Skały drobnoklastyczne z pogranicza triasu i jury (retyk–hetang), nagromadzone w dawnej bruździe śródpolskiej były przedmiotem badań geochemicznych w Państwowym Instytucie Geologicznym – Państwowym Instytucie Badawczym w Warszawie. 94 próbki iłowców i mułowców, pochodzące z sześciu archiwalnych rdzeni wiertniczych, przeanalizowano metodami ICP-MS i XRF, na zawartość pierwiastków ziem rzadkich (REE) i innych pierwiastków śladowych. Wyniki wskazują, że źródłem większości badanych mułowców i iłowców były skały osadowe górnej skorupy kontynentalnej starych obszarów kratonicznych, których protolit miał charakter umiarkowanie felzytowy. Procesy wietrzenia i recyklingu zmodyfikowały, do pewnego stopnia, pierwotny skład chemiczny. Jednak w retyku i wczesnym hetangu, w południowo-wschodnim segmencie bruzdy, niektóre dane geochemiczne sugerują większą dostawę z wulkanicznego protolitu o charakterze maficznym. Ponadto, w kilku próbkach zaobserwowano wyraźne wzbogacenie w pierwiastki ziem rzadkich, w wyniku domieszki minerałów akcesorycznych, będących głównymi nośnikami REE. Tym niemniej, na podstawie obecnie otrzymanych wyników, koncentracje REE (i innych pierwiastków śladowych) w bruździe śródpolskiej są niskie i mają one naukowe znaczenie wskaźnikowe, natomiast nie mają znaczenia surowcowego.
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Fine-grained siliciclastic rocks from the Triassic-Jurassic transition (Rhaetian–Hettangian) in the former Mid-Polish Trough were the subject of the geochemical study at the Polish Geological Institute – National Research Institute in Warsaw. Ninety-four samples of claystones and mudstones from six archived drill cores were analysed by ICP-MS and XRF for rare earth elements (REE) and other trace elements. The results indicate that the sources of most of the claystones and mudstones were sedimentary rocks of the upper continental crust of old cratonic areas, where the protolith had a moderately felsic character. Weathering and recycling processes modified the original chemical composition to some extent. However, during Rhaetian and early Hettangian, some geochemical data in the south-eastern segment of the MPT suggest significant input from a mafic volcanic protolith. Moreover, a clear enrichment in rare-earth elements was observed in few samples, caused by admixtures of accessory minerals (being a main carrier of REE). Nevertheless, based on currently obtained data, the Rhaetian–Hettangian concentrations of REE (and other trace elements) in the MPT are low and they are of scientific indicative significance, not of raw material importance.
Badania przedstawione w artykule miały na celu opracowanie charakterystyki struktury Zaosia pod kątem jej wykorzystania do składowania CO2. Przeanalizowano dziewięć profili sejsmicznych, które skalibrowano danymi z sześciu głębokich otworów wiertniczych. Interpretacja objęła głównie utwory dolnojurajskie, w obrębie których wytypowano poziomy zbiornikowe i uszczelniające, perspektywiczne pod względem podziemnego składowania CO2. Analizowana struktura charakteryzuje się dobrymi zamknięciami z dwóch stron. Od strony południowo-wschodniej, a szczególnie północno-zachodniej zamknięcie jest natomiast bardzo połogie i trudno jednoznacznie określić poziom bezpieczeństwa rozpatrywanej antykliny. Przeprowadzona interpretacja danych sejsmicznych nie wykazała obecności deformacji nieciągłych w obrębie poziomów dolnojurajskich.
EN
The goal of the research was to characterize potential of the Zaosie structure for safe CO2 sequestration. Nine seismic profiles calibrated with six deep boreholes were analyzed. Interpretation was focused on the Lower Jurassic deposits, comprising reservoir and seal formations which were selected for CO2 geological storage. The analyzed structure is properly closed from NE and SW sides. However, to NW and SE the Zaosie anticline has very gently dipping flanks which causes that the safety level is difficult to asses. At the present stage of the study the interpretation of seismic data from the Zaosie area do not reveal any significant faults in the Lower Jurassic formations.
