The lignite samples collected from Giral lignite field of Barmer basin have been subjected to petrological investigation. The data generated has been discussed to understand the evolution of the paleomires of these li...The lignite samples collected from Giral lignite field of Barmer basin have been subjected to petrological investigation. The data generated has been discussed to understand the evolution of the paleomires of these lignites. The present study reveals that these low rank C coals are chiefly composed of huminite group macerals, mainly telohuminite and detrohuminite, while liptinite and inertinite group macerals occur in subordinate amounts. Not much variation in the maceral composition from Seam-I to Seam-VIII has been observed. Barmer lignites are characterized by a very high GI （〉10） and moderate TPI indicating topogenous mire in the basin which was permanently flooded. The GI and TPI values and the petrography-based facies critical models indicate that these lignites originated mostly under wet forest swamp to clastic marsh having telmatic to limno-telmatic conditions with a moderate rate of subsidence and a very slow fall in ground water table. Further, the GWI and VI values are suggestive of mesotrophic to rheotrophic hydrological conditions having the dominance of herbaceous to marginal aquatic vegetation. There were spells of periodic drowning of peat especially during the formation of Seam-VII. Moderately high concentration of calcium in these lignites along with the presence of framboidal pyrite indicate enhanced sulphate-reducing bacterial activity present in carbonate and sulphate-rich waters in the basin during peat formation.展开更多
Mand-Raigarh coalfield is one of the largest coalfields in the Mahanadi basin. The Geological Survey of India carried out initial study primarily on exploration. However, detailed petrographic and geochemical characte...Mand-Raigarh coalfield is one of the largest coalfields in the Mahanadi basin. The Geological Survey of India carried out initial study primarily on exploration. However, detailed petrographic and geochemical characters of the coals have not been done so far. This investigation is an attempt for petrographic and geochemical appraisal of the coals. Moreover, effort is also made for possible interpretation on development of coal facies. The results drawn from 30 composite coal samples suggest coals are rich in vitrinite, with collotelinite as the dominant maceral while liptinite macerals register low concentration. Dominant mineral assemblages found were clay minerals, pyrite was recorded as disseminated, framboidal and euhedral forms, carbonates recorded were mainly siderites. The vitrinite reflectance random （VRo） mean values range from 0.44 % to 0.56 %, and the rank of coal is suggested as high volatile ＇B＇ to ＇A＇ sub- bituminous in rank. The rock-eval pyrolysis reveal TOC content varying from 37 % to 68.83 %, while low hydrocarbon generating potential is evident from low $2 and Tmax values. The Hydrogen Index （HI） versus Oxygen Index （OI） plot reveal that the samples belong to Kerogen type--II-III with input dominantly from terrestrial source, some samples also fall in Kerogen type--II domain indicating lacustrine input. Vitrinite reflectance result indicate that the samples are immature and approaching oil window, which is in agreement with data of the Rock-Eval parameters. The gelification index （GI） and tissue preservation index （TPI） indicate that the coal developed in a telematic set up with high tree density. The ground water index （GWI） and vegetation index （VI） demonstrate that the peat developed as an ombrogenous bog.展开更多
Lignite samples collected from Vastan, Rajpardi and Tadkeshwar lignite mines of Cambay basin （Gujarat） were subjected to organic petrographic investigations and geochemical analyses and the data, thus generated, is ...Lignite samples collected from Vastan, Rajpardi and Tadkeshwar lignite mines of Cambay basin （Gujarat） were subjected to organic petrographic investigations and geochemical analyses and the data, thus generated, is used to reconstruct the paleodepositional history of these lignite sequences. The lignites of Cambay basin dominantly comprise huminite maceral group （71.6%-86.3%） followed by liptinite （10.1%-19.3%） and inertinite （3.6%-11.0%） maceral groups. The mineral matter varies from 9.0% to 20.0%. The petrography based facies model indicates that these lignites have high values of gelification index （GI） and low tissue preservation index revealing a continuous wet condition in the basin and a relatively slower rate of subsidence during the decay of organic matter. On several occasions, during the formation of seams in Tadkeshwar, Rajpardi and Vastan mines, the value of GI exceeded 10 which indicates a forest permanently flooded and the cause of pronounced degree of degradation. However, few sections in Tadkeshwar seam had relatively drier spells of environmental conditions due to fluctuation in the water table as revealed by moderately high content of inertinite macerals. This is specially indicated by the occurrence of funginite which normally thrives in the upper oxy- genated peatigenic layer and indicates prevalence of oxic conditions during plant deposition. Such conditions prevailed during a transgressive phase but there were intermittent fluvial activities also giving rise to supratidal flood plain as reflected in the form of associated carbonaceous shales in the basin.展开更多
