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1
Dubinko, V. Kh, V. A. Varkov, and V. P. Efimenko. "Experience of using secondary zinc silumin AK9Ts6." Metal Science and Heat Treatment 29, no. 5 (May 1987): 387–89. http://dx.doi.org/10.1007/bf00715849.
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2
Tripković, S., S. Marković, S. Matijašević, B. Jordović, and M. Martinović. "A Study of the use of Secondary Silumin in the Production of Castings for the Automobile Industry." Cast Metals 4, no. 1 (January 1991): 25–30. http://dx.doi.org/10.1080/09534962.1991.11819051.
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3
Pešek, Ladislav. "Experimental Analysis of Local Stress State and Deformation in the Critical Area of Combustion Engine Cylinder." Key Engineering Materials 586 (September 2013): 63–66. http://dx.doi.org/10.4028/www.scientific.net/kem.586.63.
Повний текст джерелаАнотація:
The article is focused on local stress simulation as well as local deformation analysis in a cylinder of piston combustion engine. Design of the exhaust pipe system has to fulfill special requirements with regard to the combined loading due to high pressures and temperatures. There is a special role of the exhaust pipe barrier, which is situated in the exhaust gas pipe. This barrier separates the main air hole from the secondary lateral auxiliary air holes. The exhaust pipe barrier seems to be a critical point of the cylinder. The finite-element analysis applied on the silumin-cast cylinder is presented in the paper in order to prove the critical places with high stress concentration. The local strength of the cylinder material was estimated using a material model based on relation between the strength and the mean distance between the secondary dendrite arms (SDAS) in the as-cast microstructure. Due to local heterogeneities there are differences in the local strength value at the various places of the microstructure. The simulation of stress distribution was performed by use of the finite-element method. Based on the relation „local stress/local strength“ the individual critical places in the cylinder were defined and located.
4
Mityayev, A. A., I. P. Volchok, R. A. Frolov, K. N. Loza, O. V. Hnatenko, and V. V. Lukinov. "COMPLEX MODIFICATION OF SECONDARY SILUMINS." Science and Transport Progress. Bulletin of Dnipropetrovsk National University of Railway Transport, no. 6(54) (December 10, 2014): 87. http://dx.doi.org/10.15802/stp2014/33180.
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5
Taran, Yu N., A. G. Prigunova, S. S. Petrov, L. P. Seleznev, E. I. Korzh, and Yu V. Bychkov. "Multiphase crystallization of secondary magnesium silumins." Metal Science and Heat Treatment 31, no. 7 (July 1989): 535–38. http://dx.doi.org/10.1007/bf00802273.
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6
Volchok, I. P., A. A. Mityatev, O. V. Liutova, A. A. Krulikovska, and T. V. Vanarha. "Increasing of the secondary silumins fracture resistance." Metaloznavstvo ta obrobka metalìv 95, no. 3 (September 15, 2020): 46–53. http://dx.doi.org/10.15407/mom2020.03.046.
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7
Snegirev, A. I., and B. V. Slobodin. "Interaction of oxide phases of graphite-containing crucibles with secondary silumins." Refractories 37, no. 8 (August 1996): 269–70. http://dx.doi.org/10.1007/bf02281128.
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8
Volchok, Ivan, Olexandr Mityayev, Roman Frolov, Olha Krulikovska, and Tetiana Vaniarkha. "Increasing secondary silumins quality in the condi-tions of prezent day production." Bulletin of Kharkov National Automobile and Highway University, no. 91 (December 24, 2020): 105. http://dx.doi.org/10.30977/bul.2219-5548.2020.91.0.105.
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9
Woodcock, N. H., and T. C. Pharaoh. "Silurian fades beneath East Anglia." Geological Magazine 130, no. 5 (September 1993): 681–90. http://dx.doi.org/10.1017/s0016756800020999.
Повний текст джерелаАнотація:
AbstractCore material from proven or probable Silurian sedimentary rocks beneath East Anglia has been re-examined. Four recognizable facies probably represent an environmental transition from anoxic basin slope or outer shelf through oxygenated outer shelf to storm-dominated inner shelf. This transition could have occurred laterally, from east to west across the Anglian Basin, or in time, from Llandovery (early Silurian) up to Př (late Silurian). Partial biostratigraphical constraints allow either interpretation, but the regional setting favours a marked facies transition through time as the Anglian Basin shallowed prior to the Acadian Orogeny. Reddening of the Silurian is mostly secondary beneath the sub-Triassic unconformity.
10
Mityayev, O., and I. Volchok. "Influence of Intermetallic Phases on Fracture Resistance of Silumins." Archives of Foundry Engineering 13, no. 4 (December 1, 2013): 83–86. http://dx.doi.org/10.2478/afe-2013-0087.
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Abstract In secondary aluminium alloys iron is the main detrimental impurity. It forms intermetallic phases which have lamellar shape, high brittleness and weak crystallographic conformity with the matrix. In the work the influence of intermetallic phases on the initiation and propagation of microcracks, mechanical and service properties of aluminium alloys has been investigated.
11
He, Bizhu, Xiufu Qiao, Cunli Jiao, Zhiqin Xu, Zhihui Cai, Xianpu Guo, and Yinli Zhang. "Palaeo-earthquake events during the late Early Palaeozoic in the central Tarim Basin (NW China): evidence from deep drilling cores." Geologos 20, no. 2 (July 8, 2014): 105–23. http://dx.doi.org/10.2478/logos-2014-0006.
Повний текст джерелаАнотація:
Abstract Various millimetre-, centimetre- and metre-scale soft-sediment deformation structures (SSDS) have been identified in the Upper Ordovician and Lower-Middle Silurian from deep drilling cores in the Tarim Basin (NW China). These structures include liquefied-sand veins, liquefaction-induced breccias, boudinage-like structures, load and diapir- or flame-like structures, dish and mixed-layer structures, hydroplastic convolutions and seismic unconformities. The deformed layers are intercalated by undeformed layers of varying thicknesses that are petrologically and sedimentologically similar to the deformed layers. The SSDS developed in a shelf environment during the early Late Ordovician and formed initially under shear tensile stress conditions, as indicated by boudinage-like structures; during the latest Ordovician, SSDS formed under a com-pressional regime. The SSDS in the Lower-Middle Silurian consist mainly of mixed layers and sand veins; they formed in shoreline and tidal-flat settings with liquefaction features indicating an origin under a compressional stress regime. By Silurian times, the centre of tectonic activity had shifted to the south-eastern part of the basin. The SSDS occur at different depths in wells that are close to the syn-sedimentary Tazhong 1 Fault (TZ1F) and associated reversed-thrust secondary faults. Based on their characteristics, the inferred formation mechanism and the spatial association with faults, the SSDS are interpreted as seismites. The Tazhong 1 fault was a seismogenic fault during the later Ordovician, whereas the reversed-direction secondary faults became active in the Early-Middle Silurian. Multiple palaeo-earthquake records reflect pulses and cyclicity, which supports secondary tectonic activity within the main tectonic movement. The range of SSDS structures reflects different developments of tectonic activity with time for the various tectonic units of the centralbasin. The effects of the strong palaeo-earthquake activity coincide with uplift, fault activity and syn-tectonic sedimentation in the study area during the Late Ordovician to Middle Silurian.
12
Volchok, I. P., O. L. Skuibida, O. V. Liutova, and N. V. Shyrokobokova. "QUALITY IMPROVEMENT OF SECONDARY SILUMINS BY USING REFINING-MODIFYING, HEAT AND LASER TREATMENTS." Science and Transport Progress. Bulletin of Dnipropetrovsk National University of Railway Transport, no. 5(53) (November 19, 2014): 101. http://dx.doi.org/10.15802/stp2014/30427.
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13
Belov, V. D., and N. A. Belov. "About some aspects of production of cast shapes from “secondary” silumins in Russia." Metal Science and Heat Treatment 53, no. 9-10 (January 2012): 434–39. http://dx.doi.org/10.1007/s11041-012-9411-9.
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14
Li, Minghui, Mingliang Li, Haiping Huang, Lei Gong, and Debao Zheng. "Differences of Pore Features in Marine Shales between Lower Cambrian and Lower Silurian Formations of Upper Yangtze Area, South China." Energies 15, no. 3 (January 24, 2022): 820. http://dx.doi.org/10.3390/en15030820.
