Journal articles: 'Lower Silurian'

1

Yin, T. H., and A. T. Mu. "Lower Silurian Graptolites from Tungtzu*." Bulletin of the Geological Society of China 25, no. 1 (June 1, 2009): 211–19. http://dx.doi.org/10.1111/j.1755-6724.1945.mp25001008.x.

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McCANN, TOMMY. "Lower Palaeozoic evolution of the northeast German Basin/Baltica borderland." Geological Magazine 135, no. 1 (January 1998): 129–42. http://dx.doi.org/10.1017/s0016756897007863.

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The Vendian–Silurian succession from a series of boreholes in northeast Germany has been petrographically and geochemically investigated. Evidence suggests that the more northerly Vendian and Cambrian succession was deposited on a craton which became increasingly unstable in Ordovician times. Similarly, the Ordovician-age succession deposited in the Rügen area indicates a strongly active continental margin tectonic setting for the same period. By Silurian times the region was once more relatively tectonically quiescent. Although complete closure of the Tornquist Sea was not complete until latest Silurian times, the major changes in tectonic regime in the Eastern Avalonia/Baltica area recorded from the Ordovician suggest that a significant degree of closure occurred during this time.

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Yi, Wang, Hao Shou-Gang, Chen Xu, Rong Jia-Yu, Li Guo-Xiang, Liu Jianbo, and Xu Honghe. "Sphenothallus from the Lower Silurian of China." Journal of Paleontology 77, no. 3 (May 2003): 583–88. http://dx.doi.org/10.1017/s0022336000044267.

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The genus Sphenothallus was erected by Hall (1847, p. 261), who originally considered it a land plant. Sphenothallus was later classified as a marine invertebrate. Moore and Harrington (1956, p. F65) regarded Sphenothallus as a hydrozoan or scyphozoan. Van Iten et al. (1992, p. 139) supported Moore and Harrington's idea, and argued that it displays a close relationship to conularids (also see Li, 2000, p. 91). However, Mason and Yochelson (1985, p. 93–94) suggested that Sphenothallus is an annelid or “worm” (also see Fauchald et al., 1986, p. 64; Feldmann et al., 1986, p. 344–345; Choi, 1990, p. 403; Bartels et al., 1998, p. 114–117). The exact phylogenetic affinity of Sphenothallus is still debated.

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Ausich, William I. "Brassfield Compsocrinina (Lower Silurian crinoids) from Ohio." Journal of Paleontology 61, no. 3 (May 1987): 552–62. http://dx.doi.org/10.1017/s0022336000028717.

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Four compsocrinine camerate crinoids are described from the Lower Silurian Brassfield Formation of southwestern Ohio. These late early or early middle Llandoverian crinoids are assigned to the Periechocrinidae and include Tirocrinus trochos n. gen. and sp., Ibanocrinus petalos n. gen. and sp., Acacocrinus anebos n. sp., and the taxon Dimerocrinites? vagans Foerste, herein referred to periechocrinid incertae sedis.These Brassfield forms are the oldest known members of the Periechocrinacea and Periechocrinidae. Diagnoses of these supergeneric concepts are broadened to include the morphologic variability embodied within the Brassfield forms but not otherwise present in later periechocrinaceans.

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YI, WANG, HAO SHOU-GANG, CHEN XU, RONG JIA-YU, LI GUO-XIANG, LIU JIANBO, and XU HONGHE. "SPHENOTHALLUS FROM THE LOWER SILURIAN OF CHINA." Journal of Paleontology 77, no. 3 (May 2003): 583–88. http://dx.doi.org/10.1666/0022-3360(2003)077<0583:sftlso>2.0.co;2.

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Eriksson, Mats. "Lower Silurian polychaetaspid polychaetes from Gotland, Sweden." GFF 119, no. 3 (September 1997): 213–30. http://dx.doi.org/10.1080/11035899709546480.

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7

Krstic, Branislav, Ljubinka Maslarevic, and Milan Sudar. "On the graptolite schist's formation, Silurian-Lower Devonian, in the Carpatho-Balkanides of eastern Serbia." Annales g?ologiques de la Peninsule balkanique, no. 66 (2005): 1–8. http://dx.doi.org/10.2298/gabp0566001k.

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The fabric of the Silurian and a part of the Lower Devonian in the Carpatho-Balkanides of eastern Serbia, i.e. in two large geotectonic units, the Kucaj Unit (Getic) and the Luznica Unit (West Kraishte), is reviewed in this paper. Silurian sediments of the Serbian part of the Carpatho-Balkanides are made of the Graptolite Schists Formation, from the lower part of the acuminatus Zone at the Ordovician-Silurian boundary to the transgrediens Zone at the Silurian-Devonian boundary. The presence of all parts of the Silurian is proved on the basis of graptolite faunas: Llandovery (Rhuddnanian, Aeronian, Telychian), Wenlock (Sheinwoodian, Homerian), Ludlow (Gorstian, Ludfordian) and Pridoli. Two Lower Devonian (Lochkovian) zones (uniformis and hercynicus), with which the deposition of the Graptolite Schists Formation ended in eastern Serbia is also described. Data on the geochemical characteristics of the Graptolite Schists Formation are presented as well.

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Higgins, A. K., J. R. Ineson, J. S. Peel, F. Surlyk, and M. Sønderholm. "Lower Palaeozoic Franklinian Basin of North Greenland." Bulletin Grønlands Geologiske Undersøgelse 160 (January 1, 1991): 71–139. http://dx.doi.org/10.34194/bullggu.v160.6714.

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The Franklinian Basin extends from the Canadian Arctic Islands to eastern North Greenland, a distance of approximately 2000 km. In the North Greenland segment about 8 km of Lower Palaeozoic strata are well exposed and permit the recognition of 7 stages in the evolution of the basin. With the exception of the first stage of basin initiation, which occurred dose to the Precambrian-Cambrian boundary, each stage is differentiated into a southern shelf and slope, and a northern deep-water trough. The position of the boundary between the shelf and trough was probably controlled by deep seated normal faults and, with time, the basin expanded southwards leading to a final foundering of the shelf areas during the Silurian. The 7 stages in the evolution of the Franklinian Basin in North Greenland are: 1, Late Proterozoic? - Early Cambrian shelf (basin initiation); 2, Early Cambrian carbonate platform and incipient trough; 3, Early Cambrian siliciclastic shelf and turbidite trough; 4, Late Early Cambrian - Middle Ordovician carbonate shelf and starved trough; 5, Middle Ordovician - Early Silurian aggradational carbonate platform, starved slope and trough; 6, Early Silurian ramp and rimmed shelf, and turbidite trough; 7, Early - Late Silurian drowning of the platform. Basin evolution and sedimentation patterns in the eastem part of the Franklinian Basin were strongly influenced by the dosure of the lapetus Ocean and Caledonian orogenic uplift in eastern North Greenland. The Franklinian Basin in North Greenland was finally closed in Devonian - Early Carboniferous times, resulting in strong deformation of the northern part of the Franklinian trough sequence during the Ellesmerian Orogeny.

