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Sample records for middle ordovician dalby

  1. Echinoderms from Middle and Upper Ordovician rocks of Kentucky

    Science.gov (United States)

    Parsley, R.L.

    1981-01-01

    The Middle and Upper Ordovician limestones of Kentucky, especially the Lexington Limestone, have yielded a diverse silicified echinoderm fauna, including: Stylophora-Enoploura cf. E. punctata; Paracrinoidea-A mygdalocystites; Crinoidea, Inadunata-Hybocrir/us tumidus, Hybocystites problem,aticus, Carabocrinus sp., Cupulocrinus sp., Heterocrinus sp.; Cyclocystoidea-Cyclocystoides sp. A rhombiferan cystoid, A mecystis laevis, from the Edinburg Formation, Virginia, is also discussed. No new taxa are introduced.

  2. Anatomy of the middle ordovician sevier shale basin, eastern Tennessee

    Science.gov (United States)

    Shanmugam, Ganapathy; Walker, Kenneth R.

    1983-04-01

    The Sevier Shale basin in eastern Tennessee comprises one of the thickest clastic sequences (nearly 2500 m) of Middle Ordovician age in North America. The lower one-half of the sequence is composed of Lenoir, Whitesburg, Blockhouse and Sevier Formations, in ascending order. The sequence ranges in age from Whiterockian to lower Wilderness in North American stages. The Middle Ordovician sequence exhibits tidal flat (Mosheim Member of Lenoir Fm.), subtidal (main body of Lenoir Fm.), slope (Whitesburg Fm.), anoxic basin (Blockhouse Fm), turbidite and contourite (Sevier Fm.) facies. The Sevier basin evolved in five stages: First, a widespread marine transgression initiated carbonate-shelf deposition in the study area. Second, a major tectonic downwarping event caused the stable shelf to break and subside rapidly at a rate of 60-65 cm 1000 yrs -1, and areas of shelf facies became areas of slope and basin facies. Third, global transgressions maintained the deep anoxic conditions for nearly 10 Ma. Fourth, turbidites began to fill the basin from a westward-prograding submarine fan system. Fifth, contour currents reworked the turbidites and progressively ventilated the Sevier basin. The basin-filling process terminated with shallow-water/subaerial clastics at the end of Middle Ordovician.

  3. The Middle Ordovician Knox unconformity in the Black Warrior Basin

    Science.gov (United States)

    Dwyer, Gary S.; Repetski, John E.

    2012-01-01

    Analysis of well core and cuttings from the Black Warrior Basin in Mississippi reveals the presence of a Middle Ordovician (Whiterockian) erosional unconformity interpreted to be equivalent to the well-known Knox-Beekmantown unconformity in eastern North America. The unconformity occurs at the top of a peritidal dolostone unit known informally as the upper dolostone, whose stratigraphic placement has been the subject of a long-standing controversy. The unconformity, which represents the Sauk-Tippecanoe megasequence boundary on the North American craton, was previously thought to be short-lived or altogether absent in the Black Warrior Basin.

  4. Trilobites from the Middle Ordovician Stairway Sandstone, Amadeus Basin, central Australia

    DEFF Research Database (Denmark)

    Jakobsen, Kristian Grube; Nielsen, Arne Thorshøj; Harper, David Alexander Taylor;

    2014-01-01

    During the Middle Ordovician (Darriwilian) sandstones and siltstones were deposited in the epicontinental Larapintine Sea, which covered large parts of central Australia. The Darriwilian Stairway Sandstone has, for the first time, been sampled stratigraphically for macrofossils to track marine be...

  5. Dalbybogen / The Dalby Book. Angersfragmentet / The Angers Fragment. Hamburgbibelen / The Hamburg Bible

    DEFF Research Database (Denmark)

    Petersen, Erik

    2006-01-01

    Dalbybogen / The Dalby Book; Angersfragmentet / The Angers Fragment; Hamburgbibelen / The Hamburg Bible......Dalbybogen / The Dalby Book; Angersfragmentet / The Angers Fragment; Hamburgbibelen / The Hamburg Bible...

  6. Organic geochemistry of Mid-Continent middle and Late Ordovician oils

    Energy Technology Data Exchange (ETDEWEB)

    Longman, M.W.; Palmer, S.E.

    1987-08-01

    Ordovician oils in Mohawkian and Cincinnatian reservoirs of the US Mid-Continent retain the biochemical imprint of Middle and Upper Ordovician oceanic life before the evolution of land plants and most vertebrates. Thus, these oils have some geochemical features that distinguish them from younger oils. These features include (1) a predominance of n-C/sub 15/, n-C/sub 17/, and n-C/sub 19/ alkanes in the saturated hydrocarbon fraction, (2) relatively low amounts of longer chain n-alkanes, (3) low amounts of chlorophyll-derived isoprenoids, such as pristane and phytane, and (4) abundant C/sub 29/ sterane relative to C/sub 27/ with rearranged forms (diasteranes) predominant over normal steranes. Ordovician oils also generally contain little sulfur and have a somewhat variable light stable carbon isotopic composition with delta/sup 13/C/sub sat/ and delta/sup 13/C/sub aro/ values of -28 to -31 per thousand (PDB), but these features are typical of many marine oils. The unusual chemistry of these Ordovician oils supports the interpretation of Reed, Illich, and Horsfield (1986) that prokaryotic organisms provided the organic matter for most Ordovician oils. Although their claim for Gloeocapsamorpha (a problematic unicellular prokaryote, possibly a blue-green alga or an unusually large bacterium) cannot be proven from oil chemistry alone, knowing that indigenous Mid-Continent Ordovician oils were derived from prokaryotic organisms may aid in future exploration for these reservoirs. 7 figures, 3 tables.

  7. A primitive cladid crinoid from the Jiacun Group, Tibet (Darriwilian, Middle Ordovician)

    DEFF Research Database (Denmark)

    Donovan, Stephen K.; Harper, David A.T.; Renbin, Zhan;

    2012-01-01

    A collection of numerous crinoid pluricolumnals from the uppermost Darriwilian (Middle Ordovician) of Tibet were derived from one biological species of crinoid. The specimens were collected from well-lithified, bioclastic shelf limestones of the upper part of the Lower Chiatsun Group, Pygodus serra...

  8. Brachiopod associations from the Middle Ordovician of the Oslo Region, Norway

    DEFF Research Database (Denmark)

    Candela, Yves; Hansen, Thomas

    2010-01-01

    The marine upper Darriwilian (Middle Ordovician) Elnes Formation of southern Norway contains very rich and diverse invertebrate faunas. Stratigraphically detailed recent collections of these well-preserved faunas have permitted a more thorough description of the various faunal groups and their pr...

  9. Middle Ordovician brachiopods from the Stairway Sandstone, Amadeus Basin, central Australia

    DEFF Research Database (Denmark)

    Jakobsen, Kristian Grube; Brock, Glenn A.; Nielsen, Arne Thorshøj

    2014-01-01

    Middle Ordovician brachiopod faunas from the Amadeus Basin, central Australia are poorly known. The Darriwilian Stairway Sandstone was sampled stratigraphically for macrofossils in order to provide new information on marine benthic diversity in this clastic-dominated, shallow-water palaeoenvironm...

  10. Middle to Late Ordovician faunal studies from central Australia and Tasmania during the Great Ordovician Biodiversification Event

    DEFF Research Database (Denmark)

    Jakobsen, Kristian Grube

    , but the preservation and low number of specimens prevent formal definition of additional new taxa. Although highly endemic at species level, the investigated brachiopod, trilobite and mollusc faunas display a high degree of overall similarity at generic level with Middle Ordovician faunas from North China. Other...... from the Stairway Sandstone, whereas nine brachiopod and five mollusc taxa have been documented from the Cashions Creek Limestone. The new trilobite species Basilicus (Parabasilicus) brumbyensis sp. nov. is described along with the new brachiopod species Amadeuphyla joanae gen. et sp. nov....... and Paralenorthis luritjaorum sp. nov. As well as the new bivalve species Modiolopsis pojetai sp. nov. and Sthenodonta paenesymmetrica sp. nov. All new species derive from the Stairway Sandstone. Several other trilobites, brachiopods and bivalves, described in open nomenclature, probably represent new species...

  11. Contact metamorphism in Middle Ordovician arc rocks (SW Sardinia, Italy): New paleogeographic constraints

    Science.gov (United States)

    Costamagna, Luca Giacomo; Elter, Franco Marco; Gaggero, Laura; Mantovani, Federico

    2016-11-01

    In the early Cambrian Bithia Formation in the Variscan foreland of Sardinia, a Middle Ordovician granitic intrusion (478-457 Ma) is hosted by marly metasedimentary rocks that were affected by high-temperature (HT) metamorphism. A detailed structural-petrographical transect was conducted through the granitic intrusion and its host rocks. Field data and relationships between HT/low-pressure (LP) mineral assemblages in the metasedimentary rocks (Grt + Wo + Ves in carbonate lenses and And in pelite) demonstrate that the study area was affected by a polyphase HT overprint (I: T = 520-620 °C at XCO2 = 0.1, P: 0.2-0.4 GPa; and II: T = 600-670 °C at XCO2 = 0.1, P = 0.2-0.4 GPa) that pre-dates the Variscan tectonic, metamorphic, and igneous phases. In the Canigò or Canigou Massif (Eastern Pyrenees), the Somail Massif (Montagne Noire), and the Ruitor Massif (Internal Massifs, NW Alps), Middle Ordovician orthogneiss with relict igneous textures are deciphered despite being overprinted by Variscan amphibolite-to-granulite-facies metamorphism and subsequent Alpine low-grade metamorphism. Comparisons of associated igneous and metasedimentary rocks in the Sardinia foreland with the High-Grade Metamorphic Complex in the Variscan Axial Zone and the Canigou Massif indicate a convergent Middle Ordovician evolution that was overprinted by HT Variscan metamorphism.

  12. Palaeomagnetism of Middle Ordovician Carbonate Sequence, Vaivara Sinimäed Area, Northeast Estonia, Baltica

    Science.gov (United States)

    Plado, Jüri; Preeden, Ulla; JÕeleht, Argo; Pesonen, Lauri J.; Mertanen, Satu

    2016-10-01

    The hill range of Vaivara Sinimäed in northeast Estonia consists of several narrow east- to northeast-trending glaciotectonic fold structures. The folds include tilted (dips 4-75°) Middle Ordovician (early Darriwilian) layered carbonate strata that were studied by mineralogical, palaeomagnetic, and rock magnetic methods in order to specify the postsedimentational history of the area and to obtain a better control over the palaeogeographic position of Baltica during the Ordovician. Mineralogical studies revealed that (titano)magnetite, hematite, and goethite are carriers of magnetization. Based on data from 5 sites that positively passed a DC tilt test, a south-easterly downward directed component A ( D ref = 154.6°± 15.3°, I ref = 60.9°± 9.7°) was identified. The component is carried by (titano)magnetite, dates to the Middle Ordovician ( Plat = 17.9°, Plon = 47.3°, K = 46.7, A95 = 11.3°), and places Baltica at mid-southerly latitudes. Observations suggest that in sites that do not pass the tilt test, the glaciotectonic event has caused some rotation of blocks around their vertical axis.

  13. Periodic anoxic shelf in the Early-Middle Ordovician transition: ichnosedimentologic evidence from west-central Utah, USA

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    Ichnosedimentologic evidence of periodic anoxic shelf in the Early-Middle Ordovician transition includes lower ichnodiversity, shallower bioturbation and burrowing depth (<4 cm ), rare domichnia, tiny Chondrites occupying shallower or shallowest tiering, widely distributed nodules of limonite pseudomorphs after pyrite, occurrence of trace fossils being closely associated with the storm event layers, and stratigraphic successions with orbital cyclostratigraphic architecture. It is suggested that lower atmospheric oxygen level during the Early Paleozoic, the Ordovician radiation, dramatic transgression and warmer temperatures would result in the periodic anoxia in the Early-Middle Ordovician transition. This episode began at the later Early Ordovician and lasted about 3.4 Ma on the basis of orbital cyclostratigraphy.

  14. Temporal Distribution of Diagnostic Biofabrics in the Lower and Middle Ordovician in North China:Clues to the Geobiology of the Great Ordovician Biodiversification Event

    Institute of Scientific and Technical Information of China (English)

    LIU Jianbo; ZHAN Renbin

    2009-01-01

    The temporal distribution of the diagnostic biofabrics In the Lower and Middle Ordovician in North China distinctly illustrates that the sedimentary systems on the paleoplate have been changed markedly as consequences of the Great Ordovician Biodiversification Event (GOBE).The pre-GOBE sedimentary systems deposited in Tremadoc display widespread microbialite and flat-pebble conglomerates,and a less extent of bioturbation.Through the transitional period of early Floian,the sedimentary systems in the rest of the Early and Mid-Ordovician change to GOBE type and are characterized by intensive bioturbation and vanishing flat-pebble conIglomerates and subtidal microbial sediments.The irreversible changes in sedimentary systems in North China are Iinked to the GOBE,which conduced the increase in infaunal tiering,the expansion of infaunal ecospace,and the appearance of new burrowers related to the development of the Paleozoic Evolutionary Fauna during the Ordovician biodiversification.Thus,changes in sedimentary systems during the pivotal period of the GOBE were consequences of a steep diversification of benthic faunas rather than the GOBE's environmental background.

  15. Graphic correlation of Argentine Precordillera and North American Lower/Middle Ordovician sections

    Institute of Scientific and Technical Information of China (English)

    Walter C.Sweet; Guillermo L.Albanesi

    2006-01-01

    @@ Present work demonstrates that a level equivalent to the proposed Whiterockian basal GSSP can be located graphically in a composite section anchored by the Niquivil section of the Argentine Precordillera. The FAD of Cooperignathus aranda in the Niquivil composite section, a candidate for GSSP of the Lower/Middle Ordovician boundary, projects to a level very close to the FAD of Tripodus laevis in the Whiterockian reference section. The conodont-based framework reported here includes the potential for recognition of the proposed Whiterock Canyon-based GSSP, the Cooperignathus aranda-based GSSP, and, possibly, the Baltoniodus triangularisbased GSSP, recently proposed.

  16. Cambrian-lower Middle Ordovician passive carbonate margin, southern Appalachians: Chapter 14

    Science.gov (United States)

    Read, J. Fred; Repetski, John E.

    2012-01-01

    The southern Appalachian part of the Cambrian–Ordovician passive margin succession of the great American carbonate bank extends from the Lower Cambrian to the lower Middle Ordovician, is as much as 3.5 km (2.2 mi) thick, and has long-term subsidence rates exceeding 5 cm (2 in.)/k.y. Subsiding depocenters separated by arches controlled sediment thickness. The succession consists of five supersequences, each of which contains several third-order sequences, and numerous meter-scale parasequences. Siliciclastic-prone supersequence 1 (Lower Cambrian Chilhowee Group fluvial rift clastics grading up into shelf siliciclastics) underlies the passive margin carbonates. Supersequence 2 consists of the Lower Cambrian Shady Dolomite–Rome-Waynesboro Formations. This is a shallowing-upward ramp succession of thinly bedded to nodular lime mudstones up into carbonate mud-mound facies, overlain by lowstand quartzose carbonates, and then a rimmed shelf succession capped by highly cyclic regressive carbonates and red beds (Rome-Waynesboro Formations). Foreslope facies include megabreccias, grainstone, and thin-bedded carbonate turbidites and deep-water rhythmites. Supersequence 3 rests on a major unconformity and consists of a Middle Cambrian differentiated rimmed shelf carbonate with highly cyclic facies (Elbrook Formation) extending in from the rim and passing via an oolitic ramp into a large structurally controlled intrashelf basin (Conasauga Shale). Filling of the intrashelf basin caused widespread deposition of thin quartz sandstones at the base of supersequence 4, overlain by widespread cyclic carbonates (Upper Cambrian lower Knox Group Copper Ridge Dolomite in the south; Conococheague Formation in the north). Supersequence 5 (Lower Ordovician upper Knox in the south; Lower to Middle Ordovician Beekmantown Group in the north) has a basal quartz sandstone-prone unit, overlain by cyclic ramp carbonates, that grade downdip into thrombolite grainstone and then storm

  17. Middle Ordovician Bioturbation Structures from Southeastern Margin of Ordos Basin and Their Environmentary Interpretation

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    Trace fossils were discovered in the Middle Ordovician Badou Member of Fengfeng Formation and the Member 1 of Jinsushan Formation in Mt. Jinsu of the Fuping region which lies at the southeastern margin of the Ordos basin. The rocks of the fore-mentioned parts contain a considerable amount of bioturbation structures, in which ichnogenus and ichnospecies can not be identified, and abundant stromatolites.The distributions and characteristics of the bioturbation structures are analyzed and summarized in this paper. The paleoenvironments of related formations and members were interpreted in the method of semiquantitative analysis of bioturbation structures with researches on stromatolites and sedimentology. It is suggested that Fuping zone, located in the southeastern margin of the Ordos basin, was a carbonate platform where stromatolite-developing tidal flat and low-energy subtidal open platform environments dominated. Also that this zone experienced three paleogeographic evolutions from tidal flat to low-energy subtidal open platform environments, that is, three larger-scale eustatisms occurred during the sedimentary period of Middle Ordovician Badou Member of Fengfeng Formation to the Member 1 of Jinsushan Formation.

  18. Conodont dating of the Middle Ordovician breccia cap-rock limestone on Osmussaar Island, northwestern Estonia

    Directory of Open Access Journals (Sweden)

    Johanna I. S. Mellgren

    2012-08-01

    Full Text Available Various mechanisms have hitherto been suggested to explain the formation of the Kundan (Middle Ordovician Osmussaar Breccia in northwestern Estonia. Following the recent discovery of L-chondritic chromite in these peculiar, sand-penetrated strata, it seems plausible that the breccia is impact-related. Herein, the conodont faunas of three thin limestone intervals overlying the breccia at Osmussaar Island have been investigated, with the aim of establishing the age of the event in terms of the Baltoscandian conodont-based biostratigraphical scheme. Based on the presence of Microzarkodina ozarkodella, the limestone directly overlying the breccia is assigned to the M. ozarkodella Subzone of the Lenodus (Eoplacognathus? pseudoplanus Zone. This is reinforced by means of a faunal shift between this sample interval and the subsequent one, which is directly comparable with a faunal shift in the Mäekalda section, mainland Estonia. The middle, orthoceratite-yielding interval is assigned to the uppermost L. (E.? pseudoplanus Zone (or, alternatively, the lowermost Eoplacognathus suecicus Zone, whereas the uppermost interval, an oolitic limestone, is referable to the E. foliaceus Subzone, corresponding to the lower part of the Lasnamägi Stage. These results support a connection between the Osmussaar event and the stratigraphic interval yielding abundant meteorites and/or high levels of L-type chromite in Sweden, as they both can be referred to the lower and/or middle part of the Kunda Stage. The minor difference in age between the first limestones deposited after the brecciation and the meteorite and L-chromite-yielding interval in Baltoscandia can be explained as caused by a period of non-deposition, seen as numerous hiatuses of various extent in the Kunda Stage in northwestern Estonia.

  19. Statistically significant faunal differences among Middle Ordovician age, Chickamauga Group bryozoan bioherms, central Alabama

    Energy Technology Data Exchange (ETDEWEB)

    Crow, C.J.

    1985-01-01

    Middle Ordovician age Chickamauga Group carbonates crop out along the Birmingham and Murphrees Valley anticlines in central Alabama. The macrofossil contents on exposed surfaces of seven bioherms have been counted to determine their various paleontologic characteristics. Twelve groups of organisms are present in these bioherms. Dominant organisms include bryozoans, algae, brachiopods, sponges, pelmatozoans, stromatoporoids and corals. Minor accessory fauna include predators, scavengers and grazers such as gastropods, ostracods, trilobites, cephalopods and pelecypods. Vertical and horizontal niche zonation has been detected for some of the bioherm dwelling fauna. No one bioherm of those studied exhibits all 12 groups of organisms; rather, individual bioherms display various subsets of the total diversity. Statistical treatment (G-test) of the diversity data indicates a lack of statistical homogeneity of the bioherms, both within and between localities. Between-locality population heterogeneity can be ascribed to differences in biologic responses to such gross environmental factors as water depth and clarity, and energy levels. At any one locality, gross aspects of the paleoenvironments are assumed to have been more uniform. Significant differences among bioherms at any one locality may have resulted from patchy distribution of species populations, differential preservation and other factors.

  20. Conodont Biostratigraphy of the Middle Cambrian through Lowermost Ordovician in Hunan, South China

    Institute of Scientific and Technical Information of China (English)

    DONG Xiping; John E. REPETSKI; Stig M. BERGSTR(O)M

    2004-01-01

    Since 1985, samples with a total weight of more than 14,000 kg, mainly from three key sections in western and northwestern Hunan, South China, have been processed for conodonts. In strata older than the late Late Cambrian paraconodonts have proved useful for stratigraphic subdivision and correlation. Thirteen conodont zones are proposed in the Middle Cambrian through lowermost Ordovician. The correlation between these zones and those of North China, western U.S.A., western Newfoundland, Canada, and Iran is discussed. In ascending order, these 13 zones are as follows: The Gapparodus bisulcatus-Westergaardodina brevidens Zone, Shandongodus priscus-Hunanognathus tricuspidatus Zone,Westergaardodina quadrata Zone, Westergaardodina matsushitai-W. grandidens Zone, Westergaardodina lui-W. ani Zone,Westergaardodina cf. calix-Prooneotodus rotundatus Zone, Proconodontus tenuiserratus Zone, Proconodontus Zone,Eoconodontus Zone, Cordylodus proavus Zone, Cordylodus intermedius Zone, Cordylodus lindstromi Zone, and Cordylodus angulatus Zone (lower part). The Westergaardodina lui-W. ani and Westergaardodina cf. calix-Prooneotodus rotundatus Zones replace the Westergaardodina proligula and Westergaardodina cf. behrae-Prooneotodus rotundatus Zones, respectively, in the lowermost Upper Cambrian. Two new species (Westergaardodina lui and Westergaardodina ani)and one conditionally identified species (Westergaardodina cf. calix) are described.

  1. Deposition in anoxic Taconic foreland basin, late Middle Ordovician, New York

    Energy Technology Data Exchange (ETDEWEB)

    Hay, B.J.; Cisne, J.L.

    1984-12-01

    The Taconic foreland basin resulted from a collision between the North American craton and the Ammonoosuc arc. The basin is positioned between a broad carbonate shelf on the west and the clastic arc terrane. In the downslope direction, basin deposits changed from distal shelf carbonates (Trenton Limestone), to coeval interbedded hemipelagic black shales and calcilutites on the slope (Dolgeville Formation and Utica Shale), to silty shales, siltstones, and sandstones laid down by turbidites on the basin floor (Snake Hill Shale). From the distribution of organic carbon and the concentration of benthic epifauna and infauna, it can be inferred that conditions were aerobic on the shelf (>1 ml/L O/sub 2/), anaerobic on the slope (<0.4 ml/L O/sub 2/), and dysaerobic on the basin floor (<1 ml/L O/sub 2/). Through time, four long-term anaerobic and dysaerobic cycles are revealed, lasting between 500,000 and 1,000,000 yr. Anaerobic cycles are characterized by over 50% higher organic carbon values, lack of infaunal burrowing traces, and a highly impoverished benthic epifauna. Dysaerobic cycles are marked by lower organic carbon contents, sporadic burrowing traces, and a slightly more diverse and abundant benthic epifauna. The longest anaerobic cycle occurred during the transgressive phase that led to widespread deposition of black shale over the carbonate platform. Anoxic conditions in the Taconic foreland basin may have been influenced by the prevailing global oceanographic conditions during the Middle Ordovician.

  2. Cyclic sedimentation patterns in Middle Ordovician Trenton group in central Pennsylvania

    Energy Technology Data Exchange (ETDEWEB)

    Gardiner, M.A.

    1984-12-01

    The carbonate facies of the Middle Ordovician Trenton Group show repetitive sequences of micrite, bioclastic limestone, and siliciclastic shale. Five repetitive patterns based on sedimentologic and paleontologic data are present (in ascending order): 1) biosparite, 2) intrabiosparite, 3) pelsparite, 4) micrite, 5) alternating micrite and shale. The biosparite is of peritidal origin and is overlain by a stromatolitic cap. The average sequence thickness is 30-40 cm (12-16 in.). The intrabiosparite is a fining-upward sequence that grades to pelsparite with a micrite cap (total thickness averages 16 cm or 6 in.). This sequence is indicative of intershoal or shoaling conditions. Overlying the intrabiosparite sequence in pelsparite grading into a micrite cap. The pelsparite averages 8 cm (3 in.) in thickness, and is of shallow sublittoral origin. Highly burrowed micrite (2-6 cm or 0.8-2.4 in. thick), with a hardground cap, indicates periodic exposure. The upper unit is a deeper, sublittoral sequence of alternating kerogenic micrite and siliciclastic shale, ranging in thickness from 20 to 90 cm (7.9 to 35.4 in.). This pattern indicates a deepening of the carbonate shelf into a deeper, anoxic basin below wave base. These sequences are a result of storm deposition as indicated by shell and intraclast lags, by fining-upward trends, and by abrupt contacts between individual sequences. The series of sequences is a result of the decreasing effects of these storms in the deeper water facies.

  3. A Darriwilian (Middle Ordovician bivalve-dominated molluscan fauna from the Stairway Sandstone, Amadeus Basin, central Australia

    Directory of Open Access Journals (Sweden)

    Kristian G. Jakobsen

    2016-12-01

    Full Text Available A bivalve-dominated molluscan fauna is described from the Darriwilian (Middle Ordovician Stairway Sandstone, Amadeus Basin, central Australia. The fauna comprises 16 species of bivalves and rostroconchs plus six gastropod species which are treated under open nomenclature. Two new bivalves, Sthenodonta paenesymmetrica sp. nov. and Modiolopsis pojetai sp. nov., are described. The relatively low-diverse molluscan fauna constitutes around 62% of the total benthic macrofauna. Approximately 75% of the molluscs comprise bivalves, especially nuculoids, which were biogeographically restricted to low latitudes during the Ordovician. The molluscan assemblage displays a very high degree of endemism at species level, though the bivalve Sthenodonta eastii also occurs in the Georgina Basin farther to the northeast. This indicates a possible marine connective seaway between the Georgina and Amadeus basins during the Darriwilian. Nuculites, Cyrtodonta, and Modiolopsis are cosmopolitan and previously reported from North China, Avalonia, and Southern Gondwana.

  4. The World's second oldest strophomenoid-dominated benthic assemblage in the first Dapingian (Middle Ordovician) brachiopod fauna identified from Iran

    Science.gov (United States)

    Popov, L. E.; Cocks, L. R. M.

    2017-06-01

    Rocks previously mapped as Devonian at Gerd-Kuh in the Eastern Alborz Mountains of Iran have yielded Middle Ordovician faunas including the brachiopods described here, the first rhynchonelliform brachiopods of Dapingian age ever described from Iran. The shells described are defined as a new Dirafinesquina Benthic Association, and which is the second oldest strophomenoid-dominated assemblage from anywhere in the World. There are six brachiopods, three of which are newly named as the strophomenoid Dirafinesquina antiqua sp. nov., the orthoid Zhanorthis gerdkuhensis gen. et sp. nov., and the porambonitoid Eoporambonites raziabadensis sp. nov.

  5. Origins of natural gas and the main controlling factors of gas accumulation in the Middle Ordovician assemblages in Jingxi area, Ordos Basin

    Directory of Open Access Journals (Sweden)

    Xinshe Liu

    2016-05-01

    Full Text Available During the progressive exploration of the Jingbian Gas Field in the Ordos Basin, multiple gas-bearing regions have been discovered in the dolomite reservoirs in the Middle Ordovician assemblages of Lower Paleozoic in Jingxi area, but these gas-bearing regions and intervals are significantly different in terms of gas enrichment degrees. So far, however, the reasons for the difference have not been figured out. In this paper, the origin and source of natural gas in the Middle Ordovician assemblages in Jingxi area was investigated on the basis of geochemical data (e.g. natural gas composition and carbon isotope, and then the main factors controlling the gas accumulation were analyzed. It is shown that the natural gas in the Middle Ordovician assemblages in the Middle Ordovician assemblages in Jingxi area is similar to that in the Upper Ordovician assemblages and Upper Paleozoic reservoir in terms of genesis and sources, and they are mainly the Upper Paleozoic coaliferous gas with some oil-derived gas. Under the influence of hydrocarbon generation center of coal source rocks and the source–rock–reservoir contact relationship, the proportion of coaliferous gas increases areally from the north to the south and vertically from Ma55 sub-member of the Lower Ordovician Majiagou Fm. It is concluded that the natural gas enrichment degree is controlled by the gas charging capacity at the hydrocarbon-supplying windows. Second, the vertical migration and distribution of natural gas is dominated by the differences of Ma55−Ma510 transport pathways. And third, the lateral migration direction of natural gas and the range of gas accumulation are controlled by the superimposition relationship between structures and reservoirs.

  6. Middle and Upper Ordovician conodonts of the Moscow Syneclise: New data on stratigraphy of the Borehole Gavrilov Yam-1 section

    Science.gov (United States)

    Tolmacheva, T. Yu.; Zaitsev, A. V.; Alekseev, A. S.

    2013-07-01

    On the basis of the first data on the taxonomic composition and stratigraphic distribution of conodont assemblages in the Borehole Gavrilov Yam-1 section (central part of the Moscow Syneclise), its biostratigraphic subdivision is proposed with specification of some formations previously substantiated by finds of acritarchs and benthic faunal assemblages. The Nefedovo Formation, which was previously attributed to the Volkhov Horizon (Dapingian Stage), is correlated by conodonts with the Kunda Horizon (basal part of the Darriwilian Stage). The middle part of the overlying Veksa Formation, which was formerly considered to be of Kunda age, yielded conodonts that mark the lower boundary of the Azeri Horizon. Conodonts found in the Mitino Formation with highly ambiguous age allow it to be correlated with the Jöhvi and Keila horizons of the Sandbian Stage (Upper Ordovician). The lower part of the Varlyga Formation, which is attributed to the Lower Silurian in the regional stratigraphic scale, is correlated by conodonts with the Oandu and Rakvere regional stages (lower part of the Katian Stage, Upper Ordovician). In total, 44 conodont species were found in 79 samples; most of them are illustrated. A brief description is given for representatives of the genera Pectinognathus, Phragmodus, and Semiacontiodus. The conodont assemblage includes species distributed in the northwestern part of the East European Platform (Baltoscandian paleobasin) and taxa characteristic of the Timan-Pechora region.

  7. The environmental response of Middle Ordovician large organic walled microfossils from the Goldwyer and Nita Formations, Canning Basin, Western Australia.

    Science.gov (United States)

    Winchester-Seeto, T; Foster, C; O'Leary, T

    2000-12-01

    Middle Ordovician large organic walled microfossils (chitinozoans, scolecodonts, hydrozoans and foraminiferal linings) were recovered from the upper Goldwyer and lower Nita formations, Canning Basin, Western Australia, from three cores (WMC Santalum 1A, Kunzea 1 and Acacia 2). Petrophysical logs of these cores reveal an overall upward shallowing supersequence, overprinted by numerous transgression/regression couplets that can be correlated over 100km.Analysis of the abundance of the microfossils with respect to the gamma log signatures reveals that both chitinozoan abundance and diversity decrease as water depth shallows; however, the opposite is not always true and other factors probably intervene. Scolecodonts show an increase in abundance in transgressions, while hydrozoans and foraminiferal linings show no consistent response to trangressive or regressive phases. Cyathochitina hunderumensis tends to dominate chitinozoan assemblages where there is a transgression, while species of Belonechitina replace Cy. hunderumensis in regressive phases.

  8. Periodic anoxic shelf in the Early-Middle Ordovician transition: ichnosedimentologic evidence from west-central Utah, USA

    Institute of Scientific and Technical Information of China (English)

    GONG; Yiming

    2001-01-01

    [1]Fortey, R. A., Droser, M. L., Trilobites at the base of the Middle Ordovician, western United States, Journal of Paleontology. 1996. 70(1): 73-99.[2]Droser. M. L., Sheehan, P. M., Palaeoecology of the Ordovician radiation: Resolution of large scale patterns with individual clade histories, palaeogeography and environments, Geobios, 1997, 20:221-229.[3]Li, X., Droser, M. L., Lower and Middle Ordovician shell beds from the Basin and Range Province of the western United States (California, Nevada, and Utah), Palaios, 1999, 14: 215-233.[4]Miller. J. F., Loch, J. D., Stitt, J. H. et al., Origins of the great Ordovician biodiversification: the record at Lawson Cove, Ibex area, Utah, USA, Acta Universitatis Carolinae-Geologica, 1999, 43( 1/2): 459-462.[5]Tolmacheva, T. Y., Holmer, L. E., Dronov, A. et al., Early Ordovician (Hunneberg-Volkhov) facial and faunal changes in the east Baltic, Acta Universitatis Carolinae-Geologica, 1999, 43(1/2): 467-470.[6]Sprinkle, J., Guensgurg, T. E., Rozhnov, S. V., Correlation anomaly shown by Ordovician shelly and trace fossils in Baltic Russia: redating the Ordovician radiation, Acta Universitatis Carolinae-Geologica, 1999, 43(1/2): 471-474.[7]Carrera, M. G.. Sanchez, T M., Benedetto, J. L., Paleoenvironmental controls on biofacies in the early Ordovician limestones of the Argentine Precordillera, Acta Universitatis Carolinae-Geologica, 1999, 43(1/2): 475-477.[8]Sepkoski. J. J. Jr., A factor analytic description of the Phanerozoic marine fossil record, Paleobiology, 1981, 7: 36-53.[9]Sepkoski, J. J. Jr., The Ordovician radiations: Diversification and extinction shown by global genus-level taxonomic data,in Ordovician Odyssey: Short Papers of the Seventh International Symposium on the Ordovician System (eds. Cooper, J. D.. Droser, M. L., Finney, S. C.), Fullerton, CA, Pacific Section, Society of Sedimentary Geology (SEPM), 1995, 78:393-396.[10]Hintze. L. F.. Lower Ordovician detailed

  9. Middle-Upper Ordovician (Darriwilian-Early Katian) Positive Carbon Isotope Excursions in the Northern Tarim Basin, Northwest China:Implications for Stratigraphic Correlation and Paleoclimate

    Institute of Scientific and Technical Information of China (English)

    Cunge Liu; Guorong Li; Dawei Wang; Yongli Liu; Mingxia Luo; Xiaoming Shao

    2016-01-01

    ABSTRACT:Three positive carbon isotope excursions are reported from Middle–Upper Ordovician in Tahe oil-gas field, northern Tarim Basin. Based on conodont biostratigraphy, the Middle Darriwilian Isotope Carbon Excursion (MDICE) and the Guttenberg Carbon Isotope Excursion (GICE) are identified from Darriwilian to Early Katian by the aid of whole-rock carbon isotope data from two well cores. Positive excursion within conodont Pygodus anserinus zone is developed in Early Sandbian, and the fluctuation range is no less than MDICE. Because the range of this excursion in the generalized global carbon isotope curve is short, previous studies paid little attention to it, and named Early Sandbian Isotope Carbon Excursion (ESICE) in this paper. Furthermore, these positive excursions are not directly related to sea level fluctuations and the MDICE and GICE identified in northern Tarim can be globally correlated to that in southern China, North America, South America, and Europe. The Saergan Fm. source rocks of Middle-Upper Ordovician in Kalpin Dawangou outcrop are in accord with the geologic time of MDICE and ESICE, and GICE have strong ties to the source rock of Lianglitag Fm. in basin. Abundant organic carbon burial is an important factor in genesis of positive isotope carbon excursions. Positive oxygen isotope excursion, conodont fauna turnover, decreased conodont total diversity, and the change of sedimentary facies indicated that dramatic changes of paleoceanographic environment of Early-Middle Ordovician in Tarim Basin started from the end of Darriwillian, and an obvious icehouse climate of Late Ordovician occurred in ESICE.

  10. The chromium isotopic composition of an Early to Middle Ordovician marine carbonate platform, eastern Precordillera, San Juan, Argentina

    DEFF Research Database (Denmark)

    D'Arcy, Joan Mary; Frei, Robert; Gilleaudeau, Geoffrey Jon;

    A broad suite of redox proxy data suggest that despite ocean and atmosphere oxygenation in the late Neoproterozoic, euxinic conditions persisted in the global deep oceans until the at least Ordovician [1,2,3]. Major changes in the sulphur isotopic composition of carbonate associated sulphate and ...

  11. Early to Middle Ordovician back-arc basin in the southern Appalachian Blue Ridge: characteristics, extent, and tectonic significance

    Science.gov (United States)

    Tull, James; Holm-Denoma, Christopher S.; Barineau, Clinton I.

    2014-01-01

    Fault-dismembered segments of a distinctive, extensive, highly allochthonous, and tectonically significant Ordovician (ca. 480–460 Ma) basin, which contains suites of bimodal metavolcanic rocks, associated base metal deposits, and thick immature deep-water (turbiditic) metasediments, occur in parts of the southern Appalachian Talladega belt, eastern Blue Ridge, and Inner Piedmont of Alabama, Georgia, and North and South Carolina. The basin's predominantly metasedimentary strata display geochemical and isotopic evidence of a mixed provenance, including an adjacent active volcanic arc and a provenance of mica (clay)-rich sedimentary and felsic plutonic rocks consistent with Laurentian (Grenvillian) upper-crustal continental rocks and their passive-margin cover sequences. Geochemical characteristics of the subordinate intercalated bimodal metavolcanic rocks indicate formation in a suprasubduction environment, most likely a back-arc basin, whereas characteristics of metasedimentary units suggest deposition above Neoproterozoic rift and outer-margin lower Paleozoic slope and rise sediments within a marginal basin along Ordovician Laurentia's Iapetus margin. This tectonic setting indicates that southernmost Appalachian Ordovician orogenesis (Taconic orogeny) began as an extensional accretionary orogen along the outer margin of Laurentia, rather than in an exotic (non-Laurentian) arc collisional setting. B-type subduction polarity requires that the associated arc-trench system formed southeast of the palinspastic position of the back-arc basin. This scenario can explain several unique features of the southern Appalachian Taconic orogen, including: the palinspastic geographic ordering of key tectonic elements (i.e., back-arc, arc, etc.), and a lack of (1) an obducted arc sensu stricto on the Laurentian margin, (2) widespread Ordovician regional metamorphism, and (3) Taconic klippen to supply detritus to the Taconic foreland basin.

  12. Geochronology and Geochemistry of Middle-Late Ordovician Granites and Gabbros in the Erguna Region, NE China:Implications for the Tectonic Evolution of the Erguna Massif

    Institute of Scientific and Technical Information of China (English)

    Shuo Zhao; Wenliang Xu; Wei Wang; Jie Tang; Yihan Zhang

    2014-01-01

    Zircon U-Pb ages, Hf isotope data and whole-rock major and trace element data for the Middle to Late Ordovician gabbros and granites in the Erguna Massif, NE China were presented in this paper. The petrogenesis of these rocks and the Early Paleozoic tectonic evolution of the massif were discussed. Zircons from the granites and gabbros are of magmatic origin based on their cathodolumi-nescence (CL) images. The206Pb/238U ages obtained from 20 spots on zircons from the granites range from 446±9 to 464±10 Ma, yielding a weighted mean age of 455±10 Ma; and 16 spots on zircons from the gabbros range from 465±10 to 466±7 Ma, yielding a weighted mean age of 465±2 Ma. Chemically, the Late Ordovician granites in the Erguna Massif are weakly peraluminous and similar to A-type granites. The granites and gabbros are all enriched in light rare earth elements and large ion lithophile elements (e.g., Rb, K), and depleted in heavy rare earth elements and high field strength elements (e.g., Nb, Ta, and Ti); they all exhibit marked negative Eu anomalies. Their zirconεHf(t) values range mainly from +1.86 to +6.21 (for the granites) and +1.39 to +3.89 (for the gabbros), except for one spot with a value of -0.27 (for a gabbro). TheTDM1 ages for the gabbros andTDM2 ages for the granites vary from 928 to 1 091 Ma and from 1 287 to 1 675 Ma, respectively. It is concluded that the primary magma of the granites could have been derived by partial melting of Mesoproterozoic newly accreted crustal ma-terial, whereas the primary magma of the gabbros originated by partial melting of a depleted mantle wedge that had been metasomatized by fluids derived from a subducted slab. These Middle-Late Or-dovician granites and gabbros constitute a typical bimodal igneous rock association, implying an exten-sional environment that was probably related to the post-collisional development of the Erguna and Xing’an massifs in the early Early Paleozoic.

  13. Revision of the plectorthoid brachiopod Platystrophia dentata (Pander, 1830 from the Middle Ordovician of the East Baltic

    Directory of Open Access Journals (Sweden)

    Michael A. Zuykov

    2011-08-01

    Full Text Available Due to the scanty description of Porambonites dentata Pander, 1830 and loss of its single type specimen, the name dentata has been subsequently attributed to various Ordovician to Silurian species of the genus Platystrophia s.l. with two costae in the sulcus and three on the fold. In The Natural History Museum, London, there is a complete shell identified presumably by Christian Pander himself as Spirifer dentatus from Pulkowa. That specimen is selected here as neotype to Platystrophia dentata, i.e. to a species, which on the basis of new material is restricted to the lower Darriwilian in the St Petersburg region. Considering differences in the interior of the dorsal valve, the other species (some with subspecies of the so-called dentata-group, especially from the stratigraphically younger strata, are discussed and excluded from the material described here of P. dentata.

  14. Tectonic and regional metamorphic implications of the discovery of Middle Ordovician conodonts in cover rocks east of the Green Mountain massif, Vermont

    Science.gov (United States)

    Ratcliffe, N.M.; Harris, A.G.; Walsh, G.J.

    1999-01-01

    Middle Ordovician (late Arenigian - early Caradocian) conodonts were recovered from a dolostone lens in carbonaceous schist 30 m below the base of the Pinney Hollow Formation in the Eastern Cover sequence near West Bridgewater, Vermont. These are the first reported fossils from the metamorphic cover sequence rocks east of the Green Mountain, Berkshire, and Housatonic massifs of western New England. The conodonts are recrystallized, coated with graphitic matter, thermally altered to a color alteration index (CAI) of at least 5, and tectonically deformed. The faunule is nearly monospecific, consisting of abundant Periodon aculeatus Hadding? and rare Protopanderodus. The preponderance of Periodon and the absence of warm, shallow-water species characteristic of the North American Midcontinent Conodont Province suggest a slope or basin depositional setting. The conodont-bearing carbonaceous schist is traceable 3 km southeast to the Plymouth area, where it had been designated the uppermost member of the Plymouth Formation, previously regarded as Early Cambrian in age. The age and structural position of the carbonaceous schist above dolostones of the Plymouth Formation but below the Pinney Hollow Formation (upper Proterozoic and Lower Cambrian?) suggest that this unit may be correlative or time transgressive with the Ira Formation, which underlies the Taconic allochthons in the Vermont Valley. Such a correlation supports the concept of placing the western limit of the root zone of the Taconic allochthons beneath the Pinney Hollow Formation. An approximate absolute age assignment for the conodont-bearing rock is between 470 and 454 Ma. This suggests that dynamothermal metamorphism during the Taconian orogeny on the east flank of the Green Mountains was younger than early Caradocian, which is in accord with the middle Caradocian age of the Ira Formation west of the Green Mountain massif.

  15. A giant Ordovician anomalocaridid.

    Science.gov (United States)

    Van Roy, Peter; Briggs, Derek E G

    2011-05-26

    Anomalocaridids, giant lightly sclerotized invertebrate predators, occur in a number of exceptionally preserved early and middle Cambrian (542-501 million years ago) biotas and have come to symbolize the unfamiliar morphologies displayed by stem organisms in faunas of the Burgess Shale type. They are characterized by a pair of anterior, segmented appendages, a circlet of plates around the mouth, and an elongate segmented trunk lacking true tergites with a pair of flexible lateral lobes per segment. Disarticulated body parts, such as the anterior appendages and oral circlet, had been assigned to a range of taxonomic groups--but the discovery of complete specimens from the middle Cambrian Burgess Shale showed that these disparate elements all belong to a single kind of animal. Phylogenetic analyses support a position of anomalocaridids in the arthropod stem, as a sister group to the euarthropods. The anomalocaridids were the largest animals in Cambrian communities. The youngest unequivocal examples occur in the middle Cambrian Marjum Formation of Utah but an arthropod retaining some anomalocaridid characteristics is present in the Devonian of Germany. Here we report the post-Cambrian occurrence of anomalocaridids, from the Early Ordovician (488-472 million years ago) Fezouata Biota in southeastern Morocco, including specimens larger than any in Cambrian biotas. These giant animals were an important element of some marine communities for about 30 million years longer than previously realized. The Moroccan specimens confirm the presence of a dorsal array of flexible blades attached to a transverse rachis on the trunk segments; these blades probably functioned as gills.

  16. Refraction and reflection seismic investigations for geological energy-storage site characterization: Dalby (Tornquist Zone), southwest Sweden

    Science.gov (United States)

    Malehmir, Alireza; Bergman, Bo; Andersson, Benjamin; Sturk, Robert; Johansson, Mattis

    2017-04-01

    Three high-resolution, 5 m shot and receiver spacing using 141-172 receivers, refraction and reflection seismic profiles for the planning of a major underground energy-storage site near the town of Dalby-Lund within the Scania Tornquist suture zone in southwest of Sweden were acquired during August 2015. The site is situated ca. 1 km north of the RFZ (Romeleåsen fault and flexure zone) with a complex geologic and tectonic history. Near vertical dikes are observed from several quarries in the area crosscutting granitic-gneissic-amphibiotic rocks and form clear magnetic lineaments. These dikes likely have also acted as surfaces on which further faulting have occurred. Although a major high-speed and traffic road runs in the middle of the study area, the seismic data show excellent quality particularly for the data along two profiles (profiles 2 and 3) perpendicular to the road, and slightly noisy, due to high wind, for the data along a profile (profile 4) parallel to the road. A bobcat-mounted drop hammer (500 kg) was used to generate the seismic signal. To provide continuity from one side of the road to another, 51 wireless recorders connected to 10 Hz geophones and operating in an autonomous mode were used. GPS times of the source impacts were used to extract the data from the wireless recorders and then merged with the data from the cabled recorders (also 10 Hz geophones). Three shot records per source position were generated and vertically stacked to improve the signal-to-noise ratio. First arrivals are clear in most shot gathers allowing them to be used for traditional refraction seismic data analysis and also for more advanced traveltime tomography. The velocity models obtained through traveltime tomography clearly depict bedrock surface and its undulations and in many places show good correlation with the boreholes recently drilled in the area. At places where bedrock is intersected at greater depths than usual, for example 25 m at one place, depression

  17. Late Ordovician (post-Sardic) rifting branches in the North Gondwanan Montagne Noire and Mouthoumet massifs of southern France

    DEFF Research Database (Denmark)

    Javier Álvaro, J.; Colmenar Lallena, Jorge; Monceret, Eric

    2016-01-01

    Upper Ordovician-Lower Devonian rocks of the Cabrières klippes (southern Montagne Noire) and the Mouthoumet massif in southern France rest paraconformably or with angular discordance on Cambrian-Lower Ordovician strata. Neither Middle-Ordovician volcanism nor associated metamorphism is recorded...

  18. Magnetic properties of the remagnetized Middle-Ordovician limestones of the Ponón Trehué Formation (San Rafael Block, central-western Argentina): Insights into the Permian widespread Sanrafaelic overprint

    Science.gov (United States)

    Fazzito, Sabrina Y.; Rapalini, Augusto E.

    2016-10-01

    The widespread Sanrafaelic remagnetization reset most of the early Cambrian to mid-Ordovician carbonate platform of the Argentine Precordillera and the calcareous units of the San Rafael Block. We conducted a detailed rock-magnetic study on the Middle-Ordovician limestones of the Ponón Trehué Formation at both limbs of a tight anticline exposed in the San Rafael Block (Mendoza province, central-western Argentina) that are carriers of a syntectonic magnetization of Permian age. We found that the magnetic overprint in the Ponón Trehué Formation is carried by both pyrrhotite and magnetite, with goethite and subordinate haematite likely related to weathering. Hysteresis parameters, frequency dependence of magnetic susceptibility, Cisowski and modified Lowrie-Fuller tests suggest the presence of ultrafine particles of chemical origin. Demagnetization of natural remanent magnetization and of three-axis isothermal remanence confirm pyrrhotite and magnetite as important contributors to the remanence. Both minerals carry the same magnetic syntectonic component suggesting a coeval or nearly coeval remanence acquisition and therefore mineral formation. This and the results of the magnetic fabric analyses indicate an authigenic origin of the magnetic minerals during folding associated with the Sanrafaelic tectonic phase (ca. 280 Ma). Although the chemically active (oxidizing?) fluids expelled from the orogen as it developed in the early Permian is a viable explanation for the Sanrafaelic remagnetization, the role of the nearly coeval magmatism in Precordillera and the San Rafael Block remains to be properly evaluated.

  19. High-resolution conodont oxygen isotope record of Ordovician climate change

    Science.gov (United States)

    Chen, J.; Chen, Z.; Algeo, T. J.

    2013-12-01

    The Ordovician Period was characterized by several major events, including a prolonged 'super greenhouse' during the Early Ordovician, the 'Great Ordovician Biodiversification Event (GOBE)' of the Middle and early Late Ordovician, and the Hirnantian ice age and mass extinction of the latest Ordovician (Webby et al., 2004, The Great Ordovician Biodiversification Event, Columbia University Press). The cause of the rapid diversification of marine invertebrates during the GOBE is not clear, however, and several scenarios have been proposed including widespread development of shallow cratonic seas, strong magmatic and tectonic activity, and climate moderation. In order to investigate relationships between climate change and marine ecosystem evolution during the Ordovician, we measured the oxygen isotopic composition of single coniform conodonts using a Cameca secondary ion mass spectrometer. Our δ18O profile shows a shift at the Early/Middle Ordovician transition that is indicative of a rapid 6 to 8 °C cooling. This cooling event marks the termination of the Early Ordovician 'super greenhouse' and may have established cooler tropical seawater temperatures that were more favorable for invertebrate animals, setting the stage for the GOBE. Additional cooling episodes occurred during the early Sandbian, early Katian, and Hirnantian, the last culminating in a short-lived (extinction. Our results differ from those of Trotter et al. (2008, 'Did cooling oceans trigger Ordovician biodiversification? Evidence from conodont thermometry,' Science 321:550-554). Instead of a slow, protracted cooling through the Early and Middle Ordovician, our high-resolution record shows that cooling occurred in several discrete steps, with the largest step being at the Early/Middle Ordovician transition.

  20. δ13C chemostratigraphy of the Middle and Upper Ordovician succession in the Tartu-453 drillcore, southern Estonia, and the significance of the HICE

    Directory of Open Access Journals (Sweden)

    Heikki Bauert

    2014-12-01

    Full Text Available The δ13C isotope data from the Tartu-453 core section in southern Estonia enabled creation of a continuous Ordovician carbon isotope record, ranging from the Floian to the end of the Hirnantian. Five positive δ13C excursions and one negative δ13C excursion were recognized. Most of the positive excursions correspond to those defined on the Baltoscandian carbon isotope chemostratigraphic scheme, except for the Paroveja and Rakvere ICEs which are not well expressed in the Tartu-453 curve. Besides the positive δ13C excursions, a distinctive negative δ13C excursion, the Lower Sandbian NICE, was recorded in the Tartu-453 succession. The well-expressed HICE extends about 10 m higher than the traditional Ordovician–Silurian boundary (between the Porkuni and Juuru regional stages into the Juuru Regional Stage, suggesting that the Ordovician–Silurian boundary is positioned significally higher than traditionally suggested for the East Baltic area.

  1. Ordovician faunas of Burgess Shale type.

    Science.gov (United States)

    Van Roy, Peter; Orr, Patrick J; Botting, Joseph P; Muir, Lucy A; Vinther, Jakob; Lefebvre, Bertrand; el Hariri, Khadija; Briggs, Derek E G

    2010-05-13

    The renowned soft-bodied faunas of the Cambrian period, which include the Burgess Shale, disappear from the fossil record in the late Middle Cambrian, after which the Palaeozoic fauna dominates. The disappearance of faunas of Burgess Shale type curtails the stratigraphic record of a number of iconic Cambrian taxa. One possible explanation for this loss is a major extinction, but more probably it reflects the absence of preservation of similar soft-bodied faunas in later periods. Here we report the discovery of numerous diverse soft-bodied assemblages in the Lower and Upper Fezouata Formations (Lower Ordovician) of Morocco, which include a range of remarkable stem-group morphologies normally considered characteristic of the Cambrian. It is clear that biotas of Burgess Shale type persisted after the Cambrian and are preserved where suitable facies occur. The Fezouata biota provides a link between the Burgess Shale communities and the early stages of the Great Ordovician Biodiversification Event.

  2. Ordovician Graptolite Rhabdosome Complication and Its Implications on Sea Level Changes

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    A total of four times of rhabdosome complication events, i.e., the lateral branching of graptolite stipes during the Late Middle Ordovician, the secondary branching of graptolite stipes at the earliest Upper Ordovician, the early Qiantangjiangian of Upper Ordovician and the middle Qiantangjiangian, respectively, is discussed in this paper. These events and other adaptation events demonstrate close relationships between a diverse graptolite fauna and sea level changes, and consequently can be employed to study sea level fluctuations. It is safe to conclude that the complication of rhabdosome started at the maximum flooding surface (MFS) and terminated at the beginning of regression.

  3. Asteroid breakup linked to the Great Ordovician Biodiversification Event

    Science.gov (United States)

    Schmitz, Birger; Harper, David A. T.; Peucker-Ehrenbrink, Bernhard; Stouge, Svend; Alwmark, Carl; Cronholm, Anders; Bergström, Stig M.; Tassinari, Mario; Xiaofeng, Wang

    2008-01-01

    The rise and diversification of shelled invertebrate life in the early Phanerozoic eon occurred in two major stages. During the first stage (termed as the Cambrian explosion), a large number of new phyla appeared over a short time interval ~540Myrago. Biodiversity at the family, genus and species level, however, remained low until the second stage marked by the Great Ordovician Biodiversification Event in the Middle Ordovician period. Although this event represents the most intense phase of species radiation during the Palaeozoic era and led to irreversible changes in the biological make-up of Earth's seafloors, the causes of this event remain elusive. Here, we show that the onset of the major phase of biodiversification ~470Myrago coincides with the disruption in the asteroid belt of the L-chondrite parent body-the largest documented asteroid breakup event during the past few billion years. The precise coincidence between these two events is established by bed-by-bed records of extraterrestrial chromite, osmium isotopes and invertebrate fossils in Middle Ordovician strata in Baltoscandia and China. We argue that frequent impacts on Earth of kilometre-sized asteroids-supported by abundant Middle Ordovician fossil meteorites and impact craters-accelerated the biodiversification process.

  4. Diversity history of Ordovician graptolites and its relationship with environmental change

    Institute of Scientific and Technical Information of China (English)

    ZHANG YuanDong; CHEN Xu

    2008-01-01

    Statistical analysis based on global data indicated that the planktonic graptolites presented a distinguished pattern from that of benthic communities during the great Ordovician biodiversification. The graptolites started to diversify from the beginning of Ordovician and reached an acme in the early Middle Ordovician, but subsequently underwent a steady decline to the end of Ordovician. During the Ordovician, many clades of the graptolites made their originations, flourishing and replacements.However, in different regions and distinct environments across the world, graptolites may presumably display distinct patterns of radiation and evolution, a hypothesis to be tested. Herein a study of the graptolite diversity in the Early to Middle Ordovician in the Upper Yangtze Region (Platform) and Jiangnan Region (Slope), South China, is conducted. The results indicate that graptolites underwent a remarkable increase in both regions, but with distinct magnitude, scope, process and patterns. The diversification of graptolites in the Upper Yangtze Region, though less prominent, is divided into four stages and includes two peaks. In the Jiangnan Region, the graptolite diversification is far more prominent and includes three stages and one peak. Based on the distinct diversity histories and composition of graptolites in the two representative regions, a 'deep-water origin and shallow-water dispersal' model is proposed for the Ordovician graptolite faunas. According to the model, the major graptolite faunas of Ordovician originated in the deep-water region on the continental slope, the source of the graptolite novelties, and subsequently spread into shallow-water region on the shelf.Besides, we also conduct a comparison study of the Ordovician graptolite diversity in South China and other major regions. The results display that the graptolites diversified globally in the Early and Middle Ordovician. At the beginning of Ordovician, graptolites underwent a significant ecological

  5. Diversity history of Ordovician graptolites and its relationship with environmental change

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    Statistical analysis based on global data indicated that the planktonic graptolites presented a distinguished pattern from that of benthic communities during the great Ordovician biodiversification. The graptolites started to diversify from the beginning of Ordovician and reached an acme in the early Middle Ordovician, but subsequently underwent a steady decline to the end of Ordovician. During the Ordovician, many clades of the graptolites made their originations, flourishing and replacements. However, in different regions and distinct environments across the world, graptolites may presumably display distinct patterns of radiation and evolution, a hypothesis to be tested. Herein a study of the graptolite diversity in the Early to Middle Ordovician in the Upper Yangtze Region (Platform) and Jiangnan Region (Slope), South China, is conducted. The results indicate that graptolites underwent a remarkable increase in both regions, but with distinct magnitude, scope, process and patterns. The diversification of graptolites in the Upper Yangtze Region, though less prominent, is divided into four stages and includes two peaks. In the Jiangnan Region, the graptolite diversification is far more prominent and includes three stages and one peak. Based on the distinct diversity histories and composition of graptolites in the two representative regions, a ’deep-water origin and shallow-water dispersal’ model is proposed for the Ordovician graptolite faunas. According to the model, the major graptolite faunas of Ordovician originated in the deep-water region on the continental slope, the source of the graptolite novelties, and subsequently spread into shallow-water region on the shelf. Besides, we also conduct a comparison study of the Ordovician graptolite diversity in South China and other major regions. The results display that the graptolites diversified globally in the Early and Middle Ordovician. At the beginning of Ordovician, graptolites underwent a significant

  6. Volcanism and Tectonic Evolution in the North Qilian Mountains during Ordovician Period

    Institute of Scientific and Technical Information of China (English)

    1998-01-01

    The Ordovician marine volcanic rocks in the north Qilian mountains are discussed in this paper. According to geology, petrotectonic assemblage and geochemistry, a new model about plate tectonic evolution of the north Qilian mountains is set up. The Ordovician marine volcanic rocks in the north Qilian mountains which characterized by the geological features of tectonic melange of continent to continent collision underwent complicated tectonic movement, and can be classified into three main kinds of petrotectonic assemblages. During Ordovician period, north Qilian area was a polyisland ocean which consisted of three ocean basins separated by the middle microcontinental blocks.

  7. 中上扬子晚奥陶世赫南特期岩相古地理%Lithofacies palaeogeography of the Late Ordovician Hirnantian in the middle-upper Yangtze region of China

    Institute of Scientific and Technical Information of China (English)

    刘伟; 许效松; 余谦; 闫剑飞; 门玉澎; 张海全

    2012-01-01

    The beginning of Hirnantian in Late Ordovician was followed by a global episode of Gondwana glaciation. Typical deposits were Guanyinqiao Formation deposits in the middle-upper Yangtze region of China during the period of the global sea-level fall caused by the ice-sheet growth. There, the worldwide spread Hirnantia-Dalmanitina fauna was abundant. According to lithologic characters, sedimentary structures, and biological assemblages and their preserved states, Hirnantian can be mainly classified as tidal flat facies and neritic shelf facies. There are several subfacies and microfacies in this study area. In the tidal flat facies, the Guanyinqiao Formation is mainly composed of carbon-argillaceous limestone and calcareous mudstone, including benthos of brachiopodas and trilobites of Hirnantia-Dalmanitina fauna. In the neritic shelf facies, however, the Hirnantian stage is composed of black siliceous shale and radiolarian chert in Normalograptus extraordinarius zone in the upper part of the Wufeng Formation and the Guanyinqiao Formation is absent. The results show that the Hirnantian, in succession of the paleogeographic framework in the late Katian stage, also has the characteristics of the semi-restricted shallow sea. Regionally, it succeeds the environment of the neritic shelf facies in the late Katian stage in the north of the upper Yangtze and the most part of the middle Yangtze region, as well as the tidal flat facies among the middle Sichuan uplift, middle Guizhou uplift and Kangdian old land. In the neritic shelf facies, the Guanyinqiao Formation shelly facies limestone deposited only in the Huangling anticline-Shenlongjia in the middle Hubei, Chengkou in Chongqing and Songxi in the southeast of Hubei as sea level was falling. In the tidal flat facies, the intraclast beach deposits distributed mainly over the north margin of the middle Guizhou uplift, but those deposits were absent in some lower areas. Within the process of sea-level falling to the lowest, in

  8. ORIGIN,DISPERSAL AND BIOGEOGRAPHIC AFFINITY OF THE MIDDLE-LATE ORDOVICIAN AND THE LLANDOVERY RUGOSE CORALS IN THE YANGTZE REGION%扬子区中、晚奥陶世和兰多维利世四射珊瑚起源、扩散及生物古地理关系

    Institute of Scientific and Technical Information of China (English)

    何心一; 陈建强

    2004-01-01

    The Middle Ordovician Llandovery rugose corals are abundant in the Yangtze region, especially in the Early Silurian. Altogether 123 genera of Rugosa,which contain 4 genera of Middle Ordovician,25 genera of Late Ordovician,and 94 genera of Llandovery respectively,have been reported from this region, of which 30 genera first appeared in the Yangtze region and then dispersed to Europe and North America and other adjacent regions. The following may represent the earliest occurrence age of the referred genera. Calostylis in the Middle Ordovician(Llandeilo)of southern Sichuan; Aphyllum and Cantrillia in the middle Ashgill of western Zhejiang; the streptelasmatids Briantelasma, Pycnactis and Tunguselasma in the late Ruddanian of northeastern Guizhou; the columnariids Ceriaster, Stauria, Amplexoides and Synamplexoides , and the cystiphyllids Maikottia, Rhizophyllum among others in the Middle Llandovery of northeastern Guizhou, South China. Based on these data, We may regard that the Yangtze region may have been one of the origin centers for the Ordovician and Silurian rugose corals. This paper deals with the Middle Ordovician to Llandovery rugose coral faunas in the Yangtze region, especially with their palaeobiogeographic affinities. The Middle Ordovician Rugosa of this region is characterized by the calostylids Calostylis and Yohophyllum . The Late Ordovician (mid Ashgill) rugosan fauna from the Sanjushan Formation of western Zhejiang Province contains some Australian elements (Hillophyllum, Bowanophyllum) , while the late Ashgill rugose fauna from the Guanyinqiao Bed in the Upper Yangtze region shows a high degree of similarity to that of North Europe, indicating that Yangtze and Europe have a close pala eobiogeographic affinity with each other. The Llandovery rugose fauna in the Yangtze region is much closer with that of Siberia, Kazakhstan and Australia.%扬子区中奥陶世-志留纪兰多维利世四射珊瑚产出丰富,尤以兰多维利世

  9. Refined Ordovician timescale reveals no link between asteroid breakup and biodiversification.

    Science.gov (United States)

    Lindskog, A; Costa, M M; Rasmussen, C M Ø; Connelly, J N; Eriksson, M E

    2017-01-24

    The catastrophic disruption of the L chondrite parent body in the asteroid belt c. 470 Ma initiated a prolonged meteorite bombardment of Earth that started in the Ordovician and continues today. Abundant L chondrite meteorites in Middle Ordovician strata have been interpreted to be the consequence of the asteroid breakup event. Here we report a zircon U-Pb date of 467.50±0.28 Ma from a distinct bed within the meteorite-bearing interval of southern Sweden that, combined with published cosmic-ray exposure ages of co-occurring meteoritic material, provides a precise age for the L chondrite breakup at 468.0±0.3 Ma. The new zircon date requires significant revision of the Ordovician timescale that has implications for the understanding of the astrogeobiologic development during this period. It has been suggested that the Middle Ordovician meteorite bombardment played a crucial role in the Great Ordovician Biodiversification Event, but this study shows that the two phenomena were unrelated.

  10. Ordovician rafinesquinine brachiopods from peri-Gondwana

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    Jorge Colmenar

    2016-06-01

    Full Text Available The study of the strophomenide brachiopods of the subfamily Rafinesquininae present in the main Upper Ordovician sections, representing the Mediterranean margin of Gondwana, has revealed an increase in diversity of the group at the region during that time. The studied collections are from the Moroccan Anti-Atlas, the Iberian and the Armorican massifs, the Iberian Chains, Pyrenees, Montagne Noire, Sardinia, and Bohemia. Two genera of the subfamily Rafinesquininae have been recorded. Of them, the cosmopolitan Rafinesquina is the only one previously reported from the region and Kjaerina is found for the first time outside Avalonia, Baltica, and Laurentia. Additionally, two new subgenera have been described, Kjaerina (Villasina and Rafinesquina (Mesogeina. Furthermore, the new species Rafinesquina (Mesogeina gabianensis, Rafinesquina (Mesogeina loredensis, Kjaerina (Kjaerina gondwanensis, Kjaerina (Villasina pedronaensis, Kjaerina (Villasina pyrenaica, and Kjaerina (Villasina meloui have been described. In addition, other species of these genera previously known from isolated localities in the region, such as Rafinesquina pseudoloricata, Rafinesquina pomoides, and Hedstroemina almadenensis are revised and their geographic range expanded. The adaptive radiation experienced by the rafinesquinines at the Mediterranean region during middle to late Katian, was probably related to changes in the regime of sedimentation and water temperature caused by the global warming Boda event.

  11. Nacre in Molluscs from the Ordovician of the Midwestern United States

    Directory of Open Access Journals (Sweden)

    Steven D.J. Baumann

    2013-01-01

    Full Text Available Nacre was previously thought to be primitive in the Mollusca, but no convincing Cambrian examples are known. This aragonitic microstructure with crystal tablets that grow within an organic framework is thought to be the strongest, most fracture-resistant type of shell microstructure. Fossils described herein from the Ordovician of Iowa, Indiana, and Ohio provide supporting evidence for the hypothesis that sometime between the middle Cambrian and late Ordovician, nacre originated in cephalopod, bivalve, and possibly gastropod lineages. The correlation of independent origins of fracture-resistant nacre with increasing shell-crushing abilities of predators during the Cambrian-Ordovician suggests an early pulse in the evolutionary arms race between predators and molluscan prey.

  12. Hydrocarbon charging histories of the Ordovician reservoir in the Tahe oil field, Tarim Basin, China

    Institute of Scientific and Technical Information of China (English)

    李纯泉; 陈红汉; 李思田; 张希明; 陈汉林

    2004-01-01

    The Ordovician reservoir of the Tahe oil field went through many tectonic reconstructions, and was characterized by multiple hydrocarbon chargings. The aim of this study was to unravel the complex charging histories. Systematic analysis of fluid inclusions was employed to complete the investigation. Fluorescence observation of oil inclusions under UV light, and microthermometry of both oil and aqueous inclusions in 105 core samples taken from the Ordovician reservoir indicated that the Ordovician reservoir underwent four oil chargings and a gas charging. The hydrocarbon chargings occurred at the late Hercynian, the Indo-Sinian and Yanshan, the early Himalaya, the middle Himalaya, and the late Himalaya,respectively. The critical hydrocarbon charging time was at the late Hercynian.

  13. Hydrocarbon charging histories of the Ordovician reservoir in the Tahe oil field, Tarim Basin, China

    Institute of Scientific and Technical Information of China (English)

    李纯泉; 陈红汉; 李思田; 张希明; 陈汉林

    2004-01-01

    The Ordovician reservoir of the Tahe oil field went through many tectonic reconstructions, and was charac-terized by multiple hydrocarbon chargings. The aim of this study was to unravel the complex charging histories. Systematicanalysis of fluid inclusions was employed to complete the investigation. Fluorescence observation of oil inclusions underUV light, and microthermometry of both oil and aqueous inclusions in 105 core samples taken from the Ordovician reservoirindicated that the Ordovician reservoir underwent four oil chargings and a gas charging. The hydrocarbon chargings oc-curred at the late Hercynian, the Indo-Sinian and Yanshan, the early Himalaya, the middle Himalaya, and the late Himalaya,respectively. The critical hydrocarbon charging time was at the late Hercynian.

  14. Hydrocarbon source rocks in marine clastic of the Middle-Upper Ordovician Queerquek Formation in the eastern Tarim Basin, China%塔里木盆地东部中-上奥陶统却尔却克组海相碎屑岩中的有效烃源岩

    Institute of Scientific and Technical Information of China (English)

    高志勇; 张水昌; 李建军; 张宝民; 顾乔元; 卢玉红

    2011-01-01

    对塔里木盆地东部中-上奥陶统却尔却克组碎屑岩中多个泥岩样品的热解有机碳分析、英东2井岩心详细描述及多条二维地震剖面的综合解释表明,在巨厚的却尔却克组碎屑岩地层的中下部存在一套累计厚度约100m的海相烃源岩.这套烃源岩总有机碳含量可达1.23%;具有较高的自然伽马值和低电阻率值;在地震剖面上具明显的强相位反射特征.该套烃源岩在塔里木盆地东部均有分布,向东、西两方向分别超覆尖灭于罗西台地边缘和古城-轮古东台地边缘,在南北方向上,分别断失在车尔臣断裂、孔雀河断裂发育处,其中西北缘超覆在孔雀河斜坡处.却尔却克组海相烃源岩是在海侵背景下,大规模海底扇发育间歇期,水体相对安静时沉积的一套深水陆棚-盆地相泥岩.%Hydrocarbon source rocks usually occurred in a marine carbonate environment in Tarim Basin during Ordovician, no effective source rocks have been found in the Middle-Upper Ordovician thick marine clastic. The analysis of pyrolyzed organic carbon in some mudstones systematically sampled from the Queerquek Formation in the eastern Tarim Basin, the detailed observation and description of cores from the Queerquek Formation of Well Yingdong-2, and the comprehensive interpretation of various 2-dimensional seismic sections indicated that a suite of marine hydrocarbon source rocks with a total accumulated thickness of nearly 100m occurs at the middle and lower parts of the Middle-Upper Ordovician thick Queerquek marine clastic. This suite of source rocks, which has TOC as high as 1.23%, is electronically characterized by a higher natural gamma-ray value and lower electric resistivity, indicating a relatively pure mudstone, and is obviously of high amplitude reflection in seismic sections. Widely distributed in the eastern Tarim Basin, these source rocks overlapped and pinched out eastward in the Luoxi platform margin and westward in

  15. Ordovician chitinozoan diversification events in China

    Institute of Scientific and Technical Information of China (English)

    WANG; Xiaofeng; CHEN; Xiaohong

    2004-01-01

    Correlative study of the Ordovician chitinozoan biostratigraphy in China with graptolite and conodont biozones, and comprehensive analysis of the sequence- and event-stratigraphic indicated that 17 chitinozoan zones and 5 main chitinozoan diversification events subsequently occurring could be recognized in the Ordovician System of China. The 5 events comprise: event 1-appearance of the earliest Ordovician chitinozoans, event 2-appearance of C. symmetrica, event 3-juvenile radiation of chitinozoans, event 4-appearance of chitinozoans with high diversity, and event 5-development of chitinozoans of deep-water facies. The age and feature of each event and its relation with the sea-level change and other geological event are discussed.