Повний текст джерелаАнотація:
Lower Cambrian shale and lower Silurian shale are both typical of oil-prone kerogen and siliceous composition, but different in thermal maturities. Porosity differences were determined in marine shales between the two shales. Measurements were utilized including organic geochemistry, XRD, scanning electron microscopy (SEM) and N2 gas adsorption. Pore volume (PV) of lower Silurian shale was approximately 1.5 times higher than that of lower Cambrian shale, and pore surface area (PSA) of lower Silurian shale was almost 2.5 times higher than that of lower Cambrian shale. Lower Cambrian shale and lower Silurian shale possess similar materials, but distinctive thermal degrees. Evolution mechanisms of different types of pores, especially organic matter (OM)-hosted pores, may trigger this different pore features. Pores of rigid framework are the residue of primary interparticle pores during the burial history. Pores associated with clay flakes can be preserved well adjacent to rigid grains or secondary minerals acting as rigid frameworks or grain supporters. Dissolved pores in both lower Cambrian shale and lower Silurian shale barely contribute to the total porosity and mean little to the permeability. Both excessive OM content and over thermal maturity are detrimental to development of OM-hosted pores. Rigid particles, clay flakes, and OM commonly co-exist within shale matrix. Rigid grains act as supporters, clay flakes confine ample space, and OM first migrates into and provides secondary OM-hosted pores. In this condition, pores can be preserved owing to associating matrix with good mechanic and chemical stability. The significant differences of structural settings result into various hydrocarbon explosion efficiency and different pressure circumstance, which consequently leads to the different pore features between the two shales. For lower Cambrian shale, overpressure circumstance diminish if hydrocarbon expels outside of the shale system, and OM-hosted pores destroy through compaction. Sustaining overpressure and abundant residue hydrocarbon (migrated OM) make positive contributions to the pore properties, in terms of numbers, diameters and connectivity of the lower Silurian shale samples.
15
Harper, David A., Fred J. Longstaffe, Moire A. Wadleigh, and Robert H. McNutt. "Secondary K-feldspar at the Precambrian–Paleozoic unconformity, southwestern Ontario." Canadian Journal of Earth Sciences 32, no. 9 (September 1, 1995): 1432–50. http://dx.doi.org/10.1139/e95-116.
Повний текст джерелаАнотація:
The Precambrian–Paleozoic boundary in the subsurface of southwestern Ontario commonly is characterized by secondary K-feldspar. In the weathered and altered Precambrian granitoid gneisses at the unconformity, secondary K-feldspar has replaced preexisting minerals, and also occurs as discrete crystals of adularia, overgrowths on altered minerals, and microcrystalline veinlets. The K-feldspar is chemically pure (Or99–100) and has high δ18O values (+18.9 to +21.4‰ Vienna Standard Mean Ocean Water), features that indicate crystallization at low temperatures. Secondary K-feldspar also occurs in Cambro-Ordovician clastic and carbonate rocks that immediately overlie the Precambrian basement. K/Ar (453 ± 9 to 412 ± 8 Ma) and Rb/Sr (440 ± 50 Ma) dates obtained for secondary K-feldspar from the Precambrian host rocks suggest that its crystallization is unrelated to Precambrian weathering or early diagenesis of the immediately overlying Cambro-Ordovician strata. Estimated crystallization temperatures for the secondary K-feldspar (≥100 °C) exceed presumed burial temperatures for the Precambrian–Paleozoic boundary in southwestern Ontario during Late Ordovician–Silurian time. We infer that secondary K-feldspar formed from a hot brine that moved preferentially along the Precambrian–Paleozoic unconformity. The wide distribution of secondary K-feldspar of Late Ordovician–Silurian age throughout mid-continental North America at the Precambrian–Paleozoic boundary records the regional extent of this process. Some Cambro-Ordovician rocks elsewhere in the mid-continent also contain secondary K-feldspar and illitic clay of Late Pennsylvanian–Early Permian age, suggesting more than one episode of fluid movement. Major pulses of orogenic activity may have initiated brine migration. We speculate that the brine originated as connate (sea) water trapped in lower Paleozoic strata, and was modified by rock–water interaction at elevated temperatures, and by mixing with meteoric water.
16
Peters, Shanan E., and Kennard B. Bork. "Secondary tiering on crinoids from the Waldron Shale (Silurian: Wenlockian) of Indiana." Journal of Paleontology 72, no. 5 (September 1998): 887–94. http://dx.doi.org/10.1017/s0022336000027219.
Повний текст джерелаАнотація:
Superbly preserved specimens of Eucalyptocrinites tuberculatus from the Waldron Shale (Silurian, Wenlockian) of Indiana have been found with epibionts attached in living position to their stems. The rhynchonellid brachiopod Stegerhynchus indianense, the tabulate coral Favosites forbesi, the annelids? Spirorbis and Cornulites, bryozoans, and rarely the ichnogenus Tremichnus utilized living crinoids as secondary tiering surfaces. Crinozoans also attached to upright crinoid columns, and their holdfasts are the most abundant epibionts on pluricolumnals. Eucalyptocrinites crassus individuals contributed to the success of their epibionts by providing stable attachment surfaces elevated up to one meter above the sediment-water interface. Although crinoid-epibiont relationships are frequently blurred by taphonomic processes, articulated crinoid specimens and encrusters on pluricolumnals suggest that secondary tiering was a significant paleoecological element in the Waldron Shale.
17
Danshchikova, I. I., T. V. Maidl, A. V. Zhuravlev, and V. S. Nikiforova. "Silurian carbonate reservoir rocks of the joint zone of the Khoreyver depression and the Chernyshev ridge." Proceedings of the Komi Science Centre of the Ural Division of the Russian Academy of Sciences 3 (2021): 41–48. http://dx.doi.org/10.19110/1994-5655-2021-3-41-48.
Повний текст джерелаАнотація:
The paper presents a comprehensive study of low-capacity Silurian carbonate reservoir rocks in the northeastern regions of the Timan-Pechora province. Silurian deposits in the sections of the Khosedayu swell, the Talbey block, and the Makarikha-Salyukin anticlinal zone are mainly secondary dolomites and, to a lesser extent, limestones, as well as with low-power interlayers of agrillites, clay dolomites, dolomite-anhydrite rocks. The deposits were formed in coastal-marine and shallow-marine conditions. As a result of the conducted studies, it was noted that dolomites with a shadow biohermal structure have the best filtration properties in the Lower Silurian, and bioclastic limestones – in the Upper Silurian. The reservoir rocks of the Talbey block of the Chernyshev ridge have the best filtration-capacitive properties. The main volume of the void space in the first case is associated with cavities and cracks, in the second one – with matrix porosity. However, the signs of modern karst in the salts of Malo-Tavrotinsky strata observed from the core indicate a possible reformation of the deposits, which requires more careful attention when predicting deposits. The results obtained can contribute to the design of a rational system for the development of hydrocarbon deposits.
18
Frýda, Jiří. "Oldest representatives of the superfamily Cirroidea (Vetigastropoda) with notes on early phylogeny." Journal of Paleontology 71, no. 5 (September 1997): 839–47. http://dx.doi.org/10.1017/s0022336000035782.
Повний текст джерелаАнотація:
Two new genera, Barrandecirrus (Porcelliinae) and Pernericirrus (Agnesiinae), from Upper Silurian marine sediments of the Prague Basin (Barrandian area, central Bohemia) are described. Both these genera belong to the family Porcelliidae and represent the oldest representatives of the superfamily Cirroidea (Vetigastropoda). The sinistrally coiled teleoconch of Barrandecirrus filiformis (Perner) suggests that the pseudobilaterally symmetrical teleoconch of the younger genera of Porcelliinae (Porcellia and Coloniacirrus) is a secondary shell character that originated during post-Silurian evolution of this group. In addition, the sinistral, low trochospiral teleoconch of early Agnesiinae [Pernericirrus sinistorsus (Perner) and Agnesia costata (Goldfuss)] as well as the asymmetrical position of the selenizone and the sinistral teleoconch in early Porcelliinae (Barrandecirrus filiformis) support the opinion that both Porcelliinae and Agnesiinae arose from the same stock. Data presented also suggest that the superfamily Cirroidea evolved during the Silurian or earlier, and it has developed parallel to and independently of other larger groups of the Vetigastropoda such as the Pleurotomarioidea and the Trochoidea.
19
Buchan, Kenneth L., and Joseph P. Hodych. "Early Silurian paleolatitude for central Newfoundland from paleomagnetism of the Wigwam Formation." Canadian Journal of Earth Sciences 29, no. 8 (August 1, 1992): 1652–61. http://dx.doi.org/10.1139/e92-130.
Повний текст джерелаАнотація:
Redbeds and minor volcanic rocks of the Early Silurian Wigwam Formation of the Botwood Group were sampled in the Exploits Subzone of the Dunnage Zone of central Newfoundland. At 18 sedimentary and 3 volcanic sites thermal demagnetization isolated a shallow northward (or southward) magnetization (D = 356.0°, I = −16.8°; k = 12.9; α95 = 9.2°; n = 21 site means) after correction for the tilt of bedding. A positive fold test demonstrates that this remanence predates regional Siluro–Devonian folding. A primary age for the remanence is indicated by positive conglomerate tests on volcanic clasts, and reversals correlated with sedimentary stratigraphy. Antiparallel remanence directions at sites of opposite polarity indicate that the primary remanence is not partially overprinted by a secondary component. The Exploits Subzone of the Dunnage Zone is interpreted to have been at low paleolatitudes (8.5°S ± 5°) during the Early Silurian. We reached a similar conclusion for the Notre Dame Subzone of the Dunnage Zone in a previous paleomagnetic study of Early Silurian redbeds and volcanic rocks of the King George IV Lake area. The low paleolatitudes obtained for the Wigwam and King George IV Lake rocks do not differ significantly and, hence, provide no evidence for a large ocean between the two subzones in the Early Silurian. However, the azimuthal orientation of the subzones at that time is still uncertain, and an ocean with its axis oriented in a north–south direction would not be detected by the paleomagnetic method.
