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Tytuł:
The Jurassic succession at Lisadele Lake (Tulsequah map area, British Columbia, Canada) and its bearing on the tectonic evolution of the Stikine terrane
Autorzy:
Shirmohammad, F.
Smith, P.
Anderson, R.
McNicoll, V.
Powiązania:
https://bibliotekanauki.pl/articles/2061004.pdf
Data publikacji:
2011
Wydawca:
Państwowy Instytut Geologiczny – Państwowy Instytut Badawczy
Tematy:
ammonites
chronology
Stikinia
terranes
Middle Jurassic
Lower Jurassic
Opis:
Jurassic rocks in the central Tulsequah map area include conglomerates and interbedded fossiliferous finer clastics of the Takwahoni Formation (Laberge Group) which unconformably overlie Triassic rocks. Ammonite collections document the Pliensbachian, Toarcian and Bajocian stages. We refine the age and provenance of episodes of coarse clastic input and confirm the progressive change of dominant clast lithology from reworked sedimentary rocks above the Triassic-Jurassic unconformity to volcanic, plutonic and then metamorphic clasts in the Upper Toarcian. The uppermost coarse clastic unit is a Bajocian chert-pebble conglomerate which, along with the immediately underlying black mudstone, we include in the Bowser Lake Group. Together with regional correlations, this confirms that the age of the basal part of the Bowser Lake Group is diachronous, younging southwards into Stikinia. Sandstone petrofacies trends and changes in conglomerate clast composition indicate arc uplift and dissection followed by Middle Jurassic orogen recycling. The isotopic ages of detrital zircons and granite clasts compared with the biochronologically constrained ages of the enclosing strata suggests that processes of intrusion, arc uplift, unroofing, and clastic deposition during the Early Jurassic occurred over intervals of significantly less than five million years.
Źródło:
Volumina Jurassica; 2011, 9, 1; 43-60
1896-7876
1731-3708
Pojawia się w:
Volumina Jurassica
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Indirect biostratigraphy in condensed successions: a case history from the Bajocian of Normandy (NW France)
Autorzy:
Pavia, G.
Martire, L.
Powiązania:
https://bibliotekanauki.pl/articles/2061355.pdf
Data publikacji:
2009
Wydawca:
Państwowy Instytut Geologiczny – Państwowy Instytut Badawczy
Tematy:
taphonomy
condensation
biostratigraphy
ammonites
Middle Jurassic
Normandy
Opis:
The fossil assemblages of the Bajocian of Normandy are affected by taphonomic condensation, and the use of these assemblages for biostratigraphy must be carried out with great care because of the taphonomic reworking (reelaboration) of most of them. Nevertheless such beautiful fossils, ammonites in particular, retain their value at least as taxonomic references if their relative stratigraphic position is recognized. Such a goal has been achieved in the Bretteville section, where the "Oolithe Ferrugineuse de Bayeux" Formation (OFB), consisting of 14 beds contained within 170 cm of strata, is exposed. Each bed contains a condensed ammonite assemblage in which the overall chronologic interval represented by fossils is longer than the time of sedimentation of the bed, and no ammonites can be defined as contemporaneous with the enclosing matrix, except for the topmost two beds. The timing of biologic and sedimentary events in this Fe-oolitic succession must thus be established in an indirect way, through a stratigraphy of fossils based on their taphonomically delayed first occurrence. In particular, we can only define the maximum age of each layer, constrained by the youngest recorded fossil. On the basis of this approach, the lower part of the OFB is shown to fall within the middle to upper part of the Bajocian Stage (Humphriesianum to Parkinsoni chrons), whereas the uppermost OFB can be referred to as the uppermost Bajocian (latest Parkinsoni Chron). We conclude that, at Bretteville and in general for the Fe-oolites of Normandy, fossiliferous horizons with condensed assemblages have no value for definition of the biostratigraphic standard scale, and that indirect biostratigraphy is useful to assign minimal chronologic values to taxa when (1) their stratigraphical range has not yet been established in expanded successions, (2) they are new taxa, and (3) they are present only in a condensed succession that suffered from the same taphonomic constraints as the Bajocian of Normandy.
