New borehole data (from boreholes drilled after 2014) and reinterpretation of historical well logs enabled to update the acreage and reserve potential of Upper Permian (Zechstein) stratiform potash-bearing deposits in SW Poland (Fore-Sudetic area). These deposits, referred to as the Older Potash (K2) and the Younger Potash (K3), are included in the Stassfurt (Z2) and Leine (Z3) cyclothems. Within the present-day extent of both units, several prospective areas with the maximum depth to the potash seam of 2 km and its thickness over 2 m have been contoured. Foreach such area, predicted reserves of potash rock have been calculated (using such parameters as the area, average potash seam thickness, and specific weight of potash rock assumed at 2.1 Mg/m3). 7prospective areas (defined by 98 wells) of the Older Potash (K2) deposits have the reserves estimated at 3. 2 bln Mg and a total surface area of 454 km2. 6 areas (contoured by 23 wells) of the Younger Potash (K3) deposits characterize rocks of predicted reserves of 288.8mln Mg and a total surface area over 60 km2. Therefore, the area of SW Poland offers a relatively high resource potential for potash salts and a more detailed geological insight (and possible future exploitation) of 13 prospective areas with total predicted reserves of 3.53 bln Mg and a total surface area of up to 514 km2. Preliminary calculation of possible amounts of K2O in these reserves (assuming a low average K2O content at 1%) suggests 35.32mln Mg of potassium oxide. Because the potash-bearing seams in the study area are composed mainly of chloride K-Mg minerals such as sylvine (KCl) and carnallite (KClMg · Cl2 · 6H2O) easily dissolved in water, these seams are favourable for relatively cheap exploitation by underground leaching.
Przestrzenny model budowy geologicznej tzw .bloku Gorzowa, obejmujący otoczenie Gorzowa Wielkopolskiego w zachodniej Polsce, obrazuje architekturę sedymentacyjno-tektoniczną basenu depozycyjnego od utworów karbonu w podłożu waryscyjskim na głęb 2,5-4,5 km p p m po osady kenozoiku Przy konstrukcji modelu wykorzystano dane z 23 zdjęć sejsmicznych 3D, ponad tysiąca linii sejsmicznych 2D oraz dane z 300 głębokich (>500 m) odwiertów. Istotnym komponentem modelu są utwory ewaporatowe (siarczany i sole) permu górnego (cechsztyn), stanowiące od ok 1/4 do ok 1/3 wypełnienia basenu w strefach poduszek solnych. Tworzy je 10 siarczanowych (anhydryty) i 9 litostratygraficznych wydzieleń solnych (w tym 2 wydzielenia soli K–Mg), przypisanych odpowiednio cyklotemom od PZ1 do PZ4 cechsztynu. Opisy materiału rdzeniowego z 53 otworów wiertniczych (na blisko 280 otworów rejestrujących utwory cechsztynu) umożliwiły wyróżnienie szeregu litofacji, reprezentujących różne środowiska depozycji ewaporatów. Dla utworów siarczanowych wyróżniono następujące litofacje: otwartego basenu siarczanowego (z partiami głębszymi), platformy siarczanowej, laguny siarczanowej (z partiami płytszymi), laguny i panwi solno-siarczanowej oraz sebkhy siarczanowej. W przypadku utworów solnych są to facje: otwartego basenu solnego (z partiami głębszymi i płytszymi), laguny solnej (z partiami płytszymi), laguny solno-siarczanowej, panwi solnej z przejściem do saliny, saliny oraz nadmorskiego (przeradzającego się w śródlądowy) zbiornika jeziornego typu playa. Analiza rozkładu miąższości poszczególnych wydzieleń i wymienionych litofacji pozwoliła opracować mapy przypuszczalnej paleomorfologii kolejnych basenów ewaporatowych: siarczanowych (6 map) i solnych (6 map) oraz przekroje geologiczne poszczególnych cyklotemów (4 przekroje). Wartości korelacji między miąższością siarczanów rozpoczynających depozycję ewaporatów w każdym z cykli a miąższością nadległych soli oraz tychże soli do kończących cykl siarczanów umożliwiły określenie typu ewaporatowego basenu depozycyjnego. Jedynie zbiorniki sedymentacyjne utworów najstarszej soli kamiennej (Na1) i anhydrytu stropowego (A3r/A3g) reprezentują basen typu „wypełnieniowego” (infill evaporite basin; wysoka ujemna wartość współczynnika korelacji), pozostałe badane ewaporaty powstały w basenach typu „niestabilnego” (fluctuating evaporite basin; niska ujemna i dodatnia wartość współczynnika korelacji). W interpretacjach rozkładu miąższości ewaporatów uwzględniono także wpływ tektoniki post- i syndepozycyjnej, szczególnie aktywnej podczas formowania ewaporatów cyklotemów PZ2 i PZ3.