20
Larsen, P. H. "Soft sediment deformation structures in Silurian turbidites from North Greenland." Bulletin of the Geological Society of Denmark 35 (October 29, 1986): 19–23. http://dx.doi.org/10.37570/bgsd-1986-35-03.
Повний текст джерелаАнотація:
Turbidite beds in the Silurian turbidite sequence, North Greenland, show soft sediment deformation structures suggesting that the structureless (in respect of traction structures) sandstones divisions of the turbidites were deposited by direct suspension sedimentation from high-density flows. The deposits may have resulted from multiple successive depositional events within the same turbidity flow. Reworking and shear- ing of the newly formed loosely packed high-density suspension deposits caused by the still moving flow above create secondary soft sediment deformation structures which may be used as current indicators if other structures are absent (e.g. flute casts).
21
KUROVETS, Ihor, Yulia LYSAK, Pavlo CHEPUSENKO, Stepan MYKHALCHUK, and Roman-Danylo KUCHER. "Geological-petrophysical characteristic of Silurian deposits of the Volyn-Podillya edge of the East-European Platform." Geology and Geochemistry of Combustible Minerals 4, no. 181 (December 27, 2019): 17–31. http://dx.doi.org/10.15407/ggcm2019.04.017.
Повний текст джерелаАнотація:
Taking into consideration well logging of the Silurian deposits of the Volyn-Podillya plate, the materials of laboratory investigations of petrophysical parameters of reservoir rocks were analyzed and systematized. Studied were capacity-filtration properties of reservoir rocks as well as their lithological-petrographical and structural-textural features. An analysis of the distribution of petrophysical parameters of the Silurian deposits of the Volyn-Podillya plate was executed by the methods of mathematic statistics. Main statistics and correlation coefficients between individual parameters were calculated, histograms of the distribution of the porosity factor Kpor and the permeability factor Kper, volumetric weight δ and carbonation C in rocks were compiled, regression equations between parameters and their alteration with depth were formed. Petrophysical parameters of the samples available for carbonate and terrigenous rocks of Silurian were analyzed separately. Executed investigations of petrophysical properties of rocks testify that in the Silurian deposits the carbonate reservoirs with the complex structure of the porous space were distributed. A visible alteration of capacity-filtration parameters of rocks of Silurian deposits is observed with depth. Porosity of rocks decreases with depth, but permeability increases that is a confirmation of the formation of the secondary fractured-covernous porosity. Increase in the permeability factor with depth is characteristic of carbonate rocks. According to geological-geophysical data available, the reservoir rocks with better capacity-filtration properties are distributed in the zone of the barrier reef. The best reservoir parameters are characteristic of cavernous dolomites and limestones at the Lokachy area and in the region of Lutsk. Reservoir rocks of porous type are practically absent at depths over 2500 m. Here a significant role in improving of collecting properties of rocks belongs to their fracturing. Microfractures are observed in clayed limestones, marls and clay rocks. Under favourable geodynamic conditions the subvertical zones of disconsolidation occur in which composite reservoir rocks with fracture porosity may be formed.
22
Holmer, Lars E., Leonid Popov, and Michael G. Bassett. "Ordovician–Silurian Chileida—First Post-Cambrian Records of an Enigmatic Group of Brachiopoda." Journal of Paleontology 88, no. 3 (May 2014): 488–96. http://dx.doi.org/10.1666/13-104.
Повний текст джерелаАнотація:
Brachiopods of the order Chileida have been recorded previously only from rocks of early to mid-Cambrian age (Botomian–Amgaian). They are typified by having a calcareous strophic shell with a delthyrium and colleplax, and these characters are shown to be present in species of the two new generaTolenandTrifissura, from the Late Ordovician of Kazakhstan and the Silurian of Sweden and Britain, respectively. In specimens ofTrifissura, the triangular colleplax is phosphatized secondarily by bacterial activity. It is suggested that the phosphatized colleplax represents an organic pad and that served as the original attachment structure ofTrifissuraby encrustation.TolenandTrifissurarepresent the first post-Cambrian record of chileides from the Ordovician and Silurian; the new family Trifissuridae forms the first phylogenetic link between Cambrian chileides and Carboniferous–Permian isogrammides.
23
Seguin, Maurice K., and Allen A. Petryk. "Paleomagnetic study of the Late Ordovician–Early Silurian platform sequence of Anticosti Island, Quebec." Canadian Journal of Earth Sciences 23, no. 12 (December 1, 1986): 1880–90. http://dx.doi.org/10.1139/e86-176.
Повний текст джерелаАнотація:
Eighteen sites (152 samples, 441 specimens) from the Late Ordovician — Early Silurian sequence of Anticosti Island were studied paleomagnetically. Six sites were collected in the Vauréal Formation, seven in the Ellis Bay Formation, three in the Becscie Formation, and one each in the Gun River and Jupiter formations. The lithologies sampled consisted of limestones, sandy limestones, marls, and sandy calcareous shales drawn from a sedimentary platform sequence of predominantly inter-bedded limestones and shales. The specimens were demagnetized in alternating fields (AF) and thermally and were found to be quite stable. Two components of magnetization were isolated. The memory carrier is fine- to medium-grained magnetite; AF and thermal cleanings are about equally efficient. The average directions of residual magnetization are D = 167°, I = 37°, α95 = 18°; D = 315°, I = −24°, α95 = 17 °for components B and C, respectively. The corresponding paleopoles for the B and C components are 129°E, 19°N (dp = 12°, dm = 21°) and 341°E, 16°S (dp = 10°, dm = 18°).Component A is most probably composed of component C and the present Earth's field (PEF); it was chiefly observed in the more altered Vauréal Formation and in the altered top part of the cored samples. The most common component in the Ellis Bay, Becscie, Gun River, and Jupiter formations is component C. Component B is mainly found in the Becscie and Ellis Bay formations. Both components B and C are isolated in the 300–500 °C and 10–40 mT ranges. Component C is either older than component B or synchronous and of reverse polarity to component B. If this last alternative is correct, then the Ordovician and Silurian formations are overprinted by a pre-Kiaman magnetization. The more plausible scenario is the following: component B is secondary, of pre-Middle Carboniferous age, and overprinted on an older secondary magnetization (component C), the acquisition age of which is confined to the Silurian–Carboniferous time interval.
24
Timonina, N. N., and I. I. Danshchikova. "Reservoirs in carbonates of the lower oil and gas-bearing complex of the Timan-Pechora Province (for the anniversary of T. V. Maydl)." Vestnik of Geosciences, no. 1 (February 26, 2021): 40–43. http://dx.doi.org/10.19110/geov.2021.1.6.
Повний текст джерелаАнотація:
The paper presents Tatyana V. Maydl’s researches of formation and patterns of distribution of natural reservoirs in carbonate deposits of the Timan-Pechora oil and gas province. Tatyana Viktorovna Maydl is a recognized specialist in oil and gas geology. Her significant contribution to the development of the theoretical base of formation of carbonate deposits in the region, reconstruction of sedimentation conditions, finding degree of influence of secondary transformations on the reservoir and filtration properties of carbonate rocks, development of the basis for geological models of carbonate reservoirs, are analyzed. In the field of studying the morphology of the void space in low-capacity carbonate reservoirs, T. V. Maydl found that in the Lower Silurian dolomites with a shadow biohermal structure had the best filtration features, and in the Upper Silurian — bioclastic limestones. The main volume of the void space in the first type is associated with caverns and cracks, in the second — with matrix porosity. We showed that the results of T. V. Maydl’s work were not only of theoretical, but also of practical importance.
25
Ponomarenko, E. S. "Lithological and isotopic (δ 13C and δ 18O) features of the Upper Silurian back-reef lagoon deposits of the Ilych River Basin, the Northern Urals". Vestnik of Geosciences 11 (2021): 43–54. http://dx.doi.org/10.19110/geov.2021.11.4.