Źródło:
Volumina Jurassica; 2009, 7, 1; 67-76
1896-7876
1731-3708
Pojawia się w:
Volumina Jurassica
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Provenance of heavy minerals to the Middle and Upper Jurassic epicontinental deposits of NW Poland
Autorzy:
Bembenek, Kinga
Woronko, Barbara
Ziółkowski, Piotr
Powiązania:
https://bibliotekanauki.pl/articles/2058859.pdf
Data publikacji:
2021
Wydawca:
Państwowy Instytut Geologiczny – Państwowy Instytut Badawczy
Tematy:
Middle Jurassic
Upper Jurassic
weathering indices
sea level change
stratigraphic gaps
Opis:
The source of clastic material supplied to the epicontinental sea during the Middle and Late Jurassic in the Pomeranian Segment of the northern part of the Mid-Polish Trough is analysed, using deposits from the Rzeczyn PIG-1 borehole that represent the Łyna, Chociwel, Brda, Pałuki, Kcynia and Rogoźno formations. Heavy mineral analysis, including weathering indices (ZTR, GZI, RZI and Q) and standardised scores for each mineral species, shows that each formation is characterized by a different heavy minerals association. In each association, transparent minerals include both ultrastable minerals (zircon, tourmaline and rutile), occurring in various proportions, and unstable minerals. This indicates that deposits subject to earlier multiple reworking were eroded from the surrounding landmasses. Most probably these deposits represented Triassic rocks, although fresh weathering covers were also eroded. The main direction of clastic material supply was from the N and NW, and to a lesser degree from the NE. The main reasons for changes in the source areas were probably sea level oscillations, while during regressions, exposed parts of the seabed became source areas of clastic material. Conversely, during transgressions, parts of the seabed became cut off from the supply of clastic material from eroded landmasses.
Źródło:
Geological Quarterly; 2021, 65, 1; 2
1641-7291
Pojawia się w:
Geological Quarterly
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Temperature and isotopic relations in carbonate minerals in the Middle Jurassic sideritic rocks of central and southern Poland
Autorzy:
Jarmołowicz-Szulc, K.
Kozłowska, A.
Powiązania:
https://bibliotekanauki.pl/articles/2060537.pdf
Data publikacji:
2016
Wydawca:
Państwowy Instytut Geologiczny – Państwowy Instytut Badawczy
Tematy:
fluid inclusions
isotopes
carbonate minerals
sideritic rocks
Middle Jurassic
Opis:
The present study assesses the physico-chemical character of the fluids responsible for the genesis of carbonate minerals in the Middle Jurassic sideritic rocks at the northeastern margin of the Holy Cross Mts. and in the Częstochowa region. These rocks occur at present at depths between 30 and 600 m. Fluid inclusion and isotopic analyses have been performed in the carbonate minerals from sideritic sandstones, clayey siderites and sideritic coquinas. Siderite is the main carbonate mineral of the sideritic rocks. Calcite and ankerite are also present. The siderite is represented by two varieties, Mg-rich siderite (sideroplesite, less commonly – pistomesite) and siderite. Two generations of siderite have been distinguished – an early and a late one. The early siderite was formed at temperatures of about 20°C in the zone of microbiological methanogenesis from marine waters with some influence of meteoric waters (δ18O from –7.84 to –1.92‰ VSMOW). The late siderite crystallized at temperatures of about 62–110°C from pore waters enriched in 18O (δ18O >0‰ VSMOW) as compared with the isotopic composition of the waters responsible for the early siderite generation. The conducted fluid inclusion analyses point to formation of the cements from complex fluids of brine and carbon dioxide character, with densities slightly exceeding 1 g/cm3 and salinities varying from 10.5 to 16.9 wt.% NaCl eq. and from 6.4 to 14.0 wt.% NaCl eq. in the Holy Cross Mts. and in the Częstochowa region, respectively. The homogenization temperatures lie in the intervals of 62–110°C and 60–97°C, respectively and represent elevated values compared with data from the Polish Lowlands. Apart from burial, other heat sources must have been important for the lithogenesis of the Middle Jurassic deposits.
