Phosphatic microspherules and their geobiological implications from the Frasnian-Famennian transition at the Yangdi section,Guilin, South China

Abundant perfectly-preserved phosphatic microspherules have been discovered across the Frasnian-Famennian(F-F)transition from the Yangdi section in Guilin,Guangxi,South China.They are mostly spherical or elliptical in shape and about 150μm in diameter with smooth exterior surfaces.Each microspherule consistently possesses a small dimple on the surface.The internal texture of microspherules consists of concentric light-colored apatite and dark-colored organic matter bands alternating around a central core.Conodonts have also been found preserved together with phosphatic microspherules in the same horizon,and the abundance of the former is obviously higher than that of the latter.Laser Raman spectral studies show close similarities in spectral patterns between the outer shells of phosphatic microspherules and the blade of the conodont genus Palmatolepis sp.,as well as between the microspherule nucleus and the platform of the same conodont genus.Furthermore,the statistical results and geochemical data demonstrate that the elevated abundance of phosphatic microspherules roughly coincides with the blooms of bacteria and algae,but is later than the sharp increase of oceanic nutrients.The phosphatic microspherules are interpreted here to be the‘otoliths’secreted by conodont animals based on the compositional similarities between phosphatic microspherules and conodonts and their interrelated abundances.In addition,an analogous study reveals morphological and textural similarities between fish otoliths and phosphatic microspherules.The formation of phosphatic microspherules is probably related to seawater eutrophication.We speculate that the explosive growth of bacteria and algae is probably caused by the enrichment of nutrients that is most likely associated with the increase of terrestrial inputs,submarine hydrothermal activities or the upwelling anoxic bottom waters in the late Devonian,which would stimulate the conodont animals to secrete phosphatic microspherules—the‘otoliths’of conodont animals.This study reveals the coupling relationship between organisms and environments from the perspective of phosphatic microspherules and provides new evidence for the cause of faunal crisis during the Late Devonian F-F transition.     

Dimorphism in Calceola sandalina (Linneé, 1771)

Based on studying the ontogenetic development of Calceola sandalina in the Early Devonian Yukiang Formation from Guangxi Zhuang Autonomous Region, South China, it is for the first time to issue the evidence indicating the existence of sexual dimorphism in Calceola sandalina. The new discovery will add important data on sexual dimorphism throughout the non-colonial fossil metazoan, and it also may throw lights on studying the taxonomy and phylogeny of Calceola sandalina and its relevant taxa.     

Dimorphism in Calceola sandalina (Linneé, 1771)

Based on studying the ontogenetic development of Calceola sandalina in the Early Devonian Yukiang Formation from Guangxi Zhuang Autonomous Region, South China, it is for the first time to issue the evidence indicating the existence of sexual dimorphism in Calceola sandalina. The new discovery will add important data on sexual dimorphism throughout the non-colonial fossil metazoan, and it also may throw lights on studying the taxonomy and phylogeny of Calceola sandalina and its relevant taxa.     

Geodynamic evolution of Korea: A view

Abstract Evidence for South Korean Palaeozoic geodynamic evolution is restricted to the Ogcheon Belt, which is a complex polycyclic domain forming the boundary between the Precambrian Gyeonggi Block to the northwest and the Ryeongnam Block to the southeast. Two independent sub-zones can be distinguished: the Taebaeksan Zone to the northeast and the Ogcheon Zone sensu stricto. The Taebaeksan Zone and Ryeongnam Block display characteristic features of the North China palaeocontinent. This domain remained relatively stable during the Palaeozoic. In contrast, the Ogcheon Belt s. s. is a highly mobile zone that belongs to the South China palaeocontinent and corresponds to a rift that opened during the Early Palaeozoic. In lowermost Devonian times, the rift basin was closed and the Ogcheon Belt was structured in a pile of nappes. From the lack of suture in the Ogcheon Belt it can be inferred that the Gyeonggi Block belongs to the South China palaeocontinent. Thus, the boundary between the North China and South China blocks should be located to the north of Gyeonggi Block, that is, in the Palaeozoic Imjingang Belt. From the Middle Carboniferous, sedimentation started again on a weakly subsiding paralic platform located in the hinterland of the Late Palaeozoic orogen of southwest Japan. In the Late Carboniferous, increasing subsidence recorded extensional tectonics related to the opening of the Yakuno Oceanic Basin (southwest Japan). In the Middle Permian, the end of marine influences in the platform and emplacement of terrestrial coal measures, may be correlated with the closure of the oceanic area and subsequent ophiolite obduction. In Late Permian to Early Triassic times, the Honshu Block (the eastern palaeomargin of the Yakuno Basin) collided with Sino-Korea. Post-collisional intracontinental tectonics reached the Ogcheon Belt in the Middle Triassic (Songnim tectonism). Ductile dextral shear zones associated with synkinematic granitoids were emplaced in the southwest of the belt. In the Upper Triassic, the late stages of the intracontinental transcurrent tectonics generated narrow intramontane troughs (Daedong Supergroup). The Daedong basins were deformed during two tectonic events, in the Middle (?) and Late Jurassic. The Upper Jurassic to Lower Cretaceous basins (Gyeongsang Supergroup), that are controlled by left-lateral faults, may have resulted from the same tectonic event.     

