Andean Plateau Geology related to Pliocene Climate. The carving of canyons into the mountainside has

Andean Plateau Geology related to Pliocene Climate.The carving of canyons into the mountainside has long been interpreted by geologists as a result of the process of uplift and weathering, but new evidence has suggested that in the Andean Plateau region, climate change has also played a roll.Richard O. Lease and Professor Todd A. Ehlers of the Department of Geosciences of the University of Tübinge analysed a series of canyons and incisions along the Eastern margin of the Andean Plateau using geochemical methods. They looked at grains of zircon and apatite using a technique known as uranium-thorium-helium thermochronology. This method looks at the rate of decay of Uranium and Thorium to Helium. As the rocks creating the mountains cool and are uplifted they begin to cool. The minerals zircon and apatite “store” helium within their crystal structure and it works as a geological clock. Measuring the amounts of Uranium, Thorium and Helium within the crystal structure can reveal the age of cooling.Using this technique, the authors have found that the Miocene (23.03-5.332Ma) period of uplift and faulting was followed by a period of incision 4-3Ma. This period of incision correlates to a shift in global climate from early Pliocene warming to late Pliocene cooling. The authors believe that a global cooling trend and lowered sea surface temperatures enhanced the transport of moisture to the Andean Plateau. This in turn increased rates of river erosion leading to deeper canyons being carved.The geochemical methods used for this study have allowed the authors to pin-point the timing of increased rates of river incision; the results show that several canyons along the 1250km stretch of Plateau studied were formed during the Pliocene period, and it is the authors conclusion that a global shift in temperature across the Pliocene was responsible for Canyon incision in the Eastern Margin of the Andean Plateau.-LLLinks;http://www.sciencedaily.com/releases/2013/08/130816094639.htmhttp://www.alphagalileo.org/ViewItem.aspx?ItemId=133731&CultureCode=enhttp://www.sciencemag.org/content/341/6147/774Image Javier Etcherverry__ -- source link

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