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GEOLOGY AND KARST PROCESSES OF GUANGXI PROVINCE, CHINA Erica Xu

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GEOLOGIC SETTING

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China's 3-step topographic zonationChina's 3-step topographic zonation

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GENERAL ORIGINS Chemistry CO 2 + H 2 O H 2 CO 3 H + + HCO 3 - H + + CaCO 3 Ca 2+ + (HCO 3 ) - CaCO 3 + H 2 O + CO 2 Ca 2+ + 2HCO 3 -

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Climates

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Rainfall

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Bedrock High purity: limestone and dolostoneHigh purity: limestone and dolostone Compactness: highly durable of mechanical weatheringCompactness: highly durable of mechanical weathering

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KARST FEATURES AND LANDFORMS Karst ValleysKarst Valleys Allogenic valleysAllogenic valleys Blind and dry valleysBlind and dry valleys Pocket valleysPocket valleys

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Fenglin (tower karst) Fengcong (cockpit karst) Karst TowersKarst Towers

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Fenglin (tower karst)

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(1)(1) A huge thickness of limestone (2)(2) A layer of alluvium overlying the limestone of a karst plain (3)(3) A water table that is stable and is maintained at the level of the karst plain (4)(4) Major inflows of water and clastic sediment that can recharge and maintain the alluvial plain (5)(5) Slow tectonic uplift that matches surface denudation (6)(6) Equilibrium between rates of surface lowering and lateral planation Requirements for FenglinRequirements for Fenglin

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Fengcong (cockpit karst)

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Cockpit karst in JamaicaCockpit karst in Jamaica

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Natural Bridges e.g., Elephant Rock