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    Wyświetlanie 1-14 z 14
    Tytuł:
    A hitherto unknown river type from the Archaean at Bhurkuli (Jharkhand, E India)
    Autorzy:
    van Loon, A. J.
    De, S.
    Powiązania:
    https://bibliotekanauki.pl/articles/94253.pdf
    Data publikacji:
    2017
    Wydawca:
    Uniwersytet im. Adama Mickiewicza w Poznaniu
    Tematy:
    conglomerates
    fluvial system
    pebble characteristics
    Precambrian
    Singhbhum Craton
    zlepieńce
    system fluwialny
    charakterystyka żwirkowa
    prekambr
    Opis:
    The Archaean granitoid pluton of the Singhbhum craton in E India is overlain by Archaean to Palaeoproterozoic metasediments. These sediments are still poorly known and their stratigraphy is under debate. Several scattered, most probably Meso- to Neoarchaean, conglomerates are present in the state of Jharkhand that differ so much in characteristics that they are probably not related to each other. The sedimentology of a series of conglomerate patches and layers near Bhurkuli has been investigated, including the characteristics of the clasts. It is deduced on the basis of these characteristics and the sedimentological context that the Bhurkuli conglomerates represent the channel facies of a river system that differed from the types of fluvial systems that exist nowadays.
    Źródło:
    Geologos; 2017, 23, 2; 109-122
    1426-8981
    2080-6574
    Pojawia się w:
    Geologos
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    A new type of slumping-induced soft-sediment deformation structure: the envelope structure
    Autorzy:
    Byun, Uk Hwan
    van Loon, A. J. (Tom)
    Kwon, Yi Kyun
    Ko, Kyoungtae
    Powiązania:
    https://bibliotekanauki.pl/articles/950457.pdf
    Data publikacji:
    2019
    Wydawca:
    Uniwersytet im. Adama Mickiewicza w Poznaniu
    Tematy:
    Gyeokpori Formation
    Cretaceous
    lacustrine environment
    slumping
    conglomerate
    kreda
    środowisko jeziorne
    opadanie
    konglomerat
    Opis:
    The sediments of the Cretaceous Gyeokpori Formation in south-western South Korea accumulated in a lake in which mainly siliciclastic rocks were deposited, with some interbedded volcaniclastics. The nearby volcanic activity resulted in unstable lake margins inducing a dominance of gravity-flow deposits. The high sedimentation rate facilitated soft-sediment deformation on the sloping margin. The deposition of numerous gravity-flow deposits resulted in a vertically heterolithic stratification. The slumps are composed of different lithologies, which is expressed in different types of deformation due to the difference in cohesion between sandy and mussy layers within the slumps. Coarser-grained (cohesionless) slumps tend to show more chaotic deformation of their lamination or layering. The difference in slumping behaviour of the cohesive and non-cohesive examples is explained and modelled. A unique soft-sediment deformation structure is recognized. This structure has not been described before, and we call it ‘envelope structure’. It consists of a conglomerate mass that has become entirely embedded in fine-grained sediment because slope failure took place and the fine-grained material slumped down with the conglomerate ‘at its back’. The cohesive laminated mudstone formed locally slump folds that embedded the non-cohesive overlying conglomerate unit, possibly partly due to the bulldozing effect of the latter. This structure presumably can develop when the density contrast with the underlying and overlying deposits is exceptionally high. The envelope structure should be regarded as a special – and rare – type of a slumping-induced deformation structure.
