Digital mapping of coastal boulders – high-resolution data acquisition to infer past and recent transport dynamics     

Fabian Boesl  Max Engel  Rodrigo C. Eco  JaN B. Galang  Lia A. Gonzalo  Francesca Llanes  Eva Quix  Helmut Brückner 《Sedimentology》2020,67(3):1393-1410

Coastal boulder fields provide clues to long-term frequency-magnitude patterns of coastal flooding events and have the potential to play an important role in coastal hazard assessment. Mapping boulders in the field is time and labour-intensive, and work on intertidal reef platforms, as in the present study, is physically challenging. By addressing coastal scientists who are not specialists in remote sensing, this contribution reports on the possibilities and limitations of digital applications in boulder mapping in Eastern Samar, Philippines, where recent supertyphoons Haiyan and Hagupit induced high waves, coastal flooding and boulder transport. It is demonstrated how satellite imagery of sub-metre resolution (from Pléiades and WorldView-3 imagery) enables efficient analysis of transport vectors and distances of larger boulders, reflecting variation in latitudes of both typhoon tracks and approaching angles of typhoon-generated waves. During the investigated events, boulders with a-axes of up to 8 m were clearly identified to have been shifted for up to 32 m, mostly along the seaward margin of the boulder field. It is, however, hard to keep track of smaller boulders, and the length of a-axes and b-axes including their orientation is often impossible to map with sufficient accuracy. Orthophotographs and digital surface models created through the application of an unmanned aerial vehicle and the ‘Structure from Motion’ technique provide ultra-high-resolution data, and have the potential to not only improve the results of satellite image analysis, but also those from field mapping and may significantly reduce overall time in the field. Orthophotographs permit unequivocal mapping of a-axes and b-axes including their orientation, while precise values for c-axes can be derived from the respective digital surface models. Volume of boulders is best inferred from boulder-specific Structure from Motion-based three-dimensional models. Battery power, flight speed and altitude determine the limits of the area covered, while patches shielded by the boulders are difficult to resolve. For some tasks, field mapping remains mandatory and cannot be replaced by currently available remote sensing tools: for example, sampling for rock type, density and age dating, recording of lithological separation of boulders from the underlying geological unit and of geomorphic features on a millimetre to decimetre-scale, or documentation of fine-grained sediment transport in between the boulders in supratidal settings. In terms of future events, the digital products presented here will provide a valuable reference to track boulder transport on a centimetre to decimetre-scale and to better understand the hydrodynamics of extreme-wave events on a fringing reef coastline.  相似文献   

Pure elastic stiffness of sand represented by response envelopes derived from cyclic triaxial tests with local strain measurements     

Knittel  Lukas  Wichtmann  Torsten  Niemunis  Andrzej  Huber  Gerhard  Espino  Edgar  Triantafyllidis  Theodoros 《Acta Geotechnica》2020,15(8):2075-2088

Acta Geotechnica - The elastic stiffness of a fine sand at small to moderate strains ( $$\varepsilon \le 2 \times 10^{-4}$$ ) has been studied based on cyclic triaxial tests on cube-shaped samples...  相似文献   

In situ LA-ICPMS Isotopic and Geochronological Studies on Carbonatites and Phoscorites from the Guli Massif,Maymecha-Kotuy,Polar Siberia     

Mahdi Ghobadi  Axel Gerdes  Lia Kogarko  Heidi Hoefer  Gerhard Brey 《Geochemistry International》2018,56(8):766-783

