Based on the interpretations of three seismic profiles and one wide-angle seismic profile across the Northwest Sub-basin,South China Sea.stratigraphic sequences,deformation characteristics and an extension model for t...Based on the interpretations of three seismic profiles and one wide-angle seismic profile across the Northwest Sub-basin,South China Sea.stratigraphic sequences,deformation characteristics and an extension model for this sub-basin have been worked out.Three tectonic-stratigraphic units are determined.Detailed analyses of extension show that the event occurred mainly during the Paleogene and resulted in the formation of half-grabens or grabens distributed symmetrically around the spreading center.Sediments are characterized by chaotic and discontinuous reflectors,indicating clastic sediments. Farther to the southwest,the sub-basin features mainly continental rifting instead of sea-floor spreading. The rifting would have been controlled by the shape of the massif and developed just along the northern edge of the Zhongsha-Xisha Block,rather than joined the Xisha Trough.After 25 Ma.a southward ridge jump triggered the opening of the Southwest Sub-basin.The NW-directed stress caused by the sea-floor spreading of the Northwest Sub-basin may have prevented the continuous opening of the sub-basin.After that the Northwest Sub-basin experienced thermal cooling and exhibited broad subsidence.The deep crustal structure shown by the velocity model from a wide-angle seismic profile is also symmetrical around the spreading center,which indicates that the Northwest Sub-basin might have opened in a pure shear model.展开更多
The western Liaodong （辽东） Bay subbasin displays examples of segment, linkage of extensional fault, and fault-related folds. The Liaoxi （辽西） extensional fault system consists of a series of NNE- and NE-trending...The western Liaodong （辽东） Bay subbasin displays examples of segment, linkage of extensional fault, and fault-related folds. The Liaoxi （辽西） extensional fault system consists of a series of NNE- and NE-trending segments that were linked through relay ramps. The fault hanging walls are characterized by a series of en echelon synclines with axial traces sub-parallel to the faults. The synclines are doubly plunging located on the hanging wall of normal faults, with the strata dip sub-parallel to the fault. These folds result from along-strike displacement variations of the individual fault segments, as well as from extensional fault-related folding. In the study area, the synclines are separated by transverse intra-basin highs and relay ramps that formed where segment linkage occurred. These hanging wall synclines and their relation to fault displacement variations indicate that they are formed by extensional fault-related fold.展开更多
The Pearl River Mouth Basin, which is situated on the northern margin of the South China Sea, has attracted great attention not only because of its tectonic setting but also because of its abundant hydrocarbon resourc...The Pearl River Mouth Basin, which is situated on the northern margin of the South China Sea, has attracted great attention not only because of its tectonic setting but also because of its abundant hydrocarbon resources. We have analyzed the Cenozoic tectonic subsidence history of 4 drilled wells and 43 artificial wells from the Zhu 1 Sub-basin of the Pearl River Mouth Basin by back-stripping, using newly interpreted seismic profiles. We also calculated the average tectonic sub- sidence rates of the four sags in the Zhu 1 Sub-basin. The rifting and post-rifting stages are separated by abrupt changes in the tectonic subsidence curves and average subsidence rates. In the eastem sags of the Zhu 1 Sub- basin, tectonic subsidence started to slow at ca. 30 Ma, compared with ca. 23.8 Ma in the western sags. This probably corresponds to the timing of break-up and suggests that tiffing in the Pearl River Mouth Basin ended earlier in the eastern sags than in the western sags. Anomalously accelerated tectonic subsidence occurred at 17.5-16.4 Ma during the post-tiffing stage, with average subsidence rates as high as 301.9 m/Myr. This distin- guishes the Pearl River Mouth Basin from classical Atlantic passive continental marginal basins, which demonstrate exponentially decaying post-rift tectonic subsidence.展开更多
The Bohai Bay basin comprises some very important and well documented subtle traps known in China, which have been the major exploration focus and have become a major petroleum play since the 1990s. However, recent ex...The Bohai Bay basin comprises some very important and well documented subtle traps known in China, which have been the major exploration focus and have become a major petroleum play since the 1990s. However, recent exploration showed that the oil-bearing proper-ties of some sand lens reservoirs may vary significantly and the accumulation mechanisms for these lithological subtle traps are not well understood. Based on statistical analysis of oil-bearing properties for 123 sand lens reservoirs in the Jiyang Sub-basin and combined with detailed anatomy of