Повний текст джерелаАнотація:
The Upper Silurian is widely developed in the Northern Urals, where it is represented by various facies. The continental slope facies and the reef shoal facies are well documented in the geological literature, while as back-reef lagoon facies have not yet been characterized in detail. The studied objects included two sections of the back-reef deposits in the Ilych River basin. In this work, we characterize rock types the make up the sections, and their isotopic characteristics. The Late Silurian back-reef lagoon was characterized by a mosaic sediments distribution, which included the island areas between which there were areas with a quiet hydrodynamic regime. In the latter, mainly muddy carbonates were accumulated, represented by clotted fenestral limestones. The area of small islands was characterized by a wide distribution of lime sands, which clastic material was derived from probable paleosoil carbonates. They are characterized by slightly increased δ 13C values, which, probably, reflects isotopic fractionation at the evaporative geochemical barrier. Dolomitization and karstification are described among secondary alterations in the studied sections. Cementstones is interpreted as karst cavities precipitates.
26
Lavoie, Denis, and Claude Morin. "Hydrothermal dolomitization in the Lower Silurian Sayabec Formation in northern Gaspé – Matapédia (Québec): constraint on timing of porosity and regional significance for hydrocarbon reservoirs." Bulletin of Canadian Petroleum Geology 52, no. 3 (September 1, 2004): 256–69. http://dx.doi.org/10.2113/52.3.256.
Повний текст джерелаАнотація:
Abstract The study of dolostone of the Lower Silurian Sayabec Formation of the Lac Matapédia syncline, at the western end of the Gaspé Peninsula, sheds new light on porosity development and reservoir potential of the area. The dolomitized section is close to the Shickshock Sud Fault that cuts the southern limb of the syncline. The dolostone occurs either as a highly brecciated unit or as stratiform replacement of peritidal carbonates at the base of the formation. Residual bitumen is seen in the breccia as well as filling of small secondary vugs and fractures within the stratiform dolostone. The dolostone consists predominantly of replacive matrix dolomite; petrography and oxygen and carbon stable isotope ratios (δ18OVPDB = −6.3 to −7.8‰ and δ13CVPDB = 1.2 to 3.3‰) of the matrix dolomite indicate early burial formation with later recrystallization in the presence of high temperature fluids. Saddle dolomite is found as a pore-filling cement in secondary dissolution pores and fractures. Oxygen stable isotope ratios of the saddle dolomite cement (δ18OVPDB = −14.5 and −15.3‰) indicate precipitation at high temperature. Dull luminescent burial calcite cement follows saddle dolomite. Later dissolution is locally apparent in carbonates as scalloped surfaces covered by finely laminated, bright-very dull luminescent calcites. Petrography and stable isotope ratios of the calcite (δ18OVPDB = −10.1 and −11.2‰ and δ13CVPDB = −2.3 and −6.9‰) suggest precipitation from meteoric waters. Meteoric dissolution and luminescent-zoned calcite cements are related to a Pridolian sea level lowstand. This event provides a first age constraint on the timing of the hydrothermal dolomitization and hydrocarbon charge of the Sayabec Formation along the northern edge of the Gaspé Belt. The Shickshock Sud Fault channelled the hydrothermal fluids, which dolomitized the Sayabec Formation shortly after initial burial. A recent regional seismic program showed compressive structures (duplexes, backthrust, triangle zone) in the Sayabec Formation inferred to have occurred in latest Silurian–Early Devonian that generated structural traps superimposed on the stratigraphic (shaly facies) and diagenetic (tight non-dolomitized limestone) seals. Seismic anomalies (“flat spots”) in the Lower Silurian section in eastern Quebec suggest the presence of hydrocarbon-filled reservoirs.
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Katkova, V. I., T. M. Beznosova, and V. N. Filippov. "Pseudo-morphogenesis in the shells of the Silurian brachiopods." Proceedings of the Komi Science Centre of the Ural Division of the Russian Academy of Sciences 3 (2021): 49–55. http://dx.doi.org/10.19110/1994-5655-2021-3-49-55.
Повний текст джерелаАнотація:
The analysis of paleontological data, the study of mineral matter transformation involving live organisms in various rocks is important for the understanding of the events of the geological past. The aim of this work is to identify the bio-genic factor in the process of pseudo-morphogenesis in the shell sashes of the Early Silurian brachiopods from the car-bonate rocks of the Chernyshev Ridge. Structural and microscopic methods (Shimadzu XRD 6000; Fourier spectrometer InfraLum FT-02; JSM 6400 JEOL; VEGA3 TESCAN; MIN-8) were used to study quartz pseudomorphoses in the sashes of four shells of the Early Silurian brachiopods Borealis sр. of Pentamerida order from the carbonate strata of the Chernyshev Ridge. The salicification of the brachiopod shell walls resulted in the complete replacement of the original carbonate skeleton with a change in its structural organization. It is established that quartz is the main mineral component of the intra-shell material and secondary dolomite crystals and newly formed calcite aggregates. The paper discusses the participation of Early Paleozoic and modern cyanobacterial symbionts in the replacement of primary calcite with quartz and the formation of quartz crystalline aggregates on the shell walls. It is shown that quartz on the surface of shell sashes and in the intra-shell substance of brachiopods has undergone repeated transformations due to the combination of ancient and modern weathering processes.
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Gilligan, M., A. Costanzo, M. Feely, G. K. Rollinson, E. Timmins, T. Henry, and L. Morrison. "Mapping arsenopyrite alteration in a quartz vein-hosted gold deposit using microbeam analytical techniques." Mineralogical Magazine 80, no. 5 (August 2016): 739–48. http://dx.doi.org/10.1180/minmag.2016.080.019.
Повний текст джерелаАнотація:
AbstractAn unworked quartz vein-hosted gold deposit occurs in the Clew bay area of County Mayo, western Ireland. The veins are late-Caledonian in age and transect greenschist-facies poly-deformed Silurian quartzites. The veins contain disseminated arsenopyrite that may be a primary mineral source for elevated levels of arsenic (As) found in groundwater samples recovered from wells related spatially to the gold deposit. Levels from 5 to 188 μg/L (significantly above the 7.5 μg/L threshold for safe drinking water) have been detected. A series of element distribution maps using a scanning electron microscope (Hitachi model S-4700) linked to an energy-dispersive spectrometer (INCA® Oxford Instruments) and mineral distribution maps generated by QEMSCAN® (Quantitative Evaluation of Minerals by Scanning electron microscopy) were used to map the distribution of the primary arsenopyrite and related secondary As-bearing phases. Laser Raman microspectroscopy was used to identify the secondary As-bearing phases. 'Island weathering' of primary arsenopyrite together with hydrated pseudomorphs of arseniosiderite, pharmacosiderite and scorodite after arsenopyrite are recorded. Circulating groundwater hydrates the primary arsenopyrite, providing the release mechanism that forms the secondary As-bearing phases that occur as microfracture infills together with muscovite and biotite. The textural relationships between the primary and secondary As minerals indicate their potential as mineral sources of As that could enter transport pathways leading to its release into groundwater.
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Schmitz, B. "An iridium anomaly in the Ludlow Bone Bed from the Upper Silurian, England." Geological Magazine 129, no. 3 (May 1992): 359–62. http://dx.doi.org/10.1017/s0016756800019294.
Повний текст джерелаАнотація:
AbstractThe Ludlow Bone Bed in the Upper Silurian of the Welsh Borderland shows an anomalously high concentration of iridium (0.49 ppb) compared with background (0.040 ppb Ir). Considering the overall major and trace element pattern and the mineralogy of the bone bed, it appears that the bulk of their has precipitated from sea water and is not primarily related to an asteroid impact event. A secondary relation of the Ir to such an event, however, cannot be excluded. The profound sedimentological similarity (skeletal sands and hummocky cross-stratification) between the Ir-carrying ‘storm deposit’ at the Cretaceous–Tertiary boundary at Brazos River, Texas, and the LBB and overlying sediments may indicate such a relation.
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Patterson, Colin. "Bony Fishes." Short Courses in Paleontology 7 (1994): 57–84. http://dx.doi.org/10.1017/s2475263000001264.
Повний текст джерелаАнотація:
Bony fishes or osteichthyans comprise two main monophyletic groups: the actinopterygians (rayfins, including the staples of the fish market and aquarium) and sarcopterygians (lobefins, fringefins or tasselfins, including lungfishes, coelacanths, and, perhaps unexpectedly or inconveniently, all land vertebrates or tetrapods). In the broadest terms, the two groups have similar histories, each with beginnings in the late Silurian or earliest Devonian, each with a primary radiation in the late Devonian and Mississippian, a secondary radiation in the Mesozoic, and a major Tertiary radiation, and each with an extant diversity of roughly 25,000 species (Nelson, 1994, p. 2). The remainder of this course (eight topics) is devoted to sarcopterygians, so I shall give almost all my space to the other half of bony fish diversity, the actinopterygians.
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Jeppsson, Lennart, and Mikael Calner. "The Silurian Mulde Event and a scenario for secundo–secundo events." Transactions of the Royal Society of Edinburgh: Earth Sciences 93, no. 2 (June 2002): 135–54. http://dx.doi.org/10.1017/s0263593300000377.