In this study we present a fresh isotopic data, as well as U–Pb ages from different REE-minerals in carbonatites and phoscorites of Guli massif using in situ LA-ICPMS technique. The analyses were conducted on apatites and perovskites from calcio-carbonatite and phoscorite units, as well as on pyrochlores and baddeleyites from the carbonatites. The ⁸⁷Sr/⁸⁶Sr ratios obtained from apatites and perovskites from the phoscorites are 0.70308–0.70314 and 0.70306–0.70313, respectively; and 0.70310–0.70325 and 0.70314–0.70327, for the pyrochlores and apatites from the carbonatites, respectively.Furthermore, the in situ laser ablation analyses of apatites and perovskites from the phoscorite yield εNd from 3.6 (±1) to 5.1 (±0.5) and from 3.8 (±0.5) to 4.9 (±0.5), respectively; εNd of apatites, perovskites and pyrochlores from carbonatite ranges from 3.2 (±0.7) to 4.9 (±0.9), 3.9 (±0.6) to 4.5 (±0.8) and 3.2 (±0.4) to 4.4 (±0.8), respectively. Laser ablation analyses of baddeleyites yielded an eHf(t)d of +8.5 (± 0.18); prior to this study Hf isotopic characteristic of Guli massif was not known. Our new in situ εNd, ⁸⁷Sr/⁸⁶Sr and eHf data on minerals in the Guli carbonatites imply a depleted source with a long time integrated high Lu/Hf, Sm/Nd, Sr/Rb ratios.In situ U–Pb age determination was performed on perovskites from the carbonatites and phoscorites and also on pyrochlores and baddeleyites from carbonatites. The co-existing pyrochlores, perovskites and baddeleyites in carbonatites yielded ages of 252.3 ± 1.9, 252.5 ± 1.5 and 250.8 ± 1.4 Ma, respectively. The perovskites from the phoscorites yielded an age of 253.8 ± 1.9 Ma. The obtained age for Guli carbonatites and phoscorites lies within the range of ages previously reported for the Siberian Flood Basalts and suggest essentially synchronous emplacement with the Permian-Triassic boundary.  相似文献   

Zoning and exsolution in alkali feldspars from Laacher See volcano (Western Germany): constraints on temperature history prior to eruption     

Smruti?Sourav?RoutEmail authorView author&#;s OrcID profile  Gerhard?W?rner 《Contributions to Mineralogy and Petrology》2018,173(11):95

Compositional zoning and exsolution patterns of alkali feldspars in carbonatite-bearing cognate syenites from the 6.3 km³ (D.R.E) phonolitic Laacher See Tephra (LST) deposit in western Germany (12.9 ka) are reported. These rocks represent the cooler outer portion and crystal-rich products of a cooling magma reservoir at upper crustal levels. Major and trace-element difference between cores and rims in sanidine crystals represent two generations of crystal growth separated by unmixing of a carbonate melt. Trace-element differences measured by LA–ICP–MS are in accordance with silicate–carbonate unmixing. Across the core–rim boundary, we extracted gray-scale profiles from multiple accumulations of back-scattered electron images. Gray scales directly represent K/Na ratios owing to low concentrations of Ba and Sr (<?30 ppm). Diffusion gradients are modeled to solve for temperature using known pre-eruptive U–Th zircon ages (0–20 ky) of each sample (Schmitt et al., J Petrol 51:1053–1085, 2010). Estimated temperatures range from 630 °C to 670 °C. For the exsolution boundaries, a diffusive homogenization model is constrained by the solvus temperature of ~ 712^_725 °C and gives short time scales of only 15–50 days. Based on our results, we present a model for the temperature–time history of these rocks. The model also constrains the thermal variation across the cooling crystal-rich carapace of the magma reservoir over 20 ka and suggests a thermal reactivation of cumulates, the cooling carapace, and probably the entire system only a few years prior to the explosive eruption of the remaining molten core of the phonolitic magma reservoir.  相似文献   

Geochronology,stratigraphy and geochemistry of Cambro-Ordovician,Silurian and Devonian volcanic rocks of the Saxothuringian Zone in NE Bavaria (Germany)—new constraints for Gondwana break up and ocean–island magmatism     

Höhn  Stefan  Koglin  Nikola  Klopf  Lisa  Schüssler  Ulrich  Tragelehn  Harald  Frimmel  Hartwig E.  Zeh  Armin  Brätz  Helene 《International Journal of Earth Sciences》2018,107(1):359-377

International Journal of Earth Sciences - Stratigraphically well-defined volcanic rocks in Palaeozoic volcano-sedimentary units of the Frankenwald area (Saxothuringian Zone, Variscan Orogen) were...  相似文献   

Estimation of unrecorded groundwater abstractions in Jordan through regional groundwater modelling     

Gropius  M.  Dahabiyeh  M.  Al Hyari  M.  Brückner  F.  Lindenmaier  F.  Vassolo  S. 《Hydrogeology Journal》2022,30(6):1769-1787

