Kinematics of Footwall Exhumation at Oceanic Detachment faults: Solid‐Block Rotation and Apparent Unbending.

Seafloor spreading at slow rates can be accommodated on large‐offset oceanic detachment faults (ODFs), that exhume lower crustal and mantle rocks in footwall domes termed oceanic core complexes (OCCs). Footwall rocks experience large rotation during exhumation, yet important aspects of the kinematics—particularly the relative roles of solid‐block rotation and flexure—are not clearly understood. Using a high‐resolution numerical model, we explore the exhumation kinematics in the footwall beneath an emergent ODF/OCC. A key feature of the models is that footwall motion is dominated by solid‐block rotation, accommodated by the nonplanar, concave‐down fault interface. A consequence is that curvature measured along the ODF is representative of a neutral stress configuration, rather than a "bent" one. Instead, it is in the subsequent process of "apparent unbending" that significant flexural stresses are developed in the model footwall. The brittle strain associated with apparent unbending is produced dominantly in extension, beneath the OCC, consistent with earthquake clustering observed in the Trans‐Atlantic Geotraverse at the Mid‐Atlantic Ridge. Key Points: Numerical models of footwall exhumation show a significant component of solid‐block rotationBrittle footwall deformation away from the detachment fault is dominated by "apparent unbending""Unbending" since curvature gets reduced, "apparent" as the footwall is not bent in the first place [ABSTRACT FROM AUTHOR]