  16. Bioerosion of Inorganic Hard Substrates in the Ordovician of Estonia (Baltica.

    Directory of Open Access Journals (Sweden)

    Olev Vinn

    Full Text Available The earliest bioeroded inorganic hard substrates in the Ordovician of Estonia appear in the Dapingian. Hardgrounds are also known from the Sandbian and Katian. Most of the bioerosion of inorganic hard substrates occurs as the boring Trypanites Mägdefrau, 1932 along with some possible Gastrochaenolites borings. North American hardground borings are more diverse than those in Baltica. In contrast to a worldwide trend of increasing boring intensity, the Estonian record seems to show no increase in boring intensities during the Middle and Late Ordovician. Hardgrounds seem to be more common during the temperate climate interval of the Ordovician calcite sea in Estonia (seven hardgrounds during 15 my than in the part with a tropical climate (four hardgrounds during 12 my. Bioerosion is mostly associated with carbonate hardgrounds, but cobbles and pebbles broken from the hardgrounds are also often penetrated by Trypanites borings. The general diversity of boring ichnotaxa in Baltica increased from one ichnospecies in the Cambrian to seven by the end of Ordovician, showing the effect of the GOBE on bioeroding ichnotaxa. The diversity of inorganic hard substrate borers increased by only two times. This difference can be explained by the wider environmental distribution of organic as compared to inorganic substrates in the Ordovician seas of Baltica, and their more continuous temporal availability, which may have caused increased specialization of several borers. The inorganic substrates may have been bioreroded only by the generalists among boring organisms.

  17. Ordovician chitinozoan biozonation of the Brabant Massif, Belgium.

    Science.gov (United States)

    Samuelsson, J; Verniers, J

    2000-12-01

    Chitinozoans from seven Ordovician units (Abbaye de Villers, Tribotte, Rigenée, Ittre, Bornival, and Brutia formations and a new unnamed unit, here provisionally called the Asquempont unit) belonging to the mainly concealed Brabant Massif, Belgium are described herein. Fifty-six samples were taken from rocks cropping out at the south-eastern rim of the massif in the Orneau, Dyle-Thyle and Senne-Sennette valleys. Microfossil preservation is moderate to poor, and the chitinozoans occur in low numbers. Taxonomically, the recovered chitinozoans are distributed into 29 taxa, some placed under open nomenclature. Together with earlier published graptolite and acritarch data, the analysis of the chitinozoan assemblages resulted in an improved chronostratigraphy of the investigated formations. We propose a local chitinozoan biozonation with 11 zones for the Brabant Massif. The oldest investigated units yielded chitinozoans typical for North Gondwana, and younger units (starting in the middle Caradoc), yielded some taxa also common in Baltica. As the Brabant Massif formed part of the microcontinent Avalonia, the chitinozoan assemblages recovered from the massif support the inferred drifting of Avalonia from high latitudes towards middle latitudes in the Ordovician as was suggested earlier.

  18. Principal aspects of the Ordovician biotic radiation

    Institute of Scientific and Technical Information of China (English)

    2010-01-01

    The Ordovician radiation is among the major bioevents in earth history that have drawn great attention from geologists all over the world, and there have been hundreds of publications treating various aspects of this radiation. The study of the event involves a broad spectrum of research fields and concerns many scientific questions. Many opinions and hypotheses have been proposed on the triggering and controlling factors of the radiation. Herein the authors critically review the study of the Ordovician radiation and dissect four principal aspects by synthesizing the studies over the past years: (1) relationships of the radiation to fossil clades, ecotypes, and environments, such as water depth, latitude, and climate; (2) the ecological structure and food webs of Ordovician marine organisms; (3) fossil records and true biodiversities; and (4) likely triggering and controlling factors of the Ordovician radiation. The authors also recommend approaches to furthering studies of these aspects.

  19. The origin and initial rise of pelagic cephalopods in the Ordovician.

    Directory of Open Access Journals (Sweden)

    Björn Kröger

    Full Text Available BACKGROUND: During the Ordovician the global diversity increased dramatically at family, genus and species levels. Partially the diversification is explained by an increased nutrient, and phytoplankton availability in the open water. Cephalopods are among the top predators of today's open oceans. Their Ordovician occurrences, diversity evolution and abundance pattern potentially provides information on the evolution of the pelagic food chain. METHODOLOGY/PRINCIPAL FINDINGS: We reconstructed the cephalopod departure from originally exclusively neritic habitats into the pelagic zone by the compilation of occurrence data in offshore paleoenvironments from the Paleobiology Database, and from own data, by evidence of the functional morphology, and the taphonomy of selected cephalopod faunas. The occurrence data show, that cephalopod associations in offshore depositional settings and black shales are characterized by a specific composition, often dominated by orthocerids and lituitids. The siphuncle and conch form of these cephalopods indicate a dominant lifestyle as pelagic, vertical migrants. The frequency distribution of conch sizes and the pattern of epibionts indicate an autochthonous origin of the majority of orthocerid and lituitid shells. The consistent concentration of these cephalopods in deep subtidal sediments, starting from the middle Tremadocian indicates the occupation of the pelagic zone early in the Early Ordovician and a subsequent diversification which peaked during the Darriwilian. CONCLUSIONS/SIGNIFICANCE: The exploitation of the pelagic realm started synchronously in several independent invertebrate clades during the latest Cambrian to Middle Ordovician. The initial rise and diversification of pelagic cephalopods during the Early and Middle Ordovician indicates the establishment of a pelagic food chain sustainable enough for the development of a diverse fauna of large predators. The earliest pelagic cephalopods were slowly

  20. Ordovician Cephalopod Biofacies of South China and Its Provincialization

    Institute of Scientific and Technical Information of China (English)

    Xiao Chuantao; Chen Zhiyong; Liu Li; He Youbin

    2006-01-01

    The research on biofacies and its provincialization is of important significance not only for the increasing of precision of stratigraphic subdivision and correlation in South China, the reconstruction of ancient environment and paleogeography and even the guiding of oil and gas exploration, but also for the study of paleobiogeogrphy and sea level changes of southern China in Ordovician. On the basis of the studies of the ecological characteristics of Ordovician cephalopods from South China, eighteen cephalopod biofacies are recognized and described:(1)Open platform Proterocameroceras biofacies;(2) Restricted platform Pseudoectenolites-Xiadongoceras biofacies;(3)Open platform Retroclitend oceras Pararetroclitendoceras biofacies;(4) Open platform Pronajaceras-Mamagouceras biofacies; (5) Shelf slope-basin Cyclostomiceras biofacies; (6) Open platform Cameroceras-Cyrtovaginoceras biofacies;(7) Open platform Coreanoceras-Manchuroceras biofacies; (8) Shelf slope-basin KaipingocerasKyminoceras biofacies; (9) Inner shelf Bathmoceras-Protocycloceras biofacies; (10) Middle shelf Dideroceras-Ancistroceras biofacies; ( 11 ) Deep-water shelf Lituites-Cyclolituites biofacies; (12) Stagnant basin Lituites-Trilacinoceras biofacies; (13) Deep-water basin Paraendoceras-Sactorthoceras biofacies; (14) Deep-water shelf Sinoceras-Michelinoceras-Disoceras biofacies; (15) Deep-water shelf Beloitoceras-Jiangshanoceras biofacies; (16) Deep-water shelf-basin Eurasiaticoceras biofacies; (17)Shelf-slope Jiangxiceras-Yushanoceras biofacies; (18) Deep-water basin Michelinoceras biofacies. The cephalopods of these biofacies, their ecological characteristics, and living conditions are elucidated in this article. The association law of cephalopod biofacies in time and space shows that there were three cephalopod biofacies provinces in South China during the Ordovician, I.e. , Yangtze biofacies province, East Guizhou (贵州)-West Hunan (湖南) biofacies province (mixed-type biofacies province

  1. Phylogenetic Clustering of Origination and Extinction across the Late Ordovician Mass Extinction.

    Directory of Open Access Journals (Sweden)

    Andrew Z Krug

    Full Text Available Mass extinctions can have dramatic effects on the trajectory of life, but in some cases the effects can be relatively small even when extinction rates are high. For example, the Late Ordovician mass extinction is the second most severe in terms of the proportion of genera eliminated, yet is noted for the lack of ecological consequences and shifts in clade dominance. By comparison, the end-Cretaceous mass extinction was less severe but eliminated several major clades while some rare surviving clades diversified in the Paleogene. This disconnect may be better understood by incorporating the phylogenetic relatedness of taxa into studies of mass extinctions, as the factors driving extinction and recovery are thought to be phylogenetically conserved and should therefore promote both origination and extinction of closely related taxa. Here, we test whether there was phylogenetic selectivity in extinction and origination using brachiopod genera from the Middle Ordovician through the Devonian. Using an index of taxonomic clustering (RCL as a proxy for phylogenetic clustering, we find that A both extinctions and originations shift from taxonomically random or weakly clustered within families in the Ordovician to strongly clustered in the Silurian and Devonian, beginning with the recovery following the Late Ordovician mass extinction, and B the Late Ordovician mass extinction was itself only weakly clustered. Both results stand in stark contrast to Cretaceous-Cenozoic bivalves, which showed significant levels of taxonomic clustering of extinctions in the Cretaceous, including strong clustering in the mass extinction, but taxonomically random extinctions in the Cenozoic. The contrasting patterns between the Late Ordovician and end-Cretaceous events suggest a complex relationship between the phylogenetic selectivity of mass extinctions and the long-term phylogenetic signal in origination and extinction patterns.

  2. Late Ordovician (post-Sardic) rifting branches in the North Gondwanan Montagne Noire and Mouthoumet massifs of southern France

    Science.gov (United States)

    Javier Álvaro, J.; Colmenar, Jorge; Monceret, Eric; Pouclet, André; Vizcaïno, Daniel

    2016-06-01

    Upper Ordovician-Lower Devonian rocks of the Cabrières klippes (southern Montagne Noire) and the Mouthoumet massif in southern France rest paraconformably or with angular discordance on Cambrian-Lower Ordovician strata. Neither Middle-Ordovician volcanism nor associated metamorphism is recorded, and the subsequent Middle-Ordovician stratigraphic gap is related to the Sardic phase. Upper Ordovician sedimentation started in the rifting branches of Cabrières and Mouthoumet with deposition of basaltic lava flows and lahar deposits (Roque de Bandies and Villerouge formations) of continental tholeiite signature (CT), indicative of continental fracturing. The infill of both rifting branches followed with the onset of (1) Katian (Ka1-Ka2) conglomerates and sandstones (Glauzy and Gascagne formations), which have yielded a new brachiopod assemblage representative of the Svobodaina havliceki Community; (2) Katian (Ka2-Ka4) limestones, marlstones, and shales with carbonate nodules, reflecting development of bryozoan-echinoderm meadows with elements of the Nicolella Community (Gabian and Montjoi formations); and (3) the Hirnantian Marmairane Formation in the Mouthoumet massif that has yielded a rich and diverse fossil association representative of the pandemic Hirnantia Fauna. The sealing of the subaerial palaeorelief generated during the Sardic phase is related to Silurian and Early Devonian transgressions leading to onlapping patterns and the record of high-angle discordances.

  3. A Laurentian margin back-arc: the Ordovician Wedowee-Emuckfaw-Dahlonega basin

    Science.gov (United States)

    Barineau, Clinton I.; Tull, James F.; Holm-Denoma, Christopher S.

    2015-01-01

    Independent researchers working in the Talladega belt, Ashland-Wedowee-Emuckfaw belt, and Opelika Complex of Alabama, as well as the Dahlonega gold belt and western Inner Piedmont of Alabama, Georgia, and the Carolinas, have mapped stratigraphic sequences unique to each region. Although historically considered distinct terranes of disparate origin, a synthesis of data suggests that each includes lithologic units that formed in an Ordovician back-arc basin (Wedowee-Emuckfaw-Dahlonega basin—WEDB). Rocks in these terranes include varying proportions of metamorphosed mafic and bimodal volcanic rock suites interlayered with deep-water metasedimentary rock sequences. Metavolcanic rocks yield ages that are Early–Middle Ordovician (480–460 Ma) and interlayered metasedimentary units are populated with both Grenville and Early–Middle Ordovician detrital zircons. Metamafic rocks display geochemical trends ranging from mid-oceanic-ridge basalt to arc affinity, similar to modern back-arc basalts. The collective data set limits formation of the WEDB to a suprasubduction system built on and adjacent to upper Neoproterozoic–lower Paleozoic rocks of the passive Laurentian margin at the trailing edge of Iapetus, specifically in a continental margin back-arc setting. Overwhelmingly, the geologic history of the southern Appalachians, including rocks of the WEDB described here, indicates that the Ordovician Taconic orogeny in the southern Appalachians developed in an accretionary orogenic setting instead of the traditional collisional orogenic setting attributed to subduction of the Laurentian margin beneath an exotic or peri-Laurentian arc. Well-studied Cenozoic accretionary orogens provide excellent analogs for Taconic orogenesis, and an accretionary orogenic model for the southern Appalachian Taconic orogeny can account for aspects of Ordovician tectonics not easily explained through collisional orogenesis.

  4. Ordovician paleomagnetism of eastern Yunnan, China

    Energy Technology Data Exchange (ETDEWEB)

    Fang, Wu; Van der Voo, R. (Univ. of Michigan, Ann Arbor (USA)); Liang, Qizhong (Yunnan Institute of Geological Sciences, Kunming (China))

    1990-06-01

    Three magnetic components have been isolated in Ordovician formations of the Yangtze Paraplatform (South China Block). Two of these (Daqing A and Hongshiya B components) yield paleopoles that conform to the Carboniferous to Triassic segment of the apparent polar wander path for South China, and are therefore interpreted as remagnetizations. The third component (declination/inclination = 301{degree}/+66{degree}, N = 5 sites, k = 21.4, {alpha}{sub 95} = 17{degree}) passes the fold test and is interpreted as primary (late Early Ordovician). The paleopole, at 39{degree}S, 236{degree}E, and the paleolatitude of 48{degree}S support an Ordovician position of South China adjacent to Gondwana.

  5. Redox fluctuations in the Early Ordovician oceans

    DEFF Research Database (Denmark)

    D'Arcy, Joan Mary; Gilleaudeau, Geoffrey Jon; Peralta, Silvio

    2017-01-01

    are a potential sink for dissolved Cr in the ocean and could effectively capture the Cr isotope composition of ambient seawater. Thus, the Cr isotopic composition (δ53Cr) of carbonates has the potential to record changes in the oxygenation state of ancient oceans. To test the potential of this system, we measured...... δ53Cr values of limestones and dolostones from an Early Ordovician marine carbonate platform (Cerro La Silla section of the Precordillera, San Juan, Argentina). An increasing number of studies support the hypothesis that the Early Ordovician oceans were stratified with respect to oxygen......, accompanied by exceptionally low Cr concentrations (

  6. Ordovician palaeogeography with new palaeomagnetic data from the Montagne Noire (Southern France)

    Science.gov (United States)

    Nysæther, E.; Torsvik, T. H.; Feist, R.; Walderhaug, H. J.; Eide, E. A.

    2002-10-01

    A joint palaeomagnetic and 40Ar/ 39Ar study has been performed on two olistolithic blocks from the Cabrières Wildflysch in the Montagne Noire region of the Massif Central in France. There, andesitic volcanic and volcaniclastic rocks of Llanvirn-Early Caradoc age (ca 470-458 Ma) occur. Despite extensive secondary alteration, destruction of the dominant magnetic mineral phase and 40Ar/ 39Ar whole rock experiments that demonstrate that the volcanic rocks suffered significant argon loss, a positive fold test and the presence of dual polarities suggest that a primary, Ordovician magnetisation has mostly survived. This is one of the few documented cases where the argon system was substantially reset whilst a subordinate set of small, relatively unaltered magnetite grains, probably hosted in silicates, still carry the original, in this case Ordovician, remanence. The new data show that the Montagne Noire region was located at high southerly latitudes (68° +17/ -15) during the Mid-Ordovician. This latitude represents the location for NW Gondwana of which the Massif Central was a part. Palaeomagnetic data from all the Central European massifs and terranes demonstrate a close link to the Gondwana Margin during the Lower and Middle Ordovician.

  7. Ordovician eunicid polychaetes of Estonia and surrounding areas: review of their distribution and diversification.

    Science.gov (United States)

    Hints, O

    2000-12-01

    Scolecodonts, the jaws of polychaete worms, are common and diverse palynomorphs in the Ordovician rocks of Estonia and surrounding areas. Some 120 apparatus-based species representing about 40 genera have been recorded thus far. Relatively long stratigraphical ranges of the majority of species reflect a low rate of evolution of jawed polychaetes. However, some individual species, as well as structural changes in the assemblages, appear to be useful for stratigraphical purposes. Environmental events like those in the middle Caradoc and late Ashgill had some impact on polychaete faunas, but less than on several other groups. In order to study the spatial distribution of eunicids, faunas of particular intervals of the Ordovician were investigated. Quantitative analysis revealed that polychaete assemblages with a very consistent qualitative and quantitative composition were widespread over long distances within the belts of similar facies conditions in the Baltoscandian Palaeobasin. On the other hand, it appears that species of Ordovician jawed polychaetes were strongly influenced by particular facies, and accordingly well differentiated along the palaeobasin gradient. The decrease in diversity and abundance towards the deeper-water part of the palaeobasin indicates that the majority of Ordovician eunicids preferred relatively shallow-water conditions. The increase in differentiation of environments is accompanied by an increase in differentiation of polychaete assemblages.

  8. Ordovician and Silurian acritarch assemblages from the west Leinster and Slievenamon areas of southeast Ireland.

    Science.gov (United States)

    Maziane-Serraj, N; Brück, P M.; Higgs, K T.; Vanguestaine, M

    2000-12-01

    The Lower Palaeozoic sequences west of the Leinster Granite and in the Slievenamon Inlier of southeast Ireland have been palynologically re-investigated. Most of the productive samples yielded sufficient identifiable acritarchs for positive stratigraphical age determinations for several of the formations. The samples also include rare cryptospores, scolecodonts and tubular structures. Previous work in the area west of the Leinster Granite proposed an unbroken succession from Early Ordovician Ribband Group turbidites and volcanics passing up conformably to Early Ordovician to Late Silurian Kilcullen Group. The new palynological data clearly show that the Kilcullen Group in this area is entirely Silurian (Llandovery-early Wenlock) in age, also results obtained from the same group at Slievenamon confirm the previously reported Silurian age. Ordovician acritarchs found in the Kilcullen Group of both study areas are reworked and range in age from late Tremadoc to Llanvirn. The new data reveal a major stratigraphic break between the Ribband Group dated as Early and Middle Ordovician and the Silurian Kilcullen Group. This major break extends some hundreds of kms southwest to the Dingle Peninsula and possibly equates with a similar discontinuity in the Isle of Man to the northeast. This break would thus appear to be a major feature within the northwestern Avalonian margin sequence.

  9. δ13C chemostratigraphy in the upper Tremadocian through lower Katian (Ordovician carbonate succession of the Siljan district, central Sweden

    Directory of Open Access Journals (Sweden)

    Oliver Lehnert

    2014-12-01

    Full Text Available Based on δ13C data from two drillcores recovered from the Siljan district, we present a first continuous carbon isotope record of the upper Tremadocian–lower Katian limestone succession of central Sweden. New names for some isotopic carbon excursions from the Cambrian–Ordovician boundary through the basal Darriwilian are introduced. The Mora 001 core from the western part of the Siljan impact structure ranges through the Lower–Middle Ordovician, whereas the Solberga 1 core from its eastern part ranges through the Middle–lower Upper Ordovician. Upper Tremadocian and Floian units are extremely condensed and include extensive stratigraphic gaps. Multiple hardgrounds, sometimes with minor karstic overprint, imply recurrent periods of erosion and/or non-deposition. Like in other parts of Sweden, the Dapingian and Darriwilian succession is characterized by a relatively complete sedimentary record and low sedimentation rates.

  10. Hydrogeochemical characterization of groundwaters and porewaters beneath the Bruce nuclear site: evidence for diffusion-dominated transport in the Ordovician

    Energy Technology Data Exchange (ETDEWEB)

    Clark, I. [Univ. of Ottawa, Ottawa, ON (Canada); Al, T. [Univ. of New Brunswick, Fredericton, NB (Canada); Jensen, M.; Kennell, L. [Nuclear Waste Management Organization, Toronto, ON (Canada); Raven, K. [Geofirma Engineering Limited, Ottawa, ON (Canada)

    2011-07-01

    Investigations of the controls on solute transport in porewater and groundwater below the Bruce nuclear site involved laboratory-scale diffusion measurements, as well as measurements of natural tracer (δ{sup 18}O, δ{sup 2}H, {sup 87}Sr/{sup 86}Sr, Cl and Br) distributions and isotopic compositions of CH{sub 4}, CO{sub 2} and helium ({sup 3}He/{sup 4}He) in the porewaters and groundwaters. The analyses were performed on samples collected from drilled boreholes, DGR-1 through DGR-6, during site characterization activities and the results are summarized below. With the exception of just a few samples from the Upper Silurian, the effective diffusion coefficient (D {sub e}) values measured from DGR cores are all less than 10{sup -11} m{sup 2}/s, which is approximately one order of magnitude lower than measured De values from international programs in sedimentary rock. The majority of the data are in the range 10{sup -13} < D{sub e} < 10{sup -11} m{sup 2}/s, with Lower Silurian and Upper Ordovician shale samples representing the higher end of this range because of their relatively high porosity (7 to 9%). The low porosity of the Middle Ordovician limestone (< 2%) results in low D{sub e} values, clustering in the range 10{sup -13} < D{sub e} < 10{sup -12} m{sup 2}/s. The δ{sup 18}O, Cl, and Br profiles in the Middle Ordovician carbonates define trends of decreasing δ{sup 18}O values and tracer concentrations with depth, and are interpreted to result from an extremely long period of diffusion-dominated transport (~300 Ma). Near the base of the Middle Ordovician carbonates the δ{sup 2}H data display a slight enrichment, which could represent upward diffusion of deuterium-enriched water originating in the underlying Precambrian shield. A Precambrian shield influence on the Ordovician porewater chemistry is inferred from the measured {sup 87}Sr/{sup 86}Sr ratios in the Middle Ordovician carbonates, which are elevated above values expected for porewater in equilibrium

  11. Basic Ordovician magmatism of the Spanish Central System: Constraints on the source and geodynamic setting

    Science.gov (United States)

    Orejana, D.; Villaseca, C.; Merino Martínez, E.

    2017-07-01

    New geochemical and geochronological data obtained from metabasites intrusive into pre-Floian metasedimentary and metaigneous rocks of the Spanish Central System (Revenga and El Caloco sectors) represent a complex pre-Variscan magmatic event. Analysed samples exhibit tholeiitic affinity but relatively high incompatible element contents. These rocks can be distinguished from similar tholeiitic SCS metabasites because they represent more primitive liquids with higher metal (Cr, Ni) and LILE contents and display a slightly enriched isotopic (Sr, Nd) composition. These data point to the involvement of several mantle sources including lithospheric sections with a crustal imprint. Two samples yield Ordovician U-Pb zircon intrusion ages of 473.1 (+ 3.8/- 6.8) and 453.3 ± 4.6 Ma. This episode of basic magmatism is not coetaneous with the abundant Cambrian-Ordovician felsic orthogneisses of the Central Iberian Zone and likely represents a rifting context (Rheic Ocean opening) which started about 477 Ma. A comparison with Lower to Middle Paleozoic magmatic rocks from other west European terranes implies a heterogeneous evolution from the Ediacaran to Middle Paleozoic in the northern margin of Gondwana. While western terranes (e.g., Armorican Massif, Saxo-Thuringian Zone, Ossa-Morena Zone) display monotonous shelf sedimentation and magmatic quiescence from the Upper Ordovician to Variscan collision, eastern terranes (e.g., Central Iberian Zone, Corsica-Sardinia, Alps, Pyrenees) exhibit magmatism of contrasting geochemical affinity, including basic alkaline and tholeiitic series, indicative of a more complex tectonic evolution.

  12. Accumulation process and model for the Ordovician buried hill reservoir in the western Lunnan area, the Tarim Basin

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    The Ordovician buried hill reservoir in the western Lunnan area, a type of dissolved fracture and cavernous reservoir, is mainly composed of heavy oil. The oil is the mixture sourcing from the Middle-Lower Cambrian and Middle-Lower Ordovician, with three stages of pool forming process: (1) the destruction and parallel migration/accumulation during the late Caledonian to early Hercynian; (2) the oil and gas accumulation during the late Hercynian characterized by adjustment upward along faults and parallel migration/accumulation; (3) the formation of heavy oil during the latest Hercynian. The Ordovician buried hill reservoir is affected by the diffusion of light oil and gas but had no hydrocarbon charging during the late Yanshan period to Himalayan period, but in this period, formed the association of heavy oil and dissolved gas cracked from crude oil with dry coefficient of 0.91-0.96. The study on accumulation process of the Ordovician buried hill reservoir has important implications for the exploration potential of early oil and gas accumulation in the cratonic area of the Tarim Basin.

  13. The roles of Lazarus taxa and refugia through the Ordovician-Silurian transition: data from the Brachiopoda

    Science.gov (United States)

    Rong, J.-Y.; Boucot, A. J.; Harper, D. A.; Zhan, R.-B.; Neuman, R. B.

    2003-04-01

    Global analyses of nearly 90 families and 275 genera of brachiopods from the middle Ashgill through the Hirnantian (Ordovician) to the lower-middle Rhuddanian (Silurian) suggest that about 60% and 40% of the total number of genera were eliminated at the first and second phases of the end Ordovician extinction event, respectively. Among the 85 surviving genera, about 50 with declining and 10 with proliferating abundances are known from the Hirnantian together with about 20 provisional Lazarus taxa. The Lazarus taxa are essentially survivors and form the extremity of the declining genera. The distributions of declining genera and relicts during the crisis interval shows a random and sporadic pattern, suggesting there was no single, common refugium for end Ordovician brachiopods. In addition to their biological attributes, a markedly decreased population size together with taphonomic failure and poor preservation, and collecting bias have contributed towards the distributional trends apparent during the event. The development of declining genera during the extinction may be linked to their palaeogeographical setting, the phylogenetic history of the taxa, and the ambient environmental conditions. This new global database has significantly reduced the number of Lazarus taxa and minimizes the number of possible locations for collective refugia during the end Ordovician crisis. Nevertheless, the atrypids, athyridids, pentamerids, and spiriferids had more limited distributions during the crisis interval but formed the locus for a Silurian diversification of the phylum into carbonate environments possibly around the Rhuddanian-Aeronian boundary.

  14. Cambrian to Lower Ordovician complexes of the Kokchetav Massif and its fringing (Northern Kazakhstan): Structure, age, and tectonic settings

    Science.gov (United States)

    Degtyarev, K. E.; Tolmacheva, T. Yu.; Tretyakov, A. A.; Kotov, A. B.; Shatagin, K. N.

    2016-01-01

    A comprehensive study of the Lower Palaeozoic complexes of the Kokchetav Massif and its fringing has been carried out. It has allowed for the first time to discover and investigate in detail the stratified and intrusive complexes of the Cambrian-Early Ordovician. Fossil findings and isotope geochronology permitted the determination of their ages. The tectonic position and internal structures of those complexes have also been defined and their chemical features have been analyzed as well. The obtained data allowed us to put forward a model of the geodynamic evolution of Northern Kazakhstan in the Late Ediacaran-Earliest Ordovician. The accumulation of the oldest Ediacaran to Earliest Cambrian siliciclastics and carbonates confined to the Kokchetav Massif and its fringing occurred in a shallow shelf environment prior to its collision with the Neoproterozoic Daut island arc: complexes of the latter have been found in the northeast of the studied area. The Early Cambrian subduction of the Kokchetav Massif under the Daut island arc, their following collision and exhumation of HP complexes led to the formation of rugged ground topography, promoting deposition of siliceous-clastic and coarse clastic units during the Middle to early Late Cambrian. Those sediments were mainly sourced from eroded metamorphic complexes of the Kokchetav Massif basement. At the end of the Late Cambrian to the Early Ordovician within the boundaries of the massif with the Precambrian crust, volcanogenic and volcano-sedimentary units along with gabbros and granites with intraplate affinities were formed. Simultaneously in the surrounding zones, which represent relics of basins with oceanic crust, N-MORB- and E-MORB-type ophiolites were developed. These complexes originated under extensional settings occurred in the majority of the Caledonides of Kazakhstan and Northern Tian Shan. In the Early Floian Stage (Early Ordovician) older heterogeneous complexes were overlain by relatively monotonous

  15. 塔里木盆地古城低凸起中下奥陶统白云岩稀土元素地球化学特征及其成因%REE Geochemical Characteristics and Genesis of the Middle-Lower Ordovician Dolomite in the Gucheng Low Uplift of the Tarim Basin

    Institute of Scientific and Technical Information of China (English)

    张振伟

    2016-01-01

    The Middle-Lower Ordovician dolomite in the Gucheng Low Uplift of the Tarim Basin is the main reservoir of natural gas in the area.Based on characteristics of texture and structures,six kinds of dolomite have been classified in this paper.They include fine to micritic dolomite,fine to crystalline anhedral dirty dolomite,fine to medium sized euhedral dolomite,medium to coarse grained dirty dolomite,medium to coarse grained clean dolomite,and saddle dolomite.Their REE contents have been measured.Results show that the total contents of REE are relatively low,with positive correlations between the REE and LaN/YbN or LREE/HREE ratios,but poor correlations between the REE and δEu orδCe values. The REE distribution patterns of various types of dolomite are generally flat,slightly right declined,and LREE slightly en-riched,with very limited differences among them.The genetic types of various kinds of dolomite are slightly different.They include penecontemporaneous evaporative pumping dolomitization,penecontemporaneous seepage reflux dolomitization, shallow burial dolomitization,and hydrothermal dolomitization.%中下奥陶统白云岩是塔里木盆地古城低凸起主要的天然气储集层,按结构特征将其分为粉-微晶白云石、粉-细晶级他形脏白云石、粉-中晶级自形白云石、中-粗晶脏白云石、中-粗晶干净白云石和鞍形白云石等6种类型,对不同类型白云岩的稀土元素分析结果表明,研究区样品的REE总体含量偏低,与LaN/YbN、LREE/HREE大致呈正相关,与 δEu、δCe的相关性较差.不同类型白云石稀土元素配分曲线差别不大,均为总体平缓、略向右倾,显示轻稀土略微富集.不同类型白云石成因类型略有不同,主要为同生期蒸发泵成因、同生期渗透回流成因、浅埋藏成因和热液成因等4种成因类型.

  16. Complexity in benthic-pelagic marine ecosystems in the late Ordovician (central New York)

    Energy Technology Data Exchange (ETDEWEB)

    Byrne, S.M.

    1985-01-01

    Cisne and Chandlee (1982) outlined a paleogeographic model for marine invertebrates collected from Middle Ordovician strata in central New York. Subsequent interpretations of their stratigraphic and geographic distributions were based on control by levels of oxygen. Especially critical were the presumed distribution of the trilobite Triarthus and three graptolites, Orthograptus, Climacograptus, and Corynoides, which were supposed to have occupied vertically stratified habitats in the water column. In order to test this general thesis 42 stratigraphically discrete samples were collected from continuously exposed Late Ordovician mudstones in central New York, which contained taxa virtually identically to those employed by Cisne. The sampling interval spanned about 1.5 million years and over 1/4 of the samples contained relatively large numbers of graptolites. Over 3000 graptolite rhabdosomes were identified. The later Ordovician Orthograptus are preserved both with and without Climacograptus and with various benthic taxa. However neither Orthograptus nor Climacograptus display a consistent stratigraphic pattern, and Triarthus co-occurred with both graptolites, introducing a discordant note into any attempt at a simple modeling of early Paleozoic benthic/pelagic ecosystems.

  17. Revision of annulated orthoceridan cephalopods of the Baltoscandic Ordovician

    Directory of Open Access Journals (Sweden)

    B. Kröger

    2006-02-01

    Full Text Available The annulated orthoceridans of the Middle and Late Ordovician of Baltoscandia are described and their systematic frame is revised. The revision of these nautiloids, which are part of the Orthocerida and Pseudorthocerida, is based on the investigation of characters of the septal neck, the siphuncular tube, and the apex. An unequivocal terminology of these characters is suggested and applied. The shape of the septal neck and the siphuncular tube are described for the first time in Palaeodawsonoceras n. gen., Striatocycloceras n. gen., Dawsonoceras fenestratum Eichwald, 1860, and Gorbyoceras textumaraneum (Roemer, 1861. Ctenoceras sweeti n. sp. is erected. The apex of Dawsonoceras barrandei Horný, 1956 is figured and described for the first time. The distribution of the character states of the apex and the septal neck support the emendation of the families Orthoceratidae, Dawsonoceratidae, and Proteoceratidae. The analysis shows also that the families Kionoceratidae, and Leuroceratidae must be refused because they represent not natural groups. However, it is also shown that the present knowledge is not sufficient to establish an unequivocal classification of the Middle, and Late Ordovician annulate cephalopods. Die orthoceriden Cephalopoden des Mittleren bis Späten Ordoviziums im Baltoskandium werden beschrieben und revidiert. Die Revision dieser Cephalopoden, welche zu den Orthocerida und Pseudorthocerida gehören, stützt sich auf die Untersuchung der Apikalenden, der Septalduten und der Form der Siphonalröhre. Eine eindeutige Terminologie für diese Merkmale wird vorgeschlagen und angewandt. Die Form der Septalduten und der Siphonalröhre von Palaeodawsonoceras n. gen., Striatocycloceras n. gen., Dawsonoceras fenestratum, Eichwald, 1860 und Gorbyoceras textumaraneum (Roemer, 1861 wird erstmals beschrieben. Die Art Ctenoceras sweeti n. sp. wird aufgestellt. Der Apex von Dawsonoceras barrandei Horný, 1956 wird erstmals beschrieben und

  18. Appalachian Blue Ridge cover sequence ranges at least into the Ordovician

    Science.gov (United States)

    Tull, James F.; Ausich, William I.; Groszos, Mark S.; Thompson, Troy W.

    1993-03-01

    The first direct evidence that stratified rocks of the central core of the southern Appalachian Blue Ridge range in age into the Paleozoic comes from a pelmatozoan echinoderm column discovered within a unit directly above the Murphy Marble in North Carolina. Before this discovery most geologists had considered all stratified rocks of the Blue Ridge east of the frontal imbricate thrust blocks to be Late Proterozoic or Early Cambrian(?). The echinoderm fragment is in a lower amphibolite facies interbedded mica schist-impure marble zone that lies directly above the Murphy Marble. Rocks above the Murphy Marble are dominantly turbiditic metaclastic rocks with minor carbonate and metavolcanic rocks, interpreted as having formed within a successor basin unconformably above upper Precambrian rift facies and lower Paleozoic drift facies rocks of the Laurentian passive margin. An upper bound for the age of the successor basin in the Murphy belt has not been established; similar sequences in the Talladega belt to the southwest, and possibly the Foothills belt to the west, range at least into the Devonian. Most Appalachian tectonic models assert that during the Taconic orogeny a Middle Ordovician synorogenic clastic wedge, now located in the easternmost Tennessee foreland salient, was derived by erosion from the metamorphosed pre-Ordovician Blue Ridge basement and cover sequence to the east, which was uplifted as part of an advancing Taconic crystalline thrust wedge. The presence of Ordovician or younger rocks described here, which were deposited east of the proposed Taconic orogenic front, suggests the need to modify models for Taconic clastic wedge formation in the southern Appalachians. The results presented here also suggest that peak metamorphism in the region was post-Ordovician, and thus was probably not contemporaneous with the Taconic orogeny, as previously thought.

  19. Precisely locating the Ordovician equator in Laurentia

    DEFF Research Database (Denmark)

    Jin, Jisuo; Harper, David A.T.; Cocks, L. Robin M.

    2013-01-01

    The Late Ordovician equatorial zone, like the zone today, had few hurricane-grade storms within 100 of the equator, as emphasized by the preservation of massive-bedded Thalassinoides ichnofacies in a trans-Laurentian belt more than 6000 km long, from the southwestern United States to North...... Greenland. That belt also includes nonamalgamated shell beds dominated by the brachiopod Proconchidium, which would not have been preserved after hurricane-grade storms. The belt lacks such storm-related sedimentary features as rip-up clasts, hummocky cross-stratification, or large channels. In contrast...

  20. Microfossils in the Ordovician erratic boulders from South-western Finland

    Directory of Open Access Journals (Sweden)

    Nõlvak, J.

    1995-12-01

    Full Text Available Chitinozoans, ostracods and acritarchs found in four glacially transported limestone boulders from the south-western coast of Finland have been studied in order to test the usefulness of these microfossil groups in age determinations. Also rare specimens of conodonts, inarticulated brachiopods and foraminifers were found. Baltic limestone (or Östersjö limestone was the most problematic, because only fossils with calcitic or phosphatic shells are preserved. It is concluded that the boulders identified correlate with the Uhaku and Rakvere stages of the Middle Ordovician.

  1. Sedimentary facies and palaeogeography during the middle and late Darriwilian to the early Katian (Ordovician) and hydrocarbon exploration in central and southern Hunan%湘中湘南地区奥陶纪达瑞威尔中晚期-凯迪早期岩相古地理及其油气地质意义

    Institute of Scientific and Technical Information of China (English)

    葛祥英; 牟传龙; 周恳恳; 梁薇

    2011-01-01

    湘中湘南地区在早古生代时期,由于受海平面变化以及全球古气候的影响,形成了有利于烃源岩形成的沉积环境.笔者通过对湘中湘南地区的奥陶纪达瑞威尔中晚期-凯迪早期开展沉积相、岩相古地理和油气地质等研究,结合前人所取得的相关研究成果,将该区划分为陆架相、盆地相和陆架边缘相.陆架相主要由砂质板岩、砂岩、黑色页岩和硅质岩组成;陆架边缘相为粉砂-细粒石英砂岩、长石石英砂岩夹条带状板岩、炭质板岩和硅质岩等组成;而盆地相为一套炭质页岩和硅质岩组成的黑色岩系,代表了一种平静还原的滞流缺氧环境.该套岩性有机质含量高,具较高的生烃潜力,且分布范围广,是湘中湘南地区达瑞威尔-凯迪阶的富烃沉积区,也是下一步油气地质调查和勘探的重要层位.%The areas of central and southern Hunan sandwiched between the Yangtze and Cathaysian landmasses are believed to be the favourable sedimentary environments for the formation of source rocks due to the sea-level changes and global palaeoclimatic changes during the Early Palaeozoic. The middle and late Darriwilian to the early Katian ( Ordovician) sedimentary strata dominantly consist of the Yanxi and Modaoxi Formations in central Hunan, and Baimachong and Shuangjiakou Formations in southern Hunan, and may be divided, on the basis of sedimentary facies and palaeogeography and petroleum geology, into continental shelf facies, basin facies and continental shelf-margin facies. The continental shelf facies is made up of sandy slate, sandstone, black shale and siliceous rocks. The continental shelf-margin facies is built up of silty to fine-grained quartz sandstone and feldspathic quartz sandstone, intercalated with banded slate, carbonaceous slate and siliceous rocks. The basin facies is assembled by a succession of black rock series including carbonaceous shale and siliceous rocks, representing

  2. 塔中地区中—下奥陶统碳酸盐岩孔洞—裂缝储集系统划分及其特征%Reservoir Architectural System in the Middle-Lower Ordovician Carbonate Rock of Tazhong Areas in Tarim

    Institute of Scientific and Technical Information of China (English)

    潘建国; 卫平生; 蔡忠贤; 杨海军; 王宏斌; 张虎权

    2012-01-01

    塔里木盆地塔中地区下奥陶统鹰山组是—套由喀斯特改造的碳酸盐岩储层,其储集空间主要为裂缝或与裂缝相关的溶蚀孔洞,岩石基质孔隙很低.这些储集空间主要是由多期表生溶蚀作用与后期上升型溶蚀作用叠加改造的结果,因此储层结构复杂、非均质性强.针对这类储层的发育特点,从储层地质静态描述的角度,按系统论思想,明确了“孔洞—裂缝储集系统”的科学内涵,提出了以缝洞储集单元为核心的解剖思路和方法,并以多种地球物理方法包括叠前裂缝预测技术、碳酸盐岩古地貌分析技术、地震一测井联合波阻抗反演技术以及三维地震属性提取及雕刻等所揭示的信息为基础,综合考虑储层发育的构造及其水文地质边界条件,对缝洞储集单元进行了划分.在此基础上,结合钻井岩心及测井分析获得储集空间类型、结构及其成因信息,将该区缝洞储集单元划分为表生岩溶型、热液岩溶型和裂缝型3种成因类型,明确了部分储集单元的成因属性.%The Yingshan Formation of Middle-Lower Ordovician in Tazhong uplift in Tarim is an important fracture and karst-modified carbonate reservoir. Main pore types in this reservoir include fractures .vug and caves, which mainly resulted from multi-stage epigenetic dissolution and post-stage hypogenetic excavation. The reservoir architectural systems are of extreme heterogeneity and significant compartmentalization. This study presents an architectural hierarchy for the reservoirs not controlled by facices according to the system theory. ()n the basis of integrated information revealed by a variety of methods, such as geophysical methods including prestack fracture prediction technology, paleo-geomorphological analysis technology, seismic-logging wave impedance inversion technology, three-dimensional seismic attribute extraction technology, and well-logging explanation, core observation etc

  3. Digestive structures in Ordovician trilobites Colpocoryphe and Flexicalymene from the Barrandian area of Czech Republic

    Directory of Open Access Journals (Sweden)

    Oldřich Fatka

    2015-11-01

    Full Text Available Two recently discovered specimens of the abundant calymenoid trilobite Colpocoryphe Novák in Perner, 1918 from the Middle Ordovician Šárka Formation and one specimen of Flexicalymene (Flexicalymene pragensis Vaněk & Vokáč, 1997 from the Upper Ordovician Bohdalec Formation, all from the Prague Basin, display remains of the digestive system. In Colpocoryphe, an internal mould of an articulated exoskeleton contains a post-stomach part of the alimentary canal preserved through the narrow axial region of the occipital ring, all thoracic segments as well as in the axial part of the pygidial shield. The anterior part of the digestive system is poorly known as the specimen shows the hypostome preserved in situ and the space between the glabella and the hypostome is represented by an empty cavity associated with probable remains of gut diverticulae on both sides of the cephalon. The second, incomplete specimen consists of five posterior thoracic segments articulated with the pygidium. The axial region of this specimen is preserved with a clearly discernible segmented intestine which terminates at the axial tip and then bends ventrally. In an enrolled specimen of Flexicalymene pragensis, supposed remains of the alimentary tract are comparatively poorly preserved but discernible in the middle and posterior parts of the thoracic axis and in the anterior part of the pygidial axis. Digestive structures within the family Calymenidae have not been described previously. Earlier discoveries of the digestive system in Ordovician trilobites of the Barrandian area are briefly reviewed.

  4. The ages and tectonic setting of the Faja Eruptiva de la Puna Oriental, Ordovician, NW Argentina

    Science.gov (United States)

    Bahlburg, Heinrich; Berndt, Jasper; Gerdes, Axel

    2016-07-01

    The Ordovician Faja Eruptiva de la Puna Oriental is a magmatic, predominantly intrusive belt in the Puna of northwestern Argentina with a N-S extension of ca. 400 km. Scarce isotope geochemical ages and biostratigraphic data on some of the folded Faja Eruptiva country rocks assign the magmatism either to the Lower and lower Middle Ordovician, or to the latest Ordovician. Interpretations of origin and tectonic framework of the Faja Eruptiva are controversial and vary between arc, back-arc and collisional-orogenic settings. We present high-resolution La-ICP-MS U-Pb age and Hf isotope data on zircons from 10 plutonic samples covering the magmatic belt along a length of 200 km in the northern Argentinian Puna. The xenocrystic and magmatic zircon age data have a wide spread between 2700 Ma and 440 Ma. Concordia and weighted mean age data document protracted magmatism in two phases between 480 and 460 Ma, and between 453 and 444 Ma, and constrain the time of the last intrusions at 444 ± 3 Ma and at 445 ± 2 Ma thus defining this last and main phase of intrusion at 444 Ma. εHf(t) values define a main vertical trend centered at 500 Ma with εHf(t) values between + 3 and - 16 indicating significant mixing of juvenile early Paleozoic melts with Paleoproterozoic crustal components. A second trend is formed by zircons with ages between 1.1 Ga and c. 500 Ma and predominantly positive εHf values between + 8 and - 3 and originates in juvenile mantle compositions between 1.6 and 1.1 Ga. The spread of the zircon and Hf data document that the Faja Eruptiva intrusives have experienced large-scale contamination by the hosting crustal basement. It follows that the basement of the Puna is formed either by the upper Proterozoic-lower Cambrian Puncoviscana Formation as an erosional product of the Proterozoic orogenic belts of SW Amazonia or that the Puna including its Puncoviscana basement is underlain by a crust shaped by these orogenies. The main intrusive event at 444 Ma has been

  5. A new age model for the Late Ordovician bentonites in Oslo, Norway

    Science.gov (United States)

    Gottschalk Ballo, Eirik; Eivind Augland, Lars; Hammer, Øyvind; Svensen, Henrik

    2017-04-01

    During the Late Ordovician, explosive volcanic eruptions led to the deposition of worldwide bentonites. Some of the largest of these eruptions took place in the Sandbian and produced the Milbrig and Deicke K-bentonites of North America and the Kinnekulle K-bentonite of Scandinavia. We have studied the classic locality of Hagemann and Spjeldnæs (1955) - one of the most complete sections of Ordovician bentonites in Europe. The bentonites are present in the Arnestad Formation comprising dark shale with carbonate nodule beds grading into an increasingly more carbonate rich environment. Through a 50-meter interval we have identified 33 bentonites of which 10 have not previously been reported from this locality. The bentonites have an average thickness of 4.9 cm with a few exceptions such as the Kinnekulle K-bentonite (35 cm) and the Grimstorp B (13 cm). We have measured magnetic susceptibility of two 2-3 meter intervals with a sampling distance of 5 cm, using a handheld magnetic susceptibility meter in the field. These data show significant periodicity peaks that correlate well with Milankovitch cycles and are suggested to represent astronomically forced changes in sediment supply. This study further presents high-precision U-Pb zircon ages of five bentonites from the section, including the Kinnekulle K-bentonite and Grimstorp B. These two beds were previously dated by Svensen et al. (2015) from a locality south of Oslo. Our new data improves the precision of the ages of these two key beds, and constrain the duration of the entire interval and thus the onset and termination of the late Ordovician volcanic system that deposited these tephras. We conclude that the Oslo section provides a high-resolution age model to understand one of the most intense volcanic periods of the Paleozoic by combining radiometric and cyclostratigraphic data. BIBLIOGRAPHY Hagemann, F. and Spjeldnæs, N. (1955). "The Middle Ordovician of the Oslo region, Norway. 6. Notes on bentonites (K

  6. Phylogenetic paleobiogeography of Late Ordovician Laurentian brachiopods

    Directory of Open Access Journals (Sweden)

    Jennifer E. Bauer

    2014-12-01

    Full Text Available Phylogenetic biogeographic analysis of four brachiopod genera was used to uncover large-scale geologic drivers of Late Ordovician biogeographic differentiation in Laurentia. Previously generated phylogenetic hypotheses were converted into area cladograms, ancestral geographic ranges were optimized and speciation events characterized as via dispersal or vicariance, when possible. Area relationships were reconstructed using Lieberman-modified Brooks Parsimony Analysis. The resulting area cladograms indicate tectonic and oceanographic changes were the primary geologic drivers of biogeographic patterns within the focal taxa. The Taconic tectophase contributed to the separation of the Appalachian and Central basins as well as the two midcontinent basins, whereas sea level rise following the Boda Event promoted interbasinal dispersal. Three migration pathways into the Cincinnati Basin were recognized, which supports the multiple pathway hypothesis for the Richmondian Invasion.

  7. New Data on Ordovician Eocrinoids and Paracrinoids of the Baltic Region

    Science.gov (United States)

    Rozhnov, S.

    2009-04-01

    Eocrinoids are widespread in the Ordovician beds of the Baltic Region, often dominating in benthic communities of the Middle Ordovician. They are represented by 12 genera. New records allow the improvement of their morphology, stratigraphic and geographical distribution. Rhipidocystis was one of the first to appear in the Baltic basin (Upper Billingen of the eastern Baltic Basin); it reached its acme in the Volkhov and became scarce rare in subsequent strata, although survived up to the Uhaku. In the Azeri or Lasnamyagi, it gave rise to the close related genus Neorhipidocystis, which rarely occurs in the Lasnamyagi, Uhaku and Kukruze Regional Stages. New data on the arrangement of pores, morphology variability in the brachiols strongly suggest that Rhipidocystis is close to Volkhovian Paracryptocrinites and Cryptocrinites, which evolved from the last genus in the Azeri. Bockia, which occurs in the Azeri, Lasnamyagi, Uhaku and Kukruze, is closely related to Cryptocrinites and differs from it in the considerably larger size, greater number of plates, extended apertural part, and branching brachiolas. These five genera belong to the same lineage of closely related Ordovician eocrinoids, which is named the cryptocrinid-rhipidocystid lineage. In North America, a similar eocrinoid lineage developed in parallel. The two lineages probably evolved from a common ancestor, which inhabited eastern Gondwana in the Early Ordovician. Plates of Rhopalocystidae are abundant in the Volkhovian Regional stage; they show distinctive sutural pores, which are characteristic of the other branch of Ordovician eocrinoids, widespread in the northern marginal area of Gondwana. The thecal fragments, which are scarce in the Baltic Region, allow the reconstruction of only the distal part; however, it is evident that the Baltic genus differs sharply in shape from Gondwanian rhopalocystids. A unique eocrinoid specimen, with a spherical theca composed of many plates and a column similar in

  8. An Ordovician variation on Burgess Shale-type biotas.

    Science.gov (United States)

    Botting, Joseph P; Muir, Lucy A; Jordan, Naomi; Upton, Christopher

    2015-04-24

    The Cambrian Burgess Shale-type biotas form a globally consistent ecosystem, usually dominated by arthropods. Elements of these communities continued into the Early Ordovician at high latitude, but our understanding of ecological changes during the Great Ordovician Biodiversification Event (GOBE) is currently limited by the paucity of Ordovician exceptionally preserved open-marine faunas. Here we clarify the early stages of the GOBE by describing a new open-marine Konservat-Lagerstätte from the Early Ordovician of Wales. The Afon Gam Biota includes many lineages typical of the Cambrian Burgess Shale-type biotas, but the most abundant groups were sponges, algae and worms, with non-trilobite arthropods being unexpectedly rare. Labile tissues occur abundantly in the sponges and are also present in other groups, including brachiopods and hyoliths. Taphonomic biases are considered and rejected as explanations for arthropod rarity; the preserved biota is considered to be an approximation to the original community composition. We note that other exceptionally preserved communities in the Welsh Ordovician are also sponge-dominated, suggesting a regional change in benthic ecology during the early stages of the GOBE.

  9. Effect of the Ordovician paleogeography on the (instability of the climate

    Directory of Open Access Journals (Sweden)

    A. Pohl

    2014-11-01

    Full Text Available The Ordovician Period (485–443 Ma is characterized by abundant evidence for continental-sized ice sheets. Modeling studies published so far require a sharp CO2 drawdown to initiate this glaciation. They mostly used non-dynamic slab mixed-layer ocean models. Here, we use a general circulation model with coupled components for ocean, atmosphere, and sea ice to examine the response of Ordovician climate to changes in CO2 and paleogeography. We conduct experiments for a wide range of CO2 (from 16 to 2 times the preindustrial atmospheric CO2 level (PAL and for two continental configurations (at 470 and at 450 Ma mimicking the Middle and the Late Ordovician conditions. We find that the temperature-CO2 relationship is highly non-linear when ocean dynamics are taken into account. Two climatic modes are simulated as radiative forcing decreases. For high CO2 concentrations (≥ 12 PAL at 470 Ma and ≥ 8 PAL at 450 Ma, a relative hot climate with no sea ice characterizes the warm mode. When CO2 is decreased to 8 PAL and 6 PAL at 470 and 450 Ma, a tipping point is crossed and climate abruptly enters a runaway icehouse leading to a cold mode marked by the extension of the sea ice cover down to the mid-latitudes. At 450 Ma, the transition from the warm to the cold mode is reached for a decrease in atmospheric CO2 from 8 to 6 PAL and induces a ~9 °C global cooling. We show that the tipping point is due to the existence of a 95% oceanic Northern Hemisphere, which in turn induces a minimum in oceanic heat transport located around 40° N. The latter allows sea ice to stabilize at these latitudes, explaining the potential existence of the warm and of the cold climatic modes. This major climatic instability potentially brings a new explanation to the sudden Late Ordovician Hirnantian glacial pulse that does not require any large CO2 drawdown.

  10. Tropical shoreline ice in the late Cambrian: Implications for earth's climate between the Cambrian Explosion and the Great Ordovician Biodiversification Event

    Science.gov (United States)

    Runkel, Anthony C.; MacKey, T.J.; Cowan, Clinton A.; Fox, David L.

    2010-01-01

    Middle to late Cambrian time (ca. 513 to 488 Ma) is characterized by an unstable plateau in biodiversity, when depauperate shelf faunas suffered repeated extinctions. This poorly understood interval separates the Cambrian Explosion from the Great Ordovician Biodiversification Event and is generally regarded as a time of sustained greenhouse conditions. We present evidence that suggests a drastically different climate during this enigmatic interval: Features indicative of meteoric ice are well preserved in late Cambrian equatorial beach deposits that correspond to one of the shelf extinction events. Thus, the middle to late Cambrian Earth was at least episodically cold and might best be considered a muted analogue to the environmental extremes that characterized the Proterozoic, even though cooling in the two periods may have occurred in response to different triggers. Such later Cambrian conditions may have significantly impacted evolution preceding the Ordovician radiation.

  11. A sulfidic driver for the end-Ordovician mass extinction

    DEFF Research Database (Denmark)

    Hammarlund, Emma; Dahl, Tais Wittchen; Harper, David Alexander Taylor

    2012-01-01

    The end-Ordovician extinction consisted of two discrete pulses, both linked, in various ways, to glaciation at the South Pole. The first phase, starting just below the Normalograptus extraordinarius Zone, particularly affected nektonic and planktonic species, while the second pulse, associated...... with the Normalograptus persculptus Zone, was less selective. Glacially induced cooling and oxygenation are two of many suggested kill mechanisms for the end-Ordovician extinction, but a general consensus is lacking. We have used geochemical redox indicators, such as iron speciation, molybdenum concentrations, pyrite...... framboid size distribution and sulfur isotopes to analyze the geochemistry in three key Hirnantian sections. These indicators reveal that reducing conditions were occasionally present at all three sites before the first pulse of the end-Ordovician extinction, and that these conditions expanded towards...

  12. Organic geochemistry of mid-continent Ordovician oils

    Energy Technology Data Exchange (ETDEWEB)

    Palmer, S.E.

    1985-01-01

    Early Paleozoic oils retain the biochemical imprint of oceanic life prior to evolution of land plants and vertebrates. Thus, these oils have geochemical features which make them unique with respect to younger oils, but also share some common properties with the latter. Characteristic mid-continent Ordovician oil features include predominance of n-C/sub 14/ to n-C/sub 19/ over n-C/sub 20/+ alkanes in the C/sub 15/+ saturate hydrocarbon fraction, low amounts of isoprenoids and abundant C/sub 27/ and C/sub 29/ diasteranes relative to normal steranes. Properties common to both Ordovician and younger oils are: nearly equal amounts of C/sub 15/+ n-alkanes, cycloalkanes, and aromatics and pristane/phytane ratios of 0.7 to 1.6. Collectively, these Ordovician oils have a relatively negative stable carbon isotopic composition but are not unique with respect to other marine oils. Although terpane distributions are generally similar to geologically-younger oils, the Ordovician oils contain significant amounts of C/sub 19/, C/sub 20/, and C/sub 21/ tricyclic diterpanes relative to the C/sub 23/ homolog as well as large contributions by C/sub 31/+ pentacyclic triterpanes. Presence of long-chained n-alkanes, C/sub 29/ steranes, and C/sub 24/ tetracyclic terpanes, which are generally accepted as input from land plants in, e.g., Tertiary deposits, are also present in Ordovician oils. The characteristics listed above describe oils from the Williston and Michigan basins as well as Ordovician oils from Kansas and Oklahoma.

  13. Depositional Architecture of Late Cambrian-Early Ordovician Siliciclastic Barik Formation; Al Huqf Area, Oman

    Science.gov (United States)

    Abbasi, Iftikhar Ahmed

    2017-04-01

    Early Paleozoic siliciclastics sediments of the Haima Supergroup are subdivided into a number of formations and members based on lithological characteristics of various rock sequences. One of the distinct sandstone sequence, the Barik Formation (Late Cambrian-Early Ordovician) of the Andam Group is a major deep gas reservoir in central Oman. The sandstone bodies are prospective reservoir rocks while thick shale and clay interbeds act as effective seal. Part of the Barik Formation (lower and middle part) is exposed in isolated outcrops in Al Huqf area as interbedded multistoried sandstone, and green and red shale. The sandstone bodies are up to 2 meters thick and can be traced laterally for 300 m to over 1 km. Most of sandstone bodies show both lateral and vertical stacking. Two types of sandstone lithofacies are identified on the basis of field characteristics; a plane-bedded sandstone lithofacies capping thick red and green color shale beds, and a cross-bedded sandstone lithofacies overlying the plane-bedded sandstone defining coarsening upward sequences. The plane-bedded sandstone at places contains Cruziana ichnofacies and bivalve fragments indicating deposition by shoreface processes. Thick cross-bedded sandstone is interpreted to be deposited by the fluvial dominated deltaic processes. Load-casts, climbing ripples and flaser-bedding in siltstone and red shale indicate influence of tidal processes at times during the deposition of the formation. This paper summarizes results of a study carried out in Al Huqf area outcrops to analyze the characteristics of the sandstone-body geometry, internal architecture, provenance and diagenetic changes in the lower and middle part of the formation. The study shows build-up of a delta complex and its progradation over a broad, low-angle shelf where fluvial processes operate beside shoreface processes in a vegetation free setting. Keywords: Andam Group, Barik Formation, Ordovician sandstone, Al Huqf, Central Oman,

  14. Early-Mid Ordovician brachiopod diversification in South China

    Institute of Scientific and Technical Information of China (English)

    ZHAN Renbin; RONG Jiayu; CHENG Jinhui; CHEN Pengfei

    2005-01-01

    Affected by paleogeographic position, paleoclimatic condition and depositional environments, the increase of the Early-Mid Ordovician brachiopod diversity of South China commenced at the beginning of the Ordovician (early Tremadoc), accelerated from the Tetragraptus approximatus Biozone (base of Arenig), and reached its first acme in the Didymograptus eobifidus Biozone (mid early Arenig) when the number of brachiopod genera was over 7 times as great as that at the start of the Ordovician. This was the first radiation in the history of brachiopod macroevolution in South China, which occurred nearly 5 graptolitic biozones earlier than the global trend of the great Ordovician biodiversification (in the lower part of the Undulograptus austrodentatus Biozone). It is also characterized by (1) the origination or first occurrences of some major groups, such as the punctate dalmanelloids and the pseudopunctate strophomenoids including Plectambonitoidea (cardinal process simple or absent) and Strophomenoidea (cardinal process bilobed) in South China; (2) niche expansion, particularly in the first occupation of deeper water benthic regimes by the Euorthisina-Nocturnellia Association developed at Houping, Chengkou, northern Chongqing; and (3) the differentiation of brachiopod faunas under different environmental conditions. The gradual and increasing separation from Gondwana may have been one of the factors responsible for the radiation in South China.

  15. Relations between spatial distribution and sequence types of the Cambrian-Ordovician marine source rocks in Tarim Basin

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    Marine source rocks are considered to be mainly composed of the Cambrian-Ordovician deposit in Tarlm Basin. Based on the previous studies made by other researchers, the authors calculated the thickness and distribution scale of these Cambrian-Ordovician source rocks by integrating sequence stratigraphy with investigations on sedimentary environments, well-shooting demarcating and calibrating the thickness of unknown source rocks with the thickness of the known ones according to characteristics of the source rocks that have "double track" seismic lineup reflectance. The results showed that the distribution area of the Lower-Cambrian Yuertusi Fm. source rock in platform inner depressions, slopes and deep basins is much bigger than that of the Middle Cambrian evaporite-lagoon source rock. Moreover, the former is superior to the latter In terms of the source rock quality. Likewise,the Middle-Ordovician Heituao Fm. source rock in the slopes and deep basins has a much wider distribution and better quality than the Upper Ordovician, and its quality is also better than those of the Shaergan and Yinggan Fms. source rock within platforms as well as the lime-mud-mound source rock along the fringe of the Upper-Ordovician platform. Most good Lower-Cambrian source rocks of the Kalpin outcrop lie on the initial ingression surface or in the condensed member of the Type Ⅰ sequence.In this section, the source rock in Type Ⅱ is inferior to that in Type Ⅰ, even being far from an effective one (TOC: <0.5%). Likewise, the good Middle-Ordovician Heituao source rock also lies on the initial ingression surface or in the condensed member of the Type Ⅰ sequence, while the poor Yinggan source rock and the lime-mud-mound along the fringe of the platform develop all in the Type Ⅱ sequence. Under the condition of the same sea-level rising altitude and time, the Ingression displacement (S1) at the base border in Type lis larger than S2 in Type Ⅱ. Thus, the distribution of the source

  16. Ordovician palynology: balance and future prospects at the beginning of the third millennium.

    Science.gov (United States)

    Servais, T; Paris, F

    2000-12-01

    Ordovician palynologic studies started in the 1930s when Eisenack first described Palaeozoic "hystrichospheres" (later named acritarchs), and defined the chitinozoans and melanosclerites. During the ensuing two decades, Ordovician palynologic investigations were mostly descriptive. It was the rise of the oil industry in the 1950s and 1960s, which accelerated palynologic research, particularly with the recognition that acritarchs and chitinozoans were biostratigraphically important groups for Ordovician stratigraphy. Today, more than 700 publications deal with Ordovician acritarchs, and about 400 papers concern Ordovician chitinozoans. In addition to these two palynomorph groups, other less important organic-walled microorganisms have been studied. These include plant remains (spores, cuticles), scolecodonts and such enigmatic groups as the melanosclerites and the mazuelloids. This paper summarises the research on Ordovician palynomorphs during the 20th century and looks ahead to the types of research that may be important and most fruitful for Ordovician palynology at the beginning of the new millenium. Particular attention is paid to the C.I.M.P./I.G.C.P. no. 410 joint meeting "Ordovician Palynology and Palaeobotany," held in Prague during the 8th International Symposium on the Ordovician System. A brief account is given concerning the global Ordovician chronostratigraphy and the correlation of the main regional series and stages.

  17. The Ordovician Sierras Pampeanas-Puna basin connection: Basement thinning and basin formation in the Proto-Andean back-arc

    Science.gov (United States)

    Büttner, Steffen H.

    2009-11-01

    The Ordovician Sierras Pampeanas, located in a continental back-arc position at the Proto-Andean margin of southwest Gondwana, experienced substantial mantle heat transfer during the Ordovician Famatina orogeny, converting Neoproterozoic and Early Cambrian metasediments to migmatites and granites. The high-grade metamorphic basement underwent intense extensional shearing during the Early and Middle Ordovician. Contemporaneously, up to 7000 m marine sediments were deposited in extensional back-arc basins covering the pre-Ordovician basement. Extensional Ordovician tectonics were more effective in mid- and lower crustal migmatites than in higher levels of the crust. At a depth of about 13 km the separating boundary between low-strain solid upper and high-strain lower migmatitic crust evolved to an intra-crustal detachment. The detachment zone varies in thickness but does not exceed about 500 m. The formation of anatectic melt at the metamorphic peak, and the resulting drop in shear strength, initiated extensional tectonics which continued along localized ductile shear zones until the migmatitic crust cooled to amphibolite facies P-T conditions. P-T-d-t data in combination with field evidence suggest significant (ca. 52%) crustal thinning below the detachment corresponding to a thinning factor of 2.1. Ductile thinning of the upper crust is estimated to be less than that of the lower crust and might range between 25% and 44%, constituting total crustal thinning factors of 1.7-2.0. While the migmatites experienced retrograde decompression during the Ordovician, rocks along and above the detachment show isobaric cooling. This suggests that the magnitude of upper crustal extension controls the amount of space created for sediments deposited at the surface. Upper crustal extension and thinning is compensated by newly deposited sediments, maintaining constant pressure at detachment level. Thinning of the migmatitic lower crust is compensated by elevation of the crust

  18. Ordovician gas exploration breakthrough in the Gucheng lower uplift of the Tarim Basin and its enlightenment

    Directory of Open Access Journals (Sweden)

    Wang Zhaoming

    2014-10-01

    Full Text Available A steady high yield natural gas flow was tapped in the Ordovician strata of Well Gucheng 6 drilled in the Gucheng lower uplift in the Tarim Basin in 2012, marking the discovery of another carbonate gas exploration field after the other two fields in the middle and northern Tarim Basin (the so called Tazhong and Tabei in the industry. The exploration in the Gucheng lower uplift has experienced three stages: the first stage, marine facies clastic exploration from 1995 to 2003, focusing on the Devonian Donghe sandstone lithologic traps, the Silurian overlapping lithologic traps, and the Upper Ordovician shelf slope turbidites; the second stage focusing on the reef shoal carbonate reservoirs from 2003 to 2006, during which oil and gas were first discovered in Well Gucheng 4; the third stage can be divided into two periods, in the first period, deeper insight into interbed karstification reservoir exploration, intense research on tricky seismic issues, selection of favorable zones, and 3D seismic deployment in advance laid a robust foundation for breakthroughs in oil and gas exploration; and during 2009–2012, through an in-depth investigation, Well Gucheng 6 was drilled, bringing about the major breakthrough in oil and gas exploration in this study area. This success proves that the Lower Paleozoic carbonate rocks in the Gucheng area have good geological conditions and broad prospect for oil and gas exploration, which give us enlightenment in three aspects: a. new insight into geologic understanding is the prerequisite of exploration breakthrough; b. addressing bottleneck technologies, and acquiring 3D seismic data are the guarantees of exploration breakthrough; and c. emancipation of mind and persistent exploration are key to the findings in new domains.

  19. A sulfidic driver for the end-Ordovician mass extinction

    DEFF Research Database (Denmark)

    Hammarlund, Emma U.; Dahl, Tais Wittchen; Harper, David A.T.

    2012-01-01

    with the Normalograptus persculptus Zone, was less selective. Glacially induced cooling and oxygenation are two of many suggested kill mechanisms for the end-Ordovician extinction, but a general consensus is lacking. We have used geochemical redox indicators, such as iron speciation, molybdenum concentrations, pyrite...... to an increase in pyrite burial during the early Hirnantian. The S-isotope excursion coincides with a major positive carbon isotope excursion indicating elevated rates of organic carbon burial as well. We argue that euxinic conditions prevailed and intensified in the early Hirnantian oceans...... shelves. In our model, the expansion of euxinic conditions during the N. extraordinarius Zone was generated by a reorganization of nutrient cycling during sea level fall, and we argue, overall, that these dynamics in ocean chemistry played an important role for the end-Ordovician mass extinction. During...

  20. The onset of the 'Ordovician Plankton Revolution' in the late Cambrian

    DEFF Research Database (Denmark)

    Servais, Thomas; Perrier, Vincent; Danelian, Taniel

    2016-01-01

    The 'Great Ordovician Biodiversification Event' comprises the rapid diversification of marine organisms during the Ordovician Period. It is now clear that this adaptive radiation started for some organisms already in the Cambrian and continued for others beyond the end of the Ordovician, making...... during the late Cambrian and Early Ordovician, in particular in relation to the SPICE event. Our analyses include the changing diversities of the phytoplankton (acritarchs), diverse groups of zooplankton (e.g., radiolarians, graptolites, chitinozoans) and the switch to a planktonic mode of life of fossil...

  1. Conodonts, stratigraphy, and relative sea-level changes of the tribes hill formation (lower ordovician, east-central New York)

    Science.gov (United States)

    Landing, E.D.; Westrop, S.R.; Knox, L.A.

