Chapter 14 Cambrian-Ordovician history

1997 ◽  
Vol 17 (1) ◽  
pp. 257-271 ◽  
Author(s):  
W. Brian Harland
Keyword(s):  
Late Ordovician ◽  
Early Cambrian ◽  
The South ◽  
Thermal Event ◽  
Early Ordovician

Cambrian-Ordovician history is well documented in Svalbard with late Early Cambrian faunas and a range of Ordovician faunas to provide a basis for correlation. Not so extensive as Vendian, the rocks crop out in four areas: (i) only slightly deformed strata in the youngest Hecla Hoek (Oslobreen) Group in northeastern Svalbard yield especially rich Early to Mid-Ordovician faunas, (ii) The Hornsundian Geosyncline in south Spitsbergen with more variable facies and tectonic complications also exhibits Early Cambrian and Canadian strata, (iii) The Bjornoya succession reveals a marked hiatus between Vendian and Early and Mid-Ordovician strata, (iv) In western Svalbard the lack of Cambrian and Early Ordovician strata marks a distinct Mid Ordovician tectono-thermal event to be followed by ?Late Ordovician and Early Silurian strata. Indeed the above four areas correspond to distinct terranes which, having different affinities especially with areas in Greenland, give evidence of relatively distant areas and environments of formation. Evidence of Cambro-Ordovician volcanism is not recorded.Figure 14.1 lists the successions in the four areas mentioned according to the classification of rock units as abstracted from chapters 6, 7, 8, 9, 10 and 11, where their regional settings may be found. The outcrops are plotted on Fig. 14.2. The northeastern Svalbard strata are separated by Hinlopenstretet. This waterway divides Ny Friesland and Olav V Land in Spitsbergen from northwestern Nordaustlandet and occupies a syncline, but the successions although differently named are essentially continuous. In southern Spitsbergen the fjord Hornsund separates the successions to the south in Sorkapp Land

Early Ordovician alkali-ultramafic Zhilandy complex (Central Kazakhstan): structure and age of formation

2019 ◽  
Vol 484 (1) ◽  
pp. 61-65
Author(s):  
R. M. Antonuk ◽  
A. A. Tretyakov ◽  
K. E. Degtyarev ◽  
A. B. Kotov
Keyword(s):  
Complex Formation ◽  
Central Asian Orogenic Belt ◽  
Early Cambrian ◽  
Early Ordovician ◽  
Late Cambrian ◽  
Central Asian ◽  
Geochronological Study ◽  
Three Stages ◽  
Late Neoproterozoic ◽  
Quartz Monzodiorites

U–Pb geochronological study of amphibole-bearing quartz monzodiorites of the alkali-ultramafic Zhilandy complex in Central Kazakhstan, whose formation is deduced at the Early Ordovician era (479 ± 3 Ma). The obtained data indicate three stages of intra-plate magmatism in the western part of the Central Asian Orogenic Belt: Late Neoproterozoic stage of alkali syenites of the Karsakpay complex intrusion, Early Cambrian stage of ultramafic-gabbroid plutons of the Ulutau complex formation, and Late Cambrian–Early Ordovician stage of formation of the Zhilandy complex and Krasnomay complex intrusions.

scholarly journals Studying of Cultural Properties of Pyricularia oryzae Cav. Strains in the South of Russia

2021 ◽  
Vol 12 (1) ◽  
pp. 21-28
Author(s):  
Dmitry Nartymov ◽  
Evgeny Kharitonov ◽  
Elena Dubina ◽  
Sergey Garkusha ◽  
Margarita Ruban ◽  
...  
Keyword(s):  
Pyricularia Oryzae ◽  
Blast Disease ◽  
The South ◽  
Directional Growth ◽  
Rice Plants ◽  
Affected Plant ◽  
Cultural Traits ◽  
Plant Form ◽  
Using Data

This article presents the results of the development of a methodology for describing the main morphological and cultural traits of the Pyricularia oryzae Cav. strains widespread in the south of Russia. At the same time, the types of traits are identified and listed, which make it possible to unambiguously determine the uniqueness and variety of the pathogen. The relationships and patterns established using cluster and statistical analysis make it possible to identify the conditions for the development of a pathogen that determine its predominant forms. Thus, research shows that leaf forms of P. oryzae strains isolated from rice plants with leaf form of blast disease have an equally directional growth pattern of a colony with a felt structure, and strains isolated from neck-affected plant form often produce a zone of a colony with a clumpy structure. The classification of cultural traits will make it possible to obtain scientifically grounded and comparable data that can be used in the analysis of the interaction of P. oryzae strains with rice plants on various varieties and in various agro-technological conditions in order to improve and rationalize agricultural activities. The study opens up the possibility of using data in breeding, making it possible to identify forms of a pathogen that infect certain varieties.

