位于帕米尔前缘逆冲推覆体(Pamir Front Thrust,PFT)东端的木什滑脱背斜,是帕米尔弧形推覆构造带最前缘和最新的变形带。对地形横剖面、纵剖面和水系发育特征的分析表明,木什背斜总体上具有由西向东扩展生长的特征。在背斜核部及北翼发...位于帕米尔前缘逆冲推覆体(Pamir Front Thrust,PFT)东端的木什滑脱背斜,是帕米尔弧形推覆构造带最前缘和最新的变形带。对地形横剖面、纵剖面和水系发育特征的分析表明,木什背斜总体上具有由西向东扩展生长的特征。在背斜核部及北翼发育数级开阔平坦的沿轴向展布的河流阶地,阶地可划分为4期。利用阶地堆积细颗粒石英光释光测年获得阶地面T2a、T3和T4的形成年龄分别为(15.8±2.40)ka、(55.1±10.3)ka、(131.4±23.9)ka。伴随背斜的生长扩展,河流阶地面发生了横向和纵向掀斜,并形成断层陡坎和褶皱陡坎。木什背斜晚第四纪的缩短和隆升主要是通过褶皱翼旋转机制进行的,估算其最小缩短速率为(1.6±0.3)mm/a,最小隆升速率为(1.9±0.3)mm/a。与此同时,沿轴向背斜发生了向东的侧向迁移和旋转。根据背斜垂直隆升与侧向扩展之间的关系,估算背斜在131～16ka期间向东的侧向迁移扩展速率较快,为(14.6±3.6)mm/a;自16ka至今,侧向迁移扩展速率迅速减小至(1.7±0.3)mm/a,背斜向东的迁移扩展可能已基本停止,而以侧向旋转为主。展开更多
Relief surveying and chronology study were carried out on the deformed river terraces across the Artushi anticline belt in the northwestern Tarim Basin. The crust shortening rate of this anticline belt since late Plei...Relief surveying and chronology study were carried out on the deformed river terraces across the Artushi anticline belt in the northwestern Tarim Basin. The crust shortening rate of this anticline belt since late Pleistocene was calculated to be up to 5-6 mm/a. The total crust shortening rate from the northwestern Tarim Basin to southwestern Tianshan since late Pleistocene was estimated to be over 10 mm/a.展开更多
The Kunlun Pass Basin, located in the middle of the eastern Kunlun Mountains, received relatively continuous late Cenozoic sediments from the surrounding mountains, archiving great information to understand the deform...The Kunlun Pass Basin, located in the middle of the eastern Kunlun Mountains, received relatively continuous late Cenozoic sediments from the surrounding mountains, archiving great information to understand the deformation and uplift histories of the northern Tibetan Plateau. The Kunlun-Yellow River Movement, identified from the tectonomorphologic and sedimentary evolution of the Kunlun Pass Basin by Cui Zhijiu et al. (1997, 1998), is roughly coincident with many important global and Plateau climatic and environmental events, becoming a crucial time interval to understand tectonic-climatic interactions. However, the ages used to constrict the events remain great uncertainty. Here, we present the results of detailed magnetostratigraphy of the late Cenozoic sediments in the Kunlun Pass Basin, which show the basin sediments were formed between about 3.6 Ma and 0.5 Ma and the Kunlun-Yellow River Movement occurred at 1.2 to ～0.78 Ma. The lithology, sedimentary facies and lithofacies associations divide the basin into five stages of tectonosedimentary evolution, indicating the northern Tibetan Plateau having experienced five episodes of tectonic uplifts at ～3.6, 2.69－2.58, 1.77, 1.2, 0.87 and ～0.78 Ma since the Pliocene.展开更多
The combined use of conventional, isotopic and geochemical techniques provides a powerful tool with which to determine sedimentary provenance, from which interpretations on Himalayan evolution and tectonics can be mad...The combined use of conventional, isotopic and geochemical techniques provides a powerful tool with which to determine sedimentary provenance, from which interpretations on Himalayan evolution and tectonics can be made.Here we present the results of conventional bulk\|composition petrography, single grain isotopic (Ar\|Ar white mica ages, U\|Pb ages and Sm\|Nd on monazite) and whole rock Sm\|Nd, Sr (in prep) study on the Dharamsala formation (Early to Middle Miocene molasse) of Northern India. The petrography and mica cooling ages show an abrupt shift in the provenance