    Źródło:
    Geologos; 2019, 25, 2; 111-124
    1426-8981
    2080-6574
    Pojawia się w:
    Geologos
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Depositional environment of the Bagh-e-Vang Formation – the only occurrence of upper Lower Permian in Iran
    Autorzy:
    Yegane, Bizhan Yousefi
    Van Loon, A.J. (Tom)
    Fard, Sakine Arefi
    Farahpour, Mohammad Mehdi
    Sharahi, Safoora Yasbolaghi
    Powiązania:
    https://bibliotekanauki.pl/articles/1841615.pdf
    Data publikacji:
    2021
    Wydawca:
    Uniwersytet im. Adama Mickiewicza w Poznaniu
    Tematy:
    limestones
    microfacies analysis
    transgression conglomerate
    barrier deposits
    lagoonal environment
    Tabas Block
    wapienie
    analiza mikrofacjalna
    konglomerat
    transgresja
    osady
    laguna
    Opis:
    A transgression of the Tethys Ocean occurred in east central Iran, like in other areas of the Tethys Ocean, around the Yakhtashian/Bolorian (regional chronostratigraphical units corresponding with the Artinskian/Kungurian of the Early Permian) transition. This led to the development of a carbonate platform that is represented in the Shirgesht area on the northern part of the Tabas Block by the Bagh-e-Vang Formation, which constitutes the only known sedimentary unit from the late Early Permian in Iran. Field data and thin-section analysis indicate deposition on a carbonate ramp with barriers separating a lagoonal area with intertidal mud flats from the open-marine environment. The overall transgres-sive development is indicated by the presence of open-marine sediments on top of the barrier and lagoonal sediments.
    Źródło:
    Geologos; 2021, 27, 1; 1-14
    1426-8981
    2080-6574
    Pojawia się w:
    Geologos
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Dumpstones as records of overturning ice rafts in a Weichselian proglacial lake (Rügen Island, NE Germany)
    Autorzy:
    Pisarska-Jamroży, M.
    Van-Loon, A. J. T.
    Bronikowska, M.
    Powiązania:
    https://bibliotekanauki.pl/articles/2060089.pdf
    Data publikacji:
    2018
    Wydawca:
    Państwowy Instytut Geologiczny – Państwowy Instytut Badawczy
    Tematy:
    dumpstones
    dropstones
    ice-rafted debris
    Weichselian
    glaciolacustrine sediments
    Opis:
    Dumpstones and dropstones up to 0.8 m in size occur in a silty/sandy Weichselian glaciolacustrine succession near Dwasieden on Rügen Island in the SW Baltic Sea (NE Germany). The deposits are exceptional because two levels of dumpstones and dropstones are present, suggesting two dumping phases interrupting characteristic fine-grained glaciolacustrine sedimentation. Plastic downwarping of sediments below the dumpstones and dropstones result in soft-sediment deformation structures. The distribution and orientation of the long axes of the clasts are useful tools for the reconstruction of the state of the lake bottom, as well as for the water depth. The horizontal position of the gravels and boulders (parallel to the bedding) suggests deposition in relatively shallow-water. The dumping events are linked to iceberg rafting in a glacial lake during the Weichselian Glaciation (MIS 2).
    Źródło:
    Geological Quarterly; 2018, 62, 4; 917-924
    1641-7291
    Pojawia się w:
    Geological Quarterly
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Interaction between turbidity currents and a contour current – a rare example from the Ordovician of Shaanxi province, China
    Autorzy:
    Li, Hua
    van Loon, A. J. (Tom)
    He, Youbin
    Powiązania:
    https://bibliotekanauki.pl/articles/950462.pdf
    Data publikacji:
    2019
    Wydawca:
    Uniwersytet im. Adama Mickiewicza w Poznaniu
    Tematy:
    contourites
    turbidites
    reworking
    Ordos basin
    Pingliang formation
    kontury
    turbidyty
    przeróbka
    zlewnia
    Ordos
    Pingliang
    Opis:
    The silty top parts of graded turbidites of the Late Ordovician Pingliang Formation, which accumulated along the southern margin of the Ordos Basin (central China), have been reworked by contour currents. The reworking of the turbidites can be proven on the basis of paleocurrent directions in individual layers: the ripple-cross-bedded sandy divisions of some turbidites show transport directions consistently into the downslope direction (consistent with the direction of other gravity flows), but in the upper, silty fine-grained division they show another direction, viz. alongslope (consistent with the direction that a contour current must have taken at the same time). Both directions are roughly perpendicular to each other. Moreover, the sediment of the reworked turbidites is better sorted and has better rounded grains than the non-reworked turbidites. Although such type of reworking is well known from modern deep-sea environments, this has rarely been found before in ancient deep-sea deposits. The reworking could take place because the upper divisions of the turbidites involved are silty and consequently relatively easily erodible, while the contour current had locally a relatively high velocity – and consequently a relatively large erosional capability – because of confinement within a relatively narrow trough.