EN
A geological 3D model of the so-called Gorzów Block, located in the Gorzów Wielkopolski area in western Poland, presents the sedimentary-tectonic architecture of the depositional basin, including the deposit succession from Carboniferous rocks at the bottom (depth 2 5–4 5 km b s l ; Variscan basement) to Cenozoic sediments at the top. The model has been developed using a database of 23 3D and over a thousand of 2D seismic sections, as well as of 300 deep (>500 m) boreholes. Upper Permian (Zechstein) evaporites (sulphates and salts) constituted c.a. 1/3 to 1/4 of the whole basin infill in zones of their thickness maxima They were drilled in 280 boreholes and represent 10 sulphate (anhydrite) and 9 salt lithostratigraphic units (including two K–Mg salts units), corresponding to the Zechstein cyclothems from PZ1 to PZ4. Core description of 58 boreholes allowed distinguishing several lithofacies attributed to various evaporate depositional environments, such as: open sulphate or salt basin (including deeper parts), sulphate platform, sulphate lagoon (including shallower parts), salt-sulphate lagoon and pan, and sulphate sabkha, salina and seaside lake, transforming into an inland one of playa type. Thickness and lithofacies distribution of following evaporite lithostratigraphic units of four Zechstein cyclothems is illustrated by geological cross-sections and the thickness-palaeofacies maps of corresponding evaporate depositional basins. These maps present supposed location of palaeomorphological structures as shoals, platforms, islands, evaporitic (sulphate and salt) pans, lagoons and basins with their deeper and shallower parts. Also the lists of commented parameters of evaporite units (top and bottom depth, thickness and their statistics such as minimum, maximum and average values) are provided. The thickness ratio value of sulphates to chlorides in following cyclothem successions enabled to define the type of evaporate depositional basin. Most of studied Zechstein evaporitic basins represented the “fluctuating” basin type (low negative and positive ratio values), in which the local subsidence and the changing precipitation and accumulation rate were dominant factors with a minor role of basin palaeobathymetry. Only the sedimentary basins of Oldest Halite (Na1, PZ1 cyclothem) and Top Anhydrite (A3r, PZ3 cyclothem) were classified as the “infill” evaporate basin type (high negative ratio value), where the precipitated evaporites adapted to the inherited former basin bottom morphology producing thicker sulphates on basin shoals and thicker salts in its depressions. Thickness differences indicated also the role of post- and synsedimentary tectonics, active especially during deposition of PZ2 and PZ3 evaporites.
The sedimentary and stratigraphic patterns established for Zechstein of the western part of the Peribaltic Syneclise (and in particular the eastern Łeba Elevation) were applied to other parts of the East European Craton (EEC) in Poland: the eastern Peribaltic Syneclise and the Podlasie region. A very large number of mostly fully-cored borehole sections in the Puck Bay region certainly predestines the eastern Łeba Elevation area to use it as a model. The most part of the EEC, except of its part adjacent to the Teisseyre-Tornquist Zone, during the Zechstein deposition represents the marginal parts of the basin. The fauna occurring in the Zechstein carbonate deposits of the EEC makes it possible to distinguish between the Zechstein Limestone and the younger carbonate strata, but certainly not between the Main Dolomite and the Platy Dolomite and hence the facies models for the Zechstein that have been previously developed in the western part of the Peribaltic Syneclise augmented by sequence stratigraphic approach seem to be the best tool to apply in other peripheral areas in the EEC area. The Zechstein sequence in the western part of the Peribaltic Syneclise consists, in general terms, of three parts: (1) carbonate platform of the Zechstein Limestone (occurring only in the north-westernmost corner of the study area and passing into basin facies dominant in the most part of the area); (2) the PZ1 evaporite platform system composed of sulphate platforms and adjacent basin system and constituting the major part of the Zechstein sequence; and (3) the Upper Anhydrite-PZ3 cover. There is a consensus, as far as the western part of the Peribaltic Syneclise is concerned, that the Platy Dolomite platform is wider than the Main Dolomite platform. In the easternmost part of the Peribaltic Syneclise, the stratigraphical interpretations are diverse. We have included the anhydrite overlying the Zechstein Limestone into the Upper Anhydrite, and concluded that the overlying interbedded mudstone and anhydrite also belong to the Upper Anhydrite. When above the Upper Anhydrite one carbonate unit occurs, it is assigned either to the Main Dolomite and Platy Dolomite, or to the Platy Dolomite. The same conclusion is proposed for the marginal parts of the Podlasie Bay. The deposition of Zechstein Limestone resulted in the origin of carbonate platforms along the basin margins which changed an inherited topographic setting. The