with higher\|grade metamorphic source\|rocks replaced by sedimentary and very low\|grade metasedimentary source\|rocks up\|section. The break in composition corresponds to the transition between the Lower and Upper members of the unit, which took place between 17 5 and 17Ma (depositional ages constrained by magnetostratigraphy, Maithani and Burbank unpublished data). This event, with all likelihood tectonic in nature, interrupted and reversed the unroofing trend well documented in the classic Dagshai\|Kasauli sandstone suite of the Indian foreland basin (Najman 2000) and continued through the Lower Dharamsala. In addition U\|Pb ages and Sm\|Nd ratios on single detrital monazite grain suggest three sources, High Himalayan Series which has been effected by the earliest Himalayan metamorphism, low\|grade or un\|metamorphosed High Himalayan equivalents and grains in the youngest sediments which carry ENd(0) values identical to the Lesser Himalayan Series.展开更多
Background: Relatively little data are available, particularly from the more generalizable perspective of a population- based investigation, describing recent trends in death rates due to coronary heart disease(CHD). ...Background: Relatively little data are available, particularly from the more generalizable perspective of a population- based investigation, describing recent trends in death rates due to coronary heart disease(CHD). The objectives of this observational study were to describe changes over a twelve year period(1990- 2001) in death rates due to CHD and acute myocardial infarction(AMI) in residents of the Worcester, Massachusetts, metropolitan area(2000 census=478,000). A secondary study goal was to describe changes in death rates attributed to CHD over time separately in men and in women, in persons of different ages, and according to location of death. Methods: Death datatapes were obtained from the Massachusetts Department of Public Health for greater Worcester residents who died over the period 1990 to 2001. Results: Marked declines were observed in the population death rates(per 100,000) due to CHD(1990 death rate=322; 2001 death rate=224) and AMI(1990 death rate=137; 2001 death rate=87) in the greater Worcester population. Declines in the annual death rates attributed to CHD were observed in both the hospital(4.4% decline) and out- of- hospital setting(1.6% decline) as well as for patients dying from AMI(annual declines of 4.8% and 1.9% respectively). Reductions in CHD death rates over time were observed in men and in women and in persons of all ages. Conclusions: The present results demonstrate encouraging declines in community death rates due to CHD and AMI over time and the impact of evolving primary and secondary prevention efforts.展开更多
文摘位于帕米尔前缘逆冲推覆体(Pamir Front Thrust,PFT)东端的木什滑脱背斜,是帕米尔弧形推覆构造带最前缘和最新的变形带。对地形横剖面、纵剖面和水系发育特征的分析表明,木什背斜总体上具有由西向东扩展生长的特征。在背斜核部及北翼发育数级开阔平坦的沿轴向展布的河流阶地,阶地可划分为4期。利用阶地堆积细颗粒石英光释光测年获得阶地面T2a、T3和T4的形成年龄分别为(15.8±2.40)ka、(55.1±10.3)ka、(131.4±23.9)ka。伴随背斜的生长扩展,河流阶地面发生了横向和纵向掀斜,并形成断层陡坎和褶皱陡坎。木什背斜晚第四纪的缩短和隆升主要是通过褶皱翼旋转机制进行的,估算其最小缩短速率为(1.6±0.3)mm/a,最小隆升速率为(1.9±0.3)mm/a。与此同时,沿轴向背斜发生了向东的侧向迁移和旋转。根据背斜垂直隆升与侧向扩展之间的关系,估算背斜在131～16ka期间向东的侧向迁移扩展速率较快,为(14.6±3.6)mm/a;自16ka至今,侧向迁移扩展速率迅速减小至(1.7±0.3)mm/a,背斜向东的迁移扩展可能已基本停止,而以侧向旋转为主。
基金This work was supported by the National Natural Science Foundation of China (Grant No. 49834005) the Commission of Science and Technology of China (Grant No. 96-913-07-01) and the Key Project of the Earthquake Joint Foundation (Grant No. 9507438).