Źródło:
Geological Quarterly; 2016, 60, 4; 881-892
1641-7291
Pojawia się w:
Geological Quarterly
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Cyclic sedimentation in the Middle Jurassic of central Poland
Autorzy:
Dadlez, J.
Powiązania:
https://bibliotekanauki.pl/articles/2059894.pdf
Data publikacji:
2002
Wydawca:
Państwowy Instytut Geologiczny – Państwowy Instytut Badawczy
Tematy:
Central Poland
Middle Jurassic
stratigraphy
cyclic sedimentation
salt mobility
Opis:
Nine boreholes were drilled in the late eighties in central Poland to investigate the Middle Jurassic sedimentary successions. The boreholes were arranged in three lines (Ciechocinek, Brześć Kujawski and Wojszyce lines) running across three anticlines underlain by salt pillows. Long intervals of boreholes have been cored, often with 100% core recovery, thus enabling a detailed examination of sedimentary evolution. Sequences are composed of a full range of clastic rocks, from conglomerates through sandstones and heteroliths to shales. They are arranged in sedimentary cycles, predominantly regressive (coarsening upwards). These are interpreted as deposited in a shallow, wave/storm-dominated, shelf environment, each cycle being a result of progradation of fore-shore to near-shore heteroliths and sands over the shales of an open sea. The basin was probably non-tidal or microtidal. These essential (lower order) cycles, equivalents of the IVth order cycles in the world-wide scheme, are assembled in higher order cycles which resemble the IIIrd order cycles of that scheme. The bases of the higher order cycles are good lithostratigraphic markers, three of them being probably equivalents of chronostratigraphic boundaries (bases of the upper Aalenian, upper Bajocian and Bathonian, respectively). Correlation of borehole sections points to limited salt movement of the Ciechocinek and Wojszyce salt pillows during the Middle Jurassic. These are indicated, first of all, by thickness reductions seen in boreholes located above the tops of salt pillows. In the Ciechocinek area, the upward movement of salt occurred during the latest Bajocian/earliest Bathonian while in the Wojszyce area - during the early Bathonian. Coarser clastics were shed into the basin from the south-west, north-west (along the Mid-Polish Trough) and north-east during the Aalenian, and mainly from the north-east (from the East European Craton) in later times.
Źródło:
Geological Quarterly; 2002, 46, 3; 321-336
1641-7291
Pojawia się w:
Geological Quarterly
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Sedimentological study of the Nikolčice Formation : evidence of the Middle Jurassic transgression onto the Bohemian Massif (subsurface data)
Autorzy:
Nehyba, S.
Opletal, V.
Powiązania:
https://bibliotekanauki.pl/articles/2060331.pdf
Data publikacji:
2017
Wydawca:
Państwowy Instytut Geologiczny – Państwowy Instytut Badawczy
Tematy:
Nikolčice Formation
Middle Jurassic
provenance
shallow marine
nearshore depositional environment
Opis:
The Jurassic sedimentary succession along the eastern margin of the Bohemian Massif starts with mostly fluvial deposits of the Gresten Formation and continues after marine transgression with the deposition of the Nikolčice Formation (Middle Jurassic, Callovian). The provenance and depositional environment of the Nikolčice Formation showed that deposition occurred within offshore, transitional zone, shoreface, foreshore and littoral sand bar environments; however, shoreface and foreshore deposits dominate in the cores studied. The crystalline units along the eastern margins of the Bohemian Massif represent the primary source of deposits of the Nikolčice Formation. An important role was played by acidic and intermediate plutonites and highly metamorphosed metasedimentary rocks (granulite and amphibolite metamorphic facies), which indicates an advanced stage of erosion of the source area. The role of volcanic and intrusive rocks was small. The primary source was followed by an additional recycled source from older sedimentary rocks (especially the Moravo-Silesian Paleozoic deposits – the Líšeň Formation, the Myslejovice Formation). A similarity of the source areas for the Nikolčice Formation and the underlying Gresten Formation was recognized. Identified differences in their source areas are mainly explained by varied erosional levels due to successive exhumation of the source Variscan orogen and possibly also by an expansion of the source area.
