Cyclicities in Triassic platform carbonates: synchronizing radio-isotopic and orbital clocks     

Roland Mundil  Rainer Zühlke  Thilo Bechstädt  Arndt Peterhänsel  Sven O. Egenhoff  Felix Oberli  Martin Meier  Peter Brack  Hans Rieber 《地学学报》2003,15(2):81-87

ABSTRACT Sedimentary cycles recorded in young sediments are often attributed to fluctuations of the Earth's climate on a 10⁴−10⁶-year scale which in turn is governed by periodic variations in solar insolation linked to orbital (Milankovitch) parameters. A spectacular example of cyclic stratal patterns in ancient deposits is the Middle Triassic Latemar carbonate platform (W Dolomites, N Italy). Based on spectral analyses from previous studies, a superimposition of precession (∼20 ka) and eccentricity (∼100 ka) controlled sea-level fluctuations has been suggested to account for the stacking hierarchy at Latemar, with ∼20 ka being assigned to each highest-order depositional cycle. Zircon U–Pb isotopic ages from volcanic-ash layers within the cyclic succession, corroborated by biostratigraphic constraints, suggest that the average time interval for every individual cycle is significantly smaller than the shortest Milankovitch period and therefore challenge previously published interpretations relating distinct spectral peaks to the above mentioned hierarchy. However, our new spectral data indicate that cyclicities resembling Milankovitch characteristics might exist, but on an entirely different scale. Our findings show that frequency spectra should only be interpreted in combination with robust age control. They also encourage the search for complementary mechanisms controlling carbonate deposition.  相似文献   

Shelf to basin transition in the Cambrian-Lower Ordovician of Sardinia (Italy) discussion     

Thilo Bechstädt  Maria Boni  Matthias Selg 《International Journal of Earth Sciences》1989,78(2):679-683

  相似文献   

Das Frühstadium der alpinen Geosynklinalentwicklung im westlichen Drauzug     

Dr. Thilo Bechstädt  Dr. Rainer Brandner  Univ.-Prof. Dr. Helfried Mostler 《International Journal of Earth Sciences》1976,65(1):616-648

Zusammenfassung Tektonische Aktivität in der Mitteltrias des nordmediterranen Raumes führte zu einer Gliederung des zuvor bestehenden weiträumigen Schelfbereiches. Dieser hatte sich nach der variszischen Gebirgsbildung konsolidiert und wird nun in den sich neu formenden Tethys-Ozean miteinbezogen. Ab dem Mittelanis beeinflußt dieser Ozean auch die Sedimentation im Drauzug. Hier wurden in der Mitteltrias zwei analoge Sedimentationsabläufe beobachtet. Jede dieser Abfolgen beginnt mit dem Zerbrechen starrer Plattformen unter Herausgestaltung von Becken. Die Randposition des Drauzuges zu einem schuttliefernden Hinterland einerseits und das Auftreten von Karbonatplattformen im Ablagerungsbereich andererseits ermöglichen jeweils eine Wiederauffüllung der Beckenbereiche. Analoge Entwicklungen in den Nördlichen Kalkalpen und Südalpen unterstreichen die Großräumigkeit dieser tektogenetischen Prozesse.Ein Vergleich mit Sedimentabfolgen auf inaktiven Plattenrändern, Orten rezenter geosynklinaler Sedimentation, zeigt ganz ähnliche Anfangsstadien geosynklinaler Entwicklung. Diese äußern sich im Drauzug zunächst in Form auslaufender Grabenbruchsysteme, die in weiterer Folge über das Stadium eines Rot-Meer-Grabens mit entsprechendem Vulkanismus, zu einem Früh-Bahama-Typus hinführen. Erst im Jura wird mit dem Übergreifen tektonischer Aktivität auf wesentlich größere Areale und einem damit verbundenen erneuten Vorgreifen des Ozeans das Orthogeosynklinalstadium eingeleitet.