THE BRONZE SHIELD FROM THE BURIAL OF A MEDIEVAL ARCHER IN THE KUZNETSK DESPRESSION

2021 ◽  
Vol 27 ◽  
pp. 265-270
Author(s):  
PILIPENKO S. ◽  
◽  
SULEIMENOV M. ◽  
Keyword(s):  
Significant Role ◽  
Western Siberia ◽  
Volga Region ◽  
Burial Ground ◽  
The South ◽  
Protective Shield

A number of works written by leading Siberian weapons experts are devoted to the classification of this piece of personal armour. Issues of weapons development played a significant role in the lives of the medieval people in the South of Western Siberia. One of the most frequently encountered categories of inventory in the burials of nomads includes ranged weapons: parts of bows, arrows, quivers. Yu.S. Khudyakova [1980, p. 118] and VV. Gorbunova [2006, p. 35-62]. However, bow sets are not limited to bows, arrows and quivers. There are also other parts of archery equipment known from the nomadic antiquities of the Volga region, such as archers’ rings and pavises [Rudenko, 2005, p. 27-35], items that have never been found in the South of Western Siberia until recently. During his exploration of burial ground 3 from mound 3 of Konevo, A.M. Ilyushin [2012, p. 37] found a bronze plate, which he believed belonged to plate armour. However, further study of the objects found in burial ground 3 of mound 3 of Konevo, raised doubts whether this attribution of the excavated bronze plate is justified. Acquaintance with the materials of burial 3 of mound 3 of the Konevo burial ground, raised doubts about such an attribution of the revealed bronze plate. Keywords: medieval nomads, archeology, bow, arrows, protective shield, pavise, gastagna, archer, Kuznetsk Depression

scholarly journals Decoupled evolution of soft and hard substrate communities during the Cambrian Explosion and Great Ordovician Biodiversification Event

2016 ◽  
Vol 113 (25) ◽  
pp. 6945-6948 ◽  
Author(s):  
Luis A. Buatois ◽  
Maria G. Mángano ◽  
Ricardo A. Olea ◽  
Mark A. Wilson
Keyword(s):  
Late Ordovician ◽  
Hard Substrate ◽  
Cambrian Explosion ◽  
Early Cambrian ◽  
Continuous Increase ◽  
Late Cambrian ◽  
Unconsolidated Sediment ◽  
Underlying Causes ◽  
Hard Substrates ◽  
Shed Light

Contrasts between the Cambrian Explosion (CE) and the Great Ordovician Biodiversification Event (GOBE) have long been recognized. Whereas the vast majority of body plans were established as a result of the CE, taxonomic increases during the GOBE were manifested at lower taxonomic levels. Assessing changes of ichnodiversity and ichnodisparity as a result of these two evolutionary events may shed light on the dynamics of both radiations. The early Cambrian (series 1 and 2) displayed a dramatic increase in ichnodiversity and ichnodisparity in softground communities. In contrast to this evolutionary explosion in bioturbation structures, only a few Cambrian bioerosion structures are known. After the middle to late Cambrian diversity plateau, ichnodiversity in softground communities shows a continuous increase during the Ordovician in both shallow- and deep-marine environments. This Ordovician increase in bioturbation diversity was not paralleled by an equally significant increase in ichnodisparity as it was during the CE. However, hard substrate communities were significantly different during the GOBE, with an increase in ichnodiversity and ichnodisparity. Innovations in macrobioerosion clearly lagged behind animal–substrate interactions in unconsolidated sediment. The underlying causes of this evolutionary decoupling are unclear but may have involved three interrelated factors: (i) a Middle to Late Ordovician increase in available hard substrates for bioerosion, (ii) increased predation, and (iii) higher energetic requirements for bioerosion compared with bioturbation.

scholarly journals A weather regime characterisation of winter biomass aerosol transport from southern Africa

