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Wyszukujesz frazę "mesozoic" wg kryterium: Temat


Wyświetlanie 1-4 z 4
Tytuł:
New data on Callovian (Middle Jurassic) belemnites and palynomorphs from the Northern Caucasus, southwest Russia
Autorzy:
Dzyuba, O. S.
Goryacheva, A. A.
Ruban, D. A.
Gnezdilova, V. V.
Zayats, P. P.
Powiązania:
https://bibliotekanauki.pl/articles/94375.pdf
Data publikacji:
2016
Wydawca:
Uniwersytet im. Adama Mickiewicza w Poznaniu
Tematy:
macroinvertebrates
microfossils
condensed section
Mesozoic
Adygeja
makrobezkręgowce
mikroskamieliny
mezozoik
Opis:
Palaeontological data on the Caucasus are highly important for large-scale stratigraphical and palaeobiogeographical assessment of the northern Tethyan margin, but this information is often scarce and not available in English. Field studies in the Northern Caucasus have now permitted to amass some new data. Two belemnite species are described from the stratotype section of the Kamennomostskaja Formation (Callovian, Middle Jurassic) near the town of Kamennomostskij in Adygeja (Northern Caucasus). These are Belemnopsis subhastata (von Zieten, 1831) and Rhopaloteuthis ominosa Gustomesov, 1968. The latter is a rare species, and the present find allows new insights into its taxonomy. A palynological analysis of the belemnite-bearing sample was carried out, and a diverse assemblage of dinocysts, acritarchs and prasinophytes, plus pollen and spores recognised. The most abundant palynomorphs are Micrhystridium and Classopollis. Data on belemnites coupled with those on palynomorphs indicate the early Callovian age of the sample level. This interpretation differs slightly from previous conclusions based on ammonites and dinocysts. If this age is correct, the degree of condensation of Callovian deposits in the section studied was lesser than previously assumed.
Źródło:
Geologos; 2016, 22, 1; 49-59
1426-8981
2080-6574
Pojawia się w:
Geologos
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Mesozoic mass extinctions and angiosperm radiation: does the molecular clock tell something new?
Autorzy:
Ruban, Dmitry A.
Powiązania:
https://bibliotekanauki.pl/articles/94220.pdf
Data publikacji:
2012
Wydawca:
Uniwersytet im. Adama Mickiewicza w Poznaniu
Tematy:
angiosperms
radiation
mass extinction
molecular clock
Mesozoic
promieniowanie
masowe wyginięcie
zegar molekularny
mezozoik
Opis:
Angiosperms evolved rapidly in the late Mesozoic. Data from the genetic-based approach called ’molecular clock’ permit an evaluation of the radiation of flowering plants through geological time and of the possible influences of Mesozoic mass extinctions. A total of 261 divergence ages of angiosperm families are considered. The radiation of flowering plants peaked in the Albian, early Campanian, and Maastrichtian. From the three late Mesozoic mass extinctions (Jurassic/Cretaceous, Cenomanian/Turonian, and Cretaceous/Palaeogene), only the Cretaceous/Palaeogene event coincided with a significant, abrupt, and long-term decline in angiosperm radiation. If their link will be further proven, this means that global-scale environmental perturbation precluded from many innovations in the development of plants. This decline was, however, not unprecedented in the history of the angiosperms. The implication of data from the molecular clock for evolutionary reconstructions is limited, primarily because this approach deals with only extant lineages.
Źródło:
Geologos; 2012, 18, 1; 37-42
1426-8981
2080-6574
Pojawia się w:
Geologos
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Possibilities and restrictions of heavy-mineral analysis for the reconstruction of sedimentary environments and source areas
Autorzy:
Derkachev, A.N.
Nikolaeva, N. A.
Powiązania:
https://bibliotekanauki.pl/articles/94357.pdf
Data publikacji:
2013
Wydawca:
Uniwersytet im. Adama Mickiewicza w Poznaniu
Tematy:
heavy-mineral assemblages
sedimentary environments
ODP cores
Mesozoic folded belts
złoża ciężkich minerałów
środowiska sedymentacyjne
Opis:
The possible reconstruction of ancient sedimentary environments on the basis of heavy-minerals assemblages is presented by means of discriminant lithogeodynamic diagrams that compare modern and ancient sedimentary environments. This is exemplified by Mesozoic-Cenozoic deposits recovered from ODP cores obtained from the Philippine and Japan Seas, the Japan Trench and the North Atlantic, as well as by deposits from folded areas onshore. On the basis of the comparative analysis, it can be deduced that the main tendencies in mineral assemblages of modern deposits that depend on the structural-tectonic conditions, are fairly well preserved in Cenozoic deposits (including the deposits recovered by ODP drilling). On the other hand, the environmental reconstruction of folded and faulted pre-Cenozoic continental areas on the basis of their heavy-mineral assemblages, by comparing them with supposed modern analogs, is not always possible with much certainty. The main reasons may be either a considerable change in the composition of the initial (primary) mineral assemblages as a result of intralayer solution or the absence, at the time of deposition, of geodynamic environments that closely resembled modern ones.
Źródło:
Geologos; 2013, 19, No. 1-2; 147-158
1426-8981
2080-6574
Pojawia się w:
Geologos
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Characterisation of potholes formed on bedrock sandstones at Loei Dun, Phetchabun Geopark, Thailand
Autorzy:
Singtuen, Vimoltip
Junjuer, Thitaree
Powiązania:
https://bibliotekanauki.pl/articles/2204353.pdf
Data publikacji:
2022
Wydawca:
Uniwersytet im. Adama Mickiewicza w Poznaniu
Tematy:
geomorphology
landforms
geotourism
lithic arenite
geoheritage
Mesozoic
Nam Phong Formation
geomorfologia
ukształtowanie terenu
geoturystyka
piasowiec lity
geodziedzictwo
mezozoiczny
Opis:
Phetchabun National Geopark comprises varied geosites; one of the fluvial bedrock landforms distinguished here is Loei Dun. This shows many potholes in Mesozoic sandstone of the Nam Phong Formation (Khorat Group). A genetic study of the occurrence of the Loei Dun potholes lends it a higher geoheritage value. For the present study we did fieldwork and carried out petrographical and geotechnical analyses so as to classify and characterise the potholes and consider geotourism potentials. Petrographically, the bedrock sandstone is a lithic arenite which consists of 82-96 percent very fine to coarse, well-sorted subangular sand with low sphericity and calcite cementation. Our geotechnical analysis of the bedrock sandstone suggests that pothole occurrence may be linked to low rock strength and slake durability index with high rock absorption and porosity at Loei Dun. Field studies confirmed the impact of other factors such as joints/faults, fluvial conditions and biological weathering. There are five types of pothole, viz., simple ones, potholes with external furrows, compound potholes, breached potholes and lateral ones. The present study adds educational value to the Loei Dun geosite at Phetchabun Geoparks and cultural and economic aspects can be further strengthened through the development of geotourism in the area.
Źródło:
Geologos; 2022, 28, 1; 39--50
1426-8981
2080-6574
Pojawia się w:
Geologos
Dostawca treści:
Biblioteka Nauki
Artykuł
    Wyświetlanie 1-4 z 4

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