Fission-track dating evidence from 5 apatite samples and 4 zircon samples, and modeled time-temperature thermal history indicate that since Late Jurassic-Cretaceous (150-106 Ma), the uplift process of Mt. Bogda can be...Fission-track dating evidence from 5 apatite samples and 4 zircon samples, and modeled time-temperature thermal history indicate that since Late Jurassic-Cretaceous (150-106 Ma), the uplift process of Mt. Bogda can be divided into four stages of thermal evolution: 150-106, 75-65, 44-24 and 13-9 Ma. Before 44-24 Ma, the cooling rate and uplifting rate of the southern and northern segments of Mt. Bogda are almost the same, showing that the uplifting of Mt. Bogda is an overall process. Since 44-24 Ma, the uplifting of the southern and northern segments of Mt. Bogda has shown differences. During 42-11 Ma, the northern segment of Mt. Bogda was at a steady stage, with the cooling rate being {0.03℃/Ma} and the uplifting rate being {0.001} mm/a. From 11 Ma to the present, the northern segment of Mt. Bogda was at a rapid cooling and uplifting stage, with the cooling rate being {5.72℃/Ma} and the uplifting rate being {0.19} mm/a. However, the southern segment of Mt. Bogda has been at a rapid cooling and uplifting stage since 26 Ma, with the cooling rate being {1.24℃/Ma} and the uplifting rate being {0.041} mm/a during 26-9 Ma; {4.88℃/Ma} and {0.163} mm/a from 9 Ma till now.展开更多
Glacial features in the geological record provide essential clues about past behavior of climate. Of the numerous physical systems on earth, glaciers are one of most responsive to climate change, especially small glac...Glacial features in the geological record provide essential clues about past behavior of climate. Of the numerous physical systems on earth, glaciers are one of most responsive to climate change, especially small glaciers, their direct marginal response taking only a few years or decades to be expressed. Accelerating recession of modern glaciers raises the issue of the climate＇s impact on water runoff. Data based on topographic maps and Advanced Spaceborne Thermal Emission and Radiometer （ASTER） imagery show the trends that are highly variable over time and within the region. An analysis of the local topographic settings of very small （〈0.5 km2） glaciers was conducted to investigate their influence on recent changes in these glaciers. Among 137 glaciers, 12 disappeared completely. The study reveals that glaciers situated in favorable locations had tiny relative area reduction, while those in less favorable settings generally had large area loss or even disappeared. It is suggested that most of the small glaciers studied have retreated as far as they are likely to under the climatic conditions of the late 20th century. Undoubtedly, the strong retreating of small glaciers exerts adverse effects on the hydro- logic cycle and local socioeconomic development.展开更多
文摘Fission-track dating evidence from 5 apatite samples and 4 zircon samples, and modeled time-temperature thermal history indicate that since Late Jurassic-Cretaceous (150-106 Ma), the uplift process of Mt. Bogda can be divided into four stages of thermal evolution: 150-106, 75-65, 44-24 and 13-9 Ma. Before 44-24 Ma, the cooling rate and uplifting rate of the southern and northern segments of Mt. Bogda are almost the same, showing that the uplifting of Mt. Bogda is an overall process. Since 44-24 Ma, the uplifting of the southern and northern segments of Mt. Bogda has shown differences. During 42-11 Ma, the northern segment of Mt. Bogda was at a steady stage, with the cooling rate being {0.03℃/Ma} and the uplifting rate being {0.001} mm/a. From 11 Ma to the present, the northern segment of Mt. Bogda was at a rapid cooling and uplifting stage, with the cooling rate being {5.72℃/Ma} and the uplifting rate being {0.19} mm/a. However, the southern segment of Mt. Bogda has been at a rapid cooling and uplifting stage since 26 Ma, with the cooling rate being {1.24℃/Ma} and the uplifting rate being {0.041} mm/a during 26-9 Ma; {4.88℃/Ma} and {0.163} mm/a from 9 Ma till now.
基金supported by the National Basic Research Program of China (No. 2010CB951003)the Knowledge Innovation Project of the Chinese Academy of Sciences (No. KZCX2-EW-311)the National Natural Science Foundation of China (Nos. 1141001040, J0930003/J0109)
文摘Glacial features in the geological record provide essential clues about past behavior of climate. Of the numerous physical systems on earth, glaciers are one of most responsive to climate change, especially small glaciers, their direct marginal response taking only a few years or decades to be expressed. Accelerating recession of modern glaciers raises the issue of the climate＇s impact on water runoff. Data based on topographic maps and Advanced Spaceborne Thermal Emission and Radiometer （ASTER） imagery show the trends that are highly variable over time and within the region. An analysis of the local topographic settings of very small （〈0.5 km2） glaciers was conducted to investigate their influence on recent changes in these glaciers. Among 137 glaciers, 12 disappeared completely. The study reveals that glaciers situated in favorable locations had tiny relative area reduction, while those in less favorable settings generally had large area loss or even disappeared. It is suggested that most of the small glaciers studied have retreated as far as they are likely to under the climatic conditions of the late 20th century. Undoubtedly, the strong retreating of small glaciers exerts adverse effects on the hydro- logic cycle and local socioeconomic development.