---

Tectonic activity during the middle Triassic in the northern Mediterranean region led to the differentiation of a broad shelf area. This shelf had been consolidated after the Variscan orogeny and gradually became now incorporated in the newly forming Tethys ocean. Starting with the middle Anisian, this oceanic influence may be observed in the Drau belt, where two analogous sedimentary sequences, following one another, are developed. The history of each of these sequences begins with the disruption of rigid platforms and the formation of basins. The conditions for renewed filling of the basin areas were brought to pass: on the one hand by the marginal position of the Drau belt, near an hinterland supplying clastic material, and on the other hand by the association with carbonate platforms within the depositional area. Analogous developments in the Northern Calcareous Alps and in the Southern Alps emphasize the great regional scale of the tectonic processes envolved.A comparison of the Drau range with depositional areas on the margins of inactive plates — areas of geosynclinal sedimentation — shows very similar initial geosynclinal stages. In the Drau range the development of extensive graben systems can be observed first. Later on the Red sea graben type of stage with corresponding volcanism can be found, and later on the development of an cearly Bahama type of stage. The orthogeosynclinal stage was introduced later on, in the Jurassic, with a renewed marine transgression as a result of tectonic activity on a still greater scale.

---

Résumé L'activité tectonique dans le domaine méditérranéen septentrional, au Trias moyen, entraîna un morcellement de l'immense Plateau Continental qui existait auparavant. La consolidation de ce plateau avait eu lieu après les plissements hercyniens; il se vit ensuite impliqué dans la nouvelle formation de l'Océan Tethys. C'est à partir de l'Anisien moyen que cet océan exerce une influence sur la sédimentation dans le Drauzug. On y observa, au Trias moyen, deux déroulements de sédimentation analogues. Chacun d'entre eux commence par la cassure de plaques rigides pendant l'édification des bassins. La position du Drauzug en bordure par rapport à un arrière-pays fournissant des détritiques d'une part, et par rapport à l'apparition de plates-formes carbonatées dans la zone de sédimentation d'autre part, permettent chaque fois un remblaiement dans les domaines en bassins. Des développements semblables dans les Alpes Calcaires Septentrionales et dans les Alpes Méridionales soulignent la grande étendue de ces processus tectogénétiques.Une comparaison avec des séries sédimentaires en bordure de plaques inactives, en des endroits où la sédimentation géosynclinale est récente, montre des phases initiales de développement géosynclinal tout à fait identiques. Ce développement se manifeste dans le Drauzug tout d'abord sous la forme de systèmes de fosses d'effondrement qui s'en écartent et qui, par la suite, passent par l'intermédiairé d'une phase du type «Fosse Mer Rouge «avec volcanisme correspondant, mènent au type «Bahama précoce». C'est seulement au Jurassique, avec l'intervention de l'activité tectonique sur des aires beaucoup plus grandes et, avec, par là, une avance renouvelée de l'océan, que s'est produit la phase orthogéosynclinale.

---

. «». , , . . . . . , . , « », « » . , .

  相似文献   

An ArcGIS® Approach to Include Tectonic Structures in Point Data Regionalization     

Andreas Darsow  Maria‐Theresia Schafmeister  Thilo Hofmann 《Ground water》2009,47(4):591-597

Point data derived from drilling logs must often be regionalized. However, aquifers may show discontinuous surface structures, such as the offset of an aquitard caused by tectonic faults. One main challenge has been to incorporate these structures into the regionalization process of point data. We combined ordinary kriging and inverse distance weighted (IDW) interpolation to account for neotectonic structures in the regionalization process. The study area chosen to test this approach is the largest porous aquifer in Austria. It consists of three basins formed by neotectonic events and delimited by steep faults with a vertical offset of the aquitard up to 70 m within very short distances. First, ordinary kriging was used to incorporate the characteristic spatial variability of the aquitard location by means of a variogram. The tectonic faults could be included into the regionalization process by using breaklines with buffer zones. All data points inside the buffer were deleted. Last, IDW was performed, resulting in an aquitard map representing the discontinuous surface structures. This approach enables one to account for such surfaces using the standard software package ArcGIS^®; therefore, it could be adopted in many practical applications.  相似文献   

Common-reflection-surface stack — a real data example     

Jürgen Mann  Rainer Jger  Thilo Müller  German Hcht  Peter Hubral 《Journal of Applied Geophysics》1999,42(3-4)

