Thermal and mechanical evolution of the Michigan Basin     

W.F. Haxby  D.L. Turcotte  J.M. Bird 《Tectonophysics》1976,36(1-3)

We examine the formation of the Michigan Basin in terms of elastic flexure of the lithosphere. The shape of the flexure accurately determines the flexural rigidity of the lithosphere and the lateral extent of the load responsible for the flexure. The amplitude of differential subsidence then gives the magnitude of the load. Gravity anomalies in the southern peninsula of Michigan further restrain the dimensions of the load. We propose a model for the formation of the Michigan Basin involving mantle diapirs. We suggest that the first stage in its evolution was diapiric penetration of the lithosphere by hot asthenospheric mantle rock to the vicinity of the Moho. The heating of the lower crust by these hot rocks caused the transformation of lower crust, meta-stable gabbroic rocks to eclogite. Initially the lighter mantle rocks nearly balanced the heavier eclogite. As the mantle rocks cooled by conduction, the basin subsided under the load of the eclogite. The thermal contraction mechanism is supported by evidence that the flexural rigidity of the lithosphere increases with time. This is the effect of thickening of the elastic lithosphere as cooling progresses.  相似文献   

On the applicability of a universal elastic trench profile     

J.G. Caldwell  W.F. Haxby  D.E. Karig  D.L. Turcotte 《Earth and Planetary Science Letters》1976,31(2):239-246

Using thin elastic plate theory and neglecting horizontal applied forces, a universal deflection profile applicable to many oceanic trenches is derived. This theoretical profile is compared with bathymetric profiles from the central Aleutian, Kuril, Bonin, and Mariana trench-outer rise regions. The profiles were corrected for sediment thickness and age variation of the lithosphere. Good agreement between theory and observation is found. The distance from the first point of zero deflection seaward of the trench to the point of maximum height of the outer rise is directly related to the flexural rigidity of the lithosphere. The thickness of the elastic lithosphere is found to vary between 20 and 29 km for the trench profiles considered. The good agreement obtained shows that horizontal forces may be neglected and that the bending lithosphere behaves elastically in the cases considered. The analysis shows that only unreasonably large horizontal forces would affect the universal deflection curve. It is concluded that although the near-surface lithosphere may be subject to brittle fracture, the deeper lithosphere is capable of transmitting elastic stresses as high as 9 kbar.  相似文献