Źródło:
Geological Quarterly; 2017, 61, 1; 138--155
1641-7291
Pojawia się w:
Geological Quarterly
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Geochemistry of Middle Jurassic mudstones (Kraków-Częstochowa area, southern Poland): interpretation of the depositional redox conditions
Autorzy:
Szczepanik, P.
Witkowska, M.
Sawłowicz, Z.
Powiązania:
https://bibliotekanauki.pl/articles/2059479.pdf
Data publikacji:
2007
Wydawca:
Państwowy Instytut Geologiczny – Państwowy Instytut Badawczy
Tematy:
Middle Jurassic
Częstochowa Clay Formation
palaeoenvironment
geochemical parameters
redox conditions
Opis:
Middle Bathonian iron-bearing dark grey mdstones and claystones from the Kraków-Czestochowa Upland (southern Poland) were subjected to geochemical and mineralogical study in order to evaluate palaeo-redox conditions of their deposition and diagenesis. They are mainly composed of kaolinite, with smaller amounts of other clay minerals and detrital quartz. Organic matter is composed of type III and/or IV kerogen and its d13C is between -23 and -24‰, suggesting a mainly terrigenous source, with a possible admixture of marine input. Most geochemical parameters: (total organic carbon) TOC/S, U/Th, Ni/Co, V/Cr, (Cu+Mo)/Zn ratios, authigenic uranium content, and Fe-TOC-S relationship, indicate deposition under oxygenated bottom water conditions. By contrast, DOP (degree of pyritization) and V/V+Ni indices suggest a dysoxic environment. However, DOP probably reflects redox conditions in the sediment during diagenesis rather than in the over laying water column. The composition of the organic matter and the domination of pyrite euhedra over framboids indicates that the V/V+Ni ratio may not be reliable for determination of redox conditions in the rocks studied. There is no significant difference between the geochemical indices of host rocks with nodules and those with out them.
Źródło:
Geological Quarterly; 2007, 51, 1; 57-66
1641-7291
Pojawia się w:
Geological Quarterly
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Berthierine in the Middle Jurassic sideritic rocks from southern Poland
Autorzy:
Kozłowska, A.
Maliszewska, A.
Powiązania:
https://bibliotekanauki.pl/articles/2059646.pdf
Data publikacji:
2015
Wydawca:
Państwowy Instytut Geologiczny – Państwowy Instytut Badawczy
Tematy:
berthierine
sideritic rocks
Middle Jurassic
Holy Cross Mountains
Częstochowa region
Opis:
A characteristic green and yellow-brown clay mineral from sideritic rocks was studied from 14 boreholes penetrating the Middle Jurassic strata of the northeastern margin of the Holy Cross Mountains and Częstochowa region, using polarizing and scanning electron microscopes, cathodoluminescence and X-ray analysis and revealing the presence of berthierine. In these sideritic rocks, berthierine occurs mainly in Lower and Middle Bathonian strata deposited in shoreface and deltaic environments of the northeastern margin of the Holy Cross Mountains, and in Upper Bajocian deposits of both areas studied. It forms the clay cement of sideritic rocks, fills voids in bioclasts and is also present in ooids. Ooids consisting of berthierine have been affected by mechanical compaction and mainly carbonate replacement. Berthierine ooids, replaced by sideroplesite, pistomesite, Fe-calcite or ankerite, and rarely by pyrite and altered by kaolinite, occur commonly. Berthierine ooids of the Bathonian sideritic rocks are typically better preserved, compared to those from the Bajocian and Aalenian. Berthierine crystallised in the eodiagenesis stage in suboxic conditions below the water-sediment interface, where iron-bearing freshwater mixed with sea water. It is chemically and structurally unstable and, during the mesodiagenetic stage at higher temperatures, could transform to chamosite by recrystallisation.
