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Bo Wang - One of the best experts on this subject based on the ideXlab platform.
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timing of initiation of extension in the tianshan based on structural geochemical and geochronological analyses of bimodal volcanism and Olistostrome in the bogda shan nw china
International Journal of Earth Sciences, 2011Co-Authors: Bo Wang, Jacques Charvet, Yuan ZhangAbstract:This paper describes an Olistostrome formation and accompanied bimodal volcanic rocks occurring in the Baiyanggou area, south of Bogda Shan. The main lithotectonic units consist of Olistostrome, volcanic rocks and turbidite. The Olistostrome is tectonically underlain by Upper Carboniferous limestone and sandstone along a NEE-trending detachment fault. Paleo-growth fault is locally observed. The Olistostrome unit includes plenty of blocks of limestone, sandstone, rhyolite and volcaniclastic rocks, and a matrix of graywacke. Limestone blocks are dated as Pennsylvanian-Bashkirian in age by the coral and brachiopod fossils that are extensively recognized in the Upper Carboniferous strata. The volcanic unit consists of pillowed and massive basalt and rhyolite, the latter occur as an 8- to 10-meter-thick layer above the Olistostrome unit. The turbidite unit is mainly composed of chert, siliceous mudstone and sandstone, within which the Bouma sequence can be locally recognized. Meter-wide gabbro and diabase dykes intrude these three units. Geochemically, rhyolites are characterized by high ACNK value of >1.1, depletion of Ba, Nb and Sm, and enrichment in Rb, Th and Zr. Basaltic rocks are rich in K2O, they show a LREE-enriched pattern and depletion in Ba, Nb and Zr, and enrichment in Ti, Ce and Hf, similar to continental rift-type tholeiite series. A gabbro porphyrite intruding the Olistostrome was dated at 288 ± 3 Ma by a sensitive high-resolution ion microprobe (SHRIMP) zircon U–Pb method, and a rhyolite at 297 ± 2 Ma by a laser ablation inductively coupled plasma mass spectrometer (LA-ICPMS) zircon U–Pb method. The Baiyanggou Olistostrome and accompanying bimodal volcanic series are linked to an extensional setting that developed in the south of the Bogda Shan. Several lines of evidence, e.g. occurrence of large-scale strike-slip shear zones, large number of mantle-derived magmatic rocks and available geochronological data, demonstrate a significant geodynamic change from convergence to extension in the Chinese Tianshan belt, even in the whole Central Asian Orogenic Belt. The extension in the Chinese Tianshan belt is initiated at ca. 300 Ma, i.e. around Carboniferous–Permian boundary times, and the peak period of intra-plate magmatism occurred in the interval of 300–250 Ma.
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the post collision intracontinental rifting and Olistostrome on the southern slope of bogda mountains xinjiang
Acta Petrologica Sinica, 2005Co-Authors: Bo Wang, Michel Faure, Jacques Charvet, Dominique CluzelAbstract:A regional-scale tectonic event of closure of ocean and collision-orogeny took place in the interval from Late Devonian to Late Carboniferous in the Xinjiang area. At the late stage of collision, some tectonic changes occurred in the piedmont area. The preliminary framework of mountains-basins of northern Xinijiang was composed of both Late Carboniferous-Early Permian orogenic belt and piedmont basins. In the direction toward continent, post-collision intracontinental rifting and Olistostrome developed well. The bedded diabase and bimodal volcanic rocks were distributed in the Early Permian strata in the piedmont area. The most typical area is located on the southern slope of Bogda Mountains, namely the Qijiaojing-Cheguluquan segment of Harm city and the Baiyanggou section of Urumgi. This paper studied the geometrical, petrological and geochemical features of intracontinent bimodal volcanic rocks and Olistostrome. Of them, post-collision Olistostrome is the first time discovery by us. In the Qijiaojing-Cheguluquan segment, basalt and rhyolite are ranged alternately that overlie the Early Permian red molasses. This post-collision bimodal volcanic series with a big thickness is distributed in parallel with the sub-E-W mountain extension. In the Baiyanggou section, post-collision underwater Olistostrome co-exists with underwater eruption and is composed of Olistostrome zone, pillow lava and pore basalt zone, and siliceous shale and siltstone zone; the bottom plane is contacted with Late Carboniferous limestone and sandstone series by a NEE-trending detachment fault.
Jaroslava Hajna - One of the best experts on this subject based on the ideXlab platform.