    1996-01-01

    Tremadocian onlap is recorded by the Tribes Hill Formation. The formation is a lower Lower Ordovician (upper conodont Fauna B Interval(?)- Rossodus manitouensis Zone) depositional sequence that unconformably overlies the Upper Cambrian Little Falls Formation. Depositional environments and stratigraphy indicate that the Tribes Hill was deposited on a wave-, not tide-, dominated shelf and that a uniform, 'layer-cake' stratigraphy is present. The deepening-shoaling sequence of the Tribes Hill includes the: 1) Sprakers Member (new; peritidal carbonate and overlying tempestite limestone and shale); 2) Van Wie Member (new; subtidal shale and limestone); 3) Wolf Hollow Member (revised; massive carbonates with thrombolitic cap); and 4) Canyon Road Member (new; glauconitic limestone and overlying evaporitic dolostone). The shoaling half-cycle of the Tribes Hill is older than a shoaling event in western Newfoundland, and suggests epeirogenic factors in earliest Ordovician sea-level change in east Laurentia. Conodont and trilobite biofacies track lithofacies, and Rossodus manitouensis Zone conodonts and Bellefontia Biofacies trilobites appear in the distal, middle Tribes Hill Formation. Twenty-four conodont species are illustrated. Ansella? protoserrata new species, lapetognathus sprakersi new species, Leukorhinion ambonodes new genus and species, and Laurentoscandodus new genus are described.

  2. Geodynamic setting and geochemical signatures of Cambrian?Ordovician rift-related igneous rocks (Ossa-Morena Zone, SW Iberia)

    Science.gov (United States)

    Sánchez-García, T.; Bellido, F.; Quesada, C.

    2003-04-01

    An important rifting event, accompanied by massive igneous activity, is recorded in the Ossa-Morena Zone of the SW Iberian Massif (European Variscan Orogen). It likely culminated in the formation of a new oceanic basin (Rheic ocean?), remnants of which appear presently accreted at the southern margin of the Ossa-Morena Zone. Rifting propagated diachronously across the zone from the Early Cambrian to the Late Ordovician, but by Early Ordovician time, the existence of a significant tract of new ocean is evidenced by a breakup unconformity. Although early stages of rifting were not accompanied by mantle-derived igneous activity, a pronounced increase of the geothermal gradient is indicated by partial melting of metasedimentary protoliths in the upper and middle crust, and by coeval core-complex formation. Geochemistry of the main volume of igneous rocks, emplaced some million years later during more mature stages of rifting, suggests an origin in a variably enriched asthenospheric source, similar to that of many OIB, from which subsequent petrogenetic processes produced a wide range of compositions, from basalt to rhyolite. A tectonic model involving collision with, and subsequent overriding of, a MOR is proposed to account for the overall evolution, a present-day analogue for which lies in the overriding of the East Pacific Rise by North America and the rifting of Baja California.

  3. Vestiges of an Ordovician west-vergent thin-skinned Ocloyic thrust belt in the Argentine Precordillera, southern Central Andes

    Science.gov (United States)

    Thomas, William A.; Astini, Ricardo A.

    2007-08-01

    Collision of the down-going, Laurentia-derived Argentine Precordillera terrane with the Gondwanan margin drove the Ordovician Ocloyic orogeny, including subduction volcanism, metamorphism, and top-to-west shearing east of the Precordillera. In the Precordillera, above passive-margin carbonates (Lower Ordovician San Juan Limestone and older carbonates), a Middle to Upper Ordovician westward-prograding synorogenic clastic wedge of black shale (Gualcamayo Shale) and coarser clastic sediment (Las Vacas Conglomerate and Trapiche Formation) fills a peripheral foreland basin. New research has identified vestiges of a west-directed thin-skinned Ocloyic foreland thrust belt that has been fragmented by east-directed Andean thrusting. The El Corral thrust sheet, with hanging-wall detachment in the San Juan Limestone, extends over a west-directed footwall frontal ramp and extensive flat to low-angle footwall cutoff in the Gualcamayo and Las Vacas formations. Las Vacas conglomerates in the footwall include olistoliths (10-m scale) exclusively of San Juan Limestone and Gualcamayo Shale; the beds in some olistoliths are folded. The advancing El Corral thrust sheet successively supplied and overrode the stratigraphically restricted olistoliths. In the El Corral footwall, tight west-vergent folds and faults within an anticlinorium in the San Juan Limestone and Gualcamayo Shale suggest a deeper (unexposed) thrust fault, the Los Celestitos fault. West of the anticlinorium, easterly dip (restored to remove Andean deformation) beneath an angular unconformity between Las Vacas and Trapiche beds is consistent geometrically with the trailing limb of a west-vergent fault-propagation anticline in the hanging wall of the subsurface Los Celestitos fault. The same angular unconformity truncates the El Corral fault and hanging-wall strata. In the Trapiche Formation, contrasting sedimentary facies from sandy turbidites westward to limestone-clast megabeds and olistoliths suggest another frontal

  4. The Late Ordovician deglaciation sequence of the SW Murzuq Basin (Libya)

    DEFF Research Database (Denmark)

    Moreau, Julien

    2011-01-01

    Rocks of Late Ordovician to Silurian age are well exposed on the western rim of theMurzuq Basin (Ghat-Tikiumit area,Libya)where seismic-scale exposures allow spectacular insights into the growth and decay of the LateOrdovician (Hirnantian) ice sheet.The ¢nal deglaciation left a complex topography...

  5. Characterization of Ordovician carbonate reservoirs, southeastern Saskatchewan, Canada

    Institute of Scientific and Technical Information of China (English)

    QING Hai-ruo

    2004-01-01

    The discovery of the prolific Ordovician Red River reservoirs in 1995 in southeastern Saskatchewan was the catalyst for extensive exploration activity which resulted in the discovery of more than 15 new Red River pools. The best yields of Red River production to date have been from dolomite reservoirs. Understanding the processes of dolomitization is, therefore, crucial for the prediction of the connectivity, spatial distribution and heterogeneity of dolomite reservoirs.The Red River reservoirs in the Midale area consist of 3~4 thin dolomitized zones, with a total thickness of about 20 m, which occur at the top of the Yeoman Formation. Two types of replacement dolomite were recognized in the Red River reservoir: dolomitized burrow infills and dolomitized host matrix. The spatial distribution of dolomite suggests that burrowing organisms played an important role in facilitating the fluid flow in the backfilled sediments. This resulted in penecontemporaneous dolomitization of burrow infills by normal seawater. The dolomite in the host matrix is interpreted as having occurred at shallow burial by evaporitic seawater during precipitation of Lake Almar anhydrite that immediately overlies the Yeoman Formation. However, the low δ18O values of dolomited burrow infills (-5.9‰~ -7.8‰, PDB) and matrix dolomites (-6.6‰~ -8.1‰, avg. -7.4‰ PDB) compared to the estimated values for the late Ordovician marine dolomite could be attributed to modification and alteration of dolomite at higher temperatures during deeper burial, which could also be responsible for its 87Sr/86Sr ratios (0.7084~0.7088) that are higher than suggested for the late Ordovician seawaters (0.7078~0.7080). The trace amounts of saddle dolomite cement in the Red River carbonates are probably related to "cannibalization" of earlier replacement dolomite during the chemical compaction.

  6. Ordovician ash geochemistry and the establishment of land plants

    Directory of Open Access Journals (Sweden)

    Parnell John

    2012-08-01

    Full Text Available Abstract The colonization of the terrestrial environment by land plants transformed the planetary surface and its biota, and shifted the balance of Earth’s biomass from the subsurface towards the surface. However there was a long delay between the formation of palaeosols (soils on the land surface and the key stage of plant colonization. The record of palaeosols, and their colonization by fungi and lichens extends well back into the Precambrian. While these early soils provided a potential substrate, they were generally leached of nutrients as part of the weathering process. In contrast, volcanic ash falls provide a geochemically favourable substrate that is both nutrient-rich and has high water retention, making them good hosts to land plants. An anomalously extensive system of volcanic arcs generated unprecedented volumes of lava and volcanic ash (tuff during the Ordovician. The earliest, mid-Ordovician, records of plant spores coincide with these widespread volcanic deposits, suggesting the possibility of a genetic relationship. The ash constituted a global environment of nutrient-laden, water-saturated soil that could be exploited to maximum advantage by the evolving anchoring systems of land plants. The rapid and pervasive inoculation of modern volcanic ash by plant spores, and symbiotic nitrogen-fixing fungi, suggests that the Ordovician ash must have received a substantial load of the earliest spores and their chemistry favoured plant development. In particular, high phosphorus levels in ash were favourable to plant growth. This may have allowed photosynthesizers to diversify and enlarge, and transform the surface of the planet.

  7. Hydrocarbon Accumulation Conditions of Ordovician Carbonate in Tarim Basin

    Institute of Scientific and Technical Information of China (English)

    LI Qiming; WU Guanghui; PANG Xiongqi; PAN Wenqin; LUO Chunshu; WANG Chenglin; LI Xinsheng; ZHOU Bo

    2010-01-01

    Based on comprehensive analysis of reservoir-forming conditions,the diversity of reservoir and the difference of multistage hydrocarbon charge are the key factors for the carbonate hydrocarbon accumulation of the Ordovician in the Tarim Basin.Undergone four major deposition-tectonic cycles,the Ordovician carbonate formed a stable structural framework with huge uplifts,in which are developed reservoirs of the reef-bank type and unconformity type,and resulted in multistage hydrocarbon charge and accumulation during the Caledonian,Late Hercynian and Late Himalayan.With low matrix porosity and permeability of the Ordovician carbonate,the secondary solution pores and caverns serve as the main reservoir space.The polyphase tectonic movements formed unconformity reservoirs widely distributed around the paleo-uplifts; and the reef-bank reservoir is controlled by two kinds of sedimentary facies belts,namely the steep slope and gentle slope.The unconventional carbonate pool is characterized by extensive distribution,no obvious edge water or bottom water,complicated oil/gas/water relations and severe heterogeneity controlled by reservoirs.The low porosity and low permeability reservoir together with multi-period hydrocarbon accumulation resulted in the difference and complex of the distribution and production of oil/gas/water.The distribution of hydrocarbon is controlled by the temporal-spatial relation between revolution of source rocks and paleo-uplifts.The heterogenetic carbonate reservoir and late-stage gas charge are the main factors making the oil/gas phase complicated.The slope areas of the paleo-uplifts formed in the Paleozoic are the main carbonate exploration directions based on comprehensive evaluation.The Ordovician of the northern slope of the Tazhong uplift,Lunnan and its periphery areas are practical exploration fields.The Yengimahalla-Hanikatam and Markit slopes are the important replacement targets for carbonate exploration.Gucheng,Tadong,the deep layers of

  8. Seawater fluid inclusions preserved within Cambrian-Ordovician marine cements indicate Cambrian-Ordovician seawater precipitated low-magnesium calcite

    Energy Technology Data Exchange (ETDEWEB)

    Johnson, W.J.; Goldstein, R.H. (Univ. of Kansas, Lawrence, KS (United States). Dept. of Geology)

    1992-01-01

    The San Saba Member of the Wilberns Formation (Llano Uplift, Texas) contains a series of Late Cambrian-Early Ordovician hardgrounds. Bladed low-Mg calcite cements are truncated at hardground surfaces and overlain by shallow marine limestones, indicating a syndepositional shallow marine origin. Primary one-phase fluid inclusions within bladed cements have marine salinities, suggesting that these low-Mg calcite cements formed as a precipitate from Late Cambrian and Early Ordovician seawater and have not undergone recrystallization. Stable isotope analysis of the bladed cement yields delta O-18 values that cluster between [minus]5.6--[minus]6.0 ([per thousand] PDB) which is comparable to those previously reported for Early Ordovician marine calcite. The delta C-13 values are more positive than those reported for this time interval (0.6--1.3 [per thousand] PDB). Trace element analysis indicates that strontium content ranges from 200 to 2,200 ppm. Iron ranges from below detection by electron microprobe to 800 ppm. Mg is generally below detection, however, cements in one hardground display Mg contents that increase progressively toward pore centers. Trace element data lack covariance that would suggest recrystallization. In addition, closed system recrystallization cannot be supported here due to a lack of microdolomite inclusions. Stable isotope, trace element, and fluid inclusion data are consistent with submarine cementation at or below the sediment-water interface. These cements have not undergone significant recrystallization and preserve a primary low Mg calcite mineralogy. These data suggest that early Paleozoic seawater differed chemically from modern seawater. Moreover, preservation of ancient seawater, within fluid inclusions, may provide a direct means of determining those differences.

  9. Did intense volcanism trigger the first Late Ordovician icehouse?

    Science.gov (United States)

    Buggisch, Werner; Joachimski, Michael M.; Lehnert, Oliver; Bergström, Stig M.; Repetski, John E.; Webers, Gerald F.

    2010-01-01

    Oxygen isotopes measured on Late Ordovician conodonts from Minnesota and Kentucky (United States) were studied to reconstruct the paleotemperature history during late Sandbian to Katian (Mohawkian–Cincinnatian) time. This time interval was characterized by intense volcanism, as shown by the prominent Deicke, Millbrig, and other K-bentonite beds. A prominent carbon isotope excursion (Guttenberg δ13C excursion, GICE) postdates the Millbrig volcanic eruptions, and has been interpreted to reflect a drawdown of atmospheric carbon dioxide and climatic cooling. The oxygen isotope record in conodont apatite contradicts this earlier interpretation. An increase in δ18O of 1.5‰ (Vienna standard mean ocean water) just above the Deicke K-bentonite suggests an abrupt and short-lived cooling that possibly initiated a first short-term glacial episode well before the major Hirnantian glaciation. The decrease in δ18O immediately after the mega-eruptions indicates warming before the GICE, and no cooling is shown in the GICE interval. The coincidence of the Deicke mega-eruption with a cooling event suggests that this major volcanic event had a profound effect on Late Ordovician (late Mohawkian) climate.

  10. Ordovician Basement Hydrocarbon Reservoirs in the Tarim Basin, China

    Institute of Scientific and Technical Information of China (English)

    YAN Xiangbin; LI Tiejun; ZHANG Tao

    2004-01-01

    Ordovician marine carbonate basement traps are widely developed in the paleo-highs and paleo-slopes in the Tarim Basin. Reservoirs are mainly altered pore-cavity-fissure reservoirs. Oil sources are marine carbonate rocks of the Lower Paleozoic. Thus, the paleo-highs and paleo-slopes have good reservoiring conditions and they are the main areas to explore giant and large-scale oil reservoirs. The main factors for their reservoiring are: (1) Effective combination of fenestral pore-cavity-fracture reservoirs, resulting from multi-stage, multi-cyclic karstification (paleo-hypergene and deep buried) and fracturing, with effective overlying seals, especially mudstone and gypsum mudstone in the Carboniferous Bachu Formation, is essential to hydrocarbon reservoiring and high and stable production; (2) Long-term inherited large rises and multi-stage fracture systems confine the development range of karst reservoirs and control hydrocarbon migration, accumulation and reservoiring; (3) Long-term multi-source hydrocarbon supply, early reservoiring alteration and late charging adjustment are important reservoiring mechanisms and determine the resource structure and oil and gas properties. Favorable areas for exploration of Ordovician carbonate basement hydrocarbon reservoirs in the Tarim Basin are the Akekule rise, Katahe uplift, Hetianhe paleo-high and Yakela faulted rise.

  11. Allogenic succession in Late Ordovician reefs from southeast China: a response to the Cathaysian orogeny

    Directory of Open Access Journals (Sweden)

    Qijian Li

    2015-02-01

    Full Text Available Several Late Ordovician (late Katian reef complexes are known from the border area of Jiangxi and Zhejiang provinces in southeast China. We studied two coral–stromatoporoid reefs exposed in the Xiazhen Formation at Zhuzhai (Yushan, Jiangxi. The reefs have a combined thickness of 7.4 m and are metazoan-dominated with most reef-builders in growth position. Stromatoporoids and tabulate corals constitute the framework of the reefs. Stromatoporoids (mostly Clathrodictyon dominate the first unit and show a vertical increase in proportion and dominance from the middle part to the top of the unit, whereas tabulate corals (dominated by Catenipora and Agetolites are the main reef-builders in the second unit where stromatoporoids are rare. We attribute this change to a greater tolerance of tabulate corals to turbidity, allowing them to thrive in the muddy facies of the upper unit. This facies change is probably related to the increasing terrestrial input from the northwestward expansion of the Cathaysian Land during the late Katian. The Cathaysian orogeny also led to a short-term exposure of the sea floor in the study area, which terminated the reef growth.

  12. Origin and evolution of palaeokarst within the Lower Ordovician (Ibexian) Goodwin Formation (Pogonip Group)

    Institute of Scientific and Technical Information of China (English)

    Robert; J.; Kervin; Adam; D.; Woods

    2012-01-01

    Palaeokarst within the Lower to Middle Ordovician Goodwin Formation, Pogonip Group (upper Ibexian-lower Whiterockian) was examined in detail at Meiklejohn Peak, Nevada USA in order to determine its origin, evolution, and relationship to sea level change. Detailed outcrop and petrographic examination of dolostone breccias and host rock reveals that palaeokarst was formed and affected by two distinct cycles of sea level change. A relative transgression resulted in deposition of lagoonal, ooid shoal, and shallow subtidal facies as sea level rose. Exposure of the carbonate platform led to the formation of multiple phreatic caves below the water table, as well as the development of numerous vadose conduits from the downward percolation of meteoric waters. Vadose water flow through early cave-wall and cave-roof collapse breccias resulted in rounding of smaller breccias clasts via physical transport and corrosion, while subsidence of subsurface karst led to the formation of a palaeodoline at the exposure surface. A second relative transgression deposited lagoonal sediments over the older karst; subsequent re-exposure of the carbonate platform resulted in the development of small breccia pockets as well as grikes within the youngest lagoonal sediments, and may have led to further corrosion of the older, deeper subsurface karst. The distal location of the study area within the carbonate platform suggests karst formation was the result of a substantial drop in relative sea level; the presence of multiple generations of palaeokarst imply that at least two higher-frequency cycles of sea-level change overprint the larger regression.

  13. Hirnantian (latest Ordovician bio- and chemostratigraphy of the Stirnas-18 core, western Latvia

    Directory of Open Access Journals (Sweden)

    Hints, Linda

    2010-03-01

    Full Text Available Integrated study of the uppermost Ordovician Porkuni Stage in the Stirnas-18 core, western Latvia, has revealed one of the most complete Hirnantian successions in the eastern Baltic region. The interval is characterized by two shallowing upwards depositional sequences that correspond to the Kuldiga and Saldus formations. The whole-rock carbon stable isotope curve indicates a long rising segment of the Hirnantian carbon isotope excursion, with the highest peak in the upper part of the Kuldiga Formation. The bioclast carbon and oxygen curves fit well with the whole-rock carbon data. Micro- and macrofossil data enabled seven combined associations to be distinguished within the Hirnantian strata. The early Porkuni fauna of the Spinachitina taugourdeaui Biozone, with pre-Hirnantian affinities, is succeeded by an interval with a Hindella–Cliftonia brachiopod association, a specific polychaete fauna, the chitinozoan Conochitina scabra, and the conodont Noixodontus girardeauensis. The middle part of the Kuldiga Formation is characterized by a low-diversity Dalmanella testudinaria brachiopod association, high diversity of scolecodonts, and the occurrence of the chitinozoan Lagenochitina prussica. From the middle part of the Kuldiga Formation the youngest occurrence yet known of the conodont Amorphognathus ordovicicus is reported. Also typical of the Kuldiga Formation is the occurrence of the trilobite Mucronaspis mucronata. The uppermost Hirnantian Saldus Formation contains no shelly fauna, but yields redeposited conodonts and at least partly indigenous chitinozoans and scolecodonts. Palaeontological criteria and stable isotope data enable correlation of the Stirnas section with other Hirnantian successions in the Baltic region and elsewhere.

  14. Ordovician ocean plate stratigraphy and thrust duplexes of the Ballantrae Complex, SW Scotland: Implications for the pelagic deposition rate and forearc accretion in the closing Iapetus Ocean

    Science.gov (United States)

    Fujisaki, Wataru; Asanuma, Hisashi; Suzuki, Kazue; Sawaki, Yusuke; Sakata, Shuhei; Hirata, Takafumi; Maruyama, Shigenori; Windley, Brian F.

    2015-11-01

    The Ballantrae Complex (at Bennane Lea in SW Scotland) contains important ocean plate stratigraphy (basalt, chert, mudstone, sandstone) in an accretionary prism that is associated with a classic Ordovician ophiolite. We used the ocean plate stratigraphy to sub-divide the prism into 11 tectonic units. To determine the depositional age of bedded cherts, zircons were separated from 9 tuff beds from 6 different units. All the tuffs have early to middle Ordovician ages, even though their present positions are mutually distant. These ages are consistent with microfossil records of radiolaria and graptolites. The stratigraphic-structural relationships demonstrate that the ocean plate stratigraphy has been repeated by bedding-parallel thrusts; this is typical of a modern accretionary duplex. We calculated the sedimentation rate of Early to Middle Ordovician bedded cherts at Bennane Lea on the basis of U-Pb zircon ages obtained from several tuff beds; the data indicate that the depositional rate (0.6-3 m/myr) was as slow as that of Mesozoic-Cenozoic equivalents defined by radiolaria. The age spectra of detrital zircons from Ballantrae sandstones show prominent single peaks at ca. 467 and 478 Ma, and a lack of Precambrian zircons. Integration of our new zircon ages with published isotopic data and palaeo-geographic maps indicates that the sandstones were deposited near an intra-oceanic arc and far from any continent containing Precambrian rocks. The pelagic-to-clastic sediments at Bennane Lea were deposited in the closing Iapetus Ocean from ca. 477 Ma to ca. 464 Ma, when they were accreted with the intra-oceanic arc of Ballantrae.

  15. Early-Middle Paleozoic subduction-collision history of the south-eastern Central Asian Orogenic Belt: Evidence from igneous and metasedimentary rocks of central Jilin Province, NE China

    Science.gov (United States)

    Pei, Fu-Ping; Zhang, Ying; Wang, Zhi-Wei; Cao, Hua-Hua; Xu, Wen-Liang; Wang, Zi-Jin; Wang, Feng; Yang, Chuan

    2016-09-01

    To constrain the Early-Middle Paleozoic tectonic evolution of the south-eastern segment of the Central Asian Orogenic Belt (CAOB), we undertook zircon U-Pb dating and analyzed major and trace elements and zircon Hf isotope compositions of Late Cambrian to Middle Devonian igneous and metasedimentary rocks in central Jilin Province, NE China. LA-ICP-MS zircon U-Pb dating indicates that the Early-Middle Paleozoic magmatism in central Jilin Province can be divided into four episodes: Late Cambrian (ca. 493 Ma), Middle Ordovician (ca. 467 Ma), Late Ordovician-Early Silurian (ca. 443 Ma), and Late Silurian-Middle Devonian (425-396 Ma). The progression from subduction initiation to maturity is recorded by Late Cambrian low-K tholeiitic meta-diabase, Middle Ordovician medium-K calc-alkaline pyroxene andesite, and Late Ordovician to Early Silurian low-K tonalite, which all have subduction-related characteristics and formed in an evolving supra-subduction zone setting. Late Silurian to Middle Devonian calc-alkaline igneous rocks, with the lithological association of granodiorite, monzogranite, rhyolite, dacite, and trachydacite, show progressively increasing K2O contents from medium K to shoshonite series. Furthermore, the Early-Middle Devonian monzogranites are characterized by high K2O, Sr/Y, and [La/Yb]N values, indicating they were generated by the melting of thickened lower crust. These results suggest a transition from subduction to post-orogenic setting during the Late Silurian-Middle Devonian. Our interpretation is supported by the maximum age of molasse deposition in the Zhangjiatun member of the Xibiehe Formation. Overall, we suggest that Late Cambrian tholeiitic meta-diabase, Middle Ordovician pyroxene andesite, and Late Ordovician-Early Silurian tonalite formed above the northward-subducting and simultaneously seaward-retreating of Paleo-Asian Ocean plate. Subsequently, the northern arc collided with the North China Craton and post-orogenic extension occurred

  16. Composition and significance of the Katian (Upper Ordovician conodont fauna of the Vaux Limestone (‘Calcaire des Vaux’ in Normandy, France

    Directory of Open Access Journals (Sweden)

    Annalisa Ferretti

    2014-12-01

    Full Text Available Study of new conodont collections from the Vaux Limestone exposed at its classical locality at Saint-Hilaire-la-Gérard in the Sées syncline, the conodont fauna of which was previously described in a preliminary way by Weyant et al. (1977, Un épisode calcaire ashgillien dans l’est du Massif armoricain; incidence sur l’âge des dépôts glacio-marins fini-ordoviciens. Comptes Rendus de l'Académie des Sciences, Paris, 284, Série D, 1147–1149, has provided significant new information about Late Ordovician conodonts from Normandy. A more precise age of this formation has been established based on an unexpectedly abundant conodont fauna of low diversity. Representatives of Amorphognathus, Hamarodus, Sagittodontina, Scabbardella and Eocarniodus are present and the fauna is referable to the middle Katian–lower Hirnantian A. ordovicicus Zone. Our study, the first illustrating Ordovician conodonts from Normandy, shows that the fauna is closely similar to middle Katian faunas from other parts of continental Europe and represents the Sagittodontina robusta–Scabbardella altipes biofacies of the Mediterranean Province.

  17. Accretion Rates of Meteorites and Cosmic Dust in the Early Ordovician

    National Research Council Canada - National Science Library

    Birger Schmitz; Bernhard Peucker-Ehrenbrink; Maurits Lindström; Mario Tassinari

    1997-01-01

    ... an interval of the Early Ordovician than at present. Osmium isotope and iridium analyses of whole-rock limestone indicate a coeval enhancement of one order of magnitude in the influx rate of cosmic dust...

  18. Global Stratotype Section and Point for base of the Ordovician System

    Institute of Scientific and Technical Information of China (English)

    R. A. Cooper; G. S. Nowlan; S. H. Williams

    2001-01-01

    @@ The Global Stratotype Section and Point for base of the Ordovician System and base of the lowest Ordovician stage (Tremadocian) is exposed in the coastal platform at Green Point, western Newfoundland, at the 101.8 m level, within Bed 23, in the measured section (Lower Broom Point Member, Green Point Formation), coinciding with the first appearance of the conodont Iapetognathus fluctivagus Nicoll, Miller, Nowlan,Repetski and Ethington, 1999, and 4.8 m below the earliest planktic graptolites.

  19. Very low-temperature metamorphism in Ordovician metasedimentary rocks above and below the Sardic unconformity, SW Sardinia, Italy

    Science.gov (United States)

    Franceschelli, M.; Battaglia, S.; Cruciani, G.; Pasci, S.; Puxeddu, M.

    2017-03-01

    In the Iglesiente region, the Cabitza and Monte Argentu Formations are separated by an angular unconformity known as the Sardic unconformity. This is related to an early Ordovician mild compressional phase, known as the "Sardic phase". The pelitic samples from the structurally lower Cabitza Formation consist of alternating reddish phyllosilicate-rich and whitish phyllosilicate-poor, sialic layers, whose S0 bedding plane is parallel to a pre-Variscan S1P schistosity overprinted by the Variscan S1V schistosity. Pelitic samples from the Monte Argentu Formation are characterized by a Variscan S1V axial plane schistosity. Samples from the two formations consist of quartz and phyllosilicates. The latter are potassic white mica, chlorite, paragonite, locally kaolinite, and pyrophyllite. The illite crystallinity values determined for the Cabitza samples are 0.25-0.31, with an average of 0.29; meanwhile, the Monte Argentu samples produce values of 0.33-0.38, with an average of 0.35. The chlorite crystallinity and b0 of potassic white mica values show greater heterogeneity in the Cabitza than the Monte Argentu samples. The b0 values and P-T pseudosections allow us to confirm that there is no significant difference in the P-T metamorphism conditions between the Cabitza and Monte Argentu samples. The Iglesiente region, which is considered to be the rift zone behind the Middle Ordovician Sarcidano-Barbagia volcanic arc, underwent the "Sardic phase", giving rise to E-W folds. These were first overprinted by weak E-W, and then by stronger N-S-oriented Variscan deformation events.

  20. Lithostratigraphy of Upper Ordovician strata exposed in Kentucky

    Science.gov (United States)

    Weir, Gordon Whitney; Peterson, Warren Lee; Swadley, W.C.

    1984-01-01

    Ordovician formations above the Lexington Limestone crop out in the Blue Grass region of Kentucky and along the Cumberland River and its tributaries. The formations are all conformable and in places intertongue and intergrade. The major Ordovician units above the Lexington Limestone in the Blue Grass region are: The Clays Ferry Formation, the Kope Formation, the Garrard Siltstone, the Fairview Formation, the Calloway Creek Limestone, the Grant Lake Limestone, the Ashlock Formation, the Bull Fork Formation, and the Drakes Formation. The Clays Ferry Formation is made up of subequal amounts of fossiliferous limestone and shale and minor siltstone; the Clays Ferry is as much as 300 ft thick and intertongues with the Lexington Limestone and the Kope Formation. The Kope Formation resembles the partly equivalent Clays Ferry but has a higher shale content (60-80 percent) and thicker layers of shale; the Kope, as much as 275 ft thick, is mostly restricted to the northern part of the State. The Garrard Siltstone, which consists of very calcitic siltstone and minor shale, overlies the Clays Ferry Formation in the southeastern part of the Blue Grass region; the Garrard, as much as 100 ft thick, feathers out into the upper part of the Clays Ferry in southern central and northern east-central Kentucky. The Fairview Formation is characterized by even-bedded limestone interlayered with nearly equal amounts of shale and minor siltstone. The Fairview crops out in the northern part of the Blue Grass region, where it generally overlies the Kope Formation or the Garrard Siltstone; it grades southward into the Calloway Creek Limestone. The Calloway Creek contains more limestone (generally at least 70 percent) and is more irregularly and thinner bedded than the Fairview. The Grant Lake Limestone is composed of nodular-bedded limestone (70-90 percent), interlayered and intermixed with shale; it overlies the Fairview Formation in the northern part of the Blue Grass region and the Calloway

  1. An acercostracan marrellomorph (Euarthropoda) from the Lower Ordovician of Morocco

    Science.gov (United States)

    Legg, David A.

    2016-04-01

    Enosiaspis hrungnir gen. et sp. nov., a new species of marrellomorph arthropod from the Lower Ordovician (Tremadocian) Fezouata biota of Morocco, is described. This taxon is characterised by the possession of a cordiform dorsal carapace with an anterior notch and a doublure-like structure formed from fused marginal spines, covering the entire body. The head comprises at least five segments which bear an anterior pair of antenna, followed by three pairs of potentially biramous, geniculate appendages. The trunk possesses around 25 pairs of delicate, almost filamentous appendages, which decrease in size posteriorly. Similar features are also found in Xylokorys chledophilia from the Silurian of England, and Vachonisia rogeri from the Devonian of Germany, indicating acercostracan affinities for E. hrungnir. This was tested using a phylogenetic analysis which resolved this taxon as sister taxon to a group composed of the formerly mentioned taxa. The similarities between the ventral spinose carapace doublure of E. hrungnir and the mediolateral spines of marrellid marrellomorphs further support claims that the dorsal shield of acercostracans evolved from the fusion of spinose anlagen, akin to the formation of the carapace of crustaceans.

  2. Crouching shells, hidden sponges: Unusual Late Ordovician cavities containing sponges

    Science.gov (United States)

    Park, Jino; Lee, Jeong-Hyun; Hong, Jongsun; Choh, Suk-Joo; Lee, Dong-Chan; Lee, Dong-Jin

    2017-01-01

    Marine cavities harbouring cryptic organisms have been ubiquitous throughout the Phanerozoic. However, our knowledge of early cryptic communities is as yet insufficient, and how metazoans began to utilize such habitats remains unknown. In this study, we document demosponge remains within intraskeletal cavities embedded in the micritic succession of a shallow carbonate platform in the Upper Ordovician (Katian) Xiazhen Formation of South China. Molluscs (gastropods, bivalves, and nautiloids) and corals (the solitary rugosan Tryplasma and colonial agetolitids) within the succession commonly contain patches of "spicular" demosponge remains (11%; n = 45/415), mainly occupying intraskeletal spaces with areas of 1-30 mm2 in thin-section. Sponge occurrence varies according to sedimentary facies: within lime mudstone facies, sponges commonly occur both inside and outside intraskeletal cavities, suggesting that sponges would have inhabited and become preserved within any available space in this environment. In contrast, when other sessile organisms co-occur in wackestone to packstone facies, there are fewer sponge occurrences both inside and outside cavities, possibly due to competition in open habitats and/or their poorer preservation in such environments. Overall, this result suggests that sponges would have exploited cryptic habitats by normal expansion of the open-surface biota. In addition, compared with coeval reef and hardground crypts, the Xiazhen intraskeletal cryptic biota is monotonous in composition, suggesting "decoupled" occupation of cryptic habitats in different environments.

  3. A remarkable new Middle Sandbian (Ordovician) hexactinellid sponge in Baltic erratics

    NARCIS (Netherlands)

    Botting, J.P.; Rhebergen, F.

    2011-01-01

    A new species of complex hexactinellid sponge, Haljalaspongia inaudita, is described from fluvially transported blocks found in northwestern Germany, near the Dutch border, but which probably originated from the eastern Baltic region. The heavily folded wall is composed of multiple spicule layers, i

  4. Trans-Atlantic application of the Baltic Middle and Upper Ordovician carbon isotope zonation

    Directory of Open Access Journals (Sweden)

    Stig M. Bergström

    2015-02-01

    Full Text Available Application of the recently introduced Baltic d13C isotope zonation to a composite North American Darriwilian through Hirnantian succession shows that in most intervals there is good trans-Atlantic agreement not only between the isotope zones but also with the available biostratigraphic data. This indicates that this isotope zonation is a useful tool for improving previously uncertain long-distance correlations.

  5. Ordovician and Silurian Phi Kappa and Trail Creek formations, Pioneer Mountains, central Idaho; stratigraphic and structural revisions, and new data on graptolite faunas

    Science.gov (United States)

    Dover, James H.; Berry, William B.N.; Ross, Reuben James

    1980-01-01

    Recent geologic mapping in the northern Pioneer Mountains combined with the identification of graptolites from 116 new collections indicate that the Ordovician and Silurian Phi Kappa and Trail Creek Formations occur in a series of thrust-bounded slices within a broad zone of imbricate thrust faulting. Though confirming a deformational style first reported in a 1963 study by Michael Churkin, our data suggest that the complexity and regional extent of the thrust zone were not previously recognized. Most previously published sections of the Phi Kappa and Trail Creek Formations were measured across unrecognized thrust faults and therefore include not only structural repetitions of graptolitic Ordovician and Silurian rocks but also other tectonically juxtaposed lithostratigraphic units of diverse ages as well. Because of this discovery, the need to reconsider the stratigraphic validity of these formations and their lithology, nomenclature, structural distribution, facies relations, and graptolite faunas has arisen. The Phi Kappa Formation in most thrust slices has internal stratigraphic continuity despite the intensity of deformation to which it was subjected. As revised herein, the Phi Kappa Formation is restricted to a structurally repeated succession of predominantly black, carbonaceous, graptolitic argillite and shale. Some limy, light-gray-weathering shale occurs in the middle part of the section, and fine-grained locally pebbly quartzite is present at the base. The basal quartzite is here named the Basin Gulch Quartzite Member of the Phi Kappa. The Phi Kappa redefined on a lithologic basis represents the span of Ordovician time from W. B. N. Berry's graptolite zones 2-4 through 15 and also includes approximately 17 m of lithologically identical shale of Early and Middle Silurian age at the top. The lower contact of the formation as revised is tectonic. The Phi Kappa is gradationally overlain by the Trail Creek Formation as restricted herein. Most of the coarser

  6. Palaeomagnetic evidence from the Ordovician and Silurian of northwest Peninsular Malaysia

    Science.gov (United States)

    Haile, N. S.

    1980-06-01

    The Ordovician and Silurian Setul Limestone of the Langkawi Islands, northwest Peninsular Malaysia, has a mean magnetic vector of D = 338°, I = 62° after cleaning and correction for tilt. This is equivalent to a palaeolatitude of 43°, and a palaeomagnetic pole at 46°N, 76°E. The Silurian part of the Setul limestone also shows a similar direction. The Ordovician results are equivalent to a palaeolatitude of 43°, N or S. Recent reconstructions, based on palaeontology, place Indochina and China in the northern hemisphere in the Ordovician; if this is correct, a palaeolatitide of 43° for Langkawi would imply that Malaya-Indochina was the most northerly continental fragment at that time.

  7. High potential for weathering and climate effects of non-vascular vegetation in the Late Ordovician

    Science.gov (United States)

    Porada, P.; Lenton, T. M.; Pohl, A.; Weber, B.; Mander, L.; Donnadieu, Y.; Beer, C.; Pöschl, U.; Kleidon, A.

    2016-07-01

    It has been hypothesized that predecessors of today's bryophytes significantly increased global chemical weathering in the Late Ordovician, thus reducing atmospheric CO2 concentration and contributing to climate cooling and an interval of glaciations. Studies that try to quantify the enhancement of weathering by non-vascular vegetation, however, are usually limited to small areas and low numbers of species, which hampers extrapolating to the global scale and to past climatic conditions. Here we present a spatially explicit modelling approach to simulate global weathering by non-vascular vegetation in the Late Ordovician. We estimate a potential global weathering flux of 2.8 (km3 rock) yr-1, defined here as volume of primary minerals affected by chemical transformation. This is around three times larger than today's global chemical weathering flux. Moreover, we find that simulated weathering is highly sensitive to atmospheric CO2 concentration. This implies a strong negative feedback between weathering by non-vascular vegetation and Ordovician climate.

  8. High potential for weathering and climate effects of non-vascular vegetation in the Late Ordovician

    Science.gov (United States)

    Porada, Philipp; Lenton, Tim; Pohl, Alexandre; Weber, Bettina; Mander, Luke; Donnadieu, Yannick; Beer, Christian; Pöschl, Ulrich; Kleidon, Axel

    2017-04-01

    Early non-vascular vegetation in the Late Ordovician may have strongly increased chemical weathering rates of surface rocks at the global scale. This could have led to a drawdown of atmospheric CO2 and, consequently, a decrease in global temperature and an interval of glaciations. Under current climatic conditions, usually field or laboratory experiments are used to quantify enhancement of chemical weathering rates by non-vascular vegetation. However, these experiments are constrained to a small spatial scale and a limited number of species. This complicates the extrapolation to the global scale, even more so for the geological past, where physiological properties of non-vascular vegetation may have differed from current species. Here we present a spatially explicit modelling approach to simulate large-scale chemical weathering by non-vascular vegetation in the Late Ordovician. For this purpose, we use a process-based model of lichens and bryophytes, since these organisms are probably the closest living analogue to Late Ordovician vegetation. The model explicitly represents multiple physiological strategies, which enables the simulated vegetation to adapt to Ordovician climatic conditions. We estimate productivity of Ordovician vegetation with the model, and relate it to chemical weathering by assuming that the organisms dissolve rocks to extract phosphorus for the production of new biomass. Thereby we account for limits on weathering due to reduced supply of unweathered rock material in shallow regions, as well as decreased transport capacity of runoff for dissolved weathered material in dry areas. We simulate a potential global weathering flux of 2.8 km3 (rock) per year, which we define as volume of primary minerals affected by chemical transformation. Our estimate is around 3 times larger than today's global chemical weathering flux. Furthermore, chemical weathering rates simulated by our model are highly sensitive to atmospheric CO2 concentration, which implies

  9. Carbon isotope stratigraphy of an ancient (Ordovician) Bahamian-type carbonate platform: Implications for preservation of global seawater trends

    Science.gov (United States)

    Saltzman, M.; Leslie, S. A.; Edwards, C. T.; Diamond, C. W.; Trigg, C. R.; Sedlacek, A. R.

    2013-12-01

    . Few studies of ancient carbonates have attempted to explicitly compare C-isotope trends in both restricted platform settings and open marine settings (e.g., Immenhauser et al. 2002). We studied a restricted Bahamian-type carbonate platform of Middle-Late Ordovician (Darriwilian-early Sandbian) age included in the St. Paul Group of Maryland, notable for sedimentologic evidence of severe restriction and a general lack of open marine macrofauna. We are able to correlate the C-isotope curve from the St. Paul Group to other sections globally by using a combination of conodont microfossils and measurement of Sr isotopes on conodont apatite. Coeval C-isotope trends from open marine settings in the western United States and Estonia are comparable to the restricted platform in Maryland. In our Ordovician example, local factors appear to have modified the magnitude of the global trends, but not the timing and direction. A remaining question is whether magnitude differences are a function of sedimentation rate and completeness. We continue to test hypotheses of global correlations of C-isotope trends in the Middle-Late Ordovician by utilizing the rapidly changing Sr isotope curve at that time.

  10. Ordovician Intrusive-related Gold-Copper Mineralization in West-Central New South Wales, Australia

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    Three major types of Ordovician intrusive-related gold-copper deposits are recognized in central-west New South Wales,, Australia: porphyry, skam and high sulphidation epithermal deposits.These deposits are mainly distributed within two Ordovician volcano-intrusive belts of the Lachlan Fold Be1t: the Orange-Wellington Belt and the Parkes-Narromine Belt. Available isotopic age data suggest that mineralization of the three types of deposits is essentially coeval with the Ordovician intrusive rocks (480-430 Ma). Porphyry gold-copper deposits can be further divided into two groups. The first group is associated with monzoniteshowing shoshonitic features represented by Cadia and Goonumbla. The second group is associated with diorite and dacite, including the Copper Hill and Cargo gold-copper deposits. Gold skarn is associated with Late Ordovician (430-439 Ma) monzonitic intrusive complexes in the Junction Reefs area (Sheahan-Grants, Frenchmans, and Cornishmens), Endeavour 6, 7 and 44, Big and Little Cadia. The epithermal gold deposits with high sulphidation including Gidginbung (Temora) and Peak Hill mainly occur within Ordovician andesite and volcaniclastic rocks, and are associated with advanced argillic alteration. Available isotopic age data indicate that both alteration and mineralization of the porphyry, skam and epithermal gold-copper deposits are broadly coeval with the Late Ordovician hoshonitic mangmatism, which is thought to result from the melting of sub-continental lithosphere caused by Palaeozoic subduction events. The Ordovician intrusive-related gold-copper deposits are restricted to two longitudinal parallel volcano-intrusive belts, rarely extending outside them. Diagonal intra-belt trends of mineralization are common, particularly at the intersections of longitudinal and transverse (oblique) fault/fracture zones basedon the authors'review of available geological data. The locations of these gold-copper deposits are obviously influenced by transverse

  11. Paleoredoc and pyritization of soft-bodied fossils in the Ordovician Frankfort Shale of New York

    DEFF Research Database (Denmark)

    Farrell, Una C.; Briggs, Derek E. G.; Hammarlund, Emma U.

    2013-01-01

    Multiple beds in the Frankfort Shale (Upper Ordovician, New York State), including the original "Beecher's Trilobite Bed," yield fossils with pyritized soft-tissues. A bed-by-bed geochemical and sedimentological analysis was carried out to test previous models of soft-tissue pyritization by inves......Multiple beds in the Frankfort Shale (Upper Ordovician, New York State), including the original "Beecher's Trilobite Bed," yield fossils with pyritized soft-tissues. A bed-by-bed geochemical and sedimentological analysis was carried out to test previous models of soft-tissue pyritization...

  12. Accretion rates of meteorites and cosmic dust in the Early Ordovician.

    Science.gov (United States)

    Schmitz, B; Peucker-Ehrenbrink, B; Lindstrom, M; Tassinari, M

    1997-10-03

    Abundant fossil meteorites in marine, condensed Lower Ordovician limestones from Kinnekulle, Sweden, indicate that accretion rates of meteorites were one to two orders of magnitude higher during an interval of the Early Ordovician than at present. Osmium isotope and iridium analyses of whole-rock limestone indicate a coeval enhancement of one order of magnitude in the influx rate of cosmic dust. Enhanced accretion of cosmic matter may be related to the disruption of the L chondrite parent body around 500 million years ago.

  13. Chief sources of brachiopod recovery from the end Ordovician mass extinction with special references to progenitors

    Institute of Scientific and Technical Information of China (English)

    戎嘉余; 詹仁斌

    1999-01-01

    Survivor, Lazarus and progenitor taxa are sources of biotic recovery following mass extinction. Investigations of the benthic brachiopods through the latest Ordovician mass extinction shows that progenitors developed many evolutionary novelties and successful surviving mechanisms. They are superior to survivors and Lazarus taxa in their ability to adapt to environmental changes. They are the primary source of macroevolution and the ancestors of a number of new taxa. Three kinds of progenitors are recognized based on the Ordovician-Silurian brachiopods from South China: survivor-progenitors, crisis-progenitors and Lazarus-progenitors; the last has the strongest ability to resist adverse environments, and is the most diverse and abundant.

  14. A world-wide reunion of Ordovician & Silurian geologists in Nanjing

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    @@ Hosted by the CAS Nanjing Institute of Geology and Paleontology(NIGPAS), the 10th International Symposium on the Ordovician System, the 3rd International Symposium on the Silurian System and the 4th Annual Meeting of the IGCP 503 Project were jointly held from 27 to 30 June in Nanjing, capital of East China's Jiangsu Province.

  15. Hanadirella: A new problematic arthropod(?) from the Lower Ordovician (Llanvirn) Tabuk Formation, central Saudi Arabia

    NARCIS (Netherlands)

    El-Khayal, A.A.

    1985-01-01

    The new genus Hanadirella - with the type species H. bramkampi - from the Lower Ordovician (Llanvirn) of central Saudi Arabia represents a segmented organism which appears to have an arthropod affinity. The problematic genus is oval hat-shaped, less than 1 mm in diameter. Its affinity and palaeoecol

  16. Upper Ordovician and Lower Silurian chitinozoans from central Nevada and Arctic Canada.

    Science.gov (United States)

    Soufiane, A; Achab, A

    2000-12-01

    Late Ordovician and Early Silurian chitinozoans from the uppermost Vinini Formation, and the Hanson Creek Formation in central Nevada and the lower Cape Phillips Formation, Cape Manning section, in Arctic Canada have been re-investigated and a new chitinozoan biozonation is proposed. The Upper Ordovician of central Nevada can easily be correlated to that of Arctic Canada through the common occurrence of the Ordochitina nevadensis biozone in both regions. No such correlation, however, is possible with the Late Ordovician of Anticosti Island in eastern Canada because of the absence of the index Upper Ordovician chitinozoan zonal species of central Nevada such as Belonechitina tenuispinata sp. nov, Ordochitina nevadensis sp. nov. and Nevadachitina vininica gen. nov., sp. nov. in the former area.One new genus, Nevadachitina, and nine new species, Eisenackitina ripae, Belonechitina martinica, Nevadachitina vininica, Nevadachitina praevininica, Ordochitina nevadensis, Belonechitina tenuispinata, Belonechitina parvispinata, Tanuchitina laurentiana, Angochitina hansonica are described and illustrated in this paper and four species are left in open nomenclature.

  17. Ordovician stratigraphic divisions and correlation of Maigaiti slope in Tarim Basin and its significance%塔里木盆地麦盖提斜坡奥陶纪地层划分对比及意义

    Institute of Scientific and Technical Information of China (English)

    刘忠宝; 张福顺; 高山林; 岳勇

    2016-01-01

    以碳同位素值的波动变化与沉积环境、海平面升降及地层界面突变等地质事件相对应为理论依据,开展碳同位素地层研究,建立了各组值域划分标准,解决碳酸盐岩地层缺乏标准生物化石情况下,地层归属难确定的问题。指出奥陶系自下而上碳同位素曲线呈现稳定-上升-正漂移的过程。其中,下统蓬莱坝组—鹰山组δ13C值范围为(-4.2~-0.2)×10-3,始终为负值;中统一间房组δ13C值范围为(-0.4~0.6)×10-3,以分布在零值附近为特征;上统恰尔巴克组—良里塔格组δ13C值范围(0.7~3.1)×10-3,均为正值。在此基础上,开展了巴楚典型露头剖面与麦盖提斜坡井下奥陶系碳同位素地层与岩石地层对比研究,提出麦盖提斜坡中部及东部断洼区发育上奥陶统,除东部断裂带外,普遍残存下奥陶统顶部泥晶灰岩段。%Based on the theory of corresponding relation between carbon isotope value fluctuation with sedi-mentary environment,sea level eustacy,formation interface mutation,etc,the authors study the stratigraphy by carbon isotopic method,and establish the classification standards for each unit,which solved the difficult problems on determining of the strata without index fossils in carbonate rocks.The Ordovician carbon isotopic curves present a process of stable-rising-positive drift in descending order.The δ1 3 C values vary from -4. 2 ×1 0 -3 to -0. 2 × 1 0 -3 in Lower Ordovician Penglaiba Formation and Yingshan Formation,characterized by the values below zero;from -0. 4 ×1 0 -3 to 0. 6 ×1 0 -3 in Middle Ordovician Yijianfang Formation,characterized by distributed near the zero value,and vary from 0. 7 ×1 0 -3 to 3. 1 ×1 0 -3 in Upper Ordovician Qiaerbake Formation and Lianglitage For-mation,featured by the values all above zero.On this basis,with the carbon isotopic standards,the correlation of the Lower Ordovician strata

  18. The Cambrian-Ordovician rocks of Sonora, Mexico, and southern Arizona, southwestern margin of North America (Laurentia): chapter 35

    Science.gov (United States)

    Page, William R.; Harris, Alta C.; Repetski, John E.; Derby, James R.; Fritz, R.D.; Longacre, S.A.; Morgan, W.A.; Sternbach, C.A.

    2013-01-01

    Cambrian and Ordovician shelf, platform, and basin rocks are present in Sonora, Mexico, and southern Arizona and were deposited on the southwestern continental margin of North America (Laurentia). Cambrian and Ordovician rocks in Sonora, Mexico, are mostly exposed in scattered outcrops in the northern half of the state. Their discontinuous nature results from extensive Quaternary and Tertiary surficial cover, from Tertiary and Mesozoic granitic batholiths in western Sonora, and from widespread Tertiary volcanic deposits in the Sierra Madre Occidental in eastern Sonora. Cambrian and Ordovician shelf rocks were deposited as part of the the southern miogeocline on the southwestern continental margin of North America.

  19. Quantitative evaluation of microplankton palaeobiogeography in the Ordovician-Early Silurian of the northern Trans European Suture Zone: implications for the timing of the Avalonia-Baltica collision.

    Science.gov (United States)

    Vecoli, M; Samuelsson, J

    2001-05-01

    Quantitative analysis of assemblage similarity among chitinozoan and acritarch associations recovered from various sedimentary sequences across the Trans European Suture Zone (TESZ; southern Baltic Sea and northern Germany region), permits evaluation of changes in microplankton palaeobiogeography during the Ordovician in the study area. The present data confirm strong palaeobiogeographic differences between the lower Ordovician of the Rügen area, and the coeval domains of the East European Platform (EEP), corroborating the idea that the subsurface of Rügen should be considered palaeogeographically as the eastern extension of Avalonia.Cluster analysis of chitinozoan assemblages from numerous wells in the Rügen area, and one well from the southern margin of the EEP indicates that chitinozoan bioprovincialism reached its maximum during the Llanvirn; during this period, the Rügen microplankton communities were clearly Gondwanan in character. Calculations using the coefficient of similarity support the conclusion of a high similarity between Llanvirn acritarch assemblages from the Rügen subsurface and from coeval Perigondwana localities (e.g. Tunisia). Since the early Caradoc, this Gondwanan affinity of the Rügen microfossils starts to lessen, and becomes negligible during the late Caradoc. During latest Caradoc-early Ashgill through Llandovery times the chitinozoan assemblages from either side of the TESZ are undistinguishable. If palaeobiogeographical differentiation is primarily related to palaeolatitudinal distance, then the present data support closure of the Tornquist Ocean during late Caradoc-Ashgill times. The presence of reworked Llanvirn acritarchs of Perigondwanan affinity in middle Ashgill sedimentary sequences at the southern margin of the EEP, clearly shows that by this time erosion of an uplifted area was taking place. Accordingly, the closure of the Tornquist Ocean, and consequent Avalonia-Baltica collision must have taken place during the time

  20. A Stranger in the Midst: Searching for Relict Grains from Rare Meteorite Types in Mid-Ordovician Limestone Strata

    Science.gov (United States)

    Martin, E.; Schmitz, B.

    2016-08-01

    A layer of Mid-Ordovician limestone harbors exceptional amounts of L-chondritic chromite grains. The layer also contains grains from potentially rarer types of meteorites, following the discovery of the fossil meteorite Österplana 065.

  1. Petrography, Geochemistry and Proposed Genesis of Ordovician Oolitic Iron Formation Members of the Lashkarak Formation, Eastern Alborz

    Directory of Open Access Journals (Sweden)

    Mansoore Maghsoudloo Mahalli

    2016-07-01

    Full Text Available Introduction Oolitic iron formations are sedimentary rocks with >5 vol.% oolites and >15 wt.% iron, corresponding to 21.4 wt.% Fe2O3 (Young, 1989; Petranek and Van Houten, 1997; Mucke and Farshad, 2005. In Iran, new iron oolite-bearing members have been identified in the Lashkarak Formation (lower-middle Ordovician in the Abarsej, Dehmola and Simehkuh sections, eastern Alborz (Ghobadi Pour et al., 2011. At present, the mineralogy and geochemistry of these members are not known. Consequently, research reported here was conducted to reveal the mineralogical and geochemical characteristics of Ordovician oolitic iron formationmembers and to discuss their genesis and economic importance. Materials and Analyses Field geology and sampling was carried out to collect 25 samples from the ooliticiron formation members in the Abarsej, Dehmola and Simehkuh section in eastern Alborz. Samples were prepared for polished-thin sections (n=10, XRD analysis (n=15. Whole-rock chemical analysis (n=15 by XRF for major elements and by ICP-ES for trace elements was performed by laboratories at the SarCheshmeh copper mine complex, Kerman, Iran. One sample was analyzed by SEM at the Wales Museum, UK. Results Microscopic studies show that the oolitic iron formation members are hosted by carbonate argillite rocks. They are mainly composed of oolites rather than pisoliths (small bodies somewhat larger and more irregular than oolites, whereas oolites have mainly ellipsoidal forms and locally spherical shapes. Most (6 oolites show banding with a central core. Simple oolites without a core are scarce. Mineralogically, oolites are mainly chamositic and hematitic in composition; goethite, pyrite and glauconite occur in traces and siderite is absent. Quartz, calcite and zircon are accessory minerals which are present in the groundmass. Geochemically, TFeO % of the oolitic iron formation horizons ranges from 8 to 48 % with an average of 21%. The CaO content ranges from 2 to 37% and

  2. Evidence For Diffusion Dominant Solute Transport In The Ordovician Sediments Of The Michigan Basin

    Science.gov (United States)

    Sykes, J. F.; Normani, S. D.; Yin, Y.

    2011-12-01

    A Deep Geologic Repository (DGR) for Low and Intermediate Level Radioactive Waste has been proposed by Ontario Power Generation for the Bruce site near Tiverton, Ontario, 225 km northwest of Toronto. The DGR concept envisions a repository excavated at a depth of 680 m within the low permeability (less than 10e-14 m/s) limestone Cobourg Formation beneath 200 m of Ordovician age shale. The attributes of the hydrogeologic environment for the DGR, and the potential for solute transport from a repository, were assessed using numerical models for hypothesis testing and numerical experiments. Data for the analyses included Westbay pressure measurements from the DGR site investigation boreholes. These data indicate that the Cambrian sandstone and the Niagaran Group in the Silurian are over-pressured relative to density corrected hydrostatic levels while the Ordovician limestone and shale are significantly under-pressured. The abnormal pressures provide evidence that solute transport in the low permeable Ordovician sediments is diffusion dominant. Sedimentary basins, when at hydrological equilibrium, normally show a near-hydrostatic pressure distribution. Under certain conditions, some excess pressure or pressure greater than hydrostatic can develop in low-permeability layers or other hydraulically isolated parts of systems. The processes commonly invoked to explain these over-pressures are compaction, hydrocarbon migration, diagenesis, tectonic stress or more simply topographic effects. Explanations of abnormal under-pressures include osmosis, exhumation, glaciation unloading, crustal flexure and the presence of a non-wetting gas phase in pores. A requirement of both abnormal over-pressures and under-pressures is low hydraulic conductivity in either the formation in which the abnormal pressures are observed, or in the overlying and underlying formations. Hydraulic conductivity estimates from straddle packer tests in the DGR boreholes confirm that the hydraulic

  3. Unusual Deep Water sponge assemblage in South China-Witness of the end-Ordovician mass extinction.

    Science.gov (United States)

    Li, Lixia; Feng, Hongzhen; Janussen, Dorte; Reitner, Joachim

    2015-11-05

    There are few sponges known from the end-Ordovician to early-Silurian strata all over the world, and no records of sponge fossils have been found yet in China during this interval. Here we report a unique sponge assemblage spanning the interval of the end-Ordovician mass extinction from the Kaochiapien Formation (Upper Ordovician-Lower Silurian) in South China. This assemblage contains a variety of well-preserved siliceous sponges, including both Burgess Shale-type and modern type taxa. It is clear that this assemblage developed in deep water, low energy ecosystem with less competitors and more vacant niches. Its explosion may be related to the euxinic and anoxic condition as well as the noticeable transgression during the end-Ordovician mass extinction. The excellent preservation of this assemblage is probably due to the rapid burial by mud turbidites. This unusual sponge assemblage provides a link between the Burgess Shale-type deep water sponges and the modern forms. It gives an excellent insight into the deep sea palaeoecology and the macroevolution of Phanerozoic sponges, and opens a new window to investigate the marine ecosystem before and after the end-Ordovician mass extinction. It also offers potential to search for exceptional fossil biota across the Ordovician-Silurian boundary interval in China.

  4. Unusual Deep Water sponge assemblage in South China—Witness of the end-Ordovician mass extinction

    Science.gov (United States)

    Li, Lixia; Feng, Hongzhen; Janussen, Dorte; Reitner, Joachim

    2015-11-01

    There are few sponges known from the end-Ordovician to early-Silurian strata all over the world, and no records of sponge fossils have been found yet in China during this interval. Here we report a unique sponge assemblage spanning the interval of the end-Ordovician mass extinction from the Kaochiapien Formation (Upper Ordovician-Lower Silurian) in South China. This assemblage contains a variety of well-preserved siliceous sponges, including both Burgess Shale-type and modern type taxa. It is clear that this assemblage developed in deep water, low energy ecosystem with less competitors and more vacant niches. Its explosion may be related to the euxinic and anoxic condition as well as the noticeable transgression during the end-Ordovician mass extinction. The excellent preservation of this assemblage is probably due to the rapid burial by mud turbidites. This unusual sponge assemblage provides a link between the Burgess Shale-type deep water sponges and the modern forms. It gives an excellent insight into the deep sea palaeoecology and the macroevolution of Phanerozoic sponges, and opens a new window to investigate the marine ecosystem before and after the end-Ordovician mass extinction. It also offers potential to search for exceptional fossil biota across the Ordovician-Silurian boundary interval in China.

  5. Did the amalgamation of continents drive the end Ordovician mass extinctions?

    DEFF Research Database (Denmark)

    Mac Ørum Rasmussen, Christian; Harper, David Alexander Taylor

    2011-01-01

    Global biodiversity has been punctuated throughout the Phanerozoic by extinction events that vary in their degree of intensity and devastation. The mass extinction event that occurred at the end of the Ordovician Period rapidly removed a wide range of species. Because taxonomic loss occurred during...... – was not the sole reason for the crisis. Based on a large, bibliographic database of rhynchonelliform brachiopods that specifically operates within very narrow time-slices where every locality has been precisely georeferenced for the Upper Ordovician–Lower Silurian interval, we show that the extinctions were...... the extent of the extinctions and the subsequent diversity rebound, demonstrates that a reduction in ¿-diversity was perhaps the most important manifestation of the end Ordovician crisis and further raises the question whether this could be applied to other large Phanerozoic perturbations in biodiversity...

  6. Remains of early Ordovician mantle-derived magmatism in the Santander Massif (Colombian Eastern Cordillera)

    Science.gov (United States)

    Mantilla Figueroa, Luis C.; Bissig, Thomas; Cottle, John M.; Hart, Craig J. R.

    2012-10-01

    An Early Ordovician magmatic event has been documented in the Santander Massif (north-Eastern Cordillera, Colombia). Three U/Pb laser ablation ages of 477 ± 2 Ma (Arenig), were obtained from metamorphosed and foliated calc-alkaline diorites. The 176Hf/177Hf values in zircons from these meta-diorites, yielded epsilon Hf values (ɛHft) > 0 (Mean = 2 ± 1, at 477 Ma). These data allow interpretation of the origin of these zircons from a radiogenic initial Hf isotope source, which is characteristic of the Earth's mantle. This, together with the fact that the rocks have been affected subsequently by tectonometamorphic processes, suggests that the early Ordovician diorites have been emplaced in a supra-subduction tectonic setting, related to onset of the Iapetus Ocean closure.

  7. Biogeographic and bathymetric determinants of brachiopod extinction and survival during the Late Ordovician mass extinction

    DEFF Research Database (Denmark)

    Finnegan, Seth; Mac Ørum Rasmussen, Christian; Harper, David A. T.

    2016-01-01

    The Late Ordovician mass extinction (LOME) coincided with dramatic climate changes, but there are numerous ways in which these changes could have driven marine extinctions. We use a palaeobiogeographic database of rhynchonelliform brachiopods to examine the selectivity of Late Ordovician......–Early Silurian genus extinctions and evaluate which extinction drivers are best supported by the data. The first (latest Katian) pulse of the LOME preferentially affected genera restricted to deeper waters or to relatively narrow (less than 35°) palaeolatitudinal ranges. This pattern is only observed...... in the latest Katian, suggesting that it reflects drivers unique to this interval. Extinction of exclusively deeper-water genera implies that changes in water mass properties such as dissolved oxygen content played an important role. Extinction of genera with narrow latitudinal ranges suggests that interactions...

  8. A new glyptorthid species (Brachiopoda: Orthida from the Upper Ordovician of Estonia

    Directory of Open Access Journals (Sweden)

    Linda Hints

    2010-09-01

    Full Text Available A new glyptorthid brachiopod species Bassettella alata with surface pits and lamellose frills is described from the Upper Ordovician Haljala and Keila stages of northern Estonia. The new species appears in the Jõhvi Substage of theHaljala Stage (mid-Sandbian and is somewhat younger than the type species B. ;gracilis appearing in the lower Idavere Substage of the same stage in NW Russia. In the uppermost Keila Stage (lowermost Katian, B. ;alata belongs to a mixed faunal association of the marginal facies of the Vasalemma Formation comprising the oldest Ordovician reefs in Estonia. The distribution pattern of brachiopods of the genus Bassettella shows a westward shift in time and changes in shell morphology from subrectangular to subtriangular with alate cardinal extremities.

  9. First record of the Ordovician fauna in Mila-Kuh, eastern Alborz, northern Iran

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    Mohammad-Reza Kebria-ee Zadeh

    2015-05-01

    Full Text Available Restudy of the Cambrian–Ordovician boundary beds, traditionally assigned to the Mila Formation Member 5 in Mila-Kuh, northern Iran, for the first time provides convincing evidence of the Early Ordovician (Tremadocian age of the uppermost part of the Mila Formation. Two succeeding trilobite assemblages typifying the Asaphellus inflatus–Dactylocephalus and Psilocephalina lubrica associations have been recognized in the uppermost part of the unit. The Tremadocian trilobite fauna of Mila-Kuh shows close similarity to contemporaneous trilobite faunas of South China down to the species level, while affinity to the Tremadocian fauna of Central Iran is low. The trilobite species Dactylocephalus levificatus and brachiopod species Tritoechia tenuis from the Tremadocian of Mila-Kuh are new to science.

  10. The conodont Iapetognathus and its value for defining the base of the Ordovician System

    Science.gov (United States)

    Miller, J. E.; Repetski, John E.; Nicoll, R. S.; Nowlan, G. S.; Ethington, R. L.

    2014-01-01

    Nicoll et al. (1999, Brigham Young University Geology Studies 44, 27–101) published the taxonomy of species of the ramiform conodont Iapetognathus Landing in Fortey et al. (1982, The Cambrian–Ordovician boundary: sections, fossil distributions, and correlations, National Museum of Wales, Geological Series No. 3, Cardiff, 95–129) and its ancestorIapetonudus Nicoll et al., 1999. Cooper et al. (2001, Episodes 24, 19–28) used the First Appearance Datum of Iapetognathus fluctivagus Nicoll et al., 1999 to mark the base of the Ordovician System at Green Point, Newfoundland. Terfelt et al. (2012, Lethaia 45, 227–237) re-evaluated Iapetognathus at Green Point and made several taxonomic and stratigraphic conclusions, nearly all of which we refute herein.

  11. Conodont biostratigraphy in the Middle–Upper Ordovician boundary beds of Estonia

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    Viira, Viive

    2008-03-01

    Full Text Available Conodonts of the uppermost Uhaku, the Kukruse, and the lower Haljala stages (uppermost Darriwilian and lower Sandbian of Estonia are discussed. The distribution of conodonts within the Pygodus serra, P. anserinus, and Amorphognathus tvaerensis zones is considered on the basis of 2 outcrop and 15 drill core sections. Judging by the Global Stratotype Section, Fågelsång, Sweden, the base of the Upper Ordovician Series should be lower than the first appearance of A. tvaerensis. The Estonian material shows that elements of A. tvaerensis from the lowermost range of the species are of a morphotype similar to A. inaequalis. It is proposed that the A. inaequalis Subzone be upgraded to the A. inaequalis Zone. The best level for the Middle–Upper Ordovician boundary in Estonia is at the lower boundary of the Kukruse Stage below the appearance of A. tvaerensis and/or A. inaequalis.

  12. Late Ordovician-Early Silurian chitinozoans from north-eastern and western Illinois, USA

    Science.gov (United States)

    Butcher, A.; Mikulic, Donald G.; Kluessendorf, Joanne

    2010-01-01

    Samples of uppermost Ordovician and Silurian strata from two cores from north-eastern and western Illinois were processed for chitinozoans. Due to apparent sea-floor oxidation or palaeoenvironmental constraints, very few samples yielded specimens, but those that did allow tentative correlation with established biostratigraphical zonations for the Chitinozoa. Samples from the Wilhelmi Formation of core DH76-21 in north-eastern Illinois yielded Spinachitina fragilis, a typically earliest Silurian taxon. A sample from the Maquoketa Group strata of core Principia #4, western Illinois, yielded a monospecific assemblage of Conochitina elegans, which is suggestive of a late Ordovician age. Higher in this core, a sample from the upper strata of the Bowling Green Dolomite yielded an assemblage indicating a late Rhuddanian to Aeronian age, including Angochitina hansonica, previously only described from strata in Nevada, and one new species, Fungochitina illinoisensis. ?? 2009 Elsevier B.V. All rights reserved.

  13. A new glyptorthid species (Brachiopoda: Orthida) from the Upper Ordovician of Estonia

    OpenAIRE

    Linda Hints

    2010-01-01

    A new glyptorthid brachiopod species Bassettella alata with surface pits and lamellose frills is described from the Upper Ordovician Haljala and Keila stages of northern Estonia. The new species appears in the Jõhvi Substage of theHaljala Stage (mid-Sandbian) and is somewhat younger than the type species B. ;gracilis appearing in the lower Idavere Substage of the same stage in NW Russia. In the uppermost Keila Stage (lowermost Katian), B. ;alata belongs to a mixed faunal association of the ma...

  14. New biostratigraphically important chitinozoans from the Kukruse Regional Stage, Upper Ordovician of Baltoscandia

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    Jaak Nõlvak

    2015-08-01

    Full Text Available Three new chitinozoan species, Conochitina savalaensis, Conochitina viruana and Belonechitina intonsa, are described. All these species are stratigraphically restricted to the Kukruse age (lowermost Sandbian, Laufeldochitina stentor chitinozoan Zone and have been recorded in numerous East Baltic sections as well as from NE Poland and NW Ukraine and Sweden. Their short temporal range and relative abundance point to a great biostratigraphical value for regional correlations near the base of the Upper Ordovician.

  15. Ordovician graptolite-bearing strata in southern Jiangxi with a special reference to the Kwangsian Orogeny

    Institute of Scientific and Technical Information of China (English)

    2010-01-01

    The Ordovician graptolite sequence of the Yongxin-Chongyi area in southern Jiangxi was suggested as a standard for the correlation of Ordovician in the Zhujiang region of South China. Based on a restudy of the Upper Ordovician graptolites, the Shikou and Huamianlong formations are recognized herein as a part of the Hanjiang Formation, corresponding only to the Dipla-canthograptus caudatus-Diplacanthograptus spiniferus Zone. Two graptolite zones in the Longxi Formation of Yongxin and Chongyi, the Nemagraptus gracilis Zone and Climacograptus bicornis Zone, are redefined here. A rapid replacement of facies from the typical deep-water graptolitic black shale of Longxi Formation to the rapidly-accumulated, shallow-water clastic deposits of Hanjiang Formation indicates the tectonic initiation of the Kwangsian Orogeny. The thick clastic deposits of the Han-jiang Formation are proposed to come from a nearby source area that rose during the Kwangsian Orogeny. The D. caudatus-D. spiniferus graptolite Zone of the Hanjiang Formation indicates the initiation time of this tectonic event.

  16. From northern Gondwana passive margin to arc dismantling: a geochemical discrimination of Ordovician volcanisms (Sardinia, Italy)

    Science.gov (United States)

    Gaggero, L.; Oggiano, G.; Buzzi, L.; Funedda, A.