Jordan suffers from water scarcity and groundwater covers the majority of Jordan’s water supply. Therefore, there is an urgent need to manage this resource conscientiously. A regional numerical groundwater flow model, developed as part of a decision support system for the country of Jordan, allows for quantification of the overexploitation of groundwater resources and enables determination of the extent of unrecorded agricultural groundwater abstraction. Groundwater in Jordan is abstracted from three main aquifers partly separated by aquitards. With updated geological, structural, and hydrogeological data available in the country, a regional numerical groundwater flow model for the whole of Jordan and the southernmost part of Syria was developed using MODFLOW. It was first calibrated for a steady-state condition using data from the 1960s, when groundwater abstraction was negligible. After transient calibration using groundwater level measurements from all aquifers, model results reproduce the large groundwater-level declines experienced in the last decades, which have led to the drying out of numerous springs. They show a reversal of groundwater flow directions in some regions, due to over-abstraction, and demonstrate that documented abstractions are not sufficient to cause the observed groundwater-level decline. Only after considering irrigation water demand derived from remote sensing data, the model is able to simulate these declines. Illegal abstractions can be quantified and predictive scenarios show the potential impact of different management strategies on future groundwater resources.

  相似文献   

Causes and consequences of long-term groundwater overabstraction in Jordan     

Brückner  Florian  Bahls  Rebecca  Alqadi  Mohammad  Lindenmaier  Falk  Hamdan  Ibraheem  Alhiyari  Mohammad  Atieh  Ala’a 《Hydrogeology Journal》2021,29(8):2789-2802

Hydrogeology Journal - In 2017, a comprehensive review of groundwater resources in Jordan was carried out for the first time since 1995. The change in groundwater levels between 1995 and 2017 was...  相似文献   

Time variable Earth’s gravity field from SLR satellites   总被引：4，自引：4，他引：0  

Krzysztof Sośnica  Adrian Jäggi  Ulrich Meyer  Daniela Thaller  Gerhard Beutler  Daniel Arnold  Rolf Dach 《Journal of Geodesy》2015,89(10):945-960

  相似文献   

A comment on the article “A collinearity diagnosis of the GNSS geocenter determination” by P. Rebischung,Z. Altamimi,and T. Springer     

Michael Meindl  Gerhard Beutler  Daniela Thaller  Rolf Dach  Stefan Schaer  Adrian Jäggi 《Journal of Geodesy》2015,89(2):189-194

  相似文献   

Holocene hydrological variability of Lake Ladoga,northwest Russia,as inferred from diatom oxygen isotopes     

Svetlana S. Kostrova  Hanno Meyer  Hannah L. Bailey  Anna V. Ludikova  Raphael Gromig  Gerhard Kuhn  Yuri A. Shibaev  Anna V. Kozachek  Alexey A. Ekaykin  Bernhard Chapligin 《Boreas: An International Journal of Quaternary Research》2019,48(2):361-376

This article presents a new comprehensive assessment of the Holocene hydrological variability of Lake Ladoga, northwest Russia. The reconstruction is based on oxygen isotopes of lacustrine diatom silica (δ¹⁸O_diatom) preserved in sediment core Co 1309, and is complemented by a diatom assemblage analysis and a survey of modern isotope hydrology. The data indicate that Lake Ladoga has existed as a freshwater reservoir since at least 10.8 cal. ka BP. The δ¹⁸O_diatom values range from +29.8 to +35.0‰, and relatively higher δ¹⁸O_diatom values around +34.7‰ between c. 7.1 and 5.7 cal. ka BP are considered to reflect the Holocene Thermal Maximum. A continuous depletion in δ¹⁸O_diatom since c. 6.1 cal. ka BP accelerates after c. 4 cal. ka BP, indicating Middle to Late Holocene cooling that culminates during the interval 0.8–0.2 cal. ka BP, corresponding to the Little Ice Age. Lake‐level rises result in lower δ¹⁸O_diatom values, whereas lower lake levels cause higher δ¹⁸O_diatom values. The diatom isotope record gives an indication for a rather early opening of the Neva River outflow at c. 4.4–4.0 cal. ka BP. Generally, overall high δ¹⁸O_diatom values around +33.5‰ characterize a persistent evaporative lake system throughout the Holocene. As the Lake Ladoga δ¹⁸O_diatom record is roughly in line with the 60°N summer insolation, a linkage to broader‐scale climate change is likely.  相似文献