Thirty-five years ago, the idea of a young Qinghai-Tibetan Plateau was proposed based on a comprehensive investigation on the Qinghai-Tibetan Plateau. This hypothesis suggested that the plateau began to rise from a pl...Thirty-five years ago, the idea of a young Qinghai-Tibetan Plateau was proposed based on a comprehensive investigation on the Qinghai-Tibetan Plateau. This hypothesis suggested that the plateau began to rise from a planation surface （relict surface） that was less than 1000 m high formed during the Miocene to Pliocene. The fast uplift, i.e., the Qingzang Movement, began since -3.6 Ma, evidenced by massive molasse deposits around the plateau margin and the synchronous occurrence of faulted basins within the plateau. However, later studies challenged this idea and suggested earlier （8, 14 or 35 Ma） formation of the huge plateau topography. Here we reevaluate the Qingzang Movement on the basis of our previous results and in light of new studies in the recent decades. The plateau margin has been subjected to intensive incision by very large drainages and shows the landscape characteristics of an ＂infant＂ stage of the geomorphological cycle. However, these drainages were not formed until 1.7-1.9 Ma; headwater erosion has not yet reached the hinterland of the plateau, so the interior of Tibet is free of significant erosion despite its lofty elevation, and remains an ＂old stage＂ landform. If the mean erosion rate is equivalent to the sum of clastic and soluble discharges of the modern rivers draining the Tibetan Plateau, it should have been worn down to a lowland within 8.6 Ma, ignoring tectonic uplift and isostasy. The massive conglomerate around the plateau margin began to deposit at about 3.6 Ma, indicating an increased relief after that time. Furthermore, the Hipparion fauna sites were widely distributed, and elephants, giraffes, and rhinos were abundant in the Qaidam Basin until the early Pliocene. Cenozoic climate change alone is not able to account for the dense occurrence of Hipparion fauna, unless the paleo-elevation of Tibet was lowered. The rise of Tibet since the Qingzang Movement has had a great influence on the Asian interior aridification.展开更多
The various types of granite landforms in the Huangshan Mt. are distributed in a concentric pattern. The remaining parts of the planation surface are in the center; domical peaks, castle peaks, pointed peaks, and ridg...The various types of granite landforms in the Huangshan Mt. are distributed in a concentric pattern. The remaining parts of the planation surface are in the center; domical peaks, castle peaks, pointed peaks, and ridges are arranged from the center to the periphery accordingly. This reveals that knick points are still near the center and the center area is the common divide of the radial water system. It is inferred that the granite bodies in the Huangshan Mt. were exposed to erosion in Miocene and Pliocene, and the planation surface was also formed then. After the slight uplift in late Pliocene, a light-incised surface was formed. Then, in early Quaternary, there were intense uplifts and incisions so that deep incised surface was formed. The above process is still in progress, and results in high peaks and deep gorges outside of the center area. However, due to the limited catchment area in the center, headward erosion is mild, and the current landforms in the Huangshan Mt. can be maintained for a long time.展开更多
基金supported by the National Natural Science Foundation of China(Grant Nos.41330745,41171014&41271017)the Priority Academic Program Development of Jiangsu Higher Education Institutions
文摘Thirty-five years ago, the idea of a young Qinghai-Tibetan Plateau was proposed based on a comprehensive investigation on the Qinghai-Tibetan Plateau. This hypothesis suggested that the plateau began to rise from a planation surface （relict surface） that was less than 1000 m high formed during the Miocene to Pliocene. The fast uplift, i.e., the Qingzang Movement, began since -3.6 Ma, evidenced by massive molasse deposits around the plateau margin and the synchronous occurrence of faulted basins within the plateau. However, later studies challenged this idea and suggested earlier （8, 14 or 35 Ma） formation of the huge plateau topography. Here we reevaluate the Qingzang Movement on the basis of our previous results and in light of new studies in the recent decades. The plateau margin has been subjected to intensive incision by very large drainages and shows the landscape characteristics of an ＂infant＂ stage of the geomorphological cycle. However, these drainages were not formed until 1.7-1.9 Ma; headwater erosion has not yet reached the hinterland of the plateau, so the interior of Tibet is free of significant erosion despite its lofty elevation, and remains an ＂old stage＂ landform. If the mean erosion rate is equivalent to the sum of clastic and soluble discharges of the modern rivers draining the Tibetan Plateau, it should have been worn down to a lowland within 8.6 Ma, ignoring tectonic uplift and isostasy. The massive conglomerate around the plateau margin began to deposit at about 3.6 Ma, indicating an increased relief after that time. Furthermore, the Hipparion fauna sites were widely distributed, and elephants, giraffes, and rhinos were abundant in the Qaidam Basin until the early Pliocene. Cenozoic climate change alone is not able to account for the dense occurrence of Hipparion fauna, unless the paleo-elevation of Tibet was lowered. The rise of Tibet since the Qingzang Movement has had a great influence on the Asian interior aridification.
基金Supported by the National Natural Science Foundation of China (Grant No. 40701017)
文摘The various types of granite landforms in the Huangshan Mt. are distributed in a concentric pattern. The remaining parts of the planation surface are in the center; domical peaks, castle peaks, pointed peaks, and ridges are arranged from the center to the periphery accordingly. This reveals that knick points are still near the center and the center area is the common divide of the radial water system. It is inferred that the granite bodies in the Huangshan Mt. were exposed to erosion in Miocene and Pliocene, and the planation surface was also formed then. After the slight uplift in late Pliocene, a light-incised surface was formed. Then, in early Quaternary, there were intense uplifts and incisions so that deep incised surface was formed. The above process is still in progress, and results in high peaks and deep gorges outside of the center area. However, due to the limited catchment area in the center, headward erosion is mild, and the current landforms in the Huangshan Mt. can be maintained for a long time.