typical sand lens reservoirs and NMR experiments, it has been shown that the structural and sedimentary factors, hydrocarbon generation and expulsion conditions of the sur-rounding source rocks, as well as the petrophysical properties of sand lens reservoirs are the main controlling factors for the formation of sand lens reservoirs. The formation of a sand lens reservoir depends on the interaction between the hydrocarbon accumulation driving force and the resistance force. The driving force is made up of the differential capillary pressure between sandstones and sources rocks and the hydrocarbon diffusion force, and as well as the hydro-carbon expansion force. The resistance force is the friction resistance force for hydrocarbons and water to move through the pore throats of the sand lens. The sedimentary environment, source rock condition and sand reservoir properties can change from unfavorable to favorable depend-ing on the combination of these factors. When these three factors all reach certain thresholds, the sand lens reservoirs may begin to be filled by hydrocarbons. When all of these conditions be-come favorable for the formation of sand lens reservoirs, the reservoir would have high oil satu-ration. This approach has been applied to evaluating the potential of petroleum accumulation in the sand lens reservoirs in the third member of the Neogene Shahejie Formation in the Jiyang Sub-basin.展开更多
This study used 2D seismic profiles to investigate the Cenozoic evolution of faults in the Huizhou Sub-basin. It aims to define the basin structure style through describing the geometric fea- tures of the faults and q...This study used 2D seismic profiles to investigate the Cenozoic evolution of faults in the Huizhou Sub-basin. It aims to define the basin structure style through describing the geometric fea- tures of the faults and quantitatively analyzing their activities. The results indicate that the boundary faults in the Huizhou Sub-basin display en echelon arrangement in plan view, which indicates that, it was caused by a kind of oblique extension. Calculating the fault slips shows long-term activities of faults occurred in the basin, and some boundary faults kept active after 5.5 Ma. The evolution history of the fault system is reconstructed. Initially, during the Eocene-Early Oligocene, mainly NNE-NE and NW trending faults and NE striking grabens and half-grabens formed in the basin and a series of faults system controlled the deposition. During the Late Oligocene--Early Miocene, the structural ac- tivities were relatively weak, the fault activity and the fault growth rate decreased sharply. Finally, in the late stage from Late Miocene to the present, the structure movement was re-activated, and some faults were also reactivated. Our study will help better understand the structural features and evolu- tion of the petroleum-bearing basins in the northern margin of the South China Sea.展开更多
Landslide is one of the major natural disasters which cause extensive loss of life and property. During the last three decades, different researchers have developed different methodologies to prepare landslide suscept...Landslide is one of the major natural disasters which cause extensive loss of life and property. During the last three decades, different researchers have developed different methodologies to prepare landslide susceptibility mapping and hazard assessment in the world. The main goal of this paper is to apply a fuzzy logic approach to landslide susceptibility mapping in the Garuwa sub-basin area, East Nepal. Eight different causative factors are considered： slope angle, slope aspect, slope shape, relative relief, distance from drainage, land use, geology, and distance from active faults. Likelihood ratios are obtained for each class of causative factors by comparison with past landslide occurrences. Then, the likelihood ratios are normalized between zero and one to obtain fuzzy membership values. Next, different fuzzy operators are applied to generate landslide susceptibility maps. Compar- ison with the landslide inventory map reveals that the fuzzy gamma （γ） operator with a y-value of 0.70 yields the best prediction accuracy which is then used to produce the final landslide susceptibility zonation map.展开更多
Drought is a natural phenomenon posing severe implications for soil,groundwater and agricultural yield.It has been recognized as one of the most pervasive global change drivers to affect the soil.Soil being a weakly r...Drought is a natural phenomenon posing severe implications for soil,groundwater and agricultural yield.It has been recognized as one of the most pervasive global change drivers to affect the soil.Soil being a weakly renewable resource takes a long time to form,but it takes no time to degrade.However,the response of soil to drought conditions as soil loss is not manifested in the existing literature.Thus,this study makes a concerted effort to analyze the relationship between drought conditions and soil erosion in the middle sub-basin of the Godavari River in India.MODIS remote sensing data was utilized for