Sample records for early silurian radiolarians

  1. Thermally Altered Silurian Cyanobacterial Mats: A Key to Earth's Oldest Fossils

    NASA Astrophysics Data System (ADS)

    Kazmierczak, Józef; Kremer, Barbara

    2009-10-01

    Diagenetic changes in thermally altered cyanobacterial mats from early Silurian black radiolarian cherts of southwestern Poland (Bardzkie Montains, Sudetes) have been studied. These early diagenetically silicified mats are composed of variously degraded remains of benthic microbes that resemble some modern chroococcalean and pleurocapsalean cyanobacteria. Two modes of degradational processes have been recognized in the studied mats: (i) early postmortem biodegradation and (ii) late diagenetic thermal or thermobaric degradation. The latter led to partial transformation of the fossilized organic remnants of cyanobacterial sheaths and capsules, which resulted in the formation of objects morphologically distant from the original microbiota but preserved features that allow for their identification as bona fide biogenic structures. Some of these thermally generated Silurian fossils are highly similar to the controversial microfossil-like carbonaceous structures described from the Early Archean Apex Chert of Australia. This similarity opens a promising way for credible recognition of remnants of cyanobacteria and similar microbiota in other thermally metamorphosed Archean sedimentary rocks

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

    NASA Astrophysics Data System (ADS)

    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.

  3. Early Silurian Foraminifera from Gondwana - an early origin of the multichambered globothalamids?

    NASA Astrophysics Data System (ADS)

    Kaminski, Michael

    2017-04-01

    Early Silurian foraminifera until now have been regarded to consist of simple single-chambered monothalamids and two-chambered tubothalamids with an agglutinated wall. Although pseudo-multichambered agglutinated foraminifera first appeared in the mid-Ordovician (Kaminski et al. 2009), the origin of true multichambered forms was not believed to have taken place until the early or middle Devonian at the earliest (Holcová, 2002). New discoveries from the Lower Silurian Qusaiba Shale Member in Saudi Arabia point to an earlier origin of the multichambered globothalamid Foraminifera than the currently accepted estimate of 350 Ma (Pawlowski et al. 2003). The agglutinated foraminiferal genera Ammobaculites and Sculptobaculites have been recovered from dark graptolite-bearing claystones of Telychian age, from the transitional facies between the Qusaiba and Sharawa Members of the Qasim Formation at the type locality near Qusaiba town, Saudi Arabia. The multichambered lituolids occur as rare components in a foraminiferal assemblage consisting mostly of monothalamids. This new finding revises our understanding of the early evolution of the multichambered globothalamid foraminifera. The fossil record now shows that the globothalamids were already present in Gondwana by 435 m.y. Holcová, K. 2002. Silurian and Devonian foraminifers and other acid-resistant microfossils from the Barrandian area. Acta Musei Nationalis Pragae, Series B, Historia Naturalis, 58 (3-4), 83-140. Kaminski, M.A., Henderson, A.S., Cetean, C.G. & Waskowska-Oliwa, A. 2009. A new family of agglutinated foraminifera: the Ammolagenidae n.fam., and the evolution of multichambered tests. Micropaleontology, 55 (5), 487-494. Pawlowski, J., Holzmann, M., Berney, C., Fahrni, J.F., Gooday, Aj., Cedhagen, T., Habura, A., & Bowser, SS. 2003. The evolution of early Foraminifera. Proceedings of the National Academy of Sciences, 100 (20), 11494-11498

  4. Finding of two new radiolarian associations calibrated with ammonoids in the Vaca Muerta Formation (Late Jurassic-Early Cretaceous), Neuquén Basin, Argentina

    NASA Astrophysics Data System (ADS)

    Vennari, Verónica V.; Pujana, Ignacio

    2017-04-01

    An association of ammonoids and radiolarians retrieved from a sedimentary section of the Vaca Muerta Formation at Vega de Escalone, Neuquén Basin, Argentina, was analized under a strict stratigraphic control. Nine ammonoid assemblage biozones were identified, indicating an age span from Early Tithonian to Late Berriasian/earlymost Valanginian for the Vaca Muerta Formation at the studied section. In connection to the ammonoid record, two radiolarian faunas were identified and named J3A1 and J3B1. Fauna J3A1, corresponding to the Virgatosphinctes andesensis Biozone, is dominated by nasellarian genera and represents the first Lower Tithonian radiolarian fauna described from the Neuquén Basin. Fauna J3B1, linked to the interval assigned to the Substeueroceras koeneni Biozone (Late Tithonian-Early Berriasian), yields abundant representatives of the Pantanellid Family. The presence of Complexapora kozuri (Kiessling and Zeiss) and Loopus primitivus (Matsuoka and Yao), two important radiolarian primary markers of the Late Jurassic in North America, supports a Late Tithonian age for at least part of the S. koeneni Biozone in the studied area. Nor certain Berriasian radiolarian faunas nor elements of the Vallupinae Family were identified so far at the Vega de Escalone section.

  5. The major-ion composition of Silurian seawater

    USGS Publications Warehouse

    Brennan, S.T.; Lowenstein, T.K.

    2002-01-01

    One-hundred fluid inclusions in Silurian marine halite were analyzed in order to determine the major-ion composition of Silurian seawater. The samples analyzed were from three formations in the Late Silurian Michigan Basin, the A-1, A-2, and B Evaporites of the Salina Group, and one formation in the Early Silurian Canning Basin (Australia), the Mallowa Salt of the Carribuddy Group. The results indicate that the major-ion composition of Silurian seawater was not the same as present-day seawater. The Silurian ocean had lower concentrations of Mg2+, Na+, and SO2-4, and much higher concentrations of Ca2+ relative to the ocean's present-day composition. Furthermore, Silurian seawater had Ca2+ in excess of SO2-4. Evaporation of Silurian seawater of the composition determined in this study produces KC1-type potash minerals that lack the MgSO4-type late stage salts formed during the evaporation of present-day seawater. The relatively low Na+ concentrations in Silurian seawater support the hypothesis that oscillations in the major-ion composition of the oceans are primarily controlled by changes in the flux of mid-ocean ridge brine and riverine inputs and not global or basin-scale, seawater-driven dolomitization. The Mg2+/Ca2+ ratio of Silurian seawater was ~1.4, and the K+/Ca2+ ratio was ~0.3, both of which differ from the present-day counterparts of 5 and 1, respectively. Seawaters with Mg2+/Ca2+ 2 (e.g., modern seawater) facilitate the precipitation of aragonite and high-magnesian calcite. Therefore, the early Paleozoic calcite seas were likely due to the low Mg2+/Ca2+ ratio of seawater, not the pCO2 of the Silurian atmosphere. Copyright ?? 2002 Elsevier Science Ltd.

  6. Equivalent radiolarian ages from ophiolitic terranes of Cyprus and Oman

    USGS Publications Warehouse

    Blome, Charles D.; Irwin, William P.

    1985-01-01

    Radiolarian biostratigraphy shows that umberiferous strata overlying the Troodos ophiolite in Cyprus are Turonian in age and are thus essentially contemporaneous with similar strata that overlie the Samail ophiolite in Oman. However, this radiolarian age is markedly older than Campanian isotopic ages measured on the underlying rocks of the Troodos ophiolite. The revised age for the umbers indicates that the Troodos lavas were formed no later than Turonian time. The presence of overlying autochthonous Maastrichtian chalks restricts the emplacement of the Troodos ophiolite to the Late Cretaceous (Santonian to early Maastrichtian).

  7. Radiolarian biostratigraphy of the Quinn River Formation, Black Rock terrane, north-central Nevada: correlations with eastern Klamath terrane geology

    USGS Publications Warehouse

    Blome, C.D.; Reed, K.M.

    1995-01-01

    The Quinn River Formation, Black Rock terrane, Quinn River Crossing, is one of the few Nevadan sections of Permian and Triassic strata that are unaffected by Sonoman deformation. The formation consists of: 1) a basal tuff overlain by limestone and ferruginous dolomite, 2) interbedded radiolarian-bearing chert and argillite, 3) siltstone and carbonaceous shale, and 4) partly volcaniclastic rocks. All but the uppermost (barren) chert samples contain Late Permian radiolarian taxa. These radiolarians suggest that early Wordian conodonts reported from near the top of the chert and argillite unit are reworked. Poorly preserved Early(?) or Middle triassic radiolarians and Middle Triassic ammonites and pectenacid bivalves from the middle part of the volcaniclastic unit indicate the Early Triassic deposition cannot be documented at Quinn River. The ages of the Quinn River brachiopod, conodont, and radiolarian faunas resemble those of the Dekkas and Pit Formations, eastern Klamath terrane, northern California. The analogous Quinn River and eastern Klamath rock types and faunal ages, as well as similar hiatuses in their stratigraphic records, suggest that they may be lateral equivalents that formed in the same island-arc sedimentary basin. -from Authors

  8. Peri-equatorial paleolatitudes for Jurassic radiolarian cherts of Greece

    USGS Publications Warehouse

    Aiello, I.W.; Hagstrum, J.T.; Principi, G.

    2008-01-01

    Radiolarian-rich sediments dominated pelagic deposition over large portions of the Tethys Ocean during middle to late Jurassic time as shown by extensive bedded chert sequences found in both continental margin and ophiolite units of the Mediterranean region. Which paleoceanographic mechanisms and paleotectonic setting favored radiolarian deposition during the Jurassic, and the nature of a Tethys-wide change from biosiliceous to biocalcareous (mainly nannofossil) deposition at the beginning of Cretaceous time, have remained open questions. Previous paleomagnetic analyses of Jurassic red radiolarian cherts in the Italian Apennines indicate that radiolarian deposition occurred at low peri-equatorial latitudes, similar to modern day deposition of radiolarian-rich sediments within equatorial zones of high biologic productivity. To test this result for other sectors of the Mediterranean region, we undertook paleomagnetic study of Mesozoic (mostly middle to upper Jurassic) red radiolarian cherts within the Aegean region on the Peloponnesus and in continental Greece. Sampled units are from the Sub-Pelagonian Zone on the Argolis Peninsula, the Pindos-Olonos Zone on the Koroni Peninsula, near Karpenissi in central Greece, and the Ionian Zone in the Varathi area of northwestern Greece. Thermal demagnetization of samples from all sections removed low-temperature viscous and moderate-temperature overprint magnetizations that fail the available fold tests. At Argolis and Koroni, however, the cherts carry a third high-temperature magnetization that generally exhibits a polarity stratigraphy and passes the available fold tests. We interpret the high-temperature component to be the primary magnetization acquired during chert deposition and early diagenesis. At Kandhia and Koliaky (Argolis), the primary declinations and previous results indicate clockwise vertical-axis rotations of ??? 40?? relative to "stable" Europe. Due to ambiguities in hemispheric origin (N or S) and thus

  9. Origin and Evolution of The Early- Silurian Land Vascular Plants: Evidence From Biomarkers

    NASA Astrophysics Data System (ADS)

    Jin, R.

    2016-12-01

    Origin and early evolution of land vascular plants, is one of the most intriguing hotspots in the life science research. During the 1970s and 1980s,Pinnatiramosus qianensis was found in early-Silurian strata in guizhou of south China.43 years have passed. But so far, the biological characteristics and belonging of the age of this unique plant have been debated again and again, up in the air.Biomarkers have a good stability in the process of organic evolution, no more or less changed, so they have a special `function of mark'. While biomarkers can provide information about organic matter of hydrocarbon source rock (the source), the period of deposition and burial (diagenesis) environmental conditions, and many other aspects of information.This paper obtained the sedimentary environment, source of organic matter input and other relevant information, through extracting and analyzing biomarkers of the 26 samples in the late Ordovician to early Silurian strata in NorthGuizhou areas. According to the results, Pr/Ph of late Ordovician Meitan Fm-early Silurian Hanjiadian Fm is high.It manifests more pristane, characterized by reductive environment. At the bottom of the Hanjiadian Fm, Pr/Ph has a volatility.Some huge environmental changes may have taken place in the corresponding period. N-alkanes do not have parity advantage or has even carbon advantage slightly.The peak carbon is mainly in low carbon number.(C21 + C22)/(C28 + C29) is high.Aquatic organisms is a major source of organic matter during this period,C21-/C22+ is low.This may be caused by the relatively serious loss of light hydrocarbon during the separation of components. In the Hanjiadian Fm,information of C29/C27 sterane ratios and oleanane index showed a trend of rising at the same time, indicating that during this period, there was a gradual increase input in the number of higher plants.The stable carbon isotope of saturated hydrocarbon and aromatic hydrocarbon in the Hanjiadian Fm also gradually become

  10. Classification of radiolarian images with hand-crafted and deep features

    NASA Astrophysics Data System (ADS)

    Keçeli, Ali Seydi; Kaya, Aydın; Keçeli, Seda Uzunçimen

    2017-12-01

    Radiolarians are planktonic protozoa and are important biostratigraphic and paleoenvironmental indicators for paleogeographic reconstructions. Radiolarian paleontology still remains as a low cost and the one of the most convenient way to obtain dating of deep ocean sediments. Traditional methods for identifying radiolarians are time-consuming and cannot scale to the granularity or scope necessary for large-scale studies. Automated image classification will allow making these analyses promptly. In this study, a method for automatic radiolarian image classification is proposed on Scanning Electron Microscope (SEM) images of radiolarians to ease species identification of fossilized radiolarians. The proposed method uses both hand-crafted features like invariant moments, wavelet moments, Gabor features, basic morphological features and deep features obtained from a pre-trained Convolutional Neural Network (CNN). Feature selection is applied over deep features to reduce high dimensionality. Classification outcomes are analyzed to compare hand-crafted features, deep features, and their combinations. Results show that the deep features obtained from a pre-trained CNN are more discriminative comparing to hand-crafted ones. Additionally, feature selection utilizes to the computational cost of classification algorithms and have no negative effect on classification accuracy.

  11. Expansion and diversification of high-latitude radiolarian assemblages in the late Eocene linked to a cooling event in the southwest Pacific

    NASA Astrophysics Data System (ADS)

    Pascher, K. M.; Hollis, C. J.; Bohaty, S. M.; Cortese, G.; McKay, R. M.; Seebeck, H.; Suzuki, N.; Chiba, K.

    2015-12-01

    The long-term cooling trend from middle to late Eocene was punctuated by several large-scale climate perturbations that culminated in a shift to "icehouse" climates at the Eocene-Oligocene transition. We present radiolarian micro-fossil assemblage and foraminiferal oxygen and carbon stable isotope data from Deep Sea Drilling Project (DSDP) sites 277, 280, 281, and 283 and Ocean Drilling Project (ODP) Site 1172 to identify significant oceanographic changes in the southwest Pacific through this climate transition (~ 40-30 Ma). We find that the Middle Eocene Climatic Optimum at ~ 40 Ma, which is truncated but identified by a negative shift in foraminiferal δ18O values at Site 277, is associated with a small increase in radiolarian taxa with low-latitude affinities (5 % of total fauna). In the early late Eocene at ~ 37 Ma, a positive oxygen isotope shift at Site 277 is correlated with the Priabonian Oxygen Isotope Maximum (PrOM). Radiolarian abundance, diversity, and preservation increase within this cooling event at Site 277 at the same time as diatom abundance. A negative δ18O excursion above the PrOM is correlated with a late Eocene warming event (~ 36.4 Ma). Radiolarian abundance and diversity decline within this event and taxa with low-latitude affinities reappear. Apart from this short-lived warming event, the PrOM and latest Eocene radiolarian assemblages are characterised by abundant high-latitude taxa. High-latitude taxa are also abundant during the late Eocene and early Oligocene (~ 38-30 Ma) at DSDP sites 280, 281, 283 and 1172 and are associated with very high diatom abundance. We therefore infer a northward expansion of high-latitude radiolarian taxa onto the Campbell Plateau in the latest Eocene. In the early Oligocene there is an overall decrease in radiolarian abundance and diversity at Site 277, and diatoms are scarce. These data indicate that, once the Antarctic Circumpolar Current was established in the early Oligocene (~ 30 Ma), a frontal system

  12. Lower Silurian `hot shales' in North Africa and Arabia: regional distribution and depositional model

    NASA Astrophysics Data System (ADS)

    Lüning, S.; Craig, J.; Loydell, D. K.; Štorch, P.; Fitches, B.

    2000-03-01

    Lowermost Silurian organic-rich (`hot') shales are the origin of 80-90% of Palaeozoic sourced hydrocarbons in North Africa and also played a major role in petroleum generation on the Arabian Peninsula. In most cases, the shales were deposited directly above upper Ordovician (peri-) glacial sandstones during the initial early Silurian transgression that was a result of the melting of the late Ordovician icecap. Deposition of the main organic-rich shale unit in the North African/Arabian region was restricted to the earliest Silurian Rhuddanian stage ( acuminatus, atavus and probably early cyphus graptolite biozones). During this short period (1-2 m.y.), a favourable combination of factors existed which led to the development of exceptionally strong oxygen-deficiency in the area. In most countries of the study area, the post-Rhuddanian Silurian shales are organically lean and have not contributed to petroleum generation. The distribution and thickness of the basal Silurian `hot' shales have been mapped in detail for the whole North African region, using logs from some 300 exploration wells in Libya, Tunisia, Algeria and Morocco. In addition, all relevant, accessible published and unpublished surface and subsurface data of the lower Silurian shales in North Africa and Arabia have been reviewed, including sedimentological, biostratigraphic and organic geochemical data. The lowermost Silurian hot shales of northern Gondwana are laterally discontinuous and their distribution and thickness were controlled by the early Silurian palaeorelief which was shaped mainly by glacial processes of the late Ordovician ice age and by Pan-African and Infracambrian compressional and extensional tectonism. The thickest and areally most extensive basal Silurian organic-rich shales in North Africa occur in Algeria, Tunisia and western Libya, while on the Arabian Peninsula they are most prolific in Saudi Arabia, Oman, Jordan and Iraq. The hot shales were not deposited in Egypt, which was a

  13. The largest Silurian vertebrate and its palaeoecological implications

    PubMed Central

    Choo, Brian; Zhu, Min; Zhao, Wenjin; Jia, Liaotao; Zhu, You'an

    2014-01-01

    An apparent absence of Silurian fishes more than half-a-metre in length has been viewed as evidence that gnathostomes were restricted in size and diversity prior to the Devonian. Here we describe the largest pre-Devonian vertebrate (Megamastax amblyodus gen. et sp. nov.), a predatory marine osteichthyan from the Silurian Kuanti Formation (late Ludlow, ~423 million years ago) of Yunnan, China, with an estimated length of about 1 meter. The unusual dentition of the new form suggests a durophagous diet which, combined with its large size, indicates a considerable degree of trophic specialisation among early osteichthyans. The lack of large Silurian vertebrates has recently been used as constraint in palaeoatmospheric modelling, with purported lower oxygen levels imposing a physiological size limit. Regardless of the exact causal relationship between oxygen availability and evolutionary success, this finding refutes the assumption that pre-Emsian vertebrates were restricted to small body sizes. PMID:24921626

  14. A revised 87Sr/86Sr curve for the Silurian: Implications for global ocean chemistry and the Silurian timescale

    USGS Publications Warehouse

    Cramer, Bradley D.; Munnecke, Axel; Schofield, D.I.; Haase, K.M.; Haase-Schramm, A.

    2011-01-01

    Recent recalibration of the Silurian timescale and improved global chronostratigraphic correlation of Silurian strata significantly altered the Silurian 87Sr/86Sr curve and the temporal extent of available data. Whereas previous Silurian 87Sr/86Sr composites showed a generally monotonic increase throughout the Silurian, revisions to the Silurian timescale now require a major increase in the rate of change in 87Sr/86Sr at or near the onset of the Gorstian Age of the Ludlow Epoch. Similarly, improved chronostratigraphic correlations between Silurian outcrops on Anticosti Island, Canada, and Gotland, Sweden, indicate that the middle part of the Telychian Age, which is roughly 10%-15% of the total duration of the Silurian period, is undersampled and underrepresented in Silurian 87Sr/86Sr composites. A revised Silurian 87Sr/86Sr curve based on 241 new and published analyses confirms the significant increase in the rate of change of 87Sr/86Sr toward more radiogenic values near the base of the Ludlow Series. On the basis of these data, we propose that the rapid trend toward more radiogenic 87Sr/86Sr values is indicative of increased weathering of old sialic crust exposed during the Silurian uplift of portions of Baltica, Laurentia, and Avalonia. Importantly, however, the actual rate of change of 87Sr/86Sr will remain equivocal until the durations of Silurian epochs and ages are better constrained. ?? 2011 by The University of Chicago. All rights reserved.

  15. Cretaceous radiolarians from Baliojong ophiolite sequence, Sabah, Malaysia

    NASA Astrophysics Data System (ADS)

    Jasin, Basir; Tongkul, Felix

    2013-10-01

    The Baliojong ophiolite sequence exposed along the Baliojong River in Northern Sabah consists of volcanic rocks, mostly basalts, overlain by sedimentary layers consisting of well-bedded cherts, mudstones and sandstones. The ophiolite sequence occurs as steeply-dipping overturned thrust slices oriented approximately north-south. A total of 42 chert samples were collected from the sedimentary layers. However, most of the samples contain poorly preserved radiolarians. Only nine samples yielded moderately well-preserved radiolarians from three selected thrust slices. A total of 32 taxa were identified. Based on the stratigraphic distribution of selected taxa, the radiolarians can be divided into two assemblage zones. The first assemblage zone is Dictyomitra communis Zone characterized by the occurrence of Dictyomitra communis, Archaeodictyomitra (?) lacrimula, Sethocapsa (?) orca, Dictyomitra pseudoscalaris, and Pantanellium squinaboli. The assemblage indicates Barremian to Aptian in age. The second assemblage zone Pseudodictyomitra pseudomacrocephala Zone contains Pseudodictyomitra pseudomacrocephala, Dictyomitra gracilis, Dictyomitra montesserei, Xitus mclaughlini, and Dictyomitra obesa. This assemblage indicates an age of Albian and the presence of Pseudodictyomitra tiara suggests the age may extend up to Cenomanian. Each thrust slice yielded more or less similar radiolarian assemblages indicating that they all came from the same sedimentary layers.

  16. Evidence for changes in subsurface circulation in the late Eocene equatorial Pacific from radiolarian-bound nitrogen isotope values

    NASA Astrophysics Data System (ADS)

    Robinson, Rebecca S.; Moore, Theodore C.; Erhardt, Andrea M.; Scher, Howie D.

    2015-07-01

    Microfossil-bound organic matter represents an important archive of surface ocean environmental information. Sedimentary nitrogen (N) isotope reconstructions of surface nitrate consumption and nitrogen source changes are made using fossil diatom (autotrophs) and planktic foraminiferal (heterotrophs)-bound organic matter with success. However, because diatoms and planktic foraminifera are poorly preserved and sedimentary organic matter content is near zero during the late Eocene, our ability to examine nutrient dynamics across this important climate transition is limited. Here we present new data exploring the use of N isotope records from radiolarian tests. A comparison of surface ocean nitrate and core top bulk and radiolarian N isotope values (as δ15N) from the equatorial Pacific indicates that radiolarian-N records δ15N variability with fidelity but that a significant offset exists between bulk sedimentary and diatom δ15N values and those measured from radiolarians (~7.1 ± 1.1‰). A downcore profile of radiolarian δ15N values is compared to siliceous microfossil assemblage changes across the Eocene-Oligocene boundary. Average of radiolarian-bound δ15N values is 0.5 ± 2.0‰, which, when corrected using the offset derived from the modern surface samples, suggests that the mean nitrogen isotopic composition of the early Cenozoic eastern Pacific was not significantly different from today. The overall trend, of decreasing δ15N values with decreasing export productivity, is consistent with either a regional decline in pelagic denitrification or a large-scale change in nutrient sources to the eastern equatorial Pacific (EEP), both linked to the cooling climate and changing intermediate water circulation. Decreasing/low δ15N values cooccur with high radiolarian species turnover at ~35.5 and 34 Ma, suggestive of a significant ecological change in the EEP, consistent with cooling and water mass distribution changes. The preliminary results suggest that

  17. A New Noncalcified Dasycladalean Alga from the Silurian of Wisconsin

    USGS Publications Warehouse

    LoDuca, S.T.; Kluessendorf, Joanne; Mikulic, Donald G.

    2003-01-01

    Noncalcified thalli, consisting of a narrow main axis with numerous branched hairlike laterals in whorls and a subapical array of undivided clavate laterals, from the Silurian (Llandovery) Brandon Bridge Formation of southeastern Wisconsin, constitute the basis for a new genus and species of dasycladalean alga, Heterocladus waukeshaensis. A relationship within the family Triploporellaceae is indicated by the whorled arrangement of the laterals and the absence of gametophores on mature specimens. A compilation of occurrence data suggests that noncalcified dasyclads, as a whole, were more abundant and diverse during the Ordovician and Silurian than at any other time in their history. The heterocladous thallus architecture of this alga adds to a wide range of morphological variation documented among Ordovician and Silurian dasyclads, the sum of which indicates that Dasycladales underwent a significant evolutionary radiation during the early Paleozoic.

  18. Silurian to Early Carboniferous plate tectonic model of Central Europe

    NASA Astrophysics Data System (ADS)

    Golonka, Jan; Barmuta, Jan; Barmuta, Maria

    2014-05-01

    The presented plate tectonic model focuses on Silurian to Early Carboniferous evolution of Central Europe with special attention given to the Sudetes region (north and north-east part of the Bohemian Massif). During our studies, we tested alternative models focused on the position of the Armorican terranes, known as the Armorican Terrane Assembly (ATA) (e.g.: Matte, 2001) and tried to refine the existing reconstructions, which describe Armorica as an individual continent during the Late Silurian and Devonian (e.g. Lewandowski, 2003, Winchester, 2002). Our plate tectonic model depict that these small blocks were scattered along the northern margin of Gondwana, where they formed the "Armorican Spour" as suggested by Kroner and Romer (2013). The seaways were present between blocks. Because of the north dipping subduction zone along the southern margin of the Laurussia continent the back-arc basin and island arc were formed. The narrowing of the Rheic ocean led to the complicated collision of Gondwana and Laurussia. Three main stages of this event can be distinguished: (1) collision of the Armorican Spour with the Laurussian island arc, (2) back-arc basin closure, (3) final Gondwana and Laurussian collision. Those stages correlate well with Variscan Subduction Zone System proposed by Kroner and Romer (2013). Interactive modeling performed in GPlates, shows that the presented model is valid from kinematic and geometrical point of view. Kroner U., Romer R., L., 2013, Two plates - many subduction zones: the Variscan orogeny reconsidered. Gondwana Research, 24: 298-329. Lewandowski M., 2003, Assembly of Pangea: Combined paleomagnetic and paleoclimatic approach, Advances in Geophysics, 46: 199-236 Matte P., 2001, The Variscan collage and orogeny (480 290 Ma) and the tectonic definition of the Armorica microplate: a review. Terra Nova, 13: 122¨C128. Winchester J., A., The Pace TMR Network Team, 2002, Palaeozoic amalgamation of Central Europe: new results from recent

  19. Silurian pinnacle reefs of the Canadian Arctic

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    De Freitas, T.A.; Dixon, O.A.; Mayr, U.

    1993-04-01

    Pinnacle reefs are commonly an attractive target for oil exploration because they are usually porous carbonate bodies entombed in impervious, deep-water shales that provide both the source and the seal for hydrocarbons. Silurian pinnacle reefs, the first described in the Canadian Arctic Archipelago, are exposed on Ellesmere and Devon Islands. Two main reef trends occur, one of early middle Llandovery to middle Ludlow age and a second of middle Ludlow to Late Silurian or Early Devonian age. Reefs of both phases contain lime mudstone cores: some are stromatactoid-rich and others consist predominantly of microbialite-rich lime mudstone or microbial boundstone. Faciesmore » sequences of both reef phases show evidence of upward-shallowing overall, but, in the older reefs, isochronous capping facies are dominated either by coral-mirian or by stromatoporoid boundstone and floatstone. This difference perhaps reflects variation in wave stress and apparent ability of a few corals,thickly encrusted by or associated with microbial boundstone and skeletal algae, to withstand greater wave energy than a stromatoporoid-coral-rich reef community. These reefs constitute one of the bright prospects of hydrocarbon exploration in rocks of the Franklinian succession. 43 refs., 9 figs.« less

  20. Late Jurassic-Early Cretaceous radiolarian age constraints from the sedimentary cover of the Amasia ophiolite (NW Armenia), at the junction between the Izmir-Ankara-Erzinçan and Sevan-Hakari suture zones

    NASA Astrophysics Data System (ADS)

    Danelian, T.; Asatryan, G.; Galoyan, Gh.; Sahakyan, L.; Stepanyan, J.

    2016-01-01

    The Amasia ophiolite, situated at the northernmost corner of Armenia, is part of the Sevan-Hakari suture zone which links with the Izmir-Ankara-Erzinçan suture zone in northern Turkey. Three new radiolarian assemblages have been extracted from siliceous sedimentary rocks that accumulated on the Amasia ophiolite in an oceanic setting. Two of these assemblages were extracted from red-brownish bedded cherts overlying basaltic lavas; one of these is likely to be middle Oxfordian to early Kimmeridgian in age, while the second correlates with the Berriasian. Similar time-equivalent lava-chert sequences have been dated recently using radiolarians from the Stepanavan, Vedi and Sevan ophiolite units, where they are considered to relate to submarine volcanic activity in the back-arc marginal basin in which the Armenian ophiolites were formed. The third radiolarian assemblage, of late Barremian age, was extracted from a more than 15-m-thick volcaniclastic-chert sequence. The related volcanic activity is likely to have been subaerial and probably relates to the formation of an oceanic volcanic plateau; no Cretaceous subaerial volcanism has been previously recorded in the Lesser Caucasus area.

  1. Environmental determinants of radiolarian assemblages in the western Pacific since the last deglaciation

    NASA Astrophysics Data System (ADS)

    Hernández-Almeida, I.; Cortese, G.; Yu, P.-S.; Chen, M.-T.; Kucera, M.

    2017-08-01

    Radiolarians are a very diverse microzooplanktonic group, often distributed in regionally restricted assemblages and responding to specific environmental factors. These properties of radiolarian assemblages make the group more conducive for the development and application of basin-wide ecological models. Here we use a new surface sediment data set from the western Pacific to demonstrate that ecological patterns derived from basin-wide open-ocean data sets cannot be transferred on semirestricted marginal seas. The data set consists of 160 surface sediment samples from three tropical-subtropical regions (East China Sea, South China Sea, and western Pacific), combining 54 new assemblage counts with taxonomically harmonized data from previous studies. Multivariate statistical analyses indicate that winter sea surface temperature at 10 m depth (SSTw) was the most significant environmental variable affecting the composition of radiolarian assemblages, allowing the development of an optimal calibration model (Locally Weighted-Weighted Averaging regression inverse deshrinking, R2cv = 0.88, root-mean-square error of prediction = 1.6°C). The dominant effect of SSTw on radiolarian assemblage composition in the western Pacific is attributed to the East Asian Winter Monsoon (EAWM), which is particularly strong in the marginal seas. To test the applicability of the calibration model on fossil radiolarian assemblages from the marginal seas, the calibration model was applied to two downcore records from the Okinawa Trough, covering the last 18 ka. We observe that these assemblages find most appropriate analogs among modern samples from the marginal basins (East China Sea and South China Sea). Downcore temperature reconstructions at both sites show similarities to known regional SST reconstructions, providing proof of concept for the new radiolarian-based SSTw calibration model.

  2. Radiolarian indicators of El Nino and anti-El Nino events in Holocene sediments of Santa Barbara basin

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Weinheimer, A.L.

    Radiolarian distributions and physical oceanographic data from the Santa Barbara basin indicate the following. Strong anti-El Nino periods can be characterized by (1) intermediate radiolarian density, (2) high percentage of transition-central radiolarian fauna, and (3) low percentage and number of warm-water radiolarian fauna. This distribution pattern is attributed to strong wind-driven upwelling and reduced northward transport by the California Countercurrent during anti-El Nino periods. Strong El Nino periods are typically (1) high in radiolarian density, and (2) low in percentage but high in number of warm-water fauna. This distribution is attributed to reduced wind-driven upwelling, enhanced northward countercurrent transport, andmore » geostrophic doming of the cold-water masses in the shear zone between the California Current and California Countercurrent.« less

  3. A new osteichthyan from the late Silurian of Yunnan, China.

    PubMed

    Choo, Brian; Zhu, Min; Qu, Qingming; Yu, Xiaobo; Jia, Liantao; Zhao, Wenjin

    2017-01-01

    Our understanding of early gnathostome evolution has been hampered by a generally scant fossil record beyond the Devonian. Recent discoveries from the late Silurian Xiaoxiang Fauna of Yunnan, China, have yielded significant new information, including the earliest articulated osteichthyan fossils from the Ludlow-aged Kuanti Formation. Here we describe the partial postcranium of a new primitive bony fish from the Kuanti Formation that represents the second known taxon of pre-Devonian osteichthyan revealing articulated remains. The new form, Sparalepis tingi gen. et sp. nov., displays similarities with Guiyu and Psarolepis, including a spine-bearing pectoral girdle and a placoderm-like dermal pelvic girdle, a structure only recently identified in early osteichthyans. The squamation with particularly thick rhombic scales shares an overall morphological similarity to that of Psarolepis. However, the anterior flank scales of Sparalepis possess an unusual interlocking system of ventral bulges embraced by dorsal concavities on the outer surfaces. A phylogenetic analysis resolves Sparalepis within a previously recovered cluster of stem-sarcopterygians including Guiyu, Psarolepis and Achoania. The high diversity of osteichthyans from the Ludlow of Yunnan strongly contrasts with other Silurian vertebrate assemblages, suggesting that the South China block may have been an early center of diversification for early gnathostomes, well before the advent of the Devonian "Age of Fishes".

  4. Glacial - interglacial changes of northwest Pacific stratification, inferred from deep and shallow living radiolarians

    NASA Astrophysics Data System (ADS)

    Hays, J. D.

    2009-12-01

    Shallow (0-200m) and deep (200 to1000m) living radiolarian flux is used to measure past production from within discrete intervals of the ocean’s water column. Deep-living faunas can also be used as proxies for export production, for they remineralize it and respond geographically and temporally to varying export. Few members of the mesopelagic community leave a fossil record, but of those that do, radiolarians are the most abundant and diverse group. In northwest Pacific late Pleistocene (glacial) sediments, deep-living radiolarian flux dominates over shallow-living flux, but the reverse is true in Holocene sediments, with the dramatic dominance change occurring across the Pleistocene-Holocene boundary. Changing primary productivity can’t cause these flux changes, for shallow-living faunas have access to the same carbon flux as do deep-living faunas, but rather they signal a major reorganization of the radiolarian fauna within the water column and suggest greater glacial than Holocene carbon export. In the Holocene world-ocean, the only region where deep-living radiolarian flux dominates over shallow-living flux is in the Sea of Okhotsk, suggesting environmental similarities between this sea and the northwest Pacific. In winter, cold Siberian air chills the upper hundred meters of the Sea of Okhotsk, promoting the spread of vast sea ice fields. High productivity in a thin (10-15m) summer mixed layer depletes nutrients Between 15 and about 150m exists a layer of cold (-1 to 0 degrees C.) intermediate water, within which radiolarian concentrations are low, but these concentrations increase between 200 and 500m in warmer intermediate water (Nimmergut and Abelmann, 2002). This radiolarian stratification results in greater deep- than shallow-living radiolarian flux to the sea floor. A similar water structure in the glacial northwest Pacific is the probable cause of similar flux patterns between the glacial northwest Pacific and Holocene Sea of Okhotsk. If so then

  5. Agglutinated foraminifera from the Ludlow (Silurian) of Ireland

    NASA Astrophysics Data System (ADS)

    Kaminski, Michael; Ferretti, Annalisa; Messori, Fabio; Papazzoni, Cesare Andrea; Sevastopulo, George

    2017-04-01

    Agglutinated foraminifera are one of the most primitive groups of foraminifera, possibly already appearing in the Cryogenian but usually rare in lower Paleozoic rocks. Their mean standing diversity slowly increased during Cambrian and Ordovician times, reaching a stable value of about 50 genera in the mid-Silurian which remained fairly constant up to the Triassic. An assemblage of agglutinated foraminifera was unexpectedly found in conodont residue from material collected in the Dingle Peninsula, County Kerry, southwestern Ireland. This material comes from rare calcareous occurrences in volcanoclastics previously known for their rich trilobite and conodont assemblages. The limestones are trilobite-crinoidal silty wackestone to packstone, with local brachiopod concentrations, documenting brachiopod-trilobite-crinoidal dominated communities of shallow and well-ventilated water that might have periodically colonized the bottom intercalating with volcanic events and then successively redeposited in deeper waters. The conodont fauna indicates an early Ludlow (Gorstian-earliest Ludfordian) age (Kaminski et al., 2016). The foraminiferal assemblage has limited potential for stratigraphical correlation as long-range taxa are present, but it represents the first record from the Silurian of Ireland. The assemblage is dominated by tubothalamids (Rectoammodiscus and rare Sansabaina), with less abundant monothalamids (Psammosiphonella and Psammosphaera). The assemblage displays low diversity compared with other assemblages described from the British Isles (Kircher & Brasier, 1989). At the species level, this assemblage is identical to those described previously from the Silurian of North America but with lower diversity. Only Rectoammodiscus diai had apparently a wider geographic distribution, including not only the central USA (Oklahoma and Kansas) but also the Welsh Borderlands and Senegal. The affinities with the assemblages reported at several localities in the central

  6. Silurian gastropoda from southeastern and west-central Alaska

    USGS Publications Warehouse

    Rohr, D.M.; Blodgett, R.B.; Fryda, J.

    2008-01-01

    Additional Silurian (Ludlovian) gastropods are described from the Heceta Formation in the Alexander terrane on Prince of Wales Island, southeastern Alaska. Species include Spinicharybdis krizi n. sp., Spinicharybdis boucoti n. sp., Morania wagneri n. sp., Haplospira craigi n. sp., Australonema sp., Pachystrophia cf. gotlandica (Lindstro??m, 1884), and Medfrazyga gilmulli n. sp. An additional new Silurian species, Morania nixonforkensis n. sp., is described from the Nixon Fork subterrane of the Farewell terrane of west-central Alaska. The spine-bearing Spinicharybdis is placed into a new subfamily Spinicharybdiinae together with Hystricoceras Jahn, 1894. Joint occurrences of genera Beraunia, Coelocaulus, and Morania, as well as members of subfamily Spinicharybdiinae in the gastropod fauna from the Heceta Formation, support its close relationship with gastropod fauna of Bohemia. Additionally, the occurrence of the genus Medfrazyga suggests a faunal link between the Alexander and Farewell terranes of Alaska. Medfrazyga gilmulli n. sp. is the oldest known and the only early Paleozoic member of the family Palaeozygopleuridae. Copyright ?? 2008, The Paleontological Society.

  7. New Radiolarian Age Constraints on the Emplacement History of the Manipur Ophiolitic Complex, India: the Timing of 'soft Collision'

    NASA Astrophysics Data System (ADS)

    Kachovich, S.; Aitchison, J. C.; Lokho, K.; Stojanovic, D.

    2016-12-01

    The Manipur Ophiolite complex in the Indo-Burman ranges is characterised by a north-south trending belt of ophiolitic and related oceanic volcanic and sedimentary rocks. The ophiolite is considered to have formed in Jurassic time as part of an intra-oceanic subduction zone. It was subsequently emplaced onto the continental margin of India. Although the ophiolite is extensively disrupted, well-exposed outcrops exist in new road cuttings. We present new results from investigations of associated oceanic pelagic sequences amongst which radiolarian microfossils help to constrain the timing for the emplacement event. Pelagic sediments assigned to the Disang Formation that crop out near Khamasom village, west of Ukhrul city are characterised by extensive fault-bounded packages of reddish-coloured, radiolarian-bearing mudstones. They yield abundant well-preserved, late Palaeocene to early Eocene radiolarians. As the ophiolitic rocks are thrust over these radiolarian-bearing sediments, they provide a precise biostratigraphic maximum age with which to constrain any ophiolite emplacement event. Elsewhere along the length of the Indus-Yarlung Tsangpo suture zone from NW India (Spongtang, Ladakh) in the west as well as at Zhongba, Sangdanlin and Gyantse across Tibet, correlative radiolarian faunas provide similar age constraints suggesting that this event was broadly coeval. Collision of an intra-oceanic island arc system with northern margin of the Indian continent over such an extensive strike length must be of regional significance. Moreover, given that this was an intra-Tethyan system it's collision (the `soft-collision' postulated by Curray et al. 1982) must pre-date later (hard) continent-continent collision. Reference: Curray, J.R., Emmel, F.J., Moore, D.G., Raitt, R.W., 1982. Structure, tectonics, and geological history of the northeastern Indian Ocean. In; Nairn, A.E.M. The Ocean Basins and Margins vol. 6: 399-450, Plenum Press.

  8. Polygenetic Karsted Hardground Omission Surfaces in Lower Silurian Neritic Limestones: a Signature of Early Paleozoic Calcite Seas

    NASA Astrophysics Data System (ADS)

    James, Noel P.; Desrochers, André; Kyser, Kurt T.

    2015-04-01

    Exquisitely preserved and well-exposed rocky paleoshoreline omission surfaces in Lower Silurian Chicotte Formation limestones on Anticosti Island, Quebec, are interpreted to be the product of combined marine and meteoric diagenesis. The different omission features include; 1) planar erosional bedding tops, 2) scalloped erosional surfaces, 3) knobs, ridges, and swales at bedding contacts, and 4) paleoscarps. An interpretation is proposed that relates specific omission surface styles to different diagenetic-depositional processes that took place in separate terrestrial-peritidal-shallow neritic zones. Such processes were linked to fluctuations in relative sea level with specific zones of diagenesis such as; 1) karst corrosion, 2) peritidal erosion, 3) subtidal seawater flushing and cementation, and 4) shallow subtidal deposition. Most surfaces are interpreted to have been the result of initial extensive shallow-water synsedimentary lithification that were, as sea level fell, altered by exposure and subaerial corrosion, only to be buried by sediments as sea level rose again. This succession was repeated several times resulting in a suite of recurring polyphase omission surfaces through many meters of stratigraphic section. Synsedimentary cloudy marine cements are well preserved and are thus interpreted to have been calcitic originally. Aragonite components are rare and thought to have to have been dissolved just below the Silurian seafloor. Large molluscs that survived such seafloor removal were nonetheless leached and the resultant megamoulds were filled with synsedimentary calcite cement. These Silurian inner neritic-strandline omission surfaces are temporally unique. They are part of a suite of marine omission surfaces that are mostly found in early Paleozoic neritic carbonate sedimentary rocks. These karsted hardgrounds formed during a calcite-sea time of elevated marine carbonate saturation and extensive marine cement precipitation. The contemporaneous greenhouse

  9. Evidences of Silurian dextral transpression in the Scandinavian Caledonides

    NASA Astrophysics Data System (ADS)

    Torgersen, Espen; Viola, Giulio

    2017-04-01

    The Scandinavian Caledonides are classically interpreted as a fold and thrust belt resulting from the collision between Laurentia and Baltica during the Silurian, which involved the up-to-400 km ESE-wards translation of nappes onto the Baltoscandian platform. It has been suggested that the Caledonian fold and thrust belt formed through several distinct orogenic episodes, from early shortening in the Late Ordovician to orogenic collapse in the Devonian. The classic Caledonian, orogen-perpendicular ESE-ward nappe transport is constrained by abundant and consistently oriented stretching lineations across the entire orogen and unambiguous kinematic indicators. However, there is also a large number of NW-SE-trending and roughly orogen-parallel lineations, particularly in the upper ophiolite- and eclogite-bearing nappes, which are more challenging to interpret with the traditional orogeny evolution model. The analysis of the areal extent, spatial distribution and geometrical relationships of the Caledonian nappes in southern and central Norway, however, offers new insights and allows for new constraints on the bulk kinematic framework of the shortening history of the belt. Here we present new, first-order geological observations that demonstrate a two-fold compressional history and associated strain partitioning during Caledonian convergence. More specifically, we propose that Late Ordovician NNW-SSE shortening caused early compression, followed by WNW-ESE Early Silurian shortening, which resulted in strain partitioning along the planar fabrics and discontinuities from the earlier event. In detail, orogen-parallel dextral wrench tectonics caused significant lateral displacement along at least three, orogen-scale NE-SW striking corridors, wherein the nappes appear to be consistently displaced in a dextral fashion. We propose that the Møre-Trøndelag Fault Complex, which accommodated significant sinistral displacements during the later Devonian orogenic collapse

  10. Sperm carriers in Silurian sea scorpions

    NASA Astrophysics Data System (ADS)

    Kamenz, Carsten; Staude, Andreas; Dunlop, Jason A.

    2011-10-01

    Invasion of the land by arachnids required adaptations of numerous organs, such as gills evolving into lungs, as well as mechanisms facilitating sperm transfer in a terrestrial environment. Many modern arachnids use spermatophores for this purpose, i.e. sperm transmitters detached from the body. Exceptionally preserved Silurian (423 Ma) fossils of Eurypterus tetragonophthalmus Fischer, 1839 (Chelicerata: Eurypterida) preserve so-called `horn organs' which we here demonstrate as being equivalent to the spermatophore-producing parts of the genital tract in certain modern arachnids. This clarifies a long-running debate about sexing eurypterids based on the shape of the median abdominal (or genital) appendage. To our knowledge this is also the oldest direct evidence for spermatophore-mediated sperm transfer in the fossil record and suggests that eurypterids had evolved mating techniques using spermatophores as early as the Silurian, a valuable prerequisite for life on land. Spermatophores are absent in sea spiders (Pycnogonida) and horseshoe crabs (Xiphosura); thus the shared presence of sclerotized sperm-transfer devices in eurypterids and arachnids is a novel character, newly elucidated here, which offers explicit support for (Eurypterida + Arachnida). For this clade the name Sclerophorata n. nov. is proposed. Arachnida can be further defined by fusion of the originally paired genital opening.

  11. Radiolarians decreased silicification as an evolutionary response to reduced Cenozoic ocean silica availability

    PubMed Central

    Lazarus, David B.; Kotrc, Benjamin; Wulf, Gerwin; Schmidt, Daniela N.

    2009-01-01

    It has been hypothesized that increased water column stratification has been an abiotic “universal driver” affecting average cell size in Cenozoic marine plankton. Gradually decreasing Cenozoic radiolarian shell weight, by contrast, suggests that competition for dissolved silica, a shared nutrient, resulted in biologic coevolution between radiolaria and marine diatoms, which expanded dramatically in the Cenozoic. We present data on the 2 components of shell weight change—size and silicification—of Cenozoic radiolarians. In low latitudes, increasing Cenozoic export of silica to deep waters by diatoms and decreasing nutrient upwelling from increased water column stratification have created modern silica-poor surface waters. Here, radiolarian silicification decreases significantly (r = 0.91, P < 0.001), from ≈0.18 (shell volume fraction) in the basal Cenozoic to modern values of ≈0.06. A third of the total change occurred rapidly at 35 Ma, in correlation to major increases in water column stratification and abundance of diatoms. In high southern latitudes, Southern Ocean circulation, present since the late Eocene, maintains significant surface water silica availability. Here, radiolarian silicification decreased insignificantly (r = 0.58, P = 0.1), from ≈0.13 at 35 Ma to 0.11 today. Trends in shell size in both time series are statistically insignificant and are not correlated with each other. We conclude that there is no universal driver changing cell size in Cenozoic marine plankton. Furthermore, biologic and physical factors have, in concert, by reducing silica availability in surface waters, forced macroevolutionary changes in Cenozoic low-latitude radiolarians. PMID:19458255

  12. Radiolarians decreased silicification as an evolutionary response to reduced Cenozoic ocean silica availability.

    PubMed

    Lazarus, David B; Kotrc, Benjamin; Wulf, Gerwin; Schmidt, Daniela N

    2009-06-09

    It has been hypothesized that increased water column stratification has been an abiotic "universal driver" affecting average cell size in Cenozoic marine plankton. Gradually decreasing Cenozoic radiolarian shell weight, by contrast, suggests that competition for dissolved silica, a shared nutrient, resulted in biologic coevolution between radiolaria and marine diatoms, which expanded dramatically in the Cenozoic. We present data on the 2 components of shell weight change--size and silicification--of Cenozoic radiolarians. In low latitudes, increasing Cenozoic export of silica to deep waters by diatoms and decreasing nutrient upwelling from increased water column stratification have created modern silica-poor surface waters. Here, radiolarian silicification decreases significantly (r = 0.91, P < 0.001), from approximately 0.18 (shell volume fraction) in the basal Cenozoic to modern values of approximately 0.06. A third of the total change occurred rapidly at 35 Ma, in correlation to major increases in water column stratification and abundance of diatoms. In high southern latitudes, Southern Ocean circulation, present since the late Eocene, maintains significant surface water silica availability. Here, radiolarian silicification decreased insignificantly (r = 0.58, P = 0.1), from approximately 0.13 at 35 Ma to 0.11 today. Trends in shell size in both time series are statistically insignificant and are not correlated with each other. We conclude that there is no universal driver changing cell size in Cenozoic marine plankton. Furthermore, biologic and physical factors have, in concert, by reducing silica availability in surface waters, forced macroevolutionary changes in Cenozoic low-latitude radiolarians.

  13. A technique for extracting Radiolaria from radiolarian cherts.

    NASA Technical Reports Server (NTRS)

    Pessagno, E. A., Jr.; Newport, R. L.

    1972-01-01

    Differential solution of Mesozoic radiolarian cherts with hydrofluoric acid has yielded well-preserved, matrix-free Radiolaria. This technique allows the full utilization of Radiolaria in interpreting the stratigraphy of ophiolite sequences and of other successions where cherts are prevalent.

  14. Molecular marker to identify radiolarian species -toward establishment of paleo-environmental proxy-

    NASA Astrophysics Data System (ADS)

    Ishitani, Y.

    2017-12-01

    Marine fossilized unicellular plankton are known to have many genetically divergent species (biological species) in the single morphological species and these biological species show the species-specific environments much more precisely than that of morphological species. Among these plankton, Radiolaria are one of the best candidates for time- and environmental-indicators in the modern and past oceans, because radiolarians are the only group which represent entire water column from shallow to deep waters. However, the ecology and evolution of radiolarian were traditionally studied in paleontology and paleoceanography by morphological species. Even Radiolaria has a huge potential for novel proxy of wide and deep environments, there is no criterion to identify the biological species. The motivation for this study is setting the quantitative delimitation to establish the biological species of radiolarians based on molecular data, for leading the future ecological and paleo-environmental study. Identification of the biological species by ribosomal DNA sequences are mainly based on two ways: one is the evolutionary distance of the small subunit (SSU) rDNA, the internal transcribed spacer region of ribosomal DNA (ITS1 and 2), and the large subunit (LSU) rDNA; and the other is the secondary structure of ITS2. In the present study, all four possible genetic markers (SSU, ITS1, ITS2, and LSU rDNA) were amplified from 232 individuals of five radiolarian morphological species and applied to examine the evolutionary distance and secondary structure of rDNA. Comprehensive survey clearly shows that evolutionary distance of ITS1 rDNA and the secondary structure of ITS2 is good to identify the species. Notably, evolutionary distance of ITS1 rDNA is possible to set the common delimitation to identify the biological species, as 0.225 substitution per site. The results show that the ITS1 and ITS 2 rDNA could be the criterion for radiolarian species identification.

  15. Silurian sequence stratigraphy in the North American craton, Great Lakes area

    USGS Publications Warehouse

    Shaver, R.H.; ,

    1996-01-01

    A notable circumstance of late Early through Late Silurian sedimentation on the Great Lakes area craton is that at least two and possibly three cycles of third-order duration (if eustatically considered) are recognized in basin and shallow-platform settings alike. Both virtually pure and siliciclastic-rich carbonate rocks exist in parts of platform-situated sections in contrast to siliciclastic-rich to evaporite-dominated basin sections. Knowledge of the reef history, together with evidence of incidental periodic incursions of siliciclastic sediments, permitted understanding of a regional event or sequence stratigraphy more than 15 years ago before conventional biostratigraphic and physical stratigraphic evidence became adequate to corroborate. This midwestern US and Ontario Silurian record has become strategic for testing different schools of thought that champion either tectonism or eustasy to explain cyclical sequences.

  16. Abrupt global-ocean anoxia during the Late Ordovician-early Silurian detected using uranium isotopes of marine carbonates.

    PubMed

    Bartlett, Rick; Elrick, Maya; Wheeley, James R; Polyak, Victor; Desrochers, André; Asmerom, Yemane

    2018-05-21

    Widespread marine anoxia is hypothesized as the trigger for the second pulse of the Late Ordovician (Hirnantian) mass extinction based on lithologic and geochemical proxies that record local bottom waters or porewaters. We test the anoxia hypothesis using δ 238 U values of marine limestones as a global seawater redox proxy. The δ 238 U trends at Anticosti Island, Canada, document an abrupt late Hirnantian ∼0.3‰ negative shift continuing through the early Silurian indicating more reducing seawater conditions. The lack of observed anoxic facies and no covariance among δ 238 U values and other local redox proxies suggests that the δ 238 U trends represent a global-ocean redox record. The Hirnantian ocean anoxic event (HOAE) onset is coincident with the extinction pulse indicating its importance in triggering it. Anoxia initiated during high sea levels before peak Hirnantian glaciation, and continued into the subsequent lowstand and early Silurian deglacial eustatic rise, implying that major climatic and eustatic changes had little effect on global-ocean redox conditions. The HOAE occurred during a global δ 13 C positive excursion, but lasted longer indicating that controls on the C budget were partially decoupled from global-ocean redox trends. U cycle modeling suggests that there was a ∼15% increase in anoxic seafloor area and ∼80% of seawater U was sequestered into anoxic sediments during the HOAE. Unlike other ocean anoxic events (OAE), the HOAE occurred during peak and waning icehouse conditions rather than during greenhouse climates. We interpret that anoxia was driven by global cooling, which reorganized thermohaline circulation, decreased deep-ocean ventilation, enhanced nutrient fluxes, stimulated productivity, which lead to expanded oxygen minimum zones. Copyright © 2018 the Author(s). Published by PNAS.

  17. New paleontological and geological data on the Ordovician and Silurian of Bolivia

    NASA Astrophysics Data System (ADS)

    Gagnier, P. Y.; Blieck, A.; Emig, C. C.; Sempere, T.; Vachard, D.; Vanguestaine, M.

    1996-11-01

    The oldest vertebrates of South America are from the thick Anzaldo (=Cuchupunata) Formation in central Bolivia. At the scale of the basin, the Anzaldo is overlain by the San Benito, Tokochi, Cancañiri, Llallagua and Kirusillas/Uncía formations. The Anzaldo was classically dated Caradoc (early Late Ordovician), but recent paleontological data have suggested a Llanvirn age (early Middle Ordovician). The only significant fossil invertebrates recently collected in the Anzaldo, viz., lingulid brachiopods, give an age not older than Late Ordovician. Fossils from the Tokochi suggest a Caradoc age. The microfossils (acritarchs and foraminifers mainly) collected in the Cancañiri and Kirusillas/Uncía formations indicate an Ashgill to Wenlock age (late Late Ordovician to late Early Silurian) for these formations. A Caradoc (or perhaps older) age thus seems more correct for the Anzaldo Formation. These new paleontological data have major implications on our knowledge of the Ordovician-Silurian basins of Bolivia: 1) transition from a Middle Ordovician marine foreland basin to a Late Ordovician-Llandovery glacial-marine to turbidite trough in the Altiplano occurred in the (late?) Caradoc; 2) a major sea-level rise developed around the Llandovery-Wenlock boundary; 3) a fossiliferous limestone member of shallow origin and early Wenlock age is present approximately between Cochabamba and Santa Cruz.

  18. Planktonic foraminifers and radiolarians from the Coniacian-santonian deposits of the Mt. Ak-Kaya, Crimean Mountains, Ukraine

    NASA Astrophysics Data System (ADS)

    Korchagin, O. A.; Bragina, L. G.; Bragin, N. Yu.

    2012-02-01

    The first data on the distribution of planktonic foraminifers and radiolarians in the Mt. Ak-Kaya section, the central Crimean Mountains, are considered. According to the analyzed distribution of foraminifers, the Upper Cretaceous deposits of the section are subdivided into three biostratigraphic units: the Marginotruncana austinensis-Globotruncana desioi (presumably upper Coniacian), Sigalia carpatica (uppermost Coniacian-lower Santonian), and Contusotruncana fornicata-Marginotruncana marginata (upper Santonian) beds. Subdivisions substantiated by distribution of radiolarians are the Alievium praegallowayi-Crucella plana (upper Coniacian-lower Santonian), Alievium gallowayi-Crucella espartoensis (the upper Santonian excluding its uppermost part), and Dictyocephalus (Dictyocryphalus) (?) legumen-Spongosaturninus parvulus (the uppermost Santonian) beds. The Contusotruncana fornicata-Marginotruncana marginata Beds are concurrent to the middle part of the Marsupites laevigatus Zone coupled with the Marsupites testudinarius Zone (the uppermost Santonian). The Alievium gallowayi-Crucella espartoensis Beds are correlative with the upper part of the Alievium gallowayi Zone in the Californian radiolarian zonation. The cooccurring assemblages of planktonic foraminifers and radiolarians provide a possibility to correlate the Coniacian-Santonian deposits within the Crimea-Caucasus region.

  19. A late Frasnian (Late Devonian) radiolarian, sponge spicule, and conodont fauna from the Slaven Chert, northern Shoshone Range, Roberts Mountains allochthon, Nevada

    USGS Publications Warehouse

    Boundy-Sanders, S. Q.; Sandberg, C.A.; Murchey, B.L.; Harris, A.G.

    1999-01-01

    Co-occuring conodonts, radiolarians, and sponge spicules from the type locality of the Slaven Chert, northern Shoshone Range, Nevada, indicate that the radiolarian and sponge spicule assemblage described herein correlates with the Late rhenana conodont Zone (late Frasnian). The moderately well preserved radiolarians are the first Frasnian-age fauna described from the Western Hemisphere. They include spumellarians, Ceratoikiscum, and Paleoscenidium, and a radiolarian which we have assigned to a new genus, Durahelenifore Boundy-Sanders and Murchey, with its type species, Durahelenifore robustum Boundy-Sanders and Murchey. Sponge spicules include umbellate microscleres of the Subclass Amphidiscophora, Order Hemidiscosa, previously documented only in Pennsylvanian and younger rocks.

  20. Silurian Gastropoda from the Alexander terrane, southeast Alaska

    USGS Publications Warehouse

    Rohr, D.M.; Blodgett, R.B.

    2008-01-01

    Gastropods are described from Ludlow-age strata of the Heceta Limestone on Prince of Wales Island, southeast Alaska. They are part of a diverse megabenthic fauna of the Alexander terrane, an accreted terrane of Siberian or Uralian affinities. Heceta Limestone gastropods with Uralian affinities include Kirkospira glacialis, which closely resembles "Pleurotomaria" lindstromi Oehlert of Chernyshev, 1893, Retispira cf. R. volgulica (Chernyshev, 1893), and Medfracaulus turriformis (Chernyshev, 1893). Medfracaulus and similar morphotypes such as Coelocaulus karlae are unknown from rocks that are unquestionably part of the North American continent (Laurentia) during Late Silurian time. Beraunia is previously known only from the Silurian of Bohemia. Pachystrophia has previously been reported only from western North American terranes (Eastern Klamath, York, and Farewell terranes) and Europe. Bathmopterus Kirk, 1928, is resurrected and is only known from the Silurian of southeast Alaska. Newly described taxa include Hecetastoma gehrelsi n. gen. and n. sp. and Baichtalia tongassensis n. gen. and n. sp. ??2008 The Geological Society of America.

  1. Late Quaternary paleoceanographic changes in the southwestern Okhotsk Sea: Evidence from geochemical, radiolarian, and diatom records

    NASA Astrophysics Data System (ADS)

    Okazaki, Yusuke; Takahashi, Kozo; Katsuki, Kota; Ono, Ayumu; Hori, Joichi; Sakamoto, Tatsuhiko; Uchida, Masao; Shibata, Yasuyuki; Ikehara, Minoru; Aoki, Kaori

    2005-08-01

    High-resolution analyses of geochemical parameters (biogenic opal, calcium carbonate, organic carbon, and nitrogen) and microfossil assemblages (diatoms and radiolarians) on Core MD01-2412 clarified detailed paleoceanographic changes such as sea-ice cover and biological production in the southwestern Okhotsk Sea during the last 115 kyr. An age model of Core MD01-2412 was established based on δ 18O stratigraphy, accelerator mass spectrometer (AMS) 14C, and tephrochronology. Sea-ice history reconstructed by siliceous microplankton records indicated that the present sea-ice condition was formed during the last 8 kyr. Only during Marine Isotope Stage (MIS) 2 was the duration of sea-ice cover in this region much longer than that of today (4-5 months a year). Two diatom species, Thalassionema nitzschioides and Fragilariopsis doliolus, revealed that the Soya Warm Current Water (SWCW) flowed into the Okhotsk Sea near the site of Core MD01-2412 during the last 12-14 kyr and during MIS 5a, and was associated with sea-level rise. Biological productivity rapidly increased during MIS 1, associated with sea-ice retreat. Two major increases of organic carbon (OC) contents (wt%) and C org/N ratios were observed, and the timings of these events were 15.8-16.7 ka (Event 1) and 13.1-13.6 ka (Event 2). Corresponding to these events, the abundance of Cycladophora davisiana, an intermediate water dwelling radiolarian species, increased. This high C. davisiana abundance can be correlated to the input of terrestrial organic matter from the submerged shelf to the intermediate water. Apart from the radiolarians, the production of diatoms in the surface waters was suppressed by the development of well-stratified surface water along with sea-ice melting during the early Holocene. Diatom production increased gradually during the last 10 kyr with enhanced vertical mixing.

  2. Early Silurian to Early Carboniferous ridge subduction in NW Junggar: Evidence from geochronological, geochemical, and Sr-Nd-Hf isotopic data on alkali granites and adakites

    NASA Astrophysics Data System (ADS)

    Zhang, Chen; Santosh, M.; Liu, Luofu; Luo, Qun; Zhang, Xin; Liu, Dongdong

    2018-02-01

    The Central Asian Orogenic Belt (CAOB) evolved through a long-lived orogeny involving multiple episodes of subduction and accretion marking a major phase of continental growth during the Paleozoic. The northern part of the Western Junggar region (NW Junggar) offers a window into these processes, particularly to constrain the timing of closure of the Paleo-Asian Ocean. Here we report geochemical, geochronological, and isotopic data from K-feldspar granites and adakitic rocks from the NW Junggar region. Zircon U-Pb ages suggest that the granites were emplaced during Early Silurian to the Early Carboniferous (434-328 Ma). The granites show geochemical characteristics similar to those of A-type granites, with high SiO2 (71.13-76.72 wt%), Na2O + K2O (8.00-9.59 wt%), and Al2O3 (12.28-14.08 wt%), but depleted Sr, Nb, Ta and Eu. They display moderate to high positive εNd(t) and εHf(t) values (4.26-8.21 and 7.69-14.60, respectively) and young Nd and Hf model ages (T2DM-Nd = 489-740 Ma and T2DM-Hf = 471-845 Ma), suggesting magma derivation through partial melting of lower crust in the Boshchekul-Chingiz and Zharma-Saur arcs. The adakites are characterized by high Sr content (406.5-751.6 ppm), and low Y (13.8-16.4 ppm) and Yb (1.5-1.8 ppm) content, yielding relatively high Sr/Y ratios (25.38-49.41) similar to those of modern adakites. They have high positive εNd(t) and εHf(t) values (7.85-8.25 and 13.23-15.97, respectively) and young Nd and Hf model ages (T2DM-Nd = 429-535 Ma and T2DM-Hf = 355-550 Ma), indicating that their source magmas were likely derived from partial melting of the oceanic crust beneath the Boshchekul-Chingiz arc. The petrogenesis and distribution of the A-type granites and adakites, as well as the tectonic architecture of the region, suggest that a ridge subduction event might have occurred during the Early Silurian to Early Carboniferous. In combination with previous studies in the Chinese Altai, we suggest a two-sided ridge subduction model for the

  3. Silurian K-bentonites of the Dnestr Basin, Podolia, Ukraine

    USGS Publications Warehouse

    Huff, W.D.; Bergstrom, Stig M.; Kolata, Dennis R.

    2000-01-01

    The Dnestr Basin of Podolia, Ukraine, is an epicratonic basin consisting of neritic carbonate and calcareous mudstone facies including a nearly complete Silurian sequence ranging from late Llandovery to late Pridoli in age. The Silurian section has served as a standard for regional and interregional studies as a consequence of its well-documented macro- and microfaunal assemblages. Approximately 24 mid- to Late Silurian K-bentonites are present in this succession, and their lateral persistence has aided in establishing regional correlations. The K-bentonites range from 1 to 40 cm in thickness and occur in the Bagovitsa (late Wenlock), Malinovtsy (Ludlow) and Skala (Pridoli) Formations. Discrimination diagrams based on immobile trace elements together with rare earth element data suggest the K-bentonites had a volcanic origin in a collision margin setting related to subduction. Thickness and stratigraphic distribution considerations are consistent with a source area in the Rheic Ocean.

  4. Radiolarians, foraminifers, and biostratigraphy of the Coniacian-Campanian deposits of the Alan-Kyr Section, Crimean Mountains

    NASA Astrophysics Data System (ADS)

    Bragina, L. G.; Beniamovsky, V. N.; Kopaevich, L. F.

    2016-01-01

    Data on the distribution of radiolarians and planktonic and benthic foraminifers are obtained for the first time from the Alan-Kyr Section (Coniacian-Campanian), in the central regions of the Crimean Mountains. Radiolarian biostrata, previously established from Ak-Kaya Mountain (central regions of the Crimean Mountains) were traced: Alievium praegallowayi-Crucella plana (upper Coniacian-lower Santonian), Alievium gallowayi-Crucella espartoensis (upper Santonian without the topmost part), and Dictyocephalus (Dictyocryphalus) (?) legumen-Spongosaturninus parvulus (upper part of the upper Santonian). Radiolarians from the Santonian-Campanian boundary beds of the Crimean Mountains are studied for the first time, and Prunobrachium sp. ex gr. crassum-Diacanthocapsa acanthica Beds (uppermost Santonian-lower Campanian) are recognized. Bolivinoides strigillatus Beds (upper Santonian) and Stensioeina pommerana-Anomalinoides (?) insignis Beds (upper part of the upper Santonian-lower part of the lower Campanian) are recognized. Eouvigerina aspera denticulocarinata Beds (middle and upper parts of the lower Campanian) and Angulogavelinella gracilis Beds (upper part of the upper Campanian are recognized on the basis of benthic foraminifers. These beds correspond to the synchronous biostrata of the East European Platform and Mangyshlak. Marginotruncana coronata- Concavatotruncana concavata Beds (Coniacian-upper Santonian), Globotruncanita elevata Beds (terminal Santonian), and Globotruncana arca Beds (lower Campanian) are recognized on the basis of planktonic foraminifers. Radiolarian and planktonic and benthic foraminiferal data agree with one another. The position of the Santonian-Campanian boundary in the Alan-Kyr Section, which is located stratigraphically above the levels of the latest occurrence of Concavatotruncana concavata and representatives of the genus Marginotruncana, is refined, i.e., at the level of the first appearance of Globotruncana arca. A gap in the Middle

  5. Radiolarian Indices of Paleoproductivity Variation in the late Pleistocene Benguela Upwelling System, ODP Site 1084

    NASA Astrophysics Data System (ADS)

    Bittniok, B. B.; Lazarus, D. B.; Diester-Haass, L.; Billups, K.; Meyers, P.

    2006-12-01

    Changes in export productivity play a significant role in ocean carbon budgets and global climate change. Proxies for export productivity can be difficult to interpret: benthic foraminifera accumulation rates (BFAR) can be affected by carbonate dissolution in organic-carbon rich sediments; bulk opal can be affected by silica limitation of source waters. Recent work (Lazarus et al. 2006; Mar. Micropal.) has shown that a new index based on radiolarian faunal changes (WADE ratio) correlates well to total organic carbon (TOC) values from the same samples over the long term (latest Miocene-Recent) history of productivity in the Benguela Upwelling System (BUS). We present new data on variation in export productivity proxies (WADE, TOC, carbonate, radiolarian opal, BFAR) for the last glacial-interglacial cycle from ODP Site 1084, located just offshore from the main coastal upwelling cells of the BUS. Our age model, from mean Quaternary sedimentation rates (Leg 175 Scientific Results), is in accordance with cyclic variation in other climate sensitive parameters (carbonate and color reflectance). Although opal content and radiolarian preservation is only moderate in our samples, WADE values vary significantly and suggest higher productivity during the last glacial, in accordance with current interpretations of BUS history. Radiolarian opal accumulation is also higher during the last glacial, suggesting that silica limitation (opal paradox) conditions did not dominate over this time period. Similar results for bulk opal have been reported from late Quaternary piston cores from the more northerly Congo upwelling region (Schneider et al, 1997; Paleoc.). We conclude that WADE ratios are a useful proxy for late Pleistocene productivity in the BUS at glacial- interglacial time scales.

  6. Main consistent patterns of Stromatoporoid Development in the Late Ordovician and Silurian in the North Urals Palaeobasin

    NASA Astrophysics Data System (ADS)

    Antropova, E.

    2009-04-01

    In the history of the Earth there have been no basins with similar characteristics. The North Urals palaeobasin had its own unique features. The dominant benthic organisms of basin ecosystem during the Ordovician and Silurian were stromatoporoids, corals, and brachiopods. This fauna is vitally important for the aims of stratigraphy so long as conodonts are extremely rare in sections of the Northern Urals area. The most complete ordering of stromatoporoid complexes has been established and made it possible to estimate rates and measures of extinction at a level of the province. It was also found out that stromatoporoids were organisms responsive to subtle changes of environment and that they accommodated differently to those changing conditions. The evolution of stromatoporoids was accompanied by phylogenetic reorganization and formation of endemic communities in the Late Ordovician and Early Silurian. In the Late Silurian taxonomical diversity of stromatoporoids was mainly controlled by migration processes and cosmopolites with wide palaeogeographic links prevailed in the palaeobasin. Therefore palaeobasin at that time was open to stromatoporoid fauna migration which is confirmed by the occurrence of genera and species that disperse in coeval deposits of many areas, for example, Baltic States, Sweden, Ukraine (Podolia), Western Siberia, Arctic islands of Russia, Mongolia, Canada (islands). The evolution of stromatoporoid communities in the Ordovician-Silurian was intermitted by biotic crises. The analysis of stromatoporoid development helps to define crucial points of ecosystem's reorganizations coinciding with critical geological and biotic events in the history of the North Urals palaeobasin existence, as well as global events during the Ordovician and Silurian (Hirnantian Event, Ireviken Event, Lau Event). The analysis of crises indicates local dependence of stromatoporoid biodiversity on depositional environments. Large local biocenos reorganizations and biotic

  7. Radiolarian biochronology of upper Anisian to upper Ladinian (Middle Triassic) blocks and tectonic slices of volcano-sedimentary successions in the Mersin Mélange, southern Turkey: New insights for the evolution of Neotethys

    NASA Astrophysics Data System (ADS)

    Tekin, U. Kagan; Bedi, Yavuz; Okuyucu, Cengiz; Göncüoglu, M. Cemal; Sayit, Kaan

    2016-12-01

    The Mersin Ophiolitic Complex located in southern Turkey comprises two main structural units; the Mersin Mélange, and a well-developed ophiolite succession with its metamorphic sole. The Mersin Mélange is a sedimentary complex including blocks and tectonic slices of oceanic litosphere and continental crust in different sizes. Based on different fossil groups (Radiolaria, Conodonta, Foraminifera and Ammonoidea), the age of these blocks ranges from Early Carboniferous to early Late Cretaceous. Detailed fieldwork in the central part of the Mersin Mélange resulted in identification of a number of peculiar blocks of thick basaltic pillow-and massive lava sequences alternating with pelagic-clastic sediments and radiolarian cherts. The oldest ages obtained from the radiolarian assemblages from the pelagic sediments transitional to the volcano-sedimentary succession in some blocks are middle to late Late Anisian. These pelagic sediments are overlain by thick sandstones of latest Anisian to middle Early Ladinian age. In some blocks, sandstones are overlain by clastic and pelagic sediments with lower Upper to middle Upper Ladinian radiolarian fauna. Considering the litho- and biostratigraphical data from Middle Triassic successions in several blocks in the Mersin Mélange, it is concluded that they correspond mainly to the blocks/slices of the Beysehir-Hoyran Nappes, which were originated from the southern margin of the Neotethyan Izmir-Ankara Ocean. As the pre-Upper Anisian basic volcanics are geochemically evaluated as back-arc basalts, this new age finding suggest that a segment of the Izmir-Ankara branch of the Neotethys was already open prior to Middle Triassic and was the site of intraoceanic subduction.

  8. Comparison of unitary associations and probabilistic ranking and scaling as applied to mesozoic radiolarians

    NASA Astrophysics Data System (ADS)

    Baumgartner, Peter O.

    A database on Middle Jurassic-Early Cretaceous radiolarians consisting of first and final occurrences of 110 species in 226 samples from 43 localities was used to compute Unitary Associations and probabilistic ranking and scaling (RASC), in order to test deterministic versus probabilistic quantitative biostratigraphic methods. Because the Mesozoic radiolarian fossil record is mainly dissolution-controlled, the sequence of events differs greatly from section to section. The scatter of local first and final appearances along a time scale is large compared to the species range; it is asymmetrical, with a maximum near the ends of the range and it is non-random. Thus, these data do not satisfy the statistical assumptions made in ranking and scaling. Unitary Associations produce maximum ranges of the species relative to each other by stacking cooccurrence data from all sections and therefore compensate for the local dissolution effects. Ranking and scaling, based on the assumption of a normal random distribution of the events, produces average ranges which are for most species much shorter than the maximum UA-ranges. There are, however, a number of species with similar ranges in both solutions. These species are believed to be the most dissolution-resistant and, therefore, the most reliable ones for the definition of biochronozones. The comparison of maximum and average ranges may be a powerful tool to test reliability of species for biochronology. Dissolution-controlled fossil data yield high crossover frequencies and therefore small, statistically insignificant interfossil distances. Scaling has not produced a useful sequence for this type of data.

  9. Foraminiferal and radiolarian biostratigraphy of the youngest (Late Albian through Late Cenomanian) sediments of the Tatra massif, Central Western Carpathians

    NASA Astrophysics Data System (ADS)

    Bąk, Krzysztof; Bąk, Marta

    2013-06-01

    Bąk, K. and Bąk M. 2013. Foraminiferal and radiolarian biostratigraphy of the youngest (Late Albian through Late Cenomanian) sediments of the Tatra massif, Central Western Carpathians. Acta Geologica Polonica, 63 (2), 223-237. Warszawa. The foraminiferal and radiolarian biostratigraphy of selected sections of the Zabijak Formation, the youngest sediments of the Tatra massif (Central Western Carpathians), have been studied. Benthic foraminifers, mainly agglutinated species, occur abundantly and continuously throughout the studied succession, while planktic foraminifers are generally sparse. Five planktic and two benthic foraminiferal zones have been recognized. The marly part of the Zabijak Formation comprises the Pseudothalmanninella ticinensis (Upper Albian) through the Rotalipora cushmani (Upper Cenomanian) planktic foraminiferal zones, and the Haplophragmoides nonioninoides and Bulbobaculites problematicus benthic foraminiferal zones. The radiolarians were recognized exclusively in the Lower Cenomanian part of the formation.

  10. Radiolarian biostratigraphic data from the Casiguran Ophiolite, Northern Sierra Madre, Luzon, Philippines: Stratigraphic and tectonic implications

    NASA Astrophysics Data System (ADS)

    Queano, Karlo L.; Marquez, Edanjarlo J.; Aitchison, Jonathan C.; Ali, Jason R.

    2013-03-01

    Results from the first detailed radiolarian biostratigraphic study conducted in Luzon are reported. The data were obtained from cherts associated with the Casiguran Ophiolite, a dismembered ophiolite mass consisting of serpentinized peridotites, gabbros, dolerite dikes and pillow basalts exposed along the eastern coast of the Northern Sierra Madre, Luzon, Philippines. Cherts and limestone interbeds conformably overlie the ophiolite. The radiolarian assemblages from the cherts constrain the stratigraphic range of the cherts to the Lower Cretaceous (upper Barremian-lower Aptian to Albian). This new biostratigraphic result is in contrast with the Upper Cretaceous stratigraphic range previously reported in the region. Radiolarian biostratigraphic results from the Casiguran Ophiolite provide additional evidence for the existence of Mesozoic oceanic substratum upon which Luzon and neighboring regions within the Philippine archipelago were likely built. Interestingly, the result closely resembles those reported for the ophiolite in southeastern Luzon as well as the oceanic crust of the Huatung Basin situated east of Taiwan and the ophiolites in eastern Indonesia. In light of this, along with previously gathered geochemical data from the ophiolites, a common provenance is being looked into for these crust-upper mantle sequences in the western Pacific region.

  11. Silurian deltaic progradation, Tassili n'Ajjer plateau, south-eastern Algeria: Sedimentology, ichnology and sequence stratigraphy

    NASA Astrophysics Data System (ADS)

    Djouder, Hocine; Lüning, Sebastian; Da Silva, Anne-Christine; Abdallah, Hussein; Boulvain, Frédéric

    2018-06-01

    to the distal Cruziana ichnofacies. In contrast, the uppermost part of the Silurian deposits becomes progressively coarser and fluvial in response to the progradation of the North African Akakus deltaic system, during regional sea level fall and uplifting of the region. These progradational deposits exhibit well-preserved trace fossils with moderate to high degree of bioturbation, such as Skolithos or the so-called "Tigillites" pipe-rock, Cruziana isp., Rusophycus isp., Monocraterion isp., and Syringomorpha. The SIL-1 MS is bounded by a post-glacial latest Hirnantian unconformity on the basal (SB1), as confirmed by the moderately diverse early Silurian graptolite faunas, and by the Caledonian unconformity on the top (SB7). Each of the three formations of SIL-1 MS reveals two major 3rd-order progradational sequences, commonly delineated by discontinuity surfaces (in ascending order, SB1 to SB7), and in turn, these six sequences (i.e. Si-1 to Si-6) are subdivided into at least ten shorter-term cycles. The regional extent of each unconformity is directly linked to significant facies changes and to inflection points on the global sea level curve.

  12. Chemostratigraphic and U-Pb geochronologic constraints on carbon cycling across the Silurian-Devonian boundary

    NASA Astrophysics Data System (ADS)

    Husson, Jon M.; Schoene, Blair; Bluher, Sarah; Maloof, Adam C.

    2016-02-01

    The Devonian Period hosts extraordinary changes to Earth's biosphere. Land plants began their rise to prominence, with early vascular vegetation beginning its colonization of near-shore environments in the latest Silurian. Across the Silurian-Devonian (Pridoli-Lochkovian) transition, carbon isotope analyses of bulk marine carbonates (δC13carb) from Laurentian and Baltic successions reveal a positive δC13carb shift. Known as the Klonk Event, values reach + 5.8 ‰, making it one of the largest carbon isotope excursions in the Phanerozoic. Assigning rates and durations to these significant events requires a robust, precise Devonian time scale. Here we present 675 micritic matrix and 357 fossil-specific δC13carb analyses from the lower Devonian Helderberg Group of New York and West Virginia that exhibit the very positive δC13carb values observed in other Silurian-Devonian basins. This chemostratigraphic dataset is coupled with 66 ID-TIMS U-Pb dates on single zircons from six ash falls intercalated within Helderberg sediments, including dates on the stratigraphically lowest Devonian ashes yet developed. In this work, we (a) demonstrate that matrix and fossil-specific δC13carb values track one another closely in the Helderberg Group, (b) estimate the Silurian-Devonian boundary age in New York to be 421.3 ± 1.2 Ma (2σ; including decay constant uncertainties), and (c) calculate the time required to evolve from baseline to peak δC13carb values at the onset of the Klonk event to be 1.00 ± 0.25 Myr. Under these constraints, a steady-state perturbation to the global carbon cycle can explain the observed excursion with modern fluxes, as long as DIC concentration in the Devonian ocean remained below ∼2× the modern value. Therefore, potential drivers, such as enhanced burial of organic carbon, need not rely on anomalously high total fluxes of carbon to explain the Klonk Event.

  13. Silurian Micrometeorite Flux: The Demise of the Mid-Ordovician L-Chondrite Reign.

    NASA Astrophysics Data System (ADS)

    Martin, E.; Schmitz, B.

    2017-12-01

    Earth's sedimentary record holds information about the micrometeorite flux through time, reflecting the collisional evolution of the asteroid belt. Around 466 Ma ago in the mid-Ordovician period the L-chondrite parent body breakup (LCPB) took place in the main asteroid belt causing a massive increase, up to two orders of magnitude, in the flux of meteorites to Earth (Schmitz, 2013). What did the meteorite flux look like after the breakup event? And when in time can we see a decrease in the fraction of L-chondritic micrometeorites? We dissolved in acids condensed, marine limestone representing the mid-Ordovician and the late Silurian about 0.5 and 40 Ma, respectively after the LCPB, and searched the residues for spinel grains from equilibrated ordinary chondrites (EC). We used 102 kg from the mid-Ordovician Komstad Limestone Formation, Killeröd quarry in Sweden, and 321 kg from the Silurian Kok Formation, Cellon section in Austria. Elemental analyses of the spinel grains were used to link the grains to different types of meteorites. In the large grain size fraction (63-355 µm) there are 4.5 EC grains/kg of rock in the mid-Ordovician sample and only 0.03 EC grains/kg in the Silurian sample. Because the two formations formed at about the same rate (a few mm per kyr) the results represent strong evidence for a major tailing off in the L-chondritic meteorite contribution by the late Silurian. The EC grains have been divided into the H, L, and LL groups based on the TiO2 content. The results show that the fraction of L chondrites compared to H and LL chondrites had declined significantly by the late Silurian. In the study of Heck et al. (2016) it was shown that ≥99% of the ordinary chondritic micrometeorites were L chondrites right after the LCPB. Our data indicate that the L-chondrite fraction had decreased to 60% by the Silurian, with the H and LL chondrites making up 30% and 10% respectively of the flux.

