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  • 1
    Call number: K-98-0112(1-4)
    Pages: 1 Kt. in 4 Bl. : mehrfarb.
    Branch Library: AWI Library
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  • 2
    Publication Date: 2016-01-09
    Description: Geochronological studies in northern Wedel Jarlsberg Land, southwestern Svalbard (Norway), showed that the Tonian (c. 950 Ma) igneous rocks were subjected to metamorphism during the Torellian (c. 640 Ma) and early Caledonian (470–460 Ma) events. Predominant augen gneisses, derived from a Tonian protolith, are intercalated in that area, with schists comprising two distinct metamorphic mineral assemblages. The M1 (Torellian) assemblage containing garnet-I + quartz + plagioclase-I + biotite-I + muscovite-I was formed under amphibolite-facies conditions at c. 550–600 °C and 5–8 kbar (1 kbar = 100 MPa). The M2 (Caledonian) assemblage comprising garnet-II + quartz + plagioclase-II + biotite-II + muscovite-II + zoisite + chlorite crystallized at c. 500–550 °C and 9–12 kbar, corresponding to epidote–amphibolite facies conditions. The M2 mineral assemblage constitutes the pervasive Caledonian fabric of the schists that was subsequently reactivated in a left-lateral strike-slip shear regime. The subsequent c. 70° clockwise rotation of the original structure to its present position was caused by a large-scale passive rotation during the Paleogene Eurekan orogeny. The new pressure–temperature estimates suggest that metamorphic basement in the study area was consolidated during the Torellian middle-grade event and then overprinted by Caledonian moderate- to high-pressure subduction-related metamorphism. A following sinistral shear zone assembled the present structure of basement units. Our results pose a question about the possible extent of Torellian precursor to the Caledonian basement across the High Arctic and the scale of its subsequent involvement in early Caledonian subduction. In conjunction with previous studies, the results suggest a possible correlation between southwestern Spitsbergen and the Pearya Terrane in Ellesmere Island.
    Print ISSN: 0008-4077
    Electronic ISSN: 1480-3313
    Topics: Geosciences
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  • 3
    Publication Date: 2016-11-09
    Description: The evolution of the Eurekan deformation zones in the Arctic is closely related to the development of the circum-Greenland plate boundaries in Early Cenozoic times (53 – 34 Ma). Mostly, the Eurekan Orogeny or deformation has been interpreted as a predominantly compressive tectonic event, but the Eurekan deformational history in the Arctic was not the result of a single tectonic episode. It rather represents a complex sequence of successive tectonic stages, which produced a number of intra-continental deformation zones with changing, sometimes opposing, lateral, oblique and convergent kinematics in the Canadian Arctic Archipelago, north and NE Greenland, and Svalbard. The interaction between the continental plates, especially in combination with the development of transform faults, resulted onshore in the formation of several complex deformation zones and areas of Eurekan deformation. The Eurekan deformation can be divided into two major tectonic stages: the first phase in the Early Eocene was dominated by orthogonal compression in the West Spitsbergen Fold-and-Thrust Belt along the west margin of the Barents Shelf and contemporaneous sinistral strike-slip tectonics along the Wegener Fault and on Ellesmere Island, whereas the second phase in the Late Eocene was characterized by dextral strike-slip and compression on Ellesmere Island and contemporaneous dextral transpression and transtension along the De Geer Fracture Zone or Hornsund Fault Complex between NE Greenland and Spitsbergen.
    Print ISSN: 0016-7649
    Topics: Geosciences
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  • 4
    Publication Date: 2017-09-30
    Description: The 400 km long transect through Ellesmere Island is located perpendicular to the North American continental margin between the Arctic Ocean in the NNW and the Greenland–Canadian Shield in the SSE. It provides an insight into the structural architecture and tectonic history of the upper parts of the continental crust. The northernmost segment of the transect is dominated by the composite Pearya Terrane, which amalgamated with the Laurentian margin during the Late Devonian–Early Carboniferous Ellesmerian Orogeny. The Neoproterozoic to Devonian Franklinian Basin is exposed south of the terrane boundary and most probably overlies the crystalline basement of the Greenland–Canadian Shield. The structures along the transect in this area are dominated by kilometre-scale Ellesmerian folding of the Franklinian Basin deposits above a deep-seated detachment, which is suggested to be located at the boundary between the basement of the Canadian Shield and the overlying 〉8 km thick Franklinian Basin. Following the development of the Late Mississippian–Palaeogene Sverdrup Basin, the complex Eurekan deformation reactivated Ellesmerian thrust faults and probably parts of the associated deep-seated detachment. In addition, large Eurekan strike-slip faults affected and displaced pre-Eocene deposits and tectonic structures, particularly in the northern part of the transect. Supplementary material: The complete transect (Segment 1 to 5) through Ellesmere Island between the Arctic Ocean in the NNW and Kane Basin in the SSE is available at https://doi.org/10.6084/m9.figshare.c.3783608
    Print ISSN: 0305-8719
    Electronic ISSN: 2041-4927
    Topics: Geosciences
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  • 5
    Publication Date: 2017-09-30
    Description: The New Siberian Islands are affected by a number of Mesozoic tectonic events. The oldest event (D1a) is characterized by NW-directed thrusting within the South Anyui Suture Zone combined with north–south-trending sinistral strike-slip in the foreland during the Early Cretaceous. This compressional deformation was followed by dextral transpression along north–south-trending faults, which resulted in NE–SW shortening in the Kotelny Fold Zone (D1b). The dextral deformation can be related to a north–south-trending boundary fault zone west of the New Siberian Islands, which probably represented the Laptev Sea segment of the Amerasia Basin Transform Fault in pre-Aptian–Albian times. The presence of a transform fault west of the islands may be an explanation for the long and narrow sliver of continental lithosphere of the Lomonosov Ridge and the sudden termination of the South Anyui Suture Zone against the present Laptev Sea Rift System. The intrusion of magmatic rocks 114 myr ago was followed by NW–SE-trending sinistral strike-slip faults of unknown origin (D2). In the Late Cretaceous–Paleocene, east–west extension (D3) west of the New Siberian Islands initiated the development of the Laptev Sea Rift System, which continues until today and is largely related to the development of the Eurasian Basin.
