porphyry and Paradise Porphyry occurring beneath the sedimentary units. Both give a Frasnian age that can be correlated with the Boyd Volcanic Complex. The sedimentary samples are from the basal and upper sections of the Rosemeath Formation, a fluvial ‘redbed’ consisting of conglomerate, coarse sandstone, and associated red siltstone and mudstone. Detrital zircons from the basal conglomeratic section at Kilbrechin indicate a dominant provenance from local Silurian granites and volcanics and a maximum depositional age that can be correlated with the Frasnian‐Famennian Merrimbula Group. However, detrital zircons from the upper coarse sandstone section of the Rosemeath Formation at Endeavour Lookout challenge the positive correlation trend with a lack of Silurian‐age grains and a presence of grains ranging from Late Devonian to Early Carboniferous in age. These results imply either that the south coast correlation is not valid for the upper sequences, or that the Merrimbula Group sequences also extend upward into the Carboniferous. The general coarseness of the Rosemeath Formation also suggests a relatively local provenance. No Early Carboniferous source is known in the immediate vicinity suggesting that Early Carboniferous igneous activity in this region of the Lachlan Orogen may have been more extensive than is currently realised.     

广西黎塘孤立台地吉维特阶-法门阶碳酸盐台地生态系到菌藻生态系的演变及其意义

自泥盆纪埃姆斯期, 广西受陆内裂陷影响, 形成碳酸盐台地与台沟间列的构造格局.吉维特期开始, 六景及相邻的黎塘一带逐渐形成孤立台地的沉积背景.吉维特期, 六景剖面的民塘组为以竹节石为特色的礁前斜坡生态系, 尽管目前没有出露生物礁, 从礁前角砾岩可以恢复曾经存在的礁生态系.而黎塘一带塘家湾组为以珊瑚、层孔虫、腕足类为主要特色的台地生态系.弗拉斯期, 六景剖面的谷闭组则为少量珊瑚、腕足、层孔虫为特色的局限-半开放台地生态系.黎塘一带的桂林组仍为以珊瑚、层孔虫、腕足类为主要特色的台地生态系.六景、黎塘地区自法门期开始发生生态系突变, 六景剖面的融县组和黎塘一带的东村组发育藻礁丘或藻席为特色的藻生态系.该生态系的突变是F-F生物群集绝灭造成的生物类群突变的结果.生态系的特征也与吉维特-弗拉斯期烃源岩的形成、演化密切相关.      

广西全州地区晚泥盆世牙形石和腕足类生物地层

广西东北部泥盆系发育良好,化石丰富,对研究中国华南地区泥盆纪生物地层具有重要意义。对广西全州地区东山剖面上泥盆统佘田桥组、锡矿山组和孟公坳组进行了系统的化石采集及室内分析,共获得104枚牙形石化石和34件腕足类化石。经鉴定,牙形石共21属19种,腕足类化石共6属9种。根据化石种属在东山剖面上的分布,自下而上可划分出8个牙形石带:Icriodus brecis带,Schmidtognathus hermanni-Polygnathus cristatus带,Schmidtognatus wittekindtii带,Palmatolepis linguiformis带,Palmatolepis triangularis带,Palmatolepis rhomboidea带,Icriodus cornutus带和Palmatolepis gracilis manca-Rhodalepis polylophodontiformis带,指示研究区内佘田桥组、锡矿山组、孟公坳组分别对应国际年代地层单位的弗拉斯阶上部、法门阶下部和法门阶中上部,并通过Palmatolepis triangularis的首现确立了该地区弗拉斯阶和法门阶(F-F)的界线;在东山剖面共划分出2个腕足类组合带:弓石燕(Cyrtospirifer)组合带和云南贝(Yunnanella)-帐幕石燕(Tenticosififer)组合带,它们分别与东山剖面中牙形石Palmatolepis falsiovalis-Palmatolepis linguiformis带、Palmatolepis rhomboidea-Palmatolepis marginifera带对应。     

Cephalopod limestone deposition on a shallow pelagic ridge: the Tafilalt Platform (upper Devonian, eastern Anti-Atlas, Morocco)

As a result of early Variscan tectonic movements and of differential subsidence, a platform and basin topography was created along the northern margin of the Sahara Craton during the late Devonian. In the Moroccan Anti-Atlas Mountains, the Tafilalt Platform is an approximately N-S running ridge which developed since the late Middle Devonian. It separated a slowly subsiding shallow basin in the east (Tafilalt Basin) from a rapidly subsiding furrow in the west (Mader Basin). Platform deposits are characterized by highly reduced thicknesses, shallow subtidal to supratidal deposits in the late Frasnian and by unconformities at the Lower/Upper Frasnian and the Frasnian/Famennian boundaries. After a local transgression over emergent areas in the north, water depth probably never reached more than several tens to about 100 m in the lower Famennian. Cephalopod limestones of this age, deposited on the platform, represent a very diverse facies pattern comprising quartz-rich brachiopod coquinas, crinoidal limestones, thick-bedded cephalopod limestones and nodular limestones. Sedimentation rates ranged from 1 to 5 mm/ 1000 yr. In the late Famennian more uniform marl and nodular limestone facies suggest slightly deeper environments. Platform margins are characterized by higher rates of subsidence, debris flow deposits and slump structures. In the relatively shallow Tafilalt Basin, marls with intercalated nodular limestones were deposited. In the Mader Basin, sandy and calcareous turbidites suggest deeper water conditions in the late Devonian. During the Strunian/Tournaisian the whole area was overwhelmed by a thick deltaic sequence. The general facies distribution is in agreement with depositional models of other Upper Devonian and Lower Carboniferous cephalopod limestones in the European Variscan orogenic belts. In all these cases, condensed cephalopod limestones occupy a distinct palaeogeographic position in predictable facies sequences that reflect pre-orogenic phases in the Variscan geodynamic cycle. Moreover, close parallels exist with condensed sequences in the Triassic and Jurassic that occur in a very similar position within the Alpine orogenic cycle.     

南秦岭镇安盆地泥盆纪沉积体系与古地理演化

通过对南秦岭镇安盆地泥盆系露头剖面的详细研究，将该区泥盆系划分为海岸、陆棚、斜坡-盆地及碳酸盐岩四种沉积体系，沉积体系及岩相组合具有南北向分异、东西向展布的特点。从地层由南向北超覆，相类型由北部的近源相至南部的远源相，以及碎屑搬运方向总体从北向南的变化趋势，更加确定了以前认为北部存在一个消失的古陆的认识。根据沉积体系及岩相组合的演化，把研究区的沉积盆地演化归纳为初始坳陷、拗陷和强裂断陷三个发展阶段，在不同的发展阶段具不同的环境格局，由北向南表现为：D2吉微特期古陆-海岸-陆棚；D2弗拉斯期古陆-碳酸盐台地-陆棚；D3法门期块断隆起-海岸-陆棚-斜坡-盆地-台地。