    Źródło:
    Geologos; 2019, 25, 1; 15-30
    1426-8981
    2080-6574
    Pojawia się w:
    Geologos
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Intrastratal flow in the Cretaceous Gyeokpori Formation (SW South Korea)
    Autorzy:
    Byun, Uk Hwan
    Van Loon, A.J. (Tom)
    Kwon, Yi Kyun
    Ko, Kyoungtae
    Powiązania:
    https://bibliotekanauki.pl/articles/2060260.pdf
    Data publikacji:
    2020
    Wydawca:
    Państwowy Instytut Geologiczny – Państwowy Instytut Badawczy
    Tematy:
    intrastratal flow
    Gyeokpori Formation
    soft-sediment deformation structures
    lacustrine environment
    Cretaceous
    Opis:
    Intrastratal flow is a process that is still poorly understood, rarely described and difficult to interpret in ancient rocks. Sediments in the Cretaceous lacustrine Gyeokpori Formation of southwestern South Korea contain some chaotically deformed sandstone layers with deformed mudstone clasts that are ascribed to this process. The interpretation is based on the fact that these layers cannot be explained as a result of subaqueous debris flows or mass transport, whereas the sedimentary context, including the presence of other soft-sediment deformation structures, indicates that intrastratal flow must have been physically possible. The sedimentary setting was a lake in which mainly siliciclastic rocks were deposited, with some interbedded volcaniclastics. The nearby volcanic activity caused seismic shocks that affected the unstable lake margins resulting in the dominance of gravity-flow deposits, but also in a high sedimentation rate that facilitated soft-sediment deformation partly caused by intrastratal flow. This must have happened fairly frequently during a probably limited time-span, as several layers showing traces of intrastratal flow are present within a succession of only <1 m thick. The combined data on the geological setting and our findings regarding the origin of the various soft-sediment deformation structures may help to recognize the traces left by intrastratal flow elsewhere in the geological record.
    Źródło:
    Geological Quarterly; 2020, 64, 3; 611--625
    1641-7291
    Pojawia się w:
    Geological Quarterly
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Reconstruction of sediment provenance and transport processes from the surface textures of quartz grains from Late Pleistocene sandurs and an ice-marginal valley in NW Poland
    Autorzy:
    Woronko, B.
    Pisarska-Jamroży, M.
    van Loon, A. J.
    Powiązania:
    https://bibliotekanauki.pl/articles/94315.pdf
    Data publikacji:
    2015
    Wydawca:
    Uniwersytet im. Adama Mickiewicza w Poznaniu
    Tematy:
    quartz grain micromorphology
    ice-marginal valley
    sandur
    Weichselian glaciation
    Polska
    mikromorfologia ziaren kwarcu
    pradolina
    zlodowacenie północnopolskie
    Polska
    Opis:
    During the Pomeranian phase of the Weichselian glaciation (~17–16 ka), the Toruń-Eberswalde ice-marginal valley (NW Poland and easternmost Germany) drained water from the Pomeranian ice sheet, while intensive aeolian processes took place across Europe in the foreland of the Scandinavian ice sheet (‘European Sand Belt’). The micromorphology of the quartz grains in the Toruń-Eberswalde ice-marginal valley shows no traces of these aeolian processes, or only vague signs of aeolian abrasion. This is unique among the aeolian sediments in other Pleistocene ice-marginal valleys in this part of Europe. The study of the surfaces of the quartz grains shows that the supply of grains by streams from the south was minimal, which must be ascribed to the climate deterioration during the Last Glacial Maximum, which resulted in a decrease of the discharge of these extraglacial rivers to the ice-marginal valley.