Źródło:
Geological Quarterly; 2015, 59, 3; 551--564
1641-7291
Pojawia się w:
Geological Quarterly
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Tubular tempestites from Jurassic mudstones of southern Poland
Autorzy:
Leonowicz, P. M.
Powiązania:
https://bibliotekanauki.pl/articles/2059866.pdf
Data publikacji:
2016
Wydawca:
Państwowy Instytut Geologiczny – Państwowy Instytut Badawczy
Tematy:
tubular tempestite
shallow-marine mudstone
omission surface
Lower Jurassic
Middle Jurassic
Silesian-Cracow region
Opis:
This paper presents tubular tempestites from southern Poland and their application for environmental and sequence stratigraphy interpretation. Tubular tempestites are present in muddy successions of the Lower Jurassic Ciechocinek Formation and in the Middle Jurassic Częstochowa Ore-Bearing Clay Formation in the Silesian-Kraków region. They occur as sand-filled tubes of Spongeliomorpha and Thalassinoides entrenched in the mudstone, which form two characteristic horizons. Tubes were emplaced in semi-consolidated substrate and filled with sand brought by storm-generated bottom currents. The trace fossils reveal features typical of Glossifungites ichnofacies associated firmgrounds, which record discontinuities in the stratigraphical record, linked with a depositional hiatus or condensation and erosion of the sea-floor. The coincidence of these horizons with early phases of regional transgressions suggests that they represent transgressive surfaces of erosion. Their limited spatial extent probably resulted from varying intensity of erosion, which locally scoured deeply down to already consolidated substrate, whereas in other places erosion was weaker or even absent, and thus it is not marked in the sedimentary record there.
Źródło:
Geological Quarterly; 2016, 60, 2; 385--394
1641-7291
Pojawia się w:
Geological Quarterly
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Dinosaur assemblages from the Middle Jurassic Shaximiao Formation and Chuanjie Formation in the Sichuan-Yunnan Basin, China
Autorzy:
Li, K.
Yang, Ch.
Hu, F.
Powiązania:
https://bibliotekanauki.pl/articles/2061002.pdf
Data publikacji:
2011
Wydawca:
Państwowy Instytut Geologiczny – Państwowy Instytut Badawczy
Tematy:
dinosaurs
Shaximiao Formation
Chuanjie Formation
Sichuan Basin
Yunnan Basin
Middle Jurassic
Opis:
The Shaximiao Formation (Sichuan Basin, China), and the corresponding Chuanjie Formation of the neighboring Yunnan Basin (Sichuan-Yunnan Basin), representing continental Mesozoic strata, are distinguished from other Chinese Mesozoic units because of the large area over which they are distributed, their lithological characteristics and their abundant vertebrate fossils. This paper analyses and summarizes the dinosaur fossils from the Shaximiao Formation and compares them to other vertebrate groups of the same or similar ages, both in China and abroad. For the first time, this paper presents the viewpoint that the upper member of the Shaximiao Formation is of Middle Jurassic age (Bathonian–Callovian). Furthermore, we claim that the entire Shaximiao Formation is of Bajocian–Callovian age (middle-late part of Middle Jurassic). This conclusion is supported by the age inferred from invertebrate fossils and radiometric dating (165–178 Ma). The composition, evolution and geological age of the vertebrate fauna (particularly dinosaur fossils), as well as their comparison to the dinosaur fauna from the other parts of the Sichuan-Yunnan Basin (Chuanjie Fm.) is discussed. Middle Jurassic dinosaur assemblages from China show marked differences compared with other dinosaur assemblages in the world, and this is explained by geographical isolation.
