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Structural Interpretation of the Mamfe Sedimentary Basin of Southwestern Cameroon along the Manyu River Using Audiomagnetotellurics Survey  [PDF]
Jean Jacques Nguimbous-Kouoh,Eric M. Takam Takougang,Robert Nouayou,Charles Tabod Tabod,Eliezer Manguelle-Dicoum
ISRN Geophysics , 2012, DOI: 10.5402/2012/413042
Abstract: Five audiofrequency magnetotelluric AMT soundings were collected northwest-southeast along the Manyu river in the Mamfe sedimentary basin of southwestern Cameroon. The soundings were performed with frequencies in the range 3 to 2500?Hz and covered a distance of approximately 28?km. Sounding curves and geoelectric and geological sections were processed, and the results were compared with rocks' resistivity to characterize the lithostratigraphy of the eastern part of the basin. The results show above 1000?m depth, sedimentary layers with resistivities in the range of 1 to 100?Ohm-m, which decrease with depth. We identified three types of sedimentary rocks: laterite-clay mixture, shale, and sandstones. Various faults were also identified, illustrating the structural complexity of the Mamfe basin, along the Manyu River. 1. Introduction The geological studies of the Mamfe basin (southwestern Cameroon) were carried out for the first time by Le Fur [1], Dumort [2], and Paterson et al. [3]. These initial studies provided the framework for the first geological map of the area. The geophysical studies in the area integrate gravity works by Collignon [4], Fairhead and Okereke [5], Fairhead and Okereke [6], Fairhead et al. [7], Ndougsa-Mbarga [8], and Ndougsa-Mbarga et al. [9]. The geophysical studies also include audio-magnetotelluric (AMT) works by Manguelle-Dicoum et al. [10], Nguimbous-Kouoh [11], Nouayou [12], and Tabod et al., [13] to map subsurface resistivities. The aim of this paper is to use AMT field data to characterize the shallow structure of the Mamfe sedimentary basin along the Manyu River. To achieve this, various interpretation techniques were employed. The sounding curves were interpreted to derive the stratigraphy under each AMT station. A pseudosection and geoelectric and geological resistivity sections were then derived along the AMT profile, to deduce the continuity of the subsurface layers and the distribution of associated electrical resistivities. The combination of geoelectrical sections and pseudosections enables a more thorough interpretation [11, 14–18]. The AMT profile has five stations: Ndwap (M1), Abonando (M2), Esagem1 (M3), Esagem2 (M4), and Baku (M5). 2. Geology of the Study Area The Mamfe sedimentary basin is a rifting basin formed in response to the Gondwana break-up and subsequent separation of the South American and African plates. It lies on an NW-SE trending trough with a length of 130?km and a width of 60?km and constitutes a small prolongation of the Benue trough where important oil fields have been discovered (Figure
Structural Interpretation of the Mamfe Sedimentary Basin of Southwestern Cameroon along the Manyu River Using Audiomagnetotellurics Survey  [cached]
Jean Jacques Nguimbous-Kouoh,Eric M. Takam Takougang,Robert Nouayou,Charles Tabod Tabod
ISRN Geophysics , 2012, DOI: 10.5402/2012/413042
Abstract:
Gravity anomalies, sub-surface structure and oil and gas migration in the Mamfe, Cameroon-Nigeria, sedimentary basin
Ndougsa-Mbarga, Théophile;Manguelle-Dicoum, Eliezer;Campos-Enriquez, José-Oscar;Yene Atangana, Quentin;
Geofísica internacional , 2007,
Abstract: preliminary gravity results for the mamfe basin in the border region of northwestern cameroon with southeastern nigeria are reported. no geophysical studies were available for this important area, which is genetically related to oil and gas deposits in the benue trough. regional and residual gravity components were obtained by least-square fitting of a third-degree polynomial surface to the bouguer anomaly. the residual anomalies feature two ne-sw gravity lows attributed to sedimentary infill about the localities of ekok and agbokem, and about mukonyong, mamfe and bachuo akagbe. the gravity highs to the north and south are associated with outcrops of the basement complex. this structure corresponds to two major basins separated by a structural high. the deeper western sub-basin comprises two sub-basins separated by a minor structural high possibly related to the crystalline basement. these sub-basins tend to be shallower in the eastern direction possibly indicating the direction of migration of hydrocarbons. more detailed gravity and seismic studies may lead to discoveries of structural or stratigraphic traps. we conclude that the area is a promising prospect in terms of oil and gas prospecting.