The present paper entails the results of the investigations carried out on the lignite deposits of Kachchh Basin. The lignite samples were drawn from five lignite seams from Panandhro lignite field （Seam-I to -V） an...The present paper entails the results of the investigations carried out on the lignite deposits of Kachchh Basin. The lignite samples were drawn from five lignite seams from Panandhro lignite field （Seam-I to -V） and eight lignite seams （Seam-I to -VIII） from the Matanomadh lignite field which are currently operational. The petrographic analysis of the lignites indicates a dominance of huminite group of macerals which is mainly contributed by ulminite-A, ulminite-B, attrinite, densinite, and phlobaphinite. Liptinite （chiefly sporinite, cutinite, resinite, and liptodetrinite） and inertinite （chiefly fusinite, funginite, and inertodetrinite） groups occur in subordinated amount. The mineral matter occurs in moderate concentration. Though sulfur content is high in these lignites, there is no fixed trend of variation of sulfur from bottom seam to top seam. The investigation reveals a flooded forest swamp having high rate of degradation. However, there were a few drier periods indicated by relatively more inertinite macerals. The petrography-based models indicate that the Kachchh lignites of Gujarat evolved in coastal marshy setting under transgressive phase. However, there were few intermittent fluvial activities giving rise to supratidal flood plain. This led to the formation of the associated carbonaceous shales in the basin.展开更多
Soil moisture affects various hydrological processes, including evapotranspiration, infiltration, and runoff. Forested areas in the lower western Himalaya in India constitute the headwater catchments for many hill str...Soil moisture affects various hydrological processes, including evapotranspiration, infiltration, and runoff. Forested areas in the lower western Himalaya in India constitute the headwater catchments for many hill streams and have experienced degradation in forest cover due to grazing, deforestation and other human activities. This change in forest cover is likely to alter the soil moisture regime and, consequently, flow regimes in streams. The effect of change in forest cover on soil moisture regimes of this dry region has not been studied through long term field observations. We monitored soil matric potentials in two small watersheds in the lower western Himalaya of India. The watersheds consisted of homogeneous land covers of moderately dense oak forest and moderately degraded mixed oak forest. Observations were recorded at three sites at three depths in each watershed at fortnightly intervals for a period of three years. The soil moisture contents derived from soil potential measurements were analyzed to understand the spatial, temporal and profile variations under the two structures of forest cover. The analysis revealed large variations in soil moisture storage at different sites and depths and also during different seasons in each watershed. Mean soil moisture storage during monsoon, winter and summer seasons was higher under dense forest than under degraded forest. Highest soil moisture content occurred at shallow soil profiles, decreasing with depth in both watersheds. A high positive correlation was found between tree density and soil moisture content. Mean soil moisture content over the entire study period was higher under dense forest than under degraded forest. This indicated a potential for soil water storage under well managed oak forest. Because soil water storage is vital for sustenance of low flows, attention is needed on the management of oak forests in the Himalayan region.展开更多
文摘The lignite samples collected from Giral lignite field of Barmer basin have been subjected to petrological investigation. The data generated has been discussed to understand the evolution of the paleomires of these lignites. The present study reveals that these low rank C coals are chiefly composed of huminite group macerals, mainly telohuminite and detrohuminite, while liptinite and inertinite group macerals occur in subordinate amounts. Not much variation in the maceral composition from Seam-I to Seam-VIII has been observed. Barmer lignites are characterized by a very high GI （〉10） and moderate TPI indicating topogenous mire in the basin which was permanently flooded. The GI and TPI values and the petrography-based facies critical models indicate that these lignites originated mostly under wet forest swamp to clastic marsh having telmatic to limno-telmatic conditions with a moderate rate of subsidence and a very slow fall in ground water table. Further, the GWI and VI values are suggestive of mesotrophic to rheotrophic hydrological conditions having the dominance of herbaceous to marginal aquatic vegetation. There were spells of periodic drowning of peat especially during the formation of Seam-VII. Moderately high concentration of calcium in these lignites along with the presence of framboidal pyrite indicate enhanced sulphate-reducing bacterial activity present in carbonate and sulphate-rich waters in the basin during peat formation.
文摘Mand-Raigarh coalfield is one of the largest coalfields in the Mahanadi basin. The Geological Survey of India carried out initial study primarily on exploration. However, detailed petrographic and geochemical characters of the coals have not been done so far. This investigation is an attempt for petrographic and geochemical appraisal of the coals. Moreover, effort is also made for possible interpretation on development of coal facies. The results drawn from 30 composite coal samples suggest coals are rich in vitrinite, with collotelinite as the dominant maceral while liptinite macerals register low concentration. Dominant mineral assemblages found were clay minerals, pyrite was recorded as disseminated, framboidal and euhedral forms, carbonates recorded were mainly siderites. The vitrinite reflectance random （VRo） mean values range from 0.44 % to 0.56 %, and the rank of coal is suggested as high volatile ＇B＇ to ＇A＇ sub- bituminous in rank. The rock-eval pyrolysis reveal TOC content varying from 37 % to 68.83 %, while low hydrocarbon generating potential is evident from low $2 and Tmax values. The Hydrogen Index （HI） versus Oxygen Index （OI） plot reveal that the samples belong to Kerogen type--II-III with input dominantly from terrestrial source, some samples also fall in Kerogen type--II domain indicating lacustrine input. Vitrinite reflectance result indicate that the samples are immature and approaching oil window, which is in agreement with data of the Rock-Eval parameters. The gelification index （GI） and tissue preservation index （TPI） indicate that the coal developed in a telematic set up with high tree density. The ground water index （GWI） and vegetation index （VI） demonstrate that the peat developed as an ombrogenous bog.
