New age constraints on the western Betic intramontane basins: A late Tortonian closure of the Guadalhorce Corridor?          下载免费PDF全文

Marlies van der Schee  Bas C. J. van den Berg  Walter Capella  Dirk Simon  Francisco J. Sierro  Wout Krijgsman 《地学学报》2018,30(5):325-332

Several gateways connected the Mediterranean with the Atlantic during the late Miocene but the timing of closure and therefore their role prior to and during the Messinian Salinity Crisis (5.97–5.33 Ma) is still under debate. The timing of closure of the Guadalhorce Corridor is especially disputed as the common lack of marine microfossils hampers precise age determination. Here we present new biostratigraphic age constraints on the sediments of the Ronda, Antequera and Arcos regions, which formed the northern part of the Guadalhorce Corridor. The general presence of Globorotalia menardii 4 in the youngest deep‐marine sediments of all three regions indicates a late Tortonian age, older than 7.51 Ma. We conclude that the Guadalhorce Corridor closed during the late Tortonian, well before the onset of the Messinian Salinity Crisis and that the late Tortonian tectonic uplift of the eastern Betics extended into the western Betics.  相似文献   

Correction: Hydraulic tomography analysis of municipal-well operation data with geology-based groundwater models     

Tong  Xin  Illman  Walter A.  Berg  Steven J.  Luo  Ning 《Hydrogeology Journal》2021,29(5):1999-2000

Hydrogeology Journal - A Correction to this paper has been published: https://doi.org/10.1007/s10040-021-02351-x  相似文献   

An Automatic Well Planner for Complex Well Trajectories     

Kristoffersen  Brage S.  Bellout  Mathias C.  Silva  Thiago L.  Berg  Carl F. 《Mathematical Geosciences》2021,53(8):1881-1905

Mathematical Geosciences - A data-driven automatic well planner procedure is implemented to develop complex well trajectories by efficiently adapting to near-well reservoir properties and geometry....  相似文献   

River channel and bar patterns explained and predicted by an empirical and a physics‐based method     

Maarten G. Kleinhans  Jan H. van den Berg 《地球表面变化过程与地形》2011,36(6):721-738

Our objective is to understand general causes of different river channel patterns. In this paper we compare an empirical stream power‐based classification and a physics‐based bar pattern predictor. We present a careful selection of data from the literature that contains rivers with discharge and median bed particle size ranging over several orders of magnitude with various channel patterns and bar types, but no obvious eroding or aggrading tendency. Empirically a continuum is found for increasing specific stream power, here calculated with pattern‐independent variables: mean annual flood, valley gradient and channel width predicted with a hydraulic geometry relation. ‘Thresholds’, above which certain patterns emerge, were identified as a function of bed sediment size. Bar theory predicts nature and presence of bars and bar mode, here converted to active braiding index (B_i). The most important variables are actual width–depth ratio and nonlinearity of bed sediment transport. Results agree reasonably well with data. Empirical predictions are somewhat better than bar theory predictions, because the bank strength is indirectly included in the empirical prediction. In combination, empirical and theoretical prediction provide partial explanations for bar and channel patterns. Increasing potential‐specific stream power implies more energy to erode banks and indeed correlates to channels with high width–depth ratio. Bar theory predicts that such rivers develop more bars across the width (higher B_i). At the transition from meandering to braiding, weakly braided rivers and meandering rivers with chutes are found. Rivers with extremely low stream power and width–depth ratios hardly develop bars or dynamic meandering and may be straight or sinuous or, in case of disequilibrium sediment feed, anastomosing. Copyright © 2010 John Wiley & Sons, Ltd.  相似文献   

Seismic risk ranking for large dams in South Africa     

Mayshree Singh  Andrzej Kijko  Leo van den Berg 《Acta Geophysica》2011,59(1):72-90

Earthquake motion is one of the extreme loads acting on large dams. Dam owners and regulators must therefore ensure that dams are safely operated and present minimal risk to the public in case of extreme loads such as floods and earthquakes. Owners of many dams or officials in charge of dam safety programs may consider comparative assessment of the seismic risk associated with their dams and establish priorities for detailed evaluation. South Africa has in excess of 100 large state-owned dams and the characteristics of these dams have been used to perform a basic seismic hazard assessment and rank the vulnerability of these dams from the lowest to highest. One of the most decisive factors that contributes to the risk of a dam is the wall type; with gravity and earthfill dams being the most vulnerable to earthquake motion. Another aspect that needs further investigation is the downstream hazard potential which, if known to a better degree of accuracy, can provide more reasonable estimates of the risk factors.  相似文献   

