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Mikrofacje i diageneza wapieni oolitowych najniższego triasu w profilu Gorzów Wielkopolski IG 1 (zachodnia Polska)

Jasionowski Marek, Becker Anna

Przegląd Geologiczny

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2023

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Vol. 71, nr 5

292--297

EN

Lowermost Triassic oolitic limestones occur in the Gorzów Wielkopolski IG 1 borehole as thin intercalations (mostly less than 1 m thick) within laminated or massive reddish brown mudstones or sandy mudstones of the Baltic and Pomerania formations of the Lowerand Middle Buntsandstein, respectively. In order to characterize the microfacies and diagenesis of the limestones, 46 thin sections from 44 core specimens were investigated. The limestone intercalations are poorly diversified in terms of microfacies, especially in the lower part of the section (Baltic Formation), where almost exclusively fine-grained, well-sorted ooid grainstones occur. The upper part of the section (Pomerania Formation) is more diverse. In addition to grainstones similar to those of the Baltic Formation, coarse-grained and/or poorly sorted ooid grainstones, subordinate stromatolites, oncoid grainstones, and mudstones are present. The limestones are almost completely devoid of bioclasts. The only organic remains present in the thin sections are single rounded plates composed of apatite (possibly fish scales) and, even rarer, snail shells and small shells of other organisms (bivalves?, ostracods?), now dissolved (probably originally aragonitic) and visible only due to the preserved coatings of micritic calcite cement previously precipitated on them. The diagenesis of these deposits has not been very intensive and involves mainly cementation by calcite and subordinately by anhydrite, recrystallization of some ooids and other grains (including carbonate bioclasts), and to alesser extent by dissolution under pressure.

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Katalog basenów sedymentacyjnych Polski

Cymerman Zbigniew, Grabowski Jacek, Jasionowski Marek, Kasiński Jacek, Kiersnowski Hubert, Krobicki Michał, Leszczyński Krzysztof, Narkiewicz Marek, Pacześna Jolanta, Peryt Tadeusz

Prace Państwowego Instytutu Geologicznego

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2023

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T. 207

9--90

PL

Na obszarze Polski wyróżniono 48 basenów sedymentacyjnych obejmujących utwory od ediakaru po pliocen. Opierając się głównie na dostępnych opracowaniach publikowanych, w tym kartograficznych, określono granice basenów, stosując oprogramowanie ArcGIS, a także zestawiono krótkie opisy poszczególnych jednostek. W opisach zarysowano ich zasadnicze cechy: plan strukturalny, wiek wypełnienia osadowego i jego charakterystykę, powierzchnię wychodni, zasięg regionalny na tle elementów tektoniki i paleogeografii oraz genezę. Baseny zaliczono do czterech ogólnych kategorii regionalnych: epikontynentalne (24), włączone w górotwór (14), śródgórskie (4) i związane z terranami (6). Większość opisanych jednostek (32) należy do basenów wychodzących poza granice Polski. Powierzchnia wychodni basenów (w granicach kraju) mieści się w szerokim zakresie: od 11 km2 (basen zgorzelecki) do 284 761 km2 (mezozoiczny basen Niżu Polskiego), przy średnim obszarze 27 290 km2. Nieliczne baseny (w zależności od interpretacji podłoża: 9–15) są rozwinięte bezpośrednio na fundamencie krystalicznym, znaczna większość została nałożona na jednostki powstałe wcześniej, nierzadko w wyniku reaktywacji dawniejszych ram tektonicznych. Głównie na podstawie prac publikowanych przedstawiono zarys genezy poszczególnych basenów, a także wstępnie zaliczono je do ośmiu kategorii genetycznych: obrzeże pasywne, pasmo fałdowo-nasuwcze, basen: przedgórski, przedłukowy, pull-apart, śródkratoniczny, ryftowy i załukowy. Baseny poligenetyczne, o wieloetapowej historii rozwoju, zaliczono do kategorii odnoszącej się do etapu inicjacji basenu. Luki w rozpoznaniu niektórych opisanych basenów sprawiają, że w miarę dopływu nowych materiałów badawczych może ulec zmianie ich definicja, ewentualnie nastąpi ich wewnętrzny podział regionalny lub stratygraficzny, czy też połączenie z sąsiednimi jednostkami.