    Źródło:
    Geologos; 2015, 21, 2; 105-115
    1426-8981
    2080-6574
    Pojawia się w:
    Geologos
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Seismic and non-seismic soft-sediment deformation structures in the Proterozoic Bhander Limestone, central India
    Autorzy:
    Sarkar, S.
    Choudhuri, A.
    Banerjee, S.
    Van Loon, A. J.
    Bose, P. K.
    Powiązania:
    https://bibliotekanauki.pl/articles/94668.pdf
    Data publikacji:
    2014
    Wydawca:
    Uniwersytet im. Adama Mickiewicza w Poznaniu
    Tematy:
    seismites
    soft-sediment deformation structures
    basin subsidence
    Proterozoic
    India
    sejsmity
    struktury deformacji
    osady miękkie
    proterozoik
    Indie
    Opis:
    Numerous soft-sediment deformation structures occur within the Proterozoic Bhander Limestone of an intracratonic sag basin in a 750 m long section along the Thomas River, near Maihar, central India. Part of these deformation structures have most probably a non-seismic origin, but other structures are interpreted as resulting from earthquake-induced shocks. These seismic structures are concentrated in a 60 cm thick interval, which is interpreted as three stacked seismites. These three seismites are traceable over the entire length of the section. They divide the sedimentary succession in a lower part (including the seismites) deposited in a hypersaline lagoon, and an upper open-marine (shelf) part. Most of the soft-sediment deformations outside the seismite interval occur in a lagoonal intraclastic and muddy facies association. The SSDS within the seismite interval show a lateral continuity. They record simultaneous fluidisation and liquefaction. The bases of each of the three composing seismite bands are defined by small-scale shear folds, probably recording an earthquake and aftershocks. The presence of the three seismite bands at the boundary between the lagoonal and the overlying open-marine oolitic facies association suggests that the seismic event also triggered basin subsidence.
    Źródło:
    Geologos; 2014, 20, 2; 89-103
    1426-8981
    2080-6574
    Pojawia się w:
    Geologos
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Slide origin of breccia lenses in the Cambrian of the North China Platform: new insight into mass transport in an epeiric sea
    Autorzy:
    Van, Loon A. J. (Tom)
    Han, Zuozhen
    Han, Yu
    Powiązania:
    https://bibliotekanauki.pl/articles/94404.pdf
    Data publikacji:
    2012
    Wydawca:
    Uniwersytet im. Adama Mickiewicza w Poznaniu
    Tematy:
    breccia lenses
    sliding
    epeiric sea
    Chaomidian Formation
    Furongian
    North China Platform
    poślizg
    morze epikontynentalne
    formacja Chaomidian
    Furong
    platforma północnokoreańska
    Opis:
    An oolite in the Furongian (Late Cambrian) Chaomidian Formation in Shandong Province, China, which was deposited on the North China Platform in an epeiric sea, contains several limestone breccia lenses of various dimensions (centimetres to decimetres thick and decimetres to more than 10 metres in length) in an E-trending section. The oolite, which is approximately 40 cm thick, was originally thicker, as indicated by a planar truncation surface that formed by wave abrasion. The breccia lenses in this oolite are generally mound-shaped with a flat base and a convex top. The western margin of the lenses is commonly rounded whereas the eastern margin commonly has a tail (consisting of a rapidly eastwards thinning breccia horizon that gradually ends in a horizon of isolated clasts). Some of the breccia lenses are underlain by a shear zone. The formation of the breccia lenses cannot be easily explained by normal depositional or deformational processes. It is concluded that the lenses represent fragments of a partly consolidated layer, consisting of both rounded and angular platy clasts, which slid down over a very gently inclined sedimentary surface which acted - possibly together with a water film - as a lubricant layer. During transport, the layer broke up into several discrete bodies that formed small ‘highs’ at the sedimentary surface of the shallow epeiric sea. Subsequently, waves partially eroded the lenses, mostly at their margins, producing their mound-shaped form. Sliding of blocks is known from a wide variety of environments in the sedimentary record; however, this is the first description of the sliding of blocks in an epeiric sea. This indicates that such a low-relief submarine carbonate setting is, like its siliciclastic counterparts, susceptible to this process.