  14. Using enteric pathogens to assess sources of fecal contamination in the Silurian Dolomite Aquifer: Preliminary results

    USGS Publications Warehouse

    Muldoon, Maureen A; Borchardt, Mark A.; Spencer, Susan K.; Hunt, Randall J.; Owens, David

    2018-01-01

    The fractured Silurian dolomite aquifer is an important, but vulnerable, source of drinking water in northeast Wisconsin (Sherrill in Geology and ground water in Door County, Wisconsin, with emphasis on contamination potential in the Silurian dolomite, 1978; Bradbury and Muldoon in Hydrogeology and groundwater monitoring of fractured dolomite in the Upper Door Priority Watershed, Door County, Wisconsin, 1992; Muldoon and Bradbury in Assessing seasonal variations in recharge and water quality in the Silurian aquifer in areas with thicker soil cover. p 45, 2010). Areas underlain by the Silurian dolomite aquifer are extremely vulnerable to groundwater contamination from various land-use activities, especially the disposal of human wastewater and dairy manure. Currently there is no consensus as to which source of wastewater generates the greater impact to the aquifer.

  15. Using enteric pathogens to assess sources of fecal contamination in the silurian dolomite aquifer: preliminary results

    USDA-ARS?s Scientific Manuscript database

    The fractured Silurian dolomite aquifer is an important, but vulnerable, source of drinking water in northeast Wisconsin. Areas underlain by the Silurian dolomite aquifer are extremely vulnerable to groundwater contamination from various land-use activities, especially the disposal of human wastewat...

  16. Distribution of living radiolarians and its response on the environments in spring from the section South China Sea

    NASA Astrophysics Data System (ADS)

    Zhang, L.; Hu, W.; Chen, M.; Zeng, L.; Xiang, R.; Zhou, W.

    2013-12-01

    The composition and spatial (horizontal and vertical) distribution of living radiolarians in spring was firstly studied in the section (18°N and 113°E) South China Sea. Vertical plankton tows were collected at depth-intervals from 0 to 300 m in spring using a closing-type net with 62 um mesh size. And we distinguished the living specimens by staining with Rose Bengal. It dominated by tropical-subtropical warm species in spring from the studied areas. The abundance of nassellarians was the almost same as that of spumellarians in the upper-surface waters (0-25m). In the below-surface waters (25-50m), nassellarian abundance was the almost twice that of spumellarians. And the abundances generally decreased with depth (more than 50m), but nasselarian abundance reduced more quickly. The results showed that the horizontal and vertical distribution patterns of living radiolarians were closely related to the mesoscale eddies. The horizontal distributions of radiolarian abundance were uneven and pachy, which may be related to the complicated mecoscale eddies during the sampling period. That is, there were comparatively high abundances in the upper-surface waters where had the cold eddies development. But in the cold eddies of Meigong River mouth, radiolarian abundance was low due to the large input of fresh water, suggesting that low salinity had more important influence than the nutrient on the radiolarian development and reproduction. Vertically, the highest abundances occurred at the mixed layer in the cold eddies, and gradually decreased with depth. However, in the warm eddies, the maximum abundances were in the thermocline layers, where had an abundant supply of nutrients for radiolarians. This study showed that Didymocyrtis tetrathalamus tetrathalamus mostly occurred at the mixed layer, which should be closely related to the cold eddies and rich nutrition and be limited by the fresh water. Based on the distribution of Didymocyrtis tetrathalamus tetrathalamus, we

  17. New observations of the early land plant Eocooksonia Doweld from the Pridoli (Upper Silurian) of Xinjiang, China

    NASA Astrophysics Data System (ADS)

    Xue, Jinzhuang; Wang, Qi; Wang, Deming; Wang, Yi; Hao, Shougang

    2015-04-01

    As an early land plant previously reported from the Upper Silurian (Pridoli) of Xinjiang, Northwest China and Central Kazakhstan, the circumscription of Eocooksonia sphaerica (Senkevitsch) Doweld remains ill-defined because of the paucity of specimens and poor preservation in marine deposits. New specimens of this plant are described from the Pridoli-aged Wutubulake Formation of the Junggar Basin, Xinjiang. New observations and comparisons with the type material from Kazakhstan confirm the pseudomonopodial branching pattern, which forms an apparent main axis with lateral dichotomously branching systems. Our specimens demonstrate that the terminal sporangia of Eocooksonia Doweld consist of a central body and a border with four to eight elongate-triangular emergences, a character shown in the published illustrations of the type material but not mentioned in the original diagnosis. Eocooksonia may be close to Cooksonia Lang and Pertonella Fanning, Edwards et Richardson in affinities, particularly to the latter that has terminal discoidal sporangia with spiny emergences. It is deduced that the sporangial central body of Eocooksonia contains sporogenous tissues, which are covered by a distal surface wall with radiated emergences. One sporangium specimen of an unnamed plant is also described from the Wutubulake Formation of Xinjiang; it shows a central body with a wide border lacking emergences, and represents a taxon superficially similar to Eocooksonia.

  18. Silurian and Devonian in Vietnam—Stratigraphy and facies

    NASA Astrophysics Data System (ADS)

    Thanh, Tống Duy; Phương, Tạ Hoàng; Janvier, Philippe; Hùng, Nguyễn Hữu; Cúc, Nguyễn Thị Thu; Dương, Nguyễn Thùy

    2013-09-01

    Silurian and Devonian deposits in Viet Nam are present in several zones and regions, including Quang Ninh, East Bac Bo, and West Bac Bo Zones of the Bac Bo Region, the Dien Bien-Nghe An and Binh Tri Thien Zones of the Viet-Lao Region, and the South Trung Bo, and Western Nam Bo Zones of the South Viet Nam Region (Fig. 1). The main lithological features and faunal composition of the Silurian and Devonian Units in all these zones are briefly described. The Silurian consists of deep-water deposits of the upper parts of the Co To and Tan Mai Formations in the Quang Ninh Zone, the upper parts of the Phu Ngu Formation in the East Bac Bo Zone and the upper parts of the Long Dai and Song Ca Formations in the Viet-Lao Region. Shallow water facies Silurian units containing benthic faunas are more widely distributed, including the upper part of the Sinh Vinh and Bo Hieng Formations in the West Bac Bo Zone, the Kien An Formation in the Quang Ninh Zone, and, in the Viet-Lao Region, the Dai Giang Formation and the upper part of the Tay Trang Formation. No Lower and Middle Devonian deposits indicate deep water facies, but they are characterized by different shallow water facies. Continental to near shore, deltaic facies characterize the Lower Devonian Song Cau Group in the East Bac Bo Zone, the Van Canh Formation in the Quang Ninh Zone, and the A Choc Formation in the Binh Tri Thien Zone. Similar facies also occur in the Givetian Do Son Formation of the Quang Ninh Zone, and the Tan Lap Formation in the East Bac Bo Zone, and consist of coarse terrigenous deposits—cross-bedded conglomerates, sandstone, etc. Most Devonian units are characterized by shallow marine shelf facies. Carbonate and terrigenous-carbonate facies dominate, and terrigenous facies occur in the Lower and Middle Devonian sections in some areas only. The deep-water-like facies is characteriztic for some Upper Devonian formations in the Bac Bo (Bang Ca and Toc Tat Formations) and Viet-Lao Regions (Thien Nhan and

  19. Paleoclimatic and paleolatitude settings of accumulation of radiolarian siliceous-volcanogenic sequences in the middle Mesozoic Pacific: Evidence from allochthons of East Asia

    NASA Astrophysics Data System (ADS)

    Vishnevskaya, V. S.; Filatova, N. I.

    2017-09-01

    Jurassic-Cretaceous siliceous-volcanogenic rocks from nappes of tectonostratigraphic sequences of the East Asia Middle Cretaceous Okhotsk-Koryak orogenic belt are represented by a wide range of geodynamic sedimentation settings: oceanic (near-spreading zones, seamounts, and deep-water basins), marginal seas, and island arcs. The taxonomic compositions of radiolarian communities are used as paleolatitude indicators in the Northern Pacific. In addition, a tendency toward climate change in the Mesozoic is revealed based on these communities: from the warm Triassic to the cold Jurassic with intense warming from the Late Jurassic to the Early Cretaceous. Cretaceous warming led to heating of ocean waters even at moderately high latitudes and to the development of Tethyan radiolarians there. These data are confirmed by a global Cretaceous temperature peak coinciding with a high-activity pulse of the planetary mantle superplume system, which created thermal anomalies and the greenhouse effect. In addition, the Pacific superplume attributed to this system caused accelerated movement of oceanic plates, which resulted in a compression setting on the periphery of the Pacific and the formation of the Okhotsk-Koryak orogenic belt on its northwestern framing in the Middle Cretaceous, where Mesozoic rocks of different geodynamic and latitudinal-climate settings were juxtaposed into allochthonous units.

  20. Silurian trace fossils in carbonate turbidites from the Alexander Arc of southeastern Alaska

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Soja, C.M.

    Early to Late Silurian (Wenlock-Ludlow) body and trace fossils from the Heceta Formation are preserved in the oldest widespread carbonates in the Alexander terrane of southeastern Alaska. They represent the earliest shelly benthos to inhabit a diversity of marine environments and are important indicators of the early stages in benthic community development within this ancient island arc. The trace fossils are significant because they add to a small but growing body of knowledge about ichnofaunas in deep-water Paleozoic carbonates. Proximal to medial carbonate turbidites yield a low-diversity suite of trace fossils that comprises five distinct types of biogenic structures. Beddingmore » planes reveal simple epichnial burrows (Planolites), cross-cutting burrows (Fucusopsis), and tiny cylindrical burrows. These and other casts, including chondrites( )-like burrow clusters, represent the feeding activities (fodinichnia) of preturbidite animals. Hypichnial burrows and rare endichnial traces reflect the activities of postturbidite animals. Broken and offset traces indicate that infaunal biota commenced burrowing before slumping and subsequent soft-sediment deformation. The abundance and density of trace fossils increases offshore in the medial turbidites associated with a decrease in the size and amount of coarse particles and with an increase in mud and preserved organic material. Although diversity levels are similar in the proximal and medial turbidite facies, they are much lower than in Paleozoic siliciclastic turbidites. This may reflect unfavorable environmental conditions for infaunal biota or paleobiogeographic isolation of the Alexander terrane during the Silurian. A greater use of trace fossils in terrane analysis will help to resolve this issue and should provide new data for reconstructing the paleogeography of circum-Pacific terranes.« less

  1. Vitrinite equivalent reflectance of Silurian black shales from the Holy Cross Mountains, Poland

    NASA Astrophysics Data System (ADS)

    Smolarek, Justyna; Marynowski, Leszek; Spunda, Karol; Trela, Wiesław

    2014-12-01

    A number of independent methods have been used to measure the thermal maturity of Silurian rocks from the Holy Cross Mountains in Poland. Black shales are characterized by diverse TOC values varying from 0.24-7.85%. Having calculated vitrinite equivalent reflectance using three different formulas, we propose that the most applicable values for the Silurian rocks are those based on Schmidt et al. (2015) equation. Based on this formula, the values range from % 0.71 VReqvVLR (the vitrinite equivalent reflectance of the vitrinite-like macerals) to % 1.96 VReqvVLR. Alternative, complementary methods including Rock Eval pyrolysis and parameters based on organic compounds (CPI, Pr/n-C17, Ph/n-C18, MPI1, and MDR) from extracts did not prove adequate as universal thermal maturity indicators. We have confirmed previous suggestions that Llandovery shales are the most likely Silurian source rocks for the generation of hydrocarbons in the HCM.

  2. A comparative analysis of pre-Silurian crustal building blocks of the northern and the southern Appalachian orogen

    USGS Publications Warehouse

    Hibbard, J.P.; van Staal, C.R.; Rankin, D.W.

    2007-01-01

    The New York promontory serves as the divide between the northern and southern segments of the Appalachian orogen. Antiquated subdivisions, distinct for each segment, implied that they had lithotectonic histories that were independent of each other. Using new lithotectonic subdivisions we compare first order features of the pre-Silurian orogenic 'building blocks' in order to test the validity of the implication of independent lithotectonic histories for the two segments. Three lithotectonic divisions, termed here the Laurentian, Iapetan, and the peri-Gondwanan realms, characterize the entire orogen. The Laurentian realm, composed of native North American rocks, is remarkably uniform for the length of the orogen. It records the multistage Neoproterozoic-early Paleozoic rift-drift history of the Appalachian passive margin, formation of a Taconic Seaway, and the ultimate demise of both in the Middle Ordovician. The Iapetan realm encompasses mainly oceanic and magmatic arc tracts that once lay within the Iapetus Ocean, between Laurentia and Gondwana. In the northern segment, the realm is divisible on the basis of stratigraphy and faunal provinciality into peri-Laurentian and peri-Gondwanan tracts that were amalgamated in the Late Ordovician. South of New York, stratigraphic and faunal controls decrease markedly; rock associations are not inconsistent with those of the northern Appalachians, although second-order differences exist. Exposed exotic crustal blocks of the peri-Gondwanan realm include Ganderia, Avalonia, and Meguma in the north, and Carolinia in the south. Carolinia most closely resembles Ganderia, both in early evolution and Late Ordovician-Silurian docking to Laurentia. Our comparison indicates that, to a first order, the pre-Silurian Appalachian orogen developed uniformly, starting with complex rifting and a subsequent drift phase to form the Appalachian margin, followed by the consolidation of Iapetan components and ending with accretion of the peri

  3. In search of a Silurian Total Petroleum System in the Appalachian Basin of New York, Ohio, Pennsylvania, and West Virginia

    USGS Publications Warehouse

    Ryder, Robert T.; Swezey, Christopher S.; Trippi, Michael H.; Lentz, Erika E.; Avary, K. Lee; Harper, John A.; Kappel, William M.; Rea, Ronald G.

    2007-01-01

    This report provides an evaluation of the source rock potential of Silurian strata in the U.S. portion of the northern Appalachian Basin, using new TOC and RockEval data. The study area consists of all or parts of New York, Ohio, Pennsylvania, and West Virginia. The stratigraphic intervals that were sampled for this study are as follows: 1) the Lower Silurian Cabot Head Shale, Rochester Shale, and Rose Hill Formation; 2) the Lower and Upper Silurian McKenzie Limestone, Lockport Dolomite, and Eramosa Member of the Lockport Group; and 3) the Upper Silurian Wills Creek Formation, Tonoloway Limestone, Salina Group, and Bass Islands Dolomite. These Silurian stratigraphic intervals were chosen because they are cited in previous publications as potential source rocks, they are easily identified and relatively continuous across the basin, and they contain beds of dark gray to black shale and (or) black argillaceous limestone and dolomite.

  4. Biogeography of late Silurian and devonian rugose corals

    USGS Publications Warehouse

    Oliver, W.A.

    1977-01-01

    Three marine benthic faunal realms can be recognized in the Early and Middle Devonian. The Eastern Americas Realm consisted of most of the eastern half of North America and South America north of the Amazon. This realm extended in a southwest direction from the Devonian equator to approximately 35??S and was an isolated epicontinental sea during much of its history. The Eastern Americas Realm was bounded on the west by the Transcontinental Arch, on the north by the Canadian Shield and on the east and southeast by a peninsular extension of the Old Red Continent. These barriers were emergent during much, but not all, of Devonian time. Seaways beyond these barriers belonged to the Old World Realm. The Malvinokaffric Realm that was farther south was apparently temperate to arctic in climate and latitudinal position and contained few corals. Rugose corals in the Eastern Americas Realm show increasing generic-level endemism from the Late Silurian through the Early Devonian; during the late Early Devonian, 92% of the rugosan genera are not known anywhere else in the world. Endemism decreased through the Middle Devonian to zero in the early Late Devonian. The Early Devonian increase in endemism paralleled, and was probably related to, the development of the Old Red Continent as a barrier between America and Africa-Europe. The waning of endemism in the Middle Devonian reflects the breaching of the land barriers. This permitted some migration in and out of the realm in early Middle Devonian time but greatest movements were in late Middle Devonian time. Principal migration directions were from western or Arctic North America into the Michigan-Hudson Bay area and from the southern Appalachian area into Africa. ?? 1977.

  5. Stratigraphy of the Silurian outcrop belt on the east side of the Cincinnati Arch in Kentucky, with revisions in the nomenclature

    USGS Publications Warehouse

    McDowell, Robert C.

    1983-01-01

    , is predominantly grayish-green clay shale with a thin (0.5-3 ft) dolomite member (the Waco, or its northern equivalent, the Dayton Dolomite Member, reduced in rank from Dayton Limestone) near the base. North of Bath County, the Lulbegrud Shale and Dayton Dolomite Members are reassigned to the underlying Drowning Creek Formation, the Estill Shale Member is elevated to formational status, and the Alger is dropped. The Bisher Dolomite, which overlies the Estill Shale in the northernmost part of the Silurian belt, ranges from 0 to 300 ft in thickness and is composed of medium-to coarse-grained, gray, fossiliferous dolomite. The Silurian section overlies Upper Ordovician rocks in apparent conformity, although faunal studies suggest a minor hiatus, and is overlain by Middle to Upper Devonian rocks in a regional angular unconformity that truncates the entire Silurian section at the southwest end of the outcrop belt, where it is nearest the axis of the Cincinnati Arch. All of the units recognized in the Silurian appear to thicken eastward, away from the axis of the arch and towards the Appalachian basin. This, with the presence of isolated remnants of the Brassfield near the axis, suggest that formation of the arch was initiated in Early Silurian time by subsidence of its eastern flank.

  6. Stratigraphic Framework and Depositional Sequences in the Lower Silurian Regional Oil and Gas Accumulation, Appalachian Basin: From Licking County, Ohio, to Fayette County, West Virginia

    USGS Publications Warehouse

    Ryder, Robert T.

    2006-01-01

    The Lower Silurian regional oil and gas accumulation was named by Ryder and Zagorski (2003) for a 400-mile (mi)-long by 200-mi-wide hydrocarbon accumulation in the central Appalachian basin of the Eastern United States and Ontario, Canada. From the early 1880s to 2000, approximately 300 to 400 million barrels of oil and eight to nine trillion cubic feet of gas have been produced from the Lower Silurian regional oil and gas accumulation (Miller, 1975; McCormac and others, 1996; Harper and others, 1999). Dominant reservoirs in the regional accumulation are the Lower Silurian 'Clinton' and Medina sandstones in Ohio and westernmost West Virginia and coeval rocks in the Lower Silurian Medina Group (Grimsby Sandstone (Formation) and Whirlpool Sandstone) in northwestern Pennsylvania and western New York. A secondary reservoir is the Upper Ordovician(?) and Lower Silurian Tuscarora Sandstone in central Pennsylvania and central West Virginia, a more proximal eastern facies of the 'Clinton' sandstone and Medina Group (Yeakel, 1962; Cotter, 1982, 1983; Castle, 1998). The Lower Silurian regional oil and gas accumulation is subdivided by Ryder and Zagorski (2003) into the following three parts: (1) an easternmost part consisting of local gas-bearing sandstone units in the Tuscarora Sandstone that is included with the basin-center accumulation; (2) an eastern part consisting predominantly of gas-bearing 'Clinton' sandstone-Medina Group sandstones that have many characteristics of a basin-center accumulation (Davis, 1984; Zagorski, 1988, 1991; Law and Spencer, 1993); and (3) a western part consisting of oil- and gas-bearing 'Clinton' sandstone-Medina Group sandstones that is a conventional accumulation with hybrid features of a basin-center accumulation (Zagorski, 1999). With the notable exception of the offshore part of Lake Erie (de Witt, 1993), the supply of oil and (or) gas in the hybrid-conventional part of the regional accumulation continues to decline because of the many

  7. Phaeodarian radiolarians as potential indicators of thermal maturation

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Casey, R.E.

    1986-04-01

    Phaeodarian radiolarian skeletons contain large amounts of organic matter, and discolored phaeodarian skeletons are observed in the fossil record, which suggests that the skeletons may be useful as thermal maturation indicators. Such a maturation index would be useful in Monterey-type rocks that are difficult to interpret with conventional thermal maturation indexes. Phaeodarians extracted from plankton samples, Holocene Santa Barbara and Orca basin sediments, and Neogene Monterey rocks with siliceous facies were subjected to different temperatures of varying duration in pyrolysis experiments. To calibrate the observed phaeodarian color changes with a known standard, Holocene pine pollen were subjected to the samemore » treatment. These phaeodarian go through the same color change spectrum as do the pollen, but they appear to lag slightly behind the pollen color changes.« less

  8. A not-so-big crisis: re-reading Silurian conodont diversity in a sequence-stratigraphic framework

    NASA Astrophysics Data System (ADS)

    Jarochowska, Emilia; Munnecke, Axel

    2016-04-01

    Conodonts are extensively used in Ordovician through Triassic biostratigraphy and fossil-based geochemistry. However, their distribution in rock successions is commonly taken at face value, without taking into account their diverse and poorly understood ecology. Multielement taxonomy, ontogenetic and environmental variability, difficulties in extraction, and relative rarity all contribute to the general lack of quantitative studies on conodont stratigraphic distribution and temporal turnover. With respect to Silurian conodonts, the concept of recurrent conodont extinction events - the so called Ireviken, Mulde and Lau events - has become a standard in the stratigraphic literature. The concept has been proposed based on qualitative observations of local extirpations of open-marine pelagic or nekto-benthic taxa and temporary dominance of shallow-water species in the Silurian succession of the Swedish island of Gotland. These changes coincided with positive carbon isotope excursions, abrupt facies shifts, "blooms" of benthic fauna, and changes in reef communities, which have all been combined into a general view of Silurian bio-geochemical events. This view posits a deterministic, reproducible pattern in Silurian conodont diversity, attributed to recurrent ecological or geochemical conditions. The growing body of sequence-stratigraphic interpretations across these events in Gotland and other sections worldwide indicate that in all cases the Silurian "events" are associated with rapid global regressions. This suggests that faunal changes such as the dominance of shallow-water, low-diversity conodont fauna and the increase of benthic invertebrate diversity and abundance represent predictable consequences of the variation in the completeness of the rock record and preservation potential of different environments. Our studies in Poland and Ukraine indicate that the magnitude of change in the taxonomic composition of conodont assemblages across the middle Silurian global

  9. Bimodal Silurian and Lower Devonian volcanic rock assemblages in the Machias-Eastport area, Maine

    USGS Publications Warehouse

    Gates, Olcott; Moench, R.H.

    1981-01-01

    Exposed in the Machias-Eastport area of southeastern Maine is the thickest (at least 8,000 m), best exposed, best dated, and most nearly complete succession of Silurian and Lower Devonian volcanic strata in the coastal volcanic belt, remnants of which crop out along the coasts of southern New Brunswick, Canada, and southeastern New England in the United States. The volcanics were erupted through the 600-700-million-year-old Avalonian sialic basement. To test the possibility that this volcanic belt was a magmatic arc above a subduction zone prior to presumed Acadian continental collision, samples representing the entire section in the Machias-Eastport area of Maine were chemically analyzed. Three strongly bimodal assemblages of volcanic rocks and associated intrusives are recognized, herein called the Silurian, older Devonian, and younger Devonian assemblages. The Silurian assemblage contains typically nonporphyritic high-alumina tholeiitic basalts, basaltic andesites, and diabase of continental characterand calc-alkalic rhyolites, silicic dacites, and one known dike of andesite. These rocks are associated with fossiliferous, predominantly marine strata of the Quoddy, Dennys, and Edmunds Formations, and the Leighton Formation of the Pembroke Group (the stratigraphic rank of both is revised herein for the Machias-Eastport area), all of Silurian age. The shallow marine Hersey Formation (stratigraphic rank also revised herein) of the Pembroke Group, of latest Silurian age (and possibly earliest Devonian, as suggested by an ostracode fauna), contains no known volcanics; and it evidently was deposited during a volcanic hiatus that immediately preceded emergence of the coastal volcanic belt and the eruption of the older Devonian assemblage. The older Devonian assemblage, in the lagoonal to subaerial Lower Devonian Eastport Formation, contains tholeiitic basalts and basaltic andesites, typically with abundant plagioclase phenocrysts and typically richer in iron and

  10. Arthrophycus in the Silurian of Alabama (USA) and the problem of compound trace fossils

    USGS Publications Warehouse

    Rindsberg, Andrew K.; Martin, A.J.

    2003-01-01

    Arthrophycus brongniartii (Harlan, 1832) is common in marginal-marine deposits in the Silurian Red Mountain Formation of Alabama. The ichnospecies, the second to be named in North America, is revived and emended after long disuse. Transitional forms to Rusophycus isp. and other morphologic evidence indicate that the maker of Arthrophycus was an arthropod, perhaps a trinucleine (raphiophorid?) trilobite. Interconnection of Arthrophycus and Nereites biserialis, as well as intergradation of Arthrophycus with Cruziana aff. quadrata, Phycodes flabellum, and Asterosoma ludwigae, indicate that these Red Mountain trace fossils were made by the same species of arthropod. Possible relationships with Arthrophycus alleghaniensis (Harlan, 1831) in the Silurian belt from Ontario to Tennessee are also explored. Ichnofamily Arthrophycidae Schimper, 1879 is emended. The ichnofamily is interpreted as chiefly the work of arthropods. Arthrophycus and other trace fossils from the Silurian of Alabama constitute a test case to build criteria for recognizing the members of complexes of trace fossils. In general, criteria such as interconnection of different forms, intergradation among unconnected forms, similarity of size, similarity of morphologic elements, and co-occurrence should be examined in order to determine the biologic and ethologic interrelationships of trace fossils. ?? 2003 Elsevier Science B.V. All rights reserved.

  11. Intermediate to deep water hydrographic changes of the Japan Sea over the past 10 Myr, inferred from radiolarian data (IODP Exp. 346, Site U1425)

    NASA Astrophysics Data System (ADS)

    Matsuzaki, Kenji M.; Itaki, Takuya; Tada, Ryuji; Kurokawa, Shunsuke

    2017-04-01

    The Japan Sea is a back-arc basin opened under a continental rifting during the Early to Middle Miocene (ca. 25-13 Ma). This area is characterized by active tectonism, which drastically modified the Japan Sea paleogeography such as the sill depth of its key straits. In modern condition, the Japan Sea is connected to adjacent marginal seas and the Pacific Ocean by four straits shallower than 130 m. These straits are the Tsushima Strait connecting to the East China Sea, the Tsugaru Strait connecting to the Pacific, and the Soya and Mamiya Straits connecting to the Sea of Okhotsk. Therefore, the intermediate and deep water of the Japan Sea is isolated, leading the formation of a unique and regional deep sea water, known as the Japan Sea Proper Water. However, past studies show that during the late Miocene and Pliocene, only the Tsugaru Strait connecting to the North Pacific was opened. This strait was deeper during Plio-Miocene and have likely enable inflow of deep to intermediate water of the North Pacific in the Japan Sea. Radiolarians are one of the planktic micro-organisms group bearing siliceous skeletons. Their species comprise shallow to deep water dwellers, sensitive to changes in sea water physical/ecological properties forced by climate changes. Their fossils are known for be well preserved in the deep-sea sediments of the North Pacific. Therefore, in this study we propose to monitor changes in intermediate to deep water hydrography of the Japan Sea since the late Miocene, using radiolarian as an environmental proxy. In 2013 the IODP Expedition 346 retrieved sediment cores at different sites in the Japan Sea. In this study, we have analyzed 139 core sediments samples collected at Site U1425. This site is situated in the middle of the Yamato Bank. We selected this site because the past 10 Myr could be recovered continuously without hiatuses. Changes in radiolarian assemblages reveal that the oceanographic setting of the Japan Sea changed drastically at ca. 2

  12. Intracellular diversity of the V4 and V9 regions of the 18S rRNA in marine protists (radiolarians) assessed by high-throughput sequencing.

    PubMed

    Decelle, Johan; Romac, Sarah; Sasaki, Eriko; Not, Fabrice; Mahé, Frédéric

    2014-01-01

    Metabarcoding is a powerful tool for exploring microbial diversity in the environment, but its accurate interpretation is impeded by diverse technical (e.g. PCR and sequencing errors) and biological biases (e.g. intra-individual polymorphism) that remain poorly understood. To help interpret environmental metabarcoding datasets, we investigated the intracellular diversity of the V4 and V9 regions of the 18S rRNA gene from Acantharia and Nassellaria (radiolarians) using 454 pyrosequencing. Individual cells of radiolarians were isolated, and PCRs were performed with generalist primers to amplify the V4 and V9 regions. Different denoising procedures were employed to filter the pyrosequenced raw amplicons (Acacia, AmpliconNoise, Linkage method). For each of the six isolated cells, an average of 541 V4 and 562 V9 amplicons assigned to radiolarians were obtained, from which one numerically dominant sequence and several minor variants were found. At the 97% identity, a diversity metrics commonly used in environmental surveys, up to 5 distinct OTUs were detected in a single cell. However, most amplicons grouped within a single OTU whereas other OTUs contained very few amplicons. Different analytical methods provided evidence that most minor variants forming different OTUs correspond to PCR and sequencing artifacts. Duplicate PCR and sequencing from the same DNA extract of a single cell had only 9 to 16% of unique amplicons in common, and alignment visualization of V4 and V9 amplicons showed that most minor variants contained substitutions in highly-conserved regions. We conclude that intracellular variability of the 18S rRNA in radiolarians is very limited despite its multi-copy nature and the existence of multiple nuclei in these protists. Our study recommends some technical guidelines to conservatively discard artificial amplicons from metabarcoding datasets, and thus properly assess the diversity and richness of protists in the environment.

  13. Assessment of potential shale-oil and shale-gas resources in Silurian shales of Jordan, 2014

    USGS Publications Warehouse

    Schenk, Christopher J.; Pitman, Janet K.; Charpentier, Ronald R.; Klett, Timothy R.; Tennyson, Marilyn E.; Mercier, Tracey J.; Nelson, Philip H.; Brownfield, Michael E.; Pawlewicz, Mark J.; Wandrey, Craig J.

    2014-01-01

    Using a geology-based assessment methodology, the U.S. Geological Survey estimated means of 11 million barrels of potential shale-oil and 320 billion cubic feet of shale-gas resources in Silurian shales of Jordan.

  14. The Cannery Formation--Devonian to Early Permian arc-marginal deposits within the Alexander Terrane, Southeastern Alaska

    USGS Publications Warehouse

    Karl, Susan M.; Layer, Paul W.; Harris, Anita G.; Haeussler, Peter J.; Murchey, Benita L.

    2011-01-01

    The Cannery Formation consists of green, red, and gray ribbon chert, siliceous siltstone, graywacke-chert turbidites, and volcaniclastic sandstone. Because it contains early Permian fossils at and near its type area in Cannery Cove, on Admiralty Island in southeastern Alaska, the formation was originally defined as a Permian stratigraphic unit. Similar rocks exposed in Windfall Harbor on Admiralty Island contain early Permian bryozoans and brachiopods, as well as Mississippian through Permian radiolarians. Black and green bedded chert with subordinate lenses of limestone, basalt, and graywacke near Kake on Kupreanof Island was initially correlated with the Cannery Formation on the basis of similar lithology but was later determined to contain Late Devonian conodonts. Permian conglomerate in Keku Strait contains chert cobbles inferred to be derived from the Cannery Formation that yielded Devonian and Mississippian radiolarians. On the basis of fossils recovered from a limestone lens near Kake and chert cobbles in the Keku Strait area, the age of the Cannery Formation was revised to Devonian and Mississippian, but this revision excludes rocks in the type locality, in addition to excluding bedded chert on Kupreanof Island east of Kake that contains radiolarians of Late Pennsylvanian and early Permian age. The black chert near Kake that yielded Late Devonian conodonts is nearly contemporaneous with black chert interbedded with limestone that also contains Late Devonian conodonts in the Saginaw Bay Formation on Kuiu Island. The chert cobbles in the conglomerate in Keku Strait may be derived from either the Cannery Formation or the Saginaw Bay Formation and need not restrict the age of the Cannery Formation, regardless of their source. The minimum age of the Cannery Formation on both Admiralty Island and Kupreanof Island is constrained by the stratigraphically overlying fossiliferous Pybus Formation, of late early and early late Permian age. Because bedded radiolarian

  15. Depositional environment and organic matter accumulation of Upper Ordovician–Lower Silurian marine shale in the Upper Yangtze Platform, South China

    USGS Publications Warehouse

    Li, Yangfang; Zhang, Tongwei; Ellis, Geoffrey S.; Shao, Deyong

    2017-01-01

    tandem with enhanced stratification of the water column promoted anoxic conditions favorable for the preservation of organic matter. During Early Silurian time, organic matter accumulation was principally controlled by changes in sea level, which affected terrigenous flux, redox conditions, and the degree of nutrition recycling.

  16. Silurian shale origin for light oil, condensate, and gas in Algeria and the Middle East

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Zumberge, J.E.; Macko, S.

    1996-01-01

    Two of the largest gas fields in the world, Hasi R'Mel, Algeria and North Dome, Qatar, also contain substantial condensate and light oil reserves. Gas to source rock geochemical correlation is difficult due to the paucity of molecular parameters in the former although stable isotope composition is invaluable. However, by correlating source rocks with light oils and condensates associated with gas production using traditional geochemical parameters such as biomarkers and isotopes, a better understanding of the origin of the gas is achieved. Much of the crude oil in the Ghadames/Illizi Basins of Algeria has long been thought to have beenmore » generated from Silurian shales. New light oil discoveries in Saudi Arabia have also been shown to originate in basal euxinic Silurian shales. Key sterane and terpane biomarkers as well as the stable carbon isotopic compositions of the C15+ saturate and aromatic hydrocarbon fractions allow for the typing of Silurian-sourced, thermally mature light oils in Algeria and the Middle East. Even though biomarkers are often absent due to advanced thermal maturity, condensates can be correlated to the light oils using (1) carbon isotopes of the residual heavy hydrocarbon fractions, (2) light hydrocarbon distributions (e.g., C7 composition), and (3) compound specific carbon isotopic composition of the light hydrocarbons. The carbon isotopes of the C2-C4 gas components ran then be compared to the associated condensate and light oil isotopic composition.« less

  17. Silurian shale origin for light oil, condensate, and gas in Algeria and the Middle East

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Zumberge, J.E.; Macko, S.

    Two of the largest gas fields in the world, Hasi R`Mel, Algeria and North Dome, Qatar, also contain substantial condensate and light oil reserves. Gas to source rock geochemical correlation is difficult due to the paucity of molecular parameters in the former although stable isotope composition is invaluable. However, by correlating source rocks with light oils and condensates associated with gas production using traditional geochemical parameters such as biomarkers and isotopes, a better understanding of the origin of the gas is achieved. Much of the crude oil in the Ghadames/Illizi Basins of Algeria has long been thought to have beenmore » generated from Silurian shales. New light oil discoveries in Saudi Arabia have also been shown to originate in basal euxinic Silurian shales. Key sterane and terpane biomarkers as well as the stable carbon isotopic compositions of the C15+ saturate and aromatic hydrocarbon fractions allow for the typing of Silurian-sourced, thermally mature light oils in Algeria and the Middle East. Even though biomarkers are often absent due to advanced thermal maturity, condensates can be correlated to the light oils using (1) carbon isotopes of the residual heavy hydrocarbon fractions, (2) light hydrocarbon distributions (e.g., C7 composition), and (3) compound specific carbon isotopic composition of the light hydrocarbons. The carbon isotopes of the C2-C4 gas components ran then be compared to the associated condensate and light oil isotopic composition.« less

  18. Ultrastructure of a colonial radiolarian collozoum inerme and a cytochemical determination of the role of its zooxanthellae.

    PubMed

    Anderson, O R

    1976-01-01

    Collozoum inerme (Müller) is a colonial Radiolarian containing numerous cells bound in a common gelatinous matrix. The cells do not posses a skeleton as observed in many unicellular Radiolaria, but the cytoplasmic organization is similar. The cells are multinucleate and a complex system of cellular processes containing mitochondria, Golgi, and numerous vacuoles radiate out from the nuclear region. The endoplasm is connected to the ectoplasm across a double membrane boundary by thin cytoplasmic strands called fusules whose structure resemble those in unicellular Radiolaria. The ectoplasm contains a lacy network of vacuoles containing an osmiophilic substance. Rhizopodia emerge from the ectoplasmic sheath. Some are thin and densely granular. Larger diameter rhizopodia, containing less dense cytoplasm, sequester the zooxanthellae which present a typical dinoflagellate fine structure. Some of the zooxanthellae are apparently cultivated since they are sometimes observed dividing and persist in large numbers when colonies are cultivated under illumination for several weeks in the laboratory. However, colonies maintained in the dark have a decline in number of zooxanthellae and light microscopic examination shows they are being drawn into the ectoplasm of the radiolarian cells. Electron microscopic examination of zooxanthellae drawn into the ectoplasm sheath indicates they are digested. C. inerme is a remarkable example of a simple cellular aggregate that has exploited its colonial habit to culture algae and use them as food thus possibly enhancing the viability of the colony.

  19. Cyclicity in Silurian island-arc carbonates, Alexander terrane, Alaska

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Kittredge, L.E.; Soja, C.M.

    1993-03-01

    Silurian carbonates from Alaska (Alexander terrane) record the evolution of a submarine platform during waning volcanism in an island arc. A detailed stratigraphic analysis of a 47 meter-thick sequence revealed the existence of cyclically repeated limestones: coral-stromatoporoid wackestones alternate with oncoid packstones and bioturbated, silty lime mudstones. The coral-stromatoporoid deposits are characterized by a low-diversity assemblage of dendroid corals, massive stromatoporoids, Atrypoidea brachiopods, and rare occurrences of biostromes associated with Solenopora, high-spired gastropods, and crinoids. Oncoids typically are 2-6 mm in diameter and form massive, meter-thick units. Coated grains are symmetrically developed, have a shell or algal nucleus, and aremore » also a minor component of coral-stromatoporoid beds. These lithologic units form seven, shallowing-upwards cycles (parasequences) that range in thickness from 3-9 meters. Coral-stomatoporoid wackestones form the base of each cycle and grade upwards into oncoid packstones with silty, lime mudstones at the top. This succession of lithofacies within each cycle reflects an increase in energy levels from relatively deeper water environments to relatively shallower ones. The lack of abrasion in the corals and stromatoporoids suggests predominantly quiet-water conditions in shallow subtidal areas affected by periodic turbulence. Comparison with correlative sections in Alaska and lack of correspondence with global sea level curves suggest that the primary cause of cyclicity was tectonic perturbations with secondary eustatic effects. Cyclic deposition in peri/subtidal sites was terminated by rapid drowning of the carbonate platform during late Silurian orogenesis.« less

  20. Properties of Silurian shales from the Barrandian Basin, Czech Republic

    NASA Astrophysics Data System (ADS)

    Weishauptová, Zuzana; Přibyl, Oldřich; Sýkorová, Ivana

    2017-04-01

    Although shale gas-bearing deposits have a markedly lower gas content than coal deposits, great attention has recently been paid to shale gas as a new potential source of fossil energy. Shale gas extraction is considered to be quite economical, despite the lower sorption capacity of shales, which is only about 10% of coal sorption capacities The selection of a suitable locality for extracting shale gas requires the sorption capacity of the shale to be determined. The sorption capacity is determined in the laboratory by measuring the amount of methane absorbed in a shale specimen at a pressure and a temperature corresponding to in situ conditions, using high pressure sorption. According to the principles of reversibility of adsorption/desorption, this amount should be roughly related to the amount of gas released by forced degassing. High pressure methane sorption isotherms were measured on seven representative samples of Silurian shales from the Barrandian Basin, Czech Republic. Excess sorption measurements were performed at a temperature of 45oC and at pressures up to 15 MPa on dry samples, using a manometric method. Experimental methane high-pressure isotherms were fitted to a modified Langmuir equation. The maximum measured excess sorption parameter and the Langmuir sorption capacity parameter were used to study the effect of TOC content, organic maturity, inorganic components and porosity on the methane sorption capacity. The studied shale samples with random reflectance of graptolite 0.56 to 1.76% had a very low TOC content and dominant mineral fractions. Illite was the prevailing clay mineral. The sample porosity ranged from 4.6 to 18.8%. In most samples, the micropore volumes were markedly lower than the meso- and macropore volumes. In the Silurian black shales, the occurrence of fractures parallel with the original sedimentary bending was highly significant. A greater proportion of fragments of carbonaceous particles of graptolites and bitumens in the

  1. Early Forest Soils and Their Role in Devonian Global Change

    PubMed

    Retallack

    1997-04-25

    A paleosol in the Middle Devonian Aztec Siltstone of Victoria Land, Antarctica, is the most ancient known soil of well-drained forest ecosystems. Clay enrichment and chemical weathering of subsurface horizons in this and other Devonian forested paleosols culminate a long-term increase initiated during the Silurian. From Silurian into Devonian time, red clayey calcareous paleosols show a greater volume of roots and a concomitant decline in the density of animal burrows. These trends parallel the decline in atmospheric carbon dioxide determined from isotopic records of pedogenic carbonate in these same paleosols. The drawdown of carbon dioxide began well before the Devonian appearance of coals, large logs, and diverse terrestrial plants and animals, and it did not correlate with temporal variation in volcanic or metamorphic activity. The early Paleozoic greenhouse may have been curbed by the evolution of rhizospheres with an increased ratio of primary to secondary production and by more effective silicate weathering during Silurian time.

  2. Millennial-scale variations of late Pleistocene radiolarian assemblages in the Bering Sea related to environments in shallow and deep waters

    NASA Astrophysics Data System (ADS)

    Itaki, Takuya; Kim, Sunghan; Rella, Stephan F.; Uchida, Masao; Tada, Ryuji; Khim, Boo-Keun

    2012-02-01

    A high-resolution record of the radiolarian assemblage from 60 to 10 ka was investigated using a piston core (PC-23A) obtained from the northern slope of the Bering Sea. Faunal changes based on the 29 major radiolarian taxa demonstrated that the surface and deep water conditions in the Bering Sea were related to the orbital and millennial-scale climatic variations known as glacial-interglacial and Dansgaard-Oeschger (D-O) cycles, respectively. During interstadial periods of the D-O cycles, the assemblage was characterized by increases in the high-latitude coastal species Rhizoplegma boreale and the upper-intermediate water species Cycladophora davisiana, while the sea-ice related species Actinomma boreale and A. leptodermum and many deep-water species such as Dictyophimus crisiae and D. hirundo tended to be reduced. This trend was more apparent in two laminated intervals at 15-13.5 and 11.5-11 ka, which were correlated with well-known ice-sheet collapse events that occurred during the last deglaciation: melt-water pulse (MWP)-1A and MWP-1B, respectively. The radiolarian faunal composition in these periods suggests that oceanic conditions were different from today: (1) surface water was affected by increased melt-water discharge from continental ice-sheet, occurring at the same time as an abrupt increase in atmospheric temperature, (2) upper-intermediate water (ca. 200-500 m) was well-ventilated and organic-rich, and (3) lower-intermediate water (ca. 500-1000 m) was oxygen-poor. Conversely, the sea-ice season might have been longer during stadial periods of the D-O cycles and the last glacial maximum (LGM) compared to the interstadial periods and the earliest Holocene. In these colder periods, deep-water species were very abundant, and this corresponded to increases in the oxygen isotope value of benthic foraminifera. Our findings suggest that the oxygen-rich water was present in the lower-intermediate layer resulting from intensified ventilation.

  3. The preliminary data on the Aeronian (Silurian) machaerids from Lithuania (Baltic Basin)

    NASA Astrophysics Data System (ADS)

    Radzevičius, S.; Ekleris, A.

    2012-04-01

    Machaerids are stem-Lophotrochozoans, closely related to the Annelids, and known from the Early Ordovician to Middle Permian. Machaerids is a group of worm-like benthic marine, bilaterally symmetrical, armoured invertebrate. Their body is covered by an external scleritome. The scleritome is imbricated of longitudinally arranged series of plates or sclerites. Completely articulated specimens of machaeridians are very rare, yet the systematic position of machaerids is controversial. Machaeridians had been assigned to different groups, such as barnacles, mollusks, echinoderms and annelids. The latter is prevailing, however their exact place within the annelids still remains unresolved. New findings of disarticulated Silurian machaerids have been recorded in western Lithuania, Geniai-1 core. This well has been drilled with exploration purposes regarding the Cambrian oil reservoir; therefore the biggest part of the Silurian core has not been collected. The exceptions are some parts of the Llandovery and Ludlow, which have partially recovered well core, but the identification of the precise stratigraphical position is complicated. Disarticulated sclerites of machaeridians have been found at the 1756.4 m depth, in the argillite, together with some graptolites and brachiopods. Several rhabdosome fragments of Normalograptus scalaris (Hisinger) were found together with the machaenid sclerites as well. N. scalaris has wide biostratigraphical distribution from the Rhudanian to the lower part of Telychian, which comprises the convolutus - triangulates graptolite biozones, corresponding to the 1756.8 - 1756 m depth. Convolutus - triangulates biozones represent Aeronian, and the machaeridian sclerites come from this interval, together with the Jonsea grayi (Davidson) brachiopod shells, which are very common and correspond to the BA 5-6 benthic assemblage, as well as do the graptolites found together. In previous studies, two orders of machaerids have been recognized: the

  4. SHRIMP U-Pb evidence for a Late Silurian age of metasedimentary rocks in the Merrimack and Putnam-Nashoba terranes, eastern New England

    USGS Publications Warehouse

    Wintsch, R.P.; Aleinikoff, J.N.; Walsh, G.J.; Bothner, Wallace A.; Hussey, A.M.; Fanning, C.M.

    2007-01-01

    . Thus, the Kittery should not be considered part of the Laurentian-derived Merrimack terrane; it more likely correlates with the early Silurian Fredericton terrane of northeastern New England and Maritime Canada.

  5. Hydraulic Testing of Silurian and Ordovician Strata at the Bruce Site

    NASA Astrophysics Data System (ADS)

    Beauheim, R. L.; Avis, J. D.; Chace, D. A.; Roberts, R. M.; Toll, N. J.

    2009-05-01

    Ontario Power Generation is proposing a Deep Geologic Repository (DGR) for the long-term management of its Low and Intermediate Level Radioactive Waste (L&ILW) within a Paleozoic-age sedimentary sequence beneath the Bruce Site near Tiverton, Ontario, Canada. The concept envisions that the DGR would be excavated at a depth of approximately 680 m within the Ordovician Cobourg Formation, a massive, dense, argillaceous limestone. A key attribute of the Bruce site is the extremely low permeabilities associated with the thick Ordovician carbonate and argillaceous bedrock formations that will host and enclose the DGR. Such rock mass permeabilities are thought sufficiently low to contribute toward or govern a diffusion-dominated transport regime. To support this concept, hydraulic testing was performed in 2008 and 2009 in two deep boreholes at the proposed repository site, DGR-3 and DGR-4. The hydraulic testing was performed using a straddle-packer tool with a 30.74-m test interval. Sequential tests were performed over the entire open lengths of the boreholes from the F Unit of the Silurian Salina Formation into the Ordovician Gull River Formation, a distance of approximately 635 m. The tests consisted primarily of pressure-pulse tests, with a few slug tests performed in several of the higher permeability Silurian units. The tests are analyzed using the nSIGHTS code, which allows the entire pressure history a test interval has experienced since it was penetrated by the drill bit to be included in the test simulation. nSIGHTS also allows the model fit to the test data to be optimized over an n-dimensional parameter space to ensure that the final solution represents a true global minimum rather than simply a local minimum. The test results show that the Ordovician-age strata above the Coboconk Formation (70+ m below the Cobourg) have average horizontal hydraulic conductivities of 1E-13 m/s or less. Coboconk and Gull River hydraulic conductivities are as high as 1E-11 m

  6. Geology and ground water in Door County, Wisconsin, with emphasis on contamination potential in the Silurian Dolomite

    USGS Publications Warehouse

    Sherrill, Marvin G.

    1978-01-01

    Door County is in northeastern Wisconsin and is an area of 491 square miles. The county forms the main body of the peninsula between Green Bay and Lake Michigan. The land surface is an upland ridge controlled by the underlying bedrock. The west edge of the ridge forms an escarpment facing Green Bay. Silurian dolomite is the upper bedrock unit throughout most of the county and is the most important aquifer. This bedrock is exposed in much of the county, particularly north of Sturgeon Bay; elsewhere, it is covered by a generally thin mantle of soil or drift. The bedrock units are divided into two major aquifer systems in Door County; the Silurian dolomite aquifer system and the sandstone aquifer system, consisting of Ordovician and Cambrian bedrock units. These two major systems are separated by the Maquoketa Shale of Ordovician age, a nearly impermeable, generally nonproductive unit. The Silurian dolomite aquifer system is itself divided into the Niagaran aquifer and the underlying Alexandrian aquifer. Water occurs in the Silurian dolomite aquifer system in two types of openings-nearly vertical joints (fractures) and horizontal to slightly dipping bedding-plane joints. Vertical joints are more common in the upper part of the Niagaran aquifer. These yield small amounts of water to wells. Bedding-plane joints transmit most of the water in the lower part of the Niagaran aquifer and in the Alexandrian aquifer. The bedding-plane joints, because they are poorly interconnected, act as semiartesian conduits separated by impermeable rock. Eight water-bearing zones in generally continuous bedding-plane joints have been mapped. The dolomite is recharged from direct precipitation and snowmelt. It discharges water to pumping wells and by natural springs discharge to Lake Michigan and Green Bay and to interior lakes and streams. Wells in the Silurian dolomite aquifer system have adequate yields to meet most needs, except in the southwest corner of the county, where the dolomite

  7. Sedimentology of the Ripogenus Formation, Maine: A Silurian carbonate-siliciclastic depositional system

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Comrie, T.A.; Caldwell, D.W.

    The Ripogenus Formation of north-central Maine is shallow marine unit of probable Wenlockian age characterized by interbeds of sandstone and limestone less than 50 cm. in thickness and separated by sharp, often erosional, contacts. Reefal material with abundant stromatoporoids is exposed in the eastern part of the formation and is overlain locally by Silurian andesite and Siluro-Devonian redbeds. Sediment size and bed thickness decrease to the west, as does the relative amount of carbonate sediment. Common fossils also include stromatolites, brachiopods, gastropods, crinoids, and corals. Large fossils, notably the stromatoporoids and stromatolites, are often found in growth position, but smallermore » fossils are usually found to have been abraided and transported. The formation was deposited in an area shown by paleogeographic reconstructions to have been located just south of the equator (probably near one or more islands) in the lapetus Ocean prior to its closure. Although sedimentary structures are often not well preserved due to its closure. Although sedimentary structures are often not well preserved due to soft-sedimentary deformation and slight metamorphism, there is some evidence of storm-controlled deposition. Deposition of this unit and other Silurian carbonates found in Maine and the Maritime Provinces are unlike those found throughout N. America in that they are the product of localized deposition in an unstable tectonic environment.« less

  8. Geochemical characteristics and reservoir continuity of Silurian Acacus in Ghadames Basin, Southern Tunisia

    NASA Astrophysics Data System (ADS)

    Mahmoudi, S.; Mohamed, A. Belhaj; Saidi, M.; Rezgui, F.

    2017-11-01

    The present work is dealing with the study of lateral and vertical continuity of the multi-layers Acacus reservoir (Ghadames Basin-Southern Tunisia) using the distribution of hydrocarbon fraction. For this purpose, oil-oil and source rock-oil correlations as well as the composition of the light fractions and a number of saturate and aromatic biomarkers parameters, including C35/C34 hopanes and DBT/P, have been investigated. Based on the ratios of light fraction and their fingerprints, the Acacus reservoir from Well1 and Well2 have found to be laterally non-connected although the hydrocarbons they contain have the same source rock. Moreover, the two oil samples from two different Acacus reservoir layers crossed by Well3-A3 and A9, display a similar hydrocarbons distribution, suggesting vertical reservoir continuity. On the other hand, the biomarker distributions of the oils samples and source rocks assess a Silurian ;Hot shale; that is the source rock feeding the Acacus reservoir. The biomarker distribution is characterized by high tricyclic terpanes contents compared to hopanes for the Silurian source rock and the two crude oils. This result is also confirmed by the dendrogram that precludes the Devonian source rocks as a source rock in the study area.

  9. Origin of Silurian reefs in the Alexander Terrane of southeastern Alaska

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Soja, C.M.

    1991-04-01

    Lower to Upper Silurian (upper Llandovery-Ludlow) limestones belonging to the Heceta Formation record several episodes of reef growth in the Alexander terrane of southeastern Alaska. As the oldest carbonates of wide-spread distribution in the region, the Heceta limestones represent the earliest development of a shallow-marine platform within the Alexander arc and the oldest foundation for reef evolution. These deposits provide important insights into the dynamic processes, styles, and bathymetry associated with reef growth in tectonically active oceanic islands. Massive stromatoporoids, corals, and red algae are preserved in fragmental rudstones and represent a fringing reef that formed at the seaward edgemore » of the incipient marine shelf. Accessory constituents in this reef include crinoids and the cyanobacterium Girvanella. Small biostromes were constructed by ramose corals and stromatoporoids on oncolitic substrates in backreef or lagoonal environments. These buildups were associated with low-diversity assemblages of brachiopods and with gastropods, amphiporids, calcareous algae and cyanobacteria. Microbial boundstones reflect the widespread encrustation of cyanobacteria and calcified microproblematica on shelly debris as stromatolitic mats that resulted in the development of a stromatactoid-bearing mud mound and a barrier reef complex. Epiphytaceans, other microbes, and aphrosalpingid sponges were the primary frame-builders of the barrier reefs. These buildups attained significant relief at the shelf margin and shed detritus as slumped blocks and debris flows into deep-water sites along the slope. The similarity of these stromatolitic-aphrosalpingid reefs to those from Siluro-Devonian strata of autochthonous southwestern Alaska suggests paleobiogeographic ties of the Alexander terrane to cratonal North America during the Silurian.« less

  10. Paleomagnetic and oxygen isotopic evidence for long term diagenesis in radiolarian chert, Pindos Mountains, Greece

    NASA Astrophysics Data System (ADS)

    Baltuck, Miriam

    1987-02-01

    Paleomagnetics was used in an attempt to improve chronostratigraphy in the Middle and Upper Jurassic radiolarian chert and siliceous mudstone of the Pindos Zone, Greece. Remanent magnetism studies showed strong magnetic intensity but scattered orientation. Orientation of some pressure solution features in the radiolarities indicates their formation under horizontal pressure, a condition which in Pindos geologic history would only have occurred during early Cretaceous or Cenozoic tectonics, indicating very late diagenesis in these parts of the section. From time of deposition to later time at which diagenesis can be documented, the Earth's magnetic field would have reversed many times. Remagnetization during solution-precipitation steps of silica diagenesis could complicate the rock magnetics. Oxygen isotopic and major element analyses of radiolarite lithologies show a systematic variation of rate of silica diagenesis in different host lithologies, thus solution-precipitation would occur at widely differing times throughout the section lithologies. If the dissolution of the silica cement were physically to free magnetic material from an earlier orientation, the result could be a partial shift toward alignment with the ambient magnetic field. Alternatively, complete reorientation of particles could have occurred at varying times in different parts of the section as a function of host lithology. During the northward movement and clockwise rotation of the Apulian subplate (including Pindos) these different lithologies could completely reorient during different stages of silica diagenesis, locking the orientation of iron magnetic moments into alignment with the ambient magnetic field at time of precipitation to result in a strong intensity but scattered orientation of Pindos rock magnetics.

  11. Oldest near-complete acanthodian: the first vertebrate from the Silurian Bertie Formation Konservat-Lagerstätte, Ontario.

    PubMed

    Burrow, Carole J; Rudkin, David

    2014-01-01

    The relationships between early jawed vertebrates have been much debated, with cladistic analyses yielding little consensus on the position (or positions) of acanthodians with respect to other groups. Whereas one recent analysis showed various acanthodians (classically known as 'spiny sharks') as stem osteichthyans (bony fishes) and others as stem chondrichthyans, another shows the acanthodians as a paraphyletic group of stem chondrichthyans, and the latest analysis shows acanthodians as the monophyletic sister group of the Chondrichthyes. A small specimen of the ischnacanthiform acanthodian Nerepisacanthus denisoni is the first vertebrate fossil collected from the Late Silurian Bertie Formation Konservat-Lagerstätte of southern Ontario, Canada, a deposit well-known for its spectacular eurypterid fossils. The fish is the only near complete acanthodian from pre-Devonian strata worldwide, and confirms that Nerepisacanthus has dentigerous jaw bones, body scales with superposed crown growth zones formed of ondontocytic mesodentine, and a patch of chondrichthyan-like scales posterior to the jaw joint. The combination of features found in Nerepisacanthus supports the hypothesis that acanthodians could be a group, or even a clade, on the chondrichthyan stem. Cladistic analyses of early jawed vertebrates incorporating Nerepisacanthus, and updated data on other acanthodians based on publications in press, should help clarify their relationships.

  12. Acid processing of pre-Tertiary radiolarian cherts and its impact on faunal content and biozonal correlation

    USGS Publications Warehouse

    Blome, C.D.; Reed, K.M.

    1993-01-01

    Destruction of radiolarians during both diagenesis and HF processing severely reduces faunal abundance and diversity and affects the taxonomic and biostratigraphic utility of chert residues. The robust forms that survive the processing represent only a small fraction of the death assemblage, and delicate skeletal structures used for species differentiation, are either poorly preserved or dissolved in many coeval chert residues. First and last occurrences of taxa in chert sequences are likely to be coarse approximations of their true stratigraphic ranges. Precise correlation is difficult between biozonations based solely on index species from cherts and those constructed from limestone faunas. Careful selection of samples in sequence, use of weaker HF solutions, and study of both chert and limestone faunas should yield better biostratigraphic information. -from Authors

  13. [sup 40]Ar/[sup 39]Ar mineral ages from southwestern Penobscot Bay, Maine: Evidence for Silurian metamorphism

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    West, D.P. Jr.; Guidotti, C.V.; Lux, D.R.

    1992-01-01

    The nature and timing of metamorphic events in the Coastal Lithotectonic Block of Maine remain poorly understood. Immediately west and southwest of Penobscot Bay the rocks are polymetamorphic showing evidence for at least two episodes of amphibolite facies metamorphism and later, perhaps regionally extensive, retrograde events. Hornblende mineral separates from two amphibolites din the Port Clyde area have identical Ar-40/Ar-39 plateau ages of 414.0 [+-] 3.3 and 414.0 [+-] 3.9 Ma. These ages are interpreted to reflect the time of cooling following the last significant thermal event in this area. Biotite from an amphibolite in the Port Clyde area givesmore » a total gas age of 346.5 [+-] 3.2 Ma. Hornblende from an amphibolite 7 km to the west near Friendship gives a nearly concordant release spectrum with a plateau age of 369.0 [+-] 3.7 Ma. Coexisting biotite from this amphibolite gives a total gas age of 289.2 [+-] 2.7 Ma. Muscovite from the Waldoboro pluton has a nearly concordant release spectrum with a plateau age of 306.3 [+-] 2.2 Ma. Biotite from this sample gives a total gas age of 288.9 [+-] 2.2 Ma. The 414.0 Ma hornblende cooling ages from the Port Clyde area reflect cooling following a significant high grade Silurian thermal event. This Silurian metamorphism is the same age as tectonothermal events in the Nashoba Terrane in eastern Massachusetts, the Kingston Complex in southern New Brunswick, the Aspy Terrane in Cape Breton island, Nova Scotia, and the Hermitage Flexure in southern Newfoundland.d Thus a distinctive Silurian tectonothermal province located along the western edge of the Avalon Zone appears to extend discontinuously from Massachusetts to Newfoundland.« less

  14. Diversity-dependent evolutionary rates in early Palaeozoic zooplankton.

    PubMed

    Foote, Michael; Cooper, Roger A; Crampton, James S; Sadler, Peter M

    2018-02-28

    The extent to which biological diversity affects rates of diversification is central to understanding macroevolutionary dynamics, yet no consensus has emerged on the importance of diversity-dependence of evolutionary rates. Here, we analyse the species-level fossil record of early Palaeozoic graptoloids, documented with high temporal resolution, to test directly whether rates of diversification were influenced by levels of standing diversity within this major clade of marine zooplankton. To circumvent the statistical regression-to-the-mean artefact, whereby higher- and lower-than-average values of diversity tend to be followed by negative and positive diversification rates, we construct a non-parametric, empirically scaled, diversity-independent null model by randomizing the observed diversification rates with respect to time. Comparing observed correlations between diversity and diversification rate to those expected from this diversity-independent model, we find evidence for negative diversity-dependence, accounting for up to 12% of the variance in diversification rate, with maximal correlation at a temporal lag of approximately 1 Myr. Diversity-dependence persists throughout the Ordovician and Silurian, despite a major increase in the strength and frequency of extinction and speciation pulses in the Silurian. By contrast to some previous work, we find that diversity-dependence affects rates of speciation and extinction nearly equally on average, although subtle differences emerge when we compare the Ordovician and Silurian. © 2018 The Author(s).

  15. Organoporosity Evaluation of Shale: A Case Study of the Lower Silurian Longmaxi Shale in Southeast Chongqing, China

    PubMed Central

    Chen, Fangwen; Lu, Shuangfang; Ding, Xue

    2014-01-01

    The organopores play an important role in determining total volume of hydrocarbons in shale gas reservoir. The Lower Silurian Longmaxi Shale in southeast Chongqing was selected as a case to confirm the contribution of organopores (microscale and nanoscale pores within organic matters in shale) formed by hydrocarbon generation to total volume of hydrocarbons in shale gas reservoir. Using the material balance principle combined with chemical kinetics methods, an evaluation model of organoporosity for shale gas reservoirs was established. The results indicate that there are four important model parameters to consider when evaluating organoporosity in shale: the original organic carbon (w(TOC0)), the original hydrogen index (I H0), the transformation ratio of generated hydrocarbon (F(R o)), and the organopore correction coefficient (C). The organoporosity of the Lower Silurian Longmaxi Shale in the Py1 well is from 0.20 to 2.76%, and the average value is 1.25%. The organoporosity variation trends and the residual organic carbon of Longmaxi Shale are consistent in section. The residual organic carbon is indicative of the relative levels of organoporosity, while the samples are in the same shale reservoirs with similar buried depths. PMID:25184155

  16. Molecular diversity of early foraminifera

    NASA Astrophysics Data System (ADS)

    Holzmann, Maria; Pawlowski, Jan

    2017-04-01

    Monothalamid foraminifera are a diverse group that is characterized by single-chambered agglutinated or organic test. They occur in all marine habitats and are also present in terrestrial and freshwater environments. Monothalamids branch at the base of foraminiferal tree, as a paraphyletic group with some clades branching at the base of Globothalamea and Tubothalamea. We have currently more than 1500 sequences of monothalamids in our database that can be divided in at least 20 clades among which certain are particularly well presented by sequence numbers and/or number of different species. These are members of clade BM that contain Bathysiphon and Micrometula, clade C that contains among others xenophyophorans, saccaminids, and a large variety of organic-walled or agglutinated genera, clade E that contains the genera Psammophaga, Vellaria and Nellya and four clades that contain freshwater foraminifera. In general, the monothalamid clades comprise both agglutinated and organic-walled genera. Some common genera, such as Crithionina, Saccammina, Hippocrepina, are polyphyletic. Our results clearly show that monothalamids are highly diverse and their molecular diversity by far surpasses their morphological variety. Based on phylogenomic studies, monothalamids evolved early in the evolution of eukaryotes, as a part of the supergroup of Rhizaria, comprising also radiolarians and other amoeboid protists. The monothalamids have diverged from ancestral radiolarians, probably about 1000 million years ago, but the exact time is difficult to infer because of the uncertainties concerning a calibration of a eukaryotic phylogenomic tree.

  17. Stable isotopic perturbation at the Ordovician-Silurian transition in NE Poland

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Hoffman, A.; Gruszczynski, M.; Malkowski, K.

    1992-01-01

    An interpretation of the time series of stable isotopic proportions of carbon, oxygen, and sulfur in rock samples from subsurface Ordovician-Silurian transition in north-eastern Poland demonstrates a clearcut perturbation that must imply some global scale controlling factors. This perturbation is particularly emphasized by its comparison to the sustained secular Paleozoic trend in isotopic characteristics of the oceanic system. On the other hand, this isotopic perturbation contrasts with unidirectional local changes in geochemical elemental proportions in the same rock samples. The perturbation is most parsimoniously explained as linked to the onset of a major glaciation. Its relationship to the second largestmore » mass extinction in the history of the biosphere still remains to be elucidated.« less

  18. Environmental reconstructions of the upper 500 m of the southern Indian Ocean over the last 40 ka using Radiolarian (Protista) proxies

    NASA Astrophysics Data System (ADS)

    Rogers, John; De Deckker, Patrick

    2011-04-01

    In 2007, we demonstrated that radiolarians are proxies for a wide range of oceanic physico-chemical properties from the surface to depths of up to 500 m below sea level. In this study, our results are refined and Correspondence Analysis (CA) scores derived from census counts of radiolarian subfossils from southern Indian Ocean core-tops are correlated with the physico-chemical properties of the region obtained from the 2005 World Ocean Database. Calibration and regression techniques are employed to reconstruct palaeoenvironmental conditions spanning the last 40 ka for four Indian Ocean cores MD88-769 [46°04'S 90°06'E], MD88-770 [46°01'S 96°27'E], MD94-102 [43°30'S 79°50'E], and MD94-103 [45°35'S 86°31'E], all from close to the Southeast Indian Ridge. For the first time, reconstructions of temperature, salinity, dissolved oxygen, and the silicate, nitrate, and phosphate concentrations for a range of water depths are proved possible. Changes of the oceanic environment and the movement of water masses over the last 40 ka, as suggested by these reconstructions, are discussed. During Marine Isotope Stages 2 and 3 (MIS-2 and MIS-3), the water column at some of the core sites has similar characteristics to the waters south of the Polar Front today. At the MIS-1/MIS-2 transition, the development of the Subantarctic Mode Water is apparent. Temperature reconstructions include evidence of the Antarctic Cold Reversal and the Holocene Optimum.

  19. Lithologies of the basement complex (Devonian and older) in the National Petroleum Reserve - Alaska

    USGS Publications Warehouse

    Dumoulin, Julie A.; Houseknecht, David W.

    2001-01-01

    Rocks of the basement complex (Devonian and older) were encountered in at least 30 exploratory wells in the northern part of the NPRA. Fine-grained, variably deformed sedimentary rocks deposited in a slope or basinal setting predominate and include varicolored (mainly red and green) argillite in the Simpson area, dark argillite and chert near Barrow, and widespread gray argillite. Chitinozoans of Middle-Late Ordovician and Silurian age occur in the dark argillite and chert unit. Sponge spicules and radiolarians establish a Phanerozoic age for the varicolored and gray argillite units, both of which contain local interbeds of chert-rich sandstone and silt-stone. Conglomerate and sandstone, also chert-rich but interbedded with mudstone and coal and of Early-Middle Devonian age, occur in the Topagoruk area; these strata formed in a fluvial environment. At East Teshekpuk, granite of probable Devonian age was penetrated. Brecciated, quartz-veined rock of uncertain protolith that may be part of the basement complex was encountered in the Ikpikpuk well. Seismic data indicate that angular unconformities truncate all sedimentary units of the basement complex in NPRA. Rocks correlative in age and lithofacies with the dark argillite and chert unit occur in the subsurface near Prudhoe Bay. Other argillite units in NPRA have similarities to basement rocks in the subsurface adjacent to ANWR and the Ordovician-Silurian Iviagik Group at Cape Lisburne, but lack the interbedded limestones found in the ANWR strata, and are less metamorphosed than, and compositionally distinct from, the Iviagik. The Topagoruk conglomerate and the East Teshekpuk granite resemble the Ulungarat formation and the Okpilak batholith, respectively, in the northeastern Brooks Range.

  20. Corrigendum to "Decadal to millennial variations in water column parameters in pelagic marine environments of the Western Tethys (Carpathian realm) during Middle-Late Jurassic - Evidence from the radiolarian record" [Glob. Planet. Chang. 162 (2018) 148-162

    NASA Astrophysics Data System (ADS)

    Bąk, Marta; Bąk, Krzysztof; Michalik, Mariola

    2018-04-01

    The authors regret (Abstract. The causal link between changes in Middle-Late Jurassic radiolarian habitat group abundances, microfacies and water column conditions in the Western Tethys was studied based on the examination of siliceous limestones and cherts from the Tatra Mountains, Central Western Carpathians. Deposition occurred on a morphological high with incised pelagic sedimentation within a tropical zone. High-resolution quantitative analyses of millimetre-thick microlaminae show changes in microfacies constituents that most likely record the fluxes of nutrients and biological activity in superficial waters. Variability of radiolarian assemblages that are classified to represent (i) upwelling and (ii) stratified water taxa suggest successive changes in water conditions that fluctuated between periods of upwelling and periods of formation of a thick, stratified, warm superficial layer above a deep thermocline during middle Bajocian-late Oxfordian time. Such variations would be strongly influenced by ocean-atmosphere global circulation patterns, which are caused by pressure gradients and are the result of Walker circulation along the equatorial part of the Tethys and the Panthalassa Ocean, including the duration of El Niño-like and La Niña-like cycles, which affect sea surface temperature trends on decadal scales. The fluctuations in radiolarian assemblages in the sediments indicate that long-term palaeoceanographic changes occurred on multi-decadal to centennial-scales during the Bajocian, but lengthened in duration to millennial-scale during the Bathonian through the Oxfordian.)

  1. Carbonate rocks of the Seward Peninsula, Alaska: Their correlation and paleogeographic significance

    USGS Publications Warehouse

    Dumoulin, Julie A.; Harris, Alta; Repetski, John E.

    2014-01-01

    associated calcareous metaturbidites of Ordovician age as well as shallow-water Silurian dolostones. Scattered metacarbonate rocks are chiefly Cambrian, Ordovician, Silurian, and Devonian dolostones that formed in shallow, warm-water settings with locally restricted circulation and marbles of less constrained Paleozoic age. Carbonate metaturbidites occur on the northeast and southeast coasts and yield mainly Silurian and lesser Ordovician and Devonian conodonts; the northern succession also includes debris flows with meter-scale clasts and an argillite interval with Late Ordovician graptolites and lenses of radiolarian chert. Mafic igneous rocks at least partly of Early Devonian age are common in the southern succession. Carbonate rocks on Seward Peninsula experienced a range of deformational and thermal histories equivalent to those documented in the Brooks Range. Conodont color alteration indices (CAIs) from Seward Peninsula, like those from the Brooks Range, define distinct thermal provinces that likely reflect structural burial. Penetratively deformed high-pressure metamorphic rocks of the Nome Complex (CAIs ≥5) correspond to rocks of the Schist belt in the southern Brooks Range; both record subduction during early stages of the Jurassic–Cretaceous Brooks Range orogeny. Weakly metamorphosed to unmetamorphosed strata of the York terrane (CAIs mainly 2–5), like Brooks Range rocks in the Central belt and structural allochthons to the north, experienced moderate to shallow burial during the main phase of the Brooks Range orogeny. The nature of the contact between the York terrane and the Nome Complex is uncertain; it may be a thrust fault, an extensional surface, or a thrust fault later reactivated as an extensional fault. Lithofacies and biofacies data indicate that, in spite of their divergent Mesozoic histories, rocks of the York terrane and protoliths of the Nome Complex formed as part of the same lower Paleozoic carbonate platform. Stratigraphies in both

  2. A Bohemian-type Silurian (Wenlockian) pelecypod faunule from Arctic Canada.

    USGS Publications Warehouse

    Pojeta, J.; Norford, B.S.

    1987-01-01

    The pelecypod genera Slava and Rhombopteria are reported for the first time from Canada, where they occur in a limestone concretion within the Cape Phillips Formation, Cornwallis Island, Arctic Archipelago. These genera are characteristic of Silurian rocks in Bohemia, Czechoslovakia. Graptolites from the same concretion indicate the Monograptus ludensis Zone (uppermost Wenlockian); this age is substantiated by associated conodonts, trilobites, vertebrates, and pelecypods but with less precision. It is difficult to explain the occurrence of Slava and Rhombopteria in the middle of Laurentia on the basis of some map reconstructions of the Wenlockian world. The Canadian material of Slava novaterra n. sp. and Rhombopteria cf. R. mira (Barrande) is described. Leptodesma (Leptodesma) sp. A and an indeterminate grammysiid pelecypod from the same concretion are illustrated. Information is provided to show that Newsomella Foerste, from Wenlockian-Ludlovian rocks of Illinois, Wisconsin, and Tennessee, is not a subgenus of Rhombopteria Jackson. -Authors

  3. Conodont and Radiolarian Data from the De Long Mountains Quadrangle and Adjacent Areas, Northern Alaska

    USGS Publications Warehouse

    Dumoulin, Julie A.; Harris, Anita G.; Blome, Charles D.; Young, Lorne E.

    2006-01-01

    INTRODUCTION This report presents biostratigraphic data from 289 collections at 189 localities in the De Long Mountains, Misheguk Mountain, and Noatak quadrangles (fig. 1); most of these data have never been previously published. The collections were made during studies of the Red Dog massive sulfide deposit in 1998?2004 and in support of regional mapping projects in 1979, 1981, 1983, and 1997?98. The collections?mostly conodonts and some radiolarians?tightly constrain the age of many stratigraphic units of Devonian through Triassic age exposed within the study area, and provide additional data on the depositional environments and thermal history of these rocks. The data are presented in a series of tables, organized by fossil type, stratigraphic unit, and location. Tables 1?12 contain conodont data, mostly from the De Long Mountains quadrangle. All of these collections were initially examined, or were reevaluated, from 1997 through 2004, and complete faunal lists are given for all samples. Table 13 lists ages and conodont color alteration indices (CAIs) of 27 collections from 24 localities in the Noatak quadrangle; updated faunal lists were not prepared for these samples. Radiolarian data?all from the De Long Mountains quadrangle?are given in table 14; these collections were analyzed between 1998 and 2003. Collection localities are shown in four maps (sheets 1, 2). Map 1 (sheet 1) shows all outcrop samples from the De Long Mountains and western Misheguk Mountain quadrangle (locs. 1-121). Maps 2?4 (sheets 1, 2) show all drill hole sample localities; samples come from the Su-Lik deposit and in and around the Anarraaq deposit (map 2, locs. 122?135), in and adjacent to the Red Dog deposits (Paalaaq, Aqqaluk, Main, and Qanaiyaq) (map 3, locs. 136?158), and from drill holes along the Port Road in the Noatak quadrangle (map 4, locs. 159?160). Map 4 (sheet 2) also shows all outcrop samples from the Noatak quadrangle (locs. 161?189). The text summarizes the lithofacies

  4. Hydrogeology and simulation of ground-water flow in the Silurian-Devonian aquifer system, Johnson County, Iowa

    USGS Publications Warehouse

    Tucci, Patrick; McKay, Robert M.

    2006-01-01

    The greatest limitation to the model is the lack of measured or estimated water-budget components for comparison to simulated water-budget components. Because the model is only calibrated to measured water levels, and not to water-budget components, the model results are nonunique. Other model limitations include the relatively coarse grid scale, lack of detailed information on pumpage from the quarry and from private developments and domestic wells, and the lack of separate water-level data for the Silurian- and Devonian-age rocks.

  5. Paleomagnetism and paleogeography of Jurassic radiolarian cherts from the Northern Apennines of Italy

    USGS Publications Warehouse

    Aiello, I.W.; Hagstrum, J.T.

    2001-01-01

    Oriented samples of Jurassic radiolarian chert were collected from the Tuscan domain (continental margin) and the Ligurid domain (oceanic) of the northern Apennines for paleomagnetic study to determine the paleogeographic origins of these rocks. The oceanic rocks are all thermochemically overprinted by a mostly reversed-polarity component of magnetization (B) that was likely acquired during late Miocene regional uplift of the northern Apennines. This component also dominates the lower brittle chert of the Tuscan Cherts, but disappears upsection in the more clay-rich and ductile siliceous marlstones. In addition, the Tuscan Cherts retain an inferred primary magnetization (C), isolated at temperatures between 560 and 660 degrees C, which passes a fold test and shows a polarity stratigraphy. This component indicates a paleolatitude of 11 degrees + or -4 degrees N, and a counterclockwise vertical-axis rotation of 29 degrees + or -9 degrees with respect to the southern Alps of Italy, of 49 degrees + or -8 degrees with respect to Africa, and of 91 degrees + or -8 degrees with respect to Eurasia. Our results suggest that the Tuscan domain was farther south than other deep-water continental margin sections of Adria, and that transcurrent faulting might have played a significant role in the orogenic evolution of the northern Apennines.

  6. An exceptionally preserved myodocopid ostracod from the Silurian of Herefordshire, UK

    PubMed Central

    Siveter, David J.; Briggs, Derek E. G.; Siveter, Derek J.; Sutton, Mark D.

    2010-01-01

    An exceptionally preserved new ostracod crustacean from the Silurian of Herefordshire, UK, represents only the third fully documented Palaeozoic ostracod with soft-part preservation. Appendages, gills, gut system, lateral compound eyes and even a medial eye with a Bellonci organ are preserved, allowing assignment of the fossil to a new genus and species of cylindroleberidid myodocope (Myodocopida, Cylindroleberididae). The Bellonci organ is recorded for the first time in fossil ostracods. The find also represents a rare occurrence of gills in fossil ostracods and confirms the earliest direct evidence of a respiratory-cum-circulatory system in the group. The species demonstrates remarkably conserved morphology within myodocopes over a period of 425 Myr. Its shell morphology more closely resembles several families of myodocopes other than the Cylindroleberididae, especially the Cypridinidae and Sarsiellidae, thus questioning the utility of the carapace alone in establishing the affinity of fossil ostracods. PMID:20106847

  7. The Oldest Actinopterygian Highlights the Cryptic Early History of the Hyperdiverse Ray-Finned Fishes.

    PubMed

    Lu, Jing; Giles, Sam; Friedman, Matt; den Blaauwen, Jan L; Zhu, Min

    2016-06-20

    Osteichthyans comprise two divisions, each containing over 32,000 living species [1]: Sarcopterygii (lobe-finned fishes and tetrapods) and Actinopterygii (ray-finned fishes). Recent discoveries from China highlight the morphological disparity of early sarcopterygians and extend their origin into the late Silurian [2-4]. By contrast, the oldest unambiguous actinopterygians are roughly 30 million years younger, leaving a long temporal gap populated by fragments and rare body fossils of controversial phylogenetic placement [5-10]. Here we reinvestigate the enigmatic osteichthyan Meemannia from the Early Devonian (∼415 million years ago) of China, previously identified as an exceptionally primitive lobe-finned fish [3, 7, 11, 12]. Meemannia combines "cosmine"-like tissues taken as evidence of sarcopterygian affinity with actinopterygian-like skull roof and braincase geometry, including endoskeletal enclosure of the spiracle and a lateral cranial canal. We report comparable histological structures in undoubted ray-finned fishes and conclude that they are general osteichthyan features. Phylogenetic analysis places Meemannia as an early-diverging ray-finned fish, resolving it as the sister lineage of Cheirolepis [13] plus all younger actinopterygians. This brings the first appearance of ray-fins more in line with that of lobe-fins and fills a conspicuous faunal gap in the otherwise diverse late Silurian-earliest Devonian vertebrate faunas of the South China Block [4]. Copyright © 2016 The Author(s). Published by Elsevier Ltd.. All rights reserved.

  8. Geochronology, stratigraphy and geochemistry of Cambro-Ordovician, Silurian and Devonian volcanic rocks of the Saxothuringian Zone in NE Bavaria (Germany)—new constraints for Gondwana break up and ocean-island magmatism

    NASA Astrophysics Data System (ADS)

    Höhn, Stefan; Koglin, Nikola; Klopf, Lisa; Schüssler, Ulrich; Tragelehn, Harald; Frimmel, Hartwig E.; Zeh, Armin; Brätz, Helene

    2018-01-01

    Stratigraphically well-defined volcanic rocks in Palaeozoic volcano-sedimentary units of the Frankenwald area (Saxothuringian Zone, Variscan Orogen) were sampled for geochemical characterisation and U-Pb zircon dating. The oldest rock suite comprises quartz keratophyre, brecciated keratophyre, quartz keratophyre tuff and basalt, formed in Upper Cambrian to Tremadocian time (c. 497-478 Ma). Basaltic volcanism continued until the Silurian. Quartz keratophyre shows post-collisional calc-alkaline signature, the Ordovician-Silurian basalt has alkaline signature typical of continental rift environments. The combined datasets provide evidence of Cambro-Ordovician bimodal volcanism and successive rifting until the Silurian. This evolution very likely resulted from break-up of the northern Gondwana margin, as recorded in many terranes throughout Europe. The position at the northern Gondwana margin is supported by detrital zircon grains in some tuffs, with typical Gondwana-derived age spectra mostly recording ages of 550-750 Ma and minor age populations of 950-1100 and 1700-2700 Ma. The absence of N-MORB basalt in the Frankenwald area points to a retarded break-off of the Saxothuringian terrane along a continental rift system from Uppermost Cambrian to Middle Silurian time. Geochemical data for a second suite of Upper Devonian basalt provide evidence of emplacement in a hot spot-related ocean-island setting south of the Rheic Ocean. Our results also require partial revision of the lithostratigraphy of the Frankenwald area. The basal volcanic unit of the Randschiefer Formation yielded a Tremadocian age and, therefore, should be attributed to the Vogtendorf Formation. Keratophyre of the Vogtendorf Formation, previously assigned to the Tremadoc, is most likely of Upper Devonian age.

  9. Global analyses of brachiopod faunas through the Ordovician and Silurian transition: Reducing the role of the Lazarus effect

    USGS Publications Warehouse

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

    2006-01-01

    Global analyses of 88 families and 284 genera of brachiopods from middle Ashgill, Late Ordovician, to early-middle Rhuddanian, Early Silurian, indicate that 18.6% and 12.5% of families and 51.0% and 41.3% of genera were eliminated in the first and second phases of the end-Ordovician mass extinction, respectively, with the total loss of 28.4% of families and 69.0% of genera in the crisis. New investigation demonstrates that brachiopods, at both generic and familial levels, suffered greater during the first phase than during the second phase. Four groups (victims, relicts, survivors, and new arrivals) are distinguished by their stratigraphical ranges. Generic survivors, occurring in the Kosov Province during the Hirnantian, can be split into three types with respect to their changing abundance: increasing, declining, and Lazarus taxa. Among the 88 genera that survived, numerous declining genera occurred in the Hirnantian: 16 Lazarus families and 18 Lazarus genera are provisionally known and may be regarded as end members of the declining type. Comparison of the abundance, population size, and distribution patterns of declining and Lazarus taxa shows important similarities between these two types which contribute to a better understanding of the nature of Lazarus taxa. In addition to these biological attributes, taphonomic failure and generally poor preservation, together with collecting bias and inadequate systematic data, are clearly involved. More collections will undoubtedly globally reduce the number of Lazarus taxa. A single, common refugium for end-Ordovician brachiopods probably did not exist; rather, these taxa used paleogeographically scattered locations in a range of environments for survival. ?? 2006 NRC Canada.