Повний текст джерелаАнотація:
ABSTRACTGraphic correlation using graptolites and conodonts provides a high-resolution timescale for correlating from coastal to deep oceanic sections and, thereby, also a detailed record of the sequence of changes during the Mulde Secundo-Secundo Event. That interval includes sedimentary facies otherwise unknown in older Wenlock to early Ludlow strata on Gotland. The identified sequence of changes includes a detailed record of, in order: two extinctions (Datum points 1 and 1·5); widespread deposition of carbon-rich sediments extensive enough to cause a δ13C increase of c. 4.8‰, the onset, maximum and end of a sea-level fall and rise of at least 16 m during 30 kyr; a third extinction (Datum 2); a disaster fauna; and a slow faunal recovery. Thus, a secondary result of the event was a weakened greenhouse effect triggering a glaciation: the Gannarve Glaciation (new term). The order of changes proves that regression did not cause the extinctions. Faunal and sea-level changes, as well as the sedimentary succession, fit well with predictions based on an oceanic model. Extinctions were primarily caused by a severe drop in primary planktonic productivity, causing starvation among planktonic larvae in non-coastal settings. The Grötlingbo Bentonite (new term), the thickest in the Wenlock of Gotland, was deposited across the basin shortly after Datum 2. Temporal resolution is high enough to permit some comparison with Quaternary glaciations.
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Eagle, Ryan M., William D. Birch, and Stafford McKnight. "Phosphate minerals in granitic pegmatites from the Mount Wills District, north-eastern Victoria." Proceedings of the Royal Society of Victoria 127, no. 2 (2015): 55. http://dx.doi.org/10.1071/rs15018.
Повний текст джерелаАнотація:
Tin- and tantalum-bearing LCT-type granitic pegmatites occur in a 45 km long belt between Eskdale and Mount Wills in north-eastern Victoria. Near Mount Wills, several compositionally zoned rare-element pegmatites contain complex assemblages of primary and secondary phosphate minerals, many of which are rare and previously unrecorded in Victoria. The phosphate assemblages can be divided into Al-rich and Fe–Mn-rich suites, in addition to ubiquitous fluorapatite. The Al-rich phosphate suite includes montebrasite, scorzalite, bertossaite and brazilianite. The Fe‒Mn phosphate suite includes heterosite, phosphoferrite, wolfeite, alluaudite (sp.), arrojadite (sp.) and jahnsite (sp.), derived from the metasomatic alteration of primary triplite. Further hydrothermal alteration of this assemblage has resulted in a secondary suite of strengite, rockbridgeite, phosphosiderite, whiteite, jahnsite and whitmoreite forming in etch cavities and fractures. A Late Silurian age of 420±4 Ma was obtained from one of the dykes via CHIME radiometric dating of monazite, suggesting a similar age for the adjacent Mount Wills Granite, which has not been reliably dated. This highly fractionated, peraluminous granite is presumed to be the source of the rare-element pegmatites based on their close spatial relationship.
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Eagle, Ryan M., William D. Birch, and Stafford McKnight. "Corrigendum to: Phosphate minerals in granitic pegmatites from the Mount Wills District, north-eastern Victoria." Proceedings of the Royal Society of Victoria 129, no. 1 (2017): 53. http://dx.doi.org/10.1071/rs15018_co.
Повний текст джерелаАнотація:
Tin- and tantalum-bearing LCT-type granitic pegmatites occur in a 45 km long belt between Eskdale and Mount Wills in north-eastern Victoria. Near Mount Wills, several compositionally zoned rare-element pegmatites contain complex assemblages of primary and secondary phosphate minerals, many of which are rare and previously unrecorded in Victoria. The phosphate assemblages can be divided into Al-rich and Fe–Mn-rich suites, in addition to ubiquitous fluorapatite. The Al-rich phosphate suite includes montebrasite, scorzalite, bertossaite and brazilianite. The Fe‒Mn phosphate suite includes heterosite, phosphoferrite, wolfeite, alluaudite (sp.), arrojadite (sp.) and jahnsite (sp.), derived from the metasomatic alteration of primary triplite. Further hydrothermal alteration of this assemblage has resulted in a secondary suite of strengite, rockbridgeite, phosphosiderite, whiteite, jahnsite and whitmoreite forming in etch cavities and fractures. A Late Silurian age of 420±4 Ma was obtained from one of the dykes via CHIME radiometric dating of monazite, suggesting a similar age for the adjacent Mount Wills Granite, which has not been reliably dated. This highly fractionated, peraluminous granite is presumed to be the source of the rare-element pegmatites based on their close spatial relationship.
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Zdarska, Zdenka, and Jana Nebesarova. "Ultrastructure of the secondary osmoregulatory canals in the scolex and neck region of Silurotaenia siluri (Batsch, 1786) (Cestoda: Proteocephalidae)." Folia Parasitologica 53, no. 1 (March 1, 2006): 73–75. http://dx.doi.org/10.14411/fp.2006.008.
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Savidge, Rodney Arthur. "Learning from the past – the origin of wood." Forestry Chronicle 84, no. 4 (August 1, 2008): 498–503. http://dx.doi.org/10.5558/tfc84498-4.
Повний текст джерелаАнотація:
Trees were on Earth 394 million years ago (394 Ma) as spore-producing Archaeopteris progymnosperms having largediameter trunks of secondary xylem (morphotype Callixyon) produced by vascular cambium. Plants of smaller stature with primary xylem cores were present in Late Silurian (416 Ma), but they lacked cambium and it remains unclear how and when the first trees evolved. Progymnosperms faded and gymnosperms arose during Middle Carboniferous, and conifers, ginkgos, cycads, tree ferns and cordaites were well established by the Carboniferous–Permian transition (299 Ma). Woods of the earliest conifers were different from those of today, and not until Late Triassic (220 Ma) did any begin producing secondary xylem similar to modern woods, the xylem phenotypes of Cupressaceae and Araucariaceae emerging much earlier than those of Pinaceae and flowering plants. Conifers have persisted and done relatively well despite major extinction events, severe climate change, insectivory, herbivory and microbial activity, all of which were in effect before as well as during the appearance of trees on Earth. Approximately 600 conifer species continue to exist, and the survivors presumably possess the physiological fitness needed to adapt to an ever-changing biosphere. However, this is speculative because their physiology remains less than well understood. Forestry interventions such as planting one species to the exclusion of others have the potential to exacerbate as well as sustain the ongoing existence of our remaining conifers. Key words: bordered pit, cambium, cell biology, cellulose, evolution, lignin, paleobotany, protoplasmic autolysis, secondary growth, wood formation, xylogenesis
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Morrison, M. A., G. L. Hendry, and P. T. Leat. "Regional and tectonic implications of parallel Caledonian and Permo-Carboniferous lamprophyre dyke swarms from Lismore, Ardgour." Transactions of the Royal Society of Edinburgh: Earth Sciences 77, no. 4 (1987): 279–88. http://dx.doi.org/10.1017/s0263593300023178.
Повний текст джерелаАнотація:
ABSTRACTGeochemical data are presented for 166 minor intrusions collected across the axis of the Ardgour swarm in the Isle of Lismore. The intrusions can be divided into: an alkali basalt-camptonite-monchiquite group resembling other Scottish Permo-Carboniferous dykes; a group of calc-alkaline (shoshonitic) lamprophyres, diorites and porphyrites with affinities to the late Silurian-early Devonian appinite suite of Scotland; and Tertiary dolerites. The different groups cannot be unambiguously distinguished in the field and secondary alteration precludes petrographic division in many cases. The data indicate that Caledonian and Permo-Carboniferous lamprophyres have probably been confused in previous accounts of dyke distributions in the region. In Lismore the two groups have identical azimuths but the Caledonian intrusions appear to have a greater aggregate volume. The implications for tectonic and regional models of the area are discussed.
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Esanullah, Yosamin, Japan Trivedi, Benedicta Nwani, and Madison Barth. "Optimal Zwitterionic Surfactant Slug for an Improved Oil Recovery in Oil Wet Carbonate Rocks - Silurian Dolomite." Alberta Academic Review 2, no. 2 (September 10, 2019): 27–28. http://dx.doi.org/10.29173/aar40.
