A New Species of Amsassia from the Ordovician of Korea and South China: Paleobiological and Paleogeographical Significance

A new species of the probable calcareous alga Amsassia, A. koreanensis, is recognized from the Duwibong Formation (Middle Ordovician, Darriwilian) of the Taebaeksan Basin in mid-eastern Korea. This is the first report of the genus from the Korean Peninsula, expanding its geographical range to the eastern Sino-Korean Block. The new species also occurs in the Xiazhen Formation (Upper Ordovician, Katian) at Zhuzhai in the South China Block. Amsassia koreanensis is the smallest species of this modular genus, having a maximum module diameter of 0.28 mm. Module increase is by bipartite, tripartite and quadripartite types of longitudinal axial fission, but unlike other species of the genus, quadripartite fission is common. The types of fission are comparable to those in some Tetradiida (now Prismostylales, florideophycean rhodophyte algae), although the processes of fission are different. The distribution of A. koreanensis further strengthens the biogeographical connection between the Sino-Korean and South China blocks, suggesting that these two paleocontinents were located closer together during the Middle to Late Ordovician than previously speculated.     

Biostratigraphy of Paleozoic Tabulata and Heliolitida of Central Asia

In Soviet Central Asia (Tien Shan and Pamirs) corals are unknown in the Lower Ordovician, rare and unstudied in the Middle Ordovician. The tabulate coral record from the Upper Ordovician, Silurian and Devonian is excellent and numerous common and Key genera and species are enumerated for each stage or substage. Tabulata reached their peak development in the Wenlock, and had markedly decreased in numbers and variety by late Middle Devonian time. Tabulata are rare in Upper Devonian and later rocks but occur through the Carboniferous and into the Upper Permian. -- W. A. Oliver, Jr.     

新疆塔中地区奥陶系地层划分与岩性研究

新疆塔中地区奥陶系分布广泛。主要根据化石、岩性特征、对比等将研究区内奥陶系划分为三统四组:下奥陶统蓬莱坝组与下伏上寒武统丘里塔格下亚群呈假整合接触,鹰山组归为中下奥陶统,一间房组划为中奥陶统,良里塔格组划归上奥陶统。良里塔格组可细分为3个岩性段,鹰山组可划分为4个岩性段。良里塔格组与鹰山组之间存在区域地层缺失和不整合,桑塔木组与上覆地层呈不整合接触,与下伏良里塔格组由于所处的位置不同呈整合或不整合接触。     

从塔里木盆地看中国海相生油问题

塔里木盆地厚达 5～ 7km的海相寒武、奥陶系 ,可划分出下、中寒武统和中、上奥陶统两套工业性烃源岩。油源对比证实 :盆地目前保存下来的海相成因工业性油藏 ,主要来源于中上奥陶统泥灰岩。正是因为塔里木盆地比四川、鄂尔多斯盆地多了一套中等成熟的中上奥陶统油源岩 ,所以能够找到海相油田。笔者认为 :海相工业性烃源岩不必很厚 ,但w (TOC)应≥0 .5% ,碳酸盐岩要含泥质 ;海相源岩往往并不发育在凹陷中心 ,而发育在 4种有利沉积相带上 ;碳酸盐岩具有“双重母质”的特点 ,浮游藻类偏油 ,底栖藻类偏气。海相源岩的形成模式有“保存模式”和“生产力模式”两种 ,分别对应于塔里木寒武系和中上奥陶统烃源岩。塔里木古生代克拉通早期活动、晚期稳定、持续降温的演化史 ,有利于海相油气的多期成藏和晚期保存。     

First biostratigraphical constraints on the pre-Upper Ordovician sequences of the Pyrenees based on organic-walled microfossils

The first age constraint on the upper part of the pre-Upper Ordovician series of the Pyrenees is presented. Data are based on acritarchs from the Jujols Group in the La Molina area on the southern slope of the Canigó massif, near the Upper Ordovician unconformity. The new data allow us to attribute a Late Cambrian (Furongian) to Early Ordovician age to the upper part of the Jujols Group and to support the absence of well developed Middle Ordovician strata in the Pyrenees. Our results confirm the occurrence of an Upper Ordovician unconformity and highlight the “Sardic” affinity of the pre-Upper Ordovician sequences in the Pyrenees. These sequences differ markedly from the pre-Upper Ordovician series of the Iberian Massif.     

