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„Rój” mioceńskich stożków krewasowych w Konińskim Zagłębiu Węgla Brunatnego, Polska środkowa – stan wiedzy

Chomiak Lilianna, Dziamara Mariusz, Klęsk Jakub, Wachocki Robert, Widera Marek

Przegląd Geologiczny

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2024

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Vol. 72, nr 5

215--224

EN

In the years 2015-2022, at least several relatively large lenses of inter-lignite sands were discovered and examined in lignite opencast mines near Konin in central Poland. They were interpreted as crevasse splays formed on the surface of Mid-Miocene mires (backswamps) during periodic floods. Due to the compaction of peat and the tectonic activity of the current lignite-rich deposit areas (grabens), the crevasse splays represent various genetic-facies types and subtypes. They may be single or numerous palaeoforms creating complexes of crevasse splays. Unfortunately, these inter-lignite sand bodies pose a significant obstacle to mining activities. Nevertheless, in relation to single fossil splays described in world literature, the abundance of such palaeoforms in the vicinity of Konin allows them to be jokingly called a “swarm” of Miocene crevasse splays.

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The geology of the deepest Cenozoic lignite-rich grabens in Poland with particular reference to their lithostratigraphy: a comparative study

Widera Marek, Klęsk Jakub, Urbański Paweł

Geology, Geophysics and Environment

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2024

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Vol. 50, no. 2

131--143

EN

The thickest lignite seams in Poland are located in tectonic depressions such as the Kleszczów, Złoczew, and Lubstów grabens, as well as the Zittau (Żytawa) Basin. Their depth ranges from 220 m to 550 m, while the maximum lignite thickness ranges from approximately 90 m to over 250 m. The areas selected for this study include two Miocene lignite seams that have been exploited or prepared for mining, i.e. the third Ścinawa lignite seam (ŚLS-3) and the second Lusatian lignite seam (LLS-2). Currently, more than 95% of the Polish lignite production comes from the exploitation of these seams. Both lignite seams are accompanied by siliciclastic sediments that are lithologically very diverse. The lignite-rich grabens examined in this study form isolated structures and their individual geology is complex. Hence, apart from the Lubstów Graben, local lithostratigraphy is applied for each case, an approach that makes it difficult to compare the lithological units and their stratigraphic position with the Paleogene and Neogene lithostratigraphy used for the Polish Lowlands area. Therefore, it seems appropriate to present an outline of the geology of the Polish regions bearing most of the lignite seams, including a brief overview of their lithological and palaeotectonic characteristics. However, it is first necessary to clarify and compare the lithostratigraphy of the Cenozoic sediments that fill the studied grabens.

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Four in one : a new crevasse-splay complex in the middle Miocene of central Poland

Widera Marek, Dziamara Mariusz, Klęsk Jakub, Wachocki Robert

Annales Societatis Geologorum Poloniae

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2024

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Vol. 94, No. 1

1--18

EN

This article focuses on a newly identified set of crevasse splays in the lignite-bearing Miocene of Poland. The sand bodies studied are situated within the First Mid-Polish Lignite Seam (MPLS-1) in the Tomisławice opencast mine, located near Konin in central Poland. The sand bodies form an alluvial complex of four superposed crevasse splays, separated by lignite layers, 0.1–0.8 m thick. They are considered to be overbank lateral splays, emplaced laterally by a fluvial channel, rather than its terminal splays. Their combined thickness reaches ~5 m, their length is <0.6 km and width <0.4 km, and their total area is ~0.1 km2. Nearly half of the sediments examined are subaerial deposits, while the rest are typical of crevasse-splay microdeltas, accumulated in a floodplain subaqueous environment. The sand bodies with local clay lenses are both underlain and overlain by, as well as interbedded with a range of lignite lithotypes, representing various sub-environments of a mid-Miocene mire (backswamp) realm. The estimated time span for the formation of the entire crevasse-splay complex, recording four short-term floods, is at least 48 kyr. The crevasse-splay complex is one of the best developed in lignite/coal successions worldwide. However, it poses a major technical obstacle to mining activity in the Konin Lignite Mine.