    2009-04-01

    In Sardinia, one of the southernmost remain of the European Variscan belt, a crustal section through northern Gondwanan paleodomains is largely preserved. It bears significant evidence of igneous activity, recently detailed in field relationships and radiometric dating (Oggiano et al., submitted). A Cambro - Ordovician (491.7 ± 3.5 Ma ÷ 479.9 ± 2.1 Ma, LA-ICP-MS U-Pb zircon age) bimodal volcanic suite occurs with continuity in external and inner Variscan nappes of Sardinia below the so-called Sardic unconformity. The igneous suite represents an intraplate volcanic activity developed through subsequent episodes: i) an intermediate explosive and effusive volcanism, i.e. pyroclastic fall deposits and lava flows, embedded into epicontinental clastic sediments, culminating in silicic ignimbrite eruptions, and ii) mafic effusives. Geochemical data document a transitional, within-plate signature, e.g. the average Th/Ta (4.5) and La/Nb (2.7) overlap the upper continental crust values. The volcanites are characterized by slight fractionation of LREEs, nearly flat HREE abundance. The negative Eu anomaly increases towards evolved compositions. Some prominent HREE depletion (GdCN/YbCN = 13.8), and the high Nb/Y suggest a garnet-bearing source. The high 87Sr radiogenic content (87Sr/86Sr 490 Ma = 0.71169) and the epsilon Nd 490 Ma value of -6.54 for one dacite sample, imply a time integrated LREE-enriched source with a high Rb/Sr, such as a metasedimentary source. The stratigraphy of the succession and the geochemical composition of igneous members suggest a volcanic passive margin along the northern Gondwana at the early Ordovician. The bimodal Mid-Ordovician arc volcanism (465.4 ± 1.4 Ma, U-Pb zircon age; Oggiano et al., submitted) is developed in the external nappes (e.g. in Sarrabus and Sarcidano) and in the foreland occurs as clasts at the base of the Hirnantian succession (Leone et al. 1991). The Mid Ordovician sub-alkalic volcanic suite has reliable stratigraphic and

  17. Early Paleozoic paleogeography of the northern Gondwana margin: new evidence for Ordovician-Silurian glaciation

    Science.gov (United States)

    Semtner, A.-K.; Klitzsch, E.

    1994-12-01

    During the Early Paleozoic, transgressions and the distribution of sedimentary facies on the northern Gondwana margin were controlled by a regional NNW-SSE to almost north-south striking structural relief. In Early Silurian times, a eustatic highstand enabled the sea to reach its maximum southward extent. The counterclockwise rotation of Gondwana during the Cambrian and Early Ordovician caused the northern Gondwana margin to shift from intertropical to southern polar latitudes in Ordovician times. Glacial and periglacial deposits are reported from many localities in Morocco, Algeria, Niger, Libya, Chad, Sudan, Jordan and Saudi Arabia. The Late Ordovician glaciation phase was followed by a period of a major glacioeustatic sea-level rise in the Early Silurian due to the retreat of the ice-cap. As a consequence of the decreasing water circulation in the basin centers (Central Arabia, Murzuk- and Ghadames basins), highly bituminous euxinic shales were deposited. These shales are considered to be the main source rock of Paleozoic oil and gas deposits in parts of Saudi Arabia, Libya and Algeria. The following regression in the southern parts of the Early Silurian sea was probably caused by a second glacial advance, which was mainly restricted to areas in Chad, Sudan and Niger. Evidence for glacial activity and fluvioglacial sedimentation is available from rocks overlying the basal Silurian shale in north-east Chad and north-west Sudan. The Early Silurian ice advance is considered to be responsible for the termination of euxinic shale deposition in the basin centers.

  18. Marine ostracod provinciality in the Late Ordovician of palaeocontinental Laurentia and its environmental and geographical expression.

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    Mohibullah Mohibullah

    Full Text Available BACKGROUND: We examine the environmental, climatic and geographical controls on tropical ostracod distribution in the marine Ordovician of North America. METHODOLOGY/PRINCIPAL FINDINGS: Analysis of the inter-regional distribution patterns of Ordovician Laurentian ostracods, focussing particularly on the diverse Late Ordovician Sandbian (ca 461 to 456 Ma faunas, demonstrates strong endemicity at the species-level. Local endemism is very pronounced, ranging from 25% (e.g. Foxe basin to 75% (e.g. Michigan basin in each basin, a pattern that is also reflected in other benthic faunas such as brachiopods. Multivariate (ordination analyses of the ostracod faunas allow demarcation of a Midcontinent Province and a southern Marginal Province in Laurentia. While these are most clearly differentiated at the stratigraphical level of the bicornis graptolite biozone, analyses of the entire dataset suggest that these provinces remain distinct throughout the Sandbian interval. Differences in species composition between the provinces appear to have been controlled by changes in physical parameters (e.g. temperature and salinity related to water depth and latitude and a possible regional geographic barrier, and these differences persist into the Katian and possibly the Hirnantian. Local environmental parameters, perhaps operating at the microhabitat scale, may have been significant in driving local speciation events from ancestor species in each region. CONCLUSIONS/SIGNIFICANCE: Our work establishes a refined methodology for assessing marine benthic arthropod micro-benthos provinciality for the Early Palaeozoic.

  19. Brachiopod faunas after the end Ordovician mass extinction from South China: Testing ecological change through a major taxonomic crisis

    Science.gov (United States)

    Huang, Bing; Harper, David A. T.; Rong, Jiayu; Zhan, Renbin

    2017-05-01

    Classification of extinction events and their severity is generally based on taxonomic counts. The ecological impacts of such events have been categorized and prioritized but rarely tested with empirical data. The ecology of the end Ordovician extinction and subsequent biotic recovery is tracked through abundant and diverse brachiopod faunas in South China. The spatial and temporal ranges of some 6500 identified specimens, from 10 collections derived from six localities were investigated by network and cluster analyses, nonmetric multidimensional scaling and a species abundance model. Depth zonations and structure of brachiopod assemblages along an onshore-offshore gradient in the late Katian were similar to those in the latest Ordovician-earliest Silurian (post-extinction fauna). Within this ecological framework, deeper-water faunas are partly replaced by new taxa; siliciclastic substrates continued to be dominated by the more 'Ordovician' orthides and strophomenides, shallow-water carbonate environments hosted atrypides, athyridides and pentamerides, with the more typical Ordovician brachiopod fauna continuing to dominate until the late Rhuddanian. The end Ordovician extinctions tested the resilience of the brachiopod fauna without damage to its overall ecological structure; that commenced later at the end of the Rhuddanian.

  20. South East Asia as a part of an Ordovician Gondwanaland—a palaeobiogeographic test of a tectonic hypothesis

    Science.gov (United States)

    Burrett, Clive; Stait, Bryan

    1985-10-01

    The hypothesis that Thailand and Malaysia (the Sibumasu block) were adjacent to Australia in the Early Palaeozoic has been tested by an examination of the Ordovician sequences and faunas of Sibumasu and Australia. The relatively stenogeographic nautiloids of the two areas are remarkably similar and have a Simpson Index of 0.92 at the generic level. Two new genera of discosorids are restricted to the two blocks and Georgina and Mesaktoceras are found elsewhere only in Tibet. Very close affinities are also evident between the gastropod, polyplacophoran and rostroconch molluscs. The Ordovician brachiopod faunas are also very close including the genus Spanodonta. Other very close similarities are found between the Upper Cambrian trilobite faunas and the Ordovician conodonts and stromatoporoids. No Ordovician faunas younger than Upper Whiterockian were found during this study in either northern Australia or Sibumasu and a stratigraphic gap probably exists from the Upper Whiterockian to the Upper Ordovician over most of the two blocks. These remarkably close faunal similarities are good evidence in favour of the hypothesis that Sibumasu was adjacent to Australia during the Early Palaeozoic. Similarly close faunal relationships between North China, South East Asia, Tibet and Australia may also suggest close proximity of those blocks during the Early Palaeozoic.

  1. Carbon isotope composition and correlation across the Cambrian-Ordovician boundary in Kalpin Region of the Tarim Basin, China

    Institute of Scientific and Technical Information of China (English)

    JING XiuChun; DENG ShengHui; ZHAO ZongJu; LU YuanZheng; ZHANG ShiBen

    2008-01-01

    Biostratigraphically constrained sequences at the Wushi Yingshan and Kalpin Cement Plant sections (Kalpin Region; Tarim Basin) were densely sampled for geochemical studies.Carbonates across the Cambrian-Ordovician boundary of both sections mainly record negative carbon isotope values.Stable isotope curves show four negative and four positive excursions appearing alternately at the Wushi Yingshan section and five negative alternating with five positive excursions at the Kalpin Cement Plant section.The carbon isotope logs of these two sections are correlated with the international Cambrian-Ordovician boundary key sections: (1) Dayangcha section in China, (2) Green Point section in Canada, (3) Black mountain section in Australia and (4) Lowson Cove section in USA.These correlations suggest that the Cambrian-Ordovician boundary of the Wushi Yingshan section and the Kalpin Cement Plant section can be placed within a particular horizon that also corresponds to the observed biostratigraphic units.

  2. Carbon isotope composition and correlation across the Cambrian-Ordovician boundary in Kalpin Region of the Tarim Basin, China

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    Biostratigraphically constrained sequences at the Wushi Yingshan and Kalpin Cement Plant sections (Kalpin Region; Tarim Basin) were densely sampled for geochemical studies. Carbonates across the Cambrian-Ordovician boundary of both sections mainly record negative carbon isotope values. Stable isotope curves show four negative and four positive excursions appearing alternately at the Wushi Yingshan section and five negative alternating with five positive excursions at the Kalpin Cement Plant section. The carbon isotope logs of these two sections are correlated with the international Cambrian-Ordovician boundary key sections: (1) Dayangcha section in China, (2) Green Point section in Canada, (3) Black mountain section in Australia and (4) Lowson Cove section in USA. These correlations suggest that the Cambrian-Ordovician boundary of the Wushi Yingshan section and the Kalpin Cement Plant section can be placed within a particular horizon that also corresponds to the observed biostratigraphic units.

  3. Dolomitization and sedimentary cyclicity of the Ordovician, Silurian, and Devonian rocks in South Estonia

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    Kallaste, Toivo

    2006-03-01

    Full Text Available The distribution and composition of dolomitized rocks and stoichiometry of dolomite in southern Estonia in the Ordovician, Silurian, and Devonian were studied on the background of the facies, sedimentary cyclicity (nine shallowing-up cycles, and evolution of the palaeobasins. The composition of rocks and lattice parameters of dolomite were investigated using the X-ray diffraction, X-ray fluorescence, titration and gravimetric analyses, and porosity measurements. The formation of dolostones is directly determined by the cyclic evolution of palaeobasins. Dolomitized rocks belong to the shallow-water inner shelf or tidal/lagoonal facies belt of regressive phases of sedimentary cycles. Sediments of the deep shelf/transitional environment and transgressive phases are not dolomitized. The most stoichiometric is secondary replacive dolomite of Silurian and upper Ordovician dolostones, formed during the early diagenesis of normal-marine (saline shallow-shelf calcitic sediments. The content of insoluble residue does not affect the stoichiometry. The changes in lattice parameters are induced by the Ca/Mg ratio in the dolomite lattice. The dolomite of the dolostones contacting limestone or containing calcite has an expanded lattice. The primary (syngenetic dolostone of the lagoonal or tidal flat belt has also an expanded lattice. No dolomitizing effect of the waters of the Devonian palaeobasin on the underlying rocks was revealed. The whole data set of the studied dolostones is consistent with the marine water environment in the palaeobasin at the corresponding time and shows no sign of the inflow of external fluids. It suggests that the microbial model of dolomite formation may characterize the Ordovician, Silurian, and Devonian in southern Estonia. The occurrence of dolostones between undolomitized rocks limits the time of dolomitization to the early diagenetic stage.

  4. Geochemical changes across the Ordovician-Silurian transition on the Yangtze Platform,South China

    Institute of Scientific and Technical Information of China (English)

    2009-01-01

    The trace element and rare earth element(REE) variations across the Ordovician-Silurian succession are presented from two outcrop sections on the Yangtze Platform:the Nanbazi section,Guizhou Province,deposited in a shallow platform interior setting,and the Wangjiawan section,Hubei Province,deposited in a deeper basinal environment.Geochemical analysis of closely spaced samples through three intervals,the Wufeng,Guanyinqiao and Longmaxi,revealed vast palaeoceanographic changes.Some geochemical proxies,including Th/U,Ni/Co,V/Cr,and V/(V+Ni) ratios,together with sedimentary facies and biotic data,indicate that an anoxic condition on the most of the Yangtze Platform during the Wufeng and Longmaxi intervals,but an oxic condition during the Guanyinqiao time.The shift of the anoxic to the oxic environment during the Guanyinqiao time coincided with a global sea-level lowstand,in parallel with the global glaciation.The Longmaxian anoxic environment was a result of a global sea-level rise,which may be synchronized with a mainly catastrophic event in the latest Ordovician.Although the two sections generally show similar variation patterns of trace and REE concentrations and some element ratios,a minor difference occurs between the Wangjiawan and Nanbazi sections,likely reflecting a difference in depositional setting during the accumulation.Such an oceanic oxygen-level variation may add a useful constraint to the current arguments on the cause and consequence of the latest Ordovician mass extinction.

  5. The Peerless structure, Daniels County, northeastern Montana: A probable late Ordovician impact structure

    Science.gov (United States)

    Comstock, J. M.; Dietz, R. D.; Morrow, J. R.

    2004-05-01

    The Peerless structure is an ~6 km-diameter sub-surface anomaly located in Daniels County, northeastern Montana. The disruption of sedimentary rock in the structure lies between 2624 to 2818 m below the topographic surface. Seismic mapping shows a typical complex crater composed of a central uplift ~2 km across, which shows structural uplift of up to 90 m, an annular ring ~4 km across, and an outer rim ~6 km in diameter. The youngest disrupted rock unit is the upper Ordovician Red River formation, which indicates that the structure was formed about 430-450 Ma ago.

  6. The Late Ordovician crisis: the Large Igneous Province hypothesis tested by global carbon cycle modeling.

    Science.gov (United States)

    Lefebvre, Vincent; Servais, Thomas; François, Louis; Averbuch, Olivier

    2010-05-01

    The causes of the well-known Late Ordovician-Hirnantian glaciation remain largely debated. This global cooling event is generally attributed to a severe decrease of atmospheric pCO2 during a time of general greenhouse climate but its duration is not fully determined. The climate perturbation is synchronous with one of the biggest biotic crisis of the Earth history. Some authors have shown that, considering the Ashgillian paleogeography, a drop in pCO2 below a threshold of 8x to 10x PAL (Present Atmospheric Level) may induce a decrease in temperature in high latitudes so that the installation of an ice-sheet on Gondwana could be possible. Such a process requires an intensification of silicate weathering and/or organic carbon burial that are the two major processes potentially driving a decrease in atmospheric pCO2 at the geologic time scale. The Late Ordovician is known to be a period of high mantellic activity marked by a lack of reversal magnetic field and high volcanic activity. Barnes (2004) and Courtillot and Olson (2007) link this process to a superplume event that may give rise to continental basalt flooding. In the present study, we tested this hypothesis with a global carbon cycle numerical box-model coupled with an Energy Balance Climate Model. The Model is an upgrade of that used by Grard et al. (2005) to simulate the environmental impact of the Siberian traps at the P/T boundary. The configuration of the box-model has been set using the Late Ordovician paleogeography. In each oceanic box, the model calculates the evolution of carbon, phosphorus and oxygen concentrations and alkalinity. It also calculates atmospheric pCO2, atmospheric and oceanic δ13C. We tested different scenarios of Large Igneous Province (LIP) emplacements and organic carbon cycle interactions simulating atmospheric pCO2 drops of amplitude large enough to produce the Hirnantian glaciation. We show that the hypothesis of low latitude LIP well accounts for the Late Ordovician climate

  7. Redox conditions and marine microbial community changes during the end-Ordovician mass extinction event

    Science.gov (United States)

    Smolarek, Justyna; Marynowski, Leszek; Trela, Wiesław; Kujawski, Piotr; Simoneit, Bernd R. T.

    2017-02-01

    The end-Ordovician (Hirnantian) crisis is the first globally distinct extinction during the Phanerozoic, but its causes are still not fully known. Here, we present an integrated geochemical and petrographic analysis to understand the sedimentary conditions taking place before, during and after the Late Ordovician ice age. New data from the Zbrza (Holy Cross Mountains) and Gołdap (Baltic Depression) boreholes shows that, like in other worldwide sections, the total organic carbon (TOC) content is elevated in the upper Katian and uppermost Hirnantian to Rhudannian black shales, but depleted (below 1%) during most of the Hirnantian. Euxinic conditions occurred in the photic zone in both TOC-rich intervals. This is based on the maleimide distribution, occurrence of aryl isoprenoids and isorenieratane, as well as a dominance of tiny pyrite framboids. Euxinic conditions were interrupted by the Hirnantian regression caused by glaciation. Sedimentation on the deep shelf changed to aerobic probably due to intense thermohaline circulation. Euxinia in the water column occurred directly during the time associated with the second pulse of the mass extinction with a termination of the end-Ordovician glaciation and sea level rise just at the Ordovician/Silurian (O/S) boundary. In contrast, we suggest based on inorganic proxies that bottom water conditions were generally oxic to dysoxic due to upwelling in the Rheic Ocean. The only episode of seafloor anoxia in the Zbrza basin was found at the O/S boundary, where all inorganic indicators showed elevated values typical for anoxia (U/Th > 1.25; V/Cr > 4.25; V/(V + Ni): 0.54-0.82 and Mo > 10-25 ppm). Significant differences in hopanes to steranes ratio and in C27-C29 sterane distribution between the Katian, Rhudannian and Hirnantian deposits indicate changes in marine microbial communities triggered by sharp climate change and Gondwana glaciation. The increase from biomarkers of cyanobacteria (2α-methylhopanes) after the O

  8. Sea Level and Paleoenvironment Control on Late Ordovician Source Rocks, Hudson Bay Basin, Canada

    Science.gov (United States)

    Zhang, S.; Hefter, J.

    2009-05-01

    Hudson Bay Basin is one of the largest Paleozoic sedimentary basins in North America, with Southampton Island on its north margin. The lower part of the basin succession comprises approximately 180 to 300 m of Upper Ordovician strata including Bad Cache Rapids and Churchill River groups and Red Head Rapids Formation. These units mainly comprise carbonate rocks consisting of alternating fossiliferous limestone, evaporitic and reefal dolostone, and minor shale. Shale units containing extremely high TOC, and interpreted to have potential as petroleum source rocks, were found at three levels in the lower Red Head Rapids Formation on Southampton Island, and were also recognized in exploration wells from the Hudson Bay offshore area. A study of conodonts from 390 conodont-bearing samples from continuous cores and well cuttings from six exploration wells in the Hudson Bay Lowlands and offshore area (Comeault Province No. 1, Kaskattama Province No. 1, Pen Island No. 1, Walrus A-71, Polar Bear C-11 and Narwhal South O-58), and about 250 conodont-bearing samples collected from outcrops on Southampton Island allows recognition of three conodont zones in the Upper Ordovician sequence, namely (in ascendant sequence) Belodina confluens, Amorphognathus ordovicicus, and Rhipidognathus symmetricus zones. The three conodont zones suggest a cycle of sea level changes of rising, reaching the highest level, and then falling during the Late Ordovician. Three intervals of petroleum potential source rock are within the Rhipidognathus symmetricus Zone in Red Head Rapids Formation, and formed in a restricted anoxic and hypersaline condition during a period of sea level falling. This is supported by the following data: 1) The conodont Rhipidognathus symmetricus represents the shallowest Late Ordovician conodont biofacies and very shallow subtidal to intertidal and hypersaline condition. This species has the greatest richness within the three oil shale intervals to compare other parts of Red

  9. Hydraulic testing of low-permeability Silurian and Ordovician strata, Michigan Basin, southwestern Ontario

    Science.gov (United States)

    Beauheim, Richard L.; Roberts, Randall M.; Avis, John D.

    2014-02-01

    Straddle-packer hydraulic testing was performed in 31 Silurian intervals and 66 Ordovician intervals in six deep boreholes at the Bruce nuclear site, located near Tiverton, Ontario, as part of site-characterization activities for a proposed deep geologic repository (DGR) for low- and intermediate-level radioactive waste. The straddle-packer assembly incorporated a hydraulic piston to initiate in situ pulse tests within low hydraulic conductivity (condition and relative to the overlying Silurian strata and underlying Black River Group and Cambrian strata. These underpressures could not persist if hydraulic conductivities were not as low as those measured.

  10. Reproductive cyst and operculum formation in the Cambrian-Ordovician galeate-plexus microfossils

    DEFF Research Database (Denmark)

    Agic, Heda; Moczydlowska, Malgorzata; Canfield, Donald Eugene

    2016-01-01

    Unicellular organic-walled microfossils from the Cambrian-Ordovician transition in Estonia (ca. 490-480million years ago) exhibit rare characters reflecting their function as reproductive algal cysts. The studied assemblages record the evolutionary history of phytoplankton in the early Palaeozoic......-organisms. Due to strong morphological and ecological similarities between galeate fossils and dasycladalean cysts, and the antiquity of this algal order, galeates may be positioned within green algae, more specifically Dasycladales. The unique morphology of the operculum-bearing microbiota would have required...

  11. The cephalopods of the Boda Limestone, Late Ordovician, of Dalarna, Sweden

    Directory of Open Access Journals (Sweden)

    Björn Kröger

    2013-03-01

    Full Text Available The late Katian, Late Ordovician Boda Limestone of Dalarna, Sweden contains a rich cephalopod assemblage. The assemblage consists of 61 species, of 31 genera, comprising almost all major Ordovician cephalopod orders. Most common and diverse are the Orthocerida. The Ascocerida are also remarkably comman and diverse. The new ascocerid species, Redpathoceras bullatum sp. nov., R. depressum sp. nov., R. magnum sp. nov., and Probillingsites scandinavicum sp. nov., give reason to revise current hypotheses on the origin an evolution of this group. An ascocerid origin from barrandeoceratids or aspidoceratids is hypothesised. The absence of actinocerids in the Boda Limestone is notable, and is interpreted as an indication of relatively cool or/and deep depositional environments. The dominance of orthocerids is provisionally interpreted as evidence for nutrient-rich waters during the time of the deposition of the Boda Limestone. Additionally, the assemblage contains the new barrandeocerids >em>Schuchertoceras fryi sp. nov., Siljanoceras varians gen. et sp. nov., Warburgoceras gen. nov. (for Cyrtoceras longitudinale Angelin in Angelin & Lindström, 1880, the new endocerid Cameroceras turrisoides sp. nov., the new oncocerid Cyrtorizoceras thorslundi sp. nov., and the new orthocerids Dawsonoceras stumburi sp. nov., Isorthoceras angelini sp. nov., I. curvilineatum sp. nov., Nathorstoceras adnatum gen. et sp. nov., N. kallholnense gen. et sp. nov., Palaeodawsonocerina? nicolletoides sp. nov., Pleurorthoceras osmundsbergense sp. nov., and Striatocycloceras isbergi sp. nov.

  12. Late Ordovician glaciogenic reservoir heterogeneity: An example from the Murzuq Basin, Libya

    Energy Technology Data Exchange (ETDEWEB)

    Le Heron, Daniel Paul [CASP, Department of Earth Sciences, University of Cambridge, West Building, 181A Huntingdon Road, CB30DH Cambridge (United Kingdom); Craig, Jonathan [ENI E and P, V. Emilia, 1, San Donato Milanese, MI 20097 (Italy); Sutcliffe, Owen E. [Neftex Petroleum Consultants Ltd., 80A Corinthian Court, Milton Park, Abingdon, Oxfordshire OX14 4RY (United Kingdom); Whittington, Robert [IGES, University of Wales, Aberystwyth, Ceredigion SY23 3DB (United Kingdom)

    2006-07-15

    In North Africa, Late Ordovician glaciogenic reservoirs contain large volume of recoverable hydrocarbon reserves, but their heterogeneity and internal complexity means they are poorly understood. To improve this understanding, this paper presents the case study of the Murzuq Basin, SW Libya, and a synthesis of the stratigraphic architecture of Upper Ordovician glaciogenic reservoirs (the Mamuniyat Formation) within it. Particular attention is paid to regionally extensive stratigraphic boundaries and the geometry of sandstone units of potential reservoir quality. Four disconformity-bound units are recognised, the bounding surfaces of which are flat or of high relief. Unit 1 (the oldest) and Unit 3 are mud-dominated and tend towards non-reservoir. In contrast, Units 2 and 4 (the youngest) are sand-dominated, have poor to excellent reservoir quality but distinctly different sedimentological architectures across the basin. Unit 2 comprises transitions from glaciofluvial/intertidal sandstones to offshore turbidites and formed exclusively during glacial retreat. The occurrence of a significant palaeotopography affected sandbody geometry with glaciofluvial/intertidal deposits concentrating in the lee of these palaeohighs or infilling the bottom of tunnel valleys. Unit 4 is a compound stratigraphic unit recording the effects of glacial retreat and isostatic rebound. In deep marine settings, turbidite fans were deposited during retreat but in shallow water settings, structural reactivation and sediment reworking had a more profound effect on sedimentation. Sedimentological architectures are variable at this level and include prograding coarse clastic wedges (away from a palaeohigh) or the infill of half-graben basins during isostatic rebound. (author)

  13. Platystrophia (Orthida and new related Ordovician and Early Silurian brachiopod genera

    Directory of Open Access Journals (Sweden)

    Harper, David A. T.

    2007-03-01

    Full Text Available More than 150 Ordovician and Early Silurian brachiopod species have been assigned to the genus Platystrophia King, 1850 mainly on the basis of their Spirifer-like shell exteriors. King’s concept of the genus was based on Platystrophia biforata King, which is not conspecific with Terebratulites biforatus Schlotheim, traditionally regarded as the type species of Platystrophia. Porambonites costatus Pander, 1830 is formally proposed as the type species of the genus to replace P. biforata; the latter is considered to be a nomen dubium. In our revised diagnosis, Platystrophia is restricted to a group of Arenig to upper Caradoc species from Baltica and Avalonia, whereas the Ashgill and lower Silurian taxa of these regions, hitherto assigned to Platystrophia, are placed in the new genus Neoplatystrophia. Platystrophia ponderosa Foerste, 1909 from the Upper Ordovician of North America is proposed as the type species of a new genus Vinlandostrophia. Two new species, Platystrophia baltica and Platystrophia pogrebovi from the Llanvirn–Caradoc of the East Baltic are also described.

  14. Influence of Ordovician carbonate reservoir beds in Tarim Basin by faulting

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    The quality of the Ordovician carbonate reservoir beds in the Tarim Basin is closely related to the development of secondary pores,fractures and cavities. Karstification is important in improving the properties of reservoir beds,and karstification related to unconformity has caught wide attention. Compared with the recent research on the unconformity karst reservoir bed improvement,this paper shows a new way of carbonate reservoir bed transformation. Based on field survey,core and slices observation,transformation of Ordovician carbonate reservoir beds by faulting can be classified into three types: (1) Secondary faults and fracturs generated by faulting improved carbonate reservoir bed properties,which were named the Lunnan or Tazhong82 model; (2) upflow of deep geothermal fluids caused by faulting,with some components metasomatizing with carbonate and forming some secon-dary deposit,such as fluorite. It can improve carbonate reservoir bed properties obviously and is named the Tazhong 82 model; and (3) the faulting extending up to the surface increased the depth of supergene karstification and the thickness of reservoir bed. It is named the Hetianhe model. Trans-formation effect of carbonate reservoir beds by faulting was very significant,mainly distributed on the slopes or on the edge or plunging end of the uplift.

  15. The significance of 24-norcholestanes, triaromatic steroids and dinosteroids in oils and Cambrian-Ordovician source rocks from the cratonic region of the Tarim Basin, NW China

    Science.gov (United States)

    Li, Meijun; Wang, T.-G.; Lillis, Paul G.; Wang, Chunjiang; Shi, Shengbao

    2012-01-01

    Two oil families in Ordovician reservoirs from the cratonic region of the Tarim Basin are distinguished by the distribution of regular steranes, triaromatic steroids, norcholestanes and dinosteroids. Oils with relatively lower contents of C28 regular steranes, C26 20S, C26 20R + C27 20S and C27 20R regular triaromatic steroids, dinosteranes, 24-norcholestanes and triaromatic dinosteroids originated from Middle–Upper Ordovician source rocks. In contrast, oils with abnormally high abundances of the above compounds are derived from Cambrian and Lower Ordovician source rocks. Only a few oils have previously been reported to be of Cambrian and Lower Ordovician origin, especially in the east region of the Tarim Basin. This study further reports the discovery of oil accumulations of Cambrian and Lower Ordovician origin in the Tabei and Tazhong Uplifts, which indicates a potential for further discoveries involving Cambrian and Lower Ordovician sourced oils in the Tarim Basin. Dinosteroids in petroleum and ancient sediments are generally thought to be biomarkers for dinoflagellates and 24-norcholestanes for dinoflagellates and diatoms. Therefore, the abnormally high abundance of these compounds in extracts from the organic-rich sediments in the Cambrian and Lower Ordovician and related oils in the cratonic region of the Tarim Basin suggests that phytoplankton algae related to dinoflagellates have appeared and might have flourished in the Tarim Basin during the Cambrian Period. Steroids with less common structural configurations are underutilized and can expand understanding of the early development history of organisms, as well as define petroleum systems.

  16. The Environmental Context of Gastropods on Western Laurentia (Basin and Range Province) during the Great Ordovician Biodiversification Event

    Science.gov (United States)

    Dahl, Robyn Mieko

    2015-01-01

    Gastropods are a major component of modern marine ecosystems and can be found in nearly every type of marine ecosystem. They experienced their first notable radiation during the Great Ordovician Biodiversification Event (~470 Ma), during which their diversity tripled. This study examines the gastropod assemblage preserved in the Basin and Range…

  17. Rare finds of the coiled cephalopod Discoceras from the Upper Ordovician of Bornholm, Denmark

    DEFF Research Database (Denmark)

    Rasmussen, Jan Audun; Surlyk, Finn

    2012-01-01

    n. sp. and D. vasegaardense n. sp., occur in shales of the Upper Ordovician Lindegård Formation. The nautiloids are preserved as external molds in laminated siliciclastic mudstones. The very rare occurrence of cephalopods, combined with the apparently endemic nature of the Discoceras fauna, may...

  18. Migration, filling history and geochemical characteristics of Ordovician natural gases in the Tahe Oilfield, Tarim Basin, Northwest China

    Institute of Scientific and Technical Information of China (English)

    WANG Jie; LIU Wenhui; QIN Jianzhong; LIU Keyu; GU Yi

    2009-01-01

    Ordovician natural gases in the Tahe Oilfield are composed predominantly of hydrocarbon gases dominated by methane with a significant amount of heavy hydrocarbon gas component. The non-hydrocarbon gases include N2, CO2 and minor H2S. The Ordovician natural gases are believed to have originated from the same source rocks, and are composite of gases differing in thermal maturity. Carbon dioxide was derived from thermal metamorphism of Ordovician carbonate rocks. The generation of natural gases involves multiple stages from mature normal oil and condensate-associated gas to thermally cracked gas at the maturity to over-maturity stages. In the main part of the Tahe Oilfield, the Ordovician natural gases appear to be filled in two major phases with a typical petroleum-associated gas from southeast to northwest and from east to west in the early stage; and a thermally cracked gas from east to west in the late stage. At the same time, the oil/gas filling boundary has been primarily established between the two stages.

  19. 鄂尔多斯盆地西缘奥陶纪生物礁及其储集性能%Ordovician organic reefs and their reservoir property on the west margin of Ordos Basin, China

    Institute of Scientific and Technical Information of China (English)

    周俊烈; 陈洪德; 赵俊兴; 苏中堂; 张成弓; 王玉萍; 郝哲敏

    2013-01-01

    Based on the sedimentary and petroleum geology theory and through the observation of outcrops, cores, and slices and testing analysis, the authors study the Ordovician organic reefs on the west margin of Ordos Basin. The authors reach out a conclusion that the Ordovician organic reefs on the west margin of Ordos Basin are the coral reefs of the Lower Ordovician Zhuozishan Formation located in Wuhai Zhuozishan in the north, the stromatoporoids-sponge reefs of the Lower Ordovician Kelimoli Formation of Well Qitan 1 in the middle and the coral reefs of the Upper Ordovician Beiguoshan Formation in Shijiezigou in the south. The reefs in the north develop earlier than that in the south. The north reefs have grown 2 — 3 phases and that in the south 4 phases. The aquatic environment of the reefs in the north is relatively shallow and the reefs in the south has a deep aquatic environment. The coexistence of different shoals and the reefs develops the reef-bank reservoirs. The reservoir spaces are mainly the organic lattice poles and dissolved poles dissolved by fabrics selectively. The physical conditions show the reservoir property is poor. But, the reefs located on the platform margin are beneficial to developing the reef-bank reservoirs, so the platform margin can be the exploration target.%应用沉积学和石油地质学理论,通过野外剖面观测、岩心观察、室内薄片和测试分析,对鄂尔多斯盆地西缘奥陶纪生物礁进行了详细研究,认为有北部的乌海桌子山地区下奥陶统桌子山组珊瑚生物礁,中部的棋探1井下奥陶统克里摩里组层孔虫—海绵生物礁和南部的石节子沟上臭陶统背锅山组珊瑚生物礁.北部生物礁发育的时代早,南部晚;北段礁体生长发育2~3期,南段发育可达4期;北段及南段生物礁生长的水体环境相对较浅,中部相对较深.生物礁与各种滩共生,发育礁滩型储层,生物格架孔和组构选择性溶蚀的溶孔是其主要储集

  20. Late Ordovician brachiopod distribution and ecospace partitioning in the Tvären crater system, Sweden

    DEFF Research Database (Denmark)

    Frisk, Asa M.; Harper, David A. T.

    2013-01-01

    Patterns of distribution and ecospace utilization of Late Ordovician brachiopods in a recently formed, contemporary meteorite crater are described and analyzed. Rhynchonelliformean brachiopod communities, dominated by a wide range of orthides and strophomenides, colonized the newly formed crater....... At the crater rim communities were established early on, although the crater depression was not inhabited until deposition of the upper third of the remaining crater fill. The crater formed a protected but restricted microenvironment where sediments four times the thickness of the nearby basinal succession...... of the guild structure of the fauna permits explanation of a local biodiversity hotspot in otherwise low-diversity strata elsewhere in the Scandinavian region. The Tvaren impact event had an important palaeobiologic effect upon the fossil record as it served as a local pump and reservoir for biodiversity...

  1. The anatomy, taphonomy, taxonomy and systematic affinity of Markuelia: Early Cambrian to Early Ordovician scalidophorans

    Science.gov (United States)

    Dong, X.-P.; Bengtson, S.; Gostling, N.J.; Cunningham, J.A.; Harvey, T.H.P.; Kouchinsky, A.; Val'Kov, A.K.; Repetski, J.E.; Stampanoni, M.; Marone, F.; Donoghue, P.C.J.

    2010-01-01

    Markuelia is a vermiform, annulated introvertan animal known as embryonic fossils from the Lower Cambrian to Lower Ordovician. Analysis of an expanded and revised dataset for Introverta shows that the precise position of Markuelia within this clade is dependent on the taxa included. As a result, Markuelia is assigned to the scalidophoran total group to reflect uncertainty as to whether it is a stem-scalidophoran or a stem-priapulid. The taxonomy of the genus is revised to provide an improved taxonomic framework for material assigned to Markuelia. Five species are recognized: M. secunda Val'kov, M. hunanensis Dong and Donoghue, M. lauriei Haug et al., M. spinulifera sp. nov. and M. waloszeki sp. nov. Finally, the preservation of Markuelia is evaluated in the light of both the taphonomy of the fossil embryos themselves and the experimental taphonomy of the priapulid Priapulus caudatus, which has been proposed as both a close relative and an anatomical analogue of Markuelia. ?? The Palaeontological Association.

  2. Did a gamma-ray burst initiate the late Ordovician mass extinction?

    CERN Document Server

    Melott, A; Laird, C M; Martin, L; Medvedev, M; Thomas, B; Cannizzo, J K; Gehrels, N; Jackman, C H

    2003-01-01

    At least five times in the history of life, the Earth experienced mass extinctions that eliminated a large percentage of the biota. Many possible causes have been documented, and gamma-ray bursts (GRB) may also have contributed. GRB produce a flux of radiation detectable across the observable Universe. A GRB within our own galaxy could do considerable damage to the Earth's biosphere. Rate estimates suggest that a number of such GRB may lie within the fossil record. The late Ordovician mass extinction shows a water-depth dependent extinction pattern that is a natural result of the attenuation of the strong ultraviolet radiation expected to result from a nearby GRB. In addition, a GRB would trigger global cooling which is associated with this mass extinction.

  3. A review of Lower and Middle Palaeozoic biostratigraphy in west peninsular Malaysia and southern Thailand in its context within the Sibumasu Terrane

    Science.gov (United States)

    Cocks, L. R. M.; Fortey, R. A.; Lee, C. P.

    2005-03-01

    Fossils from the Cambrian to Devonian rocks of southern Thailand, the Langkawi Islands, mainland Kedah, Perlis, north Perak and central West Peninsular Malaysia are listed and reviewed, and their stratigraphy and correlation reassessed. The hitherto anomalous record of the trilobite Dalmanitina from Malaysia is reviewed and found to be of latest Ordovician (Hirnantian) age, rather than Lower Silurian age as previously reported, and is considered a probable synonym of the widespread Mucronaspis mucronata. A new stratigraphical nomenclature is erected for part of the Langkawi, mainland Kedah and Perlis area successions, in which the term Setul Limestone (which stretched from the Ordovician to the Devonian) is abandoned and replaced by the Middle Ordovician Kaki Bukit Limestone, the late Ordovician and early Silurian Tanjong Dendang Formation, the Silurian Mempelam Limestone, and the early Devonian Timah Tasoh Formation, all underlying the paraconformity with the late Devonian Langgun Red Beds. There was a single depositional basin in the generally shallow-water and cratonic areas of southern Thailand, Langkawi, and mainland Kedah and Perlis, in contrast to the deeper-water basin of north Perak. Only Silurian rocks are dated with certainty within another basin in central West Malaysia, near Kuala Lumpur, which were also cratonic and shallow-water, although to the east in west Pahang there are basal Devonian deeper-water sediments with graptolites. The area is reviewed in its position within the Sibumasu Terrane, which, in the Palaeozoic, also included central and northern Thailand, Burma (Myanmar) and southwest China (part of Yunnan Province).

  4. Tectonic overprint on magnetic fabric of the Ordovician Thetford Mines Ophiolite (Canada)

    Science.gov (United States)

    Di Chiara, Anita; Morris, Antony; Anderson, Mark W.; Menegon, Luca

    2017-04-01

    Studies in modern oceanic settings suggest locally along low-spreading ridges both lower crust and upper mantle peridotites may be exhumed to the seafloor in features known as oceanic core complexes (OCC). Examples of OCC on geological record can be preserved in ophiolites, relict of oceanic crust obducted onto continental margins, as for example the Jurassic Mirdita Ophiolite (Albania), suggesting that this spreading mode was active in the past. In order to understand such dynamics further, we investigated the OCC preserved in the Thetford Mines Ophiolite (TMO). TMO is part of the Southern Quebec ophiolites in the Canadian Appalachians (Quebec region), divided into three lithotectonic assemblages: The Humber Zone, a remnant of the Laurentian continental margin; The Cambrian-Ordovician Dunnage Zone, a remnant of the Iapetus Ocean and including the TMO and other ophiolites; and Silurian-Devonian Gaspé Belt, the sedimentary cover sequence. These were subjected to polyphase deformation, experiencing two Paleozoic orogenies: The Ordovician Taconian Orogeny (the Humber and Dunnage zones were amalgamated) and the Devonian Acadian orogeny which deformed and metamorphosed both the Dunnage Zone and the overlying Gaspe Belt. Here we present results from 12 paleomagnetic sites sampled on Humber zone on pillow lavas, dykes, layered gabbros and serpentinized dunites. Our results from AMS experiments show that these rocks, formed by fundamentally different magmatic processes, share a common magnetic fabric, with a kmin axis NW-SE orientated and the kmax steeply plunging to the NE. Additional processing of acquired BSE images and chemical mapping analyses at the SEM show that the kmax of the magnetic fabric is parallel to the elongation of magnetic particles (Iron rich minerals). This remarkably consistent fabric has a tectonic origin and is consistent with shortening perpendicular to the regional trend of fold axes.

  5. The Lawn Hill annulus: An Ordovician meteorite impact into water-saturated dolomite

    Science.gov (United States)

    Darlington, Vicki; Blenkinsop, Tom; Dirks, Paul; Salisbury, Jess; Tomkins, Andrew

    2016-12-01

    The Lawn Hill Impact Structure (LHIS) is located 250 km N of Mt Isa in NW Queensland, Australia, and is marked by a highly deformed dolomite annulus with an outer diameter of 18 km, overlying low metamorphic grade siltstone, sandstone, and shale, along the NE margin of the Georgina Basin. This study provides detailed field observations from sections of the Lawn Hill annulus and adjacent areas that demonstrate a clear link between the deformation of the dolomite and the Lawn Hill impact. 40Ar-39Ar dating of impact-related melt particles provides a time of impact in the Ordovician (472 ± 8 Ma) when the Georgina Basin was an active depocenter. The timing and stratigraphic thickness of the dolomite sequence in the annulus suggest that there was possibly up to 300 m of additional sedimentary rocks on top of the currently exposed Thorntonia Limestone at the time of impact. The exposed annulus is remarkably well preserved, with preservation attributed to postimpact sedimentation. The LHIS has an atypical crater morphology with no central uplift. The heterogeneous target materials at Lawn Hill were probably low-strength, porous, and water-saturated, with all three properties affecting the crater morphology. The water-saturated nature of the carbonate unit at the time of impact is thought to have influenced the highly brecciated nature of the annulus, and restricted melt production. The impact timing raises the possibility that the Lawn Hill structure may be a member of a group of impacts resulting from an asteroid breakup that occurred in the mid-Ordovician (470 ± 6 Ma).

  6. Biostratigraphy and chronostratigraphy of the Cambrian-Ordovician great American carbonate bank

    Science.gov (United States)

    Taylor, John F.; Repetski, John E.; Loch, James D.; Leslie, Stephen A.

    2012-01-01

    The carbonate strata of the great American carbonate bank (GACB) have been subdivided and correlated with ever-increasing precision and accuracy during the past half century through use of the dominant organisms that evolved on the Laurentian platform through the Cambrian and the Ordovician. Trilobites and conodonts remain the primary groups used for this purpose, although brachiopods, both calcareous and phosphatic, and graptolites are very important in certain facies and intervals. A series of charts show the chronostratigraphic units (series and stages) currently in use for deposits of the GACB and the biostratigraphic units (zones, subzones, and biomeres) whose boundaries delineate them. Older and, in some cases obsolete, stages and faunal units are included in the figures to allow users to relate information from previous publications and/or industry databases to modern units. This chapter also provides a brief discussion on the use of biostratigraphy in the recognition and interregional correlation of supersequence boundaries within the Sauk and Tippecanoe megasequences, and the varied perspectives on the nature of biostratigraphic units and their defining taxa during the past half century. Also included are a concise update on the biomere concept, and an explanation of the biostratigraphic consequences of a profound change in the dynamics of extinction and replacement that occurred on the GACB in the Early Ordovician when the factors responsible for platformwide biomere-type extinctions faded and ultimately disappeared. A final section addresses recent and pending refinements in the genus and species taxonomy of biostratigraphically significant fossil groups, the potential they hold for greatly improved correlation, and the obstacles to be overcome for that potential to be realized.

  7. Strontium Isotope Composition and Characteristic Analysis of Cambrian-Ordovician Carbonate in the Region of Tazhong, Tarim Basin

    Institute of Scientific and Technical Information of China (English)

    Huang Wenhui; Yang Min; Yu Bingsong; Fan Tailiang; Chu Guangzhen; Wan Huan; Zhu Jingquan; Wang Xu; Wu Shiqiang

    2006-01-01

    The research on the trace elements of Ordovician carbonates plays an important part in the whole work on reservoir in Tazhong ( 塔中 ) area. This paper systematically studies the characteristics and sedimentary settings of Ordovician dolomites in Tazhong area, Tarim basin, and debates their enrichment of mechanisms and different element existing patterns. The study makes use of ICP-MS analysis technology to test the strontium and manganese content of 109 samples from four wells in the Tazhong area, Tarim basin and strontium isotope composition tests have also been done on 25 samples from wells Zhong-1 and Zhong-4 on VG354 solid isotope mass spectrograph. By means of analyzing contents of strontium andmanganese elements, doing research on the strontium isotope composition characteristics from wells Zhong-1 and Zhong-4 and comparing the results of strontium analysis to the global Ordovician marine carbonate and its evolution trend, in the combination of sedimentary facies characteristics of isolated wells in this area, we can come to the following cognitions: (1) The marine carbonate strontium isotope curve in the Tazhong area of Tarim basin is consistent to the global evolution trend which is overall descending with time, the direct reason of which is the evolution of paleogeographic environment.The Ordovician paleogeographic environment goes through restricted platform to open platform and then shallow marine shelf in Tazhong area, Tarim basin. Dolomitization is another subordinate reason and the inversion of fluid with high manganese can lead to heavy strontium; (2) The fact that the 87 Sr/86 Sr ratios of the Upper Ordovician in Tazhong area have an apparent mono-decline trend with the time going by,which is similar to the global strontium isotope ratio, is suggesting that the variation of the Upper Ordovician sea level is starting, the overall trend of which is the rising of the sea level; (3) Compared to the global seawater strontium ratios, the 87 Sr/86 Sr

  8. Geodatabase of the datasets used to represent the four aquifer subunits of the Cambrian-Ordovician aquifer system, Illinois, Iowa, Michigan, Minnesota, and Wisconsin

    Data.gov (United States)

    U.S. Geological Survey, Department of the Interior — This geodatabase includes spatial datasets that represent the Cambrian-Ordovician aquifer system in the States of Wisconsin, Michigan, Minnesota, Iowa, and Illinois....

  9. Calibrating water depths of Ordovician communities: lithological and ecological controls on depositional gradients in Upper Ordovician strata of southern Ohio and north-central Kentucky, USA

    Directory of Open Access Journals (Sweden)

    Carlton E. Brett

    2015-02-01

    Full Text Available Limestone and shale facies of the Upper Ordovician Grant Lake Formation (Katian: Cincinnatian, Maysvillian are well exposed in the Cincinnati Arch region of southern Ohio and north-central Kentucky, USA. These rocks record a gradual change in lithofacies and biofacies along a gently northward-sloping ramp. This gradient spans very shallow, olive-gray, platy, laminated dolostones with sparse ostracodes in the south to offshore, nodular, phosphatic, brachiopod-rich limestones and marls in the north. This study uses facies analysis in outcrop to determine paleoenvironmental parameters, particularly those related to water depth (e.g., position of the photic zone and shoreline, relative degree of environmental energy. Within a tightly correlated stratigraphic interval (the Mount Auburn and Straight Creek members of the Grant Lake Formation and the Terrill Member of the Ashlock Formation, we document the occurrence of paleoenvironmental indicators, including desiccation cracks and light-depth indicators, such as red and green algal fossils and oncolites. This permitted recognition of a ramp with an average gradient of 10–20 cm water depth per horizontal kilometer. Thus, shallow subtidal (“lagoonal” deposits in the upramp portion fall within the 1.5–6 m depth range, cross-bedded grainstones representing shoal-type environments fall within the 6–18 m depth range and subtidal, shell-rich deposits in the downramp portion fall within the 20–30 m depth range. These estimates match interpretations of depth independently derived from faunal and sedimentologic evidence that previously suggested a gentle ramp gradient and contribute to ongoing and future high-resolution paleontologic and stratigraphic studies of the Cincinnati Arch region.

  10. Carbon and strontium isotope variations and responses tosea-level fluctuations in the Ordovician of the Tarim Basin

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    Abstract In the Ordovician, a carbonate platform system grading from the platformal interioreastwards to basin was developed in the Tazhong area of the Tarim Basin, and the study column islocated in the place where the paleoslope occurred. The isotope compositions of the carbonatesthere are thus considered as having reflected those of simultaneous sea waters in view of its goodconnection with the open seas. The carbon and strontium isotope compositions of the Ordoviciancarbonates in the Tazhong area are analyzed, and their relationships to the sea-level fluctuationsare discussed as well. Studies have revealed that the carbon isotope composition is related posi-tively with the sea-level fluctuations, whereas an opposing situation occurs to the strontium isotopevariation. Similar responses of carbon and strontium isotope compositions to the sea-level fluctua-tions are reported elsewhere in the world, suggesting that the Ordovician sea-level fluctuations ofthe Tarim Basin were of eustatic implication.

  11. Ordovician sponges (Porifera and other silicifications from Baltica in Neogene and Pleistocene fluvial deposits of the Netherlands and northern Germany

    Directory of Open Access Journals (Sweden)

    Rhebergen, Freek

    2009-03-01

    Full Text Available Fluvial deposits of Miocene to Early Pleistocene age in Germany and the Netherlands were laid down in the delta of the Eridanos River System, but the exact provenance of this material continues to be a subject of discussion. The aim of the present study is twofold. Firstly, a comparison of Ordovician sponges in these deposits with those from northern Estonia and the St Petersburg region (Russia demonstrates that these erratics originated from the drainage area of the Pra Neva, a tributary of the Eridanos. Secondly, the importance of Late Ordovician silicified boulders, which yield forms of preservation that are unknown in comparable fossils, preserved in situ, is outlined. Some recommendations for future studies are made.

  12. Proposed Auxiliary Boundary Stratigraphic Section and Point (ASSP) for the base of the Ordovician System at Lawson Cove, Utah, USA

    Science.gov (United States)

    Miller, James F.; Evans, Kevin R.; Ethington, Raymond L.; Freeman, Rebecca; Loch, James D.; Repetski, John E.; Ripperdan, Robert; Taylor, John F.

    2016-01-01

    The Global boundary Stratotype Section and Point (GSSP) for the base of the Ordovician System is at the First Appearance Datum (FAD) of the conodont Iapetognathus fluctivagus at Green Point in Newfoundland, Canada. Strata there are typical graptolitic facies that were deposited near the base of the continental slope.We propose establishing an Auxiliary boundary Stratotype Section and Point (ASSP) at the FAD of I. fluctivagus at the Lawson Cove section in the Ibex area of Millard County, Utah, USA. There, strata consist of typical shelly facies limestones that were deposited on a tropical carbonate platform and contain abundant conodonts, trilobites, brachiopods, and other fossil groups. Cambrian and Ordovician strata in this area are ~5300m thick, with the Lawson Cove section spanning 243m in three overlapping segments. Six other measured and studied sections in the area show stratigraphic relationships similar to those at Lawson Cove. Faunas have been used to divide these strata into 14 conodont and 7 trilobite zonal units. The widespread olenid trilobite Jujuyaspis occurs ~90cm above the proposed boundary at Lawson Cove; this genus is generally regarded as earliest Ordovician. Rhynchonelliform and linguliform brachiopods are common to abundant and are useful for correlation. The FAD of Iapetognathus fluctivagus and occurrences of Jujuyaspis and the Lower Ordovician planktonic graptolite Anisograptus matanensis all occur within a 2.4m interval of strata at a nearby section. Non-biological correlation tools include a detailed sequence stratigraphic classification and a detailed carbon-isotope profile. Especially useful for correlation is a positive 13C excursion peak ~15cm below the proposed boundary horizon. All of these correlation tools form an integrated framework that makes the Lawson Cove section especially useful as an ASSP for global correlation of strata with faunas typical of shallow, warm-water, shelly facies.

  13. Sm-Nd isotopic compositions of Cambrian-Ordovician strata at the Jinggangshan area in Jiangxi Province:Tectonic implications

    Institute of Scientific and Technical Information of China (English)

    SHEN WeiZhou; LING HongFei; SHU LiangShu; ZHANG FangRong; XIANG Lei

    2009-01-01

    Whole-rock Sm-Nd Isotopes were investigated for Cambrian-Ordovician strata from the Jinggangshan area beTween the Yangtze Block and Cathysla Block in South China. These strata were deposited as a greatly thick unit of muddy-sandy laminas with intercalated carbonate and organic carbon-bearing layers. They have low ε(t) values of -13.9 to -7.9 and old Nd model ages of 1842 to 2375 Ma. In t-tdiagram, they are far away from the concordant line but fall within the evolution zone of the Proterozoic crust of South China. This indicates that the Cambrian-Ordovician strata are mainly composed of mat-ters eroded from ancient Paleoproterozoic crust that may mainly consist of continental-derived detrital sediments with high maturity in the Cathyaia Block. However, the Ordovician Jueshangou Formation and Dui'erehi Formation have ε(t) values of -10.5 and -7.9 at the higher end of the above range and Nd model ages of 1842 to 2059 Ma at the lower end of the above range. This suggests involvement of more detritus that were eroded from the relatively juvenile crust from Late Paleoproterozoic to the Early Neoproterozoic. All the Nd model ages for the Cambrian-Ordovlcian sedimentary rocks in the Cathysia Block and the southeastern margin of the Yangtze Block are older than 1800 Ma, suggesting that no material from the Early Paleozoic depleted mantle-derived magmas was involved in these regions.

  14. Chronostratigraphy of the Trenton Group and Utica Shale, Pt. II: Stratigraphic correlations using Ordovician glasses in K-bentonites

    Energy Technology Data Exchange (ETDEWEB)

    Delano, J.W.; Tice, S. (State Univ. of New York, Albany, NY (United States). Dept. of Geological Sciences); Mitchell, C.E.; Goldman, D. (State Univ. of New York, Buffalo, NY (United States). Dept. of Geology); Samson, S.D. (Syracuse Univ., NY (United States). Dept. of Geology)

    1992-01-01

    Rhyolitic glasses in the form of pristine melt inclusions that occur within quartz phenocrysts are being used for the geochemical fingerprinting of Ordovician K-bentonites in the northern Appalachian Basin. These melt inclusions are samples of pre-eruptive magma that became trapped during phenocryst growth in the deep crustal magma chambers. Plinian eruptions led to quenching of the enclosed rhyolitic magma to form glass when the quartz phenocrysts were blasted into the atmosphere. Preservation of this Ordovician glass is due to its being hermetically sealed within a mineral (quartz) that is resistant to weathering and diagenetic alteration. Chemical compositions of glasses in four Ordovician K-bentonites from the Mohawk Valley of New York State have been acquired using high-precision, electron microprobe analyses. The elements Mg, Cl, Ca, Ti, and Fe are often diagnostic. The accompanying figure illustrates one combination of elements that is effective in distinguishing K-bentonites, which are not stratigraphically equivalent. These K-bentonites were selected to test competing chronostratigraphies of the northern Appalachian Basin and indicate problems with the model by Cisne et al.

  15. Effect of Faulting on Ordovician Carbonate Buried-Hill Reservoir Beds in Hetianhe Gas Field,Tarim Basin

    Institute of Scientific and Technical Information of China (English)

    Lü Xiuxiang; Bai Zhongkai; Li Jianjiao; Wang Weiguang; Fu Hui; Wang Qinghua

    2008-01-01

    Ordovician carbonate buried-hill reservoir beds in the Hetianhe (和田河) gas field,located in the Mazhatage (玛扎塔格) structural belt on the southern margin of the Bachu (巴楚) faulted uplift,southwestern Tarim basin,were studied.Based on field survey,core and slice observation,the general characteristics of carbonate buried-hill reservoir beds and specifically Ordovician carbonate buried-hill reservoir beds in the Hetianhe gas field were discussed.The karst zone of the reservoir beds in Hetianhe gas field was divided into superficial karst zone,vertical infiltration karst zone,lower subsurface flow karst zone,and deep sluggish flow zone from top to bottom.The effects of faulting on Ordovician carbonate buried-hill reservoir beds in the Hetianhe gas field were obvious.The faulting intensified the karstification and increased the depth of denudation.Faulting and subsequent fracture growth modified the reservoir beds and improved the physical property and quality of the reservoir beds.Moreover,faulting enhanced the development of the dissolution holes and fractures and increased the thickness of the effective reservoir beds.Meanwhile,faulting made the high porosity-permeability carbonate belts,which created conditions for the hydrocarbon accumulation,develop near the fault zone.

  16. Organic geochemical evidence for nitrogen-limited oligotrophic seas in the Late Ordovician

    Science.gov (United States)

    Rohrssen, M.; Love, G. D.

    2011-12-01

    The Late Ordovician (~450-44 Ma) was a period of drastic environmental change, beginning in a hothouse climate with epeiric seaways near a Phanerozoic high and concluding with the Hirnantian glaciation, large positive carbon isotope excursion(s) (Hirnantian isotopic carbon excursion, HICE) and one of the Big Five mass extinctions. Warm sea temperatures and low oxidant concentrations relative to modern likely made intervals of the Late Ordovician particularly suited to the development of extensive denitrification in oxygen minimum zones (OMZs), contributing to nitrogen limitation of marine ecosystems. Mixed carbonate/siliciclastic deposits on Anticosti Island, Canada, provide an excellent opportunity to assemble stratigraphic lipid biomarker records of microbial community structure and response to environmental change associated with the Hirnantian glaciation in a tropical epeiric seaway. Lipid biomarkers extracted from Anticosti rocks yield low thermal maturities, consistent with the shallow burial history of the island and lack molecules likely derived from contamination (e.g. zero oleanane from angiosperms). In addition, Anticosti bitumens bear the C29 sterane predominance and low C28/C29 sterane ratio expected from Lower Paleozoic rocks. Anticosti biomarkers reveal unusual environmenal conditions throughout the Hirnantian at Anticosti. Despite the presence of unequivocally marine fossils, Anticosti bitumens contain no detectable 24-n-propylcholestane, usually a robust marker of marine environmental conditions. Anticosti bitumen have high abundances of 3β-methylhopanes (4-11% of C30 αβ-hopane), molecules which are commonly associated with Type I methanotrophic bacteria. Moderate abundances of 2α-methylhopane (2-4% C30 αβ-hopane) with only trace quantities of gammacerane are found. Hopane/sterane ratios, reflecting a highercontribution of bacteria relative to eukaryotes, range from 1.8 to 11.2 (average 4.8), higher than the Phanerozoic marine average of 0

  17. Paleomagnetic study of Cambrian Ordovician rocks in the Eastern Precordillera of Argentina: some constraints on the Andean uplift of this block

    Science.gov (United States)

    Rapalini, A. E.; Bordonaro, O.; Berquo, T. S.

    2000-11-01

    A paleomagnetic study on several carbonatic units (limestones to dolomites) of the Argentine Precordillera, spanning the Middle Cambrian to Arenig, is reported. Sampling was done at 23 sites (140 samples) in five localities of the Eastern Precordillera of San Juan province: Zonda (1), Juan Pobre (2) and La Flecha (3) creeks, Loma Redonda (4) and Cerro Pedernal de los Berros (5). Standard AF and thermal demagnetization indicated two different magnetic behaviors. Samples from localities 1 and 2 showed a single, post-tectonic magnetic component attributed to a Recent viscous or chemical remagnetization. Samples from localities 3 to 5 showed two magnetic components: a low unblocking temperature (350°C) magnetization coincident with that found at the previous localities and a high temperature one (up to 500°C). This second component was also found to be post-folding (post-Devonian?) and its in situ mean direction is Dec: 277.1°, Inc: 69.4, α95: 9.3°, N=10. This is not consistent with any expected direction for the study area between Carboniferous and Recent times. It is therefore inferred that the rocks carrying it underwent substantial tectonic rotation since its recording. Comparison with the magnetization carried by similar Early Ordovician limestones in the Central Precordillera and the San Rafael Block, and assigned to a Permian remagnetizing event, suggests that the same process affected the carbonatic rocks in the Eastern Precordillera and, therefore, the age of the component is likely Permian. Restoration of the in situ mean direction to the expected direction for a Permian remagnetization can be obtained by a 40° ccw rotation around an axis plunging 30° to N30°E. This is compatible with uplifting of the Eastern Precordillera as a series of quasi-rigid blocks along a major E dipping N to NE backthrust during the Andean orogeny.

  18. Comparison of iron isotope variations in modern and Ordovician siliceous Fe oxyhydroxide deposits

    Science.gov (United States)

    Moeller, Kirsten; Schoenberg, Ronny; Grenne, Tor; Thorseth, Ingunn H.; Drost, Kerstin; Pedersen, Rolf B.

    2014-02-01

    Formation pathways of ancient siliceous iron formations and related Fe isotopic fractionation are still not completely understood. Investigating these processes, however, is difficult as good modern analogues to ancient iron formations are scarce. Modern siliceous Fe oxyhydroxide deposits are found at marine hydrothermal vent sites, where they precipitate from diffuse, low temperature fluids along faults and fissures on the seafloor. These deposits exhibit textural and chemical features that are similar to some Phanerozoic iron formations, raising the question as to whether the latter could have precipitated from diffuse hydrothermal fluids rather than from hydrothermal plumes. In this study, we present the first data on modern Fe oxyhydroxide deposits from the Jan Mayen hydrothermal vent fields, Norwegian-Greenland Sea. The samples we investigated exhibited very low δ56Fe values between -2.09‰ and -0.66‰. Due to various degrees of partial oxidation, the Fe oxyhydroxides are with one exception either indistinguishable from low-temperature hydrothermal fluids from which they precipitated (-1.84‰ and -1.53‰ in δ56Fe) or are enriched in the heavy Fe isotopes. In addition, we investigated Fe isotope variations in Ordovician jasper beds from the Løkken ophiolite complex, Norway, which have been interpreted to represent diagenetic products of siliceous ferrihydrite precursors that precipitated in a hydrothermal plume, in order to compare different formation pathways of Fe oxyhydroxide deposits. Iron isotopes in the jasper samples have higher δ56Fe values (-0.38‰ to +0.89‰) relative to modern, high-temperature hydrothermal vent fluids (ca. -0.40‰ on average), supporting the fallout model. However, formation of the Ordovician jaspers by diffuse venting cannot be excluded, due to lithological differences of the subsurface of the two investigated vent systems. Our study shows that reliable interpretation of Fe isotope variations in modern and ancient marine

  19. Advances in the Ordovician graptolite biostratigraphy of the St Petersburg area, Russia

    Directory of Open Access Journals (Sweden)

    Suyarkova, Anna A.

    2009-03-01

    Full Text Available The Ordovician shallow-water shelf deposits rich in benthic fauna are exposed along the Russian part of the Baltic–Ladoga Klint. Graptolites occur only at some stratigraphic levels, being comparatively numerous in marls and clays and very rare in carbonate layers. Since the 19th century graptolites have been collected from exposures of the Pakerort, Hunneberg, Billingen, and Volkhov regional stages (Tremadocian–Dapingian, while in the Uhaku–Idavere stratigraphic interval (Darriwilian–lower Sandbian rare graptolites have been found in boreholes. Up to now, only some collections have been systematically studied. On the basis of new graptolite finds, recently the Pterograptus elegans Biozone was established in the upper Aseri Stage and the Nemagraptus gracilis Biozone in the lower Kukruse Stage. Detailed sampling of the Shundorovo Formation (upper Idavere Stage resulted in the discovery of numerous diplograptids at five stratigraphic levels, in association with various dendroids. These diplograptids were provisionally assigned to ?Archiclimacograptus antiquus lineatus Elles & Wood. A systematic description of the late Darriwilian and early Sandbian diplograptids is under preparation.

  20. Ripple marks as indicators of Late Ordovician sedimentary environments in Northwest Estonia

    Directory of Open Access Journals (Sweden)

    Hints, Linda

    2008-03-01

    Full Text Available Late Ordovician sedimentary environments promoting the development of ripple marks in shallow shelf carbonate deposits of northern Estonia are analysed. Ripple marks are described using different parameters (wavelength, height, and wave and asymmetry indexes. Rippled bedding is exposed in a large area in the uppermost Keila Stage, on the upper boundary of micritic-peloidal limestones (Pääsküla Member of the Kahula Formation. Beds with ripples are overlain by organodetrital lime­stones (Saue Member of the Kahula Formation transitional to grainstones or mud mounds of the Vasalemma Formation. The content of peloids in the Pääsküla Member is relatively high and their size (0.04–0.06 mm corresponds to the grain size of sediments capable of forming ripple marks. Weakly asymmetrical sinusoidal ripple marks are oriented in a north–south direction and have likely been formed in the shallow-water zone of the shoal at some distance from the shore. The wave-current origin of the studied ripples can be inferred from ripple indexes. Ripples were subjected to some erosion and in the shallowing-upwards conditions a rocky bottom with the Trypanites ichnofacies evolved. The rippled surface terminates a small-scale cycle (parasequence of the depositional sequence.

  1. Late Ordovician geographic patterns of extinction compared with simulations of astrophysical ionizing radiation damage

    CERN Document Server

    Melott, Adrian L

    2008-01-01

    Based on the intensity and rates of various kinds of intense ionizing radiation events such as supernovae and gamma-ray bursts, it is likely that the Earth has been subjected to one or more events of potential mass extinction level intensity during the Phanerozoic. These induce changes in atmospheric chemistry so that the level of Solar ultraviolet-B radiation reaching surface and near-surface waters may be approximately doubled for up to one decade. This UVB level is known from experiment to be more than enough to kill off many kinds of organisms, particularly phytoplankton. It could easily induce a crash of the photosynthetic-based food chain in the oceans. Certain regularities in the latitudinal distribution of damage are apparent in computational simulations of the atmospheric changes. It was previously proposed that the late Ordovician extinction is a candidate for a contribution from an ionizing radiation event, based on environmental selectivity in trilobites. We confront this hypothesis with data from...

  2. Graptolite community responses to global climate change and the Late Ordovician mass extinction.

    Science.gov (United States)

    Sheets, H David; Mitchell, Charles E; Melchin, Michael J; Loxton, Jason; Štorch, Petr; Carlucci, Kristi L; Hawkins, Andrew D

    2016-07-26

    Mass extinctions disrupt ecological communities. Although climate changes produce stress in ecological communities, few paleobiological studies have systematically addressed the impact of global climate changes on the fine details of community structure with a view to understanding how changes in community structure presage, or even cause, biodiversity decline during mass extinctions. Based on a novel Bayesian approach to biotope assessment, we present a study of changes in species abundance distribution patterns of macroplanktonic graptolite faunas (∼447-444 Ma) leading into the Late Ordovician mass extinction. Communities at two contrasting sites exhibit significant decreases in complexity and evenness as a consequence of the preferential decline in abundance of dysaerobic zone specialist species. The observed changes in community complexity and evenness commenced well before the dramatic population depletions that mark the tipping point of the extinction event. Initially, community changes tracked changes in the oceanic water masses, but these relations broke down during the onset of mass extinction. Environmental isotope and biomarker data suggest that sea surface temperature and nutrient cycling in the paleotropical oceans changed sharply during the latest Katian time, with consequent changes in the extent of the oxygen minimum zone and phytoplankton community composition. Although many impacted species persisted in ephemeral populations, increased extinction risk selectively depleted the diversity of paleotropical graptolite species during the latest Katian and early Hirnantian. The effects of long-term climate change on habitats can thus degrade populations in ways that cascade through communities, with effects that culminate in mass extinction.

  3. A Lipid Biomarker Stratigraphic Record through the Late Ordovician Mass Extinction

    Science.gov (United States)

    Rohrssen, M.; Love, G. D.; Fike, D. A.; Finnegan, S.; Fischer, W. W.; Jones, D. S.

    2010-12-01

    The Late Ordovician (~450-440 Ma) was a period of major environmental change, as indicated by evidence for short-duration (history of strata on the island, lack signs of petroleum-derived contamination (e.g. zero oleanane signal from angiosperms and other self-checks), and yield the C29 sterane predominance and low C28/C29 sterane ratios typical of the Early Paleozoic. These sediments, which bear marine fossils, lack the marine marker 24-n-propylcholestane, and have high 3β-methylhopane (4-11% of C30 αβ-hopane) and moderate 2α-methylhopane (2-4% C30 αβ-hopane) indices, most commonly associated with methanotrophs and cyanobacteria, respectively. Gammacerane is present only in trace amounts. Hopane/sterane ratios range from 1.8 to 11.2 (average = 4.7), with most values significantly above the Phanerozoic marine average values of 0.5-2.0, indicating a high contribution of bacterial input to sedimentary organic matter. Lower hopane/sterane values (average = 2.2) are generally found coincident with the carbon isotope excursion. Taken together, the lipid biomarker data suggest a stressed oligotrophic marine ecosystem in which N2-fixing bacterial communities dominate over eukaryotic algae, possibly as a response to nitrate-limitation in the low-sulfate Paleozoic ocean.

  4. The Species-Area Relationship in the Late Ordovician: A Test Using Neutral Theory

    Directory of Open Access Journals (Sweden)

    Steven M. Holland

    2013-04-01

    Full Text Available The fundamental biodiversity number, θ, as proposed by Hubbell, should be positively correlated with province area. Because θ can be calculated from preserved relative abundance distributions, this correlation can be tested in the fossil record for regions with known provinces. Late Ordovician (443–458 Ma strata of Laurentia are divided into four geochemically and biologically distinct regions that reflect provinces in the epicontinental sea. We use existing and newly obtained bed-level census data to test whether Hubbell’s θ is positively correlated with the area of these four regions, corresponding roughly to the Appalachian Basin, Cincinnati Arch, Upper Mississippi Valley, and western United States and Canada. Results indicate a positive relationship between province area and θ that suggests the influence of provincial area, among other factors, on diversity. This correlation highlights the inherent link between diversity and abundance structure at local and regional scales, such that changes at one scale will necessarily affect the other. Since diversity at these smaller spatial scales is an important component of global biodiversity, determining the nature of this relationship in the fossil record has implications for understanding how diversity is assembled globally throughout the Phanerozoic.

  5. Regional hydrogeology of the Silurian and Ordovician sedimentary rock underlying Niagara Falls, Ontario, Canada

    Science.gov (United States)

    Novakowski, Kentner S.; Lapcevic, Patricia A.

