| 塔里木盆地北部寒武纪海平面变化研究 |
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| 引用本文： | 于炳松.塔里木盆地北部寒武纪海平面变化研究[J].沉积学报,1996,14(1):33-39. |
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| 作者姓名： | 于炳松 |
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| 作者单位： | 中国科学院地球化学研究所矿床地球化学开放研究实验室 贵阳 550002 |
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| 摘 要： | 在以往的沉积学研究中，常常用剖面中的相对水深变化来讨论海平面的变化规律。本文通过对塔里木盆地北部寒武纪上超点变化曲线与肖尔布拉克地区寒武系露头剖面中相对水深变化曲线的对比研究发现，上超点变化曲线与相对水深变化曲线具有明显的差异，前者在寒武纪呈持续上升趋势，而后者除早期有一快速上升外，总体呈持续下降趋势，这说明相对水深变化虽与海平面变化存在着本质的联系，但单凭露头剖面中相对水深变化的研究是难以对海平面变化作出正确估价的，还必须综合考虑基底沉降、沉积物供给等多种因素的影响。计算机模拟结果也证实了，在碳酸盐台地的浅水处，当基底沉降速率较低时，无论是海平面上升还是下降时期，相对水深均呈现持续下降趋势。为了能从露头剖面的地层层序中来了解海平面的变化规律，本文应用作者改进后的Ｆｉｓｃｈｅｒ图解和数学方法对肖尔布拉克寒武系剖面进行了海平面变化的重建，结果发现，它们与上超点变化曲线的变化趋势完全一致。这充分说明了海平面变化对沉积层序的控制作用，同时也告诉我们，不能简单地利用露头剖面中的相对水深变化来研究地质历史时期的海平面变化规律。只有在排除了不同沉积背景上基底沉降速率和沉积物供给速率对沉积层序的控制效应后，才能从露头剖面?
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| 关 键 词： | 海平面变化 上超点变化 相对水深变化 寒武纪 塔里木盆地北部 |
| 收稿时间： | 1994-12-10 |
Study on Sea-level Change of Cambrian in Northern Tarim Basin |
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| Institution: | Institute of Geochemistry,Chinese Academy of Sciences, Guiyang. 550002 |
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| Abstract: | The study on sea-level change in geological history is one of the most important aspects in sedimentology and paleooceanography, and it is also the theoretical basis and key content of sequence stratigraphy. With the development of geoscience toward system science,the study of global sea level change has become an important frontier problem. In the study of sedimentology, we used to discuss the sea level change with the relative change of water depth in outcrop section, but the evidence from the study of seismic stratigraphy and sedimentology of Cambrian in northern Tarim Basin indicates that the relative change of water depth in outcrop section is quite different from the relative change of coastal onlap reflecting the relative sea level change. The relative change of coastal onlap got from the seismic stratigraphic research shows steady rising in Cambrian, but the relative change of water depth in outcrop section is gradually falling. Thus, it can be seen that although the relative change of water depth got from the study of outcrop section has a great deal to do with sea level change, it can not stand for sea level change completely. The reason is that the relative change of water depth is not only controlled by sea level change, and it is also controlled by basement subsidence and sediment supply, so under the condition of the same sea level change, the relative change of water depth will be quite different in the different site with different velocity of basement subsidence and sediment supply. Even if the basement subsidence is uniform in the basin, it will also change from place to place because of the different velocities of sediment supply (or productivities).Computer simulating results confirm that it is entirely possible that whether sea level is rising or falling, the water depth will decrease on the very shallow carbonate platform where the basement subsidence is relatively slow. This is because the carbonate productivity is very high and the production of carbonate sediments can keep pace with the increase of accommodation at all time, and even can exceed it at some time. As a result, the keeping-up carbonate system will generate,resulting in the decrease of water depth. In order to understand the rule of sealevel change from the outcrop section, the tendency of sea-level change has been reconstructed with the mathematical method and the developed Fischer Plot, and the results show that the reconstructed tendency of sea-level change is the same as that of the change of coastal onlap reflecting the relative change of sea-level change, which proves that the sea-level change has an important control over depositional sequences, but it is difficult to evaluate the sealevel change only on the relative change of water depth from outcrop section. It is only after removing the effects of basement subsidence and sediment productivity that the correct information of sea-level change can be obtained from the outcrop section. |
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