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a giant late precambrian chert bearing Olistostrome discovered in the bohemian massif a record of ocean plate stratigraphy ops disrupted by mass wasting along an outer trench slope
Gondwana Research, 2019Co-Authors: Jaroslava Hajna, Lukas Ackerman, Martin Svojtka, Jan PasavaAbstract:Abstract An intriguing example of chert–graywacke Olistostrome is exceptionally well preserved within the late Neoproterozoic to early Cambrian Blovice accretionary wedge, Bohemian Massif. The Olistostrome exhibits a block-in-matrix fabric defined by chert blocks isolated within the graywacke matrix. The major and trace element composition indicates two distinct types of cherts that formed either in a hydrothermal pelagic or hemipelagic environment supplied with a distal terrigenous material. The former is documented by elevated contents of Fe, Co, Zn, Ni, and Ti whereas the latter by high Al2O3 contents, relatively lower LaN/CeN ratios, and higher Eu/Eu* and Ce/Ce* values. Based on these geochemical data integrated with field observations and detrital zircon U–Pb ages of the host graywackes (determined using laser ablation ICP-MS), a new model for the origin of chert–graywacke association is proposed. The cherts are interpreted as representing pelagic and hemipelagic members of the Ocean Plate Stratigraphy (OPS) that formed in a sedimentary basin, carried on top of a subducting plate towards the trench. While moving over the outer swell (rise), the chert basin was intensely fractured and disrupted into large blocks or slabs. Subsequent motion of the plate brought the blocks onto an outer trench slope where they became gravitationally unstable to slide down and mix in the trench with distal, ca. 580–570 Ma turbidites derived from the overriding plate. Finally, this chert–graywacke Olistostrome was covered by younger, ca. 560–547 Ma trench-fill turbidites (devoid of chert blocks) and accreted to the accretionary wedge toe, deformed, buried, and exhumed back to the wedge surface. We propose that such an Olistostrome composed of pelagic/hemipelagic chert blocks and terrigenous, arc-derived graywacke matrix represents a rarely documented case of submarine, outer trench slope mass-wasting deposits and may be considered a new type of subduction-related melanges. We coin the term outer-trench-slope melange.
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Growth of accretionary wedges and pulsed ophiolitic mélange formation by successive subduction of trench-parallel volcanic elevations
Terra Nova, 2014Co-Authors: Jaroslava Hajna, Václav KachlíkAbstract:Fault-bounded coherent belts alternating with belts of melanges are common in accretionary wedges and are usually interpreted as a result of imbrication along subduction zone megathrusts. Using the Neoproterozoic/early Cambrian Blovice accretionary complex (BAC), Bohemian Massif, as a case example, we present a new model for the origin of alternating belts through the repetition of several cycles of (1) offscraping and deformation of trench-fill sediments to form the coherent units, interrupted by (2) arrival and subduction of linear, trench-parallel volcanic elevations. The latter process leads to an increase in the wedge taper, triggering mass-wasting and formation of Olistostromes. At the same time, ophiolitic melanges form by disruption of an upper part of the volcanic ridge and incorporation of the disrupted ocean-floor succession into the Olistostromes. Specifically, the BAC represents a complete section across an accretionary wedge and records three such major pulses of ophiolitic melange formation through subduction of an outboard back-arc basin.
Anna Waśkowska - One of the best experts on this subject based on the ideXlab platform.
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Sedimentary and diapiric mélanges in the Skrzydlna area (Outer Carpathians of Poland) as indicators of basinal and structural evolution
Journal of the Geological Society, 2019Co-Authors: Aneta Siemińska, Anna Waśkowska, Krzysztof Starzec, Marek WendorffAbstract:The Dukla Nappe in the Skrzydlna area exposes two types of melange reflecting two different phases of basinal and tectonic evolution of the Outer West Carpathian orogen in its Polish sector. The Oligocene-age sedimentary melange (Olistostrome) is related to growth of the accretionary wedge, whereas the Miocene-age diapiric melange postdates the orogenic thrusting. Textural and structural features of the very coarse-grained sedimentary melange suggest non-cohesive debris flows and high-density turbidity currents as predominant emplacement mechanisms. Growth strata, associated with progressive unconformities, and facies contrast between the underlying fine-grained unit and the overlying Olistostrome reflect a considerable uplift of the source area and rotation of the adjacent part of the basin floor. The Olistostrome and the overlying turbidite succession form a retrogressive sequence interpreted as a submarine canyon infill grading to a small submarine fan. The diapiric melange, injected into the Oligocene-age succession of the Dukla Nappe, contains the Early and Late Cretaceous-age blocks and matrix derived from the underlying Silesian Nappe. The features reflecting diapiric emplacement include matrix proportion increase and block content decrease towards the melange margins, scaly fabric and shear zones. Both melanges, interpreted in the past as chaotic bodies, upon detailed examination reveal genesis-related subtle internal organization.