Permo-Mesozoic Mid-Polish Trough formed eastern segment of the Southern Permian Basin, within which thick series of the Upper Permian (Zechstein) evaporites, including rock salt, have been deposited. During subsidence phase the presence of thick salt series led to regional decoupling between sub-salt basement and supra salt Mesozoic sedimentary cover, and to development of various salt structures. Evolution of salt pillows and diapirs was genetically related to activity of the basement fault zones. The Goleniów, Dzwonowo-Człopa, Damasławek, Mogilno, Kłodawa and Lubień salt diapirs have been analyzed using conventional seismic reflection data acquired during petroleum exploration, and - in case of Damasławek and Lubień diapirs - shallow high-resolution seismic data. Interpretation of available seismic data gave new insight into geometry of these salt structures, finally shaped during Late Cretaceous-Palaeogene inversion of the Mid-Polish Trough and partly modified during younger (Neogene- Quaternary) phases of their tectonic activity.
The Cenozoic tectonic evolution of the Polish Platform reflects repeated changes in loading condi tions at the Al pine–Carpathian and Arctic–North Atlantic margins of the European continent. After the Late Cretaceous–Paleocene main phase of the Mid-Polish Basin inversion, a second phase of limited uplift of the Mid-Polish Swell occurred during the Middle–Late Eocene. End Eocene and Early Oligocene subsidence of narrow grabens on the Fore-Sudetic Monocline was coeval with normal fault ing in the East Alpine foredeep basin and the development of the Central European rift system. At the sametime the Outer Carpathian flysch basins were rearranged, presumably in response to the build-up of compressional stresses at crustal levels, whilst subsidence and erosion patterns changed in the Carpathian Foreland from being dominated by the NW–SE trending Mid-Pol ish Swell to being controlled by the development of the W–E trending Meta-Carpathian Swell. At the end of the Oligocene the Fore-Sudetic graben system propagated into the area of the Trans-European Suture Zone and the Sudetes and remained active during the Early and Middle Miocene. This was paralleled by intensified subduction activity and thrusting of the Carpathians and the development of their flexural foredeep basin. A short early Sarmatian episode of basement in volving transpression along the SW margin of the Mid-Pol ish Swell correlates with the termination of north-directed nappe transport in the Outer Carpathians. This was followed by eastward migration of the subsidence centre of the Carpathian Foredeep Basin and the gradual termination of tectonic activity in the grabens of the Polish Lowlands. After a period ofpost-orogenic relaxation the present-day compressional stress regime built up during the Pliocene and Quaternary. Intensified ridge push forces exerted on the Arctic–North Atlantic passive margins contribute to this compressional stress field that is dominated by collision-related stresses reflecting continued indentation of the Adriatic Block. This sequence of events is interpreted in terms of changing tectonic loads in the Carpathians, Alps and at the NW passive margin of Europe. The complex and diachronous interaction of mechanically coupled and uncoupled plates along collision zones probably underlies the temporally varying response of the Carpathian Foreland that in addition was complicated by the heterogeneous structure of its lithosphere. Progressively increasing ridge push on the passive margin played a secondary role in the stress differentiation of the study area.
Late Jurassic is the key epoch for an idea of the existence of the southeastern segment of the Mid-Polish Trough. New data on the evolution of Upper Jurassic deposits in the Carpathian Foredeep substrate provide information that there is a complete Oxfordian through Valanginian succession in the area of thick Oxfordian and Kimmeridgian deposits, proving the occurrence of the trough. Thickness of the Oxfordian and Kimmeridgian succession is twice to three times smaller than previously assumed. The facies development patterndistinguishes this area from the rest of the Late Jurassic basin. The sponge megafacies ranges up into the lower most Tithonian in this region.Tithonian Štramberk-type reefs occur near the Carpathian thrust front and alongside. The Late Jurassic and earliest Cretaceous facies are latitudinally arranged. Starting from the latest Middle Jurassic, the study area showed strong structural and facies relations to the Tethys do main. The collected data contradict the hypothesis that the Mid-Pol ish Trough continues in the Carpathian Foredeep substrate.
