Late Mesozoic–Cenozoic evolution of the southwestern Barents Sea
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Abstract:
Three geological provinces are recognized, separated by major fault zones: the oceanic Lofoten Basin and the Vestbakken volcanic province in the west; the southwestern Barents Sea basin province; and the eastern region which has largely acted as a stable platform since Late Paleozoic times. Since Middle Jurassic times, two structural stages are recognized in the southwestern Barents Sea: Late Mesozoic rifting and basin formation; and Early Tertiary rifting and opening of the Norwegian–Greenland Sea. This evolution reflects the main plate tectonic episodes in the North Atlantic–Arctic break-up of Pangea. Middle–Late Jurassic and Early Cretaceous structuration were characterized by regional extension accompanied by strike-slip adjustments along old structural lineaments, which developed as the Bjørnøya, Tromsø and Harstad basins. Late Cretaceous development was more complex, with extension west of the Senja Ridge and the Veslemøy High, and halokinesis in the Tromsø Basin. Tertiary structuration was related to the two-stage opening of the Norwegian–Greenland Sea and the formation of the predominantly sheared western Barents Sea continental margin. Tectonic activity shifted towards the west in successive phases. The southwestern Barents Sea basin province developed within the De Geer Zone in a region of rift-shear interaction. Initially, oblique extension linked the Arctic and North Atlantic rift systems (Middle Jurassic–Early Cretaceous). Later, a continental megashear developed (Late Cretaceous–Paleocene), and finally a sheared-rifted margin formed during the opening of the Norwegian–Greenland Sea (Eocene–Recent).Cite
This paper features the structural evolution of the eastern margin of Eurasia in Late Mesozoic and Cenozoic. It is characterized by three stages of development: the riftogenic stage (Jurassic-Early Cretaceous), the platform stage (Late Cretaceous) and the neotectonic one (Paleogene-Quarternary). The boundaries between these stages are distinctly fixed by the geological time limits of planetary range. It is demonstrated that the riftogenic and neotectonic stages were characterized by a high degree of geodynamic activity, and the platform one by a decrease in contrast of tectonic movements. The main river net was formed in the Early Cretaceous and in the Neogene. It experienced a serious reconstruction accompanied by the formation of the Amur River valley being similar to the modern one.
Neogene
Paleogene
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Abstract Palaeomagnetic data, and specifically remagnetizations, are used to constrain the geometric reconstruction at 100 Ma of three anticlines cored by gabbroic intrusions and Triassic shales in the Central High Atlas, Morocco. Previous palaeomagnetic results have revealed that the Mesozoic sediments of this region acquired a pervasive remagnetization at the end of the Early Cretaceous. The restoration of palaeomagnetic vectors to the remagnetization stage (100 Ma) allows us to determine the dip of the beds during this period and, thereby, to reconstruct structures during that time and determine the relative contributions of Mesozoic magmatic/diapiric uplift vs. Cenozoic compression to the present‐day dip. Our results indicate that three major anticlines in the Central High Atlas (Tasraft, Tassent and Tissila) were initiated to different degrees before the Late Cretaceous and were reactivated during Cenozoic compression to acquire their present‐day geometry. We also discuss the origin of these structures.
Anticline
Cenomanian
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Paleontologists long have argued that the most important evolutionary radiation of mammals occurred during the early Cenozoic, if not that all eutherians originated from a single common post-Cretaceous ancestor. Nonetheless, several recent molecular analyses claim to show that because several interordinal splits occurred during the Cretaceous, a major therian radiation was then underway. This claim conflicts with statistical evidence from the well-sampled latest Cretaceous and Cenozoic North American fossil record. Paleofaunal data confirm that there were fewer mammalian species during the latest Cretaceous than during any interval of the Cenozoic, and that a massive diversification took place during the early Paleocene, immediately after a mass extinction. Measurement data show that Cretaceous mammals were on average small and occupied a narrow range of body sizes; after the Cretaceous-Tertiary mass extinction, there was a rapid and permanent shift in the mean. The fact that there was an early Cenozoic mammalian radiation is entirely compatible with the existence of a few Cretaceous splits among modern mammal lineages.
Extinction (optical mineralogy)
Fossil Record
Evolution of mammals
Mammal
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Nine species of fossil isopods have been studied from Cretaceous to Pleistocene rocks of North America. This represents all known species from the Mesozoic and Cenozoic fossil record on this continent. Four species of Palaega were studied. Palaega goedertorum Wieder and Feldmann, 1989, from upper Eocene to lower Miocene rocks of Washington state, has served recently as the basis for restructuring the genus. Emendations are made to species descriptions of Palaega guadalupensis and P. williamsonensis from the Cretaceous rocks of Texas. The fourth species of Palaega, P. lamnae , also from the Cretaceous rocks of Texas, although of doubtful affinities with this genus, was not removed due to lack of sufficient information to reassign it. Two new species are described, Cirolana enigma , from Lower Cretaceous rocks of South Dakota, and Archaeoniscus texanus , from the Cretaceous of Texas. This is the first report of Cirolana from the fossil record. Two sphaeromatid isopods were included: one, Sphaeroma burkartii from Tertiary rocks of Mexico, was not located for study; the other, Eocopea oculata , is from Miocene rocks of southern California. Two specimens of the valviferan genus Saduria , from Pleistocene deposits in Canada, were also studied.
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The present paper is dedicated to the history of development of the Pamirs and the adjacent parts of Asia during the Mesozoic and Cenozoic. An attempt has been made to reproduce the character of the fluctuations of the territory. For this purpose sedimentary facies and thickness diagrams have been prepared for different divisions of the Mesozoic and Cenozoic. The development of the Pamirs and the adjacent parts of Asia during the Triassic, the Jurassic, and the Early Cretaceous is discussed. ‐ ‐Auth English summ.
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The oolithias of dinosaurs,as special fossil eggs, take an important role in subdividing and contrasting of the continental strata in Mesozoic. It is found abundantly in more than ten basins among fifty Mesozoic Cenozoic sedimentary basins in the northern, southern and western of Henan Province. Based on the vertical occurrences characteristics of the oolithias of dinosaurs in the strata, and with the aids of charophytes, sporo pollen, ostracods, dinosaur skeletons, as well as isotopic ages and the tectonic evolution of these sedimentary basins, the authors conclude that the ages of the strata were Late Cretaceous, and that the oolithias assemblages such as (the lower group) Longiteroolithus Dendoolithus Faveoloolithus Dictroolithus, (the middle group) Spheroolithus Paraspheroolithus Dendroolithus, (the upper group) Elongatoolithus Macroolithus may be used respectively as the signs of the early ,middle and later periods of the Late Cretaceous.
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This paper features the structural evolution of the eastern margin of Eurasia in Late Mesozoic and Cenozoic.It is characterized by three stages of development: the riftogenic stage (Jurassic-Early Cretaceous), the platform stage (Late Cretaceous) and the neotectonic one (Paleogene-Quarternary). The boundaries between these stages are distinctly fixed by the geological time limits of planetary range. It is demonstrated that the riftogenic and neotectonic stages were characterized by a high degree of geodynamic activity, and the platform one by a decrease in contrast of tectonic movements. The main river net was formed in the Early Cretaceous and in the Neogene. It experienced a serious reconstruction accompanied by the formation of the Amur River valley being similar to the modem one.
Neogene
Paleogene
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