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Discussion of ‘Olistostromes of the Pieniny Klippen Belt, Northern Carpathians’
Geological Magazine, 2016Co-Authors: Jan Golonka, M. Krobicki, Anna Waśkowska, Marek Cieszkowski, Andrzej ŚlączkaAbstract:J. Golonka, M. Krobicki, A. Waśkowska, M. Cieszkowski & A. Ślączka reply: We welcome the comments by our Slovakian colleagues and their critique of our results, particularly as we have discussed and published papers together several times about our ideas, sometimes, more or less, disputable (Aubrecht et al. 2003, 2006; Krobicki et al. 2003; Krobicki, Aubrecht & Golonka, 2003; Golonka et al. 2006; Pienkowski et al. 2008). We are pleased to see such warm reaction to our work/paper, which is focused on one of the rudimentary questions in the Pieniny Klippen Belt (PKB) area. How many/what kind of olistoliths/Olistostromes occur within the inner structure of the PKB, and when and why did they originate mostly during the Palaeogene part of the Mesozoic–Cenozoic history of this region? We expected this discussion earlier. The content of our paper was presented at the 6 th Meeting of the Central European Tectonic Studies Group (CETeG) in Upohlav, Pieniny Klippen Belt, Slovakia (Cieszkowski et al. 2008), and later, at the XIX Congress of the Carpathian–Balkan Geological Association in Thessaloniki, Greece (Cieszkowski et al. 2010; Golonka et al. 2010). Some ideas were also briefly mentioned in the paper by Cieszkowski et al. (2009) in a journal issue edited by D. Plasienka. We assume that the comments are based on recent investigation, because the authors list the grants received to conduct the research. Therefore, the submitted comments sometimes present a point of view different from that published previously by some of the authors of the comments (RA, JM) (see Aubrecht et al. 2003; Krobicki, Aubrecht & Golonka, 2003; Wierzbowski et al. 2006; Pienkowski et al. 2008). The statement, ‘Certainly there are many still unresolved problems in the geology of the PKB, and it ought to be said that the co-authors of this discussion also do not fully agree with all interpretations formulated and illustrated by the first author’ perhaps explains this controversy. Of course, we agree that ‘there are many still unresolved problems in the geology of the PKB’. We also agree with the statement ‘Olistostromes and olistoliths are quite frequent, but not omnipresent’. We depicted the distribution of the olistoliths and their relationship to the non-olistolith tectonic units of the PKB in Golonka et al. (2015, figs 3, 8).
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Olistostromes of the Pieniny Klippen Belt, Northern Carpathians
Geological Magazine, 2014Co-Authors: Jan Golonka, M. Krobicki, Anna Waśkowska, Marek Cieszkowski, Andrzej ŚlączkaAbstract:The Olistostromes form two belts within the Pieniny Klippen Belt (PKB) in the Northern Carpathians. They mark an early stage of the development of the accretionary prism. The first belt was formed during Late Cretaceous time as a result of subduction of the southern part of the Alpine Tethys. The fore-arc basin originated along this subduction zone, with synorogenic flysch deposits. Huge olistoliths deposited within the Cretaceous–Palaeogene flysch of the Zlatne Basin, presently located in the vicinity of the Haligovce village (eastern Slovakia), provide a good example of the fore-arc Olistostrome setting. The second belt is related to the movement of the accretionary prism, which overrode the Czorsztyn Ridge during Late Cretaceous–Paleocene time. The destruction of this ridge led to the formation of submarine slumps and olistoliths along the southern margin of the Magura Basin. The Upper Cretaceous – Paleocene flysch sequences of the Magura Basin constitute the matrix of Olistostromes. The large Homole block in the Jaworki village represents the best example of the Magura Basin olistolith. Numerous examples of olistoliths were documented in western Slovakia, Poland, eastern Slovakia and Ukraine. The Olistostromes formed within the Zlatne and Magura basins orginated during the tectonic process, forming the Olistostrome belts along the strike of the PKB structure.