Повний текст джерелаАнотація:
The increase in energy demand has led to extensive research and development on economically, environmentally and technically feasible ways of improving the ever-growing energy demand. A common derivative of energy is from hydrocarbons, specifically oil. The process of oil recovery can be divided into primary, secondary, and tertiary recovery (also known as enhanced oil recovery). Once the internal pressure of a reservoir has depleted enough during primary and secondary recovery, more advanced techniques in enhanced oil recovery mechanisms are used to recover 50-80% of oil in the reservoir. Tertiary recovery includes the use of surfactants to reduce interfacial tension (IFT) or alter wettability. In this work, a zwitter ionic surfactant at two different concentrations is evaluated for its ability to reduce the interfacial tension between oil and water, as well as altering wettability in silurian dolomite. To achieve this, fluid-fluid analysis was done by a compatibility test, phase behavior test and interfacial tension measurements. Rock-fluid analysis was also completed by means of floatation test, carried out with carbonate rock particles to analyze the surfactant’s ability to alter wettability. Solution pH measurements were taken to validate the qualitative floatation test results. Results show that the surfactant, chembetaine C surfactant, is compatible with all ranges of salinities investigated, though was not able to produce a winsor type III micro-emulsion. The results of the interfacial tension measurements are in line with the phase behavior test, as none of the measurements were at ultra-low values. Surfactant retention is likely to occur with the analyzed zwitterionic surfactant based on the fluid-fluid analysis. Qualitative results from the floatation test show that the wettability of the carbonate rock particles cannot be significantly altered to more water-wet conditions. The pH of the solution remains at alkaline values, which can be beneficial in enhanced oil recovery in producing soap in situ, also known as saponification. Overall, tests conclude that this zwitterionic surfactant at 1% concentration would be most effective at 10,000 ppm salinity brine, though overall is not suitable for chemically enhanced oil recovery.
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Jemth, Per, Elin Karlsson, Beat Vögeli, Brenda Guzovsky, Eva Andersson, Greta Hultqvist, Jakob Dogan, Peter Güntert, Roland Riek, and Celestine N. Chi. "Structure and dynamics conspire in the evolution of affinity between intrinsically disordered proteins." Science Advances 4, no. 10 (October 2018): eaau4130. http://dx.doi.org/10.1126/sciadv.aau4130.
Повний текст джерелаАнотація:
In every established species, protein-protein interactions have evolved such that they are fit for purpose. However, the molecular details of the evolution of new protein-protein interactions are poorly understood. We have used nuclear magnetic resonance spectroscopy to investigate the changes in structure and dynamics during the evolution of a protein-protein interaction involving the intrinsically disordered CREBBP (CREB-binding protein) interaction domain (CID) and nuclear coactivator binding domain (NCBD) from the transcriptional coregulators NCOA (nuclear receptor coactivator) and CREBBP/p300, respectively. The most ancient low-affinity “Cambrian-like” [540 to 600 million years (Ma) ago] CID/NCBD complex contained less secondary structure and was more dynamic than the complexes from an evolutionarily younger “Ordovician-Silurian” fish ancestor (ca. 440 Ma ago) and extant human. The most ancient Cambrian-like CID/NCBD complex lacked one helix and several interdomain interactions, resulting in a larger solvent-accessible surface area. Furthermore, the most ancient complex had a high degree of millisecond-to-microsecond dynamics distributed along the entire sequences of both CID and NCBD. These motions were reduced in the Ordovician-Silurian CID/NCBD complex and further redistributed in the extant human CID/NCBD complex. Isothermal calorimetry experiments show that complex formation is enthalpically favorable and that affinity is modulated by a largely unfavorable entropic contribution to binding. Our data demonstrate how changes in structure and motion conspire to shape affinity during the evolution of a protein-protein complex and provide direct evidence for the role of structural, dynamic, and frustrational plasticity in the evolution of interactions between intrinsically disordered proteins.
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Geert, Konert, Abdulkader M. Afifi, Sa’id A. Al-Hajri, and Henk J. Droste. "Paleozoic Stratigraphy and Hydrocarbon Habitat of the Arabian Plate." GeoArabia 6, no. 3 (July 1, 2001): 407–42. http://dx.doi.org/10.2113/geoarabia0603407.
Повний текст джерелаАнотація:
ABSTRACT The Paleozoic section became prospective during the early 1970s when the enormous gas reserves in the Permian Khuff reservoirs were delineated in the Gulf and Zagros regions, and oil was discovered in Oman. Since then, frontier exploration has targeted the Paleozoic System throughout the Middle East, driven by various economic considerations. The Paleozoic sequences were essentially deposited in continental to deep marine clastic environments at the Gondwana continental margin. Carbonates only became dominant in the Late Permian. The sediments were deposited in arid to glacial settings, reflecting the drift of the region from equatorial to high southern latitudes and back. Following late Precambrian rifting that formed salt basins in Oman and the Arabian Gulf region, the Cambrian-Devonian sequences were deposited on a peneplained continental platform. The entire region was affected by the Hercynian Orogeny, which climaxed during the Carboniferous. The orogeny manifested itself in a change in basin geometry, inversion tectonics, regional uplift and tectonism along the Zagros fault zone. This deformation caused widespread erosion of the Devonian-Carboniferous and older sections, and was probably caused by collision along the northern margin of Gondwana. The Paleozoic tectonic super cycle ended with the onset of break-up tectonics in the Permian, and the deposition of Khuff carbonates over the newly formed eastern passive margin. A major Paleozoic petroleum system embraces reservoir seal pairs spanning the Silurian to Permian sequences. Hydrocarbons occur in a variety of traps, and are sourced by the Silurian ‘hot shale’. A second petroleum system occurs in areas charged from upper Precambrian source rocks in the salt basins. Hydrocarbon expulsion estimates, taking into account secondary migration losses, suggest that some one trillion barrels of oil equivalent (BOE) may have been trapped from the Silurian ‘hot shale’ alone. However, the long and complex hydrocarbon geological evolution of the basin, combined with low acoustic contrasts between target rock units, difficult surface conditions, tight reservoirs, and deep subsurface environments, posed significant challenges to exploration and development. The critical success factor is the continuous innovative effort of earth scientists and subsurface engineers to find integrated technology solutions, that will render the Paleozoic plays economically viable.
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Friedman, William E., and Martha E. Cook. "The origin and early evolution of tracheids in vascular plants: integration of palaeobotanical and neobotanical data." Philosophical Transactions of the Royal Society of London. Series B: Biological Sciences 355, no. 1398 (June 29, 2000): 857–68. http://dx.doi.org/10.1098/rstb.2000.0620.
Повний текст джерелаАнотація:
Although there is clear evidence for the establishment of terrestrial plant life by the end of the Ordovician, the fossil record indicates that land plants remained extremely small and structurally simple until the Late Silurian. Among the events associated with this first major radiation of land plants is the evolution of tracheids, complex water–conducting cells defined by the presence of lignified secondary cell wall thickenings. Recent palaeobotanical analyses indicate that Early Devonian tracheids appear to possess secondary cell wall thickenings composed of two distinct layers: a degradation–prone layer adjacent to the primary cell wall and a degradation–resistant (possibly lignified) layer next to the cell lumen. In order to understand better the early evolution of tracheids, developmental and comparative studies of key basal (and potentially plesiomorphic) extant vascular plants have been initiated. Ultra–structural analysis and enzyme degradation studies of wall structure (to approximate diagenetic alterations of fossil tracheid structure) have been conducted on basal members of each of the two major clades of extant vascular plants: Huperzia (Lycophytina) and Equisetum (Euphyllophytina). This research demonstrates that secondary cell walls of extant basal vascular plants include a degradation–prone layer (‘template layer’) and a degradation–resistant layer (‘resistant layer’). This pattern of secondary cell wall formation in the water–conducting cells of extant vascular plants matches the pattern of wall thickenings in the tracheids of early fossil vascular plants and provides a key evolutionary link between tracheids of living vascular plants and those of their earliest fossil ancestors. Further studies of tracheid development and structure among basal extant vascular plants will lead to a more precise reconstruction of the early evolution of water–conducting tissues in land plants, and will add to the current limited knowledge of spatial, temporal and cytochemical aspects of cell wall formation in tracheary elements of vascular plants.
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Cardoso, Tereza Regina Machado, and Maria Antonieta da Conceição Rodrigues. ""Complexo" Veryhachium: acritarcos indicativos do Siluriano?"." Anuário do Instituto de Geociências 28, no. 1 (June 1, 2005): 143–57. http://dx.doi.org/10.11137/2005_1_143-157.
Повний текст джерелаАнотація:
Acritarchs are known to be related to cysts of marine microphytoplankton, and are reliable indicators of marine paleoenvironments. The acritarch genus Veryhachium was erected by Deunff (1954) to encompass an entire plexus of microfossils first recorded in Paleozoic strata of England and France. It includes a variety of organic-walled microphytoplanktonic organisms consisting of a smooth or granulated, hollow vesicle with triangular to polygonal shape. The vesicle is provided with up to eight, tapered and long, often bent, unbranched processes, which are hollow and present either smooth or granulated walls. The oldest known representatives of Veryhachium are from the Upper Cambrian, but the genus becomes most abundant and diversified in succeeding Paleozoic intervals. By contrast, post-Paleozoic records include only two species from the Cretaceous, and three Tertiary species which Stancliffe & Sarjeant (1994) regard as anomalous forms. The occurrence of Veryhachium in recent sediments of Bolivia has been attributed by several authors to the reworking of Paleozoic strata. Due to the long stratigraphic range of most of its species, the genus has generally played a secondary role in biostratigraphic zonations. Our palynological study of the Trombetas Group (Amazonas basin, northern Brazil), based on numerous outcrops and Eletronorte shallow core-drills, together with core samples of a single Petrobras well, has recorded such Silurian species as Veryhachium owensii, V. oklahomense, V. pertonense, V. longispinosu, V. rhomboidium and V. lairdii. They occur together with more age-diagnostic Silurian species belonging to the genera Deunffia and Domasia. The diversity of Veryhachium in the Trombetas Group highlights not only its importance as a paleoenvironmental indicator, but also its usefulness in characterizing regional palynomorphs assemblages in Paleozoic basins of Western Gondwana.
