Tibetan Uplift
Wednesday, 26. March 2008, 16:24:42
Let me just quote the Concluding Remarks from the paper:
We propose a temporally and spatially differential surface-uplift history of the Tibetan Plateau . Our integrated study suggests that the central plateau (the Lhasa and southern Qiangtang terranes) was uplifted by the Late Paleogene. A high proto-Tibetan Plateau may have contributed to climatic changes farther north in central Asia. Intriguingly, this timing also corresponds to a period of pronounced global cooling and changes in ocean chemistry. The plateau subsequently expanded as a result of the continued northward collision of India with Asia. To the south, the Himalayan rose during the Neogene. To the north, the Qilian Shan rapidly uplifted in the Late Cainozoic. These ranges constitute the modern southern and northern margins, respectively, of the Tibetan Plateau.
Late Paleogene - The Paleogene period ended around 23 million years ago
Neogene - The Neogene period started around 23 million years ago
Late Cainozoic - The Cainozoic Era covers the 65.5 million years since the Cretaceous–Tertiary extinction event at the end of the Cretaceous that marked the demise of the last non-avian dinosaurs and the end of the Mesozoic Era. The Cainozoic era is ongoing. The Cainozoic is divided into two periods, the Paleogene and Neogene.
The surface uplift history of the Tibetan Plateau and Himalaya is among the most interesting topics in geosciences because of its effect on regional and global climate during Cainozoic time, its influence on monsoon intensity, and its reflection of the dynamics of continental plateaus.
One of the many analytical techniques used in the study was Fission Track Analyses. This technique seems to have become quite popular lately - at least in many of the papers I have been reading. Apatite fission track analysis has become an important and successful tool in low-temperature thermochronology and during the last decade it became applied in numerical tectonic modelling, assessing tectonic hazards, landscape development, tectonic geomorphology, dating processes of mountain building, hydrocarbon exploration, sedimentary burial history, and much more.
Here is a paragraph from Wikipedia’s article on Fission Track Dating:
Fission track dating is a radiometric dating technique based on analyses of the damage trails, or tracks, left by fission fragments in certain uranium bearing minerals and glasses. Uranium-238 undergoes spontaneous fission decay at a known rate. The fragments emitted by this fission process leave trails of damage in the crystal structure of the minerals enclosing the uranium. Etching of polished surfaces of these minerals reveals the spontaneous fission tracks for counting by optical microscopic means. The number of tracks correlates directly with the age of the sample and the uranium content. To determine the uranium content the sample is annealed by heating and exposed to a barrage of thermal neutrons. The neutron bombardment produces an induced fission of the uranium-235 in the sample and the resulting new induced tracks are used to determine the uranium content of the sample as the U-235:U-238 ratio is well known. Alternatively, a uranium-free piece of mica, the external detector, is attached to the sample and both sample and mica are exposed to a barrage of thermal neutrons. The resulting induced fission of the uranium-235 in the sample creates new induced track in the external detector, which are revealed by etching. The ratio of spontaneous tracks to induced tracks is proportional to the age.
• http://paleochick.blogspot.com/2008/03/new-findings-from-tibetan-plateau.html
• http://www.terradaily.com/reports/New_Findings_From_Tibetan_Plateau_Suggest_Uplift_Occurred_In_Stages_999.html
• http://www.physorg.com/news125598631.html
• http://geology.cr.usgs.gov/capabilities/gronemtrac/geochron/fission/tech.html
• http://www.mnsu.edu/emuseum/archaeology/dating/dat_fission.html