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9

Lin, Tuo, Jin Chuan Zhang, Bo Li, Wei He, and Xuan Tang. "Accumulation Conditions and Gas Content Characteristics of the Lower Silurian in Northwestern Hunan, China." Advanced Materials Research 868 (December 2013): 192–95. http://dx.doi.org/10.4028/www.scientific.net/amr.868.192.

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The Lower Silurian marine shale is widely distributed in Northwestern Hunan and features in a large thickness of dark shale showed at outcrops. However, the accumulation conditions and gas content is unknown. The sedimentary facies, thickness and distribution, organic matter types and content, maturity, reservoir properties and gas content of the Lower Silurian black shale in Northwestern Hunan were investigated by field observation, sampling and experimental analysis. The results show that the black shales sedimentary environment is deep water continental shelf, with featured in abundant fossil. The burial depth of the Lower Silurian black shale is 0-3000 m, and its thickness is 10-40m while the average TOC is 1.0% and average Ro is 2.9%. For the disadvantaged sedimentary facies and shallow depth, the maximum gas content of the Lower Silurian black shale from well site desorption test is 0.59m3/t only, but the result of isothermal adsorption simulate test show that the Lower Silurian black shale have a good adsorption capacity, and can generate a large number of shale gas in Northwestern Hunan where better deposition conditions and suitable depth exist in.

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10

Bassett, M. G., B. J. Bluck, R. Cave, C. H. Holland, and J. D. Lawson. "Silurian." Geological Society, London, Memoirs 13, no. 1 (1992): 17–56. http://dx.doi.org/10.1144/gsl.mem.1992.013.01.07.

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AbstractThe history of establishment of the Silurian System (and hence of the Silurian Period) and its principal divisions has been reviewed by Cocks et al. (1971) and Holland (1984, 1989a). The System itself, three of the four Series into which it is divided, and the Stages within these three, are all based upon localities in Britain. The names of all the divisions shown in Fig. I have been ratified by the International Union of Geological Sciences. The two major divisions, Lower Silurian and Upper Silurian, remain informal, but they are useful when degree of precision in correlation does not allow reference at the level of Series (Holland 1989a). The boundary stratotypes are all described in Holland & Bassett (1989). Graptolite Biozones have proved especially useful for international correlation in the Silurian and the sequence of Biozones used in Britain is shown in Fig. 1. Correlation of the Biozones wth the global Standard Series and Stages is shown approximately, but is not known with exactitude in all cases.Geodetically the position of the British Isles in the Silurian remained astride the 25°S latitude, a position it had reached in the later Ordovician (Briden et al. 1973); movementwas confined to rotation. During this time the south magnetic pole wandered, in terms of present geography, from near to southwest Africa, to the Horn of Africa in early Silurian times, then back along the equator to west Africa/Brazil at the end of the Silurian.The Llandovery Epoch was chracterized by marine transgressions. Thus in

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11

Wilson, Reginald A., and Sandra L. Kamo. "The Salinic Orogeny in northern New Brunswick: geochronological constraints and implications for Silurian stratigraphic nomenclature1This article is one of a series of papers published in this CJES Special Issue: In honour of Ward Neale on the theme of Appalachian and Grenvillian geology." Canadian Journal of Earth Sciences 49, no. 1 (January 2012): 222–38. http://dx.doi.org/10.1139/e11-041.

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The Salinic Orogeny is defined to encompass tectonic interactions that affect all elements of Ganderia involved in the closure of the Tetagouche–Exploits back-arc basin between the Late Ordovician and Early Devonian. Hence, the D1 and D2 deformations in the Miramichi Highlands and Elmtree Inlier of northern New Brunswick are Salinic events, and onlap of Lower Silurian rocks onto exhumed parts of the Brunswick Subduction Complex represents the earliest (Salinic A) of three Silurian unconformities in the region. Upper Ordovician to Lower Silurian rocks of the Matapédia successor basin contain widespread evidence of Middle Silurian tectonism (e.g., disconformities, angular unconformities, and fold interference patterns) created by Devonian overprinting of Silurian folds lacking axial planar cleavage (Salinic B). Recent U–Pb radioisotopic dating of chemically abraded zircon from rhyolite just above the Salinic B unconformity has yielded an age of 422.3 ± 0.3 Ma; combined with late Early Silurian fossil ages just below the unconformity, this indicates a ca. 5 million year Middle Silurian hiatus. Finally, Upper Silurian (Ludfordian) rocks are locally disconformably overlain by polymictic conglomerates that form the base of the Devonian section (Salinic C). All Silurian rocks in northeastern New Brunswick have historically been included in the Chaleurs Group; however, unconformities and local stratigraphic variations (especially compared with the type locality) support the introduction of new higher rank names in New Brunswick. Hence, the Quinn Point Group is introduced to incorporate Lower Silurian rocks, the Petit Rocher Group to include Upper Silurian sedimentary rocks in the Nigadoo River Syncline, and the Dickie Cove Group for Upper Silurian volcanic rocks in the Charlo – Jacquet River area. Upper Silurian rocks west of Campbellton that are contiguous with the Chaleurs Group in Quebec, will remain part of the Chaleurs Group.

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12

D’hulst, Alan, Georges Beaudoin, Michel Malo, Marc Constantin, and Pierre Pilote. "Geochemistry of Sainte-Marguerite volcanic rocks: implications for the evolution of Silurian–Devonian volcanism in the Gaspé Peninsula." Canadian Journal of Earth Sciences 45, no. 1 (January 1, 2008): 15–29. http://dx.doi.org/10.1139/e07-012.

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The Lower Devonian Sainte-Marguerite volcanic rocks are part of a Silurian–Devonian volcanic sequence deposited between the Taconian and Acadian orogenies in the Gaspé Peninsula, Quebec, Canada. The Sainte-Marguerite unit includes basaltic and dacitic lava flows with calc-alkaline and volcanic-arc affinities. Such affinities are also recorded by the trace-element signature in Lower Silurian and most Lower Devonian volcanic units of the Gaspé Peninsula. However, most of the other Silurian–Devonian volcanic rocks occurring in the Gaspé Peninsula have been previously interpreted to have erupted in an intracontinental setting. A back-arc setting for the Gaspé Peninsula between the Taconian and Acadian orogenies could account for these subduction volcanic-arc signatures, though a metasomatized lithospheric mantle magma source, unrelated to subduction, cannot be excluded. Lower Silurian and Lower Devonian volcanic rocks in the central part of the Gaspé Peninsula show an arc affinity, whereas Upper Silurian and Lower to Middle Devonian volcanic rocks, located in the south and north of the Gaspé Peninsula, respectively, show a within-plate affinity. The Lower Devonian Archibald Settlement and Boutet volcanic rocks of the southern and northern Gaspé Peninsula, respectively, show a trend toward a within-plate affinity. This suggests that within-plate volcanism migrated from south to north through time in an evolving back-arc environment and that the subduction signature of Lower Silurian and Lower Devonian rocks results from a source that melted only under the central part of the Gaspé Peninsula.