Biotic recovery from the Late Devonian F-F mass extinction event in China

The Frasnian-Famennian (F-F) mass extinction is one of the five great extinctions of marine life during the Phanerozoic. The F-F event killed most of the Devonian reefs, the characteristic Devonian corals, stromatoporoids, bryozoans, nearly all tentaculites, a few superfamilies of brachiopods, such as Atrypacea and Pentameracea and some important elements of goniatites, such as Manticoceras. The end-Frasnian was a phase of mass extinction. A large number of shelly benthos were killed by the F-F event. Early and middle Famennian was the survival interval. The marine faunas were very rare at that time. The late Famennian was the recovery interval. There appeared to have many new taxa in the Strunian stage. It lacked a radiation interval in Late Devonian Famennian because another event (the D-C mass extinction) happened at the Devonian-Carboniferous boundary. Several causes for the F-F mass extinction have been proposed by some geologists, which have been grouped into two broad types, terrestrial and extraterrestrial. The former is related to sea level changes, climate changes and anoxic water event. The latter is linked with some forms of meteorite impact. A large-scale eustatic change of sea level and black shales representing an anoxic environment has been invoked to explain one of the causes for the F-F mass extinction.     

A critical review of the case for,and against,extraterrestrial impact at the K/T boundary

The discovery of an excess of Ir and other noble metals in approximately chondritic proportions at numerous sites, synchronous with the Cretaceous/Tertiary (K/T) boundary, provided hard evidence for earlier suggestion that extraterrestrial envents may have coincided with many global geologic boundaries. Further support for the impact hypothesis arose from the identification of abundant microspherules and shocked quartz in K/T boundary marine and nonmarine deposits, respectively, and the discovery of an apparent periodicity in the megaextinction event record. However continuing doubts about the impact origin of the K/T spherical forms and associated geochemical anomalies, uncertainty about the range and extent of the shocked quartz distribution, and the lack of a large, suitably-aged crater, has led to an alternative hypothesis calling upon purely endogenic processes to account for the boundary layer phenomena. Advocates of this opposing theory generally call upon large scale, possibly periodic injection of mantle material directly into the lithosphere. While a number of arguments can be made from the the existing data base for and against both competing theories, other evidence suggests that additional phenomena, including sudden changes in the physical and chemical conditions of the oceans, natural combustion on a global scale, and/or widespread sediment-contaminated volcanism, may have contributed to the dramatic transition recorded in the K/T boundary rock record.     

Variations in trace elements,isotopes, and organic geochemistry during the Hangenberg Crisis,Devonian–Carboniferous transition,northeastern Vietnam

The Hangenberg Crisis at the Devonian–Carboniferous boundary is known as a polyphase extinction event that affected more than 45 % of marine and terrestrial genera. As the cause of this event is still debated, analyses were carried out on sedimentary samples from the Devonian–Carboniferous Pho Han Formation in northeastern Vietnam to reconstruct the paleoenvironment around the time of this event using stable carbon isotopes; total sulfur; manganese; vanadium; molybdenum; and sedimentary organic matter, such as dibenzothiophenes, cadalene, and regular steranes. These geochemical signatures provide a high‐resolution redox history for this section and show that transgression‐driven high primary productivity, possibly enhanced by terrestrial input, caused severe oxygen depletion along the continental margin of the South China block during the Hangenberg Crisis.     