The simulation of a zero-offset (ZO) stack section from multi-coverage reflection data is a standard imaging method in seismic processing. It significantly reduces the amount of data and increases the signal-to-noise ratio due to constructive interference of correlated events. Conventional imaging methods, e.g., normal moveout (NMO)/dip moveout (DMO)/stack or pre-stack migration, require a sufficiently accurate macro-velocity model to yield appropriate results, whereas the recently introduced common-reflection-surface stack does not depend on a macro-velocity model. For two-dimensional seismic acquisition, its stacking operator depends on three wavefield attributes and approximates the kinematic multi-coverage reflection response of curved interfaces in laterally inhomogeneous media. The common-reflection-surface stack moveout formula defines a stacking surface for each particular sample in the ZO section to be simulated. The stacking surfaces that fit best to actual events in the multi-coverage data set are determined by means of coherency analysis. In this way, we obtain a coherency section and a section of each of the three wavefield attributes defining the stacking operator. These wavefield attributes characterize the curved interfaces and, thus, can be used for a subsequent inversion. In this paper, we focus on an application to a real land data set acquired over a salt dome. We propose three separate one-parametric search and coherency analyses to determine initial common-reflection-surface stack parameters. Optionally, a subsequent optimization algorithm can be performed to refine these initial parameters. The simulated ZO section obtained by the common-reflection-surface stack is compared to the result of a conventional NMO/DMO/stack processing sequence. We observe an increased signal-to-noise ratio and an improved continuity along the events for our proposed method — without loss of lateral resolution.  相似文献   

Silica diagenesis in Cenozoic mudstones of the North Viking Graben: physical properties and basin modelling          下载免费PDF全文

Thilo Wrona  Christopher A.‐L. Jackson  Mads Huuse  Kevin G. Taylor 《Basin Research》2017,29(Z1):556-575

Silica diagenesis can significantly change physical properties of the host strata and release large volumes of water. Predicting these changes and their timing is essential to understanding compaction, fluid flow and rock deformation in sedimentary basins. In this paper, the influence of silica diagenesis (opal‐A/CT transformation) on physical properties is determined, the sediment volume affected by these changes is mapped, and a new technique to model silica diagenesis is introduced. A petrophysical analysis of 16 exploration wells shows that the opal‐A/CT transformation leads to a porosity reduction of c.20% (from 49 to 29%) in Cenozoic mudstones of the North Viking Graben. Using three‐dimensional seismic reflection data, it is shown that the c.50 m thick opal‐A/CT transformation zone covers an area of >1500 km², equating to a minimum volume of 75 km³. The spatial and temporal evolution of opal‐A/CT transformation is simulated using an innovative basin modelling approach, the results of which indicate that the transformation started around Middle‐to‐Late Eocene times and then migrated upwards until it gradually fossilised between the Miocene and present. These findings are important, as they help understanding how these sediments compact and when fluids are released by diagenesis.  相似文献   

Inventory and evolution of glacial lakes since the Little Ice Age: Lessons from the case of Switzerland     

Nico Mölg  Christian Huggel  Thilo Herold  Florian Storck  Simon Allen  Wilfried Haeberli  Yvonne Schaub  Daniel Odermatt 《地球表面变化过程与地形》2021,46(13):2551-2564

Retreating glaciers give way to new landscapes with lakes as an important element. In this study, we combined available data on lake outlines with historical orthoimagery and glacier outlines for six time periods since the end of the Little Ice Age (LIA; ~1850). We generated a glacial lake inventory for modern times (2016) and traced the evolution of glacial lakes that formed in the deglaciated area since the LIA. In this deglaciated area, a total of 1192 lakes formed over the period of almost 170 years, 987 of them still in existence in 2016. Their total water surface in 2016 was 6.22 ± 0.25 km². The largest lakes are > 0.4 km² (40 ha) in size, while the majority (> 90%) are smaller than 0.01 km². Annual increase rates in area and number peaked in 1946–1973, decreased towards the end of the 20th century, and reached a new high in the latest period 2006–2016. For a period of 43 years (1973–2016), we compared modelled overdeepenings from previous studies to actual lake genesis. For a better prioritization of formation probability, we included glacier-morphological criteria such as glacier width and visible crevassing. About 40% of the modelled overdeepened area actually got covered by lakes. The inclusion of morphological aspects clearly aided in defining a lake formation probability to be linked to each modelled overdeepening. Additional morphological variables, namely dam material and type, surface runoff, and freeboard, were compiled for a subset of larger and ice-contact lakes in 2016, constituting a basis for future hazard assessment.  相似文献   