    1988-12-01

    Due to concern over the potential for widespread groundwater contamination in the sedimentary rock underlying the Niagara Falls area, this study was done to investigate the hydrogeology of the Silurian and Ordovician stratigraphy underlying the Upper Niagara River and the Eastern Niagara Peninsula. Seven boreholes (up to 150 m deep) were drilled, instrumented with multiple packer casing, tested for permeability, sampled for inorganic and organic solutes and monitored for hydraulic head to provide data for a conceptual model of regional groundwater flow. Results show that there are at least three distinct groundwater flow regimes in the bedrock. The uppermost regime consists of fracture zones in the Guelph and Lockport Formations, within which hydraulic conductivity, hydraulic head measurements and geochemical analyses indicate active groundwater circulation primarily discharging towards the Niagara Gorge and Escarpment. Underlying the Lockport Formation are an overpressured (high hydraulic head) regime in the Clinton-Upper Cataract-Lower Queenston Formation and an underpressured (low hydraulic head) regime in the Lower Cataract-Upper Queenston Formation. In both regimes, geochemical analyses and permeability measurements indicate very old and saline groundwater which probably has undergone minimal migration since pre-Pleistocene time. The implication based on the study so far, is that potential groundwater contamination below the bottom of the Lockport Formation is probably not significant in the Niagara Falls area except adjacent to the Niagara Gorge where vertical permeability in the lower flow regimes may be enhanced.

  6. Graptolite community responses to global climate change and the Late Ordovician mass extinction

    Science.gov (United States)

    Sheets, H. David; Mitchell, Charles E.; Melchin, Michael J.; Loxton, Jason; Štorch, Petr; Carlucci, Kristi L.; Hawkins, Andrew D.

    2016-07-01

    Mass extinctions disrupt ecological communities. Although climate changes produce stress in ecological communities, few paleobiological studies have systematically addressed the impact of global climate changes on the fine details of community structure with a view to understanding how changes in community structure presage, or even cause, biodiversity decline during mass extinctions. Based on a novel Bayesian approach to biotope assessment, we present a study of changes in species abundance distribution patterns of macroplanktonic graptolite faunas (˜447-444 Ma) leading into the Late Ordovician mass extinction. Communities at two contrasting sites exhibit significant decreases in complexity and evenness as a consequence of the preferential decline in abundance of dysaerobic zone specialist species. The observed changes in community complexity and evenness commenced well before the dramatic population depletions that mark the tipping point of the extinction event. Initially, community changes tracked changes in the oceanic water masses, but these relations broke down during the onset of mass extinction. Environmental isotope and biomarker data suggest that sea surface temperature and nutrient cycling in the paleotropical oceans changed sharply during the latest Katian time, with consequent changes in the extent of the oxygen minimum zone and phytoplankton community composition. Although many impacted species persisted in ephemeral populations, increased extinction risk selectively depleted the diversity of paleotropical graptolite species during the latest Katian and early Hirnantian. The effects of long-term climate change on habitats can thus degrade populations in ways that cascade through communities, with effects that culminate in mass extinction.

  7. The Ordovician acritarch genera Tranvikium and Ampullula: their relationship and taxonomy.

    Science.gov (United States)

    Uutela; Sarjeant

    2000-10-01

    A restudy of the Ordovician (Arenig-Llanvirn) acritarch taxa Tranvikium polygonale Tynni, 1982, and Ampullula suetica Righi, 1991, indicates that they represent extremes in a single morphological plexus. At one extreme are forms with a polar 'excystment' aperture (closed by an operculum or two opercular pieces) and a smaller opening (plugged or open) at the opposite pole; at the other are forms lacking a polar aperture but having, at the opposite pole, a tube open distally and plugged or open basally. New morphological terms for these structures are proposed. The genera and species are treated as synonyms and an emended diagnosis is given for Tranvikium polygonale, incorporating this whole morphological plexus. The possible purposes of the structures exhibited and the likely affinity of T. polygonale to various groups of algae are discussed. The emendation of Ampullula by Brocke (1997) is rejected and the genus Stelomorpha Yin, 1994 retained, with an emended diagnosis. The new combination Stelomorpha princeps (Brocke, 1997) Uutela and Sarjeant is proposed.

  8. Ordovician and Late Paleozoic Early Mesozoic tectonothermal history of the La Noria area, northern Acatlán Complex, southern Mexico: Record of convergence in the Rheic and paleo-Pacific Oceans

    Science.gov (United States)

    Hinojosa-Prieto, H. R.; Nance, R. D.; Keppie, J. D.; Dostal, J. V.; Ortega-Rivera, A.; Lee, J. K. W.

    2008-12-01

    The La Noria area lies in the northern part of the polydeformed Acatlán Complex, (southern Mexican Mixteca terrane), and the rocks record the following sequence of events: (i) Early-Middle Ordovician deposition of the volcaniclastic El Epazote and Las Calaveras units; (ii) late Middle Ordovician intrusion of the 467 ± 16 Ma megacrystic, peraluminous, rift-related granitoids; (iii) late Devonian, D 1, greenschist facies deformation; (iv) intrusion of the Los Malpasos leucogranite and associated minor intrusions; (v) Middle Mississippian, D 2, dextral N-S deformation also under greenschist facies metamorphic conditions; and (vi) undated D 3 kink band development. U-Pb LA-ICPMS detrital zircon ages: (a) the El Epazote unit yielded: a mean 206Pb/ 238U age from the youngest five concordant 206Pb/ 238Pb age of 488 ± 10 Ma, with other age peaks at ca. 506, ca. 1077, and ca. 1779 Ma and a few concordant Neoproterozoic ages: and (b) the Las Calaveras unit yielded a mean 206Pb/ 238U age from the sixteen youngest detrital zircons of 466 ± 10 Ma with other population age peaks ca. 1111, and ca. 1753 Ma. These data imply that granitoid intrusion was roughly synchronous with deposition of some of the host rocks. Whereas sources for most of the detrital zircons may be found in either the Acatlán and Oaxacan complexes, Laurentia or Gondwana, a Neoproterozoic source is most likely in Amazonia. The rocks record three low-grade deformational episodes: (i) D 1 produced a weak compositional banding and/or schistosity (S 1) under greenschist facies conditions; (ii) D 2, also occurred under greenschist facies conditions, and developed tight to isoclinal folds (F 2) in S 1 and an axial planar spaced-cleavage (S 2) that is co-planar with S 1; and (iii) D 3 produced reverse and conjugate kink bands (F 3) that deform the S 1/S 2 composite foliation. The leucogranite and related dikes that intrude the complex record only the latter two deformational events. Ca. 330 Ma 40Ar/ 39Ar

  9. Carbon and strontium isotope variations and responses tosea-level fluctuations in the Ordovician of the Tarim Basin

    Institute of Scientific and Technical Information of China (English)

    JIANG; Maosheng

    2001-01-01

    , Sedimentary response to sea-level rise during Middle Ordovician in the Guizhou and Hunan regions (in Chinese with English abstract), Scientia Geologica Sinica, 1998, 33(1): 93- 101.

  10. SHRIMP zircon U-Pb dating from K-bentonite in the top of Ordovician of Wangjiawan Section, Yichang, Hubei,China

    Institute of Scientific and Technical Information of China (English)

    HU YanHua; ZHOU JiBin; SONG Biao; LI Wei; SUN WeiDong

    2008-01-01

    The Global boundary Stratotype Section and Point (GSSP) for the base of the Hirnantian Stage (the latest stage of the Ordovician System) is defined at a point 0.39m below the base of the Kuanyinchiao Bed in the Wangjiawan North Section, which is the upper most "golden spike" of the Ordovician.However, this "golden spike" is lack of reliable geochronology data. This article gives a sensitive high resolution ion microprobe (SHRIMPII) zircon U-Pb dating for a K-bentonite sample from the Kuanyinchiao Bed in the Wangjiawan North Section. The age of the K-bentonite sample is 443.2+1.6 Ma, that is to say, the isotopic age of the uppermost of Hirnantian Stage, the point of Ordovician-Silurian boundary,should be near to, but slightly younger than 443.2±1.6 Ma. This age is identical to the Ordovician-Silurian boundary age 443.7±1.5 Ma as declared by International Commission on Stratigraphy (ICS). So, this research provides some good geochronlogical data for the Hirnantian Stage and the Ordovician-Silurian boundary as well as the global correlation.

  11. Reconstructing Cambro-Ordovician Seawater Composition using Clumped Isotope Paleothermometry on Calcitic and Phosphatic Brachiopods

    Science.gov (United States)

    Bergmann, K.; Robles, M.; Finnegan, S.; Hughes, N. C.; Eiler, J. M.; Fischer, W. W.

    2012-12-01

    A secular increase in δ18O values of marine fossils through early Phanerozoic time raises questions about the evolution of climate and the water cycle. This pattern suggests two end-member hypotheses 1) surface temperatures during early Paleozoic time were very warm, in excess of 40°C (tropical MAT), or 2) the isotopic composition of seawater increased by up to 7-8‰. It has been difficult to evaluate these hypotheses because the δ18O composition of fossils depends on both temperature and the δ18O of water. Furthermore, primary isotopic signatures can be overprinted by diagenetic processes that modify geological materials. This too could explain the decrease in δ18O values of marine fossils with age. Carbonate clumped isotope thermometry can constrain this problem by providing an independent measure of crystallization temperature and, when paired with classical δ18O paleothermometry, can determine the isotopic composition of the fluid the mineral last equilibrated with. Combined with traditional tools, this method has the potential to untangle primary isotopic signatures from diagenetic signals. We measured the isotopic ordering of CO3 groups (Δ47) substituted into the phosphate lattice of phosphatic brachiopods in Cambrian strata. Phosphatic fossils are generally less soluble than carbonates in surface and diagenetic environments, and so are hypothesized to provide a more robust record of primary growth conditions. They also provide an archive prior to the rise of thick shelled calcitic fossils during the Ordovician Radiation. Additionally, measurements of the δ18O of the CO3 groups can be compared with the δ18O of PO4 groups to test whether their mutual fractionation is consistent with primary growth and the apparent temperature recorded by carbonate clumped isotope measurements. We are constructing a phosphatic brachiopod calibration for carbonate clumped isotope thermometry, and Δ47 values of CO2 extracted from modern phosphatic brachiopods suggest

  12. Geochemistry of the Cambrian-Ordovician aquifer system in the northern Midwest, United States: D in Regional aquifer-system analysis

    Science.gov (United States)

    Siegel, D.I.

    1989-01-01

    Distributions of solutes in aquifers of Cambrian and Ordovician age were studied in Minnesota, Wisconsin, Iowa, Illinois, northwestern Indiana, and northern Missouri to determine the sources of solutes and the probable chemical mechanisms that control regional variations in water quality. This work is part of the Northern Midwest Regional Aquifer-System Analysis project, whose objective is to describe and model the regional hydrogeology of the Cambrian- Ordovician aquifer system in the study region. The data base used included more than 3,000 ground-water-quality analyses from all major aquifers, but especially from the St. Peter, Jordan, and Mount Simon Sandstones and their equivalents. Regional variations in the water chemistry of glacial drift and other sedimentary units that overlie the Cambrian-Ordovician aquifer system in recharge areas in Minnesota, Iowa, Wisconsin, and Illinois were also studied, but to a lesser degree.

  13. Shale gas reservoir characteristics of Ordovician-Silurian formations in the central Yangtze area, China

    Science.gov (United States)

    Shan, Chang'an; Zhang, Tingshan; Wei, Yong; Zhang, Zhao

    2016-07-01

    The characteristics of a shale gas reservoir and the potential of a shale gas resource of Ordovician-Silurian age in the north of the central Yangtze area were determined. Core samples from three wells in the study area were subjected to thin-section examination, scanning electron microscopy, nuclear magnetic resonance testing, X-ray diffraction mineral analysis, total organic carbon (TOC) testing, maturity testing, gas-bearing analysis, and gas component and isothermal adsorption experiments. A favorable segment of the gas shale reservoir was found in both the Wufeng Formation and the lower part of the Longmaxi Formation; these formations were formed from the late Katian to early Rhuddanian. The high-quality shale layers in wells J1, J2, and J3 featured thicknesses of 54.88 m, 48.49 m, and 52.00 m, respectively, and mainly comprised carbonaceous and siliceous shales. Clay and brittle minerals showed average contents of 37.5% and 62.5% (48.9% quartz), respectively. The shale exhibited type II1 kerogens with a vitrinite reflectance ranging from 1.94% to 3.51%. TOC contents of 0.22%-6.05% (average, 2.39%) were also observed. The reservoir spaces mainly included micropores and microfractures and were characterized by low porosity and permeability. Well J3 showed generally high gas contents, i.e., 1.12-3.16 m3/t (average 2.15 m3/t), and its gas was primarily methane. The relatively thick black shale reservoir featured high TOC content, high organic material maturity, high brittle mineral content, high gas content, low porosity, and low permeability. Shale gas adsorption was positively correlated with TOC content and organic maturity, weakly positive correlated with quartz content, and weakly negatively correlated with clay content. Therefore, the Wufeng and Longmaxi formations in the north of the central Yangtze area have a good potential for shale gas exploration.

  14. Shale gas reservoir characteristics of Ordovician-Silurian formations in the central Yangtze area, China

    Science.gov (United States)

    Shan, Chang'an; Zhang, Tingshan; Wei, Yong; Zhang, Zhao

    2017-03-01

    The characteristics of a shale gas reservoir and the potential of a shale gas resource of Ordovician-Silurian age in the north of the central Yangtze area were determined. Core samples from three wells in the study area were subjected to thin-section examination, scanning electron microscopy, nuclear magnetic resonance testing, X-ray diffraction mineral analysis, total organic carbon (TOC) testing, maturity testing, gas-bearing analysis, and gas component and isothermal adsorption experiments. A favorable segment of the gas shale reservoir was found in both the Wufeng Formation and the lower part of the Longmaxi Formation; these formations were formed from the late Katian to early Rhuddanian. The high-quality shale layers in wells J1, J2, and J3 featured thicknesses of 54.88 m, 48.49 m, and 52.00 m, respectively, and mainly comprised carbonaceous and siliceous shales. Clay and brittle minerals showed average contents of 37.5% and 62.5% (48.9% quartz), respectively. The shale exhibited type II1 kerogens with a vitrinite reflectance ranging from 1.94% to 3.51%. TOC contents of 0.22%-6.05% (average, 2.39%) were also observed. The reservoir spaces mainly included micropores and microfractures and were characterized by low porosity and permeability. Well J3 showed generally high gas contents, i.e., 1.12-3.16 m3/t (average 2.15 m3/t), and its gas was primarily methane. The relatively thick black shale reservoir featured high TOC content, high organic material maturity, high brittle mineral content, high gas content, low porosity, and low permeability. Shale gas adsorption was positively correlated with TOC content and organic maturity, weakly positive correlated with quartz content, and weakly negatively correlated with clay content. Therefore, the Wufeng and Longmaxi formations in the north of the central Yangtze area have a good potential for shale gas exploration.

  15. Logging Evaluation of the Ordovician Carbonate Reservoir Beds in the Lungudong Region,Tarim Basin

    Institute of Scientific and Technical Information of China (English)

    YANG Wenjing; XIAO Chengwen; LIU Luofu; QI Guangzhong; JIANG Zhenxue; YUAN Yunchun; WANG Weili; YANG Song

    2010-01-01

    In recent years,great progress has been made constantly in oil and gas exploration in the Lungudong region of the Tarim Basin.However,progress has been slow in the evaluation of its main oil-producing horizons-the Ordovician carbonate reservoir beds.Based on previous researches and on the various data such as drilling,geology and oil test,in combination with the interpretation of each single-well imaging and conventional logging data,and through analysis and comparison,the identification methods in imaging and conventional logging for four types of carbonate reservoir beds in this region are summarized in this paper.Calculation formulas for four reservoir bed parameters,i.e.shale content,porosity,permeability and oil saturation in this region are proposed;and reservoir beds in this region are divided into three levels (Ⅰ,Ⅱ and Ⅲ) by combining oil test data and logging data,The lower limits of the effective porosity of reservoir beds and the fracture porosity of effective reservoir beds are determined as 1.8% and 0.04%,respectively.The physical property parameters are calculated by conventional logging curves,and the most advantageous areas for reservoir development are predicted comprehensively.On the plane,the high-value zones of reservoir bed parameters are mainly concentrated in the N-S-trending strike-slip fault,the Sangtamu fault horst zone and near the LG38 well area;vertically,the reservoir bed parameters of the Yijianfang Formation are better than those of the Yingshan and Lianglitage formations.

  16. Storm deposits (tempestites) in Ordovician cratonic carbonates (Arbuckle Group, south-central Oklahoma)

    Energy Technology Data Exchange (ETDEWEB)

    Goldhammer, R.K.; Elmore, R.D.

    1983-03-01

    The Early Ordovician Kindblade Formation (Arbuckle Group), exposed in the Arbuckle Mountains of south-central Oklahoma, is a shallow marine epicontinental carbonate sequence that contains numerous storm deposits. The storm deposits (tempestites) are of two types, proximal and distal; the latter dominates in terms of both number and aggregate thickness. Distal tempestites consist of a fining upward sequence, 5 to 50 cm (2 to 20 in.) thick, that overlies an eroded hardground or firmground. The sequence consists of a lag lithoclastic grainstone that grades up into a laminated peloidal grainstone and then into mudstone. Primary sedimentary features such as laminations, burrows, and allochems are truncated at the surfaces, and borings are filled with unsorted lithoclasts. The lithoclasts at the base of the sequence are bored, generally well rounded, discoid in shape, and consist of mudstone, peloidal packstone, and oolitic grainstone. The overlying mudstone is sparsely fossiliferous and bioturbated with burrows either selectively dolomitized or infilled with lithoclastric grainstone. Proximal tempestites consist of coarse lithoclastic flat pebble conglomerate beds approximately 1 m (3.25 ft) thick that are interbedded with ooid grainstone and overlie mudstone. The contact between the units is sharp and erosional. The lithoclasts are of variable composition and may be up to 20 cm (7.75 in.) in diameter. The two types of tempestites occur in crude cycles, which consist of distal deposits overlain by proximal tempestites and ooid grainstones. The abundance of the storm deposits in the section, approximately one every 20 cm (7.75 in.), indicates that hundreds of storm-induced events are recorded in the Kindblade Formation.

  17. High potential for chemical weathering and climate effects of early lichens and bryophytes in the Late Ordovician

    Science.gov (United States)

    Porada, Philipp; Lenton, Tim; Pohl, Alexandre; Weber, Bettina; Mander, Luke; Donnadieu, Yannick; Beer, Christian; Pöschl, Ulrich; Kleidon, Axel

    2016-04-01

    Non-vascular vegetation in the Late Ordovician may have considerably increased global chemical weathering, thereby reducing atmospheric CO2 concentration and contributing to a decrease in global temperature and the onset of glaciations. Usually, enhancement of weathering by non-vascular vegetation is estimated using field experiments which are limited to small areas and a low number of species. This makes it difficult to extrapolate to the global scale and to climatic conditions of the past, which differ markedly from the recent climate. Here we present a global, spatially explicit modelling approach to estimate chemical weathering by non-vascular vegetation in the Late Ordovician. During this period, vegetation probably consisted of early forms of today's lichens and bryophytes. We simulate these organisms with a process-based model, which takes into account their physiological diversity by representing multiple species. The productivity of lichens and bryophytes is then related to chemical weathering of surface rocks. The rationale is that the organisms dissolve rocks to extract phosphorus for the production of new biomass. To account for the limited supply of unweathered rock material in shallow regions, we cap biotic weathering at the erosion rate. We estimate a potential global weathering flux of 10.2 km3 yr-1 of rock, which is around 12 times larger than today's global chemical weathering. The high weathering potential implies a considerable impact of lichens and bryophytes on atmospheric CO2 concentration in the Ordovician. Moreover, we find that biotic weathering is highly sensitive to atmospheric CO2, which suggests a strong feedback between chemical weathering by lichens and bryophytes and climate.

  18. Hydrogeology of the Cambrian-Ordovician aquifer system in the northern Midwest: B in Regional aquifer-system analysis

    Science.gov (United States)

    Young, H.L.; Siegel, D.I.

    1992-01-01

    The Cambrian-Ordovician aquifer system contains the most extensive and continuous aquifers in the northern Midwest of the United States. It is the source of water for many municipalities, industries, and rural water users. Since the beginning of ground-water development from the aquifer system in the late 1800's, hydraulic heads have declined hundreds of feet in the heavily pumped Chicago-Milwaukee area and somewhat less in other metropolitan areas. The U.S. Geological Survey has completed a regional assessment of this aquifer system within a 161,000-square-mile area encompassing northern Illinois, northwestern Indiana, Iowa, southeastern Minnesota, northern Missouri, and Wisconsin.

  19. Glacial Ordovician new evidence in the Pakhuis Formation, South Africa : sedimentological investigation and palaeo-environnemental reconstruction

    Science.gov (United States)

    Portier, E.; Buoncristiani, Jf.; Deronzier, Jf.

    2009-04-01

    During the Late Ordovician (Hirnantian) an ice sheet covered a great part of the Gondwana. In Africa, several studies present the stratigraphy and the complexity of these glacial records. The different glacial landsystems correspond to several glacial cycles, related to rapid ice front oscillations and are grouped into two major ice-sheet advances, separated by a major ice sheet recession. The study was performed on three well outcropping Late Ordovician sections in South Africa. The Ordovician IV is described as the Pakhuis Rm, and is divided into three different lithological members (known as Sneekop, Oskop and Sternbras Mb) that could be related to two major glacial cycles. In the first cycle (pool the two first Mb), facies association indicate continental environment, with : massive sandy tillites with facetted and striated erratics, subaerial outwash plain to glaciolacustrine cross bedded sands and laminated silts. Near Clanwilliam, the outcrops exhibit a high lateral variability in facies and thickness, ranging from a few meters to several tens of meters. The second cycle is dominated by clear marine sedimentation and may be interpreted as a transgressive sequence, quite different from what occurred in North Gondwana. Typical facies define shoreface environment, and periglacial evidence such as dropstones at base are encountered, passing progressively to a clear offshore environment at top of the series, likely Silurian aged, and known as Cederberg fm. Two glacial pavements were also described. The most spectacular one was firstly described by Visser et al. 1974 and should be interpreted as an intra-formational glacial pavement, with striae indicating a flow from East to West. This pavement is overlying a newly discovered glacial floor which exhibits grooves, crescents marks, en echelon fractures, with the same E-W general orientation, and shaped as ‘roches moutonnées', which are typical evidences of glacial erosion on indurated substratum. Reconstructing

  20. Storm deposits as graves in Early Life: the Fezouata Lagerstätte case (Lower Ordovician, Morocco)

    Science.gov (United States)

    Vaucher, Romain; Pittet, Bernard; Hormière, Hélène; Martin, Emmanuel L. O.; Lefebvre, Bertrand

    2016-04-01

    The Fezouata Shale (Early Ordovician, Morocco) is renowned in the palaeontological community for its Konservat-Lagerstätte (Tremadocian in age) that yielded thousands of exceptionally well-preserved fossils (EPF) from the Great Ordovician Biodiversification Event. Lower Ordovician deposits in the central Anti-Atlas Mountain (Zagora area) are expressed by the Fezouata Shale and the Zini Formation. They consist in ca. 900m of siltstones and sandstones deposited in an epicontinental sea at the periphery of the Gondwanaland. Sedimentologic field analysis and sequence analysis were achieved on ten stratigraphic sections in order to constrain the palaeoenvironmental context of the Fezouata Biota and to predict the location (geographically and stratigraphically) of new Lagerstätten. Sedimentary structures (cm- to m-scale symmetrical ripples) and geometries (lobe, lobe-channel) point to storm dominance on the sedimentation but peculiar sedimentary features suggest a tide modulation. Thus, a wave-dominated tide-modulated model of deposition recording proximal offshore to shoreface environments for the Fezouata Shale and shoreface to foreshore environments for the overlying Zini Fm is proposed. Layers yielding EPF are argillaceous siltstones (with wave ripples of cm-scale wavelength) always overlain by fine-grained sandstones (distal storm deposits, few cm-thick, several m-long, with cm- to dm-scale hummocky cross-stratifications). Fast burying by storm deposits appear to be of prime importance to initiate the exceptional preservation of the soft tissues of animals in the fossil record. According to the model of deposition it correspond to environments close to the storm weather wave base. Lower Ordovician succession was deposited during a 2nd order cycle, although 3rd and 4th order cycles were also identified. Encoding these different orders of sea level fluctuations giving a value of "1" for the deepest part of sequences (for each order) and a value of "0" for the

  1. Discovery of the messaoudensis–trifidum acritarch assemblage (upper Tremadocian–lower Floian, Lower Ordovician in the subsurface of Morocco

    Directory of Open Access Journals (Sweden)

    Hendrik Nowak

    2015-02-01

    Full Text Available The upper Tremadocian to lower Floian messaoudensis–trifidum acritarch assemblage was first described from the Skiddaw Group of England and subsequently from several localities on the Gondwanan margin that were positioned in high southern latitudes during the Early Ordovician. It is here reported for the first time from North Africa, from the Fezouata formations (Tremadocian to Floian in the AZ-1 borehole, southeastern Morocco. The assemblage is comparable with that from the Skiddaw Group, with Cymatiogalea deunffii, C. messaoudensis, C. velifera, Caldariola glabra glabra, Stelliferidium trifidum and Veryhachium lairdii s.l. The Moroccan assemblage indicates a late Tremadocian age.

  2. The hydrothermal karstification and its effect on Ordovician carbonate reservoir in Tazhong uplift of Tarim Basin, Northwest China

    Institute of Scientific and Technical Information of China (English)

    WU; MaoBing; WANG; Yi; ZHENG; MengLin; ZHANG; WeiBiao; LIU; ChunYan

    2007-01-01

    With a detailed study on petrology, mineralogy and geochemistry of some important Ordovician carbonate well core samples in Tazhong uplift of Tarim Basin, the distinguishing symbols of hydrothermal karstification are first put forward as the phenomena of rock hot depigmentation, hot cataclasm and the appearance of typical hydrothermal minerals such as fluorite, barite, pyrite, quartz and sphalerite. The main homogenization temperatures of primary fluid inclusions in fluorite are from 260 to 310℃, indicating the temperature of hydrothermal fluid. The fluid affected the dissolved rocks and showed typical geochemistry features with low contents of Na and Mg, and high contents of Fe, Mn and Si. The ratio of 3He/4He is 0.02Ra, indicating the fluid from the typical continental crust. The hydrothermal fluid karstification pattern may be described as follows: the hot fluid is from the Permian magma, containing dissolving ingredients of CO2 and H2S, and shifts along fault, ruptures and unconformity, and dissolves the surrounding carbonates while it flows. The mechanism of hydrothermal karstification is that the mixture of two or more fluids, which have different ion intensity and pH values, becomes a new unsaturated fluid to carbonates. The hydrothermal karstification is an important process to form hypo-dissolved pinholes in Ordovician carbonates of Tazhong uplift of Tarim Basin, and the forming of hydrothermal minerals also has favorable influence on carbonate reservoirs.

  3. Large-scale Tazhong Ordovician Reef-fiat Oil-Gas Field in the Tarim Basin of China

    Institute of Scientific and Technical Information of China (English)

    ZHOU Xinyuan; WANG Zhaoming; YANG Haijun; ZHANG Lijuan; HAN Jianfa; WANG Zhenyu

    2009-01-01

    The Tazhong reef-flat oil-gas field is the first large-scale Ordovician organic reef type oil-gas field found in China.Its organic reefs were developed in the early Late Ordovician Lianglitag Formation, and are the first large reefs of the coral-stromatoporoid hermatypic community found in China.The organic reefs and platform-margin grain banks constitute a reef-fiat complex, mainly consisting of biolithites and grainstones.The biolithites can be classified into the framestone, bafflestone.bindstone etc.The main body of the complex lies around the wells from Tazhong-24 to Tazhong-82, trending northwest, with the thickness from 100 to 300 m, length about 220 km and width 5-10 km.It is a reef-flat lithologic hydrocarbon reservoir, with a very complex hydrocarbon distribution:being a gas condensate reservoir as a whole with local oil reservoirs.The hydrocarbon distribution is controlled by the reef complex.generally located in the upper 100-200 m part of the complex,and largely in a banded shape along the complex.On the profile,the reservoir shows a stratified feature.with an altitude difierence of almost 2200 m from southeast to northwest.The petroleum accumulation is controlled by karst reservoir beds and the northeast strike-slip fault belt. The total geologic reserves had reached 297.667 Mt by 2007.

  4. Pore structure characteristics of the relative water-resisting layer on the top of the Ordovician in Longgu Coal Mine

    Institute of Scientific and Technical Information of China (English)

    Rong Huren; Bai Haibo⇑

    2014-01-01

    In order to study the permeability and water-resisting ability of the strata on the top of the Ordovician in Longgu Coal Mine, this paper tested the permeability and porosity of the strata, investigated the fracture and pore structure features of the strata, and identified the main channels which govern the permeability and water-resisting ability of the strata. The permeability of the upper, central and lower strata shows as 2.0504 ? 10?3-2.782762 ? 10?3, 4.1092 ? 10?3-7.3387 ? 10?3 and 2.0891 ? 10?3-3.2705 ? 10?3 lm2, respectively, and porosity of that is 0.6786-0.9197%, 0.3109-0.3951%and 0.9829-1.8655%, respectively. The results indicate that:(1) the main channels of the relative water-resisting layer are the pore throats with a diameter more than 6 lm;(2) the major proportion of pore throats in the vertical flow channel and the permeability first increases and then sharply decreases; (3) the fractures occurring from the top to 20 m in depth of the strata were filled and there occurred almost no fracture under the depth of 40 m;and (4) the ratio of turning point of the main flow channel in the strata on top of Ordovician can be used to confirm the thickness of filled water-resisting layers.

  5. Fenxiang biota: a new Early Ordovician shallow-water fauna with soft-part preservation from China.

    Science.gov (United States)

    Balinski, Andrzej; Sun, Yuanlin

    Our perception of biodiversity in the geological past is incomplete and biased because most organisms did not have mineralized skeletons and therefore had little chance of fossilization. This especially refers to shallow-water marine environments, rarely represented by localities with exceptional preservation of fossil material (known as taphonomic windows or Konservat-Lagerstätten). Such extraordinary "windows" may markedly broaden our knowledge of biodiversity of the past. Here, we show a review of the invertebrate fossils from recently discovered locality in the Lower Ordovician Fenxiang Formation of Hubei Province in southern China revealing exceptional preservation of soft tissues. The fauna, generally of shallow-water aspect, contains linguloid brachiopods with a remarkably preserved pedicle, the oldest traces of nematode life activities, the oldest reliable record of hydroids, the first fossil antipatharian corals, a pyritized colonial organism of unknown affinity, supposed arthropod appendages, probable phosphatized scalidophoran worm embryo and other fossils. Our discovery supports the opinion that the famous soft-bodied preservation of Burgess Shale- or Chengjiang-type did not vanish from the fossil record in post-Cambrian times. The new finding represents a prelude to the Great Ordovician Biodiversification Event and provides evidence for calibration of molecular clock of several invertebrate lineages.

  6. Chitinozoan zonation of the Late Ordovician and the Early Silurian of the island of Anticosti, Québec, Canada.

    Science.gov (United States)

    Soufiane; Achab

    2000-04-01

    A reappraisal of chitinozoan distribution across the Ordovician-Silurian boundary on the Island of Anticosti has led to the recognition of a new zone, the Ancyrochitina ellisbayensis biozone, in the uppermost part of the Ellis Bay Formation. This biozone lies between the well defined Upper Ordovician Spinachitina taugourdeaui biozone and the lowest Silurian (Rhuddanian) Plectochitina nodifera biozone of the Becscie Formation. The occurrence of such diagnostic species as P. nodifera, Belonechitina postrobusta, Conochitina electa and Ancyrochitina ramosaspina in the Lower Silurian of Anticosti points to a close similarity to faunas in Estonia and north Latvia and indicates an age ranging from the Parakidograptus acuminatus to the Coronograptus cyphus in terms of graptolite zones. The chitinozoan biozonation harmonizes with that based on conodonts and, to a lesser extent, with the known graptolite faunal succession. Five new species: Ancyrochitina ellisbayensis sp. nov., Clathrochitina postconcinna sp. nov., Conochitina gunriveris sp. nov., Clathrochitina perexilis sp. nov., Bursachitina basiconcava sp. nov. and three species in open nomenclature are described.

  7. Estimating relative paleolongitudes with the assumption of middle Paleozoic true polar wander

    Science.gov (United States)

    van der Voo, R.; Bazhenov, M.

    2003-04-01

    Three new paleomagnetic poles have been obtained from Lower Ordovician, Lower Silurian, and Middle Devonian rocks in the Chingiz Range, Kazakhstan (see Bazhenov et al. presentation in session MG3, this meeting). They form an apparent polar wander (APW) loop that resembles similar loops for Ordovician through Devonian poles from Baltica, Laurentia and Gondwana. The latter have previously been attributed to true polar wander (TPW) in an admittedly speculative paper (Van der Voo, 1994, EPSL, vol. 122, pp. 239-243). A characteristic of TPW is that all continents should see its expression manifested in their APW paths, especially if relative plate velocities were much less than TPW rates. Paleopoles from Siberia and the China blocks do not contradict a TPW signature for the Ordovician through Devonian interval, but the results are not complete enough to establish a loop in the APW paths. However, the paleopoles from the Chingiz block in Kazakhstan fit the requisite looping pattern. Even though TPW remains speculative for this interval until it has been shown that all continents have similarly shaped APW paths, there are two interesting issues that are related to TPW. (1) If TPW occurred, similarly shaped APW paths from all continents can be superposed and the Euler rotations necessary for this superposition place the continents in their ancient relative positions to first approximation. This implies that a rough estimate of relative paleolongitudes can be obtained. (2) Superposition of the APW paths should not lead to overlap in continental positions, so that the absence of overlaps constitutes one possible test of the TPW hypothesis. The currently available data from the major continents pass this test.

  8. Hydrothermal recrystallization of the Lower Ordovician dolomite and its significance to reservoir in northern Tarim Basin

    Institute of Scientific and Technical Information of China (English)

    2010-01-01

    Discovered in S15 and some other wells, the Lower Ordovician in the northern Tarim Basin consists mainly of brown gray-dark gray very fine-fine crystalline dolomite, with a minor portion of locally light gray-white medium-coarse crystalline dolomite. Silicification can be observed in the medium-coarse dolomite, and some euhedral drusy quartz can also be found in pores and fractures of the dolomite. The homogenization temperature of the fluid inclusions in the medium-coarse dolomite is between 110 and 200°C with maximum between 140 and 190°C, and the salinity is between 10.7 and 18.5 wt.% NaCl Eq. The homogenization temperature and salinity of the fluid inclusions in the medium-coarse dolomite are similar to those in the drusy quartz. Compared with the very fine-fine dolomite, the medium-coarse phase contains relatively high Fe and Mn. The average concentration of FeO and MnO in the medium-coarse dolomite is 1.917% and 0.323%, respectively. The medium-coarse dolomite has a remarkable negative Eu anomaly, consistent with the REE pattern of the intermediate-felsic igneous rocks in the Tarim Basin. The oxygen isotopic composition of the medium-coarse dolomite is relatively lighter than that of the very fine-fine dolomite. The δ18OPDB values of the medium-coarse dolomite are between -10.35‰ and -7.31‰. The δ18OSMOW values of the fluid associated with the medium-coarse dolomite can be calculated according to homogenization temperature and oxygen isotope fractionation factor between dolomite and fluid, and the calculated values are between +4‰ and +10‰, consistent with those of the hydrothermal fluid. The medium-coarse dolomite has relatively high 87Sr/86Sr ratios as well, indi- cating an origin associated with intermediate-felsic igneous rock. The homogenization temperature, element composition, REE pattern, oxygen and strontium isotopes demonstrate that the medium-coarse dolomite is the result of recrystallization of very fine-fine dolomite under

  9. Distribution and significance of crystalline, perlitic and vesicular textures in the Ordovician Garth Tuff (Wales)

    Science.gov (United States)

    McArthur, A. N.; Cas, R. A. F.; Orton, G. J.

    Diverse spherulitic and granular crystalline fabrics, perlitic textures and fabrics related to the growth and migration of vesicles occur in the Garth Tuff, a largely welded Ordovician ignimbrite. Defining the distribution of such textures helps to constrain the ignimbrite's cooling and degassing history. Suites of spherulitic and perlitic textures closely reflect variation in cooling rates. Seven facies are defined based on the style and intensity of crystallisation: (1) a medium to coarsely crystalline, equigranular facies; (2) an intensely spherulitic facies; (3) a sparsely spherulitic facies; (4) a pectinate facies; (5) a microcrystalline to cryptocrystalline, equigranular facies; (6) a lithophysal facies; and (7) a transitional perlite-pectinate facies. Textural changes from facies 1 to 5 reflect progressively higher cooling rates. Facies 1 occurs in proximal settings in the ignimbrite's core. Facies 2 to 5 successively envelop facies 1, with facies 2 becoming the dominant fabric in the ignimbrite's core in medial settings. Facies 5 is typically developed in the originally glassy perlitic zones at the ignimbrite's welded margins. Crystallisation under hydrous conditions is reflected by second-boiling textures in the sporadically developed lithophysal facies. The seventh facies reflects a subtle interplay between cooling, hydration and crystallisation which locally prevented perlitic fracturing. The distribution of amygdales reflects patterns of volatile migration and entrapment. In the lower levels of the ignimbrite, amygdales occur in irregular concentrations or rare subvertical pipe-like structures. Pipe-like structures attest to fumarolic activity while the ignimbrite was in a rheomorphic state. Amygdales are widespread and evenly distributed in the upper levels of the ignimbrite. However, the top of the welding profile is characterised by a thin, poorly vesiculated, originally vitrophyric horizon that abruptly caps an intense concentration of amygdales

  10. New zircon ages on the Cambrian-Ordovician volcanism of the Southern Gemericum basement (Western Carpathians, Slovakia): SHRIMP dating, geochemistry and provenance

    Science.gov (United States)

    Vozárová, Anna; Rodionov, Nickolay; Šarinová, Katarína; Presnyakov, Sergey

    2017-09-01

    The Southern Gemericum basement in the Inner Western Carpathians, composed of low-grade volcano-sedimentary rock complexes, constitutes a record of the polyphase Cambrian-Ordovician continental volcanic arc volcanism. These metavolcanic rocks are characterized by the enrichment in K, Rb, Ba, Th and Ce and Sm relative to Ta, Nb, Hf, Zr, Y and Yb that are the characteristic features for volcanic arc magmatites. The new SHRIMP U-Pb zircon data and compilation of previously published and re-evaluated zircon ages, contribute to a new constrain of the timing of the Cambrian-Ordovician volcanism that occurred between 496 and 447 Ma. The following peaks of the volcanic activity of the Southern Gemericum basement have been recognized: (a) mid-late Furongian at 492 Ma; (b) Tremadocian at 481 Ma; (c) Darriwilian at 464 Ma prolonged to 453 Ma within the early Upper Ordovician. The metavolcanic rocks are characterized by a high zircon inheritance, composed of Ediacaran (650-550 Ma), Tonian-Stenian (1.1-0.9 Ma), and, to a lesser extent, Mesoproterozoic (1.3 Ga), Paleoproterozoic (1.9 Ga) and Archaean assemblages (2.6 Ga). Based on the acquired zircon populations, it could be deduced that Cambrian-Ordovician arc crust was generated by a partial melting of Ediacaran basement in the subduction-related setting, into which old crustal fragments were incorporated. The ascertained zircon inheritances with Meso-, Paleoproterozoic and Archaean cores indicate the similarities with the Saharan Metacraton provenance.

  11. Vertical variation of trace elements and its relation to the water-bearing capacity of Ordovician strata,in Datun coal field

    Institute of Scientific and Technical Information of China (English)

    LIU Huai-zhong; HAN Bao-ping

    2009-01-01

    We tested for fourteen trace elements in samples collected from the Ordovician strata in Datun coal field. The vertical concentration variation of these trace elements is reported. The relationship of the variation to the water-beating capacity of the Ordovician strata is discussed. The minimum concentration of eleven (of 14 total) trace elements appears in the lower Majiagou formation. The maximum concentrations mainly appear in the Badou and Jiawang formations: eight maxima are located in Badou and four more are in Jiawang. The study of karst development and the water-bearing capacity of Ordovician strata shows that karst is well developed in the Majiagou formation and there is a consequent high water-beating capacity in this formation: Badou and Jiawang formations are contrary to this situation. The results illustrate that the minimum concentrations of most trace elements within certain Ordovician formations can be taken as strong evidence for the existence of a well developed karst and a high wa-ter-bearing capacity.

  12. Similar morphological and chemical variations of Gloeocapsomorpha prisca in Ordovician sediments and cultured Botryococcus braunii as a response to changes in salinity

    NARCIS (Netherlands)

    Sinninghe Damsté, J.S.; Derenne, S.; Metzger, P.; Largeau, C.; Bergen, P.F. van; Gatellier, J.P.; Leeuw, J.W. de; Berkaloff, C.

    1992-01-01

    Most Ordovician source rocks consist of accumulation of a colonial marine microorganism, Gloeocapsomorpha prisca (G. prisca) whose nature, ecology and affinity with extant organisms have been in dispute for years. Furthermore, recent studies have shown major differences in phenol moieties between tw

  13. Chitinozoan biostratigraphy and carbon isotope stratigraphy from the Upper Ordovician Skogerholmen Formation in the Oslo Region. A new perspective for the Hirnantian lower boundary in Baltica

    DEFF Research Database (Denmark)

    Amberg, Chloé E. A.; Vandenbroucke, Thijs R. A.; Nielsen, Arne Thorshøj

    2017-01-01

    The end-Ordovician has received wide attention because it hosts major global events including mass extinctions, glaciations, significant sea-level fluctuations, and large-scale perturbations of the Earth's carbon cycle. Knowing the order and timing of these events and their components is crucial ...

  14. NEW INFORMATION ON LATE ORDOVICIAN AND EARLY SILURIAN RUGOSE CORALS IN NORTHERN GUIZHOU PROVINCE%黔北晚奥陶世和早志留世四射珊瑚新资料

    Institute of Scientific and Technical Information of China (English)

    何心一; 陈建强

    2003-01-01

    报道黔北早志留世中期(Middle Llandovery)地层中新发现的四射珊瑚7属--Cantrillia,Neocantrillia,Prototryplasma,Pycnostylus, Dalmanophyllum?,Rhegmaphyllum, Schlotheimophyllum,并描述产自黔东北石阡奥陶纪末期(Late Ashgill)观音桥层四射珊瑚2种--Grewingkia cf. bilateralis Neuman, Brachyelasma cf. medioseptatum(Neuman)及晚奥陶世(Early Ashgill期)涧草沟组中首次发现的四射珊瑚Crassilasma sp..全文共描述四射珊瑚13属18种,其中6新种,它们是 Crassilasma fenggangense sp. nov., C. crebrumseptatum sp. nov., Dinophyllum insolitum sp. nov., Neocantrillia silurica sp. nov., Prototryplasma guizhouense sp. nov., Schlotheimophyllum regeneranum sp. nov..%7 genera of rugose corals are reported from the middle Llandovery in northern Guizhou Province of China for the first time. They are Cantrillia,Neocantrillia,Prototryplasma,Pycnostylus,Dalmanophyllum?, Rhegmaphyllum and Schlotheimophyllum. In addition, two species(Grewingkia cf. bilateralis(Neuman) and Brachyelasma cf. medioseptatum(Neuman) ) collected from the late Ashgill Guanyinqiao Beds in the Shiqian County of northern Guizhou Province, and one species(Crassilasma sp.)from the early Ashgill Jiancaogou (Jiantsaohou) Formation in the same area are described. These data enrich further the content of the Late Ordovician and Early Silurian rugose coral fauna in Yangtze region, and are considerably significant for study on origin, evolution and disperse of some Early Paleozoic rugose corals. Altogether 18 species assigned to 13 genera are described. Among them 6 species are new. They are Crassilasma fenggangense sp. nov., C. crebrumseptatum sp. nov., Dinophyllum insolitum sp. nov., Neocantrillia silurica sp. nov., Prototryplasma guizhouense sp. nov., and Schlotheimophyllum regeneranum sp. nov.

  15. 塔里木盆地塔中地区奥陶系碳酸盐岩封盖性能%Sealing capacity of the Ordovician carbonate rocks in Tazhong area,the Tarim Basin

    Institute of Scientific and Technical Information of China (English)

    钱一雄; 何治亮; 陈强路; 李慧莉; 路清华; 蔡习尧; 尤东华

    2012-01-01

    利用5口区探井碳酸盐岩的矿物组成、微孔特征和测井资料等对塔里木盆地塔中地区奥陶系碳酸盐岩封盖性能进行了研究.结果表明,塔中奥陶系良里塔格组和鹰山组位于中成岩A-B亚段和晚成岩A亚段.良里塔格组中颗粒灰岩的突破压力为1.81 ~ 29.76 MPa,突破半径为13.89~77.35 nm,变化较大;泥灰岩的突破压力为14.33 MPa,突破半径为9.77 nm;含泥质条带泥晶灰岩的突破压力为3.15 ~5.41 MPa,突破半径为25.90~44.51 nm.鹰山组灰云岩的突破压力为0.98 ~ 10.35 MPa,突破半径为13.52~142.60 nm.因此,良里塔格组泥灰岩、部分颗粒灰岩及鹰山组云灰岩均有一定的封盖能力,其连续厚度大于5 m,突破压力大于5 MPa,突破半径介于10 ~ 20 nm,孔喉半径小于0.1 μm.塔中鹰山组内分布稳定、厚4~10m的高电阻含云灰岩构成的致密层段可作为局部封盖层,是中1井奥陶系鹰山组上油、下气油气分布的主要原因之一.%Mineral composition, micro-pore characteristics and well-logs from five wells were used to study the sealing capacity of the Ordovician carbonate rocks in Tazhong area,Tarim Basin. The Ordovician Lianglitage and Yingshan formations are at substage A-B of the middle diagenetic stage and substage A of the late diagenetic stage. For the Lianglitage Formation grainstone,the breakthrough pressure (BP) is 1. 81 -29. 76 Mpa,and the threshold radius (TR) is 13. 89 -77. 35 nm,. For the marlstones,the BP is 14. 33MPa and TR is 25. 9 -44. 51 nm. For the micritic limestone with band of argillite, the BP is 0. 98 - 10. 35 Mpa and the TR is 13. 52 - 142. 60 nm. The BP and the TR of the Yingshan Formation limy dolomites are 0. 98 - 10. 35 Mpa and 13. 52 - 142. 60 nm. Thus, the marlstone and partial grainstone of the Lianglitage Formation and the Yingshan Formation dolomite limestone have certain sealing capacity,with thickness over 5 m,BP over 5 Mpa,TR between 10-20 nm,pore throat radium

  16. Disentangling the record of diagenesis, local redox conditions, and global seawater chemistry during the latest Ordovician glaciation

    Science.gov (United States)

    Ahm, Anne-Sofie C.; Bjerrum, Christian J.; Hammarlund, Emma U.

    2017-02-01

    The Late Ordovician stratigraphic record integrates glacio-eustatic processes, water-column redox conditions and carbon cycle dynamics. This complex stratigraphic record, however, is dominated by deposits from epeiric seas that are susceptible to local physical and chemical processes decoupled from the open ocean. This study contributes a unique deep water basinal perspective to the Late Ordovician (Hirnantian) glacial record and the perturbations in seawater chemistry that may have contributed to the Hirnantian mass extinction event. We analyze recently drilled cores and outcrop samples from the upper Vinini Formation in central Nevada and report combined trace- and major element geochemistry, Fe speciation (FePy /FeHR and FeHR /FeT), and stable isotope chemostratigraphy (δ13COrg and δ34SPy). Measurements of paired samples from outcrop and core reveal that reactive Fe is preserved mainly as pyrite in core samples, while outcrop samples have been significantly altered as pyrite has been oxidized and remobilized by modern weathering processes. Fe speciation in the more pristine core samples indicates persistent deep water anoxia, at least locally through the Late Ordovician, in contrast to the prevailing interpretation of increased Hirnantian water column oxygenation in shallower environments. Deep water redox conditions were likely decoupled from shallower environments by a basinal shift in organic matter export driven by decreasing rates of organic matter degradation and decreasing shelf areas. The variable magnitude in the record of the Hirnantian carbon isotope excursion may be explained by this increased storage of isotopically light carbon in the deep ocean which, in combination with increased glacio-eustatic restriction, would strengthen lateral- and vertical gradients in seawater chemistry. We adopt multivariate statistical methods to deconstruct the spatial and temporal re-organization of seawater chemistry during the Hirnantian glaciation and attempt to

  17. Discovery of effective scale source rocks of the Ordovician Majiagou Fm in the Ordos Basin and its geological significance

    Directory of Open Access Journals (Sweden)

    Jianqi Tu

    2016-10-01

    Full Text Available There have been different views on the origins of gas reservoirs of Ordovician Majiagou Fm in the Ordos Basin, but none of them supports the opinion that there are scale source rocks (TOC>0.5% in the Majiagou Fm. In this paper, a series of analysis was made on cores and cutting samples taken from recent newly-drilled wells in the Ordovician reservoirs in the central–eastern areas of the Ordos Basin. Accordingly, the organic abundance features of different types of source rocks in the Majiagou Fm were presented, and for the first time, it was discovered and verified that there are effective scale source rocks with high organic abundance. Based on these analysis and studies, the following results were achieved. First, the effective source rocks of Majiagou Fm are composed of thin–thick layered dark dolomite-bearing mudstones, dolomitic mudstones and argillaceous dolomites, and their enrichment and distribution are obviously controlled by sedimentary facies. During the sedimentation of Majiagou Fm, the effective scale source rocks developed better at the regressive stage than at the transgressive stage. The effective source rocks are primarily distributed in the upper part of Ma 5 Member (especially concentrated in the third and fourth sub-members and secondly in Ma 3 Member, Ma 1 Member and the middle–lower part of Ma 5 Member. Second, the effective source rocks are areally distributed in a dual-girdle form around the Mizhi Salt Depression, and those in the secondary depressions are medium–thick layered, with a large total thickness and high organic abundance. Third, the effective source rocks in the center of Mizhi Depression and the secondary uplifts are thin-layered, with a small total thickness and low organic abundance. And fourth, the organic abundance of the effective source rocks varies from 0.30% to 8.45%. Phytoplankton and Acritarchs are the main parent materials of hydrocarbon, and organic matters are of sapropel or sapropel

  18. Middle Ear Infections

    Science.gov (United States)

    ... Listen Español Text Size Email Print Share Middle Ear Infections Page Content Article Body What are the ... illness. What if a child with a middle ear infection is in great pain and discomfort? The ...

  19. Ear Infection (Middle Ear)

    Science.gov (United States)

    Ear infection (middle ear) Overview By Mayo Clinic Staff An ear infection (acute otitis media) is most often a bacterial or viral infection that affects the middle ear, the air-filled space behind the eardrum that ...

  20. Sedimentological and diagenetic controls on Cambro-Ordovician reservoir quality in the southern Hassi Messaoud area (Saharan Platform, Algeria)

    Energy Technology Data Exchange (ETDEWEB)

    Djarnia, M.R.; Fekirine, B. [CRD-Sonatrach, Boumerdes (Algeria)

    1998-12-31

    The Cambro-Ordovician reservoirs of the Hassi-Messaoud area comprise quartzitic sandstones, which rest unconformably on granitic basement and are capped by the Hercynian unconformity. Two sequence stratigraphic cycles are identified: a lower cycle of lowstand, transgressive and highstand deposits, and an upper cycle in which only lowstand deposits are preserved below the Hercynian unconformity. Petrographic and scanning electron microscope studies were conducted in two wells in the southern Hassi Messaoud area on five sandstone units. Reservoir quality is found to bear a strong relationship to clay content and mineralogy. Comparative diagenetic studies carried out within both the oil-bearing and the water-bearing parts of the reservoirs have determined that all the secondary processes occurred under freely operating diagenesis, pre-dating oil emplacement in the structure. (author)

  1. Ordovician magmatism in the Lévézou massif (French Massif Central): tectonic and geodynamic implications

    Science.gov (United States)

    Lotout, Caroline; Pitra, Pavel; Poujol, Marc; Van Den Driessche, Jean

    2017-03-01

    New U-Pb dating on zircon yielded ca. 470 Ma ages for the granitoids from the Lévézou massif in the southern French Massif Central. These new ages do not support the previous interpretation of these granitoids as syn-tectonic intrusions emplaced during the Late Devonian-Early Carboniferous thrusting. The geochemical and isotopic nature of this magmatism is linked to a major magmatic Ordovician event recorded throughout the European Variscan belt and related to extreme thinning of continental margins during a rifting event or a back-arc extension. The comparable isotopic signatures of these granitoids on each side of the eclogite-bearing leptyno-amphibolitic complex in the Lévézou massif, together with the fact that they were emplaced at the same time, strongly suggest that these granitoids were originally part of a single unit, tectonically duplicated by either isoclinal folding or thrusting during the Variscan tectonics.

  2. Early Paleozoic (Late Cambrian-Early Ordovician) acritarchs from the metasedimentary Baden-Baden-Gaggenau zone (Schwarzwald, SW Germany).

    Science.gov (United States)

    Montenari, M; Servais, T

    2000-12-01

    The metasediments of the low-grade metamorphosed Baden-Baden-Gaggenau zone of the northern Schwarzwald (southwestern Germany) have been analyzed palynologically. From 133 samples representing different metasedimentary units, only three samples of the upper part of the Traischbach Serie provide extremely poorly-preserved palynomorphs. The assemblage consists of the galeate acritarch genera Caldariola, Cymatiogaleaand Stelliferidium, as well as specimens of diacromorph and polygonomorph acritarchs. Although determinations are difficult at the generic level and essentially impossible at the specific level, the assemblage can be attributed to an interval between the Late Cambrian and Early Ordovician. This is the first biostratigraphical age assignment for the metasediments of the Baden-Baden-Gaggenau zone, which can possibly be correlated with the Villé Unit of the northern Vosges Mountains (eastern France).

  3. The eoorthid brachiopod Apheoorthina in the Lower Ordovician of NW Argentina and the dispersal pathways along western Gondwana

    Directory of Open Access Journals (Sweden)

    Diego F. Muñoz

    2016-08-01

    Full Text Available The eoorthid brachiopod Apheoorthina is reported for the first time from the Lower Ordovician of NW Argentina. It is represented by a species similar to A. ferrigena from the Tremadocian of the Prague Basin, increasing the faunal affinities between the Central Andean Basin and the South European microcontinents, in particular the Bohemian region (Perunica. Nine out of the fourteen brachiopod genera reported from the Tremadocian of the Central Andean Basin (~64% are shared with the Mediterranean region, four of which (~28% have been recorded in the Prague Basin, and two (Kvania and Apheoorthina are restricted to the Central Andes and Perunica. Dispersal pathways around Gondwana are analyzed in the light of major factors affecting large-scale distribution of brachiopods (environment, larval capacity for dispersal, oceanic currents. The presence in Apheoorthina aff. ferrigena of a well-preserved larval protegulum measuring 420 μm in width and 210 μm in length strongly suggests that this species had planktotrophic larvae capable of long-distance dispersal. According to recent ocean-atmosphere general circulation models for the Ordovician Period, the Central Andean margin was dominated by the cold-water Antarctica Current. Despite the complex non-zonal pattern produced by current deflections around the peri-Gondwanan microcontinents, the general westward circulation sense favoured larval dispersal from the Andean region to North Africa, Avalonia, the Armorican Terrane Assemblage, and Perunica. On the other hand, the eastwards flowing Gondwana Current connected the North Gondwana waters with the South American epicontinental seas, which could explain the reversed migration of some brachiopods.

  4. 中国新疆北部奥陶—志留系岩石组合的古构造、古地理意义%Significance of Paleostructure and Paleogeography of Ordovician-Silurian Rock Associations in Northern Xinjiang,China

    Institute of Scientific and Technical Information of China (English)

    何国琦; 李茂松

    2001-01-01

    Traditional tectonic ideas are that the orogenic belts in the northern Xinjiang were formed mainly in the late Paleozoic.However,new data show that there is almost continuous early Paleozoic orogenic belt surrounding the Junggar Basin.The facts will change the traditional idea which only emphasizes the late Paleozoic orogenesis.According to the new data,authors reconstructed the early Paleozoic geologic evolution of the Northern Xinjiang.The Junggar and adjacent old lands began to breakup in the Sinian period.The ancient ocean between those old lands came up to the biggest size at early Ordovician.The inferential Junggar old land often situated below sea level in the period of cracking and spreading of the old land.The ancient ocean of the Northern Xinjiang began to shrink and the old continental margin became active margin in the late Ordovician.Then,convergence,collision and orogenesis were took place among the Junggar,Yili and Siberia old lands.The late Ordovician and early-middle Silurian forearc or back-arc foreland basins might develop on the side of earn Junggar old land of the early Paleozoic orogenic belts.%近年的研究结果表明,在准噶尔盆地周边地区存在有几乎连续分布的早古生代造山带,这个事实有可能改变历来只强调北疆晚古生代造山作用的传统认识。震旦纪是准噶尔及其相邻古陆裂解的开始阶段,经寒武纪至早奥陶世,古洋已发展到最大规模。在区域性古陆裂解和伸展的背景下,推测准噶尔古陆经常位于海平面以下。晚奥陶世北疆的古洋开始收缩,古陆缘区转化成活动陆缘,准噶尔古陆先后与伊犁古陆和西伯利亚古陆汇聚和碰撞造山,在这两条早古生代造山带的近准噶尔古陆一侧,可能发育晚奥陶世至早、中志留世的弧前或弧后盆地和前陆拗陷。

  5. Inferred paleotectonic settings and paleogeography at 500-450 Ma based on geochemical evaluation of Ordovician volcanics and gabbros of the Upper Allochthon, Mid Norway

    Science.gov (United States)

    Hollocher, K.; Roberts, D.; Robinson, P.; Walsh, E.

    2012-04-01

    Evaluation of major- and trace-element analyses of Ordovician volcanics and gabbros from the Støren Nappe of the Upper Allochthon, Mid Norway, including 87 new analyses, covers the Late Cambrian-earliest Ordovician ophiolite complexes and overlying Ordovician volcanics. The older rocks have mainly MORB-like compositions likely formed in a back-arc basin, plus less abundant oceanic-arc basalts and andesites. Compositions characteristic of fore-arc environments are absent. The Upper Allochthon has three elements: A) The Gula Nappe of probable Cambrian and Tremadocian, epicontinental sedimentary rocks, B) The Støren and Meråker nappes with their basal suprasubduction-zone ophiolitic volcanics and intrusions plus younger Ordovician successions, C) In northwestern parts of the Støren Nappe, a complex of predominantly calc-alkaline arc intrusive rocks 482 to 441 Ma. The structural and stratigraphic history indicates obduction of ophiolites occurred at 480-475 Ma soon after formation, followed by uplift, erosion, and deposition of conglomerates incorporating ophiolite debris. The overlying sequence includes shelly Toquima-Table Head faunas of Laurentian affinity and younger strata into Upper Ordovician. Field relations suggest that the ophiolites were obducted onto rocks of the Gula Complex. A Tremadocian, graptolite-bearing black shale/phyllite in the eastern part of the Gula has close geochemical affinities with the reducing V- and U-enriched Alum shale of the Baltoscandian margin, black shales in the lower Köli nappes of the Upper Allochthon in Sweden, and similar shales in the Gander and Avalon zones of Maritime Canada. Such shales originated in high-latitude (40-50° south) cool-water environments, as existed in Late Cambrian-earliest Ordovician Baltica, Avalonia, and Ganderia, and have not been recorded in equatorial paleolatitudes, such as the earliest Ordovician margin of Laurentia. Our paleotectonic account for these features is in three time slices: 1) A

  6. Tectonic and eustatic control on the distribution of black-shale source beds in the Wufeng and Longmaxi formations (Ordovician-Silurian),South China

    Institute of Scientific and Technical Information of China (English)

    SU Wenbo; ZHAO Huijing; LI Zhiming; Ettensohn F.R.; Johnson M.E.; Huff W.D.; WANG Wei; MA Chao; LI Lu; ZHANG Lei

    2007-01-01

    It is known that high-quality,black-shale source rocks occur in the uppermost Ordovician Wufeng Formation and in the lowermost Silurian Longmaxi Formation in South China.Hence,it is important to understand their lithostratigraphy and the controls on their deposition.A review of lithostratigraphic criteria for subdividing the two adjacent formations provides new regional correlations between the formations and related stratigraphic successions and facies.Both the black shales and the related,overlying flysch deposits at the Ordovician-Silurian transition in South China appear to have migrated northwestward in time and space,reflecting probable flexural control in a foreland basin that developed in response to subduction-type orogeny southeast of the Yangtze block.The black shales also contain K-bentonites from explosive,felsic-intermediate volcanism,the distribution of which also supports orogeny to the southeast.Finally,the analysis of sequence stratigraphy,which shows that the initiation of transgressive system tracts (TST) and condensed section (CS) in the related third-order sequences coincided with the two black-shale horizons respectively,indicates that the main controlling factors for the deposition of the Ordovician-Silurian black shales in South China are (1)northwestwardly migrating,foreland-basin subsidence caused by deformational loading related to episodic accretion of the Cathaysia block to the Yangtze block during this period,and (2) the anoxic,sediment-starved water column caused by rapid rise of the sea-level during the two successive phases of third-order global sea-level rise near the Ordovician-Silurian transition in South China.In future exploration for hydrocarbon source rocks in the area,it is important to consider likely flexural and eustatic causes for subsiding,deep,anoxic seas in recognizing other source rock intervals,and our understanding of the Wufeng and Longmaxi formations may serve as models for future source rock exploration.

  7. The effects of the final stages of the Late Ordovician glaciation on marine palynomorphs (chitinozoans, acritarchs, leiospheres) in well Nl-2 (NE Algerian Sahara).

    Science.gov (United States)

    Paris, F; Bourahrouh, A; Hérissé, A L.

    2000-12-01

    Palynomorph assemblages, especially chitinozoans and acritarchs, from the Upper Ordovician of well Nl-2 (north-east of the Algerian Sahara) are studied in order to precisely date the ultimate effects of the Late Ordovician glaciation and to document the impact of this major climatic stress on the diversity of the palynoplankton. References are made to stable isotope excursions and to global eustatic sea level variations in order to improve the local age determination. The Hassi el Hadjar Formation, i.e. glacio-marine diamictites, is interpreted as a transgressive event resulting from the melting of the northern Gondwana ice cap. It yields poorly preserved and moderately diverse chitinozoans of late Hirnantian age. Acritarchs are more abundant in the lower part of these "microconglomeratic clays", but display a low diversity and are badly preserved throughout the whole formation. Reworked individuals are recorded in both groups. The marine sediments of the M'Kratta Formation of latest Hirnantian age contain better preserved, more abundant and more diverse palynomorph assemblages, especially in the Upper Member. The composition of this palynoplankton indicates a fairly good faunal and phytoplankton recovery after the early Hirnantian climatic stress.The extinction of the Ordovician forms, and the appearance of Silurian type taxa occur only in the uppermost Hirnantian, i.e. following with a slight delay the glacial event. The overlying black shales of Wenlock age (lower part of the Oued Mehaiguène Formation) are indicative of marine anoxic environments. They yield a virtually exclusive, but enormous number of Tasmanacea. The very peculiar composition of this palynoplankton seems to be independent of the Late Ordovician glaciation and is most likely related to the factors that, later, generated and maintained anoxic conditions in this area.A new species of chitinozoan, Spinachitina oulebsiri sp. nov. from the latest Hirnantian M'Kratta Formation, is described and

  8. Beijing Tibet Middle School

    Institute of Scientific and Technical Information of China (English)

    2005-01-01

    The year marks the 20th anniversary of the Central Government decision to run Tibet middle schools in the hinterland. At present, there are such schools or Tibetan classes in 26 provinces and municipalities directly under the Central Government. They work to train technical personnel and teachers for Tibet. Launched in 1987, the Beijing Tibet Middle School has since trained more than 2,800 middle and high school students for Tibet. Many of them returned to Tibet for construction.

  9. Fostering a Middle Class

    Institute of Scientific and Technical Information of China (English)

    YAO BIN

    2011-01-01

    Though there is no official definition of "middle class" in China,the tag has become one few Chinese people believe they deserve anyway.In early August,the Chinese Academy of Social Sciences released a report on China's urban development,saying China had a middle-class population of 230 million in 2009,or 37 percent of its urban residents.It also forecast half of city dwellers in China would be part of the middle class by 2023.

  10. The characteristics and sources of natural gases from Ordovician weath-ered crust reservoirs in the Central Gas Field in the Ordos Basin

    Institute of Scientific and Technical Information of China (English)

    LI Xianqing; HU Guoyi; LI Jian; HOU Dujie; DONG Peng; SONG Zhihong; YANG Yunfeng

    2008-01-01

    The Central Gas Field is a famous large-sized gas field in the Ordos Basin of China. However, identification of main gas sources of the Ordovician reservoirs in this gas field remains puzzling. On the basis of a lot of geochemical data and geological research on natural gases, the characteristics and sources of natural gases from Ordovician weathered crust reservoirs in the Central Gas Field in the Ordos Basin were studied. The results indicated that natural gases from Ordovician weathered crust reservoirs in the Central Gas Field in the Ordos Basin have similar chemical and isotopic com-positions to highly mature and over-mature dry gases. Both coal-derived gases and oil-type gases coexist in the Central Gas Field in the Ordos Basin. The former was derived mainly from Carboniferous-Permian coal measures and the latter from Lower Paleozoic marine carbonates. It is suggested that coal-derived gases occur in the eastern part of the Central Gas Field while oil-type gases may be pro-duced mainly in the northern, western and southern parts of the Central Gas Field in the Ordos Basin.

  11. Distribution of the Ordovician Fluid in the Tahe Oilfield and Dynamic Response of Cave System $48 to Exploitation

    Institute of Scientific and Technical Information of China (English)

    LOU Zhanghua; ZHU Rong; YUN Lu; RAN Qihua; SU Danyang; LI Mei

    2008-01-01

    The Tahe Oilfield is a complex petroleum reservoir of Ordovician carbonate formation and made up of spatially overlapping fracture-cavity units. The oilfield is controlled by a cave system resulting from structure-karst cyclic sedimentation. Due to significant heterogeneity of the reservoir, the distribution of oil and water is complicated. Horizontally, a fresh water zone due to meteoric water can be found in the north part of the Akekule uplift. A marginal freshening zone caused by water released from mudstone compaction is found at the bottom of the southern slope. Located in a cross- formationai flow discharge zone caused by centripetal and the centrifugal fows, the main part of the Tahe Oilfield, featuring high salinity and concentrations of CI- and K++Na+, is favorable for accumulation of hydrocarbon. Three types of formation water in the Tahe Ordovician reservoir are identified: (1) residual water at the bottom of the cave after oil and gas displacement, (2) residual water in fractures/pores around the cave after oil and gas displacement, and (3) interlayer water below reservoirs. The cave system is the main reservoir space, which consists of the main cave, branch caves and depressions between caves. Taking Cave System $48 in the Ordovician reservoir as an example, the paper analyzes the fluid distribution and exploitation performance in the cave system. Owing to evaporation of groundwater during cross-formational flow, the central part of the main cave, where oil layers are thick and there is a high degree of displacement, is characterized by high salinity and Brconcentration. With high potential and a long stable production period, most wells in the central part of the main cave have a long water-free oil production period. Even after water breakthrough, the water content has a slow or stepwise increase and the hydrochemistral characteristics of the produced water in the central part of the main cave are uniform. From the center to the edge of the main

  12. SHRIMP U-Pb dating and Hf isotopic analyses of Middle Ordovician meta-cumulate gabbro in central Qiangtang, northern Tibetan Plateau

    Institute of Scientific and Technical Information of China (English)

    2010-01-01

    Metabasites consisting of metamorphic ultra-mafic rocks, cumulate gabbro, gabbro (diabase), basalt, and plagiogranite are exposed at the Taoxinghu area in central Qiangtang, northern Tibetan Plateau. Zircon SHRIMP U-Pb dating for the cumulate gabbro yields a weighted mean age of 467±4 Ma, which is the oldest and most reliable magmatic age in this area. Zircon 176Hf/177Hf ratios range from 0.282615 to 0.282657, with εHf(t) values of 5.02±0.28, indicating that the cumulate gabbro was mainly derived from the depleted mantle. In addition, geochemical data of metabasites suggest that they have similar characteristics to those in the mid-ocean ridge basalts (MORB). The Taoxinghu metabasites may represent the fragment of Early Paleozoic ophiolite in the "Central Uplift" of the Qiangtang, northern Tibetan Plateau.

  13. U-Pb Zircon geochronology of the Cambro-Ordovician metagranites and metavolcanic rocks of central and NW Iberia

    Science.gov (United States)

    Talavera, C.; Montero, P.; Bea, F.; González Lodeiro, F.; Whitehouse, M.