Źródło:
Volumina Jurassica; 2011, 9, 1; 21-42
1896-7876
1731-3708
Pojawia się w:
Volumina Jurassica
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Carbonate-clastic sediments of the Dudziniec Formation in the Kościeliska Valley (High-Tatric series, Tatra Mountains, Poland) : role of syndepositional tectonic activity in facies development during the Early and Middle Jurassic
Autorzy:
Jezierska, A.
Łuczyński, P.
Staśkiewicz, A.
Powiązania:
https://bibliotekanauki.pl/articles/2060544.pdf
Data publikacji:
2016
Wydawca:
Państwowy Instytut Geologiczny – Państwowy Instytut Badawczy
Tematy:
carbonates
clastics
synsedimentary tectonics
Dudziniec Formation
Lower and Middle Jurassic
Tatra Mts.
Opis:
Sediments of the Dudziniec Formation (Lower Jurassic – Aalenian) outcropping in the Kościeliska Valley (autochthonous unit of the High-Tatric series) are represented by a range of mixed carbonate-clastic deposits. Seven lithofacies have been distinguished based on lithology, sedimentary structures, colour and composition of intra- and extraclasts, with sandstones and crinoidal limestones as end members of a continuous spectrum of facies. The study area represents a shallower part of the sedimentary basin located in the vicinity of source areas, as compared to the Chochołowska Valley region located in the west. Facies characteristics and distribution were controlled mainly by synsedimentary tectonic activity, with sandy varieties representing periods of faulting with enhanced influx of extraclasts, and with crinoidal limestones corresponding to intervals of relative tectonic stability. Such influence of synsedimentary tectonics on the deposition in the Early Jurassic strongly resembles the Middle Jurassic development in the High-Tatric area. Neptunian dykes cutting the Dudziniec Formation, and most probably filled by Lower Jurassic sediments, are yet another indication of tectonic instability of the area in the Early Jurassic.
Źródło:
Geological Quarterly; 2016, 60, 4; 869--880
1641-7291
Pojawia się w:
Geological Quarterly
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Skały syderytowe jury środkowej Kujaw : studium petrologiczne
The Middle Jurassic sideritic rocks of the Kujawy area : petrological study
Autorzy:
Maliszewska, A.
Kozłowska, A.
Kuberska, M.
Powiązania:
https://bibliotekanauki.pl/articles/2075830.pdf
Data publikacji:
2018
Wydawca:
Państwowy Instytut Geologiczny – Państwowy Instytut Badawczy
Tematy:
syderytowe skały
diageneza
jura środkowa
Kujawy
sideritic rocks
diagenesis
Middle Jurassic
Kujawy area
Opis:
The paper presents the results of new mineralogical and petrographic analyses of Middle Jurassic sideritic rocks in the Kujawy area. The scope of the research has been extended to the Ciechocinek-Brześć Kujawski-Wojszyce zone, where clayey and sandy siderites and sideritic coquina form only inserts in siliciclastic rocks. Early diagenetic sideroplesite and mesodiagenetic sideroplesite, Fe-dolomite, ankerite, pistomestite and calcite occur among carbonate minerals. They are accompanied by an early diagenetic green mineral called chamosite and identified as berthierine in the XRD analysis. The richest mineral composition occurs in the sideritic coquina containing various shell elements, often also ooids. It is suggested that the formation of the coquina in the Klodawa-Łęczyca anticline area was caused by saline movements of the Cimmerian orogeny. The start-up and blending of salt masses and the rockfracture contributed to the intensive circulation of mineralizing solutions and the development of diagenetic processes, especially the replacement of unstable components and the cementation of Jurassic sediments throughout the Kujawy area.
Źródło:
Przegląd Geologiczny; 2018, 66, 4; 240--251
0033-2151
Pojawia się w:
Przegląd Geologiczny
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Konkrecje hiatusowe z iłów rudonśnych Wyżyny Krakowsko-Częstochowskiej
Hiatus concretions fromthe ore-bearing clays of the Cracow-Czestochowa Upland (Polish Jura)
Autorzy:
Zatoń, M.
Marynowski, L.
Bzowska, G.
