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The Middle Jurassic (Bajocian–Bathonian) flora of the Tabas Block, central Iran

Maleki Saeed

Geologos

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2024

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Vol. 30, No. 1

33--44

EN

The present study discusses the outcome of palynlogical and palaeobotanocal investigations of Middle Jurassic strata of the Tabas Block. The most commonly identified spore type is a trilete spore, Klukisporites, which accounts for 30 per cent, and the genus Ischyosporites which makes up 12 per cent of the spore collection. Plant fossils recovered from the borehole studied are indicative of a varied assemblage, starting with a diverse range of ferns and followed by Cycadophytes, Ginkgophytes and Coniferophytes. The predominance of the Lowland group in the Tabas Block during the Bajocian–Bathonian, as indicated by the Sporomorph EcoGroup (SEG) and Plant EcoGroup (PEG) models, suggests that the strata studied were laid down mainly in a lowland environment. Dinoflagellate cysts were found in locations that correspond to river and coastal ecogroups, hinting at marine influence.

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Uwęglony i zsylifikowany pień kordaita w warstwach libiąskich (westfal D – moskow) koło Chrzanowa, Górnośląskie Zagłębie Węglowe

Lipiarski I., Pawlikowski M.

Przegląd Geologiczny

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2014

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Vol. 62, nr 1

22–-27

EN

The sample in the formof the drill core 9 cm long and 6 cm in diameter reveals exclusively secondary wood. No growth rings have been observed. Tracheids have the width 20–50 μm (mean 25 μm) in the tangential section. Pitting on the radial walls is mainly uniseriate, partly biseriate or triseriate. The uniseriate pits are circular or oval. The biseriate and triseriate pits are polygonal (often hexagonal), distributed adjacent to each other, and densely cover the whole width of the walls. The diameter of the pits is 12±2 μm. The poruses are circular. Medullary rays are mostly uniseriate, composed of 1–46 layers; mostly between a fifteen or so and 30 layers. As the investigations are at the preliminary stage, the author prefers to use only the generic term to name the wood, namely Dadoxylon sp., without giving it a species designation. Mineralogical investigation of silicified wood was conducted using polarizing light microscope. Observations showed various the optical orientation of quartz crystals filling up cells of wood. It is observed as differentiated disapperance of polarized light. This phenomenon documents that beginning of growth of quartz crystals (center of crystallization) was located at various places of cell walls. This situation is the result of beginning of destruction of organic compounds of wall structure of cells at various places. Additionally investigation documents various intensity of silification of cordaitalean structure. Because of this the process of silification is different at various parts of tissues and one can observe parts fully petrified and completely without mineralization. The structure of wood tissues is at same places damaged by crystallizing quartz. This phenomenon is observed at the tissues where silification was continued and size of newly formed quartz crystals is overgrowth size wood cells of wood. Mentioned zones of cell destruction are especially well seen at placed where silification developed parallel to orientation of biological wood structures. In summary one can say that mentioned processes were the reason of only partial petrification (silification) of examined cordaitalean second wood.

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The earliest Pleistocene interglacials in Lithuania in the context of global environmental changes

Baltrūnas V., Zinkutė R., Šeirienė V., Katinas V., Karmaza B., Kisielienė D., Stakėnienė R., Pukelytė V.

Geological Quarterly

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2014

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Vol. 58, No. 1

145--162

EN

Investigations have been carried out in order to reconstruct the palaeoenvironmental changes during the earliest Pleistocene interglacials and to establish their relation to global environmental changes. Three sections in east Lithuania exposing the earliest Pleistocene lacustrine deposits lying between the Kalviai (Glacial B, Nidanian?) and Dzūkija (Sanian 1) and between Dzūkija (Sanian 1) and Dainava (Sanian 2) glacial deposits were selected for study. Until now the Šlavė-2 and Vindžiūnai-136 successions were considered to have formed during the Vindžiūnai (Augustovian?, Malopolanian) Interglacial and the Kudrė-915 succession during the Turgeliai (Cromerian IV, Ferdynandovian) Interglacial. Geochemical, palaeomagnetic, magnetic susceptibility, anisotropy of magnetic susceptibility and palaeobotanical proxies were applied to establish the cyclicity and dynamics of palaeoenvironmental change. The data obtained enable the subdivision of the section into units related to changes in the sedimentary environment. The Matuyama/Brunhes boundary and Jaramillo subchron of the Matuyama chron have been recognized in the Šlavė section. The results enable correction of the stratigraphic position of the sections studied. The sedimentation in the Šlavė section took place during the Early Pleistocene, while that at the Vindžiūnai-136 and Kudrė-915 took place during two different Middle Pleistocene interglacials.

