Revealing stellar brightness profiles by means of microlensing fold caustics     

M. Dominik 《Monthly notices of the Royal Astronomical Society》2004,353(1):118-132

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The Cretaceous/Paleogene (K‐Pg) boundary at the J Anomaly Ridge,Newfoundland (IODP Expedition 342, Hole U1403B)          下载免费PDF全文

Dominik Loroch  Alexander Deutsch  Jasper Berndt  André Bornemann 《Meteoritics & planetary science》2016,51(7):1370-1385

We present results of an in‐situ geochemical study using laser‐ablation inductively coupled plasma–mass spectrometry (LA‐ICP‐MS) analyses along a ~4.3 cm long section across the K‐Pg event bed, drilled during IODP Expedition 342 at J Anomaly Ridge south of St. John's, Newfoundland. This section comprises the Maastrichtian with a sharp boundary to the graded, between 1.5 and 1.8 cm thick ejecta layer with totally altered impact glass spherules, which in turn is topped by Danian sediments. The porous and clayey material required elaborate preparation in order to yield reliable data. The ejecta bed shows a highly variable depletion in rare earth elements that even results in strongly subchondritic concentrations. The Ce/Ce* varies strongly (0.81–34), Ni/Cr ranges from 0.38 to 2.79. The maximum platinum group elements (PGE) concentrations are located in one LA‐spot exactly at the basis of the ejecta layer; they amount (in μg g^?1) to 0.35 (Rh), 1.64 (Pd), 2.79 (Pt), and 0.86 (Au). The Nb/Ta ratio increases in the Ma from ~10 to 35.9 toward the ejecta horizon, which itself has higher Nb, Ta, Zr, and Hf concentrations than the background sedimentation, combined with low Nb/Ta (~5–10), and low Zr/Hf (~20–30). The overall result is that alteration processes changed totally the original geochemical characteristics of this K‐Pg spherule bed. To explain the exorbitant element mobility at distances of hundreds of μm, we discuss a combination of mostly reducing redox processes and interaction with organic compounds. This study demonstrates the high potential of in‐situ analyses with high spatial resolution at complex geological materials. Moreover, our results indicate that some caution is necessary in determining the projectile type in impactites via PGE ratios.  相似文献   

Landslide susceptibility analysis based on ArcGIS and Artificial Neural Network for a large catchment in Three Gorges region,China   总被引：1，自引：0，他引：1  

Renneng Bi  Markus Schleier  Joachim Rohn  Dominik Ehret  Wei Xiang 《Environmental Earth Sciences》2014,72(6):1925-1938

A landslide susceptibility map is very important and necessary to efficiently prevent and mitigate the losses brought by natural hazard for a large area. For the purpose of landslide susceptibility analysis for the whole Xiangxi catchment (3,209 km²), Artificial Neural Network (ANN) analysis was applied as the main method. The whole catchment was divided into two parts: the training area and the implementation area. The backwater area (559 km²) of Xiangxi catchment was used as the training area for the ANN method. In the training area the correlations between the landslide distribution and its causative factors, which includes lithology, slope angle, slope curvature and river network, have been analyzed based on the geological map and digital elevation model (DEM). The back-propagation training algorithm in ANN was selected to train the sample data from the training area, which were composed of input data (causative factors) and target output data (landslide occurrence), in order to find the correlations between them. Based on these correlations and input data in the implementation area (causative factors), the network output data were obtained for the implementation area. In the end, a map of landslide susceptibility, which was established by network output data, was presented for Xiangxi catchment. ArcGIS was applied to extract and quantify input information from a DEM for susceptibility analysis and also to present the result visually. As a result, a landslide susceptibility map, in which 70 % of all landslides are rightly classified in the training area (backwater area), was created for Xiangxi catchment.  相似文献   

The Purpose and Age of Underwater Walls in the Bay of Elaia of Western Turkey: A Multidisciplinary Approach     

Martin Seeliger  Dominik Brill  Stefan Feuser  Melanie Bartz  Ercan Erkul  Daniel Kelterbaum  Andreas Vtt  Christina Klein  Felix Pirson  Helmut Brückner 《Geoarchaeology》2014,29(2):138-155

Pergamum (modern: Bergama) was operating an important harbour used by military forces and merchants at the city of Elaia during Hellenistic and Roman Imperial times. Harbour‐related facilities such as warehouses, breakwaters and wharfs document the importance of this harbour site not only for the Pergamenians. This paper focuses on the purpose and age of six submerged wall structures situated approximately 1 km south of the ancient closed harbour basin of Elaia. Geoelectric cross‐sections and semi‐aquatic coring near these walls failed to detect any solid basement under the walls which excludes their possible use as breakwaters or wharfs. Instead, the walls were most likely delineating and separating evaporation ponds of salt works, which compares well with similar structures from other periods and places around the Mediterranean. Combined OSL and ¹⁴C‐dating determined the construction age of the installation between the 4th and 6th centuries A.D. Subsequent (re‐)uses are likely and are in agreement with findings from archaeological surveys.  相似文献   