    2013-01-01

    New U-Pb zircon data from metagranites and metavolcanic rocks of the Schist-Graywacke Complex Domain and the Schistose Domain of Galicia Tras-os-Montes Zone from central and NW Iberia contribute to constrain the timing of the Cambro-Ordovician magmatism from Central Iberian and Galicia Tras-os-Montes Zones which occurred between 498 and 462 Ma. The crystallization ages of the metagranites and metavolcanic rocks from the northern Schist-Graywacke Complex Domain are as follows: (a) in west Salamanca, 489 ± 5 Ma for Vitigudino, 486 ± 6 Ma for Fermoselle and 471 ± 7 Ma for Ledesma; (b) in northern Gredos, 498 ± 4 Ma for Castellanos, 492 ± 4 Ma for San Pelayo and 488 ± 3 Ma for Bercimuelle; (c) in Guadarrama, 490 ± 5 Ma for La Estación I, 489 ± 9 Ma for La Cañada, 484 ± 6 Ma for Vegas de Matute (leucocratic), 483 ± 6 Ma for El Cardoso, 482 ± 8 Ma for La Morcuera, 481 ± 9 Ma for Buitrago de Lozoya, 478 ± 7 Ma for La Hoya, 476 ± 5 Ma for Vegas de Matute (melanocratic), 475 ± 5 Ma for Riaza, 473 ± 8 Ma for La Estación II and 462 ± 11 Ma for La Berzosa; and (d) in Toledo, 489 ± 7 Ma for Mohares and 480 ± 8 Ma for Polán. The crystallization ages of the metagranites from the Schistose Domain of Galicia Tras-os-Montes Zone are 497 ± 6 Ma for Laxe, 486 ± 8 Ma for San Mamede, 482 ± 7 Ma for Bangueses, 481 ± 5 Ma for Noia, 480 ± 10 for Rial de Sabucedo, 476 ± 9 Ma for Vilanova, 475 ± 6 Ma for Pontevedra, 470 ± 6 Ma for Cherpa and 462 ± 8 Ma for Bande. This magmatism is characterized by an average isotopic composition of (87Sr/86Sr)485Ma ≈ 0.712, (ɛNd)485Ma ≈ -4.1 and (TDM) ≈ 1.62 Ga, and a high zircon inheritance, composed of Ediacaran-Early Cambrian (65 %) and, to a lesser extent, Cryogenian, Tonian, Mesoproterozoic, Orosirian and Archean pre-magmatic cores. Combining our geochronological and isotopic data with others of similar rocks from the European Variscan Belt, it may be deduced that Cambro-Ordovician magmas from this belt were mainly

  14. The Middle East.

    Science.gov (United States)

    Blouin, Virginia; And Others

    This sixth grade resource unit focuses on Middle East culture as seen through five areas of the social sciences: anthropology-sociology, geography, history, economics, and political science. Among objectives that the student is expected to achieve are the following: 1) given general information on the Middle East through the use of film, visuals,…

  15. Middle East Respiratory Syndrome

    Centers for Disease Control (CDC) Podcasts

    2014-07-07

    This podcast discusses Middle East Respiratory Syndrome, or MERS, a viral respiratory illness caused by Middle East Respiratory Syndrome Coronavirus—MERS-CoV.  Created: 7/7/2014 by National Center for Immunization and Respiratory Diseases (NCIRD).   Date Released: 7/7/2014.

  16. DEFINING THE MIDDLE CLASS

    Institute of Scientific and Technical Information of China (English)

    2011-01-01

    Classifying the middle class remains controversial despite its alleged growth China’s cities housed more than 230 million middle-class residents in 2009 or 37 percent of the urban population,according to the 2011 Blue Book of Cities in China released on August 3.

  17. DEFINING THE MIDDLE CLASS

    Institute of Scientific and Technical Information of China (English)

    WANG HAIRONG

    2011-01-01

    China's cities housed more than 230 million middle-class residents in 2009ot 37 percent of the urban population,according to the 2011 Blue Book of Cities in China released on August 3.In China's main urban centers,Beijing and Shanghai,the middle class accounted for 46 percent and 38 percent,respectively,of the local population.

  18. Cosmic-ray exposure ages of fossil micrometeorites from mid-Ordovician sediments at Lynna River, Russia

    CERN Document Server

    Meier, Matthias M M; Lindskog, Anders; Maden, Colin; Wieler, Rainer

    2014-01-01

    We measured the He and Ne concentrations of 50 individual extraterrestrial chromite grains recovered from mid-Ordovician (lower Darriwilian) sediments from the Lynna River section near St. Petersburg, Russia. High concentrations of solar wind-like He and Ne found in most grains indicate that they were delivered to Earth as micrometeoritic dust, while their abundance, stratigraphic position and major element composition indicate an origin related to the L chondrite parent body (LCPB) break-up event, 470 Ma ago. Compared to sediment-dispersed extraterrestrial chromite (SEC) grains extracted from coeval sediments at other localities, the grains from Lynna River are both highly concentrated and well preserved. As in previous work, in most grains from Lynna River, high concentrations of solar wind-derived He and Ne impede a clear quantification of cosmic-ray produced He and Ne. However, we have found several SEC grains poor in solar wind Ne, showing a resolvable contribution of cosmogenic 21Ne. This makes it possi...

  19. Isotopic evidence for glacial meltwater recharge to the Cambrian-Ordovician aquifer, north-central United States

    Science.gov (United States)

    Siegel, D.I.; Mandle, R.J.

    1984-01-01

    The chemistry of water in the Cambrian-Ordovician aquifer in six midwestern states has been studied as part of the Northern Midwest Regional Aquifer-System Analysis of the U.S. Geological Survey. Dissolved-solids concentrations generally increase perpendicular to the direction of regional groundwater flow, from less than 400 mg/liter in southeast Minnesota, southwest Wisconsin, and northeast Iowa to more than 10,000 mg/liter in northwest Missouri. Isotopic ratios of hydrogen and oxygen are significantly depleted from north to south, with an areal distribution approximately parallel to the distribution of dissolved solids. For example, ??18O in southern Iowa and northern Missouri is about 6 parts per thousand lighter than ??18O of modern recharge water in Minnesota and Wisconsin. Covariance between ??18O and ??D of the groundwater, similar to that of modern precipitation, suggests that the differences in isotopic ratios between groundwater and modern recharge water reflect meteoric signatures of water during past recharge events rather than geochemical processes such as isotopic exchange with aquifer materials. The pronounced parallelism between the distribution of isotopes and dissolved solids over large areas probably reflects largescale recharge of Pleistocene glacial meltwater into the aquifer system, which probably had a paleoflow system with a gradient from northeast to southwest rather than from northwest to southeast. ?? 1984.

  20. Tectonic evolution of Tarim basin in Cambrian–Ordovician and its implication for reservoir development, NW China

    Indian Academy of Sciences (India)

    Yu Bingsong; Ruan Zhuang; Zhang Cong; Pan Yinglu; Lin Changsong; Wang Lidong

    2016-03-01

    In order to find the impact of regional tectonic evolution of Tarim basin on the inside distribution of sedimentary facies and reservoir development, this paper, based on the research of plate-tectonic evolution of Tarim basin, conducts an in-depth analysis on the basin’s inside sedimentary response to the Eopaleozoicregional geodynamic reversion from extension to convergence around Tarim plate, and concludes that the regional geodynamic environment of surrounding areas closely contributes to the formation and evolution of paleo-uplifts, differentiation of sedimentary facies in platform, distribution of high-energyreef and bank facies belts, conversion of sedimentary base level from fall to rise, obvious change of lithology from dolomite to limestone, and formation of several unconformity surfaces in Ordovician system in the basin. A series of sedimentary responses in the basin are controlled by regional dynamic setting, which not only controls the distribution of reservoirs in reef and bank facies but also restricts the development and distribution of karst reservoirs controlled by the unconformity surfaces. This offers the macro geological evidences for us to further analyze and evaluate the distribution of favorable reservoirs.

  1. Burial Dissolution of Ordovician Granule Limestone in the Tahe Oilfield of the Tarim Basin, NW China, and Its Geological Significance

    Institute of Scientific and Technical Information of China (English)

    LIU Chunyan; LIN Changsong; WANG Yi; WU Maobing

    2008-01-01

    With a comprehensive study on the petrology, geology and geochemistry of some Ordovician granule limestone samples in the Tahe Oilfieid of the Tarim Basin, two stages of burial dissolution were put forward as an in-source dissolution and out-source dissolution based on macro-microcosmic petrology and geochemistry features. The main differences in the two stages arc in the origin and moving pass of acid fluids. Geochemical evidence indicates that burial dissolution fluids might be ingredients of organic acids, CO2 and H2S associated with organic matter maturation and hydrocarbon decomposition, and the in-source fuid came from organic matter in the granule limestone itself, but the out-source was mainly from other argillaceous carbonate rocks far away. So, the forming of a burial dissolution reservoir resulted from both in-source and the out-source dissolutions. The granule limestone firstly formed unattached pinholes under in-source dissolution in situ, and afterwards suffered wider dissolution with out-source fluids moving along unconformities, seams, faults and associate fissures. The second stage was much more important, and the mineral composition in the stratum and heat convection of the fluid were also important in forming favorable reservoirs.

  2. An Evaluation of the Carbon Sequestration Potential of the Cambro-Ordovician Strata of the Illinois and Michigan Basins

    Energy Technology Data Exchange (ETDEWEB)

    Kirksey, Jim; Ansari, Sajjad; Malkewicz, Nick; Leetaru, Hannes

    2014-01-01

    The Knox Supergroup is a significant part of the Cambrian-Ordovician age sedimentary deposition in the Illinois Basin. While there is a very small amount of oil production associated with the upper Knox, it is more commonly used as a zone for both Class I and Class II disposal wells in certain areas around the state. Based on the three penetrations of the Knox Formation at the Illinois Basin – Decatur Project (IBDP) carbon dioxide (CO2) sequestration site in Macon County, Illinois, there is potential for certain zones in the Knox to be used for CO2 sequestration. More specifically, the Potosi member of the Knox Formation at about –3,670 feet (ft) subsea depth would be a candidate as all three penetrations had massive circulation losses while drilling through this interval. Each well required the setting of cement plugs to regain wellbore stability so that the intermediate casing could be set and successfully cemented to surface. Log and core analysis suggests significant karst porosity throughout the Potosi member. The purpose of this study is to develop a well plan for the drilling of a CO2 injection well with the capability to inject 3.5 million tons per annum (3.2 million tonnes per annum [MTPA] CO2 into the Knox Formation over a period of 30 years.

  3. Reinterpretation of the Ordovician rotations in NW Argentina and Northern Chile: a consequence of the Precordillera collision?

    Science.gov (United States)

    Spagnuolo, Cecilia M.; Rapalini, Augusto E.; Astini, Ricardo A.

    2011-04-01

    Early Paleozoic paleomagnetic data from NW Argentina and Northern Chile have shown large systematic rotations within two domains: one composed of the Western Puna that yields very large (up to 80°) counter-clockwise rotations, and the other formed by the Famatina Ranges and the Eastern Puna that shows (~40°) clockwise rotations around vertical axes. In several locations, lack of significant rotations in younger rocks constrains this kinematic pattern to have occurred during the Paleozoic. Previous tectonic models have explained these rotations as indicative of rigid-body rotations of large para-autochthonous crustal blocks or terranes. A different but simple tectonic model that accounts for this pattern is presented in which rotations are associated to crustal shortening and tectonic escape due to the collision of the allochthonous terrane of Precordillera in the Late Ordovician. This collision should have generated dextral shear zones in the back arc region of the convergent SW Gondwana margin, where systematic domino-like clockwise rotations of small crustal blocks accommodate crustal shortening. The Western Puna block, bordering the Precordillera terrane to the north, might have rotated counterclockwise as an independent microplate due to tectonic escape processes, in a fashion similar to the present-day relationship between the Anatolia block and the Arabian microplate.

  4. Tectonic evolution of Tarim basin in Cambrian-Ordovician and its implication for reservoir development, NW China

    Science.gov (United States)

    Bingsong, Yu; Zhuang, Ruan; Cong, Zhang; Yinglu, Pan; Changsong, Lin; Lidong, Wang

    2016-03-01

    In order to find the impact of regional tectonic evolution of Tarim basin on the inside distribution of sedimentary facies and reservoir development, this paper, based on the research of plate-tectonic evolution of Tarim basin, conducts an in-depth analysis on the basin's inside sedimentary response to the Eopaleozoic regional geodynamic reversion from extension to convergence around Tarim plate, and concludes that the regional geodynamic environment of surrounding areas closely contributes to the formation and evolution of paleo-uplifts, differentiation of sedimentary facies in platform, distribution of high-energy reef and bank facies belts, conversion of sedimentary base level from fall to rise, obvious change of lithology from dolomite to limestone, and formation of several unconformity surfaces in Ordovician system in the basin. A series of sedimentary responses in the basin are controlled by regional dynamic setting, which not only controls the distribution of reservoirs in reef and bank facies but also restricts the development and distribution of karst reservoirs controlled by the unconformity surfaces. This offers the macro geological evidences for us to further analyze and evaluate the distribution of favorable reservoirs.

  5. Fracture system influence on the reservoirs rock formation of Ordovician-Devonian carbonates in West Siberia tectonic depression

    Science.gov (United States)

    Koveshnikov, A. E.; Nesterova, A. C.; Dolgaya, T. F.

    2016-09-01

    During the Paleozoic period from the beginning of the Cambrian to the end of the Carboniferous in the boundaries of the West Siberia tectonic depression there occurred the sea, where the carbonate platforms were formed by the limestones accumulation. All the area at the end of the Carboniferous period was turned to land. Resulting from Gertsynskaya folding in the times of Permian - Triassic the formed deposits were folded and denudated to a considerable extent. Besides, the reservoir rocks of the crust of weathering including redeposited one, were formed as a result of hypergenesis, during the continental stand of the area in the near-surface zone. A new geological prospecting unit has been suggested which underlies these crusts of weathering and formed during fracture tectonic processes with hydrothermal-metasomatic limestones reworking and the processes of hydrothermal leaching and dolomitization. So, in the carbonate platforms the system of fissure zones related to tectonic disturbance was formed. This has a dendrite profile where the series of tangential, more thinned fractures deviate from the stem and finish in pores and caverns. The carbonate platforms formation in the West Siberia tectonic depression has been analyzed, their dynamics and gradual increasing from the minimal in Ordovician and Silurian to maximal at the end of the Late Devonian has been shown.

  6. Palaeogeography and palaeoecology of early Floian (Early Ordovician cephalopods from the Upper Fezouata Formation, Anti-Atlas, Morocco

    Directory of Open Access Journals (Sweden)

    B. Kröger

    2012-08-01

    Full Text Available In the central Anti-Atlas (Morocco, the Early Ordovician succession consists of about 1000 m of fossiliferous argillites and siltstones. The Upper Fezouata Formation (Floian contains a comparatively rich and abundant cephalopod association. A small collection of these cephalopods is described herein for the first time. The cephalopods are interpreted as autochthonous or parautochthonous, representing a fauna, which originally lived nektobenthically in the open water above the sediments or related to the sea bottom. The cephalopod associations of the Upper Fezouata Formation are similar to other contemporaneous assemblages known from higher palaeolatitudes and associated with deeper depositional settings and in siliciclastically dominated deposits. They are composed almost exclusively of slender orthocones, in this case predominantly of Destombesiceras zagorense n. gen., n. sp., which is interpreted as an early discosorid. Bathmoceras australe Teichert, 1939 and Bathmoceras taichoutense n. sp. from the Upper Fezouata Formation are at present the earliest unambiguous occurrences of bathmocerid cephalopods. Epizoans on the shell of a specimen of Rioceras are the earliest evidence of bryozoans growing as potential hitchhikers on cephalopod shells, indicating an early exploitation of a pseudoplanktonic lifestyle in this phylum. doi:10.1002/mmng.201200004

  7. On middle cube graphs

    Directory of Open Access Journals (Sweden)

    C. Dalfo

    2015-10-01

    Full Text Available We study a family of graphs related to the $n$-cube. The middle cube graph of parameter k is the subgraph of $Q_{2k-1}$ induced by the set of vertices whose binary representation has either $k-1$ or $k$ number of ones. The middle cube graphs can be obtained from the well-known odd graphs by doubling their vertex set. Here we study some of the properties of the middle cube graphs in the light of the theory of distance-regular graphs. In particular, we completely determine their spectra (eigenvalues and their multiplicities, and associated eigenvectors.

  8. Middle Helladic Period

    DEFF Research Database (Denmark)

    Sarri, Kalliopi

    1999-01-01

    The Middle Bronze Age on Mainland Greece is also known as the Middle Helladic period. The chronological framework of this period extends from the beginnings of the second millenium - roughly 1900 - until 1550 BC, that is until the beginnings of the Mycenaean period. The Middle Helladic period...... is considered as the dark period of the cultural decline. The remains of the material culture reveal a clear retrogression while the information available on the social stratification and economy are so few and problematic in interpretation that this period is considered as the "Middle Age of Greek Prehistory......". About 1900 BC, the period during which the first palaces of Crete were being built, Mainland Greece was entering a long period of decline during which economic features changed radically. A large number of metals and imported products became particularly rare while composite forms of economic...

  9. 鄂尔多斯盆地苏里格地区奥陶系马家沟组白云石化%Dolomitization of Ordovician Majiagou Formation in Sulige region, Ordos Basin

    Institute of Scientific and Technical Information of China (English)

    付金华; 王宝清; 孙六一; 包洪平; 徐波

    2011-01-01

    The Ordovician Majiagou Formation in Sulige region of the Ordos Basin was deposited in hypersaline restricted epicontinental environment. It is mainly composed of carbonate rocks with thin evaporate interbeds. The dolomites are classified into 3 kinds; micrite, fine-medium crystal dolomite, and dolomite filled in pores and fractures. The Na concentrations range from 0 to 2 099 X 10-6, the Sr concentrations range from 0 to 70 X 10-6,the Mn concentrations range from 0 to 112 X 10-6, and the Fe concentrations range from 39 to 86 746 X 10-6 in dolomites. The dolomites are characterized with varied Na, low Sr and Mn, and high Fe concentrations. The 18O values for dolomites range from -16. 00%0 to -5. 73%o, and the 13C values range from -11. 46%0 to 1. 90%. (PDB). It indicates that carbonate rocks have experienced leaching and burial diagenesis. Most filled dolomites have lower 18O and 13C values than surrounding components, indicating that the former was formed later. The dolomites are characterized with low degrees of order and less stoichiometry. The 87Sr/86 Sr values of dolomites range from 0. 707 977±0. 000 070 to 0. 711 791±0. 000 064, most of which are higher than that corresponding to global boundary between middle and upper Ordovician. Microbial dolomitization is the reason for dolomite genesis.%苏里格地区马家沟组为一套碳酸盐岩为主,夹蒸发岩的地层,沉积于超盐度的局限陆表海环境.白云石分为以泥晶结构为主的,以细—中晶结构为主和充填于孔、缝中3类.白云石Na含量(0~2 099)×10-6,Sr含量(0~70)×10-5,Mn含量(0~112)×10-6,Fe含量(39~86 746)×10-6,以变化较大的Na含量、低的Sr和Mn含量,高的Fe含量为特征.白云石δ18()值在-16.00‰~-5.73‰之间,δ13C值在-11.46‰~1.90‰之间,说明碳酸盐岩经历了淋滤作用和埋藏作用.大多数孔、缝充填白云石较围岩组分有较低的δ18O和δ13C值,说明孔缝充填的白云石形成较晚.白云石以低

  10. Rescuing Middle School Astronomy

    Science.gov (United States)

    Mayo, L. A.; Janney, D.

    2010-12-01

    There is a crisis in education at the middle school level (Spellings, 2006). Recent studies point to large disparities in middle school performance in schools with high minority populations. The largest disparities exist in areas of math and science. Astronomy has a universal appeal for K-12 students but is rarely taught at the middle school level. When it is taught at all it is usually taught in isolation with few references in other classes such as other sciences (e.g. physics, biology, and chemistry), math, history, geography, music, art, or English. The problem is greatest in our most challenged school districts. With scores in reading and math below national averages in these schools and with most state achievement tests ignoring subjects like astronomy, there is little room in the school day to teach about the world outside our atmosphere. Add to this the exceedingly minimal training and education in astronomy that most middle school teachers have and it is a rare school that includes any astronomy teaching at all. In this presentation, we show how to develop and offer an astronomy education training program for middle school teachers encompassing a wide range of educational disciplines that are frequently taught at the middle school level. The prototype for this program was developed and launched in two of the most challenged and diverse school systems in the country; D.C. Public Schools, and Montgomery County (MD) Public Schools.

  11. Lipid Biomarkers of the Maquoketa Formation, Iowa: Transect of a Paleobathymetry Gradient in the Lead-Up to the Late Ordovician Mass Extinction

    Science.gov (United States)

    Rohrssen, M.; Love, G. D.

    2012-12-01

    The Late Ordovician (~450-44 Ma) was a period of drastic environmental change, beginning in a hothouse climate with epeiric seaways near a Phanerozoic high and concluding with the Hirnantian glaciation, large positive carbon isotope excursion(s) (Hirnantian isotopic carbon excursion, HICE) and one of the Big Five mass extinctions. The two-phased expression of the Late Ordovician mass extinction has been attributed to regression-driven habitat loss and the consequences of cooling climate, followed by transgression of oxygen-deficient bottom water onto previously oxygenated shelves. Lipid biomarker records indicate substantial changes in microbial communities during the glacial maximum and mass extinction (Rohrssen et al., in press); to fully uncouple the effects of sea level-driven facies change from more regional or global factors we have analyzed lipid biomarkers along a shallow to deep water paleobathymetry gradient in central Laurentia across a transgressive-regressive cycle. We compare results from the Maquoketa Formation to previous work on Hirnantian- and Katian-age rocks to develop a better understanding of the association of microbial communities with Late Ordovician-age epeiric sea and upwelling environments. During deposition of the Katian-age Maquoketa Formation, Iowa was bounded to the north by exposed highlands of the Transcontinental Arch and separated from the southeastern half of the Laurentian epeiric seaway by a northeast-southwest trending shelf-break into the deeper waters of the Seebree Trough, a depression thought to have connected central and eastern Laurentia to the open ocean. As a result of this paleotopography, samples of the Maquoketa Formation collected from drill cores BS5 (Clayton County), SS-15 (Jackson County), and H33 (Des Moines County) in a transect from northeastern to southeastern Iowa capture the change in facies from carbonate-rich platform to shale with phosphatic intervals at the shelf-break in contemporaneous deposits

  12. Subsolidus alkali metasomatism in the metamorphosed Ordovician acid volcanics and volcaniclastics of the Gelnica Group (Gemeric Superunit, Western Carpathians

    Directory of Open Access Journals (Sweden)

    Mária Šimurková

    2016-06-01

    Full Text Available The Early Paleozoic Gelnica Group (Gemeric Superunit, Western Carpathians is composed of low-grade metamorphosed flysch-like sedimentary complexes alternated with volcanogenic complexes built up mostly by acid volcaniclastic rocks. Volcaniclastic rocks and small rhyolite bodies Ordovician in age underwent subsolidus alkali metasomatism locally overprinted by multiple stages of younger metamorphic and hydrothermal alterations. The observed variability in chemical compositions indicates that the most of acid volcanic and volcaniclastic rocks experienced potassic or sodium metasomatic alteration, the unaltered or Mg-metasomatised rocks occur less frequently. The dominating K-metasomatism is related mainly to the K-feldspar, partly also biotite and muscovite/sericite formation at the expense of matrix or original feldspar phenocrysts. The Na-metasomatism is connected with albite formation. The highest concentrations of alkalies (up to 13.52 wt. % K2O and 7.08 wt. % Na2O respectively have been found in rocks originally represented by glassy dacites. The elements like Al, Ti and Zr remain immobile in alkaline metasomatic processes in contrast to Rb or metals. Based on the results from areas with analogical geological structure and evolution, especially the Bergslagen area in Sweden, we suppose that alkali metasomatism in the Gelnica Group is a product of hydrothermal system caused by the infiltration and circulation of sea water. The areas with K-, Na- or Mg-metasomatism represent different parts of the original hydrothermal system, where the K-metasomatism was probably its lower temperature section. This hydrothermal system probably mobilised some metals (Cu, Pb, Zn, Fe, Mn for the formation of stratiform sulfide and oxide mineralizations or served as the metal pre-concentrator for younger siderite-sulfide vein deposits.

  13. Origin and timing of siderite cementation in Upper Ordovician glaciogenic sandstones from the Murzuq basin, SW Libya

    Energy Technology Data Exchange (ETDEWEB)

    El-ghali, M.A.K.; Mansurbeg, H. [Department of Earth Science, Uppsala University, Villavaegen 16, SE 75236 Uppsala (Sweden); Tajori, K.G. [Department of Earth Science, Faculty of Science, Al-Fateh University, P.O. Box 13696, Tripoli (Libya); Ogle, N.; Kalin, R.M. [School of Civil Engineering, Environmental Engineering Research Centre, The Queen' s University of Belfast, Stranmillis Road, Belfast BT9 5AG (United Kingdom)

    2006-05-15

    The origin and timing of siderite cementation have been constrained in relation to depositional facies and sequence stratigraphy of Upper Ordovician glaciogenic sandstones from the Murzuq basin, SW Libya. Optical microscope, backscattered electron imagery, and carbon and oxygen stable isotope analysis have revealed that siderite is of eo- and mesogenetic origin. Eogenetic siderite is Mg-poor with a mean composition of (Fe{sub 91.7}Mg{sub 1.5}Ca{sub 0.3}Mn{sub 6.5})CO{sub 3}, and occurs in paraglacial, tide-dominated deltaic highstand systems tract (HST) sandstones, in paraglacial, foreshore to shoreface HST sandstones and in postglacial, Gilbert-type deltaic lowstand systems tract (LST) sandstones. This siderite is typically of meteoric water origin that influxed into the LST and HST sandstones during relative sea level fall and basinward shift of the strandline. Mesogenetic siderite, which engulfs and thus postdates quartz overgrowths and illite, is Mg-rich with a mean composition of (Fe{sub 72.2}Mg{sub 21.7}Ca{sub 0.8}Mn{sub 5.3})CO{sub 3} and occurs in the paraglacial, tide-dominated deltaic HST sandstones, in paraglacial foreshore to shoreface HST sandstones, in glacial, tide-dominated estuarine transgressive systems tract (TST) sandstones, in postglacial, Gilbert-type deltaic LST sandstones, and in postglacial, shoreface TST sandstones. {delta}{sup 18}O{sub V-PDB} values of this siderite, which range between -22.6 and -13.8%%, suggest that precipitation has occurred from evolved formation waters with {delta}{sup 18}O values between -14.0 and +1.0%% and was either meteoric, mixed marine-meteoric and/or marine in origin by assuming postdating quartz overgrowths and illite temperature between 80 and 130{sup o}C. (author)

  14. Review and palaeoecological analysis of the late Tremadocian – early Floian (Early Ordovician cephalopod fauna of the Montagne Noire, France

    Directory of Open Access Journals (Sweden)

    B. Kröger

    2011-02-01

    Full Text Available The Early Ordovician successions of the southern Montagne Noire consist of a thick sequence of predominantly siliciclastic sediments of which the late Tremadocian St. Chinian Formation and the earliest Floian La Maurerie Formation contain a comparatively rich and abundant cephalopod association. The cephalopods of the St. Chinian and La Maurerie Formation are interpreted as generally authochthonous, representing a fauna which originally lived in the open water above the sediments or related to the sea bottom. The cephalopod associations of the St. Chinian and La Maurerie formations are similar to other contemporaneous assemblages known from higher palaeolatitudes and associated with deeper depositional settings. They are composed almost exclusively of longiconic orthocones, in this case predominantly of eothinoceratids and baltocerids. The occurrences of Annbactrocera, and Bactroceras in the St. Chinian Formation are at present the earliest unambiguous reports of the Orthocerida. The available data suggest an initial expansion of orthoceroid cephalopod faunas from open water habitats of high paleo-latitudes, and a subsequent expansion on the carbonate platforms during the Floian. The presence of the eothinoceratid Saloceras in abundance demonstrates the Gondwanan affinity of the assemblage whilst adding further support for the presence of a "Saloceras realm" that may have extended along the margins of East and West Gondwana at least into intermediate latitudes. The following new taxa are proposed: Annbactroceras n. gen., Annbactroceras felinense n. sp., Cyclostomiceras thorali n. sp., Felinoceras n. gen., Felinoceras constrictum n. sp., Lobendoceras undulatum n. sp., Rioceratidae n. fam., Saloceras murvielense n. sp., Thoraloceras n. gen., Thoraloceras bactroceroides n. sp. doi:10.1002/mmng.201000013

  15. Discovery and its geological significance of the mantle-derived helium in the inclusions of the Ordovician oil-bearing reservoir rocks in the Huanghua depression, China

    Institute of Scientific and Technical Information of China (English)

    ZHANG Xiaobao; XU Yongchang; SUN Mingliang; CHENG Keming; LIU Wenhui; LI Xiufen; MA Liyuan

    2004-01-01

    The values of the helium isotopes in the inclusions of the Ordovician reservoir rocks in the Kongxi buried hill belt in the Huanghua depression were first measured and the source of helium and its geological significance were investigated in comparison with those of the helium isotopes in the conclusions in the Ordovician rocks in the Ordos basin and the Tarim basin. The input of the mantle-derived helium into the inclusions in the carbonate reservoir rocks was found from the Konggu 3 well, the Konggu 4 well, and the Konggu 7 well in the Kongxi buried hill belt. The 3He/4He and R/Ra in the conclusions in the Ordovician oil-bearing reservoir rocks in the Konggu 7 well average 2.54×10-6(3) (sample quantity, the same below) and 1.82(3), respectively. The percent of the mantle-derived helium in the inclusions of the reservoir rocks in the Konggu 7 well reaches up to an average of 23.0%(3). The age of the contribution of the mantle-derived helium to the inclusions in the Kongxi buried hill belt is in the Late Triassic or the Early Tertiary. The finding of the mantle-derived helium shows that the interaction of the deep crust with mantle and the activity of deep faults occurred, the terrestrial heat flow value was high, and mantle-derived inorganic gas pools might be formed in the Kongxi buried hill belt. The finding of the mantle-derived helium in the inclusions of oil-bearing reservoir rocks also provides a new way for researching the activity of mantle-derived matter and its associated geological problems.

  16. 9th International Symposium on the Ordovician System, 7th International Graptolite Conference & Field Meeting of the International Subcommission on Silurian Stratigraphy

    Institute of Scientific and Technical Information of China (English)

    FlorencioG.Acenolaza; GuillermoF.Acenolaza; SilvioH.Peralta; MatildeS.Beresi

    2004-01-01

    The “9th International Symposium on the Ordovician System, 7th International Graptolite Conference & Field Meeting of the International Subcommission on Silurian Stratigraphy” commenced on August 12,2003, by receiving in San Juan City to all participants of the pre-symposia field trip through the Precordillera of Mendoza and San Juan provinces, western Argentina. On August 13, the field trip began with the purpose to show significant Lower Paleozoic outcrops from diverse settings of the Precordillera geological province. This fivedays excursion was led by Drs. S. H. Peralta.

  17. 塔里木盆地塔中地区下奥陶统白云岩成因%Genesis of Lower Ordovician Dolomite in Central Tarim Basin

    Institute of Scientific and Technical Information of China (English)

    李鹏春; 陈广浩; 曾乔松; 易金; 胡罡

    2011-01-01

    塔里木盆地塔中地区下奥陶统白云岩广泛发育,岩石类型复杂多样,主要包括结晶白云岩、残余颗粒白云岩、残余灰质白云岩、藻云岩、亮边雾心白云岩、环带白云岩及少量膏云岩等结构类型。白云岩交代现象明显,δ18O普遍为中—高负值(-3.2‰~-8.7‰);δ13C值基本为低中负值(-3‰~-0.77‰),Z值大多集中在118~123之间,成岩温度大部分集中于36~51℃范围,属于低温白云岩。白云岩具有低Mg/Ca比值,而Fe/Mn比值变化较大;白云石成分显示高铁白云石和低铁白云石之分;Sr同位素组成(0.708 8~0.709 7)普遍与海水锶同位素组成相当,但也存在个别具有较高的87Sr/86Sr比值(0.710 1~0.710 9)。结合塔中地区奥陶系古地理演变特征,白云岩化类型可划分为准同生期白云石化作用和埋藏白云石化作用。准同生期白云石化作用发生于海底(主要是潮间)成岩环境,主要是在潮坪环境或滩相环境中,其白云岩形成温度较低,具低87Sr/86Sr比值,白云石单矿物具低Fe含量;而埋藏白云岩化存在两种模式,一种为早期浅埋藏过程中的卤水回流模式,其白云岩形成温度亦较低,具高87Sr/86Sr比值,白云石单矿物具高Fe含量;另一类发生于还原性较强晚期埋藏较深的成岩环境,在埋藏阶段白云岩化程度得到进一步加强和调整,其白云岩形成温度较高,白云石捕获的包裹体均一温度较高,盐度较低。%Lower Ordovician dolomites in the central Tarim basin are of various types and extensively distributed.Seven dolostone types could be documented based on fabrics and structures,which are crystalline dolomite,residual-grain dolomite,residual calcite dolomite,algal dolomite,cloudy centers and clear rims dolomite,clitellum dolomite and gypes dolomite.It’s characterised by middle-high δ18O negative value(-3.2%~-8.7‰),low-middle δ13C negative value(-3%~-0.77

  18. Middle managers service leadership

    Directory of Open Access Journals (Sweden)

    Lucio Roberto Lescano Duncan

    2011-12-01

    Full Text Available A big challenge in modern service organization is to focus on customers and to forge their satisfaction and loyalty. Innovation, information technology and value added are decisive factors, however the main aspect to consider is the human factor. It is necessary to focus on people in order to improve the service capability within the organization.Middle manager is the link between the strategy designed by top management and the execution to deliver services, that is realized by employees guided by leaders of middle level. Our study is focused on middle manager service orientation as the pillar to get a customer focus and to forge the service employees' performance.We consider that middle managers have to asume a service leadership in order to foster the productivity and employees' commitment. In that sense we focus especially on middle managers' main roles. Those are the key aspect to deploy a service culture, and at the same time to promote employees' satisfaction that drives their performance and development.

  19. Middle matching mining algorithm

    Institute of Scientific and Technical Information of China (English)

    GUO Ping; CHEN Li

    2003-01-01

    A new algorithm for fast discovery of sequential patterns to solve the problems of too many candidate sets made by SPADE is presented, which is referred to as middle matching algorithm. Experiments on a large customer transaction database consisting of customer_id, transaction time, and transaction items demonstrate that the proposed algorithm performs better than SPADE attributed to its philosophy to generate a candidate set by matching two sequences in the middle place so as to reduce the number of the candidate sets.

  20. On the middle class

    OpenAIRE

    MacLennan, Michael; Magalhães, Beatrix Judice

    2013-01-01

    The Middle class as a concept has evolved over time, taking on various meanings at various points throughout history, becoming an object to aspire to for poor people, an object of desire for a strong government, a buzzword for politicians the world over, and the source of new customers for firms, and the global economy more broadly. This special issue of Poverty in Focus, exclusively devoted to the exploration of themes related to the middle class is part of a larger endeavour initiated by Th...

  1. Early Permian extensional shearing of an Ordovician granite: The Saint-Eutrope "C/S-like" orthogneiss (Montagne Noire, French Massif Central)

    Science.gov (United States)

    Pitra, Pavel; Poujol, Marc; Van Den Driessche, Jean; Poilvet, Jean-Charles; Paquette, Jean-Louis

    2012-08-01

    Dating the magmatic events in the Montagne Noire gneiss dome is a key point to arbitrate between the different interpretations of the Late Carboniferous-Early Permian tectonics in this southern part of the Variscan belt. The Saint-Eutrope orthogneiss crops out along the northern flank of the dome. We show that the protolith of this orthogneiss is an Ordovician granite dated at 455 ± 2 Ma (LA-ICP-MS U-Pb dating on zircon). This age is identical to that previously obtained on the augen orthogneiss of the southern flank, strongly suggesting that both orthogneiss occurrences have the same Ordovician protolith. The Saint-Eutrope orthogneiss experienced intense shearing along the Espinouse extensional detachment at ca. 295 Ma (LA-ICP-MS U-Pb-Th on monazite), an age close to that determined previously on mica by the 39Ar-40Ar method and contemporaneous with the emplacement age of the syntectonic Montalet granite farther to the west. This normal sense shearing reworked previous fabrics related to Variscan thrusting that can be still observed in the augen orthogneiss of the southern flank, and is responsible for the spectacular "C/S-like" pattern of the Saint-Eutrope orthogneiss. This work also shows that care is needed when dealing with C/S-type structures, since they can develop not only in syntectonic intrusions, but also in orthogneisses affected by an intense secondary deformation, at decreasing temperature.

  2. REE Compositions of Lower Ordovician Dolomites in Central and North Tarim Basin, NW China: A Potential REE Proxy for Ancient Seawater

    Institute of Scientific and Technical Information of China (English)

    ZHANG Xuefeng; HU Wenxuan; JIN Zhijun; ZHANG Juntao; QIAN Yixiong; ZHU Jingquan; ZHU Dongya; WANG Xiaolin; XIE Xiaomin

    2008-01-01

    Rare earth dement compositions of Lower Ordovician dolomites in the Central and Northern Tarim Basin are studied. Most dolomite samples are more or less contaminated by clay minerals. Their rare earth element compositions have been consequently changed, showing both seawater-like and non-seawater-like features. The clay contamination should be disposed before the REE data are used. Through ICP-MS and ICP-AES analyses, the REE features are well documented. The clay contamination is quantitatively determined by microscopic investigation, trace elements and REE contents. The dolomites, at least in the Tarim Basin, are thought to be pure when their total LREE contents are less than 3x10-6. Through comparison, the pure dolomites show similarities in REE patterns but differences in REE contents with co-existing pure limestone, which indicates that dolomitization may slightly change the REE compositions. Nevertheless, whatever the change is, the pure dolomites may act as a potential REE proxy for Ordovician seawater, which would be significant for ancient massive dolomite strata that lack limestone.

  3. A swollen crinoid pluricolumnal from the Upper Ordovician of northern Kentucky, USA: the oldest record of an amorphous paleopathologic response in Crinoidea?

    Directory of Open Access Journals (Sweden)

    James R. Thomka

    2014-12-01

    Full Text Available Swollen or otherwise malformed crinoid remains are relatively common in the Phanerozoic. However, published reports typically describe swellings associated with a discrete pit, boring, embedment structure or encruster, and, moreover, are overwhelmingly from Silurian or younger strata. Here, the rare occurrence of an amorphously swollen crinoid pluricolumnal is described from the Upper Ordovician (Katian Grant Lake Formation of north-central Kentucky, USA. This represents one of the oldest examples of crinoid malformation potentially resulting from interaction with a parasite or epibiont, one of the oldest examples of swelling in a crinoid column, and likely represents the oldest record of amorphous swelling. The pluricolumnal is morphologically generalized, making definitive identification difficult. Potential candidates include the diplobathrid camerate Pycnocrinus and the large, morphologically aberrant disparid Anomalocrinus. Regardless, if generated by an antagonistic biotic interaction, this specimen seems to support the hypothesis that crinoids with large calyxes and relatively complex arm morphologies were preferentially utilized as hosts for parasites and commensals over crinoids with simpler morphologies in the Ordovician.

  4. The GSSP of the Second (Upper) Stage of the Lower Ordovician Series: Diabasbrottet at Hunneberg, Province of Vaeistergoetland, Southwestern Sweden

    Institute of Scientific and Technical Information of China (English)

    StigM.Bergstroem; AnitaLoefgren; JoergMaletz

    2004-01-01

    Diabasbrottet, selected by the International Subcommisson on Ordovician Stratigraphy and in 2002 ratified by the International Commission on Stratigraphy as the GSSP of the Second (Upper) Stage of the Lower Ordovician, is located on the Hunneberg Mountain in southwestern Sweden. The stratigraphic succession represents an outer shelf environment near the Baltic Shield margin. The shale-dominated, biostratigraphically complete, richly fossiliferous boundary interval is completely exposed in a disused quarry. The GSSP is in the lower TФyen Shale 2.1 m above the top of the Cambrian and is marked by the first appearance of the graptolite Tetragraptus approximatus Nicholson. The boundary interval contains a diverse graptolite fauna and biostratigraphically diagnostic conodonts and trilobites that make it possible to define the boundary in terms of zone schemes based on these groups. In this respect, the Diabasbrottet and nearby sections are unique in the world among described localities having this boundary interval. Based on the appearance of T. approximatus, the base of the Second Stage can be identified in many graptolitiferous successions round the world but this level is currently more difficult to recognize precisely in some carbonate sequences outside Baltoscandia. We propose the Second Stage be called the Floan Stage. It is named for the Village of Flo, which is situated about 5 km southeast of the GSSP.

  5. New insights from U Pb zircon dating of Early Ordovician magmatism on the northern Gondwana margin: The Urra Formation (SW Iberian Massif, Portugal)

    Science.gov (United States)

    Solá, A. R.; Pereira, M. F.; Williams, I. S.; Ribeiro, M. L.; Neiva, A. M. R.; Montero, P.; Bea, F.; Zinger, T.

    2008-12-01

    The Central Iberian-Ossa-Morena transition zone (SW Iberian Massif) represents a segment of the northern Gondwana margin with a long geodynamic evolution, characterized by the superposition of Cadomian and Variscan events. The Early Ordovician is mainly represented by porphyritic felsic volcaniclastic rocks (the Urra Formation) that pass up into a siliciclastic sediments typical of the Central Iberian Zone (Lower Ordovician Armorican Quartzite Formation). The Urra Formation unconformably overlies the previously deformed and metamorphosed Ediacaran sediments of the Série Negra (with Ossa-Morena Zone paleogeographic affinity). New SHRIMP zircon data obtained from the Urra Formation volcaniclastic rocks indicate an Early Ordovician age ( 206Pb/ 238U ages ranging from 494.6 ± 6.8 Ma to 488.3 ± 5.2 Ma) for this magmatic event. The inherited zircon cores indicate the presence of multicycle protoliths with different Precambrian ages: Neoproterozoic (698-577 Ma), Paleoproterozoic (2.33 Ga) and Paleoarchean (3.2-3.3 Ga). There is a noticeable lack of Meso- to Neoarchean and Mesoproterozoic ages. The data support the hypothesis that the volcaniclastic rocks were derived by partial melting of Cadomian basement (linked to a West African Craton provenance). The Urra Formation volcaniclastic rocks have rhyolitic to dacitic compositions, are peraluminous and similar to calc-alkaline high-K series suites elsewhere. Isotopic signatures present a wide range of values ( 87Sr/ 86Sr) t = 0.7085-0.7190, more restricted ɛNd t (- 2.65 to - 0.35) and δ18O = 9.63-10.34‰, compatible with magmas derived from crustal rocks, including portions of the lower crust. Some samples show disturbance of the Rb-Sr system as shown by unrealistic values for ( 87Sr/ 86Sr) t < 0.703, probably due to Variscan deformation and metamorphism. The volcaniclastic rocks with a significant sedimentary contribution (upper unit) are distinguished from the others by the lowest values of ɛNd t (- 5.53 to - 4

  6. Geochemistry and jasper beds from the Ordovician Løkken ophiolite, Norway: origin of proximal and distal siliceous exhalites

    Science.gov (United States)

    Grenne, Tor; Slack, John F.

    2005-01-01

    Stratiform beds of jasper (hematitic chert), composed essentially of SiO2 (69-95 wt %) and Fe2O3 (3-25 wt %), can be traced several kilometers along strike in the Ordovician L??kken ophiolite, Norway. These siliceous beds are closely associated with volcanogenic massive sulfide (VMS) deposits and are interpreted as sea-floor gels that were deposited by fallout from hydrothermal plumes in silica-rich seawater, in which plume-derived Fe oxyhydroxide particles promoted flocculation and rapid settling of large (???200 ??m) colloidal particles of silica-iron oxyhydroxide. Concentrations of chalcophile elements in the jasper beds are at the parts per million level implying that sulfide particle fallout was insignificant and that the Si-Fe gel-forming plumes were mainly derived from intermediate- (100??-250??C) to high-temperature (>250??) white smoker-type vents with high Fe/S ratios. The interpreted setting is similar to that of the Lau basin, where high-temperature (280??-334??C) white smoker venting alternates or overlaps with sulfide mound-forming black smoker venting. Ratios of Al, Sc, Th, Hf, and REE to iron are very low and show that the detrital input was lifetime of 200 years or less. The lack of thick jasper beds near the L??kken VMS orebody, which is larger than the H??ydal orebody by more than two orders of magnitude, probably reflects a shift to anoxic conditions during L??kken mineralization. This environment limited oxidation of iron in the hydrothermal plume and formation of the ferric oxyhydroxides necessary for the flocculation of silica and sea-floor deposition of the gel precursor of the jasper beds. Distal pyritic and iron-poor cherts are more common than jasper in ancient VMS-hosting sequences. The origin of these other types of siliceous exhalite is enigmatic but at least in some cases involved sulfidation, reduction to magnetite, or dissolution of the original ferric iron in precursor Si-rich gels, either by hydrothermal or diagenetic processes

  7. Middle East Reform Halts

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    The chaos in Iraq poses a great threat to the U.S. plan in the Middle East While the fighting between Israel and Lebanon-based Hezbollah becomes fiercer, security in Iraq also keeps deteriorating, making the region a petrol can that may blow up anytime.

  8. Utopia Middle School

    Science.gov (United States)

    Cloud, Michelle

    2006-01-01

    The following excerpt allows the reader to briefly peer into an ideal school setting: For the purposes of this paper, the fictitious school will be named Utopia Middle School or U.M.S. U.M.S embodies and exemplifies the perfect school. At U.M.S., the campus administrators perform at a level of excellence that motivates, empowers and supports all…

  9. Fostering a Middle Class

    Institute of Scientific and Technical Information of China (English)

    2011-01-01

    Though there is no official definition of "middle class" in China, the tag has become one few Chinese people believe they deserve anyway.In early August, the Chinese Academy of Social Sciences released a report on China’s urban development,

  10. Model Middle Schools

    Science.gov (United States)

    Shapiro, Arthur; And Others

    1973-01-01

    Provides three models as approaches to organizing the middle school in a variety of exciting ways: (1) an oscillating system, where students in communities move between basic studies and related arts and physical education, (2) an immersion system, where students in communities spend full time moving between interdisciplinary areas, and (3) a…

  11. Genesis and Distribution of the Cambro-Ordovician Dolomite in Tarim Basin%塔里木盆地寒武-奥陶系白云岩成因及分布规律

    Institute of Scientific and Technical Information of China (English)

    郑剑锋; 沈安江; 刘永福; 陈永权

    2011-01-01

    塔里木盆地寒武-奥陶系发育的白云岩主要有4种成因,分别对应萨布哈、渗透回流、埋藏、热液等4种白云石化模式,根据岩石学和地球化学特征可以较好地识别出这4种白云岩。综合分析古地理、古气候等背景资料,总结了塔里木盆地不同成因白云岩在垂向及平面上的分布规律:萨布哈白云岩和渗透回流白云岩的发育受沉积相控制,主要发育于中下寒武统;埋藏白云岩的发育受成岩相控制,物性好的台缘、台内礁滩体及有裂缝沟通构成的开放体系最容易先发生埋藏白云石化作用;热液白云岩主要发育在具有上覆隔挡层的不整合面之下地层及大断裂发育带附近。%The dolomites of Cambro-Ordovician in Tarim basin are of four geneses,corresponding with four kinds of dolomitization ones such as sabakha dolomite,seepage reflux dolomite,buried dolomite and hydrothermal dolomite,which can be properly identified from the lithologic characteristics and geochemical characteristics.This paper comprehensively analyzes the paleogeographic and paleoclimate data,concludes the vertical and lateral distributions of dolomites with different geneses in Tarim basin: the development of sabakha dolomite and seepage reflux dolomite are controlled by sedimentary facies and mainly developed in Lower-Middle Cambrian;the development of burial dolomite are controlled by diagenetic facies,but the reef and shoal with high porosity as well as open system connected with fracture passage are easy to dolomitize;hydrothermal dolomite mainly develops below unconformity and near the discordogenic fault.

  12. Evidence of the latest Ordovician sea level drop on Avalonia in the Condroz Inlier, Belgium, and dating with chitinozoans by comparison with the Ashgill type area, Cautley District, U.K.

    Science.gov (United States)

    Vanmeirhaeghe, J.; Vandenbroucke, T.; Verniers, J.

    2003-04-01

    Recently, two conglomerate levels were discovered in the latest Ordovician Génicot Formation in the Puagne area, western Condroz Inlier, Belgium (Herbosch et al. 2001; in press). In the middle of the latter formation, a lower matrix-supported conglomerate approximately 1.2 m thick and with an erosional base is separated by 5.5 m of mudstone and siltstone from a second pebble-supported conglomerate of 2.05 m thick. A local chitinozoan biozonation places both conglomerates in the late Ashgill (stage 6). The sediments of the unit are supposed to be deposited on a moderately deep shelf. However, the sudden presence of the two conglomerates, the lower one with an erosional base, is interpreted as the sedimentological response to the sea level drop associated with the Hirnantian glaciation and deglaciation event (Vanmeirhaeghe &Verniers, submitted). This poster presents the results of a comparison of the chitinozoan biozonation of the Puagne area with that of the Ashgill type area in the Howgill Fells inliers, northern England, U.K. This resulted in a more accurate dating of the two conglomerates and of the complete Génicot and the underlying Fosses Formations in Belgium. A summary of all evidence of the Hirnantian glaciation on the Avalonia microcontinent is shown. HERBOSCH, A., VERNIERS, J., DEBACKER, T., BILLIAERT, B., DE SCHEPPER, S., BELMANS, M. (2001). The Lower Palaeozoic stratigraphy and sedimentology of the Brabant Massif in the Dyle and Orneau valleys and of the Condroz Inlier at Fosses: an excursion guidebook. Pre-symposium excursion of the International Symposium on "Early Palaeozoic Palaeogeographies and Biogeographies of Western Europe and North Africa", Lille USTL, September 22-26, 2001, 1-77. HERBOSCH, A., VERNIERS, J., DEBACKER, T., BILLIAERT, B., DE SCHEPPER, S., BELMANS, M. (2002). The Lower Palaeozoic stratigraphy and sedimentology of the Brabant Massif in the Dyle and Orneau valleys and of the Condroz Inlier at Fosses: an excursion guidebook

  13. Provenance variability along the Early Ordovician north Gondwana margin: Paleogeographic and tectonic implications of U-Pb detrital zircon ages from the Armorican Quartzite of the Iberian Variscan belt

    NARCIS (Netherlands)

    Shaw, J.; Gutiérrez-Alonso, G.; Johnston, S.T.; Pastor-Galán, D.

    2014-01-01

    Detrital zircon laser ablation–inductively coupled plasma–mass spectrometry U-Pb age data from the Lower Ordovician Armorican Quartzite (deformed passive margin strata of Gondwanan affinity) of the Iberian Massif are presented herein. The S-shaped coupled Iberian oroclines defined within these zones

  14. The Global Stratotype Section and Point(GSSP) for the base of the Katian Stage of the Upper Ordovician Series at Black Knob Ridge,Southeastern Oklahoma,USA

    Institute of Scientific and Technical Information of China (English)

    Daniel Goldman; Stephen A.Leslie; Jaak N(o)lvak; Seth Young; Stig M.Bergstr(o)m; Warren D.Huff

    2007-01-01

    @@ The Global Boundary Stratotype Section and Point (GSSP)for the Katian Stage of the Upper Ordovician Series is defined as the 4.0 m-level above the base of the Bigfork Chert in the Black Knob Ridge section,southeastern Oklahoma.

  15. Middle Ear Infections (For Parents)

    Science.gov (United States)

    ... Feeding Your 1- to 2-Year-Old Middle Ear Infections KidsHealth > For Parents > Middle Ear Infections Print ... 3 years old. A Close Look at the Ear To understand how ear infections develop, let's review ...

  16. A reference region for the Ordovician-Silurian boundary: the Oued In Djerane, Algerian SaharaUne région de référence pour la limite Ordovicien-Silurien : l'Oued In Djerane, Sahara algérien

    Science.gov (United States)

    Legrand, Philippe

    2000-01-01

    The melting chronology of the Latest Ordovician inlandsis takes on a particular importance in northern Gondwana. A continuous sequence of Diplograptid range zones has been defined from outcrops in the Oued In Djerane, but its comparison with the sequence observed in the stratotype of the Silurian-Ordovician boundary is problematic because of the endemic character of the Saharan species. Moreover, some difficulties are linked to the definition of the Ordovician-Silurian boundary, which, in the Algerian Sahara, probably lies in the Pseudorthograptus (?) kiliani zone. A definite regional diachronism in the melting of the ice-cap has also been confirmed.

  17. My Middle School Life

    Institute of Scientific and Technical Information of China (English)

    高懿; 吕静

    2004-01-01

    It is generally believed that the best time of one's hfe is their youth, and we spend most of it in our schools. So school is like a cradle which supports us from our childhood through adulthood. It also serves as a bridge between family and society. As a teenager, I have already studied more than 6 years in middle school, during which period I have gained notonly a great deal of knowledge but some valuable experience as well. The most important of all are the many unforgettable activities of school, which make my hfe more colorful.Looking back on my nearly 7 years' middle school hfe, I'd hke to divide it into two parts,that is, help and enjoyment.

  18. Stuck in the Middle

    Institute of Scientific and Technical Information of China (English)

    YIN PUMIN

    2011-01-01

    Sun Lijun works as a software engineer at a Beijing-based IT company and earns around 8,000 yuan ($1254)a month.His relative y high income means his friends and colleagues,as well as China's statistical agencies,regard him as middle class.Sun,however,does not think he is worthy of being included in a category that is traditionally associated with security and comfort.

  19. The mafic rocks of Shao La (Kharta, S. Tibet): Ordovician basaltic magmatism in the greater himalayan crystallines of central-eastern Himalaya

    Science.gov (United States)

    Visonà, Dario; Rubatto, Daniela; Villa, Igor M.

    2010-04-01

    In the Kharta area, east of Mount Everest, the Greater Himalayan Crystallines are significantly richer in mafic rocks than the surrounding areas, Sikkim-West Bhutan and Makalu-Cho Oyu. These rocks are lenses with a complex metamorphic history. The mafic lenses of Shao La, in the Greater Himalayan Sequence south of Kharta, are here considerated as dismembered dykes apparently escaped the Himalayan high-temperature metamorphism and only record a low-grade metamorphic event. They are calc-alkaline medium-K basalts to basaltic andesites, consisting of plagioclase (core 62% An and rim 55% An), augite (Wo 43-47En36 36-37Fs 16-20), hypersthene (Wo 1.6-3.3En 50-52Fs 46-48), and minor brown hornblende, biotite and ilmenite. They show strong enrichment in low ionic potential elements relative to high-field-strength elements, and only minor Ce and P enrichment with respect to MORB. Combined Sr-Nd systematics suggest contamination of a basic magma from a subcontinental mantle source with a small amount of crust (about 4 vol.%). This in turn indicates that the Shao La basalts and basaltic andesites have the geochemical fingerprint of a supra-subduction zone magma. U-Pb dating of zircon from one sample yielded an age of 457 ± 6 Ma for the crystallisation of the Shao La basic rocks, assigning them to the Cambro-Ordovician Bhimphedian orogenic event. The age and geochemical characteristics of the Shao La rocks are similar to those of the basic rocks of the Cambro-Ordovician Mandi pluton further west. This suggests the existence of an extensive supra-subduction zone magmatism along the Indian margin of Gondwana. Like the bimodal granite-gabbro magmatism in the Mandi-Kaplas area, the Shao La basic rocks are contemporaneous with the emplacement of granitic plutons in the Everest-Kharta area. This acid plutonism is interpreted as crustal melt triggered by the upwelling of metasomatised mantle in a back-arc setting. The age of basic and acidic plutonism in the Everest-Kharta area is

  20. End Ordovician extinctions

    DEFF Research Database (Denmark)

    Harper, David A. T.; Hammarlund, Emma; Rasmussen, Christian M. Ø.

    2014-01-01

    across a range of water depths. In all about 85% of marine species were removed. Proposed kill mechanisms for the first phase have included glaciallyinduced cooling, falling sea level and chemical recycling in the oceans, but a general consensus is lacking. The second phase is more clearly linked to near...

  1. Latest Cambrian-Early Ordovician rift-related magmatic activity in the Kouřim Unit, Bohemian Massif

    Science.gov (United States)

    Soejono, Igor; Machek, Matej; Sláma, Jiří; Janoušek, Vojtěch

    2017-04-01

    inherited from the source, represented most likely by recycled immature arc-related material (?metagraywackes). The real tectonic setting of this Late Cambrian magmatic activity seems rather indicated by the within-plate geochemistry of the metadiorite. These results bring further evidence for the presence of the Late Cambrian-Early Ordovician extensional event documented throughout the basement of the European Variscan Belt. Together with other occurrences of bimodal magmatism, as well as metamorphic and sedimentary record, indicate an important period of lithospheric thinning. This overall Early Palaeozoic rift-related architecture is often considered as a consequence of the Rheic Ocean opening.

  2. Proto-Pacific-margin source for the Ordovician turbidite submarine fan, Lachlan Orogen, southeast Australia: Geochemical constraints

    Science.gov (United States)

    Offler, R.; Fergusson, C. L.

    2016-04-01

    The Early Palaeozoic proto-Pacific Pacific margin of Gondwana was characterised by a huge turbidite submarine fan with abundant clastic detritus derived from unknown sources within Gondwana. These deposits are widespread in the Lachlan Orogen of southeast Australia and include the Ordovician Adaminaby Group. Here we show that the mudstones and sandstones of the Adaminaby Group have chemical compositions that indicate the detritus in them was derived from a felsic, continental source similar in composition to Post Archean Australian Shales (PAAS). Chondrite normalised REE patterns showing LREE enrichment, flat PAAS normalised patterns and elemental ratios La/Sc, Cr/Th, Cr/V, Th/Sc and Th/U, have been used to support this interpretation. The dominance of quartz, and to a lesser degree plagioclase and biotite in the sandstones, suggests that the source was mainly granodioritic to tonalitic in composition. Th/Yb and Ta/Yb ratios indicate that the source was probably calc-alkaline, continental and shoshonitic. In addition, the presence of detrital muscovite, low-grade metamorphic and felsic volcanic clasts, demonstrates that a low-grade metamorphic terrane and volcanic arc contributed to the detritus observed in the samples. The presence of well-rounded zircons and tourmalines, very high Zr contents, high Zr/Sc and higher Cr/V ratios in some samples particularly in the Shoalhaven River area, indicate that some of the detritus was recycled. SiO2 versus (Al2O3 + K2O + Na2O) plots suggest the source areas experienced conditions varying from humid/semi-humid to semi-arid. Textural features and weathering trends of samples from all locations follow a curved pathway on Al2O3 - (CaO* + Na2O) - K2O (ACNK) diagrams, and indicate that the clays formed from weathering had been K-metasomatised prior to penetrative deformation. Chemical indices of alteration (CIA) reveal that even the freshest sandstones are altered and others are moderately to strongly altered. Discrimination

  3. Arc-continent collision and the formation of continental crust: A new geochemical and isotopic record from the Ordovician Tyrone Igneous Complex, Ireland

    Science.gov (United States)

    Draut, Amy E.; Clift, Peter D.; Amato, Jeffrey M.; Blusztajn, Jerzy; Schouten, Hans

    2009-01-01

    Collisions between oceanic island-arc terranes and passive continental margins are thought to have been important in the formation of continental crust throughout much of Earth's history. Magmatic evolution during this stage of the plate-tectonic cycle is evident in several areas of the Ordovician Grampian-Taconic orogen, as we demonstrate in the first detailed geochemical study of the Tyrone Igneous Complex, Ireland. New U-Pb zircon dating yields ages of 493 2 Ma from a primitive mafic intrusion, indicating intra-oceanic subduction in Tremadoc time, and 475 10 Ma from a light rare earth element (LREE)-enriched tonalite intrusion that incorporated Laurentian continental material by early Arenig time (Early Ordovician, Stage 2) during arc-continent collision. Notably, LREE enrichment in volcanism and silicic intrusions of the Tyrone Igneous Complex exceeds that of average Dalradian (Laurentian) continental material that would have been thrust under the colliding forearc and potentially recycled into arc magmatism. This implies that crystal fractionation, in addition to magmatic mixing and assimilation, was important to the formation of new crust in the Grampian-Taconic orogeny. Because similar super-enrichment of orogenic melts occurred elsewhere in the Caledonides in the British Isles and Newfoundland, the addition of new, highly enriched melt to this accreted arc terrane was apparently widespread spatially and temporally. Such super-enrichment of magmatism, especially if accompanied by loss of corresponding lower crustal residues, supports the theory that arc-continent collision plays an important role in altering bulk crustal composition toward typical values for ancient continental crust. ?? 2009 Geological Society of London.

  4. MIDDLE CLASS MOVEMENTS

    OpenAIRE

    Dr. K. Sravana Kumar

    2016-01-01

                The middle class is placed between labour and capital. It neither directly awns the means of production that pumps out the surplus generated by wage labour power, nor does it, by its own labour, produce the surplus which has use and exchange value. Broadly speaking, this class consists of the petty bourgeoisie and the white-collar workers. The former are either self-employed or involved in the distribution of commodities and t...

  5. MIDDLE CLASS MOVEMENTS

    OpenAIRE

    Dr. K. Sravana Kumar

    2016-01-01

                The middle class is placed between labour and capital. It neither directly awns the means of production that pumps out the surplus generated by wage labour power, nor does it, by its own labour, produce the surplus which has use and exchange value. Broadly speaking, this class consists of the petty bourgeoisie and the white-collar workers. The former are either self-employed or involved in the distribution of commodities and t...

  6. Designing as middle ground

    DEFF Research Database (Denmark)

    Nickelsen, Niels Christian Mossfeldt; Binder, Thomas

    2010-01-01

    The theoretical background in this chapter is science and technology studies and actor network theory, enabling investigation of heterogeneity, agency and perfor-mative effects through ‘symmetric’ analysis. The concept of design is defined as being imaginative and mindful to a number of actors...... in a network of humans and non-humans, highlighting that design objects and the designer as an authority are constructed throughout this endeavour. The illustrative case example is drawn from product development in a rubber valve factory in Jutland in Denmark. The key contribution to a general core of design...... research is an articulation of design activity taking place as a middle ground and as an intermixture between a ‘scientific’ regime of knowledge transfer and a capital ‘D’ ‘Designerly’ regime of authoring....

  7. Regions. [Africa, Middle East].

    Science.gov (United States)

    1985-03-01

    This discussion of population focuses on the regions of Africa and the Middle East. In South Africa more white women are working but fewer black women work. The overall result is that the percentage of women who work is declining. Marita de Beer, research liaison executive at the South African Advertising Research Foundation, reports that the female population grew by 31% in the past 10 years while the number of working women has grown by only 11%. Among blacks the female population rose by 36%, but the number of workers among them declined by about 1%. Married women are among the fastest growing groups of working women in South Africa. The most recent estimate of the population of Nigeria is 92 million. According to Professor Vremudia Diejomaoh, Nigeria's population will probably reach 155 million by 2000 with 33% living in urban areas. In Saudi Arabia the Pan Arab Research Center recently completed a census of retail outlets in 3 metropolitan areas: Jeddah, Riyadh, and Dammam. The types of outlets surveyed include large supermarkets, small supermarkets, groceries with and without deep freeze, tobacco shops, meat shop/delis, small cafeterias, large restaurants/hotels, cosmetics shops or perfumeries, camera stores, toy shops, pharmacies, watch and gift shop, newsstands, department store, and appliance outlets. Using the Census of Retail Outlets as a base, Pan Arab Research Center also has a new distribution audit system that will cover 500 outlets. By plotting Arab countries according to their population policies and their current growth rates, it is possible to project where the middle class will grow fastest in the Arab world. The countries that have declining growth rates and strong population programs designed to encourage lower fertility rates among women are Egypt, Tunisia, Morocco, Algeria, and Lebanon. The countries most likely to have a better per capita distribution of resources within this decade are those where governments encourage reductions in

  8. TWO NEW ORDOVICIAN TRILOBITE GENERA FROM WESTERN MARGINAL AREAS OF THE NORTH CHINA PLATFORM%华北地台西缘两个奥陶纪三叶虫新属

    Institute of Scientific and Technical Information of China (English)

    周志毅; 周志强

    2006-01-01

    @@ In connection with the preparation of a chapter of the monograph "Trilobite record of China" on the Ordovician trilobites, a large number of Chinese species were critically reviewed. Among others, two of them previously described from western marginal areas of the North China Platform respectively by Lu in Lu et al. (1976) as Bulbaspis ordosensis and by Zhou and Dean (1986) as Ischylophyma? zhiqiangi ought to be reassigned to new genera.

  9. Calculus in the Middle School?

    Science.gov (United States)

    Barger, Rita H.; McCoy, Ann C.

    2010-01-01

    This article presents an example of how middle school teachers can lay a foundation for calculus. Although many middle school activities connect directly to calculus concepts, the authors have decided to look in depth at only one: the concept of change. They will show how teachers can lead their students to see and appreciate the calculus…

  10. Calculus in the Middle School?

    Science.gov (United States)

    Barger, Rita H.; McCoy, Ann C.

    2010-01-01

    This article presents an example of how middle school teachers can lay a foundation for calculus. Although many middle school activities connect directly to calculus concepts, the authors have decided to look in depth at only one: the concept of change. They will show how teachers can lead their students to see and appreciate the calculus…

  11. 塔中Ⅱ区奥陶系鹰山组岩溶古地貌恢复方法研究%Reconstruction of karst palaeogeomorphology for the Ordovician Yingshan formation in the central Tarim basin

    Institute of Scientific and Technical Information of China (English)

    邓兴梁; 张庆玉; 梁彬; 淡永; 李景瑞; 郝彦珍

    2015-01-01

    As part the central uplift of the Tarim basin,the Tazhong (central Tarim)II area is a low swell of the middle section of this uplift belt.In this area,before sedimentation of the Lianglitage formation,the strata of the Tumuxiuke,Yijianfang and Yingshan formations had experienced erosion of different degrees, leading to destruction of the original landforms.To delineate the karst paleomorphology of the top Yingshan formation is of great importance for modeling of karst reservoirs and forecasting favorable blocks in explora-tion.This work compares methods for paleogeomorphology reconstruction.The impression method can well describe micro morphology,but its resulting regional tectonic trends do not accord with the real ones.While the residual thickness and residual thickness trend surface method is able to build the palaeostructure at that time,but cannot depict the micro morphology.To solve this problem,this study proposes a combination ap-proach of “residual thickness of trend surface and impression residuals”to recover the ancient karst land-form.This new method not only facilitates the paleogeomorphology restoration of the Tazhong area,but al-so helps computer modeling.The research suggests that the Ordovician Yingshan formation of the Tazhong II area can be divided into three kinds of second-order geomorphic units,karst platform,karst basin,karst gentle slope,and gives the index system for subdivision of these landform units.%塔中地区在构造上是塔里木盆地中央隆起的一部分,属于中央隆起带中段的塔中低凸起。良里塔格组沉积之前吐木休克组、一间房组、鹰山组地层遭受不同程度的剥蚀,精确雕刻鹰山组顶面古岩溶地貌,对岩溶储层地质建模及有利区块预测具有重要意义。论文对比了不同古地貌恢复方法:认为印模法可以很好地雕刻微地貌形态,但是区域构造趋势却与实际不符;残厚与残厚趋势面法构建了当时的古构造,但

  12. 内蒙古西部额济纳旗晚奥陶世生物地理和奥陶-志留系分界%LATE ORDOVICIAN BIOGEOGRAPHY AND ORDOVICIAN-SILURIAN BOUNDARY IN THE ZHUSILENHAIERHAN AREA, EJIN, WESTERN INNER MONGOLIA

    Institute of Scientific and Technical Information of China (English)

    戎嘉余; 陈旭; 詹仁斌; 周志强; 郑昭昌; 王怿

    2003-01-01

    Upper Ordovician-lowest Silurian strata crop out near Danmianshan, about 10 km west of Zhusilenghaierhan Mt., about 55 km south of Yagan, 135 km east of Ejin Banner town, western Inner Mongolia (Alxa block). The strata along with their related major fossil groups (such as graptolites, corals and trilobites) have been studied by Zheng et al. (1982), Zhu et al. (1987), and Ge et al. (1990). Recent field examination in this area was carried out by the authors in the summer of 2002. Our subsequent investigation on collections has led to the discovery Holorhynchus (virgianids, Brachiopoda) from the Late Ordovician rocks, to make sure that there occur no latest Ordovician Hirnantia fauna, and to define the Ordovician-Silurian boundary on the basis of the occurrence of Normalograptus lubricus. The Ashgill brachiopod biogeography is discussed.Holorhynchus giganteus Kiaer, 1902 has been found from the Badanjilin Fomation (mid Ashgill) at the No. 3 section of Zheng et al. (1987) in this area for the first time. This is also the first record of the genus Holorhynchus in Late Ordovician of China. Holorhynchus has been known to be characterized by the total absence of a ventral median septum, together with smooth shell exterior and short, separated outer brachial plates (e.g. St. Joseph, 1938; Cocks, 1982). Through sectioning, however, the discovery of an apical median setum in ventral valve of immature specimens (less than 8mm wide) of H. giganteus led to a revised generic diagnosis for the genus (see Rong et al. in preparation). Actually, this structure is also known from an internal mold material and a transverse section of the identical species in South Norway (Cocks, 1982) and Zeravshano-Gissar Mountains, Tadzhikistan (Nikiforova and Sapel'nikov, 1973) respectively. Holorhynchus from the Badanjilin Formation at the No.3 section of Zheng et al. (1987) is associated with the brachiopods Altaethyrella, Ovalospira, Leptellina, Sowerbyella, Pectenospira, and the Agetolites

  13. Digestive and appendicular soft-parts, with behavioural implications, in a large Ordovician trilobite from the Fezouata Lagerstätte, Morocco

    Science.gov (United States)

    Gutiérrez-Marco, Juan C.; García-Bellido, Diego C.; Rábano, Isabel; Sá, Artur A.