  10. The Lower Silurian Osmundsberg K-bentonite. Part II: Mineralogy, geochemistry, chemostratigraphy and tectonomagmatic significance

    USGS Publications Warehouse

    Huff, W.D.; Bergstrom, Stig M.; Kolata, Dennis R.; Sun, H.

    1998-01-01

    The Lower Silurian Osmundsberg K-bentonite is a widespread ash bed that occurs throughout Baltoscandia and parts of northern Europe. This paper describes its characteristics at its type locality in the Province of Dalarna, Sweden. It contains mineralogical and chemical characteristics that permit its regional correlation in sections elsewhere in Sweden as well as Norway, Estonia, Denmark and Great Britain. The < 2 ??m clay fraction of the Osmundsberg bed contains abundant kaolinite in addition to randomly ordered (RO) illite/smectite (I/S). Modelling of the X-ray diffraction tracings showed the I/S consists of 18% illite and 82 % smectite. The high smectite and kaolinite content is indicative of a history with minimal burial temperatures. Analytical data from both pristine melt inclusions in primary quartz grains as well as whole rock samples can be used to constrain both the parental magma composition and the probable tectonic setting of the source volcanoes. The parental ash was dacitic to rhyolitic in composition and originated in a tectonically active collision margin setting. Whole rock chemical fingerprinting of coeval beds elsewhere in Baltoscandia produced a pronounced clustering of these samples in the Osmundsberg field of the discriminant analysis diagram. This, together with well-constrained biostratigraphic and lithostratigraphic data, provides the basis for regional correlation and supports the conclusion that the Osmundsberg K-bentonite is one of the most extensive fallout ash beds in the early Phanerozoic. The source volcano probably lay to the west of Baltica as part of the subduction complex associated with the closure of Iapetus.

  11. Failed Silurian continental rifting at the NW margin of Gondwana: evidence from basaltic volcanism of the Prague Basin (Teplá-Barrandian Unit, Bohemian Massif)

    NASA Astrophysics Data System (ADS)

    Tasáryová, Zuzana; Janoušek, Vojtěch; Frýda, Jiří

    2018-06-01

    The Silurian volcanic rocks of the Prague Basin represent within-plate, transitional alkali to tholeiitic basalts, which erupted in a continental rift setting through the thick Cadomian crust of the Teplá-Barrandian Unit (Bohemian Massif). Despite the variable, often intense alteration resulting in post-magmatic replacement of the basalt mass due to carbonatization, the geochemical signatures of Silurian basalts are still sufficiently preserved to constrain primary magmatic processes and geotectonic setting. The studied interval of Silurian volcanic activity ranges from Wenlock (Homerian, 431 Ma) to late Ludlow (Gorstian, 425 Ma) with a distinct peak at the Wenlock/Ludlow boundary ( 428 Ma). Trace-element characteristics unambiguously indicate partial melting of a garnet peridotite mantle source. Wenlock basalts are similar to alkaline OIB with depleted radiogenic Nd signature compared to Ludlow basalts, which are rather tholeiitic, EMORB-like with enriched radiogenic Nd signature. The correlation of petrogenetically significant trace-element ratios with Nd isotopic compositions points to a mixing of partial melts of an isotopically heterogeneous, possibly two-component mantle source during the Wenlock-Ludlow melting. Lava eruptions were accompanied by intrusions of doleritic basalt and meimechite sills. The latter represent olivine-rich cumulates of basaltic magmas of probably predominantly Ludlow age. Meimechites with dolerites and, to a lesser extent, some lavas were subject to alteration due to wall-rock-fluid interaction. The trigger for the Wenlock-to-Ludlow (431-425 Ma) extension and related volcanism in the Prague Basin is related to far-field forces, namely slab-pull regime due to progressive closure of the Iapetus Ocean. The main stage of the Baltica-Laurentia collision then caused the Prague Basin rift failure at ca. 425 Ma that has never reached an oceanic stage.

  12. An edrioasteroid from the Silurian Herefordshire Lagerstätte of England reveals the nature of the water vascular system in an extinct echinoderm.

    PubMed

    Briggs, Derek E G; Siveter, Derek J; Siveter, David J; Sutton, Mark D; Rahman, Imran A

    2017-09-13

    Echinoderms are unique in having a water vascular system with tube feet, which perform a variety of functions in living forms. Here, we report the first example of preserved tube feet in an extinct group of echinoderms. The material, from the Silurian Herefordshire Lagerstätte, UK, is assigned to a new genus and species of rhenopyrgid edrioasteroid, Heropyrgus disterminus The tube feet attach to the inner surface of compound interradial plates and form two sets, an upper and a lower, an arrangement never reported previously in an extant or extinct echinoderm. Cover plates are absent and floor plates are separated creating a large permanent entrance to the interior of the oral area. The tube feet may have captured food particles that entered the oral area and/or enhanced respiration. The pentameral symmetry of the oral surface transitions to eight columns in which the plates are vertically offset resulting in a spiral appearance. This change in symmetry may reflect flexibility in the evolutionary development of the axial and extraxial zones in early echinoderm evolution. © 2017 The Author(s).

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

    USGS Publications Warehouse

    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

  14. Silurian extension in the Upper Connecticut Valley, United States and the origin of middle Paleozoic basins in the Québec embayment

    USGS Publications Warehouse

    Rankin, D.W.; Coish, R.A.; Tucker, R.D.; Peng, Z.X.; Wilson, S.A.; Rouff, A.A.

    2007-01-01

    Pre-Silurian strata of the Bronson Hill arch (BHA) in the Upper Connecticut Valley, NH-VT are host to the latest Ludlow Comerford Intrusive Suite consisting, east to west, of a mafic dike swarm with sheeted dikes, and an intrusive complex. The rocks are mostly mafic but with compositions ranging from gabbro to leucocratic tonalite. The suite is truncated on the west by the Monroe fault, a late Acadian thrust that carries rocks of the BHA westward over Silurian-Devonian strata of the Connecticut Valley-Gaspe?? trough (CVGT). Dikes intrude folded strata with a pre-intrusion metamorphic fabric (Taconian?) but they experienced Acadian deformation. Twenty fractions of zircon and baddeleyite from three sample sites of gabbrodiorite spanning nearly 40 km yield a weighted 207Pb/206Pb age of 419 ?? 1 Ma. Greenschist-facies dikes, sampled over a strike distance of 35 km, were tholeiitic basalts formed by partial melting of asthenospheric mantle, with little or no influence from mantle or crustal lithosphere. The dike chemistry is similar to mid-ocean ridge, within-plate, and back-arc basin basalts. Parent magmas originated in the asthenosphere and were erupted through severely thinned lithosphere adjacent to the CVGT. Extensive middle Paleozoic basins in the internides of the Appalachian orogen are restricted to the Que??bec embayment of the Laurentian rifted margin, and include the CVGT and the Central Maine trough (CMT), separated from the BHA by a Silurian tectonic hinge. The NE-trending Comerford intrusions parallel the CVGT, CMT, and the tectonic hinge, and indicate NW-SE extension. During post-Taconian convergence, the irregular margins of composite Laurentia and Avalon permitted continued collision in Newfoundland (St. Lawrence promontory) and coeval extension in the Que??bec embayment. Extension may be related to hinge retreat of the northwest directed Brunswick subduction complex and rise of the asthenosphere following slab break-off. An alternative hypothesis is

  15. Petrophysics of Lower Silurian sandstones and integration with the tectonic-stratigraphic framework, Appalachian basin, United States

    USGS Publications Warehouse

    Castle, J.W.; Byrnes, A.P.

    2005-01-01

    Petrophysical properties were determined for six facies in Lower Silurian sandstones of the Appalachian basin: fluvial, estuarine, upper shoreface, lower shoreface, tidal channel, and tidal flat. Fluvial sandstones have the highest permeability for a given porosity and exhibit a wide range of porosity (2-18%) and permeability (0.002-450 md). With a transition-zone thickness of only 1-6 m (3-20 ft), fluvial sandstones with permeability greater than 5 md have irreducible water saturation (Siw) less than 20%, typical of many gas reservoirs. Upper shoreface sandstones exhibit good reservoir properties with high porosity (10-21%), high permeability (3-250 md), and low S iw (<20%). Lower shoreface sandstones, which are finer grained, have lower porosity (4-12%), lower permeability (0.0007-4 md), thicker transition zones (6-180 m [20-600 ft]), and higher S iw. In the tidal-channel, tidal-flat, and estuarine facies, low porosity (average < 6%), low permeability (average < 0.02 md), and small pore throats result in large transition zones (30-200 m; 100-650 ft) and high water saturations. The most favorable reservoir petrophysical properties and the best estimated production from the Lower Silurian sandstones are associated with fluvial and upper shoreface facies of incised-valley fills, which we interpret to have formed predominantly in areas of structural recesses that evolved from promontories along a collisional margin during the Taconic orogeny. Although the total thickness of the sandstone may not be as great in these areas, reservoir quality is better than in adjacent structural salients, which is attributed to higher energy depositional processes and shallower maximum burial depth in the recesses than in the salients. Copyright ??2005. The American Association of Petroleum Geologists. All rights reserved.

  16. Transitional changes in microfossil assemblages in the Japan Sea from the Late Pliocene to Early Pleistocene related to global climatic and local tectonic events

    NASA Astrophysics Data System (ADS)

    Itaki, Takuya

    2016-12-01

    Many micropaleontological studies based on data from on-land sections, oil wells, and deep-sea drilling cores have provided important information about environmental changes in the Japan Sea that are related to the global climate and the local tectonics of the Japanese Islands. Here, major changes in the microfossil assemblages during the Late Pliocene to Early Pleistocene are reviewed. Late Pliocene (3.5-2.7 Ma) surface-water assemblages were characterized mainly by cold-temperate planktonic flora and fauna (nannofossils, diatoms, radiolarians, and planktonic foraminifera), suggesting that nutrient-rich North Pacific surface waters entered the Japan Sea via northern straits. The common occurrence of Pacific-type deep-water radiolarians during this period also suggests that deep water from the North Pacific entered the Japan Sea via the northern straits, indicating a sill depth >500 m. A weak warm-water influence is recognized along the Japanese coast, suggesting a small inflow of warm water via a southern strait. Nannofossil and sublittoral ostracod assemblages record an abrupt cooling event at 2.75 Ma that correlates with the onset of the Northern Hemisphere glaciation. Subsequently, cold intermediate- and deep-water assemblages of ostracods and radiolarians increased in abundance, suggesting active ventilation and the formation of the Japan Sea Proper Water, associated with a strengthened winter monsoon. Pacific-type deep-water radiolarians also disappeared around 2.75 Ma, which is attributed to the intermittent occurrence of deep anoxic environments and limited migration from the North Pacific, resulting from the near-closure or shallowing of the northern strait by a eustatic fall in sea level and tectonic uplift of northeastern Japan. A notable reduction in primary productivity from 2.3 to 1.3 Ma also suggests that the nutrient supply from the North Pacific was restricted by the near-closure of the northern strait. An increase in the abundance of subtropical

  17. Quantitative prediction of fractures using the finite element method: A case study of the lower Silurian Longmaxi Formation in northern Guizhou, South China

    NASA Astrophysics Data System (ADS)

    Liu, Jingshou; Ding, Wenlong; Yang, Haimeng; Jiu, Kai; Wang, Zhe; Li, Ang

    2018-04-01

    Natural fractures have long been considered important factors in the production of gas from shale reservoirs because they can connect pore spaces and enlarge transport channels, thereby influencing the migration, accumulation and preservation of shale gas. Industrial-level shale gas production has been initiated in the lower Silurian Longmaxi Formation in northern Guizhou, South China. However, it is important to quantitatively predict the distribution of natural fractures in the lower Silurian shale reservoirs to locate additional 'sweet spots' in northern Guizhou. In this study, data obtained from outcrops, cores, thin sections, field-emission scanning electron microscope (FE-SEM) images and X-ray diffraction (XRD) were used to determine the developmental characteristics and controlling factors of these fractures. Correlation analysis indicated that the mechanical parameters of the Longmaxi shale are mainly related to the total organic carbon (TOC), quartz, clay, calcite and dolomite contents. The spatial variations in the mechanical parameters of the Longmaxi shale were determined based on the spatial variations in the TOC and mineral contents. Then, a heterogeneous geomechanical model of the study area was established based on interpretations of the fault systems derived from seismic data and acoustic emission (AE) experiments performed on samples of the relevant rocks. The paleotectonic stress fields during the Yanshanian period were obtained using the finite element method (FEM). Finally, a fracture density calculation model was established to analyze the quantitative development of fractures, and the effects of faults and mechanical parameters on the development of fractures were determined. The results suggest that the main developmental period of tectonic fractures in the Longmaxi Formation was the Early Yanshanian period. During this time, the horizontal principal stress conditions were dominated by a SE-NW-trending (135-315°) compressional stress field

  18. The Silurian Hoedongri Formation in the Taebaeksan Basin of Korea Revisited: its Significance in the Tectonic Reconstruction of East Asia

    NASA Astrophysics Data System (ADS)

    Chae, S.; Hong, J.; Jung, S.; Ree, J.

    2011-12-01

    The Silurian Hoedongri Formation of the Taebaeksan Basin of South Korea has been used as a key unit to the correlation of tectonic provinces of East Asia since the South China craton (or Yangtz block) contains Silurian-Devonian sequences as well as Cambrian-Ordovician ones in the Paleozoic basins while the North China craton (or Sino-Korea block) is devoid of Silurian-Devonian sequences. In the Biryongdong area near the type locality of the Hoedongri Formation, it has been reported that the gray limestone of the Hoedongri Formation unconformably overlies brownish gray limestone of the Ordovician Haengmae Formation. However, our detailed examination on the Biryongdong section reveals that both of the brownish gray and gray limestones are mylonitic marbles with the boundary between the two units being a healed fault breccia zone (~ 12 m thick). The main difference of the two units is that repeated cycles of plastic deformation and fracturing occurred in the underlying brownish gray marble ('Haengmae') while the gray marble ('Hoedongri') deformed mainly by intracrystalline plasticity. The mylonitic foliation strikes NW with a low to moderate dip angle (20-60°) to NE. The ridge-in-groove type lineation on foliation surface trends NNW. The shape-preferred foliation of elongated calcite grains are oblique to the mylonitic foliation defined by layers with a grain-size variation, indicating a top-to-the-SSE shear sense. The mylonitic marble consists of elongated remnant grains (80-120 μm) with deformation twins and dynamically recrystallized matrix grains (10-40 μm). Grain boundaries and twin boundaries are lobate or wavy, indicating dynamic boundary migration. Some layers of the gray mylonitic marble are composed entirely of larger (80-120 μm) elongated calcite grains. In the brownish gray mylonitic marble unit, layers of brittle fracturing overprinting mylonitic foliation occur. In some of these layers, fragments (several cm - tens of cm) of the mylonitic marble are

  19. Precise U/Pb zircons dates of bentonites in Upper Ordovician and Lower Silurian reference sections in North America and Britain.

    NASA Astrophysics Data System (ADS)

    Suarez, S. E.; Brookfield, M. E.; Catlos, E. J.; Stockli, D. F.; Batchelor, R. A.

    2016-12-01

    The end of the Ordovician marks one of the greatest of the Earth's mass extinctions. One hypothesis explains this mass extinction as the result of a short-lived, major glaciation preceded by episodes of increased volcanism brought on by the Taconic orogeny. K-bentonites, weathered volcanic ash, provide evidence for increased volcanism. However, there is a lack of modern precise U-Pb dating of these ashes and some confusion in the biostratigraphy. The aim of this study is to obtain more precise U-Pb zircon ages from biostratigraphically constrained bentonites which will lead to better correlation of the Upper Ordovician and Lower Silurian relative time scales, as well as time the pulses of eruption. Zircon grains were extracted from the samples by heavy mineral separation and U-Pb dated using the Laser Ablation-Inductively Coupled Plasma-Mass Spectrometer at the University of Texas-Austin. We report here 3 precise U-Pb zircon ages from the Trenton Group, Ontario, Canada, and Dob's Linn, Scotland. The youngest age from the top of the Kirkfield Formation in Ontario is 448.0 +/- 18 Ma, which fits with existing late Ordovician stratigraphic ages. At Dob's Linn, Scotland, the site of the Ordovician/Silurian Global Boundary Stratigraphic Section and Point (GSSP), the youngest age for DL7, a bentonite 5 meters below the GSSP is 402.0 +/- 12.0 Ma, and for DL24L, a bentonite 8 meters above the GSSP is 358.2 +/- 7.9 Ma. These are Devonian ages in current timescales - the current age for the GSSP is 443.8 +/- 1.8 Ma, based on an U/Pb dates from a bentonite 1.6 meters above the GSSP at Dob's Linn. We are confident that our techniques rule out contamination and the most likely explanation is that the small zircons we analyzed either suffered Pb loss, or grew overgrowths during low grade hydrothermal metamorphism of the sediments during the intrusion of the Southern Upland Devonian granites during the Caledonian orogeny. These Devonian ages suggest that the 443.8 +/- 1.8 Ma age

  20. Integrated biostratigraphy of foraminifers, radiolarians and conodonts in shallow and deep water Middle Permian (Capitanian) deposits of the "Rader slide", Guadalupe Mountains, West Texas

    USGS Publications Warehouse

    Nestell, M.K.; Nestell, G.P.; Wardlaw, B.R.; Sweatt, M.J.

    2006-01-01

    A diverse assemblage of microfossils is present in a 6m thick sequence of three debris flow deposits interbedded with thin turbidite limestone beds and fine grained siliciclastics exposed above the megaconglomerate in a section (known as the "Rader Slide" in numerous guidebook stops) of the Rader Limestone Member of the Bell Canyon Formation of Capitanian age (Middle Permian) in the Guadalupe Mountains of West Texas. Each debris flow, derived from nearby Capitan Reef shelf-margin and slope deposits, contains a distinct microfossil assemblage. Small foraminifers and fusulinaceans, conodonts, radiolarians, sponge spicules, fish dermal plates and teeth, and other fragmental fossils are present in this sequence. Conodonts are relatively scarce in the first (or lowest) debris flow, except in its upper part, but they are common to abundant in the other two debris flows, and very abundant in several of the thin turbidite limestone beds. All of the conodonts present appear to be morphotypes of one population of the species Jinogondolella postserrata, except for one new conodont species, and the Jinogondolella postserrata Zone is clearly documented in this sequence. The debris flows contain the fusulinaceans Rauserella, rare Codonofusiella, Polydiexodina, Leella? and various species of the small foraminifers Globivalvulina, Hemigordius, Baisalina, Abadehella, Deckerella, Neoendothyranella, Vachardella, Geinitzina, and Polarisella. Some of the thin turbidite limestone beds contain a foraminiferal assemblage similar to that found in the debris flows, but with lower diversity. Many small foraminiferal species appear to be endemic, although a few are closely related to species known in Permian age strata in Italy, Greenland, the Russian Far East, northeastern part of Russia (Omolon massif), and the Zechstein of Germany and the Baltic area. Two thin limestone beds above the second debris flow contain primarily radiolarian species known from the Follicucullus japonicus Zone of

  1. A Silurian-early Devonian slab window in the southern Central Asian Orogenic Belt: Evidence from high-Mg diorites, adakites and granitoids in the western Central Beishan region, NW China

    NASA Astrophysics Data System (ADS)

    Zheng, Rongguo; Xiao, Wenjiao; Li, Jinyi; Wu, Tairan; Zhang, Wen

    2018-03-01

    hybridized by the mantle peridotite. On the basis of our data and combined with previous data, we conclude that a Silurian-early Devonian slab window model accounts for all geological records in the western segment of the Central Beishan. We further propose that magmatic events associated with a slab window played an important role in crustal growth of the Central Asian Orogenic Belt.

  2. Geomorphology and Tectonics at the Intersection of Silurian and Death Valleys, Southern California - 2005 Guidebook Pacific Cell Friends of the Pleistocene

    USGS Publications Warehouse

    Miller, David M.; Valin, Zenon C.

    2007-01-01

    This publication describes results from new regional and detailed surficial geologic mapping, combined with geomorphologic, geochronologic, and tectonic studies, in Silurian Valley and Death Valley, California. The studies address a long-standing problem, the tectonic and geomorphic evolution of the intersection between three regional tectonic provinces: the eastern California shear zone, the Basin and Range region of southern Nevada and adjacent California, and the eastern Mojave Desert region. The chapters represent work presented on the 2005 Friends of the Pleistocene field trip and meeting as well as the field trip road log.

  3. The 1997 core drilling through Ordovician and Silurian strata at Röstånga, S. Sweden: preliminary stratigraphic assessment and regional comparison

    USGS Publications Warehouse

    Bergstrom, Stig M.; Huff, W.D.; Koren', T.; Larsson, K.; Ahlberg, P.; Kolata, Dennis R.

    1999-01-01

    A core drilling at Ro??sta??nga, the first such drilling ever undertaken in this classical Lower Paleozoic outcrop area in W-central Scania, penetrated an approximately 96 m thick succession of Lower Silurian-upper Middle Ordovician marine rocks. The drilling was stopped at a depth of 132.59 m in an interval of crushed rocks, probably a prominent fault zone, that proved impossible to drill through. The core contains a stratigraphical sequence from the basal Upper Llandoverian (Telychian Stage) to the upper Middle Ordovician (Harjuan Stage). The following units are recognized in descending stratigraphic order (approximate thickness in parenthesis): Kallholn Formation (35 m), Lindega??rd Mudstone (27 m), Fja??cka Shale (13 m), Mossen Formation (0.75 m), Skagen Formation (2.5 m), and Sularp Shale (19 m+). Except for the Skagen Formation, the drilled sequence consists of shales and mudstones with occasional thin limestone interbeds and is similar to coeval successions elsewhere in Scania. There are 11 K-bentonite beds in the Kallholn Formation, 2(3?) in the Lindega??rd Mudstone, 1 in the Mossen Formation, 7 in the Skagen Formation, and 33 in the Sularp Shale. The core serves as an excellent Lower Silurian-upper Middle Ordovician reference standard not only for the Ro??sta??nga area but also for southernmost Sweden in general because the cored sequence is the stratigraphically most complete one known anywhere in this region.

  4. Chemostratigraphical Characterisation of the Lower Silurian Formigoso Formation: A Case Study from Aralla (Cantabrian Mountains, Province Leon, NW Spain)

    NASA Astrophysics Data System (ADS)

    Ferriday, T.; Montenari, M.

    2012-04-01

    The Silurian black shale deposits of the peri-Gondwanan region are one of the most important Palaeozoic source rocks for hydrocarbons world-wide. Despite intensive research, questions regarding the genesis and the palaeoenvironmental and palaeogeographic factors controlling the deposition of these shales are a matter of ongoing debate. The area investigated lies within the Cantabria-Asturias Arc of Northern Spain in the autonomous region of Castilla y León. The Cantabrian Arc formed as a result of the collision between Gondwana and Laurussia during the formation of the supercontinent Pangea and has been divided into five major tectonostratigraphic units. The 'Folds and Nappes' unit is of particular interest, especially the contained Somiedo-Corecillas thrust system, as here the best preserved Formigoso-sections and exposures can be found. This study focuses on the deposition of the L-Silurian black shales of the Formigoso Formation (Fm) within the Somiedo-Corecillas thrust system at Aralla, approximately 10km east-southeast of San Emiliano. A high resolution geochemical analysis of major and trace elements has been utilised on a 25cm scale throughout the section. A total of 241 samples were prepared and analysed using a NITON XL3t X-ray fluorescence instrument. The data obtained have provided new insights into the sedimentation patterns and the prevailing environmental conditions during deposition of the Formigoso Fm. Initial results show prominent regular cycles within the concentrations of red/ox-sensitive chemical elements, starting from the very onset of the anoxic black shales; these repetitions become less apparent towards to top of the formation. Eight cyclic pulses are clearly evident in the concentrations of the elements Uranium (U), Thorium (Th), Vanadium (V) and Chromium (Cr) and apparent in Rubidium (Rb), Zinc (Zn), Copper (Cu), Nickel (Ni), Titanium (Ti), Sulphur (S) and Barium (Ba). The cyclic behaviour of U4+ between 'Anoxia'-U enriched (18ppm)- and

  5. Collision of the Tacheng block with the Mayile-Barleik-Tangbale accretionary complex in Western Junggar, NW China: Implication for Early-Middle Paleozoic architecture of the western Altaids

    NASA Astrophysics Data System (ADS)

    Zhang, Ji'en; Xiao, Wenjiao; Luo, Jun; Chen, Yichao; Windley, Brian F.; Song, Dongfang; Han, Chunming; Safonova, Inna

    2018-06-01

    Western Junggar in NW China, located to the southeast of the Boshchekul-Chingiz (BC) Range and to the north of the Chu-Balkhash-Yili microcontinent (CBY), played a key role in the architectural development of the western Altaids. However, the mutual tectonic relationships have been poorly constrained. In this paper, we present detailed mapping, field structural geology, and geochemical data from the Barleik-Mayile-Tangbale Complex (BMTC) in Western Junggar. The Complex is divisible into Zones I, II and III, which are mainly composed of Cambrian-Silurian rocks. Zone I contains pillow lava, siliceous shale, chert, coral-bearing limestone, sandstone and purple mudstone. Zone II consists of basaltic lava, siliceous shale, chert, sandstone and mudstone. Zone III is characterized by basalt, chert, sandstone and mudstone. These rocks represent imbricated ocean plate stratigraphy, which have been either tectonically juxtaposed by thrusting or form a mélange with a block-in-matrix structure. All these relationships suggest that the BMTC is an Early-Middle Paleozoic accretionary complex in the eastern extension of the BC Range. These Early Paleozoic oceanic rocks were thrust onto Silurian sediments forming imbricate thrust stacks that are unconformably overlain by Devonian limestone, conglomerate and sandstone containing fossils of brachiopoda, crinoidea, bryozoa, and plant stems and leaves. The tectonic vergence of overturned folds in cherts, drag-related curved cleavages and σ-type structures on the main thrust surface suggests top-to-the-NW transport. Moreover, the positive εNd(t) values of volcanic rocks from the Tacan-1 drill-core, and the positive εHf(t) values and post-Cambrian ages of detrital zircons from Silurian and Devonian strata to the south of the Tacheng block indicate that its basement is a depleted and juvenile lithosphere. And there was a radial outward transition from coral-bearing shallow marine (shelf) to deep ocean (pelagic) environments, and from

  6. Palaeomagnetism and geochemistry of Early Palaeozoic rocks of the Barrandian (Teplé-Barrandian Unit, Bohemian Massif): palaeotectonic implications

    NASA Astrophysics Data System (ADS)

    Patočka, F.; Pruner, P.; Štorch, P.

    The Barrandian area (the Teplá-Barrandian unit, Bohemian Massif) provided palaeomagnetic results on Early Palaeozoic rocks and chemical data on siliciclastic sediments of both Middle Cambrian and Early Ordovician to Middle Devonian sedimentary sequences; an outcoming interpretation defined source areas of clastic material and palaeotectonic settings of the siliciclastic rock deposition. The siliciclastic rocks of the earliest Palaeozoic sedimentation cycle, deposited in the Cambrian Příbram-Jince Basin of the Barrandian, were derived from an early Cadomian volcanic island arc developed on Neoproterozoic oceanic lithosphere and accreted to a Cadomian active margin of northwestern Gondwana. Inversion of relief terminated the Cambrian sedimentation, and a successory Prague Basin subsided nearby since Tremadocian. Source area of the Ordovician and Early Silurian shallow-marine siliciclastic sediments corresponded to progressively dissected crust of continental arc/active continental margin type of Cadomian age. Since Late Ordovician onwards both synsedimentary within-plate basic volcanics and older sediments had been contributing in recognizable proportions to the siliciclastic rocks. The siliciclastic sedimentation was replaced by deposition of carbonate rocks throughout late Early Silurian to Early Devonian period of withdrawal of the Cadomian clastic material source. Above the carbonates an early Givetian flysch-like siliciclastic suite completed sedimentation in the Barrandian. In times between Middle Cambrian and Early/Middle Devonian boundary interval an extensional tectonic setting prevailed in the Teplá-Barrandian unit. The extensional regime was related to Early Palaeozoic large-scale fragmentation of the Cadomian belt of northwestern Gondwana and origin of Armorican microcontinent assemblage. The Teplá-Barrandian unit was also engaged in a peri-equatorially oriented drift of Armorican microcontinent assemblage throughout the Early Palaeozoic: respective

  7. A new crustacean from the Herefordshire (Silurian) Lagerstätte, UK, and its significance in malacostracan evolution

    PubMed Central

    Briggs, Derek E. G.; Siveter, Derek J.; Sutton, Mark D.; Legg, David

    2017-01-01

    Cascolus ravitis gen. et sp. nov. is a three-dimensionally preserved fossil crustacean with soft parts from the Herefordshire (Silurian) Lagerstätte, UK. It is characterized by a head with a head shield and five limb pairs, and a thorax (pereon) with nine appendage-bearing segments followed by an apodous abdomen (pleon). All the appendages except the first are biramous and have a gnathobase. The post-mandibular appendages are similar one to another, and bear petal-shaped epipods that probably functioned as a part of the respiratory–circulatory system. Cladistic analysis resolves the new taxon as a stem-group leptostracan (Malacostraca). This well-preserved arthropod provides novel insights into the evolution of appendage morphology, tagmosis and the possible respiratory–circulatory physiology of a basal malacostracan. PMID:28330926

  8. Linking the southern West Junggar terrane to the Yili Block: Insights from the oldest accretionary complexes in West Junggar, NW China

    NASA Astrophysics Data System (ADS)

    Ren, Rong; Han, Bao-Fu; Guan, Shu-Wei; Liu, Bo; Wang, Zeng-Zhen

    2018-06-01

    West Junggar is known to tectonically correlate with East Kazakhstan; however, the tectonic link of the southern West Junggar terrane to adjacent regions still remains uncertain. Here, we examined the oldest accretionary complexes, thus constraining its tectonic evolution and link during the Early-Middle Paleozoic. They have contrasting lithologic, geochemical, and geochronological features and thus, provenances and tectonic settings. The Laba Unit was derived from the Late Ordovician-Early Devonian continental arc system (peaking at 450-420 Ma) with Precambrian substrate, which formed as early as the Early Devonian and metamorphosed during the Permian; however, the Kekeshayi Unit was accumulated in an intra-oceanic arc setting, and includes the pre-Late Silurian and Late Silurian subunits with or without Precambrian sources. Integrated with the regional data, the southern West Junggar terrane revealed a tectonic link to the northern Yili Block during the Late Silurian to Early Devonian, as suggested by the comparable Precambrian zircon age spectra between the southern West Junggar terrane and the micro-continents in the southern Kazakhstan Orocline, the proximal accumulation of the Laba Unit in the continental arc atop the Yili Block, and the sudden appearance of Precambrian zircons in the Kekeshayi Unit during the Late Silurian. This link rejects the proposals of the southern West Junggar terrane as an extension of the northern Kazakhstan Orocline and the Middle Paleozoic amalgamation of West Junggar. A new linking model is thus proposed, in which the southern West Junggar terrane first evolved individually, and then collided with the Yili Block to constitute the Kazakhstan continent during the Late Silurian. The independent and contrasting intra-oceanic and continental arcs also support the Paleozoic archipelago-type evolution of the Central Asian Orogenic Belt.

  9. Cryptic Disc Structures Resembling Ediacaran Discoidal Fossils from the Lower Silurian Hellefjord Schist, Arctic Norway.

    PubMed

    Kirkland, Christopher L; MacGabhann, Breandán A; Kirkland, Brian L; Daly, J Stephen

    2016-01-01

    The Hellefjord Schist, a volcaniclastic psammite-pelite formation in the Caledonides of Arctic Norway contains discoidal impressions and apparent tube casts that share morphological and taphonomic similarities to Neoproterozoic stem-holdfast forms. U-Pb zircon geochronology on the host metasediment indicates it was deposited between 437 ± 2 and 439 ± 3 Ma, but also indicates that an inferred basal conglomerate to this formation must be part of an older stratigraphic element, as it is cross-cut by a 546 ± 4 Ma pegmatite. These results confirm that the Hellefjord Schist is separated from underlying older Proterozoic rocks by a thrust. It has previously been argued that the Cambrian Substrate Revolution destroyed the ecological niches that the Neoproterozoic frond-holdfasts organisms occupied. However, the discovery of these fossils in Silurian rocks demonstrates that the environment and substrate must have been similar enough to Neoproterozoic settings that frond-holdfast bodyplans were still ecologically viable some hundred million years later.

  10. Undiscovered oil and gas resources of Lower Silurian Qusaiba-Paleozoic total petroleum systems, Arabian Peninsula

    USGS Publications Warehouse

    Ahlbrandt, T.S.; Pollastro, R.M.; Schenk, C.J.

    2002-01-01

    The U.S. Geological Survey (USGS) recently completed an assessment of the undiscovered conventional oil and gas potential of 128 of the world’s petroleum provinces (U.S. Geological Survey World Energy Assessment Team, 2000). In each province, the USGS defined Total Petroleum Systems, and Assessment Units in each Total Petroleum System, and then quantitatively estimated the undiscovered conventional oil and gas resources. Of the eight global regions studied by the USGS, the Arabian Peninsula portion of the Middle East region was estimated to contain the greatest volumes of undiscovered oil and gas. The Lower Silurian Qusaiba Member of the Qalibah Formation is the source rock for some of the most important Total Petroleum Systems of the Middle East region. For example, the sources of the gas in the supergiant North field of Qatar and Iran and recent giant light oil discoveries in central Saudi Arabia were largely organic-rich, Qusaiba marine mudstones.

  11. Cryptic Disc Structures Resembling Ediacaran Discoidal Fossils from the Lower Silurian Hellefjord Schist, Arctic Norway

    PubMed Central

    MacGabhann, Breandán A.; Kirkland, Brian L.; Daly, J. Stephen

    2016-01-01

    The Hellefjord Schist, a volcaniclastic psammite-pelite formation in the Caledonides of Arctic Norway contains discoidal impressions and apparent tube casts that share morphological and taphonomic similarities to Neoproterozoic stem-holdfast forms. U-Pb zircon geochronology on the host metasediment indicates it was deposited between 437 ± 2 and 439 ± 3 Ma, but also indicates that an inferred basal conglomerate to this formation must be part of an older stratigraphic element, as it is cross-cut by a 546 ± 4 Ma pegmatite. These results confirm that the Hellefjord Schist is separated from underlying older Proterozoic rocks by a thrust. It has previously been argued that the Cambrian Substrate Revolution destroyed the ecological niches that the Neoproterozoic frond-holdfasts organisms occupied. However, the discovery of these fossils in Silurian rocks demonstrates that the environment and substrate must have been similar enough to Neoproterozoic settings that frond-holdfast bodyplans were still ecologically viable some hundred million years later. PMID:27783643

  12. Silurian sponges and some associated fossils from the Heceta Limestone, Prince of Wales Island, southeastern Alaska

    USGS Publications Warehouse

    Rigby, J.K.; Rohr, D.M.; Blodgett, R.B.; Britt, B.B.

    2008-01-01

    A small faunule of hypercalcified agelasiid demosponges has been recovered from outcrops of the Silurian Heceta Formation on Prince of Wales Island in southeastern Alaska. Included are abundant Girtyocoeliana epiporata (Rigby and Potter, 1986), of the Girtyocoeliidae Finks and Rigby, 2004; fragments of Alaskaspongiella laminosa n. gen. and sp., Polyplacospongia nodosa n. gen. and sp., and Monolaminospongia gigantia n. gen. and sp., of the Auriculospongiidae Termier and Termier, 1977, and Cladospongia alaskensis n. gen. and sp., Virgulaspongia uniforma n. gen. and sp., and Stipespongia laminata n. gen. and sp. of the Preperonidellidae Finks and Rigby, 2004. Also included are a few fossils of uncertain taxonomic placement, including Turbospongia biperforata n. gen. and sp., along with a small, chambered, tubular fragment and several porous tubular stems that may be additional poriferans. Some isolated octactine-based heteractinid spicules were also recovered from the etched residues. Copyright ?? 2008, The Paleontological Society.

  13. Metal-induced malformations in early Palaeozoic plankton are harbingers of mass extinction

    PubMed Central

    Vandenbroucke, Thijs R. A.; Emsbo, Poul; Munnecke, Axel; Nuns, Nicolas; Duponchel, Ludovic; Lepot, Kevin; Quijada, Melesio; Paris, Florentin; Servais, Thomas; Kiessling, Wolfgang

    2015-01-01

    Glacial episodes have been linked to Ordovician–Silurian extinction events, but cooling itself may not be solely responsible for these extinctions. Teratological (malformed) assemblages of fossil plankton that correlate precisely with the extinction events can help identify alternate drivers of extinction. Here we show that metal poisoning may have caused these aberrant morphologies during a late Silurian (Pridoli) event. Malformations coincide with a dramatic increase of metals (Fe, Mo, Pb, Mn and As) in the fossils and their host rocks. Metallic toxins are known to cause a teratological response in modern organisms, which is now routinely used as a proxy to assess oceanic metal contamination. Similarly, our study identifies metal-induced teratology as a deep-time, palaeobiological monitor of palaeo-ocean chemistry. The redox-sensitive character of enriched metals supports emerging ‘oceanic anoxic event' models. Our data suggest that spreading anoxia and redox cycling of harmful metals was a contributing kill mechanism during these devastating Ordovician–Silurian palaeobiological events. PMID:26305681

  14. Metal-induced malformations in early Palaeozoic plankton are harbingers of mass extinction

    NASA Astrophysics Data System (ADS)

    Vandenbroucke, Thijs R. A.; Emsbo, Poul; Munnecke, Axel; Nuns, Nicolas; Duponchel, Ludovic; Lepot, Kevin; Quijada, Melesio; Paris, Florentin; Servais, Thomas; Kiessling, Wolfgang

    2015-08-01

    Glacial episodes have been linked to Ordovician-Silurian extinction events, but cooling itself may not be solely responsible for these extinctions. Teratological (malformed) assemblages of fossil plankton that correlate precisely with the extinction events can help identify alternate drivers of extinction. Here we show that metal poisoning may have caused these aberrant morphologies during a late Silurian (Pridoli) event. Malformations coincide with a dramatic increase of metals (Fe, Mo, Pb, Mn and As) in the fossils and their host rocks. Metallic toxins are known to cause a teratological response in modern organisms, which is now routinely used as a proxy to assess oceanic metal contamination. Similarly, our study identifies metal-induced teratology as a deep-time, palaeobiological monitor of palaeo-ocean chemistry. The redox-sensitive character of enriched metals supports emerging `oceanic anoxic event' models. Our data suggest that spreading anoxia and redox cycling of harmful metals was a contributing kill mechanism during these devastating Ordovician-Silurian palaeobiological events.

  15. The geology of a part of Acadia and the nature of the Acadian orogeny across Central and Eastern Maine

    USGS Publications Warehouse

    Tucker, R.D.; Osberg, P.H.; Berry, H.N.

    2001-01-01

    The zone of Acadian collision between the Medial New England and Composite Avalon terranes is well preserved in Maine. A transect from northwest (Rome) to southeast (Camden) crosses the eastern part of Medial New England comprising the Central Maine basin, Liberty-Orrington thrust sheet, and Fredericton trough, and the western part of Composite Avalon, including the Graham Lake, Clarry Hill, and Clam Cove thrust sheets. U-Pb geochronology of events before, during, and after the Acadian orogeny helps elucidate the nature and distribution of tectonostrati& graphic belts in this zone and the timing of some Acadian events in the Northern Appalachians. The Central Maine basin consists of sedimentary and volcanic rocks of Middle Ordovician (???470 to ???460 Ma) age overlain with probable conformity by latest Ordovician(?) through earliest Devonian marine rift and flysch sedimentary rocks; these are intruded by weakly to undeformed plutonic rocks of Early and Middle Devonian age (???399??378 Ma). The Fredericton trough consists of Early Silurian gray pelite and sandstone to earliest Late Silurian calcareous turbidite, deformed and variably metamorphosed prior to the emplacement of Late Silurian (???422 Ma) and Early to Late Devonian (???418 to ???368 Ma) plutons. The Liberty-Orrington thrust sheet consists of Cambrian(?)-Ordovician (>???474 to ???469 Ma and younger) clastic sedimentary and volcanic rocks intruded by highly deformed Late Silurian (???424 to ???422 Ma) and Devonian (???418 to ???389 Ma) plutons, possibly metamorphosed in Late Silurian time (prior to ???417 Ma), and metamorphosed to amphibolite facies in Early to Middle Devonian time (???400 to ???381 Ma). The Graham Lake thrust sheet contains possible Precambrian rocks, Cambrian sedimentary rocks with a volcanic unit dated at ???503 Ma, and Ordovician rocks with possible Caradocian Old World fossils, metamor& phosed and deformed in Silurian time and intruded by mildly to undeformed Late Silurian (???421 Ma

  16. Facies patterns and conodont biogeography in Arctic Alaska and the Canadian Arctic Islands: Evidence against juxtaposition of these areas during early Paleozoic time

    USGS Publications Warehouse

    Dumoulin, Julie A.; Harris, A.G.; Bradley, D.C.; De Freitas, T. A.

    2000-01-01

    Differences in lithofacies and biofacies suggest that lower Paleozoic rocks now exposed in Arctic Alaska and the Canadian Arctic Islands did not form as part of a single depositional system. Lithologic contrasts are noted in shallow- and deep-water strata and are especially marked in Ordovician and Silurian rocks. A widespread intraplatform basin of Early and Middle Ordovician age in northern Alaska has no counterpart in the Canadian Arctic, and the regional drowning and backstepping of the Silurian shelf margin in Canada has no known parallel in northern Alaska. Lower Paleozoic basinal facies in northern Alaska are chiefly siliciclastic, whereas resedimented carbonates are volumetrically important in Canada. Micro- and macrofossil assemblages from northern Alaska contain elements typical of both Siberian and Laurentian biotic provinces; coeval Canadian Arctic assemblages contain Laurentian forms but lack Siberian species. Siberian affinities in northern Alaskan biotas persist from at least Middle Cambrian through Mississippian time and appear to decrease in intensity from present-day west to east. Our lithologic and biogeographic data are most compatible with the hypothesis that northern Alaska-Chukotka formed a discrete tectonic block situated between Siberia and Laurentia in early Paleozoic time. If Arctic Alaska was juxtaposed with the Canadian Arctic prior to opening of the Canada basin, biotic constraints suggest that such juxtaposition took place no earlier than late Paleozoic time.

  17. Equatorial origin for Lower Jurassic radiolarian chert in the Franciscan Complex, San Rafael Mountains, southern California

    USGS Publications Warehouse

    Hagstrum, J.T.; Murchey, B.L.; Bogar, R.S.

    1996-01-01

    Lower Jurassic radiolarian chert sampled at two localities in the San Rafael Mountains of southern California (???20 km north of Santa Barbara) contains four components of remanent magnetization. Components A, B???, and B are inferred to represent uplift, Miocene volcanism, and subduction/accretion overprint magnetizations, respectively. The fourth component (C), isolated between 580?? and 680??C, shows a magnetic polarity stratigraphy and is interpreted as a primary magnetization acquired by the chert during, or soon after, deposition. Both sequences are late Pliensbachian to middle Toarcian in age, and an average paleolatitude calculated from all tilt-corrected C components is 1?? ?? 3?? north or south. This result is consistent with deposition of the cherts beneath the equatorial zone of high biologic productivity and is similar to initial paleolatitudes determined for chert blocks in northern California and Mexico. This result supports our model in which deep-water Franciscan-type cherts were deposited on the Farallon plate as it moved eastward beneath the equatorial productivity high, were accreted to the continental margin at low paleolatitudes, and were subsequently distributed northward by strike-slip faulting associated with movements of the Kula, Farallon, and Pacific plates. Upper Cretaceous turbidites of the Cachuma Formation were sampled at Agua Caliente Canyon to determine a constraining paleolatitude for accretion of the Jurassic chert sequences. These apparently unaltered rocks, however, were found to be completely overprinted by the A component of magnetization. Similar in situ directions and demagnetization behaviors observed in samples of other Upper Cretaceous turbidite sequences in southern and Baja California imply that these rocks might also give unreliable results.

  18. The Lower Silurian Osmundsberg K-bentonite. Part I: Stratigraphic position, distribution, and palaeogeographic significance

    USGS Publications Warehouse

    Bergstrom, Stig M.; Huff, W.D.; Kolata, Dennis R.

    1998-01-01

    A large number of Lower Silurian (Llandovery) K-bentonite beds have been recorded from northwestern Europe, particularly in Baltoscandia and the British Isles, but previous attempts to trace single beds regionally have yielded inconclusive results. The present study suggests that based on its unusual thickness, stratigraphic position and trace element geochemistry, one Telychian ash bed, the Osmundsberg K-bentonite, can be recognized at many localities in Estonia, Sweden and Norway and probably also in Scotland and Northern Ireland. This bed, which is up to 115 cm thick, is in the lower-middle turriculatus Zone. The stratigraphic position, thickness variation and geographic distribution of the Osmundsberg K-bentonite are illustrated by means of 12 selected Llandovery successions in Sweden, Estonia, Norway, Denmark, Scotland and Northern Ireland. In Baltoscandia, the Osmundsberg K-bentonite shows a trend of general thickness increase in a western direction suggesting that its source area was located in the northern Iapetus region between Baltica and Laurentia. Because large-magnitude ash falls like the one that produced the Osmundsberg K-bentonite last at most a few weeks, such an ash bed may be used as a unique time-plane for a variety of regional geological and palaeontological studies.

  19. Off-platform Silurian sequences in the Ambler River quadrangle: A section in Geologic studies in Alaska by the U.S. Geological Survey during 1987

    USGS Publications Warehouse

    Dumoulin, Julie A.; Harris, Anita G.

    1988-01-01

    Lithofacies changes in coeval upper Paleozoic rocks have been used to unravel the tectonic history of northern Alaska (for example, Mayfield and others, 1983). Conodont biostratigraphy and detailed petrologic studies are now revealing facies differences in lower Paleozoic rocks that can also be used to constrain their tectono-sedimentary framework (Dumoulin and Harris, 1987). A basic element of basin analysis is the discrimination of shallow-water shelf and platform sequences from deeper water slope and basinal deposits. This report documents several new localities of deeper water, off-platform Silurian deposits in the Ambler River quadrangle and briefly outlines some of their paleogeographic implications.

  20. Nature, origin, and production characteristics of the Lower Silurian regional oil and gas accumulation, central Appalachian basin, United States

    USGS Publications Warehouse

    Ryder, R.; Zagorski, W.A.

    2003-01-01

    Low-permeability sandstones of the Lower Silurian regional oil and gas accumulation cover about 45,000 mi2 (117,000 km2) of the Appalachian basin and may contain as much as 30 tcf of recoverable gas resources. Major reservoirs consist of the "Clinton" sandstone and Medina Group sandstones. The stratigraphically equivalent Tuscarora Sandstone increases the area of the Lower Silurian regional accumulation (LSRA) by another 30,000 mi2 (78,000 km2). Approximately 8.7 tcf of gas and 400 million bbl of oil have been produced from the Clinton/Medina reservoirs since 1880. The eastern predominantly gas-bearing part of the LSRA is a basin-center gas accumulation, whereas the western part is a conventional oil and gas accumulation with hybrid features of a basin-center accumulation. The basin-center accumulations have pervasive gas saturation, water near irreducible saturation, and generally low fluid pressures. In contrast, the hybrid-conventional accumulations have less-pervasive oil and gas saturation, higher mobile-water saturation, and both normal and abnormally low fluid pressures. High mobile-water saturation in the hybrid-conventional reservoirs form the updip trap for the basin-center gas creating a broad transition zone, tens of miles wide, that has characteristics of both end-member accumulation types. Although the Tuscarora Sandstone part of the basin-center gas accumulation is pervasively saturated with gas, most of its constituent sandstone beds have low porosity and permeability. Commercial gas fields in the Tuscarora Sandstone are trapped in naturally fractured, faulted anticlines. The origin of the LSRA includes (1) generation of oil and gas from Ordovician black shales, (2) vertical migration through an overlying 1000-ft (305-m)-thick Ordovician shale; (3) abnormally high fluid pressure created by oil-to-gas transformation; (4) updip displacement of mobile pore water by overpressured gas; (5) entrapment of pervasive gas in the basin center; (6) postorogenic

  1. Early Paleozoic development of the Maine-Quebec boundary Mountains region

    USGS Publications Warehouse

    Gerbi, C.C.; Johnson, S.E.; Aleinikoff, J.N.; Bedard, J.H.; Dunning, G.R.; Fanning, C.M.

    2006-01-01

    Pre-Silurian bedrock units played key roles in the early Paleozoic history of the Maine-Quebec Appalachians. These units represent peri-Laurentian material whose collision with the craton deformed the Neoproteozoic passive margin and initiated the Appalachian mountain-building cycle. We present new field, petrological, geochronological, and geochemical data to support the following interpretations related to these units. (1) The Boil Mountain Complex and Jim Pond Formation do not represent part of a coherent ophiolite. (2) Gabbro and tonalite of the Boil Mountain Complex intruded the Chain Lakes massif at ca. 477 Ma. (3) The Skinner pluton, an arc-related granodiorite, intruded the Chain Lakes massif at ca. 472 Ma. (4) The Attean pluton, with a reconfirmed age of ca. 443 Ma, is unrelated to Early Ordovician orogenesis. (5) The most likely timing for the juxtaposition of the Jim Pond Formation and the Boil Mountain Complex was during regional Devonian deformation. These interpretations suggest that the Boundary Mountains were once part of a series of arcs extending at least from central New England through Newfoundland. ?? 2006 NRC Canada.

  2. Geology and ground water in Door County, Wisconsin, with emphasis on contamination potential in the Silurian dolomite

    USGS Publications Warehouse

    Sherrill, Marvin G.

    1977-01-01

    Door County, a recreational and fruit-growing area bordering Lake Michigan in northeastern Wisconsin, has had a long history of ground-water contamination from surface and near-surface sources. Contamination is most severe in late summer when fruit-canning operations and the influx of tourists create additional wastes. Silurian dolomite is the upper bedrock unit in the county and yields generally adequate supplies of very hard water with locally objectionable concentrations of iron and nitrate. Thin soil cover and well-fractured dolomitic bedrock give easy entry to ground-water contaminants throughout large parts of Door County. Many contaminants enter the dolomite by surface or near-surface seepage. There is little attenuation of contamination concentrations in the well-jointed dolomite, and contaminants may travel long distances underground in a relatively short time. The major source of ground-water contamination is bacteria, from individual waste-disposal systems, agricultural, industrial, and municipal wastes. Areas of the county underlain by contaminated zones include only a small percentage of the total ground-water system and are separated by large volumes of ground water free of contamination. (Woodard-USGS)

  3. Early Paleozoic magmatic events in the eastern Klamath Mountains, northern California

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Wallin, E.T.; Mattinson, J.M.; Potter, A.W.

    1988-02-01

    New U-Pb zircon ages for nine samples of tonalite and pegmatitic trondhjemite from the Trinity ophiolite and associated melange reveal a complex history of magmatic activity extending back into the earliest Cambrian, much older than previously believed. Earlier investigations, based on limited data, recognized lower Paleozoic crustal elements in the eastern Klamath terrane (EKT) ranging in age from Middle Ordovician to Early to Middle Devonian. The new work in the Yreka-Callahan area of the EKT confirms the Ordovician (440-475 Ma) and younger ages, but reveals for the first time the presence of tonalitic rocks that crystallized during a narrow timemore » interval at about 565-570 Ma. The authors also recognize younger, Late Silurian magmatism at 412 Ma. In the context of available mapping, these ages indicate that the Trinity ophiolite is broadly polygenetic because parts of it yield crystallization ages that span approximately 150 m.y. Superjacent dismembered units of probable early Paleozoic age may be tectonostratigraphically equivalent to the Sierra City melange in the northern Sierra Nevada.« less

  4. Composition of natural gas and crude oil produced from 10 wells in the Lower Silurian "Clinton" Sandstone, Trumbull County, Ohio: Chapter G.7 in Coal and petroleum resources in the Appalachian basin: distribution, geologic framework, and geochemical character

    USGS Publications Warehouse

    Burruss, Robert A.; Ryder, Robert T.; Ruppert, Leslie F.; Ryder, Robert T.

    2014-01-01

    Natural gases and associated crude oils in the “Clinton” sandstone, Medina Group sandstones, and equivalent Tuscarora Sandstone in the northern Appalachian basin are part of a regional, continuous-type or basin-centered accumulation. The origin of the hydrocarbon charge to regional continuoustype accumulations is poorly understood. We have analyzed the molecular and stable isotopic composition of gases and oils produced from 10 wells in the “Clinton” sandstone in Trumbull County, Ohio, in an initial attempt to identify the characteristics of the accumulated fluids. The analyses show that the fluids have remarkably uniform compositions that are similar to previously published analyses of oils (Cole and others, 1987) and gases (Laughrey and Baldasarre, 1998) in Early Silurian reservoirs elsewhere in Ohio; however, geochemical parameters in the oils and gases suggest that the fluids have experienced higher levels of thermal stress than the present-day burial conditions of the reservoir rocks. The crude oils have an unusual geochemical characteristic: they do not contain detectable levels of sterane and triterpane biomarkers. The origin of these absences is unknown.

  5. Late Wenlock (middle Silurian) bio-events: Caused by volatile boloid impact/s

    NASA Technical Reports Server (NTRS)

    Berry, W. B. N.; Wilde, P.

    1988-01-01

    Late Wenlockian (late mid-Silurian) life is characterized by three significant changes or bioevents: sudden development of massive carbonate reefs after a long interval of limited reef growth; sudden mass mortality among colonial zooplankton, graptolites; and origination of land plants with vascular tissue (Cooksonia). Both marine bioevents are short in duration and occur essentially simultaneously at the end of the Wenlock without any recorded major climatic change from the general global warm climate. These three disparate biologic events may be linked to sudden environmental change that could have resulted from sudden infusion of a massive amount of ammonia into the tropical ocean. Impact of a boloid or swarm of extraterrestrial bodies containing substantial quantities of a volatile (ammonia) component could provide such an infusion. Major carbonate precipitation (formation), as seen in the reefs as well as, to a more limited extent, in certain brachiopods, would be favored by increased pH resulting from addition of a massive quantity of ammonia into the upper ocean. Because of the buffer capacity of the ocean and dilution effects, the pH would have returned soon to equilibrium. Major proliferation of massive reefs ceased at the same time. Addition of ammonia as fertilizer to terrestrial environments in the tropics would have created optimum environmental conditions for development of land plants with vascular, nutrient-conductive tissue. Fertilization of terrestrial environments thus seemingly preceded development of vascular tissue by a short time interval. Although no direct evidence of impact of a volatile boloid may be found, the bioevent evidence is suggestive that such an impact in the oceans could have taken place. Indeed, in the case of an ammonia boloid, evidence, such as that of the Late Wenlockian bioevents may be the only available data for impact of such a boloid.

  6. Early Silurian (Llandoverian) Leask Point and Charlton Bay bioherms, Manitoulin Island, Ontario, Canada

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Mielczarek, W.; Copper, P.

    1986-08-01

    About 300 bioherms are known in the Llandoverian Manitoulin Formation of eastern Manitoulin Island. In the South Bay area, the large Leask Piont bioherm and Charlton Bay patch-reef complex lack a distinct skeletal growth framework. Bioherms consist of mudstone and wackestone, with isolated lenses of bafflestone, boundstone, floatstone. Fossils are scarce, but crinozoans and bryozoans comprise about 90% of the bioclasts. Other fauna include stromatoporoids, corals, brachiopods, gastropods, trilobites, and probable algae (algae are difficult to identify and may have played a significant role). Faunal ratios remained relatively constant during mound growth. Soft substrates with sedimentation rates of a fewmore » millimeters per year are suggested by bedding type and morphologic dominance of lamellar and tabular corals and stromatoporoids. An increased sedimentation rate, resulting from shoaling, is indicated by more overturned, broadly conical corals in the upper parts of the mounds. Shoaling may be responsible for cessation of mound growth. Lithoclasts are more common in the upper parts of the mounds. They formed when semiconsolidated muds were disturbed and redeposited during storms. Megarippled interreef surface areas, largely devoid of coral growth, indicate mud instability at Charlton Bay. Lack of suitable stable substrates may have hampered coral development. Dolomitization was postdepositional. The diagenetic sequence occurred in three stages: 1)selective pyritization and silicification, formation of an early muddy dolomite replacing the mud fraction of the dolostone, lithification and formation of rare calcite cement and neomorphic syntaxial rims; 2)clear, coarse dolomite replacing pore-filling calcite cement, syntaxial rims, and unaltered macrofossils, stylolitization, grain-to-grain dissolution; and 3)a late dolomite found mainly as fine rhombs in stylolites, solution seams, and intraskeletal pore space.« less

  7. Early Middle Ordovician evidence for land plants in Argentina (eastern Gondwana).

    PubMed

    Rubinstein, C V; Gerrienne, P; de la Puente, G S; Astini, R A; Steemans, P

    2010-10-01

    • The advent of embryophytes (land plants) is among the most important evolutionary breakthroughs in Earth history. It irreversibly changed climates and biogeochemical processes on a global scale; it allowed all eukaryotic terrestrial life to evolve and to invade nearly all continental environments. Before this work, the earliest unequivocal embryophyte traces were late Darriwilian (late Middle Ordovician; c. 463-461 million yr ago (Ma)) cryptospores from Saudi Arabia and from the Czech Republic (western Gondwana). • Here, we processed Dapingian (early Middle Ordovician, c. 473-471 Ma) palynological samples from Argentina (eastern Gondwana). • We discovered a diverse cryptospore assemblage, including naked and envelope-enclosed monads and tetrads, representing five genera. • Our discovery reinforces the earlier suggestion that embryophytes first evolved in Gondwana. It indicates that the terrestrialization of plants might have begun in the eastern part of Gondwana. The diversity of the Dapingian assemblage implies an earlier, Early Ordovician or even Cambrian, origin of embryophytes. Dapingian to Aeronian (Early Silurian) cryptospore assemblages are similar, suggesting that the rate of embryophyte evolution was extremely slow during the first c. 35-45 million yr of their diversification. The Argentinean cryptospores predate other cryptospore occurrences by c. 8-12 million yr, and are currently the earliest evidence of plants on land. © The Authors (2010). Journal compilation © New Phytologist Trust (2010).

  8. Quaternary radiolarian biostratigraphy in the subarctic northeastern Pacific (IODP Expedition 341 Site U1417) and synchroneity of bioevents across the North Pacific

    NASA Astrophysics Data System (ADS)

    Matsuzaki, Kenji M.; Suzuki, Noritoshi

    2018-01-01

    Expedition 341 of the Integrated Ocean Drilling Program (IODP) retrieved sediment cores spanning the time interval between the Pleistocene and Miocene from the southern Gulf of Alaska. Onboard Pleistocene radiolarian biostratigraphy is hereby refined by increasing the sampling resolution. The 178 core samples from the upper 190 m CCSF-B (Composite Core Depth Scale F-B) of Site U1417 contained faunal elements similar to the northwestern Pacific; for example, the three biozones in the northwestern Pacific (i.e., Eucyrtidium matuyamai, Stylatractus universus and Botryostrobus aquilonaris) were also recognized in the Gulf of Alaska, spanning 1.80-1.13 Ma, 1.13-0.45 Ma, and the last 0.45 Myr, respectively. Based on the age model that we used in this study and the shipboard paleomagnetic reversal events, the first occurrences (FOs) of Amphimelissa setosa and Schizodiscus japonicus in the northeastern Pacific were preliminarily determined to be 1.48 and 1.30 Ma, respectively. The last occurrence (LO) of Eucyrtidium matuyamai and the FO of Lychnocanoma sakaii, both well-established bioevents in the northwestern Pacific, were dated at 0.80 and 1.13 Ma, respectively. The LO of E. matuyamai is a synchronous event at 1.05 ± 0.1 Ma in the North Pacific, while the FOs of A. setosa and S. japonicus at 1.48 and 1.30 Ma, respectively, are significantly older than what has been found elsewhere.

  9. Paleozoic strata of the Dyckman Mountain area, northeastern Medfra quadrangle, Alaska: A section in Geologic studies in Alaska by the U.S. Geological Survey, 1998

    USGS Publications Warehouse

    Dumoulin, Julie A.; Bradley, Dwight C.; Harris, Anita G.

    2000-01-01

    Paleozoic rocks in the Dyckman Mountain area (northeastern Medfra quadrangle; Farewell terrane) include both shallowand deep-water lithologies deposited on and adjacent to a carbonate platform. Shallow-water strata, which were recognized by earlier workers but not previously studied in detail, consist of algal-laminated micrite and skeletal-peloidal wackestone, packstone, and lesser grainstone. These rocks are, at least in part, of Early and (or) Middle Devonian age but locally could be as old as Silurian; they accumulated in shallow subtidal to intertidal settings with periodically restricted water circulation. Deepwater facies, reported here for the first time, are thin, locally graded beds of micrite and calcisiltite and subordinate thick to massive beds of lime grainstone and conglomerate. Conodonts indicate an age of Silurian to Middle Devonian; the most tightly dated intervals are early Late Silurian (early to middle Ludlow). These strata formed as hemipelagic deposits, turbidites, and debris flows derived from shallow-water lithologies of the Nixon Fork subterrane. Rocks in the Dyckman Mountain area are part of a broader facies belt that is transitional between the Nixon Fork carbonate platform to the west and deeper water, basinal lithologies (Minchumina “terrane”) to the east. Transitional facies patterns are complex because of Paleozoic shifts in the position of the platform margin, Mesozoic shortening, and Late Cretaceous-Tertiary disruption by strike-slip faulting.

  10. Composition of natural gas and crude oil produced from 14 wells in the Lower Silurian "Clinton" Sandstone and Medina Group Sandstones, northeastern Ohio and northwestern Pennsylvania: Chapter G.6 in Coal and petroleum resources in the Appalachian basin: distribution, geologic framework, and geochemical character

    USGS Publications Warehouse

    Burruss, Robert A.; Ryder, Robert T.; Ruppert, Leslie F.; Ryder, Robert T.

    2014-01-01

    The geochemical processes that control the distribution of hydrocarbons in the regional accumulation of natural gas and crude oil in reservoirs of Early Silurian age in the central Appalachian basin are not well understood. Gas and oil samples from 14 wells along a down-dip transect through the accumulation in northeastern Ohio and northwestern Pennsylvania were analyzed for molecular and stable isotopic compositions to look for evidence of hydrocarbon source, thermal maturation, migration, and alteration parameters. The correlation of carbon and hydrogen stable isotopic composition of methane with thermal maturation indicates that the deepest gases are more thermally mature than independent estimates of thermal maturity of the reservoir horizon based on the conodont alteration index. This correlation indicates that the natural gas charge in the deepest parts of the regional accumulation sampled in this study originated in deeper parts of the Appalachian basin and migrated into place. Other processes, including mixing and late-stage alteration of hydrocarbons, may also impact the observed compositions of natural gases and crude oils.

  11. Middle Jurassic Radiolaria from a siliceous argillite block in a structural melange zone near Viqueque, Timor Leste: Paleogeographic implications

    NASA Astrophysics Data System (ADS)

    Haig, David W.; Bandini, Alexandre Nicolas

    2013-10-01

    Thin-bedded siliceous argillite forming a large block within a structural melange zone at Viqueque, Timor Leste, has yielded a Middle Jurassic (late Bathonian-early Callovian) radiolarian assemblage belonging to Unitary Association Zone 7. Fifty-five species are recognized and illustrated, forming the most diverse radiolarian fauna yet documented from the Jurassic of Timor. The fauna shows little similarity in species content to the few other assemblages previously listed from the Middle or Late Jurassic of Timor, and also has few species in common with faunas known elsewhere in the region from Rotti, Sumatra, South Kalimantan, and Sula. Based on lithofacies similarities and age, the siliceous argillite succession in the melange block at Viqueque is included in the Noni Group originally described as the lower part of the Palelo Series in West Timor. In terms of lithofacies, the Noni Group is distinct from other stratigraphic units known in Timor. It may be associated with volcanic rocks but age relationships are uncertain, although some of the radiolarian cherts in the Noni Group in West Timor have been reported to include tuffaceous sediment. The deep-water character of the siliceous hemipelagite-pelagite facies, the probable volcanic association, and an age close to that of continental breakup in the region suggest deposition in a newly rifted Indian Ocean. In Timor's tectonostratigraphic classification scheme, the Noni Group is here placed in the "Indian Ocean Megasequence".

  12. New Evidence for opening of the Black Sea; U-Pb analysis of detrital zircons and paleocurrent measurements of the Early Cretaceous turbidites

    NASA Astrophysics Data System (ADS)

    Akdoğan, Remziye; Okay, Aral I.; Sunal, Gürsel; Tari, Gabor; Kylander-Clark, Andrew R. C.

    2015-04-01

    Shelf to submarine turbidite fan deposits of the Early Cretaceous crop out over a large area along the southern coast of the Black Sea. Early Cretaceous turbidites have a thickness of over 2000 meters in the Central Pontides. The shelf of this turbidite basin, represented by shallow marine clastics and carbonates, crops out along the Black Sea coast between Zonguldak and Amasra. Paleocurrent directions in the Lower Cretaceous turbidites were measured in 90 localities using mostly flute and groove casts and to a lesser extend cross-beds. At the eastern part of the basin, the paleocurrents were from north to south. It is scattered in the west of the basin, however, the main paleocurrent directions were from the north. Detrital zircons were analyzed using LA-ICP-MS in eleven samples from the turbiditic sandstones and two samples from the shelf sandstones. Four samples are from the western part (two samples from shelf sediments), four samples from the central part and five samples from the eastern part of the Lower Cretaceous basin. 1085 of 1348 zircon analyses are concordant with rates of 95-105% and the zircon ages range between 141 ± 4 Ma (Berriasian) and 3469 ± 8 Ma (Paleoarchean). 22% of the detrital zircon ages are Paleoproterozoic, 20% Archean, 16% Carboniferous, 13% Neoproterozoic, 8% Permian, 6% Triassic, 5% Mesoproterozoic and 11% other ages. In the western part of the basin the Carboniferous zircons constitute the main population with a less dominant peak at Ordovician, Cambrian and Late Neoproterozoic. The zircons from the center of the basin show scattered distribution with dominant populations in the Triassic, Permian, Carboniferous, Silurian, Paleoproterozoic, Early Neoproterozoic-Late Mesoproterozoic, and minor peak at Late Neoarchean. On the other hand, zircons from the eastern most part of the basin, show dominant peaks in the Paleoproterozoic, Mesoarchean and Permian with minor peaks in Triassic, Carboniferous and Silurian. Anatolia and the Balkans

  13. Paleomagnetism of Jurassic radiolarian chert above the Coast Range ophiolite at Stanley Mountain, California, and implications for its paleogeographic origins

    USGS Publications Warehouse

    Hagstrum, J.T.; Murchey, B.L.

    1996-01-01

    Upper Jurassic red tuffaceous chert above the Coast Range ophiolite at Stanley Mountain, California (lat 35??N, long 240??E), contains three components of remanent magnetization. The first component (A; removed by ???100-???200 ??C) has a direction near the present-day field for southern California and is probably a recently acquired thermoviscous magnetization. A second component (B; removed between ???100 and ???600 ??C) is identical to that observed by previous workers in samples of underlying pillow basalt and overlying terrigenous sedimentary rocks. This component has constant normal polarity and direction throughout the entire section, although these rocks were deposited during a mixed polarity interval of the geomagnetic field. The B magnetization, therefore, is inferred to be a secondary magnetization acquired during accretion, uplift, or Miocene volcanism prior to regional clockwise rotation. The highest temperature component (C; removed between ???480 and 680 ??C) is of dual polarity and is tentatively interpreted as a primary magnetization, although it fails a reversal test possibly due to contamination by B. Separation of the B and C components is best shown by samples with negative-inclination C directions, and a corrected mean direction using only these samples indicates an initial paleolatitude of 32??N ?? 8??. Paleobiogeographic models relating radiolarian faunal distribution patterns to paleolatitude have apparently been incorrectly calibrated using the overprint B component. Few other paleomagnetic data have been incorporated in these models, and faunal distribution patterns are poorly known and mostly unqualified. The available data, therefore, do not support formation of the Coast Range ophiolite at Stanley Mountain near the paleoequator or accretion at ???10??N paleolatitude, as has been previously suggested based on paleomagnetic data, but indicate deposition near expected paleolatitudes for North America (35??N ?? 4??) during Late Jurassic

  14. A Late Silurian U-Pb zircon age for Linville metadiabase, Grandfather Mountain window, North Carolina

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Fetter, A.H.; Goldberg, S.A.

    1993-03-01

    Linville metadiabase intrudes both Precambrian basement within the Grandfather Mountain window and nonconformably overlying Grandfather Mountain Formation. It occurs as sill-like and dike-like bodies, and is apparently not recognized outside of the window. Major element data classify the composition of the rock as tholeiitic basalt. Zircon was separated from a metadiabase body intruding metasiltstone of the Grandfather Mountain Formation west of Cranberry Knob. Zircon are clear, euhedral, with a l/w ratio of 3:1. Two abraded fractions (75-150 and < 75 [mu]m, both NM-2[degree]) yield concordant ages, which the authors report as 415 [plus minus] 3 Ma (2[sigma]), a weighted meanmore » of the two [sup 207]Pb/[sup 206]Pb ages. This Late Silurian (Ludlow) age is interpreted as the time of crystallization. Previously, similarities in mode of occurrence and major element composition have been used to correlate Linville metadiabase with late Precambrian mafic rocks within and outside of the window, as field relations do not constrain its age. Linville metadiabase thus is an unlikely candidate for feeders to the Montezuma metabasalt, which occurs as a flow immediately above metarhyolite dated as 742 [plus minus] 2 Ma (2[sigma]). Linville metadiabase may be one component of a magmatic pulse spanning 10-20 m.y. associated with the Acadian orogeny. The new zircon age places constraints on the timing of metamorphism and deformation, as Linville metadiabase is foliated, containing metamorphic assemblages from the biotite zone of the greenschist facies. The age and fabric relations are permissive evidence of post-Taconic, Acadian or Alleghanian orogeny.« less

  15. Rock Magnetic Investigation of Soils and Sediments Overlying the Hydrocarbon-Bearing Silurian Pinnacle Reefs in the Michigan Basin

    NASA Astrophysics Data System (ADS)

    Smirnov, A. V.; Tresnak, J. P.; Anderson, K. L.

    2017-12-01

    Hydrocarbon reservoirs may be associated with significant magnetic anomalies arguably caused by diagenetic alteration of iron-bearing minerals in hydrocarbon seepage environments. However, complete understanding of the physical mechanisms and pathways of hydrocarbon-induced magnetic alteration requires a robust and representative observational database. In order to facilitate the fundamental understanding of the magnetic signature of hydrocarbons, we conducted an investigation of the relationship between the hydrocarbon migration and magnetic properties of sediments overlaying the oil-bearing formations of the Silurian northern pinnacle reef belt of the Michigan Basin. Several hundreds of near-surface soil and sediment samples were collected across several long transects across the trend of the Niagaran Reef System and represented areas both over and away from known hydrocarbon sources. The samples were investigated by a variety of microscopy and rock magnetic methods. Our data indicate that the relationship between the hydrocarbon reservoirs and low-field magnetic susceptibility over the Niagaran pinnacle reef belt in the Michigan Basin is not straightforward. Both very high and very low susceptibility values have been observed within the extent of the reef belt in the studied area. The observed magnetic susceptibility anomalies may reflect the hydrological gradients in the uppermost glaciofluvial aquifer. However, a good correlation with the Devonian hydrocarbon reservoirs outside of the reef belt indicates a potential of the surface magnetic susceptibility method for hydrocarbon detection at a smaller scale.

  16. Transgressive-regressive events and facies through the Upper Ordovician - Lower Silurian of Peary Land, North Greenland

    NASA Astrophysics Data System (ADS)

    Harper, D. A. T.; Rasmussen, C. M. Ø.; Munnecke, A.; Jin, J.; Stouge, S.; Rasmussen, J. A.

    2012-04-01

    Key sections through the Upper Ordovician (Katian-Hirnantian) and Lower Silurian (Rhuddanian) in Peary Land, North Greenland, demonstrate a succession of events related to the waxing and waning of contemporary glaciation on the far-off supercontinent of Gondwana. The Børglum River Formation was deposited in the palaeoequatorial marginal seas of Laurentia during the Katian. The upper Børglum River Formation contains a thick (130 m) unit of thick-bedded carbonate with pervasive Thalassinoides ichnofacies, which is also typical of the Selkirk Member (c. 40 m) of the Red River Formation in Canada and coeval rocks in Nevada. In addition to these ichnofossils, the shelly faunas are also similar, emphasized by the dominance of giant nautiloids, relatively abundant stromatoporoids and receptaculitids, and large gastropods. The Thalassinoides ichnofacies points to a remarkable palaeogeographic extension from an intracratonic basin to a pericratonic shelf over a distance of 11,000 km. This facies consistency implies a near homogeneous and stable depositional environment along the palaeoequator of Laurentia during the Late Ordovician. The succeeding Turesø Formation is more variable and less laterally extensive, characterized in its lower part by mud mounds, shelly coquinas and peritidal, cyclical deposits in a regressive sequence. These shallower-water facies are associated with a marked positive carbon isotope excursion that elsewhere is associated with the end Ordovician extinction. Following a probable hiatus, transgression is associated with the sequential development of Viridita and Virgiana dominated coquinas during the Rhudannian, taxa with widespread distributions across the rest of Laurentia and beyond.

  17. In search of a Silurian total petroleum system in the Appalachian basin of New York, Ohio, Pennsylvania, and West Virginia: Chapter G.11 in Coal and petroleum resources in the Appalachian basin: distribution, geologic framework, and geochemical character

    USGS Publications Warehouse

    Ryder, Robert T.; Swezey, Christopher S.; Trippi, Michael H.; Lentz, Erika E.; Avary, K. Lee; Harper, John A.; Kappel, William M.; Rea, Ronald G.; Ruppert, Leslie F.; Ryder, Robert T.

    2014-01-01

    Although the TOC analyses in this study indicate that good to very good source rocks are present in the Salina Group and Wills Creek Formation of southwestern Pennsylvania and northern West Virginia, data are insufficient to propose a new Silurian total petroleum system in the Appalachian basin. However, the analytical results of this investigation are encouraging enough to undertake more systematic studies of the source rock potential of the Salina Group, Wills Creek Formation, and perhaps the Tonoloway Formation (Limestone) and McKenzie Limestone (or Member).

  18. A new probable stem lineage crustacean with three-dimensionally preserved soft parts from the Herefordshire (Silurian) Lagerstätte, UK

    PubMed Central

    Siveter, Derek J; Sutton, Mark D; Briggs, Derek E.G; Siveter, David J

    2007-01-01

    A new arthropod with three-dimensionally preserved soft parts, Tanazios dokeron, is described from the Wenlock Series (Silurian) of Herefordshire, England, UK. Serial grinding, digital photographic and computer rendering techniques yielded ‘virtual fossils’ in the round for study. The body tagmata of T. dokeron comprise a head shield and a long trunk. The head shield bears six pairs of horn-like spines and the head bears five pairs of appendages. The antennule, antenna and mandible are all uniramous, and the mandible includes a gnathobasic coxa. Appendages four and five are biramous and similar to those of the trunk: each comprises a limb base with an endite, an enditic membrane, and two epipodites, plus an endopod and exopod. The hypostome bears a large cone-like projection centrally, and there may be a short labrum. The trunk has some 64 segments and at least 60 appendage pairs. A very small telson has the anus sited ventrally in its posterior part and also bears a caudal furca. Comparative morphological and cladistic analyses of T. dokeron indicate a crustacean affinity, with a probable position in the eucrustacean stem group. As such the epipodites in T. dokeron are the first recorded in a eucrustacean stem taxon. The new species is interpreted as a benthic or nektobenthic scavenger. PMID:17609185

  19. Placoderms (Armored Fish): Dominant Vertebrates of the Devonian Period

    NASA Astrophysics Data System (ADS)

    Young, Gavin C.

    2010-05-01

    Placoderms, the most diverse group of Devonian fishes, were globally distributed in all habitable freshwater and marine environments, like teleost fishes in the modern fauna. Their known evolutionary history (Early Silurian-Late Devonian) spanned at least 70 million years. Known diversity (335 genera) will increase when diverse assemblages from new areas are described. Placoderms first occur in the Early Silurian of China, but their diversity remained low until their main evolutionary radiation in the Early Devonian, after which they became the dominant vertebrates of Devonian seas. Most current placoderm data are derived from the second half of the group's evolutionary history, and recent claims that they form a paraphyletic group are based on highly derived Late Devonian forms; 16 shared derived characters are proposed here to support placoderm monophyly. Interrelationships of seven placoderm orders are unresolved because Silurian forms from China are still poorly known. The relationship of placoderms to the two major extant groups of jawed fishes—osteichthyans (bony fishes) and chondrichthyans (cartilaginous sharks, rays, and chimaeras)—remains uncertain, but the detailed preservation of placoderm internal braincase structures provides insights into the ancestral gnathostome (jawed vertebrate) condition. Placoderms provide the most complex morphological and biogeographic data set for the Middle Paleozoic; marked discrepancies in stratigraphic occurrence between different continental regions indicate strongly endemic faunas that were probably constrained by marine barriers until changes in paleogeography permitted range enlargement into new areas. Placoderm distributions in time and space indicate major faunal interchange between Gondwana and Laurussia near the Frasnian-Famennian boundary; closure of the Devonian equatorial ocean is a possible explanation.

  20. The Berriasian-Valanginian boundary interval based on calpionellids from the Taraises Formation, Cuencamé de Ceniceros, Durango, NW Mexico: Biostratigraphic, paleoecologic and paleobiogeographic significance

    NASA Astrophysics Data System (ADS)

    Omaña, Lourdes; González-Arreola, Celestina; Núñez-Useche, Fernando

    2017-12-01

    A section from the lower part of the Taraises Formation located in the central-east part of Durango State, northern Mexico was studied. The succession consists of a grey and reddish limestone interstratified with marl levels. The calcareous strata provide a microfossil assemblage that consists of calpionellids, planktonic and benthonic foraminifera, and radiolarians. Based on the first appearance of Calpionellites darderi the Berriasian-Valanginian boundary was defined for the first time from the Taraises Formation. Also, the zones and subzones of this interval were described, the Calpionellopsis Zone, Oblonga Subzone and Praecalpionellites murgeanui Subzone for the late Berriasian and the Calpionellites Zone, Darderi and Major Subzones for the early Valanginian. The paleoenvironmental changes in the studied section are documented from the microfaunal association and mineralogical composition. The abundant occurrence of radiolarians in the early Valanginian might suggest an increase in nutrient input. In addition, the presence of tiny barite crystals, ankerite, siderite and dolomite rhombs confirms high fertility, implying oxygen-depleted conditions that could be considered a prelude of the mid-Valanginian Weissert Event. The predominant wackestone texture along with the occurrence of calpionellids and planktonic foraminifera indicate a pelagic basin environment. The microfaunal association is characteristic of the Tethys Realm.

  1. Discriminating signal from noise in the fossil record of early vertebrates reveals cryptic evolutionary history

    PubMed Central

    Sansom, Robert S.; Randle, Emma; Donoghue, Philip C. J.

    2015-01-01

    The fossil record of early vertebrates has been influential in elucidating the evolutionary assembly of the gnathostome bodyplan. Understanding of the timing and tempo of vertebrate innovations remains, however, mired in a literal reading of the fossil record. Early jawless vertebrates (ostracoderms) exhibit restriction to shallow-water environments. The distribution of their stratigraphic occurrences therefore reflects not only flux in diversity, but also secular variation in facies representation of the rock record. Using stratigraphic, phylogenetic and palaeoenvironmental data, we assessed the veracity of the fossil records of the jawless relatives of jawed vertebrates (Osteostraci, Galeaspida, Thelodonti, Heterostraci). Non-random models of fossil recovery potential using Palaeozoic sea-level changes were used to calculate confidence intervals of clade origins. These intervals extend the timescale for possible origins into the Upper Ordovician; these estimates ameliorate the long ghost lineages inferred for Osteostraci, Galeaspida and Heterostraci, given their known stratigraphic occurrences and stem–gnathostome phylogeny. Diversity changes through the Silurian and Devonian were found to lie within the expected limits predicted from estimates of fossil record quality indicating that it is geological, rather than biological factors, that are responsible for shifts in diversity. Environmental restriction also appears to belie ostracoderm extinction and demise rather than competition with jawed vertebrates. PMID:25520359

  2. Geology of the Cupsuptic quadrangle, Maine

    USGS Publications Warehouse

    Harwood, David S.

    1966-01-01

    Ordovician in age. The quartz monzonite is considered to be Late Devonian. Five tectonic events are inferred from the structural features in the area. The earliest was a period of folding producing tightly-appressed, northeast-trending folds in the rocks of pre-Silurian age. In the second stage the folded pre-Silurian rocks were uplifted, eroded, and truncated to produce a major unconformity between the Middle Ordovician and Lower Silurian rocks. These events constitute the Taconic orogeny. The third tectonic event was a period of folding, probably of Middle Devonian age, that warped the unconformity and overlying rocks into open, gently-plunging, east-trending folds. This period of folding undoubtedly changed the attitude of the early folds in the pre-Silurian units but it did not produce any recognizable, cross-cutting planar features in the older rocks. The fourth tectonic event was a period of igneous intrusion that locally deformed the northeast-trending folds in the pre-Silurian rocks into a macroscopic drag fold plunging at 80 degrees in a direction S.10?w. A north-trending, subvertical slip cleavage was produced locally during this period of Late Devonian (?) deformation. A period of faulting, possibly of Triassic age, dislocated some of the earlier features. The rocks are in the chlorite zone of regional metamorphism, but have been contact metamorphosed to sillimanite-bearing hornfels adjacent to the quartz monzonite stocks. The chemical changes in chlorite, biotite, garnet, cordierite, and muscovite in the chlorite, biotite, andalusite, and sillimanite zones have been-studied by optical and x-ray methods and by partial chemical analyses. The progressive changes in mineral assemblages have been graphically portrayed on quaternary diagrams and ternary projections.

  3. Characteristics of discrete and basin-centered parts of the Lower Silurian regional oil and gas accumulation, Appalachian basin; preliminary results from a data set of 25 oil and gas fields

    USGS Publications Warehouse

    Ryder, Robert T.