Lower Anhydrite deposits are lowstand systems tracts (LST) deposits, lacking in more marginal parts of the western and eastern Peribaltic Syneclise and in the major part of the Podlasie Bay. The accommodation space existed and/or created during the Lower Anhydrite and the Oldest Halite deposition in the Baltic and Podlasie bays was filled and at the onset of the Upper Anhydrite deposition, a roughly planar surface existed except in the area ad jacent to the main Polish basin. The Upper Anhydrite deposits are transgressive systems tracts deposits and then highstand systems tracts deposits and they encroached the Zechstein Limestone platforms. The Upper Anhydrite deposition was terminated by sea level fall, and the Upper Anhydrite deposits in the marginal areas became subject to karstification. The Main Dolomite transgression took place in several phases but its maximum limit did not reach the Upper Anhydrite limit. The deposition of the PZ2 chlorides (LST deposits) resulted in the filling of the accommodation space that was inherited after the deposition of the Main Dolomite and the Basal Anhydrite. Subsequently, the area became exposed, and marine deposits (Grey Pelite and Platy Dolomite) related to the last major transgression during the life of the Zechstein basin that resulted in a flooding of the exposed surface of older Zechstein deposits, including the area that was emergent during deposition of the PZ2 cycle. Microbial carbonates, being stromatolites and thrombolites, are a common feature of all Zechstein carbonate units but in particular this is the case of the Platy Dolomite. There are no direct premises allowing for convincing settlement doubts regarding the stratigraphical position of the upper carbonate unit in many cases, but several lines of evidence suggest that, as in the entire Zechstein basin, the Main Dolomite considerably shifted basinward, and the Platy Dolomite - landward, although it is difficult to ascertain whether the original Platy Dolomite extent was similar to or greater than the limit of the Zechstein Limestone as elsewhere in the Zechstein Basin.
Analiza obecnego występowania i zróżnicowania miąższości utworów ewaporatowych (siarczanowych i chlorkowych) górnego permu (cechsztyn) na obszarze centralnej części monokliny przedsudeckiej, bazująca na danych z 635 archiwalnych otworów wiertniczych, umożliwiła przedstawienie obrazu przypuszczalnej paleogeografii basenów siarczanowych i chlorkowych w przypadku niektórych ewaporatowych wydzieleń litostratygraficznych kolejnych czterech cyklotemów. Utwory siarczanowe i chlorkowe cyklotemów PZ1 i PZ3 oraz siarczany cyklotemu PZ2 (anhydryt podstawowy [A2]) powstały w zbiornikach o wyraźnie zróżnicowanej batymetrii, ze strefami płytszymi (bariera i płycizny) i głębszymi (baseny). Akumulacja tych osadów następowała według schematu występującego w basenie typu „wypełnieniowego”, w którym na etapie depozycji soli chlorki wypełniają głównie obniżenia dna wcześniejszego zróżnicowanego batymetrycznie zbiornika siarczanowego, zaakcentowane różnym tempem osadzania siarczanów (szybszym na płycinach i wolniejszym w basenach). Lokalne występowanie pozostałych ewaporatów cyklotemów PZ2 i PZ4 nie pozwala otworzyć paleogeografii ich zbiorników depozycji. Omówiono też wykształcenie wydzieleń ewaporatowych, wykorzystując dane z terenów sąsiadujących z obszarem badań w sytuacji braku miejscowego materiału rdzeniowego.Tektonika dysjunktywna (sieci uskoków i dwa rowy tektoniczne) w różnym stopniu przemodelowała pierwotne rozmieszczenie ewaporatów i spowodowała ich lokalny wzrost miąższości w strefach przyuskokowych.
EN
Analysis of recent extension and thickness of Upper Permian (Zechstein) evaporites (sulphates and chlorides) in the area of central Fore-Sudetic Monocline, based on data from 635 archive boreholes, enabled to reconstruct the possible palaeographic images of both sulphate and chloride basins, represented some evaporitic lithostratigraphic units of four Zechstein cyclothemes. Sulphates and chlorides of PZ1 and PZ3 cyclothemes as well as sulphates of PZ2 cyclotheme (Basal Anhydrite [A2] unit) have deposited in the basins with distinctly varied bathymetry, where existed the shallow (barrier and shoals) and the deeper (basins) parts. Their accumulation realized the depositional scheme of the „infill” type of evaporitic basin, after which dominant infill by chlorides took place in the deeps of former sulphate basin with differentiated bathymetry accentuated by other accumulate rate of sulphates (a higher on bottom shoals and slower in the deeps). Local occurrence of other evaporate units of PZ2 and PZ4 cyclothemes eliminated creation of similar palaeogeographic images for their depositional basins. Commented evaporite units were characterized by data representative for their age equivalents drilled in the nearest areas because of extremely rare core data form the study area. Disjunctive tectonics (fault systems and two tectonic grabens) modified in a different rate the primary extent of studied evaporites as well as it was responsible for their local thickness increase in the near-fault zones.
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