文摘Lignite samples collected from Vastan, Rajpardi and Tadkeshwar lignite mines of Cambay basin （Gujarat） were subjected to organic petrographic investigations and geochemical analyses and the data, thus generated, is used to reconstruct the paleodepositional history of these lignite sequences. The lignites of Cambay basin dominantly comprise huminite maceral group （71.6%-86.3%） followed by liptinite （10.1%-19.3%） and inertinite （3.6%-11.0%） maceral groups. The mineral matter varies from 9.0% to 20.0%. The petrography based facies model indicates that these lignites have high values of gelification index （GI） and low tissue preservation index revealing a continuous wet condition in the basin and a relatively slower rate of subsidence during the decay of organic matter. On several occasions, during the formation of seams in Tadkeshwar, Rajpardi and Vastan mines, the value of GI exceeded 10 which indicates a forest permanently flooded and the cause of pronounced degree of degradation. However, few sections in Tadkeshwar seam had relatively drier spells of environmental conditions due to fluctuation in the water table as revealed by moderately high content of inertinite macerals. This is specially indicated by the occurrence of funginite which normally thrives in the upper oxy- genated peatigenic layer and indicates prevalence of oxic conditions during plant deposition. Such conditions prevailed during a transgressive phase but there were intermittent fluvial activities also giving rise to supratidal flood plain as reflected in the form of associated carbonaceous shales in the basin.
文摘The present paper entails the results of the investigations carried out on the lignite deposits of Kachchh Basin. The lignite samples were drawn from five lignite seams from Panandhro lignite field （Seam-I to -V） and eight lignite seams （Seam-I to -VIII） from the Matanomadh lignite field which are currently operational. The petrographic analysis of the lignites indicates a dominance of huminite group of macerals which is mainly contributed by ulminite-A, ulminite-B, attrinite, densinite, and phlobaphinite. Liptinite （chiefly sporinite, cutinite, resinite, and liptodetrinite） and inertinite （chiefly fusinite, funginite, and inertodetrinite） groups occur in subordinated amount. The mineral matter occurs in moderate concentration. Though sulfur content is high in these lignites, there is no fixed trend of variation of sulfur from bottom seam to top seam. The investigation reveals a flooded forest swamp having high rate of degradation. However, there were a few drier periods indicated by relatively more inertinite macerals. The petrography-based models indicate that the Kachchh lignites of Gujarat evolved in coastal marshy setting under transgressive phase. However, there were few intermittent fluvial activities giving rise to supratidal flood plain. This led to the formation of the associated carbonaceous shales in the basin.
基金Impact assessment of land use on hydrologic regime in selected micro-watersheds in lesser Himalayas,Uttarakhand,India
文摘Soil moisture affects various hydrological processes, including evapotranspiration, infiltration, and runoff. Forested areas in the lower western Himalaya in India constitute the headwater catchments for many hill streams and have experienced degradation in forest cover due to grazing, deforestation and other human activities. This change in forest cover is likely to alter the soil moisture regime and, consequently, flow regimes in streams. The effect of change in forest cover on soil moisture regimes of this dry region has not been studied through long term field observations. We monitored soil matric potentials in two small watersheds in the lower western Himalaya of India. The watersheds consisted of homogeneous land covers of moderately dense oak forest and moderately degraded mixed oak forest. Observations were recorded at three sites at three depths in each watershed at fortnightly intervals for a period of three years. The soil moisture contents derived from soil potential measurements were analyzed to understand the spatial, temporal and profile variations under the two structures of forest cover. The analysis revealed large variations in soil moisture storage at different sites and depths and also during different seasons in each watershed. Mean soil moisture storage during monsoon, winter and summer seasons was higher under dense forest than under degraded forest. Highest soil moisture content occurred at shallow soil profiles, decreasing with depth in both watersheds. A high positive correlation was found between tree density and soil moisture content. Mean soil moisture content over the entire study period was higher under dense forest than under degraded forest. This indicated a potential for soil water storage under well managed oak forest. Because soil water storage is vital for sustenance of low flows, attention is needed on the management of oak forests in the Himalayan region.