    1998-01-01

    Oil and gas trapped in Lower Silurian 'Clinton' sands and Medina Group sandstone constitute a regional hydrocarbon accumulation that extends 425 mi in length from Ontario, Canada to northeastern Kentucky. The 125-mi width of the accumulation extends from central Ohio eastward to western Pennsylvania and west-central New York. Lenticular and intertonguing reservoirs, a gradual eastward decrease in reservoir porosity and permeability, and poorly segregated gas, oil, and water in the reservoirs make it very difficult to recognize clear-cut geologic- and production-based subdivisions in the accumulation that are relevant to resource assessment. However, subtle variations are recognizable that permit the regional accumulation to be subdivided into three tentative parts: a western gas-bearing part having more or less discrete fields; an eastern gas-bearing part having many characteristics of a basin-centered accumulation; and a central oil- and gas-bearing part with 'hybrid' fields that share characteristics of both discrete and basin-centered accumulation. A data set of 25 oil and gas fields is used in the report to compare selected attributes of the three parts of the regional accumulation. A fourth part of the regional accumulation, not discussed here, is an eastern extension of basin-centered accumulation having local commercial gas in the Tuscarora Sandstone, a proximal facies of the Lower Silurian depositional system. A basin-centered gas accumulation is a regionally extensive and commonly very thick zone of gas saturation that occurs in low-permeability rocks in the central, deeper part of a sedimentary basin. Another commonly used term for this type of accumulation is deep-basin gas accumulation. Basin-centered accumulation is a variety of continuous-type accumulation. The 'Clinton' sands and Medina Group sandstone part of the basin-centered gas accumulation is characterized by: a) reservoir porosity ranging from about 5 to 10 percent; b) reservoir permeability

  4. The diversification of Paleozoic fire systems and fluctuations in atmospheric oxygen concentration

    PubMed Central

    Scott, Andrew C.; Glasspool, Ian J.

    2006-01-01

    By comparing Silurian through end Permian [≈250 million years (Myr)] charcoal abundance with contemporaneous macroecological changes in vegetation and climate we aim to demonstrate that long-term variations in fire occurrence and fire system diversification are related to fluctuations in Late Paleozoic atmospheric oxygen concentration. Charcoal, a proxy for fire, occurs in the fossil record from the Late Silurian (≈420 Myr) to the present. Its presence at any interval in the fossil record is already taken to constrain atmospheric oxygen within the range of 13% to 35% (the “fire window”). Herein, we observe that, as predicted, atmospheric oxygen levels rise from ≈13% in the Late Devonian to ≈30% in the Late Permian so, too, fires progressively occur in an increasing diversity of ecosystems. Sequentially, data of note include: the occurrence of charcoal in the Late Silurian/Early Devonian, indicating the burning of a diminutive, dominantly rhyniophytoid vegetation; an apparent paucity of charcoal in the Middle to Late Devonian that coincides with a predicted atmospheric oxygen low; and the subsequent diversification of fire systems throughout the remainder of the Late Paleozoic. First, fires become widespread during the Early Mississippian, they then become commonplace in mire systems in the Middle Mississippian; in the Pennsylvanian they are first recorded in upland settings and finally, based on coal petrology, become extremely important in many Permian mire settings. These trends conform well to changes in atmospheric oxygen concentration, as predicted by modeling, and indicate oxygen levels are a significant control on long-term fire occurrence. PMID:16832054

  5. Return to Black Mountain: Palaeomagnetic Reassessment of the Chatsworth and Ninmaroo Formations, Western Queensland

    NASA Astrophysics Data System (ADS)

    Anderson, K.; Lackie, M.; Clark, D.; Schmidt, P.

    2003-04-01

    Palaeomagnetic results from Cambrian-Ordovician carbonate sequences sampled at Black Mountain, Mt Datson, and near Chatsworth Station are presented. A palaeomagnetic reassessment of these carbonates was designed in an effort to constrain regional magnetisation. Remanent magnetisations within these carbonates were found to be variably developed with most specimens displaying two of the five isolated components. PF, for which goethite is the identified remanence carrier, is thought to reflect a viscous remanent magnetisation of Recent origin. Component TR, held by haematite, has a palaeomagnetic pole consistent with other Tertiary Australian palaeopoles and most probably was acquired as a consequence of prolonged weathering during this period. The A component has a palaeomagnetic pole at 54.7°S, 262.3°E (dp=2.3°, dm=4.5°) after unfolding. This direction, constrained by positive fold and reversal test statistics, falls near the Early Devonian segment of the Australian APWP, perhaps reflecting a remagnetisation event associated with the intracratonic Alice Springs Orogeny. A Late Ordovician or Early Silurian remanence, component B, is also described. At 100% unfolding, the associated palaeopole lies at 8.0°S, 216.8°E (dp=2.6°, dm=5.1°). A third Palaeozoic, and presumed primary or early diagenetic, component, C, also passes applied fold and reversal tests and has a palaeomagnetic pole at 48.6°N, 186.0°E (dp=2.1°S, dm=4.0°). This palaeopole is consistent with Cambrian poles from other parts of cratonic Australia. Components A, B, and C are comparable to palaeomagnetic results reported in the earlier investigation of this region (Ripperdan and Kirschvink, 1992). A comparison of results between this and an earlier study are presented. Discrepancies in interpretation between the two palaeomagnetic surveys stem from choices in polarity for pre-Silurian palaeomagnetic poles as invoking alternate polarities for pre-Silurian palaeopoles makes the OVP1 direction of

  6. Early Depositional History of the Eocene Izu-Bonin Mariana Arc, Western Pacific Ocean

    NASA Astrophysics Data System (ADS)

    Waldman, R.; Marsaglia, K. M.; Tepley, F. J., III

    2015-12-01

    volcanism at the site. Subunit IVC consists of 46 meters of fine-grained turbidites composed of tuffaceous siltstone, along with radiolarian mudstone and vitric tuff layers. Ongoing studies of the volcanic components will provide additional insight into the source(s) of volcanics throughout the arc's early development.

  7. Possible continuous-type (unconventional) gas accumulation in the Lower Silurian "Clinton" sands, Medina Group and Tuscarora Sandstone in the Appalachian Basin; a progress report of the 1995 project activities

    USGS Publications Warehouse

    Ryder, Robert T.; Aggen, Kerry L.; Hettinger, Robert D.; Law, Ben E.; Miller, John J.; Nuccio, Vito F.; Perry, William J.; Prensky, Stephen E.; Filipo, John J.; Wandrey, Craig J.

    1996-01-01

    INTRODUCTION: In the U.S. Geological Survey's (USGS) 1995 National Assessment of United States oil and gas resources (Gautier and others, 1995), the Appalachian basin was estimated to have, at a mean value, about 61 trillion cubic feet (TCF) of recoverable gas in sandstone and shale reservoirs of Paleozoic age. Approximately one-half of this gas resource is estimated to reside in a regionally extensive, continuous-type gas accumulation whose reservoirs consist of low-permeability sandstone of the Lower Silurian 'Clinton' sands and Medina Group (Gautier and others, 1995; Ryder, 1995). Recognizing the importance of this large regional gas accumulation for future energy considerations, the USGS initiated in January 1995 a multi-year study to evaluate the nature, distribution, and origin of natural gas in the 'Clinton' sands, Medina Group sandstones, and equivalent Tuscarora Sandstone. The project is part of a larger natural gas project, Continuous Gas Accumulations in Sandstones and Carbonates, coordinated in FY1995 by Ben E. Law and Jennie L. Ridgley, USGS, Denver. Approximately 2.6 man years were devoted to the Clinton/Medina project in FY1995. A continuous-type gas accumulation, referred to in the project, is a new term introduced by Schmoker (1995a) to identify those natural gas accumulations whose reservoirs are charged throughout with gas over a large area and whose entrapment does not involve a downdip gas-water contact. Gas in these accumulations is located downdip of the water column and, thus, is the reverse of conventional-type hydrocarbon accumulations. Commonly used industry terms that are more or less synonymous with continuous-type gas accumulations include basin- centered gas accumulation (Rose and others, 1984; Law and Spencer, 1993), tight (low-permeability) gas reservoir (Spencer, 1989; Law and others, 1989; Perry, 1994), and deep basin gas (Masters, 1979, 1984). The realization that undiscovered gas in Lower Silurian sandstone reservoirs of the

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

    NASA Astrophysics Data System (ADS)

    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.

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

    PubMed Central

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

    2015-01-01

    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. PMID:26538179

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

    PubMed

    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.

  11. Paleobiogeography, high-resolution stratigraphy, and the future of Paleozoic biostratigraphy: Fine-scale diachroneity of the Wenlock (Silurian) conodont Kockelella walliseri

    USGS Publications Warehouse

    Cramer, Bradley D.; Kleffner, Mark A.; Brett, Carlton E.; McLaughlin, P.I.; Jeppsson, Lennart; Munnecke, Axel; Samtleben, Christian

    2010-01-01

    The Wenlock Epoch of the Silurian Period has become one of the chronostratigraphically best-constrained intervals of the Paleozoic. The integration of multiple chronostratigraphic tools, such as conodont and graptolite biostratigraphy, sequence stratigraphy, and ??13Ccarb chemostratigraphy, has greatly improved global chronostratigraphic correlation and portions of the Wenlock can now be correlated with precision better than ??100kyr. Additionally, such detailed and integrated chronostratigraphy provides an opportunity to evaluate the fidelity of individual chronostratigraphic tools. Here, we use conodont biostratigraphy, sequence stratigraphy and carbon isotope (??13Ccarb) chemostratigraphy to demonstrate that the conodont Kockelella walliseri, an important guide fossil for middle and upper Sheinwoodian strata (lower stage of the Wenlock Series), first appears at least one full stratigraphic sequence lower in Laurentia than in Baltica. Rather than serving as a demonstration of the unreliability of conodont biostratigraphy, this example serves to demonstrate the promise of high-resolution Paleozoic stratigraphy. The temporal difference between the two first occurrences was likely less than 1million years, and although it is conceptually understood that speciation and colonization must have been non-instantaneous events, Paleozoic paleobiogeographic variability on such short timescales (tens to hundreds of kyr) traditionally has been ignored or considered to be of little practical importance. The expansion of high-resolution Paleozoic stratigraphy in the future will require robust biostratigraphic zonations that embrace the integration of multiple chronostratigraphic tools as well as the paleobiogeographic variability in ranges that they will inevitably demonstrate. In addition, a better understanding of the paleobiogeographic migration histories of marine organisms will provide a unique tool for future Paleozoic paleoceanography and paleobiology research. ?? 2010

  12. Tectono-stratigraphy and low-grade metamorphism of Late Permian and Early Jurassic accretionary complexes within the Kurosegawa belt, Southwest Japan: Implications for mechanisms of crustal displacement within active continental margin

    NASA Astrophysics Data System (ADS)

    Hara, Hidetoshi; Kurihara, Toshiyuki; Mori, Hiroshi

    2013-04-01

    We characterize the tectono-stratigraphic architecture and low-grade metamorphism of the accretionary complex preserved in the Kurosegawa belt of the Kitagawa district in eastern Shikoku, Southwest Japan, in order to understand its internal structure, tectono-metamorphic evolution, and assessments of displacement of continental fragments within the complex. We report the first ever documented occurrence of an Early Jurassic radiolarian assemblage within the accretionary complex of the Kurosegawa belt that has been previously classified as the Late Permian accretionary complex, thus providing a revised age interpretation for these rocks. The accretionary complex is subdivided into four distinct tectono-stratigraphic units: Late Permian mélange and phyllite units, and Early Jurassic mélange and sandstone units. The stratigraphy of these four units is structurally repeated due to an E-W striking, steeply dipping regional fault. We characterized low-grade metamorphism of the accretionary complex via illite crystallinity and Raman spectroscopy of carbonaceous material. The estimated pattern of low-grade metamorphism showed pronounced variability within the complex and revealed no discernible spatial trends. The primary thermal structure in these rocks was overprinted by later tectonic events. Based on geological and thermal structure, we conclude that continental fragments within the Kurosegawa belt were structurally translated into both the Late Permian and Early Jurassic accretionary complexes, which comprise a highly deformed zone affected by strike-slip tectonics during the Early Cretaceous. Different models have been proposed to explain the initial structural evolution of the Kurosegawa belt (i.e., micro-continent collision and klippe tectonic models). Even if we presuppose either model, the available geological evidence requires a new interpretation, whereby primary geological structures are overprinted and reconfigured by later tectonic events.

  13. Petrology and diagenetic history of the upper shale member of the Late Devonian-Early Mississippian Bakken Formation, Williston Basin, North Dakota

    USGS Publications Warehouse

    Neil S. Fishman,; Sven O. Egenhoff,; Boehlke, Adam; Lowers, Heather A.

    2015-01-01

    The organic-rich upper shale member of the upper Devonian–lower Mississippian Bakken Formation (Williston Basin, North Dakota, USA) has undergone significant diagenetic alteration, irrespective of catagenesis related to hydrocarbon generation. Alteration includes precipitation of numerous cements, replacement of both detrital and authigenic minerals, multiple episodes of fracturing, and compaction. Quartz authigenesis occurred throughout much of the member, and is represented by multiple generations of microcrystalline quartz. Chalcedonic quartz fills radiolarian microfossils and is present in the matrix. Sulfide minerals include pyrite and sphalerite. Carbonate diagenesis is volumetrically minor and includes thin dolomite overgrowths and calcite cement. At least two generations of fractures are observed. Based on the authigenic minerals and their relative timing of formation, the evolution of pore waters can be postulated. Dolomite and calcite resulted from early postdepositional aerobic oxidation of some of the abundant organic material in the formation. Following aerobic oxidation, conditions became anoxic and sulfide minerals precipitated. Transformation of the originally opaline tests of radiolaria resulted in precipitation of quartz, and quartz authigenesis is most common in more distal parts of the depositional basin where radiolaria were abundant. Because quartz authigenesis is related to the distribution of radiolaria, there is a link between diagenesis and depositional environment. Furthermore, much of the diagenesis in the upper shale member preceded hydrocarbon generation, so early postdepositional processes were responsible for occlusion of significant original porosity in the member. Thus, diagenetic mineral precipitation was at least partly responsible for the limited ability of these mudstones to provide porosity for storage of hydrocarbons.

  14. The geology of Burnsville Cove, Bath and Highland Counties, Virginia

    USGS Publications Warehouse

    Swezey, Christopher; Haynes, John T.; Lambert, Richard A.; White, William B.; Lucas, Philip C.; Garrity, Christopher P.

    2015-01-01

    Burnsville Cove is a karst region in Bath and Highland Counties of Virginia. A new geologic map of the area reveals various units of limestone, sandstone, and siliciclastic mudstone (shale) of Silurian through Devonian age, as well as structural features such as northeast-trending anticlines and synclines, minor thrust faults, and prominent joints. Quaternary features include erosional (strath) terraces and accumulations of mud, sand, and gravel. The caves of Burnsville Cove are located within predominantly carbonate strata above the Silurian Williamsport Sandstone and below the Devonian Oriskany Sandstone. Most of the caves are located within the Silurian Tonoloway Limestone, rather than the Silurian-Devonian Keyser Limestone as reported previously.

  15. Ultrastructural morphology of the reproductive swarmers of Sphaerozoum punctatum (Huxley) from the East China Sea.

    PubMed

    Yuasa, Tomoko; Takahashi, Osamu

    2014-04-01

    Reproductive swarmers of the polycystine radiolarian Sphaerozoum punctatum (Huxley) collected from the East China Sea were examined using light, scanning and transmission electron microscopy. The swarmer cells were about 8-10 μm in length with a pear-like shape and a conical end with two flagella. A nucleus, mitochondria, Golgi body, lipid droplets and, characteristically, a single, large, vacuole-bound SrSO₄ crystal were present in the cytoplasm. Centering on the crystal inclusion, swarmers swam in a rapid rotational movement both clockwise and anticlockwise. Small subunit (SSU) rDNA sequences obtained for the reproductive swarmer cells from S. punctatum show a monophyletic group together with colonial spumellarians and grouped with S. punctatum from Bermuda in the clade. The morphological features and molecular phylogeny of the reproductive swarmers of S. punctatum show evidence of ancestral traits of radiolarians; acantharians and polycystines have a common ancestry. In addition, SrSO₄ inclusion of the swarmer cell may be a form of ballast deposited by the swarmer to allow proper positioning in the water column. We hypothesize that radiolarian-affiliated sequences from SSU rDNA clone libraries of marine picoeukaryotes may be derived from the picoplanktonic cells of radiolarians; i.e., small flagellated life stages such as reproductive swarmers or gametes. Copyright © 2013 Elsevier GmbH. All rights reserved.

  16. Environmental Conditions in a Carpathian Deep Sea Basin During the Period Preceding Oceanic Anoxic Event 2 - A Case Study from the Skole Nappe

    NASA Astrophysics Data System (ADS)

    Bąk, Krzysztof; Bąk, Marta; Górny, Zbigniew; Wolska, Anna

    2015-01-01

    Hemipelagic green clayey shales and thin muddy turbidites accumulated in a deep sea environment below the CCD in the Skole Basin, a part of the Outer Carpathian realm, during the Middle Cenomanian. The hemipelagites contain numerous radiolarians, associated with deep-water agglutinated foraminifera. These sediments accumulated under mesotrophic conditions with limited oxygen concentration. Short-term periodic anoxia also occurred during that time. Muddy turbidity currents caused deposition of siliciclastic and biogenic material, including calcareous foramini-fers and numerous sponge spicules. The preservation and diversity of the spicules suggests that they originate from disarticulation of moderately diversified sponge assemblages, which lived predominantly in the neritic-bathyal zone. Analyses of radiolarian ecological groups and pellets reflect the water column properties during the sedimentation of green shales. At that time, surface and also intermediate waters were oxygenated enough and sufficiently rich in nutri-ents to enable plankton production. Numerous, uncompacted pellets with nearly pristine radiolarian skeletons inside show that pelletization was the main factor of radiolarian flux into the deep basin floor. Partly dissolved skeletons indicate that waters in the Skole Basin were undersaturated in relation to silica content. Oxygen content might have been depleted in the deeper part of the water column causing periodic anoxic conditions which prevent rapid bacterial degra-dation of the pellets during their fall to the sea floor.

  17. Preliminary Results from Outcrop-Based Spectral Gamma-Ray Measurements on the Lower Silurian Longmaxi Shale, in Chongqing and Its Adjacent Areas

    NASA Astrophysics Data System (ADS)

    Zou, C.; Nie, X.; Qiao, L.; Pan, L.; Hou, S.

    2013-12-01

    The Longmaxi Shale in the Lower Silurian has been recognized as a favorable target of shale gas exploration in Sichuan basin, China. One important feature of shale gas reservoirs is of high total organic carbon (TOC). Many studies have shown that the spectral gamma-ray measurements are positively correlated to the TOC contents. In this study, the spectral gamma ray responses of five shale outcrop profiles are measured in Chongqing and its adjacent areas, Sichuan basin. Three of the five profiles are located in Qijiang, Qianjiang and Changning in Chongqing, and the other two are located in Qilong and Houtan in Guizhou. The main lithologies of the profiles include mainly black shale, gray shale and silty shale. The spectral gamma-ray measurements provide the contents of potassium (K), uranium (U), and thorium (Th). The result of the five profiles shows that the K and Th contents of gray shale are close to the ones of black shale, while the U contents in the black shale are significantly higher than that in the other rocks. The TOC contents are estimated by using the outcrop-based measurements with an empirical formula. The result shows that the TOC contents are the highest in black shale of Changning profile. It indicates that there is a most promising exploration potential for shale gas in this area. In the future, the outcrop data will be used to construct detailed lithofacies profiles and establish relationships between lithofacies both in outcrop and the subsurface gamma-ray logs. Acknowledgment: We acknowledge the financial support of the National Natural Science Foundation of China (41274185) and the Fundamental Research Funds for the Central Universities.

  18. Permo-Triassic radiolaria from the Semanggol Formation, northwest Peninsular Malaysia

    NASA Astrophysics Data System (ADS)

    Jasin, Basir

    1997-02-01

    A total of 32 species of radiolaria were identified from 20 chert samples at eight localities of the Semanggol Formation in north and south Kedah. Three assemblages of Radiolaria were recognised representing the Early Permian Pseudoalbaillella scalprata m. rhombothoracata. Late Permian Albaillella levis, and Middle Triassic Triassocampe deweveri Assemblage-Zone. The Pseudoalbaillella scalprata m. rhombothoracata Assemblage-Zone is discovered from Bukit Kampung Yoi and Bukit Larek, north Kedah. The Albaillella levis Assemblage-Zone is recorded from Bukit Tok Bertanduk, north Kedah and Merbau Palas, south Kedah. The Triassocampe deweveri Assemblage-Zone is found from the Lanjut Malau area, north Kedah. The radiolarian assemblages indicate that the age of the chert sequence in the Semanggol Formation ranges from Early permian to Middle Triassic.

  19. Some contrasting biostratigraphic links between the Baker and Olds Ferry Terranes, eastern Oregon

    USGS Publications Warehouse

    Nestell, Merlynd K.; Blome, Charles D.

    2016-01-01

    New stratigraphic and paleontologic data indicate that ophiolitic melange windows in the Olds Ferry terrane of eastern Oregon contain limestone blocks and chert that are somewhat different in age than those present in the adjacent Baker terrane melange. The melange windows in the Olds Ferry terrane occur as inliers in the flyschoid Early and Middle Jurassic age Weatherby Formation, which depositionally overlies the contact between the melange-rich Devonian to Upper Triassic rocks of the Baker terrane on the north, and Upper Triassic and Early Jurassic volcanic arc rocks of the Huntington Formation on the south. The Baker terrane and Huntington Formation represent fragments of a subduction complex and related volcanic island arc, whereas the Weatherby Formation consists of forearc basin sedimentary deposits. The tectonic blocks in the melange windows of the Weatherby Formation (in the Olds Ferry terrane) are dated by scarce biostratigraphic evidence as Upper Pennsylvanian to Lower Permian and Upper Triassic. In contrast, tectonic blocks of limestone in theBaker terrane yield mostly fusulinids and small foraminifers of Middle Pennsylvanian Moscovian age at one locality.Middle Permian (Guadalupian) Tethyan fusulinids and smaller foraminifers (neoschwagerinids and other Middle Permian genera) are present at a few other localities. Late Triassic conodonts and bryozoans are also present in a few of the Baker terrane tectonic blocks. These limestone blocks are generally embedded in Permian and Triassic radiolarian bearing chert or argillite. Based on conodont, radiolarian and fusulinid data, the age limits of the meange blocks in the Weatherby Formation range from Pennsylvanian to Late Triassic.

  20. Reevaluation of the Piermont-Frontenac allochthon in the Upper Connecticut Valley: Restoration of a coherent Boundary Mountains–Bronson Hill stratigraphic sequence

    USGS Publications Warehouse

    Rankin, Douglas W.; Tucker, Robert D.; Amelin, Yuri

    2013-01-01

    The regional extent and mode and time of emplacement of the Piermont-Frontenac allochthon in the Boundary Mountains–Bronson Hill anticlinorium of the Upper Connecticut Valley, New Hampshire–Vermont, are controversial. Moench and coworkers beginning in the 1980s proposed that much of the autochthonous pre–Middle Ordovician section of the anticlinorium was a large allochthon of Silurian to Early Devonian rocks correlated to those near Rangeley, Maine. This ∼200-km-long allochthon was postulated to have been transported westward in the latest Silurian to Early Devonian as a soft-sediment gravity slide on a hypothesized Foster Hill fault. New mapping and U-Pb geochronology do not support this interpretation. The undisputed Rangeley sequence in the Bean Brook slice is different from the disputed sequence in the proposed larger Piermont-Frontenac allochthon, and field evidence for the Foster Hill fault is lacking. At the type locality on Foster Hill, the postulated “fault” is a stratigraphic contact within the Ordovician Ammonoosuc Volcanics. The proposed Foster Hill fault would place the Piermont-Frontenac allochthon over the inverted limb of the Cornish(?) nappe, which includes the Emsian Littleton Formation, thus limiting the alleged submarine slide to post-Emsian time. Mafic dikes of the 419 Ma Comerford Intrusive Complex intrude previously folded strata attributed to the larger Piermont-Frontenac allochthon as well as the autochthonous Albee Formation and Ammonoosuc Volcanics. The Lost Nation pluton intruded and produced hornfels in previously deformed Albee strata. Zircons from an apophysis of the pluton in the hornfels have a thermal ionization mass spectrometry 207Pb/206Pb age of 444.1 ± 2.1 Ma. Tonalite near Bath, New Hampshire, has a zircon sensitive high-resolution ion microprobe 206Pb/238U age of 492.5 ± 7.8 Ma. The tonalite intrudes the Albee Formation, formerly interpreted as the Silurian Perry Mountain Formation of the proposed allochthon

  1. Hydrologic environment of the Silurian salt deposits in parts of Michigan, Ohio, and New York

    USGS Publications Warehouse

    Norris, Stanley E.

    1978-01-01

    The aggregate thickness of evaporites (salt, gypsum, and anhydrite) in the Silurian Salina sequence in Michigan exceeds 1200 feet in areas near the periphery of the Michigan basin, where the salt beds are less than 3000 feet below land surface. In northeast Ohio the aggregate thickness of salt beds is as much as 200 feet in places, and in western New York it is more than 500 feet, where th beds are less than 3000 feet deep. The salt-bearing rocks dip regionally on the order of 50 feet per mile; those in Michigan dip toward the center of the Michigan basin, and those in Ohio and New York, in the Appalachian basin, dip generally southward. The rocks in both basins thicken downdip. Minor folds and faults occur in the salt-bearing rocks in all three states. Some of this defrmation has been attenuated or absorbed bo the salt beds. Occuring near the middle of thick sedimentary sequences, the salt beds are bounded aboe and below by beds containing water having dissolved-solids concentrations several times that seawter. The brines occur commonly in discrete zones of high permeability at specific places in the stratigraphic sequence. In northeast Ohio two prominent brine zones are recognized by the driller, the Devonian Oriskany Sandstone, or 'first water' zone, above the Salina Formation, and the Newburg or 'second water' zone below the Salina. In each aquifer there is a vertical component of hydraulic head, but little brine probably moves through the salt beds because their permeability is extremely low. Also, ther is little evidence of dissolution of the salt in areas distant from the outcrop, suggesting that if brine does move through the salt, movement is at a slow enough rate so that, in combination with the saturated or near-saturated condition of the water, it precludes significant dissolution. Principal brine movement is probably in the permeable zones in the direction of the hydraulic gradient. Two areas in Michigan and one area each in Ohio and New York appear

  2. Hydrogeology and groundwater quality at monitoring wells installed for the Tunnel and Reservoir Plan System and nearby water-supply wells, Cook County, Illinois, 1995–2013

    USGS Publications Warehouse

    Kay, Robert T.

    2016-04-04

    Groundwater-quality data collected from 1995 through 2013 from 106 monitoring wells open to the base of the Silurian aquifer surrounding the Tunnel and Reservoir Plan (TARP) System in Cook County, Illinois, were analyzed by the U.S. Geological Survey, in cooperation with the Metropolitan Water Reclamation District of Greater Chicago, to assess the efficacy of the monitoring network and the effects of water movement from the tunnel system to the surrounding aquifer. Groundwater from the Silurian aquifer typically drains to the tunnel system so that analyte concentrations in most of the samples from most of the monitoring wells primarily reflect the concentration of the analyte in the nearby Silurian aquifer. Water quality in the Silurian aquifer is spatially variable because of a variety of natural and non-TARP anthropogenic processes. Therefore, the trends in analyte values at a given well from 1995 through 2013 are primarily a reflection of the spatial variation in the value of the analyte in groundwater within that part of the Silurian aquifer draining to the tunnels. Intermittent drainage of combined sewer flow from the tunnel system to the Silurian aquifer when flow in the tunnel systemis greater than 80 million gallons per day may affect water quality in some nearby monitoring wells. Intermittent drainage of combined sewer flow from the tunnel system to the Silurian aquifer appears to affect the values of electrical conductivity, hardness, sulfate, chloride, dissolved organic carbon, ammonia, and fecal coliform in samples from many wells but typically during less than 5 percent of the sampling events. Drainage of combined sewer flow into the aquifer is most prevalent in the downstream parts of the tunnel systems because of the hydraulic pressures elevated above background values and long residence time of combined sewer flow in those areas. Elevated values of the analytes emplaced during intermittent migration of combined sewer flow into the Silurian aquifer

  3. The implications of a Silurian and other thylacocephalan crustaceans for the functional morphology and systematic affinities of the group

    PubMed Central

    2014-01-01

    Background Thylacocephala is a group of enigmatic extinct arthropods. Here we provide a full description of the oldest unequivocal thylacocephalan, a new genus and species Thylacares brandonensis, which is present in the Silurian Waukesha fauna from Wisconsin, USA. We also present details of younger, Jurassic specimens, from the Solnhofen lithographic limestones, which are crucial to our interpretation of the systematic position of Thylacocephala. In the past, Thylacocephala has been interpreted as a crustacean ingroup and as closely related to various groups such as cirripeds, decapods or remipeds. Results The Waukesha thylacocephalan, Thylacares brandonensis n. gen. n. sp., bears compound eyes and raptorial appendages that are relatively small compared to those of other representatives of the group. As in other thylacocephalans the large bivalved shield encloses much of the entire body. The shield lacks a marked optical notch. The eyes, which project just beyond the shield margin, appear to be stalked. Head appendages, which may represent antennulae, antennae and mandibles, appear to be present. The trunk is comprised of up to 22 segments. New details observed on thylacocephalans from the Jurassic Solnhofen lithographic limestones include antennulae and antennae of Mayrocaris bucculata, and endites on the raptorial appendages and an elongate last trunk appendage in Clausocaris lithographica. Preserved features of the internal morphology in C. lithographica include the muscles of the raptorial appendage and trunk. Conclusions Our results indicate that some ‘typical’ thylacocephalan characters are unique to the group; these autapomorphies contribute to the difficulty of determining thylacocephalan affinities. While the new features reported here are consistent with a eucrustacean affinity, most previous hypotheses for the position of Thylacocephala within Eucrustacea (as Stomatopoda, Thecostraca or Decapoda) are shown to be unlikely. A sister group relationship

  4. The implications of a Silurian and other thylacocephalan crustaceans for the functional morphology and systematic affinities of the group.

    PubMed

    Haug, Carolin; Briggs, Derek E G; Mikulic, Donald G; Kluessendorf, Joanne; Haug, Joachim T

    2014-08-22

    Thylacocephala is a group of enigmatic extinct arthropods. Here we provide a full description of the oldest unequivocal thylacocephalan, a new genus and species Thylacares brandonensis, which is present in the Silurian Waukesha fauna from Wisconsin, USA. We also present details of younger, Jurassic specimens, from the Solnhofen lithographic limestones, which are crucial to our interpretation of the systematic position of Thylacocephala. In the past, Thylacocephala has been interpreted as a crustacean ingroup and as closely related to various groups such as cirripeds, decapods or remipeds. The Waukesha thylacocephalan, Thylacares brandonensis n. gen. n. sp., bears compound eyes and raptorial appendages that are relatively small compared to those of other representatives of the group. As in other thylacocephalans the large bivalved shield encloses much of the entire body. The shield lacks a marked optical notch. The eyes, which project just beyond the shield margin, appear to be stalked. Head appendages, which may represent antennulae, antennae and mandibles, appear to be present. The trunk is comprised of up to 22 segments. New details observed on thylacocephalans from the Jurassic Solnhofen lithographic limestones include antennulae and antennae of Mayrocaris bucculata, and endites on the raptorial appendages and an elongate last trunk appendage in Clausocaris lithographica. Preserved features of the internal morphology in C. lithographica include the muscles of the raptorial appendage and trunk. Our results indicate that some 'typical' thylacocephalan characters are unique to the group; these autapomorphies contribute to the difficulty of determining thylacocephalan affinities. While the new features reported here are consistent with a eucrustacean affinity, most previous hypotheses for the position of Thylacocephala within Eucrustacea (as Stomatopoda, Thecostraca or Decapoda) are shown to be unlikely. A sister group relationship to Remipedia appears compatible

  5. Timing of terrane accretion in eastern and east-central Maine

    NASA Astrophysics Data System (ADS)

    Ludman, Allan

    1986-05-01

    The Norumbega fault zone is often cited as a post-Acadian suture between exotic blocks, even though stratigraphic, structural, and metamorphic data indicate that there is little offset of the Silurian-Devonian strata that the zone cuts in eastern Maine. Similarly, the Kingman fault zone has been shown by gravity and geochemical studies to separate distinct crustal blocks, whereas mapping shows that it lies entirely within a Silurian turbidite package. These conflicts are resolved if the two fault zones represent boundaries between Ordovician or older crustal blocks that had accreted to form a composite terrane prior to deposition of the cover sequences. The faults now mapped within these younger rocks formed by reactivation of the pre-Silurian boundaries during late Acadian time; movement continued until the late Carboniferous. Most of the accretionary history of Maine had thus ended before the Silurian. A complex composite terrane may have formed during Cambrian-Ordovician time that (1) interacted with cratonic North America during the Taconian orogeny and (2) became the “basement” upon which the Silurian and Lower Devonian strata of eastern Maine were deposited.

  6. Geochemical Characteristics of Granitoids in southwest Tianshan: Four Stages for Geodynamic Evolution of the Southwest Tianshan Orogenic Belt

    NASA Astrophysics Data System (ADS)

    Zhu, Y.

    2016-12-01

    Paleozoic intrusive rocks widely exposed in the west Tianshan orogenic belt provides key to understand the geodynamic evolution of the central Asian orogenic belt. A synthesis involving the data for Chinese Yili-central Tianshan and southwest Tianshan and comparison of Kyrgyz Tianshan with a broader dataset including zircon U-Pb ages, zircon Hf isotopic composition, major and trace elements for Paleozoic intrusions are presented to classify the Paleozoic intrusive rocks in four categories which corresponding to subduction of the Terskey Ocean, initial subduction stage of South Tianshan Ocean (STO), major subduction stage of the STO, and collisional to post-collisional stages. The subduction of the Terskey Oceanic crust finally caused the closure of the Terskey Ocean and the opening of the South Tianshan back-arc basin. The development of the Southwest Tianshan back-arc basin formed the STO, which subducted under the Yili-central Tianshan during early Silurian to early Carboniferous, and consequently formed huge arc magmatic rocks. Both the Silurian and early Carboniferous intrusions showing arc geochemical characteristics were derived from partial melting of juvenile arc-derived rocks with involvement of old continental crust. The STO finally closed by the end of early Carboniferous. Afterwards, geodynamic setting changed from convergence to extensional during late Carboniferous to early Permian periods. There is a significant geodynamic change from convergence to extension during late Carboniferous to early Permian, which may be resulted from breakoff of the subducted slab (Fig. 1). Such processes caused upwelling of asthenosphere and triggered partial melting of continental crust, as evidenced by emplacement of voluminous granitic rocks. References: An F, et al, 2013. Journal of Asian Earth Sciences, 78: 100-113; Zhu YF, 2011. Ore Geology Reviews, 40: 108-121; Zhu YF, et al, 2009. Geological Society, London, 166: 1085-1099; Zhu YF et al, 2016. Journal of Earth

  7. Continental erosion and the Cenozoic rise of marine diatoms

    NASA Astrophysics Data System (ADS)

    Cermeño, Pedro; Falkowski, Paul G.; Romero, Oscar E.; Schaller, Morgan F.; Vallina, Sergio M.

    2015-04-01

    Marine diatoms are silica-precipitating microalgae that account for over half of organic carbon burial in marine sediments and thus they play a key role in the global carbon cycle. Their evolutionary expansion during the Cenozoic era (66 Ma to present) has been associated with a superior competitive ability for silicic acid relative to other siliceous plankton such as radiolarians, which evolved by reducing the weight of their silica test. Here we use a mathematical model in which diatoms and radiolarians compete for silicic acid to show that the observed reduction in the weight of radiolarian tests is insufficient to explain the rise of diatoms. Using the lithium isotope record of seawater as a proxy of silicate rock weathering and erosion, we calculate changes in the input flux of silicic acid to the oceans. Our results indicate that the long-term massive erosion of continental silicates was critical to the subsequent success of diatoms in marine ecosystems over the last 40 My and suggest an increase in the strength and efficiency of the oceanic biological pump over this period.

  8. Continental erosion and the Cenozoic rise of marine diatoms

    PubMed Central

    Cermeño, Pedro; Falkowski, Paul G.; Romero, Oscar E.; Schaller, Morgan F.; Vallina, Sergio M.

    2015-01-01

    Marine diatoms are silica-precipitating microalgae that account for over half of organic carbon burial in marine sediments and thus they play a key role in the global carbon cycle. Their evolutionary expansion during the Cenozoic era (66 Ma to present) has been associated with a superior competitive ability for silicic acid relative to other siliceous plankton such as radiolarians, which evolved by reducing the weight of their silica test. Here we use a mathematical model in which diatoms and radiolarians compete for silicic acid to show that the observed reduction in the weight of radiolarian tests is insufficient to explain the rise of diatoms. Using the lithium isotope record of seawater as a proxy of silicate rock weathering and erosion, we calculate changes in the input flux of silicic acid to the oceans. Our results indicate that the long-term massive erosion of continental silicates was critical to the subsequent success of diatoms in marine ecosystems over the last 40 My and suggest an increase in the strength and efficiency of the oceanic biological pump over this period. PMID:25831504

  9. Continental erosion and the Cenozoic rise of marine diatoms.

    PubMed

    Cermeño, Pedro; Falkowski, Paul G; Romero, Oscar E; Schaller, Morgan F; Vallina, Sergio M

    2015-04-07

    Marine diatoms are silica-precipitating microalgae that account for over half of organic carbon burial in marine sediments and thus they play a key role in the global carbon cycle. Their evolutionary expansion during the Cenozoic era (66 Ma to present) has been associated with a superior competitive ability for silicic acid relative to other siliceous plankton such as radiolarians, which evolved by reducing the weight of their silica test. Here we use a mathematical model in which diatoms and radiolarians compete for silicic acid to show that the observed reduction in the weight of radiolarian tests is insufficient to explain the rise of diatoms. Using the lithium isotope record of seawater as a proxy of silicate rock weathering and erosion, we calculate changes in the input flux of silicic acid to the oceans. Our results indicate that the long-term massive erosion of continental silicates was critical to the subsequent success of diatoms in marine ecosystems over the last 40 My and suggest an increase in the strength and efficiency of the oceanic biological pump over this period.

  10. Bedrock geologic map of the Nashua South quadrangle, Hillsborough County, New Hampshire, and Middlesex County, Massachusetts

    USGS Publications Warehouse

    Walsh, Gregory J.; Jahns, Richard H.; Aleinikoff, John N.

    2013-01-01

    The bedrock geology of the 7.5-minute Nashua South quadrangle consists primarily of deformed Silurian metasedimentary rocks of the Berwick Formation. The metasedimentary rocks are intruded by a Late Silurian to Early Devonian diorite-gabbro suite, Devonian rocks of the Ayer Granodiorite, Devonian granitic rocks of the New Hampshire Plutonic Suite including pegmatite and the Chelmsford Granite, and Jurassic diabase dikes. The bedrock geology was mapped to study the tectonic history of the area and to provide a framework for ongoing hydrogeologic characterization of the fractured bedrock of Massachusetts and New Hampshire. This report presents mapping by G.J. Walsh and R.H. Jahns and zircon U-Pb geochronology by J.N. Aleinikoff. The complete report consists of a map, text pamphlet, and GIS database. The map and text pamphlet are only available as downloadable files (see frame at right). The GIS database is available for download in ESRITM shapefile and Google EarthTM formats, and includes contacts of bedrock geologic units, faults, outcrops, structural geologic information, photographs, and a three-dimensional model.

  11. Stream capture to form Red Pass, northern Soda Mountains, California

    USGS Publications Warehouse

    Miller, David; Mahan, Shannon

    2014-01-01

    Red Pass, a narrow cut through the Soda Mountains important for prehistoric and early historic travelers, is quite young geologically. Its history of downcutting to capture streams west of the Soda Mountains, thereby draining much of eastern Fort Irwin, is told by the contrast in alluvial fan sediments on either side of the pass. Old alluvial fan deposits (>500 ka) were shed westward off an intact ridge of the Soda Mountains but by middle Pleistocene time, intermediate-age alluvial fan deposits (~100 ka) were laid down by streams flowing east through the pass into Silurian Valley. The pass was probably formed by stream capture driven by high levels of groundwater on the west side. This is evidenced by widespread wetland deposits west of the Soda Mountains. Sapping and spring discharge into Silurian Valley over millennia formed a low divide in the mountains that eventually was overtopped and incised by a stream. Lessons include the importance of groundwater levels for stream capture and the relatively youthful appearance of this ~100-200 ka feature in the slowly changing Mojave Desert landscape.

  12. Evidence of photosymbiosis in Palaeozoic tabulate corals.

    PubMed

    Zapalski, Mikolaj K

    2014-01-22

    Coral reefs form the most diverse of all marine ecosystems on the Earth. Corals are among their main components and owe their bioconstructing abilities to a symbiosis with algae (Symbiodinium). The coral-algae symbiosis had been traced back to the Triassic (ca 240 Ma). Modern reef-building corals (Scleractinia) appeared after the Permian-Triassic crisis; in the Palaeozoic, some of the main reef constructors were extinct tabulate corals. The calcium carbonate secreted by extant photosymbiotic corals bears characteristic isotope (C and O) signatures. The analysis of tabulate corals belonging to four orders (Favositida, Heliolitida, Syringoporida and Auloporida) from Silurian to Permian strata of Europe and Africa shows these characteristic carbon and oxygen stable isotope signatures. The δ(18)O to δ(13)C ratios in recent photosymbiotic scleractinians are very similar to those of Palaeozoic tabulates, thus providing strong evidence of such symbioses as early as the Middle Silurian (ca 430 Ma). Corals in Palaeozoic reefs used the same cellular mechanisms for carbonate secretion as recent reefs, and thus contributed to reef formation.

  13. Post-Taconic blueschist suture in the northern Appalachians of northern New Brunswick, Canada

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    van Staal, C.R.; Ravenhurst, C.E.; Roddick, J.C.

    1990-11-01

    A narrow belt of Late Ordovician-Early Silurian blueschist, at least 70 km long, separates an allochthonous fragment of back-arc oceanic crust of the Middle Ordovician Fournier Group from underlying, rift-related volcanic rocks of the Middle Ordovician Tetagouche Group in northern New Brunswick, Canada. The basalts on both sides of the blueschist belt are predominantly metamorphosed to greenschist facies conditions. The blueschist belt is interpreted to be an out-of-sequence thrust zone that accommodated tectonic transport of higher pressure rocks on top of lower pressure rocks during post-peak blueschist facies metamorphism. The blueschists have higher Fe{sub 2}O{sub 3}/FeO ratios and total ironmore » contents in comparison to otherwise chemically equivalent basalts of the Fournier and Tetagouche Groups that have been metamorphosed into greenschists. The blueschist belt was probably the site of channelized flow of oxidizing fluids during active deformation ina subduction complex formed during the closure of a wide Taconic back-arac basin in Late Ordovician-Silurian time.« less

  14. Silurian carbonate high-energy deposits of potential tsunami origin: Distinguishing lateral redeposition and time averaging using carbon isotope chemostratigraphy

    NASA Astrophysics Data System (ADS)

    Jarochowska, Emilia; Munnecke, Axel

    2015-01-01

    Stable carbon isotope curves are used as a precise stratigraphic tool in the Paleozoic, even though they are commonly based on shallow-water carbonate record, characterized by low stratigraphic completeness. Identification of episodes of large-scale redeposition and erosion may improve δ13Ccarb-based correlations. Here, a series of at least three episodes of high-energy onshore redeposition are described from the Makarivka Member (new unit) of the Ustya Formation from the Homerian (middle Silurian) of Podolia, Ukraine. The Makarivka Member is emplaced within a tidal flat succession. Its most prominent part is divided into a lower polymictic conglomerate of sand- to boulder-sized clasts representing a range of subtidal facies, and an upper heterolithic unit composed of grainstone and mudstone laminae. The aim of the study is to identify the mechanism of deposition of the allochthonous conglomeratic material in this Member. Based on analogies with recent tsunami deposits, the conglomerate is interpreted to reflect the strongest landward-directed current in the tsunami run-up phase, and the heterolith - alternating high-density landward currents, stagnant intervals allowing mud and land-derived debris to settle, and backwash flows. The tsunamite was deposited during an interval of decreasing isotopic values of the Mulde excursion, a global δ13C excursion reaching + 5.2‰ in the studied sections. Clast redeposition in an interval characterized by rapidly changing δ13Ccarb offers the opportunity to evaluate the degree of temporal and spatial averaging caused by the tsunami. The clasts in the polymictic conglomerate show scattered δ13Ccarb values (- 0.3‰ to + 2.1‰) compared to homogenous (1.3‰ to 1.6‰) values in the matrix. The presence of clasts characterized by low δ13Ccarb values is explained by their decrease with bathymetry rather than erosion of pre-excursion strata, whereas high values characterize material entrained from the sea-floor and strata

  15. Palynological tracers of eustatic and climatic changes in the Late Ordovician on the North Gondwanan Margin

    NASA Astrophysics Data System (ADS)

    Le Hérissé, A.; Vecoli, M.

    2003-04-01

    The short-lived Hirnantian glacio-eustatic interval (1 My or less) caused about 60 per cent loss of total marine animal genera. This icehouse climate is also responsible for significant changes on the evolution of the plankton and the distribution of related microfossil assemblages, from pre-glacial to post-glacial episodes. This is clearly confirmed on different upper Ordovician sections from various paleogeographic location on the North Gondwanan margin. The effects of the glaciation did not correspond exactly to a cataclysmic event, because the palynomorphs do not show accelerated rates of extinction, in the inhospitable environment. It could also be noted that the origins of the Silurian communities are rooted in the upper Ordovician prior to the glaciation, with appearance of precursors (or -ahead of time-) forms, that diversified later in the Silurian. Nevertheless, the harsh climatic conditions associated to sea-level drop, caused a reduction in the number of taxa, with a scenario composed of three separate critical events: 1. a selective survival of ubiquitous taxa which are tolerant to the sea-level drawdown and of few taxa that appear specifically adapted to cold environments (Rawtheyan-early Hirnantian); 2. an adaptation of the sympagic microflora, to the variations of the sea-ice cover during deglaciation, including polymorphism and speciations (Hirnantian); 3. a slow recovery acompanying the climatic restoration and transgression in the latest Ordovician and early Silurian. Modifications in abundance and diversity of the microfossil assemblages, in the percentages of reworked elements and of amorphic organic matter are interpreted as evidence of a series of advances and retreats of the continental ice, of important changes of sea-surface conditions, of differences in the rate of melting of the icebergs during the deglaciation, as well as post-glacial isostatic rebounds. Our investigation demonstrates that the analysis of the evolution of palynomorph

  16. Bayesian Morphological Clock Methods Resurrect Placoderm Monophyly and Reveal Rapid Early Evolution in Jawed Vertebrates.

    PubMed

    King, Benedict; Qiao, Tuo; Lee, Michael S Y; Zhu, Min; Long, John A

    2017-07-01

    The phylogeny of early gnathostomes provides an important framework for understanding one of the most significant evolutionary events, the origin and diversification of jawed vertebrates. A series of recent cladistic analyses have suggested that the placoderms, an extinct group of armoured fish, form a paraphyletic group basal to all other jawed vertebrates. We revised and expanded this morphological data set, most notably by sampling autapomorphies in a similar way to parsimony-informative traits, thus ensuring this data (unlike most existing morphological data sets) satisfied an important assumption of Bayesian tip-dated morphological clock approaches. We also found problems with characters supporting placoderm paraphyly, including character correlation and incorrect codings. Analysis of this data set reveals that paraphyly and monophyly of core placoderms (excluding maxillate forms) are essentially equally parsimonious. The two alternative topologies have different root positions for the jawed vertebrates but are otherwise similar. However, analysis using tip-dated clock methods reveals strong support for placoderm monophyly, due to this analysis favoring trees with more balanced rates of evolution. Furthermore, enforcing placoderm paraphyly results in higher levels and unusual patterns of rate heterogeneity among branches, similar to that generated from simulated trees reconstructed with incorrect root positions. These simulations also show that Bayesian tip-dated clock methods outperform parsimony when the outgroup is largely uninformative (e.g., due to inapplicable characters), as might be the case here. The analysis also reveals that gnathostomes underwent a rapid burst of evolution during the Silurian period which declined during the Early Devonian. This rapid evolution during a period with few articulated fossils might partly explain the difficulty in ascertaining the root position of jawed vertebrates. © The Author(s) 2016. Published by Oxford University

  17. Re-Os systematics and age of pyrite associated with stratiform Zn-Pb mineralization in the Howards Pass district, Yukon and Northwest Territories, Canada

    NASA Astrophysics Data System (ADS)

    Kelley, Karen D.; Selby, David; Falck, Hendrik; Slack, John F.

    2017-03-01

    Stratiform Zn-Pb deposits hosted in unmetamorphosed carbonaceous and siliceous mudstones of the Ordovician to Silurian Duo Lake Formation define the Howards Pass district in Yukon Territory and Northwest Territories, western Canada. Collectively, the deposits are amongst the largest in the world, containing drill-indicated and inferred resources of 423 Mt at 4.84 % Zn and 1.59 % Pb. Sulphide textures include (a) fine-scale laminations of sphalerite, galena, and pyrite from <0.05 mm to 1 cm thick, interbedded with carbonaceous sedimentary rock; (b) layers of coarse sulphide that are structurally controlled by microfolds; and (c) veins that cut bedding and sulphide laminations. The finely interlaminated nature of sulphides with mudstone has been used as evidence for syngenetic mineralizing processes, whereas paleomagnetic data determined on coarse layered sulphides suggest a Middle Jurassic age of mineralization. Here, we present new rhenium-osmium (Re-Os) isotopic data for 12 pyrite separates obtained from 4 laminated sulphide-rich samples from the XY Central (XYC) and Don (DON) deposits and for 1 unmineralized organic-rich mudstone ˜20 m stratigraphically below the sulphide-bearing zone. Pyrite separates that lack mudstone inclusions ("pure") from the XYC deposit contain 2.2 to 4.0 ppb Re and 93.4 to 123.4 ppt Os; pure pyrite from the DON deposit is significantly more enriched in Re and Os (34-37 ppb Re; 636.8-694.9 ppt Os). The 187Re/188Os values of pure pyrite separates from the XYC and DON deposits range from 137.6 to 197 and 182.1 to 201.4, respectively. Regression of all pure pyrite Re-Os data from both deposits yields an isochron age of 442 ± 14 Ma (MSWD = 7.4) and an initial 187Os/188Os (Osi) value of 0.71 ± 0.07. The Re-Os age indicates that the early phase of pyrite precipitation (and by inference, sphalerite and galena) occurred during the early Silurian, consistent with biostratigraphic ages of the host rocks. The Osi value of ˜0.8 for earliest

  18. Astronomical pacing of the global silica cycle recorded in Mesozoic bedded cherts

    NASA Astrophysics Data System (ADS)

    Ikeda, Masayuki; Tada, Ryuji; Ozaki, Kazumi

    2017-06-01

    The global silica cycle is an important component of the long-term climate system, yet its controlling factors are largely uncertain due to poorly constrained proxy records. Here we present a ~70 Myr-long record of early Mesozoic biogenic silica (BSi) flux from radiolarian chert in Japan. Average low-mid-latitude BSi burial flux in the superocean Panthalassa is ~90% of that of the modern global ocean and relative amplitude varied by ~20-50% over the 100 kyr to 30 Myr orbital cycles during the early Mesozoic. We hypothesize that BSi in chert was a major sink for oceanic dissolved silica (DSi), with fluctuations proportional to DSi input from chemical weathering on timescales longer than the residence time of DSi (<~100 Kyr). Chemical weathering rates estimated by the GEOCARBSULFvolc model support these hypotheses, excluding the volcanism-driven oceanic anoxic events of the Early-Middle Triassic and Toarcian that exceed model limits. We propose that the Mega monsoon of the supercontinent Pangea nonlinearly amplified the orbitally paced chemical weathering that drove BSi burial during the early Mesozoic greenhouse world.

  19. Depositional settings, correlation, and age carboniferous rocks in the western Brooks Range, Alaska

    USGS Publications Warehouse

    Dumoulin, Julie A.; Harris, Anita G.; Blome, Charles D.; Young, Lorne E.

    2004-01-01

    The Kuna Formation (Lisburne Group) in northwest Alaska hosts the Red Dog and other Zn-Pb-Ag massive sulfide deposits in the Red Dog district. New studies of the sedimentology and paleontology of the Lisburne Group constrain the setting, age, and thermal history of these deposits. In the western and west-central Brooks Range, the Lisburne Group includes both deep- and shallow-water sedimentary facies and local volcanic rocks that are exposed in a series of thrust sheets or allochthons. Deep-water facies in the Red Dog area (i.e., the Kuna Formation and related rocks) are found chiefly in the Endicott Mountains and structurally higher Picnic Creek allochthons. In the Red Dog plate of the Endicott Mountains allochthon, the Kuna consists of at least 122 m of thinly interbedded calcareous shale, calcareous spiculite, and bioclastic supportstone (Kivalina unit) overlain by 30 to 240 m of siliceous shale, mudstone, calcareous radiolarite, and calcareous lithic turbidite (Ikalukrok unit). The Ikalukrok unit in the Red Dog plate hosts all massive sulfide deposits in the area. It is notably carbonaceous, is generally finely laminated, and contains siliceous sponge spicules and radiolarians. The Kuna Formation in the Key Creek plate of the Endicott Mountains allochthon (60–110 m) resembles the Ikalukrok unit but is unmineralized and has thinner carbonate layers that are mainly organic-rich dolostone. Correlative strata in the Picnic Creek allochthon include less shale and mudstone and more carbonate (mostly calcareous spiculite). Conodonts and radiolarians indicate an age range of Osagean to early Chesterian (late Early to Late Mississippian) for the Kuna in the Red Dog area. Sedimentologic, faunal, and geochemical data imply that most of the Kuna formed in slope and basin settings characterized by anoxic or dysoxic bottom water and by local high productivity.

  20. Zircon U-Pb age, Hf isotopic compositions and geochemistry of the Silurian Fengdingshan I-type granite Pluton and Taoyuan mafic-felsic Complex at the southeastern margin of the Yangtze Block

    NASA Astrophysics Data System (ADS)

    Zhong, Yufang; Ma, Changqian; Zhang, Chao; Wang, Shiming; She, Zhenbing; Liu, Lei; Xu, Haijin

    2013-09-01

    This work presents an integrated study of zircon U-Pb ages and Hf isotope along with whole-rock geochemistry on Silurian Fengdingshan I-type granites and Taoyuan mafic-felsic intrusive Complex located at the southeastern margin of the Yangtze Block, filling in a gap in understanding of Paleozoic I-type granites and mafic-intermediate igneous rocks in the eastern South China Craton (SCC). The Fengdingshan granite and Taoyuan hornblende gabbro are dated at 436 ± 5 Ma and 409 ± 2 Ma, respectively. The Fengdingshan granites display characteristics of calc-alkaline I-type granite with high initial 87Sr/86Sr ratios of 0.7093-0.7127, low ɛNd(t) values ranging from -5.6 to -5.4 and corresponding Nd model ages (T2DM) of 1.6 Ga. Their zircon grains have ɛHf(t) values ranging from -2.7 to 2.6 and model ages of 951-1164 Ma. The Taoyuan mafic rocks exhibit typical arc-like geochemistry, with enrichment in Rb, Th, U and Pb and depletion in Nb, Ta. They have initial 87Sr/86Sr ratios of 0.7053-0.7058, ɛNd(t) values of 0.2-1.6 and corresponding T2DM of 1.0-1.1 Ga. Their zircon grains have ɛHf(t) values ranging from 3.2 to 6.1 and model ages of 774-911 Ma. Diorite and granodiorite from the Taoyuan Complex have initial 87Sr/86Sr ratios of 0.7065-0.7117, ɛNd(t) values from -5.7 to -1.9 and Nd model ages of 1.3-1.6 Ga. The petrographic and geochemical characteristics indicate that the Fengdingshan granites probably formed by reworking of Neoproterozoic basalts with very little of juvenile mantle-derived magma. The Taoyuan Complex formed by magma mixing and mingling, in which the mafic member originated from a metasomatized lithospheric mantle. Both the Fengdingshan and Taoyuan Plutons formed in a post-orogenic collapse stage in an intracontinental tectonic regime. Besides the Paleozoic Fengdingshan granites and Taoyuan hornblende gabbro, other Neoproterozoic and Indosinian igneous rocks located along the southeastern and western margin of the Yangtze Block also exhibit decoupled

  1. Tectono-thermal Evolution of the Lower Paleozoic Petroleum Source Rocks in the Southern Lublin Trough: Implications for Shale Gas Exploration from Maturity Modelling

    NASA Astrophysics Data System (ADS)

    Botor, Dariusz

    2018-03-01

    The Lower Paleozoic basins of eastern Poland have recently been the focus of intensive exploration for shale gas. In the Lublin Basin potential unconventional play is related to Lower Silurian source rocks. In order to assess petroleum charge history of these shale gas reservoirs, 1-D maturity modeling has been performed. In the Łopiennik IG-1 well, which is the only well that penetrated Lower Paleozoic strata in the study area, the uniform vitrinite reflectance values within the Paleozoic section are interpreted as being mainly the result of higher heat flow in the Late Carboniferous to Early Permian times and 3500 m thick overburden eroded due to the Variscan inversion. Moreover, our model has been supported by zircon helium and apatite fission track dating. The Lower Paleozoic strata in the study area reached maximum temperature in the Late Carboniferous time. Accomplished tectono-thermal model allowed establishing that petroleum generation in the Lower Silurian source rocks developed mainly in the Devonian - Carboniferous period. Whereas, during Mesozoic burial, hydrocarbon generation processes did not develop again. This has negative influence on potential durability of shale gas reservoirs.

  2. The evolution of Phanerozoic seawater - Isotope paleothermometry finds consensus on Early Paleozoic warmth and constant seawater δ18O

    NASA Astrophysics Data System (ADS)

    Grossman, E. L.; Henkes, G. A.; Passey, B. H.; Shenton, B.; Yancey, T. E.; Perez-Huerta, A.

    2015-12-01

    Evolution of metazoan life is closely linked to the Phanerozoic evolution of ocean temperatures and chemistry. Oxygen isotopic evidence for early Phanerozoic paleotemperatures has been equivocal, with decreasing δ18O values with age being interpreted as warmer early oceans, decreasing seawater δ18O with age, or increasing diagenetic alteration in older samples. Here we compare an updated compilation of oxygen isotope data for carbonate and phosphate fossils and microfossils (Grossman, 2012, Geol. Time Scale, Elsevier, 195-220) with a compilation of new and existing clumped isotope data. Importantly, these data are curated based on sample preservation with special consideration given to screening techniques, and tectonic and burial history. Burial history is critical in the preservation of carbonate clumped isotope temperatures in particular, which can undergo reordering in the solid state. We use a model derived for reordering kinetics (Henkes et al., 2014, Geochim. Cosmochim. Acta 139:362-382) to screen clumped isotope data for the effects of solid-state burial alteration. With minor but significant exceptions (Late Cretaceous, Early Triassic), average δ18O values (4 m.y. window, 2 m.y. steps) for post-Devonian brachiopods, belemnites, and foraminifera, representing tropical-subtropical surface ocean conditions, yield average isotopic temperatures below 30°C (assuming a seawater δ18O value [ -1‰ VSMOW] of an "ice-free" world). In contrast, Ordovician to Devonian data show sustained temperatures of 35-40°C. Likewise, isotopic paleotemperatures from conodont apatite, known to be resistant to isotopic exchange, follow the same pattern. Clumped isotope data derived from Paleozoic brachiopod shells that experienced minimal burial (< 100 °C) and <1% reordering according to the taxon-specific clumped isotope reordering model yield typical temperatures of 25-30°C for the Carboniferous, and 35-40°C for the Ordovician-Silurian. Inserting clumped temperatures and

  3. Hydrology, water quality, and effects of drought in Monroe County, Michigan

    USGS Publications Warehouse

    Nicholas, J.R.; Rowe, Gary L.; Brannen, J.R.

    1996-01-01

    Monroe County relies heavily on its aquifers and streams for drinking water, irrigation, and other ~ses; however, increased water use, high concentrations of certain constituents in ground water, and droughts may limit the availability of water resources. Although the most densely populated parts of the county use water from the Great Lakes, large amounts of ground water are withdrawn for quarry dewatering, domestic supply, and irrigation.Unconsolidated deposits and bedrock of Silurian and Devonian age underlie Mon_roe County. The unconsolidated deposits are mostly clayey and less than 50 feet thick. Usable amounts of ground water generally are obtained from thin, discontinuous surficial sand deposits or, in the northwestern part of the county, from deep glaciofluvial deposits. In most of the county, however, ground water in unconsolidated deposits is highly susceptible to effects of droughts and to contamination.The bedrock is mostly carbonate rock, and usable quantities of ground water can be obtained from fractures and other secondary openings throughout the county. Transmissivities of the Silurian-Devonian aquifer range from 10 to 6,600 feet squared per day. Aquifer tests and historical informati.on indicate that the Silurian-Devonian aquifer is confmed throughout most of the county. The major recharge area for the Silurian-Devonian aquifer in Monroe County is in the southwest, and groundwater flow is mostly southeastward toward Lake Erie. In the northeastern and southeastern parts of the county, the potentiometric surface of the SilurianDevonian aquifers has been lowered by pumpage to below the elevation of Lake Erie.Streams and artificial drains in Monroe County are tributary to Lake Erie. Most streams are perennial because of sustained discharge from the sand aquifer and the Silurian-Devonian aquifer; however, the lower reaches of River Raisin and Plum Creek lost water to the Silurian-Devonian aquifer in July 1990.The quality of ground water and of

  4. Bedrock geologic map of the Littleton and Lower Waterford quadrangles, Essex and Caledonia Counties, Vermont, and Grafton County, New Hampshire

    USGS Publications Warehouse

    Rankin, Douglas W.

    2018-06-13

    The bedrock geologic map of the Littleton and Lower Waterford quadrangles covers an area of approximately 107 square miles (277 square kilometers) north and south of the Connecticut River in east-central Vermont and adjacent New Hampshire. This map was created as part of a larger effort to produce a new bedrock geologic map of Vermont through the collection of field data at a scale of 1:24,000. A large part of the map area consists of the Bronson Hill anticlinorium, a post-Early Devonian structure that is cored by metamorphosed Cambrian to Devonian sedimentary, volcanic, and plutonic rocks. The northwestern part of the map is divided by the Monroe fault which separates Early Devonian rocks of the Connecticut Valley-Gaspé trough from rocks of the Bronson Hill anticlinorium.The Bronson Hill anticlinorium is the apex of the Middle Ordovician to earliest-Silurian Bronson Hill magmatic arc that contains the Ammonoosuc Volcanics, Partridge Formation, and Oliverian Plutonic suite, and extends from Maine, down the eastern side of the Connecticut River in New Hampshire, to Long Island Sound. The deformed and partially eroded arc is locally overlain by a relatively thin Silurian section of metasedimentary rocks (Clough Quartzite and Fitch Formation) that thickens to the east. The Silurian section near Littleton is disconformably overlain by a thicker, Lower Devonian section that includes mostly metasedimentary rocks and minor metavolcanic rocks of the Littleton Formation. The Bronson Hill anticlinorium is bisected by a series of northeast-southwest trending Mesozoic normal faults. Primarily among them is the steeply northwest-dipping Ammonoosuc fault that divides older and younger units (upper and lower sections) of the Ammonoosuc Volcanics. The Ammonoosuc Volcanics are lithologically complex and predominantly include interlayered and interfingered rhyolitic to basaltic volcanic and volcaniclastic rocks, as well as lesser amounts of metamorphic and metasedimentary rocks

  5. Astronomical pacing of the global silica cycle recorded in Mesozoic bedded cherts

    PubMed Central

    Ikeda, Masayuki; Tada, Ryuji; Ozaki, Kazumi

    2017-01-01

    The global silica cycle is an important component of the long-term climate system, yet its controlling factors are largely uncertain due to poorly constrained proxy records. Here we present a ∼70 Myr-long record of early Mesozoic biogenic silica (BSi) flux from radiolarian chert in Japan. Average low-mid-latitude BSi burial flux in the superocean Panthalassa is ∼90% of that of the modern global ocean and relative amplitude varied by ∼20–50% over the 100 kyr to 30 Myr orbital cycles during the early Mesozoic. We hypothesize that BSi in chert was a major sink for oceanic dissolved silica (DSi), with fluctuations proportional to DSi input from chemical weathering on timescales longer than the residence time of DSi (<∼100 Kyr). Chemical weathering rates estimated by the GEOCARBSULFvolc model support these hypotheses, excluding the volcanism-driven oceanic anoxic events of the Early-Middle Triassic and Toarcian that exceed model limits. We propose that the Mega monsoon of the supercontinent Pangea nonlinearly amplified the orbitally paced chemical weathering that drove BSi burial during the early Mesozoic greenhouse world. PMID:28589958

  6. Astronomical pacing of the global silica cycle recorded in Mesozoic bedded cherts.

    PubMed

    Ikeda, Masayuki; Tada, Ryuji; Ozaki, Kazumi

    2017-06-07

    The global silica cycle is an important component of the long-term climate system, yet its controlling factors are largely uncertain due to poorly constrained proxy records. Here we present a ∼70 Myr-long record of early Mesozoic biogenic silica (BSi) flux from radiolarian chert in Japan. Average low-mid-latitude BSi burial flux in the superocean Panthalassa is ∼90% of that of the modern global ocean and relative amplitude varied by ∼20-50% over the 100 kyr to 30 Myr orbital cycles during the early Mesozoic. We hypothesize that BSi in chert was a major sink for oceanic dissolved silica (DSi), with fluctuations proportional to DSi input from chemical weathering on timescales longer than the residence time of DSi (<∼100 Kyr). Chemical weathering rates estimated by the GEOCARBSULFvolc model support these hypotheses, excluding the volcanism-driven oceanic anoxic events of the Early-Middle Triassic and Toarcian that exceed model limits. We propose that the Mega monsoon of the supercontinent Pangea nonlinearly amplified the orbitally paced chemical weathering that drove BSi burial during the early Mesozoic greenhouse world.

  7. The influence of pre-existing basement structures on salt tectonics in the Upper Silurian Salina Group, Appalachian Basin, NE Pennsylvania: results from 3D seismic analysis and analogue modelling

    NASA Astrophysics Data System (ADS)

    Harding, M. R.; Rowan, C. J.

    2013-12-01

    The Upper Silurian Salina Group in Pennsylvania's Appalachian basin consists of several hundred feet of highly deformable and mobile salt that was a significant influence on the tectonic and structural development of the Appalachian Mountains during the late Paleozoic. Understanding how halokinesis and décollement thrusting of the Salina Group has contributed to the present-day structure of the Appalachian Basin is of intense current interest due to the energy resource potential of the overlying Marcellus Shale and underlying Utica Shale. Seismic data suggest that halokinesis of the Salina Group in the Appalachian Basin might be strongly influenced by the presence of preexisting faults in the underlying Neoproterozoic basement, which suggests that these structures may have interacted with the Salina Group or its interior during deformation. We examine these apparent interactions in more detail using high-resolution 3D seismic data from the Appalachian Basin of NE Pennsylvania to identify and characterize salt tectonic-related structures developed above and within the Salina Group during orogenesis, verify their geographic association with major basement faults, and document how reactivation of these preexisting faults might have influenced later deformation within and above the salt units. We also present the results of sandbox modelling of thin-skinned thrusting in a salt-analogue décollement. Multiple runs in the presence and absence of preexisting basement structures provide insight into how the modern structures observed in the seismic data initiated and evolved during progressively more intense orogenesis, and better constrain the physical processes that control the structural linkage through the Salina décollement.

  8. Geology and hydrocarbon potential of the Oued Mya Basin, Algeria

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Benamrane, O.; Messaoudi, M.; Messelles, H.

    1992-01-01

    The hydrocarbon System Ourd Mya is located in the Sahara Basin. It is one of the producing basin in Algeria. The stratigraphic section consists of Paleozoic and Mesosoic, it is about 5000m thick. In the eastern part, the basin is limited by the Hassi-Messaoud high zone which is a giant oil field producing from the Cambrian sands. The western part is limited by Hassi R'mel which is one of the biggest gas field in the world, it is producing from the triassic sands. The Mesozoic section is laying on the lower Devonian and in the eastern part, on the Cambrian.more » The main source rock is the Silurian shale with an average thickness of 50m and a total organic matter of 6% (14% in some cases). Results of maturation modeling indicate that the lower Silurian source is in the oil window. The Ordovician shales are also a source rock, but in a second order. Clastic reservoirs are in the Triassic sequence which is mainly fluvial deposits with complex alluvial channels, it is the main target in the basin. Clastic reservoirs within the lower Devonian section have a good hydrocarbon potential in the east of the basin through a southwest-northeast orientation. The late Triassic-Early Jurassic evaporites overlie the Triassic clastic interval and extend over the entire Oued Mya Basin. This is considered as a super-seal evaporate package, which consists predominantly of anhydrite and halite. For Paleozoic targets, a large number of potential seals exist within the stratigraphic column. The authors infer that a large amount of the oil volume generated by the Silurian source rock from the beginning of Cretaceous until now, still not discovered could be trapped within structure closures and mixed or stratigraphic traps related to the fluvial Triassic sandstones, marine Devonian sands and Cambro-Ordovician reservoirs.« less

  9. Lithofacies and stratigraphy of the Lisburne and Etivluk groups in the Lisburne 1 well and adjacent outcrops

    USGS Publications Warehouse

    Dumoulin, Julie A.; Bird, Kenneth J.

    2002-01-01

    The Lisburne 1 well in the thrust belt of the central Brooks Range penetrated 17,000 ft of imbricated, chiefly Ellesmerian sequence strata in the Endicott Mountains allochthon. Five thrust repeats of the Lisburne Group (Carboniferous) and overlying Etivluk Group (Permian-Jurassic) were drilled. Lithofacies analyses of >350 thin sections of cores and cuttings, and biostratigraphy based on foraminifers and conodonts, allow detailed correlation with coeval units in adjacent outcrops and provide data on the depositional setting and reservoir and source rock potential of these strata. The late Early- Late Mississippian (Osagean-Chesterian) Lisburne Group consists mainly of skeletal wackestone to grainstone, locally completely dolomitized. An interval of abundant glauconite and detrital quartz in the lower Lisburne may mark a sequence-bounding unconformity. Dolostone in the upper part of the unit has maximum porosities of 10-13% and common residual hydrocarbons. The uppermost Lisburne is thinly interbedded mudstone, chert, and shale that are locally dolomitic, phosphatic, spiculitic, and organic-rich; conodonts from this interval in outcrop represent an outer shelf to slope biofacies. The Etivluk Group here encompasses the Siksikpuk and Otuk Formations. The Siksikpuk is mainly varicolored shale and radiolarian chert, with a basal interval of glauconitic, pyritic sandstone. Phosphatic and organic-rich shale, radiolarian chert, and pelecypod coquinas make up the Otuk. Outcrop and subsurface data indicate that the Lisburne Group in this area accumulated near the seaward margin of a shallow-water carbonate platform that drowned during the Late Mississippian; outer shelf or deeper conditions predominated throughout deposition of the upper Lisburne and the Etivluk Group.

  10. Publications - GMC 53B | Alaska Division of Geological & Geophysical

    Science.gov Websites

    Richfield Oil Company Wide Bay Unit #1, Alaska Peninsula Authors: Unknown Publication Date: Unknown Unknown, [n.d.], Scanning electron micrographs of selected radiolarians from the Richfield Oil Company

  11. Surface geology of the Jeptha Knob cryptoexplosion structure, Shelby County, Kentucky

    USGS Publications Warehouse

    Cressman, Earle Rupert

    1981-01-01

    . The faulted and brecciated beds are overlain by nearly horizontal dolomite and shale of Early and Middle Silurian age. The basal 5 ft of the oldest Silurian unit, the Brassfield Formation, contains calcarenite and calcirudite composed, in large part, of locally derived fragments from the Upper Ordovician formations. The Jeptha Knob structure was formed in latest Late Ordovician or earliest Early Silurian time. At the time of formation, the area was either very slightly above or very slightly below sea level; the sediments were already largely indurated. At the onset of Silurian deposition, the area of the central uplift was probably a broad shallow depression not more than about 15 ft deep, possibly surrounded by a rim of Upper Ordovician rocks or rock fragments. The origin of the Jeptha Knob structure cannot be determined from the available data. Shatter cones and coesite, considered by many to be definitive criteria far origin by impact, have not been found. On the other hand, geophysical studies indicate that there is no coincident uplift of the basement, and there is no certain relation of Jeptha Knob to any obvious structural trend.

  12. Shoshonitic- and adakitic magmatism of the Early Paleozoic age in the Western Kunlun orogenic belt, NW China: Implications for the early evolution of the northwestern Tibetan plateau

    NASA Astrophysics Data System (ADS)

    Wang, Jian; Hattori, Keiko; Liu, Jianguo; Song, Yue; Gao, Yongbao; Zhang, Han

    2017-08-01

    as their sources. Combined with the geological development of the area, we propose that a local extension in the WKT over the subducting Paleo-Tethys has induced the upwelling of asthenospheric mantle and partial melting in the lower crust during mid-Ordovician to early Silurian. The primary shoshonitic melt evolved into the parental magmas for the shoshonitic rocks and adakitic rocks through fractional crystallization of hornblende.

  13. Light and electron microscopic observations of the reproductive swarmer cells of nassellarian and spumellarian polycystines (Radiolaria).

    PubMed

    Yuasa, Tomoko; Takahashi, Osamu

    2016-06-01

    We observed reproductive swarmer cells of the nassellarian and spumellarian polycystine radiolarians Didymocyrtis ceratospyris, Pterocanium praetextum, Tetrapyle sp., and Triastrum aurivillii using light, scanning and transmission electron microscopy. The swarmer cells had subspherical to ovoid or spindle shapes with two unequal flagella tapered to whip-like ends. The cell size was approximately 2.5-5.5μm long and 1.6-2.2μm wide, which is significantly smaller than that of the collodarian (colonial or naked) polycystine radiolarians. Transmission electron microscopy revealed that the swarmer cells possessed a nucleus, mitochondria with tubular cristae, Golgi body, and small lipid droplets in the cytoplasm; they also had a large vacuole in which a single crystalline inclusion (approx. 1.0-1.5μm) that was probably celestite (SrSO4) was enclosed. The swarmer cells were released directly from the parent cells. At that time, morphological change such as encystment was not observed in the parent cells, and the axopodia remained extended in a period of swarmer reproduction for floating existence. This may have prevented the polycystine swarmers from rapidly sinking down to great depths. Thus, we concluded that the polycystine radiolarians release the swarmer cells into the photic layer in the same way as the symbiotic acantharians. Copyright © 2016 Elsevier GmbH. All rights reserved.

  14. Publications - GMC 53A | Alaska Division of Geological & Geophysical

    Science.gov Websites

    quartz sand grains from ARCO Alaska, Inc. West Mikkelsen St. #1 Authors: Unknown Publication Date Reference Unknown, [n.d.], Scanning electron micrographs of selected radiolarians and quartz sand grains

  15. Algoma-, Superior-, and oolitic-type iron deposits of the Islamic Republic of Mauritania (phase V, deliverable 83): Chapter O in Second projet de renforcement institutionnel du secteur minier de la République Islamique de Mauritanie (PRISM-II)

    USGS Publications Warehouse

    Taylor, Cliff D.; Finn, Carol A.; Anderson, Eric D.; Joud, M. Y.; Taleb, M. A.; Horton, John D.

    2015-01-01

    Phanerozoic oolitic ironstones are hosted in the upper Silurian and lower Devonian rocks of the Gara Bouya Ali Group and the Zemmour Group in the Tindouf Basin in northern Mauritania and in the end Ordovician Tichit Group, the Silurian Oued Chig Group, and the lower Devonian Tenemouj Group in the Taoudeni Basin near Tidjikja. These rock groups define 11 permissive tracts for Algoma-, Superior-, and oolitic-type iron deposits in Mauritania.

  16. Final Remedial Investigation Report Area of Contamination (AOC) 57. Volume I. Text Sections 1 Through 10, Figures and Tables

    DTIC Science & Technology

    2000-06-01

    duckweed ( Lemna minor ), and bur-reed (Sparganium sp.). The forested wetland to the southeast of Cold Spring Brook has a sparse canopy cover of red...FORMATION (Lower Devonian and Silurian) Carbonaceous slate and phyllite, with minor metagraywacke to the west (Zen, 1983; Peck, 1975). Bedding is...Allmendinger (1975). So OAKDALE FORMATION (Silurian) Metasiltstone and phyllite. It is fine- grained and consists of quartz and minor feldspar and ankerite, and

  17. Supra-subduction zone extensional magmatism in Vermont and adjacent Quebec: Implications for early Paleozoic Appalachian tectonics

    USGS Publications Warehouse

    Kim, J.; Coish, R.; Evans, M.; Dick, G.

    2003-01-01

    Metadiabasic intrusions of the Mount Norris Intrusive Suite occur in fault-bounded lithotectonic packages containing Stowe, Moretown, and Cram Hill Formation lithologies in the northern Vermont Rowe-Hawley belt, a proposed Ordovician arc-trench gap above an east-dipping subduction zone. Rocks of the Mount Norris Intrusive Suite are characteristically massive and weakly foliated, have chilled margins, contain xenoliths, and have sharp contacts that both crosscut and are parallel to early structural fabrics in the host metasedimentary rocks. Although the mineral assemblage of the Mount Norris Intrusive Suite is albite + actinolite + epidote + chlorite + calcite + quartz, intergrowths of albite + actinolite are probably pseudomorphs after plagioclase + clinopyroxene. The metadiabases are subalkaline, tholeiitic, hypabyssal basalts with preserved ophitic texture. A backarc-basin tectonic setting for the intrusive suite is suggested by its LREE (light rare earth element) enrichment, negative Nb-Ta anomalies, and Ta/Yb vs. Th/Yb trends. Although no direct isotopic age data are available, the intrusions are broadly Ordovician because their contacts are clearly folded by the earliest Acadian (Silurian-Devonian) folds. Field evidence and geochemical data suggest compelling along-strike correlations with the Coburn Hill Volcanics of northern Vermont and the Bolton Igneous Group of southern Quebec. Isotopic and stratigraphic age constraints for the Bolton Igneous Group bracket these backarc magmas to the 477-458 Ma interval. A tectonic model that begins with east-dipping subduction and progresses to outboard west-dipping subduction after a syncollisional polarity reversal best explains the intrusion of deformed metamorphosed metasedimentary rocks by backarc magmas.

  18. Annual flux of radiolaria and other shelled plankters in the eastern equatorial atlantic at 853 m: seasonal variations and polycystine species-specific responses

    NASA Astrophysics Data System (ADS)

    Boltovskoy, Demetrio; Alder, Viviana A.; Abelmann, Andrea

    1993-09-01

    Polycystine radiolarians, phaeodarians, tintinnids, tintinnid cysts and mollluscs (chiefly pteropod protoconchae) were counted in 20 time-series sediment trap samples retrieved in the eastern equatorial Atlantic (01°47.5'N, 11°07.6'W) at 853 m, between 1 March 1989 and 16 March 1990. In addition, polycystine species were identified. Mean annual fluxes, in ind. m -2 day -1, were: polycystines: 28,446; tintinnids: 27,275; foraminifers: 17,816; tintinnid (and probably other ciliates') cysts: 14,632; phaeodarians: 1370; and molluscs: 1192. These yields are noticeably higher than most previous data from various areas of the World Ocean, which in part is attributed to the inclusion of particles <10 μm. Only 3% of the polycystines and 30% of the phaeodarians were represented by "live" cells (i.e. with protoplasm). Indirect evidence suggests that foraminifer and radiolarian fluxes probably reflect fairly well their abundances in the plankton; for the tintinnids, however, only about 0.1% of the loricae 853 m intact. With the exception of tintinnid cysts and molluscs, fluxes for the groups counted were clearly correlated with total mass and organic carbon flux and, presumably, with primary production; in the study area both peak in July-September and in January-April. It is concluded that tintinnid high reproduction rates are responsible for tightest associations between the output of their loricae and total flux. The fluxes of Foraminifera and Radiolaria, which have longer life spans ( ca 1 month), are more loosely correlated with total flux, and often show peaks approximately 20-40 days after those of the latter. Molluscs, with life spans of ca 1 year, do not correlate with total flux. Juvenile Nassellaria comprised up to 44% of all polycystine shells (mean 25%). In total, 187 polycystine taxa were recorded, yet only six accounted for more than 50% of all the individuals identified. Although some species did vary in relative abundance in association with total and

  19. Selective dissolution of siliceous microfossils observed in a box core from the north-east equatorial Pacific

    USGS Publications Warehouse

    Kadko, D.; Blueford, J.R.; Burckle, L.H.; Barron, J.

    1983-01-01

    A box core taken at 11??50.3??? N and 137??28.2??? W in the Central Pacific manganese nodule province was studied to determine the pattern of diatom and radiolarian preservation with depth in the sediment, as well as to observe downcore variations in clay mineralogy. We observed marked deterioration of the siliceous microfossils within the upper 30 cm of this sediment; over this depth interval the Quaternary diatoms disappear first, followed deeper downcore by the dissolution of Quaternary radiolarians. Tertiary microfossils in general were the most corrosion resistant, and the residual microfossil assemblage in the lower part of the core consisted of fragmented, robust Tertiary forms. Consequently, the apparent biostratigraphical age of the sediment appeared much greater than the age suggested by mineralogical and radioisotopic data. ?? 1983 Nature Publishing Group.