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Prytchin, M. E., E. I. Soroka, and V. N. Puchkov. "Novel U-Pb isotopic zircon data on the rhyolite of the Saf’yanovskoe Cu-Zn deposit (Middle Urals)." LITHOSPHERE (Russia) 21, no. 6 (December 29, 2021): 884–93. http://dx.doi.org/10.24930/1681-9004-2021-21-6-884-893.
Повний текст джерелаАнотація:
Research subject. Zircons from the Saf’yanovskoe Cu-Zn deposit rhyolite (Middle Urals). For the first time, zircon U-Pb dating for the rhyolite of the ore-bearing volcanic-sedimentary rocks of the Saf’yanovskoe deposit was performed. The volcanites are characterized by an andesite-rhyodacite composition and are localized at the southern edge of the Rezhevskaya structural-formation zone (SFZ) of the Eastern Ural megazone. A number of publications assign these rocks either to the basalt-rhyolite formation of the Middle Devonian, or to the basalt-andesite-dacite-rhyolite formation of the Lower-Middle Devonian.Aim. To estimate the age of the ore-bearing volcanic rocks under study using the U-Pb SHRIMP-II isotop ic system of zircon from the rhyolite of the eastern side of the Saf’yanovskoe deposit. By its chemical composition, the rhyolite belongs to the silicic varieties of subvolcanic rocks. Methods and results. The U-Pb isotopic system of zircon was studied by 5-collector mass-spectrometer of high precision and emission of the secondary ions SHRIMP-II (ASI, Australia) in the VSЕGEI Institute. U-Pb relations were investigated by a procedure developed by I.S. Williams. The U-Pb data obtained based on 13 zircon grains showed the age of 422.8 ± 3.7 Ma. Conclusions. The U-Pb dating of zircon obtained previously from the lens-shaped andesite bodies of the western side of the Safyanovskoe deposit gave the age of 422.8 Ma, which corresponds to the Przydoli series epoch of the Upper Silurian. We established that, among the volcanic rocks of the Saf’yanovskoe deposit, the effusive formations of the Upper Silurian are present.
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Farquhar, R. M., S. J. Haynes, M. A. Mostaghel, A. G. Tworo, R. W. Macqueen, and I. R. Fletcher. "Lead isotope ratios in Niagara Escarpment rocks and galenas: implications for primary and secondary sulphide deposition." Canadian Journal of Earth Sciences 24, no. 8 (August 1, 1987): 1625–33. http://dx.doi.org/10.1139/e87-156.
Повний текст джерелаАнотація:
Galenas occurring in vugs and veins in the dolomites of the Eramosa, Goat Island, and Gasport members of the Middle Silurian Lockport Formation in the Niagara Escarpment have a small but significant range in lead isotopic composition. These differences are recorded in specimens from exposures in the Niagara Gorge in the east to the Guelph quarry, 100 km to the northwest. The galena isotopic data fit linear trends on 207Pb/204Pb–206Pb/204Pb and 208Pb/204Pb–206Pb/204Pb plots within experimental error. The most radiogenic ratios are anomalous, giving model ages (based on the growth curves of Zartman and Doe) up to 200 Ma younger than the most likely age of primary deposition of ~ 300 Ma. Sulphides currently being deposited from springs at the floor of the Vinemount quarry have a lead isotopic composition similar to that of some of the galena in the overlying dolomites. Rocks from several of the formations exposed at this site contain lead only slightly more radiogenic than the most radiogenic galenas. These results are consistent with the hypothesis of Haynes and Mostaghel that the modern sulphides result from local solution and redeposition of older sulphides. Previously published isotopic ratios for lead in the potassium feldspar constituents of ~ 300 Ma plutonic intrusives in the Appalachians cluster around the least radiogenic galena ratios and suggest that the lead in the Niagara Peninsula galenas has been remobilized from rock units in the Appalachian Basin. Grenville crystalline basement rocks do not appear to have contributed significantly to this lead. A single sample of galena from the Eramosa Member, exposed in the Ebel quarry in the Michigan Basin at the northwestern extension of the escarpment, has 207Pb/204Pb and 206Pb/204Pb ratios that are substantially more radiogenic than those in any of the galenas from the Niagara region of the Appalachian Basin and a 208Pb/204Pb ratio that lies significantly below the linear distribution defined by the Niagara region data set. We tentatively interpret this difference as reflecting derivation of the lead in the two basins from different crustal blocks.
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Gunn, RH. "Shallow groundwaters in weathered volcanic, granitic and sedimentary rocks in relation to dryland salinity in southern New South Wales." Soil Research 23, no. 3 (1985): 355. http://dx.doi.org/10.1071/sr9850355.
Повний текст джерелаАнотація:
Soils affected by secondary salinization were studied in six areas on the Southern Tablelands of New South Wales. All the salt-affected areas are underlain by, or occur in close proximity to, deeply weathered volcanic, granitic and sedimentary rocks which commonly contain stores of soluble salts, dominantly sodium chloride. The chemical composition of shallow groundwaters in the areas was monitored by piezometers for periods of up to two years. Water levels in the piezometers responded rapidly to rainfall, but the ionic composition of the waters generally remained fairly uniform. All waters are dominated by sodium chloride; those with the highest contents occurred in volcanic and granitic rocks, followed by Ordovician sediments and the lowest contents were in Silurian sediments. The chlorine contents in samples of weathered rocks follow a similar sequence. Electron microprobe analyses indicate that the chlorine-bearing minerals in the unaltered rocks are principally biotite, hornblende and potassium, sodium and calcium feldspars. No salt-affected soils were found in areas underlain by unweathered rocks.
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Abu-Ali, Mahdi A., Jean-Luc L. Rudkiewicz, Jim G. McGillivray, and Françoise Behar. "Paleozoic Petroleum System of Central Saudi Arabia." GeoArabia 4, no. 3 (July 1, 1999): 321–36. http://dx.doi.org/10.2113/geoarabia0403321.
Повний текст джерелаАнотація:
ABSTRACT An integrated geochemical model was developed to reconstruct the history of expulsion, migration and entrapment of Paleozoic oil and gas in the main regional Permian Unayzah Sandstone Reservoir in Central Saudi Arabia. The model indicates that by the Late Jurassic, approximately 140 million years ago (Ma), the principal Paleozoic source rock, the Lower Silurian Qusaiba “hot” shale, was mature in the deepest hydrocarbon “kitchens”. Hydrocarbon expulsion started during the Aptian and Albian (late Early to early Middle Cretaceous, 100 to 120 Ma). Expulsion of oil and gas is linked to three geochemical events. Primary kerogen cracking led to a first episode of expulsion about 120 Ma. Secondary heavy component and oil cracking resulted in a second episode of expulsion at approximately 100 Ma. Between 20 to 10 Ma, later uplift, and the resulting pressure drop in the source rock, led to a third expulsion phase. The first two expulsion episodes were gradual, whereas the third was more rapid and related to uplift of the Arabian Arch, opening of the Red Sea and the Zagros Orogeny during the Miocene. Expulsion of oil nearly terminated after the Late Cretaceous, while gas continued to be expelled, though at a lower rate, in the Tertiary. Peak gas expulsion occurred post Early Eocene with significant gas generation from secondary cracking of oil retained in the source rock. Gas was sourced either directly from kerogen, or from secondary cracking of heavy absorbed components or non-migrated oils. The expulsion of gas coincides with oil expulsion for the first two episodes because the gas and oil formed as a single phase. As a result of Tertiary Uplift, gas separated from the oil and re-migrated in the final episode (20 to 10 Ma).
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Davis, D. W., C. N. Sutcliffe, A. M. Thibodeau, J. Spalding, D. Schneider, A. Cruden, J. Adams, A. Parmenter, M. Jensen, and Z. Zajacz. "Hydrochronology of a proposed deep geological repository for low- and intermediate-level nuclear waste in southern Ontario from U–Pb dating of secondary minerals: response to Silurian and Cretaceous events." Canadian Journal of Earth Sciences 57, no. 4 (April 2020): 464–76. http://dx.doi.org/10.1139/cjes-2019-0004.