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13

Liu, Weiwei, Kun Zhang, Zhenxue Jiang, Shu Jiang, Yan Song, Chengzao Jia, Yizhou Huang, et al. "Effect of the hydrothermal activity in the Lower Yangtze region on marine shale gas enrichment: A case study of Lower Cambrian and Upper Ordovician-Lower Silurian shales in Jiangye-1 well." Open Geosciences 10, no. 1 (October 25, 2018): 582–92. http://dx.doi.org/10.1515/geo-2018-0046.

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Abstract Finding favorable sites for the exploration of shale gas, is still one of the important areas of research that needs immediate attention. The content of organic matter in shale plays a crucial role in the hydrocarbon generation potential, reservoir space and gas-bearing capacity of shales. Therefore, studying the sedimentary environment of organic shale can provide a scientific basis for locating favorable exploration areas for shale gas. The article takes the Lower Cambrian and the Upper Ordovician-Lower Silurian shales in the Yangtze region as the research object and selects representative wells to quantitatively calculate the existence of excess silicon in shale siliceous minerals and the content of excess silicon. Then, the origin of excess silicon can be clarified by the Al, Fe and Mn elemental analysis. Finally, the sedimentary organic matter enrichment mechanism is analyzed from water oxidation-reduction environments and biological productivity. The results of the study show that the excess silicon in the Lower Cambrian and Upper Ordovician-Lower Silurian shales in the Lower Yangtze region is of hydrothermal origin. The hydrothermal activity improves biological fertility on the one hand; whereas on the other hand, it can enhance the reducing capacity of the bottom water conducive for the preservation of organic matter thereby enriching the sedimentary organic matter. The place near the junction of Yangtze plate and Cathaysian plate, where hydrothermal activities were more intense, provided favorable loci for shale gas exploration in the Lower Yangtze region. It was observed that, since the hydrothermal activity was stronger in the Early Cambrian than in the Late Ordovician-Early Silurian times, the total organic carbon (TOC) content of the Lower Cambrian shale was higher than that of the Upper Ordovician-Lower Silurian shales.

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COCKS, L. ROBIN M., RICHARD A. FORTEY, and ADRIAN W. A. RUSHTON. "Correlation for the Lower Palaeozoic." Geological Magazine 147, no. 2 (September 14, 2009): 171–80. http://dx.doi.org/10.1017/s0016756809990562.

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AbstractThe global correlation standards now agreed for the Ordovician and Silurian systems, and partly so for the Cambrian System, are summarized. Correlation of the international series and stages with the traditional and revised British series and stages is reviewed, as well as with those in North America (Laurentia).

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15

Šliaupa, Saulius, Jurga Lazauskienė, Saulius Lozovskis, and Rasa Šliaupienė. "Distribution of organic matter and evaluation of brittleness index of the Lower Silurian shales of west Lithuania based on interpretation of well logs." Baltica 33, no. 2 (December 28, 2020): 146–65. http://dx.doi.org/10.5200/baltica.2020.2.3.

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There is little known of the basic parameters of the Lower Silurian graptolitic black shales that are considered the most prospective unconventional gas reservoir in west Lithuania, situated in the deep central part of the Baltic sedimentary basin. Hundreds of deep oil exploration wells have been drilled in the area of interest, owing to extensive exploration of oil fields. The lower and middle Llandovery interval was mainly drilled with coring, while most of the section was covered by only logging. Therefore, the knowledge of major parameters of the Lower Silurian shales is rather obscure and is based on scarce rock sample data. The gamma-ray, electrical resistivity and sonic logs were utilised, together with mineralogical studies of rock samples to document vertical and lateral distribution of organic matter. Also, the brittleness index was defined to characterise the whole Lower Silurian section. Some unexpected trends were identified that may redirect exploration strategy in west Lithuania. The combined application of mineralogical studies and well logs indicate a much higher exploitation quality of the Lower Silurian shales than previously believed. A higher organic matter content and brittleness were derived from logging data in the Lower Silurian shales.

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16

Grahn, Yngve. "Lower Silurian Chitinozoa and biostratigraphy of subsurface Gotland." GFF 117, no. 2 (June 1995): 57–65. http://dx.doi.org/10.1080/11035899509546199.

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Karatajute-Talimaa, Valentina, and Moya Meredith Smith. "Early acanthodians from the Lower Silurian of Asia." Transactions of the Royal Society of Edinburgh: Earth Sciences 93, no. 3 (September 2002): 277–99. http://dx.doi.org/10.1017/s0263593300000444.

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ABSTRACTAbundant microvertebrate remains from the Siberian Platform are described as early acanthodians. All are preserved with both excellent morphology and histology. They are assigned to a new order, Tchunacanthida, with two new families, Lenacanthidae and Tchunacanthidae. These comprise two new genera, Lenacanthus and Tchunacanthus with type species L. priscus sp. nov. and T. obruchevisp.nov. The evidence from the morphology and histology is that they are the most ancient acanthodian scales so far found. The total collection of vertebrate material from the Irkutsk amphitheatre is described, together with their geological distribution, geographical range and systematic palaeontology. Head scales, tesserae of three morphotypes, transitional scales and body scales have been found. All comprise morphological sets as determined by comparison of morphology using SEM and of histology using Nomarsky interference optics. Observations of growth were possible from details of concentric lines on the crown and also from incremental layers seen in both horizontal and vertical sections. Starting from the primordial scale, consecutive layers are added, coronally, laterally, and deep in the corium onto the base; these occurred simultaneously in both crown and base. A type of areal-superpositional growth occurred in some body scales but in other scales there was little superpositional growth. It is concluded that Tchunacanthus possessed very solid body armour with tightly joined scales covering a large area of the body, and scale bases deeply set in the corium. Both tissues of the scales, dentine and bone, feature enclosed cells. This character is regarded as primitive within acanthodians, as in derived forms both tissues are acellular. Acanthodian scales are one of many examples of transformation from cellular to acellular tissue in evolution.

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18

Peel, John S., and Lennart Jeppsson. "The problematic fossilJinonicellafrom the Lower Silurian of Gotland." GFF 128, no. 1 (March 2006): 39–42. http://dx.doi.org/10.1080/11035890601281039.