  20. Palaeomagnetic results from the Palaeozoic of Istanbul: A hypothesis for Remagnetization

    NASA Astrophysics Data System (ADS)

    Lom, Nalan; Domeier, Mathew; Ülgen, Semih Can; İşseven, Turgay; Celal Şengör, Ali Mehmet

    2016-04-01

    The Istanbul Zone in northwestern Turkey is a part of a larger continental fragment called the Rhodope-Pontide Fragment. The Istanbul Zone differs from its surroundings by its continuous, well-developed sedimentary sequence extending from the early-medial Ordovician to the early Carboniferous. The İstanbul Zone has a complicated deformation history related to the Hercynide (or Scythide), Cimmeride and Alpide orogenies. Although the region of Istanbul shows essentially no metamorphism and only a weak cleavage development, constraining the entire history of the deformation in the İstanbul Zone marginal fold and thrust belt is a difficult task, primarily due to the multiple deformation phases. But yet it is not impossible. The Palaeozoic sequence is cut by late Cretaceous plutonics together with dacitic and andesitic dykes. This arc magmatism is ascribed to the north-dipping subduction of the Neo-Tethyan ocean along the İzmir-Ankara-Erzincan suture. The Palaeozoic sequence is unconformably overlain by Permian and younger sedimentary strata. In this study a total of 523 samples were obtained from 48 sites around İstanbul and Kocaeli. 465 samples collected from Palaeozoic sedimentary rocks and 58 samples belong to the dykes that cut these sediments. Specimens were demagnetized in the laboratory by using both AF and thermal treatments depending on their effectiveness. After demagnetization treatments, 290 specimens showed stable demagnetization patterns and majority of these samples have a characteristic remanent magnetization component close to the present day geomagnetic field. Demagnetization studies demonstrate variable degrees of overprinting in a large number of samples. After the application of the tilt correction, %70 of the specimens failed the fold test at site level (early Ordovician siltstones; late Silurian-early Devonian limestones; late Devonian limestones; early Carboniferous turbidites). Rest of them clearly got scattered with increasing α95 and

  1. Paleo-ocean environments before and after the Ordovician glaciation and the correlation with heterogeneous marine black shale: a stratigraphic case study of Wufeng-Longmaxi formation in Fuling, Sichuan basin, SW China

    NASA Astrophysics Data System (ADS)

    Lu, Yangbo; Hao, Fang; Lu, Yongchao

    2017-04-01

    The discovery of Fuling gas field in the Sichuan basin led China shale gas exploration to an unprecedented boom. The most important shale gas plays are the upper Ordovician Wufeng formation and Lower Silurian Longmaxi formation which demonstrate intriguing characteristics which are comprising of stable regional distribution, high abundance of organic matter, high thermal maturity and high brittle mineral content etc. As the Ordovician-Silurian transition was a critical interval in Earth's history marked by dramatic climatic, oceanic, and biological turnovers; these two advantageous organic rich shale deposited before and after Hirnantian glaciation are showing differences in many aspects. In this study, the stratigraphy and lithofacies within the stratigraphy framework of the upper Ordovician Wufeng formation and Lower Silurian Longmaxi formation in Fuling were quantitatively analyzed based on outcrops, cores, well logs data, and geochemical proxies. A total of three third-order sequences were divided based on the recognition of four third-order boundaries. The Wufeng Formation is equivalent to a third-order sequence and is subdivided into a transgressive system tract (TST) (black shale of lower Wufeng Formation) and a highstand system tract (HST) (Guanyinqiao Member of upper Wufeng Formation). Long-1 Member is equivalent to a third-order sequence and is subdivided into a TST, an early highstand system tract (EHST) and a late highstand system tract (LHST); Long-2 and Long-3 Member are combined to be one third-order sequence and is subdivided into a lowstand system tract (LST), a TST and a HST. Sequence development and sedimentary environment characteristics were analyzed within each system tract unit. TOC% was correlated to V/Cr and EF-Ni respectively within each system tract unit, suggesting paleoproductivity and water redox condition are the main controlling factors of organic enrichment and its preservation. The heterogeneity in shale lithofacies throughout the

  2. Geologic Map of the Weaverville 15' Quadrangle, Trinity County, California

    USGS Publications Warehouse

    Irwin, William P.

    2009-01-01

    terrane is faulted against the west edge of the Central Metamorphic terrane, and its northerly trend is disrupted by major left-lateral offsets along generally west-northwest-trending faults. The serpentinized peridotite-gabbro complex that forms the western base of the terrane is the Permian North Fork ophiolite, which to the east is overlain by broken formation of mafic-volcanic rocks, red chert, siliceous tuff, argillite, minor limestone, and clastic sedimentary rocks. The chert and siliceous tuff contain radiolarians of Permian and Mesozoic ages, and some are as young as Early Jurassic (Pliensbachian). Similar Pliensbachian radiolarians are found in Franciscan rocks of the Coast Ranges. The Eastern Hayfork terrane is broken formation and melange of mainly chert, sandstone, argillite, and various exotic blocks. The cherts yield radiolarians of Permian and Triassic ages but none of clearly Jurassic age. Limestone bodies of the Eastern Hayfork terrane contain Permian microfaunas of Tethyan affinity. The Western Hayfork terrane, exposed only in a small area in the southwestern part of the quadrangle, consists dominantly of mafic tuff and dark slaty argillite. Sparse paleontologic data indicate a Mesozoic age for the strata. The terrane includes small bodies of diorite that are related to the nearby Wildwood pluton of Middle Jurassic age and probably are related genetically to the stratified rocks. The terrane is interpreted to be the accreted remnants of a Middle Jurassic volcanic arc. Shortly after intrusion by Shasta Bally batholith (approx. 136 Ma), much of the southern half of the Weaverville quadrangle was overlapped by Lower Cretaceous, dominantly Hauterivian, marine strata of the Great Valley sequence, and to a lesser extent later during Oligocene and (or) Miocene time by fluvial and lacustrine deposits of the Weaverville Formation. This map of the Weaverville Quadrangle is a digital rendition of U.S. Geological Survey Miscellaneous Field

  3. The Anarraaq Zn-Pb-Ag and barite deposit, northern Alaska: Evidence for replacement of carbonate by barite and sulfides

    USGS Publications Warehouse

    Kelley, K.D.; Dumoulin, Julie A.; Jennings, S.

    2004-01-01

    The Anarraaq deposit in northern Alaska consists of a barite body, estimated to be as much as 1 billion metric tons, and a Zn-Pb-Ag massive sulfide zone with an estimated resource of about 18 Mt at 18 percent Zn, 5.4 percent Pb, and 85 g/t Ag. The barite and sulfide minerals are hosted by the uppermost part of the Mississippian Kuna Formation (Ikalukrok unit) that consists of carbonaceous and siliceous mudstone or shale interbedded with carbonate. The amount of interbedded carbonate in the Anarraaq deposit is atypical of the district as a whole, comprising as much as one third of the section. The total thickness of the Ikalukrok unit is considerably greater in the area of the deposit (210 to almost 350 m) than to the north and south (maximum of 164 m). The mineralized zone at Anarraaq is lens shaped and has a relatively flat top and a convex base. It also ranges greatly in thickness, from a few meters to more than 100 m. Textures of some of the carbonate layers are distinctive, consisting of nodules within siliceous mudstone or layers interbedded with shale. Many of the layers contain calcitized sponge spicules or radiolarians in a carbonate matrix. Textures of barite and sulfide minerals mimic those of carbonate and provide unequivocal evidence that replacement of precursor carbonate was an important process. Barite and sulfide textures include either nodular, bladed grains of various sizes that resemble spicules (observed only with iron sulfides) or well-rounded forms that are replaced radiolarians. Mineralization at Anarraaq probably occurred in a fault-bounded Carboniferous basin during early diagenesis in the shallow subsurface. The shape and size of the mineralized body suggest that barite and sulfides replaced calcareous mass flow deposits in a submarine channel. The distribution of biogenic and/or early diagenetic silica may have served as impermeable barriers to the fluids, thereby focusing and controlling fluid flow through unreplaced carbonate layers

  4. Siberia, the wandering northern terrane, and its changing geography through the Palaeozoic

    NASA Astrophysics Data System (ADS)

    Cocks, L. Robin M.; Torsvik, Trond H.

    2007-05-01

    The old terrane of Siberia occupied a very substantial area in the centre of today's political Siberia and also adjacent areas of Mongolia, eastern Kazakhstan, and northwestern China. Siberia's location within the Early Neoproterozoic Rodinia Superterrane is contentious (since few if any reliable palaeomagnetic data exist between about 1.0 Ga and 540 Ma), but Siberia probably became independent during the breakup of Rodinia soon after 800 Ma and continued to be so until very near the end of the Palaeozoic, when it became an integral part of the Pangea Supercontinent. The boundaries of the cratonic core of the Siberian Terrane (including the Patom area) are briefly described, together with summaries of some of the geologically complex surrounding areas, and it is concluded that all of the Palaeozoic underlying the West Siberian Basin (including the Ob-Saisan Surgut area), Tomsk Terrane, Altai-Sayan Terranes (including Salair, Kuznetsk Alatau, Batenov, Kobdin and West Sayan), Ertix Terrane, Barguzin Terrane, Tuva-Mongol Terrane, Central Mongolia Terrane Assemblage, Gobi Altai and Mandalovoo Terranes, Okhotsk Terrane and much of the Verkhoyansk-Kolyma region all formed parts of peri-Siberia, and thus rotated with the main Siberian Craton as those areas were progressively accreted to the main Siberian Terrane at various times during the latest Neoproterozoic and Palaeozoic. The Ertix Terrane is a new term combining what has been termed the "Altay Terrane" or "NE Xinjiang" area of China, and the Baytag, Baaran and Bidz terranes of Mongolia. The Silurian Tuvaella brachiopod fauna is restricted only to today's southern parts of peri-Siberia. Thus, allowing for subsequent rotation, the fauna occurs only in the N of the Siberian Terrane, and, as well as being a helpful indicator of what marginal terranes made up peri-Siberia, is distinctive as being the only Silurian fauna known from northern higher latitudes globally. In contrast, the other terranes adjacent to peri

  5. Regional analysis of spiculite faunas in the permian phosphoria basin: Implications for paleoceanography

    USGS Publications Warehouse

    Murchey, Benita L.

    2004-01-01

    During the Permian, the relative abundance and apparent diversity of siliceous sponges expanded over a wide range of depths in the basins from Nevada and Idaho to the open ocean. Radiolarian preservation and apparent diversity increased in the deeper Cordilleran basins as well. In the Arctic regions, significant sponge spiculites were deposited in epicratonic basins. At the same time that siliceous sponge populations expanded along the northwestern margin of Pangea, warm-water carbonate producers disappeared. Suppression of carbonate-producing organisms along the margin was critical to the accu- mulation and preservation of both the demosponge spiculites in the Eastern Belt and the spicule-rich argillites of the Central Belt. Vigorous thermohaline circulation was the major control on the paleobiogeography of the late Early, Middle, and early Late Permian along northwest Pangea. It was driven by cold, nutrient- and oxygen-rich northern waters and it produced a coastal current that swept down the margin of the supercontinent. The upwelling associated with deposition of world-class phosphorites in the Phosphoria basin was a part of this larger oceanographic system.

  6. Zirconology of lherzolites in the Nurali Massif

    NASA Astrophysics Data System (ADS)

    Krasnobaev, A. A.; Rusin, A. I.; Anfilogov, V. N.; Valizer, P. M.; Busharina, S. V.; Medvedeva, E. V.

    2017-06-01

    The age trend (SHRIMP U/Pb) of the evolution of zircon is obtained for the first time in lherzolites of the Nurali Massif. Zircons are subdivided into groups by the crystallomorphological and geochemical features. These specific features in zircon development are confirmed by the age dates. Precambrian dates (no younger than 1190 Ma) correspond to mantle sources of the lherzolite block. The Early Silurian (445-448 and 439-440 Ma) wass the time of lherzolite magmatism of 10-15 Ma in duration. The Middle Devonian (382.9 ± 8.7 Ma) corresponded to postmagmatic processes related to the effect of gabbro-diorite intrusions crowning in the Nurali Massif.

  7. Deformational history of part of the Acatlán Complex: Late Ordovician Early Silurian and Early Permian orogenesis in southern Mexico

    NASA Astrophysics Data System (ADS)

    Malone, J. R.; Nance, R. D.; Keppie, J. D.; Dostal, J.

    2002-10-01

    The Paleozoic Acatlán Complex of southern Mexico comprises polydeformed metasedimentary, granitoid, and mafic-ultramafic rocks variously interpreted as recording the closure of the Iapetus, Rheic, and Ouachitan Oceans. The complex is tectonically juxtaposed on its eastern margin against Grenville-age gneisses (Oaxacan Complex) that are unconformably overlain by Lower Paleozoic strata containing fossils of Gondwanan affinity. A thick siliciclastic unit (Chazumba and Cosoltepec Formations) at the base of the complex is considered part of a Lower Paleozoic accretionary prism with a provenance that isotopically resembles the Oaxacan Complex. This unit is tectonically overridden by a locally eclogitic mafic-ultramafic unit interpreted as a westward-obducted ophiolite, the emplacement of which was synchronous with mylonitic granitoid intrusion at ca. 440 Ma. Both units are unconformably overlain by a deformed volcano-sedimentary sequence (Tecomate Formation) attributed to a volcanic arc of presumed Devonian age. Deformed granitoids in contact with this sequence have been dated at ca. 371 (La Noria granite) and 287 Ma (Totoltepec pluton). Three phases of penetrative deformation (D 1-3) affect the Cosoltepec Formation; the last two correlate with two penetrative deformational phases that affect the Tecomate Formation. D 1 is of unknown kinematics but predates deposition of the Tecomate Formation and likely records obduction at ca. 440 Ma (Acatecan orogeny). A folded foliation in the Totoltepec pluton appears to record both deformational phases in the Tecomate Formation, bracketing D 2 and D 3 between 287 Ma and the deposition of the nonconformably overlying Leonardian Matzitzi Formation. D 2 records north-south dextral transpression and south-vergent thrusting and is attributed to the collision of Gondwana and southern Laurentia (Ouachitan orogeny) at ca. 290 Ma, the kinematics being consistent with the northward motion of Mexico that is required by most continental reconstructions for the final assembly of Pangea. D 3, which produced broadly north-south, upright folds, is also attributed to this collision and likely followed D 2 closely in the latest Paleozoic.

  8. Molecular Probes in Marine Ecology: Concepts, Techniques and Applications

    DTIC Science & Technology

    1990-03-12

    MUM genotypes. 7/11 Gisele Muller- Symbioses between cnidarians and zooxanthellae . Parker 7/12 Dror Angel The ecology of colonial radiolarians. 7/13...alaae, coral. covepods. microflaaellates. dinoflacellates) (Rob Rovan). Isolate organisms and prepare DNA. Amplify rDNA usina universal (or zooxanthella

  9. Biostratigraphical dating of the Thornton Fossil Konservat-Lagerstätte, Silurian, Illinois, USA

    USGS Publications Warehouse

    Loydell, David K.; Mullins, Gary L.; Mannik, Peep; Mikulic, Donald G.; Kluessendorf, Joanne

    2002-01-01

    Graptoloid graptolites, conodonts and chitinozoans from the lower part of the Racine Dolomite Formation at the Material Services Corporation quarry at Thornton indicate that the Fossil Konservat-Lagerstätte here is of late Sheinwoodian (early Wenlock) age. It is thus of an age approximately midway between those of the other Midwest Lagerstätten: within the Brandon Bridge Formation at Waukesha (Telychian), and the Mississinewa Shale (Gorstian) and Lecthaylus Shale (Gorstian). Conodonts indicate that the Fossil Konservat-Lagerstätte at Thornton corresponds to the ‘post Kockelella walliseri interregnum’ sensu Jeppsson (1997, Transactions of the Royal Society of Edinburgh: Earth Sciences88: 91–114)

  10. Paleozoic oil/gas shale reservoirs in southern Tunisia: An overview

    NASA Astrophysics Data System (ADS)

    Soua, Mohamed

    2014-12-01

    During these last years, considerable attention has been given to unconventional oil and gas shale in northern Africa where the most productive Paleozoic basins are located (e.g. Berkine, Illizi, Kufra, Murzuk, Tindouf, Ahnet, Oued Mya, Mouydir, etc.). In most petroleum systems, which characterize these basins, the Silurian played the main role in hydrocarbon generation with two main 'hot' shale levels distributed in different locations (basins) and their deposition was restricted to the Rhuddanian (Lllandovery: early Silurian) and the Ludlow-Pridoli (late Silurian). A third major hot shale level had been identified in the Frasnian (Upper Devonian). Southern Tunisia is characterized by three main Paleozoic sedimentary basins, which are from North to South, the southern Chotts, Jeffara and Berkine Basin. They are separated by a major roughly E-W trending lower Paleozoic structural high, which encompass the Mehrez-Oued Hamous uplift to the West (Algeria) and the Nefusa uplift to the East (Libya), passing by the Touggourt-Talemzane-PGA-Bou Namcha (TTPB) structure close to southern Tunisia. The forementioned major source rocks in southern Tunisia are defined by hot shales with elevated Gamma ray values often exceeding 1400 API (in Hayatt-1 well), deposited in deep water environments during short lived (c. 2 Ma) periods of anoxia. In the course of this review, thickness, distribution and maturity maps have been established for each hot shale level using data for more than 70 wells located in both Tunisia and Algeria. Mineralogical modeling was achieved using Spectral Gamma Ray data (U, Th, K), SopectroLith logs (to acquire data for Fe, Si and Ti) and Elemental Capture Spectroscopy (ECS). The latter technique provided data for quartz, pyrite, carbonate, clay and Sulfur. In addition to this, the Gamma Ray (GR), Neutron Porosity (ΦN), deep Resistivity (Rt) and Bulk Density (ρb) logs were used to model bulk mineralogy and lithology. Biostratigraphic and complete

  11. Geology and hydrocarbon potential of the Oued Mya basin, Algeria

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Benamrane, O.; Messaoudi, M.; Messelles, H.

    1993-09-01

    The Oued Mya hydrocarbon system is located in the Sahara basin. It is one of the best producing basins in Algeria, along with the Ghadames and Illizi basins. The stratigraphic section consists of Paleozoic and Mesozoic, and is about 5000 m thick. This intracratonic basin is limited to the north by the Toughourt saddle, and to the west and east it is flanked by regional arches, Allal-Tilghemt and Amguid-Hassi Messaoud, which culminate in the super giant Hassi Messaoud and Hassi R'mel hydrocarbon accumulations, respectively, producing oil from the Cambrian sands and gas from the Trissic sands. The primary source rockmore » in this basin is lower Silurian shale, with an average thickness of 50 m and a total organic carbon of 6% (14% in some cases). Results of maturation modeling indicate that the lower Silurian source is in the oil window. The Ordovician shales are also source rocks, but in a second order. Clastic reservoirs are in the Trissic sequence, which is mainly fluvial deposits with complex alluvial channels, and the main target in the basin. Clastic reservoirs in the lower Devonian section have a good hydrocarbon potential east of the basin through a southwest-northwest orientation. The Late Trissic-Early Jurassic evaporites that overlie the Triassic clastic interval and extend over the entire Oued Mya basin, are considered to be a super-seal evaporite package, which consists predominantly of anhydrite and halite. For paleozoic targets, a large number of potential seals exist within the stratigraphic column. This super seal does not present oil dismigration possibilities. We can infer that a large amount of the oil generated by the Silurian source rock from the beginning of Cretaceous until now still is not discovered and significantly greater volumes could be trapped within structure closures and mixed or stratigraphic traps related to the fluvial Triassic sandstones, marine Devonian sands, and Cambrian-Ordovician reservoirs.« less

  12. Permian age from radiolarites of the Hawasina nappes, Oman Mountains

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Wever, P.D.; Grissac C.B.; Bechennec, F.

    1988-10-01

    The Hawasina napper of the Oman Mountains yielded Permian radiolarians from cherts stratigraphically overlying a thick volcanic basement (Al Jil Formation) at the base of the Hamrat Duru Group. This fauna represents the first Permian radiolarians and radiolarites in the central and western Tethyan realm. A Permain age for pelagic sequences within the Hawasina Complex of Oman has major significance for regional paleogeographic reconstruction. A clear differentiation between platform (reefal sediments) and basin (radiolarites) from the base of the Late Permian (255 Ma) is implied. It suggests a flexure of the platform during Permian time; the present data implies thatmore » a zone of rifting was already developed adjacent to the northeast Gondwana platform margin during the Late Permian. The Hamrat Duru Basin corresponds to an opening intracontinental rift area (sphenochasm) between Arabia and northeast Gondwana, a reentrant of the paleo-Tethys.« less

  13. Lithofacies, age, depositional setting, and geochemistry of the Otuk Formation in the Red Dog District, northwestern Alaska

    USGS Publications Warehouse

    Dumoulin, Julie A.; Burruss, Robert A.; Blome, Charles D.

    2013-01-01

    Complete penetration of the Otuk Formation in a continuous drill core (diamond-drill hole, DDH 927) from the Red Dog District illuminates the facies, age, depositional environment, source rock potential, and isotope stratigraphy of this unit in northwestern Alaska. The section, in the Wolverine Creek plate of the Endicott Mountains Allochthon (EMA), is ~82 meters (m) thick and appears structurally uncomplicated. Bedding dips are generally low and thicknesses recorded are close to true thicknesses. Preliminary synthesis of sedimentologic, paleontologic, and isotopic data suggests that the Otuk succession in DDH 927 is a largely complete, albeit condensed, marine Triassic section in conformable contact with marine Permian and Jurassic strata. The Otuk Formation in DDH 927 gradationally overlies gray siliceous mudstone of the Siksikpuk Formation (Permian, based on regional correlations) and underlies black organic-rich mudstone of the Kingak(?) Shale (Jurassic?, based on regional correlations). The informal shale, chert, and limestone members of the Otuk are recognized in DDH 927, but the Jurassic Blankenship Member is absent. The lower (shale) member consists of 28 m of black to light gray, silty shale with as much as 6.9 weight percent total organic carbon (TOC). Thin limy layers near the base of this member contain bivalve fragments (Claraia sp.?) consistent with an Early Triassic (Griesbachian-early Smithian) age. Gray radiolarian chert dominates the middle member (25 m thick) and yields radiolarians of Middle Triassic (Anisian and Ladinian) and Late Triassic (Carnian-late middle Norian) ages. Black to light gray silty shale, like that in the lower member, forms interbeds that range from a few millimeters to 7 centimeters in thickness through much of the middle member. A distinctive, 2.4-m-thick interval of black shale and calcareous radiolarite ~17 m above the base of the member has as much as 9.8 weight percent TOC, and a 1.9-m-thick interval of limy to cherty

  14. Basin evolution and structural reconstruction of northeastern Morocco and northwestern Algeria

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Scott, S.

    1995-08-01

    The high plateau region of Morocco and northwestern Algeria contains a Permo-Triassic rift basin with over 8,000 meters of Paleozoic, Mesozoic and Tertiary sediments. The area exhibits many similarities to the prolific Triassic basins of neighboring Algeria. Previous impediments to exploration in the high plateau area focused on the inability to seismically image sub-salt, pre-Jurassic block faulted structures and the perceived lack of adequate source rocks. This study combined seismic and basin modelling techniques to decipher the pre-salt structures, interpret basin evolution, and access source rock potential. Large structural and stratigraphic features can now be discerned where Permo-Triassic block faultedmore » structures are overlain by thick Triassic-Jurassic mobile evaporate seals and sourced by underlying Paleozoic shales. Contrary to the last published reports, over 20 years ago, oil and gas generation appears to have been continuous in the Carboniferous since 350 ma. Migration directly from the Carboniferous shales to Triassic conglomerates is envisaged with adequate seals provided by the overlying Triassic-Jurassic evaporate sequence. An earlier rapid pulse of oil and gas generation between 300-340 ma from the Silurian source rocks was probably too early to have resulted in hydrocarbon accumulation in the primary Triassic targets but if reservoir is present in the Carboniferous section, then those strata may have been sourced by the Silurian shales.« less

  15. Geologic summary of the Appalachian Basin, with reference to the subsurface disposal of radioactive waste solutions

    USGS Publications Warehouse

    Colton, G.W.

    1962-01-01

    the older sequence is absent, the Early Cambrian sequence rests on the basement complex. Interbedded fine- to coarse-grained noncarbonate detrital rocks comprise the bulk of the sequence, but some volcanic and carbonate rocks are included. Next above is the Cambrian-Ordovician carbonate sequence which consists largely of limestone and dolomite. Some quartzose sandstone is present in the lower part in the western half of the basin, and much shale is present in the upper part in the southeast part of the basin. The next higher sequence is the Late Ordovician clastic sequence, which consists largely of shale, siltstone, and sandstone. Coarse-grained light-gray to red rocks are common in the sequence along the eastern side of the basin, whereas fine-grained dark-gray to black calcareous rocks are common along the west side. The Late Ordovician clastic sequence is overlain--unconformably in many places--by the Early Silurian clastic sequence. The latter comprises a relatively thin wedge of coarse-grained clastic rocks. Some of the most prolific oil- and gas-producing sandstones in the Appalachian basin are included. Among these are the 'Clinton' sands of Ohio, the Medina Sandstones of New York and Pennsylvania, and the Keefer or 'Big Six' Sandstone of West Virginia and Kentucky. Conformably overlying the Early Silurian clastic sequence is the Silurian-Devonian carbonate sequence, which consists predominantly of limestone and dolomite. It also contains a salt-bearing unit in the north-central part of the basin and a thick wedge of coarse-grained red beds in the northeastern part. The sequence is absent in much of the southern part of the basin. Large volumes of gas and much oil are obtained from some of its rocks, especially from the Oriskany Sandstone and the Huntersville Chert. The Silurian-Devonian carbonate sequence is abruptly overlain by the Devonian clastic sequence--a thick succession of interbedded shale, mudrock, siltstone, and sandstone. Colors range f

  16. Petrogenesis and tectonic implications of the Early Paleozoic granites in the western segment of the North Qilian orogenic belt, China

    NASA Astrophysics Data System (ADS)

    Wang, Nan; Wu, Cai-Lai; Lei, Min; Chen, Hong-Jie

    2018-07-01

    Early Paleozoic granitic magmatism in the North Qilian orogenic belt records a complete Wilson cycle and provides critical geological clues for unraveling the regional tectonic history. In this study, we report the results of zircon U-Pb ages, Hf isotopic analysis and systematic whole-rock geochemical data for the Late Ordovician Hongliuhe granite and Early Silurian Qingshan monzogranite in the western segment of the North Qilian orogenic belt to constrain their emplacement ages, petrogenesis, and regional evolution history. U-Pb dating reveals that the Hongliuhe granite was emplaced around 453-452 Ma, and the Qingshan monzogranite was emplaced about 440-438 Ma. A geochemical study shows that the two granites belong to the calc-alkaline to high-K calc-alkaline series. The Hongliuhe granite shows adakitic and peraluminous features, while the Qingshan monzogranite belongs to metaluminous to weak peraluminous granites. Zircons in the Hongliuhe granite show εHf(t) values ranging from -15.1 to +11.7 with two-stage Hf model ages (tDM2) of 687-2398 Ma, whereas zircons in the Qingshan monzogranite show εHf(t) values ranging from +5.7 to +11.0 with two-stage Hf model ages from 814 to 1057 Ma. The geochemical characteristics indicate that the Hongliuhe granite was a transitional I/S-type granite and was generated from a thickened lower crust with the addition of minor Paleo- to Mesoproterozoic crustal materials, which left a rutile + garnet + pyroxene ± plagioclase residue. The Qingshan monzogranite formed from the partial melting of mafic crust with minor mantle-derived materials, and the fractionation of Ti-bearing phases, apatite and pyroxene occurred during the magma's evolution, which left an amphibole and plagioclase residue. We infer that the Hongliuhe granite formed during the northward subduction of the North Qilian Ocean, while the Qingshan monzogranite was generated during the post-collision stage between the Qilian and Alxa blocks. This observation indicates

  17. Minimum age of the Neoproterozoic Seven Hundred Acre Island Formation and the tectonic setting of the Islesboro Formation, Islesboro block, Maine

    USGS Publications Warehouse

    Stewart, D.B.; Tucker, R.D.; Ayuso, R.A.; Lux, D.R.

    2001-01-01

    east by significant Late Silurian strike-slip faulting. The Late Silurian or Early Devonian Turtle Head dextral strike-slip fault separates the Islesboro block from the peri-Gondwanan St. Croix terrane to the west. The timing and nature of the movements of these faults are given from offsets of the isograds around the zircon-dated Late Silurian Sedgwick Granite (419.5 ?? 1.4 Ma) and South Penobscot Intrusive Suite (419.2 ?? 2.2 Ma). These terranes and others like them in Atlantic Canada make up a composite terrane that is different from the composite Avalonian terranes sensu stricto of southeastern New England and Atlantic Canada. The composite peri-Gondwanan terrane that included the Islesboro block was amalgamated with the margin of ancestral North America in the Silurian.

  18. Geology and hydrocarbon potential of the Hamada and Murzuq basins in western Libya

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Kirmani, K.U.; Elhaj, F.

    1988-08-01

    The Hamada and Murzuq intracratonic basins of western Libya form a continuation of the Saharan basin which stretches from Algeria eastward into Tunisia and Libya. The tectonics and sedimentology of this region have been greatly influenced by the Caledonian and Hercynian orogenies. Northwest- and northeast-trending faults are characteristic of the broad, shallow basins. The Cambrian-Ordovician sediments are fluvial to shallow marine. The Silurian constitutes a complete sedimentary cycle, ranging from deep marine shales to shallow marine and deltaic sediments. The Devonian occupies a unique position between two major orogenies. The Mesozoic strata are relatively thin. The Triassic consists of well-developedmore » continental sands, whereas the Jurassic and Cretaceous sediments are mainly lagoonal dolomites, evaporites, and shales. Silurian shales are the primary source rock in the area. The quality of the source rock appears to be better in the deeper part of the basin than on its periphery. The Paleozoic has the best hydrocarbon potential. Hydrocarbons have also been encountered in the Triassic and Carboniferous. In the Hamada basin, the best-known field is the El Hamra, with reserves estimated at 155 million bbl from the Devonian. Significant accumulations of oil have been found in the Silurian. Tlacsin and Tigi are two fields with Silurian production. In the Murzuq basin the Cambrian-Ordovician has the best production capability. However, substantial reserves need to be established before developing any field in this basin. Large areas still remain unexplored in western Libya.« less

  19. Paleozoic intrusive rocks from the Dunhuang tectonic belt, NW China: Constraints on the tectonic evolution of the southernmost Central Asian Orogenic Belt

    NASA Astrophysics Data System (ADS)

    Zhao, Yan; Sun, Yong; Diwu, Chunrong; Zhu, Tao; Ao, Wenhao; Zhang, Hong; Yan, Jianghao

    2017-05-01

    The Dunhuang tectonic belt (DTB) is of great importance for understanding the tectonic evolution of the southernmost Central Asian Orogenic Belt (CAOB). In this study, the temporal-spatial distribution, petrogenesis and tectonic setting of the Paleozoic representative intrusive rocks from the DTB were systematically investigated to discuss crustal evolution history and tectonic regime of the DTB during Paleozoic. Our results reveal that the Paleozoic magmatism within the DTB can be broadly divided into two distinct episodes of early Paleozoic and late Paleozoic. The early Paleozoic intrusive rocks, represented by a suite metaluminous-slight peraluminous and medium- to high-K calc-alkaline I-type granitoids crystallized at Silurian (ca. 430-410 Ma), are predominantly distributed along the northern part of the DTB. They were probably produced with mineral assemblage of eclogite or garnet + amphibole + rutile in the residue, and were derived from magma mixing source of depleted mantle materials with various proportions of Archean-Mesoproterozoic continental crust. The late Paleozoic intrusive rocks can be further subdivided into two stages of late Devonian stage (ca. 370-360 Ma) and middle Carboniferous stage (ca. 335-315 Ma). The former stage is predominated by metaluminous to slight peraluminous and low-K tholeiite to high-K calc-alkaline I-type granitic rocks distributed in the central part of the DTB. They were also generated with mineral assemblage of amphibolite- to eclogite-facies in the residue, and originated from magma source of depleted mantle materials mixed with different degrees of old continental crust. The later stage is represented by adakite and alkali-rich granite exposed in the southern part of the DTB. The alkali-rich granites studied in this paper were possibly produced with mineral assemblage of granulite-facies in the residue and were generated by partial melting of thickened lower continental crust. Zircon Hf isotopes and field distribution of

  20. Early Paleozoic dioritic and granitic plutons in the Eastern Tianshan Orogenic Belt, NW China: Constraints on the initiation of a magmatic arc in the southern Central Asian Orogenic Belt

    NASA Astrophysics Data System (ADS)

    Du, Long; Long, Xiaoping; Yuan, Chao; Zhang, Yunying; Huang, Zongying; Sun, Min; Zhao, Guochun; Xiao, Wenjiao

    2018-03-01

    Early Paleozoic dioritic and granitic plutons in the Eastern Tianshan Orogenic Belt (ETOB) have been studied in order to constraint the initiation of a magmatic arc formed in this region. Zircon U-Pb dating indicates that two dioritic plutons in the northern ETOB were generated in the Late Ordovician (452 ± 4 Ma) and the Early Silurian (442 ± 3 Ma), respectively. Diorites from the two plutons are characterized by enrichments in large ion lithophile elements (LILE) and highly incompatible elements, with depletions in high field strength elements (HSFE) displaying typical geochemical features of a subduction-related origin. They have positive εNd(t) values (+5.08-+6.58), relatively young Nd model ages (TDM = 0.71-1.08 Ga), with Ta/Yb (0.05-0.09) and Nb/Ta ratios (12.06-15.19) similar to those of depleted mantle, suggesting a juvenile mantle origin. Their high Ba/La (13.3-35.9), low Th/Yb (0.72-2.02), and relatively low Ce/Th (4.57-14.7) and Ba/Th (47.8-235) ratios indicate that these diorites were probably produced by partial melting of a depleted mantle wedge metasomatized by both subducted sediment-derived melts and slab-derived aqueous fluids. Zircon U-Pb dating of a granitic pluton in the northern ETOB yielded a Late Ordovician intrusion age of 447 ± 5 Ma. Granites from this pluton show calc-alkaline compositions with geochemical characteristics of I-type granites. They also show positive εNd(t) values (+6.49-+6.95) and young Nd model ages (TDM = 0.69-0.87 Ga), indicating that the granites were most likely derived from juvenile lower crust. Our new dating results on the dioritic and granitic plutons suggest that arc-type magmatism in the northern ETOB began prior to or at the Late Ordovician (452-442 Ma). In addition, north-dipping subduction of the Kangguertage oceanic lithosphere may account for the arc-type magmatism and the geodynamic process of the ETOB in the Early Paleozoic.

  1. Hydrology of carbonate aquifers in southwestern Linn County and adjacent parts of Benton, Iowa, and Johnson Counties, Iowa

    USGS Publications Warehouse

    Wahl, Kenneth; Bunker, Bill J.

    1986-01-01

    Water analyses from the Devonian and Silurian aquifers indicate that they are of similar chemical quality at most locations in the study area. However, they may commonly contain concentrations of sulfate that exceed 1,000 mil grams per liter. Dissolved-solids concentrations as much as 2,350 milligrams per liter occur in the Silurian aquifer in the western and southwestern part of the study area. Water from the Quaternary aquifer generally is suitable for most uses and dissolved-solids concentrations generally are less than 750 milligrams per liter.

  2. Late Paleozoic transpression in Buenos Aires and northeast Patagonia ranges, Argentina

    NASA Astrophysics Data System (ADS)

    Rossello, E. A.; Massabie, A. C.; López-Gamundí, O. R.; Cobbold, P. R.; Gapais, D.

    1997-12-01

    Paleozoic sediments are present in three regions in eastern central Argentina: (1) the Sierras Australes of Buenos Aires, (2) Sierras Septentrionales of Buenos Aires and (3) Northeast Patagonia. All of these deposits share a common deformational imprint imparted by late Paleozoic Gondwanan deformation. Exposures of these rocks are scattered, variably deformed, and isolated by younger sediments deposited in basins related to the Mesozoic through Tertiary opening of the South Atlantic such as the offshore Colorado Basin. The Sierras Australes of Buenos Aires outcrops are the best preserved. They are mostly located along the Sierras Australes foldbelt, with minor outliers distributed in the adjacent Claromec-basin. The Tunas Formation (early-early late? Permian) is the uppermost unit of the Pillahuincó Group (late Carboniferous-Permian) and is crucial to the understanding of the tectono-sedimentary evolution of the region during the late Paleozoic. The underlying units of the Pillahuincó Group (Sauce Grande, Piedra Azul and Bonete Formations) exhibit a depositional and compositional history characterized by glaciomarine sedimentation and postglacial transgression. They are also characterized by rather uniform quartz-rich compositions indicative of a cratonic provenance from the La Plata craton to the NE. In contrast, the sandstone-rich Tunas Formation has low quartz contents, and abundant volcanic and metasedimentary fragments; paleocurrents are consistently from the SW. Glassrich tuffs are interbedded with sandstone in the upper half of the Tunas Formation. The age of the deformation in the Sierras Australes is Permian and early-middle Triassic. This is based on metamorphic events indicated by formation of illite at 282 ± 3 Ma, 273 ± 8 Ma, 265 ± 3 Ma, and 260 ± 3 Ma ( {K}/{Ar} illite) in the Silurian Curamalal Group. Evidence of syntectonic magmatism is provided by a radiometric date of 245 ± 12 Ma ( {K}/{Ar} hornblende) for the López Lecube Granite

  3. Epipelagic mesozooplankton succession and community structure over a marine ouffall area in the northeastern South China Sea.

    PubMed

    Tseng, Li Chun; Kumar, Ram; Dahms, Hans Uwe; Chen, Chun Te; Chen, Qing Chao; Hwang, Jiang Shiou

    2008-05-01

    This study analyses distribution and abundance patterns of mesozooplankton communities at 13 stations in the coastal waters over a marine outfall area in the northeastern South China Sea. Cruises were conducted in March, June and September 2002, and plankton samples were collected with a 333 microm North Pacific net. The Mesozooplankton was dominated by calanoid Copepods, Cladocera, Chaetognatha and Pteropoda. Stations located near the entrance of the harbor provided a relatively higher abundance of Noctilucales and Radiolarians. In total, 20 zooplankton groups were identified in which, Calanoida, Cladocera, Chaetognatha, Pteropoda, Poecilostomatoida and Appendicularia comprised 92.77% of the total zooplankton abundance. Copepoda dominated in all three cruises, comprising 65.32% of the total mesozooplankton abundance. Samples collected in June recorded higher mesozooplankton abundance than March and September samples. Onshore stations recorded higher BOD values, higher abundance of Noctilucales and Radiolarians and a relativelylower abundance of the overall mesozooplankton. Total mesozooplankton abundance did not correlate significantly with temperature, pH, or dissolved oxygen, but correlated negatively with BOD.

  4. Visual observations of the vertical distribution of plankton throughout the water column above Broken Spur vent field, Mid-Atlantic Ridge

    NASA Astrophysics Data System (ADS)

    Vereshchaka, A. L.; Vinogradov, G. M.

    1999-09-01

    Visual observations were made in September 1997 during the 39 cruise of R/V "Akademik Mstislav Keldysh" with 2 deep-sea manned submersibles "Mir" aboard. During 4 dives the following plankton countings were made: 3 vertical throughout the water column during the day, 2 vertical in the upper 1000 m at night, and 1 oblique in the plume area during the day. Biomass profiles are represented for each dive for all abundant animal groups: copepods, euphausiids+decapods+mysids, chaetognaths, medusae, ctenophores, siphonophores, cyclothones, myctophides, radiolarians, and the total zooplankton. Plankton distribution shows 2 aggregations, one within the main pycnocline and the other near the plume; Gelatinous animals and radiolarians dominate in both aggregations by biomass and make a significant contribution to the plankton biomass throughout the water column. Oblique counting indicates the presence of aggregations of animals near the upper and lower borders of the plume and biomass depletion within the plume core.

  5. Early tectonic evolution of the Thomson Orogen in Queensland inferred from constrained magnetic and gravity data

    NASA Astrophysics Data System (ADS)

    Spampinato, Giovanni P. T.; Betts, Peter G.; Ailleres, Laurent; Armit, Robin J.

    2015-05-01

    The crustal architecture as well as the kinematic evolution of the Thomson Orogen in Queensland is poorly resolved because the region is concealed under thick Phanerozoic sedimentary basins and the basement geology is known from limited drill holes. Combined potential field and seismic interpretation indicates that the Thomson Orogen is characterized by prominent regional NE- and NW-trending structural grain defined by long wavelength and low amplitude geophysical anomalies. The 'smooth' magnetic signature is interpreted to reflect deeply buried source bodies in the mid- to lower crust. Short wavelength positive magnetic features that correlate with negative gravity anomalies are interpreted to represent shallower granitic intrusions. They appear to be focused along major fault zones that might have controlled the locus for magmatism. The eastern Thomson Orogen is characterized by a prominent NE structural grain and orthogonal faults and fold interference patterns resulting in a series of troughs and highs. The western Thomson Orogen consists of a series of NW-trending structures interpreted to reflect reverse faults. Sedimentation and basin development are interpreted to have initiated in the Neoproterozoic to Early Cambrian during E-W- to ENE-WSW extension, possibly related to the Rodinia break-up. This extensional event was followed by Late Cambrian shortening recorded in the Maneroo Platform and the Diamantina River Domain which possibly correlates with the Delamerian Orogeny. Renewed deposition and volcanism occurred during the Ordovician and may have continued until Late Silurian, resulting in thinned Proterozoic basement crust and extensive basin systems that formed in a distal continental back-arc environment. Our interpretation places the Thomson Orogen to the west of the Neoproterozoic passive margin preserved in the Anakie Inlier. The region is likely to represent the internal extensional architecture during the Rodinia break-up that has been

  6. Ichnology applied to sequence stratigraphic analysis of Siluro-Devonian mud-dominated shelf deposits, Paraná Basin, Brazil

    NASA Astrophysics Data System (ADS)

    Sedorko, Daniel; Netto, Renata G.; Savrda, Charles E.

    2018-04-01

    Previous studies of the Paraná Supersequence (Furnas and Ponta Grossa formations) of the Paraná Basin in southern Brazil have yielded disparate sequence stratigraphic interpretations. An integrated sedimentological, paleontological, and ichnological model was created to establish a refined sequence stratigraphic framework for this succession, focusing on the Ponta Grossa Formation. Twenty-nine ichnotaxa are recognized in the Ponta Grossa Formation, recurring assemblages of which define five trace fossil suites that represent various expressions of the Skolithos, Glossifungites and Cruziana ichnofacies. Physical sedimentologic characteristics and associated softground ichnofacies provide the basis for recognizing seven facies that reflect a passive relationship to bathymetric gradients from shallow marine (shoreface) to offshore deposition. The vertical distribution of facies provides the basis for dividing the Ponta Grossa Formation into three major (3rd-order) depositional sequences- Siluro-Devonian and Devonian I and II-each containing a record of three to seven higher-order relative sea-level cycles. Major sequence boundaries, commonly coinciding with hiatuses recognized from previously published biostratigraphic data, are locally marked by firmground Glossifungites Ichnofacies associated with submarine erosion. Maximum transgressive horizons are prominently marked by unbioturbated or weakly bioturbated black shales. By integrating observations of the Ponta Grossa Formation with those recently made on the underlying marginal- to shallow-marine Furnas Formation, the entire Paraná Supersequence can be divided into four disconformity-bound sequences: a Lower Silurian (Llandovery-Wenlock) sequence, corresponding to lower and middle units of the Furnas; a Siluro-Devonian sequence (?Pridoli-Early Emsian), and Devonian sequences I (Late Emsian-Late Eifelian) and II (Late Eifelian-Early Givetian). Stratigraphic positions of sequence boundaries generally coincide with

  7. Bedrock Geologic Map of the Old Lyme Quadrangle, New London and Middlesex Counties, Connecticut

    USGS Publications Warehouse

    Walsh, Gregory J.; Scott, Robert B.; Aleinikoff, John N.; Armstrong, Thomas R.

    2009-01-01

    The bedrock geology of the Old Lyme quadrangle consists of Neoproterozoic and Permian gneisses and granites of the Gander and Avalon terranes, Silurian metasedimentary rocks of the Merrimack terrane, and Silurian to Devonian metasedimentary rocks of uncertain origin. The Avalon terrane rocks crop out within the Selden Neck block, and the Gander terrane rocks crop out within the Lyme dome. The Silurian to Devonian rocks crop out between these two massifs. Previous mapping in the Old Lyme quadrangle includes the work by Lawrence Lundgren, Jr. Lundgren's work provides an excellent resource for rock descriptions and detailed modal analyses of rock units that will not be duplicated in this current report. New research that was not covered in detail by Lundgren is the focus of this report and includes (1) evaluation of the rocks in the core of the Lyme dome in an effort to subdivide units in this area; (2) structural analysis of foliations and folds in and around the Lyme dome; (3) geochronology of selected units within the Lyme dome; and (4) analysis of joints and the fracture properties of the rocks.

  8. Evidence for marine microfossils from amber.

    PubMed

    Girard, Vincent; Schmidt, Alexander R; Saint Martin, Simona; Struwe, Steffi; Perrichot, Vincent; Saint Martin, Jean-Paul; Grosheny, Danièle; Breton, Gérard; Néraudeau, Didier

    2008-11-11

    Amber usually contains inclusions of terrestrial and rarely limnetic organisms that were embedded in the places were they lived in the amber forests. Therefore, it has been supposed that amber could not have preserved marine organisms. Here, we report the discovery amber-preserved marine microfossils. Diverse marine diatoms as well as radiolarians, sponge spicules, a foraminifer, and a spine of a larval echinoderm were found in Late Albian and Early Cenomanian amber samples of southwestern France. The highly fossiliferous resin samples solidified approximately 100 million years ago on the floor of coastal mixed forests dominated by conifers. The amber forests of southwestern France grew directly along the coast of the Atlantic Ocean and were influenced by the nearby sea: shells and remnants of marine organisms were probably introduced by wind, spray, or high tide from the beach or the sea onto the resin flows.

  9. Limestone and chert in tectonic blocks from the Esk Head subterrane, South Island, New Zealand

    USGS Publications Warehouse

    Silberling, Norman J.; Nichols, K.M.; Bradshaw, J.D.; Blome, C.D.

    1988-01-01

    The Esk Head subterrane is a continuous belt, generally 10-20 km wide, of tectonic melange and broken formation on the South Island of New Zealand. This subterrane separates older and younger parts of the Torlesse terrane which is an extensive accretionary prism composed mostly of quartzo-feldspathic, submarine-fan deposits ranging from Permian to Early Cretaceous in age. The Esk Head subterrane of the Torlesse is especially informative because it includes within it conspicuous tectonic blocks of submarine basalt and a variety of basalt-associated seamount and sea-floor limestones and cherty rocks thought to be representative of the subducted plate. Paleogeographic inferences drawn from megafossils, bioclasts, and radiolarians, as well as from carbonate cements, indicate deposition of the oceanic sedimentary rocks at paleolatitudes somewhat lower than that of the New Zealand part of the Gondwana margin, but higher than paleoequatorial latitudes. -Authors

  10. Bedrock Geology and Asbestos Deposits of the Upper Missisquoi Valley and Vicinity, Vermont

    USGS Publications Warehouse

    Cady, Wallace Martin; Albee, Arden Leroy; Chidester, A.H.

    1963-01-01

    The upper Missisquoi Valley and vicinity as described in this report covers an area of about 250 square miles at the headwaters of the Missisquoi River in north-central Vermont. About 90 percent of the area is forested and the remainder is chiefly farm land. The topography reflects the geologic structure and varied resistance of the bedrock to erosion. Most of the area is on the east limb of the Green Mountain anticlinorium, which is the principal structural feature of Vermont. The bedrock is predominantly sedimentary and volcanic rock that has been regionally metamorphosed. It was intruded before metamorphism by mafic and ultramafic igneous rocks, and after metamorphism by felsic and mafic igneous rocks. The metamorphosed sedimentary and volcanic rocks range in age from Cambrian(?) to Middle Silurian, the intrusive igneous rocks from probably Late Ordovician to probably late Permian. Metamorphism and principal folding in the region occurred in Middle Devonian time. The metamorphosed sedimentary and volcanic rocks make up a section at least 25,000 feet thick and can be divided into nine formations. The Hazens Notch formation of Cambrian(?) and Early Cambrian age is characterized by carbonaceous schist. It is succeeded in western parts of the area by the Jay Peak formation of Early Cambrian age, which is chiefly a schist that is distinguished by the general absence of carbonaceous zones; in central parts of the area the Hazens Notch formation is followed by the Belvidere Mountain amphibolite, probably the youngest of the formations of Early Cambrian age. The Ottauquechee formation, composed of carbonaceous phyllite and quartzite, and phyllitic graywacke, is of Middle Cambrian age. The Stowe formation of Late Cambrian(?) and Early(?) Ordovician age overlies the Ottauquechee and is predominantly noncarbonaceous schist, though it also contains greenstone and carbonaceous schist and phyllite. The Umbrella Hill formation of Middle Ordovician age is characteristically a

  11. Geological fieldwork in the Libyan Sahara: A multidisciplinary approach

    NASA Astrophysics Data System (ADS)

    Meinhold, Guido; Whitham, Andrew; Howard, James P.; Morton, Andrew; Abutarruma, Yousef; Bergig, Khaled; Elgadry, Mohamed; Le Heron, Daniel P.; Paris, Florentin; Thusu, Bindra

    2010-05-01

    Libya is one of the most hydrocarbon-rich countries in the world. Its large oil and gas reserves make it attractive to international oil and gas companies, which provide the impetus for field-based research in the Libyan Sahara. North Africa is made up of several enormous intracratonic basins, two of which are found in southern Libya: the Murzuq Basin, in the southwest, and the Kufra Basin, in the southeast, separated by the Tibesti Massif. Both basins are filled with Palaeozoic and Mesozoic clastic sedimentary rocks reaching up to 5 km in thickness. These basins developed from the Cambrian onwards following an earlier period of orogenesis (the Panafrican Orogeny) in the Neoproterozoic. Precambrian metasediments and granitoids are unconformably overlain by Cambrian and Ordovician conglomerates and sandstones. They show a transitional environment from continental to shallow marine. Skolithos-bearing sandstone is common in Ordovician strata. By the Late Ordovician, ice masses had developed across West Gondwana. Upon melting of the ice sheets in the latest Hirnantian, large volumes of melt water and sediment were released that were transported to the periphery of Gondwana. In Libya, these sediments are predominantly highly mature sandstones, which, in many places, are excellent hydrocarbon reservoirs. Polished and striated surfaces in these sandstones clearly point to their glaciogenic origin. Following Late Ordovician deglaciation, black shale deposition occurred in the Silurian. Some of the shales are characterised by high values of total organic carbon (TOC). These shales are commonly referred to as ‘hot shales' due to their associated high uranium content, and are the major source rock for Early Palaeozoic-sourced hydrocarbons in North Africa. Late Ordovician glaciogenic sediments and the Early Silurian ‘hot shales' are therefore the main focus of geological research in the Libyan Sahara. Fluvial conglomerates and sandstones of Devonian age unconformably

  12. Radiolaria and pollen records from 0 to 50 ka at ODP Site 1233: Continental and marine climate records from the Southeast Pacific

    USGS Publications Warehouse

    Pisias, N.G.; Heusser, L.; Heusser, C.; Hostetler, S.W.; Mix, A.C.; Weber, M.

    2006-01-01

    Site 1233 drilled during Leg 202 of the Ocean Drilling Program provides a detailed record of marine and continental climate change in the Southeast Pacific and South American continent. Splits from over 500 samples taken at 20 cm intervals for quantitative analysis of radiolarian and pollen populations yield a temporal resolution of 200-400 years. In each sample, 39 pollen taxa and 40 radiolarian species and genera were evaluated. Age control is provided by 25 AMS 14C dates [Lamy, F., Kaiser, J., Ninnemann, U., Hebbeln, D., Arz, H.W., Stoner, J., 2004. Science 304, 1959-1962]. Multivariate statistical analyses of these data allow us to conclude the following: (1) During the past 50 ka, the region of the central Chile coast is not directly influenced by polar water from the Antarctic region. (2) Changes in ocean conditions off central Chile during this time interval primarily reflect north-south shifts in the position of the South Pacific transition zone. (3) Changes in Chilean vegetation reflect comparable latitudinal shifts in precipitation and the position of the southern westerlies. (4) The first canonical variate of radiolarian and pollen records extracted from Site 1233 are remarkably similar to each other as well as to temperature records from the Antarctic, which suggests that marine and continental climate variability in the region is tightly coupled at periods longer than 3000 years. (5) The phase coupling of these climate records, which lead variations of continental erosion based on iron abundance at the same site, are consistent with a hypothesis that erosion is linked to relatively long (i.e, few thousand years) response times of the Patagonian ice sheet, and thus is not a direct indicator of regional climate. ?? 2005 Elsevier Ltd. All rights reserved.

  13. A mid-Permian chert event: widespread deposition of biogenic siliceous sediments in coastal, island arc and oceanic basins

    USGS Publications Warehouse

    Murchey, B.L.; Jones, D.L.

    1992-01-01

    Radiolarian and conodont of Permian siliceous rocks from twenty-three areas in teh the circum-Pacific and Mediterranean regions reveal a widespread Permian Chert Event during the middle Leonardian to Wordian. Radiolarian- and (or) sponge spicule-rich siliceous sediments accumulated beneath high productivity zones in coastal, island arc and oceanic basins. Most of these deposits now crop out in fault-bounded accreted terranes. Biogenic siliceous sediments did not accumulate in terranes lying beneath infertile waters including the marine sequences in terranes of northern and central Alaska. The Permian Chert Event is coeval with major phosphorite deposition along the western margin of Pangea (Phosphoria Formation and related deposits). A well-known analogue for this event is middle Miocene deposition of biogenic siliceous sediments beneath high productivity zones in many parts of the Pacific and concurrent deposition of phosphatic as well as siliceous sediments in basins along the coast of California. Interrelated factors associated with both the Miocene and Permian depositional events include plate reorientations, small sea-level rises and cool polar waters. ?? 1992.

  14. Origin and radiation of the earliest vascular land plants.

    PubMed

    Steemans, Philippe; Hérissé, Alain Le; Melvin, John; Miller, Merrell A; Paris, Florentin; Verniers, Jacques; Wellman, Charles H

    2009-04-17

    Colonization of the land by plants most likely occurred in a stepwise fashion starting in the Mid-Ordovician. The earliest flora of bryophyte-like plants appears to have been cosmopolitan and dominated the planet, relatively unchanged, for some 30 million years. It is represented by fossilized dispersed cryptospores and fragmentary plant remains. In the Early Silurian, cryptospore abundance and diversity diminished abruptly as trilete spores appeared, became abundant, and underwent rapid diversification. This change coincides approximately with the appearance of vascular plant megafossils and probably represents the origin and adaptive radiation of vascular plants. We have obtained a diverse trilete spore occurrence from the Late Ordovician that suggests that vascular plants originated and diversified earlier than previously hypothesized, in Gondwana, before migrating elsewhere and secondarily diversifying.

  15. A Systems Approach to Identifying Exploration and Development Opportunities in the Illinois Basin: Digital Portifolio of Plays in Underexplored Lower Paleozoic Rocks [Part 1 of 2

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Seyler, Beverly; Harris, David; Keith, Brian

    2008-06-30

    This study examined petroleum occurrence in Ordovician, Silurian and Devonian reservoirs in the Illinois Basin. Results from this project show that there is excellent potential for additional discovery of petroleum reservoirs in these formations. Numerous exploration targets and exploration strategies were identified that can be used to increase production from these underexplored strata. Some of the challenges to exploration of deeper strata include the lack of subsurface data, lack of understanding of regional facies changes, lack of understanding the role of diagenetic alteration in developing reservoir porosity and permeability, the shifting of structural closures with depth, overlooking potential producing horizons,more » and under utilization of 3D seismic techniques. This study has shown many areas are prospective for additional discoveries in lower Paleozoic strata in the Illinois Basin. This project implemented a systematic basin analysis approach that is expected to encourage exploration for petroleum in lower Paleozoic rocks of the Illinois Basin. The study has compiled and presented a broad base of information and knowledge needed by independent oil companies to pursue the development of exploration prospects in overlooked, deeper play horizons in the Illinois Basin. Available geologic data relevant for the exploration and development of petroleum reservoirs in the Illinois Basin was analyzed and assimilated into a coherent, easily accessible digital play portfolio. The primary focus of this project was on case studies of existing reservoirs in Devonian, Silurian, and Ordovician strata and the application of knowledge gained to future exploration and development in these underexplored strata of the Illinois Basin. In addition, a review of published reports and exploration in the New Albany Shale Group, a Devonian black shale source rock, in Illinois was completed due to the recent increased interest in Devonian black shales across the United States

  16. Silurian "Clinton" Sandstone Reservoir Characterization for Evaluation of CO2-EOR Potential in the East Canton Oil Field, Ohio

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Ronald Riley; John Wicks; Christopher Perry

    The purpose of this study was to evaluate the efficacy of using CO2-enhanced oil recovery (EOR) in the East Canton oil field (ECOF). Discovered in 1947, the ECOF in northeastern Ohio has produced approximately 95 million barrels (MMbbl) of oil from the Silurian 'Clinton' sandstone. The original oil-in-place (OOIP) for this field was approximately 1.5 billion bbl and this study estimates by modeling known reservoir parameters, that between 76 and 279 MMbbl of additional oil could be produced through secondary recovery in this field, depending on the fluid and formation response to CO2 injection. A CO2 cyclic test ('Huff-n-Puff') wasmore » conducted on a well in Stark County to test the injectivity in a 'Clinton'-producing oil well in the ECOF and estimate the dispersion or potential breakthrough of the CO2 to surrounding wells. Eighty-one tons of CO2 (1.39 MMCF) were injected over a 20-hour period, after which the well was shut in for a 32-day 'soak' period before production was resumed. Results demonstrated injection rates of 1.67 MMCF of gas per day, which was much higher than anticipated and no CO2 was detected in gas samples taken from eight immediately offsetting observation wells. All data collected during this test was analyzed, interpreted, and incorporated into the reservoir characterization study and used to develop the geologic model. The geologic model was used as input into a reservoir simulation performed by Fekete Associates, Inc., to estimate the behavior of reservoir fluids when large quantities of CO2 are injected into the 'Clinton' sandstone. Results strongly suggest that the majority of the injected CO2 entered the matrix porosity of the reservoir pay zones, where it diffused into the oil. Evidence includes: (A) the volume of injected CO2 greatly exceeded the estimated capacity of the hydraulic fracture and natural fractures; (B) there was a gradual injection and pressure rate build-up during the test; (C) there was a subsequent, gradual

  17. Lower Cretaceous smarl turbidites of the Argo Abyssal Plain, Indian Ocean

    USGS Publications Warehouse

    Dumoulin, Julie A.; Stewart, Sondra K.; Kennett, Diana; Mazzullo, Elsa K.

    1992-01-01

    Sediments recovered during Ocean Drilling Program (ODP) Leg 123 from the Argo Abyssal Plain (AAP) consist largely of turbidites derived from the adjacent Australian continental margin. The oldest abundant turbidites are Valanginian-Aptian in age and have a mixed (smarl) composition; they contain subequal amounts of calcareous and siliceous biogenic components, as well as clay and lesser quartz. Most are thin-bedded, fine sand to mud-sized, and best described by Stow and Piper's model (1984) for fine-grained biogenic turbidites. Thicker (to 3 m), coarser-grained (medium-to-coarse sand-sized) turbidites fit Bouma's model (1962) for sandy turbidites; these generally are base-cut-out (BCDE, BDE) sequences, with B-division parallel lamination as the dominant structure. Parallel laminae most commonly concentrate quartz and/or calcispheres vs. lithic clasts or clay, but distinctive millimeter to centimeter-thick, radiolarian-rich laminae occur in both fine and coarse-grained Valanginian-Hauterivian turbidites.AAP turbidites were derived from relatively deep parts of the continental margin (outer shelf, slope, or rise) that lay below the photic zone, but above the calcite compensation depth (CCD). Biogenic components are largely pelagic (calcispheres, foraminifers, radiolarians, nannofossils); lesser benthic foraminifers are characteristic of deep-water (abyssal to bathyal) environments. Abundant nonbiogenic components are mostly clay and clay clasts; smectite is the dominant clay species, and indicates a volcanogenic provenance, most likely the Triassic-Jurassic volcanic suite exposed along the northern Exmouth Plateau.Lower Cretaceous smarl turbidites were generated during eustatic lowstands and may have reached the abyssal plain via Swan Canyon, a submarine canyon thought to have formed during the Late Jurassic. In contrast to younger AAP turbidites, however, Lower Cretaceous turbidites are relatively fine-grained and do not contain notably older reworked fossils. Early

  18. Publications - RI 2000-5 | Alaska Division of Geological & Geophysical

    Science.gov Websites

    ; Fossils; Gastropods; Geochronology; Geology; Halobia; Kahiltna Terrane; Late Silurian; Late Triassic Project; Trace Fossils Top of Page Department of Natural Resources, Division of Geological &

  19. Hydrocarbon source potential of the Tanezzuft Formation, Murzuq Basin, south-west Libya: An organic geochemical approach

    NASA Astrophysics Data System (ADS)

    El Diasty, W. Sh.; El Beialy, S. Y.; Anwari, T. A.; Batten, D. J.

    2017-06-01

    A detailed organic geochemical study of 20 core and cuttings samples collected from the Silurian Tanezzuft Formation, Murzuq Basin, in the south-western part of Libya has demonstrated the advantages of pyrolysis geochemical methods for evaluating the source-rock potential of this geological unit. Rock-Eval pyrolysis results indicate a wide variation in source richness and quality. The basal Hot Shale samples proved to contain abundant immature to early mature kerogen type II/III (oil-gas prone) that had been deposited in a marine environment under terrigenous influence, implying good to excellent source rocks. Strata above the Hot Shale yielded a mixture of terrigenous and marine type III/II kerogen (gas-oil prone) at the same maturity level as the Hot Shale, indicating the presence of only poor to fair source rocks.

  20. The Areal Extent of Continuous Type Gas Accumulations in Lower Silurian Clinton Sands and Medina Group Sandstones of the Appalachian Basin and the Environments Affected by Their Development

    USGS Publications Warehouse

    Wandrey, C.J.; Ryder, Robert T.; Nuccio, Vito F.; Aggen, Kerry L.

    1997-01-01

    In order to best preserve and manage our energy and natural resources we must understand the relationships between these resources and the impacts of their development. To further this understanding the U.S. Geological Survey is studying unconventional continuous-type and, to a lesser extent, conventional oil and gas accumulations and the environmental impacts associated with their development. Continuous-type gas accumulations are generally characterized by low matrix permeabilities, large areal extents, and no distinct water contacts. This basin scale map shows the overall extent of these accumulations and the general land use types that may be impacted by their development. The Appalachian Basin has the longest history of oil and gas exploration and production in the United States. Since Drake's Titusville discovery well was drilled in 1859, oil and gas has been continuously produced in the basin. While there is still a great deal of oil and gas production, new field discoveries are rare and relatively small. For most of the second half of the 20th century the Appalachian basin has been considered a mature petroleum province because most of the large plays have already been discovered and developed. One exception to this trend is the Lower Silurian Clinton Sands and Medina Group Gas play which is being developed in New York, Pennsylvania, and Ohio. This continuous-type gas play has been expanding since the early 1970's (see inset maps). In the 1980's economic incentives such as large increases in wellhead prices further stimulated continuous-type gas resource development. Continuous-type gas plays can be large in areal extent and in thickness. 'Sweetspots' (areas of greater prodcution) are hard to predict and generally associated with better than average permeabilities, and enhanced by natural fracture systems. With an overall success rate often approaching 90%, drilling most of the play with closely spaced wells is often the best way to maximize gas recovery

  1. Subsidence related to groundwater pumping for breweries in Merchtem area (Belgium), highlighted by Persistent Scaterrer Interferometry

    NASA Astrophysics Data System (ADS)

    Declercq, Pierre-Yves; Gerard, Pierre; Pirard, Eric; Perissin, Daniele; Walstra, Jan; Devleeschouwer, Xavier

    2017-12-01

    ERS, ENVISAT and TerraSAR-X Synthetic Aperture Radar scenes covering the time span 1992-2014 were processed using a Persistent Scatterer technique to study the ground movements in Merchtem (25 km NW of Brussels, Belgium). The processed datasets, covering three consecutive time intervals, reveal that the investigated area is affected by a global subsidence trend related to the extraction of groundwater in the deeper Cambro-Silurian aquifer. Through time the subsidence pattern is reduced and replaced by an uplift related to the rising water table attested by piezometers located in this aquifer. The subsidence is finally reduced to a zone where currently three breweries are very active and pump groundwater in the Ledo-Paniselian aquifer and in the Cambro-Silurian for process water for the production.

  2. Magnetic anisotropy of Silurian organic-rich shale rocks and calcareous concretions from Northern Poland

    NASA Astrophysics Data System (ADS)

    Niezabitowska, Dominika; Szaniawski, Rafał

    2017-04-01

    The research has been performed on Wenlockian shales of Pelplin formation from the Pomerania region located in Northern Poland. These organic-rich marine shales were deposited on the western shelf of the Baltica paleo-continent and currently they constitute the cover of East European Platform. The studied shales lie almost completely flat without signs of tectonic deformations. Rock magnetic studies were carried out with the aim of recognizing ferro- and paramagnetic minerals in shales and thus fully understanding the origin of the magnetic anisotropy. The typical dark shales and spherical calcareous concretions from two boreholes were sampled. Based on deflection of shales beds bordered with a concretions, we deduce that such concretions were formed in the early stage of diagenesis, before the final compaction and lithification of surrounding shales. We obtained similar rockmagnetic results for both of rock types. The results of thermal variation of magnetic susceptibility and hysteresis loops show that the magnetic susceptibility is mainly controlled by paramagnetic minerals, due to domination of phyllosilicate minerals, with a smaller impact of ferromagnetic phase. The results of the hysteresis studies documented the domination of low coercivity ferromagnetic minerals, that is magnetite and pyrrhotite. The deposition alignment of flocculated phyllosilicates and further compaction determine distinct bedding parallel foliation of the AMS (Anisotropy of Magnetic Susceptibility) in the both drill cores. In one of the drill core the maximal AMS axes are almost randomly distributed in the bedding plane and show only a weak tendency for grouping. In the second drill core the magnetic lineation is better defined. In the case of concretions the bedding parallel magnetic foliation is also evident but it is much weaker than in shales. In turn, the magnetic lineation in the both drill cores is well developed and the maximal AMS axes are well grouped. In both of the cores

  3. The clasts of Cretaceous marls in the conglomerates of the Konradsheim Formation (Pöchlau quarry, Gresten Klippen Zone, Austria)

    NASA Astrophysics Data System (ADS)

    Ślączka, Andrzej; Gasiñski, M. Adam; Bąk, Marta; Wessely, Godfrid

    2009-04-01

    Investigations were carried out on foraminiferids and radiolaria from redeposited clasts within the conglomerates of the Konradsheim Formation (Gresten Klippen Zone) in the area of the Pöchlau hill, east of Maria Neustift. These shales and marls are of Middle to Late Jurassic and Early Cretaceous age. In the latter clasts, foraminiferal assemblages with Tritaxia ex gr. gaultina as well as radiolaria species Angulobracchia portmanni Baumgartner, Dictyomitra communis (Squinabol), Hiscocapsa asseni (Tan), Pseudodictyomitra lodogaensis Pessagno, Pseudoeucyrtis hanni (Tan), Rhopalosyringium fossile (Squinabol) were found. In one block from the uppermost part of the sequence there is an assemblage with Caudammina (H) gigantea, Rotalipora appenninica and Globotruncana bulloides. However, the brecciated character of this block and occurrence near a fault suggest that it was probably wedged into the conglomerates of the Konradsheim Formation during tectonic movements. In pelitic siliceous limestones below the Konradsheim Limestone radiolarian assemblages of Middle Callovian to Early Tithonian age were found. They enable correlation with the Scheibbsbach Formation. In a marly sequence, above the conglomeratic limestone, the foraminiferal assemblages contain taxa from mid-Cretaceous up to Paleocene. The present biostratigraphic investigation confirmed the previous stratigraphic assignments and imply clearly that the sedimentation of deposits similar to the Konradsheim Formation also occurred at the end of the Early Cretaceous and deposition of conglomeratic limestones within the Gresten Klippen Zone, and especially within the Konradsheim Formation, was repeated several times during the Late Jurassic and Early Cretaceous.

  4. Biogeography of Radiolaria Polycystina (Protista) in the World Ocean

    NASA Astrophysics Data System (ADS)

    Boltovskoy, Demetrio; Correa, Nancy

    2016-12-01

    Analysis of 307 species of Radiolaria Polycystina in a worldwide dataset of 4774 plankton, sediment trap, and surface sediment samples allows recognizing six major biogeographic Domains. Five of them are circumglobal (Polar North, Polar South, Bi-Subpolar, Transitional and Tropical-Subtropical), and one is restricted to the Eastern Equatorial Pacific. Each Domain is characterized by a particular suite of species, all of which, however, occur widely, albeit sparsely, in one or more other Domains. Of the eight environmental variables evaluated, temperature correlates best with the partitions established. Species distributions in the water column and in the sediments are generally in agreement, but in the sediments cold water forms extend farther towards the equator than do warm water radiolarians towards the poles. In the Recent sedimentary record of planktonic Foraminifera the same phenomenon is magnified by the higher dissolution rates of warm water species, as compared with the cold water ones. Of the three major oceans, the Pacific was the most speciose, but estimates based on data corrected for sample-size show much smaller inter-oceanic differences, with ∼10 radiolarians probably being absent from either basin. The radiolarian biogeographic pattern is generally similar to those based on other planktonic and nektonic open-ocean organisms, but the degree of uniqueness of the Domains, as well as the position of the intervening boundaries, are variable, which reflects methodological differences, as well as taxon-specific traits. Partitions of the World Ocean defined on the basis of species ranges resemble the major divisions (presumably functionally homogeneous units) established on the basis of physical traits and chlorophyll fields, but secondary divisions nested within the latter are not reflected by any of the biogeographic schemes based on species distribution ranges. This conflict raises questions about the importance of several physical mechanisms for

  5. Greenhouse-icehouse transition in the Late Ordovician marks a step change in extinction regime in the marine plankton.

    PubMed

    Crampton, James S; Cooper, Roger A; Sadler, Peter M; Foote, Michael

    2016-02-09

    Two distinct regimes of extinction dynamic are present in the major marine zooplankton group, the graptolites, during the Ordovician and Silurian periods (486-418 Ma). In conditions of "background" extinction, which dominated in the Ordovician, taxonomic evolutionary rates were relatively low and the probability of extinction was highest among newly evolved species ("background extinction mode"). A sharp change in extinction regime in the Late Ordovician marked the onset of repeated severe spikes in the extinction rate curve; evolutionary turnover increased greatly in the Silurian, and the extinction mode changed to include extinction that was independent of species age ("high-extinction mode"). This change coincides with a change in global climate, from greenhouse to icehouse conditions. During the most extreme episode of extinction, the Late Ordovician Mass Extinction, old species were selectively removed ("mass extinction mode"). Our analysis indicates that selective regimes in the Paleozoic ocean plankton switched rapidly (generally in <0.5 My) from one mode to another in response to environmental change, even when restoration of the full ecosystem was much slower (several million years). The patterns observed are not a simple consequence of geographic range effects or of taxonomic changes from Ordovician to Silurian. Our results suggest that the dominant primary controls on extinction throughout the lifespan of this clade were abiotic (environmental), probably mediated by the microphytoplankton.

  6. Greenhouse−icehouse transition in the Late Ordovician marks a step change in extinction regime in the marine plankton

    PubMed Central

    Crampton, James S.; Cooper, Roger A.; Sadler, Peter M.; Foote, Michael

    2016-01-01

    Two distinct regimes of extinction dynamic are present in the major marine zooplankton group, the graptolites, during the Ordovician and Silurian periods (486−418 Ma). In conditions of “background” extinction, which dominated in the Ordovician, taxonomic evolutionary rates were relatively low and the probability of extinction was highest among newly evolved species (“background extinction mode”). A sharp change in extinction regime in the Late Ordovician marked the onset of repeated severe spikes in the extinction rate curve; evolutionary turnover increased greatly in the Silurian, and the extinction mode changed to include extinction that was independent of species age (“high-extinction mode”). This change coincides with a change in global climate, from greenhouse to icehouse conditions. During the most extreme episode of extinction, the Late Ordovician Mass Extinction, old species were selectively removed (“mass extinction mode”). Our analysis indicates that selective regimes in the Paleozoic ocean plankton switched rapidly (generally in <0.5 My) from one mode to another in response to environmental change, even when restoration of the full ecosystem was much slower (several million years). The patterns observed are not a simple consequence of geographic range effects or of taxonomic changes from Ordovician to Silurian. Our results suggest that the dominant primary controls on extinction throughout the lifespan of this clade were abiotic (environmental), probably mediated by the microphytoplankton. PMID:26811471

  7. Silurian "Clinton" Sandstone Reservoir Characterization for Evaluation of CO2-EOR Potential in the East Canton Oil Field, Ohio

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Riley, Ronald; Wicks, John; Perry, Christopher

    The purpose of this study was to evaluate the efficacy of using CO2-enhanced oil recovery (EOR) in the East Canton oil field (ECOF). Discovered in 1947, the ECOF in northeastern Ohio has produced approximately 95 million barrels (MMbbl) of oil from the Silurian “Clinton” sandstone. The original oil-in-place (OOIP) for this field was approximately 1.5 billion bbl and this study estimates by modeling known reservoir parameters, that between 76 and 279 MMbbl of additional oil could be produced through secondary recovery in this field, depending on the fluid and formation response to CO2 injection. A CO2 cyclic test (“Huff-n-Puff”) wasmore » conducted on a well in Stark County to test the injectivity in a “Clinton”-producing oil well in the ECOF and estimate the dispersion or potential breakthrough of the CO2 to surrounding wells. Eighty-one tons of CO2 (1.39 MMCF) were injected over a 20-hour period, after which the well was shut in for a 32-day “soak” period before production was resumed. Results demonstrated injection rates of 1.67 MMCF of gas per day, which was much higher than anticipated and no CO2 was detected in gas samples taken from eight immediately offsetting observation wells. All data collected during this test was analyzed, interpreted, and incorporated into the reservoir characterization study and used to develop the geologic model. The geologic model was used as input into a reservoir simulation performed by Fekete Associates, Inc., to estimate the behavior of reservoir fluids when large quantities of CO2 are injected into the “Clinton” sandstone. Results strongly suggest that the majority of the injected CO2 entered the matrix porosity of the reservoir pay zones, where it diffused into the oil. Evidence includes: (A) the volume of injected CO2 greatly exceeded the estimated capacity of the hydraulic fracture and natural fractures; (B) there was a gradual injection and pressure rate build-up during the test; (C) there was a

  8. Recent advances in the cretaceous stratigraphy of Korea

    NASA Astrophysics Data System (ADS)

    Chang, Ki-Hong; Suzuki, Kazuhiro; Park, Sun-Ok; Ishida, Keisuke; Uno, Koji

    2003-06-01

    A subrounded, accidental, zircon grain from a rhyolite sample of the Oknyobong Formation has shown an U-Pb CHIME isochron age, 187 Ma, implying its derivation from a Jurassic felsic igneous rock. Such a lower limit of the geologic age of the Oknyobong Formation, combined with its pre-Kyongsang upper limit, constrains that the Oknyobong Formation belongs to the Jasong Synthem (Late Jurassic-early Early Cretaceous) typified in North Korea. The Jaeryonggang Movement terminated the deposition of the Jasong Synthem and caused a shift of the depocenter from North Korea to the Kyongsang Basin, Southeast Korea. The Cretaceous-Paleocene Kyongsang Supergroup of the Kyongsang Basin is the stratotype of the Kyongsang Synthem, an unconformity-bounded unit in the Korean Peninsula. The unconformity at the base of the Yuchon Volcanic Group is a local expression of the interregionally recognizable mid-Albian tectonism; it subdivides the Kyongsang Synthem into the Lower Kyongsang Subsynthem (Barremian-Early Albian) and the Upper Kyongsang Subsynthem (Late Albian-Paleocene). The latter is unconformably overlain by Eocene and younger strata. The Late Permian to Early Jurassic radiolarian fossils from the chert pebbles of the Kumidong and the Kisadong conglomerates of the Aptian-Early Albian Hayang Group of the Kyongsang Basin are equivalent with those of the cherts that constitute the Jurassic accretionary prisms in Japan, the provenance of the chert pebbles in the Kyongsang Basin. Bimodal volcanisms throughout the history of the Kyongsang Basin is exemplified by the felsic Kusandong Tuff erupted abruptly and briefly in the Late Aptian when semi-coeval volcanisms were of intermediate and mafic compositions. The mean paleomagnetic direction shown by the Kusandong Tuff is in good agreement with the Early Cretaceous directions known from North China, South China and Siberia Blocks.

  9. Paleocurrent analysis of a deformed Devonian foreland basin in the northern Appalachians, Maine, USA

    USGS Publications Warehouse

    Bradley, D.C.; Hanson, L.S.

    2002-01-01

    New paleocurrent data indicate that the widespread Late Silurian and Devonian flysch and molasse succession in Maine was deposited in an ancestral, migrating foreland basin adjacent to an advancing Acadian orogenic belt. The foreland-basin sequence spread across a varied Silurian paleogeography of deep basins and small islands-the vestiges of an intraoceanic arc complex that not long before had collided with the Laurentian passive margin during the Ordovician Taconic Orogeny. We report paleocurrents from 43 sites representing 12 stratigraphic units, the most robust and consistent results coming from three units: Madrid Formation (southwesterly paleoflow), Carrabassett Formation (northerly paleoflow), and Seboomook Group (westerly paleoflow). Deformation and regional metamorphism are sufficiently intense to test the limits of paleocurrent analysis requiring particular care in retrodeformation. ?? 2002 Elsevier Science B.V. All rights reserved.

  10. Late Paleozoic deformation and exhumation in the Sierras Pampeanas (Argentina): 40Ar/39Ar-feldspar dating constraints

    NASA Astrophysics Data System (ADS)

    Löbens, Stefan; Oriolo, Sebastián; Benowitz, Jeff; Wemmer, Klaus; Layer, Paul; Siegesmund, Siegfried

    2017-09-01

    Systematic 40Ar/39Ar feldspar data obtained from the Sierras Pampeanas are presented, filling the gap between available high- (> 300 °C) and low-temperature (< 150 °C) thermochronological data. Results show Silurian-Devonian exhumation related to the late stages of the Famatinian/Ocloyic Orogeny for the Sierra de Pocho and the Sierra de Pie de Palo regions, whereas the Sierras de San Luis and the Sierra de Comechingones regions record exhumation during the Carboniferous. Comparison between new and available data points to a Carboniferous tectonic event in the Sierras Pampeanas, which represents a key period to constrain the early evolution of the proto-Andean margin of Gondwana. This event was probably transtensional and played a major role during the evolution of the Paganzo Basin as well as during the emplacement of alkaline magmatism in the retroarc.

  11. Bedrock geologic map of the Montpelier and Barre West quadrangles, Washington and Orange Counties, Vermont

    USGS Publications Warehouse

    Walsh, Gregory J.; Kim, Jonathan; Gale, Marjorie H.; King, Sarah M.

    2010-01-01

    The bedrock geology of the Montpelier and Barre West quadrangles consists of Silurian and Devonian metasedimentary rocks of the Connecticut Valley-Gaspe synclinorium (CVGS) and metasedimentary, metavolcanic, and metaintrusive rocks of the Cambrian and Ordovician Moretown and Cram Hill Formations. Devonian granite dikes occur throughout the two quadrangles but are more abundant in the Silurian and Devonian rocks. The pre-Silurian rocks are separated from the rocks of the CVGS by the informally named 'Richardson Memorial Contact,' historically interpreted as either an unconformity or a fault. The results of this report represent mapping by G.J. Walsh, Jonathan Kim, and M.H. Gale from 2002 to 2005. S.M. King assisted Kim and Gale from 2002 to 2003. A.M. Satkoski (Indiana University) assisted Walsh, and L.R. Pascale (University of Vermont) and C.M. Orsi (Middlebury College) assisted Kim and Gale as summer interns in 2003. This study was designed to map the bedrock geology in the area. This map supersedes a preliminary map of the Montpelier quadrangle (Kim, Gale, and others, 2003). A companion study in the Barre West quadrangle (Walsh and Satkoski, 2005) determined the levels of naturally occurring radioactivity in the bedrock from surface measurements at outcrops during the course of 1:24,000-scale geologic mapping to identify which rock types were potential sources of radionuclides. Results of that study indicate that the carbonaceous phyllites in the CVGS have the highest levels of natural radioactivity.

  12. Early College, Early Success: Early College High School Initiative Impact Study

    ERIC Educational Resources Information Center

    Berger, Andrea; Turk-Bicakci, Lori; Garet, Michael; Song, Mengli; Knudson, Joel; Haxton, Clarisse; Zeiser, Kristina; Hoshen, Gur; Ford, Jennifer; Stephan, Jennifer; Keating, Kaeli; Cassidy, Lauren

    2013-01-01

    In 2002, the Bill & Melinda Gates Foundation launched the Early College High School Initiative (ECHSI) with the primary goal of increasing the opportunity for underserved students to earn a postsecondary credential. To achieve this goal, Early Colleges provide underserved students with exposure to, and support in, college while they are in…

  13. Early Diagnosis and Early Intervention in Cerebral Palsy

    PubMed Central

    Hadders-Algra, Mijna

    2014-01-01

    This paper reviews the opportunities and challenges for early diagnosis and early intervention in cerebral palsy (CP). CP describes a group of disorders of the development of movement and posture, causing activity limitation that is attributed to disturbances that occurred in the fetal or infant brain. Therefore, the paper starts with a summary of relevant information from developmental neuroscience. Most lesions underlying CP occur in the second half of gestation, when developmental activity in the brain reaches its summit. Variations in timing of the damage not only result in different lesions but also in different neuroplastic reactions and different associated neuropathologies. This turns CP into a heterogeneous entity. This may mean that the best early diagnostics and the best intervention methods may differ for various subgroups of children with CP. Next, the paper addresses possibilities for early diagnosis. It discusses the predictive value of neuromotor and neurological exams, neuroimaging techniques, and neurophysiological assessments. Prediction is best when complementary techniques are used in longitudinal series. Possibilities for early prediction of CP differ for infants admitted to neonatal intensive care and other infants. In the former group, best prediction is achieved with the combination of neuroimaging and the assessment of general movements, in the latter group, best prediction is based on carefully documented milestones and neurological assessment. The last part reviews early intervention in infants developing CP. Most knowledge on early intervention is based on studies in high-risk infants without CP. In these infants, early intervention programs promote cognitive development until preschool age; motor development profits less. The few studies on early intervention in infants developing CP suggest that programs that stimulate all aspects of infant development by means of family coaching are most promising. More research is urgently needed

  14. Did volcanic activity of the Emeishan large igneous province expand in Wuchiapingian times?

    NASA Astrophysics Data System (ADS)

    Bagherpour, Borhan; Bucher, Hugo; Yuan, Dong-Xun; Shen, Shu-zhong; Leu, Marc; Zhang, Chao

    2017-04-01

    Emplacement of the Emeishan Large Igneous Province (ELIP) in the Capitanian (Middle Permian) is associated with several environmental changes (e.g. facies change, carbon cycle perturbation and temperature rise) across the Guadalupian-Lopingian (G-L) interval in South China. However, most of the reported changes are within the Capitanian stage or close to the G-L boundary. Here, we report an episode of drastic environmental changes from the Pingtang syncline (S. Guizhou) that is similar with the previously known ones but which is significantly younger. The studied section represents a protracted and stepwise facies change from a benthos rich, thick-bedded and light grey shallow water limestone (Unit A) to a 30 m-thick unit with thin-bedded dark (OM-rich) radiolarian-spiculitic facies (Unit B). The latter is overlain by an 8 m-thick unit of volcaniclastic sandstone and silts defining a succession of decimetric, cyclic and thinning upward layers (Unit C). The base of the overlying medium-bedded limestone unit (Unit D) contain radiolarian and sponge spicules whose abundance progressively decrease up section with a progressive replacement by abundant benthic faunas concomitant with the transition to thick bedded limestone. A total of five conodont index species (assigned to Clarkina) of early Wuchiapingian age were recognized from Unit A and Unit B. The observed facies transition from Unit A to Unit B indicates a drastic drowning event. Unit C represents a distal turbiditic succession and the overlying Unit D shows an upward shallowing trend back to the initial shallow marine condition. Compilation of sedimentary records across G-L in South China reveals that such drowning events tend to cluster within three discrete time intervals. The drowning events may or may not end with deposition of either volcanics or volcaniclastics. Two first clusters display drowning events overlain by ELIP volcanic rocks or volcaniclastics of ELIP origin and are of Capitanian age. Only the

  15. Early Childhood Systems: Transforming Early Learning

    ERIC Educational Resources Information Center

    Kagan, Sharon Lynn, Ed.; Kauertz, Kristie, Ed.