Geochemical and mineralogical influence of Ordovician Island Arcs on epicontinental clastic sedimentation. A study of Lower Palaeozoic sedimentation in the Oslo Region, Norway

The mineralogy and geochemistry of clastic sediments in the 1000 m thick Lower Palaeozoic marine sequence of the Oslo Region is discussed on the basis of 200 chemical (XRF) and mineralogical (X-ray diffractometer) analyses. The composition of these sediments is considered to largely be a function of the relative supply from land of the continental shield (Baltic Shield) and from island are systems to the NW in the Trondheim Region. The relative abundance of chlorite and illite is discussed in light of recent knowledge about their distribution in modern oceans. Middle Cambrian to Lowermost Ordovician black shales contain only illite as the dominant clay mineral and have a high potassium content. These sediments are thought to be derived from land on the continental shield, which during this period probably had a low relief and a warm climate where chlorite is not stable. Chlorite is introduced first in the Arenigan (L. Ordovician) and this is interpreted as evidence for transport of clastic chlorite from a developing island arc system in the Trondheim Region to the west. The highest chlorite/illite ratio in the Middle and Upper Ordovician sediments of the Oslo Region corresponds to a Taconic orogenic phase. The content of clastic chlorite in the Lower Palaeozoic of the Oslo Region is thus shown to be a sensitive indicator of palaeoenvironment and tectonic evolution of the Caledonian geosyncline. This conclusion is also supported by a systematic increase in Mg, Fe, Ni, and Cr from Lower to Middle and Upper Ordovician beds. High Cr values exceeding 0–1 % Cr in the Middle/Upper Ordovician shales are due to small grains of clastic chromite resembling those in the serpentinites of the Trondheim Region. This also suggests transport from exposed island arcs onto the epicontinental shelf.     

Microconchids

Microconchids are a group of tiny, encrusting tubeworms. They appeared in the Late Ordovician, some 450 Myr ago, flourished during the rest of Palaeozoic and Triassic, and became extinct in the Middle Jurassic. Their morphological resemblance to the sedentary polychaete genus Spirorbis, very common in marine environments, misled various authors for decades. This mistake originally gave the genus Spirorbis an enormous stratigraphical range, from Ordovician to Recent. Indeed, microconchids provide an excellent example of evolutionary convergence with respect to both their morphology and ecology. In the late 1970s these ‘spirorbids’ were interpreted as vermetid gastropods on the basis of the inner architecture and microstructure of their tubes. This idea, however, was challenged in the 1990s when detailed microstructural investigation showed them to be neither polychaetes nor gastropods, but closely related to an extinct Palaeozoic enigmatic group of organisms called tentaculitids. No thorough investigation of their origin, phylogeny and ecology has ever been conducted, but new data concerning their palaeobiology has come to the light during the last few years.     

新疆晚奥陶世鱼形动物

本文记述了新近发现的保存较好、具甲胄确切证据的奥陶纪鱼形动物化石。该化石采自新疆塔里木盆地巴楚县一间房地区依朗里克塔格山上奥陶统恰尔巴克组滨-浅海紫红色砂屑灰岩中。对所发现的鱼形动物新属新种——优雅郝氏鱼(Haoina elegantia gen.et sp.nov.)进行了生物学系统描述。郝氏鱼是我国奥陶纪已知保存较完整的古脊椎动物化石,是新科——郝氏鱼科(Haoinaspididae fam.nov.)的科型属。并依据其独特的生物学特征建立新目——郝氏鱼目(Haoinaspidiformes ord.nov.),置于无颌超纲甲胄鱼纲之下。依据牙形石化石带的时代分布,恰尔巴克组属于晚奥陶世早期,即桑比期。新发现的鱼形动物化石包括一个较完整的背侧甲片,化石表面覆盖具有特征纹饰的外骨骼甲胄,大致可分为四种不同的类型;松果区位于头甲中前部;有宽大而深陷的背侧位眶凹,位于松果体稍前的两侧,瘤突组成的嵴在凹壁呈同心圆排列,眶凹呈喇叭状开口。感觉沟系统发育,具眶上感觉沟、主侧线感觉沟和嵴间感觉沟,显示出真皮及皮下组织的管孔系统结构。根据与其他地区鱼形动物的对比和生物特征,建立了具有古特提斯特色的新的鱼形动物古地理分区——奥陶纪郝氏鱼类-巴楚鱼类古脊椎动物生物地理区系。这一化石是我国乃至亚洲目前已知发现最早具外骨骼确凿证据的鱼形动物。     

鄂尔多斯盆地两种不同成因古隆起的特征及其在油气勘探中的意义

鄂尔多斯盆地位于华北克拉通西部，是中国大型含油气盆地之一。基底结构复杂，具有明显的不均匀性，基底顸面表现为2个大型隆起，北部为伊克昭盟隆起，中南部为中央古隆起。伊盟隆起具有继承性，继承了结晶基底的形态，上石炭统太原组直接覆盖在变质基底之上。中央古隆起则是盆地西缘和南缘在元古宙秦(岭)祁(连)贺(兰)三又裂谷基础上发育的古元古代被动大陆边缘，并发展成为主动大陆边缘，于中奥陶世—中石炭世秦祁海槽向东、向北方向俯冲碰撞，形成古生代前陆盆地，其前隆部分平面上构成了L形的中央古隆起。     

Crown of crinoid from Middle Ordovician of Podkamannaya Tunguska river

A new species is described, Tunguskocrinus ivanovae, representing a new genus and family of the superfamily Homocrinicae. The crinoid was found in Middle Ordovician rocks in Siberia.—P. M. Kier.     

