The Kathmandu valley is an intermountain basin located at about 1300 and surounded by mountains around 2400m.Thick fluvio\|lacustrine sediments from late Pliocene to Quaternary are accumulated there under monsoon clim...The Kathmandu valley is an intermountain basin located at about 1300 and surounded by mountains around 2400m.Thick fluvio\|lacustrine sediments from late Pliocene to Quaternary are accumulated there under monsoon climate.We undertook palynological and sedimentological studies on 284\|m\|long drilled core that reaches the basement of the kathmandu basin,in order to clarify the paleoclimatic changes and their tectonic link with uplifting of the Himalayas..The core is lithologically divided into three members:sand predominant lower member (51m),slit and clay dominant middle member (182m) and organic silty clay predominant upper member (45m).We analyzed fossil pollens contained in muddy samples which were taken from the middle and upper member in every one meter interval.The pollen assemblage is characterized by predominance of \%Quercus,\%30%～80% of the all arboreal pollen.We inferred paleoclimatic changes on the basis of comparison between present vegetation and climate of Kathmandu valley and surrounded mountains and pollen diagram which we obtained.For the purpose of inference of paleoclimate,we used the following genera as climatic index:\%Pinus\% for cold climate, \%Quercus\% and \%Cyclobalanopsis\% for warm climate, Alnus for wet climate and Gramineae for dry climate.As the reference.we also examined amount of another eight genera,two family and all spores.The pollen diagram shows two pattern of paleoclimatic changes:oscillation pattern with seven times fluctuation of warm and cold climate in younger period (ca.115m in depth),and older less fluctuated pattern of warm climate.During the older period (209～215m in depth),one cold stage was recognized,and is characterized by predominance of Pinus and occurrence of Tsuga .展开更多
The Nawakot and Kathmandu complexes are distributed around Kathmandu area, central Nepal and that build up the Mahabharat synclinorium. The Nawakot complex is composed of mainly weakly metamorphosed sedimentary rocks....The Nawakot and Kathmandu complexes are distributed around Kathmandu area, central Nepal and that build up the Mahabharat synclinorium. The Nawakot complex is composed of mainly weakly metamorphosed sedimentary rocks. The Kathmandu complex, which occupies the large core of the synclinorium, overlies the Nawakot Complex.. These two complexes have the thrust contact called as the Mahabharat Thrust. The Kathmandu complex is subdivided into the lower Bimphedi and the upper Phulchoki Groups. The Bimphedi Group is composed of metamorphosed sedimentary rocks and the Phulchoki Group is of weakly and non\|metamorphosed sedimentary rocks. Besides its important significance, only few studies have been done in these complexes. In this paper, the present author reports preliminarily the stratigraphy of the Phulchoki Group and uppermost part of the Bimphedi Group distributed in the south of Kathmandu. In the study area, weakly to non\|metamorphosed sedimentary rocks is subdivided stratigraphically into Units I to VII in ascending order. These units are characterized by the prominent composition of rock types. Most contacts observed at each adjacent units are conformable and some are transitional. Most of units show the regional variation in accompanying rock type. Unit I: coarsely crystallized marble; Unit II: black to green phyllite; Unit III: light gray quartzose fine sandstone and gray siltstone; Unit IV: well\|bedded sandy argillaceous limestone; Unit V: purple siltstone; Unit VI: coarsely crystallized limestone; Unit VII: siltstone and sandstone. Correlation to the formations named by Stocklin’s (1980) subdivision are as follows: Unit I might be correlated to the Markhu Formation, Units II and III to the Tistung Formation, Unit IV to the Chandragiri Formation, Unit V to the Chitlang Formation, and Units VI and VII to the Godawari Formation.From the study area, some fossils are yielded. Crinoids occur from Units IV, V, VI and VII, brachiopods from Units V, VI and VII, orthocerases from Unit VI, and trilobites from Unit V.展开更多
文摘The Kathmandu valley is an intermountain basin located at about 1300 and surounded by mountains around 2400m.Thick fluvio\|lacustrine sediments from late Pliocene to Quaternary are accumulated there under monsoon climate.We undertook palynological and sedimentological studies on 284\|m\|long drilled core that reaches the basement of the kathmandu basin,in order to clarify the paleoclimatic changes and their tectonic link with uplifting of the Himalayas..The core is lithologically divided into three members:sand predominant lower member (51m),slit and clay dominant middle member (182m) and organic silty clay predominant upper member (45m).We analyzed fossil pollens contained in muddy samples which were taken from the middle and upper member in every one meter interval.The pollen assemblage is characterized by predominance of \%Quercus,\%30%～80% of the all arboreal pollen.We inferred paleoclimatic changes on the basis of comparison between present vegetation and climate of Kathmandu valley and surrounded mountains and pollen diagram which we obtained.For the purpose of inference of paleoclimate,we used the following genera as climatic index:\%Pinus\% for cold climate, \%Quercus\% and \%Cyclobalanopsis\% for warm climate, Alnus for wet climate and Gramineae for dry climate.As the reference.we also examined amount of another eight genera,two family and all spores.The pollen diagram shows two pattern of paleoclimatic changes:oscillation pattern with seven times fluctuation of warm and cold climate in younger period (ca.115m in depth),and older less fluctuated pattern of warm climate.During the older period (209～215m in depth),one cold stage was recognized,and is characterized by predominance of Pinus and occurrence of Tsuga .
文摘The Nawakot and Kathmandu complexes are distributed around Kathmandu area, central Nepal and that build up the Mahabharat synclinorium. The Nawakot complex is composed of mainly weakly metamorphosed sedimentary rocks. The Kathmandu complex, which occupies the large core of the synclinorium, overlies the Nawakot Complex.. These two complexes have the thrust contact called as the Mahabharat Thrust. The Kathmandu complex is subdivided into the lower Bimphedi and the upper Phulchoki Groups. The Bimphedi Group is composed of metamorphosed sedimentary rocks and the Phulchoki Group is of weakly and non\|metamorphosed sedimentary rocks. Besides its important significance, only few studies have been done in these complexes. In this paper, the present author reports preliminarily the stratigraphy of the Phulchoki Group and uppermost part of the Bimphedi Group distributed in the south of Kathmandu. In the study area, weakly to non\|metamorphosed sedimentary rocks is subdivided stratigraphically into Units I to VII in ascending order. These units are characterized by the prominent composition of rock types. Most contacts observed at each adjacent units are conformable and some are transitional. Most of units show the regional variation in accompanying rock type. Unit I: coarsely crystallized marble; Unit II: black to green phyllite; Unit III: light gray quartzose fine sandstone and gray siltstone; Unit IV: well\|bedded sandy argillaceous limestone; Unit V: purple siltstone; Unit VI: coarsely crystallized limestone; Unit VII: siltstone and sandstone. Correlation to the formations named by Stocklin’s (1980) subdivision are as follows: Unit I might be correlated to the Markhu Formation, Units II and III to the Tistung Formation, Unit IV to the Chandragiri Formation, Unit V to the Chitlang Formation, and Units VI and VII to the Godawari Formation.From the study area, some fossils are yielded. Crinoids occur from Units IV, V, VI and VII, brachiopods from Units V, VI and VII, orthocerases from Unit VI, and trilobites from Unit V.