Powiązania:
https://bibliotekanauki.pl/articles/2074474.pdf
Data publikacji:
2006
Wydawca:
Państwowy Instytut Geologiczny – Państwowy Instytut Badawczy
Tematy:
konkrecje hiatusowe
Wyżyna Krakowsko-Częstochowska
hiatus concretions
Middle Jurassic
Cracow-Częstochowa Upland
borers
encrusters
Opis:
Hiatus concretions are arly-diagenetic sedimentary bodies, which in their history of formation, underwent exhumation during sedimentation break and/or erosion of sea-floor. Then they were colonized by various encrusters and borers, before they were buried again. Within Middle Jurassic (Bajocian through Bathonian) clays, hiatus concretions occur in four localities in the Cracow-Częstochowa Upland (south and central Poland): Ogrodzieniec, Bugaj, Mokrsko and Krzyworzeka. Preliminary data about their mineralogy, organic geochemistry and palaeoecology is given. Mineralogical analyses showed, that except dominant high Mg-calcite (up to 87.10% of total carbonates), concretions possess minor amounts of such compounds as quartz, clay minerals (kaolinite and illite), pyrite, siderite or Mg-kutnahorite. However, high differences are observed between total organic carbon contents of concretions (TOC=0.46%) and surrounded clays (TOC = 2.16%), but their molecular composition is similar. Most of identified biomarkers are of terrestrial origin. In clay lithology, the hiatus concretions are the only sedimentary bodies that clearly mark the sedimentation pauses (hiatuses). In the investigated area, they form more or less continuous horizons. The concretions are calcitic, possessing various encrusting fauna such as bryozoans, oysters and oyster-like bivalves, serpulids, solitary corals and foraminifers. They often post-date the borings, belonging to such ichnogenera as Gastrochaenolites, Trypanites and Entobia. Some of the nodules show distinct transition from firmground (characterized by the presence of Glossifungites ichnocoenosis) to hardground (presence of Trypanites ichnocoenosis), pointing to the fact, that they formed at, or very close to, the sediment-water interface. Some concretions, like those from Bugaj and Mokrsko, are characterized by their high diversity of hard bottom communities. Those concretions are also irregular in shape; others, like those from Ogrodzieniec and Krzyworzeka, possess lower diversity. The concretions from Krzyworzeka are especially dominated by the borers, while the encrusters are sparse and not diverse. Those nodules that are wide and flat tend to be more bored on one surface only, while those that are more roundish, are bored on both sides more evenly. The degree of diversity is probably correlated with physical disturbance, causing the rolling and overturning of the exhumed concretions in the littoral zone. On the other hand, the overall diversity could be lowered due to destructive abrasion either of the shallowest borings, echinoid/gastropod scratch marks and shells of nestling bivalves, as well as more delicate epilithozoans.
Źródło:
Przegląd Geologiczny; 2006, 54, 2; 131-138
0033-2151
Pojawia się w:
Przegląd Geologiczny
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Palaeoecologic significance of the Callovian-Oxfordian trace fossils of Gangeshwar Dome, Southeast of Bhuj, Mainland Kachchh, India
Autorzy:
Bhatt, N. Y.
Patel, S. J.
