1,721,076 research outputs found
The GRACE-satellite gravity and geoid fields in analysing large-scale, cratonic or intracratonic basins
No full textThe recently released gravity potential field development derived from the Gravity
Recovery and Climate Experiment satellite allows an unprecedented opportunity to
use the gravity field to make global comparisons of structures of geological interest.
The spatial resolution of the gravity field is sufficiently good to map large-scale
or intracratonic and cratonic basins, as the areal extent of these basins is 0.5 ×
106 km2 and greater. We present the gravity anomaly, Bouguer, geoid and terrain
corrected geoid fields for a selection of nine large-scale basins and show that the
satellite-derived field can be used to successfully identify distinctive structures of these
basins, e.g., extinct rifts underlying the basins and generally the isostatic state. The
studied basins are the Eastern Barents Sea, West Siberian, Tarim, Congo, Michigan,
Amazon, Solim ˜ oes, Parnaiba and Paran`a basins. We complete the mapping of the
gravity field with a description of the basins in terms of areal extension and depth,
sedimentary age and presence and age of volcanism. Interpretation of the satellite
gravity anomalies and considerations regarding the crustal thickness as known from
seismic investigations, allows us to conclude that for the greater part of the basins
there is evidence for high-density material in the lower crust and/or upper mantle.
This density anomaly is, at least partly, compensating for the low-density sedimentary
infill instead of the crustal thinning mechanism. For our selection of basins, crustal
thickness variations and Moho topography cannot be considered as mechanisms of
compensation of the sedimentary loading, which is a clear difference to well-defined
rift basins.In press13JCR Journalreserve
New inputs from the transalp transect to the understanding of isostasy in the Eastern Alps
No full textInsights into the lithospheric structure and the tectonic setting of the Barents Sea region by isostatic considerations
No full textWe study the tectonic setting and lithospheric structure of the greater Barents Sea region by investigating its isostatic state and its gravity field. 3-D forward density modelling utilizing available information from seismic data and boreholes shows an apparent shift between the level of observed and modelled gravity anomalies. This difference cannot be solely explained by changes in crustal density. Furthermore, isostatic calculations show that the present crustal thickness of 35-37 km in the Eastern Barents Sea is greater than required to isostatically balance the deep basins of the area (>19 km). To isostatically compensate the missing masses from the thick crust and deep basins and to adequately explain the gravity field, high-density material (3300-3350 kg m-3) in the lithospheric mantle below the Eastern Barents Sea is needed. The distribution of mantle densities shows a regional division between the Western and Eastern Barents and Kara Seas. In addition, a band of high-densities is observed in the lower crust along the transition zone from the Eastern to Western Barents Sea. The distribution of high-density material in the crust and mantle suggests a connection to the Neoproterozoic Timanide orogen and argues against the presence of a Caledonian suture in the Eastern Barents Sea. Furthermore, the results indicate that the basins of the Western Barents Sea are mainly affected by rifting, while the Eastern Barents Sea basins are located on a stable continental platform
Inverse modeling of elastic thickness by convolution method - The Eastern Alps as a case example
No full text
The lithospheric density structure of the Eastern Alps
No full textThe three-dimensional (3D) lithospheric density structure of the Eastern Alps was investigated by integrating results from
reflection seismics, receiver function analyses and tomography. The modelling was carried out with respect to the Bouguer gravity
and the geoid undulations and emphasis were laid on the investigations of the importance of deep lithospheric features. Although the influence of inhomogeneities at the lithosphere–asthenosphere boundary on the potential field is not neglectable, they are overprinted by the response of the density contrast at the crust–mantle boundary and intra-crustal density anomalies. The uncertainties in the interpretations are in the same order of magnitude as the gravity field generated by the deep lithosphere.
After including the deep lithospheric geometry from the tomographic model it is shown that full isostatic equilibrium is not
achieved below the Eastern Alps. However, calculation of the isostatic lithospheric thickness shows two areas of lithospheric
thickening along the central axis of the Eastern Alps with a transition zone below the area of the TRANSALP profile. This is in
agreement with the tomographic model, which features a change in lithospheric subduction direction
Forward and inverse modelling of gravity revealing insight into crustal structures of the eastern Alps
No full textThe gravity potential derivatives as a means to classify the Barents Sea basin in the context of cratonic basins
No full textDetailed study of the gravity field and the isostatic state of the Barents Sea Region shows that the Eastern Barents Sea basins are not typical rift basins. They exhibit distinctive features such as large wavelengths, high lithospheric mantle density, thick sequences of sediments, a flat Moho and high elastic thickness. These attributes are normally associated with cratonic or intracratonic basins. To understand the geological history of the Eastern Barents Sea basins, we make a comparison with other
well studied cratonic basins: the West Siberian basin, the Michigan basin in North America, the Solimões, Amazon, Parnaìba and Paranà basins in South America, the Tarim basin in Central Asia and the Congo basin in Africa. For these basins, the structure, subsidence history and temperature evolution is relatively well known. Our analysis includes the characterization in terms of gravity, geoid undulations, isostatic state, age and igneous activity.