Calibration of the New Certified Reference Materials ERM‐AE633 and ERM‐AE647 for Copper and IRMM‐3702 for Zinc Isotope Amount Ratio Determinations     

Kirsten Moeller  Ronny Schoenberg  Rolf‐Birger Pedersen  Dominik Weiss  Shuofei Dong 《Geostandards and Geoanalytical Research》2012,36(2):177-199

The commonly used, but no longer available, reference materials NIST SRM 976 (Cu) and ‘JMC Lyon’ (Zn) were calibrated against the new reference materials ERM^®‐AE633, ERM^®‐AE647 (Cu) and IRMM‐3702 (Zn), certified for isotope amount ratios. This cross‐calibration of new with old reference materials provides a continuous and reliable comparability of already published with future Cu and Zn isotope data. The Cu isotope amount ratio of NIST SRM 976 yielded δ^65/63Cu values of ?0.01 ± 0.05‰ and ?0.21 ± 0.05‰ relative to ERM^®‐AE633 and ERM^®‐AE647, respectively, and a δ^66/64Zn_IRMM‐3702 value of ?0.29 ± 0.05‰ was determined for ‘JMC Lyon’. Furthermore, we separated Cu and Zn from five geological reference materials (BCR‐2, BHVO‐2, BIR‐1, AGV‐1 and G‐2) using a two‐step ion‐exchange chromatographic procedure. Possible isotope fractionation of Cu during chromatographic purification and introduction of resin‐ and/or matrix‐induced interferences were assessed by enriched ⁶⁵Cu isotope addition. Instrumental mass bias correction for the isotope ratio determinations by MC‐ICP‐MS was performed using calibrator‐sample bracketing with internal Ni doping for Cu and a double spike approach for Zn. Our results for the five geological reference materials were in very good agreement with literature data, confirming the accuracy and applicability of our analytical protocol.  相似文献   

The Albian to Turonian carbon isotope record from the Shilaif Basin (United Arab Emirates) and its regional and intercontinental correlation     

Dominik Hennhoefer  Aisha Al Suwaidi  Cinzia Bottini  Emina Helja  Thomas Steuber 《Sedimentology》2019,66(2):536-555

The sedimentary record of the Arabian Shelf offers a unique opportunity to study the Cretaceous (Albian–Turonian) greenhouse climate from a palaeoequatorial perspective. In particular, hemipelagic to pelagic carbonate successions from the extensive Shilaif intra‐shelf basin have the potential to produce an excellent record of carbon cycle perturbations during this interval. This study presents a 269 m thick chemostratigraphic (carbonate δ¹³C and δ¹⁸O) record from the Middle Albian to Early Turonian of central Abu Dhabi (United Arab Emirates), representing over 14 Myr of uninterrupted carbonate sedimentation. The Mauddud to Shilaif formations represent outer ramp to basinal intra‐shelf carbonates with variations from laminated organic‐rich to clean bioturbated intervals. Isotopic evidence of the latest Albian Anoxic Event (Oceanic Anoxic Event 1d), Middle Cenomanian Event I and the Cenomanian–Turonian Anoxic Event (Oceanic Anoxic Event 2) are confirmed and biostratigraphically calibrated by means of calcareous nannofossils. The carbon isotope record allows correlation with other regional records and well‐calibrated records across the Tethyan Ocean and represents a significant improvement of the chronostratigraphic framework of the United Arab Emirates (Shilaif) and Oman (Natih) intra‐shelf basins. The study further confirms that low carbon isotope values corresponding to the two source rock intervals in the Shilaif Formation clearly precede the isotopic expressions of Oceanic Anoxic Event 1d and Oceanic Anoxic Event 2.  相似文献   

Holocene and Pleistocene fringing reef growth and the role of accommodation space and exposure to waves and currents (Bora Bora,Society Islands,French Polynesia)     

Eberhard Gischler  J. Harold Hudson  Marc Humblet  Juan Carlos Braga  Dominik Schmitt  Anja Isaack  Anton Eisenhauer  Gilbert F. Camoin 《Sedimentology》2019,66(1):305-328