Lower Palaeozoic unconformities in an intracratonic platform setting: glacial erosion versus tectonics in the eastern Murzuq Basin (southern Libya)

The stratigraphic record of the eastern Murzuq Basin has been importantly influenced by deformation resulting in angular and/or deeply erosional unconformities, though the overall context is intracratonic. Major transgressive events and the Ordovician glaciation are nevertheless documented, allowing the delineation of tectonic-, eustasy- or climate-driven unconformities. Lower Palaeozoic key events and related unconformities that characterize the North Gondwana platform have therefore a signature in the eastern Murzuq Basin. The basement/cover unconformity, also known as the infra-Tassilian surface, truncates all the deformed and metamorphosed Lower Cambrian and older rocks. Above is a ?Middle Cambrian to Lower Ordovician megasequence (Murizidié and Hasawnah Fms.), which is in turn truncated by an intra-Ordovician, angular unconformity. This megasequence is unconformably overlain by a Middle Ordovician (Hawaz Fm.) to Silurian (Tanzzuft and Akakus Fms) megasequence, which includes the Upper Ordovician glaciogenic unit (Mamuniyat Fm.), bounded at the base by a polygenic glacial erosion surface showing corrugated glacial lineations, tillites, and glaciotectonic structures. The Middle Ordovician to Silurian megasequence is finally truncated by a base-Devonian, angular unconformity overlain by fluvial sandstones. Regarding the possibility that those fluvial deposits may be as younger as Late Devonian in the eastern Murzuq Basin based on palaeoflora, the so-called Caledonian unconformity might be here a much younger (mid-Eifelian?) surface, and the occurrence of the Lower Devonian “Tadrart Fm.” is questioned. The Upper Ordovician glacial erosion surface, which is sometimes referred to as the Taconic unconformity, usually truncates Middle Ordovician strata in the Murzuq Basin but reaches significantly deeper stratigraphic levels in places that have been previously involved in the intra-Ordovician deformation event. In the Murizidié (southeastern Murzuq Basin), the infra-Tassilian surface, the intra-Ordovician unconformity, and the Upper Ordovician glacial erosion surface amalgamate together. Here, an estimate of the glacial erosion depth cannot be derived from the stratigraphic hiatus beneath the glacial incision, the main part of which relate to the intra-Ordovician tectonic event. The Upper Ordovician climate-related glacial erosion surface is not a valid unconformity for a sequence hierarchy framework of the Lower Palaeozoic, although it presents most of the physical attributes of tectonic-driven unconformities.     

綦江观音桥中上奥陶统微量元素地球化学特征

中上扬子地区广泛发育着完整的奥陶系地层,其中的上奥陶统宝塔组中出现地球化学异常。綦江观音桥剖面中上奥陶统地层的地球化学研究表明,宝塔组中V、Ni出现亏损,V/(V+Ni)值表现为低值,而Th/U、Ni/Co与Sr/Ba值却表现为高值,判断晚奥陶世中宝塔期为强氧化气候,海水突然加深,是一次明显的海侵过程。中上奥陶统地球化学异常是华夏板块与扬子板块相互作用的结果。     

A Middle Ordovician crinoid from the beach gravels of Ristna Cape,Hiiumaa Island,Estonia

Reworked fossils may be exotic, but more typically are locally derived. Echinoderms have only rarely been identified from beach clasts; most commonly, these are Upper Cretaceous echinoids from the Chalk. A pebble collected from a beach in Estonia has yielded a moderately well preserved specimen of the crinoid stem, Baltocrinus (col.) antiquus (Eichwald). This species is typical of the Baltic region, only being known from the Middle Ordovician (Darriwilian) of Estonia, but is exotic because the local outcrop is Upper Ordovician to Silurian.     

New genus of bryozoans of the family Phylloporinidae

A new genus, Hemibashkirella (type species: H. bifurcata, n. sp.), is erected for a phylloporinid bryozoan found in the Middle Devonian (Eifelian stage) of Armenia. Phylloporinids have not hitherto been reported from the Devonian. The new genus appears to be a link between Chasmatoporella Nekhoroshev of the Ordovician and Silurian and Bashkirella Nikiforova of the Carboniferous and Permian. Hemibashkirella differs from Chasmatoporella in having more than two rows of zooecia on the branches and in lacking a median carina. It differs from Bashkirella in having a more sharply defined linear axis and a simpler capillary system.—H. Duncan.     