Gravity anomalies, sub-surface structure and oil and gas migration in the Mamfe, Cameroon-Nigeria, sedimentary basin  [PDF]
T. Ndougsa-Mbarga,E. Manguelle-Dicoum,J. O. Campos-Enriquez,Q. Yene Atangana
Geofísica internacional , 2007,
Abstract: Preliminary gravity results for the Mamfe Basin in the border region of northwestern Cameroon with southeastern Nigeria are reported. No geophysical studies were available for this important area, which is genetically related to oil and gas deposits in the Benue Trough. Regional and residual gravity components were obtained by least-square fitting of a third-degree polynomial surface to the Bouguer anomaly. The residual anomalies feature two NE-SW gravity lows attributed to sedimentary infill about the localities of Ekok and Agbokem, and about Mukonyong, Mamfe and Bachuo Akagbe. The gravity highs to the north and south are associated with outcrops of the basement complex. This structure corresponds to two major basins separated by a structural high. The deeper western sub-basin comprises two sub-basins separated by a minor structural high possibly related to the crystalline basement. These sub-basins tend to be shallower in the eastern direction possibly indicating the direction of migration of hydrocarbons. More detailed gravity and seismic studies may lead to discoveries of structural or stratigraphic traps. We conclude that the area is a promising prospect in terms of oil and gas prospecting.
Aptian-Late Cenomanian Fluvio-Lacustrine Lithofacies and Palynomorphs from Mamfe Basin, Southwest Cameroon, West Africa  [PDF]
Olivier A. Njoh, Miriam B. Nforsi, Junie N. Datcheu
International Journal of Geosciences (IJG) , 2015, DOI: 10.4236/ijg.2015.67064
Abstract: The sedimentary sequences in the Mamfe Basin are generally thought of as continental (fluvio-lacustrine) in origin. But the wide spread occurrence of salt springs and salt accumulations and in places gypsum, often puts to question the exclusive continentality throughout this basin’s history. The sequences studied portray a wide range of complex lithologies and lithofacies relationships and include basal and intra-formational conglomerates, sandstones, shales, carbonaceous, carbonate and halite facies respectively. All these are well exposed at several outcrop sections distributed all over the basin with some measuring up to and above 30 m in height.Sedimentary structures include: parallel aligned imbricated prismatic pebbles, plannar to trough-cross stratifications, fining upward grain size distribution and thin frequently alternating sandstone-shale beds. Palynological data have been obtained for the first time from the shally and carbonate intervals and integrated with five lithofacies associations, permitting the determination of the ages and paleo environmental reconstruction. The palynomorphs are characterized by pteridophytic spores dominated byCicatricosisporitessp.,Cyathiditessp. andDeltoidsporasp., pollen grains include gymnosperms dominated byClassopollis annulatus
Geogenic versus Anthropogenic Metals and Metalloids  [PDF]
Jeffrey Hess, Mark Sorensen
Journal of Environmental Protection (JEP) , 2018, DOI: 10.4236/jep.2018.95029
Abstract: Developing a successful strategy for investigating and remediating sites potentially impacted by metals (such as chromium [Cr], copper [Cu], lead [Pb], nickel [Ni], and zinc [Zn]) and metalloids (such as arsenic [As] and antimony [Sb]) can be challenging. These elements occur naturally and geologic materials can be enriched in these elements by natural processes. Conventional environmental investigative methods do not readily support evaluating whether metals and metalloids are geogenic (naturally occurring) or anthropogenic (from human action), or allow differentiating multiple anthropogenic sources. Geochemical methods can potentially determine whether metals and metalloids are geogenic or anthropogenic, and differentiate between possible anthropogenic sources. Conventional geo-chemical methods include whole-rock analysis using x-ray fluorescence (XRF) to yield elemental concentrations; optical petrography and powder x-ray diffraction (XRD) to determine mineral phases present; and electron microprobe (EMP) to confirm both mineral phases present and the distribution of elements within mineral phases and the rock matrix. These methods, with the exception of the EMP, can be performed in the field using portable equipment, allowing for relatively rapid assessment of sites. A case study is presented in which these techniques were successfully utilized to demonstrate, using multiple lines of evidence, that metals and metalloids present in subsurface fractured rock were geogenic and unrelated to recent industrial operations.