文摘Relief surveying and chronology study were carried out on the deformed river terraces across the Artushi anticline belt in the northwestern Tarim Basin. The crust shortening rate of this anticline belt since late Pleistocene was calculated to be up to 5-6 mm/a. The total crust shortening rate from the northwestern Tarim Basin to southwestern Tianshan since late Pleistocene was estimated to be over 10 mm/a.
基金This work was supported by the National Natu-ral Science Foundation of China(Grand Nos.40421101,40121303,40334038).
文摘The Kunlun Pass Basin, located in the middle of the eastern Kunlun Mountains, received relatively continuous late Cenozoic sediments from the surrounding mountains, archiving great information to understand the deformation and uplift histories of the northern Tibetan Plateau. The Kunlun-Yellow River Movement, identified from the tectonomorphologic and sedimentary evolution of the Kunlun Pass Basin by Cui Zhijiu et al. (1997, 1998), is roughly coincident with many important global and Plateau climatic and environmental events, becoming a crucial time interval to understand tectonic-climatic interactions. However, the ages used to constrict the events remain great uncertainty. Here, we present the results of detailed magnetostratigraphy of the late Cenozoic sediments in the Kunlun Pass Basin, which show the basin sediments were formed between about 3.6 Ma and 0.5 Ma and the Kunlun-Yellow River Movement occurred at 1.2 to ～0.78 Ma. The lithology, sedimentary facies and lithofacies associations divide the basin into five stages of tectonosedimentary evolution, indicating the northern Tibetan Plateau having experienced five episodes of tectonic uplifts at ～3.6, 2.69－2.58, 1.77, 1.2, 0.87 and ～0.78 Ma since the Pliocene.
文摘The combined use of conventional, isotopic and geochemical techniques provides a powerful tool with which to determine sedimentary provenance, from which interpretations on Himalayan evolution and tectonics can be made.Here we present the results of conventional bulk\|composition petrography, single grain isotopic (Ar\|Ar white mica ages, U\|Pb ages and Sm\|Nd on monazite) and whole rock Sm\|Nd, Sr (in prep) study on the Dharamsala formation (Early to Middle Miocene molasse) of Northern India. The petrography and mica cooling ages show an abrupt shift in the provenance with higher\|grade metamorphic source\|rocks replaced by sedimentary and very low\|grade metasedimentary source\|rocks up\|section. The break in composition corresponds to the transition between the Lower and Upper members of the unit, which took place between 17 5 and 17Ma (depositional ages constrained by magnetostratigraphy, Maithani and Burbank unpublished data). This event, with all likelihood tectonic in nature, interrupted and reversed the unroofing trend well documented in the classic Dagshai\|Kasauli sandstone suite of the Indian foreland basin (Najman 2000) and continued through the Lower Dharamsala. In addition U\|Pb ages and Sm\|Nd ratios on single detrital monazite grain suggest three sources, High Himalayan Series which has been effected by the earliest Himalayan metamorphism, low\|grade or un\|metamorphosed High Himalayan equivalents and grains in the youngest sediments which carry ENd(0) values identical to the Lesser Himalayan Series.
文摘Background: Relatively little data are available, particularly from the more generalizable perspective of a population- based investigation, describing recent trends in death rates due to coronary heart disease(CHD). The objectives of this observational study were to describe changes over a twelve year period(1990- 2001) in death rates due to CHD and acute myocardial infarction(AMI) in residents of the Worcester, Massachusetts, metropolitan area(2000 census=478,000). A secondary study goal was to describe changes in death rates attributed to CHD over time separately in men and in women, in persons of different ages, and according to location of death. Methods: Death datatapes were obtained from the Massachusetts Department of Public Health for greater Worcester residents who died over the period 1990 to 2001. Results: Marked declines were observed in the population death rates(per 100,000) due to CHD(1990 death rate=322; 2001 death rate=224) and AMI(1990 death rate=137; 2001 death rate=87) in the greater Worcester population. Declines in the annual death rates attributed to CHD were observed in both the hospital(4.4% decline) and out- of- hospital setting(1.6% decline) as well as for patients dying from AMI(annual declines of 4.8% and 1.9% respectively). Reductions in CHD death rates over time were observed in men and in women and in persons of all ages. Conclusions: The present results demonstrate encouraging declines in community death rates due to CHD and AMI over time and the impact of evolving primary and secondary prevention efforts.