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19

Steemans, P. "Silurian and Lower Emsian spores in Saudi Arabia." Review of Palaeobotany and Palynology 89, no. 1-2 (November 1995): 91–104. http://dx.doi.org/10.1016/0034-6667(95)00043-w.

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20

Watkins, Rodney, and Jeffrey J. Kuglitsch. "Lower Silurian (Aeronian) megafaunal and conodont biofacies of the northwestern Michigan Basin." Canadian Journal of Earth Sciences 34, no. 6 (June 1, 1997): 753–64. http://dx.doi.org/10.1139/e17-062.

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Lower Silurian (Llandovery: Aeronian) carbonates of the Burnt Bluff Group, northwestern Michigan Basin, represent a transect along a southward-dipping ramp that extends from tidal-flat to basin environments. Benthic megafaunas include an ostracod biofacies (tidal flat), stromatoporoid–coral biofacies (very shallow subtidal), pentamerid, crinozoan, and crinozoan–stromatoporoid biofacies (deeper subtidal), and a crinozoan–sponge biofacies (distal ramp and basin). The crinozoan–sponge biofacies, which includes diverse, small crinozoan ossicles, 19 types of siliceous sponge spicules, and at least 65 other taxa, has a biota that is similar to those of Silurian continental margins. Megafaunal biofacies indicate an Early Silurian gradient going from a shoreline in the north to water depths of perhaps 60 m in the south. The Burnt Bluff Group contains conodonts of the Icriodella discreta – Icriodella deflecta zone as an onshore biofacies with Panderodus, Kockelella, Ozarkodina, Icriodella, and Oulodus, and an offshore biofacies with Panderodus, Walliserodus, and Aspelundia.

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žigaitė, živilė, Valentina Karatajūtė-Talimaa, and Alain Blieck. "Vertebrate microremains from the Lower Silurian of Siberia and Central Asia: palaeobiodiversity and palaeobiogeography." Journal of Micropalaeontology 30, no. 2 (September 1, 2011): 97–106. http://dx.doi.org/10.1144/0262-821x11-016.

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Abstract. The biostratigraphic and palaeogeographical distributions of early vertebrate microfossils from a number of Lower Silurian localities in northwestern Mongolia, Tuva and southern Siberia were reviewed. Vertebrate microremains showed high taxonomic diversity, comprising acanthodians, chondrichthyans, putative galeaspids, heterostracans, mongolepids, tesakoviaspids, thelodonts and possible eriptychiids. The majority of taxa have lower stratigraphic levels of occurrence compared to other Silurian palaeobiogeographical provinces, such as the European-Russian or Canadian Arctic. Vertebrate microremains are numerous within the samples, which may indicate warm-water low-latitude palaeobasins with rich shelf faunas. This disagrees with the recent interpretations of the territory as a northern high-latitude Siberian palaeocontinent. The palaeobiogeographical distribution of vertebrate taxa indicates an endemic palaeobiogeographical province of connected epeiric palaeoseas with external isolation during the early Silurian. In previous works separation between Tuvan and Siberian palaeobiogeographical provinces has been suggested. After careful revision of the vertebrate microfossil record of the region, we find that differences in a few vertebrate taxa do not provide not strong enough evidence to reliably distinguish these provinces. We therefore dispute the hypothesis of two biogeographical provinces in the early Silurian of the Siberian palaeocontinent, and propose a single unified Siberian–Tuvan palaeobiogeographical province.

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Higgins, A. K., and N. J. Soper. "Cambrian - Lower Silurian slope and basin stratigraphy between northern Nyeboe Land and western Amundsen Land, North Greenland." Rapport Grønlands Geologiske Undersøgelse 126 (December 31, 1985): 79–86. http://dx.doi.org/10.34194/rapggu.v126.7913.

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Brief description is given of the Cambrian - Lower Silurian sequence in northern parts of central and western North Greenland, which underlies the turbidites of the Silurian Peary Land Group. Lower parts of the sequence pertain to the southern shelf, and upper parts to the northern slope or basin.

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Armstrong, H. A. "Conodonts from the Upper Ordovician – Lower Silurian carbonate platform of North Greenland." Bulletin Grønlands Geologiske Undersøgelse 159 (January 1, 1990): 1–151. http://dx.doi.org/10.34194/bullggu.v159.6709.

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Samples from Upper Ordovician and Lower Silurian strata of the North Greenland carbonate platform have yielded approximately 16 500 identifiable conodont elements referable to 25 multi-element genera and 71 species and subspecies. A single genus, Pseudobelodella and 17 species and subspecies are new. In addition, 8 informal groups of indeterminate species of Oulodus are described. The Upper Ordovician conodont species can be referred to 'Fauna 12' of the American Midcontinent Province where the presence of Rhipodognathus symmetrius in the late Richmondian is typical of shallow water deposits. The Ordovician-Silurian boundary is difficult to place in this study using conodonts. New conodont zonations are proposed for Lower Silurian shelf and slope biofacies; two new early Llandovery conodont zones are erected in the slope biofacies, the Aspelundia expansa Biozone (?earliest Rhuddanian to early Aeronian) and the Aspelundia fluegeli Biozone (early Aeronian to early Telychian). The Pterospathodus celloni Biozone is shown to be particularly valuable in the correlation of strata of late Llandovery age throughout North Greenland.

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Wen, Ming, Zhenxue Jiang, Kun Zhang, Yan Song, Shu Jiang, Chengzao Jia, Weiwei Liu, et al. "Difference Analysis of Organic Matter Enrichment Mechanisms in Upper Ordovician-Lower Silurian Shale from the Yangtze Region of Southern China and Its Geological Significance in Shale Gas Exploration." Geofluids 2019 (June 2, 2019): 1–14. http://dx.doi.org/10.1155/2019/9524507.

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The upper Ordovician-lower Silurian shale has always been the main target of marine shale gas exploration in southern China. However, the shale gas content varies greatly across different regions. The organic matter content is one of the most important factors in determining gas content; therefore, determining the enrichment mechanisms of organic matter is an important problem that needs to be solved urgently. In this paper, upper Ordovician-lower Silurian shale samples from the X-1 and Y-1 wells that are located in the southern Sichuan area of the upper Yangtze region and the northwestern Jiangxi area of the lower Yangtze region, respectively, are selected for analysis. Based on the core sample description, well logging data analysis, mineral and elemental composition analysis, silicon isotope analysis, and TOC (total organic carbon) content analysis, the upper Ordovician-lower Silurian shale is studied to quantitatively calculate its content of excess silicon. Subsequently, the results of elemental analysis and silicon isotope analysis are used to determine the origin of excess silicon. Finally, we used U/Th to determine the characteristics of the redox environment and the relationship between excess barium and TOC content to judge paleoproductivity and further studied the mechanism underlying sedimentary organic matter enrichment in the study area. The results show that the excess silicon from the upper Ordovician-lower Silurian shale in the upper Yangtze area is derived from biogenesis. The sedimentary water body is divided into an oxygen-rich upper water layer that has higher paleoproductivity and a strongly reducing lower water that is conducive to the preservation of sedimentary organic matter. Thus, for the upper Ordovician-lower Silurian shale in the upper Yangtze region, exploration should be conducted in the center of the blocks with high TOC contents and strongly reducing water body. However, the excess silicon in the upper Ordovician-lower Silurian shale of the lower Yangtze area originates from hydrothermal activity that can enhance the reducibility of the bottom water and carry nutrients from the crust to improve paleoproductivity and enrich sedimentary organic matter. Therefore, for the upper Ordovician-lower Silurian shale in the lower Yangtze region, exploration should be conducted in the blocks near the junction of the two plates where hydrothermal activity was active.