    2012-01-01

    In this seminal volume, leading authorities strategize about how to create early childhood systems that transcend politics and economics to serve the needs of all young children. The authors offer different interpretations of the nature of early childhood systems, discuss the elements necessary to support their development, and examine how…

  16. Geochronological framework of the early Paleozoic Bainaimiao Cu-Mo-Au deposit, NE China, and its tectonic implications

    NASA Astrophysics Data System (ADS)

    Zhou, Zhen-Hua; Mao, Jing-Wen; Ma, Xing-Hua; Che, He-Wei; Ou'yang, He-Gen; Gao, Xu

    2017-08-01

    The Bainaimiao Cu-Mo-Au deposit of NE China is an important ore deposit in the middle section of the northern margin of the North China Craton. The early Paleozoic Bainaimiao Group is the main ore-hosting rock. The mineralization at the deposit shows features of porphyry alteration and late-stage orogenesis and transformation. Zircon LA-ICP-MS U-Pb age data indicate that the ages of the Third and Fifth formations of the Bainaimiao Group are 492.7 ± 2.9 Ma (MSWD = 0.53) and 488.9 ± 3.1 Ma (MSWD = 0.92), respectively. The age of quartz diorite that intrudes the Bainaimiao Group is 459.3 ± 6.4 Ma (MSWD = 2.20). Molybdenite samples from massive Cu-Mo-bearing ores and quartz veins in the southern ore belt yield a Re-Os isochron age of 438.2 ± 2.7 Ma (MSWD = 0.16), which is consistent with the Re-Os isochron age of molybdenite in the northern ore belt, implying that the two ore belts belong to the same mineralization system. Muscovite from a post-magmatic Cu-Mo-bearing quartz-calcite vein yields an Ar-Ar isochron age of 422.5 ± 3.9 Ma (MSWD = 0.64) with an initial 40Ar/36Ar ratio of 286 ± 21. The well-defined plateau age of the muscovite is 422.4 ± 2.6 Ma (MSWD = 0.05), which represents the time of the post-magmatic orogenic transformation event. Based on our new age data and previous findings, we propose that the Bainaimiao Cu-Mo-Au deposit formed in an active continental margin setting and experienced four stages of ore mineralization: (1) a Late Cambrian-Middle Ordovician volcanic-sedimentary stage; (2) a Late Ordovician porphyry mineralization stage; (3) a Late Silurian regional metamorphism stage; and (4) an orogenic transformation stage. Subhedral and euhedral Paleoproterozoic (2402-1810 Ma) inherited zircons indicate that the Bainaimiao Group has a tectonic affinity with the North China Craton. The Central Asian Orogenic Belt, which is closely related to the complex closure of the Paleo-Asian Ocean, is favorable for prospecting for Paleozoic porphyry Cu

  17. Oxygen isotope analysis of fossil organic matter by secondary ion mass spectrometry

    NASA Astrophysics Data System (ADS)

    Tartèse, Romain; Chaussidon, Marc; Gurenko, Andrey; Delarue, Frédéric; Robert, François

    2016-06-01

    We have developed an analytical procedure for the measurement of oxygen isotope composition of fossil organic matter by secondary ion mass spectrometry (SIMS) at the sub-per mill level, with a spatial resolution of 20-30 μm. The oxygen isotope composition of coal and kerogen samples determined by SIMS are on average consistent with the bulk oxygen isotope compositions determined by temperature conversion elemental analysis - isotope ratio mass spectrometry (TC/EA-IRMS), but display large spreads of δ18O of ∼5-10‰, attributed to mixing of remnants of organic compounds with distinct δ18O signatures. Most of the δ18O values obtained on two kerogen residues extracted from the Eocene Clarno and Early Devonian Rhynie continental chert samples and on two immature coal samples range between ∼10‰ and ∼25‰. Based on the average δ18O values of these samples, and on the O isotope composition of water processed by plants that now constitute the Eocene Clarno kerogen, we estimated δ18Owater values ranging between around -11‰ and -1‰, which overall correspond well within the range of O isotope compositions for present-day continental waters. SIMS analyses of cyanobacteria-derived organic matter from the Silurian Zdanow chert sample yielded δ18O values in the range 12-20‰. Based on the O isotope composition measured on recent cyanobacteria from the hypersaline Lake Natron (Tanzania), and on the O isotope composition of the lake waters in which they lived, we propose that δ18O values of cyanobacteria remnants are enriched by about ∼18 ± 2‰ to 22 ± 2‰ relative to coeval waters. This relationship suggests that deep ocean waters in which the Zdanow cyanobacteria lived during Early Silurian times were characterised by δ18O values of around -5 ± 4‰. This study, establishing the feasibility of micro-analysis of Phanerozoic fossil organic matter samples by SIMS, opens the way for future investigations of kerogens preserved in Archean cherts and of the

  18. Is Global Anoxia an Alternative Cause for the Hirnantian Mass Extinction?

    NASA Astrophysics Data System (ADS)

    De Weirdt, Julie; Vandenbroucke, Thijs; Emsbo, Poul; McLaughlin, Patrick; Delabroye, Aurélien; Munnecke, Axel; Desrochers, André

    2017-04-01

    Cooling and glacial episodes have long been considered the main driver of Late Ordovician-Silurian (mass) extinction events that coincide with δ13Ccarb excursions. However, emerging evidence for protracted cooling during most of the Ordovician and the misalignment between major regressions and faunal turnovers in the Upper Ordovician, suggests a more complex relation between glaciations and extinctions. Emsbo et al. (2010, GSA Abstracts with Programs) demonstrated dramatic enrichments in redox sensitive metals during the early Wenlock Ireviken extinction event and suggested ocean anoxia as an alternative kill-mechanism. Vandenbroucke et al. (2015, Nature Communications), built on this idea and recorded a similar increase of redox-sensitive metals at the onset of the mid-Pridoli extinction event, coinciding with peak abundances of malformed (teratological) fossil microplankton (acritarchs and chitinozoans). By analogy with metal-induced malformations in modern marine microplankton, teratology might serve as an independent proxy for monitoring changes in the metal concentration of the Palaeozoic ocean. These data from the Ireviken and Pridoli events are the foundation for the hypothesis that many, if not all, of these Late Ordovician-Silurian extinctions are caused by large-scale 'oceanic anoxic events'. Here, we are testing this hypothesis for the most devastating extinction event in this series, the Hirnantian mass extinction. Bulk rock samples spanning the Hirnantian strata of Anticosti Island were geochemically analysed. Our choice of sections is guided by the presence of teratological acritarchs (Delabroye et al., 2012, Rev. Pal. Pal.) that overlap the base of the extinction horizon. Revealing similar results as in our the previous studies, the new XRF data show distinct peaks in redox sensitive metals, supporting ocean anoxia and metal pollution as an important factor in the Hirnantian extinction, if not its fundamental cause.

  19. Petrogenesis and tectonic setting of the Devonian Xiqin A-type granite in the northeastern Cathaysia Block, SE China

    NASA Astrophysics Data System (ADS)

    Cai, Da-wei; Tang, Yong; Zhang, Hui; Lv, Zheng-Hang; Liu, Yun-long

    2017-06-01

    Most Silurian-Devonian granites in South China are S- or I-type granites, which are suggested to be petrogenetically related to the Wuyi-Yunkai orogeny. In this paper, we present the detailed LA-ICP-MS zircon U-Pb dating, major and trace element geochemical, and Nd-Hf isotopic data for Xiqin A-type granites in the northeastern Cathaysia Block, SE China. Zircon U-Pb dating results show that the Xiqin granites were emplaced at about 410 Ma, indicating that they were generated at the end of Wuyi-Yunkai orogeny. These granites are high in K2O + Na2O (6.31-8.79 wt%), high field strength elements (Zr + Nb + Ce + Y = 427-699 ppm), rare earth elements (total REE = 221-361 ppm) as well as high Ga/Al ratios (10,000 Ga/Al = 2.50-3.10), and show characteristics typical of A-type granites. εHf(t) values of the Xiqin granites mainly vary from -0.4 to -3.1 and yield Mesoproterozoic T2DM(Hf) (mainly ranging from 1.29 to 1.45 Ga). The εNd(t) values are from -1.23 to -2.11 and T2DM(Nd) vary from 1.25 to 1.32 Ga. These isotopic data suggest that the Xiqin granites were generated by partial melting of metavolcanic rocks with minor metasedimentary rocks in the lower crust. Our data on the Xiqin granites, coupled with previous studies of Silurian-Devonian magmatism, suggest that the tectonic regime had changed to a strongly post-collisional extension environment in the Wuyi-Yunkai orogen at least since 410 Ma, and that delamination, which accounts for the change in stress from the compression to extension and asthenospheric upwelling during the early Paleozoic, plays a significant role in the generation of Xiqin A-type granites.

  20. Early Intervention.

    ERIC Educational Resources Information Center

    Nathanson, Jeanne H., Ed.

    1992-01-01

    This theme issue focuses on early intervention. The four articles presented on this theme are: (1) "Deaf Infants, Hearing Mothers: A Research Report" (Kathryn P. Meadow-Orlans, and others), reporting findings on effects of auditory loss on early development; (2) "Maintaining Involvement of Inner City Families in Early Intervention Programs through…

  1. Portable audio magnetotellurics - experimental measurements and joint inversion with radiomagnetotelluric data from Gotland, Sweden

    NASA Astrophysics Data System (ADS)

    Shan, Chunling; Kalscheuer, Thomas; Pedersen, Laust B.; Erlström, Mikael; Persson, Lena

    2017-08-01

    Field setup of an audio magnetotelluric (AMT) station is a very time consuming and heavy work load. In contrast, radio magnetotelluric (RMT) equipment is more portable and faster to deploy but has shallower investigation depth owing to its higher signal frequencies. To increase the efficiency in the acquisition of AMT data from 10 to 300 Hz, we introduce a modification of the AMT method, called portable audio magnetotellurics (PAMT), that uses a lighter AMT field system and (owing to the disregard of signals at frequencies of less than 10 Hz) shortened data acquisition time. PAMT uses three magnetometers pre-mounted on a rigid frame to measure magnetic fields and steel electrodes to measure electric fields. Field tests proved that the system is stable enough to measure AMT fields in the given frequency range. A PAMT test measurement was carried out on Gotland, Sweden along a 3.5 km profile to study the ground conductivity and to map shallow Silurian marlstone and limestone formations, deeper Silurian, Ordovician and Cambrian sedimentary structures and crystalline basement. RMT data collected along a coincident profile and regional airborne very low frequency (VLF) data support the interpretation of our PAMT data. While only the RMT and VLF data constrain a shallow ( 20-50 m deep) transition between Silurian conductive (< 30 Ωm resistivity) marlstone and resistive (> 1000 Ωm resistivity) limestone, the single-method inversion models of both the PAMT and the RMT data show a transition into a conductive layer of 3 to 30 Ωm resistivity at 80 m depth suggesting the compatibility of the two data sets. This conductive layer is interpreted as saltwater saturated succession of Silurian, Ordovician and Cambrian sedimentary units. Towards the lower boundary of this succession (at 600 m depth according to boreholes), only the PAMT data constrain the structure. As supported by modelling tests and sensitivity analysis, the PAMT data only contain a vague indication of the

  2. Infusing Early Childhood Mental Health into Early Intervention Services

    ERIC Educational Resources Information Center

    Grabert, John C.

    2009-01-01

    This article describes the process of enhancing early childhood mental health awareness and skills in non-mental health staff. The author describes a pilot training model, conducted the U.S. Army's Early Intervention Services, that involved: (a) increasing early childhood mental health knowledge through reflective readings, (b) enhancing…

  3. The characters of Palaeozoic jawed vertebrates

    PubMed Central

    Brazeau, Martin D; Friedman, Matt

    2014-01-01

    Newly discovered fossils from the Silurian and Devonian periods are beginning to challenge embedded perceptions about the origin and early diversification of jawed vertebrates (gnathostomes). Nevertheless, an explicit cladistic framework for the relationships of these fossils relative to the principal crown lineages of the jawed vertebrates (osteichthyans: bony fishes and tetrapods; chondrichthyans: sharks, batoids, and chimaeras) remains elusive. We critically review the systematics and character distributions of early gnathostomes and provide a clearly stated hierarchy of synapomorphies covering the jaw-bearing stem gnathostomes and osteichthyan and chondrichthyan stem groups. We show that character lists, designed to support the monophyly of putative groups, tend to overstate their strength and lack cladistic corroboration. By contrast, synapomorphic hierarchies are more open to refutation and must explicitly confront conflicting evidence. Our proposed synapomorphy scheme is used to evaluate the status of the problematic fossil groups Acanthodii and Placodermi, and suggest profitable avenues for future research. We interpret placoderms as a paraphyletic array of stem-group gnathostomes, and suggest what we regard as two equally plausible placements of acanthodians: exclusively on the chondrichthyan stem, or distributed on both the chondrichthyan and osteichthyan stems. PMID:25750460

  4. Bedrock geologic map of the Lisbon quadrangle, and parts of the Sugar Hill and East Haverhill quadrangles, Grafton County, New Hampshire

    USGS Publications Warehouse

    Rankin, Douglas W.

    2018-04-20

    The bedrock geologic map of the Lisbon quadrangle, and parts of the Sugar Hill and East Haverhill quadrangles, Grafton County, New Hampshire, covers an area of approximately 73 square miles (189 square kilometers) in west-central New Hampshire. This map was created as part of a larger effort to produce a new bedrock geologic map of Vermont through the collection of field data at a scale of 1:24,000. A large part of the map area consists of the Bronson Hill anticlinorium, a post-Early Devonian structure that is cored by metamorphosed Cambrian to Devonian sedimentary, volcanic, and plutonic rocks.The Bronson Hill anticlinorium is the apex of the Middle Ordovician to earliest-Silurian Bronson Hill magmatic arc that contains the Ammonoosuc Volcanics, Partridge Formation, and Oliverian Plutonic Suite, and extends from Maine, through western New Hampshire (down the eastern side of the Connecticut River), through southern New England to Long Island Sound. The deformed and partially eroded arc is locally overlain by a relatively thin Silurian section of metasedimentary rocks (Clough Quartzite and Fitch Formation) that thickens to the east. The Silurian section near Littleton is disconformably overlain by a thicker, Lower Devonian section that includes mostly metasedimentary and minor metavolcanic rocks of the Littleton Formation. The Bronson Hill anticlinorium is bisected by a series of northeast-southwest trending Mesozoic normal faults. Primarily among them is the steeply northwest-dipping Ammonoosuc fault that divides older and younger units (lower and upper sections) of the Ammonoosuc Volcanics. The Ammonoosuc Volcanics are lithologically complex and predominantly include interlayered and interfingered rhyolitic to basaltic volcanic and volcaniclastic rocks, as well as lesser amounts of slate, phyllite, ironstone, chert, sandstone, and pelite. The Albee Formation underlies the Ammonoosuc Volcanics and is predominantly composed of interbedded metamorphosed sandstone

  5. Early Literacy and Early Numeracy: The Value of Including Early Literacy Skills in the Prediction of Numeracy Development

    ERIC Educational Resources Information Center

    Purpura, David J.; Hume, Laura E.; Sims, Darcey M.; Lonigan, Cristopher J.

    2011-01-01

    The purpose of this study was to examine whether early literacy skills uniquely predict early numeracy skills development. During the first year of the study, 69 3- to 5-year-old preschoolers were assessed on the Preschool Early Numeracy Skills (PENS) test and the Test of Preschool Early Literacy Skills (TOPEL). Participants were assessed again a…

  6. Tectonic context of the penetrative fracture system origin in the Early Paleozoic shale complex (Baltic Basin, Poland/Sweden).

    NASA Astrophysics Data System (ADS)

    Jarosiński, Marek; Gluszynski, Andrzej; Bobek, Kinga; Dyrka, Ireneusz

    2017-04-01

    Characterization of natural fracture and fault pattern play significant role for reservoir stimulation design and evaluation of its results. Having structural observations limited to immediate borehole surrounding it is a common need to build up a fracture model of reservoir in a range of stimulation reservoir volume or even beyond. To do this we need both a 3D seismic model and a consistent concept of the regional tectonic evolution. We present the result of integrated tectonic study in several deep boreholes target the Lower Paleozoic shale complex of Baltic Basin (BB), combined with analysis of 3D seismic survey and outcrop screening in Scania (Swedish part of the BB). During deposition of shale complex in the Ordovician and Silurian the research area was located 200-300 km away from the continental margin of Baltica involved in the Caledonian collision with the Eastern Avalonia. This distance allowed the shale complex to avoid significant tectonic deformation. Regional seismic cross section reveals the general pattern of the BB infill characteristic for the foreland basin underwent post-collisional isostatic rebound. Due to stress changes in collisional context the shale complex was cross-cut by steep, mostly inverse faults trending NW-SE and NE-SW. The fault zones oriented NW-SE are associated with an array of en echelon faults characteristic for strike-slip displacement. In our interpretation, these faults of Silurian (Wenlock) age create pattern of the regional pop-up structure, which is simultaneously involved in the plate flexure extension. Seismic attributes (e.g. curvature or ant tracking) highlight lineaments which mostly mimic the faults orientation. However, attributes show also some artefacts that come from regular array of seismic sources and receivers, which mimic the orthogonal joint system. Structural observations on borehole core lead us to conclusion that regular, orthogonal fracture system developed after maximum burial of the complex

  7. Paleoclimatic and paleomagnetic constraints on the Paleozoic reconstructions of south China, north China and Tarim

    NASA Astrophysics Data System (ADS)

    Shangyou, Nie

    1991-10-01

    Paleomagnetic and paleoclimatic data provide the most useful latitudinal constraints for plate reconstructions. Distributions through the Paleozoic of five types of climatically sensitive sediments (coals, evaporites, reefs, dolomites and limestones) for south China, north China and Tarim are shown on 15 maps that include 1578 reliable data points. These paleoclimatic data agree reasonably well with available paleomagnetic directions, although significant divergence between the two exists for the Early Paleozoic. These data indicate the following: (1) South China was in low latitudes during the entire Paleozoic, with a subtropical position in the Cambrian. (2) North China also remained near the equator in the Early and Late Paleozoic, except for the Ordovian and the Late Permian when extensive evaporites suggest slightly higher latitudinal positions, while its Middle Paleozoic position is uncertain due to the missing stratigraphie record. (3) In south China, local tectonics appears to have played a dominant role in determining paleogeography and therefore marine sedimentation, especially after the Late Ordovician-Early Silurian, because the areal coverage of marine sediments through time is distinctly different from what would be expected from published global sea-level curves. (4) Paleoclimatic and paleomagnetic data are compatible with biogeographic data which suggest that south China was part of eastern Gondwana in the Early Paleozoic, but was widely separated from Gondwana in the Late Paleozoic, and the split between the two probably happened in the Devonian, giving rise to a major break-up unconformity in central south China.

  8. Brachytherapy in early prostate cancer--early experience.

    PubMed

    Jose, B O; Bailen, J L; Albrink, F H; Steinbock, G S; Cornett, M S; Benson, D C; Schmied, W K; Medley, R N; Spanos, W J; Paris, K J; Koerner, P D; Gatenby, R A; Wilson, D L; Meyer, R

    1999-01-01

    Use of brachytherapy with radioactive seeds in the management of early prostate cancer is commonly used in the United States. The early experience has been reported from the prostate treatment centers in Seattle for the last 10 years. In this manuscript we are reporting our early experience of 150 radioactive seed implantations in early stage prostate cancer using either Iodine 125 or Palladium 103 seeds. The average age of the patient is 66 years and the median Gleason score is 5.4 with a median PSA of 6. A brief description of the evolution of the treatment of prostate cancer as well as the preparation for the seed implantation using the volume study with ultrasound of the prostate, pubic arch study using CT scan of the pelvis and the complete planning using the treatment planning computers are discussed. We also have described the current technique which is used in our experience based on the Seattle guidelines. We plan a follow-up report with the results of the studies with longer follow-up.

  9. Hyperextension in the Caledonian margin of Baltica and its bearing on the structural and metamorphic evolution of Scandinavian Caledonides (Invited)

    NASA Astrophysics Data System (ADS)

    Andersen, T. B.

    2013-12-01

    The Scandinavian segment (~2000 km) of the Caledonian-Appalachian orogen formed by a head-on collision of Baltica and Laurentia. The collision followed rapid (>10 cm/yr) convergence, subduction and closure of the Iapetus Ocean in the Ordovician to the Middle Silurian. The collision culminated in a Himalayan type continental collision at 430 Ma, after which the continental subduction/convergence continued for 20 Myr. The terminal stage was characterized by syn- and post-orogenic extension and exhumation, which produced a template used in opening of the present-day Norwegian Sea. The Scandian collision produced a 'layer-cake' tectono-stratigraphy, but correlation of individual nappe units along strike is not trivial. The vestiges of the Iapetus can, however, be traced along the entire Scandinavian Peninsula and constitute the Iapetus suture. Rocks of assumed Laurentian origin structurally overlie the suture. The outboard units underwent several orogenic events that pre-date the Scandian collision and which took place outboard of Baltica. These will not be discussed further here. The Caledonian passive margin of Baltica was very wide, consisting of non-volcanic hyperextended segments as well as passive volcanic margin domains. Basement-cover pairs, in places with mafic dyke-swarms constitute most of these units. The Baltican and assumed Baltican units below the suture have evidence of diachronous and relatively locally developed pre-Scandian deformation and metamorphic events. In S. Norway large basement-cover units are separated by a melange with numerous solitary mantle peridotites and a number of detrital serpentinites. The melange can be traced along strike across S. Norway. Locally, an island-type ';Celtic' fauna is preserved in detrital serpentinite. Some mantle rocks were structurally emplaced, exhumed, eroded and juxtaposed with continental clastics and crust before the Early Ordovician. The melange was recently interpreted to represent an oceanic to

  10. Early literacy and early numeracy: the value of including early literacy skills in the prediction of numeracy development.

    PubMed

    Purpura, David J; Hume, Laura E; Sims, Darcey M; Lonigan, Christopher J

    2011-12-01

    The purpose of this study was to examine whether early literacy skills uniquely predict early numeracy skills development. During the first year of the study, 69 3- to 5-year-old preschoolers were assessed on the Preschool Early Numeracy Skills (PENS) test and the Test of Preschool Early Literacy Skills (TOPEL). Participants were assessed again a year later on the PENS test and on the Applied Problems and Calculation subtests of the Woodcock-Johnson III Tests of Achievement. Three mixed effect regressions were conducted using Time 2 PENS, Applied Problems, and Calculation as the dependent variables. Print Knowledge and Vocabulary accounted for unique variance in the prediction of Time 2 numeracy scores. Phonological Awareness did not uniquely predict any of the mathematics domains. The findings of this study identify an important link between early literacy and early numeracy development. Copyright © 2011 Elsevier Inc. All rights reserved.

  11. Silurian/Ordovician asymmetrical sill-like bodies from La Codosera syncline, W Spain: A case of tholeiitic partial melts emplaced in a single magma pulse and derived from a metasomatized mantle source

    NASA Astrophysics Data System (ADS)

    López-Moro, F. J.; Murciego, A.; López-Plaza, M.

    2007-07-01

    A Silurian/Ordovician extensional event in the southernmost sectors of the Central Iberian Zone is inferred from the Sm/Nd isochron obtained (436 ± 17 Ma) after the diabase sills from the La Codosera syncline. From the geochemical and mineralogical points of view, the diabase sills are subalkaline and range between high-Mg tholeiite diabases to tholeiite andesites. LREE enrichment, an Nb negative anomaly, the absence of a Ta trough and a high Nd isotope signature ( ɛNd t = + 6) are the most relevant geochemical features. The diabase bodies are up to 330 m in thickness and were sampled from bottom to top along several different sections, permitting the definition of an accumulation of clinopyroxene, olivine and plagioclase close to chilled margins at the bottom, and abundant pegmatoid layers at the top. Chemical profiles and mass-balance modelling suggest that the bulk rock and chilled margin compositions are not dissimilar, defining an unusual S-type vertical compositional profile for large (> 50 m thick) sills, which in turn strongly suggests a single magma pulse and a probable gravitational settling. Assuming chilled margin samples as the parental magma, as well as Cr-enriched samples as cumulate layers, a two-stage liquid line of descent has been established, the first one consisting of a clinopyroxene-plagioclase-olivine cumulate assemblage. A second stage in relation to the depletion in Ti, Fe and V is accounted for by ilmenite fractionation, along with that of clinopyroxene, plagioclase and olivine fractionation. Thermobarometric estimations reveal that the clinopyroxene (around 1100 °C and 197 MPa) was a late mineral phase, whereas the plagioclase (around 1200 °C) was pre- to syn-emplacement, in agreement with the presence only of plagioclase phenocrysts in the chilled margins and the very abundant positive Eu anomaly. The energy constraint modelling is consistent with the lack of a significant assimilation process owing to the high temperature contrast

  12. Early Childhood Special Education and Early Intervention Personnel Preparation Standards of the Division for Early Childhood: Field Validation

    ERIC Educational Resources Information Center

    Cochran, Deborah C.; Gallagher, Peggy A.; Stayton, Vicki D.; Dinnebeil, Laurie A.; Lifter, Karin; Chandler, Lynette K.; Christensen, Kimberly A.

    2012-01-01

    Results of the field validation survey of the revised initial and new advanced Council for Exceptional Children (CEC) Division for Early Childhood (DEC) early childhood special education (ECSE)/early intervention (EI) personnel standards are presented. Personnel standards are used as part of educational accountability systems and in teacher…

  13. Early Attachment Relationships and the Early Childhood Curriculum

    ERIC Educational Resources Information Center

    Cortazar, Alejandra; Herreros, Francisca

    2010-01-01

    This article explores the relationship between attachment theory and the early childhood curriculum. During the first years of life children develop early attachment relationships with their primary caregivers. These attachment relationships, either secure or insecure, will shape children's socio-emotional development. In the USA, the predominant…

  14. Cambrian to Devonian evolution of alluvial systems: The sedimentological impact of the earliest land plants

    NASA Astrophysics Data System (ADS)

    Davies, Neil S.; Gibling, Martin R.

    2010-02-01

    In present-day alluvial environments, the impact of vegetation on sedimentological processes and deposits is well known. A vegetated catchment may decrease sediment yield, sediment erodibility, Hortonian overland flow, aeolian winnowing of fines, the proportion of sediment transported as bedload, and may increase bank stability, infiltration into substrates, and bed roughness. Vegetation also promotes the production of chemically-weathered clays and soils and the adoption of a meandering style. It is generally understood that, prior to the evolution of terrestrial vegetation during the Early Palaeozoic, ancient alluvial systems were markedly different from modern systems, with many systems adopting a "sheet-braided" style. This understanding has previously informed the interpretations of many Precambrian pre-vegetation alluvial successions, but there has been relatively little work regarding Early Palaeozoic alluvial successions laid down prior to and during the initial colonization of the Earth's surface by plants. A comprehensive review of 144 Cambrian to Devonian alluvial successions documented in published literature was combined with original field data from 34 alluvial successions across Europe and North America. The study was designed to identify changes in alluvial style during the period that vegetation was evolving and first colonizing alluvial environments. An increase in mudrock proportion and sandstone maturity is apparent, along with a decrease in overall sand grain size through the Early Palaeozoic. These trends suggest that primitive vegetation cover promoted the production and preservation of muds from the mid Ordovician onwards and increased the residence time of sand-grade sediment in alluvial systems. The compilation also enables the first stratigraphic occurrence of certain vegetation-dependent sedimentary features to be pinpointed and related to the evolution of specific palaeobotanical adaptations. The first markedly heterolithic alluvial

  15. The Transfiguration continental red-bed Cu-Pb-Zn-Ag deposit, Quebec Appalachians, Canada

    NASA Astrophysics Data System (ADS)

    Cabral, Alexandre Raphael; Beaudoin, Georges; Taylor, Bruce E.

    2009-04-01

    The Transfiguration Cu-Pb-Zn-Ag deposit, enclosed within reduced grey sandstone, is associated with continental red beds of the Lower Silurian Robitaille Formation in the Quebec Appalachians, Canada. The Robitaille Formation rests unconformably on foliated Cambro-Ordovician rocks. The unconformity is locally cut by barite veins. The basal unit of the Robitaille Formation comprises green wacke and pebble conglomerate, which locally contain calcite nodules. The latter have microstructures characteristic of alpha-type calcretes, such as “floating” fabrics, calcite-filled fractures (crystallaria) and circumgranular cracks. Massive, grey sandstone overlies the basal green wacke and pebble conglomerate unit, which is overlain, in turn, by red, fine-grained sandstone. Mineralisation occurred underneath the red sandstone unit, chiefly in the grey sandstone unit, as disseminated and veinlet sulphides. Chalcopyrite, the most abundant Cu sulphide, replaced early pyrite. Calcrete, disseminated carbonate and vein carbonate have stable isotope ratios varying from -7.5‰ to -1.1‰ δ13C and from 14.7‰ to 21.3‰ δ18O. The negative δ13C values indicate the oxidation of organic matter in a continental environment. Sulphur isotope ratios for pyrite, chalcopyrite and galena vary from -19‰ to 25‰ δ34S, as measured on mineral concentrates by a conventional SO2 technique. Laser-assisted microanalyses (by fluorination) of S isotopes in pyrite show an analogous range in δ34S values, from -21‰ to 25‰. Negative and positive δ34S values are compatible with bacterial sulphate reduction (BSR) in systems open and closed with respect to sulphate. We interpret similarly high δ34S values for sulphide concentrates (25.1‰) and for vein barite (26.2‰) to result from rapid and complete thermochemical reduction of pore-water sulphate. Two early to late diagenetic stages of mineralisation best explain the origin of the Transfiguration deposit. The first stage was characterised

  16. Ordovician volcanic and plutonic complexes of the Sakmara allochthon in the southern Urals

    NASA Astrophysics Data System (ADS)

    Ryazantsev, A. V.; Tolmacheva, T. Yu.

    2016-11-01

    The Ordovician terrigenous, volcanic-sedimentary and volcanic sequences that formed in rifts of the active continental margin and igneous complexes of intraoceanic suprasubduction settings structurally related to ophiolites are closely spaced in allochthons of the Sakmara Zone in the southern Urals. The stratigraphic relationships of the Ordovician sequences have been established. Their age and facies features have been specified on the basis of biostratigraphic and geochronological data. The gabbro-tonalite-trondhjemite complex and the basalt-andesite-rhyolite sequence with massive sulfide mineralization make up a volcanic-plutonic association. These rock complexes vary in age from Late Ordovician to Early Silurian in certain structural units of the Sakmara Allochthon and to the east in the southern Urals. The proposed geodynamic model for the Ordovician in Paleozoides of the southern Urals reconstructs the active continental margin, whose complexes formed under extension settings, and the intraoceanic suprasubduction structures. The intraoceanic complexes display the evolution of a volcanic arc, back-, or interarc trough.

  17. Geology, Murzuk oil development could boost S. W. Libya prospects

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Thomas, D.

    1995-03-06

    With the recent involvement of Repsol, Total, and OMV in developing the 2 billion bbl oil-in-place Murzuk field complex, an infrastructure will be finally constructed in western Libya which will act as a precursor to more exploration activity and development projects in the Murzuk and Ghadames basins. Murzuk, an intra-cratonic sag basin, is a huge ladle-shaped structural basin covering more than 400,000 sq km and extending beyond the borders of southern Libya. The structure of the area is quite simple. The sub-horizontal or gently dipping strata are faulted and the faults are most frequently parallel to the anticlinal axis. Tectonicmore » movements affected the basin to a greater or lesser degree from early Paleozoic (Caledonian) to post-Eocene (Alpine) times. The paper describes the exploration history; stratigraphy; the Ordovician, Silurian and Devonian, and Carboniferous reservoirs; source rocks; oil gravity and gas content; hydrogeologic constraints; aquifer influence on hydrocarbon accumulation; geologic structures; Murzuk field development; and acreage availability.« less

  18. Bedrock geologic map of the Grafton quadrangle, Worcester County, Massachusetts

    USGS Publications Warehouse

    Walsh, Gregory J.; Aleinikoff, John N.; Dorais, Michael J.

    2011-01-01

    The bedrock geology of the 7.5-minute Grafton, Massachusetts, quadrangle consists of deformed Neoproterozoic to early Paleozoic crystalline metamorphic and intrusive igneous rocks. Neoproterozoic intrusive, metasedimentary, and metavolcanic rocks crop out in the Avalon zone, and Cambrian to Silurian intrusive, metasedimentary, and metavolcanic rocks crop out in the Nashoba zone. Rocks of the Avalon and Nashoba zones, or terranes, are separated by the Bloody Bluff fault. The bedrock geology was mapped to study the tectonic history of the area and to provide a framework for ongoing hydrogeologic characterization of the fractured bedrock of Massachusetts. This report presents mapping by G.J. Walsh, geochronology by J.N. Aleinikoff, geochemistry by M.J. Dorais, and consists of a map, text pamphlet, and GIS database. The map and text pamphlet are available in paper format or as downloadable files (see frame at right). The GIS database is available for download. The database includes contacts of bedrock geologic units, faults, outcrops, structural geologic information, and photographs.

  19. A field trip guidebook to the type localities of Marland Billings' 1935 Paleozoic bedrock stratigraphy near Littleton, New Hampshire

    USGS Publications Warehouse

    Rankin, Douglas W.; Rankin, Mary B.

    2014-01-01

    Marland Billings' classic paper published in 1937 in the Geological Society of America Bulletin established a succession of six stratigraphic units in rocks of low metamorphic grade near Littleton, New Hampshire. The two youngest units are fossiliferous in the area, with ages established at the time as “middle” Silurian and Early Devonian. Billings and students mapped the same stratigraphic section in adjacent areas of progressively higher regional metamorphic grade. This work laid the foundation upon which a major part of subsequent work in New England has been directly or indirectly built. This guidebook was written for a field trip held in March 2013 to visit roadcuts that are as close as possible in March to the type localities or areas of Billings’ six-fold stratigraphic succession. Ten stops are in rocks of chlorite grade of Acadian(?) metamorphism; the final stop visits amphibolite of the Ammonoosuc Volcanics. Fieldwork by the authors over the past 20 years confirms Billings’ broad conclusions.

  20. Identification of multiple magnetizations of the Ediacaran strata in South China

    NASA Astrophysics Data System (ADS)

    Jing, Xianqing; Yang, Zhenyu; Tong, Yabo; Wang, Heng; Xu, Yingchao

    2018-01-01

    A suspected Silurian remagnetization of the Ediacaran strata of South China was proposed decades ago by many researchers, but, there has been no systematic study of its causes and mechanisms. In this study, we investigate the multiphase remagnetization processes that affected the Ediacaran strata and the possible mechanisms of these remagnetization events. We conducted detailed palaeomagnetic, rock magnetic and scanning electron microscope (SEM) studies of samples from the Ediacaran strata in the Jiulongwan (JLWE, JLWS), Qinglinkou (QLK) and Sanxiarenjia (SXRJ) sections in the Three Gorges Area, South China. After removal of a recent viscous remanent magnetization below 150 °C, an intermediate temperature component (ITC; Dg = 27.6°, Ig = 45.3°, N = 12 sites, kg = 184.3, α95 = 3.2° for JLWE; Dg = 22°, Ig = 45.3°, N = 11 sites, kg = 789.2, α95 = 1.6° for JLWS; and Dg = 25.5°, Ig = 52.5°, N = 6 sites, kg = 533.4, α95 = 2.9° for SXRJ) was removed below 300 °C which coincides with the Jurassic results from South China, suggesting a pervasive Jurassic remagnetization. In addition, a high temperature component (HTC; Ds = 84.8°, Is = 19.2°, N = 9 sites, ks = 35.5, α95 = 8.8° for JLWE; Ds = 74.1°, Is = 49.4°, N = 7 sites, ks = 218.9, α95 = 4.1° for JLWS; and Ds = 89.5°, Is = 30.7°, N = 8 sites, ks = 129.2, α95 = 4.9° for SXRJ) was isolated between 300 and 480-540 °C. Rock magnetic and SEM studies suggest that the ITC and HTC are carried by pyrrhotite and magnetite, respectively. SEM observations also demonstrate the occurrence of massive authigenic magnetite in cavities or cracks, mineralogical changes from pyrite to Fe oxides, and the reaction between gypsum and Fe oxides. Based on similarities to the Silurian poles of South China, together with the SEM observations, we suggest that the HTC from the JLWE and SXRJ sections is a Silurian age remagnetization. The oxidation of iron sulphides and thermochemical sulphate reduction induced by the

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

    NASA Astrophysics Data System (ADS)

    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 (< 0.5 Myr) and affected intracratonic basins of Mauritania, Morocco, Algeria, Libya, Egypt and Saudi Arabia. The organisation of the glacial sedimentary record is considered to be controlled at the basin-scale by the location of fast-flowing ice streams active during glacial maxima, and by the processes of meltwater release during glacial recession. In these latter

  2. Characteristics and origin of the relatively high-quality tight reservoir in the Silurian Xiaoheba Formation in the southeastern Sichuan Basin

    PubMed Central

    Gong, Xiaoxing; Shi, Zejin; Wang, Yong; Tian, Yaming; Li, Wenjie; Liu, Lei

    2017-01-01

    A mature understanding of the sandstone gas reservoir in the Xiaoheba Formation in the southeastern Sichuan Basin remains lacking. To assess the reservoir characteristics and the origin of the high-quality reservoir in the Xiaoheba Formation, this paper uses systematic field investigations, physical property analysis, thin section identification, scanning electron microscopy and electron microprobe methods. The results indicate that the Xiaoheba sandstone is an ultra-tight and ultra-low permeability reservoir, with an average porosity of 2.97% and an average permeability of 0.56×10−3 μm2. This promising reservoir is mainly distributed in the Lengshuixi and Shuangliuba regions and the latter has a relatively high-quality reservoir with an average porosity of 5.28% and average permeability of 0.53×10−3 μm2. The reservoir space comprises secondary intergranular dissolved pores, moldic pores and fractures. Microfacies, feldspar dissolution and fracture connectivity control the quality of this reservoir. The relatively weak compaction and cementation in the interbedded delta front distal bar and interdistributary bay microfacies indirectly protected the primary intergranular pores and enhanced late-stage dissolution. Late-stage potassium feldspar dissolution was controlled by the early-stage organic acid dissolution intensity and the distance from the hydrocarbon generation center. Early-stage fractures acted as pathways for organic acid migration and were therefore important factors in the formation of the reservoir. Based on these observations, the area to the west of the Shuangliuba and Lengshuixi regions has potential for gas exploration. PMID:28686735

  3. Deep-water lithofacies and conodont faunas of the Lisburne Group, western Brooks Range, Alaska: A section in Geologic studies in Alaska by the U.S. Geological Survey, 1992

    USGS Publications Warehouse

    Dumoulin, Julie A.; Harris, Anita G.; Schmidt, Jeanine M.

    1993-01-01

    Deep-water lithofacies of the Lisburne Group occur in thrust sheets in the western part of the foreland fold and thrust belt of the Brooks Range and represent at least three discrete units. The Kuna Formation (Brooks Range allochthon) consists mostly of spiculitic mudstone and lesser shale; subordinate carbonate layers are chiefly diagenetic dolomite. Predominantly shale sections of the Kuna that contain few sponge spicules occur in the western part of the study area. The Akmalik Chert (Picnic Creek allochthon) is mostly radiolarian-spiculitic chert; rare limy beds are calcitized radiolarite. The Rim Butte unit (Ipnavik River allochthon) consists chiefly of calcareous turbidites, derived from both shallow- and deep-water sources, interbedded with spiculitic mudstone. Much of the material in the turbidites came from a contemporaneous carbonate platform and margin, but some fossils and lithic clasts were eroded from older, already lithified carbonate-platform rocks. All three units appear to be roughly coeval and are chiefly Osagean (late Early Mississippian) in age in the study area.Shallow-water lithofacies of the Lisburne Group exposed in the Howard Pass area (Brooks Range allochthon) are mostly of Meramecian (early Late Mississippian) age. Thus, these carbonate-platform rocks were not the source of the calcareous turbidites in the Rim Butte unit. Rim Butte turbidites could have been derived from older platform carbonate rocks such as those of the Utukok Formation (Kelly River allochthon) exposed mainly to the west of the Howard Pass quadrangle.

  4. Mesozoic Alpine facies deposition as a result of past latitudinal plate motion.

    PubMed

    Muttoni, Giovanni; Erba, Elisabetta; Kent, Dennis V; Bachtadse, Valerian

    2005-03-03

    The fragmentation of Pangaea as a consequence of the opening of the Atlantic Ocean is documented in the Alpine-Mediterranean region by the onset of widespread pelagic sedimentation. Shallow-water sediments were replaced by mainly pelagic limestones in the Early Jurassic period, radiolarian cherts in the Middle-Late Jurassic period, and again pelagic limestones in the Late Jurassic-Cretaceous period. During initial extension, basin subsidence below the carbonate compensation depth (CCD) is thought to have triggered the transition from Early Jurassic limestones to Middle-Late Jurassic radiolarites. It has been proposed that the transition from radiolarites to limestones in the Late Jurassic period was due to an increase in calcareous nannoplankton abundance when the CCD was depressed below the ocean floor. But in modern oceans, sediments below the CCD are not necessarily radiolaritic. Here we present palaeomagnetic samples from the Jurassic-Cretaceous pelagic succession exposed in the Lombardian basin, Italy. On the basis of an analysis of our palaeolatitudinal data in a broader palaeogeographic context, we propose an alternative explanation for the above facies tripartition. We suggest that the Lombardian basin drifted initially towards, and subsequently away from, a near-equatorial upwelling zone of high biosiliceous productivity. Our tectonic model for the genesis of radiolarites adds an essential horizontal plate motion component to explanations involving only vertical variations of CCD relative to the ocean floor. It may explain the deposition of radiolarites throughout the Mediterranean and Middle Eastern region during the Jurassic period.

  5. Early Years Practitioners' Views on Early Personal, Social and Emotional Development

    ERIC Educational Resources Information Center

    Aubrey, Carol; Ward, Karen

    2013-01-01

    Current policy guidance stresses the need for early identification of obstacles to learning and appropriate intervention. New standards for learning (Early Years Foundation Stage) place personal, social and emotional development (PSED) as central to learning and development. This paper reports a survey and follow-up interviews with early years…

  6. An outline of the palaeogeographic evolution of the Australasian region since the beginning of the Neoproterozoic

    NASA Astrophysics Data System (ADS)

    Li, Z. X.; Powell, C. McA.

    2001-04-01

    In the last 1000 million years, Australia has been part of two supercontinents: Palaeozoic Gondwanaland and Neoproterozoic Rodinia. Neoproterozoic Australia was covered by shallow epicontinental seas, and, in the late Neoproterozoic, by low-latitude glaciers. The breakup of Rodinia along the Tasman Line occurred at the end of the Sturtian glaciation (760 Ma) giving rise to the Palaeo-Pacific Ocean. Gondwanaland formed in the Early Cambrian, at the same time as the Tarim block broke away from northwestern Australia. Westward subduction of the Palaeo-Pacific Ocean along the eastern margin of Australia-Antarctica commenced during the Early Cambrian in northern Victoria Land and in the Middle Cambrian in South Australia, and culminated to the Late Cambrian-Early Ordovician Ross-Delamerian Mountains. In the Ordovician, the magmatic arc retreated from Australia's then-eastern continental margin, forming a marginal sea and offshore island arc. A shallow seaway across Australia in the Late Cambrian and Ordovician gradually gave way to desert-like conditions in Central Australia and the adjacent Canning Basin by Silurian time. The Silurian to mid-Devonian was an interval of rapidly changing palaeogeography in eastern Australia with deep volcanogenic troughs formed in a dextral transtensional tectonic setting. Widespread deformation in the Tasman orogenic zone in the Middle Devonian to Early Carboniferous, was accompanied by the development of an Andean-style magmatic arc along the Pacific continental margin of Australia. The most widespread Phanerozoic mountain-building stage in Central Australia occurred in the Late Devonian to mid-Carboniferous, as part of a world-wide Variscan orogenic episode associated with the collision of Gondwanaland with Laurussia to form Pangea. In the late Visean, Australia drifted rapidly southward from previous low latitudes to a near-polar position. Glacial conditions dominated the Late Carboniferous and earliest Permian. Transtensional basins

  7. Ernst Haeckel's ontogenetic recapitulation: irritation and incentive from 1866 to our time.

    PubMed

    Sander, Klaus

    2002-11-01

    Ernst Haeckel (1834-1919) must count among the most widely known biologists of his time. His monographs on radiolarian skeletons, sponges and medusae immediately became standard works, owing partly to lavish illustrations that later on culminated in his "Art Forms in Nature", which markedly influenced the "art nouveau" of the early 20th century. Haeckel's main impact, however, came from his numerous popular books that were crucial in transferring Darwin's ideas to continental Europe. Haeckel's main addition was his claim that ontogeny recapitulates phylogeny. It was partly founded on pre-Darwinian observations by J.F. Meckel and K.E. v. Baer who noticed that vertebrate embryos of different species resemble each other more strongly during early ontogenesis than later on. Wishing to illustrate this clearly, Haeckel clandestinely generalized some figures showing early embryos of animals and Man. This "fraud" provided ammunition for his many adversaries, most of whom felt provoked by his antireligious campaigns. The resulting controversies continued well into the 20th century but then subsided. Quite recently, however, they have flared up again, perhaps in connection with progress in molecular embryology that revealed an amazing evolutionary conservation of genes and their cooperation in signal transduction chains. The scientific publications that triggered this flare, and a selection of "Letters to the Editor" in both international science magazines and the German popular press, serve here to show that Haeckel's idea of recapitulation, while having proven its heuristic value, is still causing considerable irritation. This results from the widespread intuition that the marvels of ontogenesis and other biological phenomena must reflect some "intelligent design" rather than Darwinian evolution.

  8. Foraminifera fauna of the Tethys Ocean Basin from the Aalenian - Bajocian boundary from Bakony Mountain (Hungary)

    NASA Astrophysics Data System (ADS)

    Zsiborás, Gábor; Görög, Ágnes

    2014-05-01

    The Middle Jurassic foraminiferal fauna of the Tethys Ocean Basin is hardly known. It is especially true for the Aalenian- early Bajocian, from when only BARBIERI (1964) published some forms from Sicily. Thus the aim of our study was to give a detailed systematic description of the foraminiferal fauna and microfacies analyses of Tű zköves Gorge of Bakonycsernye, Bakony Mountains, Western Hungary. The studied succession is near to the classic Jurassic locality - which become famous by the pioneering ammonite work of GéCZY. According to the recent study of GALáCZ & EVANICS, ammonites indicate Concavum (Aalenian), Discites and Ovale (Bajocian) zones. Seventeen samples were collected from the 3.5 m thick sequence of Ammonitico Rosso type reddish and greenish grey marl with limestone nodules. For the microfacies studies thin sections were made. To extract the microfossils, each sample was dissolved in concentrated acetic acid. The layers were rich in macrofossils: the most abundant were Bositra shells and ammonites. The microfauna consist of foraminifers, ostracods, radiolarians, Echinodermata parts and rhyncholits. The preservation of the foraminiferal fauna is relatively poor. 36 taxa, 29 genera and 27 species were identified, for the paleoecological evaluation quantitative analysis and classifying into morphogroups were made. Throughout the studied succession, the foraminiferal fauna is relative monotonous, poor and low diversity in species. All these taxa have wide stratigraphical distribution, significant Aalenian or Bajocian species have not been found. At the Aalenian-Bajocian transition the foraminiferal fauna showed an impoverishment. The most abundant genus was Spirillina, its amount is more than 90% in some samples. In suborder Lagenina the most frequent genera were Lenticulina, Dentalina and Nodosaria, moreover, Vaginulina, Eoguttulina, Ramulina and Bullopora could have been found. Agglutinated forms and Paalzowella were subordinated. Porcelaneous

  9. The Identification of Rock Types in an Arid Region by Air Photo Patterns.

    DTIC Science & Technology

    1981-06-01

    Mountain, Texas. AAPG Bull. vol. 44. pp. 1785-1792. Harbour, R. L. 1972. ;eologv, 01the northern Franklin 11ountains. Texas and Neiv Mehxico. usGs Buill...Lloyd C. 1953. Upper Ordovician and Silurian Stratigraphy of Sacramento Mountains, Otero County. New Alexico. AAPG Bull. vol. 37, pp. 1894-1918. Pray

  10. Early menarche, nulliparity and the risk for premature and early natural menopause.

    PubMed

    Mishra, Gita D; Pandeya, Nirmala; Dobson, Annette J; Chung, Hsin-Fang; Anderson, Debra; Kuh, Diana; Sandin, Sven; Giles, Graham G; Bruinsma, Fiona; Hayashi, Kunihiko; Lee, Jung Su; Mizunuma, Hideki; Cade, Janet E; Burley, Victoria; Greenwood, Darren C; Goodman, Alissa; Simonsen, Mette Kildevæld; Adami, Hans-Olov; Demakakos, Panayotes; Weiderpass, Elisabete

    2017-03-01

    Are parity and the timing of menarche associated with premature and early natural menopause? Early menarche (≤11 years) is a risk factor for both premature menopause (final menstrual period, FMP <40 years) and early menopause (FMP 40-44 years), a risk that is amplified for nulliparous women. Women with either premature or early menopause face an increased risk of chronic conditions in later life and of early death. Findings from some studies suggest that early menarche and nulliparity are associated with early menopause, however overall the evidence is mixed. Much of the evidence for a direct relationship is hampered by a lack of comparability across studies, failure to adjust for confounding factors and inadequate statistical power. This pooled study comprises 51 450 postmenopausal women from nine observational studies in the UK, Scandinavia, Australia and Japan that contribute to the International collaboration for a Life course Approach to reproductive health and Chronic disease Events (InterLACE). Age at menarche (categorized as ≤11, 12, 13, 14 and 15 or more years) and parity (categorized as no children, one child and two or more children) were exposures of interest. Age at FMP was confirmed by at least 12 months of cessation of menses where this was not the result of an intervention (such as surgical menopause due to bilateral oophorectomy or hysterectomy) and categorized as premature menopause (FMP before age 40), early menopause (FMP 40-44 years), 45-49 years, 50-51 years, 52-53 years and 54 or more years. We used multivariate multinomial logistic regression models to estimate relative risk ratio (RRR) and 95% CI for associations between menarche, parity and age at FMP adjusting for within-study correlation. The median age at FMP was 50 years (interquartile range 48-53 years), with 2% of the women experiencing premature menopause and 7.6% early menopause. Women with early menarche (≤11 years, compared with 12-13 years) were at higher risk of premature

  11. Recent Coverage of Early Childhood Education Approaches in Open Access Early Childhood Journals

    ERIC Educational Resources Information Center

    Keskin, Burhanettin

    2016-01-01

    A content analysis of the coverage of the major approaches to early childhood education in the early childhood research journals, published between 2010 and 2014, that are early childhood research oriented and have free online access were investigated. Among 21 journals in early childhood education, two journals were selected for the content…

  12. Early Educational Intervention, Early Cumulative Risk, and the Early Home Environment as Predictors of Young Adult Outcomes within a High-Risk Sample

    ERIC Educational Resources Information Center

    Pungello, Elizabeth P.; Kainz, Kirsten; Burchinal, Margaret; Wasik, Barbara H.; Sparling, Joseph J.; Ramey, Craig T.; Campbell, Frances A.

    2010-01-01

    The extent to which early educational intervention, early cumulative risk, and the early home environment were associated with young adult outcomes was investigated in a sample of 139 young adults (age 21) from high-risk families enrolled in randomized trials of early intervention. Positive effects of treatment were found for education attainment,…

  13. [In-patient (early) rehabilitation].

    PubMed

    Wallesch, Claus-W; Lautenschläger, Sindy

    2017-04-01

    It is difficult to develop the financing and hospital provision of interventions for early rehabilitation within the diagnosis-related group (DRG) system. In addition to a range of partially rehabilitative complex interventions, the system recognizes three main forms of early rehabilitative interventions: geriatric, neurological/neurosurgical, and interdisciplinary and others. In this article, the appropriate definitions and cost-effectiveness of these procedures are analyzed and compared. The early rehabilitative interventions are characterized by constant cooperation in the therapeutic team, especially neurological early rehabilitation through the incorporation of nursing as a therapeutic profession. Whereas geriatric and neurological early rehabilitation are reflected in the DRG system, the former provided in many general hospitals and the latter mainly in specialized institutions, interdisciplinary early rehabilitation has only occasionally been represented in the DRG system so far. If all acute in-patients who require early rehabilitation should receive such an intervention, an additional fee must be implemented for this this interdisciplinary service.

  14. How Were Southwest Pacific Pelagic Ecosystems Affected by Extreme Global Warming During the Initial Eocene Thermal Maximum?

    NASA Astrophysics Data System (ADS)

    Hollis, C. J.; Crouch, E. M.; Dickens, G. R.

    2004-12-01

    Four sections in eastern New Zealand provide the only South Pacific record of the initial Eocene thermal maximum (IETM): a siliciclastic outer shelf section (Tawanui, Hawkes Bay) and three pelagic-hemipelagic sections forming an outer shelf-upper slope transect across a carbonate ramp (Muzzle, Dee and Mead Streams, Clarence Valley). Although the rocks are too indurated to yield reliable oxygen isotope data, the IETM is identified by bulk carbonate carbon isotopes as a sharp negative excursion followed by gradual recovery over 0.6 to 4.0 m. In all sections, the excursion is mirrored by terrigenous sediment concentration, due to reduced biogenic (carbonate and silica) input and increased terrigenous input. Increased precipitation under warm humid conditions appears to have increased terrestrial discharge, recorded by deposition of smectitic marl in pelagic settings and illite/kaolinite-bearing smectitic mudstone in neritic settings. Eutrophic conditions are inferred for the IETM interval at Tawanui based on dysoxia, carbonate dissolution, an acme for the peridinioid dinocyst Apectodinium and abundant Toweius spp in nannofossil assemblages. Continued abundance of Toweius and replacement of Apectodinium by peridinioids of the Deflandrea complex suggests that eutrophic, albeit cooler, conditions persisted for at least 0.5 Ma after the IETM. In contrast, the IETM in Clarence Valley is marked by reduced biogenic silica content but little change in carbonate, and no evidence for carbonate dissolution. Sparse, poorly preserved palynomorphs assemblages suggest organic matter was oxidised under fully oxic conditions. Reduced numbers of upwelling indicators in the siliceous microfossil assemblage and common warm-water planktic foraminifera (Morozovella spp.), nannoplankton (Discoaster spp.) and radiolarians (e.g. Podocyrtis and Theocorys spp.) signal a switch from eutrophic to oligotrophic conditions and significant warming of near-surface waters. A progressive increase in

  15. Metals in Devonian kerogenous marine strata at Gibellini and Bisoni properties in southern Fish Creek Range, Eureka County, Nevada

    USGS Publications Warehouse

    Desborough, George A.; Poole, F.G.; Hose, R.K.; Radtke, A.S.

    1979-01-01

    . In fresh rock, bluish-white opaline-like silica (chalcedonic quartz) fills microfractures, and is believed to have originated by diagenetic mobilization of opaline silica from radiolarian tests and sponge spicules. As revealed by microscopic study, the Gibellini facies originally consisted of siliceous muds, slimes, and oozes high in organic constituents. The organic matter is amorphous flaky and stringy sapropel, and probably includes remains of bacteria, phytoplankton, zooplankton, and minor higher plants. Recognizable organic remnants include radiolarian tests, sponge spicules, conodonts, brachiopod shells, algae, and humic debris. Diagnostic radiolarians indicate a Late Devonian age for the Gibellini facies of the Woodruff Formation. Some pyrite is disseminated through the rock and may be primary (syngenetic) but significant pyrite and marcasite occur in chalcedonic quartz veinlets and appear to be diagenetic. In fresh rock, black solid bitumen and liquid oil fill voids and microfractures. These early phase hydrocarbons probably were released during diagenesis from complex nonhydrocarbon molecular structures originating from living organisms, and formed without any major thermal degradation of the kerogen. Gas chromatographic analysis of the saturated hydrocarbon fraction indicates a very complex mixture dominated by branched and cyclic compounds. Conodont and palynomorph color alteration, vitrinite reflectance, and other organic geochemical data suggest that the organic matter in the rock is thermally immature and has not been subjected to temperatures greater than 60?C since deposition in Devonian time. All of these characteristics are consistent with the interpretation of a relatively low temperature and a shallow-burial history for the Gibellini facies on ridge 7129.

  16. African ancestry, early life exposures, and respiratory morbidity in early childhood.

    PubMed

    Kumar, R; Tsai, H-J; Hong, X; Gignoux, C; Pearson, C; Ortiz, K; Fu, M; Pongracic, J A; Burchard, E G; Bauchner, H; Wang, X

    2012-02-01

    Racial disparities persist in early childhood wheezing and cannot be completely explained by known risk factors. To evaluate the associations of genetic ancestry and self-identified race with early childhood recurrent wheezing, accounting for socio-economic status (SES) and early life exposures. We studied 1034 children in an urban, multi-racial, prospective birth cohort. Multivariate logistic regression was used to evaluate the association of genetic ancestry as opposed to self-identified race with recurrent wheezing (>3 episodes). Sequential models accounted for demographic, socio-economic factors and early life risk factors. Genetic ancestry, estimated using 150 ancestry informative markers, was expressed in deciles. Approximately 6.1% of subjects (mean age 3.1 years) experienced recurrent wheezing. After accounting for SES and demographic factors, African ancestry (OR: 1.16, 95% CI: 1.02-1.31) was significantly associated with recurrent wheezing. By self-reported race, hispanic subjects had a borderline decrease in risk of wheeze compared with African Americans (OR: 0.44, 95% CI: 0.19-1.00), whereas white subjects (OR: 0.46, 95% CI: 0.14-1.57) did not have. After further adjustment for known confounders and early life exposures, both African (OR: 1.19, 95% CI: 1.05-1.34) and European ancestry (OR: 0.84, 95% CI: 0.74-0.94) retained a significant association with recurrent wheezing, as compared with self-identified race (OR(whites) : 0.31, 95% CI: 0.09-1.14; OR(hispanic) : 0.47, 95% CI: 0.20-1.08). There were no significant interactions between ancestry and early life factors on recurrent wheezing. In contrast to self-identified race, African ancestry remained a significant, independent predictor of early childhood wheezing after accounting for early life and other known risk factors associated with lung function changes and asthma. Genetic ancestry may be a powerful way to evaluate wheezing disparities and a proxy for differentially distributed genetic and

  17. African ancestry, early life exposures, and respiratory morbidity in early childhood

    PubMed Central

    Kumar, R.; Tsai, H.-J.; Hong, X.; Gignoux, C.; Pearson, C.; Ortiz, K.; Fu, M.; Pongracic, J. A.; Burchard, E. G.; Bauchner, H.; Wang, X.

    2012-01-01

    Summary Background Racial disparities persist in early childhood wheezing and cannot be completely explained by known risk factors. Objective To evaluate the associations of genetic ancestry and self-identified race with early childhood recurrent wheezing, accounting for socio-economic status (SES) and early life exposures. Methods We studied 1034 children in an urban, multi-racial, prospective birth cohort. Multivariate logistic regression was used to evaluate the association of genetic ancestry as opposed to self-identified race with recurrent wheezing (>3 episodes). Sequential models accounted for demographic, socio-economic factors and early life risk factors. Genetic ancestry, estimated using 150 ancestry informative markers, was expressed in deciles. Results Approximately 6.1% of subjects (mean age 3.1 years) experienced recurrent wheezing. After accounting for SES and demographic factors, African ancestry (OR: 1.16, 95% CI: 1.02–1.31) was significantly associated with recurrent wheezing. By self-reported race, hispanic subjects had a borderline decrease in risk of wheeze compared with African Americans (OR: 0.44, 95% CI: 0.19–1.00), whereas white subjects (OR: 0.46, 95% CI: 0.14–1.57) did not have. After further adjustment for known confounders and early life exposures, both African (OR: 1.19, 95% CI: 1.05–1.34) and European ancestry (OR: 0.84, 95% CI: 0.74–0.94) retained a significant association with recurrent wheezing, as compared with self-identified race (ORwhites: 0.31, 95% CI: 0.09–1.14; ORhispanic: 0.47, 95% CI: 0.20–1.08). There were no significant interactions between ancestry and early life factors on recurrent wheezing. Conclusions and Clinical Relevance In contrast to self-identified race, African ancestry remained a significant, independent predictor of early childhood wheezing after accounting for early life and other known risk factors associated with lung function changes and asthma. Genetic ancestry may be a powerful way to

  18. Field, petrologic and detrital zircon study of the Kings sequence and Calaveras complex, Southern Lake Kaweah Roof Pendant, Tulare County, California

    NASA Astrophysics Data System (ADS)

    Buchen, Christopher T.

    U-Pb dating of detrital zircon grains separated from elastic sedimentary rocks is combined with field, petrographic and geochemical data to reconstruct the geologic history of Mesozoic rocks exposed at the southern end of the Lake Kaweah metamorphic pendant, western Sierra Nevada. Identification of rocks exposed at Limekiln Hill, Kern County, CA, as belonging to the Calaveras complex and Kings sequence was confirmed. Detrital zircon populations from two Calaveras complex samples provide Permo-Triassic maximum depositional ages (MDA) and reveal a Laurentian provenance indicating that continental accretion of the northwest-trending Kings-Kaweah ophiolite belt was in process prior to the Jurassic Period. Rock types including radiolarian metachert, metachert-argillite, and calc-silicate rocks with marble lenses are interpreted as formed in a hemipelagic environment of siliceous radiolarian deposition, punctuated by extended episodes of lime-mud gravity flows mixing with siliceous ooze forming cafe-silicate protoliths and limestone olistoliths forming marble lenses. Two samples of the overlying Kings sequence turbidites yield detrital zircons with an MDA of 181.4 +/-3.0 Ma and an interpreted provenance similar to other Jurassic metasediments found in the Yokohl Valley, Sequoia and Boyden Cave roof pendants. Age peaks indicative of Jurassic erg heritage are also present. In contrast, detrital zircon samples from the Sequoia and Slate Mountain roof pendants bear age-probability distributions interpreted as characteristic of the Snow Lake block, a tectonic sliver offset from the Paleozoic miogeocline.

  19. Middle Triassic back-arc basalts from the blocks in the Mersin Mélange, southern Turkey: Implications for the geodynamic evolution of the Northern Neotethys

    NASA Astrophysics Data System (ADS)

    Sayit, Kaan; Bedi, Yavuz; Tekin, U. Kagan; Göncüoglu, M. Cemal; Okuyucu, Cengiz

    2017-01-01

    The Mersin Mélange is a tectonostratigraphic unit within the allochthonous Mersin Ophiolitic Complex in the Taurides, southern Turkey. This chaotic structure consists of blocks and tectonic slices of diverse origins and ages set in a clastic matrix of Upper Cretaceous age. In this study, we examine two blocks at two different sections characterized by basaltic lava flows alternating with radiolarian-bearing pelagic sediments. The radiolarian assemblage extracted from the mudstone-chert alternation overlying the lavas yields an upper Anisian age (Middle Triassic). The immobile element geochemistry suggests that the lava flows are predominantly characterized by sub-alkaline basalts. All lavas display pronounced negative Nb anomalies largely coupled with normal mid-ocean basalt (N-MORB)-like high field strength element (HFSE) patterns. On the basis of geochemical modelling, the basalts appear to have dominantly derived from spinel-peridotite and pre-depleted spinel-peridotite sources, while some enriched compositions can be explained by contribution of garnet-facies melts from enriched domains. The overall geochemical characteristics suggest generation of these Middle Triassic lavas at an intra-oceanic back-arc basin within the northern branch of Neotethys. This finding is of significant importance, since these rocks may represent the presence of the oldest subduction zone found thus far from the Neotethyan branches. This, in turn, suggests that the rupturing of the Gondwanan lithosphere responsible for the opening of the northern branch of Neotethys should have occurred during the Lower Triassic or earlier.

  20. DOE Office of Scientific and Technical Information (OSTI.GOV)

    Dallmeyer, R.D.; Gee, D.G.; Beckholmen, M.

    In central portions of the Scandinavian Caledonides, greenschist facies volcanosedimentary successions within the Koeli Nappe Complex have been thrust several hundred kilometers eastward onto the Baltoscandian platform. These were derived from eugeoclinal terranes situated outboard (west) of the Baltica continent during the early Paleozoic. The Koeli Nappe Complex is tectonically underlain by higher grade units within the Seve Nappe Complex. These are composed of amphibolite and granulite facies rocks and locally contain eclogites. The Seve Nappes tectonically separate Koeli units from structurally lower allochthons derived from more inboard environments along the Baltoscandian miogeocline. Previous mineral isotopic age-determinations from Seve andmore » Koeli units have been in the 430 to 390 Ma range and have been interpreted to presumably date cooling following Scandian (Middle Silurian to Early Devonian) metamorphism. However, incremental-release /sup 40/Ar//sup 39/Ar dates recorded by minerals within some of the Koeli and Seve Nappes exposed in Jaemtland, Sweden (Taennforsen and Are districts) provide evidence of earlier tectonothermal activity. Hornblendes from the Seve and Koeli Nappe Complexes display variably discordant age spectra as a result of low-temperature, experimental evolution of loosely bound extraneous argon components. However, in most analyses plateau ages of 510 to 475 Ma (Koeli) and 465 to 455 Ma (Seve) are defined. In contrast, muscovite and biotite from all tectonic units record Scandian cooling ages between 245 and 410 Ma. The older events recorded by hornblende within these Seve and Koeli units are evidence of early Caledonian tectonothermal activity and subsequent diachronous cooling during the Early-Middle Ordovician.« less

  1. A Study of the Relationship between Early Childhood Program Attributes and Early Childhood Reading Achievement

    ERIC Educational Resources Information Center

    Washington, Novella M.

    2012-01-01

    This quantitative correlational study focuses on the relationship between early childhood program attributes and early childhood reading success. Data will be gathered from early childhood sites with grades prekindergarten through second grade in which early childhood program attributes exist and early childhood reading is measured by the…

  2. Evolution of Devonian carbonate-shelf margin, Nevada

    USGS Publications Warehouse

    Morrow, J.R.; Sandberg, C.A.

    2008-01-01

    The north-trending, 550-km-long Nevada segment of the Devonian carbonate-shelf margin, which fringed western North America, evidences the complex interaction of paleotectonics, eustasy, biotic changes, and bolide impact-related influences. Margin reconstruction is complicated by mid-Paleozoic to Paleogene compressional tectonics and younger extensional and strike-slip faulting. Reports published during the past three decades identify 12 important events that influenced development of shelf-margin settings; in chronological order, these are: (1) Early Devonian inheritance of Silurian stable shelf inargin, (2) formation of Early to early Middle 'Devonian shelf-margin basins, (3) propradation of later Middle Devonian shelf margin, (4) late Middle Devonian Taghanic ondap and continuing long-term Frasnian transgression, (5) initiation of latest Middle Devonian to early Frasnian proto-Antler orogenic forebulge, (6) mid-Frasnian Alamo Impact, (7) accelerated development of proto-Antler forebulge and backbulge Pilot basin, (8) global late Frasnian sentichatovae sea-level rise, (9) end-Frasnian sea-level fluctuations and ensuing mass extinction, (10) long-term Famennian regression and continept-wide erosion, (11) late Famennian emergence: of Ahtler orogenic highlands, and (12) end-Devonian eustatic sea-level fall. Although of considerable value for understanding facies relationships and geometries, existing standard carbonate platform-margin models developed for passive settings else-where do not adequately describe the diverse depositional and, structural settings along the Nevada Devonian platform margin. Recent structural and geochemical studies suggest that the Early to Middle Devonian-shelf-margin basins may have been fault-bound and controlled by inherited Precambrian structure. Subsequently, the migrating latest Middle to Late Devonian Antler orogenic forebulge exerted a dominant control on shelf-margin position, morphology, and sedimentation. ??Geological Society of

  3. Potential for technically recoverable unconventional gas and oil resources in the Polish-Ukrainian Foredeep, Poland, 2012

    USGS Publications Warehouse

    Gautier, Donald L.; Pitman, Janet K.; Charpentier, Ronald R.; Cook, Troy; Klett, Timothy R.; Schenk, Christopher J.

    2012-01-01

    Using a performance-based geological assessment methodology, the U.S. Geological Survey estimated mean volumes of 1,345 billion cubic feet of potentially technically recoverable gas and 168 million barrels of technically recoverable oil and natural gas liquids in Ordovician and Silurian age shales in the Polish- Ukrainian Foredeep basin of Poland.

  4. Early Childhood Diplomacy: Policy Planning for Early Childhood Development

    ERIC Educational Resources Information Center

    Vargas-Barón, Emily; Diehl, Kristel

    2018-01-01

    Children who are well nurtured, appropriately cared for, and provided with positive learning opportunities in their early years have a better chance of becoming healthy and productive citizens of nations and of the world. This article reviews the art and science of policy planning for early childhood development (ECD) from a diplomacy perspective.…

  5. Overview of Play: Its Uses and Importance in Early Intervention/Early Childhood Special Education

    ERIC Educational Resources Information Center

    Lifter, Karin; Foster-Sanda, Suzanne; Arzamarski, Caley; Briesch, Jacquelyn; McClure, Ellen

    2011-01-01

    Play is a natural activity of early childhood, which has great relevance to the fields of early intervention, early childhood special education, and early childhood education. Within these fields, ongoing tensions persist in how play is described and used. These tensions compromise activities of assessment, intervention, and curriculum development…

  6. Early Number Skills Gains and Mathematics Achievement: Intervening to Establish Successful Early Mathematics Trajectories

    ERIC Educational Resources Information Center

    Shanley, Lina; Clarke, Ben; Doabler, Christian T.; Kurtz-Nelson, Evangeline; Fien, Hank

    2017-01-01

    Early number skills, comprised of both informal and formal skills, are associated with later mathematics achievement. Thus, the development of foundational early number skills is an important aspect of early mathematics instruction. This study explored relations between early number skills gains and mathematics achievement for students at risk for…

  7. Individual differences in early adolescents' latent trait cortisol (LTC): Relation to early adversity.

    PubMed

    Stroud, Catherine B; Chen, Frances R; Doane, Leah D; Granger, Douglas A

    2016-09-01

    Substantial evidence suggests that youth who experience early adversity exhibit alterations in hypothalamic pituitary adrenal (HPA) axis functioning, thereby increasing risk for negative health outcomes. However, few studies have explored whether early adversity alters enduring trait indicators of HPA axis activity. Using objective contextual stress interviews with adolescents and their mothers to assess early adversity, we examined the cumulative impact of nine types of early adversity on early adolescents girls' latent trait cortisol (LTC). Adolescents (n = 122; M age = 12.39 years) provided salivary cortisol samples three times a day (waking, 30 min post-waking, and bedtime) over 3 days. Latent state-trait modeling indicated that the waking and 30 min post-waking samples contributed to a LTC factor. Moreover, greater early adversity was associated with a lower LTC level. Implications of LTC for future research examining the impact of early adversity on HPA axis functioning are discussed. © 2016 Wiley Periodicals, Inc. Dev Psychobiol 58:700-713, 2016. © 2016 Wiley Periodicals, Inc.

  8. Reframing Early Childhood Leadership

    ERIC Educational Resources Information Center

    Stamopoulos, Elizabeth

    2012-01-01

    Rapid changes in Australian education have intensified the role of early childhood leaders and led to unprecedented challenges. The Australian Curriculum (ACARA, 2011), mandated Australian "National Quality Framework" (NQF) for Early Childhood Education & Care (DEEWR, 2010b) and the "National Early Years Learning Framework"…

  9. Stratigraphy, geochronology, and accretionary terrane settings of two Bronson Hill arc sequences, northern New England

    USGS Publications Warehouse

    Moench, R.H.; Aleinikoff, J.N.

    2002-01-01

    off the southern Laurentian margin, but northwest of the principal Iapetan suture, or Red Indian line (RIL). The Boil Mountain-Jim Pond-Hurricane Mountain sequence was ramped northwestward over the Chain Lakes massif at ???475 Ma, on the basal Boil Mountain surface. This obduction probably occurred slightly before obduction on the Baie Verte-Brompton surface (BBL), farther NW, over the Laurentian margin, and was followed by Dead River flysch sedimentation, which ended with the abrupt onset of Ammonoosuc-sequence arc magmatism at ???470 Ma. Ammonoosuc eruptions probably ended at ???460 Ma, when Iapetus closed along the Red Indian line. During a following magmatic hiatus of ???3-5 m.y., now represented by portions of the Partridge Formation that overlie the Ammonoosuc Volcanics, subduction polarity reversed, and subduction resumed below the northwest-dipping Brunswick subduction complex (BSC) of New Brunswick, Canada. Quimby-sequence magmatism (???456-435 Ma) on the the newly accreted Laurentian margin occurred above the BSC, whose footwall is now buried to the southeast by mainly Silurian clastic sediments of the Merrimack-Fredericton trough, deposited in the "Fredericton Sea". In Silurian to Early Devonian time, the NW-dipping BSC footwall was paired with a SE-dipping subduction zone that produced arc magmas of the Coastal Volcanic belt, built on the composite Avalon and adjacent peri-Avalonian terranes. Orogen-normal extension produced by rapid rollback of both subduction zones narrowed the Fredericton Sea, produced the Central Maine and Connecticut Valley-Gaspe?? basins, and culminated in the Acadian orogeny when the sea completely closed in Early Devonian time. Published by Elsevier Science Ltd.

  10. Stratigraphy, geochronology, and accretionary terrane settings of two Bronson Hill arc sequences, northern New England

    USGS Publications Warehouse

    Moench, R.H.; Aleinikoff, J.N.

    2003-01-01

    the southern Laurentian margin, but northwest of the principal Iapetan suture, or Red Indian line. The Boil Mountain-Jim Pond-Hurricane Mountain sequence was ramped northwestward over the Chain Lakes massif at ???475 Ma, on the basal Boil Mountain surface. This obduction probably occurred slightly before obduction on the Baie Vert-Brompton surface (BBL), farther NW, over the Laurentian margin, and was followed by Dead River flysch sedimentation, which ended with the abrupt onset of Ammonoosuc-sequence arc magmatism at ???470 Ma. Ammonoosuc eruptions probably ended at ???460 Ma, when Iapetus closed along the Red Indian line. During a following magmatic hiatus of ???3-5 m.y., now represented by portions of the Partridge Formation that overlie the Ammonoosuc Volcanics, subduction polarity reversed, and subduction resumed below the northwest-dipping Brunswick subduction complex (BSC) of New Brunswick, Canada. Quimby-sequence magmatism (???456-435 Ma) on the newly accreted Laurentian margin occurred above the BSC, whose footwall is now buried to the southeast by mainly Silurian clastic sediments of the Merrimack-Fredericton trough, deposited in the "Fredericton Sea". In Silurian to Early Devonian time, the NW-dipping BSC footwall was paired with a SE-dipping subduction zone that produced arc magmas of the Coastal Volcanic belt, built on the composite Avalon and adjacent peri-Avalonian terranes. Orogen-normal extension produced by rapid rollback of both subduction zones narrowed the Fredericton Sea, produced the Central Maine and Connecticut Valley-Gaspe?? basins, and culminated in the Acadian orogeny when the sea completely closed in Early Devonian time. Published by Elsevier Science Ltd.

  11. Stratigraphy, geochronology, and accretionary terrane settings of two Bronson Hill arc sequences, northern New England

    NASA Astrophysics Data System (ADS)

    Moench, Robert H.; Aleinikoff, John N.

    the southern Laurentian margin, but northwest of the principal Iapetan suture, or Red Indian line. The Boil Mountain-Jim Pond-Hurricane Mountain sequence was ramped northwestward over the Chain Lakes massif at ∼475 Ma, on the basal Boil Mountain surface. This obduction probably occurred slightly before obduction on the Baie Vert-Brompton surface (BBL), farther NW, over the Laurentian margin, and was followed by Dead River flysch sedimentation, which ended with the abrupt onset of Ammonoosuc-sequence arc magmatism at ∼470 Ma. Ammonoosuc eruptions probably ended at ∼460 Ma, when Iapetus closed along the Red Indian line. During a following magmatic hiatus of ∼3-5 m.y., now represented by portions of the Partridge Formation that overlie the Ammonoosuc Volcanics, subduction polarity reversed, and subduction resumed below the northwest-dipping Brunswick subduction complex (BSC) of New Brunswick, Canada. Quimby-sequence magmatism (∼456-435 Ma) on the newly accreted Laurentian margin occurred above the BSC, whose footwall is now buried to the southeast by mainly Silurian clastic sediments of the Merrimack-Fredericton trough, deposited in the “Fredericton Sea”. In Silurian to Early Devonian time, the NW-dipping BSC footwall was paired with a SE-dipping subduction zone that produced arc magmas of the Coastal Volcanic belt, built on the composite Avalon and adjacent peri-Avalonian terranes. Orogen-normal extension produced by rapid rollback of both subduction zones narrowed the Fredericton Sea, produced the Central Maine and Connecticut Valley-Gaspé basins, and culminated in the Acadian orogeny when the sea completely closed in Early Devonian time.

  12. Stratigraphy, geochronology, and accretionary terrane settings of two Bronson Hill arc sequences, northern New England

    NASA Astrophysics Data System (ADS)

    Moench, Robert H.; Aleinikoff, John N.

    2002-01-01

    southern Laurentian margin, but northwest of the principal Iapetan suture, or Red Indian line (RIL). The Boil Mountain-Jim Pond-Hurricane Mountain sequence was ramped northwestward over the Chain Lakes massif at ∼475 Ma, on the basal Boil Mountain surface. This obduction probably occurred slightly before obduction on the Baie Verte-Brompton surface (BBL), farther NW, over the Laurentian margin, and was followed by Dead River flysch sedimentation, which ended with the abrupt onset of Ammonoosuc-sequence arc magmatism at ∼470 Ma. Ammonoosuc eruptions probably ended at ∼460 Ma, when Iapetus closed along the Red Indian line. During a following magmatic hiatus of ∼3-5 m.y., now represented by portions of the Partridge Formation that overlie the Ammonoosuc Volcanics, subduction polarity reversed, and subduction resumed below the northwest-dipping Brunswick subduction complex (BSC) of New Brunswick, Canada. Quimby-sequence magmatism (∼456-435 Ma) on the the newly accreted Laurentian margin occurred above the BSC, whose footwall is now buried to the southeast by mainly Silurian clastic sediments of the Merrimack-Fredericton trough, deposited in the “Fredericton Sea”. In Silurian to Early Devonian time, the NW-dipping BSC footwall was paired with a SE-dipping subduction zone that produced arc magmas of the Coastal Volcanic belt, built on the composite Avalon and adjacent peri-Avalonian terranes. Orogen-normal extension produced by rapid rollback of both subduction zones narrowed the Fredericton Sea, produced the Central Maine and Connecticut Valley-Gaspé basins, and culminated in the Acadian orogeny when the sea completely closed in Early Devonian time.

  13. Earth's early biosphere

    NASA Technical Reports Server (NTRS)

    Des Marais, D. J.

    1998-01-01

    Understanding our own early biosphere is essential to our search for life elsewhere, because life arose on Earth very early and rocky planets shared similar early histories. The biosphere arose before 3.8 Ga ago, was exclusively unicellular and was dominated by hyperthermophiles that utilized chemical sources of energy and employed a range of metabolic pathways for CO2 assimilation. Photosynthesis also arose very early. Oxygenic photosynthesis arose later but still prior to 2.7 Ga. The transition toward the modern global environment was paced by a decline in volcanic and hydrothermal activity. These developments allowed atmospheric O2 levels to increase. The O2 increase created new niches for aerobic life, most notably the more advanced Eukarya that eventually spawned the megascopic fauna and flora of our modern biosphere.

  14. Value-Added Early Learning

    ERIC Educational Resources Information Center

    Dichter, Harriet

    2011-01-01

    Elected state leaders often prioritize economic prosperity and competitiveness, which provides an important opportunity too rarely taken for investing in early education. In 2003, Pennsylvania recognized the connection between early education and the economy, and smartly embraced early learning as part of its economic prosperity and…

  15. Abnormal early cleavage events predict early embryo demise: sperm oxidative stress and early abnormal cleavage.

    PubMed

    Burruel, Victoria; Klooster, Katie; Barker, Christopher M; Pera, Renee Reijo; Meyers, Stuart

    2014-10-13

    Human embryos resulting from abnormal early cleavage can result in aneuploidy and failure to develop normally to the blastocyst stage. The nature of paternal influence on early embryo development has not been directly demonstrated although many studies have suggested effects from spermatozoal chromatin packaging, DNA damage, centriolar and mitotic spindle integrity, and plasma membrane integrity. The goal of this study was to determine whether early developmental events were affected by oxidative damage to the fertilizing sperm. Survival analysis was used to compare patterns of blastocyst formation based on P2 duration. Kaplan-Meier survival curves demonstrate that relatively few embryos with short (<1 hr) P2 times reached blastocysts, and the two curves diverged beginning on day 4, with nearly all of the embryos with longer P2 times reaching blastocysts by day 6 (p < .01). We determined that duration of the 2nd to 3rd mitoses were sensitive periods in the presence of spermatozoal oxidative stress. Embryos that displayed either too long or too short cytokineses demonstrated an increased failure to reach blastocyst stage and therefore survive for further development. Although paternal-derived gene expression occurs later in development, this study suggests a specific role in early mitosis that is highly influenced by paternal factors.

