The role of the Polochic Fault as part of the North American and Caribbean Plate boundary: Insights from the infill of the Lake Izabal Basin     

Jonathan Obrist-Farner  Andreas Eckert  Marek Locmelis  James L. Crowley  Byron Mota-Vidaure  Emanuele Lodolo  Joshua Rosenfeld  Edward Duarte 《Basin Research》2020,32(6):1347-1364

The Lake Izabal Basin in Guatemala is a major pull-apart basin along the sinistral Polochic Fault, which is part of the North American and Caribbean plate boundary. The basin infill contains information about the tectonic and sedimentological processes that have imparted a significant control on its sedimentary section. The inception of the basin has been linked to the relative importance of the Polochic Fault in the tectonic history of the plate boundary; yet, its sedimentological record and its inception age have been poorly documented. This study integrates diverse datasets, including industry reports, well logs and reports, well cuttings, vintage seismic data, outcrop observations and geochronological data to constrain the initial infill and age of inception of the basin. The integrated data show that during the Oligocene–Miocene, a marine carbonate platform was established in the region which was later uplifted and eroded in the early Miocene. The fluvial–lacustrine deposits above this carbonate platform are part of the initial infill of the basin and are constrained with zircon weighted-mean ²⁰⁶Pb/²³⁸U ages of 12.060 ± 0.008 from a volcanic tuff ~30 m above the unconformity. Sandstone, mudstone and coal dominate the interval from 12 to 4 Ma, with an increase in conglomerate correlating to the uplift of the Mico Mountains and San Gil Hill at 4 Ma. Fault switch activity between the Polochic and Motagua faults has been hypothesized to explain total offset along the Polochic Fault and the geologic and geodetic slip rates along the two faults. The 12 Ma age determined for the initial infill of the basin confirms this hypothesis. Consequently, our study confirms that at ~12 Ma the Polochic Fault served as the main fault of the plate boundary with inferred slip rates ranging from 13 to 21 mm/yr with a strong possibility that the Polochic Fault was, at some point between 15 Ma and 7 Ma, the only active fault of the plate boundary. The results of this study show that tectonic records preserved in sediments of strike-slip basins improve the understanding of the relative significance of individual faults and the implications with respect to strain partitioning throughout its tectonic history.  相似文献   

The effects of kinetic sorting on sediment mobility on steep slopes          下载免费PDF全文

Vito Bacchi  Alain Recking  Nicolas Eckert  Philippe Frey  Guillaume Piton  Mohamed Naaim 《地球表面变化过程与地形》2014,39(8):1075-1086

In poorly mobile static armour, sorting is usually considered the result of hiding/exposure effects. We called this effect ‘static sorting’ in opposition to very efficient grain‐to‐grain mechanisms produced by a mobile mixture, called ‘kinetic sorting’. We hypothesized that kinetic sorting can be an important contributor to the morphodynamics of mountain streams and attempted to demonstrate this with new flume experiments. Two long runs were produced with natural poorly sorted sediments, and with transport stages of the coarse fraction (defined by the ratio between the shear stress and the critical shear stress for transport), smaller and higher than 1, respectively. Both runs produced an efficient transfer downstream of the injected material, but with a major difference: the first run (no kinetic sorting) produced permanent armour figuring clusters, akin to what has already been observed in similar experiments; the second run (with kinetic sorting) also produced bed armouring, but this armour was periodically totally destroyed, leading to substantial bed erosion. This phenomenon was explained by kinetic sorting, the effects of which are to produce an efficient downward migration of fine materials and bed surface armouring. The consequence is that fine materials are hidden to the flow during aggradation, allowing the slope to attain values much steeper than would have been expected at equilibrium for the mixture. However, whereas the surface armouring tends to stabilize the bed, construction of a layer of fine sediments at the subsurface also contributes to making it very unstable. These two contradictory effects explain the complex bed behaviours and the existence of very large bedload and slope fluctuations. Copyright © 2014 John Wiley & Sons, Ltd.  相似文献   

A spatio-temporal modelling framework for assessing the fluctuations of avalanche occurrence resulting from climate change: application to 60 years of data in the northern French Alps   总被引：1，自引：0，他引：1  

Nicolas Eckert  E. Parent  R. Kies  H. Baya 《Climatic change》2010,101(3-4):515-553

