Recovery of strain rate variation from inversion of subsidence data
Recovery of strain rate variation from inversion of subsidence data
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作者：
N. White
尽管在过去20年中我们对大陆岩石圈变形的理解取得了相当大的进展（例如，参见参考文献1和2），但我们对地质相关尺度（~ 102 ~ 104km和~ 1 ~ 1亿年）应变率的详细时空变化知之甚少。这些测量需要约束岩石圈变形的动态模型。虽然目前尚不清楚如何从山带获得详细的应变率信息，但沉积盆地的沉降数据至少应该包含应变率张量的垂直分量信息。在这里，我展示了逆理论可以用来计算时间应变率变化，以适应在伸展沉积盆地观测到的沉降模式。不需要关于裂谷持续时间或总应变的优先信息。反计算可以很好地拟合合成数据和意大利北部白云岩的沉降数据。计算的应变率不是恒定的，而是在10−18和10−15s−1之间变化。误差分析表明，这些结果是显著的，很好地解决了。所有研究的地层剖面在伸展期间都表现出最小的应变速率，这是由幂律蠕变岩石圈变形模型预测的特征。
DESPITE considerable advances over the past 20 years in our understanding of continental lithospheric deformation (see, for example, refs 1 and 2), we know little about the detailed spatial and temporal variations in strain rate at geologically relevant scales (∼102−104km and ∼1–100 million years). Such measurements are needed to constrain dynamic models of lithospheric deformation3. Although it is not yet obvious how detailed strain-rate information can be obtained from mountain belts, subsidence data from sedimentary basins should contain information about at least the vertical component of the strain-rate tensor. Here I show that inverse theory can be used to calculate the temporal strain rate variation needed to fit observed subsidence patterns in extensional sedimentary basins. Noa prioriinformation concerning either the duration of rifting or the total strain is required. Inverse calculations produce good fits to synthetic data and to subsidence data from the Dolomites of northern Italy. Calculated strain rates are not constant but vary between 10−18and 10−15s−l. Error analysis shows that these results are significant and well resolved. All of the stratigraphic sections studied exhibit a minimum in strain rate during extension—a feature predicted by models of lithosphere deformation by power-law creep.