Devonian shallow marine ostracods from central Japan

Thirteen ostracod species including two new species, Clavofabellina fukujiensis n. sp. and Bythocypris wangi n. sp., are reported from the Middle Shale Member of the Fukuji Formation, Devonian of central Japan. The ostracods demonstrate species‐links with South China, indicating that the Hida‐Gaien Terrane of central Japan shared biogeographical affinities with the shallow marine faunas of the South China paleocontinent during the Early Devonian.     

Conodont evolution and stratotype sign of carboniferous Tournaisian-Visean boundary in South China

Sediment-successive strata of the Carboniferous Tournaisian-Visean period, i.e. Aikuanian-Datangian, are widespread in South China, where it is most possi- ble to establish the GSSP of the T\V boundary. Owing to a global drop of sea-level in the period, when the dropping-range could reach to 150 m[1], sedimentary interruptions, sudden changes of facies and disjunc- tions of organic-evolutionary chains occurred com- monly and cause sharp conflicts on division and cor- relation of the bound…     

Ambiguous biogeographical patterns mask a more complete understanding of the Ordovician to Devonian evolution of Japan

Fossil assemblages of the Ordovician to Devonian successions of Japan suggest complex temporal, environmental and geographical controls on their biogeographical signature. Thus, limited similarity at the species‐level between the trilobite, brachiopod and ostracod faunas of the South Kitakami, Hida‐Gaien and Kurosegawa terranes in part reflects the sporadic stratigraphic distribution of shelly fauna within these terranes. As a result, and with the exception of corals and pan‐tropical radiolarians, species‐level similarities are greater with other regions of East Asia and Australia than amongst the Japanese terranes. The Silurian faunas of the South Kitakami Terrane have affinities with North America, Europe, Central Asia and Australia, but there is no overriding signature to support proximity either to South China or Gondwana. Notably, brachiopod and trilobite faunas of the Middle Devonian suggest strong connections with North China. Trilobite, coral and ostracod faunas of the Hida‐Gaien Terrane show affinity, including at species level, with Siluro‐Devonian faunas from westerly‐situated palaeocontinents, especially those of Central Asian and European affinity, suggesting a continuation of the Central Asian Orogenic Belt, or of its associated lithofacies. Greater diversity of groups such as ostracods and trilobites in this terrane may signal closer links with continental shelf faunas of East Asia. The dominant biogeographical signature of the Kurosegawa Terrane is from corals and trilobites, suggesting links with the Siluro‐Devonian of Central Asia, Australia and South China. The variable biogeographic signal of the Japanese faunas may reflect the lifestyles of organisms with different physiologies and larval dispersal mechanisms, as well as the relative incompleteness of the Japanese fossil record. The present state of knowledge of the faunas cautions against placing Japan in relative proximity to the North or South China plates, or of presenting the Japanese terranes as a unified island arc to the north of the South China Plate during the Early Palaeozoic.     

Paleomagnetism of the western Cape Fold belt, South Africa, and its bearing on the Paleozoic apparent polar wander path for Gondwana

In order to test two different proposals for the poorly defined African Paleozoic apparent polar wander path (APWP), a paleomagnetic study was carried out on Ordovician through Carboniferous clastic sediments from the Cape Fold belt, west of the 22nd meridian. One proposal involves a relatively simple APWP connecting the Ordovician Gondwana poles in North Africa with the Late Paleozoic poles to the east of South Africa in a more or less straight line crossing the present equator in the Devonian. The other proposal adds a loop to this path, connecting Ordovician poles in North Africa with poles to the southwest of South Africa and then returning to central Africa. This loop would occur mainly in Silurian time. New results reported herein yield paleopoles in northern and central Africa for Ordovician to lowermost Silurian and Lower to Middle Devonian formations. The best determined paleopole of our study is for the Early Ordovician Graafwater Formation and falls at 28°N, 14°E (k = 25, α₉₅ = 8.8°, N = 28 samples). The other paleopoles are not based on sufficient numbers of samples, but can help to constrain the apparent polar wander path for Gondwana. Our results give only paleopoles well to the north of South Africa and we observe no directions within the proposed loop. Hence, if the loop is real, it must have been of relatively short duration (60–70 Ma) and be essentially of Silurian/Early Devonian age, implying very high drift velocities for Gondwana (with respect to the pole) during that interval.     