Based on a previous township-scale model, a spatio-temporal framework is proposed to study the fluctuations of avalanche occurrence possibly resulting from climate change. The regional annual component is isolated from the total variability using a two-factor nonlinear analysis of variance. Moreover, relying on a Conditional AutoRegressive sub-model for the spatial effects, the structured time trend is distinguished from the random noise with different time series sub-models including autocorrelative, periodic and change-point models. The hierarchical structure obtained takes into account the uncertainty related to the estimation of the annual component for the quantification of the time trend. Bayesian inference is performed using Monte Carlo simulations. This allows a comparison of the different time series models and the prediction of future activity in an explicit unsteady context. Application to the northern French Alps illustrates the information provided by the model’s different components, mainly the spatial and temporal terms as well as the spatio-temporal fluctuation of the relative risk. For instance, it shows no strong modifications in mean avalanche activity or in the number of winters of low or high activity over the last 60 years. This suggests that climate change has recently had little impact on the avalanching rhythm in this region. However, significant temporal patterns are highlighted: a complex combination of abrupt changes and pseudo-periodic cycles of approximately 15 years. For anticipating the future response of snow avalanches to climate change, correlating them with fluctuations of the constraining climatic factors is now necessary.  相似文献   

Transient three-dimensional modeling of riverbank filtration at Grind well field, Germany     

Vijay Shankar  Paul Eckert  Chandra Ojha  Christoph M. König 《Hydrogeology Journal》2009,17(2):321-326

Riverbank filtration (RBF) is a proven treatment step in a multi-barrier method of drinking-water supply at many sites. RBF wells induce a large amount of river water to infiltrate the river base and travel towards the wells, giving the opportunity for mixing of infiltrated surface water and groundwater. Assessment of raw water quality plays an important role in planning and operating a RBF well field. In this context, the determination of the catchment area (and land uses within the catchment) and the ratio of bank filtrate (BF) to raw groundwater (GW) are two prior steps. Transient model simulations were performed in order to study the hydraulic conditions at the RBF well field at Grind near Düsseldorf, Germany. The BF/GW ratio was determined to be 75/25. The flood events in winter, in particular, showed the BF/GW ratio to have high variation. Transient path lines in the well field were used for delineation of the catchment area.  相似文献   

Bayesian stochastic modelling for avalanche predetermination: from a general system framework to return period computations   总被引：1，自引：1，他引：0  

N. Eckert  E. Parent  M. Naaim  D. Richard 《Stochastic Environmental Research and Risk Assessment (SERRA)》2008,22(2):185-206

Stochastic models are recent but unavoidable tools for snow avalanche hazard mapping that can be described in a general system framework. For the computation of design return periods, magnitude and frequency have to be evaluated. The magnitude model consists of a set of physical equations for avalanche propagation associated with a statistical formalism adapted to the input–output data structure. The friction law includes at least one latent friction coefficient. The Bayesian paradigm and the associated simulation techniques assist considerably in performing the inference and taking estimation errors into account for prediction. Starting from the general case, simplifying hypotheses allows computing the predictive distribution of high return periods on a case-study. Only release and runout altitudes are considered so that the model can use the French database. An inversible propagation model makes it possible to work with the latent friction coefficient as if it is observed. Prior knowledge is borrowed from an avalanche path with similar topographical characteristics. Justifications for the working hypotheses and further developments are discussed. In particular, the whole approach is positioned with respect to both deterministic and stochastic hydrology.  相似文献   

Does one size fit all? An evaluation of length–weight relationships for New Zealand's freshwater fish species     

PG Jellyman  DJ Booker  SK Crow  ML Bonnett  DJ Jellyman 《新西兰海洋与淡水研究杂志》2013,47(4):450-468

Length–weight relationships are a fundamental tool for assessing populations and communities in fisheries science. Many researchers have collected length–weight data throughout New Zealand, yet parameters describing these relationships remain unpublished for many species of freshwater fish. We compiled 285,124 fish records from researchers and institutions across New Zealand to parameterise length–weight equations, using both power and quadratic models, for 53 freshwater species belonging to 13 families. The influence of location and sex on length–weight relationships was also assessed. Location, in particular, generated different length–weight relationships for 65% of the species examined. Length–weight equations were validated by comparing predicted weights against independently measured weights from 25 electrofished sites across New Zealand and the equations were highly accurate (R²>0.99). Recommendations are made about how to robustly apply this new resource which should assist freshwater fisheries researchers throughout New Zealand.  相似文献   