Rethinking the PhD in the age of neoliberalization     

Lawrence D. Berg 《GeoJournal》2015,80(2):219-224

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Distinguishing the effect of diapir growth on magnetic fabrics of syn‐diapiric overburden rocks: Basque–Cantabrian basin,Northern Spain          下载免费PDF全文

Ruth Soto  Elisabet Beamud  Eduard Roca  Eloi Carola  Ylenia Almar 《地学学报》2017,29(3):191-201

An analysis of Anisotropy of Magnetic Susceptibility was done on Aptian–Albian sediments from the Basque–Cantabrian basin. Samples were collected from 39 sites in the halokinetic sequences of the Bakio, Bermeo, Guernica and Mungia diapirs; 28 sites were sampled close to diapirs, and 11 sites were far from the diapir edges. The magnetic foliation is parallel to bedding, suggesting it reflects depositional and compaction processes, whereas the orientation of magnetic lineation varies. Far from the diapir edges, the magnetic lineation is interpreted as being related to the regional Pyrenean compression. Close to diapir edges, the observed behaviour shows that diapirs, predominantly formed by rigid ophites, have acted as buttresses, with shadow areas at their northern faces being protected from the Pyrenean compression. The high sensitivity of AMS makes it a very useful tool to distinguish deformation in halokinetic sequences related to diapir growth from that related to subsequent compression.  相似文献   

Implications of measurement metrics on soil freezing curves: A simulation of freeze–thaw hysteresis     

Renato Pardo Lara  Aaron A. Berg  Jon Warland  Gary Parkin 《水文研究》2021,35(7):e14269

Soil freeze–thaw events have important implications for water resources, flood risk, land productivity, and climate change. A property of these phenomena is the relationship between unfrozen water content and sub-freezing temperature, known as the soil freezing characteristic curve (SFC). It is documented that this relationship exhibits hysteretic behaviour when frozen soil thaws, leading to the definition of the soil thawing characteristic curve (STC). Although explanations have been given for SFC/STC hysteresis, the effect that ‘scale’ – particularly ‘measurement scale’ – may have on these curves has received little attention. The most commonly used measurement scale metric is the ‘support’, which is the spatial (or temporal) unit within which the measured variable is integrated or soil volume sampled. We show (a) measurement support can influence the range and shape of the SFC and (b) hysteresis can be attributed, in part, to the support and location of the measurements comprising the SFC/STC. We simulated lab measured temperature, volumetric water content (VWC), and permittivity from soil samples undergoing freeze–thaw transitions using Hydrus-1D and a modified Dobson permittivity model. To assess the effect of measurement support and location on SFC/STC, we masked the simulated temperature and VWC/permittivity extent to match the instrument's support and location. By creating a detailed simulation of the intra- and inter-support variability associated with the penetration of a freezing front, we demonstrate how measurement support and location can influence the temperature range over which water freezing events are captured. We show it is possible to simulate hysteresis in homogenous media with purely geometric considerations, suggesting that SFC/STC hysteresis may be more of an apparent phenomenon than mechanistically real. Lastly, we develop an understanding of how the location and support of soil temperature and VWC/permittivity measurements influence the temperature range over which water freezing events are captured.  相似文献   

The Dynamics of Small Postglacial Lake Basins and the Nature of Their Archaeological Record: A Case Study of the Middle Palaeolithic Site Neumark‐Nord 2, Germany     

Eduard Pop  Corrie Bakels  Wim Kuijper  Herman Mücher  Madeleine van Dijk 《Geoarchaeology》2015,30(5):393-413

Due to favorable conditions of preservation, sedimentary basins provide rich records of human behavior and its environmental context. The conditions for the preservation of archaeological material however vary between basin types (large, river‐fed or small, closed basins), while conditions also differ within a particular basin environment. The goal of this paper is to understand how the dynamics of a small postglacial basin such as Neumark‐Nord 2, a context that dominates the Eemian archaeological record, affected the archaeology situated at its basin margin. The approach used here is to correlate the archaeological record with reconstructions of patterns of deposition and the water conditions within the basin, using lithology, micromorphology, pollen, and macroremains from a transect running from the basin center to the margin. The results show that (1) find levels were exposed to overland flow‐induced winnowing, which vertically concentrated finds but did not cause significant transport, (2) find levels correspond to phases of increased water presence in the basin, and (3) lateral shifts in hominin activity areas may reflect adjustments in the water level. The research shows the importance of large‐scale archaeological excavations and a multidisciplinary sampling strategy that covers both the basin center and the margins, when studying postglacial basin localities like Neumark‐Nord 2.  相似文献   

Quasi-linear theory of waves and ship wave resistance in restricted waters   总被引：2，自引：0，他引：2  

Eduard Amromin  Svetlana Kovinskaya  Igor Mizine 《Ocean Engineering》2004,31(10):53-1244

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