    2017-01-01

    Trilobites were one of the most successful groups of marine arthropods during the Palaeozoic era, yet their soft-part anatomy is only known from a few exceptionally-preserved specimens found in a handful of localities from the Cambrian to the Devonian. This is because, even if the sclerotized appendages were not destroyed during early taphonomic stages, they are often overprinted by the three-dimensional, mineralised exoskeleton. Inferences about the ventral anatomy and behavioural activities of trilobites can also be derived from the ichnological record, which suggests that most Cruziana and Rusophycus trace fossils were possibly produced by the actions of trilobites. Three specimens of the asaphid trilobite Megistaspis (Ekeraspis) hammondi, have been discovered in the Lower Ordovician Fezouata Konservat-Lagerstätte of southern Morocco, preserving appendages and digestive tract. The digestive structures include a crop with digestive caeca, while the appendages display exopodal setae and slight heteropody (cephalic endopods larger and more spinose than thoracic and pygidial ones). The combination of these digestive structures and the heteropody has never been described together among trilobites, and the latter could assist in the understanding of the production of certain comb-like traces of the Cruziana rugosa group, which are extraordinarily abundant on the shallow marine shelves around Gondwana. PMID:28071705

  14. Hirnantia sagittifera (Brachiopoda and Mucronaspis mucronata s.l. (Trilobita in the Upper Ordovician of the East Baltic: taxonomy and distribution

    Directory of Open Access Journals (Sweden)

    Linda Hints

    2012-05-01

    Full Text Available The brachiopod Hirnantia sagittifera (M’Coy and trilobite morphs of the genus Mucronaspis from the topmost Ordovician Porkuni Stage of the central East Baltic are described and compared with those from the Hirnantian Stage of other regions. These important Hirnantian taxa occur in the Livonian Tongue of the Central Baltoscandian Facies Belt of the Baltic Basin, where the Porkuni Stage is represented by the non-graptolitic Kuldiga and Saldus formations. Hirnantia sagittifera appears in the lowermost part of the Porkuni Stage and is rather widely distributed in the basin in spite of its rare finds in each locality. Our study of trilobites of the genus Mucronaspis has enabled us to observe morphological changes in its exoskeleton in time and to identify a succession of five morphotypes (morphs. In some characteristics these morphs are similar to those of different alleged species of the genus Mucronaspis (M. olini, M. danai, M. ganabina, M. mucronata but they cannot be definitely assigned to any of these species due to some variances. However, here for the first time a stratigraphically ordered collection is presented, which deserves attention in revising the taxonomy of highly variable Mucronaspis. The described brachiopods and trilobites occur mainly in the strata correlated with the Normalograptus extraordinarius graptolite Biozone. However, the uppermost finds of both taxa come from strata correlated with the N. persculptus Biozone.

  15. The regional stratotype section and point for the base of the Hirnantian Stage (the uppermost Ordovician at Mirny Creek, Omulev Mountains, Northeast Russia

    Directory of Open Access Journals (Sweden)

    Koren, Tatyana N.

    2008-03-01

    Full Text Available A complete Hirnantian sequence comprising the Normalograptus extraordinarius and N. persculptus biozones is well developed at the Mirny Creek section in the Omulev Mountains. The underlying beds are assigned to the Appendispinograptus supernus Biozone, and in the overlying strata the lower boundary of the Silurian is precisely defined at the base of the Akidograptus ascensus Biozone. Due to the completeness of the sedimentary and palaeontological record, the Mirny Creek section can be considered as a reference section for the Hirnantian Stage. The succession, about 100 m thick, is composed of calcareous siltstones and marls with pebble-shaped limestones, deposited at a high sedimentation rate in shallow shelf settings. The regional stratotype section and point (RSSP for the lower boundary of the Hirnantian is established at the base of member 68, where Normalograptus extraordinarius first appears. This level can be precisely correlated with that at the GSSP section in Yichang and with the sections in Kazakhstan and North America. The position of the Ordovician-Silurian boundary is redefined and placed at the FAD of A. ascensus at the base of member 74.

  16. Middle Managers and the Environment

    DEFF Research Database (Denmark)

    Madsen, Henning; Ulhøi, John Parm

    1998-01-01

    ) middle managers, and (iii) workers. The project has been based partly on interviews in a small number of European companies at the forefront of environmental management and ditto educational and training institutions, and partly on more large-scale questionnaire surveys. This paper briefly describes...... the background of the overall project, and in more detail a questionnaire-based survey on environmental attitudes and training interests among middle managers in Danish companies....

  17. Research on Water-resisting Characteristics of Carbonate Rock on Top of Ordovician System in Longgu Coal Mine%龙固煤矿奥陶系顶部碳酸盐岩隔水特性分析研究

    Institute of Scientific and Technical Information of China (English)

    戎虎仁; 白海波

    2015-01-01

    To counter to the threat of the Ordovician karst aquifer during the mining of 21st coal seam in Longgu Mine, systematic analysis and research were made in this paper on the lithological property, the development degree of fissures, the filling degree, the structural characteristics of pores, the water inflow from boreholes and so on of the carbonate rock on the top of the Ordovician system. Research results showed that:①There is a relative water-resisting layer with the thickness about 60 m on the top of the Ordovician system, which was composed of Badou limestone stratum with developed fissures and high filling rate and Gezhuang dolomite stratum with nondevelopment of partial fissures;②The fissure percentage of the relative water-resisting layer of BADOU stratum and GEZHUANG on the top of Ordovician system is 2% ~9% and 2% ~3% respectively, with less residual fissures in the relative water-resisting layer and abvious pressure eliminating and water blocking effect;③ The diameter of most pores of the carbonate rock on the top of Ordovician system is less than 30μm, with poor connectivity among them, small effective pore-throat ratio and bad seepage capacity under natural condition;④Drain holes are all located in faults or fractured zones, the water flowing channels such as faults and broken rock are the main zones where the relative water-resisting layer is fractured, and they are also the places need to be detected and controlled during the mining of 21 st coal seam;and⑤There is a relative water-resisting layer in 60 m thick on the top of Ordovician system in Longgu Mine, which can provide a certain protection for the safe mining of 21st coal seam.%针对龙固煤矿21煤开采受奥陶系岩溶含水层威胁的问题,系统分析研究了奥陶系顶部碳酸盐岩的岩性、裂隙发育程度、充填程度、孔隙结构、钻孔涌水量等特性。研究结果表明:①矿区奥陶系顶部存在约60 m厚的相对隔水层,由裂隙发育且

  18. Integrating bio-, chemo- and sequence stratigraphy of the Late Ordovician, Early Katian: A connection between onshore and offshore facies using carbon isotope analysis: Kentucky, Ohio, USA

    Science.gov (United States)

    Young, Allison; Brett, Carlton; McLaughlin, Patrick

    2017-04-01

    A common problem in stratigraphic correlation is the difficulty of bridging shallow water shelf carbonates and down ramp shale-rich facies. This issue is well exemplified by the Upper Ordovician (lower Katian) Lexington Limestone of Kentucky, USA and adjacent dark shale facies in the deeper water Sebree Trough, an elongate, narrow bathymetric low abruptly north of the outcrop belt in the Ohio subsurface. Chronostratigraphic schemes for this interval have been proposed on the basis of conodont and graptolite biostratigraphy, mapping of event beds, and sequence stratigraphy through facies analysis. The relation of the siliciclastic rich offshore records of the "Point Pleasant-Utica" interval, well known to drillers because of its oil and gas potential, with the up-ramp shallow water carbonate dominated equivalents of the Lexington Formation is complicated by convoluted nomenclature, a major, abrupt change in facies, and disparity in the availability and completeness of records. Current genetic models of organic rich shale intervals, such as the Point Pleasant-Utica interval, are still lacking in detail, and will greatly benefit from detailed correlation with shallow water settings where more is understood about paleoclimatic conditions. In order to understand the development and evolution of this Late Ordovician Laurentian basin, it is important to understand the age relationships of depositional processes occurring at a range of depths, particularly in the less well studied epeiric sea setting of the "Point Pleasant-Utica" interval of Ohio and partial lateral equivalent, Lexington Formation of central Kentucky. The outcrop area of central Kentucky, exposed by the later uplift of the Cincinnati Arch, hosts numerous world-class exposures of the Lexington Formation, nearly all of which are representative of the highly fossiliferous, shallow-water marine platform carbonates. These successions display well differentiated depositional sequences, with sharp facies offsets

  19. Early Silurian (Aeronian East Point Coral Patch Reefs of Anticosti Island, Eastern Canada: First Reef Recovery from the Ordovician/Silurian Mass Extinction in Eastern Laurentia

    Directory of Open Access Journals (Sweden)

    Jisuo Jin

    2012-05-01

    Full Text Available An extensive late Aeronian patch reef swarm outcrops for 60–70 km on Anticosti Island, eastern Canada, located in the inner to mid-shelf area of a prominent tropical carbonate platform of southeastern Laurentia, at 20°–25° S paleolatitude of the southern typhoon belt. This complex, described here for the first time, includes more than 100 patch reefs, up to 60–80 m in diameter and 10 m high. Reefs are exposed three-dimensionally on present-day tidal flats, as well as inland along roads and rivers. Down the gentle 1°–2° paleoslope, the reefs grade into coral-sponge biostromes, and westerly they grade into inter-reef or deeper ‘crinoidal meadow’ facies. The reef builders were dominantly tabulate and rugose corals, with lesser stromatoporoids. Other components include crinoids, brachiopods, green algae (especially paleoporellids, and encrusting cyanobacteria: reefs display some of the earliest known symbiotic intergrowths of corals and stromatoporoids. Reefs were variably built on a base of crinoidal grainstones, meadows of baffling tabulate corals, brachiopod shells, or chlorophytes. These reefs mark an early phase of reef recovery after a prominent reef gap of 5–6 million years following the Ordovician/Silurian mass extinction events. The reefs feature a maximal diversity of calcifying cyanobacteria, corals and stromatoporoids, but low diversity of brachiopods, nautiloids and crinoids. Following the North American Stratigraphic Code, we define herein the Menier Formation, encompassing the lower two members of the existing Jupiter Formation.

  20. An autochthonous Avalonian basement source for the latest Ordovician Brenton Pluton in the Meguma terrane of Nova Scotia: U-Pb-Hf isotopic constraints and paleogeographic implications

    Science.gov (United States)

    Duncan Keppie, J.; Gregory Shellnutt, J.; Dostal, Jaroslav; Fraser Keppie, D.

    2017-06-01

    The Ediacaran-Ordovician Meguma Supergroup was thrust over Avalonia basement prior to the intrusion of post-Acadian, ca. 370 Ma, S-type granitic batholiths. This has led to two main hypotheses regarding the original location of the Meguma terrane, a continental rise prism bordering either NW Africa or Avalonia. On the other hand, the pre-Acadian, ca. 440 Ma Brenton pluton has yielded the following U/Pb LA-ICP-MS zircon data: (1) 448 ± 3 Ma population peak inferred to be the intrusive age and (2) ca. 550 and 700 Ma inherited ages common to both Avalonia and NW Africa. In contrast, Hf isotopic analyses of zircon yielded model ages ranging from 814 to 1127 Ma with most between 940 and 1040 Ma: such ages are typical of Avalonia and not NW Africa. The ages of the inherited zircons found within the Brenton pluton suggest that it was probably derived by partial melting of sub-Meguma, mid-crustal Avalonian rocks, upon which the Meguma Supergroup was deposited. Although Avalonia is commonly included in the peri-Gondwanan terranes off NW Africa or Amazonia, paleomagnetic data, faunal provinciality, and Hf data suggest that, during the Ediacaran-Early Cambrian, it was an island chain lying near the tropics (ca. 20-30 °S) and was possibly a continuation of the Bolshezemel volcanic arc accreted to northern Baltica during the Ediacaran Timanide orogenesis. This is consistent with the similar derital zircon population in the Ediacaran-Cambrian Meguma Supergroup and the Dividal Group in northeastern Baltica.

  1. Simulation of Linear-Flow Behavior Surrounding Large-Discharge Springs in the Great Valley Cambro-Ordovician Aquifer, West Virginia

    Science.gov (United States)

    Early, J. S.; Donovan, J. J.

    2002-05-01

    The Cambro-Ordovician carbonate aquifer in the Great Valley Region of Berkeley and Jefferson counties, West Virginia, is highly productive but threatened by acute water quality degradation as a result of rapid population growth. A regional-scale equivalent porous medium (EPM) model was developed using MODFLOW and MODPATH to simulate flow in the vicinity of high-discharge springs and community wells. The simulation approach was to develop an initial simplistic steady-state EPM solution using uniform K values distributed by surface-exposed geologic formation, consistent with a large calibration dataset; then this calibrated solution would be adjusted to address local issues involving large-scale heterogeneity, inferred in past studies. The initial simulation employed no anisotropy although its sensitivity was evaluated. A large database of springflows, surface-water baseflow, and target wells was available for calibration. The simulations were calibrated using two independent datasets: 1) hydraulic heads in wells, specifying flows at springs, and 2) estimated long-term average spring flows, specifying heads at springs. These calibrations did not agree; the first method produced excessive drawdowns around springs, while the second yielded very high K values and extremely low hydraulic gradients. The constant-flux method for springs was deemed more consistent with field reality but required implementation of high-contrast heterogeneity in the vicinity of springs, but not wells, to eliminate anomalous drawdown. A linear series of high-K zones was added to simulate suspected karst fracture zones and/or conduits; however, the orientation, style, and location of linear-flow zones are unknown. Simulation of variations in position and orientation of high-K karst zones shows that distinctive head patterns and transient discharge behavior may result from size, length, and relative K contrast of such zones.

  2. Assessing Alternative Processes for the Cause of Under-pressures in the Ordovician Sediments at the Eastern Flank of the Michigan Basin

    Science.gov (United States)

    Normani, S. D.; Yin, Y.; Sykes, J. F.

    2014-12-01

    This study examines the occurrence of anomalous hydraulic under-pressures observed within low hydraulic conductivity (low and intermediate level radioactive waste in Ontario, Canada. At a nominal depth of 460 to 820 m below ground surface, hydraulic formation pressures of 300 m below hydrostatic were measured within Ordovician age carbonates and shales. Three hypotheses for under-pressure formation are examined by means of 1-dimensional numerical analyses: 1) glacial ice-sheet loading; 2) sedimentary erosion and exhumation; and 3) the presence of an immiscible gas phase. Calibration of the numerical models to observed conditions was achieved through manipulation of formation hydraulic diffusivity, loading efficiencies, and hydraulic boundary conditions. In all cases, the calibrated numerical models were able to replicate the observed hydraulic pressure profiles. Simulations of glacial ice-sheet advance-retreat required three 120 ka cycles to yield observed head conditions. The exhumation model suggests that the erosion of approximately 1-2 km of overlying rock can lead to the formation of under-pressures only if the scaled hydraulic diffusivities are 3-4 orders of magnitude less than observed. The immiscible gas analysis, using TOUGH2-MP, provides a favourable match between the simulated and the measured under-pressures if the effective permeabilities are reduced by 2-3 orders of magnitude from observed values. Formation scale hydraulic properties must be exceedingly small to allow under-pressure development and preservation and reflects the value of self-analogues in developing an integrated understanding of deep-seated groundwater systems.

  3. Petroleum source rock evaluation of the Alum and Dictyonema Shales (Upper Cambrian-Lower Ordovician) in the Baltic Basin and Podlasie Depression (eastern Poland)

    Science.gov (United States)

    Kosakowski, Paweł; Kotarba, Maciej J.; Piestrzyński, Adam; Shogenova, Alla; Więcław, Dariusz

    2017-03-01

    We present geochemical characteristics of the Lower Palaeozoic shales deposited in the Baltic Basin and Podlasie Depression. In the study area, this strata are represented by the Upper Cambrian-Lower Ordovician Alum Shale recognized in southern Scandinavia and Polish offshore and a equivalent the Lower Tremadocian Dictyonema Shale from the northern Estonia and the Podlasie Depression in Poland. Geochemical analyses reveal that the Alum Shale and Dictyonema Shale present high contents of organic carbon. These deposits have the best source quality among the Lower Palaeozoic strata, and they are the best source rocks in the Baltic region. The bituminous shales complex has TOC contents up to ca. 22 wt%. The analysed rocks contain low-sulphur, oil-prone Type-II kerogen deposited in anoxic or sub-oxic conditions. The maturity of the Alum and Dictyonema Shales changes gradually, from the east and north-east to the west and south-west, i.e. in the direction of the Tornquist-Teisseyre Zone. Samples, located in the seashore of Estonia and in the Podlasie region, are immature and in the initial phase of "oil window". The mature shales were found in the central offshore part of the Polish Baltic Basin, and the late mature and overmature are located in the western part of the Baltic Basin. The Alum and Dictyonema Shales are characterized by a high grade of radioactive elements, especially uranium. The enrichment has a syngenetic or early diagenetic origin. The measured content of uranium reached up to 750 ppm and thorium up to 37 ppm.

  4. Cambro-Ordovician post-collisional granites of the Ribeira belt, SE-Brazil: A case of terminal magmatism of a hot orogen

    Science.gov (United States)

    Valeriano, Claudio de Morisson; Mendes, Julio Cezar; Tupinambá, Miguel; Bongiolo, Everton; Heilbron, Monica; Junho, Maria do Carmo Bustamante

    2016-07-01

    This work presents an overview of the geology and chemical composition of the Cambrian-Ordovician post-collisional (COPC) granites and associated rocks of Ribeira belt, SE-Brazil. These COPC granites make up some of the most picturesque and highest (>2000 m) rocky peaks and cliffs of Rio de Janeiro state, an accessible case of post-orogenic granitic magmatism associated with the terminal stages of a hot Ediacaran-Cambrian (Brasiliano-Panafrican) orogen. The COPC magmatism intruded tonalitic to granitic orthogneisses of the Rio Negro arc (∼790-600 Ma) and associated paragneisses of the São Fidelis Group. Post-collisional magmatism started ∼10 m.y. after the latest collisional event, the Buzios Orogeny, lasting discontinuously from ∼510 Ma until ∼470 Ma. The 15 largest intrusive bodies in Rio de Janeiro State are referred to in the literature as the Parati/Mangaratiba, Vila Dois Rios, Pedra Branca, Suruí, Silva Jardim, Favela, Andorinha, Teresópolis, Frade, Nova Friburgo, Conselheiro Paulino, São José do Ribeirão, Sana and Itaoca granites. They crop out as rounded/elliptical stocks or gently-dipping sheets, always with sharp contacts with the country rocks, along with pegmatite and aplitic veins and dykes. COPC granites are grey and pink undeformed medium-grained biotite monzogranites with (K-feldspar) porphyritic, mega-crystic, equigranular and serial textures. Magmatic flow foliation is frequently observed. Peripheric xenolith zones are common as well as isolated xenoliths from the country rocks. In a compilation of more than 100 chemical compositions, SiO2 contents display a major mode at 71wt%. The COPC magmatism generated high-K calc-alkaline granites and quartz monzonites with predominantly metaluminous granites. Meso to melanocratic gabbroic and dioritic enclaves also have calc-alkaline affinity and likely represent more resistant mafic xenoliths from the Rio Negro Arc.

  5. Petroleum source rock evaluation of the Alum and Dictyonema Shales (Upper Cambrian-Lower Ordovician) in the Baltic Basin and Podlasie Depression (eastern Poland)

    Science.gov (United States)

    Kosakowski, Paweł; Kotarba, Maciej J.; Piestrzyński, Adam; Shogenova, Alla; Więcław, Dariusz

    2016-05-01

    We present geochemical characteristics of the Lower Palaeozoic shales deposited in the Baltic Basin and Podlasie Depression. In the study area, this strata are represented by the Upper Cambrian-Lower Ordovician Alum Shale recognized in southern Scandinavia and Polish offshore and a equivalent the Lower Tremadocian Dictyonema Shale from the northern Estonia and the Podlasie Depression in Poland. Geochemical analyses reveal that the Alum Shale and Dictyonema Shale present high contents of organic carbon. These deposits have the best source quality among the Lower Palaeozoic strata, and they are the best source rocks in the Baltic region. The bituminous shales complex has TOC contents up to ca. 22 wt%. The analysed rocks contain low-sulphur, oil-prone Type-II kerogen deposited in anoxic or sub-oxic conditions. The maturity of the Alum and Dictyonema Shales changes gradually, from the east and north-east to the west and south-west, i.e. in the direction of the Tornquist-Teisseyre Zone. Samples, located in the seashore of Estonia and in the Podlasie region, are immature and in the initial phase of "oil window". The mature shales were found in the central offshore part of the Polish Baltic Basin, and the late mature and overmature are located in the western part of the Baltic Basin. The Alum and Dictyonema Shales are characterized by a high grade of radioactive elements, especially uranium. The enrichment has a syngenetic or early diagenetic origin. The measured content of uranium reached up to 750 ppm and thorium up to 37 ppm.

  6. Calcite Twinning in the Ordovician Martinsburg Formation, Delaware Water Gap, New Jersey, USA: Implications for Cleavage Formation and Tectonic Shortening in the Appalachian Piedmont Province

    Directory of Open Access Journals (Sweden)

    John P. Craddock

    2016-02-01

    Full Text Available A traverse across the Stone Church syncline in the Ordovician Martinsburg turbidites reveals an axial planar cleavage (N40°E, SE dips in regional thrust-related folds (N40°E, shallow plunges and five phases of sparry calcite. Calcite fillings are bedding-parallel, cleavage-parallel, and one vein set cross-cuts both earlier phases; the youngest calcite filling is a bedding-parallel fault gouge that crosscuts the cleavage and preserves top-down-to-the-southeast normal fault kinematics. Calcite veins unique to disharmonically-folded calcareous siltstones (Maxwell, 1962 were also analyzed. Stable isotopic analysis (O, C of all of the calcite phases indicates a uniform fluid source (δ13C −2.0, δ18O −13.3 VPDB and, potentially, a similar precipitation and mechanical twinning age. The twinning strains (n = 1341; average Δσ = −32 MPa; average ε1 = −2.9% in the calcite suite are consistent with SE-NW thrust shortening, and sub-horizontal shortening perpendicular to evolving axial planar cleavage planes in the Stone Church syncline. Calcareous siltstone layers within the Martinsburg Fm. turbidites share concordant bedding planes and are unique, chemically (XRF, but folded and cleaved differently than the surrounding clay-rich Martinsburg turbidites. Neither sediment type yielded detrital zircons. Electron backscatter X-ray diffraction (EBSD and calcite twinning results in a folded calcareous siltstone layer preserving a layer-normal SE-NW shortening strain and Lattice Preferred Orientation (LPO. Shortening axes for the five-phase calcite suite trends ~N40°W, consistent with tectonic transport associated with crystalline nappe emplacement of the Reading Prong within the Piedmont province.

  7. Bedded jaspers of the Ordovician Løkken ophiolite, Norway: seafloor deposition and diagenetic maturation of hydrothermal plume-derived silica-iron gels

    Science.gov (United States)

    Grenne, Tor; Slack, John F.

    2003-01-01

    Sedimentary beds of jasper (red hematitic chert) in the Ordovician Løkken ophiolite of Norway are closely associated with volcanogenic massive sulphide (VMS) deposits. The jaspers occur in the immediate hangingwall and laterally peripheral to the large Løkken (25–30 Mt) and small Høydal (0.1 Mt) VMS deposits, and are exposed discontinuously for several kilometres along strike. Massive or laminated types predominate; jasper-sulphide debris-flow deposits are also abundant near VMS deposits. The jaspers contain hematite-rich laminae showing soft-sediment deformation structures and microtextural evidence that record the presence of a colloidal precursor and an origin as gels. Early textures include: (1) straight or curved chains of hematitic filaments 3–10 µm in diameter and 20–100 µm long; (2) branching networks of 15–25 µm-thick, tubular structures surrounded by cryptocrystalline hematite and filled with quartz and euhedral hematite; (3) small (up to 10 µm) spherules composed of cryptocrystalline hematite and silica; and (4) up to 50 µm silica spherules with hematitic cores. The small filaments seem to have been deposited in varying proportions in the primary laminae, possibly together with hematitic and siliceous microspheroids. Diagenetic changes are represented by polygonal syneresis cracks, and the presence of cryptocrystalline (originally opaline) silica, chalcedony, quartz, carbonate and cryptocrystalline hematite and/or goethite forming botryoidal masses and spheroids <10 µm to 5 mm in diameter. Coarser euhedral grains of quartz, carbonate, and hematite are integral parts of these textures. Bleached, silica-rich jaspers preserve only small relics of fine-grained hematite-rich domains, and locally contain sparse pockets composed of coarse euhedral hematite±epidote.

  8. Multiple Osteomas in Middle Ear

    Directory of Open Access Journals (Sweden)

    Yongxin Li

    2012-01-01

    Full Text Available Since the first description of middle ear osteomas by Thomas in 1964, only few reports were published within the English literatures (Greinwalid et al., 1998; Shimizu et al., 2003; Cho et al., 2005; and Jang et al., 2009, and only one case of the multiple osteomas in middle ear was described by Kim et al., 2006, which arose from the promontory, lateral semicircular canal, and epitympanum. Here we describe a patient with multiple middle ear osteomas arising from the promontory, incus, Eustachian tube, and bony semicanal of tensor tympani muscle. This patient also contracted the chronic otitis media in the ipsilateral ear. The osteomas were successfully removed by performing type III tympanoplasty in one stage.

  9. The Middle Atmosphere Program: A special project for the Antarctic Middle Atmosphere (AMA)

    Science.gov (United States)

    Hirasawa, T.

    1982-01-01

    Areas of concern are: dynamics, structure, and atmospheric composition of the middle atmosphere in Antarctica; particle precipitation and interaction of the middle atmosphere with the lower ionosphere; atmospheric pollution; and the difference between the northern and southern polar middle atmosphere.

  10. The Middle School Recipe Book.

    Science.gov (United States)

    Robinson, Lynnette S., Comp.

    The purpose of this book is to provide activities, forms, and information to aid elementary and middle school counselors in improving services and programs for students. The materials included may also serve as an invaluable tool in assisting newly employed counselors in setting up their programs. This publication is organized in the format of the…

  11. Middle Level Learning Number 47

    Science.gov (United States)

    Lapham, Steven S.; Hanes, Peter; Turner, Thomas N.; Clabough, Jeremiah C.; Cole, William

    2013-01-01

    This issue's "Middle Level Learning" section presents two articles. The first is "Harriet Tubman: Emancipate Yourself!" (by Steven S. Lapham and Peter Hanes). "Argo," which won the 2012 Oscar for best picture, was about a daring escape of six U.S. diplomats from Iran during the 1979 hostage crisis. Now imagine the…

  12. Middle School Pupils Write Haiku.

    Science.gov (United States)

    Ediger, Marlow

    Pupils in the middle school can be motivated to enjoy and write haiku poetry. A student teacher taught two lessons to a sixth grade class in haiku writing. First, the student teacher read three haikus aloud to students. After discovering the characteristics of a haiku from two models, the class as a whole wrote a haiku based on slides from their…

  13. MIDDLE AGE (35 - 65 YEARS)

    African Journals Online (AJOL)

    Chantel

    Persons of middle age probably represent the bulk of patients who present with dermatological problems. ... ly emerged, particularly for the early detection of skin cancer. Such promotive ... of normal-sized terminal hair follicles on the scalp to small, hypopigmented, miniaturised hair ..... sis in the lungs or elsewhere. The nod-.

  14. Middle Level Learning Number 47

    Science.gov (United States)

    Lapham, Steven S.; Hanes, Peter; Turner, Thomas N.; Clabough, Jeremiah C.; Cole, William

    2013-01-01

    This issue's "Middle Level Learning" section presents two articles. The first is "Harriet Tubman: Emancipate Yourself!" (by Steven S. Lapham and Peter Hanes). "Argo," which won the 2012 Oscar for best picture, was about a daring escape of six U.S. diplomats from Iran during the 1979 hostage crisis. Now imagine…

  15. Neoproterozoic-middle Paleozoic tectono-magmatic evolution of the Gorny Altai terrane, northwest of the Central Asian Orogenic Belt: Constraints from detrital zircon U-Pb and Hf-isotope studies

    Science.gov (United States)

    Chen, Ming; Sun, Min; Buslov, Mikhail M.; Cai, Keda; Zhao, Guochun; Zheng, Jianping; Rubanova, Elena S.; Voytishek, Elena E.

    2015-09-01

    The Gorny Altai terrane (GA) is a key area in understanding the crustal evolution of the Central Asian Orogenic Belt (CAOB). This paper reports U-Pb and Hf-isotope data for detrital zircons from Cambrian to early Devonian sedimentary sequences to constrain their provenance, as well as the tectono-magmatic events and crustal growth in this region. Nearly all the detrital zircons are characterized by euhedral to subhedral morphology, high Th/U ratios (ca. 0.1-1.6) and typical oscillatory zoning, indicating a magmatic origin. The three samples from the Gorny Altai Group (middle Cambrian to early Ordovician) yield detrital zircon populations that are composed predominantly of 530-464 Ma grains, followed by a subordinate group of 641-549 Ma old. The Silurian and Devonian samples exhibit similar major zircon populations (555-456 Ma and 525-463 Ma, respectively), but a significant amount of additional 2431-772 Ma zircons occur in the early Devonian sample. Our results suggest that detritus from the nearby Kuznetsk-Altai intra-oceanic island arc served as a unitary source for the Cambrian-Silurian sedimentary sequences, but older detritus from other sources added to the early Devonian sequence. The low abundance of ca. 640-540 Ma detrital zircons may testify that this island arc was under a primitive stage in this period, when mafic volcanic rocks probably dominated. In contrast, the dominant population of ca. 530-470 Ma zircons may indicate an increased amount of granitic rocks in the source area, suggesting that the Kuznetsk-Altai island arc possibly evolved into a mature one in the Cambrian to early Ordovician. The ca. 530-470 Ma detrital zircons are almost exclusively featured by positive εHf(t) values and have two-stage Hf model ages of ca. 1.40-0.45 Ga, indicating that the precursor magmas were sourced predominantly from heterogeneous juvenile materials. We conclude that the late Neoproterozoic to early Paleozoic magmatism in the Kuznetsk-Altai arc made a

  16. Ancient glaciations and hydrocarbon accumulations in North Africa and the Middle East

    Science.gov (United States)

    Le Heron, Daniel Paul; Craig, Jonathan; Etienne, James L.

    2009-04-01

    At least six glaciations are purported to have affected North Africa and the Middle East region over the last one billion years, including two in the Cryogenian (Neoproterozoic), Hirnantian (Late Ordovician), Silurian, Carboniferous and Early Permian events. The sedimentary record associated with these glaciations, together with the intensity to which each has been investigated, is highly variable. As hydrocarbon exploration proceeds aggressively across the North Africa and Middle East regions, we review the relationship between glaciation and hydrocarbon accumulations. With the exception of Oman, and locally Egypt, which were tectonically active both during the Neoproterozoic and Early Palaeozoic all glaciations took place along an essentially stable passive continental margin. During the Neoproterozoic, two glaciations are recognised, referred to as older and younger Cryogenian glaciations respectively. Both of these Cryogenian events are preserved in Oman; only the younger Cryogenian has been reported in North Africa in Mauritania and Mali at the flanks of the Taoudenni Basin. The process of initial deglaciation in younger Cryogenian glaciations resulted in incision, at least locally producing large-bedrock palaeovalleys in Oman, and the deposition of glacial diamictites, gravels, sandstones and mudstones. As deglaciation progressed "cap carbonates" were deposited, passing vertically into shale with evidence for deposition in an anoxic environment. Hence, younger Cryogenian deglaciation may be associated with hydrocarbon source rock deposits. Hirnantian (Late Ordovician) glaciation was short lived (heterogeneities within these sediments, and in analogue deposits produced by glaciations of different ages. Deglacial, Early Silurian black shale represents the most important Palaeozoic source rock across the region. Existing models do not adequately explain the temporal and spatial development of anoxia, and hence of black shale/deglacial source rocks. The origins

  17. Agricultural Education Curricula in the Middle School.

    Science.gov (United States)

    Rexrode, Carl L.

    1980-01-01

    Defining the terms middle school and curriculum, the author then gives suggestions for planning the agricultural education curriculum for middle schools. Important responsibilities of the vocational agriculture teacher are discussed. (SK)

  18. Study on Rights and Interests Scope Protection of Ordovician Geothermal Single Well in Heze City%菏泽地区奥陶系地热单井开采权益保护范围的研究

    Institute of Scientific and Technical Information of China (English)

    马龙; 冯超臣

    2015-01-01

    菏泽地区地处鲁西南黄泛平原,中低温地热资源丰富,具有良好的开发应用前景。目前菏泽地热的开发利用正处于起步阶段,地热资源的开发利用主要以奥陶纪热储层地热水为主。该文对奥陶系地热单井产能测试和开采权益保护范围进行了描述,对区内地热资源开发利用和地热资源规范管理起到一定的指导作用。%Heze area locates in the yellow flood plain in southwest of Shandong province. Low temperature geother-mal resource is very rich and has very good development prospect. At present, geothermal exploitation and utiliza-tion is in starting stage. Development and utilization of geothermal resources are mainly composed of Ordovician heat reservoir geothermal water. In this paper, single well deliverability test of Ordovician geothermal and protection scope of mining rights have been described. It will guide the development and utilization and formal management of geothermal resources.

  19. MIDDLE DIATHESIS IN OLD JAVANESE LANGUAGE

    Directory of Open Access Journals (Sweden)

    Ni Ketut Ratna Erawati

    2014-09-01

    Full Text Available Abstract Old Javanese Langusage (OJL is the language of the archipelago which developed rapidly in the IX-XV centuries. The language has so many alternation verbs in the predicate of the clause structure. Therefore, the problem of the present study is interesting to explore. The term refers to the opinion proposed by Shibatani(1998 and Artawa (2003.Diathesis associated with middle in OJL was found to have three types, namely, the middle diathesis morphological, middle lexical, and middle perifrastic.

  20. Recruiting Middle School Students into Nursing

    Science.gov (United States)

    Matutina, Robin E.

    2008-01-01

    The purpose of this literature review is to illustrate the importance of initiating nursing recruitment during the middle school years. Data sources included citations from the years 1989 to 2006. The study focused on middle school students 9 to 13 years of age in Grades 6 to 8. One survey compared middle school students' perceptions of an ideal…

  1. Funding problems threaten Middle East's synchrotron

    CERN Multimedia

    McCabe, H

    1999-01-01

    Scientists will tour the Middle East to try to raise support for the Synchrotron radiation for Experimental Science and Applications in the Middle East project. The plan is to dismantle and move a decommissioned synchrotron from Berlin to the Middle East where scientists of any nationality would be able to use it (3 paragraphs).

  2. Middle Leaders' Learning in a University Context

    Science.gov (United States)

    Franken, Margaret; Penney, Dawn; Branson, Christopher

    2015-01-01

    This article focuses on the phenomenon of middle leadership in a university context and directs attention to the significance of learning as a central facet of leadership development. Drawing on the reflections of two of the authors as new middle leaders (chairpersons of departments), this article critically examines how middle leaders learn…

  3. 7 CFR 28.403 - Middling Color.

    Science.gov (United States)

    2010-01-01

    ... 7 Agriculture 2 2010-01-01 2010-01-01 false Middling Color. 28.403 Section 28.403 Agriculture..., TESTING, AND STANDARDS Standards Official Cotton Standards of the United States for the Color Grade of American Upland Cotton § 28.403 Middling Color. Middling Color is color which is within the...

  4. Secondary middle turbinate: case report

    Energy Technology Data Exchange (ETDEWEB)

    Aburjeli, Bruna de Oliveira Melim; Avila, Ana Flavia Assis de; Diniz, Renata Lopes Furletti Caldeira; Motta, Emilia Guerra Pinto Coelho; Ribeiro, Marcelo Almeida; Moreira, Wanderval, E-mail: bruninha86@hotmail.com [Radiology and Imaging Diagnosis, Hospital Mater Dei, Belo Horizonte, MG (Brazil)

    2012-11-15

    Secondary middle turbinate is an anatomical variant rarely observed in the nasal cavity, firstly described by Khanobthamchai et al. as a bone structure originating from the lateral nasal wall and covered by soft tissue. In most cases reported in the literature, this variant is bilateral, occurring without associated complications. In the present report, the authors describe the case of patient of their institution with such anatomical variation. (author)

  5. Growing a strong middle class.

    Science.gov (United States)

    O'Malley, Martin

    2009-01-01

    An important mission for the country is achieving sustainability while strengthening the middle class. American leadership and innovation can play a critical role in defining the interconnectedness of our economy and environment-and in unlocking, harnessing, and advancing green technologies. The State of Maryland has launched a Green Jobs Initiative focused on attracting green businesses, working with existing businesses to adopt sustainable practices, promoting clean energy research and use, and training the work force for ne, green-collar jobs.

  6. Middle Ground on Gun Control

    Science.gov (United States)

    2016-12-01

    effective and practical solution that the community embraced. E. THE MIDDLE GROUND Because of the current political environment , more outside the...was made to expire once the NICS was up and running.52 James Brady passed away in 2014 due to complications from the brain damage he suffered as a...readily available means. For example, poisoning is the most common method of suicide in China because pesticides and herbicides that can be deadly are

  7. The Middle East population puzzle.

    Science.gov (United States)

    Omran, A R; Roudi, F

    1993-07-01

    An overview is provided of Middle Eastern countries on the following topics; population change, epidemiological transition theory and 4 patterns of transition in the middle East, transition in causes of death, infant mortality declines, war mortality, fertility, family planning, age and sex composition, ethnicity, educational status, urbanization, labor force, international labor migration, refugees, Jewish immigration, families, marriage patterns, and future growth. The Middle East is geographically defined as Bahrain, Egypt, Iraq, Jordan, Kuwait, Lebanon, Oman, Qatar, Saudi Arabia, Syria, United Arab Emirates, Yemen, Gaza and the West Bank, Iran, Turkey, and Israel. The Middle East's population grew very little until 1990 when the population was 43 million. Population was about doubled in the mid-1950s at 80 million. Rapid growth occurred after 1950 with declines in mortality due to widespread disease control and sanitation efforts. Countries are grouped in the following ways: persistent high fertility and declining mortality with low to medium socioeconomic conditions (Jordan, Oman, Syria, Yemen, and the West Bank and Gaza), declining fertility and mortality in intermediate socioeconomic development (Egypt, Lebanon, Turkey, and Iran), high fertility and declining mortality in high socioeconomic conditions (Bahrain, Iraq, Kuwait, Qatar, Saudi Arabia, and the United Arab Emirates), and low fertility and mortality in average socioeconomic conditions (Israel). As birth and death rates decline, there is an accompanying shift from communicable diseases to degenerative diseases and increases in life expectancy; this pattern is reflected in the available data from Egypt, Kuwait, and Israel. High infant and child mortality tends to remain a problem throughout the Middle East, with the exception of Israel and the Gulf States. War casualties are undetermined, yet have not impeded the fastest growing population growth rate in the world. The average fertility is 5 births

  8. Geoscientists and the Radical Middle

    Science.gov (United States)

    Tinker, S. W.

    2015-12-01

    Addressing the great challenges facing society requires industry, government, and academia to work together. I call this overlap space, where compromises are made and real solutions determined, the Radical Middle. Radical because it can appear at times as if the loudest and most publicly influential voices lie outside of the actual solution space, content to provoke but not problem-solve. One key area where geoscientists can play a lead role in the Radical Middle is in the overlap between energy, the environment, and the economy. Globally, fossil fuels still represent 85% of the aggregate energy mix. As existing conventional oil and natural-gas reservoir production continues to slowly decline, unconventional reservoirs, led today by shale and other more expensive resources, will represent a growing part of the oil and gas production mix. Many of these unconventional reservoirs require hydraulic fracturing. The positive economic impact of hydraulic fracturing and associated natural gas and oil production on the United States economy is well documented and undeniable. Yet there are environmental concerns about fracking, and some states and nations have imposed moratoria. This energy-environment-economy space is ideal for leadership from the geosciences. Another such overlap space is the potential for geoscience leadership in relations with China, whose economy and global presence continue to expand. Although China is building major hydropower and natural-gas power plants, as well as nuclear reactors, coal is still king—with the associated environmental impacts. Carbon sequestration—onshore in brine and to enhance oil recovery, as well as offshore—could prove viable. It is vital that educated and objective geoscientists from industry, government, and academia leave their corners and work together in the Radical Middle to educate the public and develop and deliver balanced, economically sensible energy and environmental strategies.

  9. The State of the Australian Middle Class

    Directory of Open Access Journals (Sweden)

    Clive Hamilton

    2008-09-01

    Full Text Available There is a widespread view that the middle class in Australia is doing it tough, that they arefinding it increasingly difficult to maintain a decent standard of living and are suffering frommortgage stress. Indeed, some media reports have announced the end of the middle classdream.This paper tests a number of these popular views against the statistical data. It asks whetherthe typical Australian family can be said to be struggling? Are mortgages creating severeproblems for middle-class families? Is the middle class shrinking? Are families copingfinancially only because wives are going out to work?

  10. 塔里木盆地和田河气田下奥陶统白云岩成因%Dolomite Origin of Lower Ordovician in Hetian River Gas Field, Tarim Basin

    Institute of Scientific and Technical Information of China (English)

    杨威; 王清华

    2000-01-01

    塔里木盆地和田河气田是最近探明的大型碳酸盐岩气田,下奥陶统主要发育两类白云岩。下部为层状白云岩,以细晶为主,阴极发光呈紫红色和蓝紫色,有序度为0.57~0.68,Sr、Na含量低,碳氧同位素偏负,成岩深度约1500m;上部斑状灰质白云岩与层状白云岩相比,晶形较粗、以中晶为主,有序度较高、为0.85~0.90,Sr偏高、Na偏低,碳氧同位素更偏负,成岩深度约2000m。通过对上述特征综合研究,认为层状白云岩形成于早期浅埋藏海水-淡水混合环境,提出斑状灰质白云岩形成于晚期深埋藏压实流-淡水混合环境,总结了两种成因机理,建立了相关的白云石化模式。%The Hetian river gas field is a new and large gas field inMazatage fault belt of Tarim basin. Ordovician carbonate rock is principal production formation. Lower Ordovician is characterized by developed dolomitization which can greatly improve reservoir property. There are two types of dolomite in Lower Ordovician. The bedded dolomite is in lower part. Their features is fine-crystal, cathodolaminescence of violet-red and blue-violet, degree of order 0. 57~0.68, low Sr and Na content, and negative carbon oxygen isotope value, implying that the bedded dolomite was formed in environment of early shallow-buffed fresh water and seawater mixing. On the contrary the upper part patch calcareous dolomite is medium-crystal, degree of order 0.85~0.90, high-Sr content , low-Na content, and more negative value carbon oxygen isotope indicating that the patch dolomites was formed in environment of late deep-buried compaction flow and fresh water mixing. The bedded dolomite was formed in an environment of restricted platform, where water was confined and salinity was high. There was porous water of high salinity with high Mg/Ca in intergranular pore of orginal sediment. It has much higher carbon oxygen isotope value and trace element

  11. An Evaluation of the Carbon Sequestration Potential of the Cambro-Ordovician Strata of the Illinois and Michigan Basins. Part 1. Evaluation of Phase 2 CO2 Injection Testing in the Deep Saline Gunter Sandstone Reservoir (Cambro-Ordovician Knox Group), Marvin Blan No. 1 Hancock County, Kentucky Part 2. Time-lapse Three-Dimensional Vertical Seismic Profile (3D-VSP) of Sequestration Target Interval with Injected Fluids

    Energy Technology Data Exchange (ETDEWEB)

    Bowersox, Richard [Univ. of Illinois, Champaign, IL (United States); Hickman, John [Univ. of Illinois, Champaign, IL (United States); Leetaru, Hannes [Univ. of Illinois, Champaign, IL (United States)

    2012-12-20

    Part 1 of this report focuses on results of the western Kentucky carbon storage test, and provides a basis for evaluating injection and storage of supercritical CO2 in Cambro-Ordovician carbonate reservoirs throughout the U.S. Midcontinent. This test demonstrated that the Cambro- Ordovician Knox Group, including the Beekmantown Dolomite, Gunter Sandstone, and Copper Ridge Dolomite in stratigraphic succession from shallowest to deepest, had reservoir properties suitable for supercritical CO2 storage in a deep saline reservoir hosted in carbonate rocks, and that strata with properties sufficient for long-term confinement of supercritical CO2 were present in the deep subsurface. Injection testing with brine and CO2 was completed in two phases. The first phase, a joint project by the Kentucky Geological Survey and the Western Kentucky Carbon Storage Foundation, drilled the Marvin Blan No. 1 carbon storage research well and tested the entire Knox Group section in the open borehole – including the Beekmantown Dolomite, Gunter Sandstone, and Copper Ridge Dolomite – at 1152–2255 m, below casing cemented at 1116 m. During Phase 1 injection testing, most of the 297 tonnes of supercritical CO2 was displaced into porous and permeable sections of the lowermost Beekmantown below 1463 m and Gunter. The wellbore was then temporarily abandoned with a retrievable bridge plug in casing at 1105 m and two downhole pressure-temperature monitoring gauges below the bridge plug pending subsequent testing. Pressure and temperature data were recorded every minute for slightly more than a year, providing a unique record of subsurface reservoir conditions in the Knox. In contrast, Phase 2 testing, this study, tested a mechanically-isolated dolomitic-sandstone interval in the Gunter.

  12. Epidermoid cyst in Anterior, Middle

    Directory of Open Access Journals (Sweden)

    Kankane Vivek Kumar

    2016-09-01

    Full Text Available Epidermoid cysts are benign slow growing more often extra-axial tumors that insinuate between brain structures, we present the clinical, imaging, and pathological findings in 35 years old female patients with atypical epidermoid cysts which was situated anterior, middle & posterior cranial fossa. NCCT head revealed hypodense lesion over right temporal and perisylvian region with extension in prepontine cistern with mass effect & midline shift and MRI findings revealed a non-enhancing heterogeneous signal intensity cystic lesion in right frontal & temporal region extending into prepontine cistern with restricted diffusion. Patient was detoriated in night of same day of admission, emergency Fronto-temporal craniotomy with anterior peterousectomy and subtotal resection was done. The histological examination confirms the epidermoid cyst. The timing of ectodermal tissue sequestration during fetal development may account for the occurrence of atypical epidermoid cysts.

  13. The making of middle Indonesia: middle classes in Kupang Town, 1930s-1980s

    NARCIS (Netherlands)

    van Klinken, G.

    2014-01-01

    What holds Indonesia together? 'A strong leader' is the answer most often given. This book looks instead at a middle level of society. Middle classes in provincial towns around the vast archipelago mediate between the state and society and help to constitute state power. 'Middle Indonesia' is a

  14. Morality from infancy to middle childhood

    NARCIS (Netherlands)

    Pannebakker, Fieke Dineke

    2007-01-01

    In the present thesis, a homogeneous upper middle class sample of firstborn girls and their mothers were followed from infancy (18 and 24 months) to middle childhood (89 months) using questionnaires and observations. The focus of the study was on three components of moral behavior, i.e. empathy,

  15. Middle-class projects in modern Malaysia

    National Research Council Canada - National Science Library

    Fischer, Johan

    2017-01-01

    ... section of the middle class in Malaysia. Based on research projects I have carried out from the mid-1990s to the present, this article argues that an unpacking of the Malay Muslim middle class over time is important in order to understand...

  16. [Comparative ophthalmology in the Middle Ages].

    Science.gov (United States)

    Norn, M; Norn, O

    2001-01-01

    Descriptions of animal eyes in the Middle Ages in the learned work Physiologus from the 4th century, based on Aristoteles, Plutarc, the Bible etc. are commented on. The modern biologist is horrified, the historian understands the ethical - religious aspects behind the edifying stories concerning the lion, gazelle, eagle, snake, lizard, swallow etc. Medical science and theology were not separated in the Middle Ages.

  17. White Middle Class Identities and Urban Schooling

    Science.gov (United States)

    Devine, Dympna; Savage, Mike; Ingram, Nicola

    2012-01-01

    The authors review "White middle class identities and urban schooling," by D. Reay, G. Crozier and D. James. This book focuses on the perspectives of white middle-class parents who make "against"-the-grain school choices for their children in urban England. It provides key insights into the dynamics of class practising that are…

  18. Learning Leadership Skills in Middle School

    Science.gov (United States)

    Bowman, Richard F.

    2013-01-01

    For middle school students, the essence of 21st-century leadership development is being "in influence" versus being "in control." A core student leadership skill involves listening intently to others, framing others' concerns, and advancing the other person's interests. Creating contexts in which middle school…

  19. Meeting the Challenge of Middle School Teaching.

    Science.gov (United States)

    Gerber, Timothy

    1992-01-01

    Suggests that successful middle school music teachers are those who are liked by students and who expect good behavior and reasonable effort. Discusses drug abuse, intellectual underdevelopment, and other problems faced by today's adolescent students. Recommends restructuring middle schools to address student needs, improving teacher education,…

  20. Middle Region to Embrace Golden Time

    Institute of Scientific and Technical Information of China (English)

    Yan Manman

    2010-01-01

    @@ On September 23, Premier Wen Jiabao chaired the State Council's executive meeting, which discussed and passed the Planning to Boost the Rise of Middle Region, which set the goals for the middle region of significantly increasing the level of economic development, further strengthening the developing vitality, remarkably enhancing the sustainable development capacity and making new progress in building a harmonious society by 2015.

  1. Middle Region to Embrace Golden Time

    Institute of Scientific and Technical Information of China (English)

    Yan Manman

    2011-01-01

    @@ On September 23, Premier Wen Jiabao chaired the State Council's executive meeting, which discussed and passed the Planning to Boost the Rise of Middle Region, which set the goals for the middle region of significantly increasing the level of economic development, further strengthening the developing vitality, remarkably enhancing the sustainable development capacity and making new progress in building a harmonious society by 2015.

  2. Size variation in Middle Pleistocene humans.

    Science.gov (United States)

    Arsuaga, J L; Carretero, J M; Lorenzo, C; Gracia, A; Martínez, I; Bermúdez de Castro, J M; Carbonell, E

    1997-08-22

    It has been suggested that European Middle Pleistocene humans, Neandertals, and prehistoric modern humans had a greater sexual dimorphism than modern humans. Analysis of body size variation and cranial capacity variation in the large sample from the Sima de los Huesos site in Spain showed instead that the sexual dimorphism is comparable in Middle Pleistocene and modern populations.

  3. Instructional Coaching in One Middle School

    Science.gov (United States)

    Krohn, Cheryl Ann

    2013-01-01

    This qualitative study examines a model of instructional coaching in a middle school using interviews and observations of both teachers and their coaches. During the 2012-2013 school year, Creekside Middle School implemented a new model of instructional coaching that differed from the traditional model of coaching; it focused on student learning…

  4. Green chemistry education in the Middle East

    Science.gov (United States)

    Kolopajlo, Larry

    2017-06-01

    The Middle East once dominated the age of alchemy, and today it is experiencing a resurgence by transforming the age of petroleum chemicals into a greener science through Estidama. This green conversion is taking place through green chemical research and education. This report examines and reviews the understudied subject of green chemical education in the Middle East through the lens of context and history.

  5. Environmental Citizenship in Florida's Middle Schools.

    Science.gov (United States)

    Florida State Dept. of Environmental Protection, Tallahassee.

    This brochure introduces Environmental Citizenship in Florida's Middle Schools, which is a school-wide exercise aimed at making middle school students more aware of the natural world around them and their effect on that world. As many school-study areas as possible are used to help students learn how the environment can affect all aspects of their…

  6. Leading in Middle Management in Higher Education

    Science.gov (United States)

    Pepper, Coral; Giles, Wendy

    2015-01-01

    In this article we discuss the experiences of academics who occupy middle-level leadership roles in higher education. We use the term middle management to describe personnel occupying positions below the level of dean and often referred to as associate deans or heads of school. Practitioners rarely turn their attention to their own organizations,…

  7. The Making of the Black Middle Class.

    Science.gov (United States)

    Collins, Sharon M.

    1983-01-01

    Examines Black occupational mobility and factors that have influenced the growth of the Black middle class since the 1960s. Argues that the Black middle class occupies a fragile market position because Black mobility depends on fluctuating government policy rather than on free market factors. (Author/MJL)

  8. White Middle Class Identities and Urban Schooling

    Science.gov (United States)

    Devine, Dympna; Savage, Mike; Ingram, Nicola

    2012-01-01

    The authors review "White middle class identities and urban schooling," by D. Reay, G. Crozier and D. James. This book focuses on the perspectives of white middle-class parents who make "against"-the-grain school choices for their children in urban England. It provides key insights into the dynamics of class practising that are…

  9. Attachment and Socioemotional Problems in Middle Childhood

    Science.gov (United States)

    Moss, Ellen; Lecompte, Vanessa

    2015-01-01

    In this article, we will evaluate the evidence concerning links between attachment and behavior problems in the middle childhood period. We will first provide a general introduction to the question of attachment and maladaptation in the middle childhood period, and then examine the recent empirical evidence with respect to both externalizing and…

  10. Attachment in Middle Childhood: Progress and Prospects

    Science.gov (United States)

    Bosmans, Guy; Kerns, Kathryn A.

    2015-01-01

    Contrary to the substantial amount of research on infant, preschool, adolescent, and adult attachment, middle childhood has long been neglected by the international attachment research community. In the past two decades, however, there has been a steep increase in research focusing on middle childhood attachment. This article provides an overview…

  11. Middle-class projects in modern Malaysia

    DEFF Research Database (Denmark)

    Fischer, Johan

    2017-01-01

    Within the last two decades or so there has been increased scholarly focus on the emergence, consolidation and future of the middle class in developing Asia. This is also the case with the Malay Muslim middle class in Malaysia, but how this class is developing over time is not well understood even...... if the Malays constitute the largest and fastest growing section of the middle class in Malaysia. Based on research projects I have carried out from the mid-1990s to the present, this article argues that an unpacking of the Malay Muslim middle class over time is important in order to understand the broader...... picture surrounding this class and its relationship to Malaysian national repertoires such as Islamic revivalism, politics, consumer culture, social mobility and the state-market nexus. I understand middle-class projects to be the making of local class culture in Malaysia and explore these in four...

  12. Estonian Middle Semantics with Evidence from Discourse

    Directory of Open Access Journals (Sweden)

    Virve-Anneli Vihman

    2004-01-01

    Full Text Available This paper presents arguments for recognizing a middle voice in Estonian. The claim that the semantics of middle-marked verbs differs in a substantial way from the semantics of other intransitive constructions leads to the examination of the discourse pragmatics of these constructions, and the relationship between discourse patterns and their valency and argument properties. Various topicality measures show that the argument participant in middle clauses lies between that of the sole participant (S in intransitive clauses and the O of active transitive clauses. The results regarding the discourse behaviour of middle arguments constitute new evidence for the view that middle constructions differ from ordinary intransitive verbs, despite structural similarities, and mark a unique range on the scale of transitivity exhibited by verbs in Estonian.

  13. Middle East food safety perspectives.

    Science.gov (United States)

    Idriss, Atef W; El-Habbab, Mohammad S

    2014-08-01

    Food safety and quality assurance are increasingly a major issue with the globalisation of agricultural trade, on the one hand, and intensification of agriculture, on the other. Consumer protection has become a priority in policy-making amongst the large economies of the Middle East and North Africa (MENA) countries following a number of food safety incidents. To enhance food safety, it is necessary to establish markets underpinned by knowledge and resources, including analysis of international rejections of food products from MENA countries, international laboratory accreditation, improved reporting systems and traceability, continued development and validation of analytical methods, and more work on correlating sensory evaluation with analytical results. MENA countries should develop a national strategy for food safety based on a holistic approach that extends from farm-to-fork and involves all the relevant stakeholders. Accordingly, food safety should be a regional programme, raising awareness among policy- and decision-makers of the importance of food safety and quality for consumer protection, food trade and economic development.

  14. Meteorology in the Middle Ages

    Science.gov (United States)

    Ólafsson, H.; Ágústsson, H.

    2009-04-01

    Several documents written in Iceland and Norway in the Middle Ages have been investigated in order to establish to what extent navigators and other educated people in the 10th to 13th centuries knew or did not know about mountain meteorology. In the 10th century, Egils Saga describes flow from land as katabatic. In some textbooks published in the 20th century, similar flows are explained as the inverse of sea-breeze (land-breeze). Numerical simulations of similar flows as in Egils Saga reveal on the other hand, that its author was right about the katabatic nature of the flows. In the documents describing the discovery of Greenland in the late 10th century, Bjarni Herjólfsson navigated erroneously, as he entered the Greenland barrier jet. Apparently, he did not foresee that the foggy southeasterly winds would inevitably turn left as they approached Greenland. A few years later, a ship is wrecked in a windstorm at the coast of W-Iceland. The windstorm is described in detail in Laxdaela Saga and resembles very much a downslope windstorm. Until now, an error in translation into English may have prevented such an interpretation of the windstorm.

  15. [Cochlear implantation through the middle fossa approach].

    Science.gov (United States)

    Szyfter, W; Colletti, V; Pruszewicz, A; Kopeć, T; Szymiec, E; Kawczyński, M; Karlik, M

    2001-01-01

    The inner part of cochlear implant is inserted into inner ear during surgery through mastoid and middle ear. It is a classical method, used in the majority cochlear centers in the world. This is not a suitable method in case of chronic otitis media and middle ear malformation. In these cases Colletti proposed the middle fossa approach and cochlear implant insertion omitting middle ear structures. In patient with bilateral chronic otitis media underwent a few ears operations without obtaining dry postoperative cavity. Cochlear implantation through the middle fossa approach was performed in this patient. The bone fenster was cut, temporal lobe was bent and petrosus pyramid upper surface was exposed. When the superficial petrosal greater nerve, facial nerve and arcuate eminence were localised, the cochlear was open in the basal turn and electrode were inserted. The patient achieves good results in the postoperative speech rehabilitation. It confirmed Colletti tesis that deeper electrode insertion in the cochlear implantation through the middle fossa approach enable use of low and middle frequencies, which are very important in speech understanding.

  16. Imaging of the postoperative middle ear

    Energy Technology Data Exchange (ETDEWEB)

    Williams, Marc T. [Department of Medical Imaging, Fondation Ophtalmologique Adolphe de Rothschild, 25 rue Manin, 75940, Paris (France); Ayache, Denis [Department of Otorhinolaryngology, Fondation Ophtalmologique Adolphe de Rothschild, Paris (France)

    2004-03-01

    The aim of this article is twofold: (a) to present the principles and the indications of surgical treatment of middle ear pathologies; and (b) to review the imaging findings after middle ear surgery, including the normal postoperative aspects and imaging findings in patients presenting with unsatisfactory surgical results or with suspicion of postoperative complications. This review is intentionally restricted to the most common diseases involving the middle ear: chronic otitis media and otosclerosis. In these specific fields of interest, CT and MR imaging play a very important role in the postoperative follow-up and in the work-up of surgical failures and complications. (orig.)

  17. Diagenetic bitumen in Ordovician carbonate reservoirs of the northern Tarim Basin%塔北地区奥陶系碳酸盐岩中的储层沥青

    Institute of Scientific and Technical Information of China (English)

    张鼐; 王招明; 鞠凤萍; 肖中尧; 房启飞; 张宝收; 卢玉红; 余小庆

    2013-01-01

    According to the relationship between the relative intensity of D-peak, G-peak and G-D peak spacing of bitumens and the maturity of bitumen evolution, we deduced that the Dh/Gh ratio and G-D peak spacing are positively proportional to bitumen maturity. Bitumens in Ordovician reservoir in the northern Tarim Basin are thought to have evolved in three stages and the Dh/Gh ratio and G-D peak spacing of Raman measurements on these bitumens indicated that the first-stage bitumen is highly-mature carbonaceous reservoir bitumen, the second-stage one is mature asphaltene reservoir bitumen, and the third-stage one is a combination of overmature oily reservoir bitumen and asphaltene reservoir bitumen. The formation of the first- and second-stage bitumens is attributed to thermal metamorphism, while the co-existence of two different bitumens for the third-stage bitumen is mainly due to selective adsorption of rocks. The distribution and property of these three-stages bitumens in Ordovician reservoirs of the northern Tarim Basin may determine the nature of Ordovician reservoirs, which is characterized by the southern condensate oil later than the northern heavy oil. The observation of oily reservoir bitumen in the northern Halahatang-Yingmaili region can provide evidence and targets for exploring Himalayan condensate oil reservoirs in this area.%利用沥青质拉曼D峰相对强度、G峰相对强度、两峰间距宽窄与沥青演化成熟度关系,推出Dh/Gh和G-D与沥青成熟度成正比关系图.塔北奥陶系储层中发育3期储层沥青,通过3期储层沥青拉曼Dh/Gh和G-D认为:第Ⅰ期为高热成熟炭质储层沥青,第Ⅱ期为成熟沥青质储层沥青,第Ⅲ期为过成熟油质储层沥青和沥青质储层沥青共存.前两期储层沥青是由于热变质而成,第Ⅲ期两种储层沥青共存主要是岩石选择性吸附导致.3期储层沥青的分布及性质决定塔北奥陶系成藏北部老、南部新,北部重质油、南部凝析油的

  18. 中国新疆塔里木盆地上奥陶统良里塔格组的钙藻化石%CALCAREOUS ALGAE FROM THE UPPER ORDOVICIAN LIANGLITAGE FORMATION IN THE TARIM BASIN; XINJIANG; CHINA

    Institute of Scientific and Technical Information of China (English)

    刘丽静; 杨海军; 潘文庆; 吴亚生

    2012-01-01

    Calcareous algae are the algae which can precipitate carbonate to form carbonate skeletons. Calcareous algae first appear in the Cambrian; and had its first major evolutionary radiation in the Ordovician. The primary calcareous algae are green algae and red algae. This paper discusses the classification criterion of families and genera of the Dasycladales and Udotcaceae of Bryopsidales in Chiorophyta and problems existing in the system classification of Sole-noporaceac in Rhodophyta. The marginal carbonate facies of the Upper Ordovician Lianglitagc Formation include two carbonate platforms in the Tarim Basin; the Central-Bachu larim and Northern Tarim; representing the bank and reef facies with abundant calcareous algae fossils. Thus paper describes 15 species belonging to 11 genera of calcareous algae from the Upper Ordovician Lianglitage Formation of the wells in the Central-Bachu Tarim and Northern Tarim platforms. The Dasyrladales components described herein include Dasyporella;Kazakhstanelia; Vermiporella; Aphroporella;Arthroporella;and the Udoteaceae include Dimor phosiphon and Palaeoporella;; Ajakmalajsoria is regarded as a synonym of Kazakhstanelia; The Solenoporaccae described here include Solenopora; Parachaetetes; and also Petrophyton which is Corallinales incertac familiae. The genus Monilipurella has a uncertain position in the red algae or the green algae.%钙藻是可以发生生物钙化作用形成钙质“骨骼”的分属多个门类的藻类的俗称.钙藻最早出现于寒武纪,奥陶纪发生第一次辐射演化.本文系统讨论了绿藻门绒枝藻目(Dasycladalcs)、羽藻目钙扇藻科(Udoteaceae)的科和属级分类标准和红藻门珊瑚藻科、管孔藻科(Solcnoporaccac)属级分类标准及其中各属分类中存在的问题.塔里木盆地晚奥陶世在塔中—巴楚台地和塔北台地发育了一套礁滩相良里塔格组碳酸盐岩,其中含有丰富的钙藻化石.本文系统描述了来自塔里木盆地塔中

  19. Osteomas of the middle ear

    Directory of Open Access Journals (Sweden)

    Sente Marko

    2004-01-01

    Full Text Available INTRODUCTION Osteomas of the middle ear are small, single, usually unilateral, peduncular growths, off-white in color, with smooth or multilobular surface, asymptomatic or causing functional disorders (progressive hearing loss, pathological appearance of the eardrum, vertigo and otorrhea, of unclear or unknown etiology. Fleury described three types of osteomas: massive, diffuse atticoantral and localized type. The therapy is surgical. Small and asymptomatic ones are followed-up. Cremers suggests surgical intervention in cases of progressive growth and increased hearing loss. Case description Discharge and pain in the left ear started twelve years ago, accompanied by impaired hearing and tinnitus. Four months ago the symptoms aggravated and discharge and pain increased. Otomicroscopic findings revealed: perforation in the posterior attic and a prominent polypous, clustered bright red formation. Schüller X-ray showed total absence of pneumocyte cells, with distinct sclerotic changes. Retroauricular access showed a biventricular bony formation in the cavum and partly in the antrum. A cholesteatoma extended from the cavum into the antrum, above the osteatoma. The bony formation was separated transmeatally from the grip in the posterior attic using a chisel, partially removing the bone wall of the exterior aural tube, removing it completely through the mastoid antrum. The removed bony mass, sized 5 x 8 x 8 mm, included also the incus. DISCUSSION Osteoma was discovered accidentally. Regarding clinical features, it belonged to the second group, due to progressive hearing loss, recurrent episodes of otorrhea, pain, biventricular shape and association with cholesteatoma. It was removed using a combined method. It was not possible to establish when the osteoma exactly started generating. It is possible that the initial complaints twelve years ago were the first signs of illness, and chronic otitis may have occurred as a consequence of the tumor.

  20. Return of the Vampire (Middle School).

    Science.gov (United States)

    Johnson-Kuby, Sue Ann; Katz, Claudia Anne

    1996-01-01

    Presents, in the form of a conversation with a vampire, results of a teacher's research on middle school students' reading preferences. Includes a list of favorite books mentioned, favorite authors mentioned, and how students found these favorite books. (SR)

  1. Middle Level Science in a Multicultural Society.

    Science.gov (United States)

    Allen-Sommerville, Lenola

    1994-01-01

    Describes the multifaceted challenge of future and present teachers in a multicultural classroom. Equipped with specific strategies and activities, the author suggests that teachers can become more effective science educators. Provides numerous tips for the middle level science teacher. (ZWH)

  2. Green jobs and a strong middle class.

    Science.gov (United States)

    Podesta, John D

    2009-01-01

    Green jobs are critical to building a strong middle class, and millions of green jobs can be created through energy efficiency. The models already exist for this work, but we need sustained investment to bring them to scale.

  3. Middle ear infection (otitis media) (image)

    Science.gov (United States)

    Otitis media is an inflammation or infection of the middle ear. Acute otitis media (acute ear infection) occurs when there is ... which causes production of fluid or pus. Chronic otitis media occurs when the eustachian tube becomes blocked ...

  4. The Middle School Concept: "An Albatross?"

    Science.gov (United States)

    Gibson, John T.

    1978-01-01

    Differences are shown between the structure and educational philosophy of the middle school and the traditional junior high school. Characteristics of school organization which are sensitive to the needs of preadolescent youth are described. (JD)

  5. Middle-class projects in modern Malaysia

    National Research Council Canada - National Science Library

    Fischer, Johan

    2017-01-01

    .... This is also the case with the Malay Muslim middle class in Malaysia, but how this class is developing over time is not well understood even if the Malays constitute the largest and fastest growing...

  6. Peer Support for Women in Middle Management.

    Science.gov (United States)

    Levine, Sarah L.

    1987-01-01

    A small peer support group for women in middle management positions provides a mechanism for broadening perspectives, generating alternative solutions to managerial problems, and enhancing professional and personal esteem. (MLF)

  7. Middle School PE--Assertiveness Training.

    Science.gov (United States)

    Banks, William H., Jr.; Smith-Fee, Cindy

    1989-01-01

    This article describes a promising approach to the implementation of psycho-social goals in middle school physical education: assertiveness training. Assertiveness is distinguished from aggressiveness, and several assertiveness activities for the curriculum are suggested. (IAH)

  8. Supervision of Curriculum at the Middle Level.

    Science.gov (United States)

    Kienapfel, Bruce

    1984-01-01

    Effective curriculum supervision is essential to a good middle school and curriculum program, and principals can do this job through preparation, curriculum review and development, taking advantage of supervisory opportunities, and curriculum evaluation. (DCS)

  9. 鄂尔多斯盆地吴起-甘泉地区奥陶系古地貌恢复研究%Study on the Palaeogeomorphology Restoration of Ordovician in Wuqi-Ganquan area of Ordos Basin

    Institute of Scientific and Technical Information of China (English)

    吴海燕; 曹红霞; 于珺; 孙建博; 乔向阳; 强娟; 尚婷; 罗腾跃

    2016-01-01

    依据研究区215口探井的钻井、测井资料,运用沉积地质学、古地理学等方法,对鄂尔多斯盆地古隆起东侧吴起—志丹—甘泉地区的奥陶系马家沟组风化壳岩溶古地貌进行恢复。分别选取本溪组顶8号煤层和马家沟组马五41底部的凝灰岩层为作图基准面,综合利用古地质图法、“印模法”和“残厚法”,并结合铝土岩分布数据,对研究区岩溶古地貌进行恢复。同时,根据研究区不整合面上下地层厚度的组合可以划出上薄+下薄型、上薄+下厚(相对)型、上厚+下薄(相对)型等模型,自西向东将研究区岩溶古地貌划分出2个二级古地貌单元(岩溶高地、岩溶斜坡)和3个三级古地貌单元(潜台、残丘、古沟槽)。%On the basis of drilling and logging data from the 215 wells in the study area, and by means of sedimentary geol-ogy and paleogeography methods, the weathering crust karst paleogeomorphology of Ordovician Majiagou formation in wuqi-zhidan-ganquan area, where is at the eastern side of paleo uplift, has been restored in Ordos Basin. Taken the No. 8 coal seam at the top of Benxi formation and the tuff at bottom of Majiagou five 41 formation as the map reference plane, Compre-hensive utilization of the ancient geological map method impression method and residual thickness method, combined with the data of bauxite that distributed in Ordovician. At the same time, the models can be divided into “up thin plus lower thin”, “up thin plus lower thick”, “up thick plus lower thin” according to the thickness of strata unconformity, hereby the karst palaeogeomorphology also divided into two 2-level units, i. e. karst heights and karst slopes, and three 3-level u-nits, i. e. Hidden units, monadnock and trench, order.

  10. The Middle Islamic and Crusader Periods

    DEFF Research Database (Denmark)

    Walmsley, Alan George

    2008-01-01

    The book chapter presents a critical review of the archaeology of Jordan in the middle Islamic periods (8th - 17th centuries CE), presenting a new evaluation of settlement and culture in the period, and assesses the errors of past appraoches.......The book chapter presents a critical review of the archaeology of Jordan in the middle Islamic periods (8th - 17th centuries CE), presenting a new evaluation of settlement and culture in the period, and assesses the errors of past appraoches....

  11. Optical assessment of middle ear inflammation

    OpenAIRE

    Jung, David S.

    2016-01-01

    This thesis describes the development of an optical device to assess the inflammatory state of the middle ear mucosa through the ear canal, after ventilation tube insertion in otitis media with effusion in children. An optical phantom of the middle ear was developed in order to allow repeatable experiments. The phantom consists of eardrum and mucosa while all other structures are neglected. The optical properties of the phantom were determined based on literature review and experiments on...