Powiązania:
https://bibliotekanauki.pl/articles/2060982.pdf
Data publikacji:
2017
Wydawca:
Państwowy Instytut Geologiczny – Państwowy Instytut Badawczy
Tematy:
trace fossils
Gangeshwar Dome
Mainland Kachchh
India
Late-Middle Jurassic
ichnocoenoses
skamieniałości śladowe
Indie
Opis:
The shallow marine deposits of the Late-Middle Jurassic (Callovian–Oxfordian) Jumara Formation of the Gangeshwar Dome of Mainland Kachchh, India, comprise a succession of ~247 m thick clastic sediments with few non-clastic bands and contain a diverse group of ichnofauna. The succession is subdivided into seven lithofacies, viz., laminated shale-siltstone facies (LSS), sheet sandstone facies (SS), herringbone sandstone facies (HS), bivalve sandstone facies (BS), bioclastic limestone facies (BL), intraformational conglomerate facies (IC) and oolitic limestone facies (OL). The ichnofaunal study shows 29 ichnospecies of 23 ichnogenera including Arenicolites, Bifungites, Bolonia, Chondrites, Didymaulichnus, Diplocraterion, Gyrochorte, Helminthopsis, Isopodichnus, Laevicyclus, Lockeia, Monocraterion, Taenidium, Ophiomorpha, Palaeophycus, Planolites, Phycodes, Protopalaeodictyon, Rhizocorallium, Skolithos, Thalassinoides, Tisoa, and Zoophycos. These trace fossils are distributed among nine ichnocoenose, characterized by Chondrites, Diplocraterion, Gyrochorte, Ophiomorpha, Rhizocorallium, Skolithos, Taenidium, Thalassinoides and Zoophycos. Their occurrence in the facies corresponds to their trophic and ethological properties. The colonisation of the opportunistic Diplocraterion and the Skolithos ichnocoenose shows a high den¬sity and marks foreshore/nearshore environmental conditions. The Gyrochorte, the Rhizocorallium, the Taenidium and the Thalassinoides ichnocoenose indicate the typically lower energy zone of the shoreface-offshore region. The Chondrites ichnocoenosis indicates fluctuation in bottom water oxygen while the Zoophycos ichnocoenosis typically exploited a calm water niche in the offshore region. These ich-nocoenose recur throughout the sequence and belong to the Skolithos and the Cruziana ichnofacies which marked changes in energy gradient, substrate stability, water depth and mode of life of invertebrate organisms. The study of trace fossil assemblages with sediment characteristics gives a detailed and accurate picture of foreshore to offshore palaeoenvironmental conditions.
Źródło:
Volumina Jurassica; 2017, 15, 1; 17--40
1896-7876
1731-3708
Pojawia się w:
Volumina Jurassica
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Habitat and hydrocarbon potential of the Mesozoic strata in the Kraków–Rzeszów area (SE Poland)
Autorzy:
Kosakowski, P.
Więcław, D.
Kotarba, M. J.
Kowalski, A.
Powiązania:
https://bibliotekanauki.pl/articles/2058966.pdf
Data publikacji:
2012
Wydawca:
Państwowy Instytut Geologiczny – Państwowy Instytut Badawczy
Tematy:
Carpathian Foredeep substratum
Mesozoic strata
Middle Jurassic source rock
petroleum geochemistry
quality of source rocks
Opis:
The Mesozoic strata in the southeastern Poland were geochemically characterized to determine their hydrocarbon potential on the basis of 483 core samples from 36 boreholes. The Lower and Middle Triassic, Middle and Upper Jurassic, and Lower and Upper Cretaceous turned out to be highly variable. Middle Jurassic rocks represent the highest geochemical quality. Their total organic carbon (TOC) contents range between 0.0 and 17.0 wt.%, with a median of 0.89 wt.%. The highest TOC was observed in the rocks of the Tarnawa 1 borehole. In the remaining boreholes analysed the organic carbon contents were much lower and usually did not exceed 1 wt.%. Gas-prone Type-III kerogen with an admixture of Type-II kerogen is present in the study area. The lowest TOC values were observed in the Cretaceous rocks, where median values were 0.05 wt.% and 0.04 wt.% for Upper Cretaceous and Lower Cretaceous strata respectively. Low TOC contents were also observed in the Lower Triassic and Upper Jurassic strata. Accordingly, those horizons could not be regarded as effective source rocks. The petroleum potential of these stratigraphic horizons is additionally significantly reduced by low maturity, below the threshold for the generation of hydrocarbons. The Mesozoic organic matter was found to be generally immature, i.e. below 0.5% of vitrinite reflectance.
Źródło:
Geological Quarterly; 2012, 56, 1; 139-152
1641-7291
Pojawia się w:
Geological Quarterly
Dostawca treści:
Biblioteka Nauki
Artykuł
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