driving drought indices during 2000-2019.Firstly,we constricted Temperature condition index(TCI)and Vegetation Condition Index(VCI)from Land Surface Temperature(LST)and Enhanced Vegetation Index(EVI)derived from MODIS data.TCI and VCI were then integrated to determine the Vegetation Health Index(VHI).Revised Universal Soil Loss Equation(RUSLE)was utilized for estimating soil loss.The relationship between drought condition and vegetation was ascertained using the Pearson correlation.Most of the northern and southern watersheds experienced severe drought condition in the sub-basin during2000-2019.The mean frequency of the drought occurrence was 7.95 months.The average soil erosion in the sub-basin was estimated to be 9.88 t ha^(-1)year^(-1).A positive relationship was observed between drought indices and soil erosion values(r value being 0.35).However,wide variations were observed in the distribution of spatial correlation.Among various factors,the slope length and steepness were found to be the main drivers of soil erosion in the sub-basin.Thus,the study calls for policy measures to lessen the impact of drought and soil erosion.展开更多
Water resource access in the Nouhao sub-basin, assessed based on the availability of drinking water mobilization facilities, the availability of water for uses and the quality of drinking water, revealed that in 2017 ...Water resource access in the Nouhao sub-basin, assessed based on the availability of drinking water mobilization facilities, the availability of water for uses and the quality of drinking water, revealed that in 2017 the basin was covered by 1249 modern water point, main drinking water sources. On average, the sub-basin shows a ratio of 271 users per drinking water point. Communal level shows some disparity with Bittou recording the highest number of people per drinking water point, i.e., around 537. Water that can be captured in the entire sub-basin meets only 42% of the total water needs from the three mains uses: irrigation, domestic consumption and livestock. The highest demander among these uses is Irrigation with 75% of the need, i.e., approximately 12,859,995 m<sup>3</sup>. Water in 33% drinking sources of this sub basin is of poor quality. Arsenic, one of the quality parameters studied, is found in some communes of the sub-basin. 11% of the water points in Bissiga are arsenic polluted making this commune the most arsenic contaminated location. The vulnerability maps deducted from lack of water for uses;lack of drinking water works and poor water quality shows so, the exposure level of the sub-basin’ communes to some potential risks related to low water resources access.展开更多
The aim of this research work was to report a facies analysis of the N’Kappa formation, identified the clay minerals present in those facies and evaluate their oil potential. For that to be done, Lithostratigraphic d...The aim of this research work was to report a facies analysis of the N’Kappa formation, identified the clay minerals present in those facies and evaluate their oil potential. For that to be done, Lithostratigraphic descriptions were performed on three natural outcrops chosen in three different localities of the northern border of Douala sedimentary basin. Ten shaly samples were then collected on those outcrops and submit to X ray diffraction and Rock-Eval pyrolysis. Lithologically, the N’Kappa formation is made up of dark to grey shales and fine to coarse sandtones. The mineralogic content of the shales is made up of Kaolinite, dickite, low quartz and vaterite. Those shaly facies present high amount of immature organic matter (average TOC content around 2%). The petroleum potential is fair to poor (average S2 for all the samples around 3.33 mg HC/g of rock) though some samples (M1 and M2) presenting a good petroleum potential up to 6.62 kg HC/t of rock and 6.44 kg HC/t of rock respectively. They have undergone a low degree of diagenesis (early to burying diagenesis). This is evidenced by the predominance of kaolinite and dickite, low quartz and vaterite which are minerals stable at low temperature.展开更多
Ethiopia is also frequently identified as a country that is highly vulnerable to climate variability and change. The potential adverse effects of climate change on Ethiopia’s agricultural sector are a major concern, ...Ethiopia is also frequently identified as a country that is highly vulnerable to climate variability and change. The potential adverse effects of climate change on Ethiopia’s agricultural sector are a major concern, particularly given the country’s dependence on agricultural production, which is sensitive to climate change and variability. This problem calls the need to understand agroecology based vulnerability to climate change and variability to better adapt to climate risks and promote strategies for local communities so as to enhance food security. The objective of this study is to estimate and compare the level of vulnerability of smallholder farmers’ to climate change and variability from three agroecology representing Muger River sub-Basin of the upper Blue Nile basin