  16. The Fossil Fauna of the Islands Region of Western Lake Erie.

    ERIC Educational Resources Information Center

    Bowe, Lulu M., Comp.

    The islands of western Lake Erie are rock-bound isles that abound in rocky outcrops and quarries. The rocks of these islands are of two distinct types, Silurian dolomites and Devonian limestones. The dolomites, exposed in the Bass Islands and Sister Islands are virtually devoid of fossils. Conversely, the limestones of Johnson Island, Marblehead,…

  17. "Taconic" arc magmatism in the central Brooks Range, Alaska: New U-Pb zircon geochronology and Hf isotopic data from the lower Paleozoic Apoon assemblage of the Doonerak fenster

    NASA Astrophysics Data System (ADS)

    Strauss, J. V.; Hoiland, C. W.; Ward, W.; Johnson, B.; McClelland, W.

    2015-12-01

    The Doonerak fenster in the central Brooks Range, AK, exposes an important package of early Paleozoic volcanic and sedimentary rocks called the Apoon assemblage, which are generally interpreted as para-autochthonous basement to the Mesozoic-Cenozoic Brookian fold-thrust belt. Recognition in the 1970's of a major pre-Mississippian unconformity within the window led to correlations between Doonerak and the North Slope (sub-) terrane of the Arctic Alaska Chukotka microplate (AACM); however, the presence of arc-affinity volcanism and the apparent lack of pre-Mississippian deformation in the Apoon assemblage makes this link tenuous and complicates Paleozoic tectonic reconstructions of the AACM. Previous age constraints on the Apoon assemblage are limited to a handful of Middle Cambrian-Silurian paleontological collections and five K-Ar and 40Ar/39Ar hornblende ages from mafic dikes ranging from ~380-520 Ma. We conducted U-Pb geochronologic and Hf isotopic analyses on igneous and sedimentary zircon from the Apoon assemblage to test Paleozoic links with the North Slope and to assess the tectonic and paleogeographic setting of the Doonerak region. U-Pb analyses on detrital zircon from Apoon rocks yield a spectrum of unimodal and polymodal age populations, including prominent age groups of ca. 420-490, 960-1250, 1380­-1500, 1750-1945, and 2650-2830 Ma. Hf isotopic data from the ca. 410-490 Ma age population are generally juvenile (~7-10 ɛHf), implying a distinct lack of crustal assimilation during Ordovician-Silurian Doonerak arc magmatism despite its proximity to a cratonic source terrane as indicated by an abundance of Archean and Proterozoic zircon in the interbedded siliciclastic strata. These data are in stark contrast to geochronological data from the non-Laurentian portions of the AACM, highlighting a prominent tectonic boundary between Laurentian- and Baltic-affinity rocks at the Doonerak window and implying a link to "Taconic"-age arc magmatism documented along

  18. Characterization of the Helderberg Group as a geologic seal for CO 2 sequestration

    USGS Publications Warehouse

    Lewis, J.E.; McDowell, R.R.; Avary, K.L.; Carter, K.M.

    2009-01-01

    The Midwest Regional Carbon Sequestration Partnership recognizes that both the Devonian Oriskany Sandstone and the Silurian Salina Group offer potential for subsurface carbon dioxide storage in northern West Virginia. The Silurian-Devonian Helderberg Group lies stratigraphically between these two units, and consequendy, its potential as a geologic seal must be evaluated. Predominantly a carbonate interval with minor interbedded siliciclastics and chert, the Helderberg Group was deposited in an ancient epeiric sea. Although most previous investigations of this unit have concentrated on outcrops in eastern West Virginia, new information is available from an injection well drilled along the Ohio River at First Energy's R. E. Burger electric power plant near Shadyside, Ohio. Geophysical, seismic, and core data from this well have been combined with existing outcrop information to evaluate the Helderberg Group's potential as a seal. The data collected suggest that only secondary porosity remains, and permeability, if it exists, most likely occurs along faults or within fractures. ?? 2009. The American Association of Petroleum Geologists/Division of Environmental Geosciences. All rights reserved.

  19. Microbanded manganese formations; protoliths in the Franciscan Complex, California

    USGS Publications Warehouse

    Huebner, J. Stephen; Flohr, Marta J.

    1990-01-01

    The Buckeye manganese deposit, 93 km southeast of San Francisco in the California Coast Ranges, preserves a geologic history that provides clues to the origin of numerous lenses of manganese carbonate, oxides, and silicates that occur with interbedded radiolarian chert and metashale of the Franciscan Complex. Compositionally and mineralogically laminated Mn-rich protoliths were deformed and dismembered, in a manner that mimics in smaller scale the deformation of the host complex, and then were incipiently metamorphosed at blueschistfacies conditions. Eight phases occur as almost monomineralic protoliths and mixtures: rhodochrosite, caryopilite, chlorite, gageite, taneyamalite, braunite, hausmannite, and laminated chert (quartz). Braunite, gageite, and some chlorite and caryopilite layers were deposited as gel-like materials; rhodochrosite, most caryopilite, and at least some hausmannite layers as lutites; and the chert as turbidites of radiolarian sand. Some gel-like materials are now preserved as transparent, sensibly isotropic relics of materials that fractured or shattered when deformed, creating curved surfaces. In contrast, the micrites flowed between the fragments of gel-like materials. The orebody and most of its constituent minerals have unusually Mn-rich compositions that are described by the system MnO-SiO2-O2-CO2-H2O. High values of Mn/Fe and U/Th, and low concentrations of Co, Cu, and Ni, distinguish the Buckeye deposit from many high-temperature hydrothermal deposits and hydrogenous or diagenetic manganese and ferromanganese nodules and pavements. This chemical signature suggests that ore deposition was related to fluids from the sediment column and seawater. Tungsten is associated exclusively with gageite, in concentrations as high as 80 parts per million. The source of the manganese is unknown; because basalts do not occur near the deposit, it was probably manganese leached from the sediment column by reducing solutions. Low concentrations of calcium

  20. Early College Entrance in Australia

    ERIC Educational Resources Information Center

    Jung, Jae Yup; Young, Marie; Gross, Miraca U. M.

    2015-01-01

    Early college entry is an educational intervention that is being increasingly used in Australia. Following a review of the current Australian literature on early college entry, an overview is provided of the characteristics of, and the procedures associated with, one formal Australian early college entry program (the Early Admission for…

  1. The link between early onset drinking and early onset alcohol-impaired driving in young males.

    PubMed

    Zhang, Lening; Wieczorek, William F; Welte, John W

    2014-05-01

    Young drivers represent a disproportionate number of the individuals involved in alcohol-impaired driving. Although there is a known association between drinking and alcohol-impaired driving in young drivers, the link between early onset drinking and early onset alcohol-impaired driving has not been explored. The present study aimed to assess this link along with potentially confounding factors. The assessment used a proportional hazards model with data collected from the Buffalo Longitudinal Study of Young Men, a population-based sample of 625 males at aged 16-19. Controlling for the effects of potentially relevant confounds, the early onset of drinking was the most influential factor in predicting the early onset of alcohol-impaired driving. Race and the early onset of other forms of delinquency also played a significant role in the early onset of alcohol-impaired driving. Preventing an early start of drinking among adolescents may be the most critical factor to address in preventing an early start of alcohol-impaired driving.

  2. Stage boundary recognition in the Eastern Americas realm based on rugose corals

    USGS Publications Warehouse

    Oliver, W.A.

    2000-01-01

    Most Devonian stages contain characteristic coral assemblages but these tend to be geographically and facies limited and may or may not be useful for recognising stage boundaries. Within eastern North America, corals contribute to the recognition of two boundaries: the base of the Lochkovian (Silurian-Devonian boundary) and the base of the Eifelian (Lower-Middle Devonian Series boundary).

  3. Cognitive Development in Early Readers.

    ERIC Educational Resources Information Center

    Briggs, Chari; Elkind, David

    Some studies of early readers are discussed. It is pointed out that study of early readers has relevance for practical and theoretical issues in psychology and education. Of interest in this document are the following questions: (1) Are there any special talents or traits distinguishing early from non-early readers? (2) Do children who read early…

  4. Internal wave deposits in Jurassic Kermanshah pelagic carbonates and radiolarites (Kermanshah area, West Iran)

    NASA Astrophysics Data System (ADS)

    Abdi, Asad; Gharaie, Mohamad Hosein Mahmudy; Bádenas, Beatriz

    2014-12-01

    We report eventites generated by turbulence events triggered by breaking internal waves in Jurassic pelagic muds deposited in a graben area located between the Arabian and Bisotoun carbonate platforms, at the Kermanshah basin (West Iran). The 43 m-thick studied Pliensbachian-Aalenian succession at Kermanshah includes sponge spicule-radiolarian limestones and cherts with cm- to dm-thick intercalations of pyroclastic beds and coarse-grained deposits formed by neritic-derived grains and reworked pelagic material. Breaking of internal waves in localized areas reworked the available sediment on sea floor, including the erosion of cohesive pelagic muds and the resuspension of neritic-derived grains, which were resedimented from the Bisotoun platform most probably by storms or turbidity currents. The generated internal wave deposits include: flat- and round pebble limestone conglomerates, formed by deposition of pelagic clasts and neritic-derived grains near the breaker zone; laminated packstone-grainstones deposited by high-energy, upslope (swash) and downslope (backswash) flows; cm-thick packstone-grainstones with asymmetrical starved ripples and hummocy crossstratification, generated downdip by waning of backwash flows and internal wave oscillatory flows. These internal wave deposits predominate in the Pliensbachian-early Toarcian, and were related to internal waves developed along a thermocline linked to climate warming and excited by submarine volcanic eruptions, storms or tectonic shaking.

  5. THE LINK BETWEEN EARLY ONSET DRINKING AND EARLY ONSET ALCOHOL-IMPAIRED DRIVING IN YOUNG MALES

    PubMed Central

    Zhang, Lening; Wieczorek, William F.; Welte, John W.

    2014-01-01

    Background Young drivers represent a disproportionate number of the individuals involved in alcohol-impaired driving. Although there is a known association between drinking and alcohol-impaired driving in young drivers, the link between early onset drinking and early onset alcohol-impaired driving has not been explored. Objectives The present study aimed to assess this link along with potentially confounding factors. Methods The assessment used a proportional hazards model with data collected from the Buffalo Longitudinal Study of Young Men, a population based sample of 625 males at ages of 16–19 years old. Results Controlling for the effects of potentially relevant confounds, the early onset of drinking was the most influential factor in predicting the early onset of alcohol-impaired driving. Race and the early onset of other forms of delinquency also played a significant role in the early onset of alcohol-impaired driving. Conclusion Preventing an early start of drinking among adolescents may be the most critical factor to address in preventing an early start of alcohol-impaired driving. PMID:24766089

  6. Paleoenvironmental conditions across the Jurassic-Cretaceous boundary in central-eastern Mexico

    NASA Astrophysics Data System (ADS)

    Martínez-Yáñez, Mario; Núñez-Useche, Fernando; López Martínez, Rafael; Gardner, Rand D.

    2017-08-01

    The Padni section of central-eastern Mexico is characterized by pelagic, organic-rich carbonates and shales dated in this study by calpionellid biostratigraphy to the late Tithonian-late Berriasian time interval. Microfacies, pyrite framboid size, spectrometric gamma-ray and mineralogical data are herein integrated in order to reconstruct the paleoenvironmental change during the Jurassic-Cretaceous boundary. Deposits of the late Tithonian-early Berriasian are characterized by laminated, organic-rich facies with abundant radiolarian, tiny pyrite framboids and low Th/U ratios. They are linked to upwelling in a semi-restricted basin, high marine productivity and anoxic bottom waters. The early incursions of Tethyan oceanic waters into the proto-Gulf of Mexico occurred during late Tithonian as attested the appearance of calpionellids. Short and intermittent accumulations of saccocomids during early Berriasian suggest episodes of sporadic connection between the Tethys, the proto-Atlantic and the Pacific ocean during sea-level rise events. A full and stable connection between the Tethys and proto-Gulf of Mexico was established until the late Berriasian. This event is supported by the presence of open marine and bioturbated facies with a framboid population typical of dysoxic conditions, higher Th/U ratios and a decreasing pattern of the total organic carbon content. In addition to highlighting the replenishment of the oxygen supply to the basin, this facies also points to a younger age for the finalization of the Yucatán Block rotation and the end of the Gulf of Mexico opening. Deposition of the studied section occurred mostly during a Tithonian-Berriasian arid phase reported in other Tethyan and Atlantic regions. The similarity between the discrete segments of the standard gamma-ray curve defined in the studied outcrop and those reported from subsurface implies their regional continuity allowing their use for correlation purposes.

  7. Stratigraphic units overlying the Zambales Ophiolite Complex (ZOC) in Luzon, (Philippines): Tectonostratigraphic significance and regional implications

    NASA Astrophysics Data System (ADS)

    Queaño, Karlo L.; Dimalanta, Carla B.; Yumul, Graciano P.; Marquez, Edanjarlo J.; Faustino-Eslava, Decibel V.; Suzuki, Shigeyuki; Ishida, Keisuke

    2017-07-01

    The Zambales Ophiolite Complex (ZOC) on the island of Luzon, Philippines is one of the most well-studied crust-mantle sequences in the region. Several massifs comprise the ZOC, one of which is the Coto Block overlain by clastic sedimentary units previously dated as Eocene. Geochronologic studies from diabase, granodiorites and other late-stage magmatic products similarly yielded the same age. Succeeding tectonic models have therefore all been grounded on the assumption that the entire ZOC is Eocene. Recent investigations, however, revealed the presence of chert blocks within the Early to Middle Miocene clastic formation overlying the Acoje Block in the northern part of the ophiolite complex. Radiolarians extracted from the cherts yielded a stratigraphic range that suggests a Late Jurassic to Early Cretaceous age. The recognition of a much older age than previously reported of the ZOC warrants a re-examination of its actual distribution and genesis. Correlating with other similarly-aged ophiolites, we suggest defining a western Mesozoic ophiolite belt, largely extending from the west-central portion of the archipelago to the northeastern tip of Luzon island. Tentatively, we attribute the Mesozoic ophiolitic and associated rocks in western Luzon to an arc-continent collision involving the Philippine Mobile Belt and the Palawan Microcontinental Block. In addition, differences in the clastic compositions of the Cenozoic sedimentary formations provide material not only for deciphering the ZOC's unroofing history but also for constraining the timing of province linkage. The intermittent appearance of lithic fragments and detrital minerals from the ophiolite in the units of the Middle Miocene Candelaria Limestone and the Late Miocene to Early Pliocene Sta. Cruz Formation indicates significant but geographically variable contributions from the ophiolite complex. In the northern Zambales Range, the Sta. Cruz Formation caps the Coto Block and the Acoje Block of the ZOC

  8. The pre-Mesozoic tectonic unit division of the Xing-Meng orogenic belt (XMOB)

    NASA Astrophysics Data System (ADS)

    Xu, Bei; Zhao, Pan

    2014-05-01

    According to the viewpoint that the paleo-Asian ocean closed by the end of early Paleozoic and extended during the late Paleozoic, a pre-Mesozoic tectonic unit division has been suggested. Five blocks and four sutures have been recognized in the pre-Devonia stage, the five blocks are called Erguna (EB), Xing'an (XB), Airgin Sum-Xilinhot (AXB), Songliao-Hunshandak (SHB) and Jiamusi (JB) blocks and four sutures, Xinlin-Xiguitu (XXS), Airgin Sum-Xilinhot-Heihe (AXHS), Ondor Sum-Jizhong-Yanji (OJYS) and Mudanjiang (MS) sutures. The EB contains the Precambrian base with the ages of 720-850Ma and ɛHf(T)=+2.5to +8.1. The XB is characterized by the Paleoproterozoic granitic gneiss with ɛHf(T)=-3.9 to -8.9. Several ages from 1150 to 1500 Ma bave been acquired in the AXB, proving presence of old block that links with Hutag Uul block in Mongolia to the west. The Paleoproterozoic (1.8-1.9Ga) and Neoproterozoic (750-850Ma) ages have been reported from southern and eastern parts of the SHB, respectively. As a small block in east margin of the XMOB, the JB outcrops magmatite and granitic gneiss bases with ages of 800-1000Ma. The XXS is marked by blueschists with zircon ages of 490-500Ma in Toudaoqiao village, ophiolites in Xiguitu County and granite with ages of about 500Ma along the northern segment of XXS. The AXHS is characterized by the early Paleozoic arc magmatic rocks with ages from 430Ma to 490Ma, mélange and the late Devonia molass basins, which indicates a northward subduction of the SHB beneath the AXB during the early-middle Paleozoic. The OJYS is composed of the early Paleozoic volcanic rocks, diorites and granites with ages of 425-475Ma, blueschists, ophiolitic mélange, the late Silurian flysch and Early-Middle Devonian molasses in western segment, granites (420-450Ma) in middle segment, and plagiogranites (443Ma) and the late Silurian molasses in eastern segment. This suture was caused by a southward subduction of the SHB beneath the North China block. The MS

  9. Famines in Africa: is early warning early enough?

    PubMed Central

    Kim, Jeeyon Janet; Guha-Sapir, Debarati

    2012-01-01

    Following the second Sahelian famine in 1984–1985, major investments were made to establish Early Warning Systems. These systems help to ensure that timely warnings and vulnerability information are available to decision makers to anticipate and avert food crises. In the recent crisis in the Horn of Africa, alarming levels of acute malnutrition were documented from March 2010, and by August 2010, an impending food crisis was forecast. Despite these measures, the situation remained unrecognised, and further deteriorated causing malnutrition levels to grow in severity and scope. By the time the United Nations officially declared famine on 20 July 2011, and the humanitarian community sluggishly went into response mode, levels of malnutrition and mortality exceeded catastrophic levels. At this time, an estimated 11 million people were in desperate and immediate need for food. With warnings of food crises in the Sahel, South Sudan, and forecast of the drought returning to the Horn, there is an immediate need to institutionalize change in the health response during humanitarian emergencies. Early warning systems are only effective if they trigger an early response. PMID:22745628

  10. Famines in Africa: is early warning early enough?

    PubMed

    Kim, Jeeyon Janet; Guha-Sapir, Debarati

    2012-01-01

    Following the second Sahelian famine in 1984-1985, major investments were made to establish Early Warning Systems. These systems help to ensure that timely warnings and vulnerability information are available to decision makers to anticipate and avert food crises. In the recent crisis in the Horn of Africa, alarming levels of acute malnutrition were documented from March 2010, and by August 2010, an impending food crisis was forecast. Despite these measures, the situation remained unrecognised, and further deteriorated causing malnutrition levels to grow in severity and scope. By the time the United Nations officially declared famine on 20 July 2011, and the humanitarian community sluggishly went into response mode, levels of malnutrition and mortality exceeded catastrophic levels. At this time, an estimated 11 million people were in desperate and immediate need for food. With warnings of food crises in the Sahel, South Sudan, and forecast of the drought returning to the Horn, there is an immediate need to institutionalize change in the health response during humanitarian emergencies. Early warning systems are only effective if they trigger an early response.

  11. Employment and educational outcomes in early intervention programmes for early psychosis: a systematic review.

    PubMed

    Bond, G R; Drake, R E; Luciano, A

    2015-10-01

    Young adults with early psychosis want to pursue normal roles - education and employment. This paper summarises the empirical literature on the effectiveness of early intervention programmes for employment and education outcomes. We conducted a systematic review of employment/education outcomes for early intervention programmes, distinguishing three programme types: (1) those providing supported employment, (2) those providing unspecified vocational services and (3) those without vocational services. We summarised findings for 28 studies. Eleven studies evaluated early intervention programmes providing supported employment. In eight studies that reported employment outcomes separately from education outcomes, the employment rate during follow-up for supported employment patients was 49%, compared with 29% for patients receiving usual services. The two groups did not differ on enrolment in education. In four controlled studies, meta-analysis showed that the employment rate for supported employment participants was significantly higher than for control participants, odds ratio = 3.66 [1.93-6.93], p < 0.0001. Five studies (four descriptive and one quasi-experimental) of early intervention programmes evaluating unspecified vocational services were inconclusive. Twelve studies of early intervention programmes without vocational services were methodologically heterogeneous, using diverse methods for evaluating vocational/educational outcomes and precluding a satisfactory meta-analytic synthesis. Among studies with comparison groups, 7 of 11 (64%) reported significant vocational/education outcomes favouring early intervention over usual services. In early intervention programmes, supported employment moderately increases employment rates but not rates of enrolment in education. These improvements are in addition to the modest effects early programmes alone have on vocational/educational outcomes compared with usual services.

  12. The Association between Early Conduct Problems and Early Marijuana Use in College Students

    ERIC Educational Resources Information Center

    Falls, Benjamin J.; Wish, Eric D.; Garnier, Laura M.; Caldeira, Kimberly M.; O'Grady, Kevin E.; Vincent, Kathryn B.; Arria, Amelia M.

    2011-01-01

    Early conduct problems have been linked to early marijuana use in adolescence. The present study examines this association in a sample of 1,076 college students that was divided into three groups: (1) early marijuana users (began marijuana use prior to age 15; N = 126), (2) late marijuana users (began marijuana use at or after age 15; N = 607),…

  13. Geochemical study of calcite veins in the Silurian and Devonian of the Barrandian Basin (Czech Republic): evidence for widespread post-Variscan fluid flow in the central part of the Bohemian Massif

    NASA Astrophysics Data System (ADS)

    Suchy, V.; Heijlen, W.; Sykorova, I.; Muchez, Ph; Dobes, P.; Hladikova, J.; Jackova, I.; Safanda, J.; Zeman, A.

    2000-03-01

    Carbonate fracture cements in limestones have been investigated by fluid inclusion and stable isotope analysis to provide insight into fluid evolution and deformation conditions of the Barrandian Basin (Silurian-Devonian) of the Czech Republic. The fractures strike generally north-south and appear to postdate major Variscan deformation. The most common fracture cement is calcite that is locally accompanied by quartz, natural bitumen, dolomite, Mn-oxides and fluorite. Three successive generations of fracture-filling calcite cements are distinguished based on their petrographical and geochemical characteristics. The oldest calcite cements (Stage 1) are moderate to dull brown cathodoluminescent, Fe-rich and exhibit intense cleavage, subgrain development and other features characteristic of tectonic deformation. Less tectonically deformed, variable luminescent Fe-poor calcite corresponds to a paragenetically younger Stage 2 cement. First melting temperatures, Te, of two-phase aqueous inclusions in Stages 1 and 2 calcites are often around -20°C, suggesting that precipitation of the cements occurred from H 2O-NaCl fluids. The melting temperature, Tm, has values between 0 and -5.8°C, corresponding to a low salinity between 0 and 8.9 eq. wt% NaCl. Homogenization temperatures, Th, from calcite cements are interpreted to indicate precipitation at about 70°C or less. No distinction could be made between the calcite of Stages 1 and 2 based on their fluid inclusion characteristics. In some Stage 2 cements, inclusions of highly saline (up to 23 eq. wt% NaCl) brines appear to coexist with low-salinity inclusions. The low salinity fluid possibly contains Na-, K-, Mg- and Ca-chlorides. The high salinity fluid has a H 2O-NaCl-CaCl 2 composition. Blue-to-yellow-green fluorescing hydrocarbon inclusions composed of medium to higher API gravity oils are also identified in some Stages 1 and 2 calcite cements. Stage 1 and 2 calcites have δ18O values between -13.2‰ and -7.2‰ PDB

  14. Early Childhood Education.

    ERIC Educational Resources Information Center

    Elkind, David

    In five sections, this paper explores dimensions of early childhood education: schooling generally construed as nonparental instruction in knowledge, values, and skills. Section 1 looks at some of the factors which have contributed to the rapid growth of early childhood education in modern times. Section 2 briefly highlights the contributions of…

  15. Early Pregnancy Loss

    MedlinePlus

    ... known pregnancies. What causes early pregnancy loss? About one half of cases of early pregnancy loss are caused by a ... do not show any signs of an infection, one option is to wait and let the ... may take longer in some cases. Another option is to take medication that helps ...

  16. Early Retirement Payoff

    ERIC Educational Resources Information Center

    Fitzpatrick, Maria D.; Lovenheim, Michael F.

    2014-01-01

    As public budgets have grown tighter over the past decade, states and school districts have sought ways to control the growth of spending. One increasingly common strategy employed to rein in costs is to offer experienced teachers with high salaries financial incentives to retire early. Although early retirement incentive (ERI) programs have been…

  17. Rethinking Early Education

    ERIC Educational Resources Information Center

    Celeste, Eric

    2017-01-01

    The National Association for the Education of Young Children (NAEYC) says in its current policy paper that, for high-quality early education to exist outside of tiny islands across the country, the following must be addressed: (1) teacher preparation; (2) ongoing professional learning; and (3) disparity in early education teacher pay. To achieve…

  18. Biological aspects of early osteoarthritis.

    PubMed

    Madry, Henning; Luyten, Frank P; Facchini, Andrea

    2012-03-01

    Early OA primarily affects articular cartilage and involves the entire joint, including the subchondral bone, synovial membrane, menisci and periarticular structures. The aim of this review is to highlight the molecular basis and histopathological features of early OA. Selective review of literature. Risk factors for developing early OA include, but are not limited to, a genetic predisposition, mechanical factors such as axial malalignment, and aging. In early OA, the articular cartilage surface is progressively becoming discontinuous, showing fibrillation and vertical fissures that extend not deeper than into the mid-zone of the articular cartilage, reflective of OARSI grades 1.0-3.0. Early changes in the subchondral bone comprise a progressive increase in subchondral plate and subarticular spongiosa thickness. Early OA affects not only the articular cartilage and the subchondral bone but also other structures of the joint, such as the menisci, the synovial membrane, the joint capsule, ligaments, muscles and the infrapatellar fat pad. Genetic markers or marker combinations may become useful in the future to identify early OA and patients at risk. The high socioeconomic impact of OA suggests that a better insight into the mechanisms of early OA may be a key to develop more targeted reconstructive therapies at this first stage of the disease. Systematic review, Level II.

  19. Detrital zircon geochronology overlying the Naga Hills ophiolite

    NASA Astrophysics Data System (ADS)

    Roeder, T.; Aitchison, J.; Stojanovic, D.; Agarwal, A.; Ao, A.; Bhowmik, S.

    2013-12-01

    The Nagaland ophiolite in NE India represents the easternmost section of the ophiolitic belt running along the India-Asia suture. Outcrops near the border between Nagaland and Myanmar include not only a full suite of ophiolitic rocks but also high P/T blueschist rocks within a serpentinite-matrix mélange. Although Upper Jurassic radiolarians have been reported from the ophiolite itself (Baxter et al., 2011), few constraints have been placed on the timing of its emplacement onto India. Terrestrial sediments of the Phokphur Formation unconformably overlie the ophiolite. Similar to other sediments from along the ophiolite belt such as the Luiqu conglomerates in Tibet (Davis et al., 2002), they contain detritus derived from both the ophiolite and the continental margin onto which the ophiolite was emplaced. The clastic sediments of the Phokphur Formation potentially record not only the timing of ophiolite generation but also the ages of source terranes and can be used to place a minimum age constraint on the timing of ophiolite emplacement. As a contribution towards extending knowledge of the ophiolite belt and the India/Asia collision, we report preliminary results of an investigation into the sedimentology and detrital zircon geochronology of the Phokphur Formation in areas near Salumi and Zephu. Baxter, A.T., Aitchison, J.C., Zyabrev, S.V., Ali, J.R., 2011. Upper Jurassic radiolarians from the Naga Ophiolite, Nagaland, northeast India. Gondwana Research 20, 638-644. Davis, A.M., Aitchison, J.C., Badengzhu, Luo, H., Zyabrev, S., 2002. Paleogene island arc collision-related conglomerates, Yarlung-Tsangpo suture zone, Tibet. Sedimentary Geology 150, 247-273.

  20. Eco-Early Childhood Education: A New Paradigm of Early Childhood Education in South Korea

    ERIC Educational Resources Information Center

    Kim, Eunju; Lim, Jaetack

    2007-01-01

    In the early 1990s, university faculty members, early childhood educators, and preschool teachers in South Korea created a new paradigm for education. Eco-early childhood education uses an ecological point of view to reform existing child-centered education. This perspective proposes moving from child- to life-centered, individual- to…

  1. Petroleum potential of the Reggane Basin, Algeria

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Boudjema, A.; Hamel, M.; Mohamedi, A.

    1990-05-01

    The intracratonic Reggane basin is located on the Saharan platform, southwest of Algeria. The basin covers an area of approximately 140,000 km{sup 2}, extending between the Eglab shield in the south and the Ougarta ranges in the north. Although exploration started in the early 1950s, only a few wells were drilled in this basin. Gas was discovered with a number of oil shows. The sedimentary fill, mainly Paleozoic shales and sandstones, has a thickness exceeding 5,000 m in the central part of the basin. The reservoirs are Cambrian-Ordovician, Siegenian, Emsian, Tournaisian, and Visean sandstones with prospective petrophysical characteristics. Silurian Uppermore » Devonian and, to a lesser extent Carboniferous shales are the main source rocks. An integrated study was done to assess the hydrocarbon potential of this basin. Tectonic evolution source rocks and reservoirs distribution maturation analyses followed by kinetic modeling, and hydrogeological conditions were studied. Results indicate that gas accumulations could be expected in the central and deeper part of the basin, and oil reservoirs could be discovered on the basin edge.« less

  2. Course of Disinhibited Social Engagement Disorder From Early Childhood to Early Adolescence.

    PubMed

    Guyon-Harris, Katherine L; Humphreys, Kathryn L; Fox, Nathan A; Nelson, Charles A; Zeanah, Charles H

    2018-05-01

    Disinhibited social engagement disorder (DSED) is poorly understood beyond early childhood. The course of DSED signs in a sample of children who experienced severe, early deprivation from early childhood to early adolescence was examined using variable-centered (linear mixed modeling) and person-centered (growth mixture modeling) approaches. The study included 124 children with a history of institutional care from a randomized controlled trial of foster care as an alternative to institutional care and 69 community comparison children matched by age and sex. DSED signs were assessed at baseline (mean age 22 months), 30, 42, and 54 months of age, and 8 and 12 years of age using a validated caregiver report of disturbed attachment behavior. Variable-centered analyses based on intent-to-treat groups indicated that signs of DSED decreased sharply for children randomized to foster care and decreased slightly but remained high for children randomized to care as usual. Person-centered analyses showed 4 profiles (i.e., elevated, persistent modest, early decreasing, and minimal). Elevated and persistent modest courses were associated with greater placement disruptions (F 3,99  = 4.29, p = .007, partial eta-squared [η 2 ] = 0.12), older age at placement into foster care (F 3,56  = 3.41, p < .05, partial η 2  = 0.16), and more time in institutional care (F 3,115  = 11.91, p < .001, partial η 2  = 0.24) compared with decreasing and minimal courses. Early and sustained placement into families after deprivation is associated with minimal or decreasing signs of DSED across development. Shortening the amount of time children spend in institutions and preserving placements could help decrease signs of DSED into early adolescence in previously institutionalized children. Copyright © 2018 American Academy of Child and Adolescent Psychiatry. Published by Elsevier Inc. All rights reserved.

  3. Leadership Competencies in U.S. Early Intervention/Early Childhood Special Education Service Systems: A National Survey

    ERIC Educational Resources Information Center

    Bruns, Deborah A.; LaRocco, Diana J.; Sharp, Olga L.; Sopko, Kim Moherek

    2017-01-01

    In 2015, the Division for Early Childhood of the Council for Exceptional Children released a position statement on leadership in early intervention and early childhood special education (EI/ECSE). Division for Early Childhood emphasized the importance of developing and supporting high-quality leadership within and across all levels of EI/ECSE…

  4. Early Numeracy Assessment: The Development of the Preschool Early Numeracy Scales

    ERIC Educational Resources Information Center

    Purpura, David J.; Lonigan, Christopher J.

    2015-01-01

    Research Findings: The focus of this study was to construct and validate 12 brief early numeracy assessment tasks that measure the skills and concepts identified as key to early mathematics development by the National Council of Teachers of Mathematics (2006) and the National Mathematics Advisory Panel (2008)-as well as critical developmental…

  5. Timing of Orphanhood, Early Sexual Debut, and Early Marriage in Four Sub-Saharan African Countries

    PubMed Central

    Chae, Sophia

    2014-01-01

    According to a growing body of literature, some orphans are at heightened risk of early sexual debut and early marriage. This study examines a rarely explored aspect of orphanhood: the timing and type of parental death and their relationship to these outcomes. The study also explores whether education mediates orphans’ risk of early sexual initiation and early marriage. The data are drawn from the 2004 National Survey of Adolescents, which includes interviews with 12–19-year-old adolescents in Burkina Faso, Ghana, Malawi, and Uganda. Results from discrete-time event history analysis indicate that female double orphans, regardless of timing of orphanhood, have greater odds of early sexual debut than do nonorphans. Education explains little of their increased risk. In contrast, male orphans of any type reveal no increased vulnerability to early sexual debut. Uganda is the only country where female orphans, specifically double orphans and those who are paternal orphans before age 10, have greater odds of early marriage, with education accounting for a small portion of the risk. PMID:23719999

  6. Early Childhood Predictors of Low-Income Boys’ Pathways to Antisocial Behavior in Childhood, Adolescence, and Early Adulthood

    PubMed Central

    Shaw, Daniel S.; Gilliam, Mary

    2016-01-01

    Guided by a bridging model of pathways leading to low-income boys’ early-starting and persistent trajectories of antisocial behavior, the current paper reviews evidence supporting the model from early childhood through early adulthood. Using primarily a cohort of 310 low-income boys of families recruited from WIC centers in a large metropolitan area followed from infancy to early adulthood, and smaller cohorts of boys and girls followed through early childhood, we provide evidence supporting the critical role of parenting, maternal depression, and other proximal family risk factors in early childhood that are prospectively linked to trajectories of parent-reported conduct problems in early and middle childhood, youth-reported antisocial behavior during adolescence and early adulthood, as well as court-reported violent offending in adolescence. The findings are discussed in terms of the need to identify at-risk boys in early childhood and methods and platforms for engaging families in health care settings not previously used to implement preventive mental health services. PMID:28026042

  7. Early cosmology constrained

    NASA Astrophysics Data System (ADS)

    Verde, Licia; Bellini, Emilio; Pigozzo, Cassio; Heavens, Alan F.; Jimenez, Raul

    2017-04-01

    We investigate our knowledge of early universe cosmology by exploring how much additional energy density can be placed in different components beyond those in the ΛCDM model. To do this we use a method to separate early- and late-universe information enclosed in observational data, thus markedly reducing the model-dependency of the conclusions. We find that the 95% credibility regions for extra energy components of the early universe at recombination are: non-accelerating additional fluid density parameter ΩMR < 0.006 and extra radiation parameterised as extra effective neutrino species 2.3 < Neff < 3.2 when imposing flatness. Our constraints thus show that even when analyzing the data in this largely model-independent way, the possibility of hiding extra energy components beyond ΛCDM in the early universe is seriously constrained by current observations. We also find that the standard ruler, the sound horizon at radiation drag, can be well determined in a way that does not depend on late-time Universe assumptions, but depends strongly on early-time physics and in particular on additional components that behave like radiation. We find that the standard ruler length determined in this way is rs = 147.4 ± 0.7 Mpc if the radiation and neutrino components are standard, but the uncertainty increases by an order of magnitude when non-standard dark radiation components are allowed, to rs = 150 ± 5 Mpc.

  8. Early cosmology constrained

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Verde, Licia; Jimenez, Raul; Bellini, Emilio

    We investigate our knowledge of early universe cosmology by exploring how much additional energy density can be placed in different components beyond those in the ΛCDM model. To do this we use a method to separate early- and late-universe information enclosed in observational data, thus markedly reducing the model-dependency of the conclusions. We find that the 95% credibility regions for extra energy components of the early universe at recombination are: non-accelerating additional fluid density parameter Ω{sub MR} < 0.006 and extra radiation parameterised as extra effective neutrino species 2.3 < N {sub eff} < 3.2 when imposing flatness. Our constraintsmore » thus show that even when analyzing the data in this largely model-independent way, the possibility of hiding extra energy components beyond ΛCDM in the early universe is seriously constrained by current observations. We also find that the standard ruler, the sound horizon at radiation drag, can be well determined in a way that does not depend on late-time Universe assumptions, but depends strongly on early-time physics and in particular on additional components that behave like radiation. We find that the standard ruler length determined in this way is r {sub s} = 147.4 ± 0.7 Mpc if the radiation and neutrino components are standard, but the uncertainty increases by an order of magnitude when non-standard dark radiation components are allowed, to r {sub s} = 150 ± 5 Mpc.« less

  9. Desmograptus. micronematodes, a silurian dendroid graptolite, and its ultrastructure

    USGS Publications Warehouse

    Saunders, K.M.; Bates, D.E.B.; Kluessendorf, Joanne; Loydell, David K.; Mikulic, Donald G.

    2009-01-01

    Desmograptus micronematodes from Thornton quarry, Cook County, Illinois, USA, remarkably preserved in relief and encased in pyrite, is described. The internal details of the thecae, and of the stolon system, examined using the SEM, allow the reconstruction of the growth of a stipe. The stolons and stolonal nodes are formed of a dense crassal fabric, and are surrounded by a loose fabric of three-dimensional fibrils. The nodes have a complex structure of three boxes with proximal and distal nozzles. The base of a bitheca, and the base of each autothecal cup, has a central nozzle surrounded by a unique honeycomb fabric. The ultrastructure of the cortical fibrils, with their clockwise striations, is similar to that in Dendrograptus, and may be universal in the graptolites. The nodes of the stolon system appear identical to those of Acanthograptus and other dendroids, but differ from those of the extant hemichordate Rhabdopleura, which have only a diaphragm, and lack box structures. ?? The Palaeontological Association, 2009.

  10. Chekhovichia, a new generic replacement name for Rotalites Leleshus 1970 (Anthozoa: Heliolitoidea) non Lamarck 1801 (Protista: Foraminifera).

    PubMed

    Doweld, Alexander B

    2015-10-29

    The genus Rotalites was established by Leleshus (1970: 97) for fossil Upper Silurian heliolitoids (Anthozoa) from Southern Tien Shan. However, the name is preoccupied by Rotalites Lamarck (1801: 401) of Foraminifera (Protista) (cf. Loeblich & Tappan, 1987). In accordance with the International Code of Zoological Nomenclature, Chekhovichia nom. nov. is proposed here as a replacement name for Rotalites Leleshus non Lamarck.

  11. Consolidation patterns during initiation and evolution of a plate-boundary decollement zone: Northern Barbados accretionary prism

    USGS Publications Warehouse

    Moore, J.C.; Klaus, A.; Bangs, N.L.; Bekins, B.; Bucker, C.J.; Bruckmann, W.; Erickson, S.N.; Hansen, O.; Horton, T.; Ireland, P.; Major, C.O.; Moore, Gregory F.; Peacock, S.; Saito, S.; Screaton, E.J.; Shimeld, J.W.; Stauffer, P.H.; Taymaz, T.; Teas, P.A.; Tokunaga, T.

    1998-01-01

    Borehole logs from the northern Barbados accretionary prism show that the plate-boundary decollement initiates in a low-density radiolarian claystone. With continued thrusting, the decollement zone consolidates, but in a patchy manner. The logs calibrate a three-dimensional seismic reflection image of the decollement zone and indicate which portions are of low density and enriched in fluid, and which portions have consolidated. The seismic image demonstrates that an underconsolidated patch of the decollement zone connects to a fluid-rich conduit extending down the decollement surface. Fluid migration up this conduit probably supports the open pore structure in the underconsolidated patch.

  12. Early Practicum Experiences: Preservice Early Childhood Students' Perceptions and Sense of Efficacy

    ERIC Educational Resources Information Center

    Van Schagen Johnson, Amy; La Paro, Karen M.; Crosby, Danielle A.

    2017-01-01

    The current study explored early practicum experiences (those occurring before student teaching) in an early childhood birth to kindergarten teacher education program. Undergraduates enrolled in practicum courses completed questionnaires about their overall practicum experience including: socio-emotional components (their perceived fit with their…

  13. Redefining early gastric cancer.

    PubMed

    Barreto, Savio G; Windsor, John A

    2016-01-01

    The problem is that current definitions of early gastric cancer allow the inclusion of regional lymph node metastases. The increasing use of endoscopic submucosal dissection to treat early gastric cancer is a concern because regional lymph nodes are not addressed. The aim of the study was thus to critically evaluate current evidence with regard to tumour-specific factors associated with lymph node metastases in "early gastric cancer" to develop a more precise definition and improve clinical management. A systematic and comprehensive search of major reference databases (MEDLINE, EMBASE, PubMed and the Cochrane Library) was undertaken using a combination of text words "early gastric cancer", "lymph node metastasis", "factors", "endoscopy", "surgery", "lymphadenectomy" "mucosa", "submucosa", "lymphovascular invasion", "differentiated", "undifferentiated" and "ulcer". All available publications that described tumour-related factors associated with lymph node metastases in early gastric cancer were included. The initial search yielded 1494 studies, of which 42 studies were included in the final analysis. Over time, the definition of early gastric cancer has broadened and the indications for endoscopic treatment have widened. The mean frequency of lymph node metastases increased on the basis of depth of infiltration (mucosa 6% vs. submucosa 28%), presence of lymphovascular invasion (absence 9% vs. presence 53%), tumour differentiation (differentiated 13% vs. undifferentiated 34%) and macroscopic type (elevated 13% vs. flat 26%) and tumour diameter (≤2 cm 8% vs. >2 cm 25%). There is a need to re-examine the diagnosis and staging of early gastric cancer to ensure that patients with one or more identifiable risk factor for lymph node metastases are not denied appropriate chemotherapy and surgical resection.

  14. Early psychosis workforce development: Core competencies for mental health professionals working in the early psychosis field.

    PubMed

    Osman, Helen; Jorm, Anthony F; Killackey, Eoin; Francey, Shona; Mulcahy, Dianne

    2017-08-09

    The aim of this study was to identify the core competencies required of mental health professionals working in the early psychosis field, which could function as an evidence-based tool to support the early psychosis workforce and in turn assist early psychosis service implementation and strengthen early psychosis model fidelity. The Delphi method was used to establish expert consensus on the core competencies. In the first stage, a systematic literature search was conducted to generate competency items. In the second stage, a panel consisting of expert early psychosis clinicians from around the world was formed. Panel members then rated each of the competency items on how essential they are to the clinical practice of all early psychosis clinicians. In total, 1023 pieces of literature including textbooks, journal articles and grey literature were reviewed. A final 542 competency items were identified for inclusion in the questionnaire. A total of 63 early psychosis experts participated in 3 rating rounds. Of the 542 competency items, 242 were endorsed as the required core competencies. There were 29 competency items that were endorsed by 62 or more experts, and these may be considered the foundational competencies for early psychosis practice. The study generated a set of core competencies that provide a common language for early psychosis clinicians across professional disciplines and country of practice, and potentially are a useful professional resource to support early psychosis workforce development and service reform. © 2017 John Wiley & Sons Australia, Ltd.

  15. Early childhood predictors of early onset of smoking: a birth prospective study.

    PubMed

    Hayatbakhsh, Reza; Mamun, Abdullah A; Williams, Gail M; O'Callaghan, Michael J; Najman, Jake M

    2013-10-01

    Early onset of smoking is associated with subsequent abuse of other substances and development of negative health outcomes. This study aimed to examine early life predictors of onset of smoking in an Australian young cohort. Data were from the Mater Hospital and University of Queensland Study of Pregnancy (MUSP), a population-based prospective birth cohort study (1981-2012). The present study is based on a cohort of 3714 young adults who self-reported smoking status and age of onset of smoking at the 21-year follow-up. Of these, data were available for 3039 on early childhood factors collected between the baseline and 14-year follow-up of the study. Of 3714 young adults, 49.6% (49.9% males and 49.3% females) reported having ever smoked cigarettes. For those who had ever smoked, mean and median ages at first smoke were 15.5 and 16.0years, respectively. In multivariate Cox proportional hazard analysis mother's education, change in maternal marital status, maternal cigarette smoking and alcohol consumption, maternal depression and child externalizing when the child was 5years statistically significantly predicted early onset of smoking. The data suggest that individuals exposed to personal and environmental risk factors during the early stage of childhood are at increased risk of initiation to cigarette smoking at an earlier age. Identification of the pathways of association between these early life factors and initiation to cigarette smoking may help reduce risk of tobacco smoking in adolescents and its adverse consequences. Copyright © 2013 Elsevier Ltd. All rights reserved.

  16. Beyond Developmentalism? Early Childhood Teachers' Understandings of Multiage Grouping in Early Childhood Education and Care

    ERIC Educational Resources Information Center

    Edwards, Susan; Blaise, Mindy; Hammer, Marie

    2009-01-01

    Postdevelopmental perspectives in early childhood education and care increasingly reference alternative ways of understanding learning, growth and development in early learning. Drawing on these ideas, this paper examines research findings which focused on early childhood teachers' understandings of multiage grouping. The findings suggested that…

  17. Early Educational Intervention, Early Cumulative Risk, and the Early Home Environment as Predictors of Young Adult Outcomes Within a High-Risk Sample

    PubMed Central

    Pungello, Elizabeth P.; Kainz, Kirsten; Burchinal, Margaret; Wasik, Barbara H.; Sparling, Joseph J.; Ramey, Craig T.; Campbell, Frances A.

    2009-01-01

    The extent to which early educational intervention, early cumulative risk, and the early home environment were associated with young adult outcomes was investigated in a sample of 139 young adults (age 21) from high-risk families enrolled in randomized trials of early intervention. Positive effects of treatment were found for education attainment, attending college, and skilled employment; negative effects of risk were found for education attainment, graduating high school, being employed and avoiding teen parenthood. The home mediated the effects of risk for graduating high school, but not being employed or teen parenthood. Evidence for moderated mediation was found for educational attainment; the home mediated the association between risk and educational attainment for the control group, but not the treated group. PMID:20331676

  18. Evaluation of Young Children for Early Intervention and Early Childhood Special Education.

    ERIC Educational Resources Information Center

    Allen, Diana

    This technical assistance document provides guidelines for child assessment and eligibility determination for early intervention and early childhood special education programs in Oregon. An overview of the assessment process explains screening, eligibility evaluation, and assessment for the Individual Family Service Plan (IFSP). Legal requirements…

  19. EARLY CHILDHOOD PREDICTORS OF LOW-INCOME BOYS' PATHWAYS TO ANTISOCIAL BEHAVIOR IN CHILDHOOD, ADOLESCENCE, AND EARLY ADULTHOOD.

    PubMed

    Shaw, Daniel S; Gilliam, Mary

    2017-01-01

    Guided by a bridging model of pathways leading to low-income boys' early starting and persistent trajectories of antisocial behavior, the current article reviews evidence supporting the model from early childhood through early adulthood. Using primarily a cohort of 310 low-income boys of families recruited from Women, Infants, and Children Nutrition Supplement centers in a large metropolitan area followed from infancy to early adulthood and a smaller cohort of boys and girls followed through early childhood, we provide evidence supporting the critical role of parenting, maternal depression, and other proximal family risk factors in early childhood that are prospectively linked to trajectories of parent-reported conduct problems in early and middle childhood, youth-reported antisocial behavior during adolescence and early adulthood, and court-reported violent offending in adolescence. The findings are discussed in terms of the need to identify at-risk boys in early childhood and methods and platforms for engaging families in healthcare settings not previously used to implement preventive mental health services. © 2016 Michigan Association for Infant Mental Health.

  20. Climate change and the selective signature of the Late Ordovician mass extinction.

    PubMed

    Finnegan, Seth; Heim, Noel A; Peters, Shanan E; Fischer, Woodward W

    2012-05-01

    Selectivity patterns provide insights into the causes of ancient extinction events. The Late Ordovician mass extinction was related to Gondwanan glaciation; however, it is still unclear whether elevated extinction rates were attributable to record failure, habitat loss, or climatic cooling. We examined Middle Ordovician-Early Silurian North American fossil occurrences within a spatiotemporally explicit stratigraphic framework that allowed us to quantify rock record effects on a per-taxon basis and assay the interplay of macrostratigraphic and macroecological variables in determining extinction risk. Genera that had large proportions of their observed geographic ranges affected by stratigraphic truncation or environmental shifts at the end of the Katian stage were particularly hard hit. The duration of the subsequent sampling gaps had little effect on extinction risk, suggesting that this extinction pulse cannot be entirely attributed to rock record failure; rather, it was caused, in part, by habitat loss. Extinction risk at this time was also strongly influenced by the maximum paleolatitude at which a genus had previously been sampled, a macroecological trait linked to thermal tolerance. A model trained on the relationship between 16 explanatory variables and extinction patterns during the early Katian interval substantially underestimates the extinction of exclusively tropical taxa during the late Katian interval. These results indicate that glacioeustatic sea-level fall and tropical ocean cooling played important roles in the first pulse of the Late Ordovician mass extinction in Laurentia.

  1. Early Reading and Concrete Operations.

    ERIC Educational Resources Information Center

    Polk, Cindy L. Howes; Goldstein, David

    1980-01-01

    Indicated that early readers are more likely to be advanced in cognitive development than are nonearly-reading peers. After one year of formal reading instruction, early readers maintained their advantage in reading achievement. Measures of concrete operations were found to predict reading achievement for early and nonearly readers. (Author/DB)

  2. The Effectiveness of Early Intervention.

    ERIC Educational Resources Information Center

    Guralnick, Michael J., Ed.

    This book reviews research on the effectiveness of early intervention for children with disabilities or who are at risk. Program factors for children at risk and with disabilities, the effects of early intervention on different types of disabilities, and the outcomes of early intervention are explored. Chapters include: "Second-Generation Research…

  3. Early Rockets

    NASA Image and Video Library

    2004-04-15

    During the 19th century, rocket enthusiasts and inventors began to appear in almost every country. Some people thought these early rocket pioneers were geniuses, and others thought they were crazy. Claude Ruggieri, an Italian living in Paris, apparently rocketed small animals into space as early as 1806. The payloads were recovered by parachute. As depicted here by artist Larry Toschik, French authorities were not always impressed with rocket research. They halted Ruggieri's plans to launch a small boy using a rocket cluster. (Reproduced from a drawing by Larry Toschik and presented here courtesy of the artist and Motorola Inc.)

  4. Individual differences in early adolescents' latent trait cortisol: Interaction of early adversity and 5-HTTLPR.

    PubMed

    Chen, Frances R; Stroud, Catherine B; Vrshek-Schallhorn, Suzanne; Doane, Leah D; Granger, Douglas A

    2017-10-01

    The present study aimed to examine the interaction of 5-HTTLPR and early adversity on trait-like levels of cortisol. A community sample of 117 early adolescent girls (M age=12.39years) provided DNA samples for 5-HTTLPR genotyping, and saliva samples for assessing cortisol 3 times a day (waking, 30min post-waking, and bedtime) over a three-day period. Latent trait cortisol (LTC) was modeled using the first 2 samples of each day. Early adversity was assessed with objective contextual stress interviews with adolescents and their mothers. A significant 5-HTTLPR×early adversity interaction indicated that greater early adversity was associated with lower LTC levels, but only among individuals with either L/L or S/L genotype. Findings suggest that serotonergic genetic variation may influence the impact of early adversity on individual differences in HPA-axis regulation. Future research should explore whether this interaction contributes to the development of psychopathology through HPA axis functioning. Copyright © 2017 Elsevier B.V. All rights reserved.

  5. Clarifying Parent-Child Reciprocities during Early Childhood: The Early Childhood Coercion Model

    ERIC Educational Resources Information Center

    Scaramella, Laura V.; Leve, Leslie D.

    2004-01-01

    Consistent with existing theory, the quality of parent-child interactions during early childhood affects children's social relationships and behavioral adjustment during middle childhood and adolescence. Harsh parenting and a propensity toward emotional overarousal interact very early in life to affect risk for later conduct problems. Less…

  6. Risk of early surgery for Crohn's disease: implications for early treatment strategies.

    PubMed

    Sands, Bruce E; Arsenault, Joanne E; Rosen, Michael J; Alsahli, Mazen; Bailen, Laurence; Banks, Peter; Bensen, Steven; Bousvaros, Athos; Cave, David; Cooley, Jeffrey S; Cooper, Herbert L; Edwards, Susan T; Farrell, Richard J; Griffin, Michael J; Hay, David W; John, Alex; Lidofsky, Sheldon; Olans, Lori B; Peppercorn, Mark A; Rothstein, Richard I; Roy, Michael A; Saletta, Michael J; Shah, Samir A; Warner, Andrew S; Wolf, Jacqueline L; Vecchio, James; Winter, Harland S; Zawacki, John K

    2003-12-01

    In this study we aimed to define the rate of early surgery for Crohn's disease and to identify risk factors associated with early surgery as a basis for subsequent studies of early intervention in Crohn's disease. We assembled a retrospective cohort of patients with Crohn's disease diagnosed between 1991 and 1997 and followed for at least 3 yr, who were identified in 16 community and referral-based practices in New England. Chart review was performed for each patient. Details of baseline demographic and disease features were recorded. Surgical history including date of surgery, indication, and procedure were also noted. Risk factors for early surgery (defined as major surgery for Crohn's disease within 3 yr of diagnosis, exclusive of major surgery at time of diagnosis) were identified by univariate analysis. Multiple logistic regression was used to identify independent risk factors. Of 345 eligible patients, 69 (20.1%) required surgery within 3 yr of diagnosis, excluding the 14 patients (4.1%) who had major surgery at the time of diagnosis. Overall, the interval between diagnosis and surgery was short; one half of all patients who required surgery underwent operation within 6 months of diagnosis. Risk factors identified by univariate analysis as significantly associated with early surgery included the following: smoking; disease of small bowel without colonic involvement; nausea and vomiting or abdominal pain on presentation; neutrophil count; and steroid use in the first 6 months. Disease localized to the colon only, blood in the stool, use of 5-aminosalicylate, and lymphocyte count were inversely associated with risk of early surgery. Logistic regression confirmed independent associations with smoking as a positive risk factor and involvement of colon without small bowel as a negative risk factor for early surgery. The rate of surgery is high in the first 3 yr after diagnosis of Crohn's disease, particularly in the first 6 months. These results suggest that

  7. Implementing Obstetric Early Warning Systems.

    PubMed

    Friedman, Alexander M; Campbell, Mary L; Kline, Carolyn R; Wiesner, Suzanne; D'Alton, Mary E; Shields, Laurence E

    2018-04-01

    Severe maternal morbidity and mortality are often preventable and obstetric early warning systems that alert care providers of potential impending critical illness may improve maternal safety. While literature on outcomes and test characteristics of maternal early warning systems is evolving, there is limited guidance on implementation. Given current interest in early warning systems and their potential role in care, the 2017 Society for Maternal-Fetal Medicine (SMFM) Annual Meeting dedicated a session to exploring early warning implementation across a wide range of hospital settings. This manuscript reports on key points from this session. While implementation experiences varied based on factors specific to individual sites, common themes relevant to all hospitals presenting were identified. Successful implementation of early warnings systems requires administrative and leadership support, dedication of resources, improved coordination between nurses, providers, and ancillary staff, optimization of information technology, effective education, evaluation of and change in hospital culture and practices, and support in provider decision-making. Evolving data on outcomes on early warning systems suggest that maternal risk may be reduced. To effectively reduce maternal, risk early warning systems that capture deterioration from a broad range of conditions may be required in addition to bundles tailored to specific conditions such as hemorrhage, thromboembolism, and hypertension.

  8. Early Childhood Workforce Index, 2016

    ERIC Educational Resources Information Center

    Whitebook, Marcy; McLean, Caitlin; Austin, Lea J. E.

    2016-01-01

    The State of the Early Childhood Workforce (SECW) Initiative is a groundbreaking multi-year project to shine a steady spotlight on the nation's early childhood workforce. The SECW Initiative is designed to challenge entrenched ideas and policies that maintain an inequitable and inadequate status quo for early educators and for the children and…

  9. Early Attrition among Suicidal Clients

    ERIC Educational Resources Information Center

    Surgenor, P. W. G.; Meehan, V.; Moore, A.

    2016-01-01

    The study aimed to identify the level of suicidal ideation in early attrition clients and their reasons for the early termination of their therapy. The cross-sectional design involved early attrition clients (C[subscript A]) who withdrew from therapy before their second session (n = 61), and continuing clients who (C[subscript C]) progressed…

  10. Early Childhood Special Music Education

    ERIC Educational Resources Information Center

    Darrow, Alice-Ann

    2011-01-01

    The process of early intervention is a critical component of Early Childhood Special Music Education. Early intervention is the process of providing services, education, and support to young children who have disabilities or to children who are at-risk of developing needs that may affect their physical, cognitive, or emotional development. The…

  11. Indicators of Access to Early Childhood Services in the Mississippi Delta. Rural Early Childhood Report No. 5

    ERIC Educational Resources Information Center

    Shores, Elizabeth F.; Barbaro, Erin; Barbaro, Michael C.; Flenner, Michelle; Bell, Lynn

    2007-01-01

    The Early Childhood Atlas facilitates spatial analysis in early childhood services research for the promotion of greater quality and accessibility of early care and education. The Atlas team collects and geocodes federal, state and nongovernmental datasets about early childhood services, integrating selected data elements into its online mapmaking…

  12. Precursors of Adolescent Substance Use from Early Childhood and Early Adolescence: Testing a Developmental Cascade Model

    PubMed Central

    Sitnick, Stephanie; Shaw, Daniel S.; Hyde, Luke

    2013-01-01

    This study examined developmentally-salient risk and protective factors of adolescent substance use assessed during early childhood and early adolescence using a sample of 310 low-income boys. Child problem behavior and proximal family risk and protective factors (i.e., parenting, maternal depression) during early childhood, as well as child and family factors and peer deviant behavior during adolescence were explored as potential precursors to later substance use during adolescence using structural equation modeling. Results revealed that early childhood risk and protective factors (i.e., child externalizing problems, mothers’ depressive symptomatology, and nurturant parenting) were indirectly related to substance use at the age of 17 via risk and protective factors during early and middle adolescence (i.e., parental knowledge and externalizing problems). The implications of these findings for early prevention and intervention are discussed. PMID:24029248

  13. Contemporary Perspectives on Early Childhood Curriculum. Contemporary Perspectives in Early Childhood Education.

    ERIC Educational Resources Information Center

    Saracho, Olivia N. Ed.; Spodek, Bernard, Ed.

    Noting that the curriculum in early childhood education is dramatically different from that at other levels of education, this volume seeks to clarify some of the issues related to early childhood curriculum development and its bases in both personal knowledge and knowledge from the different disciplines to achieve a "balanced curriculum."…

  14. The Effect of Early Marriages and Early Childbearing on Women's Nutritional Status in India.

    PubMed

    Goli, Srinivas; Rammohan, Anu; Singh, Deepti

    2015-08-01

    The consequences of early childbearing on the growth and nutritional status of women in India has not been quantified in previous studies. Our study aimed to fill this gap by analysing the association between early marriage and early childbearing on nutritional status of Indian women, with a focus on Bihar and Andhra Pradesh, the two states accounting for the highest proportion of women marrying and giving first birth before 18 years of age. Our findings revealed that a substantial number of women were married before 18 years and thereby exposed to early pregnancy. Furthermore, a significantly higher proportion of women in the 'thin' category were married before 18 years, both in the Indian sample (33 %, p < 0.001) and in the selected states, Andhra Pradesh (31 %, p < 0.001) and Bihar (43 %, p < 0.001), compared to those women married at higher ages. Similarly, across all our samples women whose first birth was before age 18 years also had a significantly higher probability of being in the 'thin' category across all our samples. This pattern was also observed for associations between early childbirth and anemia levels. We conclude that the net effect of the early age at marriage and age at first birth on nutritional status is significant. Our results underline the need for preventing early marriages and the consequent high adolescent pregnancies in India, particularly in high prevalence states. This will help to improve nutritional status and health care utilisation among women, thereby, prevent maternal and child mortality and thus, achieve the MDGs 4-5.

  15. High normal blood pressure in early pregnancy also contribute to early onset preeclampsia and severe preeclampsia.

    PubMed

    He, Dian; Wu, Shaowen; Zhao, Haiping; Zheng, Zihe; Zhang, Weiyuan

    2017-11-27

    This study was to evaluate effects of high normal blood pressure (HNBP) in early pregnancy on total preeclampsia, early preeclampsia, and severe preeclampsia. We conducted a multicenter, national representative retrospective cohort study. HNBP was defined as systolic blood pressure between 130 and 140 mmHg or diastolic blood pressure between 85 and 90 mmHg. We used multivariable logistic regression to examine the associations of HNBP and the risks of above three types of preeclampsia. We included 58 054 women who were normotensive and nulliparous in early pregnancy. 4 809 (8.3%) fulfilled the definition of having HNBP, 16 682 (28.7%) were in normal blood pressure group, and 36 563 (63.0%) were in optimal blood pressure group. The incidence rates of total preeclampsia, early preeclampsia, and severe preeclampsia were 2.1% (1 217), 0.8% (491), and 1.4% (814), respectively. Compared to having optimal blood pressure, women with HNBP had significantly higher odds of total preeclampsia (odds ratio (OR) = 4.028, 95% confidence interval (CI) 3.377, 4.804), severe preeclampsia (OR = 3.542, 95% CI 2.851, 4.400), and early preeclampsia (OR = 8.163, 95% CI 6.219, 10.715). Our restricted cubic spline results supported the dose-response relationship between continuous blood pressure and the odds ratio of three types of preeclampsia. The fraction of early preeclampsia associated with prehypertension was 58.6%, which was higher than those of total preeclampsia (42.2%) or severe preeclampsia (40.5%). Women in early pregnancy with HNBP more likely develop total preeclampsia, early preeclampsia and severe preeclampsia, compared to those with optimal blood pressure. HNBP contribute more to early preeclampsia than severe preeclampsia. Our study provided robust epidemiological evidences for monitoring HNBP in early pregnancy to reduce the risks of preeclampsia.

  16. The Mary Ingraham Bunting Institute of Radcliffe College.

    DTIC Science & Technology

    1992-08-31

    scientists -- biologists Elena Budrene and Doris Stern, and geologist Constance Soja -- had also been fellows during the 1990-91 fellowship year. Beginning...Balanced Cross Sections" Constance X. Soja , Geology, Harvard University "Tectonic Controls on Reef Development During the Silurian" Doris Naimark Stern...other better-situated scholars like geologists Constance Soja and Barbara Sheffels, and molecular biologists Elena Budrene and Orna Resnekov, the

  17. Rethinking Early Childhood Education

    ERIC Educational Resources Information Center

    Pelo, Ann, Ed.

    2008-01-01

    "Rethinking Early Childhood Education" is alive with the conviction that teaching young children involves values and vision. This anthology collects inspiring stories about social justice teaching with young children. Included here is outstanding writing from childcare teachers, early-grade public school teachers, scholars, and parents.…

  18. Early Head Start: Research Findings. Early Childhood Highlights. Volume 1, Issue 2

    ERIC Educational Resources Information Center

    Child Trends, 2010

    2010-01-01

    Early Head Start is a federally funded community-based program for low-income families with infants and toddlers and for low-income pregnant women. Created in 1995, Early Head Start strives to promote healthy prenatal outcomes for pregnant women, to enhance the development of children ages birth to three, and to promote healthy family functioning.…

  19. Early Intervention Services for Early-Phase Psychosis - Centre for integrative psychiatry in Psychiatric Hospital "Sveti Ivan", Croatia.

    PubMed

    Matić, Katarina; Gereš, Natko; Gerlach, Josefina; Prskalo-Čule, Diana; Zadravec Vrbanc, Tihana; Lovretić, Vanja; Librenjak, Dina; Vuk Pisk, Sandra; Ivezić, Ena; Šimunović Filipčić, Ivona; Jeleč, Vjekoslav; Filipčić, Igor

    2018-06-01

    There is a growing body of evidence suggesting that early and effective management in the critical early years of schizophrenia can improve long-term outcomes. The objective of this study was to evaluate time to relapse of the patients with early-phase psychosis treated in the Centre for integrative psychiatry (CIP). We performed a retrospective cohort study on the sample of 373 early-phase psychosis patients admitted to Psychiatric Hospital "Sveti Ivan", Zagreb Croatia: from January 1, 2015 to December 31, 2017. The primary outcome was time to relapse. Patients who were admitted to group psychotherapeutic program after the end of acute treatment had 70% lower hazard for relapse (HR=0.30; 95% CI 0.16-0.58). Patients who were included first in the psychotherapeutic program and then treated and controlled in the daily hospital had 74% lower hazard for relapse (HR=0.26; 95% CI 0.10-0.67). In early-phase psychosis, integrative early intervention service has relevant beneficial effects compare to treatment as usual. These results justified the implementation of multimodal early intervention services in treatment of patients with early-phase psychosis.

  20. The Influence of the Early Retirement Process on Satisfaction with Early Retirement and Psychological Well-Being

    ERIC Educational Resources Information Center

    Potocnik, Kristina; Tordera, Nuria; Peiro, Jose Maria

    2010-01-01

    The present study explores the influence of the early retirement process on adjustment to early retirement, taking into account the roles of individual characteristics and social context in this process. We proposed a systematic model integrating perceived ability to continue working, organizational pressures toward early retirement and group…

  1. Early osteoarthritis of the knee.

    PubMed

    Madry, Henning; Kon, Elizaveta; Condello, Vincenzo; Peretti, Giuseppe M; Steinwachs, Matthias; Seil, Romain; Berruto, Massimo; Engebretsen, Lars; Filardo, Giuseppe; Angele, Peter

    2016-06-01

    There is an increasing awareness on the importance in identifying early phases of the degenerative processes in knee osteoarthritis (OA), the crucial period of the disease when there might still be the possibility to initiate treatments preventing its progression. Early OA may show a diffuse and ill-defined involvement, but also originate in the cartilage surrounding a focal lesion, thus necessitating a separate assessment of these two entities. Early OA can be considered to include a maximal involvement of 50 % of the cartilage thickness based on the macroscopic ICRS classification, reflecting an OARSI grade 4. The purpose of this paper was to provide an updated review of the current status of the diagnosis and definition of early knee OA, including the clinical, radiographical, histological, MRI, and arthroscopic definitions and biomarkers. Based on current evidence, practical classification criteria are presented. As new insights and technologies become available, they will further evolve to better define and treat early knee OA.

  2. Growth hormone and early treatment.

    PubMed

    Antoniazzi, F; Cavarzere, P; Gaudino, R

    2015-06-01

    Growth hormone (GH) treatment is approved by the US Food and Drug Administration (FDA) not only for GH deficiency (GHD) but also for other childhood growth disorders with growth failure and/or short stature. GHD is the most frequent endocrine disorder presenting with short stature in childhood. During neonatal period, metabolic effects due to congenital GHD require a prompt replacement therapy to avoid possible life-threatening complications. In childhood and adolescence, growth impairment is the most evident effect of GHD and early treatment has the aim of restore normal growth and to reach normal adult height. We reassume in this review the conditions causing GHD and the diagnostic challenge to reach an early diagnosis, and an early treatment, necessary to obtain the best results. Finally, we summarize results obtained in clinical studies about pediatric patients with GHD treated at an early age, in which a marked early catch-up growth and a normalization of adult height were obtained.

  3. Preventive child health care findings on early childhood predict peer-group social status in early adolescence.

    PubMed

    Jaspers, Merlijne; de Winter, Andrea F; Veenstra, René; Ormel, Johan; Verhulst, Frank C; Reijneveld, Sijmen A

    2012-12-01

    A disputed social status among peers puts children and adolescents at risk for developing a wide range of problems, such as being bullied. However, there is a lack of knowledge about which early predictors could be used to identify (young) adolescents at risk for a disputed social status. The aim of this study was to assess whether preventive child health care (PCH) findings on early childhood predict neglected and rejected status in early adolescence in a large longitudinal community-based sample. Data came from 898 participants who participated in TRAILS, a longitudinal study. Information on early childhood factors was extracted from the charts of routine PCH visits registered between infancy and age of 4 years. To assess social status, peer nominations were used at age of 10-12 years. Multinomial logistic regression showed that children who had a low birth weight, motor problems, and sleep problems; children of parents with a low educational level (odds ratios [ORs] between 1.71 and 2.90); and those with fewer attention hyperactivity problems (ORs = .43) were more likely to have a neglected status in early adolescence. Boys, children of parents with a low educational level, and children with early externalizing problems were more likely to have a rejected status in early adolescence (ORs between 1.69 and 2.56). PCH findings on early childhood-on motor and social development-are predictive of a neglected and a rejected status in early adolescence. PCH is a good setting to monitor risk factors that predict the social status of young adolescents. Copyright © 2012 Society for Adolescent Health and Medicine. Published by Elsevier Inc. All rights reserved.

  4. Early Intervention in Bipolar Disorder.

    PubMed

    Vieta, Eduard; Salagre, Estela; Grande, Iria; Carvalho, André F; Fernandes, Brisa S; Berk, Michael; Birmaher, Boris; Tohen, Mauricio; Suppes, Trisha

    2018-05-01

    Bipolar disorder is a recurrent disorder that affects more than 1% of the world population and usually has its onset during youth. Its chronic course is associated with high rates of morbidity and mortality, making bipolar disorder one of the main causes of disability among young and working-age people. The implementation of early intervention strategies may help to change the outcome of the illness and avert potentially irreversible harm to patients with bipolar disorder, as early phases may be more responsive to treatment and may need less aggressive therapies. Early intervention in bipolar disorder is gaining momentum. Current evidence emerging from longitudinal studies indicates that parental early-onset bipolar disorder is the most consistent risk factor for bipolar disorder. Longitudinal studies also indicate that a full-blown manic episode is often preceded by a variety of prodromal symptoms, particularly subsyndromal manic symptoms, therefore supporting the existence of an at-risk state in bipolar disorder that could be targeted through early intervention. There are also identifiable risk factors that influence the course of bipolar disorder, some of them potentially modifiable. Valid biomarkers or diagnosis tools to help clinicians identify individuals at high risk of conversion to bipolar disorder are still lacking, although there are some promising early results. Pending more solid evidence on the best treatment strategy in early phases of bipolar disorder, physicians should carefully weigh the risks and benefits of each intervention. Further studies will provide the evidence needed to finish shaping the concept of early intervention. AJP AT 175 Remembering Our Past As We Envision Our Future April 1925: Interpretations of Manic-Depressive Phases Earl Bond and G.E. Partridge reviewed a number of patients with manic-depressive illness in search of a unifying endo-psychic conflict. They concluded that understanding either phase of illness was "elusive" and

  5. Waterford Early Reading Program.

    ERIC Educational Resources Information Center

    Education Commission of the States, Denver, CO.

    This paper provides an overview of the Waterford Early Reading Program (WERP), which is designed to shift teaching and learning away from remediation and failure to prevention, early achievement, and sustained growth for every student. WERP includes three levels of instruction: emergent, beginning, and fluent readers. It targets pre-K through…

  6. Children's early helping in action: Piagetian developmental theory and early prosocial behavior.

    PubMed

    Hammond, Stuart I

    2014-01-01

    After a brief overview of recent research on early helping, outlining some central problems, and issues, this paper examines children's early helping through the lens of Piagetian moral and developmental theory, drawing on Piaget's "Moral Judgment of the Child" (Piaget, 1932/1997), "Play, Dreams, and Imitation in Childhood" (Piaget, 1945/1951), and the "Grasp of Consciousness" (Piaget, 1976). Piaget refers to a level of moral development in action that precedes heteronomous and autonomous moral reasoning. This action level allows children to begin to interact with people and objects. In his later work, Piaget explores the gradual construction of understanding from this activity level. Taken together, these elements of Piagetian theory provide a promising conceptual framework for understanding the development of early helping.

  7. Early Childhood Educators' Perceived and Actual Metalinguistic Knowledge, Beliefs and Enacted Practice about Teaching Early Reading

    ERIC Educational Resources Information Center

    Hammond, Lorraine

    2015-01-01

    Results of influential reports on early literacy have drawn attention to the need for early childhood educators to take up a more explicit, teacher-directed approach to beginning reading. Positive classroom results however are in part dependent upon teacher knowledge and this study investigated the relationship between early childhood educators'…

  8. Early presentation of primary glioblastoma.

    PubMed

    Faguer, R; Tanguy, J-Y; Rousseau, A; Clavreul, A; Menei, P

    2014-08-01

    Clinical and neuroimaging findings of glioblastomas (GBM) at an early stage have rarely been described and those tumors are most probably under-diagnosed. Furthermore, their genetic alterations, to our knowledge, have never been previously reported. We report the clinical as well as neuroimaging findings of four early cases of patients with GBM. In our series, early stage GBM occurred at a mean age of 57 years. All patients had seizures as their first symptom. In all early stages, MRI showed a hyperintense signal on T2-weighted sequences and an enhancement on GdE-T1WI sequences. A hyperintense signal on diffusion sequences with a low ADC value was also found. These early observed occurrences of GBM developed rapidly and presented the MRI characteristics of classic GBM within a few weeks. The GBM size was multiplied by 32 in one month. Immunohistochemical analysis indicated the de novo nature of these tumors, i.e. absence of mutant IDH1 R132H protein expression, which is a diagnostic marker of low-grade diffuse glioma and secondary GBM. A better knowledge of early GBM presentation would allow a more suitable management of the patients and may improve their prognosis. Copyright © 2014 Elsevier Masson SAS. All rights reserved.

  9. Sharing Books with Babies: Promoting Early Literacy in Early Care and Education. [Videotape].

    ERIC Educational Resources Information Center

    Boston Medical Center, MA. Doc4Kids Project.

    Suggesting that very young children spend every waking minute getting ready for kindergarten, this videotape for caregivers and early childhood teachers shows how to support early literacy skill development by sharing stories, relationships, and books with infants, toddlers, and preschoolers in care and education settings. The 25-minute videotape…

  10. Emotional Self-Regulation, Peer Rejection, and Antisocial Behavior: Developmental Associations from Early Childhood to Early Adolescence

    ERIC Educational Resources Information Center

    Trentacosta, Christopher J.; Shaw, Daniel S.

    2009-01-01

    This study examined relations among emotional self-regulation, peer rejection, and antisocial behavior in a sample of 122 boys from low-income families who participated in a summer camp and were followed longitudinally from early childhood to early adolescence. Emotional self-regulation strategies were coded in early childhood from a waiting task,…

  11. Late Paleozoic tectonics of the Solonker Zone in the Wuliji area, Inner Mongolia, China: Insights from stratigraphic sequence, chronology, and sandstone geochemistry

    NASA Astrophysics Data System (ADS)

    Shi, Guanzhong; Song, Guangzeng; Wang, Hua; Huang, Chuanyan; Zhang, Lidong; Tang, Jianrong

    2016-09-01

    The geology in the Wuliji area (including the Enger Us and Quagan Qulu areas) is important for understanding the Late Paleozoic tectonics of the Solonker Zone. Ultramafic/mafic rocks in the Enger Us area, previously interpreted as an ophiolitic suture, are actually lava flows and sills in a Permian turbiditic sequence and a small body of fault breccia containing serpentinite. Subduction zone features, such as accretionary complexes, magmatic arc volcanics or LP/HP metamorphism are absent. Early Permian N-MORB mafic rocks and Late Permian radiolarian cherts accompanied by turbidites and tuffeous rocks indicate a deep water setting. In the Quagan Qulu area, outcrops of the Late Carboniferous to Permian Amushan Formation are composed of volcano-sedimenary rocks and guyot-like reef limestone along with a Late Permian volcano-sedimentary unit. A dacite lava in the Late Permian volcano-sedimentary unit yields a zircon U-Pb age of 254 Ma. The gabbros in the Quagan Qulu area are intruded into the Amushan Formation and caused contact metamorphism of country rocks. Sandstones in the Upper Member of the Amushan Formation contain detrital clasts of volcanic fragments and mineral clasts of crystalline basement rocks (i.e. biotite, muscovite and garnet). Geochemical analysis of volcaniclastic sandstones shows a magmatic affinity to both continental island arc (CIA) and active continental margin (ACM) tectonic settings. A Late Permian incipient rift setting is suggested by analyzing the lithostratigraphic sequence and related magmatism in the Wuliji area. The volcano-sedimentary rocks in the Wuliji area experienced a nearly N-S shortening that was probably related to the Early Mesozoic nearly N-S compression well developed in other areas close to the Wuliji area.

  12. IODP Expedition 351 Izu-Bonin-Mariana Arc Origins: Age Model for Site U1438

    NASA Astrophysics Data System (ADS)

    Morris, A.; Aljahdali, M. H.; Bandini, A. N.; do Monte Guerra, R.; Kender, S.; Maffione, M.

    2014-12-01

    We report preliminary paleomagnetic and paleontological results from International Ocean Discovery Program (IODP) Expedition 351, which recovered an unprecedented ~1.4 km thick volcaniclastic sedimentary record documenting the initiation and subsequent evolution of the Izu-Bonin-Mariana (IBM) intra-oceanic arc-basin system. Magnetostratigraphic and biostratigraphic constraints provide a high-resolution temporal framework for interpretation of this record.Paleomagnetic analyses of archive half core samples provide a continuous record of the geomagnetic field inclination down to 847 mbsf that allows construction of a detailed site magnetostratigraphy that closely matches the Geomagnetic Polarity Timescale (Gradstein et al., 2012). A total of 87 geomagnetic reversals have been recognized in the studied succession, extending back to ~36 Ma. Despite sporadic microfossil occurrences in parts, calcareous nannofossils, planktonic foraminifera and radiolarians each contribute to the age model for the entire Site. All nannofossil marker species for Oligocene to Eocene Zones NP25 to NP19/20 are recognised. Beneath paleomagnetic control (847-1449 mbsf), foraminifera and radiolarians provide the only age control.The most salient features of the age model are that: (i) average linear sedimentation rates during the Plio-Pleistocene range from 1.4 to 2.2 cm/ka; (ii) there was a reduction in sedimentation rates to 0.25 - 0.5 cm/ka throughout the Miocene; and (iii) sedimentation rates sharply increase again in the Oligocene to Late Eocene to a maximum of ~20 cm/ka. These quantitative constraints closely match (non-quantitative) inferences based on the lithostratigraphy of the site, with fine-grained/coarse-grained sediments dominating in periods with low/high sedimentation rates respectively.

  13. IODP Expedition 351 Izu-Bonin-Mariana Arc Origins: Age model for Site U1438

    NASA Astrophysics Data System (ADS)

    Morris, Antony; Maffione, Marco; Kender, Sev; Aljahdali, Mohammed; Bandini, Alexandre; Guerra, Rodrigo do Monte

    2015-04-01

    We report preliminary paleomagnetic and paleontological results from International Ocean Discovery Program (IODP) Expedition 351, which recovered an unprecedented ~1.4 km thick volcaniclastic sedimentary record documenting the initiation and subsequent evolution of the Izu-Bonin-Mariana (IBM) intra-oceanic arc-basin system. Magnetostratigraphic and biostratigraphic constraints provide a high-resolution temporal framework for interpretation of this record. Paleomagnetic analyses of archive half core samples provide a continuous record of the geomagnetic field inclination down to 847 mbsf that allows construction of a detailed site magnetostratigraphy that closely matches the Geomagnetic Polarity Timescale (Gradstein et al., 2012). A total of 87 geomagnetic reversals have been recognized in the studied succession, extending back to ~36 Ma. Despite sporadic microfossil occurrences in parts, calcareous nannofossils, planktonic foraminifera and radiolarians each contribute to the age model for the entire Site. All nannofossil marker species for Oligocene to Eocene Zones NP25 to NP19/20 are recognised. Beneath paleomagnetic control (847-1449 mbsf), foraminifera and radiolarians provide the only age control. The most salient features of the age model are that: (i) average linear sedimentation rates during the Plio-Pleistocene range from 1.4 to 2.2 cm/ka; (ii) there was a reduction in sedimentation rates to 0.25 - 0.5 cm/ka throughout the Miocene; and (iii) sedimentation rates sharply increase again in the Oligocene to Late Eocene to a maximum of ~20 cm/ka. These quantitative constraints closely match (non-quantitative) inferences based on the lithostratigraphy of the site, with fine-grained/coarse-grained sediments dominating in periods with low/high sedimentation rates respectively.

  14. High resolution biogeochemistry in the Upper Cenomanian black shales of the Umbria-Marche Basin (central Italy)

    NASA Astrophysics Data System (ADS)

    Bombardiere, L.; Farrimond, P.; Tyson, R. V.; Forster, A.; Sinninghe-Damsté, J.

    2003-04-01

    The uppermost Cenomanian "anoxic event" (i.e. OAE2) in the Umbria-Marche Basin is recorded by a 0.7-1.2 metre thick interval (the Bonarelli Level) consisting of black, organic-rich laminated mudstones ("black shales"), radiolarian layers and grey-greenish, organic-poor claystones. The occurrence of the radiolarian layers and the organic-poor claystones defines three lithological sub-units which can be correlated at basin scale. In addition, a number of thin black shales ("Bonarelli precursors") has been observed in the limestones underlying the Bonarelli Level; their occurrence appears to be tuned with Milankovitch cycles. This study investigates palaeoproductivity and preservation in the Bonarelli Level and in the precursors using a high resolution molecular biomarker analysis. The onset of the Bonarelli deposition (i.e. the lower sub-unit) is characterized by a drastic increase in the relative abundance of compounds associated with algal precursors (e.g. steranes and phytane). Equally, the same interval shows an increase in the biomarker proxies related to the intensity of oxygen depletion (e.g. homohopane index). The other two Bonarelli sub-units also reflect fluctuations in oxic-anoxic conditions and palaeoproductivity. As the molecular compounds thought to reflect qualitative changes in palaeoproductivity and anoxia do not exhibit any significant differencies between the precursor black shales and the Bonarelli Level, the palaeoenvironmental conditions leading to organic-rich sediments were presumably similar. The results from the Italian sites have been compared with two other OAE2 localities, both characterized by proximal depositional settings: Oued Bahloul (Tunisia) and Tarfaya (Morocco). This work is supported by the European Community's Improving Human Potential Programme under contract HPRN-CT-1999-00055, C/T-NET.

  15. The At Risk Child: Early Identification, Intervention, and Evaluation of Early Childhood Strategies.

    ERIC Educational Resources Information Center

    Lennon, Joan M.

