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61.
Birgit Mingram Peer Hoth Volker Lüders Daniel Harlov 《International Journal of Earth Sciences》2005,94(5-6):1010-1022
In contrast to predominantly hydrocarbon-rich natural gases in the western part of the Central European Basin (CEB), accumulations
of natural gases from the eastern part of the North German Basin (NGB) are nitrogen-rich with up to 90% N2. This study is focused on the behaviour of fixed ammonium in clay minerals of organic-rich Palaeozoic sediments in the eastern
part of the NGB as a major source of nitrogen-rich natural gases. Carboniferous shales have been investigated for a better
understanding of nitrogen fixing during diagenesis, storage during burial and release during devolatilization processes or
fluid–rock interactions. The total nitrogen contents in the studied Carboniferous shales of the NGB reach up to 2700 ppm with
an inorganic fixed portion (in the form of NH4
+–N) of more than 60%. The results of this study indicate an increasing proportion of the mineralogically fixed ammonium with
increasing thermal maturity and storage up to catagenetic conditions. The isotopic composition of fixed-NH4 is relatively homogeneous in the majority of the shales and ranges from +1 to +3.5‰. In contrast, samples from the basin
centre show a significant decrease in ammonium contents down to 460 ppm coupled with a shift in δ15N up to +5.6‰ suggesting a release of nitrogen on a large scale. Calculation of nitrogen loss and isotopic fractionation indicate
that more than 30% of nitrogen was released as ammonium probably as a consequence of fluid-rock interaction with highly saline
brines. 相似文献
62.
Stanislaw Mazur Magdalena Scheck-Wenderoth Piotr Krzywiec 《International Journal of Earth Sciences》2005,94(5-6):782-798
Several selected seismic lines are used to show and compare the modes of Late-Cretaceous–Early Tertiary inversion within the
North German and Polish basins. These seismic data illustrate an important difference in the allocation of major zones of
basement (thick-skinned) deformation and maximum uplift within both basins. The most important inversion-related uplift of
the Polish Basin was localised in its axial part, the Mid-Polish Trough, whereas the basement in the axial part of the North
German Basin remained virtually flat. The latter was uplifted along the SW and to a smaller degree the NE margins of the North
German Basin, presently defined by the Elbe Fault System and the Grimmen High, respectively. The different location of the
basement inversion and uplift within the North German and Polish basins is interpreted to reflect the position of major zones
of crustal weakness represented by the WNW-ESE trending Elbe Fault System and by the NW-SE striking Teisseyre-Tornquist Zone,
the latter underlying the Mid-Polish Trough. Therefore, the inversion of the Polish and North German basins demonstrates the
significance of an inherited basement structure regardless of its relationship to the position of the basin axis. The inversion
of the Mid-Polish Trough was connected with the reactivation of normal basement fault zones responsible for its Permo-Mesozoic
subsidence. These faults zones, inverted as reverse faults, facilitated the uplift of the Mid-Polish Trough in the order of
1–3 km. In contrast, inversion of the North German Basin rarely re-used structures active during its subsidence. Basement
inversion and uplift, in the range of 3–4 km, was focused at the Elbe Fault System which has remained quiescent in the Triassic
and Jurassic but reproduced the direction of an earlier Variscan structural grain. In contrast, N-S oriented Mesozoic grabens
and troughs in the central part of the North German Basin avoided significant inversion as they were oriented parallel to
the direction of the inferred Late Cretaceous–Early Tertiary compression. The comparison of the North German and Polish basins
shows that inversion structures can follow an earlier subsidence pattern only under a favourable orientation of the stress
field. A thick Zechstein salt layer in the central parts of the North German Basin and the Mid-Polish Trough caused mechanical
decoupling between the sub-salt basement and the supra-salt sedimentary cover. Resultant thin-skinned inversion was manifested
by the formation of various structures developed entirely in the supra-salt Mesozoic–Cenozoic succession. The Zechstein salt
provided a mechanical buffer accommodating compressional stress and responding to the inversion through salt mobilisation
and redistribution. Only in parts of the NGB and MPT characterised by either thin or missing Zechstein evaporites, thick-skinned
inversion directly controlled inversion-related deformations of the sedimentary cover. Inversion of the Permo-Mesozoic fill
within the Mid-Polish Trough was achieved by a regional elevation above uplifted basement blocks. Conversely, in the North
German Basin, horizontal stress must have been transferred into the salt cover across the basin from its SW margin towards
the basins centre. This must be the case since compressional deformations are concentrated mostly above the salt and no significant
inversion-related basement faults are seismically detected apart from the basin margins. This strain decoupling in the interior
of the North German Basin was enhanced by the presence of the Elbe Fault System which allowed strain localization in the basin
floor due to its orientation perpendicular to the inferred Late Cretaceous–Early Tertiary far-field compression. 相似文献
63.