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Murphy, J. B. "Petrology of Upper Ordovician – Lower Silurian rocks of the Antigonish Highlands, Nova Scotia." Canadian Journal of Earth Sciences 24, no. 4 (April 1, 1987): 752–59. http://dx.doi.org/10.1139/e87-073.

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Upper Ordovician to Lower Silurian rocks in the Antigonish Highlands consist of interlayered basalts, rhyodacites, arkoses, and conglomerates overlain by a thick sequence of marine clastic rocks and minor rhyolites. The stratigraphy documents a marine transgression. The volcanic rocks were deposited in a within-plate, continental, extensional environment. The basalts display alkalic and tholeiitic affinities, and the rhyodacites were formed by anatexis of the crust. The origin of the younger rhyolites is not clear: they are compositionally distinct from the rhyodacites but may be related to them as late-stage differentiates. At present, it is not possible to evaluate whether the tectonic setting and magmatic affinities are regionally or locally controlled.The geological history is very similar to that of Lower Silurian rocks immediately north of the Antigonish Highlands at Arisaig. In the simplest sense, this indicates these areas may have been juxtaposed prior to the Late Ordovician and limits cumulative post-Silurian movement on the boundary (Hollow) fault to about 40 km.

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Eckert, James D. "The Early Silurian myelodactylid crinoid Eomyelodactylus Foerste." Journal of Paleontology 64, no. 1 (January 1990): 135–41. http://dx.doi.org/10.1017/s0022336000042311.

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Two new species of Eomyelodactylus, E. sparteus and E. uniformis, are described from the Lower Silurian of New York. Macnamaratylus murrayi Bolton from the Lower Silurian of Ontario, Canada, is redescribed and assigned to Eomyelodactylus. Together, these species permit detailed description of this poorly known myelodactylid genus.

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Yochelson, Ellis. "The Decline of The Use of "Lower Silurian" and The Rise of "Ordovician" In U.S. Geologic Literature." Earth Sciences History 16, no. 1 (January 1, 1997): 4–12. http://dx.doi.org/10.17704/eshi.16.1.6844363517t44154.

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During the 1880s and 1890s, the term "Lower Silurian" was in common use in United States geologic literature, whereas use of "Ordovician" was exceedingly rare. The few comments regarding Ordovician which appeared were mostly based on concepts of priority and advocated usage of Lower Silurian. J. D. Dana, author of the most significant textbook of the time, consistently opposed adoption of the term. However, by the early 1900s, Ordovician was widely used in the literature and in 1903 it was adopted for use by the U.S. Geological Survey. There is no record of public discussion of the move away from Lower Silurian. C. D. Walcott, employed by the USGS throughout this interval, may have played a pivotal, but private, role in this change of stratigraphic nomenclature.

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Danielsen, Erika M., and D. Jeffrey Over. "Lower Silurian conodonts from the Shine Jinst region, southwestern Mongolia." Journal of Paleontology 90, no. 1 (January 2016): 78–91. http://dx.doi.org/10.1017/jpa.2016.18.

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AbstractLower Silurian conodonts were recovered from carbonate beds in the upper Zalaa and lower Sharchuluut formations at Yamaan Us in the Shine Jinst region, Gobi-Altai Zone, of southwestern Mongolia. Conodonts are described from the Zalaa Formation for the first time; key taxa recovered includeDistomodus kentuckyensisBranson and Branson, 1947,Ozarkodina hassi(Pollock, Rexroad, and Nicoll, 1970), Pranognathus siluricus(Pollock, Rexroad, and Nicoll, 1970), andPseudolonchodina expansa(Armstrong, 1990). These species constrain the onset of the Silurian carbonate platform, upper Zalaa to lower Sharchuluut formations, to thePranognathus tenuisZone, middle Aeronian. The presence of a cosmopolitan conodont fauna places these strata from the Gobi-Altai Zone in a basin-shelf marine setting with connection and circulation to the open ocean during the Llandovery.

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Pyle, Leanne J., and Christopher R. Barnes. "Conodonts from a platform-to-basin transect, lower Ordovician to lower Silurian, northeastern British Columbia, Canada." Journal of Paleontology 77, no. 1 (January 2003): 146–71. http://dx.doi.org/10.1017/s0022336000043493.

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The conodont fauna from nine sections across a platform-to-basin transect in northeastern British Columbia includes species of Early Ordovician (Tremadocian) to Early Silurian (Llandovery) age. A collection of 9,110 conodont elements was recovered from 205 samples taken from nine stratigraphic sections that preserve the platform succession of the Kechika, Skoki, Beaverfoot, McCusker and Nonda Formations and their off-shelf equivalents, the Ospika, Robb, Kenny and Laurier Formations of the Road River Group. The fauna is assigned to 106 species representing 67 genera; the Ordovician species are representative of two faunal realms. One new genus, left in open nomenclature, is described. Five new species include Drepanoistodus latus and four new species left in open nomenclature assigned to the following genera: Walliserodus, Multioistodus?, Pseudooneotodus, and Belodina. The Midcontinent Realm zones recognized include, in ascending order, the Acodus kechikaensis, Oepikodus communis, Jumudontus gananda, Tripodus laevis to Plectodina aculeata zones, Phragmodus undatus and Gamachignathus ensifer? zones. Zonal species of the Atlantic Realm are Microzarkodina flabellum, Eoplacognathus suecicus, Baltoniodus variabilis, Pygodus anserinus, and Amorphognathus tvaerensis. The Silurian fauna, of lower diversity than the Ordovician fauna, is representative of the Distomodus staurognathoides and Pterospathodus amorphognathoides zones.

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Rubel, M., O. Hints, P. Männik, T. Meidla, V. Nestor, L. Sarv, and I. Sibul. "Lower Silurian biostratigraphy of the Viirelaid core, western Estonia." Estonian Journal of Earth Sciences 56, no. 4 (2007): 193. http://dx.doi.org/10.3176/earth.2007.01.