  12. Partnerships in the Middle East: Interventionist Endeavors?

    DEFF Research Database (Denmark)

    Aarøe Jørgensen, Jakob

    2014-01-01

    This chapter aims to analyse NATO’s two Middle Eastern and North African (MENA)1 partnership programmes – the Mediterranean Dialogue (MD) and the Istanbul Cooperation Initiative (ICI). The chapter aims to answer the questions: (1) why does NATO engage with MENA partners; (2) what are the obstacles...... that MD and ICI face, and; (3) is the new flexible partnership policy a step towards more constructive Middle Eastern partnerships?...

  13. Osteoma of the middle ear: case report

    Energy Technology Data Exchange (ETDEWEB)

    Ryu, Ji Hwa [College of Medicine, Inje University, Dongrae Paik Hospital, Busan (Korea, Republic of)

    2005-07-15

    Osteomas of the middle ear are exceedingly rare benign neoplasms. To date, only 21 cases have been reported in the literature. They arise from the promontory, the pyramidal process and the ossicles, and they are usually asymptomatic or cause some conductive hearing loss. We report here the CT and pathologic findings in a 38-year-old woman with a benign osteoma of the middle ear along with chronic otitis media.

  14. Earth Knowledge Acquired by Middle School Students

    Science.gov (United States)

    Ride, Sally

    2008-01-01

    Earth Knowledge Acquired by Middle School Students (EarthKAM), an education activity, allows middle school students to program a digital camera on board the International Space Station to photograph a variety of geographical targets for study in the classroom. Photos are made available on the web for viewing and study by participating schools around the world. Educators use the images for projects involving Earth Science, geography, physics, and social science.

  15. Avoiding the Middle-Income Trap

    Institute of Scientific and Technical Information of China (English)

    2011-01-01

    The news China surpassed Japan as the world’s second largest economy in 2010 has put China in the limelight. China’s per-capita GDP has reached $4,000, turning the country from a lower middle-income country to an upper middle-income country. But the economic growth model is still extensive and the income gap between the rich and the poor is widening.

  16. Rise of the Middle Class in China

    OpenAIRE

    Khasyanova, Adelya

    2007-01-01

    With the fast expansion of Chinese economy, it is possible to observe more than the once obvious change. With regards to consumption, China is becoming a significant player on the world market economy. Some critics have argues that a result of the 1978 changes introduced by Deng Xiaoping has been the rise of the middle class in China, previously only barely existent and practically wiped in the 1960s during the Cultural Revolution. However, whilst China's middle class is still relatively smal...

  17. 21 CFR 874.3430 - Middle ear mold.

    Science.gov (United States)

    2010-04-01

    ... 21 Food and Drugs 8 2010-04-01 2010-04-01 false Middle ear mold. 874.3430 Section 874.3430 Food... DEVICES EAR, NOSE, AND THROAT DEVICES Prosthetic Devices § 874.3430 Middle ear mold. (a) Identification. A middle ear mold is a preformed device that is intended to be implanted to reconstruct the middle...

  18. 7 CFR 28.415 - Low Middling Light Spotted Color.

    Science.gov (United States)

    2010-01-01

    ... 7 Agriculture 2 2010-01-01 2010-01-01 false Low Middling Light Spotted Color. 28.415 Section 28... Spotted Color. Low Middling Light Spotted Color is color which in spot or color, or both, is between Low Middling Color and Low Middling Spotted Color....

  19. 7 CFR 28.412 - Strict Middling Light Spotted Color.

    Science.gov (United States)

    2010-01-01

    ... 7 Agriculture 2 2010-01-01 2010-01-01 false Strict Middling Light Spotted Color. 28.412 Section 28... Light Spotted Color. Strict Middling Light Spotted Color is color which in spot or color, or both, is between Strict Middling Color and Strict Middling Spotted Color....

  20. 7 CFR 28.413 - Middling Light Spotted Color.

    Science.gov (United States)

    2010-01-01

    ... 7 Agriculture 2 2010-01-01 2010-01-01 false Middling Light Spotted Color. 28.413 Section 28.413... Spotted Color. Middling Light Spotted Color is color which in spot or color, or both, is between Middling Color and Middling Spotted Color....

  1. 7 CFR 28.411 - Good Middling Light Spotted Color.

    Science.gov (United States)

    2010-01-01

    ... 7 Agriculture 2 2010-01-01 2010-01-01 false Good Middling Light Spotted Color. 28.411 Section 28... Light Spotted Color. Good Middling Light Spotted Color is color which in spot or color, or both, is between Good Middling Color and Good Middling Spotted Color....

  2. 7 CFR 28.441 - Strict Middling Yellow Stained Color.

    Science.gov (United States)

    2010-01-01

    ... 7 Agriculture 2 2010-01-01 2010-01-01 false Strict Middling Yellow Stained Color. 28.441 Section... Strict Middling Yellow Stained Color. Strict Middling Yellow Stained Color is color which is deeper than that of Strict Middling Tinged Color....

  3. Classics Reconsidered: Tolstoy in the Middle School Classroom.

    Science.gov (United States)

    Kazemek, Francis E.

    1998-01-01

    Argues that classic authors can and should still be kept at the center of the literature curricula in the middle school. Uses Leo Tolstoy as an example, describing briefly some of Tolstoy's works that are especially appropriate for early middle school readers, later middle schoolers of average reading ability, and the most able middle school…

  4. REVISION OF THE ORDOVICIAN WUBINAOBAO FORMATION IN HONGGOR AREA, INNER MONGOLIA%内蒙古红格尔苏木地区奥陶系乌宾敖包组重新厘定

    Institute of Scientific and Technical Information of China (English)

    宝音乌力吉; 贺宏云; 宋华; 鞠文信; 韩宗庆

    2011-01-01

    During the 1:50000 regional geological survey in Honggor area on the north of Erenhot, Inner Mongolia, near the border between China and Mongolia, the Ordovician Wubinaobao formation is redefined on the basis of rock association, paleontological characteristics, depositional environment, etc. The revised Wubinaobao formation includes a set of layers of slate and siltstone with intercalations of thin limestone lenticules, containing fossils of Trilobita, Brachiopoda, etc. The strata are characterized by neritic shelf sedimentation. This redefinition is significant for the ore-prospecting in this area from now on.%2008年在内蒙古二连浩特北红格尔苏木中蒙边境一带开展1∶5万区调时,根据岩石组合、古生物特征、沉积环境等,对建组于该地区的奥陶系乌宾敖包组进行了重新厘定.重新厘定后的乌宾敖包组为原乌宾敖包组中含三叶虫、腕足等化石的一套板岩、粉砂岩夹薄层灰岩透镜体等,具浅海陆棚沉积特征的地层.该地层的重新厘定对本区开展找矿工作有指导意义.

  5. Parenting Practices and Tobacco Use in Middle School Students in Low- and Middle-Income Countries

    Science.gov (United States)

    Poms, Laura W.; Fleming, Lila C.; Jacobsen, Kathryn H.

    2012-01-01

    Background: Parenting practices have been shown to have a strong influence on adolescent tobacco use in high-income countries. This study examined whether parenting practices also were associated with tobacco use by middle school students (approximately ages 13-15) in low- and middle-income countries. Methods: A secondary analysis was performed on…

  6. Middle- and Upper-Middle-Class Parent Action for Urban Public Schools: Promise or Paradox?

    Science.gov (United States)

    Posey, Linn

    2012-01-01

    Background/Context: Recent trends suggest that middle-class parents may be a growing constituency in urban public schools and districts. Within the burgeoning literature on the middle class in urban public schools, most scholars have focused on parents' goals and orientations and/or the consequences of parental involvement in classroom and school…

  7. Talking about consumption. How an Indian middle class dissociates from middle-Class life

    NARCIS (Netherlands)

    Wessel, van M.G.J.

    2004-01-01

    Members of the middle class in the Indian city of Baroda employ a common moral discourse on consumption, one that is shaped through the operationalization of historically rooted ideals of community, family solidarity and asceticism. These ideals are set against the experience of urban middle-class

  8. Subjective Meanings and Identification With Middle Age.

    Science.gov (United States)

    Dolberg, Pnina; Ayalon, Liat

    2017-01-01

    The "middle-age" life period has not been researched extensively and lacks a theoretical conceptualization. The present study explores subjective experiences of members of this age-group. This is a qualitative research, based on in-depth interviews and thematic analysis, which looks into the life stories of 25 Israeli residents aged 48-64 years. The results indicate that the definition of middle age is not clear-cut, and some participants regard their age negatively. Yet, participants report that this period is characterized by a relief of tasks, broader choice opportunity, a sense of liberation, peace of mind, experience, self-awareness, and self-acceptance. Description of middle age as a peak in life, with concerns about future old age, came up repeatedly. Middle-aged individuals' difficulties to identify with their age-group and the social concept that dichotomizes age into young versus old are discussed. The article calls for further research of and engagement with middle age.

  9. A Primer of Middle Eastern Leadership Culture

    Directory of Open Access Journals (Sweden)

    Sheldon Greaves

    2012-01-01

    Full Text Available It is natural for someone looking in on a foreign culture from the outside to interpret what they see and frame their reactions based on their own background and assumptions. With cultures as a different as those of the Middle East and the West, the potential for blunders increases dramatically, made worse by the high political, diplomatic, military, and commercial stakes involved. Leadership culture in this region has been shaped over centuries through a variety of factors, such as reputation, family, and religion, which continue to influence decision making. The present study posits that an understanding of these factors and how they work is crucial for intelligence analysts, policy and decision makers, strategists, and scholars who must find their way through a very unfamiliar cultural landscape in the Middle East. It is hoped that this discussion will in some way assist in the creation of more effective interaction, policies, and analysis associated with the Middle East.

  10. Spatial segmentation and the black middle class.

    Science.gov (United States)

    Sharkey, Patrick

    2014-01-01

    Ethnographic studies of the black middle class focus attention on the ways in which residential environments condition the experiences of different segments of the black class structure. This study places these arguments in a larger demographic context by providing a national analysis of neighborhood inequality and spatial inequality of different racial and ethnic groups in urban America. The findings show that there has been no change over time in the degree to which majority-black neighborhoods are surrounded by spatial disadvantage. Predominantly black neighborhoods, regardless of socioeconomic composition, continue to be spatially linked with areas of severe disadvantage. However, there has been substantial change in the degree to which middle- and upper-income African-American households have separated themselves from highly disadvantaged neighborhoods. These changes are driven primarily by the growing segment of middle- and upper-income African-Americans living in neighborhoods in which they are not the majority group, both in central cities and in suburbs.

  11. Middle Class and Democracy in Latin America

    Directory of Open Access Journals (Sweden)

    Jaime Fierro

    2015-06-01

    Full Text Available The consolidation of the middle class has been interpreted by modernization and postmodernization theories as a key factor for the functioning and stability of the democratic system. However, in Latin America the middle class has tended to be associated with two contradictory positions. On the one hand, it is emphasized that it plays a stabilizing and democratic role while, on the other hand, it is linked to supporting military coups. With the purpose of elucidate such a dilemma, the relationship that can be established between the socioeconomic status and the degree of support for democracy will be examined. In order to do this, an empirical analysis from Latinbarometer surveys databases will be conducted, covering seventeen countries in the region for the period from 1996 to 2011. It will be concluded that the middle class in Latin America does not have particularly more favorable attitudes toward democracy than other social segments.

  12. [Bone Conduction and Active Middle Ear Implants].

    Science.gov (United States)

    Volkenstein, S; Thomas, J P; Dazert, S

    2016-05-01

    The majority of patients with moderate to severe hearing loss can be supplied with conventional hearing aids depending on severity and cause for hearing loss in a satisfying way. However, some patients either do not benefit enough from conventional hearing aids or cannot wear them due to inflammatory reactions and chronic infections of the external auditory canal or due to anatomical reasons. For these patients there are fully- and semi-implantable middle ear and bone conduction implants available. These devices either directly stimulate the skull (bone conduction devices), middle ear structures (active middle ear implants) or the cochlea itself (direct acoustic stimulation). Patients who failed surgical hearing rehabilitation or do not benefit from conventional hearing aids may achieve a significant better speech understanding and tremendous improvement in quality of life by implantable hearing devices with careful attention to the audiological and anatomical indication criteria.

  13. An Accelerator control middle layer using Matlab

    CERN Document Server

    Portmann, G J; Terebilo, Andrei

    2005-01-01

    Matlab is a matrix manipulation language originally developed to be a convenient language for using the LINPACK and EISPACK libraries. What makes Matlab so appealing for accelerator physics is the combination of a matrix oriented programming language, an active workspace for system variables, powerful graphics capability, built-in math libraries, and platform independence. A number of software toolboxes for accelerators have been written in Matlab – the Accelerator Toolbox (AT) for machine simulations, LOCO for accelerator calibration, Matlab Channel Access Toolbox (MCA) for EPICS connections, and the Middle Layer. This paper will describe the MiddleLayer software toolbox that resides between the high-level control applications and the low-level accelerator control system. This software was a collaborative effort between ALS and Spear but was written to easily port. Five accelerators presently use this software – Spear, ALS, CLS, and the X-ray and VUV rings at Brookhaven. The Middle Layer fu...

  14. Armageddon, oil, and the Middle East crisis

    Energy Technology Data Exchange (ETDEWEB)

    Walvoord, J.F.; Walvoord, J.E.

    1980-01-01

    This book relates the intricate subject of biblical prophecy to the current crisis in the Middle East. With the development of oil politics, Dr. Walvoord believes a new world government will emerge, centered in the Middle East, which will eclipse the United States and Russia as world powers. The world government will be subjected to catastrophic, divine judgments which precipitate a gigantic world war culminating in Armageddon. Each chapter is devoted to the scriptural explanations of events leading to the second coming of Christ. The result is a prophetic calendar summing up to the countdown to Armageddon. Some of the chapter titles include: the Arab oil blackmail; watch Jerusalen; the rising tide of world religion; the coming Middle East peace; the coming world dictator; and Armageddon: the world's death struggle.

  15. Carcinoid tumour of the middle ear

    LENUS (Irish Health Repository)

    Baig, Salman

    2012-09-01

    A case of middle ear mass in a young female from Ireland is described, who presented with left ear hearing loss and intermittent bloody discharge from the same ear. Examination under microscope revealed occlusive polyp in the left ear and a biopsy had been taken under general anaesthesia. Histopathology report described an adenoma \\/ carcinoid tumour of the middle ear confirmed by positive immunohistochemical staining. CT temporal bones revealed the extension of the disease. The patient underwent left tympanotomy and excision of the tumour. In general, these tumours are regarded as benign but may be mistaken for adenocarcinomas because of their histological heterogenecity.

  16. LINGUISTICS AND THE MIDDLE SCHOOL TEACHER

    Institute of Scientific and Technical Information of China (English)

    1996-01-01

    IntroductionDuring the three years of Senior Middle School Teacher Training at Southwest China TeachersUniversity.experiments and experience have shown that it is crucial for middle school English teachers tohave more proper and more effective principles that underpin language teaching activities.As Stern(1983)puts it,teachers need:‘Some criteria characterizing a good language teaching theory:usefulness and applicability;explicitness;coherence and consistency;comprehensiveness;explanatory power and verifiability;simplicity and clarity.’But what can be done to obtain these qualitiesThrough these years of experiments,we have found thatlinguistically-guided language teaching is more effective.

  17. Education Quality in the Middle East

    Science.gov (United States)

    Chapman, David W.; Miric, Suzanne L.

    2009-07-01

    Some of the most dramatic growth in the provision of primary and secondary education over the last decade has occurred across countries of the Middle East and North Africa (MENA). Yet student achievement across MENA is lagging compared to many other parts of the world. Low quality of education is a primary concern and one of the greatest challenges facing education and government leaders across the region. This paper summarises recent evidence regarding student learning in the MENA region and draws on Galal's model of policy formulation in considering ways that governments across the Middle East might address this problem.

  18. Law and Learning in the Middle Ages

    DEFF Research Database (Denmark)

    This volume contains papers presented at the conference on "Law and Learning in the Middle Ages" held at the Carlsberg Academy in Copenhagen in May 2005. Here, a group of European and American scholars give their contribution to the examination of the theological and legal schooling that the 'cre......This volume contains papers presented at the conference on "Law and Learning in the Middle Ages" held at the Carlsberg Academy in Copenhagen in May 2005. Here, a group of European and American scholars give their contribution to the examination of the theological and legal schooling...

  19. Study protocol: a multi-professional team intervention of physical activity referrals in primary care patients with cardiovascular risk factors—the Dalby lifestyle intervention cohort (DALICO study

    Directory of Open Access Journals (Sweden)

    Stenman Emelie

    2012-06-01

    Full Text Available Abstract Background The present study protocol describes the trial design of a primary care intervention cohort study, which examines whether an extended, multi-professional physical activity referral (PAR intervention is more effective in enhancing and maintaining self-reported physical activity than physical activity prescription in usual care. The study targets patients with newly diagnosed hypertension and/or type 2 diabetes. Secondary outcomes include: need of pharmacological therapy; blood pressure/plasma glucose; physical fitness and anthropometric variables; mental health; health related quality of life; and cost-effectiveness. Methods/Design The study is designed as a long-term intervention. Three primary care centres are involved in the study, each constituting one of three treatment groups: 1 Intervention group (IG: multi-professional team intervention with PAR, 2 Control group A (CA: physical activity prescription in usual care and 3 Control group B: treatment as usual (retrospective data collection. The intervention is based on self-determination theory and follows the principles of motivational interviewing. The primary outcome, physical activity, is measured with the International Physical Activity Questionnaire (IPAQ and expressed as metabolic equivalent of task (MET-minutes per week. Physical fitness is estimated with the 6-minute walk test in IG only. Variables such as health behaviours; health-related quality of life; motivation to change; mental health; demographics and socioeconomic characteristics are assessed with an electronic study questionnaire that submits all data to a patient database, which automatically provides feed-back to the health-care providers on the patients’ health status. Cost-effectiveness of the intervention is evaluated continuously and the intermediate outcomes of the intervention are extrapolated by economic modelling. Discussions By helping patients to overcome practical, social and cultural obstacles and increase their internal motivation for physical activity we aim to improve their physical health in a long-term perspective. The targeted patients belong to a patient category that is supposed to benefit from increased physical activity in terms of improved physiological values, mental status and quality of life, decreased risk of complications and maybe a decreased need of medication.

  20. Structure and function of the mammalian middle ear. I: Large middle ears in small desert mammals.

    Science.gov (United States)

    Mason, Matthew J

    2016-02-01

    Many species of small desert mammals are known to have expanded auditory bullae. The ears of gerbils and heteromyids have been well described, but much less is known about the middle ear anatomy of other desert mammals. In this study, the middle ears of three gerbils (Meriones, Desmodillus and Gerbillurus), two jerboas (Jaculus) and two sengis (elephant-shrews: Macroscelides and Elephantulus) were examined and compared, using micro-computed tomography and light microscopy. Middle ear cavity expansion has occurred in members of all three groups, apparently in association with an essentially 'freely mobile' ossicular morphology and the development of bony tubes for the middle ear arteries. Cavity expansion can occur in different ways, resulting in different subcavity patterns even between different species of gerbils. Having enlarged middle ear cavities aids low-frequency audition, and several adaptive advantages of low-frequency hearing to small desert mammals have been proposed. However, while Macroscelides was found here to have middle ear cavities so large that together they exceed brain volume, the bullae of Elephantulus are considerably smaller. Why middle ear cavities are enlarged in some desert species but not others remains unclear, but it may relate to microhabitat.

  1. Biotechnology in the Middle School Curriculum

    Science.gov (United States)

    Campbell, De Ann

    2007-01-01

    Biotechnology is a fairly new concept for middle school students as well as teachers. If the latest craze of TV shows focused on crime scene investigation events were not so popular, the term and concept might be even obscure to the public. There is an increased presence of biotechnology in our daily surroundings that makes it practical and…

  2. Outreach for the Middle Class Drug Misuser

    Science.gov (United States)

    Stauss, Fred F.; And Others

    1978-01-01

    Clients enrolled in drug programs tend to be young, counter-culture, or ethnic minority individuals. Describes efforts of a non-opiate drug treatment program to reach middle American drug misusers. Attempts included television public service messages and newspaper articles. This campaign was not cost-effective for attracting clients. (Author)

  3. Caught in the Middle: The Tracking Dilemma.

    Science.gov (United States)

    Stevens, Robert L.

    1992-01-01

    Middle-level educators can meet all students' needs by grouping students for appropriate instruction, rotating teachers, encouraging student-centered teaching, setting high academic expectations, developing advisory programs and activity groups, and scheduling heterogeneous classes where appropriate. Educators should not sacrifice balance and…

  4. Middle School Student Records as Dropout Indicators

    Science.gov (United States)

    Gregg, William Sherman

    2010-01-01

    Dropping out of school is associated with a wide array of negative outcomes and the extraordinarily high United States dropout rate has brought the issue to the forefront of American education. This study investigated normally collected middle school data from a suburban Colorado school district to determine the predictive value toward students…

  5. Opposites Detract: Middle School Peer Group Antipathies

    Science.gov (United States)

    Laursen, Brett; Bukowski, William M.; Nurmi, Jari-Eri; Marion, Donna; Salmela-Aro, Katariina; Kiuru, Noona

    2010-01-01

    This study examines variability in patterns of peer group antipathy. Same-grade adolescent peer groups were identified from sociometric nominations of preferred affiliates in a community sample of 600 Finnish ninth-grade middle school students (mean age = 15.0 years). Hierarchical linear modeling determined characteristics of youths in actor…

  6. Early Predictors of Middle School Fraction Knowledge

    Science.gov (United States)

    Bailey, Drew H.; Siegler, Robert S.; Geary, David C.

    2014-01-01

    Recent findings that earlier fraction knowledge predicts later mathematics achievement raise the question of what predicts later fraction knowledge. Analyses of longitudinal data indicated that whole number magnitude knowledge in first grade predicted knowledge of fraction magnitudes in middle school, controlling for whole number arithmetic…

  7. Friend Influence on Achievement during Middle Childhood

    Science.gov (United States)

    DeLay, Dawn

    2013-01-01

    This study was designed to investigate friend influence on academic achievement and task avoidance during middle childhood in a sample of 794 participants in 397 stable same-sex friendship dyads (205 girl dyads and 192 boy dyads) from four municipalities in Finland: two in Central Finland, one in Western Finland, and one in Eastern Finland.…

  8. Passive and active middle ear implants

    Directory of Open Access Journals (Sweden)

    Beutner, Dirk

    2009-01-01

    Full Text Available Besides eradication of chronic middle ear disease, the reconstruction of the sound conduction apparatus is a major goal of modern ear microsurgery. The material of choice in cases of partial ossicular replacement prosthesis is the autogenous ossicle. In the event of more extensive destruction of the ossicular chain diverse alloplastic materials, e.g. metals, ceramics, plastics or composits are used for total reconstruction. Their specialised role in conducting sound energy within a half-open implant bed sets high demands on the biocompatibility as well as the acoustic-mechanic properties of the prosthesis. Recently, sophisticated titanium middle ear implants allowing individual adaptation to anatomical variations are widely used for this procedure. However, despite modern developments, hearing restoration with passive implants often faces its limitations due to tubal-middle-ear dysfunction. Here, implantable hearing aids, successfully used in cases of sensorineural hearing loss, offer a promising alternative. This article reviews the actual state of affairs of passive and active middle ear implants.

  9. Middle School Girls' Envisioned Future in Computing

    Science.gov (United States)

    Friend, Michelle

    2015-01-01

    Experience is necessary but not sufficient to cause girls to envision a future career in computing. This study investigated the experiences and attitudes of girls who had taken three years of mandatory computer science classes in an all-girls setting in middle school, measured at the end of eighth grade. The one third of participants who were open…

  10. Ultra Physical Education in Middle Schools.

    Science.gov (United States)

    Kirkpatrick, Beth

    1987-01-01

    The physical education program at Tilford Middle School (Vinton, IA) emphasizes the development of each student's self-concept through the avenues of mental development, skill awareness and improvement, emotional and social development, and health development. The program is described. (MT)

  11. Law and Learning in the Middle Ages

    DEFF Research Database (Denmark)

    This volume contains papers presented at the conference on "Law and Learning in the Middle Ages" held at the Carlsberg Academy in Copenhagen in May 2005. Here, a group of European and American scholars give their contribution to the examination of the theological and legal schooling...

  12. Middle School Girls' Envisioned Future in Computing

    Science.gov (United States)

    Friend, Michelle

    2015-01-01

    Experience is necessary but not sufficient to cause girls to envision a future career in computing. This study investigated the experiences and attitudes of girls who had taken three years of mandatory computer science classes in an all-girls setting in middle school, measured at the end of eighth grade. The one third of participants who were open…

  13. Systems Thinking among School Middle Leaders

    Science.gov (United States)

    Shaked, Haim; Schechter, Chen

    2017-01-01

    Systems thinking is a holistic approach that puts the study of wholes before that of parts. This study explores systems thinking among school middle leaders--teachers who have management responsibility for a team of teachers or for an aspect of the school's work. Interviews were held with 93 school coordinators, among them year heads, heads of…

  14. Developing Study Guides for Middle School Learners

    Science.gov (United States)

    Conderman, Greg

    2017-01-01

    Study guides are a popular tool teachers provide to help students prepare for an upcoming test or quiz. They are especially appropriate for middle school students as they transition from reading narrative to informational text. However, some teachers are unfamiliar with various types of study guides. Therefore, this article describes various types…

  15. More Middle-Class Families Choose Charters

    Science.gov (United States)

    Whitmire, Richard

    2015-01-01

    The rise in middle-class students attending charter schools is largely masked by the overall growth of charter schools: over the last five years, the number of charter schools has grown nationally from 4,690 to just over 6,000. There are now 43 communities where at least 20 percent of the students attend charters, reports the National Alliance for…

  16. Middle Level Leadership... and All That Jazz!

    Science.gov (United States)

    Kinney, Patti; Tomlin, Dru

    2013-01-01

    Much like a Jazz group, successful middle level schools are also founded on elements of improvisation, collaboration, teamwork, and responsive communication. Just as the director of the jazz group must have a solid foundation of music theory, the skills to bring out the best in the players, and an attitude that allows others to shine, those who…

  17. Quality Middle Schools: Open and Healthy.

    Science.gov (United States)

    Hoy, Wayne K.; Sabo, Dennis J.

    This book offers hands-on suggestions for administrators who want to assess their schools' health. The goal is to improve middle schools by making sure the culture is right for all groups--students, teachers, and staff. Chapter 1, "Climate, Culture, and Quality," distinguishes between the concepts of organizational culture and climate, formulates…

  18. Opposites Detract: Middle School Peer Group Antipathies

    Science.gov (United States)

    Laursen, Brett; Bukowski, William M.; Nurmi, Jari-Eri; Marion, Donna; Salmela-Aro, Katariina; Kiuru, Noona

    2010-01-01

    This study examines variability in patterns of peer group antipathy. Same-grade adolescent peer groups were identified from sociometric nominations of preferred affiliates in a community sample of 600 Finnish ninth-grade middle school students (mean age = 15.0 years). Hierarchical linear modeling determined characteristics of youths in actor…

  19. Middle School, One-to-One

    Science.gov (United States)

    Weber, Eric G.

    2009-01-01

    Westside Middle School, located in Omaha, Nebraska, serves 950 seventh- and eighth-grade students. Over the last few years, the school's teachers and administrators have evaluated its technology status and needs. As part of this process, the staff members engaged in many activities, including developing a building-level technology plan, organizing…

  20. Curriculum Reviews: Middle/Junior High Science.

    Science.gov (United States)

    Faller, Richard

    1982-01-01

    Reviews "Pathways in Science" (Globe Book Company), designed as a complete middle/junior high school science program. Strengths (including sixth-grade readability) and weaknesses (indicating that limited process skill development may not challenge more capable students). Limited process skill development and the possibility for the program…

  1. Bullying in Middle Schools: Prevention and Intervention

    Science.gov (United States)

    Milsom, Amy; Gallo, Laura L.

    2006-01-01

    A main characteristic of a bully is his or her need to gain control over another. Bullies can gain control over others through physical force or threats, verbal teasing, and exclusion from peers. This article talks about bullying in United States middle schools, and prevention and intervention strategies for bullying. In this article, the authors…

  2. Classification Criteria in Middle and Old Age

    Science.gov (United States)

    Denney, Nancy Wadsworth

    1974-01-01

    Discusses two experiments in which middle-aged, elderly, professional, and non-professional males and females were given the Conceptual Styles Test. An analysis of variance on the percentage of complementary responses revealed significant effects for age, occupation, and th interaction between age and sex. (ED)

  3. Middle Level Leadership... and All That Jazz!

    Science.gov (United States)

    Kinney, Patti; Tomlin, Dru

    2013-01-01

    Much like a Jazz group, successful middle level schools are also founded on elements of improvisation, collaboration, teamwork, and responsive communication. Just as the director of the jazz group must have a solid foundation of music theory, the skills to bring out the best in the players, and an attitude that allows others to shine, those who…

  4. Middle America: Intra- and Interregional Connections.

    Science.gov (United States)

    Smith, Ben A.; And Others

    1988-01-01

    This is the third of a three-part series of articles examining the five geographical themes suggested in "Guidelines for Geographic Education: Elementary and Secondary Schools." Using Middle America (Mexico, Central American and the Caribbean) as a case study, this article addresses the themes of region and movement to show how the…

  5. Best Practice in Middle-School Science

    Science.gov (United States)

    Oliveira, Alandeom W.; Wilcox, Kristen C.; Angelis, Janet; Applebee, Arthur N.; Amodeo, Vincent; Snyder, Michele A.

    2013-01-01

    Using socio-ecological theory, this study explores best practice (educational practices correlated with higher student performance) in middle-school science. Seven schools with consistently higher student performance were compared with three demographically similar, average-performing schools. Best practice included instructional approaches…

  6. Theme: Junior High and Middle School Programs.

    Science.gov (United States)

    Hillison, John; And Others

    1994-01-01

    On the topic of agricultural education programs in middle/junior high schools, nine articles address developing self-concept, selecting materials, the benefits of agriscience contests, adopting new curricula, the role of Future Farmers of America in the development of adolescents, teaming science and agriculture, and the rationale for middle…

  7. Approval of Spouse in Middle Age.

    Science.gov (United States)

    Troll, Lillian E.

    A strongly positive opinion of spouse in middle age tends to be associated with social conformity and family integration. Mutually approving couples were more often politically moderate, homogamous in religious background, and had more interpersonal power than their children. They also had more highly integrated family structures with low conflict…

  8. Art Teaching: Elementary through Middle School

    Science.gov (United States)

    Szekely, George; Bucknam, Julie Alsip

    2011-01-01

    "Art Teaching" speaks to a new generation of art teachers in a changing society and fresh art world. Comprehensive and up-to-date, it presents fundamental theories, principles, creative approaches, and resources for art teaching in elementary through middle-school. Key sections focus on how children make art, why they make art, the unique…

  9. pragmatic failure in middle school english teaching

    Institute of Scientific and Technical Information of China (English)

    李娟

    2011-01-01

    as a study and research subject,pragmatics investigates the language using and language comprehension in the specific context.after more than twenty years,people have made great progress in it.but because the english learners do not know the social and cultural background of english countries well and cannot comprehend and use english combining together the context.so sometimes they make pragmatic failure when they study or communicate with others.the author finds that the pragmatic failure exists among nearly all the middle school students.while giving an account of pragmatic failures in middle school english teaching,the paper not only classifies the definition of pragmatic failure,but also provides the categories of pragmatic failure,the influence,displaying and causes of pragmatic failure in middle school english teaching.and the author gives the idea that in order to avoid the pragmatic failure during the middle school english teaching; people should cultivate and strengthen the social cultural consciousness.

  10. Best Practice in Middle-School Science

    Science.gov (United States)

    Oliveira, Alandeom W.; Wilcox, Kristen C.; Angelis, Janet; Applebee, Arthur N.; Amodeo, Vincent; Snyder, Michele A.

    2013-01-01

    Using socio-ecological theory, this study explores best practice (educational practices correlated with higher student performance) in middle-school science. Seven schools with consistently higher student performance were compared with three demographically similar, average-performing schools. Best practice included instructional approaches…

  11. Productive Struggle in Middle School Mathematics Classrooms

    Science.gov (United States)

    Warshauer, Hiroko Kawaguchi

    2015-01-01

    Prior studies suggest that struggling to make sense of mathematics is a necessary component of learning mathematics with understanding. Little research exists, however, on what the struggles look like for middle school students and how they can be productive. This exploratory case study, which used episodes as units of analysis, examined 186…

  12. A True Middle School Physical Education Program

    Science.gov (United States)

    Tenoschok, Mike

    2016-01-01

    The purpose of this article is to describe the various ways in which the developmental needs of middle school students can be met in a physical education program. The themes of exploration and individualization appear throughout the article to emphasize the importance of providing a variety of sports, games and physical activity options for middle…

  13. Five bid to host Middle East synchroton

    CERN Multimedia

    McCabe, H

    1999-01-01

    Germany is willing to donate a synchrotron to a research centre to be built somewhere in the Middle East. Bids to host the centre were submitted by Turkey, Cyprus, Iran, the Palestinian Authority and Egypt. Funding of at least 30 million US dollars still needs to be found (1 page).

  14. Job Attitudes of Agricultural Middle Managers

    OpenAIRE

    2006-01-01

    The paper analyzes middle managers' job attitudes, in particular job satisfaction, based on case studies. Employees' job satisfaction is expected to reduce human resource management risks, leading to higher loyalty, organizational commitment and motivation and resulting in less turnover. Components of job satisfaction include achievement, recognition, work itself, job security, supervision, interpersonal relationships, compensation, organization, personal life and working conditions. They cau...

  15. Efusiones subácueas del arco volcánico ordovícico en el norte del sistema de Famatina Subaqueous eruptions in the Ordovician volcanic arc in the northern Famatina System

    Directory of Open Access Journals (Sweden)

    Clara Eugenia Cisterna

    2010-03-01

    Full Text Available La sucesión volcánica - sedimentaria analizada, ubicada entre los 27°47`00" - 27°49`18" S y 68°04`52" - 68°02`27" O en la sierra de Las Planchadas, norte del Sistema de Famatina, registra la evolución de un arco volcánico ordovícico. Sus representantes volcánicos mayoritarios, lavas basálticas y en menor medida dacíticas, fragmentadas, autoclásticas e hialoclastitas indican el predominio de un volcanismo efusivo subácueo. Mientras tanto el elevado volumen de depósitos volcaniclásticos asociados, especialmente en los tramos superiores, generados por flujos gravitacionales en masa, ya sea por corrientes de turbidez, como por flujos de detritos y vinculados con episodios de sedimentación sin-volcánicos, evidencian la eficiencia de los procesos de fragmentación y de la erosión recurrente durante la evolución de esta cuenca ordovícica. El contenido fosilífero en las facies volcanogénicas y las asociaciones de limolitas, fangolitas y psamitas finas con abundante material de origen piroclástico y lapilli acrecional, atestiguan en favor de un ambiente somero para su depositación. Las características de los depósitos volcanogénicos, su proveniencia prácticamente única, la variación de sus facies, junto a las características geoquímicas de sus representantes magmáticos apoyan la idea para la región de un volcanismo de arco ligado a la evolución de la cuenca, mientras tenía lugar un intermitente aporte de sedimentos intracuencales, debidos a la inestabilidad de la misma.The volcanic - sedimentary sequence studied, exposed along the 27°47`00" - 27°49`18" S and 68°04`52" - 68°02`27" Win the sierra de Las Planchadas, northern Famatina System, records the evolution of an Ordovician volcanic arc. The main volcanic members are basaltic and dacitic lavas and significant volumes of lava-derived clastic aggregates that are produced by quench fragmentation and gravitational collapse. Fragmented lavas, autobreccias and

  16. Petrologic,geochemical characteristics and origin of the Lower Ordovician dolomite in Yubei area%玉北地区下奥陶统白云岩岩石学、地球化学特征及成因

    Institute of Scientific and Technical Information of China (English)

    黄擎宇; 张哨楠; 叶宁; 李映涛

    2014-01-01

    The petrologic ,geochemical characteristics and origin of the Lower Ordovician dolomite in Yubei area were inves -tigated through the analysis of the cores ,thin-sections,SEM,cathode luminescence ,trace element ,C-O isotope and micro-thermometry of fluid inclusions .The following results were obtained .Matrix dolomites are of two types:fine crystalline ,euhe-dral-subhedral dolomite and fine to coarse crystalline ,anhedral dolomite with saddle fillings .The origin of dolomite is close-ly related to crystal texture ( nonplanar anhedral ,planar euhedral/subhedral ) instead of crystal size .The fine crystalline ,eu-hedral-subhedral dolomite has high Sr and low Fe-Mn content ,and C and O isotope composition similar to that of seawater in Early Ordovician .So this type of dolomite was overall the product of low-temperature dolomitization associated with the Ordovician seawater during the early stage of shallow burial .In contrast ,the fine to coarse crystalline ,anhedral dolomite has low Sr,relatively high Fe and Mn content and more negative O isotope value .And its fluid inclusion microthermometry re-sult suggests that it has high homogenization temperature and salinity .Combined with the regional tectonic background ,it is believed that this type of dolomite was primarily the product of high -temperature dolomitization during late stage of shallow burial to moderate burial ,and was locally transformed by hydrothermal fluids from marine-sourced saline water in formation . Moreover ,there are two stages of saddle dolomite fillings:one is coeval with the matrix dolomite of hydrothermal dolomitiza-tion origin and the other may be associated with the thermal fluid post -magmatic activity during the Permian .%通过岩心、薄片、扫描电镜、阴极发光、微量元素、同位素和包裹体测温等分析手段,对玉北地区下奥陶统白云岩岩石学特征、地球化学特征及成因进行研究。结果表明,该区白云岩主要由细晶、自形-半

  17. There and Back Again: A Middle Scholar's Inquiry Excursion (Middle School).

    Science.gov (United States)

    Katz, Claudia Anne; Johnson-Kuby, Sue Ann

    1996-01-01

    Describes an inquiry project that middle school students complete during the first quarter of the year, and that serves as a foundation for future inquiry undertakings, research papers, and writing workshops. (SR)

  18. Prenatal evaluation of the middle ear and diagnosis of middle ear hypoplasia using MRI

    Energy Technology Data Exchange (ETDEWEB)

    Katorza, Eldad; Nahama-Allouche, Catherine; Ducou le Pointe, Hubert; Garel, Catherine [Hopital d' Enfants Armand-Trousseau, Service de Radiologie, Paris (France); Castaigne, Vanina [Hopital Saint-Antoine, Service de Gynecologie-Obstetrique, Paris (France); Gonzales, Marie; Marlin, Sandrine [Hopital d' Enfants Armand-Trousseau, Service de Genetique et Embryologie medicales, Paris (France); Galliani, Eva [Hopital d' Enfants Armand-Trousseau, Service de Chirurgie maxillo-faciale, Paris (France); Jouannic, Jean-Marie; Rosenblatt, Jonathan [Hopital d' Enfants Armand-Trousseau, Service de Gynecologie-Obstetrique, Centre pluridisciplinaire de diagnostic prenatal, Paris (France)

    2011-05-15

    Analysis of the middle ear with fetal MRI has not been previously reported. To show the contribution of fetal MRI to middle ear imaging. The tympanic cavity was evaluated in 108 fetal cerebral MRI examinations (facial and/or cerebral malformation excluded) and in two cases, one of Treacher Collins syndrome (case 1) and the other of oculo-auriculo-vertebral (OUV) spectrum (case 2) with middle ear hypoplasia identified by MRI at 27 and 36 weeks' gestation, respectively. In all 108 fetuses (mean gestational age 32.5 weeks), the tympanic cavity and T2 hypointensity related to the ossicles were well visualised on both sides. Case 1 had micro/retrognathia and bilateral external ear deformity and case 2 had retrognathism with a left low-set and deformed ear. MRI made it possible to recognize the marked hypoplasia of the tympanic cavity, which was bilateral in case 1 and unilateral in case 2. Both syndromes are characterized by craniofacial abnormalities including middle ear hypoplasia, which cannot be diagnosed with US. The middle ear cavity can be visualized with fetal MRI. We emphasize the use of this imaging modality in the diagnosis of middle ear hypoplasia. (orig.)

  19. Middle Ear Infection (Chronic Otitis Media) and Hearing Loss

    Science.gov (United States)

    ... You Middle Ear Infection (Chronic Otitis Media) and Hearing Loss Middle Ear Infection (Chronic Otitis Media) and Hearing ... learning important speech and language skills. Types of hearing loss Conductive hearing loss is a form of hearing ...

  20. Albuquerque/Middle Rio Grande Urban Waters Viewer

    Data.gov (United States)

    U.S. Environmental Protection Agency — These data have been compiled in support of the Middle Rio Grande/Albuquerque Urban Waters Partnership for the region including Albuquerque, New Mexico.The Middle...

  1. Malaysian skills development and the middle-income trap

    DEFF Research Database (Denmark)

    Søborg, Henrik

    Education, human resource training, middle-income trap and the way towards a more knowledge-based economy......Education, human resource training, middle-income trap and the way towards a more knowledge-based economy...

  2. Multiple meanings of the middle class in soweto, south Africa

    African Journals Online (AJOL)

    Keywords: class, middle class, identity, Soweto, social location, self-sufficiency ... which people middle themselves, and therefore helps us to focus on what is and is not ... The cultural and material gulf between the women is apparent from.

  3. Diagenetic environments of calcite veins hosted in marine carbonate rocks in middle Yangtze region of South China%中扬子海相碳酸盐岩中方解石脉成岩环境研究

    Institute of Scientific and Technical Information of China (English)

    王芙蓉; 何生; 杨兴业

    2011-01-01

    Analyses of thin slices, cathodoluminescence and carbon-oxygen isotope of calcite veins hosted in marine carbonate rocks distributed around Jingshan County in the middle Yangtze region of South China indicated that, two crystal forms including radial calcite and isometric texture calcite could be identified in calcite veins in the Triassic and the cathodoluminescence intensity was different. The Permian and Ordovician fractures were mainly filled with isometric texture calcite veins and the cathodoluminescence intensity was similar with that of the surrounding rocks. The δl3 CPDB value of calcite veins ranged from -6. 76‰ to 4. Ol‰and the δ18 OPDB value ranged from -17. 95‰to -5. 67‰, indicating the marine phreatic environment and the mixing phreatic environment for calcite veins deposition. Calcite veins in the Triassic were sedimentary origin, and part of calcite veins in the Permian and the Ordovician suffered latter diagenetic fluid dissolution. Fluid generated from organic-matter maturation effected the formation of calcite veins in the Permian to some degree.%通过对中扬子京山县城周边露头碳酸盐岩中方解石脉的普通薄片、阴极发光以及碳氧同位索等资料分析,认为该区露头三叠系裂隙中充填放射状和等轴粒状的方解石且阴极发光强度有差异,二叠系和奥陶系裂隙中主要为等轴粒状方解石,阴极发光与围岩相似.方解石脉的δ13CPDB位于-6.76‰~4.01‰之间,δ18OPDB在-17.95‰~-5.67‰之间,基本为海水潜流带一混合水潜流带沉积环境.三叠系方解石脉基本上为沉积碳酸盐岩,二叠系和奥陶系部分方解石脉受后期成岩流体的影响,其中二叠系有饥质成熟产生的流体对该层系方解石脉的形成有一定影响.

  4. Talent Development Middle Grades Program. What Works Clearinghouse Intervention Report

    Science.gov (United States)

    What Works Clearinghouse, 2013

    2013-01-01

    The "Talent Development Middle Grades Program" is a comprehensive reform model that transforms the structure and curriculum of large urban middle schools with the aim of improving student achievement and raising teacher and student expectations. Key features of the "Talent Development Middle Grades Program" include small…

  5. Motivation and Ways to Motivate Students of Middle School

    Institute of Scientific and Technical Information of China (English)

    朱洪琼

    2012-01-01

    Motivation is critical in English learning of middle school,thus,how to effectively motivate students in English learning is an important problem.This study intends to find ways to motivate students of middle school.Self-report data were collected from 45 students in The Experiment Middle School Attached to Yunnan Normal University by using a close-ended questionnaire.

  6. 7 CFR 28.431 - Strict Middling Tinged Color.

    Science.gov (United States)

    2010-01-01

    ... 7 Agriculture 2 2010-01-01 2010-01-01 false Strict Middling Tinged Color. 28.431 Section 28.431 Agriculture Regulations of the Department of Agriculture AGRICULTURAL MARKETING SERVICE (Standards... Color. Strict Middling Tinged Color is color which is better than Middling Tinged Color....

  7. 7 CFR 28.402 - Strict Middling Color.

    Science.gov (United States)

    2010-01-01

    ... 7 Agriculture 2 2010-01-01 2010-01-01 false Strict Middling Color. 28.402 Section 28.402... for the Color Grade of American Upland Cotton § 28.402 Strict Middling Color. Strict Middling Color is color which is within the range represented by a set of samples in the custody of the United...

  8. 7 CFR 28.423 - Middling Spotted Color.

    Science.gov (United States)

    2010-01-01

    ... 7 Agriculture 2 2010-01-01 2010-01-01 false Middling Spotted Color. 28.423 Section 28.423... REGULATIONS COTTON CLASSING, TESTING, AND STANDARDS Standards Spotted Cotton § 28.423 Middling Spotted Color. Middling Spotted Color is color which is within the range represented by a set of samples in the custody...

  9. 7 CFR 28.405 - Low Middling Color.

    Science.gov (United States)

    2010-01-01

    ... 7 Agriculture 2 2010-01-01 2010-01-01 false Low Middling Color. 28.405 Section 28.405 Agriculture..., TESTING, AND STANDARDS Standards Official Cotton Standards of the United States for the Color Grade of American Upland Cotton § 28.405 Low Middling Color. Low Middling Color is color which is within the...

  10. 7 CFR 28.404 - Strict Low Middling Color.

    Science.gov (United States)

    2010-01-01

    ... 7 Agriculture 2 2010-01-01 2010-01-01 false Strict Low Middling Color. 28.404 Section 28.404... for the Color Grade of American Upland Cotton § 28.404 Strict Low Middling Color. Strict Low Middling Color is color which is within the range represented by a set of samples in the custody of the...

  11. 7 CFR 28.442 - Middling Yellow Stained Color.

    Science.gov (United States)

    2010-01-01

    ... 7 Agriculture 2 2010-01-01 2010-01-01 false Middling Yellow Stained Color. 28.442 Section 28.442... Stained Color. Middling Yellow Stained Color is American Upland cotton which in color is deeper than Middling Tinged Color. below color grade cotton...

  12. 7 CFR 28.421 - Good Middling Spotted Color.

    Science.gov (United States)

    2010-01-01

    ... 7 Agriculture 2 2010-01-01 2010-01-01 false Good Middling Spotted Color. 28.421 Section 28.421 Agriculture Regulations of the Department of Agriculture AGRICULTURAL MARKETING SERVICE (Standards... Color. Good Middling Spotted Color is color which is better than Strict Middling Spotted Color....

  13. 7 CFR 28.434 - Low Middling Tinged Color.

    Science.gov (United States)

    2010-01-01

    ... 7 Agriculture 2 2010-01-01 2010-01-01 false Low Middling Tinged Color. 28.434 Section 28.434... REGULATIONS COTTON CLASSING, TESTING, AND STANDARDS Standards Tinged Cotton § 28.434 Low Middling Tinged Color. Low Middling Tinged Color is color which is within the range represented by a set of samples in...

  14. 7 CFR 28.432 - Middling Tinged Color.

    Science.gov (United States)

    2010-01-01

    ... 7 Agriculture 2 2010-01-01 2010-01-01 false Middling Tinged Color. 28.432 Section 28.432... REGULATIONS COTTON CLASSING, TESTING, AND STANDARDS Standards Tinged Cotton § 28.432 Middling Tinged Color. Middling Tinged Color is color which is within the range represented by a set of samples in the custody...

  15. 7 CFR 28.401 - Good Middling Color.

    Science.gov (United States)

    2010-01-01

    ... 7 Agriculture 2 2010-01-01 2010-01-01 false Good Middling Color. 28.401 Section 28.401 Agriculture..., TESTING, AND STANDARDS Standards Official Cotton Standards of the United States for the Color Grade of American Upland Cotton § 28.401 Good Middling Color. Good Middling Color is color which is within the...

  16. The use of a SQUID magnetometer for middle ear research

    NARCIS (Netherlands)

    Rutten, W.L.C.; Peters, M.J.; Brenkman, C.J.; Mol, H.; Grote, J.J.; Marel, van der L.C.

    1982-01-01

    A new technique is described for the measurement of vibrations in the temporal bones of an isolated middle ear. The precise recording of vibrations in the middle ear is of importance for the construction and improvement of a middle ear prosthesis.1 The method of measurement is based on a transformat

  17. Female Middle School Principals' Voices: Implications for School Leadership Preparation

    Science.gov (United States)

    Jones, Cathy; Ovando, Martha; High, Cynthia

    2009-01-01

    This study was an attempt to add the voices of women to the discourse of school leadership. It focused on the nature of the middle school leadership experiences of three female middle school principals, their social interactions based on gender role expectations and their own leadership perspectives. Findings suggest that middle school leadership…

  18. A Comparison of Middle School Teachers' Pupil Control Ideology

    Science.gov (United States)

    Jones, Paul; Garner, Arthur E.

    1978-01-01

    Compares pupil control ideology--discipline policy--of middle school classroom teachers with the intent of finding what attributes are needed for middle school teachers and the particular type classroom environment that facilitates optimum learning conditions for middle school children. (Author/RK)

  19. Modeling Alternative Assessment for Pre-Service Middle Level Teachers

    Science.gov (United States)

    Ziegenfuss, Robert G.

    2011-01-01

    College assessment models for our future middle school teachers must be varied, on-going, engaging, equitable and empowering. Traditional assessments do not often model the critical components of what makes assessment appropriate for middle level students. To provide the appropriate model for future middle level teachers, the establishment of…

  20. The Elusive New Middle Class in Brazil

    Directory of Open Access Journals (Sweden)

    Celia Lessa Kerstenetzky

    2015-12-01

    Full Text Available Against the background of the generalized reduction of poverty in the world, and particularly in Brazil, this article intends to gauge the socio-economic profile of Brazilian households that emerged from poverty and have been identified as integrating a "new middle class". Using indicators of standards of living from the 2008-2009 Survey on Family Budgets (POF/IBGE, we found out that, in contrast to what has been assumed on the basis of average income criteria, this social stratum is markedly heterogeneous, most of it being similar in their consumption patterns to the economically vulnerable or outright poor strata. So, we conclude that, from a sociological perspective that demands additional conditions besides income levels to identify social classes, it is a category mistake to call this social stratum a new middle class. We conjecture that this may be consequential in terms of policy priorities and choices.

  1. Diseases of the middle ear in childhood

    Directory of Open Access Journals (Sweden)

    Minovi, Amir

    2014-12-01

    Full Text Available [english] Middle ear diseases in childhood play an important role in daily ENT practice due to their high incidence. Some of these like acute otitis media or otitis media with effusion have been studied extensively within the last decades. In this article, we present a selection of important childhood middle ear diseases and discuss the actual literature concerning their treatment, management of complications and outcome. Another main topic of this paper deals with the possibilities of surgical hearing rehabilitation in childhood. The bone-anchored hearing aid BAHA and the active partially implantable device Vibrant Soundbridge could successfully be applied for children. In this manuscript, we discuss the actual literature concerning clinical outcomes of these implantable hearing aids.

  2. Middle Range Theory of Traumatic Childbirth

    Directory of Open Access Journals (Sweden)

    Cheryl Tatano Beck

    2015-03-01

    Full Text Available A middle range theory of traumatic childbirth was developed using Morse’s method of theoretical coalescence. The scope of this qualitative theory was increased by formalizing the connections between 14 individual studies all conducted by the same researcher on the same topic, with different groups, using different research designs and different types of analyses. Axioms were derived from this research program along with attributes of traumatic childbirth, posttraumatic stress, and secondary traumatic stress. This middle range theory addresses the long-term chronic consequences of a traumatic birth for mothers including its impact on breastfeeding, subsequent childbirth, and the anniversary of birth trauma. The impact on fathers and clinicians present at the traumatic birth is highlighted as secondary traumatic stress comes into play. Troubling glimpses of difficulties in mother–infant bonding are revealed.

  3. Flash Point: Middle East; A Selective Bibliography.

    Science.gov (United States)

    1984-09-01

    Legal Structures for Doing Business in Saudi Arabia: Dis- tributorship, Agency, Branch, Joint Venture and Professional Office." Frederick W. Taylor , Jr... Taylor , Jr. and Howard 0. Weissman. INTERNATIONAL LAWYER 111:331-359, Spring 1980 ’Middle East: Status of Jerusalem." Melinda Crane. HOWARD...INTERNATIONAL LAWYER 15:561-570, Fall 1981 145 .] NA Practitioner’s Introduction to Saudi Arabian Law.’ Gali Hegel . VANDER- BILT JOURNAL CY TRANSNATIONAL

  4. Water resource conflicts in the Middle East.

    Science.gov (United States)

    Drake, C

    1997-01-01

    This article discusses the causes and sources of water resource conflict in the 3 major international river basins of the Middle East: the Tigris-Euphrates, the Nile, and the Jordan-Yarmuk. The physical geography of the Middle East is arid due to descending air, northeast trade winds, the southerly location, and high evaporation rates. Only Turkey, Iran, and Lebanon have adequate rainfall for population needs. Their mountainous geography and more northerly locations intercept rain and snow bearing westerly winds in winter. Parts of every other country are vulnerable to water shortages. Rainfall is irregular. Water resource conflicts are due to growing populations, economic development, rising standards of living, technological developments, political fragmentation, and poor water management. Immigration to the Jordan-Yarmuk watershed has added to population growth in this location. Over 50% of the population in the Middle East lives in urban areas where populations consume 10-12 times more water than those in rural areas. Water is wasted in irrigation schemes and huge dams with reservoirs where increased evaporation occurs. Technology results in greater water extraction of shallow groundwater and pollution of rivers and aquifers. British colonial government control led to reduced friction in most of the Nile basin. Now all ethnic groups have become more competitive and nationalistic. The Cold War restrained some of the conflict. Israel obtains 40% of its water from aquifers beneath the West Bank and Gaza. Geopolitical factors determine the mutual goodwill in managing international water. The 3 major water basins in the Middle East pose the greatest risk of water disputes. Possible solutions include conservation, better management, prioritizing uses, technological solutions, increased cooperation among co-riparians, developing better and enforceable international water laws, and reducing population growth rates.

  5. Clinical importance of the middle meningeal artery.

    Science.gov (United States)

    Chmielewski, Przemyslaw; Skrzat, Janusz; Walocha, Jerzy

    2013-01-01

    Middle meningeal artery (MMA)is an important branch which supplies among others cranial dura mater. It directly attaches to the cranial bones (is incorporated into periosteal layer of dura mater), favors common injuries in course of head trauma. This review describes available data on the MMA considering its varability, or treats specific diseases or injuries where the course of MMA may have clinical impact.

  6. Early Predictors of Middle School Fraction Knowledge

    OpenAIRE

    Drew H. Bailey; Siegler, Robert S.; David C Geary

    2014-01-01

    Recent findings that earlier fraction knowledge predicts later mathematics achievement raise the question of what predicts later fraction knowledge. Analyses of longitudinal data indicated that whole number magnitude knowledge in first grade predicted knowledge of fraction magnitudes in middle school, controlling for whole number arithmetic proficiency, domain general cognitive abilities, parental income and education, race, and gender. Similarly, knowledge of whole number arithmetic in first...

  7. English Middle Construction and Chinese Verbs

    Institute of Scientific and Technical Information of China (English)

    刘芳

    2015-01-01

    Middle Construction(MC)is a special language sentence structure.It exists in English,West Germanic languages and Indo European languages,etc.It has a unique form and meanings.In recent years,Chinese verbal MC research is a hot topic and many Chinese scholars believe that there is a totally same structure form of MC in Chinese as well.However,that is not true.

  8. English Middle Construction and Chinese Verbs

    Institute of Scientific and Technical Information of China (English)

    刘芳

    2015-01-01

    Middle Construction (MC)is a special language sentence structure.It exists in English,West Germanic languages and Indo European languages,etc.It has a unique form and meanings.In recent years,Chinese verbal MC research is a hot topic and many Chinese scholars believe that there is a totally same structure form of MC in Chinese as well.However,that is not true.

  9. Seismicity and kinematic evolution of middle Egypt

    Science.gov (United States)

    Badawy, A.; Abdel-Monem, S. M.; Sakr, K.; Ali, Sh. M.

    2006-08-01

    Based on historical and instrumental seismicity as well as recent GPS measurements, the seismicity and kinematic evaluation of middle Egypt is presented. Middle Egypt suffered in historical times by six major earthquakes and the Ramses II temple on the west bank of the Nile in Luxor, was almost destroyed by an ancient event. The temporal distribution of recent earthquakes (1900-1997) is highly scattered with only nine events recorded. Only after the installation of the modern Egyptian national seismograph network (ENSN) the seismic record of middle Egypt increased with a total of 280 earthquakes from 1998 to 2004. Focal mechanism solutions of the largest five events during the ENSN's operation period reveal reverse faulting mechanism with minor strike-slip component on the west bank of the Nile, while a normal faulting mechanism dominate in the eastern side. The orientations of both P- and T-axes are consistent with the Red Sea-Gulf of Suez stress field. Dynamic source parameters of these five events were derived from P-wave spectra as well. Three campaigns of GPS measurements were carried out for the middle Egypt network that established after the first instrumental earthquake on 14 December 1998 in this area. The velocity vectors for each epoch of observations were calculated and deformation analysis was performed. The horizontal velocity varies between 1 and 4 mm/year across the network. The deformation pattern suggests significant contraction across the southeastern sector of the study area while, the northwestern part is characterized by an extension strain rates. High shear strain is observed along the epicenteral area of the Mw = 4.0 June 2003 earthquake possibly reflecting the stress accumulation stage of a seismic cycle.

  10. Lethal Interpersonal Violence in the Middle Pleistocene

    OpenAIRE

    Nohemi Sala; Juan Luis Arsuaga; Ana Pantoja-Pérez; Adrián Pablos; Ignacio Martínez; Quam, Rolf M.; Asier Gómez-Olivencia; José María Bermúdez de Castro; Eudald Carbonell

    2015-01-01

    Evidence of interpersonal violence has been documented previously in Pleistocene members of the genus Homo, but only very rarely has this been posited as the possible manner of death. Here we report the earliest evidence of lethal interpersonal violence in the hominin fossil record. Cranium 17 recovered from the Sima de los Huesos Middle Pleistocene site shows two clear perimortem depression fractures on the frontal bone, interpreted as being produced by two episodes of localized blunt force ...

  11. Fathers, daughters, and mourning in middle comedies

    OpenAIRE

    Sundelson, David

    1981-01-01

    This essay, part of a book about Shakespeare's treatment of fathers and father figures, discusses the middle comedies, concentrating on The Merchant of Venice. I argue that mourning for a lost father is the common psychological background of these plays, in which the characteristic fate of fathers has three stages: strength, collapse, and partial recovery. In Twelfth Night, unfinished mourning is a central feature of the plot but is transferred from fathers to brothers; in As You Like It a...

  12. Cloud effects on middle ultraviolet global radiation

    Science.gov (United States)

    Borkowski, J.; Chai, A.-T.; Mo, T.; Green, A. E. O.

    1977-01-01

    An Eppley radiometer and a Robertson-Berger sunburn meter are employed along with an all-sky camera setup to study cloud effects on middle ultraviolet global radiation at the ground level. Semiempirical equations to allow for cloud effects presented in previous work are compared with the experimental data. The study suggests a means of defining eigenvectors of cloud patterns and correlating them with the radiation at the ground level.

  13. The Middle Ages Contributions to Cardiovascular Medicine

    Science.gov (United States)

    Ranhel, André Silva; Mesquita, Evandro Tinoco

    2016-01-01

    The historical period called the Middle Ages, a long interval between the 5th and the 15th centuries, is still commonly known as the Dark Ages, especially in the area of health sciences. In the last decades, this "classic" view of the Middle Ages has been gradually modified with advances in historiographical studies and the history of science. During that period in Western Europe, knowledge about the human body suffered a regression in terms of anatomy and physiology, with the predominance of religious conceptions mainly about diseases and their treatments. Knowledge on the cardiovascular system and heart diseases has been classically described as a repetition of the concepts developed by Galen from the dissection of animals and his keen sense of observation. However, the Middle East, especially Persia, was the birth place of a lot of intellectuals who preserved the ancient knowledge of the Greeks while building new knowledge and practices, especially from the 8th to the 13th century. The invasion of the Arabs in North of Africa and the Iberian Peninsula and the eclosion of the Crusades resulted in a greater contact between the East and the West, which in turn brought on the arrival of the Arab medical knowledge, among others, to 12th century Europe. Such fact contributed to an extremely important change in the scientific medical knowledge in the West, leading to the incorporation of different concepts and practices in the field of cardiovascular Medicine. The new way of teaching and practicing Medicine of the great Arab doctors, together with the teaching hospitals and foundations in the Koran, transformed the Medicine practiced in Europe definitely. The objective of this paper is to describe the knowledge drawn up from the Middle Ages about the cardiovascular system, its understanding and therapeutic approach to cardiologists and cardiovascular surgeons. PMID:27556317

  14. The Middle Ages Contributions to Cardiovascular Medicine

    Directory of Open Access Journals (Sweden)

    André Silva Ranhel

    Full Text Available Abstract The historical period called the Middle Ages, a long interval between the 5th and the 15th centuries, is still commonly known as the Dark Ages, especially in the area of health sciences. In the last decades, this "classic" view of the Middle Ages has been gradually modified with advances in historiographical studies and the history of science. During that period in Western Europe, knowledge about the human body suffered a regression in terms of anatomy and physiology, with the predominance of religious conceptions mainly about diseases and their treatments. Knowledge on the cardiovascular system and heart diseases has been classically described as a repetition of the concepts developed by Galen from the dissection of animals and his keen sense of observation. However, the Middle East, especially Persia, was the birth place of a lot of intellectuals who preserved the ancient knowledge of the Greeks while building new knowledge and practices, especially from the 8th to the 13th century. The invasion of the Arabs in North of Africa and the Iberian Peninsula and the eclosion of the Crusades resulted in a greater contact between the East and the West, which in turn brought on the arrival of the Arab medical knowledge, among others, to 12th century Europe. Such fact contributed to an extremely important change in the scientific medical knowledge in the West, leading to the incorporation of different concepts and practices in the field of cardiovascular Medicine. The new way of teaching and practicing Medicine of the great Arab doctors, together with the teaching hospitals and foundations in the Koran, transformed the Medicine practiced in Europe definitely. The objective of this paper is to describe the knowledge drawn up from the Middle Ages about the cardiovascular system, its understanding and therapeutic approach to cardiologists and cardiovascular surgeons.

  15. The Middle Ages Contributions to Cardiovascular Medicine.

    Science.gov (United States)

    Ranhel, André Silva; Mesquita, Evandro Tinoco

    2016-04-01

    The historical period called the Middle Ages, a long interval between the 5th and the 15th centuries, is still commonly known as the Dark Ages, especially in the area of health sciences. In the last decades, this "classic" view of the Middle Ages has been gradually modified with advances in historiographical studies and the history of science. During that period in Western Europe, knowledge about the human body suffered a regression in terms of anatomy and physiology, with the predominance of religious conceptions mainly about diseases and their treatments. Knowledge on the cardiovascular system and heart diseases has been classically described as a repetition of the concepts developed by Galen from the dissection of animals and his keen sense of observation. However, the Middle East, especially Persia, was the birth place of a lot of intellectuals who preserved the ancient knowledge of the Greeks while building new knowledge and practices, especially from the 8th to the 13th century. The invasion of the Arabs in North of Africa and the Iberian Peninsula and the eclosion of the Crusades resulted in a greater contact between the East and the West, which in turn brought on the arrival of the Arab medical knowledge, among others, to 12th century Europe. Such fact contributed to an extremely important change in the scientific medical knowledge in the West, leading to the incorporation of different concepts and practices in the field of cardiovascular Medicine. The new way of teaching and practicing Medicine of the great Arab doctors, together with the teaching hospitals and foundations in the Koran, transformed the Medicine practiced in Europe definitely. The objective of this paper is to describe the knowledge drawn up from the Middle Ages about the cardiovascular system, its understanding and therapeutic approach to cardiologists and cardiovascular surgeons.

  16. Death Attitudes Among Middle-Aged Koreans.

    Science.gov (United States)

    Hong, Michin; Hong, Seunghye; Adamek, Margaret E; Kim, Mee Hye

    2017-01-01

    The purpose of this study was to examine factors affecting death attitudes among middle-aged Koreans. In addition, the study explored the interaction effect between knowledge about end-of-life care planning and the experience of death of family or friends on death attitudes. The sample was obtained from a national survey with middle-aged adults in South Korea ( n = 2,026). Multivariate regression analysis revealed significant main effects and an interaction effect between knowledge about end-of-life care planning and the experience of death on death attitudes. Greater knowledge of end-of-life care planning was associated with more positive attitudes toward death; however, the effect was stronger for those who had not experienced the death of family or friends. Being older and having greater life satisfaction were also associated with more positive attitudes toward death. This study suggests that end-of-life education can help middle-aged adults embrace the final stage of life and prepare for their own death.

  17. Carcinoid tumor of the middle ear.

    Science.gov (United States)

    Nikanne, Elina; Kantola, Olli; Parviainen, Tapani

    2004-08-01

    Although carcinoid tumors are labeled as neuroendocrine tumors they can also originate in tissue lacking neuroendocrine cells, such as that in the middle ear. Symptoms of a carcinoid tumor in the middle ear are common ear symptoms such as fullness, pain and hearing loss. Carcinoid tumors have also been considered to be slow-growing. Both these aspects can easily lead to a relatively late diagnosis of carcinoid tumor of the middle ear. The diagnosis is made histologically, and the tumor is primarily treated surgically. In the follow-up of patients, octreotide scanning has proved to be a sensitive method in cases of both recurrence and metastasis. Our patient was a 34-year-old, otherwise healthy female with left-sided acute otitis media and facial palsy in her left ear. She had also suffered from the same symptoms 4 years earlier. She was treated with an operation, and the histologic diagnosis was a carcinoid tumor. In the follow-up of the patient we used octreotide scanning.

  18. Middle East experience in palliative care.

    Science.gov (United States)

    Zeinah, Ghaith F Abu; Al-Kindi, Sadeer G; Hassan, Azza Adel

    2013-02-01

    Palliative Care (PC) is still a relatively new concept in the Middle East (ME). It was first introduced in Saudi Arabia in 1992 and only recently in countries such as Qatar, Bahrain, and the UAE. Although the majority of Middle-Eastern countries, including Palestine, Iraq, Oman and Lebanon are in the capacity building phase, others such as Saudi and Jordan already have localized provision. In the absence of any of the ME countries approaching integration with the mainstream service providers, Saudi Arabia and Jordan are currently setting examples of achievement in the field. There are still countries with little or no known Palliative Care activity (Yemen and Syria). Political issues, scarcity of resources, and lack of education and awareness seem to be the common factors restricting the progress of this field in most countries. In order to improve the suboptimal PC services in the ME, emphasis should be directed toward providing formal education to professionals and raising awareness of the public. It is also necessary to put all differences aside and develop cross-border collaborations, whether through third party organizations such as the Middle East Cancer Consortium (MECC) or otherwise. This review compiles the available literature on the history and progress of the field of PC in most ME countries, while pointing out the major obstacles encountered by the active parties of each country.

  19. Première datation U_Pb des orthogneiss œillés de la zone axiale de la Montagne noire (Sud du Massif central) : nouveaux témoins du magmatisme ordovicien dans la chaîne VarisqueU_Pb dating of Augen orthogneisses from the Axial Zone of the Montagne Noire (Southern of Massif Central): new witness of Ordovician magmatism into the Variscan Belt

    Science.gov (United States)

    Roger, Françoise; Respaut, Jean-Patrick; Brunel, Maurice; Matte, Philippe; Paquette, Jean-Louis

    2004-01-01

    We present new U-Pb results on felsic Augen orthogneisses from the Axial Zone of the Montagne Noire (French Massif Central). The data indicate Ordovician ages, 456±3 and 450±6 Ma for two samples collected at 'Pont-de-Larn' and 'Gorges d'Héric', respectively. These ages are interpreted as the igneous emplacement age of the granitic protolith. To cite this article: F. Roger et al., C. R. Geoscience 336 (2004).

  20. Middle School Adventures in Planetary Exploration

    Science.gov (United States)

    Limaye, S. S.; Pertzborn, R. A.

    1998-09-01

    During the summer of 1998 the UW-Madison Office of Space Science Education (OSSE) developed and implemented a pilot summer school program to improve the math and science performance of middle school students. The program focused on the subject of solar system exploration for the summer school offered by the Milwaukee Public Schools (MPS) for middle school students. OSSE staff collaborated with science, math, and technology teachers from two middle schools (Milwaukee Education Center and Bell Middle School) to expand upon a series of hands-on, interdisciplinary lesson plans originally developed to accompany the Planetary Society's Red Rover, Red Rover Program. For six weeks, sixty inner city middle school students had the opportunity to explore new worlds as far reaching as Mars, Mercury, Titania, Uranus and Pluto with the assistance of Planetary Scientists and staff from the UW-Madison Space Science and Engineering Center. Students were provided with computers and internet connections by AT&T to conduct on-line research on their own research topic relating to planetary exploration. Based on their own research efforts, teams of five or six students wrote a mission statement and then proceeded to create a terrain resembling their desired planetary target. Team engineers then built a computer operated Lego Dacta rover designed especially for exploring the unique features of their targeted planet. In addition to strengthening their science and math skills, students also focused on the improvement of their communication skills by maintaining a daily journal of their experiences, tribulations and successes. Students were tested in the beginning and again at the end of the program. An independent group from University of Wisconsin-Milwaukee performed overall assessment of the summer program. Based on the overall success in achieving performance enchmarks, the Milwaukee Public Schools and UW-Extension Learning Innovations Center have elected to collaborate with the OSSE to