Holocene fringing reef development around Bora Bora is controlled by variations in accommodation space (as a function of sea‐level and antecedent topography) and exposure to waves and currents. Subsidence ranged from 0 to 0·11 m kyr^?1, and did not create significant accommodation space. A windward fringing reef started to grow 8·7 kyr bp , retrograded towards the coast over a Pleistocene fringing reef until ca 6·0 kyr bp , and then prograded towards the lagoon after sea‐level had reached its present level. The retrograding portion of the reef is dominated by corals, calcareous algae and microbialite frameworks; the prograding portion is largely detrital. The reef is up to 13·5 m thick and accreted vertically with an average rate of 3·12 m kyr^?1. Lateral growth amounts to 13·3 m kyr^?1. Reef corals are dominated by an inner Pocillopora assemblage and an outer Acropora assemblage. Both assemblages comprise thick crusts of coralline algae. Palaeobathymetry suggests deposition in 0 to 10 m depth. An underlying Pleistocene fringing reef formed during the sea‐level highstand of Marine Isotope Stage 5e, and is also characterized by the occurrence of corals, coralline algal crusts and microbialites. A previously investigated, leeward fringing reef started to form contemporaneously (8·78 kyr bp ), but is thicker (up to 20 m) and solely prograded throughout the Holocene. A shallow Pocillopora assemblage and a deeper water Montipora assemblage were identified, but detrital facies dominate. At the Holocene reef base, only basalt was recovered. The Holocene windward–leeward differences are a consequence of less accommodation space on the eastern island side that eventually led to a more complex reef architecture. As a result of higher rates of exposure and flushing, the reef framework on the windward island side is more abundant and experienced stronger cementation. In the Pleistocene, the environmental conditions on the leeward island side were presumably unfavourable for fringing reef growth.  相似文献   

New estimates of potential impacts of sea level rise and coastal floods in Poland     

Paprotny  Dominik  Terefenko  Paweł 《Natural Hazards》2017,85(2):1249-1277

Natural Hazards - Polish coastal zone is thought to be one of the most exposed to sea level rise in Europe. With mean sea levels expected to increase between 28 and 98 cm by the end of the...  相似文献   

Durations of soil formation and soil development indices in a Holocene Mediterranean floodplain     

Christoph Zielhofer  Jos Manuel Recio Espejo  Miguel ngel Núnez Granados  Dominik Faust 《Quaternary International》2009,209(1-2):44

Holocene and late Pleistocene alluvial sequences of the mid-Medjerda floodplain (Northern Tunisia) reveal three types of soils with gradual transitions: Fluvisols (Calcaric), Cambisols (Calcaric) and Calcic Luvisols (Chromic). Stratigraphic cross-correlations, palaeomagnetic secular variation, and ¹⁴C and IRSL dating enable detailed information about ages and durations of soil formation in the floodplain.Weakly developed Fluvisols (Calcaric) commonly reveal late Holocene ages with soil formation durations lasting between 100 and 300 years. Hence, Holocene soil formation is detectable in the exposures from durations of around 100 years onwards. Cambisols show predominantly mid-Holocene ages. The durations of soil formation are between 800 and 5000 years. Calcic Luvisols (Chromic) feature late Pleistocene ages, with durations of soil formation between 10,000 and 40,000 years.Profile Development Indices were computed from simple field parameters like soil structure, soil colour, horizon thickness and leaching features. The derived development indices show good correlation (R² = 0.804) with the calculated durations of soil formation. Field parameters are well suited for a quantitative development index of Holocene soil formation, even if very weak developed soils are predominant. The study shows that maturity stages of Holocene alluvial soils in a homogeneous Mediterranean environment are predominantly driven by soil formation duration.  相似文献   

The mechanism of cation and oxygen isotope exchange in alkali feldspars under hydrothermal conditions   总被引：3，自引：1，他引：2  

Dominik R. D. Niedermeier  Andrew Putnis  Thorsten Geisler  Ute Golla-Schindler  Christine V. Putnis 《Contributions to Mineralogy and Petrology》2009,157(1):65-76

The mechanism of re-equilibration of albite in a hydrothermal fluid has been investigated experimentally using natural albite crystals in an aqueous KCl solution enriched in ¹⁸O at 600°C and 2 kbars pressure. The reaction is pseudomorphic and produces a rim of K-feldspar with a sharp interface on a nanoscale which moves into the parent albite with increasing reaction time. Transmission electron microscopy (TEM) diffraction contrast and X-ray powder diffraction (XRD) show that the K-feldspar has a very high defect concentration and a disordered Al, Si distribution, compared to the parent albite. Raman spectroscopy shows a frequency shift of the Si-O-Si bending vibration from ~476 cm⁻¹ in K-feldspar formed in normal ¹⁶O aqueous solution to ~457 cm⁻¹ in the K-feldspar formed in ¹⁸O-enriched solution, reflecting a mass-related frequency shift due to a high enrichment of ¹⁸O in the K-feldspar silicate framework. Raman mapping of the spatial distribution of the frequency shift, and hence ¹⁸O content, compared with major element distribution maps, show a 1:1 correspondence between the reaction rim formed by the replacement of albite by K-feldspar, and the oxygen isotope re-equilibration. The textural and chemical characteristics as well as the kinetics of the replacement of albite by K-feldspar are consistent with an interface-coupled dissolution-reprecipitation mechanism.  相似文献