Origin of terra rossa on Amdo North Mountain on the Tibetan plateau, China : Evidence from quartz(Soil Genesis, Classification and Survey)

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Terra rossa was found overlying limestone on a planar erosion surface at approximately 5100m on the summit of Amdo North Mountain on the Tibetan Plateau. The present study examined the quartz content, size distribution of the quartz grains, mineral composition, oxygen isotope ratios in the quartz, surface micro-texture and crystal morphology of the quartz in the terra rossa and its potential source rocks to determine the derivation of the terra rossa. The results indicated that the component of the terra rossa on Amdo North Mountain is a mixture of weathering products from the underlying limestone, the overlying red sandy limestone and the adjacent limestone breccia. These different parent materials can result from being introduced under gravity and other mass transport during geological epoch. Therefore, the terra rossa on Amdo North Mountain is primarily a transported sedimentary deposit, not an in situ weathering solum. The source of much of the terra rossa is likely to be weathering products on adjacent uplands under paleo-landform frame. Multiple sources appear responsible for the terra rossa on Amdo North Mountain. Eolian dust, however, does not appear to have provided a significant addition to the terra rossa formation on Amdo North Mountain.