Impact of the South Atlantic Opening on the Origin and the Tectonic of the Mamfe, Douala and Rio Del Rey Sedimentary Basins, Geodynamics Implication  [PDF]
Alain Rodrigue Nzeuga, Fran?oise Enyegueà Nyam, Robert Nouayou, James Derek Fairhead
Open Journal of Earthquake Research (OJER) , 2019, DOI: 10.4236/ojer.2019.84017
Abstract: The coastal and intracontinental sedimentary basins of Cameroon owe their origins to the opening of the South Atlantic. Among these sedimentary basins, we can mention those of Mamfe, Douala and Rio Del Rey, which are the subject of our current study. These were formed following geodynamic processes between the periods from the lower Cretaceous to the Neogene. These processes have significantly affected the basement of these basins leaving as consequences of multiple faults which would in their turn favor a rise of the magma towards the surface which then cooled to give birth to the volcanic rocks which exist there today. A study of the impact of the opening of the South Atlantic on the tectonics of these basins will be made from a geodynamic approach, relying in the first time on a qualitative and quantitative analysis of the anomaly map of the total magnetic intensity field reduced to the pole of each basin, then in a second time on the interpretation of the 2D geological models realized on a profile chosen on the anomaly map of the total magnetic intensity field reduced to the pole of each basin. At the end of this study, we will show that the opening of the South Atlantic has similarly impacted the structure of the three basins and the results of the spectral analysis show that the oceanic crust is thinner than the continental crust.
The Concentration of Iron in Real-World Geogenic PM10 Is Associated with Increased Inflammation and Deficits in Lung Function in Mice  [PDF]
Graeme R. Zosky, Thomas Iosifidis, Kara Perks, Will G. F. Ditcham, Sunalene G. Devadason, W. Shan Siah, Brian Devine, Fiona Maley, Angus Cook
PLOS ONE , 2014, DOI: 10.1371/journal.pone.0090609
Abstract: Background There are many communities around the world that are exposed to high levels of particulate matter <10 μm (PM10) of geogenic (earth derived) origin. Mineral dusts in the occupational setting are associated with poor lung health, however very little is known about the impact of heterogeneous community derived particles. We have preliminary evidence to suggest that the concentration of iron (Fe) may be associated with the lung inflammatory response to geogenic PM10. We aimed to determine which physico-chemical characteristics of community sampled geogenic PM10 are associated with adverse lung responses. Methods We collected geogenic PM10 from four towns in the arid regions of Western Australia. Adult female BALB/c mice were exposed to 100 μg of particles and assessed for inflammatory and lung function responses 6 hours, 24 hours and 7 days post-exposure. We assessed the physico-chemical characteristics of the particles and correlated these with lung outcomes in the mice using principal components analysis and multivariate linear regression. Results Geogenic particles induced an acute inflammatory response that peaked 6 hours post-exposure and a deficit in lung mechanics 7 days post-exposure. This deficit in lung mechanics was positively associated with the concentration of Fe and particle size variability and inversely associated with the concentration of Si. Conclusions The lung response to geogenic PM10 is complex and highly dependent on the physico-chemical characteristics of the particles. In particular, the concentration of Fe in the particles may be a key indicator of the potential population health consequences for inhaling geogenic PM10.
Geogenic origin of chromium and nickel in the soils and their transfer to the assimilation organs of trees in flysh area of the eastern Slovakia  [PDF]
Eva Komanická
Acta Geologica Slovaca , 2009,
Abstract: Systematic geochemical study and mapping in Slovakia, allowed to understand distribution of potentially toxic trace elements in various natural media (soil, rocks, stream sediments, groundwater and forest biomass) related to geogenic and anthropogenic sources. Anomalous concentrations of chromium and nickel of geogenic character were detected in soils developed on flysh sedimentary rocks. The main interest devoted to such soils is motivated by possible toxic effect of chromium and nickel on plants and subsequently impact on living organisms and humans. The aim of this contribution was to assess the level of chromium and nickel concentration in assimilation organs of trees (needles). It was found high content of these elements in some soils. The studied sites were Podolínec, Forbasy, Stará ubovňa, Drienica, Kamenica. Content of these elements in needles of Norway Spruce (Picea abies) and Scots Pine (Pinus sylvestris) were very high on geogenically contaminated soils with higher values in more in the acidic soils with lower values of pH.
Imprint of the Global Hubble Flow on Galactic Rotation Curves  [PDF]
Philip D. Mannheim
Physics , 1997,
Abstract: We identify an apparent imprint of the global Hubble flow on the systematics of galactic rotation curves, and discuss its possible implications for gravitational theory.
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