Interpreted seismic data located within the Grójec fault zone confumed that this zone could be regarded as a strike-slip fault zone, perpendicular to the main axis of the Mid-Polish Trough. Role of this fault zone during Permian-Early Cretaceous subsidence of the Mid-Polish Trough was minimal, and could have been related to tensional/transtensional reactivation of deep structures related to the NW edge of the Małopolska gravity high. In latest Cretaceous - early Paleogene, due to on-going inversion of the Mid-Polish Trough (in transpressional regime) and successive uplift of the Mid-Polish Swell, Grójec fault zone was reactivated. This process could be however most probably regarded as secondary to inversion tectonics and associated strike-slip movements along the NE edge of the Trough/Swell. Inversion of the 4 segment of the Mid-Polish Trough took place in Turonian? -Coniacian-Maastrichtian- early Paleogene.
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Praca ma charakter przeglądowy; zawiera odniesienia do publikacji zajmujących się osadami kredy obszaru lubelskiego: ich pozycją strukturalną, litologią, warunkami sedymentacji i warunkami paleotektonicznymi. Ewolucja basenu została scharakteryzowana na podstawie map litofacji i tempa subsydencji 7 przedziałów czasowych. Podkreślono związki rozkładu litofacji i subsydencji ze strukturami paleozoicznego i prekambryjskiego podłoża. Ewolucję paleotektonicznych warunków, kształtujących przestrzeń depozycyjną, interpretowano na podstawie lokalizacji przypuszczalnych stref synsedymentacyjnych uskoków i fałdów. Przedstawiono przesłanki na rzecz początku inwersji lubelskiego odcinka bruzdy śródpolskiej we wczesnym mastrychcie.
EN
The aim of the study is to give an overview of research dealing with Cretaceous deposits in the Lublin region, i.e. their structural position, lithology, sedimentary and palaeotectonic conditions. Reconstruction of the Cretaceous basin evolution is based on lithofacies maps and on maps of subsidence rates made for 7 time spans. Relations of lithofacies and subsidence patterns with Palaeozoic and Precambrian basement structures are emphasized. Interpretation of synsedimentary faults and folds enabled conclusions on palaeotectonic conditions that created the depositional space. Some remarks concerning Early Maastrichtian timing of the onset of inversion processes is also presented.
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Structures reactivated in the basement of the Permian-Mesozoic cover (Fig. 1A) controlled development of the SE segment of Mid-Polish Trough. Facies and thickness patterns in the area of the Laramide Miechów Depression (Złonkiewicz 2006a, b) and adjacent areas verify and complete thesis of analog modeling (McClay et al. 2002; Gutowski & Koyi 2005). They indicate an oblique extension changing from NW to WNW. The NW component affected earlier and stronger the NW part of the area. It caused transtension in reactivated fault systems: the Kraków-Lubliniec (KLF) and Lasocin-Strzelce Dislocation zones (LSDZ). Also an increasing westward tension, earlier and stronger in southern part, may be recognized. Stages of development: I. Hettangian-Bajocian - dextral tension and post-Variscan relaxations. Strike-slip activity of the KLF and LSDZ. The NW- directed stress component down-threw the NW sides of the normal faults: Opoczno-Grójec Fault and the Pilica Fault, rejuvenated on the edge of the Włoszczowa Massif. A slight westward component and relaxations formed a pull-apart rhomboedric system of basins and horsts in down-thrown sides and extended a graben or isolated basin in the LSDZ. II. Bathonian - dextral oblique extension. Dominant stress, directed to NW, supported KLF and LSDZ slip. The coincidence with an increasing westward stress, stronger in the S part, activated a system of en echelone splay faults (strike W-E), posthumous to the Zawiercie Fault (ZF). A second-order system of splay faults (mostly NNW-SSE), bound to ZF, was formed in the Włoszczowa Massif