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biostratigraphy and depositional anatomy of a large Olistostrome in the eocene hieroglyphic formation of the silesian nappe polish outer carpathians
Annales Societatis Geologorum Poloniae, 2014Co-Authors: Anna Waśkowska, Marek CieszkowskiAbstract:Ab stract: The study fo cuses on a large Olistostrome unit (~200 m thick and 4 km in strike-par al lel ex tent) em bed ded in the Mid-Eocene shaly Hi ero glyphic For ma tion of the Silesian Nappe, ex posed in the Ro?now Lake area. Foraminifer biostratigraphy and petrographic com par i sons are used to iden tify the prov e nance of olistoliths. The Olistostrome is tri par tite with re spect of its olistolith com po si tion. The lower part of the Olistostrome abounds in olistoliths of sand stones de rived from the Early Eocene turbiditic Cie?kowice For ma tion, whereas the mid dle part is dom i nated by olistoliths of Early Eocene bathyal mudshales. The up per part con tains olistoliths of Mid dle Eocene turbiditic “banded sand stones”, known from the Hi ero glyphic For ma tion and de pos ited in the bathyal zone above the CCD. The bathyal prov e nance of the Olistostrome con trasts with the abys sal or i gin of the host ing green shales. The Olistostrome unit is in ferred to be com pos ite, emplaced in the ear li est Bartonian or at the Lutetian/ Bartonian tran si tion by a se ries of at least three large de bris flows that closely fol lowed one an other. Biostratigraphical data and slump-fold vergence sug gest resedimentation from the bathyal north ern slope of the Silesian Cor dil lera that bounded the abys sal Silesian Ba sin to the south. North ward move ment of the thrust-formed cor dil lera must have warped up the base-of-slope de pos its of the Cie?kowice For ma tion, caus ing their grav i ta tional col lapse. This event destabilized the for mer lower-slope muddy de pos its, re sult ing in a sec ond phase of resedimentation by ret ro gres sive slump ing, which led to the col lapse of mid-slope sandy turbidites. The slope fail ures in volved con tem po ra ne ous Mid-Eocene sed i ment with an ad mix ture of foraminifers de rived from the up per slope or shelf mar gin and with ex otic bed rock de bris shed from the eroded cor dil lera crest. The cat a strophic multi-phase em place ment of the Olistostrome marked the last ma jor thrust ing pulse of the sec ond (Late Cre ta ceous–Late Eocene) stage of tec tonic evo lu tion of the Outer Carpathian accretionary prism.
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Role of the Olistostromes and olistoliths in tectonostratigraphic evolution of the Silesian Basin in the Outer West Carpathians
Tectonophysics, 2012Co-Authors: Marek Cieszkowski, Jan Golonka, Andrzej Ślączka, Anna WaśkowskaAbstract:Abstract The Silesian Series deposited in the proto-Silesian and Silesian basins and preserved within the Silesian Nappe, represents most complete continuous basinal sedimentary succession (Late Jurassic–Early Miocene) within the Outer Carpathians. It contains intercalations of numerous Olistostromes that occurred during every stage of flysch basin evolution, from rift and post-rift, through orogenic to postorogenic stage. The Olistostromes represent sediments of sub-marine debris-flows and avalanches. They are of different size and composition and were derived from ridges and their slopes bordering proto-Silesian and Silesian Basins. 0However the main source was the tectonically active southern slope and adjacent ridges — the Silesian and Bukowiec ridges. Composition of Olistostromes is an important source of knowledge about the geological structure and history of ridges and basin slopes, which now are not preserved. Some large olistoliths and olistoplaques have been incorrectly interpreted as thrust sheets, so detail studies of their true origin allowed correct interpretation of local tectonics.
Jan Pasava - One of the best experts on this subject based on the ideXlab platform.
