Stratal architecture and platform evolution of an early Frasnian syn‐tectonic carbonate platform,Canning Basin,Australia     

Nancy Chow  Annette D. George  Kate M. Trinajstic  Zhong‐Qiang Chen 《Sedimentology》2013,60(7):1583-1620

Facies architecture and platform evolution of an early Frasnian reef complex in the northern Canning Basin of north‐western Australia were strongly controlled by syn‐depositional faulting during a phase of basin extension. The margin‐attached Hull platform developed on a fault block of Precambrian basement with accommodation largely generated by movement along the Mount Elma Fault Zone. Recognition of major subaerial exposure and flooding surfaces in the Hull platform (from outcrop and drillcore) has enabled comparison of facies associations within a temporal framework and led to identification of three stages of platform evolution. Stage 1 records initial ramp development on the hangingwall dip slope with predominantly deep subtidal conditions that prevented any cyclic facies arrangements. This stage is characterised by basal siliciclastic deposits and a major deepening‐upward facies pattern that is capped by a sequence boundary towards the footwall (north‐west) and a major flooding surface towards the hangingwall. Stage 2 reflects the bulk of platform aggradation, significant platform growth towards the hangingwall and the development of reef margins and cyclic facies arrangements. Thickening of this stage towards the hangingwall indicates that accommodation was generated by rotation of the fault block and overlying platform. Stage 3 records a major flooding and backstep of the platform margin. The Hull platform illustrates important elements of margin‐attached carbonate platforms in a half‐graben setting, including: (i) prominent, but limited, coarse siliciclastic input that does not have a major detrimental effect on carbonate production near the rift margin in arid to semi‐arid settings; (ii) wedge‐shaped accommodation created by syn‐depositional rotation of fault blocks and tilting of the hangingwall dip slope, resulting in shallow‐water facies and subaerial exposure up‐dip of the rotational axis and deeper water facies down‐dip; and (iii) evolution of a ramp to rimmed shelf, coincident with a sequence boundary–flooding surface, that is accelerated by tilting of the hangingwall dip slope during fault‐block rotation.  相似文献   

A multidimensional fuzzy least-squares regression approach for estimating hydraulic gradients in unconfined aquifer formations and its application to the Gulf Coast aquifer in Goliad County,Texas     

Venkatesh Uddameri  E. Annette Hernandez  Felipe Estrada 《Environmental Earth Sciences》2014,71(6):2641-2651

Epistemic uncertainties arise during the estimation of hydraulic gradients in unconfined aquifers due to planar approximation of the water table as well as data gaps arising from factors such as instrument failures and site inaccessibility. A multidimensional fuzzy least-squares regression approach is proposed here to estimate hydraulic gradients in situations where epistemic uncertainty is present in the observed water table measurements. The hydraulic head at a well is treated as a normal (Gaussian) fuzzy variable characterized by a most likely value and a spread. This treatment results in hydraulic gradients being characterized as normal fuzzy numbers as well. The multidimensional fuzzy least-squares regression has an exact analytical form and as such can be implemented easily using matrix algebra methods. However, the method was noted to be sensitive to round-off and truncation errors when the epistemic uncertainties are small. A closeness index based on the cardinality of a fuzzy number is used to evaluate how well the regression model fits the fuzzy hydraulic head observations. A fuzzy Euclidian distance measure is used to compare two fuzzy numbers and to evaluate how fuzziness in the observed hydraulic heads affects the fuzziness in the estimated hydraulic gradients. The Euclidian distance measure is also used to ascertain the influence of each well on the fuzzy hydraulic gradient estimation. The fuzzy regression framework is illustrated by applying it to evaluate hydraulic gradients in the unconfined portion of the Gulf Coast aquifer in Goliad County, TX. The results from the case-study indicate that there is greater uncertainty associated with the estimation of the hydraulic gradients in the vertical (Z-axis) direction. The epistemic uncertainties in the hydraulic head data at the wells have a significant impact on the gradient estimates when they are of the same order of magnitude as the most likely values of the observed heads. The influence analysis indicated that 5 of the 13 wells in the network had a critical influence on at least one of the hydraulic gradients. Three wells along the northeastern section of the study area and bordering the Victoria County were noted to have the least influence on the regression estimates. The fuzzy regression framework along with the associated goodness-of-fit and influence measures provides a useful set of tools to characterize the uncertainties in the hydraulic heads and gradients arising from data gaps and planar water table approximation.  相似文献   

A multi-period optimization model for conjunctive surface water–ground water use via aquifer storage and recovery in Corpus Christi,Texas     