area, leading to formation of grabens and horsts. That pattern was repeated further to the S at the Carpathian front. A basin (W-E) extended at the S border of the Włoszczowa Massif. III. Callovian-Kimmeridgian up to the Hypselocyclum Chron - dextral oblique extension. Increasing westward stress resulted in pull-apart activity and changed a rhombohedric system of horsts and grabens into elongated NW-SE structures. The westward component was stronger in the S part, which resulted in left-hand rotation of the Włoszczowa Massif. The regional uplift, regression and local emersion rebuilt the late-Variscan pattern; an up-thrown Włoszczowa Massif and down-thrown adjacent NW and SE areas. IV. Kimmeridgian from the Divisum Chron onwards-Valanginian - continuation of the palaeotectonic pattern, with dominating westward stress component. Transgression-regression cycle. Extension of the pull-apart structures in the S part of an area. Evolution of the Mid-Polish Trough, extending in front of the East European Craton, depended on varying stress components, produced by extension of rifts in N proto-Atlantic and W Tethys. Palaeotectonic development locates the area of the Miechów Depression between the elevated: Upper Silesian Massif and Holy Cross Mts. (HCM). The HCM belonged to the zone of elevated elements (Gorzów Block, Wielkopolska Ridge, Piotrków Block, Upper San Anticlinorium), typical for the axial part of a basin, separating parallel zones of maximal subsidence. The subsiding zones in the SE segment of the Mid-Polish Trough were located parallel to the edges of HCM (Fig. 1B) in rejuvenated Permian grabens. Observed palaeostress activated a right-hand transfer fault in the deep structure of the Holy Cross Dislocation and formed a positive flower structure in the HCM area.
Evolution of a sedimentary basin in the Miechów Depression (MD) during the Jurassic was due to the synsedimentary tectonic activity of the Caledonian–Variscan structures. There was a local zone of maximal subsidence extending NW–SE in its area. The Włoszczowa Massif (WM) in the basement of the Permian-Mesozoic cover in central and NW part of theMD was an element of a little lesser subsidence in comparison to the adjacent NW and SE areas. A narrow graben in the Lasocin–Strzelce Dislocation Zone separated it from the Holy Cross Mts. Block (HCM). The Mid-Polish Trough invaded the MD from the NW. The edge of WM (Pilica Fault) limited a reach of the pre-Bathonian SE ingressions. In addition, transgression from an inland basin (from SE) developed since the Bathonian. Grabens and horsts elongated NNW–SSE were formed in the central part of MD. They continued further S-wards beyond the edge of the Carpathians. In the Callovian and Late Jurassic facial zones in the central and NW part of the MD were elongated NW–SE. The zone of major subsidence was located between Pągów and Kostki Małe and stretched further SE into the basin of the Carpathian Foreland. During the Late Oxfordian and Kimmeridgian the shallowest zone of the basinSWto theHCMwas located in theNpart of the WM. Structures formed in the MD area pointed at an oblique extension directed to NW. It was effected by palaeostress directed to NW, stronger in the NW part of the area and gradualy decreasing. The stress reactivated two oblique-slip fault systems: Kraków–Lubliniec and Lasocin–Strzelce. Also an increasing tension to W, stronger in its S part, might be recognized. It activated the Zawiercie Fault in the Late Bajocian and caused left-slip rotation of the WM in the Late Oxfordian. The tectonic model controlling sedimentation during the Latest Jurassic and Early Cretaceous was very similar to the pattern of subsiding and elevating zones formed in this area during Variscan compression. The Mid-Polish Trough was formed by dextral extension and reactivation of dislocations parallel to the edge of the East European Craton. The consolidated HCM-block belonged to a zone of elevated blocks, characteristic for the axial part of an extension basin.