using Livelihood Vulnerability Index. The research used quantitative and qualitative data collected through Focussed Group Discussions, key informant interviews and a questionnaire survey of 442 sampled households across three different agro-ecologies in the sub-basin. The results reveal that along with the different agro-ecological zone, households and communities experienced different degrees of climate vulnerability. These differences are largely explained by differences in exposure, sensitivity and adaptive capacity of smallholder farmers. The livelihood vulnerability analysis reveals that Kolla agroecology exhibits relatively low adaptive capacity, higher sensitivity and higher exposure to climate change and variability that is deemed to be the most vulnerable agroecology. These contributing factors to a vulnerability in Kolla agroecology are largely influenced by assets, livelihood diversification, innovation, infrastructure, socio-demographic factors, social capital, agriculture, food security, and natural disasters and climate variability. The result furthermore shows that Dega agroecology has least vulnerable owing to its higher adaptive capacity. These results suggest that designing agroecology based resilience-building adapt展开更多
River flow in the Songwe sub-basin is predicted to alter due to climate change, which would have an impact on aquatic habitats, infrastructure, and people’s way of life. Therefore, the influence of climate change sho...River flow in the Songwe sub-basin is predicted to alter due to climate change, which would have an impact on aquatic habitats, infrastructure, and people’s way of life. Therefore, the influence of climate change should be taken into account when making decisions about the sustainable management of water resources in the sub-basin. This study looked into how river discharge would react to climate change in the future. By contrasting hydrological characteristics simulated under historical climate (1981-2010) with projected climate (2011-2040, 2041-2070, and 2071-2100) under two emission scenarios, the effects of climate change on river flow were evaluated (RCP 4.5 and RCP 8.5). The ensemble average of four CORDEX regional climate models was built to address the issue of uncertainty introduced by the climate models. The SWAT model was force-calibrated using the results from the generated ensemble average for the RCP 4.5 and RCP 8.5 emission scenarios in order to mimic the river flow during past (1981-2010) and future (2011-2100) events. The increase in river flows for the Songwe sub-basin is predicted to be largest during the rainy season by both the RCP 4.5 and RCP 8.5 scenarios. Under RCP 8.5, the abrupt decrease in river flow is anticipated to reach its maximum in March 2037, when the discharge will be 44.84 m<sup>3</sup>/sec, and in March 2027, when the discharge will be 48 m<sup>3</sup>/sec. The extreme surge in river flow will peak, according to the RCA4, in February 2023, in April 2083 under RCP 4.5, and, according to the CCLM4 and RCA4, in November 2027 and November 2046, respectively. The expected decrease and increase in river flow throughout both the dry and wet seasons may have an impact on the management of the sub-water basin’s resources, biodiversity, and hydraulic structures. The right adaptations and mitigation strategies should be adopted in order to lessen the negative consequences of climate change on precipitation, temperature, and river flow in the sub-basin.展开更多
基金supported by the National Basic Research Program(973) of China (No.2007CB41170403)the National Natural Science Foundation of China(No.40806023)the Scientific Research Fund of the SIO,SOA(No.1404-10)
文摘Based on the interpretations of three seismic profiles and one wide-angle seismic profile across the Northwest Sub-basin,South China Sea.stratigraphic sequences,deformation characteristics and an extension model for this sub-basin have been worked out.Three tectonic-stratigraphic units are determined.Detailed analyses of extension show that the event occurred mainly during the Paleogene and resulted in the formation of half-grabens or grabens distributed symmetrically around the spreading center.Sediments are characterized by chaotic and discontinuous reflectors,indicating clastic sediments. Farther to the southwest,the sub-basin features mainly continental rifting instead of sea-floor spreading. The rifting would have been controlled by the shape of the massif and developed just along the northern edge of the Zhongsha-Xisha Block,rather than joined the Xisha Trough.After 25 Ma.a southward ridge jump triggered the opening of the Southwest Sub-basin.The NW-directed stress caused by the sea-floor spreading of the Northwest Sub-basin may have prevented the continuous opening of the sub-basin.After that the Northwest Sub-basin experienced thermal cooling and exhibited broad subsidence.The deep crustal structure shown by the velocity model from a wide-angle seismic profile is also symmetrical around the spreading center,which indicates that the Northwest Sub-basin might have opened in a pure shear model.