2021 ◽  
Author(s):  
Marco Gaetani ◽  
Benjamin Pohl ◽  
Maria del Carmen Alvarez Castro ◽  
Cyrille Flamant ◽  
Paola Formenti
Keyword(s):  
Spatial Distribution ◽  
Southern Africa ◽  
Forest Fires ◽  
South Atlantic ◽  
Austral Winter ◽  
The South ◽  
Predictive Tool ◽  
Weather Regime ◽  
Synoptic Variability

Abstract. During austral winter, a compact low cloud deck over South Atlantic contrasts with clear sky over southern Africa, where forest fires triggered by dry conditions emit large amount of biomass burning aerosols (BBA) in the free troposphere. Most of the BBA burden crosses South Atlantic embedded in the tropical easterly flow. However, midlatitude synoptic disturbances can deflect part of the aerosol from the main transport path towards southern extratropics. In this study, a characterisation of the synoptic variability controlling the spatial distribution of BBA in southern Africa and South Atlantic during austral winter (August to October) is presented. By analysing atmospheric circulation data from reanalysis products, a 6-class weather regime (WR) classification of the region is constructed. The classification reveals that the synoptic variability is composed by four WRs representing disturbances travelling at midlatitudes, and two WRs accounting for pressure anomalies in the South Atlantic. The WR classification is then successfully used to characterise the aerosol spatial distribution in the region in the period 2003–2017, in both reanalysis products and station data. Results show that the BBA transport towards southern extratropics is controlled by weather regimes associated with midlatitude synoptic disturbances. In particular, depending on the relative position of the pressure anomalies along the midlatitude westerly flow, the BBA transport is deflected from the main tropical route towards southern Africa or the South Atlantic. This paper presents the first objective classification of the winter synoptic circulation over South Atlantic and southern Africa. The classification shows skills in characterising the BBA transport, indicating the potential for using it as a diagnostic/predictive tool for aerosol dynamics, which is a key component for the full understanding and modelling of the complex radiation-aerosol-cloud interactions controlling the atmospheric radiative budget in the region.

scholarly journals Cloud computing activities: Guidelines on the South African income tax classification

2017 ◽  
Vol 9 (1) ◽  
pp. 228-243
Author(s):  
Shené Steenkamp ◽  
Rudie Nel
Keyword(s):  
Cloud Computing ◽  
South African ◽  
Income Tax ◽  
Computer Hardware ◽  
Correct Classification ◽  
The South ◽  
Know How ◽  
Cloud Computing Service ◽  
Source Test

The classification of income from cloud computing activities, according to the substance-over-form doctrine, is fundamental to the application of the correct taxation source test. The designation of IaaS, PaaS and SaaS, the three main cloud computing service models, clearly denotes the form of cloud computing activities as that of a service. However, the nature of cloud computing inherently raises the question of whether or not cloud computing income should not rather be classified as income from leasing activities or the imparting of know-how. In fact, the findings of this study suggest the classification would not necessarily always be that of a service. The possible classification as lease income can be either income from the lease of tangible computer hardware and/or of intellectual property (royalty income). The aim of this study was to formulate guidelines to assist in the correct classification of income from cloud computing activities. This was achieved by performing doctrinal research based on the South African and international literature.

Composition, structure and tectonic analysis of the Shangrimuce arc-continent collision zone on the northern margin of the Central Qilian, NW China

2021 ◽  
Author(s):  
Hongyuan Zhang ◽  
Zhibin Lei ◽  
Bo Yang ◽  
Qing Liu ◽  
Haijun Zhang ◽  
...  
Keyword(s):  
Shear Zones ◽  
Oceanic Lithosphere ◽  
Late Ordovician ◽  
Island Arc ◽  
Qilian Mountain ◽  
Northern Margin ◽  
Early Ordovician ◽  
Collision Zone ◽  
Two Stages ◽  
Back Arc