Catchments as reactors: a comprehensive approach for water fluxes and solute turnover   总被引：1，自引：1，他引：0  

Peter Grathwohl  Hermann Rügner  Thomas Wöhling  Karsten Osenbrück  Marc Schwientek  Sebastian Gayler  Ute Wollschläger  Benny Selle  Marion Pause  Jens-Olaf Delfs  Matthias Grzeschik  Ulrich Weller  Martin Ivanov  Olaf A. Cirpka  Ulrich Maier  Bertram Kuch  Wolfgang Nowak  Volker Wulfmeyer  Kirsten Warrach-Sagi  Thilo Streck  Sabine Attinger  Lars Bilke  Peter Dietrich  Jan H. Fleckenstein  Thomas Kalbacher  Olaf Kolditz  Karsten Rink  Luis Samaniego  Hans-Jörg Vogel  Ulrike Werban  Georg Teutsch 《Environmental Earth Sciences》2013,69(2):317-333

Sustainable water quality management requires a profound understanding of water fluxes (precipitation, run-off, recharge, etc.) and solute turnover such as retention, reaction, transformation, etc. at the catchment or landscape scale. The Water and Earth System Science competence cluster (WESS, http://www.wess.info/) aims at a holistic analysis of the water cycle coupled to reactive solute transport, including soil–plant–atmosphere and groundwater–surface water interactions. To facilitate exploring the impact of land-use and climate changes on water cycling and water quality, special emphasis is placed on feedbacks between the atmosphere, the land surface, and the subsurface. A major challenge lies in bridging the scales in monitoring and modeling of surface/subsurface versus atmospheric processes. The field work follows the approach of contrasting catchments, i.e. neighboring watersheds with different land use or similar watersheds with different climate. This paper introduces the featured catchments and explains methodologies of WESS by selected examples.  相似文献   

Exploring spiral galaxy potentials with hydrodynamical simulations     

Adrianne D. Slyz  Thilo Kranz †  Hans-Walter Rix 《Monthly notices of the Royal Astronomical Society》2003,346(4):1162-1178

We study how well the complex gas velocity fields induced by massive spiral arms are modelled by the hydrodynamical simulations that we used recently to constrain the dark matter fraction in nearby spiral galaxies. More specifically, we explore the dependence of the positions and amplitudes of features in the gas flow on the temperature of the interstellar medium (assumed to behave as a one-component isothermal fluid), the non-axisymmetric disc contribution to the galactic potential, the pattern speed  Ω_p  , and finally the numerical resolution of the simulation. We argue that, after constraining the pattern speed reasonably well by matching the simulations to the observed spiral arm morphology, the amplitude of the non-axisymmetric perturbation (the disc fraction) is left as the primary parameter determining the gas dynamics. However, owing to the sensitivity of the positions of the shocks to modelling parameters, one has to be cautious when quantitatively comparing the simulations to observations. In particular, we show that a global least-squares analysis is not the optimal method for distinguishing different models, as it tends to slightly favour low disc fraction models. Nevertheless, we conclude that, given observational data of reasonably high spatial resolution and an accurate shock-resolving hydro-code, this method tightly constrains the dark matter content within spiral galaxies. We further argue that, even if the perturbations induced by spiral arms are weaker than those of strong bars, they are better suited for this kind of analysis because the spiral arms extend to larger radii where effects like inflows due to numerical viscosity and morphological dependence on gas sound speed are less of a concern than they are in the centres of discs.  相似文献   

Discussion on the publication by H.-J. Schneider et al.     

Th. Bechstädt 《Mineralium Deposita》1978,13(2):281-284

  相似文献