Computer Simulation of Carbonate Sequences
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摘要: 本文运用一个作用—响应模式，模拟了在各种不同的海平面变化和基底沉降速率条件下，在碳酸盐台地上不同部位的沉积作用响应，从而对影响碳酸盐岩层序形成的各要素之间的相互作用作出了定量解释。通过模拟可知，在基底沉降速率一定的前提下，碳酸盐岩层序的形成受控于海平面的变化，且碳酸盐岩层序的形成对于海平面变化响应的敏感性随着水深的增加而降低；一个完整的三级海平面变化旋回在地质记录中的反映，由于其所处的沉积背景不同而呈现出明显的差异；三级海平面变化幅度对碳酸盐岩层序的形成也有明显的控制作用。形成近对称三级旋四层序的先决条件是基底沉降速率必须很低，因此，近对称三级层序可认为是稳定克拉通背景的一个鉴别标志。Abstract: The formation of carbonate sequences is mainly controlled by the sea level change and subsidence of basement. Accordingly, we can construct a theoretical model (process model) to simulate the response of sedimentation at different sites on a shallow carbonate platform under the conditions of different sea-level changes and different subsidence rates of basement, so that we can understand the interaction among the factors affecting the formation of carbonate sequences. We can get some important conclusions from simulations. Under the premise of the definite subsidence rate of basement, the formation of carbonate sequences is controlled by sealevel change, and the sensitivity of its response to sea-level change decreases with water depth, so the meter-scale carbonate cycles forming on the different settings can not be compared with each other simply. The reflection of a third-order sea-level change cycle in geologic record is quite different on different depositional settings. Under the deep water, the relative water depth will show continuously falling, and under the shallow water, rising. So, if we want to construct a relative sea-level change curve about the whole basin or the globe depending on outerop or boring sections, we have to select proper sections where the relative sea-level change can be recognized from the geologic record, otherwise the comparison of relative sea-level changes will be impossible. The amplitude of the third-order sea-level change also affects the sequence, and the carbonate strata with high-frequent forth or fifth-order cycles certainly develop under the conditions of middle to low amplitude of the third-order sea-level change. If the third-order sequence is nearly symmetric, it is certain that the subsidence rate is very low, so the nearly symmetric third-order sequence is a token of a craton basin.
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Key words:
- carbonate /
- sequence /
- sea level change
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