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Johnson, J. G. "Mictospirifer, a new genus of Lower Silurian eospiriferid brachiopods." Journal of Paleontology 69, no. 3 (May 1995): 607. http://dx.doi.org/10.1017/s0022336000035034.

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Hsü, Singwu C. "The Upper Ordovician and Lower Silurian in West Chekiang." Bulletin of the Geological Society of China 17, no. 1 (May 29, 2009): 59–64. http://dx.doi.org/10.1111/j.1755-6724.1937.mp17001005.x.

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Achab, A., R. Bertrand, and G. Van Grootel. "Chitinozoan Contribution to the Ordovician and Lower Silurian Paleobiogeography." Journal of Geology 100, no. 5 (September 1992): 621–29. http://dx.doi.org/10.1086/629612.

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Fredholm, Doris. "Agnathan vertebrates in the Lower Silurian of Gotland, Sweden." Geologiska Föreningen i Stockholm Förhandlingar 112, no. 1 (March 1990): 61–80. http://dx.doi.org/10.1080/11035899009453162.

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Mötus, Mari-Ann. "Tabulate corals from the Lower Silurian of Jämtland (Sweden)." GFF 126, no. 4 (December 1, 2004): 339–52. http://dx.doi.org/10.1080/11035890401264339.

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Wellman, Charles H. "“Phytodebris” from Scottish Silurian and Lower Devonian continental deposits." Review of Palaeobotany and Palynology 84, no. 3-4 (February 1995): 255–79. http://dx.doi.org/10.1016/0034-6667(94)00115-z.

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GUTIÉRREZ-MARCO, JUAN CARLOS, and PETR šTORCH. "Graptolite biostratigraphy of the Lower Silurian (Llandovery) shelf deposits of the Western Iberian Cordillera, Spain." Geological Magazine 135, no. 1 (January 1998): 71–92. http://dx.doi.org/10.1017/s0016756897007802.

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Eight Lower Silurian graptolite biozones (triangulatus, convolutus, linnaei, turriculatus, crispus, griestoniensis, tullbergi and spiralis) and three subzones (runcinatus–gemmatus, palmeus and hispanicus) have been recognized in the Sierra Menera, Nevera, and Tremedal massifs in the Castilian Branch of the Iberian Cordillera (Western Iberian Cordillera). Early Silurian, Rhuddanian low-diversity normalograptid faunas are also present and these, together with the rich graptolite faunas of the Aeronian triangulatus and convolutus biozones, come from black, shaly intercalations within the quartzose sandstones of the upper part of the Los Puertos Quartzite. Telychian graptolite biozones have been recognized in the succeeding black-shale sequence of the Bádenas Formation. Diachroneity of the transition from sandstones to black shales is dated by graptolites. It ranges from about the base to at least the top of the linnaei Biozone. We suggest that the Lower Silurian black shales of the Western Iberian Cordillera were deposited in a shallow, shelf environment, not much deeper than that of presumably storm-influenced sandstones of the Los Puertos Quartzite.

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Legrand, P. "The lower Silurian graptolites of Oued In Djerane: a study of populations at the Ordovician-Silurian boundary." Geological Society, London, Special Publications 20, no. 1 (1986): 145–53. http://dx.doi.org/10.1144/gsl.sp.1986.020.01.15.

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LOYDELL, DAVID K. "Early Silurian sea-level changes." Geological Magazine 135, no. 4 (July 1998): 447–71. http://dx.doi.org/10.1017/s0016756898008917.

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Global sea-level fluctuated markedly during the early Silurian, probably as a result of the waxing and waning of ice-sheets in the South American portion of Gondwana. The highest sea-levels of the Silurian are recorded by the Telychian upper crispus–lower griestoniensis and spiralis–lower lapworthi biozones. Other highstands occurred in the early Aeronian, during the convolutus Zone (mid Aeronian), guerichi Zone and late turriculatus Zone (early Telychian), and early Sheinwoodian. Low sea-levels characterized much of the argenteus and sedgwickii zones (Aeronian), the utilis Subzone (late guerichi–early turriculatus zones, early Telychian), the late Telychian (commencing in the mid lapworthi Zone) and, after a period of apparently only small amplitude sea-level fluctuations in the late Sheinwoodian and earliest Homerian, the mid–late Homerian, in particular the early nassa Zone. Facies (and faunal) changes in the Lower Silurian do not support the P and S model of Jeppsson and others, but are consistent with the sea-level changes proposed herein. Mid Telychian marine red beds appear to have been deposited during a minor sea-level fall immediately after a period of very high sea-levels, rather than during a transgressive episode as previously suggested. Comparison of the sea-level curve presented herein with those constructed in the past is hampered by the lack of precision currently possible in the correlation of early Silurian deep water (graptolitic) and shallow water (shelly) sequences. Improving the precision of this correlation should be a priority for future research.

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Boucot, A. J., Jose Henrique G. de Melo, Eugenio V. Santos Neto, and Sven Wolff. "First Clarkeia and Heterorthella (Brachiopoda; Lower Silurian) occurrence from the Paraná Basin in eastern Paraguay." Journal of Paleontology 65, no. 03 (May 1991): 512–14. http://dx.doi.org/10.1017/s0022336000030456.

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The existence of the Malvinokaffric Realm during the Silurian (Boucot, 1990) is based on the presence of three endemic brachiopod genera (Anabaia, Clarkeia, Heterorthella), and their absence in the coeval North Silurian Realm, where roughly 100 other brachiopod genera Aegiria to Zygospiraella are present. Within the Malvinokaffric Realm the vast reaches of the Paraná Basin, covering an area almost equivalent to the United States east of the Mississippi River, has previously yielded only Anabaia, and that from a single area. In light of this, the recognition of both Clarkeia and Heterorthella within the confines of the Paraná Basin is noteworthy.

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Brück, Peter M., Kenneth T. Higgs, Nadia Maziane-Serraj, and Michel Vanguestaine. "New palynological data from the Leinster Lower Palaeozoic massif, southeastern Ireland." Earth and Environmental Science Transactions of the Royal Society of Edinburgh 91, no. 3-4 (2000): 509–14. http://dx.doi.org/10.1017/s026359330000835x.

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ABSTRACTIn southeastern Ireland, the tectonic evolution of the northwestern Avalonian margin is rather poorly understood and only partially constrained. This is because the stratigraphy comprises in the main unfossiliferous turbidites. Nevertheless, some authors have attempted to define ‘terranes’ and ‘tracts’ in the region, aided by several significant Caledonoid-trending structural breaks that can be determined in the field. Palynological work was carried out in the early 1970s and established a range of ages from approximately mid Cambrian to late Silurian, although much of the succession proved barren. In the current study, the Lower Palaeozoic sequences W of the Leinster Granite and in the Slievenamon Inlier to the S have been palynologically re-investigated. Previous work proposed an unbroken succession from lower Ordovician Ribband Group turbidites and volcanics younging westwards conformably into upper Silurian Kilcullen Group sediments. The new study clearly shows that the Ordovician palynomorphs in the older part of the Kilcullen Group are reworked. In fact, there exists a major stratigraphical break between the Ribband Group dated as early Ordovician, Arenig, and the Kilcullen Group which is entirely Silurian, late Llandovery to early Wenlock in age. This major break has a minimum strike length of 150 km and is most likely much longer, extending some hundreds of kilometres SW to Dingle and possibly equating with a similar discontinuity in the Isle of Man to the NE. This break would thus appear to be a major feature within the succession of the northwestern Avalonian margin.