    Źródło:
    Geologos; 2012, 18, 4; 223-235
    1426-8981
    2080-6574
    Pojawia się w:
    Geologos
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Slope failure on a Cambrian carbonate platform, mass-flow transitions and resulting complex deposit
    Autorzy:
    Wang, Zhaopeng
    Liu, Jiaye
    Van Loon, A. J. (Tom)
    Zhu, Decheng
    Qin, Peng
    Han, Zuozhen
    Powiązania:
    https://bibliotekanauki.pl/articles/2058558.pdf
    Data publikacji:
    2020
    Wydawca:
    Państwowy Instytut Geologiczny – Państwowy Instytut Badawczy
    Tematy:
    Gushan Formation
    Middle Cambrian
    epeiric sea
    carbonate platform
    mass-flow transitions
    Opis:
    The quiet environment of the carbonate platform in the epeiric sea that existed during the Cambrian between present-day China and Korea was occasionally affected by processes that have hitherto not been described from such a setting. A conglomerate was found in the Middle Cambrian Gushan Formation near Chengouwan (Shandong Province, E China), eroded into the underlying sediments. The conglomerate is explained as a deposit consisting of material that was eroded up-slope when slope-failure took place, resulting in a slump that passed into a high-density debris flow with erosive power that passed, in turn, again into a slump. The slump came to rest when it lost its momentum on a less inclined part of the basin slope. Immediately after deposition, fluidization occurred in the lower part of the slump deposit, as proven by a funnel-shaped water-escape structure and a lateral injection of some metres long of brecciated material.
    Źródło:
    Geological Quarterly; 2020, 64, 1; 3--15
    1641-7291
    Pojawia się w:
    Geological Quarterly
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Soft-sediment deformation structures in cores from lacustrine slurry deposits of the Late Triassic Yanchang Fm. (central China)
    Autorzy:
    Yang, R.
    van Loon, A. J.
    Yin, W.
    Fan, A.
    Han, Z.
    Powiązania:
    https://bibliotekanauki.pl/articles/94445.pdf
    Data publikacji:
    2016
    Wydawca:
    Uniwersytet im. Adama Mickiewicza w Poznaniu
    Tematy:
    soft-sediment deformation structures
    low-density gravity-flow deposits
    Triassic
    lacustrine sediments
    Ordos basin
    China
    struktury deformacji
    osady miękkie
    złoża grawitacyjne o niskiej gęstości
    trias
    osady jeziorne
    zlewnia
    Ordos
    Chiny
    Opis:
    The fine-grained autochthonous sedimentation in the deep part of a Late Triassic lake was frequently interrupted by gravity-induced mass flows. Some of these mass flows were so rich in water that they must have represented slurries. This can be deduced from the soft-sediment deformation structures that abound in cores from these lacustrine deposits which constitute the Yanchang Fm., which is present in the Ordos Basin (central China). The flows and the resulting SSDS were probably triggered by earthquakes, volcanic eruptions, shear stress of gravity flows, and/or the sudden release of overburden-induced excess pore-fluid pressure. The tectonically active setting, the depositional slope and the high sedimentation rate facilitated the development of soft-sediment deformations, which consist mainly of load casts and associated structures such as pseudonodules and flame structures. Sediments with such deformations were occasionally eroded by slurries and became embedded in their deposits.