E. Annette Hernandez  Venkatesh Uddameri  Marcelo A. Arreola Jr. 《Environmental Earth Sciences》2014,71(6):2589-2604

The present study develops and evaluates a decision support system for the conjunctive management of the current surface and proposed aquifer storage and recovery (ASR) facility of the city of Corpus Christi, TX using a simulation–optimization approach. The objective of the model is to maximize water storage in the surface and subsurface storage units while meeting (1) the freshwater inflow requirements to the Corpus Christi estuary and (2) the water demands of the city and its service area. The model is parameterized using streamflow data from the U. S. Geological Survey gauging stations on the Nueces River and its tributaries as well as long-term climatic data and regional hydrogeologic information. Results indicate that a single-well field ASR facility is capable of storing approximately 925 ha-m (7,500 ac-ft) of water over a 5-year period in the Evangeline Aquifer with a total potential storage of about 2,715 ha-m (22,000 ac-ft) of water over the jurisdictional area of the Corpus Christi Aquifer Storage and Recovery Conservation District. Surplus surface water sources are seen to contribute approximately 49–96 % of the water stored in the ASR during the simulation period. The remaining storage came from either Choke Canyon Reservoir or Lake Corpus Christi, which also resulted in a slight reduction in evapotranspiration in both reservoirs. The analysis indicates that the proposed ASR system is not limited on the supply side but multiple well fields may be required to increase the storage capacity within the aquifer.  相似文献   

Combined optimization of a wind farm and a well field for wind-enabled groundwater production     

E. Annette Hernandez  Venkatesh Uddameri  Sreeram Singaraju 《Environmental Earth Sciences》2014,71(6):2687-2699

Energy requirements constitute a significant cost in groundwater production and can also add to a large carbon footprint when fossil fuels are used for power. Wind-enabled water production is advantageous as it minimizes air pollution impacts associated with groundwater production and relies on a renewable resource. Also, as groundwater extraction represents a deferrable load (i.e., it can be carried out when energy demands within an area are low), it provides a convenient way to overcome the intermittency issue associated with wind power production. Multiple turbine wind farms are needed to generate large quantities of power needed for large-scale groundwater production. Turbines must be optimally located in these farms to ensure proper propagation of kinetic energy throughout the system. By the same token, well placement must reconcile the competing objectives of minimizing interferences between production wells while ensuring the drawdowns at the property boundary are within acceptable limits. A combined simulation–optimization based model is developed in this study to optimize the combined wind energy and water production systems. The wind farm layout optimization model is solved using a re-sampling strategy, while the well field configuration is obtained using the simulated annealing technique. The utility of the developed model is to study wind-enabled water production in San Patricio County, TX. Sensitivity analysis indicated that identifying optimal placement of turbines is vital to extract maximum wind power. The variability of the wind speeds has a critical impact on the amount of water that can be produced. Innovative technologies such as variable flow pumping devices and aquifer storage recovery must be used to smooth out wind variability. While total groundwater extraction is less sensitive to uncertainty in hydrogeological parameters, improper estimation of aquifer transmissivity and storage characteristics can affect the feasibility of wind-driven groundwater production.  相似文献   

Culturing of the first 37:4 predominant lacustrine haptophyte: Geochemical,biochemical, and genetic implications     

Jaime L. Toney  Susanna Theroux  Robert A. Andersen  Annette Coleman  Linda Amaral-Zettler  Yongsong Huang 《Geochimica et cosmochimica acta》2012

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OH masers associated with bipolar outflow in ON1     

S. Nammahachak  K. Asanok  B. Hutawarakorn Kramer  R. J. Cohen  O. Muanwong  N. Gasiprong 《Monthly notices of the Royal Astronomical Society》2006,371(2):619-625

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New pulsar rotation measures and the Galactic magnetic field     

A. Noutsos  S. Johnston  M. Kramer  A. Karastergiou 《Monthly notices of the Royal Astronomical Society》2008,386(4):1881-1896

We measured a sample of 150 pulsar rotation measures (RMs) using the 20-cm receiver of the Parkes 64-m radio telescope. 46 of the pulsars in our sample have not had their RM values previously published, whereas 104 pulsar RMs have been revised. We used a novel quadratic fitting algorithm to obtain an accurate RM from the calibrated polarization profiles recorded across 256 MHz of receiver bandwidth. The new data are used in conjunction with previously known dispersion measures and the NE2001 electron-density model to study models of the direction and magnitude of the Galactic magnetic field.  相似文献   

Multivariate Prediction of Total Water Storage Changes Over West Africa from Multi-Satellite Data   总被引：1，自引：1，他引：0  