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LOYDELL, D. K., D. KALJO, and P. MÄNNIK. "Integrated biostratigraphy of the lower Silurian of the Ohesaare core, Saaremaa, Estonia." Geological Magazine 135, no. 6 (November 1998): 769–83. http://dx.doi.org/10.1017/s0016756898001423.

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Integrated graptolite, conodont and chitinozoan biostratigraphical data are presented from the lower Silurian of the Ohesaare core, Saaremaa, Estonia. A precise correlation of graptolite and conodont biozonations for much of the Telychian and Sheinwoodian is presented; this differs significantly from correlations suggested previously, which were based on inadequate graptolite data. The boundary between the celloni and amorphognathoides conodont biozones lies close to that between the spiralis and lapworthi graptolite biozones. The boundary between the bicornis and procerus conodont superzones lies mid-way through the murchisoni graptolite Biozone. The top of the procerus conodont Superzone lies at or very close to the boundary between the murchisoni and firmus graptolite biozones. The boundary between the Lower and Upper ranuliformis conodont biozones lies close to the boundary between the firmus and riccartonensis graptolite biozones. The precise position of the Llandovery–Wenlock boundary cannot be identified in the core. The newly demonstrated biozonal correlations are significant for studies of Silurian chronostratigraphy (previous estimates of the duration of the epochs and ages of the Silurian were based on inaccurate correlations) and sea-level changes. Palaeogeographically, the setting of Ohesaare is considered to be relatively deep shelf. Perhaps surprisingly, there is a major unconformity in the Llandovery of the core: much, if not all, of the Aeronian is missing, as is the lower part of the Telychian.

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Fearnhead, Fiona E., Stephen K. Donovan, Joseph P. Botting, and Lucy A. Muir. "A lower Silurian (Llandovery) diplobathrid crinoid (Camerata) from mid-Wales." Geological Magazine 157, no. 7 (March 16, 2020): 1176–80. http://dx.doi.org/10.1017/s0016756819001511.

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AbstractEarly Palaeozoic crinoids are known only patchily from the British Isles except for accumulations at starfish beds. A single, exquisitely preserved crinoid is reported from the Telychian (Llandovery, Silurian) of the Pysgotwr Grits Formation of the Llangurig area, Powys, mid-Wales. This sedimentary succession is turbiditic in origin and poorly fossiliferous. The crinoid is a diplobathrid camerate, Euptychocrinus longipinnulus sp. nov., preserved as an external mould without counterpart. It has a high, shuttlecock-like crown; a conical, unsculptured cup; low infrabasals; a pair of long, slender, feather-like arms on each ray, each bearing numerous long pinnules; and a heteromorphic column. Most previous reports of this genus have been from the Upper Ordovician – lower Silurian series of Laurentia; uncertainly, it is described from the Upper Ordovician deposits of Morocco (Gondwana). Euptychocrinus longipinnulus is the first Avalonian occurrence. The beautiful preservation of the arms, including cover plates of pinnules, contrasts with the proxistele, which is a series of ‘broken sticks’. This crinoid responded to an adverse environmental fluctuation, probably a turbidity current, by autotomizing the stem, but it was carried downslope and buried alive.

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Melchin, Michael J., Alexander D. McCracken, and Fred J. Oliff. "The Ordovician–Silurian boundary on Cornwallis and Truro islands, Arctic Canada: preliminary data." Canadian Journal of Earth Sciences 28, no. 11 (November 1, 1991): 1854–62. http://dx.doi.org/10.1139/e91-165.

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Four sections of the lower part of the Cape Phillips Formation, two outcrops on northeastern Cornwallis Island and one outcrop and one drill core from Truro Island, Northwest Territories, Canada, provide significant new data on the Ordovician–Silurian boundary. They show evidence of continuous sedimentation through the boundary interval and a continuous sequence of graptolite zones, including the bohemicus and persculptus zones, which have not been previously found in Arctic Canada. Strata yield graptolites, including uncompressed specimens, and conodonts through most of the sections. The ordovicicus conodont Zone occurs within the pacificus to lower persculptus graptolite zones. The nathani conodont Zone contains a "transitional fauna," a mixing of species typical of the preceeding ordovicicus Zone and those generally regarded as Silurian indicators. This conodont zone ranges from the middle of the persculptus graptolite Zone into the lower acuminatus graptolite Zone and, thus, spans the Ordovician–Silurian boundary. The Ordovician–Silurian faunal turnover of the conodonts, therefore, also spans the Ordovician–Silurian boundary and is not coincident with the interval of major graptolite extinction, which occurs earlier, at the end of the pacificus Zone. The base of the kentuckyensis conodont Zone occurs in the acuminatus graptolite Zone. Sedimentologic evidence of the maximum eustatic sea-level drop can be seen within the bohemicus Zone (early Hirnantian) and possibly one or several smaller scale sea-level fluctuations through the underlying zones.

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Parsley, Ronald L., and Colin D. Sumrall. "New recumbent echinoderm genera from the Bois d'Arc Formation: Lower Devonian (Lochkovian) of Coal County, Oklahoma." Journal of Paleontology 81, no. 6 (November 2007): 1486–93. http://dx.doi.org/10.1666/04-072.1.

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An echinoderm fauna from the Lower Devonian (Lochkovian) Cravatt Member of the Bois d'Arc Formation near Clarita, Oklahoma, has yielded specimens of recumbent, essentially bilaterally symmetrical taxa which are similar to Ordovician genera but absent or sparsely represented in Silurian strata. Claritacarpus smithi n. gen. and sp., is a dendrocystitid homoiostele with morphology similar to the Late Ordovician Dendrocystoides Jaekel, 1918; the anomalocystitid stylophoran Victoriacystis aff. holmesorum Ruta and Jell, 1999 shows strong affinities to Victoriacystis holmesorum Ruta and Jell, 1999, Humevale Formation, of Victoria, Australia; and the pleurocystitid rhombiferan, Turgidacystis graffhami n. gen. and sp., has close affinities to the Middle Ordovician Coopericystis Parsley, 1970 of West Virginia and Henicocystis Jell, 1983 of Victoria, Australia. Claritacarpus and Turgidacystis are North American range extensions for homoiosteles and pleurocystitids, respectively, being previously unknown from rocks younger than Upper Ordovician. Globally, Silurian homoiosteles and pleurocystitids are unknown although both occur in the Lower Devonian of Germany and Australia; additionally, Early Devonian pleurocystitids are known from Great Britain and Bohemia. These genera illustrate a pseudoextinction pattern suggesting a significant unsampled Silurian “homalozoan” and pleurocystitid history.

