Do tides affect water quality in the upper phreatic zone of a small oceanic island, Sipadan Island, Malaysia?     

M. H. Abdullah  M. B. Mokhtar  S. H. J. Tahir  A. B. T. Awaluddin 《Environmental Geology》1997,29(1-2):112-117

 Sipadan Island is a small oceanic island with limited storage of fresh groundwater. A study was carried out to determine the effect of tidal change on the groundwater quality of such an island using temperature, dissolved oxygen content, conductivity, salinity, and pH values as indicators. Overall, the results indicated that the groundwater quality changes with tides, but the trends of fluctuation differs between the observed parameters. It was found that the percentages of changes during the period of study were 0.8% (temperature), 53% (dissolved oxygen), 61% (conductivity), 58% (salinity), and 1.7% (pH) at the centre of the island; and 0.9% (temperature), 33% (dissolved oxygen), 40% (conductivity), 42% (salinity), and 9% (pH) at a station 120 m from the coast, based on 2.9-m and 2.8-m tidal ranges at each station. Received: 5 July 1995 · Accepted: 6 November 1995  相似文献   

Liquid hydrocarbon generation potential from Tertiary Nyalau Formation coals in the onshore Sarawak, Eastern Malaysia     

Mohammed Hail Hakimi  Wan Hasiah Abdullah 《International Journal of Earth Sciences》2013,102(1):333-348

Tertiary coals exposed in the north-central part of onshore Sarawak are evaluated, and their depositional environments are interpreted. Total organic carbon contents (TOC) of the coals range from 58.1 to 80.9 wt. % and yield hydrogen index values ranging from 282 to 510 mg HC/g TOC with low oxygen index values, consistent with Type II and mixed Type II–III kerogens. The coal samples have vitrinite reflectance values in the range of 0.47–0.67 Ro %, indicating immature to early mature (initial oil window). T _max values range from 428 to 436 °C, which are good in agreement with vitrinite reflectance data. The Tertiary coals are humic and generally dominated by vitrinite, with significant amounts of liptinite and low amounts of inertinite macerals. Good liquid hydrocarbons generation potential can be expected from the coals with rich liptinitic content (>35 %). This is supported by their high hydrogen index of up to 300 mg HC/g TOC and Py-GC (S ₂) pyrograms with n-alkane/alkene doublets extending beyond C₃₀. The Tertiary coals are characterised by dominant odd carbon numbered n-alkanes (n-C₂₃ to n-C₃₃), high Pr/Ph ratio (6–8), high T _m /T _s ratio (8–16), and predominant regular sterane C₂₉. All biomarkers parameters clearly indicate that the organic matter was derived from terrestrial inputs and the deposited under oxic condition.  相似文献   

Provenance and deformation history of the Eastern Thomson Orogen and implications for the Paleozoic evolution of the Tasmanides (Eastern Australia)     

R. Abdullah  U. Shaanan  K. Lynn  G. Rosenbaum 《Australian Journal of Earth Sciences》2020,67(2):153-173

Abstract

Cambrian deformation associated with the Delamerian Orogeny is most evident in the Delamerian Orogen (southwestern Tasmanides) but has also been documented in the Thomson Orogen (northern Tasmanides). The tectonic evolution of the Thomson Orogen in the context of the Delamerian Orogeny is poorly understood. In particular, tectonostratigraphic relationships between the different parts of the Thomson Orogen (Anakie Inlier, Nebine Ridge, and southern Thomson Orogen) are still unclear. New detrital zircon data from the Nebine Ridge revealed an age spectrum that is consistent with published geochronological data from the Anakie Inlier. These results, in conjunction with petrographic observations and the interpretation of geophysical data, suggest that along the eastern part of the Thomson Orogen, the?～?NNE-trending Nebine Ridge represents the southward continuation of the?～?N–S-trending Anakie Inlier. New detrital zircon geochronological data are also presented for metasedimentary rocks from both sides of the Thomson–Lachlan boundary. The results constrain the maximum age of deposition (Ordovician–Devonian), and show that both sides of the Thomson–Lachlan boundary received detritus from a similar provenance. This might suggest that the Thomson–Lachlan boundary did not play a major role as a crustal-scale boundary prior to the Devonian. We speculate that transpressional deformation along this?～?E–W boundary, during the Early Devonian, was responsible for disrupting the original belt that connected the Delamerian Orogen (Koonenberry Belt) with the eastern Thomson Orogen (Nebine Ridge and Anakie Inlier).