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Siarka i jej główne minerały w iłch poznańskich (górny neogen) oraz ich wpływ na barwę osadu

Klęsk Jakub

Przegląd Geologiczny

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2023

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Vol. 71, nr 5

249--254

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Facies and statistical analyses of a crevasse-splay complex at the Tomisławice opencast lignite mine in central Poland

Dziamara Mariusz, Kaczmarek Paweł, Klęsk Jakub, Wachocki Robert, Widera Marek

Geologos

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2023

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Vol. 29, No. 3

173--181

EN

The studied crevasse-splay complex, situated within the 1st Mid-Polish lignite seam (MPLS-1), ranks amongst the best-developed and most readily accessible for direct research of all hard coal and lignite occurrences worldwide. The sandy-coaly sediments constituting it required a number of field and laboratory tests. However, the present article focuses solely on sedimentological and statistical analyses of sediments along a selected key section, the most important results of which are presented below. First of all, data obtained in previous sedimentological studies have been confirmed, in that individual segments of this complex represent both subaerial and subaqueous types of crevasse splays. On the one hand, their sediments are characterised by an extremely high content of coalified organic matter, reaching 20–40 wt.% in some samples; on the other, these crevasse splays are composed of fine sands with a median and mean grain size of 0.15 mm. In addition, the remaining statistical parameters (standard deviation, skewness and kurtosis) indicate a very good sorting of these sands, no significant so-called ‘tails’ and a better sorting close to the sediment mean grain size value, respectively.

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Wpływ przerostów piaszczystych w węglu brunatnym na działalność górniczą : przykład ze złoża „Pątnów IV” (okolice Konina) w środkowej Polsce

Dziamara Mariusz, Glacová Veronika, Klęsk Jakub, Marschalko Marian, Wachocki Robert, Widera Marek

Przegląd Geologiczny

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2022

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Vol. 70, nr 5

376--383

EN

Lignite from the “‘Pątnów IV” deposit is mined in the Jóźwin IIB opencast by the Konin Lignite Mine. Within the exploited 1st Mid-Polish lignite seam, there are layers of sand with a thickness of over 5 m. Based on field observations and geological mapping, these sandy interbeddings are interpreted as deposits of two or three crevasse splays of different ages. Due to such a large thickness of sands, only the upper bench of the lignite seam is currently mined in the Jóźwin IIB opencast. On the other hand, the exploitation of the lower and middle lignite benches of this seam is unprofitable at present.

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Iron-bearing phases affecting the colour of upper Neogene clayey sediments from Dymaczewo Stare, west-central Poland

Klęsk Jakub, Błachowski Artur, Diduszko Ryszard, Kruszewski Łukasz, Widera Marek

Geologos

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2022

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Vol. 28, No. 2

129--139

EN

The present paper investigates the colour dependence of mineral compositions in clay-rich sedimentary strata, mainly clayey silts, the emphasis being on iron-bearing minerals (rather than clay minerals) by using powder X-ray diffraction (PXRD) and 57Fe Mössbauer spectroscopy (57Fe-MS). The PXRD-based phase analysis has demonstrated the variable compositions of samples, consisting of, inter alia, quartz, calcite or gypsum, and admixtures of potassium feldspars and plagioclase. Hematite + goethite (sample D1, dark red), goethite (sample D2, pinkish brown), poorly crystalline goethite (sample D3, orange) and jarosite (sample D4, yellow) have been distinguished. A very low jarosite content was detected in sample D5 (light grey); this did not affect its colour. The potential yellow/brown shades in sample D6 (dark grey), coming from trace amounts of jarosite, are masked by macroscopically visible organic matter. In the case of the two last-named samples (D5 and D6), with trace amounts of Fe-bearing minerals, it is most likely that the organic matter was effective in influencing the light and dark grey colour of the sediment, respectively.