塔中地区中及上奥陶统沉积相

中及上奥陶统是塔中地区主要的油气勘探目的层系之一。在综合地层划分对比的基础上，分析了塔中地区不同沉积相的分布规律。礁滩沉积和斜坡沉积构成了台地边缘相的主体。碳酸盐台地上不同期次发育的边缘相是重要的油气储集体。它们主要分布于塔中I号断裂构造带和TZ10井构造带和塔中南缘断裂构造带上，沉积厚度相对较大。因此，可以得出这样的结论，这种分布状况代表了塔中地区构造对沉积相带的控制作用。通过大量二维及三维地震资料解释分析，发现在塔中广泛分布的丘状隆起地震相、楔状前积反射地震相和杂乱反射地震相相同样多沿主要构造线延伸，内部反射杂乱，成乱岗状反射。把已经认识的沉积相类型和这些地震相的分布特征相比较，可以确定这种地震相就是碳酸盐台地边缘相沉积体。这样，就有可能利用丰富的地震资料，预测有利油气富集的储集体的展布规律。     

Ammonites and infrazonal subdivision of the Dorsoplanites panderi zone (Volgian Stage, Upper Jurassic) of the European part of Russia

Eight biohorizons, four of which were previously distinguished in Central Poland and four new (contradictionis, pommerania, kuteki, and pilicensis), were identified in the Dorsoplanites panderi zone of the Upper Jurassic Middle Volgian Substage of the European part of Russia on the basis of the succession of ammonites of the Zaraiskites genus. The peculiarities of variations of the ammonite complexes in space and time testify to the stepwise warming during the Panderi Chron and the occurrence of the significant latitudinal temperature gradient in the Middle Russian Sea. New species Zaraiskites kuteki is described.     

鱼卡煤田东部含煤地层划分探讨

鱼卡煤田是青海省重要的煤炭资源基地,主要含煤地层为中侏罗统。区内含煤地层角度不整合于奥陶系上统滩间山群之上。根据野外实剖地质剖面岩性特征自下而上划分为侏罗系中统大煤沟组、上统采石岭组、红水沟组。其中大煤沟组分为下含煤段、砂岩段、上含煤段、页岩段;采石岭组分为下部砂岩段、上部砂泥岩段。大煤沟组与以往划分的大煤沟组、石门沟组相当。     

Preliminary observations on pre-Devonian of southern Kiangsi

Existence of Sinian to lower Paleozoic formations in this area is confirmed by discoveries made since 1957, by the faculty of the Geological Department of Nanking University, of abundant fossils including graptolites, trilobites and Protospongia. Pre-Devonian strata here exceed 12,000 m in thickness and belong to typical geosynclinal sediments. Summarized in ascending order, these strata are - 1) pre-Sinian (lower Proterozoic), including the Ta-yu and Li-ch'un groups; 2) Sinian, with the Ku-t'ing group; 3) Lower Cambrian, with the Ho-t'ang formation; 4) Middle and Upper Cambrian, Pa-ch'un group; 5) Lower Ordovician, including Yin-tu-hu and Ning-kuo formations; Middle Ordovician, Hu-lo formation; Upper Ordovician, Sha-ch'un group. -- Authors.     

Trilobite biostratigraphy in the Middle and Upper Ordovician of western Leningrad Region

Biostatigraphical significance of trilobites of the Middle and Upper Ordovician in the eastern Baltic area is discussed, based on a new material from numerous outcrops from Leningrad Region. The study of the Middle and Upper Ordovician trilobites in the Mednikovo, Viivikonna, Gryazno, Khrevitsa and Elizavetino formations allows establishing two trilobite interval-zones. The zone of Chasmops odini in the upper part of the Uhaku and Kukruse stages, and the zone of Chasmops marginatus in the lower part of the Haljala Stage (the Idavere Substage). The upper part of the Haljala Stage (J~ohvi Substage) is characterized by the occurrence of Rollmops wenjukowi. Distribution and biostratigraphical significance of some trilobite taxa (Asaphus (Neoasaphus) lepidus, Illaenus intermedius, Toxochasmops maximus) is discussed.     

塔里木盆地古隆1井中上奥陶统牙形石生物地层界线研究

塔中地区古隆1井中晚奥陶世处于台缘斜坡带,地层发育齐全,奥陶系划分为3统5组,自上而下为却尔却克组、恰尔巴克组、一间房组、鹰山组与蓬莱坝组.在恰尔巴克组及一间房组分别获得了Pygouds anserinus与P.serra牙形石带,依此将中上奥陶统界线划在5875 m,两统之间不存在任何地层缺失或不整合面.认为碳酸盐岩...