Ehsan Forootan  Jürgen Kusche  Ina Loth  Wolf-Dieter Schuh  Annette Eicker  Joseph Awange  Laurent Longuevergne  Bernd Diekkrüger  Michael Schmidt  C. K. Shum 《Surveys in Geophysics》2014,35(4):913-940

West African countries have been exposed to changes in rainfall patterns over the last decades, including a significant negative trend. This causes adverse effects on water resources of the region, for instance, reduced freshwater availability. Assessing and predicting large-scale total water storage (TWS) variations are necessary for West Africa, due to its environmental, social, and economical impacts. Hydrological models, however, may perform poorly over West Africa due to data scarcity. This study describes a new statistical, data-driven approach for predicting West African TWS changes from (past) gravity data obtained from the gravity recovery and climate experiment (GRACE), and (concurrent) rainfall data from the tropical rainfall measuring mission (TRMM) and sea surface temperature (SST) data over the Atlantic, Pacific, and Indian Oceans. The proposed method, therefore, capitalizes on the availability of remotely sensed observations for predicting monthly TWS, a quantity which is hard to observe in the field but important for measuring regional energy balance, as well as for agricultural, and water resource management. Major teleconnections within these data sets were identified using independent component analysis and linked via low-degree autoregressive models to build a predictive framework. After a learning phase of 72 months, our approach predicted TWS from rainfall and SST data alone that fitted to the observed GRACE-TWS better than that from a global hydrological model. Our results indicated a fit of 79 % and 67 % for the first-year prediction of the two dominant annual and inter-annual modes of TWS variations. This fit reduces to 62 % and 57 % for the second year of projection. The proposed approach, therefore, represents strong potential to predict the TWS over West Africa up to 2 years. It also has the potential to bridge the present GRACE data gaps of 1 month about each 162 days as well as a—hopefully—limited gap between GRACE and the GRACE follow-on mission over West Africa. The method presented could also be used to generate a near-real-time GRACE forecast over the regions that exhibit strong teleconnections.  相似文献   

Characterization of contact properties in biocemented sand using 3D X-ray micro-tomography     

Dadda  Abdelali  Geindreau  Christian  Emeriault  Fabrice  Rolland du Roscoat  Sabine  Esnault Filet  Annette  Garandet  Aurélie 《Acta Geotechnica》2019,14(3):597-613

The mechanical efficiency of the biocementation process is directly related to the microstructural properties of the biocemented sand, such as the volume fraction of calcite, its distribution within the pore space (localized at the contact between grains, over the grain surfaces) and the contact properties: coordination number, contact surface area, contacts orientation and types of contact. In the present work, all these micromechanical properties are computed, for the first time, from 3D images obtained by X-ray tomography of intact biocemented sand samples. The evolution of all these properties with respect to the volume fraction of calcite is analyzed and compared between each other (from untreated sand to highly cemented sand). Whatever the volume fraction of calcite, it is shown that the precipitation of the calcite is localized at the contacts between grains. These results are confirmed by comparing our numerical results with analytical estimates assuming that the granular medium is made of periodic simple cubic arrangements of grains and by considering two extreme cases of precipitation: (1) The calcite is localized at the contact, and (2) the grains are covered by a uniform layer of calcite. In overall, the obtained results show that a small percentage of calcite is sufficient to get a large amount of cohesive contacts.

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Characterization of microstructural and physical properties changes in biocemented sand using 3D X-ray microtomography     

Abdelali Dadda  Christian Geindreau  Fabrice Emeriault  Sabine Rolland du Roscoat  Aurélie Garandet  Leslie Sapin  Annette Esnault Filet 《Acta Geotechnica》2017,12(5):955-970

An experimental study has been performed to investigate the effect of the biocalcification process on the microstructural and the physical properties of biocemented Fontainebleau sand samples. The microstructural properties (porosity, volume fraction of calcite, total specific surface area, specific surface area of calcite, etc.) and the physical properties (permeability, effective diffusion) of the biocemented samples were computed for the first time from 3D images with a high-resolution images obtained by X-ray synchrotron microtomography. The evolution of all these properties with respect to the volume fraction of calcite is analysed and compared with success to experimental data, when it is possible. In general, our results point out that all the properties are strongly affected by the biocalcification process. Finally, all these numerical results from 3D images and experimental data were compared to numerical values or analytical estimates computed on idealized microstructures constituted of periodic overlapping and random non-overlapping arrangements of coated spheres. These comparisons show that these simple microstructures are sufficient to capture and to predict the main evolution of both microstructural and physical properties of biocemented sands for the whole range of volume fraction of calcite investigated.  相似文献