EN

The catalogue provides description of 48 sedimentary basins from the territory of Poland, comprising deposits from Ediacaran to Pliocene. Basin boundaries in the Arc GIS format, as well as short descriptions of particular units, have been based mainly on published data, including cartographic materials. Descriptions include essential characteristics such as: structural plan, age and general features of a sedimentary fill, regional extent against tectonic and paleogeographic boundaries, and brief genetic considerations. The basins were ascribed to four general regional categories: epicontinental (24 units), incorporated in an orogen (14), intramontane (4), and associated with allochthonous terranes (6). The basin area, defined here as the present area of outcrops or subcrops, ranges from 11 km2 (Zgorzelec Basin) to 284,761 km2 (Mesozoic Basin of the Polish Lowlands), with a mean of 27,290 km2. Most of the described units (32) extend beyond the Polish territory into surrounding countries. Some basins (depending on the basement interpretation: 9-15) are developed directly on a crystalline basement. Majority of basins onlap earlier units, commonly due to reactivation of the pre-existing tectonic framework. A brief review of mechanisms that led to basin formation allowed the authors to ascribe the units to eight genetic categories: passive margin, fold-and-thrust belt, foreland, fore-arc, pull-apart, intracratonic, rift, and back-arc basins. In several instances of polygenetic (polyhistory) basins they were included to a category corresponding to the initial stage of basin development. The present study pinpoints some gaps in our knowledge of particular basins. Once filled, they may lead to changes in basin concepts and definitions, and also to their further subdivision or, conversely, unification.

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Marine vs. terrestrial environments during Early Triassic deposition on the northeastern margin of the Central European Basin : a multidisciplinary study on the Middle Buntsandstein of the Bartoszyce IG 1 borehole, NE Poland

Becker Anna, Fijałkowska-Mader Anna, Jasionowski Marek

Geological Quarterly

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2020

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Vol. 64, No. 4

1023--1047

EN

The Middle Buntsandstein Subgroup of the Lower Triassic of north-eastern Poland has been investigated in the context of possible marine ingressions into the Central European Basin. To better constrain these, palynofacies analysis and mineralogical analysis of mudstones were undertaken on samples taken from the Lidzbark and Malbork formations penetrated by the Bartoszyce IG 1 borehole, serving as stratotype section of both lithostratigraphic units. Microfacies and geochemical analyses, including C and O isotope analysis, were conducted additionally on oolitic limestones of the basal Lidzbark Formation (the lowermost Middle Buntsandstein), and the boron content was measured on all mudstone samples. Seven palynofacies types are distinguished: types 1 to 3 within the Malbork Formation and types 4 to 7 within the Lidzbark Formation. Types 1 and 2 originated on a floodplain, type 3 probably in a deltaic or barrier setting, and types 4 and 5 in a brackish lagoon or a more open basin, possibly of marine origin. Palynofacies type 6 reflects long transport and reworking, whereas palynofacies type 7 is interpreted as formed due to pedogenic processes. Clay minerals and quartz, accompanied by feldspars, calcite and dolomite are the main components of the mudstones investigated. The clay mineral association consists of illite or a mixture of illite and smectite, and chlorite. The Lidzbark Formation and the lowermost part of the Malbork Formation show less variability in mineralogical composition than the upper part of the Malbork Formation. Smectite admixtures were detected only in the upper part of the Malbork Formation (the uppermost Middle Buntsandstein). The boron content, achieved after aqua regia digestion, ranges from 70 to 121 mg/kg (96 mg/kg at average), oscillating generally around 90 mg/kg. A higher boron content, bound in silicate structure, is associated with the upper part of the Malbork Formation. All major mineralogical and geochemical changes coincide more or less with the transition from the supposed marine to the terrestrial environmental realm, interpreted from lithological and sedimentological observations within the lowermost part of the Malbork Formation. However, diagenetic alteration of the clay minerals, and of the boron content, could not be ruled out. The oolitic limestones, mainly grainstones, contain admixtures of quartz grains and rare bioclasts, the ooids nuclei being peloids or unrecognizable. The carbonates are almost exclusively composed of low-Mg calcite. A high content of Mg and the presence of small amounts of dolomite suggest that the ooids were primarily composed of high-Mg calcite and are comparable with similar Early Triassic deposits in Tethyan settings. The δ13C values range from -2 to +1‰ VPDB, fitting well with the known ranges of Lower Triassic marine carbonates. An observed δ13C depletion towards the top of the oolite-bearing part of the section may reflect a local shallowing trend that led to overall salinity decrease. A possible connection with the one of the global oceanic geochemical episodes has to be tested further. The results obtained suggest a marine origin of the lower Middle Buntsandstein deposits studied and document a terrestrial origin for the upper Malbork Formation.