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a giant late precambrian chert bearing Olistostrome discovered in the bohemian massif a record of ocean plate stratigraphy ops disrupted by mass wasting along an outer trench slope
Gondwana Research, 2019Co-Authors: Jaroslava Hajna, Lukas Ackerman, Martin Svojtka, Jan PasavaAbstract:Abstract An intriguing example of chert–graywacke Olistostrome is exceptionally well preserved within the late Neoproterozoic to early Cambrian Blovice accretionary wedge, Bohemian Massif. The Olistostrome exhibits a block-in-matrix fabric defined by chert blocks isolated within the graywacke matrix. The major and trace element composition indicates two distinct types of cherts that formed either in a hydrothermal pelagic or hemipelagic environment supplied with a distal terrigenous material. The former is documented by elevated contents of Fe, Co, Zn, Ni, and Ti whereas the latter by high Al2O3 contents, relatively lower LaN/CeN ratios, and higher Eu/Eu* and Ce/Ce* values. Based on these geochemical data integrated with field observations and detrital zircon U–Pb ages of the host graywackes (determined using laser ablation ICP-MS), a new model for the origin of chert–graywacke association is proposed. The cherts are interpreted as representing pelagic and hemipelagic members of the Ocean Plate Stratigraphy (OPS) that formed in a sedimentary basin, carried on top of a subducting plate towards the trench. While moving over the outer swell (rise), the chert basin was intensely fractured and disrupted into large blocks or slabs. Subsequent motion of the plate brought the blocks onto an outer trench slope where they became gravitationally unstable to slide down and mix in the trench with distal, ca. 580–570 Ma turbidites derived from the overriding plate. Finally, this chert–graywacke Olistostrome was covered by younger, ca. 560–547 Ma trench-fill turbidites (devoid of chert blocks) and accreted to the accretionary wedge toe, deformed, buried, and exhumed back to the wedge surface. We propose that such an Olistostrome composed of pelagic/hemipelagic chert blocks and terrigenous, arc-derived graywacke matrix represents a rarely documented case of submarine, outer trench slope mass-wasting deposits and may be considered a new type of subduction-related melanges. We coin the term outer-trench-slope melange.
Yuan Zhang - One of the best experts on this subject based on the ideXlab platform.
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timing of initiation of extension in the tianshan based on structural geochemical and geochronological analyses of bimodal volcanism and Olistostrome in the bogda shan nw china
International Journal of Earth Sciences, 2011Co-Authors: Bo Wang, Jacques Charvet, Yuan ZhangAbstract:This paper describes an Olistostrome formation and accompanied bimodal volcanic rocks occurring in the Baiyanggou area, south of Bogda Shan. The main lithotectonic units consist of Olistostrome, volcanic rocks and turbidite. The Olistostrome is tectonically underlain by Upper Carboniferous limestone and sandstone along a NEE-trending detachment fault. Paleo-growth fault is locally observed. The Olistostrome unit includes plenty of blocks of limestone, sandstone, rhyolite and volcaniclastic rocks, and a matrix of graywacke. Limestone blocks are dated as Pennsylvanian-Bashkirian in age by the coral and brachiopod fossils that are extensively recognized in the Upper Carboniferous strata. The volcanic unit consists of pillowed and massive basalt and rhyolite, the latter occur as an 8- to 10-meter-thick layer above the Olistostrome unit. The turbidite unit is mainly composed of chert, siliceous mudstone and sandstone, within which the Bouma sequence can be locally recognized. Meter-wide gabbro and diabase dykes intrude these three units. Geochemically, rhyolites are characterized by high ACNK value of >1.1, depletion of Ba, Nb and Sm, and enrichment in Rb, Th and Zr. Basaltic rocks are rich in K2O, they show a LREE-enriched pattern and depletion in Ba, Nb and Zr, and enrichment in Ti, Ce and Hf, similar to continental rift-type tholeiite series. A gabbro porphyrite intruding the Olistostrome was dated at 288 ± 3 Ma by a sensitive high-resolution ion microprobe (SHRIMP) zircon U–Pb method, and a rhyolite at 297 ± 2 Ma by a laser ablation inductively coupled plasma mass spectrometer (LA-ICPMS) zircon U–Pb method. The Baiyanggou Olistostrome and accompanying bimodal volcanic series are linked to an extensional setting that developed in the south of the Bogda Shan. Several lines of evidence, e.g. occurrence of large-scale strike-slip shear zones, large number of mantle-derived magmatic rocks and available geochronological data, demonstrate a significant geodynamic change from convergence to extension in the Chinese Tianshan belt, even in the whole Central Asian Orogenic Belt. The extension in the Chinese Tianshan belt is initiated at ca. 300 Ma, i.e. around Carboniferous–Permian boundary times, and the peak period of intra-plate magmatism occurred in the interval of 300–250 Ma.