1. Highlights

2. The Nebine Ridge is the southward continuation of the Anakie Inlier.

3. The Anakie Inlier and Nebine Ridge represent a northern segment of the Cambrian Delamerian–Thomson Belt.

4. ～E–W-trending crustal-scale structures at the southern Thomson Orogen were active during Devonian.

  相似文献   

Groundwater Assessment at Manukan Island,Sabah: Multidisplinary Approaches     

S. M. Praveena  C. Y. Lin  A. Z. Aris  M. H. Abdullah 《Natural Resources Research》2010,19(4):279-291

A rapid increase in the number of tourists has placed a heavy demand for freshwater on Manukan Island, a small island located offcoast of Kota Kinabalu, Sabah. Hydrochemical and numerical approaches have been applied in this study to evaluate the groundwater quality of unconfined aquifer lying in Manukan Island, Sabah, East Malaysia. This is vital to enhance better understanding about groundwater management. Hydrochemical analysis output indicated NaCl water type in sampling locations. Seawater intrusion is marked by its relatively high Na⁺, Mg²⁺, Cl⁻ and SO₄ ²⁻ concentrations. Hydrochemical analysis output clearly showed the influence of seawater in groundwater of Manukan Island. The numerical model output proved the influence of seawater in groundwater of Manukan Island by indicating the upconing process at the beneath of the pumping well. Current status of seawater intrusion in Manukan Island is about 14.6% of freshwater and seawater mixing ratio in low lying area of Manukan Island as simulated by SEAWAT-2000 model output. Numerical model SEAWAT-2000 output showed clearly that the upconing process is the possible route of seawater to influence the fresh groundwater aquifer chemistry in Manukan Island. The results have enhanced the current understanding of seawater intrusion in the study area. Future studies will focus on using numerical models to simulate and suggest suitable groundwater management plans in Manukan Island.  相似文献   

The recently compiled Turkish strong motion database: preliminary investigation for seismological parameters   总被引：5，自引：0，他引：5  

Sinan Akkar  Zehra Çağnan  Emrah Yenier  Özgür Erdoğan  M. Abdullah Sandıkkaya  Polat Gülkan 《Journal of Seismology》2010,14(3):457-479

Strong motion data recorded by the Turkish national strong motion network has been compiled and processed systematically for the first time, together with detailed geophysical and geotechnical site measurements for all of its stations. The catalog information of 18 seismological agencies and other sources were examined to obtain reliable source, geometry, and distance parameters for each event. The high quality digital and analog strong motion data was processed by a uniform methodology to remove the high- and low-frequency noise. Currently, the seismological and spectral information of 4,607 strong motion records are available for use by earth scientists and earthquake engineers. In this article, we present the fundamental features of this database and explain our methodology in their calculation. We present several comparisons of our database with other related studies to verify our approach during the computational stage of the seismological parameters. The results confirm the reliability of our calculations. The database has also enabled us to derive empirical magnitude conversion relationships to estimate moment magnitude in terms of different magnitude scales. The article ends with a discussion of the likely improvements in the European accelerometric data through contributions from this strong motion database applicable for seismically active shallow-crust regions. The findings of this article emphasize the necessity of global strong motion databases in Europe for better estimation of seismic hazard in regions of similar seismotectonic environment.  相似文献   

Modified dynamic programming approach for offline segmentation of long hydrometeorological time series   总被引：3，自引：1，他引：2  

Abdullah Gedikli  Hafzullah Aksoy  N. Erdem Unal  Athanasios Kehagias 《Stochastic Environmental Research and Risk Assessment (SERRA)》2010,24(5):547-557

For the offline segmentation of long hydrometeological time series, a new algorithm which combines the dynamic programming with the recently introduced remaining cost concept of branch-and-bound approach is developed. The algorithm is called modified dynamic programming (mDP) and segments the time series based on the first-order statistical moment. Experiments are performed to test the algorithm on both real world and artificial time series comprising of hundreds or even thousands of terms. The experiments show that the mDP algorithm produces accurate segmentations in much shorter time than previously proposed segmentation algorithms.  相似文献   

Multiphase Modeling of Geologic Carbon Sequestration in Saline Aquifers   总被引：1，自引：0，他引：1       下载免费PDF全文

Karl W. Bandilla  Michael A. Celia  Jens T. Birkholzer  Abdullah Cihan  Evan C. Leister 《Ground water》2015,53(3):362-377