Based on reflection seismic data, a regional tectonicmodel was constructed for the sub-Zechstein basement of the Pomeranian (NW) segment of theMid-Polish Trough (MPT). This model is based on the concept that the thick Zechstein salts acted on a basin-wide scale as a mechanical decoupling layer during the Mesozoic evolution of the MPT. Due to this regional decoupling effect, Mesozoic extensional faulting was mostly restricted to the sub-Zechstein salt basement whilst normal faulting played a subordinate role in the Mesozoic syn-extensional sedimentary series characterized by gradual lateral thickness changes. Locally, normal faulting affecting Mesozoic series triggered the development of salt diapirs. Mechanical decoupling ofMesozoic series fromtheir pre-Zechstein substratum played also an important role during the Late Cretaceous-Paleogene inversion of the Mid-Polish Trough. Taking into account: 1— the location of Mesozoic thickness gradients, 2—the structural configuration of the sub-Zechstein basement, and 3—the location of salt structures, a tectonic map was constructed showing the inferred sub-salt fault zones that were active during the subsidence and inversion of the Pomeranian part of the MPT. A high degree of correlation was achieved between the seismically mapped regional sub-salt structural patterns and magnetic and gravity features, as well as the main inversion structures. Moreover, a very good correlation was established between the inferred basement fault zones and the gross thickness patterns of the Triassic-Jurassic successions. The NE boundary of theMPT was generally controlled by the SW margin of the East European Craton, whilst its SW boundary coincides with a system of fault zones most probably inherited from earlier tectonic phases. Contrary to previous hypotheses, there is no evidence for important strike-slip faulting transverse to the main axis of the Pomeranian segment of the MPT.
In the area of the Polish Basin five deep seismic sounding profiles, recorded during 1991–1997, were used to compare the structure of the crystalline and consolidated crusts with that of the sedimentary cover. Repeated reactivation of deep crustal fractures controlled the thickness distribution and development of faults in Palaeozoic andMesozoic sequences.NW–SE toWNW–ESE basin-parallel and transverse N–S to NE–SW striking fracture systems are evident. The former includes the isseyre–Tornquist Zone that marks the profound crustal boundary between the East European Craton and the typical Trans-European Suture Zone (TESZ) crust that is characterized by a variably thick consolidated upper crustal layer, composed of Caledonian-deformed Early Palaeozoic and possibly Vendian sediments, and defines the NE boundary of the Permian and Mesozoic Mid-Polish Trough (MPT). Its northwestern TTZ segment was intermittently active throughout the whole geological history of the area. The SW boundary of the TESZ, marked by the Dolsk Fault across which the consolidated crustal layer is replaced by a crystalline Variscan upper crust, is only evident on profiles LT-7 and P4. The deformation front of the Variscan Externides is located some 100 km to the NE of the Dolsk Fault within the confines of the TESZ crust. On profiles TTZ-PL and P2, significant lateral changes in the thickness of the consolidated and crystalline crust of the Pomeranian, Kuiavian and Holy Cross Mts. segments of the MPT are noted that coincide with the transverse Bydgoszcz-Poznań-Toruń and Grójec fault zones. These crustal changes are associated with substantial changes in the composition and thickness of supracrustal sedimentary sequences and the degree of inversion of the MPT.
Seven high-quality reflection-seismic lines, calibrated by wells, were interpreted in an effort to assess the timing of inversion and the structural configuration of the Pomeranian and Kuiavian segments of theMid-Polish Trough. Seismostratigraphic analyses of the Upper Cretaceous successions imaged by these seismic lines in the NE and SW marginal troughs of the Mid-Polish Swell document important along-strike stratigraphic and structural changes. Thickness variations of the Upper Cretaceous series, combined with the development of erosional unconformities and associated tectonic deformations indicate that inversion movements commenced during the late Turonian and intermittently persisted into the Maastrichtian and Paleocene. Earliest inversion movements were focused on the margins of the Mid-Polish Trough where Mesozoic sequences are decoupled from the sub-Zechstein series by Zechstein salts. Whereas the NE margin of theMid-Polish Trough is devoid of compressionally reactivated salt structures, its SWmargin is characterized by strong inversion- related salt tectonics. Progressive inversion of the axial parts of the Mid-Polish Trough was accompanied by uplift of its pre-Zechstein floor to and above the level of flanking, non-inverted areas, and by deep truncation ofMesozoic series across the culmination of the evolving Mid-Polish Swell. Inversion movements ceased towards the end of the Paleocene, as evidenced by the burial of the Mid-Polish Swell beneath essentially flat lying Eocene and younger series. Turonian-Paleocene inversion of the Mid-Polish Trough is coeval with the inversion of the Bohemian Massif, the North German Basin and the Sorgenfrei-Tornquist Zone. Inversion of the Mid-Polish Trough is considered to have been controlled mainly by compressional intraplate stresses that built up in the Carpathian foreland during the collision of the Inner Carpathian orogenic wedge with the European passivemargin, attesting to their increasing mechanical coupling, commencing during the Turonian. These stresses relaxed, however, with the end-Paleocene onset of imbrication of the Outer Carpathian domain, reflecting decoupling of the Carpathian orogenic wedge from its foreland.