    Źródło:
    Geologos; 2016, 22, 3; 201-211
    1426-8981
    2080-6574
    Pojawia się w:
    Geologos
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Texture and composition of the Rosa Marina beach sands (Adriatic coast, southern Italy): a sedimentological/ecological approach
    Autorzy:
    Moretti, M.
    Tropeano, M.
    van Loon, A. J.
    Acquafredda, P.
    Baldacconi, R.
    Festa, V.
    Lisco, S.
    Mastronuzzi, G.
    Moretti, V.
    Scotti, R.
    Powiązania:
    https://bibliotekanauki.pl/articles/94295.pdf
    Data publikacji:
    2016
    Wydawca:
    Uniwersytet im. Adama Mickiewicza w Poznaniu
    Tematy:
    source-area reconstruction
    grain-size analysis
    mineralogical composition
    image analysis
    coastal erosion
    texture
    composition
    beach sands
    Rosa Marina
    Adriatic coast
    southern Italy
    rekonstrukcja obszaru źródłowego
    analiza wielkości ziarna
    skład mineralogiczny
    analiza obrazu
    erozja wybrzeża
    tekstura
    skład
    piasek plażowy
    wybrzeże Adriatyku
    południowe Włochy
    Opis:
    Beach sands from the Rosa Marina locality (Adriatic coast, southern Italy) were analysed mainly microscopically in order to trace the source areas of their lithoclastic and bioclastic components. The main cropping out sedimentary units were also studied with the objective to identify the potential source areas of lithoclasts. This allowed to establish how the various rock units contribute to the formation of beach sands. The analysis of the bioclastic components allows to estimate the actual role of organisms regarding the supply of this material to the beach. Identification of taxa that are present in the beach sands as shell fragments or other remains was carried out at the genus or family level. Ecological investigation of the same beach and the recognition of sub-environments (mainly distinguished on the basis of the nature of the substrate and of the water depth) was the key topic that allowed to establish the actual source areas of bioclasts in the Rosa Marina beach sands. The sedimentological analysis (including a physical study of the beach and the calculation of some statistical parameters concerning the grain-size curves) shows that the Rosa Marina beach is nowadays subject to erosion.
    Źródło:
    Geologos; 2016, 22, 2; 87-103
    1426-8981
    2080-6574
    Pojawia się w:
    Geologos
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    The Mesoproterozoic ‘seismite’ at Laiyuan (Hebei Province, E China) re-interpreted
    Autorzy:
    Van Loon, A. J.
    Powiązania:
    https://bibliotekanauki.pl/articles/94411.pdf
    Data publikacji:
    2014
    Wydawca:
    Uniwersytet im. Adama Mickiewicza w Poznaniu
    Tematy:
    seismites
    valley-fill
    graben sedimentation
    Wumishan Formation
    Mesoproterozoic
    Fangshan geopark
    Hebei Province
    China
    sejsmity
    mezoproterozoik
    geopark Fang Shan
    prowincja Hebei
    Chiny
    Opis:
    A 1-million m3 breccia near Laiyuan (Hebei Province, E China) occurs as a block-like lithological unit between dolostones of the 1.55–1.45 Ga (Early Mesoproterozoic) Wumishan Formation. It has previously been interpreted as a seismite, but it appears not to fulfil any of the commonly accepted criteria that jointly are considered diagnostic for seismites. Its presence in a graben-like structure with almost vertical bounding fault planes rather indicates an origin as a (submarine) valley fill. As the valley originated by tectonic activity in the form of faulting, the breccia can be considered as a secondary effect of seismic activity, but it does not represent a seismite.
    Źródło:
    Geologos; 2014, 20, 2; 139-146
    1426-8981
    2080-6574
    Pojawia się w:
    Geologos
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
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