基金supported by the project of the State Key Labo-ratory of Petroleum Resource and Prospecting and Tianjin Oil Company, CNOOC Limited (No. SC06TJ-TQL-004)
文摘The western Liaodong （辽东） Bay subbasin displays examples of segment, linkage of extensional fault, and fault-related folds. The Liaoxi （辽西） extensional fault system consists of a series of NNE- and NE-trending segments that were linked through relay ramps. The fault hanging walls are characterized by a series of en echelon synclines with axial traces sub-parallel to the faults. The synclines are doubly plunging located on the hanging wall of normal faults, with the strata dip sub-parallel to the fault. These folds result from along-strike displacement variations of the individual fault segments, as well as from extensional fault-related folding. In the study area, the synclines are separated by transverse intra-basin highs and relay ramps that formed where segment linkage occurred. These hanging wall synclines and their relation to fault displacement variations indicate that they are formed by extensional fault-related fold.
文摘The Pearl River Mouth Basin, which is situated on the northern margin of the South China Sea, has attracted great attention not only because of its tectonic setting but also because of its abundant hydrocarbon resources. We have analyzed the Cenozoic tectonic subsidence history of 4 drilled wells and 43 artificial wells from the Zhu 1 Sub-basin of the Pearl River Mouth Basin by back-stripping, using newly interpreted seismic profiles. We also calculated the average tectonic sub- sidence rates of the four sags in the Zhu 1 Sub-basin. The rifting and post-rifting stages are separated by abrupt changes in the tectonic subsidence curves and average subsidence rates. In the eastem sags of the Zhu 1 Sub- basin, tectonic subsidence started to slow at ca. 30 Ma, compared with ca. 23.8 Ma in the western sags. This probably corresponds to the timing of break-up and suggests that tiffing in the Pearl River Mouth Basin ended earlier in the eastern sags than in the western sags. Anomalously accelerated tectonic subsidence occurred at 17.5-16.4 Ma during the post-tiffing stage, with average subsidence rates as high as 301.9 m/Myr. This distin- guishes the Pearl River Mouth Basin from classical Atlantic passive continental marginal basins, which demonstrate exponentially decaying post-rift tectonic subsidence.
基金supported by the National Key Basic Research Project(973)(Grant No.G1999043310)the National Natural Science Foundation of China(Grant No.40172057)the National Tenth Five-Year Plan Project(Grant No.2001BA605A09).
文摘The Bohai Bay basin comprises some very important and well documented subtle traps known in China, which have been the major exploration focus and have become a major petroleum play since the 1990s. However, recent exploration showed that the oil-bearing proper-ties of some sand lens reservoirs may vary significantly and the accumulation mechanisms for these lithological subtle traps are not well understood. Based on statistical analysis of oil-bearing properties for 123 sand lens reservoirs in the Jiyang Sub-basin and combined with detailed anatomy of typical sand lens reservoirs and NMR experiments, it has been shown that the structural and sedimentary factors, hydrocarbon generation and expulsion conditions of the sur-rounding source rocks, as well as the petrophysical properties of sand lens reservoirs are the main controlling factors for the formation of sand lens reservoirs. The formation of a sand lens reservoir depends on the interaction between the hydrocarbon accumulation driving force and the resistance force. The driving force is made up of the differential capillary pressure between sandstones and sources rocks and the hydrocarbon diffusion force, and as well as the hydro-carbon expansion force. The resistance force is the friction resistance force for hydrocarbons and water to move through the pore throats of the sand lens. The sedimentary environment, source rock condition and sand reservoir properties can change from unfavorable to favorable depend-ing on the combination of these factors. When these three factors all reach certain thresholds, the sand lens reservoirs may begin to be filled by hydrocarbons. When all of these conditions be-come favorable for the formation of sand lens reservoirs, the reservoir would have high oil satu-ration. This approach has been applied to evaluating the potential of petroleum accumulation in the sand lens reservoirs in the third member of the Neogene Shahejie Formation in the Jiyang Sub-basin.