The Mid-Polish Swell (MPS), uplifted in the latest Cretaceous-earliest Tertiary at the site of the earlier Permian-Mesozoic Mid-Polish Trough (MPT), is adjoined to the south-west by a chain of salt diapirs which are probably underlain by a system of late Variscan deep faults in the pre-Zechstein basement. The Mesozoic reactivation of this system is responsible for the rapid thickness increase towards the axis of theMPT. Consequently, it may be regarded as the southwestern boundary of the MPT. During the phase of inversion, this system caused the mobilization of the Zechstein salt, the formation of the chain of diapirs and also (indirectly) the uplift of the regional unit of the MPS.
The Mid-Polish Trough formed the axial part of the Polish Basin belonging to a system of the Permian-Mesozoic epicontinental basins of Western and Central Europe. It was filled by several kilometres of siliciclastics and carbonates, including thick Zechstein (approximately Upper Permian) evaporites. TheMid-Polish Trough was inverted in the Late Cretaceous-Paleocene times, when it was strongly uplifted and eroded. The presence of thick salt significantly influenced Triassic evolution of the central (Kuiavian) part of theMid-Polish Trough where the Kłodawa salt structure is located. Analysis of seismic data calibrated by several deep wells point to three main stages of the Triassic evolution of this structure. During Early andMiddle Triassic Kłodawa salt pillow grew above the basement extensional fault zone, during early Late Triassic (approx. time of deposition of the Lower Gypsum Beds) Kłodawa salt structure reached diapiric stage and salt eventually extruded on to the basin floor. Last stage was characterised by rather uniform sedimentation and lack ofmajor saltmovements. Wojszyce salt pillow located north-east of the Kłodawa salt structure grew until the Late Triassic (approx. time of deposition of the Upper Gypsum Beds) when basement fault zone located below it was probably inverted. This inversion triggered formation of the salt-cored Wojszyce Anticline and was followed by localised erosion and rather uniform Norian–Rhaetian (Lower Kłodawa Beds) sedimentation above the anticline. Local tectonic activity below the anticline might have additionally enhanced growth of the Kłodawa salt diapir. The presented tectono-sedimentary model of the relationship between basement and salt tectonics and their influence on the Triassic depositional systems is compatible with results of analogue modelling of linked basement-salt tectonics, and with a model based on mesostructural studies completed for the Kłodawa salt mine.
Obszar Księżpol-Lubaczów w dolnej i środkowej jurze należał do północnego skłonu, wschodniego przedłużenia bruzdy środkowopolskiej. Opisane utwory środkowej i przypuszczalnej dolnej jury to osady klastyczne o maksymalnej miąższości rzeczywistej około 400 m. W ich najniższej części występuje cienka, około 20 m grubości seria ilasto- piaszczysta, zaliczona do dolnej jury. Środkową jurę reprezentują, od dołu, utwory piaskowcowe, którym przypisuje się wiek od aalenu do kujawu dolnego oraz leżące wyżej osady ilasto-mułowcowe, miejscami z wkładkami piaskowców, należące do kujawu środkowego i górnego, batonu oraz keloweju. W pracy przedstawiono również tektonikę i układ strukturalny badanych utworów oraz uwagi dotyczące paleogeografii. Ponadto określono związek tych osadów z podobnymi utworami występującymi na obszarach graniczących z rejonem badań.
