Comparative sedimentology between greenhouse and icehouse stratigraphic successions

丘状交叉层积被认为是风暴主导的浅海环境下的诊断性沉积构造之一。一般来说，丘状交叉层的波长随风暴层厚的增加而增加。在风暴层内，丘状交叉层的波长向上减少，这种关系可能对应于风暴波减弱阶段轨道直径的减少。此外，基于鞋底标记的古风暴流方向随着风暴层厚度的增加而与古海岸线趋于正交，这种关系可能反映了随着风暴强度的增加海岸设置程度的提高。因此，丘状交叉分层的波长被解释为海底附近风暴引起的振荡流的轨道直径的函数，其中许多反映了风暴的强度。在这里，我研究了丘状交叉分层波长的时间变化，作为显生宙风暴强度的代表。显生宙的丘状交叉层理波长呈现长期变化，在中白垩世和晚泥盆世有两个主峰，在早侏罗世和晚奥陶世有两个次峰。这些长期变化在很大程度上与全球环境变化的主要温室和冰窖周期相对应。然而，丘状交叉分层波长的峰值比独立估计的全球温度长期波动的主要暖期早或晚。这些时间滞后被解释为表明风暴加剧的阈值条件发生在全球气温极端变暖之前和之后的某个时间。研究结果表明，在未来全球变暖的最大阶段之前和/或之后，风暴强度将是最高的。少

Hummocky cross-stratification is believed to be one of diagnostic sedimentary structures in a storm-dominated shallow marine environment. In general, the wavelength of hummocky cross-stratification increases with the increase in bed thickness of tempesties. Within a tempestie bed, the wavelength of hummocky cross-stratification decreases upsection and this relationship may correspond to the decrease in the orbital diameters during the waning stage of storm waves. Furthermore, paleoflow directions of tempesties, which were investigated on the basis of sole marks, tend to more orthogonal relative to the paleo-shorelines with the increase in bed thickness of tepmestites and this relationship may reflect higher degree of coastal setup in response to the increase in storm intensities. Therefore, the wavelength of hummocky cross-stratification is interpreted to be a function of the orbital diameters of storm-induced oscillatory currents near sea floors and many reflect the intensity of storm … More waves. Here I investigated temporal variation in the hummocky cross-stratification wavelength as a proxy for the storm intensity through the Phanerozoic. The hummocky cross-stratification wavelength shows secular changes though the Phanerozoic with two major peaks at middle Cretaceous and late Devonian, together with two other secondary peaks at early Jurassic and late Ordovician. These secular changes largely correspond to major greenhouse-and-icehouse cycles of global environmental changes. The peaks of the hummocky cross-stratification wavelength, however, are earlier or later than major warmer periods of independently estimated long-term fluctuation in the global temperatures. These time lags are interpreted to indicate that the threshold conditions for the intensification of storms occurred at some times before and after the extreme warmth of global temperatures. The outcome of this study suggests that the storm intensity would be the highest before and/or after the maximum stage of the global warming with an ongoing greenhouse phase in future. Less