| 黔东湘西寒武纪碳酸盐台地边缘和斜坡沉积特征及大陆边缘构造性质讨论 |
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| 引用本文：叶红专.1991.黔东湘西寒武纪碳酸盐台地边缘和斜坡沉积特征及大陆边缘构造性质讨论[J].地球学报,12(2):13-22. |
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| 中文摘要:本文研究了寒武纪台地边缘和斜坡沉积特征、沉积模式演化及与扬子板块东南缘构造演化的关系,认为该区从寒武纪到早奥陶世为长期发育以加积和推进为主的碳酸盐台地;该区长期处于稳定下沉的构造背景,说明扬子板块东南缘已进入成熟被动陆缘阶段。在台地和斜坡上形成向上变浅或向上先变粗后变细的沉积旋回。并着重论述了斜坡碎屑流沉积类型、特征和成因机制;其碳酸盐碎屑流主要为复合支撑机制,其流动过程中普遍存在脉动性或波动性及流动转化现象;系统建立了寒武纪台地边缘模式及演化序列;探讨了板块构造演化与成矿作用关系,指出湘黔汞矿带、铅锌矿带可能与逆冲席有关。 |
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| EVOLUTION OF THE CAMBRIAN CARBONATE PLATFORM MARGIN AND SLOPE IN EAST GUIZHOU AND WEST HUNAN,——RELATIONSHIP TO TECTONICS OF YANGTZE CONTINENTAL MARGIN |
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| Abstract:Carbonate platforms tend to grow near to sea level. Thus they record the combined history of subsidence and sealevel fluctuation on passive mar- gins. Sedimentologyntology research on the Cambrian carbonate platform margin and slope in east Guizhou and west Hunan provides detailed information on subsidence history of the south-east passive margin of the Yangtze Plate as well as on sedimentary models and evolution of the margin. Main results are:1. The Cambrian and lower Ordovician carbonate platform developed on an underlying siliclastic shelf. The evolution of carbonate platform can be divided into four stages: ( 1 ) ramp evolved into steepened ramp. ( 2 ) initially drowned platform rapidly evolved into ramp, followed by accrestionary platform. ( 3 ) plalform covered by terrigenous influx rapidly evolved into ramp. followed by accretionary platform and finally by-pass margin platform. ( 4 ) by-pass margin platform evolved into a ccretionary platform.2. The Cambrian to lower Ordovician carbonate platform margin aggraded and prograded throughout this time, reflecting steady tectonic subsidence and suggesting that the south-east margin evolved into mature passive margin through crust thinning and subsidence.3. The favourable tectonic setting and climate resulted in a shallowing-upward megacycle that first coarsens upward, then fines upward. A deeper water ramp or slope shallowing upward into a marginal shoal, and eventually lagoon and tidal flats formed on platform. A coarsing and thickening upward megacycle formed on slope.4. The progradation of platform margin shifted the shelf break eastward and seaward. As a result. calcirudites of the slope cycle rise eastward.5. Episodic and uneven progradation of the platform margin produced a variety of secondary cycles of different duration.,Position, and extent.6. The geometry of slope deposits indicates development of a slope apron as well as a bass-of-slope apron in the early late Cambrian and a debris sheet at the end of the Cambrian.7. Various mud and ciast-supported fabries of debris flow sediments, and calculations of debris static sterength and paleoslope gradients show a variety of support mechanism. Pulsating movement and flow transformation to turbidity currents as well as slide transformation to flows were common in the submarine carbonate debris flows. |
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