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Rustán, Juan J., and N. Emilio Vaccari. "The aulacopleurid trilobiteMaurotarionAlberti, 1969, in the Silurian-Devonian of Argentina: systematic, phylogenetic and paleobiogeographic significance." Journal of Paleontology 84, no. 6 (November 2010): 1082–98. http://dx.doi.org/10.1666/09-166.1.

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Five new species ofMaurotarionAlberti, 1969 from the Silurian Lipeón Formation and Lower Devonian Talacasto Formation of Argentina are recognized. The comparisons with Bolivian and South African species support a Malvinokaffric clade based on librigenal synapomorphies, here erected asMaurotarion(Malvinotarion) new subgenus. The Malvinokaffric origin of the family would not be a migration from lower paleolatitudes but an Early Silurian stock of rare cosmopolitan ancestors which underwent a great Devonian radiation. Two lineages can be recognized within MalvinokaffricMaurotarion.The Silurian-Pragiandereimsilineage is a plesiomorphic one resembling Silurian representatives and involvesM.(Malvinotarion)dereimsi, M.(Malvinotarion)talacastoensenew species,M.(Malvinotarion?) new species A,M.(Malvinotarion?) new species B,M.(Malvinotarion) sp., and eventuallyM. (Malvinotarion?)cf.dereimsi.Theisaacsonilineage ranges from the Lower Pragian to Eifelian exhibiting a defined morphologic trend in the librigena. This lineage comprisesM.(Malvinotarion)isaacsoni, M.(Malvinotarion) sp. A from South Africa,M.(Malvinotarion)gauchonew species,M.(Malvinotarion)haudeinew species andM.(Malvinotarion)legrandi.A Lochkovian diversification probably took place yet an adequate assessment remains difficult. In contrast, a great evolutionary burst is recognized during the Emsian and is related to Pragian-Emsian global relative sea level curves which are coincident with those proposed from Bolivian and Argentinian basins.

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BORYSENKO, Tamara. "CORRELATION OF THE SILURIAN SEQUENCE OF THE 25-KOTYUZHINY STRUCTURAL WELL WITH THE DNIESTER REFERENCE SECTION OF THE SILURIAN IN THE VOLYN-PODILLYA PLATE." Ukrainian Geologist, no. 1-2(44-45) (June 30, 2021): 127–34. http://dx.doi.org/10.53087/ug.2021.1-2(44-45).238962.

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The paper is devoted to lithostratigraphic and biostratigraphic subdivision of the Silurian deposits of 358 m total thickness in the 25-Kotyuzhiny structural well and its comparison with the stratotypic Dniester section of the Silurian system in accordance with Legend to the geological map of Ukraine, the Volyn-Podolsky series of 1: 200 000 scale, consistent with the latest modernization of Silurian stratigraphic charts. The described section is a parastratotype for Silurian litho-stratons of the Kovel-Khotyn structural and facies zone and a reference one for Silurian deposits in the central part of this zone. The Silurian in the 25-Kotyuzhiny well is represented by the lower (Llandoverian and Wenlockian stages) and upper (Ludlovian and Przhidolian stages) series. According to the lithological-facies composition and sedimetantaion conditions during Silurian times, there are 3 major completed stages of sedimentation as transgressive-regressive cycles, corresponding to the the Yarugian, Malinovetsian and Rukshinian series, which are quite clearly subdivided into 10 suites and 12 sub-suites. In correlation with the Dniester reference section, litho-stratons of the Silurian are characterized mainly by carbonate and clay-carbonate composition, relative stable thickness and facies pattren, diversity of fauna with a predominance of shallow benthic forms. The well is characterized by bituninous manifestations indicating hydrocarbon potential of the area and its prospectivity for shale gas accumualtions in the formations of the upper Silurian in particular.

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McCobb, Lucy M. E., and Michael G. Bassett. "Machaeridians from the Lower Silurian (Llandovery, Telychian) of Shropshire, England." Journal of Paleontology 82, no. 6 (November 2008): 1207–14. http://dx.doi.org/10.1017/s0022336000055414.

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Machaeridians are marine Palaeozoic fossils, known from sediments of early Ordovician to mid Permian age (Bengtson, 1978; Cooper and Grant, 1972; Kaasa, 1992). Rare, completely articulated specimens reveal that they were long, slender, bilaterally symmetrical animals, covered by a dorsal scleritome comprising longitudinally arranged series of calcite sclerites (e.g., Adrain et al., 1991; Högström and Taylor, 2001a, 2001b). However, most known machaeridians, including those described in this paper, comprise isolated disarticulated sclerites. Until recently, the taxonomic affinities of the group were uncertain, and historically they were assigned to a number of different phyla (e.g., see Adrain, 1992). However, the recent account of an exceptionally preserved specimen with soft tissue anatomy, from the Lower Fezouata Formation (Lower Ordovician, Tremadocian) of Morocco, now indicates that machaeridians were annelid worms (Vinther et al., 2008).

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Blake, Daniel B., and Frank R. Ettensohn. "The complex morphology of a new Lower Silurian asteroid (Echinodermata)." Journal of Paleontology 83, no. 1 (January 2009): 63–69. http://dx.doi.org/10.1017/s0022336000058121.

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Gordonaster brassfieldensis is a new genus and species of Asteroidea (Echinodermata) described from the Lower Silurian Brassfield Formation of east-central Kentucky. Tentatively assigned to the poorly understood Palaeasteridae, Gordonaster shares much with Ordovician asteroids, yet it also exhibits apparent homoplasies that presage the post-Paleozoic crown group. Available specimens also indicate that the ontogenetic pattern of ossicular addition seen in the crown group was established during the Paleozoic.

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Johnson, J. G., and A. C. Lenz. "Eoplicoplasia, a new genus of Silurian–Lower Devonian ambocoeliid brachiopods." Journal of Paleontology 66, no. 3 (May 1992): 530–31. http://dx.doi.org/10.1017/s0022336000034077.

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The genus Plicoplasia Boucot, 1959 (type species P. cooperi Boucot, 1959), embraces certain Lower Devonian brachiopods of the subfamily Ambocoeliinae, family Ambocoeliidae. The geographic range of Plicoplasia includes North America (Eastern Americas Realm) and South America and South Africa (Malvinokaffric Realm).

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Journal articles on the topic 'Lower Silurian'

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