基金supported by the National Natural Science Foundation of China (Nos. 41272121, 91028009, 41102071)the Program of Introducing Talents of Discipline to Universities (No. B14031)
文摘This study used 2D seismic profiles to investigate the Cenozoic evolution of faults in the Huizhou Sub-basin. It aims to define the basin structure style through describing the geometric fea- tures of the faults and quantitatively analyzing their activities. The results indicate that the boundary faults in the Huizhou Sub-basin display en echelon arrangement in plan view, which indicates that, it was caused by a kind of oblique extension. Calculating the fault slips shows long-term activities of faults occurred in the basin, and some boundary faults kept active after 5.5 Ma. The evolution history of the fault system is reconstructed. Initially, during the Eocene-Early Oligocene, mainly NNE-NE and NW trending faults and NE striking grabens and half-grabens formed in the basin and a series of faults system controlled the deposition. During the Late Oligocene--Early Miocene, the structural ac- tivities were relatively weak, the fault activity and the fault growth rate decreased sharply. Finally, in the late stage from Late Miocene to the present, the structure movement was re-activated, and some faults were also reactivated. Our study will help better understand the structural features and evolu- tion of the petroleum-bearing basins in the northern margin of the South China Sea.
文摘Landslide is one of the major natural disasters which cause extensive loss of life and property. During the last three decades, different researchers have developed different methodologies to prepare landslide susceptibility mapping and hazard assessment in the world. The main goal of this paper is to apply a fuzzy logic approach to landslide susceptibility mapping in the Garuwa sub-basin area, East Nepal. Eight different causative factors are considered： slope angle, slope aspect, slope shape, relative relief, distance from drainage, land use, geology, and distance from active faults. Likelihood ratios are obtained for each class of causative factors by comparison with past landslide occurrences. Then, the likelihood ratios are normalized between zero and one to obtain fuzzy membership values. Next, different fuzzy operators are applied to generate landslide susceptibility maps. Compar- ison with the landslide inventory map reveals that the fuzzy gamma （γ） operator with a y-value of 0.70 yields the best prediction accuracy which is then used to produce the final landslide susceptibility zonation map.
文摘Drought is a natural phenomenon posing severe implications for soil,groundwater and agricultural yield.It has been recognized as one of the most pervasive global change drivers to affect the soil.Soil being a weakly renewable resource takes a long time to form,but it takes no time to degrade.However,the response of soil to drought conditions as soil loss is not manifested in the existing literature.Thus,this study makes a concerted effort to analyze the relationship between drought conditions and soil erosion in the middle sub-basin of the Godavari River in India.MODIS remote sensing data was utilized for driving drought indices during 2000-2019.Firstly,we constricted Temperature condition index(TCI)and Vegetation Condition Index(VCI)from Land Surface Temperature(LST)and Enhanced Vegetation Index(EVI)derived from MODIS data.TCI and VCI were then integrated to determine the Vegetation Health Index(VHI).Revised Universal Soil Loss Equation(RUSLE)was utilized for estimating soil loss.The relationship between drought condition and vegetation was ascertained using the Pearson correlation.Most of the northern and southern watersheds experienced severe drought condition in the sub-basin during2000-2019.The mean frequency of the drought occurrence was 7.95 months.The average soil erosion in the sub-basin was estimated to be 9.88 t ha^(-1)year^(-1).A positive relationship was observed between drought indices and soil erosion values(r value being 0.35).However,wide variations were observed in the distribution of spatial correlation.Among various factors,the slope length and steepness were found to be the main drivers of soil erosion in the sub-basin.Thus,the study calls for policy measures to lessen the impact of drought and soil erosion.
文摘Water resource access in the Nouhao sub-basin, assessed based on the availability of drinking water mobilization facilities, the availability of water for uses and the quality of drinking water, revealed that in 2017 the basin was covered by 1249 modern water point, main drinking water sources. On average, the sub-basin shows a ratio of 271 users per drinking water point. Communal level shows some disparity with Bittou recording the highest number of people per drinking water point, i.e., around 537. Water that can be captured in the entire sub-basin meets only 42% of the total water needs from the three mains uses: irrigation, domestic consumption and livestock. The highest demander among these uses is Irrigation with 75% of the need, i.e., approximately 12,859,995 m<sup>3</sup>. Water in 33% drinking sources of this sub basin is of poor quality. Arsenic, one of the quality parameters studied, is found in some communes of the sub-basin. 11% of the water points in Bissiga are arsenic polluted making this commune the most arsenic contaminated location. The vulnerability maps deducted from lack of water for uses;lack of drinking water works and poor water quality shows so, the exposure level of the sub-basin’ communes to some potential risks related to low water resources access.