    A review of literature was conducted in order to: (1) determine whether factors placing the young child at risk for school failure can be identified; (2) determine whether early family interventions and early childhood programs are effective; and (3) identify policy implications. Findings are summarized, and recommendations are offered. Research…

  16. Taiwanese Early Childhood Educators' Professional Development

    ERIC Educational Resources Information Center

    Hsu, Ching-Yun

    2008-01-01

    This study was designed based on a qualitative paradigm to explore the professional development of Taiwanese early childhood educators. The method of phenomenology was employed. The main research question addressed was "How do early childhood educators construe their professional development experience?" Seven Taiwanese early childhood…

  17. Resilience in mathematics after early brain injury: The roles of parental input and early plasticity.

    PubMed

    Glenn, Dana E; Demir-Lira, Özlem Ece; Gibson, Dominic J; Congdon, Eliza L; Levine, Susan C

    2018-04-01

    Children with early focal unilateral brain injury show remarkable plasticity in language development. However, little is known about how early brain injury influences mathematical learning. Here, we examine early number understanding, comparing cardinal number knowledge of typically developing children (TD) and children with pre- and perinatal lesions (BI) between 42 and 50 months of age. We also examine how this knowledge relates to the number words children hear from their primary caregivers early in life. We find that children with BI, are, on average, slightly behind TD children in both cardinal number knowledge and later mathematical performance, and show slightly slower learning rates than TD children in cardinal number knowledge during the preschool years. We also find that parents' "number talk" to their toddlers predicts later mathematical ability for both TD children and children with BI. These findings suggest a relatively optimistic story in which neural plasticity is at play in children's mathematical development following early brain injury. Further, the effects of early number input suggest that intervening to enrich the number talk that children with BI hear during the preschool years could narrow the math achievement gap. Copyright © 2017 The Authors. Published by Elsevier Ltd.. All rights reserved.

  18. 23 CFR 710.501 - Early acquisition.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 23 Highways 1 2010-04-01 2010-04-01 false Early acquisition. 710.501 Section 710.501 Highways... REAL ESTATE Property Acquisition Alternatives § 710.501 Early acquisition. (a) Real property... so based on program or project considerations. The State may undertake early acquisition for corridor...

  19. 23 CFR 710.501 - Early acquisition.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 23 Highways 1 2011-04-01 2011-04-01 false Early acquisition. 710.501 Section 710.501 Highways... REAL ESTATE Property Acquisition Alternatives § 710.501 Early acquisition. (a) Real property... so based on program or project considerations. The State may undertake early acquisition for corridor...

  20. Treatment of early Parkinson's disease.

    PubMed

    Pahwa, Rajesh; Lyons, Kelly E

    2014-08-01

    This review summarizes currently available treatment options and treatment strategies, investigational treatments, and the importance of exercise for early Parkinson's disease. The available treatment options for early Parkinson's disease have changed little in the past decade and include carbidopa/levodopa, dopamine agonists, and monoamine oxidase type B (MAO-B) inhibitors. However, we discuss changes in treatment strategies, including dosing and the use of combination therapy used in an attempt to reduce or delay the appearance of motor complications and other adverse events. We will also review several investigational treatments that have shown promise for the treatment of early Parkinson's disease, including a new extended release formulation of carbidopa/levodopa (IPX066), safinamide which inhibits MAO-B, dopamine uptake and glutamate and pardoprunox which is a 5HT-1A agonist and a partial dopamine agonist. Finally, we discuss recent studies focusing on exercise as an important component in the management of early Parkinson's disease. Advances in the management of early Parkinson's disease include evolving treatment strategies, new investigational treatments, and earlier implementation of various forms of exercise.

  1. Devonian post-orogenic extension-related volcano-sedimentary rocks in the northern margin of the Tibetan Plateau, NW China: Implications for the Paleozoic tectonic transition in the North Qaidam Orogen

    NASA Astrophysics Data System (ADS)

    Qin, Yu; Feng, Qiao; Chen, Gang; Chen, Yan; Zou, Kaizhen; Liu, Qian; Jiao, Qianqian; Zhou, Dingwu; Pan, Lihui; Gao, Jindong

    2018-05-01

    The Maoniushan Formation in the northern part of the North Qaidam Orogen (NQO), NW China, contains key information on a Paleozoic change in tectonic setting of the NQO from compression to extension. Here, new zircon U-Pb, petrological, and sedimentological data for the lower molasse sequence of the Maoniushan Formation are used to constrain the timing of this tectonic transition. Detrital zircons yield U-Pb ages of 3.3-0.4 Ga with major populations at 0.53-0.4, 1.0-0.56, 2.5-1.0, and 3.3-2.5 Ga. The maximum depositional age of the Maoniushan Formation is well constrained by a youngest detrital zircon age of ∼409 Ma. Comparing these dates with geochronological data for the region indicates that Proterozoic-Paleozoic zircons were derived mainly from the NQO as well as the Oulongbuluk and Qaidam blocks, whereas Archean zircons were probably derived from the Oulongbuluk Block and the Tarim Craton. The ∼924, ∼463, and ∼439 Ma tectonothermal events recorded in this region indicate that the NQO was involved in the early Neoproterozoic assembly of Rodinia and early Paleozoic microcontinental convergence. A regional angular unconformity between Devonian and pre-Devonian strata within the NQO suggests a period of strong mountain building between the Oulongbuluk and Qaidam blocks during the Silurian, whereas an Early Devonian post-orogenic molasse, evidence of extensional collapse, and Middle to Late Devonian bimodal volcanic rocks and Carboniferous marine carbonate rocks clearly reflect long-lived tectonic extension. Based on these results and the regional geology, we suggest that the Devonian volcano-sedimentary rocks within the NQO were formed in a post-orogenic extensional setting similar to that of the East Kunlun Orogen, indicating that a major tectonic transition from compression to extension in these two orogens probably commenced in the Early Devonian.

  2. Fossil Fishes from China Provide First Evidence of Dermal Pelvic Girdles in Osteichthyans

    PubMed Central

    Zhu, Min; Yu, Xiaobo; Choo, Brian; Qu, Qingming; Jia, Liantao; Zhao, Wenjin; Qiao, Tuo; Lu, Jing

    2012-01-01

    Background The pectoral and pelvic girdles support paired fins and limbs, and have transformed significantly in the diversification of gnathostomes or jawed vertebrates (including osteichthyans, chondrichthyans, acanthodians and placoderms). For instance, changes in the pectoral and pelvic girdles accompanied the transition of fins to limbs as some osteichthyans (a clade that contains the vast majority of vertebrates – bony fishes and tetrapods) ventured from aquatic to terrestrial environments. The fossil record shows that the pectoral girdles of early osteichthyans (e.g., Lophosteus, Andreolepis, Psarolepis and Guiyu) retained part of the primitive gnathostome pectoral girdle condition with spines and/or other dermal components. However, very little is known about the condition of the pelvic girdle in the earliest osteichthyans. Living osteichthyans, like chondrichthyans (cartilaginous fishes), have exclusively endoskeletal pelvic girdles, while dermal pelvic girdle components (plates and/or spines) have so far been found only in some extinct placoderms and acanthodians. Consequently, whether the pectoral and pelvic girdles are primitively similar in osteichthyans cannot be adequately evaluated, and phylogeny-based inferences regarding the primitive pelvic girdle condition in osteichthyans cannot be tested against available fossil evidence. Methodology/Principal Findings Here we report the first discovery of spine-bearing dermal pelvic girdles in early osteichthyans, based on a new articulated specimen of Guiyu oneiros from the Late Ludlow (Silurian) Kuanti Formation, Yunnan, as well as a re-examination of the previously described holotype. We also describe disarticulated pelvic girdles of Psarolepis romeri from the Lochkovian (Early Devonian) Xitun Formation, Yunnan, which resemble the previously reported pectoral girdles in having integrated dermal and endoskeletal components with polybasal fin articulation. Conclusions/Significance The new findings reveal

  3. Early Life Exposures and Cancer

    Cancer.gov

    Early-life events and exposures have important consequences for cancer development later in life, however, epidemiological studies of early-life factors and cancer development later in life have had significant methodological challenges.

  4. Natural course of early COPD.

    PubMed

    Rhee, Chin Kook; Kim, Kyungjoo; Yoon, Hyoung Kyu; Kim, Jee-Ae; Kim, Sang Hyun; Lee, Sang Haak; Park, Yong Bum; Jung, Ki-Suck; Yoo, Kwang Ha; Hwang, Yong Il

    2017-01-01

    Few studies have examined the natural course of early COPD. The aim of this study was to observe the natural course of early COPD patients. We also aimed to analyze medical utilization and costs for early COPD during a 6-year period. Patients with early COPD were selected from Korean National Health and Nutrition Examination Survey (KNHANES) data. We linked the KNHANES data of patients with early COPD to National Health Insurance data. A total of 2,397 patients were enrolled between 2007 and 2012. The mean forced expiratory volume in 1 second (FEV 1 ) was 78.6%, and the EuroQol five dimensions questionnaire (EQ-5D) index value was 0.9. In total, 110 patients utilized health care for COPD in 2007, and this number increased to 179 in 2012. The total mean number of days used per person increased from 4.9 in 2007 to 7.8 in 2012. The total medical cost per person also increased from 248.8 US dollar (USD) in 2007 to 780.6 USD in 2013. A multiple linear regression revealed that age, lower body mass index, lower FEV 1 (%), and lower EQ-5D score were significantly associated with medical costs. Even in early COPD patients, some of them eventually progressed and utilized health care for COPD.

  5. 28 CFR 2.43 - Early termination.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... 28 Judicial Administration 1 2012-07-01 2012-07-01 false Early termination. 2.43 Section 2.43..., YOUTH OFFENDERS, AND JUVENILE DELINQUENTS United States Code Prisoners and Parolees § 2.43 Early... shall also conduct a status review whenever the supervision officer recommends early termination of the...

  6. 28 CFR 2.43 - Early termination.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 28 Judicial Administration 1 2013-07-01 2013-07-01 false Early termination. 2.43 Section 2.43..., YOUTH OFFENDERS, AND JUVENILE DELINQUENTS United States Code Prisoners and Parolees § 2.43 Early... shall also conduct a status review whenever the supervision officer recommends early termination of the...

  7. 28 CFR 2.43 - Early termination.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 28 Judicial Administration 1 2014-07-01 2014-07-01 false Early termination. 2.43 Section 2.43..., YOUTH OFFENDERS, AND JUVENILE DELINQUENTS United States Code Prisoners and Parolees § 2.43 Early... shall also conduct a status review whenever the supervision officer recommends early termination of the...

  8. 28 CFR 2.43 - Early termination.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 28 Judicial Administration 1 2010-07-01 2010-07-01 false Early termination. 2.43 Section 2.43..., YOUTH OFFENDERS, AND JUVENILE DELINQUENTS United States Code Prisoners and Parolees § 2.43 Early... shall also conduct a status review whenever the supervision officer recommends early termination of the...

  9. 28 CFR 2.43 - Early termination.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 28 Judicial Administration 1 2011-07-01 2011-07-01 false Early termination. 2.43 Section 2.43..., YOUTH OFFENDERS, AND JUVENILE DELINQUENTS United States Code Prisoners and Parolees § 2.43 Early... shall also conduct a status review whenever the supervision officer recommends early termination of the...

  10. Stratigraphy and facies development of the marine Late Devonian near the Boulongour Reservoir, northwest Xinjiang, China

    NASA Astrophysics Data System (ADS)

    Suttner, Thomas J.; Kido, Erika; Chen, Xiuqin; Mawson, Ruth; Waters, Johnny A.; Frýda, Jiří; Mathieson, David; Molloy, Peter D.; Pickett, John; Webster, Gary D.; Frýdová, Barbora

    2014-02-01

    Late Devonian to Early Carboniferous stratigraphic units within the 'Zhulumute' Formation, Hongguleleng Formation (stratotype), 'Hebukehe' Formation and the Heishantou Formation near the Boulongour Reservoir in northwestern Xinjiang are fossil-rich. The Hongguleleng and 'Hebukehe' formations are biostratigraphically well constrained by microfossils from the latest Frasnian linguiformis to mid-Famennian trachytera conodont biozones. The Hongguleleng Formation (96.8 m) is characterized by bioclastic argillaceous limestones and marls (the dominant facies) intercalated with green spiculitic calcareous shales. It yields abundant and highly diverse faunas of bryozoans, brachiopods and crinoids with subordinate solitary rugose corals, ostracods, trilobites, conodonts and other fish teeth. The succeeding 'Hebukehe' Formation (95.7 m) consists of siltstones, mudstones, arenites and intervals of bioclastic limestone (e.g. 'Blastoid Hill') and cherts with radiolarians. A diverse ichnofauna, phacopid trilobites, echinoderms (crinoids and blastoids) together with brachiopods, ostracods, bryozoans and rare cephalopods have been collected from this interval. Analysis of geochemical data, microfacies and especially the distribution of marine organisms, which are not described in detail here, but used for facies analysis, indicate a deepening of the depositional environment at the Boulongour Reservoir section. Results presented here concern mainly the sedimentological and stratigraphical context of the investigated section. Additionally, one Late Devonian palaeo-oceanic and biotic event, the Upper Kellwasser Event is recognized near the section base.

  11. Equity Starts Early: Addressing Racial Inequities in Child Care and Early Education Policy

    ERIC Educational Resources Information Center

    Johnson-Staub, Christine

    2017-01-01

    Child care and early education policies are shaped by a history of systemic and structural racism. This has created major racial disparities in children's access to quality child care that meets their cultural and linguistic needs and enables their parents to work. Early care and education workers are overwhelmingly in low-quality jobs with…

  12. NASA Early Career Fellowship Program

    NASA Astrophysics Data System (ADS)

    Smith, H. D.

    2012-12-01

    The Early Career Fellowship program was established in 2005 to facilitate the integration of outstanding early career planetary science researchers into established research funding programs by providing tools and experience useful to maintain a successful research program. Executing a successful research program requires a few key elements such as: successful proposal writing; adequate (paid) research time; management of a laboratory; collaboration and networking; frequent and high-quality publications; and adequate start-up equipment funds. These elements may be particularly critical for early career researchers searching for a tenure- track or equivalent position. The Early Career Fellowship program recognizes the importance of these skills and provides extra funding and resources to begin a successful research program. For consideration into The Early Career Fellowship program, the candidate needs to be the P. I. or Science P.I. of a funded research proposal from one of the participating R&A program areas, be within 7 years of earning a PhD, hold a non-tenure track position, and indicate the early career candidacy when submitting the research proposal. If the research proposal is funded and the discipline scientist nominates the candidate as an early career fellow, the candidate is then considered a Fellow and eligible to propose for Step 2. Upon obtaining a tenure-track equivalent position the Fellow submits a Step 2 proposal for up to one hundred thousand dollars in start-up funds. Start-up funds may be used for salary; undergraduate and/or graduate research assistants; supplies and instrument upgrades; travel to conferences, meetings, and advisory groups; time and travel for learning new skills; publication page charges; books and journal subscriptions; computer time and/or specialized software; and other justified research-specific needs. The early career fellowship program provides resources that a more established scientist would have acquired allowing

  13. 43 CFR 10010.9 - Apply NEPA early.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... 43 Public Lands: Interior 2 2011-10-01 2011-10-01 false Apply NEPA early. 10010.9 Section 10010.9... Initiating the NEPA Process § 10010.9 Apply NEPA early. (a) The Commission will initiate early consultation... early with interested private parties and organizations, including when the Commission's own involvement...

  14. WWC Review of the Report "Early College, Early Success: Early College High School Initiative Impact Study." What Works Clearinghouse Single Study Review

    ERIC Educational Resources Information Center

    What Works Clearinghouse, 2014

    2014-01-01

    Early College High Schools partner with colleges and universities to provide students with an opportunity to earn an Associate's degree or college credits toward a Bachelor's degree at no or low cost to students. In a recent study, researchers found that attending Early College High Schools improved some high school and postsecondary outcomes for…

  15. Michigan Early Adolescent Survey: Final Report.

    ERIC Educational Resources Information Center

    Keith, Joanne; And Others

    This document contains the final report from the Michigan Early Adolescent Survey, a study undertaken to: (1) develop a profile of Michigan early adolescents that focused on out-of-school time and included biological, psychological, and sociological information; (2) develop a profile of families which included early adolescents; (3) assess the…

  16. Challenges and Limitations in Early Intervention

    ERIC Educational Resources Information Center

    Hadders-Algra, Mijna

    2011-01-01

    Research over the past three decades has shown that early intervention in infants biologically at risk of developmental disorders, irrespective of the presence of a brain lesion, is associated with improved cognitive development in early childhood without affecting motor development. However, at present it is unknown whether early intervention is…

  17. 7 CFR 1717.901 - Early approval.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... 7 Agriculture 11 2011-01-01 2011-01-01 false Early approval. 1717.901 Section 1717.901 Agriculture... for Supplemental Financing Required by 7 CFR 1710.110 § 1717.901 Early approval. (a) Conditions. If... supplemental financing early in the process, before funding is available for the concurrent RUS insured loan...

  18. Early Interventions: Keys to Successful Readers.

    ERIC Educational Resources Information Center

    Jeffreys, JoAnn; Spang, Joan

    This action research outlines an early reading intervention project for improving students' reading skills and promoting the implementation of early reading intervention programs. The targeted population includes first and second grade students in one school located in the suburbs of a major city in Illinois. The problem of early reading…

  19. Early Childhood Services in New Zealand.

    ERIC Educational Resources Information Center

    Oborn, Glennie

    2002-01-01

    Describes the types and characteristics of New Zealand early childhood education services. Specific areas addressed include: (1) Te Whaariki, the New Zealand early childhood curriculum; (2) great outdoors as a feature of early education; (3) education and care centers; (4) kindergartens and playcenters; and (5) Te Kohanga Reo, Maori language and…

  20. Variations in radiolarian assemblages in the Japan Sea since the Last Glacial Period: implications for paleoceanography Zhi Dong12, Xuefa Shi2, Xinqing Zou1, Jianjun Zou2, Muhong Chen3, Qiang Zhang3, Chendong Ge1,Yanguang Liu21. Nanjing University,China 2. First Institute of Oceanography, China 3. South China Sea Institute of Oceanology, China

    NASA Astrophysics Data System (ADS)

    Dong, Z.; Shi, X.; Zou, X.; Zou, J. J.; Chen, M.; Zhang, Q.; Ge, C.; Liu, Y.

    2017-12-01

    Japan Sea is a marginal sea located on the rim of the western Pacific, connecting with the open ocean via key straits with sill depths of less than 130 m, whichis close to the maximum drop of sea level during the Last Glacial Maximum (LGM). Tsushima Strait connects modern JS with neighboring seas and Tsushima Warm Current (TWC), the only warm current flowing into the JS, reaches the northern JS where the cold saline deep wate is formed. Previous studies show that only northern Tsugaru Strait was opened during the last deglaciation, indicating different pattern of water mass exchange between JS and adjacent seas. Few paleoceanographic reconstructions in the southern JS are available to reconstruct the history of inflow of the TWC and deep ventilation. Radiolaria comprises shallow to deep water dwellers, sensitive response to changes in sea water physical and chemical states. It is well known for being preserved in the deep-sea sediments of the North Pacific. In order to decipher the changes of paleoceanography in the JS, here we investigate SST, SSS, deep ventilation using radiolarian assemblages recorded in core KCES1 recovered from the Ulleung Basin. We identified total 108 taxa which have been counted and divided into three categories: TWC, low-salinity and deep water taxa. Changes in radiolaria reveal that the paleoceanographic conditions has changed drastically during the last glacial period. The dominance of low-salinitytaxa indicates low SSS in JS during LGM. For older interval (24-46 ka), low-salinity taxa and TWC taxa could be identified, suggesting both East China Sea Coastal Water, whose volume is higher than Holocene, and TWC flow into the JS. The TWC taxa start to increase at 19 ka, also indicated by negative excursion of TOC δ13C due to the re-open of the Tsushima Strait, coincident with the 19 ka-MWP. The increasing abundance of low-salinity taxa during the B/A warm period, indicated an enhanced influence of river discharge forced by EASM. The

  1. Early- versus Late-Onset Dysthymia

    PubMed Central

    Sansone, Lori A.

    2009-01-01

    In the current Diagnostic and Statistical Manual of Mental Disorders, dysthymic disorder is categorized as either early-onset or late-onset, based upon the emergence of symptoms before or after the age of 21, respectively. Does this diagnostic distinction have any meaningful clinical implications? In this edition of The Interface, we present empirical studies that have, within a single study, compared individuals with early-versus late-onset dysthymia. In this review, we found that, compared to those with late-onset dysthymia, early-onset patients are more likely to harbor psychiatric comorbidity both on Axis I and II, exhibit less psychological resilience, and have more prominent family loadings for mood disorders. These findings suggest that this distinction is meaningful and that the early-onset subtype of dysthymia is more difficult to effectively treat. PMID:20049145

  2. Effect of socioeconomic status disparity on child language and neural outcome: how early is early?

    PubMed

    Hurt, Hallam; Betancourt, Laura M

    2016-01-01

    It is not news that poverty adversely affects child outcome. The literature is replete with reports of deleterious effects on developmental outcome, cognitive function, and school performance in children and youth. Causative factors include poor nutrition, exposure to toxins, inadequate parenting, lack of cognitive stimulation, unstable social support, genetics, and toxic environments. Less is known regarding how early in life adverse effects may be detected. This review proposes to elucidate "how early is early" through discussion of seminal articles related to the effect of socioeconomic status on language outcome and a discussion of the emerging literature on effects of socioeconomic status disparity on brain structure in very young children. Given the young ages at which such outcomes are detected, the critical need for early targeted interventions for our youngest is underscored. Further, the fiscal reasonableness of initiating quality interventions supports these initiatives. As early life adversity produces lasting and deleterious effects on developmental outcome and brain structure, increased focus on programs and policies directed to reducing the impact of socioeconomic disparities is essential.

  3. Rifting along the northern Gondwana margin and the evolution of the Rheic Ocean: A Devonian age for the El Castillo volcanic rocks (Salamanca, Central Iberian Zone)

    NASA Astrophysics Data System (ADS)

    Gutiérrez-Alonso, G.; Murphy, J. B.; Fernández-Suárez, J.; Hamilton, M. A.

    2008-12-01

    Exposures of volcanic rocks (El Castillo) in the Central Iberian Zone near Salamanca, Spain, are representative of Paleozoic volcanic activity along the northern Gondwanan passive margin. Alkaline basalts and mafic volcaniclastic rocks of this sequence are structurally preserved in the core of the Variscan-Tamames Syncline. On the basis of the occurrence of graptolite fossils in immediately underlying strata, the El Castillo volcanics traditionally have been regarded as Lower Silurian in age. In contrast, most Paleozoic volcanic units in western Iberia are rift-related mafic to felsic rocks emplaced during the Late Cambrian-Early Ordovician, and are attributed to the opening of the Rheic Ocean. We present new zircon U-Pb TIMS data from a mafic volcaniclastic rock within the El Castillo unit. These data yield a near-concordant, upper intercept age of 394.7 ± 1.4 Ma that is interpreted to reflect a Middle Devonian (Emsian-Eifelian) age for the magmatism, demonstrating that the El Castillo volcanic rocks are separated from underlying lower Silurian strata by an unconformity. The U-Pb age is coeval with a widespread extensional event in Iberia preserved in the form of a generalized paraconformity surface described in most of the Iberian Variscan realm. However, in the inner part of the Gondwanan platform, the Cantabrian Zone underwent a major, coeval increase in subsidence and the generation of sedimentary troughs. From this perspective, the eruption age reported here probably represents a discrete phase of incipient rifting along the southern flank of the Rheic Ocean. Paleogeographic reconstructions indicate that this rifting event was coeval with widespread orogeny and ridge subduction along the conjugate northern flank of the Rheic Ocean, the so called Acadian "orogeny". We speculate that ridge subduction resulted in geodynamic coupling of the northern and southern flanks of the Rheic Ocean, and that the extension along the southern flank of the Rheic Ocean is a

  4. Natural fault and fracture network versus anisotropy in the Lower Paleozoic rocks of Pomerania (Poland)

    NASA Astrophysics Data System (ADS)

    Haluch, Anna; Rybak-Ostrowska, Barbara; Konon, Andrzej

    2017-04-01

    Knowledge of the anisotropy of rock fabric, geometry and distribution of the natural fault and fracture network play a crucial role in the exploration for unconventional hydrocarbon recourses. Lower Paleozoic rocks from Pomerania within the Polish part of Peri-Baltic Basin, as prospective sequences, can be considered a laboratory for analysis of fault and fracture arrangement in relation to the mineral composition of the host rocks. A microstructural study of core samples from five boreholes in Pomerania indicate that the Silurian succession in the study area is predominantly composed of claystones and mudstones interbedded with thin layers of tuffites. Intervals with a high content of detrital quartz or diagenetic silica also occur. Most of the Silurian deposits are abundant in pyrite framboids forming layers or isolated small concretions. Early diagenetic carbonate concretions are also present. The direction and distribution of natural faults and fractures have resulted not only from paleostress. Preliminary study reveals that the fault and fracture arrangement is related to the mechanical properties of the host rocks that depend on their fabric and mineralogical composition: subvertical fractures in mudstones and limestones show steeper dips than those within the more clayey intervals; bedding-parallel fractures occur within organic-rich claystones and along the boundaries between different lithologies; tuffites and radiolaria-bearing siliceous mudstones are more brittle and show denser nets of fractures or wider mineral apertures; and, fracture refraction is observed at competence contrast or around spherical concretions. The fault and fracture mineralization itself is prone to the heterogenity of the rock profile. Thus, fractures infilled with calcite occur in all types of the studied rocks, but mineral growth is syntaxial within marly mudstones because of chemical uniformity, and antitaxial within sillicous mudstones. Fractures infilled with quartz are

  5. Origin of the Bashierxi monzogranite, Qiman Tagh, East Kunlun Orogen, NW China: A magmatic response to the evolution of the Proto-Tethys Ocean

    NASA Astrophysics Data System (ADS)

    Zheng, Zhen; Chen, Yan-Jing; Deng, Xiao-Hua; Yue, Su-Wei; Chen, Hong-Jin; Wang, Qing-Fei

    2018-01-01

    The Qiman Tagh of the East Kunlun Orogen, NW China, lies within the Tethysides and hosts a large W-Sn belt associated with the Bashierxi monzogranite. To constrain the origin of the granitic magmatism and its relationship with W-Sn mineralization and the tectonic evolution of the East Kunlun Orogen and the Tethys, we present zircon U-Pb ages and Hf isotopic data, and whole-rock compositional and Sr-Nd-Pb isotopic data of the Bashierxi monzogranite. The granite comprises quartz, K-feldspar, plagioclase, and minor muscovite, tourmaline, biotite, and garnet. It contains high concentrations of SiO2, K2O, and Al2O3, and low concentrations of TiO2 and MgO, indicating a peraluminous high-K calc-alkaline affinity. The rocks are enriched in Rb, U, Pb, and light rare earth elements, and relatively depleted in Eu, Ba, Nb, Sr, P, and Ti, and are classified as S-type granites. Twenty zircon grains yield a weighted mean 238U/206Pb age of 432 ± 2.6 Ma (mean square weighted deviation = 1.3), indicating the occurrence of a middle Silurian magmatic event in the region. Magmatic zircons yield εHf(t) values of -6.7 to 0.7 and corresponding two-stage Hf model ages of 1663-1250 Ma, suggesting that the granite was derived from Mesoproterozoic crust, as also indicated by 207Pb/206Pb ages of 1621-1609 Ma obtained from inherited zircon cores. The inherited zircon cores yield εHf(t) values of 8.3-9.6, which indicate the generation of juvenile crust in the late Paleoproterozoic. Samples of the Bashierxi granite yield high initial 87Sr/86Sr ratios and radiogenic Pb concentrations, and negative εNd(t) values. Isotopic data from the Bashierxi granite indicate that it was derived from partial melting of ancient (early Paleozoic to Mesoproterozoic) sediments, possibly representing recycled Proterozoic juvenile crust. Middle Silurian granitic magmatism resulted from continental collision following closure of the Proto-Tethys Ocean. The Qiman Tagh represents a Caledonian orogenic belt containing

  6. Predicting Readmission at Early Hospitalization Using Electronic Clinical Data: An Early Readmission Risk Score.

    PubMed

    Tabak, Ying P; Sun, Xiaowu; Nunez, Carlos M; Gupta, Vikas; Johannes, Richard S

    2017-03-01

    Identifying patients at high risk for readmission early during hospitalization may aid efforts in reducing readmissions. We sought to develop an early readmission risk predictive model using automated clinical data available at hospital admission. We developed an early readmission risk model using a derivation cohort and validated the model with a validation cohort. We used a published Acute Laboratory Risk of Mortality Score as an aggregated measure of clinical severity at admission and the number of hospital discharges in the previous 90 days as a measure of disease progression. We then evaluated the administrative data-enhanced model by adding principal and secondary diagnoses and other variables. We examined the c-statistic change when additional variables were added to the model. There were 1,195,640 adult discharges from 70 hospitals with 39.8% male and the median age of 63 years (first and third quartile: 43, 78). The 30-day readmission rate was 11.9% (n=142,211). The early readmission model yielded a graded relationship of readmission and the Acute Laboratory Risk of Mortality Score and the number of previous discharges within 90 days. The model c-statistic was 0.697 with good calibration. When administrative variables were added to the model, the c-statistic increased to 0.722. Automated clinical data can generate a readmission risk score early at hospitalization with fair discrimination. It may have applied value to aid early care transition. Adding administrative data increases predictive accuracy. The administrative data-enhanced model may be used for hospital comparison and outcome research.

  7. Early College for All: Efforts to Scale up Early Colleges in Multiple Settings

    ERIC Educational Resources Information Center

    Edmunds, Julie A.

    2016-01-01

    Given the positive impacts of the small, stand-alone early college model and the desire to provide those benefits to more students, organizations have begun efforts to scale up the early college model in a variety of settings. These efforts have been supported by the federal government, particularly by the Investing in Innovation (i3) program.…

  8. Children with Special Needs: Lessons for Early Childhood Professionals. Early Childhood Education Series.

    ERIC Educational Resources Information Center

    Kostelnik, Marjorie J.; Onaga, Esther; Rohde, Barbara; Whiren, Alice

    Bridging the gap between child development and strategies for inclusion, this book is intended to help early childhood practitioners and pre-service teachers feel better equipped to meet the needs of all the children in their early childhood setting. Each chapter of the book is a case study introducing a child (ages birth to 8 years) with one or…

  9. Final Environmental Assessment for Construction of Fisher House II, Wright-Patterson Air Force Base, Ohio

    DTIC Science & Technology

    2008-03-25

    aquifer that supplies drinking water to much of southwestern Ohio. This is an unconsolidated aquifer of glacial origin ranging in thickness from 40 to...underlying Wright-Patterson AFB is gently dipping Ordovician and Silurian sedimentary rock. The base is located on the crest of the Cincinnati Arch...a broad anticline that drops to the north- northeast at approximately five feet per mile. This sedimentary rock consists mainly of shales with thin

  10. Positioning and early mobilisation in stroke.

    PubMed

    Keating, Moira; Penney, Maree; Russell, Petra; Bailey, Emma

    Stroke unit care, providing early rehabilitation, improves long-term outcomes for patients following a stroke. Early mobilisation and good positioning are recognised as key aspects of care in stroke units. Nurses working on stroke units have an important role because they are able to implement positioning and early mobilisation strategies 24 hours a day, reducing the risk of complications and improving functional recovery. Patients benefit if nurses work effectively with the therapy team in positioning and early mobilisation. Nurses also need appropriate training and expertise to make best use of specialist equipment.

  11. Colorado Early Childhood Study.

    ERIC Educational Resources Information Center

    Colorado State Dept. of Education, Denver. Planning and Evaluation Unit.

    The Colorado State Board of Education allocated Title IV-V funds in 1975 for a study of the status of early childhood education in Colorado. The purposes of the study were to: (1) gather data relevant to early childhood education on the status of all children from birth through age 5; (2) identify needs of children of this age within the state;…

  12. Early College High Schools

    ERIC Educational Resources Information Center

    Dessoff, Alan

    2011-01-01

    For at-risk students who stand little chance of going to college, or even finishing high school, a growing number of districts have found a solution: Give them an early start in college while they still are in high school. The early college high school (ECHS) movement that began with funding from the Bill and Melinda Gates Foundation 10 years ago…

  13. Survival After Early and Normal Retirement

    ERIC Educational Resources Information Center

    Haynes, Suzanne G.; And Others

    1978-01-01

    Describes an epidemiological study of the patterns and correlates of survival after early (age 62 to 64) and normal retirement (age 65). Death rates were significantly elevated during the first, fourth, and fifth years after early retirement. Pre-retirement health status was the only significant predictor of survival after early retirement.…

  14. Leadership in Early Childhood Special Education

    ERIC Educational Resources Information Center

    Arora, Samita Berry

    2013-01-01

    With the demands of high quality early childhood special education programs within public school settings, there is a need to place emphasis on research and training regarding early childhood leaders and managers in this complex and diverse field. The focus of this research is to examine what early childhood special education (ECSE) leadership…

  15. 29 CFR 553.225 - Early relief.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 29 Labor 3 2011-07-01 2011-07-01 false Early relief. 553.225 Section 553.225 Labor Regulations... Enforcement Employees of Public Agencies Tour of Duty and Compensable Hours of Work Rules § 553.225 Early... employees on the previous shift prior to the scheduled starting time. Such early relief time may occur...

  16. 29 CFR 553.225 - Early relief.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 29 Labor 3 2010-07-01 2010-07-01 false Early relief. 553.225 Section 553.225 Labor Regulations... Enforcement Employees of Public Agencies Tour of Duty and Compensable Hours of Work Rules § 553.225 Early... employees on the previous shift prior to the scheduled starting time. Such early relief time may occur...

  17. Processes of early stroke care and hospital costs.

    PubMed

    Svendsen, Marie Louise; Ehlers, Lars H; Hundborg, Heidi H; Ingeman, Annette; Johnsen, Søren P

    2014-08-01

    The relationship between processes of early stroke care and hospital costs remains unclear. We therefore examined the association in a population based cohort study. We identified 5909 stroke patients who were admitted to stroke units in a Danish county between 2005 and 2010.The examined recommended processes of care included early admission to a stroke unit, early initiation of antiplatelet or anticoagulant therapy, early computed tomography/magnetic resonance imaging (CT/MRI) scan, early physiotherapy and occupational therapy, early assessment of nutritional risk, constipation risk and of swallowing function, early mobilization,early catheterization, and early thromboembolism prophylaxis.Hospital costs were assessed for each patient based on the number of days spent in different in-hospital facilities using local hospital charges. The mean costs of hospitalization were $23 352 (standard deviation 27 827). The relationship between receiving more relevant processes of early stroke care and lower hospital costs followed a dose–response relationship. The adjusted costs were $24 566 (95% confidence interval 19 364–29 769) lower for patients who received 75–100% of the relevant processes of care compared with patients receiving 0–24%. All processes of care were associated with potential cost savings, except for early catheterization and early thromboembolism prophylaxis. Early care in agreement with key guidelines recommendations for the management of patients with stroke may be associated with hospital savings.

  18. [Autism: An early neurodevelopmental disorder].

    PubMed

    Bonnet-Brilhault, F

    2017-04-01

    With approximately 67 million individuals affected worldwide, autism spectrum disorder (ASD) is the fastest growing neurodevelopmental disorder (United Nations, 2011), with a prevalence estimated to be 1/100. In France ASD affects approximately 600,000 individuals (from childhood to adulthood, half of whom are also mentally retarded), who thus have a major handicap in communication and in adapting to daily life, which leads autism to be recognized as a national public health priority. ASD is a neurodevelopmental disorder that affects several domains (i.e., socio-emotional, language, sensori-motor, executive functioning). These disorders are expressed early in life with an age of onset around 18 months. Despite evidence suggesting a strong genetic link with ASD, the genetic determinant remains unclear. The clinical picture is characterized by impairments in social interaction and communication and the presence of restrictive and repetitive behaviors (DSM-5, ICD-10). However, in addition to these two main dimensions there is significant comorbidity between ASD and other neurodevelopmental disorders such as attention deficit hyperactivity disorder or with genetic and medical conditions. One of the diagnostic features of ASD is its early emergence: symptoms must begin in early childhood for a diagnosis to be given. Due to brain plasticity, early interventions are essential to facilitate clinical improvement. Therefore, general practitioners and pediatricians are on the front line to detect early signs of ASD and to guide both medical explorations and early rehabilitation. Copyright © 2017 Elsevier Masson SAS. All rights reserved.

  19. The restricted gemuk group: A triassic to lower cretaceous succession in southwestern alaska

    USGS Publications Warehouse

    Miller, M.L.; Bradley, D.C.; Bundtzen, T.K.; Blodgett, R.B.; Pessagno, E.A.; Tucker, R.D.; Harris, A.G.

    2007-01-01

    New data from an Upper Triassic to Lower Cretaceous deep marine succession-the herein reinstated and restricted Gemuk Group-provide a vital piece of the puzzle for unraveling southwestern Alaska's tectonic history. First defined by Cady et al. in 1955, the Gemuk Group soon became a regional catchall unit that ended up as part of at least four different terranes. In this paper we provide the first new data in nearly half a century from the Gemuk Group in the original type area in Taylor Mountains quadrangle and from contiguous rocks to the north in Sleetmute quadrangle. Discontinuous exposure, hints of complex structure, the reconnaissance level of our mapping, and spotty age constraints together permit definition of only a rough stratigraphy. The restricted Gemuk Group is at least 2250 m thick, and could easily be at least twice as thick. The age range of the restricted Gemuk Group is tightened on the basis of ten radiolarian ages, two new bivalve ages, one conodont age, two U-Pb zircon ages on tuff, and U-Pb ages of 110 detrital zircons from two sandstones. The Triassic part of the restricted Gemuk Group, which consists of intermediate pillow lavas interbedded with siltstone, chert, and rare limestone, produced radiolarians, bivalves, and conodonts of Carnian and Norian ages. The Jurassic part appears to be mostly siltstone and chert, and yielded radiolarians of Hettangian- Sinemurian, Pliensbachian-Toarcian, and Oxfordian ages. Two tuffs near the Jurassic-Cretaceous boundary record nearby arc volcanism: one at 146 Ma is interbedded with red and green siltstone, and a second at ca. 137 Ma is interbedded with graywacke turbidites. Graywacke appears to be the dominant rock type in the LowerCretaceous part of the restricted Gemuk Group. Detrital zircon analyses were performed on two sandstone samples using SHRIMP. One sandstone yielded a dominant age cluster of 133-180 Ma; the oldest grain is only 316 Ma. The second sample is dominated by zircons of 130-154 Ma; the

  20. Evaluating and Supporting Early Childhood Teachers

    ERIC Educational Resources Information Center

    Passe, Angèle Sancho

    2015-01-01

    There's a lot of conversation in the early childhood community on evaluating teachers to improve their performance. Raising the quality of early care and education is a priority for policymakers and practitioners on local, state, and federal levels. As a result, much attention is being focused on early childhood educators to ensure that they do a…

  1. Early Detection | Division of Cancer Prevention

    Cancer.gov

    [[{"fid":"171","view_mode":"default","fields":{"format":"default","field_file_image_alt_text[und][0][value]":"Early Detection Research Group Homepage Logo","field_file_image_title_text[und][0][value]":"Early Detection Research Group Homepage Logo","field_folder[und]":"15"},"type":"media","field_deltas":{"1":{"format":"default","field_file_image_alt_text[und][0][value]":"Early

  2. 37 CFR 1.219 - Early publication.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 37 Patents, Trademarks, and Copyrights 1 2010-07-01 2010-07-01 false Early publication. 1.219... Applications § 1.219 Early publication. Applications that will be published under § 1.211 may be published earlier than as set forth in § 1.211(a) at the request of the applicant. Any request for early publication...

  3. 37 CFR 1.219 - Early publication.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 37 Patents, Trademarks, and Copyrights 1 2011-07-01 2011-07-01 false Early publication. 1.219... Applications § 1.219 Early publication. Applications that will be published under § 1.211 may be published earlier than as set forth in § 1.211(a) at the request of the applicant. Any request for early publication...

  4. Early Restoration | NOAA Gulf Spill Restoration

    Science.gov Websites

    Early Restoration Plan. On April 20, 2011 we reached an agreement with BP to start restoration planning draft plan for the third phase of early restoration in December 2013. We are considering your comments : All Phase III information and documents Phase II Useful Links: Phase II Early Restoration Plan &

  5. Sprites and Early ionospheric VLF perturbations

    NASA Astrophysics Data System (ADS)

    Haldoupis, Christos; Amvrosiadi, Nino; Cotts, Ben; van der Velde, Oscar; Chanrion, Olivier; Neubert, Torsten

    2010-05-01

    Past studies have shown a correlation between sprites and early VLF perturbations, but the reported correlation varies widely from ~ 50% to 100%. The present study resolves these large discrepancies by analyzing several case studies of sprite and narrowband VLF observations, in which multiple transmitter-receiver VLF links with great circle paths (GCPs) passing near a sprite-producing thunderstorm were available. In this setup, the multiple links act in a complementary way that makes the detection of early VLF perturbations much more probable compared to a single VLF link that can miss several of them, a fact that was overlooked in past studies. The evidence shows that sprites are accompanied by early VLF perturbations in a one-to-one correspondence. This implies that the sprite generation mechanism may cause also sub-ionospheric conductivity disturbances that produce early VLF events. However, the one-to-one "sprite to early" event relationship, if viewed conversely as "early to sprite", appears not to be always reciprocal. This is because the number of early events detected in some cases was considerably larger than the number of sprites. Since the great majority of the early events not accompanied by sprites was caused by positive cloud to ground (+CG) lightning discharges, it is possible that sprites or sprite halos were concurrently present in these events as well but were missed by the sprite-watch detection system. In order for this option to be resolved we need more studies using highly sensitive optical systems capable of detecting weaker sprites, sprite halos and elves.

  6. Early recognition of growth abnormalities permitting early intervention

    USDA-ARS?s Scientific Manuscript database

    Normal growth is a sign of good health. Monitoring for growth disturbances is fundamental to children's health care. Early detection and diagnosis of the causes of short stature allows management of underlying medical conditions, optimizing attainment of good health and normal adult height. This rev...

  7. Integrating Computer Technology in Early Childhood Education Environments: Issues Raised by Early Childhood Educators

    ERIC Educational Resources Information Center

    Wood, Eileen; Specht, Jacqueline; Willoughby, Teena; Mueller, Julie

    2008-01-01

    The purpose of this study was to assess the educators' perspectives on the introduction of computer technology in the early childhood education environment. Fifty early childhood educators completed a survey and participated in focus groups. Parallels existed between the individually completed survey data and the focus group discussions. The…

  8. Integrating partner professionals. The Early Explorers project: Peers Early Education Partnership and the health visiting service.

    PubMed

    Barlow, J; Coe, C

    2013-01-01

      A range of voluntary sector organizations are involved in the delivery of services to children, particularly within the Early Year's sector and children's centres. Peers Early Education Partnership (PEEP) Early Explorers project is one example of the way in which explicit partnerships are being forged across statutory and voluntary sectors with the aim of improving outcomes for children and families. This paper reports an exploration of stakeholder views and experiences of two Early Explorer clinics located in areas of high deprivation.   Semi-structured interviews were conducted with a purposive sample of stakeholders (n= 25) from children's centres, PEEP, the health visiting service and service users. Data were fully transcribed and analysed using a thematic approach.   The data suggest that the two key groups of stakeholders providing Early Explorer clinics (i.e. health visitors and PEEP practitioners) had quite different objectives in terms of their early goals for the clinic, but that despite these differences good progress was achieved in terms of working together effectively. All stakeholders including service users referred to the presence of PEEP as having improved the quality of the clinic environment, and participating mothers identified a wide range of benefits from the enhanced service. However, somewhat restricted views about the role of practitioners within the clinics were identified by users, and the findings suggest that although the early goals for the clinic had been exceeded, these may have been limited in terms of true 'partnership' working.   Early Explorer clinics appeared to have enhanced the service provided within traditional child health clinics and to have provided practitioners with access to hard-to-reach families and parents with access to services that are consistent with the broader policy aims of improving parent-infant interaction. However, questions remain as to whether the benefit of 'partnership' working was fully

  9. Early anthropometric indices predict short stature and overweight status in a cohort of Peruvians in early adolescence

    PubMed Central

    Sterling, Robie; Miranda, J Jaime; Gilman, Robert H; Cabrera, Lilia; Sterling, Charles R; Bern, Caryn; Checkley, William

    2014-01-01

    While childhood malnutrition is associated with increased morbidity and mortality, less well understood is how early childhood growth influences height and body composition later in life. We revisited 152 Peruvian children who participated in a birth cohort study between 1995 and 1998, and obtained anthropometric and bioimpedance measurements 11 to 14 years later. We used multivariable regression models to study the effects of childhood anthropometric indices on height and body composition in early adolescence. Each standard deviation decrease in length-for-age at birth was associated with a decrease in adolescent height-for-age of 0.7 SD in both boys and girls (all p<0.001) and 9.7 greater odds of stunting (95% CI 3.3 to 28.6). Each SD decrease in length-for-age in the first 30 months of life was associated with a decrease in adolescent height-for-age of 0.4 in boys and 0.6 standard deviation in girls (all p<0.001) and with 5.8 greater odds of stunting (95% CI 2.6 to 13.5). The effect of weight gain during early childhood on weight in early adolescence was more complex to understand. Weight-for-length at birth and rate of change in weight-for-length in early childhood were positively associated with age- and sex-adjusted body mass index and a greater risk of being overweight in early adolescence. Linear growth retardation in early childhood is a strong determinant of adolescent stature, indicating that, in developing countries, growth failure in height during early childhood persists through early adolescence. Interventions addressing linear growth retardation in childhood are likely to improve adolescent stature and related-health outcomes in adulthood. PMID:22552904

  10. Early anthropometric indices predict short stature and overweight status in a cohort of Peruvians in early adolescence.

    PubMed

    Sterling, Robie; Miranda, J Jaime; Gilman, Robert H; Cabrera, Lilia; Sterling, Charles R; Bern, Caryn; Checkley, William

    2012-07-01

    While childhood malnutrition is associated with increased morbidity and mortality, less well understood is how early childhood growth influences height and body composition later in life. We revisited 152 Peruvian children who participated in a birth cohort study between 1995 and 1998, and obtained anthropometric and bioimpedance measurements 11-14 years later. We used multivariable regression models to study the effects of childhood anthropometric indices on height and body composition in early adolescence. Each standard deviation decrease in length-for-age at birth was associated with a decrease in adolescent height-for-age of 0.7 SD in both boys and girls (all P < 0.001) and 9.7 greater odds of stunting (95% CI 3.3-28.6). Each SD decrease in length-for-age in the first 30 months of life was associated with a decrease in adolescent height-for-age of 0.4 in boys and 0.6 standard deviation in girls (all P < 0.001) and with 5.8 greater odds of stunting (95% CI 2.6-13.5). The effect of weight gain during early childhood on weight in early adolescence was more complex to understand. Weight-for-length at birth and rate of change in weight-for-length in early childhood were positively associated with age- and sex-adjusted body mass index and a greater risk of being overweight in early adolescence. Linear growth retardation in early childhood is a strong determinant of adolescent stature, indicating that, in developing countries, growth failure in height during early childhood persists through early adolescence. Interventions addressing linear growth retardation in childhood are likely to improve adolescent stature and related-health outcomes in adulthood. Copyright © 2012 Wiley Periodicals, Inc.

  11. Reconnaissance Geologic Map of the Hayfork 15' Quadrangle, Trinity County, California

    USGS Publications Warehouse

    Irwin, William P.

    2010-01-01

    Hayfork terrane is a broken formation and melange of volcanic and sedimentary rocks, including chert and blocks of amphibolite, limestone, and serpentinized ultramafic rocks. The chert contains radiolarians of Permian and Triassic ages, but none of clearly Jurassic age. In contrast, the cherts of the North Fork terrane contain Early and Middle Jurassic radiolarians in addition to those of Permian and Triassic ages; also, some limestones of the Eastern Hayfork terrane contain fossil faunas of Tethyan affinity, but those of the North Fork terrane do not. The Western Hayfork terrane is an andesitic volcanic arc that was accreted to the Eastern Hayfork terrane. It consists mainly of metavolcaniclastic andesitic agglomerate and tuff, as well as argillite and chert, and it includes the dioritic Ironside Mountain batholith, which intruded during Middle Jurassic time. Two large patches of Western Hayfork terrane mapped in the central part of the Eastern Hayfork terrane may be exposed through windows in the Eastern Hayfork terrane, although the structural relation is not clear. The Rattlesnake Creek terrane is a melange that occupies only a small area in the southwest corner of the Hayfork quadrangle; however, it is a major unit in the Hyampom 15' quadrangle to the west. It consists mainly of broken and sheared ophiolitic rocks of probable Permian or early Mesozoic age. The Cretaceous Great Valley sequence overlap assemblage here postdates the Early Cretaceous (approximately 136 Ma) emplacement of the Shasta Bally batholith, which is widely exposed to the east in the Weaverville 15' quadrangle. The Great Valley sequence once covered much of the southern Klamath Mountains; however, in the Hayfork quadrangle, only three small patches remain near its southern boundary. Weakly consolidated nonmarine sedimentary rocks of the Weaverville Formation of mid-Tertiary age, which contain abundant fossil plants, occupy a large, shallow, east-northeast-trending graben

  12. [Early flat colorectal cancer].

    PubMed

    Castelletto, R H; Chiarenza, C; Ottino, A; Garay, M L

    1991-01-01

    We report three cases of flat early colorectal carcinoma which were detected during the examination of 51 surgical specimens of colorectal resection. Two of them were endoscopically diagnosed, but the smallest one was not seen in the luminal instrumental examination. From the bibliographic analysis and our own experience we deduce the importance of flat lesions in the development of early colorectal carcinoma, either originated from pre-existent adenoma or de novo. Flat variants of adenoma, and presumably flush or depressed ones, must be considered as important factors in the early sequence adenoma-cancer. An appropriate endoscopic equipment with employment of additional staining techniques (such as carmine indigo and methylene blue) and the correct investigation during inflation-deflation procedures facilitates the identification of small lesions, their eradication and prevention from advanced forms of colorectal carcinoma.

  13. [The early pregnancy factor (EPF) as an early marker of disorders in pregnancy].

    PubMed

    Straube, W; Römer, T; Zeenni, L; Loh, M

    1995-01-01

    The early pregnancy factor (EPF) seems to be very helpful in clinical applications such as early detection of pregnancy, differential diagnosis of failure of fertilization or implementation and prognosis of a fertilized ovum. Our purpose was to investigate the diagnostic value of single and serial measurement of EPF, especially in the differential diagnosis of abortion and extrauterine pregnancy. Women with a history of 6-16 weeks amenorrhoea with/without vaginal bleeding were included in the prospective study. The EPF-test system was carried out by means of the rosette inhibition method. EPF proved to be always positive in normal pregnant women and always negative in nonpregnant controls. In case of threatened abortion the prognosis was good, when the EPF values were positive, and poor when they became negative. Patients suffering from spontaneous and missed abortion mostly showed negative EPF-values. This was also true in ectopic pregnancies. The sensitivity and specificity of EPF-test system were 83%. The positive predictive value was observed to be 54% and the negative predictive value 95%. The EPF as an early embryonic signal may be a suitable parameter for the clinical use detecting pregnancy disturbances very early.

  14. Marital conflict and early adolescents' self-evaluation: the role of parenting quality and early adolescents' appraisals.

    PubMed

    Siffert, Andrea; Schwarz, Beate; Stutz, Melanie

    2012-06-01

    Cognitive appraisals and family dynamics have been identified as mediators of the relationship between marital conflict and children's adjustment. Surprisingly little research has investigated both meditational processes in the same study. Guided by the cognitive-contextual framework and the spillover hypothesis, the present study integrated factors from both theories early adolescents' appraisals of threat and self-blame, as well as perceived parenting quality as mediators of the link between early adolescents' perception of marital conflict and their self-evaluations (self-esteem and scholastic competence). Analyses were based on the first two waves of an ongoing longitudinal study. Participants were 176 two-parent families, and their early adolescents (50.5% girls) whose mean age was 10.61 years at Time 1 (SD =0.40) and 11.63 years at Time 2 (SD=0.39). Structural equation modeling analyses indicated that parenting quality and early adolescents' perceived threat provided indirect pathways between marital conflict and early adolescents' self-esteem 1 year later when controlling for their initial level of self-esteem. With respect to scholastic competence, only fathers' parenting was an indirect link. Self-blame did not play a role. Implications for understanding the mechanisms by which exposure to marital conflict predicts early adolescents' maladjustment are discussed.

  15. Capturing early signs of deterioration: the dutch-early-nurse-worry-indicator-score and its value in the Rapid Response System.

    PubMed

    Douw, Gooske; Huisman-de Waal, Getty; van Zanten, Arthur R H; van der Hoeven, Johannes G; Schoonhoven, Lisette

    2017-09-01

    To determine the predictive value of individual and combined dutch-early-nurse-worry-indicator-score indicators at various Early Warning Score levels, differentiating between Early Warning Scores reaching the trigger threshold to call a rapid response team and Early Warning Score levels not reaching this point. Dutch-early-nurse-worry-indicator-score comprises nine indicators underlying nurses' 'worry' about a patient's condition. All indicators independently show significant association with unplanned intensive care/high dependency unit admission or unexpected mortality. Prediction of this outcome improved by adding the dutch-early-nurse-worry-indicator-score indicators to an Early Warning Score based on vital signs. An observational cohort study was conducted on three surgical wards in a tertiary university-affiliated teaching hospital. Included were surgical, native-speaking, adult patients. Nurses scored presence of 'worry' and/or dutch-early-nurse-worry-indicator-score indicators every shift or when worried. Vital signs were measured according to the prevailing protocol. Unplanned intensive care/high dependency unit admission or unexpected mortality was the composite endpoint. Percentages of 'worry' and dutch-early-nurse-worry-indicator-score indicators were calculated at various Early Warning Score levels in control and event groups. Entering all dutch-early-nurse-worry-indicator-score indicators in a multiple logistic regression analysis, we calculated a weighted score and calculated sensitivity, specificity, positive predicted value and negative predicted value for each possible total score. In 3522 patients, 102 (2·9%) had an unplanned intensive care/high dependency unit admissions (n = 97) or unexpected mortality (n = 5). Patients with such events and only slightly changed vital signs had significantly higher percentages of 'worry' and dutch-early-nurse-worry-indicator-score indicators expressed than patients in the control group. Increasing number

  16. Early Rockets

    NASA Image and Video Library

    2004-04-15

    In addition to Dr. Robert Goddard's pioneering work, American experimentation in rocketry prior to World War II grew, primarily in technical societies. This is an early rocket motor designed and developed by the American Rocket Society in 1932.

  17. Telomere length and early severe social deprivation: linking early adversity and cellular aging

    PubMed Central

    Drury, SS; Theall, K; Gleason, MM; Smyke, AT; De Vivo, I; Wong, JYY; Fox, NA; Zeanah, CH; Nelson, CA

    2012-01-01

    Accelerated telomere length attrition has been associated with psychological stress and early adversity in adults; however, no studies have examined whether telomere length in childhood is associated with early experiences. The Bucharest Early Intervention Project is a unique randomized controlled trial of foster care placement compared with continued care in institutions. As a result of the study design, participants were exposed to a quantified range of time in institutional care, and represented an ideal population in which to examine the association between a specific early adversity, institutional care and telomere length. We examined the association between average relative telomere length, telomere repeat copy number to single gene copy number (T/S) ratio and exposure to institutional care quantified as the percent of time at baseline (mean age 22 months) and at 54 months of age that each child lived in the institution. A significant negative correlation between T/S ratio and percentage of time was observed. Children with greater exposure to institutional care had significantly shorter relative telomere length in middle childhood. Gender modified this main effect. The percentage of time in institutional care at baseline significantly predicted telomere length in females, whereas the percentage of institutional care at 54 months was strongly predictive of telomere length in males. This is the first study to demonstrate an association between telomere length and institutionalization, the first study to find an association between adversity and telomere length in children, and contributes to the growing literature linking telomere length and early adversity. PMID:21577215

  18. Unlocking the Future: Early Literacy.

    ERIC Educational Resources Information Center

    Blair, Leslie Asher, Ed.

    1999-01-01

    This newsletter of the Southwest Educational Development Laboratory (SEDL)contains a collection of articles which discuss various aspects of early literacy. Articles in the newsletter are: "Introduction: Reading Instruction, a Key to the Future"; "Ensuring Early Literacy through Coherent Instruction" (Leslie Blair);…

  19. Early extubation after cardiac surgery: emotional status in the early postoperative period.

    PubMed

    Silbert, B S; Santamaria, J D; Kelly, W J; O'brien, J L; Blyth, C M; Wong, M Y; Allen, N B

    2001-08-01

    To compare the emotional state during the first 3 days after coronary artery surgery of patients who had undergone early versus conventional extubation. A prospective, randomized, controlled trial. University hospital, single center. Eligible patients (n = 100) presenting for elective coronary artery surgery, randomized to an early extubation group or a conventional extubation group. Emotional status was measured by the Hospital Anxiety and Depression Scale (HAD), the Self Assessment Manikin (SAM), and the Multiple Affect Adjective Check List-Revised (MAACL-R). Tests were administered preoperatively and on the 1st and 3rd days postoperatively. Of patients in the conventional extubation group, 30% showed moderate-to-severe depressive symptoms (HAD score >10) on day 3 postoperatively compared with 8% of patients in the early extubation group (p = 0.02). There was a clinically insignificant increase in MAACL-R depression score on the 1st postoperative day within both groups but no other differences within or between groups in SAM or MAACL-R scores. Early extubation results in fewer patients displaying depressive symptoms on the 3rd postoperative day but appears to have little effect on other measurements of emotional status. Anesthetic management during coronary artery bypass graft surgery may play an important role in the overall well-being of the patient by decreasing the incidence of postoperative depression. Copyright 2001 by W.B. Saunders Company.

  20. Couple Therapy with Veterans: Early Improvements and Predictors of Early Dropout.

    PubMed

    Fischer, Melanie S; Bhatia, Vickie; Baddeley, Jenna L; Al-Jabari, Rawya; Libet, Julian

    2017-07-28

    Family services within Veterans Affairs Medical Centers fulfill an important role in addressing relationship distress among Veterans, which is highly prevalent and comorbid with psychopathology. However, even for evidence-based couple therapies, effectiveness is weaker compared to controlled studies, maybe because many Veteran couples drop out early and do not reach the "active" treatment stage after the 3-4 session assessment. In order to improve outcomes, it is critical to identify couples at high risk for early dropout, and understand whether couples may benefit from the assessment as an intervention. The current study examined (a) demographics, treatment delivery mode, relationship satisfaction, and psychological symptoms as predictors of dropout during and immediately following the assessment phase, and (b) changes in relationship satisfaction during assessment. 174 couples completed questionnaires during routine intake procedures. The main analyses focused on 140 male Veterans and their female civilian partners; 36.43% dropped out during the assessment phase and 24.74% of the remaining couples immediately following the first treatment session. More severe depressive symptoms in non-Veteran partners were associated with dropout during assessment. Relationship satisfaction improved significantly during the assessment phase for couples who did not drop out, with larger gains for non-Veteran partners. No demographics or treatment delivery mode were associated with dropout. Although more research is needed on engaging couples at risk for early dropout and maximizing early benefits, the findings suggest that clinicians should attend to the civilian partner's and Veteran's depressive symptoms at intake and consider the assessment part of active treatment. © 2017 Family Process Institute.

  1. How synchronous are neogene marine plankton events?

    NASA Astrophysics Data System (ADS)

    Spencer-Cervato, Cinzia; Thierstein, Hans R.; Lazarus, David B.; Beckmann, Jean-Pierre

    1994-10-01

    An electronic supplement of this material may be obtained on adiskette or Anonymous FTP from KOSMOS.AGU.ORG. (LOGIN toAGU's FTP account using ANONYMOUS as the username andGUEST as the password. Go to the right directory by typing CDAPEND. Type LS to see what files are available. Type GET and thename of the file to get it. Finally, type EXIT to leave the system.)(Paper 94PA01456, How synchronous are Neogene marine planktonevents?, by C. Spencer-Cervato, H. R. Thierstein, D. B. Lazarus, andJ-P Beckmann). Diskette may be ordered from American GeophysicalUnion, 2000 Florida Avenue, N.W., Washington, DC 20009; $15.00.Payment must accompany order.We analyzed the synchrony and diachrony of commonly used Neogene biostratigraphic events from data published in the Initial Reports of the Deep Sea Drilling Project (DSDP) and in the Proceedings of the Ocean Drilling Program (ODP). On the basis of the combined biostratigraphic and magnetostratigraphic evidence, new Neogene age models were constructed for 35 globally distributed DSDP and ODP holes. Biostratigraphic events from the four major plankton groups (calcareous nannofossils, diatoms, planktonic foraminifera, and radiolarians) were compiled from DSDP and ODP reports. After the elimination of possible sources of error such as stratigraphic hiatuses and reworking of specimens, 124 biostratigraphic events that occurred in at least four holes were analyzed in detail: for each event a biochronologic age estimate was derived by projection of the depth of the event onto the line of correlation of each hole, and from these a global mean age for each event was calculated, together with its standard deviation. Average standard deviations for event ages by fossil group are: calcareous nannofossil first appearance datums (FADs): 0.57 m.y. (21 events), calcareous nannofossil last appearance datums (LADs): 0.60 m.y. (25 events), diatom FADs: 0.57 m.y. (7 events), diatom LADs: 0.85 m.y. (14 events), planktonic foraminifera FADs: 0.88 m

  2. Early Education and Care, and Reconceptualizing Play. Advances in Early Education and Day Care.

    ERIC Educational Resources Information Center

    Reifel, Stuart, Ed.; Brown, Mac H., Ed.

    Providing a forum for current thought about the field of early education and care, this book reviews efforts worldwide to educate young children. The book examines child care quality, presents a cultural feminist perspective on caregiving, discusses curricular issues, and considers the role of play in early childhood practice. The chapters are:…

  3. Explaining Why Early-Maturing Girls Are More Exposed to Sexual Harassment in Early Adolescence

    ERIC Educational Resources Information Center

    Skoog, Therése; Bayram Özdemir, Sevgi

    2016-01-01

    In this study, we tested two competing explanations of the previously established link between early female puberty and sexual harassment in early adolescence. The sample included 680 seventh-grade Swedish girls (M[subscript age] = 13.40, SD = 0.53). Findings revealed that looking more sexually mature and being sexually active mediated the link…

  4. Sophisticated digestive systems in early arthropods.

    PubMed

    Vannier, Jean; Liu, Jianni; Lerosey-Aubril, Rudy; Vinther, Jakob; Daley, Allison C

    2014-05-02

    Understanding the way in which animals diversified and radiated during their early evolutionary history remains one of the most captivating of scientific challenges. Integral to this is the 'Cambrian explosion', which records the rapid emergence of most animal phyla, and for which the triggering and accelerating factors, whether environmental or biological, are still unclear. Here we describe exceptionally well-preserved complex digestive organs in early arthropods from the early Cambrian of China and Greenland with functional similarities to certain modern crustaceans and trace these structures through the early evolutionary lineage of fossil arthropods. These digestive structures are assumed to have allowed for more efficient digestion and metabolism, promoting carnivory and macrophagy in early arthropods via predation or scavenging. This key innovation may have been of critical importance in the radiation and ecological success of Arthropoda, which has been the most diverse and abundant invertebrate phylum since the Cambrian.

  5. Challenges facing early career academic cardiologists.

    PubMed

    Tong, Carl W; Ahmad, Tariq; Brittain, Evan L; Bunch, T Jared; Damp, Julie B; Dardas, Todd; Hijar, Amalea; Hill, Joseph A; Hilliard, Anthony A; Houser, Steven R; Jahangir, Eiman; Kates, Andrew M; Kim, Darlene; Lindman, Brian R; Ryan, John J; Rzeszut, Anne K; Sivaram, Chittur A; Valente, Anne Marie; Freeman, Andrew M

    2014-06-03

    Early career academic cardiologists currently face unprecedented challenges that threaten a highly valued career path. A team consisting of early career professionals and senior leadership members of American College of Cardiology completed this white paper to inform the cardiovascular medicine profession regarding the plight of early career cardiologists and to suggest possible solutions. This paper includes: 1) definition of categories of early career academic cardiologists; 2) general challenges to all categories and specific challenges to each category; 3) obstacles as identified by a survey of current early career members of the American College of Cardiology; 4) major reasons for the failure of physician-scientists to receive funding from National Institute of Health/National Heart Lung and Blood Institute career development grants; 5) potential solutions; and 6) a call to action with specific recommendations. Copyright © 2014 American College of Cardiology Foundation. Published by Elsevier Inc. All rights reserved.

  6. Children’s early helping in action: Piagetian developmental theory and early prosocial behavior

    PubMed Central

    Hammond, Stuart I.

    2014-01-01

    After a brief overview of recent research on early helping, outlining some central problems, and issues, this paper examines children’s early helping through the lens of Piagetian moral and developmental theory, drawing on Piaget’s “Moral Judgment of the Child” (Piaget, 1932/1997), “Play, Dreams, and Imitation in Childhood” (Piaget, 1945/1951), and the “Grasp of Consciousness” (Piaget, 1976). Piaget refers to a level of moral development in action that precedes heteronomous and autonomous moral reasoning. This action level allows children to begin to interact with people and objects. In his later work, Piaget explores the gradual construction of understanding from this activity level. Taken together, these elements of Piagetian theory provide a promising conceptual framework for understanding the development of early helping. PMID:25101027

  7. Paracontinuous boundaries within the Devonian Columbus Limestone and Delaware Formation of central Ohio

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Conkin, J.E.; Conkin, B.M.

    1994-04-01

    Internal units within the Columbus Limestone (Early Devonian Emsian [Schoharie] to Middle Devonian Eifelian [late Onesquethawan]) and the Delaware Formation (Middle Devonian early Givetian [Cazenovian]) of central Ohio are separated by disconformities of the magnitude of paracontinuities. Stauffer (1909) divided the Columbus Limestone into zones A--H and the Delaware Formation into zones I--M. Within the Columbus, the A Zone (conglomerate at the base of Bellepoint Member) disconformably overlies Late Silurian beds. The D zone at top of the Bellepoint Member (bearing the Kawkawlin Metabentonite horizon) is overlain paracontinuously by the Marblehead Member (Lower Paraspirifer acuminatus-Spirifer macrothyris to Brevispirifer gregarius-Moellerina greeneimore » zones [= E--G zones]), with the Onondagan Indian Nation Metabentonite in the top of the G Zone. The Marblehead Member is overlain paracontinuously by a bone bed at base of the Venice Member (H zone = Upper Paraspirifer acuminatus- Spirifer duodenarius'' Zone). I Zone (Dublin Shale=Marcellus) of the Delaware Formation overlies the Columbus and has two bone beds at its base; Tioga Metabentonite (restricted) overlies the I Zone bone beds and is a few tenths to 1.85 feet above the base of the I Zone. Paracontinuities and bone beds occur at the bases of J, K, and L zones. Conkin and Conkin (1975) have shown Stauffer's (1909) M Zone is an extension of his L Zone. The Olentangy paracontinuously overlies the L Zone.« less

  8. Ten Windows Into the Meteorite Flux to Earth During the Past 500 Million Years

    NASA Astrophysics Data System (ADS)

    Schmitz, B.

    2017-12-01

    Almost nothing is known about the variations through deep time in the types of meteorites arriving at Earth. In an ongoing project we are searching ancient sediments from ten different time periods through the Phanerozoic for relict extraterrestrial spinel grains from micrometeorites (Schmitz, 2013). Samples, 300-1500 kg large, of slowly formed pelagic limestone are dissolved in acids leaving a residue of extraterrestrial spinels. The time periods studied include the middle Cambrian, Ordovician before and after the breakup of the L-chondrite parent body, late Silurian, late Devonian, middle Jurassic, early and late Cretaceous, early Paleocene and late Eocene. The approach builds on complex methodological considerations and a thorough understanding also of the spinel fraction in recent meteorites is necessary. In order to obtain some insights into the changes in the meteorite flux carefully calibrated analyses of the isotopic and elemental composition of the recovered spinel grains as well as consistent data treatment is required for the different time windows. Our results indicate that the background meteorite flux has changed significantly through the Phanerozoic. The results so far suggest that there may have been a gradual long-term (on the order of hundred million years) turnover in the meteorite flux from dominance of achondrites in the early Phanerozoic to ordinary chondrites in the late Phanerozoic interrupted by short-term (a few million years) meteorite cascades from single asteroid breakup events. This scenario may change, however, as results from additional time windows emerge. B. Schmitz (2013) Extraterrestrial spinels and the astronomical perspective on Earth's geological record and evolution of life: Chemie der Erde 73:117-145.

  9. A molecular palaeobiological exploration of arthropod terrestrialization

    PubMed Central

    Carton, Robert; Edgecombe, Gregory D.

    2016-01-01

    Understanding animal terrestrialization, the process through which animals colonized the land, is crucial to clarify extant biodiversity and biological adaptation. Arthropoda (insects, spiders, centipedes and their allies) represent the largest majority of terrestrial biodiversity. Here we implemented a molecular palaeobiological approach, merging molecular and fossil evidence, to elucidate the deepest history of the terrestrial arthropods. We focused on the three independent, Palaeozoic arthropod terrestrialization events (those of Myriapoda, Hexapoda and Arachnida) and showed that a marine route to the colonization of land is the most likely scenario. Molecular clock analyses confirmed an origin for the three terrestrial lineages bracketed between the Cambrian and the Silurian. While molecular divergence times for Arachnida are consistent with the fossil record, Myriapoda are inferred to have colonized land earlier, substantially predating trace or body fossil evidence. An estimated origin of myriapods by the Early Cambrian precedes the appearance of embryophytes and perhaps even terrestrial fungi, raising the possibility that terrestrialization had independent origins in crown-group myriapod lineages, consistent with morphological arguments for convergence in tracheal systems. This article is part of the themed issue ‘Dating species divergences using rocks and clocks’. PMID:27325830

  10. Morphogenesis of early stage melanoma

    NASA Astrophysics Data System (ADS)

    Chatelain, Clément; Amar, Martine Ben

    2015-08-01

    Melanoma early detection is possible by simple skin examination and can insure a high survival probability when successful. However it requires efficient methods for identifying malignant lesions from common moles. This paper provides an overview first of the biological and physical mechanisms controlling melanoma early evolution, and then of the clinical tools available today for detecting melanoma in vivo at an early stage. It highlights the lack of diagnosis methods rationally linking macroscopic observables to the microscopic properties of the tissue, which define the malignancy of the tumor. The possible inputs of multiscale models for improving these methods are shortly discussed.

  11. Analysis of Early Military Attrition Behavior.

    DTIC Science & Technology

    1984-06-01

    military separation. Although hizh school graduation status is the primary single factor affecting attrition, age and previous employment stability...assignment like individual suitability and satisfaction do not significantly influence early attrition; the early attrition rate of nonhigh- school ...a recruit with a single previous employer. I I V IS BLANK vi * Various indicators of military job match had no significant impact on early attrition

  12. [Early mobilization. Competencies, responsibilities, milestones].

    PubMed

    Nydahl, P; Dewes, M; Dubb, R; Filipovic, S; Hermes, C; Jüttner, F; Kaltwasser, A; Klarmann, S; Klas, K; Mende, H; Rothaug, O; Schuchhardt, D

    2016-03-01

    Early mobilization is an evident, interprofessional concept to improve the outcome of intensive care patients. It reduces psychocognitive deficits and delirium and attenuates a general deconditioning, including atrophy of the respiratory pump and skeletal muscles. In this regard the interdisciplinary approach of early mobilization, taking into account different levels of mobilization, appears to be beneficial. The purpose of this study was to explore opinions on collaboration and tasks between different professional groups. During the 25th Bremen Conference on Intensive Medicine and Nursing on 20 February 2015, a questionnaire survey was carried out among the 120 participants of the German Early Mobilization Network meeting. In all, 102 questionnaires were analyzed. Most participants reported on the interdisciplinarity of the approach, but none of the tasks and responsibilities concerning early mobilization can be assigned to a single professional group. The practical implementation of mobilizing orally intubated patients may require two registered nurses as well as a physical therapist. Implementation in daily practice seems to be heterogeneous. There is no consensus regarding collaboration, competencies, and responsibilities with respect to early mobilization of intensive care patients. The approach to date has been characterized by a lack of interprofessional communication, which may lead to an inefficient use of the broad and varied base of knowledge and experienceof the different professions.

  13. Telomere lengthening early in development.

    PubMed

    Liu, Lin; Bailey, Susan M; Okuka, Maja; Muñoz, Purificación; Li, Chao; Zhou, Lingjun; Wu, Chao; Czerwiec, Eva; Sandler, Laurel; Seyfang, Andreas; Blasco, Maria A; Keefe, David L

    2007-12-01

    Stem cells and cancer cells maintain telomere length mostly through telomerase. Telomerase activity is high in male germ line and stem cells, but is low or absent in mature oocytes and cleavage stage embryos, and then high again in blastocysts. How early embryos reset telomere length remains poorly understood. Here, we show that oocytes actually have shorter telomeres than somatic cells, but their telomeres lengthen remarkably during early cleavage development. Moreover, parthenogenetically activated oocytes also lengthen their telomeres, thus the capacity to elongate telomeres must reside within oocytes themselves. Notably, telomeres also elongate in the early cleavage embryos of telomerase-null mice, demonstrating that telomerase is unlikely to be responsible for the abrupt lengthening of telomeres in these cells. Coincident with telomere lengthening, extensive telomere sister-chromatid exchange (T-SCE) and colocalization of the DNA recombination proteins Rad50 and TRF1 were observed in early cleavage embryos. Both T-SCE and DNA recombination proteins decrease in blastocyst stage embryos, whereas telomerase activity increases and telomeres elongate only slowly. We suggest that telomeres lengthen during the early cleavage cycles following fertilization through a recombination-based mechanism, and that from the blastocyst stage onwards, telomerase only maintains the telomere length established by this alternative mechanism.

  14. Early Identification of Autism

    PubMed Central

    Webb, Sara Jane; Jones, Emily J.H.

    2016-01-01

    In the first year of life, infants who later go on to develop autistic spectrum disorders (ASD) may exhibit subtle disruptions in social interest and attention, communication, temperament, and head circumference growth that occur prior to the onset of clinical symptoms. These disruptions may reflect the early course of ASD development and may also contribute to the later development of clinical symptoms through alterations in the child’s experience of his or her environment. By age 2, developmental precursors of autism symptoms can be used to diagnose children reliably, and by age 3, the diagnosis is thought to be relatively stable. The downward extension of the autism diagnosis poses important questions for therapists in designing interventions that are applicable for infants who demonstrate early risk factors. We review current knowledge of the early signs of ASD in the infancy period (0–12 months) and the manifestation of symptoms in toddlerhood (12– 36 months), noting the importance of considering the variability in onset and trajectory of ASD. Finally, we consider the implications of this emerging research for those who work or interact with young children, including the importance of early monitoring and the development and evaluation of age-appropriate interventions. PMID:28090148

  15. Early Intervention in Psychosis

    PubMed Central

    McGorry, Patrick D.

    2015-01-01

    Abstract Early intervention for potentially serious disorder is a fundamental feature of healthcare across the spectrum of physical illness. It has been a major factor in the reductions in morbidity and mortality that have been achieved in some of the non-communicable diseases, notably cancer and cardiovascular disease. Over the past two decades, an international collaborative effort has been mounted to build the evidence and the capacity for early intervention in the psychotic disorders, notably schizophrenia, where for so long deep pessimism had reigned. The origins and rapid development of early intervention in psychosis are described from a personal and Australian perspective. This uniquely evidence-informed, evidence-building and cost-effective reform provides a blueprint and launch pad to radically change the wider landscape of mental health care and dissolve many of the barriers that have constrained progress for so long. PMID:25919380

  16. Bedrock geologic map of the Miles Pond and Concord quadrangles, Essex and Caledonia Counties, Vermont, and Grafton County, New Hampshire

    USGS Publications Warehouse

    Rankin, Douglas W.

    2018-04-20

    The bedrock geologic map of the Miles Pond and Concord quadrangles covers an area of approximately 107 square miles (276 square kilometers) in east-central Vermont and adjacent New Hampshire, north of and along the Connecticut River. This map was created as part of a larger effort to produce a new bedrock geologic map of Vermont through the collection of field data at a scale of 1:24,000. The majority of the map area consists of the Bronson Hill anticlinorium, a post-Early Devonian structure that is cored by metamorphosed Cambrian to Silurian sedimentary, volcanic, and plutonic rocks. A major feature on the map is the Monroe fault, interpreted to be a west-directed, steeply dipping Late Devonian (Acadian) thrust fault. To the west of the Monroe fault, rocks of the Connecticut Valley-Gaspé trough dominate and consist primarily of metamorphosed Silurian and Devonian sedimentary rocks. To the north, the Victory pluton intrudes the Bronson Hill anticlinorium. The Bronson Hill anticlinorium consists of the metamorphosed Albee Formation, the Ammonoosuc Volcanics, the Comerford Intrusive Complex, the Highlandcroft Granodiorite, and the Joselin Turn tonalite. The Albee Formation is an interlayered, feldspathic metasandstone and pelite that is locally sulfidic. Much of the deformed metasandstone is tectonically pinstriped. In places, one can see compositional layering that was transposed by a steeply southeast-dipping foliation. The Ammonoosuc Volcanics are lithologically complex and predominantly include interlayered and interfingered rhyolitic to basaltic volcanic and volcaniclastic rocks, as well as lesser amounts of siltstone, phyllite, graywacke, and grit. The Comerford Intrusive Complex crops out east of the Monroe fault and consists of metamorphosed gabbro, diorite, tonalite, aplitic tonalite, and crosscutting diabase dikes. Abundant mafic dikes from the Comerford Intrusive Complex intruded the Albee Formation and Ammonoosuc Volcanics east of the Monroe fault. The

  17. Early intervention for psychosis

    PubMed Central

    Marshall, Max; Rathbone, John

    2014-01-01

    Background Proponents of early intervention have argued that outcomes might be improved if more therapeutic efforts were focused on the early stages of schizophrenia or on people with prodromal symptoms. Early intervention in schizophrenia has two elements that are distinct from standard care: early detection, and phase-specific treatment (phase-specific treatment is a psychological, social or physical treatment developed, or modified, specifically for use with people at an early stage of the illness). Early detection and phase-specific treatment may both be offered as supplements to standard care, or may be provided through a specialised early intervention team. Early intervention is now well established as a therapeutic approach in America, Europe and Australasia. Objectives To evaluate the effects of: (a) early detection; (b) phase-specific treatments; and (c) specialised early intervention teams in the treatment of people with prodromal symptoms or first-episode psychosis. Search methods We searched the Cochrane Schizophrenia Group Trials Register (March 2009), inspected reference lists of all identified trials and reviews and contacted experts in the field. Selection criteria We included all randomised controlled trials (RCTs) designed to prevent progression to psychosis in people showing prodromal symptoms, or to improve outcome for people with first-episode psychosis. Eligible interventions, alone and in combination, included: early detection, phase-specific treatments, and care from specialised early intervention teams. We accepted cluster-randomised trials but excluded non-randomised trials. Data collection and analysis We reliably selected studies, quality rated them and extracted data. For dichotomous data, we estimated relative risks (RR), with the 95% confidence intervals (CI). Where possible, we calculated the number needed to treat/harm statistic (NNT/H) and used intention-to-treat analysis (ITT). Main results Studies were diverse, mostly small

  18. Early identification systems for emerging foodborne hazards.

    PubMed

    Marvin, H J P; Kleter, G A; Prandini, A; Dekkers, S; Bolton, D J

    2009-05-01

    This paper provides a non-exhausting overview of early warning systems for emerging foodborne hazards that are operating in the various places in the world. Special attention is given to endpoint-focussed early warning systems (i.e. ECDC, ISIS and GPHIN) and hazard-focussed early warning systems (i.e. FVO, RASFF and OIE) and their merit to successfully identify a food safety problem in an early stage is discussed. Besides these early warning systems which are based on monitoring of either disease symptoms or hazards, also early warning systems and/or activities that intend to predict the occurrence of a food safety hazard in its very beginning of development or before that are described. Examples are trend analysis, horizon scanning, early warning systems for mycotoxins in maize and/or wheat and information exchange networks (e.g. OIE and GIEWS). Furthermore, recent initiatives that aim to develop predictive early warning systems based on the holistic principle are discussed. The assumption of the researchers applying this principle is that developments outside the food production chain that are either directly or indirectly related to the development of a particular food safety hazard may also provide valuable information to predict the development of this hazard.

  19. 75 FR 20830 - Early Learning

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-04-21

    ... meetings and written submissions, is seeking input from State agencies responsible for early learning and... intervention service providers and other providers of services to young children), students, technical... receive all written submissions of comments on the four early learning topics on or before 5 p.m...

  20. Enhanced influence of early-spring tropical Indian Ocean SST on the following early-summer precipitation over Northeast China

    NASA Astrophysics Data System (ADS)

    Han, Tingting; He, Shengping; Wang, Huijun; Hao, Xin

    2017-04-01

    The relationship between the tropical Indian Ocean (TIO) and East Asian summer monsoon/precipitation has been documented in many studies. However, the precursor signals of summer precipitation in the TIO sea surface temperature (SST), which is important for climate prediction, have drawn little attention. This study identified a strong relationship between early-spring TIO SST and subsequent early-summer precipitation in Northeast China (NEC) since the late 1980s. For 1961-1986, the correlations between early-spring TIO SST and early-summer NEC precipitation were statistically insignificant; for 1989-2014, they were positively significant. Since the late 1980s, the early-spring positive TIO SST anomaly was generally followed by a significant anomalous anticyclone over Japan; that facilitated anomalous southerly winds over NEC, conveying more moisture from the North Pacific. Further analysis indicated that an early TIO SST anomaly showed robust persistence into early summer. However, the early-summer TIO SST anomaly displayed a more significant influence on simultaneous atmospheric circulation and further affected NEC precipitation since the late 1980s. In 1989-2014, the early-summer Hadley and Ferrell cell anomalies associated with simultaneous TIO SST anomaly were much more significant and extended further north to mid-latitudes, which provided a dynamic foundation for the TIO-mid-latitude connection. Correspondingly, the TIO SST anomaly could lead to significant divergence anomalies over the Mediterranean. The advections of vorticity by the divergent component of the flow effectively acted as a Rossby wave source. Thus, an apparent Rossby wave originated from the Mediterranean and propagated east to East Asia; that further influenced the NEC precipitation through modulation to the atmospheric circulation (e.g., surface wind, moisture, vertical motion).