An important constraint in sedimentary basin evolution is the presence of the volcanism and the relative age of the volcanic strata with respect to the sedimentary package. In all the considered basins, except the Congo basin, volcanic masses are present at some time-stage and at some depth at the basin. Each of the basins exhibits some deviation from the classic isostatic equilibrium model that predicts the crustal thickness (thinning in this case) from the topographic and sedimentary load. Instead of crustal thinning, high density masses in the crust and mantle appear to be a typical feature. The basins may be divided into two groups, one in which the given basin correlates with the geoid, the second in which the geoid is independent. This iscrimination points towards different density characteristics in the integrated crustal column
New insights into the basement structure of the West Siberian basin from forward and inverse modelling of GRACE satellite gravity data
No full textThe oil- and gas-rich West Siberian Basin is underlain by a layer of flood basalts of late Permian-Triassic age that are coeval with the Siberian traps. The extent and thickness of the basalts are unknown, but knowing their thickness is important for discussions on the end-Permian mass extinction because basalt volume constrains estimates of emitted volatiles. We have used GRACE satellite and terrestrial gravity data to study the structure of the crust and basalt distribution. Published seismic sections are used to constrain the sediment isopachs and to estimate a depth-density function. We use published models of crustal thickness and basement depth to reduce the observed gravity field to the basement level. The resulting three-dimensional density model gives information on density anomalies in the lower crust and upper mantle and on the basalt thickness. We identify several rift-graben structures that are presumably filled with basalt. The lower crust below the West Siberian Basin shows considerable density variations, and these variations allow the region to be divided into four major blocks. The eastern part of the basin, toward the Siberian platform, shows an arch-shaped density increase in the lower crust that is accompanied by a linear high-density anomaly at shallower depths. Our work demonstrates the way in which the GRACE-gravity field can be applied to map geological structures like buried rifts and large basins. The same techniques can be used for other large, remote basins such as those in cratonic South America
Reinterpretation of the effective elastic thickness in terms of Young’s modulus variation applying the analytical solution for an Elastic Plate (ASEP) to the Barents Sea
No full textWe apply the analytical solution for an elastic plate (ASEP), which solves the 4th order differential equation for the flexure of a thin plate to the Barents Sea in order to calculate the flexural rigidity. To constrain our analysis we make use of a 3D density model based on the Barents50 model [Ritzmann et al. 2006]. The density model provides information about the crustal configuration, e.g. the Moho and the loading in the crust including all internal density variation. The loading in combination with the ASEP allows us to calculate the flexure Mohos, and by comparison with the reference Moho, the flexural rigidity distribution. The resulting flexural rigidity distributions will be used to validate tectonic concepts, e.g. the location of the proposed Caledonian suture. In the past the effective elastic thickness (EET) has been used synonymously for the flexural rigidity, since it was defined by the material parameters of Young's modulus and Poisson ratio, which were assumed to be constant. The application of the ASEP shows, that it is sufficient to operate with a constant value for the Poisson's ratio, as the variation does not lead to a significant change in the result. However, concerning the vertical and horizontal variation of crustal composition, which corresponds to a change of Young modulus by orders of magnitude - the use of a constant standard value in the calculation process is doubtful. For that reason the EET distribution was recalculated including the Young's modulus variation, which could be estimated by using the p- wave velocities of the Barents50 model. From the viewpoint of solid-state physics the elastic thickness concept should be reconceived. The EET corresponds theoretically to a thickness of a flexed plate, which consists of a material describable by a constant Young's modulus. Therefore the obtained EET distribution could be related to a Young's modulus variation, if the calculation was done with a constant assumed standard value. If the crust and the upper mantle have a non-uniform Young's modulus, the calculated flexural rigidity distribution is only valid for the crust but not for the lithosphere. These investigations ought to demonstrate the importance of the consideration of the Young's modulus variation in the EET calculation
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