Cosmic dust and micrometeorites in the transitional clay layer at the Cretaceous-Paleogene boundary in the gams section (Eastern Alps): Morphology and chemical composition

Results of investigation of the cosmic matter in the transitional clay layer at the Cretaceous-Paleogene boundary in the Gams section, Eastern Alps, are presented. A great diversity of iron microspherules and particles of different morphologies, pure nickel spherules, awaruite (Fe₃Ni) particles, and diamond crystals are discovered. Iron microspherules are also met in the overlying Paleocene deposits, but their diversity there is not great. The discovered metallic microspherules and particles are described, their chemical compositions are presented, and their origin is discussed.     

Late Paleozoic brachiopod faunas of the South Kitakami Belt, northeast Japan, and their paleobiogeographic and tectonic implications

Abstract    Late Paleozoic (Middle Devonian, Early Carboniferous and Middle Permian) brachiopod faunas of the South Kitakami Belt, northeast Japan, are closely related paleobiogeographically to those of the Xinjiang–Inner Mongolia–Jilin region, northwest–northeast China. This relationship suggests that the South Kitakami Belt was part of the trench or continental shelf bordering the northern and eastern margins of North China (Sino-Korea) during the Middle Devonian to Middle Permian times. Among the three models on the origin and tectonic development of the South Kitakami Belt, the strike–slip model is most consistent, but both the microcontinent model and the nappe model have considerable inconsistencies with the above paleobiogeographic and paleogeographic evidence.     

Devonian Frasnian-Famennian transitional event deposits of Guangxi, South China and their possible tsunami origin

A suite of event deposits, isochronous and interrelated in origin, occurs widely near the Frasnian- Famennian boundary in Guangxi, South China. It is mainly distributed in the facies areas of the platform-margin slope and inter-platform rift-trough. The rudstone or calcirudite occur in the Liujing section of Hengxian and Luoxiu and Baqi sections of Xiangzhou in the facies area of platform-margin slope. The turbidites are observed in the sections of Yangdi and Baisha of Guilin, Du'an of Debao, Nandong and Sanli of Wuxuan, Xiangtian, Ma'anshan of Xiangzhou, Nayi of Chongzuo, Yunpan of Shanglin in the facies area of inter-platform rift-trough. The massive homogenites occur in sections of Mangchang, Luofu and Road from Nandan to Tian'e and Ma'anshan etc in the facies area of inter-platform rift-trough. Herein event deposits can be correlated in stratohorizon to the turbidite in the bottom of the Lower triangularis Zone in Hony railroad cut of Belgium, Devils Gate of Nevada, USA, Atrous of Morocco, South Urals and Fore-Kolyma of northeastern Siberia of Russia, and erosional discontinuities and brecciation in the Frasnian-Famennian boundary in South Polish-Moravian shelf. The event deposits could be caused by a violent tsunami related to bolide impacts into ocean.     

Late Paleozoic radiolarians from the Bentong-Raub suture zone, Peninsular Malaysia

Abstract Radiolarians extracted from marine siliceous sediments from the Bentong-Raub suture zone, Peninsular Malaysia have indicated a range of ages for olistostromal blocks of bedded chert, siliceous argillite and tuffaceous argillite, and chert clasts and lenses within the mélange from the suture zone. Late Devonian (Faniennian), Early Carboniferous (Tournaisian and Viséan) and Early Permian (Wolfcampian and Leonardian) ages are represented by seven radiolarian zones from ten localities along the suture zone. In stratigraphic order these include Holoeciscus 2–3 Assemblage Zones, Albaillella paradoxa Zone, Albaillella dejendrei Zone, Albaillella cartalla Zone, Pseudoalbaillella lomentaria Zone, Albaillella sinuata Zone and Pseudoalbaillella longtanensis Zone. Fifteen genera are represented by 35 species. The range of ages from Late Devonian to Early Permian suggests that an ocean existed between the Sibumasu and East Malaya terranes from at least Late Devonian to late Early Permian time and that closure of the ocean between the two terranes could not have occurred until after late Early Permian time. The range of ages and rock types from different depositional environments, indicate that the Bentong-Raub suture zone includes a disrupted accretionary complex.     