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In the Early and Middle Jurassic, the area of Księżpol-Lubaczów constituted the northern margin of the eastern continuation of the Mid-Polish Trough. Middle and probably Lower Jurassic deposits consist of clastic rocks, approximately 400 metres thick. In its lowermost part, the thin (ca 20 m thick) clay-sandy series is considered to be of Early Jurassic age. The basal layer of the Middle Jurassic lithostratigraphic succession consists of sandstones, whose age was established as Aalenian-early Kuiavian. The upper layers of the succession are composed of clayey and muddy sediments with sandstone intercalations, representing the middle and upper Kuiavian, Bathonian and Callovian. The present study focuses on the Middle Jurassic deposits as well as the tectonic, structural and palaeogeographic problems of the area. Moreover, a comparison is made of the discussed sediments and stratigraphic index-fossils with those of the neighbouring regions.
The Mid-Polish Trough (MPT) is well recorded in the distribution of thickness of the Mesozoic sediments. Its shape was most distinctly delineated in the Early Triassic, and Early to Middle Jurassic, when thickness gradients attaining 100 m/km were reached. However, because the regional faults bordering the MPT were not active throughout its history, the existence of Mid-Polish Rift has not been confirmed. The strongest thickness gradients may have been caused by the periodical activity of the sub-Zechstein faults, which did not penetrate the Mesozoic strata due to the damping effect of plastic Zechstein salts. On the contrary, local faults, forming (mainly during the Late Triassic) syn-sedimentary grabens, are a common feature in the MPT and its surroundings. Transversal subdivision of the MPT and its slopes into at least two segments (Pomeranian and Kuiavian) is clearly visible in the thickness pattern. It is expressed by the presence of separate depocentres, reversal of asymmetry, differences in stratigraphical sequences observed on the palaeomorphological terraces south-west of the MPT, and by the structural variations after the inversion. The scale of inversion, which transformed the MPT into the Mid-Polish Swell (MPS), is unclear and needs further investigations. Estimation of the thickness of the Upper Cretaceous sediments removed by erosion is a key problem in this respect. It should take into account both, the effects of the regional inversion and the local changes resulting from the last stage of strong salt displacements.
Interpretation of seismic data from the Pomeranian segment of the Mid-Polish Trough (MPT) shows that this part of the MPT evolved in Mesozoic times as a decoupled sedimentary basin. Regional-scale decoupling was caused by the thick Zechstein salt layer. Detailed tectonic and seismostratigraphic analysis of seismic data from the vicinity of the Oświno IG 1 well allowed for significant reinterpretation of the Oświno structure, which was previously interpreted as partly pierced salt diapir. This structure developed in Triassic to Jurassic times as a listric normal fault zone detached above the salt layer, resulting from activity of a master fault present within the pre-Zechstein basement. Two pulses of increased extension could be inferred for Oświno fault zone: Late Triassic and Mid-Late Jurassic. The Oświno fault zone was reactivated in the Late Cretaceous due to the compression responsible for inversion of the MPT. Inversion-related uplift of the axial part of the MPT created a morphological gradient and the increased pressure of uplifted overburden rocks directed towards its flanks that also contributed to reactivation of the Oświno fault zone. This fault zone, together with the Drawno-Człopa salt diapiric structure and graben system of the Fore-Sudetic Monocline, have developed due to decoupled evolution of the Mid-Polish Trough.
