Abstract

The history of the crustal subsidence in the Mesozoic and Cenozoic in the West Siberian Basin – the largest sedimentary basin in the world is considered. Most researchers associate its formation with post-rift crustal subsidence, which followed an episode of strong lithospheric stretching about 250 Ma ago at the Permian–Triassic transition. A characteristic feature of post-rift subsidence is a decrease in its rate in time. During the Mesozoic–Cenozoic history, the crustal subsidence rate in Western Siberia should have decreased by an order of magnitude. However, the analysis of long (700–900 km) seismic profiles in the north of Western Siberia and in the Southern Kara Sea shows that, on average, there has been an acceleration of the crustal subsidence since the beginning of the Mesozoic in these regions. Under such conditions, lithospheric stretching in them could be responsible for only a small fraction of the total crustal subsidence by 6–7 km. In Western Siberia, the crust is close to the isostatic equilibrium. Due to this, in the absence of strong stretching, the accumulation of thick sedimentary sequences in the basin could only have been caused by rock contraction in the lower crust due to prograde metamorphic reactions. To obtain the above results, we used some simple methods for the first time to analyze the structure of the sedimentary sequences in the West Siberian Basin. Detailed seismic profiles for many other deep basins on all the continents have been published. The methods of their interpretation implemented in the present paper can be easily applied to determine the role of lithospheric stretching in the formation of deep sedimentary basins on the global scale.

中文翻译：

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下地壳进行变质作用引起的岩石收缩引起西西伯利亚沉积盆地地壳沉降

摘要

考虑了世界上最大的沉积盆地西西伯利亚盆地中生代和新生代地壳沉降的历史。大多数研究人员将其形成与裂谷后地壳沉降联系起来，这是在大约 250 Ma 前的二叠纪-三叠纪过渡期间发生的一次强烈的岩石圈拉伸事件之后发生的。裂谷后沉降的一个特征是其速率随时间的减少。在中、新生代历史中，西西伯利亚的地壳沉降速度应该减少了一个数量级。然而，对西西伯利亚北部和南喀拉海的长（700-900公里）地震剖面的分析表明，平均而言，自中生代开始以来，这些地区的地壳沉降一直在加速。 。在这种情况下，岩石圈的拉伸只能导致地壳总沉降 6-7 公里的一小部分。在西西伯利亚，地壳接近均衡状态。因此，在没有强烈拉伸作用的情况下，盆地内厚层沉积层序的堆积只能是由于进行性变质反应导致下地壳岩石收缩所致。为了获得上述结果，我们首次利用一些简单的方法对西西伯利亚盆地沉积层序的结构进行了分析。各大洲许多其他深盆地的详细地震剖面均已出版。本文所采用的解释方法可以很容易地应用于确定岩石圈拉伸在全球范围内深层沉积盆地形成中的作用。