Progress and review of the studies on the end-Triassic mass extinction event

The pioneering studies by Newell[1,2] about 40 years ago and the statistical work of Raup and Sepkoski[3] have made the end-Triassic mass extinction event of marine organisms gradually familiar to the geologists. Evidences of considerable extinction have been ob- tained both in the terrestrial and marine ecosystems[4―10]. Based on the database of Benton[11], 61 of the 257 sta-tistic animal families which lived in the Late Triassic and Early Jurassic disappeared within or at the end of the …     

The~(40)Ar/~(39)Ar geochronology constraint and geological significance of mylonites in Shangyi-Chicheng fault belt on the north of North China Craton

The Shangyi-Chicheng fault belt extending along the south boundary of the Inner Mongolia axis on the north of the North China Craton was formed in the Middle Proterozoic. This fault has special geological significance1) in the evolution of the North China…     

The unique nature in ore composition,geological backgroudd and metallogenic mechanism of non-conventional superlarge ore deposits: A preliminary discussion

The new plants documented here, including a representative of the trimerophytesPsilophyton primitiuum sp. nov., a questionable rhyniophyte or trimerophyteHedeia sinica sp. nov., a prelycopodBragwanathia sp. and two species of zosterophyllophytes,Zosterophyllum australianum Lang and Cookson 1930 and2. sp. 1, from the Posongchong Formation of southeastern Yunnan, China, add to the known floral diversity of the Early Devonian of this region. Two sections of the Posongchong Formation, Changputang section of Wenshan district and Gegu section of Mengzi district also are introduced. After comparing the plants with those of the coeval flora of Australia and considering the data of recent paleocontinental reconstructions, the authors suggest that there is a northeastern Gondwana phytogeographic unit during the early Devonian comprising Australia, South China Block and perhaps Shan-Thai Block. The similarity of the floral component between Australia and South China is discussed. Because both Australia and South China also have dominant or endemic taxa, each might be recognized as a subunit, separately characterized byHedeia for Australia andEophyllophyton for South China. Project supported by the National Natural Science Foundation of China (Grant Nos. 49372075 and 49742004)     

Devonian integrative stratigraphy and timescale of China

The Global Boundary Stratotype Sections and Points(GSSPs) for the bases of all seven international Devonian stages have been formally defined and ratified by IUGS till 1996, and nowadays, the main tasks for Devonian stratigraphers include further subdivision of these standard stages, strictly constrained absolute ages for the boundaries, and precise neritic-pelagic and marine-terrestrial correlations using multidisciplinary stratigraphy methods. Establishment of high-resolution Devonian integrative stratigraphy framework and timescale of China would play an important role in improving regional and international correlation, facilitating the recognition of important stratigraphic levels in different paleogeographic settings, and understanding the evolution pattern of biota, paleoclimate and paleoenvironment during this critical interval. Based on well-studied bio-and chronostratigraphy of Devonian in South China and adjacent areas, in combination with recent achievements in carbon isotope stratigraphy, event stratigraphy and radioactive isotope ages, this paper briefly summarize the research history and current status of Devonian chronostratigraphy of China, and for the first time introduce Devonian integrative stratigraphy framework of China.Up to date, few studies have been conducted on the astronomical cyclostratigraphy and high-resolution radioactive isotope dating in Devonian of China, which should be our main focuses in the near future.     

Origin of cyclicity in Triassic-Jurassic radiolarian bedded cherts of the Mino accretionary complex from Japan

Abstract The abundance of magnetic microspherules in a Triassic-Jurassic continuous sequence of alternating chert and shale beds in the Mino accretionary complex, central Japan, was measured systematically. Depending on time, the magnetic microspherules extracted from shale beds change in abundance considerably from the minimum 0.9ppm/cm³ at latest Triassic ( ca 208Ma) and the maximum 75ppm/cm³ at late Early Jurassic ( ca 187Ma); however, the abundance is always higher approximately 10–100 (average 70) times than those from adjacent chert bed at any stratigraphic horizon. Such systematic difference reveals the origin of radiolarian bedded chert as cyclic-rapid accumulation of biogenic SiO₂ under extremely slow accumulative environments of shale with probable aeolian dust in origin. The accumulation data for individual shale and chert beds were obtained based on the microspherule abundance and radiolarian biostratigraphy, i.e., ca 0.018g/cm²Ka for lower Jurassic shale beds and ca 1.9g/cm²Ka for adjacent chert beds.
Duration time to make a chert-shale couplet corresponds to a dominantly 15–20Ka interval (average 23 Ka) in Upper Triassic bedded cherts with a low paleolatitude, whereas a 40–45 Ka interval (average 42 Ka) in Lower Jurassic ones which may been formed in higher latitude than Triassics before the final accretion to the Asian continental margin. Depending on paleolatitude, the cyclicity of 23 and 42 Ka may correspond to Milankovitch cycles which have been well documented in deep-sea sediments.