Mechanisms for the formation of ridge-axis topography atslow-spreading ridges: a lithospheric-plate flexural model
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The seafloor topography of a slow-spreading ridge shows a number of well-documented regularities at the ridge segment scale as the result of the complex interplay between ridge-axis magmatic and tectonic processes. This paper describes tilt: results of a detailed analysis of the seafloor topography of the Mid-Atlantic Ridge neat the Atlantis transform, where marine gravity data provide independent, although non-unique, constraints on subseafloor density structure. Using: a combined topography and gravity data set, we identified the specific contributions of subseafloor density structure to the seafloor topography. We show that the observed along-axis deepening (0.3-0.8 km) fi om the midpoint of a ridge segment towards the non-transform offsets in the study area can be explained by the vertical deflection of a zero-age plate in response to along-axis crustal thickness variations. However, this effect can only account for 50-60 per cent of the observed 1.5-1.7 km deepening towards the Atlantis transform, suggesting the presence of significant stresses in the lithosphere near a transform. Results: of plate flexural calculations also predict a more elevated rift flank at the inside corner of the ridge-transform intersection than at the conjugate outside corner. Such an asymmetry in rift flank topography is calculated to be greatest near a transform fault with a significant volume of deep transform valley and when adjacent plates across the transform fault are mechanically decoupled or only weakly coupled. Together these results illustrate the complex interplay between various tectonic processes at a slow-spreading ridge.