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Upper Cretaceous (Maastrichtian) charophyte gyrogonites from the Lameta Formation of Jabalpur, Central India: palaeobiogeographic and palaeoecological implications

Khosla A.

Acta Geologica Polonica

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2014

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Vol. 64, no. 3

311--323

EN

A charophyte gyrogonite assemblage consisting of Platychara cf. sahnii, Nemegtichara grambastii and Microchara sp. is reported herein from two localities (Bara Simla Hill and Chui Hill sections) of the Lameta Formation at Jabalpur. The Lameta Formation locally underlying the Deccan traps has been shown to be pedogenically modified alluvial plain deposits containing one of the most extensive dinosaur nesting sites in the world. They are associated with dinosaur bones and freshwater ostracod assemblages that suggest a Late Cretaceous (Maastrichtian) age. This is the first detailed systematic account of charophyte gyrogonites from the Lameta Formation. This charophyte assemblage is compatible with the biostratigraphic attribution provided by the ostracods. From a biogeographic viewpoint, it exhibits considerable similarity to other infratrappean assemblages of the Nand, Dongargaon, and Dhamni-Pavna sections (Maharashtra), and some intertrappean assemblages of Kora in Gujarat, Rangapur in Andhra Pradesh and Gurmatkal in South India. Globally, the genus Microchara is well distributed throughout Eurasia, whereas the genus Platychara occurs richly in the Upper Cretaceous deposits of Europe, Asia, America and Africa. However, at the specific level, Platychara cf. sahnii shows close affinities with charophytes from the Maastrichtian of Iran whilst Nemegtichara grambastii shows distinct affinities with two species of Early Palaeogene deposits of China and Mongolia. The presence of charophyte gyrogonites in the Lameta sediments is attributed to local lacustrine and palustrine conditions within a flood plain environment.

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Wiek i historia rozwoju torfowiska w Pakosławicach (południowo-zachodnia Opolszczyzna) na podstawie badań paleobotanicznych

Maj J., Gałka M.

Przegląd Geologiczny

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2012

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Vol. 60, nr 2

110-116

EN

The result of palaeobotanical studies of biogenic sediments from Pakosławice made it possible to establish the age of limnic and peat sediments and reconstruct past plant communities and development phases of the sedimentary/sedentary basin. The investigated mire originated from overgrowth of a shallow lake. The lake formed probably as a result of thermokarst processes (permafrost thawing). Accumulation of gyttja started in the Alleröd to continue in the Younger Dryas and early Holocene (Preboreal and Boreal). The sedentation of peat deposits probably took place in the middle and late Holocene.

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Westphalian-Stephanian macrofloras of the Southern Pennines Basin, UK

Cleal C.J.

Studia Geologica Polonica

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2008

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Vol. 129

25-41

EN

The southern part of the Pennines Basin (Warwickshire, South Staffordshire and Wyre Forest coalfields) has a condensed succession of middle Langsettian to upper Asturian or lower Cantabrian strata. The Langsettian-Duckmantian part of the succession is in a grey coal-bearing facies, in which many coal seams have become vertically accreted, and in which macrofloras of the Laveineopteris loshii Subzone, Lonchopteris rugosa Zone and Neuropteris semireticulata Subzone can be recognised. Species composition and Total Species Richness diversity curves compare well with those from the Central Pennines Basin to the north, suggesting that they represent an essentially unified area of vegetation. Red beds of the Etruria Formation appear in the lower Bolsovian Substage (stratigraphically lower in the marginal southernmost part of the basin). The Etruria Formation macrofloras are not abundant, but where they do occur are not significantly less species-rich than in the contemporaneous grey coal-bearing sequence in the Central Pennines. The Etruria Formation macrofloras belong to the N. semireticulata Subzone, and there is no evidence of the overlying Laveineopters rarinervis Subzone that would indicate a late Bolsovian age. The grey, mainly arenaceous Halesowen Formation unconformably overlies the Etruria Formation, and yields low- diversity macrofloras that probably indicate the late Asturian Dicksonites plueckenetii Subzone. The succeeding red-beds of the Salop Formation yield even lower diversity macrofloras, but there is some evidence that they may belong to the Cantabrian O. cantabrica Zone. A comparison of these new data with the evidence from the Central Pennines helps confirm the robustness of Total Species Richness as a proxy for environmental change in Late Carboniferous palaeotropical coal-bearing sequences.