Adjoint models of mantle convection with seismic, plate motion, and stratigraphic constraints: North America since the Late Cretaceous
Adjoint models of mantle convection with seismic, plate motion, and stratigraphic constraints: North America since the Late Cretaceous
复制标题
DOI：
10.1029/2008gc002345
复制
发表时间：
2009-05
期刊：
影响因子：
3.7
通讯作者：
S. Spasojević;Lijun Liu;M. Gurnis
中科院分区：
文献类型：
--
作者：
S. Spasojević;Lijun Liu;M. Gurnis
我们将晚白垩世以来的地幔对流伴随模式应用于北美洲。现今的地幔结构受到地震层析成像以及板块运动和地层资料（古海岸线、钻孔构造沉降和沉积物等厚线）随时间变化的演化的制约。我们推断了上地幔和下地幔的平均粘度值，提供了晚白垩世至今北美垂直运动（相对海平面）的综合，并重建了晚白垩世法拉隆板块的几何形状。为了拟合晚白垩世海洋淹没和钻孔沉降，伴随模型要求660 km间断面上的黏度比为15:1（参考黏度为1021 Pa s），这与先前冰川后反弹研究推断的值一致。晚白垩世与Farallon板块俯冲有关的动力地形定位于北美西部，是控制大范围洪水的主要因素。美国东海岸不稳定；相反，它在新生代经历了持续的动态下沉，与整体的上升下降相一致，这解释了新泽西沿海平原的海平面与全球曲线之间的差异。东海岸的沉降进一步限制了地幔黏度结构，要求最上层地幔黏度为1020pa s。施加的限制要求法拉龙板块在晚白垩世处于平卧状态，法拉龙板块的浅倾俯冲带比之前认为的向东和向北延伸了1000公里，超出了平卧板块。
We apply adjoint models of mantle convection to North America since the Late Cretaceous. The present‐day mantle structure is constrained by seismic tomography and the time‐dependent evolution by plate motions and stratigraphic data (paleoshorelines, borehole tectonic subsidence, and sediment isopachs). We infer values of average upper and lower mantle viscosities, provide a synthesis of North American vertical motions (relative sea level) from the Late Cretaceous to the present, and reconstruct the geometry of the Farallon slab back to the Late Cretaceous. In order to fit Late Cretaceous marine inundation and borehole subsidence, the adjoint model requires a viscosity ratio across 660 km discontinuity of 15:1 (reference viscosity of 1021 Pa s), which is consistent with values previously inferred by postglacial rebound studies. The dynamic topography associated with subduction of the Farallon slab is localized in western North America over Late Cretaceous, representing the primary factor controlling the widespread flooding. The east coast of the United States is not stable; rather, it has been experiencing continuous dynamic subsidence over the Cenozoic, coincident with an overall eustatic fall, explaining a discrepancy between sea level derived from the New Jersey coastal plain and global curves. The east coast subsidence further constrains the mantle viscosity structure and requires an uppermost mantle viscosity of 1020 Pa s. Imposed constraints require that the Farallon slab was flat lying during Late Cretaceous, with an extensive zone of shallow dipping Farallon subduction extending beyond the flat‐lying slab farther east and north by up to 1000 km than previously suggested.