文摘The aim of this research work was to report a facies analysis of the N’Kappa formation, identified the clay minerals present in those facies and evaluate their oil potential. For that to be done, Lithostratigraphic descriptions were performed on three natural outcrops chosen in three different localities of the northern border of Douala sedimentary basin. Ten shaly samples were then collected on those outcrops and submit to X ray diffraction and Rock-Eval pyrolysis. Lithologically, the N’Kappa formation is made up of dark to grey shales and fine to coarse sandtones. The mineralogic content of the shales is made up of Kaolinite, dickite, low quartz and vaterite. Those shaly facies present high amount of immature organic matter (average TOC content around 2%). The petroleum potential is fair to poor (average S2 for all the samples around 3.33 mg HC/g of rock) though some samples (M1 and M2) presenting a good petroleum potential up to 6.62 kg HC/t of rock and 6.44 kg HC/t of rock respectively. They have undergone a low degree of diagenesis (early to burying diagenesis). This is evidenced by the predominance of kaolinite and dickite, low quartz and vaterite which are minerals stable at low temperature.
文摘Ethiopia is also frequently identified as a country that is highly vulnerable to climate variability and change. The potential adverse effects of climate change on Ethiopia’s agricultural sector are a major concern, particularly given the country’s dependence on agricultural production, which is sensitive to climate change and variability. This problem calls the need to understand agroecology based vulnerability to climate change and variability to better adapt to climate risks and promote strategies for local communities so as to enhance food security. The objective of this study is to estimate and compare the level of vulnerability of smallholder farmers’ to climate change and variability from three agroecology representing Muger River sub-Basin of the upper Blue Nile basin using Livelihood Vulnerability Index. The research used quantitative and qualitative data collected through Focussed Group Discussions, key informant interviews and a questionnaire survey of 442 sampled households across three different agro-ecologies in the sub-basin. The results reveal that along with the different agro-ecological zone, households and communities experienced different degrees of climate vulnerability. These differences are largely explained by differences in exposure, sensitivity and adaptive capacity of smallholder farmers. The livelihood vulnerability analysis reveals that Kolla agroecology exhibits relatively low adaptive capacity, higher sensitivity and higher exposure to climate change and variability that is deemed to be the most vulnerable agroecology. These contributing factors to a vulnerability in Kolla agroecology are largely influenced by assets, livelihood diversification, innovation, infrastructure, socio-demographic factors, social capital, agriculture, food security, and natural disasters and climate variability. The result furthermore shows that Dega agroecology has least vulnerable owing to its higher adaptive capacity. These results suggest that designing agroecology based resilience-building adapt
文摘River flow in the Songwe sub-basin is predicted to alter due to climate change, which would have an impact on aquatic habitats, infrastructure, and people’s way of life. Therefore, the influence of climate change should be taken into account when making decisions about the sustainable management of water resources in the sub-basin. This study looked into how river discharge would react to climate change in the future. By contrasting hydrological characteristics simulated under historical climate (1981-2010) with projected climate (2011-2040, 2041-2070, and 2071-2100) under two emission scenarios, the effects of climate change on river flow were evaluated (RCP 4.5 and RCP 8.5). The ensemble average of four CORDEX regional climate models was built to address the issue of uncertainty introduced by the climate models. The SWAT model was force-calibrated using the results from the generated ensemble average for the RCP 4.5 and RCP 8.5 emission scenarios in order to mimic the river flow during past (1981-2010) and future (2011-2100) events. The increase in river flows for the Songwe sub-basin is predicted to be largest during the rainy season by both the RCP 4.5 and RCP 8.5 scenarios. Under RCP 8.5, the abrupt decrease in river flow is anticipated to reach its maximum in March 2037, when the discharge will be 44.84 m<sup>3</sup>/sec, and in March 2027, when the discharge will be 48 m<sup>3</sup>/sec. The extreme surge in river flow will peak, according to the RCA4, in February 2023, in April 2083 under RCP 4.5, and, according to the CCLM4 and RCA4, in November 2027 and November 2046, respectively. The expected decrease and increase in river flow throughout both the dry and wet seasons may have an impact on the management of the sub-water basin’s resources, biodiversity, and hydraulic structures. The right adaptations and mitigation strategies should be adopted in order to lessen the negative consequences of climate change on precipitation, temperature, and river flow in the sub-basin.