Повний текст джерелаАнотація:
A record of fluid flow has been documented within a Paleozoic carbonate platform sequence by U–Pb dating of calcite in veins and vugs from rock core sampled through a shallowly dipping sequence of sedimentary rocks beneath the Bruce nuclear site, Ontario, Canada. Secondary calcite from >650 m deep Ordovician carbonate rocks yields a Silurian age of 434 ± 5 Ma possibly related to infiltration of seawater from overlying evaporitic basins as well as hydrothermal solutions that infiltrated from below. In contrast, near-surface Devonian rocks mostly give vein infill ages over the range of 80–100 Ma with evidence for younger infill down to 50 Ma. Vein calcite samples previously dated from surface outcrops of Ordovician carbonate exposed up to 500 km to the east yielded similar U–Pb ages. Coincidence of near-surface vein calcite ages indicates widespread vein emplacement synchronous with a change in direction of motion of the North American plate as well as possible erosional unroofing following passage of the region over the Great Meteor hotspot approximately 125 Myr ago. Deeper carbonate formations have remained apparently impermeable to post-Paleozoic disturbance despite these perturbations.
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Catlos, Elizabeth J., Darren F. Mark, Stephanie Suarez, Michael E. Brookfield, C. Giles Miller, Axel K. Schmitt, Vincent Gallagher, and Anne Kelly. "Late Silurian zircon U–Pb ages from the Ludlow and Downton bone beds, Welsh Basin, UK." Journal of the Geological Society 178, no. 1 (August 14, 2020): jgs2020–107. http://dx.doi.org/10.1144/jgs2020-107.
Повний текст джерелаАнотація:
The Ludlow Bone Bed (Welsh Basin) is a critical stratigraphic horizon and contains a rich assemblage of fish scales. Units above provide insights into the early evolution of animal and plant life. The bed has not yet been radioisotopically dated. Here, we report 207 secondary ion mass spectrometry (SIMS) ages from 102 zircon (ZrSiO4) grains from the Ludlow (n = 2) and stratigraphically higher Downton (n = 1) bone beds. SIMS ages are middle Ordovician (471.6 ± 20.7 Ma) to late Devonian (375.7 ± 14.6 Ma, 238U–206Pb, ±1σ analytical uncertainty). Cathodoluminescence images show that the youngest ages appear affected by alteration. Chemical abrasion isotope dilution thermal ionization mass spectrometry (CA-ID-TIMS) U–Pb geochronology was utilized to improve precision. Detrital zircon grains from Downton yield 424.91 ± 0.34/0.42/0.63 Ma and from Ludlow 424.85 ± 0.32/0.41/0.62 Ma (n = 5 each, 238U–206Pb, ±2σ analytical, tracer or systematic uncertainty). These ages provide a maximum deposition age. Results overlap the basal Přídolí age (423.0 ± 2.3 Ma) in its stratotype (Požáry Section, Reporyje, Prague, Czech Republic). The Ludlow Bone Bed marks the base of the local Downton Group, which has previously been correlated with the base of the Přídolí Series. The CA-ID-TIMS ages are older than those for other land arthropod-bearing sediments, such as the Cowie Harbour Fish Bed and Rhynie Chert.Supplementary material: An Excel file containing detailed information on the SIMS analyses, a figure showing calibration curves for AS3 standards sputtered over sessions 1 and 2, and a figure showing CA-ID-TIMS U–Pb age data (concordia and weighted mean plots) are available at https://doi.org/10.6084/m9.figshare.c.5087031
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Zhang, Wenhui, Liyuan Wang, Xupeng Lv, Xiaomin Li, Shuaiqi Yan, and Juntao Nie. "Origin of Mesozoic Porphyritic Rocks and Regional Magmatic Evolution in the Zijinshan Ore Field of Fujian Province, China: Hf-O Isotope Characteristics of Magmatic Zircons." Minerals 10, no. 12 (December 20, 2020): 1143. http://dx.doi.org/10.3390/min10121143.
Повний текст джерелаАнотація:
Mesozoic porphyritic rocks from the Zijinshan area, southwestern Fujian Province, China, are andesitic to rhyolitic in composition. The whole-rock SiO2 contents of these rocks are between 62.5% and 78.1%. Magmatic zircon from the Mesozoic porphyritic rocks was determined via secondary-ionization mass spectrometry (SIMS) for the U-Pb age and Hf and O isotopes. The zircon U-Pb ages could be mainly divided into three age groups: Group 1: ~138.8 Ma; Group 2: 109.2~107.4 Ma; and Group 3: 99.7~98.2 Ma. The εHf(t) and δ18O values of the porphyritic zircons showed that the porphyritic rocks in Group 2 were more affected by mantle-derived magma. Combined with previous research results, the medium-acidic magmatism in the southwestern Fujian Province can be divided into eight periods: Paleoproterozoic, Mesoproterozoic, Middle Neoproterozoic, Silurian to Lower Devonian, Permian to Triassic, Middle Jurassic to early Lower Cretaceous, late Lower Cretaceous, and late Lower Cretaceous to early Upper Cretaceous. The Paleoproterozoic crust was the predominant magmatic source for the subsequent Mesoproterozoic to Jurassic magmatism, but the only melts that were closely related to mineralization were derived from partial melting of the Mesoproterozoic crust and a more depleted upper mantle.
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Drake, Henrik, Nick M. W. Roberts, and Martin J. Whitehouse. "Geochronology and Stable Isotope Analysis of Fracture-Fill and Karst Mineralization Reveal Sub-Surface Paleo-Fluid Flow and Microbial Activity of the COSC-1 Borehole, Scandinavian Caledonides." Geosciences 10, no. 2 (February 3, 2020): 56. http://dx.doi.org/10.3390/geosciences10020056.
Повний текст джерелаАнотація:
The deep biosphere hosted in fractured rocks within the upper continental crust is one of the least understood and studied ecological realms on Earth. Scarce knowledge of ancient life and paleo-fluid flow within this realm is owing to the lack of deep drilling into the crust. Here we apply microscale high spatial-resolution analytical techniques to fine-grained secondary minerals in a deep borehole (COSC-1) drilled into the Silurian-Devonian Scandinavian Caledonide mountain range in central Sweden. The aim is to detect and date signs of ancient microbial activity and low-temperature fluid circulation in micro-karsts (foliation-parallel dissolution cavities in the rock) and fractures at depth in the nappe system. Vein carbonates sampled at 684 to 2210 m show a decreased C isotope variability at depths below 1050 m; likely due to decreased influence of organic-C at great depth. Micro-karsts at 122–178 m depth feature at least two generations of secondary calcite and pyrite growth in the voids as shown by secondary ion mass spectrometry analytical transects within individual grains. The younger of these two precipitation phases shows 34S-depleted δ34Spyrite values (−19.8 ± 1.6‰ vs. Vienna-Canyon Diablo Troilite (V-CDT)) suggesting microbial sulfate reduction in situ. The calcite of this late phase can be distinguished from the older calcite by higher δ18Ocalcite values that correspond to precipitation from ambient meteoric water. The late stage calcite gave two separate laser ablation inductively coupled mass spectrometry-derived U-Pb ages (9.6 ± 1.3 Ma and 2.5 ± 0.2 Ma), marking a minimum age for widespread micro-karst formation within the nappe. Several stages of fluid flow and mineral precipitation followed karst formation; with related bacterial activity as late as the Neogene-Quaternary; in structures presently water conducting. The results show that our combined high spatial-resolution stable isotope and geochronology approach is suitable for characterizing paleo-fluid flow in micro-karst; in this case, of the crystalline crust comprising orogenic nappe units.
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Ryasnoy, A. A., and V. Yu Prokofyev. "CONDITIONS FOR THE FORMATION OF SECONDARY LOWER SILURIAN DOLOMITES AND PECULIARITIES OF THE DISTRIBUTION OF VOID SPACE IN THEM (NORTH-EAST OF THE TUNGUSKA SYNECLISE)." Geology and mineral resources of Siberia, no. 2 (2021): 24–45. http://dx.doi.org/10.20403/2078-0575-2021-2-24-45.
Повний текст джерелаАнотація:
New materials on the microfauna and lithology of the Kuznetsovskaya and Sedelnikovskaya Formations of the same horizons are presented. These data have allowed us to clarify the age of the boundary Turonian–Coniacian deposits of the Middle and Upper series of the Cretaceous system. Based on a comparison with geological units of marginal regions, where finds of secretion-calcareous foraminiferal shells are known, the Сoniaсian age of the Sedelnikovskaya Formation was established. The time interval of the regional break between the Turonian and Coniacian stages was determined, apparently, corresponding to the Early Сoniacian. The studied sections of the northern region are characterized by the absence of foraminiferal assemblage known in the sections of Kamyshlovskiye wells of the Omsk depression and in some places of the Trans-Urals.