The Late Permian and Mesozoic evolution of the Mid-Polish Trough is analysed using a set of palaeotectonic cross-sections which are constrained by regional integrated depth-converted reflection seismic profiles. Results support the concept that the central and NW part of the Mid-Polish Trough can be subdivided into a Pomeranian and a Kuiavian segment. The Pomeranian segment is characterised by lower subsidence and a shallower depth to the base of the Zechstein (3500-4000 m) as compared with the Kuiavian segment. The Pomeranian basin was characterised by a nearly symmetrical structure and a single depocentre. In Kujawy, the basin displays a more complex structure with several local depocentres. In the Pomeranian segment, salt structures are poorly developed (salt pillows). These formed relatively late: during the latest Cretaceous and Early Paleocene. In the Kuiavian segment, salt structures include also salt diapirs which began to form at the end of the Muschelkalk, and were active later throughout Mesozoic times, as evidenced by lateral facies and thickness changes. During end Cretaceous and Paleocene basin inversion, the base of the Zechstein was uplifted by 3000-4000 m in the Kuiavian segment and by 2000-3000 m in the Pomeranian segment. The transition zone between the Pomeranian and Kuiavian segments, located in the area between Piła and Toruń, displays mixed features in its structure and geological evolution. Subsidence of the Mid-Polish Trough was controlled by multiple extensional pulses during which pre-existing crustal-scale faults were reactivated. Similarly, inversion of the Mid-Polish Trough involved reactivation of crustal faults. Segmentation of the Mid-Polish Trough can be related to factors including differences in its basement composition.
Late Cretaceous inversion processes and their relation to salt movements in the Pomeranian sector of the Mid-Polish Trough are described, based on deep boreholes. Two tectonic zones, inverted in the Late Cretaceous, located in the Mid-Polish Trough, were selected for study: the Koszalin-Chojnice Zone situated NE of the present-day Mid-Polish Swell in the Pomeranian Trough, within an area of non-salt anticlines, and the Drawno-Człopa-Szamotuły Zone located in the Szczecin Trough, SW of the Mid-Polish Swell, in an area of strong salt tectonics. The stratigraphic gaps present indicate that the first pulse of Late Cretaceous inversion might have occurred in the Coniacian-early Santonian in this area. Another pulse can be dated at late Campanian-early Maastrichtian. Intra-Cretaceous stratigraphic gaps reached their maximum areal extent in the Coniacian (Inoceramus involutus Zone) and Upper Campanian (Koszalin-Chojnice Zone). Over large areas, Santonian (mostly upper Santonian) deposits rest upon Turonian (including Inoceramus schloenbachi Zone), and locally on older rocks. The lithofacies maps show that thickness and lithofacies distribution in the Cenomanian was independent of the strike of the Koszalin-Chojnice Zone. Such a dependence began and was accentuated in the Coniacian. Santonian and Campanian clastic deposits, extending along the SW boundary of the Mid-Polish Swell and absent in the SW part of the Pomeranian Trough, suggest local tectonic inversion within the central part of the Mid-Polish Trough.
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Pomiary gammametryczne na rdzeniach są nową techniką wykorzystywaną w stratygrafii i sedymentologii, niestosowaną dotychczas szerzej w Polsce. W ramach kompleksowych badań basenu triasowego Niżu Polskiego pomiary takie przeprowadzono na rdzeniach dolnego i środkowego pstrego piaskowca otworów Września IG-1 oraz Gorzów Wielkopolski IG-1. Wykazały one, iż: 1. pomiary sondą ręczną dają podobne, ale dużo bardziej szczegółowe rezultaty niż geofizyczne pomiary otworowe; 2. w interpretacji pomiarów musi być uwzględniany stan zachowania rdzenia; 3. idealna korelacja pomiarów ręcznych ze skalą głębokościową rdzeni umożliwia korektę przesunięcia głębokościowego krzywej karotażowej; 4. pomiary promieniowania gamma na rdzeniach mogą być wykorzystywane do szczegółowej interpretacji sedymentologicznej osadów oraz do analizy basenowej opartej na integracji danych otworowych i sejsmicznych.
EN
GR core measurements using a hand-held scintillometer are a new technique of stratigraphical and sedimentological investigations, which have not been until! recently widely applied in Poland. Such measurements have been completed for cores of the Lower and Middle Buntsandstein of the Września 1G-1 and Gorzów Wielkopolski IG-1 research wells. Results of the measurements showed that: 1) GR core logs give similar but more detailed results in comparison with the GR well logs; 2) core preservation have to be considered during interpretation of the results; 3} detailed correlation of the GR core measurements with the core depth scale and their direct relationship to well measurements allows for precise definition of depth shift of the well log; 4) GR core measurements can be used for a very detailed sedimentological interpretation of the investigated sediments, and for basin analysis based on integration of well and seismic data.
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