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Clasts derived from rhizocretions in shallow-marine Miocene clastic deposits of northern Hungary: an example of zombie structures

Uchman Alfred, Dávid Árpád, Fodor Rozália

Geological Quarterly

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2023

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Vol. 67, No. 1

art. no. 4

EN

Disc- and cylindrical-shaped clasts of fine-grained calcareous and ferruginous rock, each with a central tunnel, occur in shallow marine brackish Miocene sandy deposits of the Egyházasgerge Formation in Hungary. Previously, these have been interpreted as enigmatic biogenic (?) structures. After field and laboratory examination and comparisons with sub-recent rhizoclasts in subsoils developed on Quaternary fine-grained deposits in SE Poland, they are re-interpreted as redeposited rhizocretions possibly washed out of the coeval continental deposits of the Salgótarján Lignite Formation. Most are fragmented and abraded. They are termed rhizoclasts and are presented as an example of zombie structures inherited from another environment where they played a different role. Such rhizoclasts can be considered as an indicator of the source of the clastic material transported from a vegetated landmass on which moderate or poorly drained soils develop and plant roots penetrate the fine-grained substrate. In such soils, iron was mobilized, then fixed by oxidation, as the water table and oxygen levels fluctuated.

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Konkrecii Tabaginskogo mysa, republika Saha (Akutia)

Alekseev V. V.

Prace Naukowe Instytutu Nafty i Gazu

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2016

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nr 209 wyd. konferencyjne

123--125

RU

Разнообразие конкреционных образований связано с разными геологическими процессами, составом осадков, породы и др. Образование конкреций есть следствие перемещения определенных веществ – углекислого кальция, углекислого железа, сернокислого кальция, кремнезема и др. к центрам, например, разложения органической материи в массе осадка. Инфильтрация растворов происходит или в еще не затвердевшей массе осадка, или через поры. Концентрация этих веществ происходит в форме сферических, эллипсоидальных, гроздевидных или ветвистых стяжений. Разнообразие морфологии конкреций зависит от характеристик среды: глубины залегания осадка, солености, состава осадка, проницаемости и др. Центром кристаллизации в основном является органическое тело (раковина, тело рака или рыбы). Конкреции образуются на всех стадиях петрогенеза – от седиментационной до метаморфической, но чаще в процессе диагенеза. Работа основана на изучении собранных образцах конкреций Табагинского мыса, который находится на территории Центральной Якутии в 40 км к югу от г. Якутска. Массовое развитие разнообразных конкреций здесь наблюдается не только в естественных горизонтах «конденсации», но и в переотложенном виде на узкой береговой линии реки Лены. По минеральному составу выделяются железо-карбонатные, железо-сульфидные (пирит-марказитовые) и известковые или сидерит – содержащие конкреции, присутствующие в среднеюрских отложениях, в составе укугутской, тюнгской, сунтарской и якутской свит.

EN

Diversity of concretionary formations is the result of various processes, precipitation chemistry, mineral composition of rocks, etc. Concretions form as certain substances such as calcium carbonate, iron carbonate, calcium sulphate, silica, etc. move to the core of decomposing organic matter in sediments. Solutions are either absorbed by the mass which has not hardened into a solid rock yet or infill the pore spaces of the sediment. The concentrations are often spherical or ovoid in shape, cluster-shaped or treeing. Morphology of concretions vary depending on characteristics of the enviroment: depth of sediment, its salinity, composition, degree of openness, geological processes, etc. Minerals crystallize around nucleous, usually organic (shell, dead and/or decade matter – like crab or fish). Concretions form at all stages of petrogenesis, from sedimentation to metamorphic, but mostly during diagenesis. The research work is based on the study of concretions samples from Tabaga Cape, which is situated in Central Yakutia, 40 km south of Yakutsk where massive concretions are observed not only in natural concretionary horizons but also as redeposits on the narrow shoreline of the Lena river. Mineral composition of concentrations can be iron-carbonate, iron-sulfide (pyrite-marcasite), limestone or siderite containing nodules, they were featured in Middle Jurassic sediments in Ukugut, Tyungsk, Suntarsk, Yakutsk suites.