Factors affecting CO2 storage capacity and efficiency with water withdrawal in shallow saline aquifers     

Fang Yang  Baojun Bai  Shari Dunn-Norman  Runar Nygaard  Andreas Eckert 《Environmental Earth Sciences》2014,71(1):267-275

Carbon sequestration in shallow aquifers can be facilitated by water withdrawal. The factors that optimize the injection/withdrawal balance to minimize potential environmental impacts have been studied, including reservoir size, well pattern, injection rate, reservoir heterogeneity, anisotropy ratio, and permeability sequence. The effects of these factors on CO₂ storage capacity and efficiency were studied using a compositional simulator Computer Modeling Group-General Equation of State Model, which modeled features including residual gas trapping, CO₂ solubility, and mineralization reactions. Two terms, storage efficiency and CO₂ relative breakthrough time, were introduced to better describe the problem. The simulation results show that simultaneous water withdrawal during CO₂ injection greatly improves CO₂ storage capacity and efficiency. A certain degree of heterogeneity or anisotropy benefits CO₂ storage. A high injection rate favors storage capacity, but reduces the storage efficiency and CO₂ breakthrough time, which in turn limits the total amount of CO₂ injected.  相似文献   

豫西崤山早元古代中酸性侵入岩锆石/斜锆石U-Pb测年及其对熊耳火山岩系时限的约束   总被引：5，自引：4，他引：1  

崔敏利  张宝林  彭澎  张连昌  沈晓丽  郭志华  黄雪飞 《岩石学报》2010,26(5):1541-1549

熊耳火山岩系是华北克拉通早元古代晚期重要的岩浆记录,其火山作用时限的厘定对于揭示华北该时期的构造格局与演化历史有重要意义。对侵入到熊耳火山岩系顶层马家河组的石英闪长岩体中的斜锆石与锆石和花岗斑岩体中的锆石进行了高精度SIMSU-Pb定年。三个样品共58个测点,石英闪长岩体中的斜锆石207Pb/206Pb平均年龄为1789±4Ma,锆石207Pb/206Pb平均年龄1778±12Ma,花岗斑岩体中的锆石207Pb/206Pb平均年龄为1786±8Ma。这些年龄数据表明石英闪长岩体从生成到侵位是一个短暂而连续的过程,这一岩体与花岗斑岩岩体基本同期。同时,由于这两个岩体侵入到了熊耳火山岩系最顶部的马家河组,因此可以限定熊耳火山岩系的上限。结合前人的年代学数据,我们提出熊耳火山岩系的岩浆作用时限在1770～1800Ma之间,峰期为1780Ma。这一研究结果从年代学上支持熊耳火山岩系形成于快速拉张的裂谷环境。  相似文献   

Mapping and monitoring of urban landuse of Hisar Town,Haryana using remote sensing techniques     

AK Jain  RS Hooda  J Nath  ML Manchanda 《Journal of the Indian Society of Remote Sensing》1991,19(2):125-134

Aerial photographs for the year 1965 and 1975 and Landsat TM (FCC) 1986 data on 1:50,000 scale were used to map and monitor the pattern of growth and development of Hisar Town during the last 20 years. The different landuse categories identified are residential, commercial, industrial, recreational, vacant lands etc. The original shape of the town was nucleated one, but presently it is star-shaped, which is due to extension of the urban centre along the radiating roads. It has mainly elongated itself along the Delhi and Rajgarh roads. The presence of Government Livestock Farm (GLF), Equine Breeding Farm and HAU Farm towards North-west of the town has completely checked its growth on these sides. The total residential-cum-commercial area has nearly doubled during 1965–1975 and trebled by 1986. The change in net area under different types of urban land-use categories, described above has also been calculated. Degraded scrub lands and sandy wasteland on the fringes of the town have been identified where further development can be planned to avoid encroachment on good agricultural lands. Recommendations have been given for future urban planning of the town.  相似文献   

Estimating rockfall release frequency from blocks deposited in protection barriers,growth disturbances in trees,and trajectory simulations     

Farvacque  Manon  Corona  Christophe  Lopez-Saez  J&#;r&#;me  Mainieri  Robin  Stoffel  Markus  Bourrier  Franck  Eckert  Nicolas  Toe  David 《Landslides》2022,19(1):7-18

Landslides - The spatial and temporal quantification of rockfall frequency remains a major challenge in mountain environments, especially also in terms of rockfall management. Approaches that have...  相似文献