<p>A 1:50000 regional survey, covering an area of about 2000 km<sup>2</sup>, was carried out in the Shangrimuce area of Qilian Mountain in Northwest China. The results show that during Caledonian, the northern margin of the Central Qilian block experienced collision with mature island arcs and subsequently northward expansion. In the Shangrimuce study area, five geological units have been identified; they are, form south to north, back-arc basin, early Ordovician island arc, inter arc basin, middle Late Ordovician island arc, and fore-arc and oceanic lithosphere amalgamation zone. </p><p>(1) back-arc basin. In the Yangyuchi- Shule River- Cuorigang- Wawusi area, there may be a back-arc spreading basin, and there should be spreading basins in this area. It is speculated that there was a northward reverse subduction in the late Ordovician, accompanied by a syenite body, a broad spectrum dyke swarms and an accretionary wedge zone in the whole area.</p><p>(2) early Ordovician island arc. In the Shangrimuce-Dander area, the Proterozoic basement granitic gneiss, the early Ordovician island arc block and the high-pressure geological body all occur in the form of thrust horses, forming a double metamorphic belt, which reveals the existence of ocean subduction to south in the early Ordovician. </p><p>(3) inter arc basin. On both banks of Tuolai River to the east of Yanglong Township, there are early Middle Ordovician inter-arc basins with oceanic crust. </p><p>(4) middle Late Ordovician island arc. To the north of Tuolai River, there is a middle Late Ordovician island arc belt. Both sides of the island arc zone experienced strong ductile shear deformation, which recorded a complex arc-continent collision. </p><p>(5) fore-arc and oceanic lithosphere amalgamation zone (Fig.1). The Yushigou area has developed a fore-arc and oceanic lithospheric amalgamation zone, with weakly deformed fore-arc flysch basin, strongly deformed siliceous rocks, pillow Basalt, diabase, gabbro, peridotite and other rock assemblages.</p><p>Combined with the characteristics of arc-continent collision zone in the Western Pacific, there are two stages of shear zone series (Fig.2). One is ductile shear zones formed by the South dipping gneissic belt, revealing the existence of oceanic subduction accretion wedge and emplacement of high-pressure rocks. Another superimposed one is north dipping. This indicates that the arc-continent collision caused by back-arc reverse subduction, which ultimately controls the overall geometric and kinematic characteristics of the shear zones in the region.</p><p><img src="https://contentmanager.copernicus.org/fileStorageProxy.php?f=gepj.8219836ca50067454890161/sdaolpUECMynit/12UGE&app=m&a=0&c=40b3389c641f2d0ca723e1527c32927e&ct=x&pn=gepj.elif&d=1" alt=""></p><p>Figure 1 United sections showing a Caledonian trench-arc system in the Qilian Mountain, NW China.</p><p><img src="https://contentmanager.copernicus.org/fileStorageProxy.php?f=gepj.8def566da50066084890161/sdaolpUECMynit/12UGE&app=m&a=0&c=e82258ecc235c4e618abd6c035b58232&ct=x&pn=gepj.elif&d=1" alt=""></p><p>Figure 2 Structural analysis at Hongyahuo, indicating two stages of deformation.</p><p>The research has been supported by projects from the Ministry of Land and Resources (No.201211024-04; 1212011121188) and the 2020 undergraduate class construction project from China University of Geosciences (Beijing) (No. HHSKE202003).</p><p> </p>

Petrogenesis of Early Cambrian granitoids in the western Kunlun orogenic belt, Northwest Tibet: Insight into early stage subduction of the Proto-Tethys Ocean

2020 ◽  
Vol 132 (9-10) ◽  
pp. 2221-2240 ◽  
Author(s):  
Jiyuan Yin ◽  
Wenjiao Xiao ◽  
Min Sun ◽  
Wen Chen ◽  
Chao Yuan ◽  
...  
Keyword(s):  
Partial Melting ◽  
Orogenic Belt ◽  
Early Cambrian ◽  
The South ◽  
The West ◽  
Juvenile Material ◽  
Tethys Ocean ◽  
West Kunlun ◽  
T Values ◽  
Oceanic Slab