3

Mikrokonkrecje syderytowe w holoceńskich osadach ujścia rzeki Gwadiana w Portugalii : raport wstępny

Wilamowski A., Boski T., Moura D.

Przegląd Geologiczny

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2013

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Vol. 61, nr 10

568--575

EN

The authors described micro-scale carbonate concretions occurring at a depth of about 41 m within Holocene sandy sediments filling the Guadiana River paleovalley, representing the transitional fluvial- -estuarine facies. Despite their minute sizes, the micro-concretions show a complex internal structure. Regular distribution of Mg, Mn and Ca can be assigned to a chemical zoning, pointing to precipitation under varying chemical conditions. Based on morphological and chemical peculiarities, four types of concretions can be distinguished. Detrital Fe-Mg-carbonates form nuclei. At first, Mn-rich carbonate precipitated as a coating, which is coherent with the sequence of precipitation of carbonates associated with bacteria-mediated oxidation of organic matter. Subsequently, the main bodies of concretions precipitated as Fe-carbonate (siderite). The last precipitation episode is marked by enrichment in Ca. The XRD patterns show the presence of a mixture of discrete carbonate phases.

4

Struktury iłów poznańskich w obserwacjach mikroskopowych jako wskaźniki poligenezy osadów

Duczmal-Czernikiewicz A.

Biuletyn Państwowego Instytutu Geologicznego

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2011

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nr 444

47--54

PL

W artykule przedstawiono cechy mikrostrukturalne iłów poznańskich w świetle analiz mikroskopowych. Przy użyciu mikroskopu polaryzacyjnego opisano struktury po korzeniach roślin, mikrokonkrecje Fe-Mn, konkrecje kalcytowe i syderytowe, pustki będące pozostałościami po mikrokryształach „róż pustyni” oraz lustra ślizgowe. Struktury te mają charakter zarówno pierwotny, jak i wtórny, co wskazuje na wielostadialny sposób formowania się iłów poznańskich. Struktury po korzeniach roślin oraz lustra ślizgowe świadczą o rozwijających się procesach glebowych w powierzchniowych warstwach osadu, natomiast powstanie konkrecji żelazowo-manganowych i węglanowych jest związane ze zmianą warunków fizykochemicznych w osadach poddanych procesom wietrzenia.

EN

This paper presents microfabric of the Poznań clays in microscopic investigations. The method allows describing the structures after plant roots, Fe-Mn globules, calcareous and siderite concretions, voids after “desert roses” microcrystallites, as well as slickensides. These features are of primary and secondary origin and indicate multistage formation of the studied sediments and polygenenetic processes in their geological history. Root remnants, and slickensides indicate pedogenesis, while microcrystallites, Fe-Mn globules and calcareous concretions were formed during the changes of physical and chemical conditions during weathering processes.

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A unique habitat of endolithic biota: hurricane-induced limestone rubble in an Albian sand-mass of the Cracow Upland, southern Poland

Marcinowski R., Radwański A.

Acta Geologica Polonica

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2009

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Vol. 59, no. 4

505-521

EN

Peculiarly shaped, relatively large (up to 30 cm in diameter) concretions of quartzitic sandstone occur in a single horizon of Upper Albian loose sands in the Cracow Upland, southern Poland. They are characterized by hollow interiors adorned with mass-aggregated moulds of the borings of diverse sponges, polychaetes and bivalves. These moulds represent the siliceous filling of borings in limestone clasts that had been subject to dissolution, leaving a hollow within the concretion that had formed around them. Synsedimentary block-faulting and jointing affected the Jurassic limestone-basement, causing the uplift of a local horst (the Glanow Horst), to within the littoral zone so that it became exposed to abrasion. It is inferred that a hurricane or catastrophic storm surge swept limestone debris fallen from the cliff out to the sandy offshore, where nucleation of soluble silica was presumably favoured by the decay of the soft tissue of live or dead rock-borers. After filling the emptyo borings and solution of the limestone clasts, the nucleation progressed intensely, finally completed by precipitation of siliceous sinter in the hollow interiors of some of the concretions during subsequent diagenesis and/or epigenesis.