Geologic carbon sequestration (GCS) is being considered as a climate change mitigation option in many future energy scenarios. Mathematical modeling is routinely used to predict subsurface CO₂ and resident brine migration for the design of injection operations, to demonstrate the permanence of CO₂ storage, and to show that other subsurface resources will not be degraded. Many processes impact the migration of CO₂ and brine, including multiphase flow dynamics, geochemistry, and geomechanics, along with the spatial distribution of parameters such as porosity and permeability. In this article, we review a set of multiphase modeling approaches with different levels of conceptual complexity that have been used to model GCS. Model complexity ranges from coupled multiprocess models to simplified vertical equilibrium (VE) models and macroscopic invasion percolation models. The goal of this article is to give a framework of conceptual model complexity, and to show the types of modeling approaches that have been used to address specific GCS questions. Application of the modeling approaches is shown using five ongoing or proposed CO₂ injection sites. For the selected sites, the majority of GCS models follow a simplified multiphase approach, especially for questions related to injection and local‐scale heterogeneity. Coupled multiprocess models are only applied in one case where geomechanics have a strong impact on the flow. Owing to their computational efficiency, VE models tend to be applied at large scales. A macroscopic invasion percolation approach was used to predict the CO₂ migration at one site to examine details of CO₂ migration under the caprock.  相似文献   

Determination of Hydraulic Conductivity from Grain‐Size Distribution for Different Depositional Environments     

Jorge Rosas  Oliver Lopez  Thomas M. Missimer  Kapo M. Coulibaly  Abdullah H.A. Dehwah  Kathryn Sesler  Luis R. Lujan  David Mantilla 《Ground water》2014,52(3):399-413

Over 400 unlithified sediment samples were collected from four different depositional environments in global locations and the grain‐size distribution, porosity, and hydraulic conductivity were measured using standard methods. The measured hydraulic conductivity values were then compared to values calculated using 20 different empirical equations (e.g., Hazen, Carman‐Kozeny) commonly used to estimate hydraulic conductivity from grain‐size distribution. It was found that most of the hydraulic conductivity values estimated from the empirical equations correlated very poorly to the measured hydraulic conductivity values with errors ranging to over 500%. To improve the empirical estimation methodology, the samples were grouped by depositional environment and subdivided into subgroups based on lithology and mud percentage. The empirical methods were then analyzed to assess which methods best estimated the measured values. Modifications of the empirical equations, including changes to special coefficients and addition of offsets, were made to produce modified equations that considerably improve the hydraulic conductivity estimates from grain size data for beach, dune, offshore marine, and river sediments. Estimated hydraulic conductivity errors were reduced to 6 to 7.1 m/day for the beach subgroups, 3.4 to 7.1 m/day for dune subgroups, and 2.2 to 11 m/day for offshore sediments subgroups. Improvements were made for river environments, but still produced high errors between 13 and 23 m/day.  相似文献   

Selection of the best fit probability distribution in rainfall frequency analysis for Qatar     

Mamoon  Abdullah Al  Rahman  Ataur 《Natural Hazards》2017,86(1):281-296

Natural Hazards - Design rainfall is widely used in urban infrastructure planning and design such as culverts and urban drainage systems. In design rainfall estimation, one of the primary steps is...  相似文献   

Facies characterization of the Surma Group (Miocene) sediments from Jalalabad gas field,Sylhet trough,Bangladesh: Study from cores and wireline log     

Farida Khanam  M. Julleh Jalalur Rahman  M. Mustafa Alam  Rashed Abdullah 《Journal of the Geological Society of India》2017,89(2):155-164

The Sylhet trough located on the north-eastern margin of present Bengal basin, contains ~22 km of Tertiary sediments and well known as a hydrocarbon producing province. A detailed facies characterization of the subsurface Miocene Surma Group sediments (especial emphasis on reservoirs sandstones) from Jalalabad gas field within the Sylhet trough has been done using core log analysis and wireline log (gamma ray) interpretation. Texture and sedimentary structures of the cores suggests that the nine individual lithofacies types which can be grouped together into three facies associations, namely, fine-grained facies associations (FFA), medium-grained facies association (MFA) and coarse-grained facies associations (CFA). Major changes in gamma ray log motifs and various bounding discontinuities indicate six para-sequence sets (basin wide) and twenty eight para-sequences (local environmental changes) within the depth range from 2200-2800 m. Detailed facies analysis of the cores and wireline log reveals that the interbedding facies within the associations in the Surma Group commonly develop small-scale fining-upward (FU) cycles, coarsening-upward (CU) and random intercalations (RD). The sediments of the Surma Group of the Jalalabad field have been interpreted as deposits of the shallow marine to tide-dominated deltaic depositional setting. The cyclic nature of sedimentation pattern of the Surma Group probably records an almost continuous existence of this prograding deltaic regime and a tectonic setting characterized by a mixture of prolonged basin subsidence and regional transgression coupled with sporadic regressive phases.  相似文献