原始網址www.sciencedaily.com/releases/2016/08/160823083555.htm
New insights into the relationship between erosion and tectonics in the Himalayas
研究人員對喜瑪拉雅地區侵蝕作用和構造運動之間的關係做出了最新觀點
Earth's
climate interacts with so called surface processes -- such as
landslides or river erosion -- and tectonics to shape the landscape
that we see. In some regions, the sheer force of these processes has
led scientists to believe that they may even influence the
development of tectonics. An international team of researchers headed
by the Cologne-based geographer Dr. Georgina King have now disproved
this assumption. The results of their study, "Northward
migration of the eastern Himalayan syntaxis revealed by
OSL-thermochronometry," will appear in Science on
19 August 2016.
地球氣候會跟所謂的地表作用，像是山崩或河流侵蝕，以及形塑我們所見地貌的板塊構造運動這兩者之間產生交互作用。在某些上述作用極為盛行的地區，科學家認為它們甚至能影響當地構造運動的發育過程。由柯隆大學的地理學家
Georgina
King博士領導的國際研究團隊卻否定了這項假說。他們的研究成果「光激發光熱定年法顯示東喜馬拉雅構造結正往北方遷移」(Northward
migration of the eastern Himalayan syntaxis revealed by
OSL-thermochronometry)將會刊登於2016年8月19日的期刊《科學》(Science)之上。
In
the eastern Himalaya, mountains exceeding 7,000 meters are
coincident with extremely powerful rivers such as the
Yarlung-Tsangpo, which is known as the "Everest of Rivers"
and runs through the deeply incised Tsangpo gorge. "In this
region the dramatic topography coupled with highly erosive rivers
means that if surface processes can control tectonics, we should be
able to record it here," says King.
喜馬拉雅山東部地區同時有超過海拔7000公尺的群山以及極端湍急的河流，像是雅魯藏布江分布其中。這些流經險峻的雅魯藏布大峽谷的河川又被稱作「河川界的聖母峰」。「此地區同時擁有劇烈起伏的地形和侵蝕能力極強的河川，代表如果地表作用可以控制構造運動，我們應該能在此找到紀錄證實這項說法。」King說。
Dr.
Georgina King heads the luminescence laboratory at the University of
Cologne's Institute of Geography. She and her team used a new
technique called luminescence thermochronometry to measure the
cooling histories of rocks as they move towards the Earth's surface
(exhumation). Their research revealed that surface processes do not
control the location of tectonic deformation, but rather are
responding to changing tectonics. The team measured the most recent
stages of exhumation, that is, the final 1-2 km of the Earth's
crust, which have risen to the surface over approximately the past 1
million years. In geological terms this is a quite recent period.
The results show that in this time period, the rate of exhumation in
the northward part of the eastern Himalayas increased. The
scientists compared this record to plausible climatic and tectonic
explanations. Using their data and data from other studies, they
were able to show that this increased exhumation rate reflected
tectonic changes and associated changes in river shape. "Our
findings fit very well with previous hypotheses for this region,
namely that there is tectonic, rather than climatic control over the
pattern of erosion rates," King notes.
Georgina
King博士領導了位於科隆大學地理研究所的螢光實驗室。她和她的研究團隊利用稱作「螢光熱定年法」(luminescence
thermochronometry
)的嶄新科技來測量當地底的岩石逐漸往地表前進(即剝蝕作用，exhumination)時，其冷卻歷程有什麼樣的變化。他們的研究顯示地表作用並不能控制構造運動在哪些地點產生變形，反之，地表作用會因構造運動的改變而隨之變化。研究團隊測量了最近一段剝蝕作用的歷程，也就是地殼最上方1至2公里處。這段地殼約莫是在過去1百萬年之內才隆昇到地表，在地質術語中可是相當近期的事件。結果顯示在這段期間，東喜馬拉雅山北側的剝蝕速率有增加的趨勢。科學家試圖將這份紀錄比對出合理的構造運動或氣候成因的解釋。利用他們自身以及其他研究得出的數據，他們認為剝蝕速率增加反映了當地構造運動的變化及伴隨產生的河道地形改變。「我們的發現跟之前對此地區的研究推論出的假說相當一致，也就是侵蝕速率的模式是受到構造運動控制，而非氣候因素。」
King強調此點。
Since
surface processes can also influence the carbon cycle, this new
research technique can also make valuable contributions to climate
research. "As we improve our understanding of the role of
surface processes in the dynamic evolution of mountains, it will
give us insights into the associated carbon fluxes and how these
influence global climate," King concludes.
既然地表作用也會影響到碳循環，這種新穎的研究方法對氣候研究來說也具有相當重大的貢獻。「隨著我們對地表作用在山脈動態演化過程中扮演的腳色有更深的認知，這些成果也能讓我們瞭解碳通量會如何隨著構造運動和地表作用變化，以及它們對全球氣候會造成什麼樣的影響。」
King總結。
引用自：University
of Cologne. "New insights into the relationship between
erosion and tectonics in the Himalayas." ScienceDaily.
ScienceDaily, 23 August 2016.
論文來源：G. E. King, F. Herman, B. Guralnik. Northward migration of the eastern Himalayan syntaxis revealed by OSL thermochronometry. Science, 2016; 353 (6301): 800
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