Abstract The west Kunlun orogenic belt, located on the northwest margin of the Tibetan Plateau, represents a crucial tectonic junction between the central Asia and Tethys domains. Its evolution was closely related to the Paleozoic subduction and closure of the Proto-Tethys Ocean, which was formed by the breakup of the Rodinia supercontinent following the Neoproterozoic. However, the early evolution of Proto-Tethys oceanic subduction (e.g., subduction initiation timing, polarity, and process) remains controversial. The source of the Early Cambrian granitoids is also unclear. To explore these questions, four Cambrian plutons (i.e., two Tianshuihai monzogranites and south Kunlun diorite and monzogranite) were chosen for geochronological and geochemical studies. Zircon U-Pb dating reveals that these plutons formed at ca. 533–513 Ma and thus represent the oldest arc-related magmatism in the west Kunlun orogenic belt. The Tianshuihai monzogranites have positive εNd(t) values (+0.76 to +1.34) and zircon εHf(t) values of +0.25 to +6.42, with low δ18Ozrn values of +5.11‰ to +7.38‰, suggesting that their source includes juvenile material. These rocks are weakly peraluminous and have relatively old Hf model ages of 1.09–1.48 Ga. Mass balance calculations show that the Tianshuihai monzogranites were derived from partial melting of Mesoproterozoic meta-igneous rocks with the addition of 22% of juvenile material. The south Kunlun monzogranites in this study are weakly peraluminous, and their lowest εNd(t) values are –9.24 to –9.27 and zircon εHf(t) values are –7.80 to –11.2. The oldest Hf model ages are 1.97–2.18 Ga, and the highest zircon δ18Ozrn values are +8.11 to +9.73‰. Their isotopic compositions are different from those of the magmas derived from partial melting of just Paleoproterozoic and Mesoproterozoic basement rocks but can be produced by a mixing source of 32% meta-igneous rock and 68% meta-sedimentary rock. The south Kunlun diorites are characterized by high Sr contents and relatively high Sr/Y (52–63) ratios but low Y, Yb, Cr, and Ni contents, like those of the thickened continental crust-derived adakites. Their Sr-Nd–Hf-O isotopic compositions indicate that their parental magma was derived from a Mesoproterozoic metaigneous basement in the garnet stability field. Based on the newly identified, oldest island arc magmatic records in the west Kunlun orogenic belt, the subduction initiation of the Proto-Tethys oceanic slab must have occurred prior to the Early Cambrian (>533 Ma). Our results, with previously published data, show that the west Kunlun orogenic belt was in an extensional setting during the Early Cambrian and that the magmatism migrated northeastward along the axis of the south Kunlun terrane between 533 Ma and 513 Ma. Therefore, considering the spatial and temporal distribution and petrogenesis of the Early–Middle Cambrian plutons in the west Kunlun orogenic belt, we propose that the Early Cambrian magmatism was most plausibly triggered by asthenospheric upwelling in response to the rollback of southward-subducted Proto-Tethys oceanic slab.

scholarly journals XIII. Researches on the structure, organization, and classification of the fossil reptilia. -Part IX., Section 3. On diademodon

1894 ◽  
Vol 185 ◽  
pp. 1029-1041 ◽  
Keyword(s):  
South African ◽  
Cape Town ◽  
Shoulder Girdle ◽  
Middle Region ◽  
The South ◽  
The West ◽  
Limb Bones ◽  
Lower Jaw

The South African fossils with broad, flat, tuberculate tooth-crowns of mammalian type all from the eastern part of Cape Colony. Some of the most interesting are known from fragments, which indicate nothing but the middle region of the sail. They are apparently extremely rare. Two species, with teeth well preserved, found ten years ago by Dr. Kannemeyer, at Wonderboom, and presented to South African Museum, Cape Town, where they were brought under my notice by Peringuey. Others were found in a fragmentary condition by Mr. Alfred of Aliwal North, to the west of that town, in a bed which appeared to me be reconstructed. There is no doubt that the fossils are from the upper part of te Karroo formation, probably of Permian age, and below the Stormberg beds, in Saurischian fossils are found allied to those of the Trias of Europe. If the teeth had occurred isolated, without the means of demonstrating their rsemblance to Theriodonts, by comparison of what remains of the skull, it would have legitimate to have referred them to Mammals. There is no evidence of affinity Accept resemblances to Theriodonts, which show that the skull had pre-frontal and frontal bones, and therefore may be inferred to have had the lower jaw composite. The teeth are such as might be expected, perhaps, in a Monotreme Mammal, their interest is therefore the greater that there is no ground for suspecting them be mammalian, other than a general resemblance of the crown to the crowns of true teeth of Ornithorhynchus. That teeth of this type should occur in a group animals in which the shoulder-girdle and pelvis have monotreme characters, and in hich the principal limb bones are intermediate in character between Monotremes Marsupials, is evidence of a closer approximation between Mammals and Pep tiles has been manifest. And so far as I am aware the only Theriodont characters remaining to distinguish these animals from Mammals are the composite lower which is covered externally by the dentary bone along its whole length, and the resence of the pre-frontal, post-frontal, and transverse bones in the skull.

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