    Print ISSN: 0305-8719
    Electronic ISSN: 2041-4927
    Topics: Geosciences
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  • 6
    Publication Date: 2017-05-13
    Description: The early Eocene (ca. 56–47.8 Ma) was an interval of exceptional warmth with reduced pole-to-equator temperature gradients. Climate proxies indicate mean annual air temperatures (MATs) and sea-surface temperatures (SSTs) exceeding 8–18 °C and frost-free, mild winters in polar areas, features that have proven difficult to reproduce with the most elaborate climate models. A full appraisal of the early Eocene polar climate has been, however, limited by possible seasonal biases associated with geochemical proxies and the lack of data from the vast Eurasian Arctic. Here we present multiproxy data from lower-middle Eocene coastal plain sediments of the New Siberian Islands (Russia) showing that taxodioid Cupressaceae, palms, and the mangrove Avicennia grew in Arctic Siberia above 72°N under air temperatures averaging 16–21 °C annually and 5.5–14 °C in winter. Kaolinite contents are exceptionally high (up to 60% of clay assemblages) and comparable to those found in present-day subtropical soils formed under high mean annual precipitation (MAP 〉1000 mm) and warm (MAT 〉15 °C) conditions. The Avicennia pollen records the northernmost mangrove growth ever documented and indicates early Eocene SSTs exceeding 13 °C in winter and 18 °C in summer. Considering the high MAP estimated for Arctic Siberia and other pan-Arctic landmasses, we propose that the heat from warm river waters draining into the Arctic might have amplified early Eocene polar warmth. Our results provide the first climate constraints for the early Eocene of Arctic Siberia and support the view that most climate models underestimate polar warming in greenhouse conditions.
    Print ISSN: 0091-7613
    Electronic ISSN: 1943-2682
    Topics: Geosciences
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  • 7
    Publication Date: 2015-08-26
    Description: Stratigraphic records from northwestern Pangea provide unique insight into global processes that occurred during the latest Permian extinction (LPE). We examined a detailed geochemical record of the Festningen section, Spitsbergen. A stepwise extinction is noted as: starting with (1) loss of carbonate shelly macrofauna, followed by (2) loss of siliceous sponges in conjunction with an abrupt change in ichnofabrics as well as dramatic change in the terrestrial environment, and (3) final loss of all trace fossils. We interpret loss of carbonate producers as related to shoaling of the lysocline in higher latitudes, in relationship to building atmospheric CO 2 . The loss of siliceous sponges is coincident with the global LPE event and is related to onset of high loading rates of toxic metals (Hg, As, Co) that we suggest are derived from Siberian Trap eruptions. The final extinction stage is coincident with redox-sensitive trace metal and other proxy data that suggest onset of anoxia after the other extinction events. These results show a remarkable record of progressive environmental deterioration in northwestern Pangea during the extinction crises.
    Print ISSN: 0016-7606
    Electronic ISSN: 1943-2674
    Topics: Geosciences
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  • 8
    Publication Date: 2017-05-25
    Description: The crustal seismic velocity model (based on receiver functions) of Ellesmere Island and the structural geological cross-section of Ellesmere Island, both documented and discussed elsewhere in this volume, are here integrated into a crustal-scale transect crossing all the main tectonic domains. The velocity model satisfies much of the observed gravity field, but implies minor modifications with potentially important implications for characterizing the lower crust over the transect. The crust of the Pearya Terrane includes a high-velocity and high-density lower crustal body, suggested to represent a mafic underplate linked to the emplacement of the High Arctic Large Igneous Province. A similar body also lies directly beneath the Hazen Plateau, but this is more likely to be inherited from earlier tectonic stages than to be linked to the High Arctic Large Igneous Province. A large-scale basement-involving thrust, possibly linked to a deep detachment of Ellesmerian age, lies immediately south of the Pearya Terrane and forms the northern backdrop to a crustal-scale pop-up structure that accommodates Eurekan-aged shortening in northern Ellesmere Island. The thickest crust and deepest Moho along the transect are below the Central Ellesmerian fold belt, where the Moho is flexured downwards to the north to a depth of about 48 km beneath the load of the structurally thickened supracrustal strata of the fold belt.
    Print ISSN: 0305-8719
    Electronic ISSN: 2041-4927
    Topics: Geosciences
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  • 9
    Publication Date: 1999-12-01
    Print ISSN: 0278-7407
    Electronic ISSN: 1944-9194
    Topics: Geosciences
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  • 10
    Publication Date: 2003-08-01
    Print ISSN: 0278-7407
    Electronic ISSN: 1944-9194
    Topics: Geosciences
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