64.
Events in eastern Germany since 1989 pose major challenges for geographical interpretation. This paper examines the spatial impacts of the post-unification economic and social upheavals in the new Länder. Using unemployment rates as a key indicator of regional differentiation, spatial variability within the new Länder is examined in terms of two fundamental dimensions. First, the relationship with former patterns of economic specialization is explored, and secondly, the effects of basic geographical properties such as settlement structure, location and peripherality. Prominent regional polarities are described, notably between major agglomeration cores and rural residuals, and between ‘bridgehead’ locations and less-accessible districts. Within this context the paper then identifies some ‘green shoots’ of recovery and new growth. It concludes by emphasizing the importance of incorporating sub-regional variations into any new framework of regional policy. 相似文献
65.
Tim Coles 《Applied geography (Sevenoaks, England)》1997,17(4):315-333
After unification in 1990 the German government was faced with the task of modernizing the economies of the five new Länder. This process has focused on service sector expansion, particularly the growth of consumer services, which were underdeveloped in the German Democratic Republic. This paper presents a preliminary survey of the impact of the political transition on the structure, organization and spatial pattern of retail services. The new retail sector is characterized by channels of distribution imported from West Germany, uneven development of retail services, and the survival of artefacts from the retail system of the socialist era. Close convergence with levels of retail provision in the old Länder has not been achieved and the changing nature of economic, legislative and political conditions render further expansion problematic. The introduction of legislation to regulate retail growth, the increasingly contested nature of retail change and the complex politics surrounding economic redevelopment in eastern Germany will influence the nature and extent of future retail development. 相似文献
66.
With the existence of eight substantial islands in the Southern California Bight, the oceanic circulation is significantly affected by island wakes. In this paper a high-resolution numerical model (on a 1 km grid), forced by a high-resolution wind (2 km), is used to study the wakes. Island wakes arise due both to currents moving past islands and to wind wakes that force lee currents in response. A comparison between simulations with and without islands shows the surface enstrophy (i.e., area-integrated square of the vertical component of vorticity at the surface) decreases substantially when the islands in the oceanic model are removed, and the enstrophy decrease mainly takes place in the areas around the islands. Three cases of wake formation and evolution are analyzed for the Channel Islands, San Nicolas Island, and Santa Catalina Island. When flows squeeze through gaps between the Channel Islands, current shears arise, and the bottom drag makes a significant contribution to the vorticity generation. Downstream the vorticity rolls up into submesoscale eddies. When the California Current passes San Nicolas Island from the northwest, a relatively strong flow forms over the shelf break on the northeastern coast and gives rise to a locally large bottom stress that generates anticyclonic vorticity, while on the southwestern side, with an adverse flow pushing the main wake current away from the island, positive vorticity has been generated and a cyclonic eddy detaches into the wake. When the northward Southern California Countercurrent passes the irregular shape of Santa Catalina Island, cyclonic eddies form on the southeastern coast of the island, due primarily to lateral stress rather than bottom stress; they remain coherent as they detach and propagate downstream, and thus they are plausible candidates for the submesoscale “spirals on the sea” seen in many satellite images. Finally, the oceanic response to wind wakes is analyzed in a spin-up experiment with a time-invariant wind that exhibits strips of both positive and negative curl in the island lee. Corresponding vorticity strips in the ocean develop through the mechanism of Ekman pumping. 相似文献
67.
Dissolved organic carbon (DOC) is the largest organic carbon reservoir in sea water and plays an imporrant role in the marine carbon cycle and other biogeochemical processes in the ocean. Accurate and precise determinalion of the bOC concentration in sea water is thus a prerequisite for any interpretation of DOC biogeochemistry. A key factor in analytical quality control is an accurate determination of the blank. The assessment and distinction of DOC blanks are essential for the precise measurements of oceanic DOC. The total DOC blank includes instrument and water blanks in the high temperature catalytic oxidation (HTCO) method. DOC can be measured accurately using the HTCO method only when the instrument blank is correctly distinguished from the total DOC blank and corrected in the sample measurements. Low DOC blanks can be achieved by extensive conditioning of new catalysts and the whole instrument system, whereas instrument blanks can be quantified by subtracting the water blank from the total DOC blank. We have been able to produce low carbon nanopure water [≤2μmol/dm3(C)] and have a low instrumental blank [< 5-6 μmol/dm3(C)] when using the HTCO method. Results of concentrations and distributions of DOC in the Gulf of Mexico and the North Atlantic are oceanographically consistent. Results from DOC measurements on samples from the international DOC methods comparison program further confirmed our low values of both nenopure water and the instrument blank. 相似文献
68.
69.
The 1989 German Bight invasion of Muggiaea atlantica 总被引:4,自引:0,他引:4
70.