Wostbrock, Jordan A. G.Planavsky, Noah J.Korenaga, JunGuo, Meng...
12页
查看更多>>摘要：There has been extensive debate about how to link sedimentary oxygen isotope records to changes in solid Earth and surface processes. We present a new model of coupled ocean-crust-mantle evolution to investigate the geological processes that are responsible for the evolution of seawater delta O-18 values. In our model, the rates of low-and high-temperature crustal alteration are constrained by mantle cooling and crustal evolution. This way, we were able to outline the possible path of solid Earth evolution that matches the observed seawater delta O-18 records. Our results suggest that marine delta O-18 values may have been as low as -10 parts per thousand to -5 parts per thousand in the late Archean. The corresponding delta'(17O) value may have been 0.015 parts per thousand +/- 0.01 parts per thousand in the late Archean and then decreased with time. The evolution of seawater delta O-18 is shown to be sufficiently sensitive to the history of continental formation, and our modeling suggests the presence of a considerable amount of continental crust in the early Archean. (C) 2022 Elsevier B.V. All rights reserved.
查看更多>>摘要：Both artificial and natural hydrosphere changes can impact regional seismicity. In the Three Gorges Reservoir (TGR) area, because of human regulation, the reservoir water level and natural rainfall show opposite seasonal patterns: when the reservoir water level is high, the precipitation amount is low, and vice versa. To investigate whether these artificial and natural factors are related to regional spatiotemporal seismicity and, if they are, to reveal the possible mechanisms, we used statistical analysis and calculated changes in stresses and pore fluid pressures due to these factors. We found that, based on the distances of the epicenters to the TGR, earthquakes can be divided into two groups: those occurring within 0-12 km and those occurring within 32-70 km. Our results show that the reservoir water-level fluctuation influences the seismicity near the TGR (0-12 km), resulting in fewer earthquakes in summer and more in winter. Stress changes caused by the elastic response to water loading play an important role in this trend. In contrast to the seasonal pattern of near-TGR seismicity, earthquakes far from the TGR (32-70 km), to some extent, show opposite pattern: more in summer and less in winter. Furthermore, we found that seismic productivity far from the TGR (32-70 km) is moderately correlated with seasonal precipitation. But it cannot be explained by the precipitation-induced pore pressure variations.(c) 2022 Elsevier B.V. All rights reserved.
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Elsevier